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pSOS System Concepts

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1. cccccccececeeeceeeeceeeeeeeenes 4 50 4 19 4 3 IP Route Table cisscdivcecenciccuecieccadasdevack becuadteceieds 4 50 4 19 4 4 IP Address Translation Table c0ceees 4 50 4 19 4 5 TCP Connection Table c cece eeeeeeeeeeeees 4 51 4 19 4 6 UDP Listener Table cece cence eeee ees 4 51 pSOSystem System Concepts vii Contents Viii 4 20 A195 SNMP ATED Sreser dunt eu TREE EA EAT aebabeattouu days weds 4 51 4 19 6 Network Interfaces cccceccececceceeeeeeceeneeeceecseeeeensenseeens 4 52 SUDCOMPONENUS 43 ed eevee ee e ie de caw deinen E EEEE EEEE A ET es 4 52 A201 PRPC Haas i runes al a eh Geena 4 53 4 20 1 1 pRPC Architecture eee ee eee se eee eees 4 53 4 20 1 2 Authentication seisce nia n 4 54 4201 98 Port Mapper aait i TE a ae 4 56 4 20 1 4 Global Variable scread a 4 56 PHILE File System Manager 5 1 5 2 5 3 5 4 5 5 VOlUME Types imiu iieii i eiie cajediete cule dias detnas peeps ante Guede uduavart a 5 2 Formatting and Initializing DiskS cece cc cece eeee eee een eee 5 4 5 2 1 Which Volume Type Should I Use ou ec cee eee eeenes 5 4 5 2 2 Format Definitions iinan a a aaa 5 5 5 2 3 Formatting Procedures ocardoies iia tane a 5 7 5 2 3 1 Hard DISKS wane Te EE E EENE 5 7 5 2 3 2 Floppy DISKS viv eiieeei tie A EERE E edtawees 5 9 Working With Volumes 2 0 0 0 eee oisi E inea ETE O aa 5 11 5 3 1 Mounting And Unmounting Volumes eseeseeceeeerer
2. Filenumber Filename Root 4 3 2 0x10000 Volume including partition Filenumber Filename sports 4 3 2 sports Volume including partition Filename pSOSystem System Concepts Chapter 5 pHILE File System Manager File Absolute Pathname Components sports 4 3 2 65536 sports Volume including partition Filenumber Filename sports 4 3 2 1 Volume including partition Filenumber Filename agenda 4 3 2 agenda Volume including partition Filename agenda 4 3 2 65536 agenda Volume including partition Filenumber Filename agenda 4 3 2 2 Volume including partition Filenumber Filename baseball 4 3 2 sports baseball Volume including partition Filename baseball 4 3 2 1 baseball Volume including partition Filenumber Filename baseball 4 3 2 0x20003 Volume including partition Filenumber Filename An example of a relative pathname is food fruit apples apples is a file in the directory fruit which is in the directory food which is a directory in the current directory stars elvis note the leading slash is another example of a relative pathname In this case the file elvis is in the directory stars which is in the root directory on the volume defined by the current directory Rules for naming files and specifying pathnames vary according to the type of volume On all volumes however the names containing only a single or double dot and are reserved A single dot refers to the current directory A
3. RESTRICTED RIGHTS LEGEND Use duplication or disclosure by the Government is subject to restrictions as set forth in subparagraph c 1 ii of the Rights in Technical Data and Computer Software clause at DFARS252 227 7013 or its equivalent Unpublished rights reserved under the copyright laws of the United States TRADEMARKS MATRIX and AutoCode are registered trademarks of Integrated Systems Inc The following are trademarks of Integrated Systems Inc DocumentIt ESp HyperBuild OpEN OpTIC pHILE pNA pREPC pRISM pRISM pROBE PRPC pSET pSOS pSOS pSOS m pSOSim pSOSystem pX11 RealSim SpOTLIGHT SystemBuild Xmath ZeroCopy SNiFF is a trademark of TakeFive Software GmbH Austria a wholly owned subsidiary of Integrated Systems Inc ELANIX Signal Analysis Module and SAM are trademarks of ELANIX Inc All other products mentioned are the trademarks service marks or registered trademarks of their respective holders Contents Contents About This Manual PULP OSE ER RA E OTEN E E R E xiii Audite sdra ie E EN A A ans ye saad Ha sie a 0a Hak xiii Organization o E E EEEE E E E EEA TE E Pesos xiv Related Documentation 3 en oe o i pand a tain enn eden Fea baa da on ba ad xiv Notation Conventions iss criesseictincians vated ecdsenedulees ove dee nddlcsnscuameddawenss XV Symbol CONVENTIONS is veces desis Gav deeded c des Seven o a a a ii ees xvi SUPDOL rassen sare suse ads wa aaaniedaiiaale
4. 1 If all other presently ready tasks have lower priority then no special scheduling takes place The task s timeslice counter stays at zero so long as it stays in the running or ready state pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel 2 If one or more other tasks of the same priority are ready the pSOS kernel moves the running task from the running state into the ready state and re enters it into the indexed ready queue behind all other ready tasks of the same priority This forces the pSOS dispatcher to switch from that last running task to the task now at the top of the ready queue The last running task s timeslice counter is given a full timeslice in preparation for its next turn to run Regardless of whether or not its roundrobin mode bit is enabled when a task becomes ready from the blocked state the pSOS kernel always inserts it into the indexed ready queue behind all tasks of higher or equal priority At the same time the task s timeslice counter is refreshed with a new full count NOTE The preemption mode bit takes precedence over roundrobin scheduling Ifthe running task has preemption disabled then it will preclude roundrobin and continue to run In general real time systems rarely require time slicing except to insure that certain tasks will not inadvertently monopolize the CPU Therefore the pSOS kernel by default initializes each task with the roundrobin mode disabled For exampl
5. On every node the pSOS m kernel internally maintains an up to date node roster at all times which indicates which nodes are presently in the system The roster is a bit map encoded in 32 bit long word entries Thus the first long word contains bits corresponding to nodes 1 32 the second nodes 33 64 etc Within a long word the rightmost least significant bit corresponds to the lowest numbered node pSOSystem System Concepts Chapter 3 pSOS Multiprocessing Kernel The map is composed of the minimum number of long words needed to encode a system with mc_nnode as specified in the Multiprocessor Configuration Table Therefore some bits in the last long word may be unused Application code and or the KI may also need to know which nodes are in the system Therefore the pSOS m kernel makes its node roster available to both at system startup and keeps each informed of any subsequent roster changes The application is provided roster information via the user provided routine pointed to by the Multiprocessor Configuration Table entry mc_roster The KI is provided roster information via the KI service ki_roster For more information on KI service calls or the Multiprocessor Configuration Table see the Configuration Tables section of the pSOSystem Programmer s Reference 3 11 Dual Ported Memory Considerations Dual ported memory is commonly used in memory bus_ based multiprocessor systems However it poses several unique p
6. s eesseerseseserseseessseseseseseseesessese 5 39 5 7 4 Block Allocation Methods cccceceeeceenececececeeeeeeeeeeees 5 41 5 7 5 How Directories Are Organized cee eeceeeeeeeeeeee nen ee 5 43 5 7 6 Logical and Physical File Sizes 2 0 0 0 ee ee eee neocon ee 5 44 5 7 7 System Calls Unique to pHILE Format eee eee ee 5 44 5 7 7 1 annex Eee e Ra saat coastal Loe tee ets 5 44 5 7 7 2 TO CK Bese ids AEE ies lo AE A hotest eet 5 45 pSOSystem System Concepts ix Contents 5 8 Sp cial Considerations serenua a e n a a eda 5 46 5 8 1 Restarting and Deleting Tasks That Use the pHILE File System Managert asescar toe i i a ea 5 46 5 8 1 1 Restarting Tasks That Use the pHILE File System Manager ccccccccccecceeceeee aa 5 46 5 8 1 2 Deleting Tasks That Use the pHILE File System Managet ccceeeeceeeeeeeeee eee enee 5 47 6 pREPC ANSIC Library 6 1 INtPOCUCHON Mevsee eeses seeds Secbenctetins a n a a beds e a r a 6 1 6 2 P ncti ns SUM Ary iiei ei iii cele cos Eii Ea E aA a EN E devs 6 2 6 3 VO aO e V a a a a E a oes vba ues 6 3 6 3 1 Files Disk Files and I O Devices ceseseseesesesreccscsseeses 6 4 6 3 2 File Data Str ctUrCnicscerionerar iire coe ae i R 6 5 6 9 3 lt Buffer Saio eoreoiiriii iee dale AA Soe EEA E ETE Bes 6 6 6 3 4 Buffering Tec nigt s iecerei eneen aa A i 6 7 6 3 5 stdin stdout Stdel resice iiie trinii KAREE Eia 6 7 6 39 60 DCLEATIS at aeeai n Ea e
7. section of the pSOSystem Programmer s Reference 2 9 2 Semaphore Operations The pSOS kernel supports the traditional P and V semaphore primitives The sm_p call requests a token If the semaphore token count is non zero then sm_p decrements the count and the operation is successful If the count is zero then the caller can elect to wait wait with timeout or return unconditionally If a task elects to wait it will either be by first in first out or by task priority order depending on the specifications given when the semaphore was created The sm_v call returns a semaphore token If no tasks are waiting at the semaphore then sm_v increments the semaphore token count If tasks are waiting then the first task in the semaphore s wait list is released from the list and made ready to run 2 10 Asynchronous Signals Each task can optionally have an Asynchronous Signal Service Routine ASR The ASR s purpose is to allow a task to have two asynchronous parts a main body and an ASR In essence just as one task can execute asynchronously from another task an ASR provides a similar capability within a task Using signals one task or ISR can selectively force another task out of its normal locus of execution that is from the task s main body into its ASR Signals provide a software interrupt mechanism This asynchronous communications capability is invaluable to many system designs Without it workarounds must depe
8. Each task carries a mode word that can be used to modify scheduling decisions or control its execution environment m Preemption Enabled Disabled If a task has preemption disabled then so long as it is ready the pSOS kernel will continue to run it even if there are higher priority tasks also ready m Roundrobin Enabled Disabled Its effects are discussed in section 2 3 5 Roundrobin by Timeslicing m ASR Enabled Disabled Each task can have an Asynchronous Signal Service Routine ASR which must be established by the as_catch system call Asynchronous signals behave much like software interrupts If a task s ASR is enabled then an as_send system call directed at the task will force it to leave its expected execution path execute the ASR and then return to the expected execution path See section 2 10 1 The ASR for more details on ASRs m Interrupt Control Allows interrupts to be disabled while a task is running On some processors you can fine tune interrupt control Details are provided in the t_mode and t_start call descriptions in pSOSystem System Calls A task s mode word is set up initially by the t_start call and can be changed dynamically using the t_mode call Some processor versions of pSOS place restrictions on which mode attributes can be changed by t_mode Details are provided in the t_mode description in pSOSystem System Calls To ensure correct operation of the application
9. Generally context refers to the state of machine registers When a task is running its context is highly dynamic and is the actual contents of these registers When the task is not running its context is frozen and kept in the TCB to be restored the next time it runs There are certain overhead structures within a TCB that are used by the psOS kernel to maintain it in various system wide queues and structures For example a TCB might be in one of several queues the ready queue a message wait queue a semaphore wait queue or a memory region wait queue It might additionally be in a timeout queue At pSOS kernel startup a fixed number of TCBs is allocated reflecting the maximum number of concurrently active tasks specified in the pSOS Configuration Table entry kc_ntask A TCB is allocated to each pSOSystem System Concepts 2 15 Chapter 2 pSOS Real Time Kernel 2 4 3 task when it is created and is reclaimed for reuse when the task is deleted Memory considerations for TCBs are given in the Memory Usage section of the pSOSystem Programmer s Reference A task s Tid contains among other things the encoded address of the task s TCB Thus for system calls that supply Tid as input the pSOS kernel can quickly locate the target task s TCB By convention a Tid value of O is an alias for the running task Thus if O is used as the Tid in a system call the target will be the calling task s TCB Task Mode Word
10. Synchronization Mutual Exclusion A pSOS based application is generally partitioned into a set of tasks and interrupt service routines ISRs Conceptually each task is a thread of independent actions that can execute concurrently with other tasks However cooperating tasks need to exchange data synchronize actions or share exclusive resources To service task to task as well as ISR to task communication synchronization and mutual exclusion the pSOS kernel provides three sets of facilities message queues events and semaphores The Message Queue Message queues provide a highly flexible general purpose mechanism to implement communication and synchronization The related system calls are listed below q_create Create a message queue q_ident Get the ID of a message queue q_delete Delete a message queue q_receive Get wait for a message from a queue q_send Post a message at the end of a queue q_urgent Put a message at head of a queue q_broadcast Broadcast a message to a queue pSOSystem System Concepts 2 7 1 Chapter 2 pSOS Real Time Kernel Like a task a message queue is an abstract object created dynamically using the q_create system call q_create accepts as input a user assigned name and several characteristics including whether tasks waiting for messages there will wait first in first out or by task priority whether the message queue has a limited length and whether a set of message buffers will be
11. The larger the unit_size the faster the rn_getseg and rn_retseg execution and the smaller the RNCB The pSOS region manager uses an efficient heap management algorithm A region s RNCB holds an allocation map and a heap structure used to manage an ordered list of free segments By maintaining free segments in order of decreasing size an rn_getseg call only needs to check the first such segment If the segment is too small then allocation is clearly impossible The caller can wait wait with timeout or return immediately with an error code If the segment is large enough then it will be split One part is returned to the calling task The other part is re entered into the heap structure If the segment exactly equals the requested segment size it will not be split When rn_retseg returns a segment the pSOS kernel always tries to merge it with its neighbor segments if one or both of them happen to be free Merging is fast because the neighbor segments can be located without searching The resulting segment is then re entered into the heap structure 2 5 4 Partitions and Buffers A memory partition is a user defined physically contiguous block of memory divided into a set of equal sized buffers Aside from having different buffer sizes partitions can have distinctive implicit attributes For example one can reside in strictly local RAM another in system wide accessible RAM Partitions must be mutually disjoint Like regions
12. The remaining functions implicitly cause memory to be released The pREPC library deallocates memory by generating a rn_retseg call to the pSOS kernel Chapter 2 _pSOS Real Time Kernel contains a complete discussion of the pSOS region memory manager 6 5 Enor Handling Most pREPC functions can generate error conditions In most such cases the pREPC library stores an error code into an internal variable maintained by pSOS called errno and returns an error indicator to pSOSystem System Concepts 6 9 Chapter 6 pREPC ANSI C Library 6 6 6 7 the calling task Usually this error indicator takes the form of a negative return value The error indicator for each function if any is documented in the individual function calls Error codes are described in detail in the error codes reference The pREPC library maintains a separate copy of errno for each task Thus an error occurring in one task will have no effect on the errno of another task A task s errno value is initially zero When an error indication is returned from a pREPC call the calling task can obtain the errno value by referencing the macro errno This macro is defined in the include file lt errno h gt Note that once the task has been created the value of errno is never reset to zero unless explicitly set by the application code The pREPC library also maintains two error flags for each opened file They are called the end of file flag and the
13. allows users to send messages with a minimum of protocol overhead However ordered reliable delivery of data is not guaranteed The IP layer is used for transmitting blocks of data called datagrams This layer provides packet routing fragmentation and reassembly of long datagrams through a network or internet Multicast IP support is implemented in the IP layer The Network Interface NI layer isolates the IP layer from the physical characteristics of the underlying network medium It is hardware dependent and is responsible for transporting packets within a single network Because it is hardware dependent the network interface is not part of pNA proper Rather it is provided by the user or by ISI asa separate piece of software In addition to the protocols described pNA supports the Address Resolution Protocol ARP the Internet Control Message Protocol ICMP and the Internet Group Management Protocol IGMP ICMP is used for error reporting and for other network management tasks It is layered above IP for input and output operations but it is pSOSystem System Concepts 4 3 4 3 1 Chapter 4 Network Programming logically a part of IP and is usually not accessed by users See Section 4 16 Internet Control Message Protocol ICMP IGMP is used by IP nodes to report their host group memberships to any immediately neighboring multicast routers IGMP is layered above IP for input and output operations but it is
14. asynchronous versions for the following pSOS system calls pSOS Synchronous Service pSOS m Asynchronous Call q_send q_asend q_urgent q_aurgent q_vsend q_avsend q_vurgent q_avurgent sm_v sm_av ev_send ev_asend Asynchronous calls operate like their synchronous counterparts except that the calling task does not wait for a reply and the destination node does not generate one An asynchronous RSC should be used only when an error is not expected If an error occurs however the pSOS m kernel on the destination node will send a packet to the source node describing the error Because the state of the calling task is unknown e g it may have been deleted the source pSOS m kernel does not attempt to directly notify the calling task Instead it checks for a user provided callout routine by examining the Multiprocessor Configuration Table entry mc_asyncerr If provided this routine is called The mc_asyncerr callout routine is passed two parameters The first parameter is the function code of the asynchronous service that generated the error and the second parameter is the task ID of the task that made the erroneous call What mc_asyncerr does is up to the user However a normal sequence of events is to perform further error pSOSystem System Concepts 3 9 Chapter 3 pSOS Multiprocessing Kernel 3 5 3 analysis and then shut down the node with a k_fatal call Other alternatives are to delete or re
15. in which case the dispatcher has no choice but to return to it Note that a running task can only be preempted by a task of higher or equal if timeslicing enabled priority Therefore the assignment of priority levels is crucial in any application A particular ready task cannot run unless all tasks with higher priority are blocked By the same token a running task can be preempted at any time if an interrupt occurs and the attendant ISR unblocks a higher priority task Roundrobin by Timesiic ing In addition to priority the pSOS kernel can use timeslicing to schedule task execution However timesliced roundrobin scheduling can be turned on off on a per task basis and is always secondary to priority considerations You can specify the timeslice quantum in the Configuration Table using the parameter kc_ticks2slice For example if this value is 6 and the clock frequency kc_ticks2sec is 60 a full slice will be 1 10 second Each task carries a timeslice counter initialized by the pSOS kernel to the timeslice quantum when the task is created Whenever a clock tick is announced to the pSOS kernel the pSOS time manager decrements the running task s timeslice counter unless it is already 0 The timeslice counter is meaningless if the task s roundrobin bit or the preemption bit is disabled If the running task s roundrobin bit and preemption bit is enabled and its time slice counter is 0 two outcomes are possible as follows
16. pSOSystem System Concepts Chapter 5 pHILE File System Manager 32 1 begin 100000 32 1 size 100000 2 begin Right after 1 100000 2 size 200000 3 begin Right after 2 50000 3 size 250000 4 begin Right after 3 50000 4 size 0 O End of list size 0 UINT err_code For system calls struct scsi_ctl_iopbiopb For de_cntrl ULONG retval iopb function SCSI_CTL_PARTITION iopb u arg parts NOTE Partition must be zero err_code de_cntrl DEVICE 4 5 0 amp iopb amp retval if err_code 0 Error handling 2 In your application use the pSOSystem system call init_vol to initialize each partition as a pHILE volume See the example on page 5 7 5 2 3 2 Hoppy Disks Using MS DOS to Format a Floppy Disk for MS DOS Volumes Execute the format command On a floppy disk format performs the physical formatting writes the boot record and initializes a volume in MS DOS format Using MS DOS to Format a Floppy Disk for pHILE Volumes 1 Execute the format command pSOSystem System Concepts 5 9 Chapter 5 pHILE File System Manager 2 In your application use the pSOSystem system call init_vol to initialize each partition as a pHILE volume Follow the example on page 5 7 but use a smaller volume_size A 1 44 megabyte 3 1 2 floppy disk has 2 880 sectors per disk so init_vol cannot have a
17. pSOSystem System Concepts 2 39 Chapter 2 pSOS Real Time Kernel 2 14 2 40 Every fatal error has an associated error code that defines the cause of the fatal error The error code appendix of psOSystem System Calls lists all pSOSystem error codes Error codes equal to or greater than 0x20000000 are available for use by application code In this case the error code is provided as an input parameter to k_fatal or k_terminate in multiprocessor systems When a fatal error occurs whether generated internally by pSOSystem or by a call to k_fatal or k_terminate the pSOS kernel passes control to an internal fatal error handler In single processor systems the fatal error handler simply performs the shutdown procedure described below In multiprocessor systems it has the additional responsibility of removing the node from the multiprocessor system The shutdown procedure is a procedure whereby the pSOS kernel attempts to halt execution in the most orderly manner possible The pSOS kernel first examines the pSOS Configuration Table entry kce_fatal If this entry is non zero the pSOS kernel jumps to this address If kc_fatal is zero and the pROBE System Debug Analyzer is present then the pSOS kernel passes control to the System Failure entry of the pROBE component Refer to the pROBE User s Manual for a description of pROBE component behavior in this case Finally if the PROBE component is absent the pSOS kernel internally e
18. reason it is usually a result of a hardware or software failure Therefore this manual refers to a node that stops running for any reason as a failed node The failure of a node may have an immediate and substantial impact on the operation of remaining nodes For example nodes may have RSCs pending on the failed node or there may be agents waiting on behalf of the failed node As such when a node fails all other nodes in the system must be notified promptly so corrective action can be taken The following paragraphs explain what happens when a node fails or leaves a system In general the master node is responsible for coordinating the graceful removal of a failed node There are three ways that a master may learn of a node failure 1 The pSOS m kernel on the failing node internally detects a fatal error condition which causes control to pass to its fatal error handler The fatal error handler notifies the master and then shuts itself down as described in Chapter 2 _pSOS Real Time Kernel 2 An application calls k_fatal without the K_GLOBAL attribute On a slave node control is again passed to the pSOS m internal fatal error handler which notifies the master node and then shuts itself down by calling the user supplied fatal error handler See section 2 13 3 An application on any node not necessarily the failing node calls k_terminate which notifies the master pSOSystem System Concepts 3 13 Chapter 3 p
19. sectors per track heads Head block sectors per track MOD heads Sector block block sectors per track sectors per track 1 Under the pHILE file system manager an MS DOS volume can be larger than 32 Mbytes Due to an MS DOS limit the number of clusters in a volume can be up to only 65 535 To support volumes larger than 32M the cluster size should be larger than 512 bytes A larger cluster size can cause inefficient use of disk space To avoid this a hard disk drive can be logically divided into partitions Each partition is used to hold one file volume Hence a partition can be either a DOS or pHILE volume Partitioning allows heterogeneous file volumes to share a single drive With partitions multiple DOS volumes can be generated to cover large disk drives When a single hard disk drive contains multiple partitions your driver must read the partition table located in the master boot sector during initialization and use the information in the table to translate sector addresses This process is called partition table block translation Your application code and driver should use the upper byte of the minor device number to encode the partition number Partition O should refer to the entire volume without partition table block translation This pSOSystem System Concepts 7 11 4 Chapter 7 I O System convention allows the pHILE file system manager and your application code to read any sector on the disk including th
20. A SM_READ_ONLY volume are disallowed 5 6 5 1 Immediate White Mode When a volume is mounted with the immediate write mode cache buffers and in memory system data structures are flushed that is written to the volume whenever they are modified Immediate write mode is equivalent to calling sync_vol explained below after every pHILE operation Unfortunately system throughput can be significantly impacted because every write operation results in at least two I O transactions one for a cache buffer and one for system data When using this mode you should avoid writing less than a block of data with one write_f system call You should collect data in a local buffer and write at least one block at a time 5 6 5 2 Contol Wiite Mode When a volume has been mounted with control write mode every time an in memory system data structure is modified it is flushed to disk For example if the contents of a File Control Block is changed it is flushed User data however is not flushed immediately and may linger in a cache buffer for an indefinite period of time Control write mode provides the same level of volume integrity as immediate write mode but provides less protection for your data in the event of a system failure Its use however can significantly improve pSOSystem System Concepts 5 29 Chapter 5 pHILE File System Manager 5 6 6 5 30 throughput The difference is most dramatic when the application is performing
21. CnslInit CnslOpen CnslRead CnsIWrite CnsiClose and CnsiCntrl Of course this is just a convention any names can be used because both the driver and the I O switch table are user provided Figure 7 3 on page 7 7 illustrates this relationship ioparms is a structure used to pass input and output parameters between the pSOS kernel and the driver It is defined as follows struct ioparms unsigned long used Usage is processor specific unsigned long tid Task ID of calling task unsigned long in_dev Input device number unsigned long status unused void in_iopb Input pointer to IO parameter block void io_data_area No longer used unsigned long err For error return unsigned long out_retval For return value pSOSystem System Concepts Chapter 7 I O System Application de_write Figure 7 3 pSOS Kemel to Driver Relationship Usage of the used parameter is different on different processors Processor specific information is provided below 68K 960 CF PPC MIPS x86 SH On 68K and 960 processors used is set to zero by the pSOS kernel on entry to the driver The driver must set used to a non zero value It is used internally by pSOS when it receives control back from the driver CAUTION Ifthe driver does not set used to a non zero value improper operation results On Coldfire PowerPC MIPS x8
22. Last Modification The pHILE file system manager maintains the time at which a file was last modified This field is initialized when a file is created thereafter it is updated whenever a file is written or when blocks are annexed to the file 5 7 2 5 The File Expansion Unit If a write_f operation extends past the current physical size of a file the pHILE file system manager will automatically expand the file to hold the new data This type of file expansion is governed by the following considerations pSOSystem System Concepts Chapter 5 pHILE File System Manager When a file is created you supply a parameter called an expansion unit that determines the minimum expansion increment to use during write_f operations This parameter specifies the minimum number of physically contiguous blocks the pHILE file system manager attempts to allocate when additional space is required by file This is a lower bound number because the number of blocks allocated is actually determined by either the expansion unit or the number of blocks needed to satisfy the current write_f operation whichever is greater 5 7 2 6 Extents A file is treated simply as a sequence of logical blocks Each such block corresponds to a physical block on the volume Because the physical blocks that comprise a file may be scattered throughout a volume the pHILE file system manager implements a structure called an extent to keep track of a file s blocks a
23. Object Table if the object resides on a slave node The maximum number of objects of all types that can be exported is specified by the Multiprocessor Configuration Table entry mc_nglbobj During pSOS m kernel initialization this entry is used to pre allocate storage space for the Global Object Table Note that the master node s Global Object Table is always much larger than Global Object Tables on slave nodes Formulae for calculating the sizes and memory usage of Global Object Tables are provided in the Memory Usage section of the pSOSystem Programmer s Reference Ident Operations on Global Objects The pSOS m Object Ident system calls e g t_ident or q_ident perform run time binding by converting an object s name into the object s ID This may require searching the object tables on the local node and or the Global Object Table on the master node To search the master node s Global Object Table slave nodes must post an IDENT request to the pSOSystem System Concepts 3 5 Chapter 3 pSOS Multiprocessing Kernel 3 5 3 6 master node On receiving this request the pSOSt m kernel on the master node searches its Global Object Table and replies to the slave node with the object s ID or an indication that the object does not exist Because objects created and exported by different nodes may not have unique names the result of this binding may depend on the order and manner in which the object tables are searche
24. a Task ian ae e ee Baa eS 2 14 2 amp 2 Task Control Block n ivti siedis aot paves tcevesrdeeentspieiiveaeases 2 15 24 3 Task Mode Word ise iat teseralgavcusesbesbececterseecceesaadedensuegs else 2 16 2AA 4 Task Stacks reoeo edhe Sel uesseees seston a E prada 2 17 2 49 Task MEMOry ar aaien tented e ATAA EAA EEA octane 2 18 2 4 6 Death of a Task oreren serais iee AEEA AEA rE EE 2 18 2 4 7 Notepad Registers neisiet e e a a a 2 19 2 48 Theldle Task vead iaaea a a A a EAE AR AATE dates 2 19 2 4 8 1 Processor Specific Information on IDLE 2 19 ptorage Allocation simsii erian eE E ati aa aA a aai 2 20 2 5 1 Regions and Segments iseensest 2 20 XOZ lt SpecialsRE SiON O erliak steed etek ee seis tee Hae setae tebe ee eee eae a 2 21 2 5 3 Allocation AlZorith hess a a a 2 22 2 5 4 Partitions and Buffers ocseuebenietutancnne n oa 2 23 Communication Synchronization Mutual Exclusion 2 24 The Message Queues iciciicsetcedaeshorn ds Jeri oe hee hes bean ecdeta a 2 24 2 7 1 The Queue Control Block cece cee eeeeeeeeeeeeeeneeeeees 2 25 21 2 Queue Operauions niuir eaen e ee eR ae 2 25 2 7 3 Messages and Message Buffers cece cece cece teen eens 2 26 2 7 4 Two Examples of Queue USsage ccc ceeeeecnscneceeeneeeeeeees 2 27 2 7 5 Variable Length Message QueCUES c cece ee eeee eee eeee 2 28 VENUS iire iieo ETE chine ETE don V EO OAA E ELAR 2 29 2 9 1 Eyvent Op rations sarre o
25. a multitasking application are created dynamically at runtime One exception is the ROOT task which is created and started by the pSOS kernel as part of its startup initialization After startup the pSOS kernel simply passes control to the ROOT task The other exception is the default IDLE task also provided as part of startup All other tasks are created by explicit system calls to the pSOS kernel when needed In some designs ROOT can initialize the rest of the application by creating all the other tasks at once In other systems ROOT might create a few tasks which in turn can create a second layer of tasks which in turn can create a third layer and so on The total number of active tasks in your system is limited by the kc_ntask specification in the pSOS Configuration Table The code segment of a task must be memory resident It can be in ROM or loaded into RAM either at startup or at the time of its creation A task s data area can be statically assigned or dynamically requested from the pSOS kernel Memory considerations are discussed in detail in the Memory Usage section of the pSOSystem Programmer s Reference 2 4 2 Task Contol Block A task control block TCB is a system data structure allocated and maintained by the pSOS kernel for each task after it has been created A TCB contains everything the kernel needs to know about a task including its name priority remainder of timeslice and of course its context
26. a new file system on the volume 5 6 pSOSystem System Concepts Chapter 5 pHILE File System Manager Table 5 1 summarizes the above information Formatting Step Where Performed Type of Disk That Requires This Step 1 Physical format Factory Hard and floppy 2 Partitioning User Hard only 3 Volume User Hard and floppy parameter record 4 File system User Hard and floppy initialization Table 5 1 Stepsto Formata Hard or Floppy Disk 5 2 3 Formatting Procedures The heading for each set of instructions below defines the disk type the volume type and the system being used i e Using MS DOS to Format a Hard Disk for MS DOS Volumes Remember that if your application uses MS DOS volumes you must format the disk using MS DOS If it uses pHILE format volumes use either MS DOS or the I O control commands of a SCSI driver 5 2 3 1 Hard Disks Using MS DOS to Format a Hard Disk for MS DOS Volumes 1 Execute the fdisk command fdisk partitions the disk 2 Execute the format command once for each partition format writes the boot records and initializes an MS DOS file system within a partition Using MS DOS to Format a Hard Disk for pHILE Volumes 1 Execute the fdisk command fdisk partitions the disk 2 In your application use the pSOSystem system call init_vol to initialize each partition as a pHILE volume init_vol writes the pHILE root block and initializes a pHILE file s
27. always one block pSOSystem System Concepts 5 41 Chapter 5 pHILE File System Manager 5 42 Case 4 An Indirect or Index Block Is Needed These are always single blocks so the allocation size is one block Indirect and index blocks are explained below After selecting the allocation size the pHILE file system manager chooses the block type Ordinary files use data blocks while pHILE data structures use control and data blocks The block type is used to decide where in the volume to search for free space If the volume was partitioned into data and control regions during initialization which is explained in more detail below only the relevant portion of the volume will be used The search does not always start with the first block in the appropriate region Rather the pHILE file system manager will start searching in the bitmap of the block last referenced This increases the chance of scanning a block in the cache and thus enhances throughput The search involves locating the first unused extent containing at least the required number of blocks This search can have three outcomes 1 A sufficiently large extent is found and allocated in which case the search is successfully completed If the length of the extent is greater than the allocation size the extent will be split 2 No extents equal to or greater than the allocation size are found In this case the pHILE file system manager will allocate the largest remai
28. and debug environment for single or multi processor target systems pSOSystem System Concepts 4 1 Chapter 4 Network Programming SNMP Simple Network Management Protocol is a standard used for managing TCP IP networks and network devices Because of its flexibility and availability SNMP has become the most viable way to manage large heterogeneous networks containing commercial or custom devices FTP Telnet TFTP pSOSystem environment includes support for the well known internet protocols File Transfer Protocol FTP and Telnet client and server side and Trivial File Transfer Protocol TFTP FTP client allows you to transfer files to and from remote systems FTP server allows remote users to read and write files from and to pHILE managed devices Telnet client enables you to login to remote systems while Telnet server offers login capabilities to the pSOSystem shell pSH from remote systems TFTP is used in pSOSystem Boot ROMs and is normally used to boot an application from a network device RPCs pSOSystem fully supports Sun Microsystems Remote Procedure Call RPC and eXternal Data Representation XDR specifications via the pRPC software component The pRPC component allows you to construct distributed applications using the familiar C procedure call paradigm With the pRPC component pSOS tasks and UNIX processes can invoke procedures for execution on other pSOSystem or UNIX machines NFS pSOSystem en
29. and do not address hardware related considerations 7 8 1 Synchronous I O A synchronous driver can be implemented using one semaphore If it is needed Type 1 mutual exclusion would require a second semaphore To avoid confusion mutual exclusion is left out of the following discussion The device s init service creates a semaphore rdy with initial count of O When a task calls read or write the driver starts the I O transaction and then uses sm_p to wait for the rdy semaphore When the I O completion interrupt occurs the device s ISR uses sm_v to return the semaphore rdy thereby waking up the waiting task When the task resumes in read or write it checks the device status and so forth for any error conditions and then returns This is shown as pseudo code below SYNC_OP DEV_ISR Begin Begin startio transfer data status sm_p rdy wait sm_v rdy get status data End End An I O transaction may of course trigger one or more interrupts If the transaction involves a single data unit or if the hardware provides DMA then there will normally only be a single interrupt per transaction Otherwise the ISR will have to keep the data transfer going at successive device interrupts until the transaction is done Only at the last interrupt of a transaction does the ISR return the semaphore to wake up the waiting task pSOSystem System Concepts 7 13 Chapter 7 I O System 7 8 2 7 14 Asynchronous I O
30. and or write operations de_cntrlI is dependent on the device It may include anything that cannot be categorized under the other five I O services de_cntrl may be used to perform multiple sub functions both input and output If a device does not require any special functions then this service can be null Note that the pSOS I O system has two interfaces one to the application the second to the device drivers These two interfaces are described in more detail later in this chapter First it is helpful to introduce the I O Switch Table 7 2 VO Switch Table The pSOS kernel calls device drivers by using the I O switch table The I O switch table is a user supplied table that contains pointers to device driver entry points The pSOS configuration table entries KC_IOJ TABLE and KC_NIO describe the I O switch table KC_IOJ TABLE points to the table and KC_NIO defines the number of drivers in the table The I O switch table is an array of pSOS_IO_J ump_Table structures This structure is defined as follows struct pSOS_IO_ Jump_Table void dev_init struct ioparms void dev_open struct ioparms void dev_close struct ioparms void dev_read struct ioparms void dev_write struct ioparms void dev_cntrl struct ioparms unsigned long rsvdl unsigned short rsvd2 unsigned short flags The index of a driver s entry pointers within the I O switch table determines the major device
31. available on your target pSOS Real time Multitasking Kernel A __ field proven multitasking kernel that provides a responsive efficient mechanism for coordinating the activities of your real time system pSOS n Multiprocessor Multitasking Kernel Extends the pSOS feature set to operate seamlessly across multiple tightly coupled or distributed processors pNA TCP IP Network Manager A complete TCP IP implemen tation including gateway routing UDP ARP and ICMP protocols uses a standard socket interface that includes stream datagram and raw sockets pRPC Remote Procedure Call Library Offers SUN compatible RPC and XDR services allows you to build distributed applications using the familiar C procedure paradigm pSOSystem System Concepts Chapter 1 Product Overview pHILE File System Manager Gives efficient access to mass storage devices both local and on a network Includes support for CD ROM devices MS DOS compatible floppy disks and a high speed proprietary file system When used in conjunction with the pNA component and the pRPC subcomponent offers client side NFS services pREPC ANSI C Standard Library Provides familiar ANSI C run time functions such as printf scanf and so forth in the target environment Figure 1 1 illustrates the pSOSystem environment C C Interface i Interrupt Handlers Figure 1 1 The pSOSystem Environment pSOSystem System Concepts 1 3 Ch
32. cache data and thus lost entirely read_vol and write_vol can read write portions of a block All the necessary caching and blocking deblocking will be performed by the pHILE file system manager as required Thus read_vol and write _vol allow a device to be accessed as a continuous sequence of bytes without regard for block boundaries NOTE read_vol is available for all local volumes write_vol is available forall local volumes exc eptC D ROM which is read only pSOSystem System Concepts 5 25 Chapter 5 pHILE File System Manager 5 6 3 5 6 4 5 26 Blocking Deblocking From the user s point of view a file is a sequence of bytes Internally however the pHILE file system manager implements a file as a sequence of logical blocks and interacts with your driver in units of blocks Therefore for each user I O request the pHILE file system manager must map the requested data bytes into logical blocks On top of this your device driver must in turn translate logical blocks into physical storage units This process of translating bytes into blocks is called blocking and deblocking The following scenarios illustrate how blocking and deblocking work When a read_f operation requests bytes that are within a block the pHILE file system manager reads the entire block and then extracts the referenced bytes from it deblocking When a write _f operation writes bytes that are within a block the pHILE file
33. can make the necessary close calls the simplest way to delete a task is to restart the task passing arguments to it that indicate that the task should delete itself Of pSOSystem System Concepts 2 41 Chapter 2 pSOS Real Time Kernel 2 14 2 2 42 course the task code must be written to check its arguments and behave accordingly Restarting Tasks That Use Components The pSOS kernel allows a task to be restarted regardless of its current state Check the sections in this manual for each component to determine its behavior on task restart It is possible to restart a task while the task is executing code within the components themselves Consider the following example 1 Task A makes a pHILE call 2 While executing pHILE code task A is preempted by task B 3 Task B then restarts task A In such situations the pHILE component will correctly return resources as required However a file system volume might be left in an inconsistent state For example if t_restart interrupts a create f operation a file descriptor FD might have been allocated but not the directory entry As a result an FD could be permanently lost But the pHILE component is aware of this danger and returns a warning via the t_restart When such a warning code is received from the pHILE component verify_vol should be used to detect and correct any resulting volume inconsistencies All components are notified of task restarts so expect such w
34. connection is established data can be transferred The send and recv system calls are designed specifically for use with sockets that have already been connected The syntax is as follows send s buf buflen flags recv s buf buflen flags A task sends data through the connection by calling the send system call send accepts as input a socket descriptor the address and length of a buffer containing the data to transmit and a set of flags A flag can be set to mark the data as out of band that is high priority so that it can receive special handling at the far end of the connection Another flag can be set to disable the routing function for the data that is the data will be dropped if it is not destined for a node that is directly connected to the sending node The socket specified by the parameter s is known as the local socket while the socket at the other end of the connection is called the foreign socket When send is called the pNA component copies the data from the buffer specified by the caller into a send buffer associated with the socket and attempts to transmit the data to the foreign socket If there are no send buffers available at the local socket to hold the data send blocks unless the socket has been marked as non blocking The size of a socket s send buffers can be adjusted with the setsockopt system call pSOSystem System Concepts 4 11 Chapter 4 Network Programming 4 4 6 4 4
35. contains host tool tutorials m psSOSystem System Calls contains detailed descriptions of all pSOSystem system calls and error codes m pSOSystem Programmer s Reference contains detailed information on pSOSystem system services interfaces and drivers configuration tables and memory usage pSOSystem System Concepts About This Manual PROBE User s Manual describes how to use the pROBE System Debugger Analyzer Based on your software configuration you may need to refer to one or more of the following manuals C Support Package User s Manual documents the C support services including the pSOSystem C Classes library and support for the C runtime ESp User s Guide PC Hosts and ESp User s Guide Workstation Hosts document the ESp front end analyzer which displays application activities and the pMONT component the target resident application monitor LAP Driver User s Guide describes the interfaces provided by the Link Access Protocol LAP drivers for OpEN product including the LAPB and LABD frame level products OpEN OSI Lower Layers User s Guide describes how to use the psOSystem Open System Interconnections OSI product named OpEN OSI Lower Layers OpEN User s Manual describes how to install and use the psOSystem OpEN Open Protocol Embedded Networking product OSPF User s Guide describes the Open Shortest Path First OSPF psSOSystem protocol driver Point to Point Protocol Driver Us
36. data status startio q_send rdy End End This simplified implementation has two weaknesses First it does not provide a way for the device driver to return status information to more than one task Second at most only one task can overlap with this device Once the device is busy all requesting processes will be made to wait Hence the term one level asynchronous A more general and complex asynchronous mechanism requires one message queue and one flag as follows The device s init service creates an empty message queue called cmdq It also initializes a flag to ready pSOSystem System Concepts Chapter 7 I O System The device s read or write service and ISR are shown below as pseudo code ASYNC_OP DEV_ISR Begin Begin q_send cmdq cmd q receive cmdq no wait t_mode no preempt on if cmd empty then if flag ready then flag ready flag busy else cmd q receive cmdq no wait flag busy if cmd empty then startio cmd exit endif else End startio cmd endif endif t_mode no preempt off End In essence the queue cmdq serves as an I O command queue for the device operation Each command message should normally contain data or a buffer pointer and also the address of a variable so that the ISR can return status information to a calling task not shown in the pseudo code The flag global variable indicates whether the device is busy with an I O transactio
37. double dot refers to the parent of the current directory pSOSystem System Concepts 5 17 Chapter 5 pHILE File System Manager 5 4 1 5 4 2 Naming Files on pHILE Format Volumes On pHILE format volumes a file is named by an ASCII string consisting of 1 to 12 characters The characters can be either upper or lowercase letters any of the digits O 9 or any of the special characters period _ underscore dollar sign or dash A name must begin with a letter or a period Names are case sensitive ABc and ABC represent different files When a pathname is specified the volume directory and filenames all are separated by either a forward slash or a backslash The following examples show permissible pathnames for files located on pHILE format volumes 0 1 fruit apples apples apples Naming Files on MS DOS Volumes Files located on MS DOS volumes are named according to standard MS DOS naming conventions Note the differences from the rules described above MS DOS filenames are not case sensitive that is abc and ABC name the same file And MS DOS names have two parts a filename and an extension The filename can be from one to eight characters and the extension may be from zero to 3 characters Filenames and extensions are separated by a dot The characters can be either upper or lowercase letters any of the digits O 9 or any of the special characters equal sign _ underscore c
38. error flag These flags are set and cleared by a number of the I O functions They can be tested by calling the feof and ferror functions respectively These flags can be manually cleared by calling the clearerr function Restarting Tasks That Use the pREPC Library It is possible to restart a task that uses the pREPC library Because the PREPC library can execute with preemption enabled it is possible to issue a restart to a task while it is in pREPC code Note that the t_restart operation does not release any memory close any files or reset errno to zero If you wish to have clean_ups then have the task check for restarts and do them as it begins execution again NOTE Restarting a task using pREPC thatis using pHILE that is has a disk file open may leave the disk volume in an inconsistent state See Section 5 8 1 1 on page 5 46 Deleting Tasks That Use the pREPC Library To avoid permanent loss of pREPC resources the pSOS kernel does not allow deletion of a task which is holding any pREPC resource Instead delete returns error code ERR_DELLC which indicates the task to be deleted holds pREPC resources pSOSystem System Concepts Chapter 6 pREPC ANSI C Library The exact conditions under which the pREPC library holds resources are complex In general any task that has made a pREPC service call may hold pREPC resources fclose O which returns all pREPC resources held by the calling task should be ca
39. external address The procedure is quite simple Because the sending node always knows the internal address it can call m_int2ext to first convert it to the external address On the receiving node m_ext2int can be used to convert and obtain the internal address for that node pSOSystem System Concepts 3 19 Chapter 3 pSOS Multiprocessing Kernel 3 20 pSOSystem System Concepts 4 Network Programming 4 1 Overview of Networking Facilities pSOSystem real time operating system provides an extensive set of networking facilities for addressing a wide range of interoperability and distributed computing requirements These facilities include TCP IP Support pSOSystem s TCP IP networking capabilities are constructed around the pNA software component pNA includes TCP UDP IP ICMP IGMP and ARP accessed through the industry standard socket programming interface pNA offers services to application developers as well as to other pSOSystem networking options such as RPC NFS FTP and so forth pNA fully supports level 2 IP multicast as specified in RFC 1112 including an implementation of IGMP pNA supports unnumbered point to point links as specified in the IP router requirements in RFC 1716 In addition pNA supports the Management Information Base for Network Management of TCP IP based Internets MIB IJ standard pNA also works in conjunction with pSOSystem cross development tools to provide a network based download
40. file The Standard defines two types of streams text streams and binary streams In the pREPC library these are identical In fact in the pREPC library a stream is identical to a file Therefore the terms file and stream have been used interchangeably in the manual pSOSystem System Concepts Chapter 6 pREPC ANSI C Library 6 4 Memory Allocation The following pREPC functions allocate blocks of memory calloc malloc realloc When any of these functions are called the pREPC library in turn calls the pSOS region manager by generating a rn_getseg call The pREPC library always requests segments from Region 0 Therefore you must reserve enough space in Region O for the memory required by your application and for the memory used by the pREPC library for file buffers see section 6 3 3 The rn_getseg call s input parameters include wait nowait and timeout options The wait nowait and timeout options used by the pREPC library when calling rn_getseg are specified in the pREPC Configuration Table Note that if the wait option is selected it is possible for any of the functions listed above to result in blocking the caller Also note that the number of bytes actually allocated by each rn_getseg call depends on Region 0 s unit_size The following functions result in memory deallocation free realloc fclose setbuf setvbuf The free function is called by a user for returning memory no longer needed
41. ipRouteType ipRouteProto ipRouteMask 4 19 4 4 IP Address Translation Table Structure and Elements MIB IT Object Type struct mib_ipnettomediareq inm_iifindex inm_iaddr inm_physaddress inm_type 4 50 ipNet ToMediaIfIndex index ipNet ToMediaNetAddress index ipNet ToMediaPhysAddress default ipNet ToMediaType pSOSystem System Concepts Chapter 4 Network Programming 4 19 4 5 TCP Connection fable Structure and Elements struct mib_tcpconnreq tc_localaddress tc_localport tc_remaddress tc_remport tc_state 4 19 4 6 UDP Listener Table Structure and Elements struct mib_udptabreq u_localaddress u_localport 4 19 5 SNMP Agents MIB IT Object Type tcpConnLocalAddress index tcpConnLocalPort index tcpConnRemAddress index tcpConnRemPort index tcpConnState default MIB IT Object Type udpLocalAddress index udpLocalPort index The following IP group operations must be handled within an SNMP agent itself rather than through ioctl MIB II Object ipRoutel flndex ipRouteMetric ipRouteAge ipRouteMask ipRoutel nfo ipRoutingDiscards pSOSystem System Concepts The value of this object cannot be because it is always determined by the IP address An SNMP agent should return 1 An SNMP agent should return 1 The values of these objects can be interrogated but not changed An SNMP agent should return 0 O as the value of this object Operation Comment Set set B
42. is a device independent addressable unit of storage The pHILE file system manager interacts with the device drivers in terms of logical blocks Logical blocks are numbered starting with 0 The conversion between logical block numbers and physical storage units such as head cylinder and sector is handled by the device driver Logical blocks must be an even multiple of the physical block size of the device On pHILE format volumes the size of a logical block is defined by the pHILE configuration table entry fc_logbsize This parameter has a large impact on system performance Within limits a larger logical block size will reduce data scattering on a device and improve throughput as a result of fewer I O operations On MS DOS volumes the logical block size is fixed at 512 bytes On CD ROM volumes the logical block size is fixed at 2048 bytes 5 3 4 NFS Volumes When used in conjunction with pRPC and pNA components the pHILE file system manager offers NFS Network File System client services This means that pSOSystem nodes can access files on remote pSOSystem System Concepts 5 13 Chapter 5 pHILE File System Manager systems that support the NFS protocol NFS servers exactly as though they were on a local disk The relationship is depicted in Figure 5 1 Application Ethemet CD ROM MS DOS pHILE Figure 5 1 How Software Components Talk With NFS To implement NFS you must have these software elements
43. isi a eee cech dec cvadiccedeedcnest onus laniteaunes 4 13 4 4 9 Non Blocking Sockets arenei aoii E EEE EEEE iS 4 13 4 4 10 Out of Band Data cece cccccecneceeeeceeeeeeneeneeeenenseeeeens 4 13 4 4 11 Socket Data Structures cee cecececee eee eeeeeeeeeneeeeenenes 4 14 4 5 The pNA Daemon Taskur iii sede eee ded ceedesececetccuengdacenebed asd 4 14 4 6 The User Signal Handler isise iiei iii EEEE EEEE 4 16 T Error Handling essiant oo sad E a Hie eed nado 4 17 4 32 Packet ROMUMG noioso a E E E E a a 4 17 AQ IP Multicast wiscevieweacuewe da uecec caine ATANA TEC NETERA 4 20 pSOSystem System Concepts 4 10 4 11 4 13 4 14 4 16 4 17 4 18 4 19 Contents Unnumbered Serial LINKS eresse e ccee ence a 4 23 Network Interface Snati athe tatebta adi haa E 4 23 4 11 1 Maximum Transmission Units MTU 0 eee 4 24 4 11 2 Hardware Addresses cccceee ec a a e a i apa 4 25 ATI 3 Gontrol Flag Seniai a E R A A deed haar 4 25 4 11 4 Network Subnet Mask cccecececececececeeeceeeeeeeenenenenens 4 26 4 11 5 Destination ACCreSs 0 ccc cececccne ce eceeeeneeeceeeeeeeeeeeuenee 4 26 4 11 6 The NU Vabletscccacciesdenconeccveseinieceaded cs Meneses oie eee 4 26 Address Resolution and ARP cccececececeeeeeesee ene eeeeeeeeeeeeeeeees 4 28 4 12 1 The ARP Tables cscten aie ciara dala dati en i a 4 29 4 12 2 Address Resolution Protocol ARP c cccceeeceeeeceeeeees 4 30 Memory M
44. loop through all the routes printf 0x 08xX 0x 08X routes i ir_idest s_addr routes i ir_nexthop s_addr ioctl s SIOCGIPROUTEIFINDEX int amp routes i pSOSystem System Concepts 4 47 Chapter 4 Network Programming printf d n routes i ir_ifindex free routes You can insert a new entry into a table by specifying an index field with a nonexistent value The following code fragment shows an example of how to add an entry into the IP Route Table int s already opened socket descriptor void add_route struct in_addr destination struct in_addr gateway struct mib_iproutereq route route ir_idest destination route ir_nexthop gateway ioctl s SIOCSIPROUTENEXTHOP amp route You can delete a table entry by setting a designated field to a prescribed value These fields and values are defined in RFC 1213 The following code fragment provides an example of deleting a TCP connection from the TCP Connection Table so that the local port can be re used int s already opened socket descriptor void delete_tcpcon struct in_addr remote_addr struct in_addr local_addr short remote_port short local_port struct mib_tcpconnreq tcpconn tcepconn tc_localaddress local_addr tcpconn tc_remaddress rem addr tcepconn tc_localport local_port tcpconn tc_remport rem_port tcpconn tc_state TCPCS_DELETETCB ioctl s SIOCSTCPCONNSTATE amp tcpconn 4 48 pSOSystem
45. number associated with the driver The pSOS_IO_J ump_Table structure is also defined in lt psoscfg h gt The flags element is defined in lt psos h gt pSOSystem System Concepts 7 3 Chapter 7 I O System flags is a 16 bit field used to control driver options Bit number 8 of flags the IO_AUTOINIT bit controls when the driver s initialization function is called If this bit is set pSOS calls the driver s initialization function after all pSOSystem components have been started and just before the root task is started This event called device auto initialization is described in detail in section 7 6 on page 7 10 Figure 7 2 illustrates the I O Switch table structure for a system with two devices 1 DEVICE 0 INIT 2 DEVICE 0 OPEN 3 DEVICE 0 CLOSE 4 DEVICE 0 READ Major Device 0 5 DEVICE 0 WRITE id 6 DEVICE 0 CNTRL 7 RESERVED 8 RESERVED RAGS 9 DEVICE 1 INIT 10 DEVICE 1 OPEN 11 DEVICE 1 CLOSE 12 DEVICE 1 READ MajorDevice 1 13 DEVICE 1 WRITE 14 DEVICE 1 CNTRL 15 RESERVED 16 RESERVED AAGS 3 Figure 7 2 Sample I O Switch Table 7 4 pSOSystem System Concepts Chapter 7 I O System 7 3 Application to pSOS Interface The application to pSOS Interface is defined by the following six system calls de_init de_open de_close de_read de_write and de_cntrl The calling convention for each is as follows err_code de_init dev iopb amp retval amp dat
46. on the source and destination nodes not to mention the packet transit times The exact measure of this overhead depends largely on the connection medium between the source and destination nodes If the medium is a memory bus the KI operations will be quite fast as is the packet transit time On the other hand if the medium is a network especially one that uses a substantial protocol the packet transit times may take milliseconds or more 3 6 System Startup and Coherency The master node must be the first node started in a pSOS m multiprocessor system After the master node is up and running other nodes may then join A slave node should not attempt to join until the master node is operational and it is the user s responsibility to ensure that this is the case In a system in which several nodes are physically started at the same time for example when power is applied to a VME card cage this is easily accomplished by inserting a small delay in the startup code on the slave nodes Alternately the ki_init service can delay returning to the pSOS m kernel until it detects that the master node is properly initialized and operational Slave nodes may join the system any time after the master node is operational Joining requires no overt action by application code running on the slave node The pSOS m kernel automatically posts a join request to the master node during its initialization process On the master node the pSOS m kernel first
47. one other field set with a valid value This field is indicated as default in the tables shown pSOSystem System Concepts Chapter 4 Network Programming After you obtain a list of indices you may set or retrieve values from fields in the tables You issue an ioctl call with command corresponding to the name of a field and arg pointing to a table specific data structure The following code fragment illustrates how all of this works by traversing the IP Route Table int s already opened socket descriptor struct mib_iproutereq routes the array of routes struct mib_args arg int num_routes len i num_routes 50 default number of routes in array routes NULL to insure it is not free d before it is allocated loop until enough memory is allocated to hold all routes do if routes if not the first iteration free routes free memory from previous iteration num_routes 2 allocate more space for the next try len sizeof struct mib_iproutereq num_routes number of bytes routes struct mib_iproutereq malloc len array itself arg len len arg buffer char routes ioctl s SIOCGIPROUTETABLE int amp arg while arg len len if full there may be more routes num_routes arg len sizeof struct mib_iprouteregq actual number puts Destination Next hop Interface for i 0 i lt num_routes itt
48. onnie eee s Ea T Ea 5 26 5 6 4 gt Cache Buttersy 6 i osteitis a E tintin nde ana 5 26 5 6 5 Synchronization Modes sssesssesseseresssreserererrererererresee 5 28 5 6 5 1 Immediate Write Mode cece eeeeeeee scenes 5 29 5 6 5 2 Control Write Mode cc cece ee seeeceeeeeeee een ee 5 29 5 6 5 3 Delayed Write Mod e cece cee eee eee eeeeeeeens 5 30 5 6 5 4 Read Only Mode cceeceeeeeeescneeeeneeeeaeenen ens 5 30 5O66 SYNE VOL taht eet atesesateae eles e a E P el AA canes 5 30 5 7 pHILE Format Volume Serce rnani ia te raia 5 31 5 7 1 How pHILE Format Volumes Are Organized 5 31 5 7 1 1 The Root Blockin ians tea vee ete eee ea deeded dened 5 32 5 7 1 2 The Root Directory sacras i er aR e a eens 5 33 5 7 1 3 The Volume Bitmap ssssssssssssssrssssssssrssrsseses 5 33 5 7 1 4 The File Descriptor List eesse 5 34 5 7 1 5 Control and Data Block Regions 5 34 5 7 2 How Files Are Organized eeseessesesessseesereserrererersreesee 5 35 5 7 2 1 The File Number asrinioiest onsena 5 35 5 7 2 2 The File Descriptors lessir nennen eonen 5 36 5 7 2 3 Fil Type S siase Monu hanenn e na a 5 36 5 7 2 4 Time of Last Modification eeeeeeeeeeeeeee 5 36 5 7 2 5 The File Expansion Unit eee ee ee ee 5 36 5 7 2 6 EXTENTS eei e E EE EEE EO Sian E E 5 37 5 7 2 7 The Extent Map ccccesivisvecvasvesvcesseccsasceeseceveees 5 38 5 7 3 Data Address Mapping
49. other file the buffer size and buffering technique of these files can be modified with the setbuf and setvbuf function calls The pREPC library attempts to open stdin stdout and stderr for a task the first time the task issues a pREPC system call If any of these files cannot be opened the pREPC library calls the k_fatal service with a Ox3F03 error code as an input parameter When opened the pathname of the files is obtained from the pREPC configuration table Even though each task maintains a separate file structure for each of the three standard files they all use the same stdin stdout and stderr device or file This may not be desirable in your application The freopen function can be used to dynamically change the pathnames of any file including stdin stdout and stderr in your system For example to change the stdout from its default value of I O device 1 00 to a disk file 2 00 std_out dat you would use the following function freopen 2 00 std_out dat w stdout When using freopen with the three standard files two rules should be observed First the mode of the standard files should not be altered from their default values and second you should not use pathnames that include the strings stdin stdout or stderr Steams Streams is a notion introduced by the X3J11 Committee Using the X3J11 Committee s terminology a stream is a source or destination of data that is associated with a
50. pSOS kernel properly and fully in the design of multitasked applications To the pSOS kernel a task does not exist either before it is created or after it is deleted A created task must be started before it can execute A created but unstarted task is therefore in an innocuous embryonic state Once started a task generally resides in one of three states m Ready m Running m Blocked A ready task is runnable not blocked and waits only for higher priority tasks to release the CPU Because a task can be started only by a call from a running task and there can be only one running task at any given instant a new task always starts in the ready state A running task is a ready task that has been given use of the CPU There is always one and only one running task In general the running task has the highest priority among all ready tasks unless the task s preemption has been turned off as described in Section 2 3 3 A task becomes blocked only as the result of some deliberate action on the part of the task itself usually a system call that causes the calling task to wait Thus a task cannot go from the ready state to blocked because only a running task can perform system calls State Transitions Figure 2 2 depicts the possible states and state transitions for a pSOS task Each state transition is described in detail below Note the following abbreviations m E for Running Executing m R for Ready m B for Blocked
51. region O if and when the queue is deleted Once a variable length message queue has been created variable length messages are sent and received using the q_vsend q_vurgent q_vbroadcast and q_vreceive service calls The calls operate exactly like their ordinary counterparts q_send q_urgent q_broadcast and q_vreceive except the caller must provide an additional parameter that specifies the length of the message The q_vreceive service call returns the length of the received message to the caller The remaining two variable length message queue services q_vident and q_vdelete are identical to their ordinary counterparts q_ident and q_delete in every respect Note that although ordinary and variable length message queues are implemented using the same underlying object service calls cannot be mixed For example q_send cannot be used to post a message to a variable length message queue Similarly q_vsend cannot be used to send a message to an ordinary queue There is one exception q_ident and q_vident are identical When searching for the named queue both return the first queue encountered that has the specified name regardless of the queue type Events The pSOS kernel provides a set of synchronization by event facilities Each task has 32 event flags it can wait on bit wise encoded in a 32 bit word The high 16 bits are reserved for system use The lower 16 event flags are user definable Two pSOS system calls provide
52. resources Refer to pSOSystem System Calls for a description of t_create and t_start A parent task creates a child task by calling t_create The parent task passes the following input parameters to the child task m Auser assigned name m A priority level for scheduling purposes m Sizes for one or two stacks m Several flags Refer to the description of t_create in pSOSystem System Calls for a description of the preceding parameters t_create acquires and sets up a Task Control Block TCB for the child task then it allocates a memory segment from Region 0 large enough for the task s stack s and any necessary extensions Extensions are extra memory areas required for optional features For example a A floating point context save area for systems with co processors m Memory needed by other system components such as pHILE PREPC pNA and so forth to hold per task data This memory segment is linked to the TCB t_create returns a task identifier assigned by the pSOS kernel The t_start call must be used to complete the creation t_start supplies the starting address of the new task a mode word that controls its initial execution behavior see section 2 4 3 Task Mode Word and an pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel optional argument list Once started the task is ready to run and is scheduled for execution based on its assigned priority With two exceptions all user tasks that form
53. roundrobin bit and preemptible bit on then the pSOS kernel will countdown the task s assigned timeslice If it is still running when its timeslice is down to zero then roundrobin scheduling will take place Details of the roundrobin scheduling can be found in section 2 3 5 Roundrobin by Timeslicing You can specify the amount of time that constitutes a full timeslice in the pSOS Configuration Table as kc_ticks2slice For instance if that value is 10 and the kc_ticks2sec is 100 then a full timeslice is equivalent to about one tenth of a second The countdown or consumption of a timeslice is somewhat heuristic in nature and might not exactly reflect the actual elapsed time a task has been running Interrupt Service Routines Interrupt service routines ISRs are critical to any real time system On one side an ISR handles interrupts and performs whatever minimum action is required to reset a device to read write some data etc On the other side an ISR might drive one or more tasks and cause them to respond to and process the conditions related to the interrupt An ISR s operation should be kept as brief as possible in order to minimize masking of other interrupts at the same or lower levels Normally it simply clears the interrupt condition and performs the necessary physical data transfer Any additional handling of the data should be deferred to an associated task with the appropriate software priority This task c
54. sector and the computed size of the partition in the driver s Partition Table No other values in the Master Boot Record are used The driver never uses cylinder head sector information If an extended partition entry is found the Starting Relative Sector start_rsect is read as an extended Boot Record and checked the same way the Master Boot Record is checked Each extended Boot Record can have an extended partition entry Thus the driver may contain a chain of Boot Records While there is no limit to the number of partitions this chain of Boot Records can contain there is a limit to the number of partitions the driver will store for its use in its Partition Table This limit is set to a default value of eight This value may be changed by editing the SCSI_LMAX_PART define statement found in the include drv_intf h file in pSOSystem and compiling the Board Support Package you are using for your application SCSI_MAX_PART can be any integer between 1 and 256 inclusive NOTE Once an extended partition entry is found no other entries in the curent Boot Record are used In other words an extended partition entry marks the end of the current disk partition table Refer to the Drivers and Interfaces section of the pSOSystem Programmer s Reference for more information on the SCSI driver interface Your driver should recognize partition O as a partition spanning the entire disk that is your driver should not perform partition tab
55. send your comments by e mail to ideas isi com pSOSystem System Concepts xvii About This Manual Table 1 Problem Report Contact Name Company Name Customer ID very important Street Address City State Country Zip Code Voice Phone Number Fax Phone Number E mail Address Product Name including components Version s Host System Target System Communication Used Ethernet serial Customer Impact Brief Description Detailed Description please attach supporting information xviii pSOSystem System Concepts About This Manual pSOSystem System Concepts xix About This Manual XX pSOSystem System Concepts 1 Product Overview 11 What is pSOSystem pSOSystem is a modular high performance real time operating system designed specifically for embedded microprocessors It provides a complete multitasking environment based on open systems standards pSOSystem is designed to meet three overriding objectives m Performance m Reliability m Ease of Use The result is a fast deterministic yet accessible system software solution Accessible in this case translates to a minimal learning curve pSOSystem is designed for quick startup on both custom and commercial hardware The pSOSystem software is supported by an integrated set of cross development tools that can reside on UNIX or DOS based computers These tools
56. synchronization by events between tasks and between tasks and ISRs ev_receive Get or wait for events ev_send Send events to a task pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel ev_send is used to send one or more events to another task With ev_receive a task can wait for with or without timeout or request without waiting one or more of its own events One important feature of events is that a task can wait for one event one of several events OR or all of several events AND 2 8 1 Event Operations Events are independent of each other The ev_receive call permits synchronization to the arrival of one or more events qualified by an AND or OR condition If all the required event bits are on i e pending then the ev_receive call resets them and returns immediately Otherwise the task can elect to return immediately or block until the desired event s have been received A task or ISR can send one or more events to another task If the target task is not waiting for any event or if it is waiting for events other than those being sent ev_send simply turns the event bit s on which makes the events pending If the target task is waiting for some or all of the events being sent then those arriving events that match are used to satisfy the waiting task The other non matching events are made pending as before If the requisite event condition is now completely satisfied the task is unblocked and made ready t
57. system manager reads the entire block merges the new data into it blocking and then writes the updated block back to the volume When a read_f or write_f operation references bytes that fit into an entire block or blocks the pHILE file system manager transfers the bytes as entire block s No blocking deblocking is necessary When a read_f or write _f operation references bytes that straddle multiple blocks the operation is broken down into separate actions The bytes at the beginning and end of the sequence will require blocking deblocking The bytes that fill blocks in the middle of the sequence if any are transferred as entire blocks Note that read and write operations are most efficient if they start at block boundaries and have byte counts that are integral multiples of the block size because no blocking deblocking is required Cache Buffers The pHILE file system manager maintains a pool or cache of buffers for blocking deblocking purposes The number of cache buffers in your system is determined by the pHILE Configuration Table entry fc_nbuf The size of the buffers in the buffer cache is determined by the pHILE Configuration Table entry fc_logbsize Each buffer when in use holds an image of a logical block A buffer can contain ordinary file data directory file data or system data structures To improve system performance the pHILE file system manager uses the buffers as an in memory cache for data recent
58. than ARP packets When pNA calls an NI it provides a packet type parameter which is either IP or ARP Similarly when the pNA component receives a packet the NI must also return a packet type All network drivers that support ARP must have some mechanism for attaching this packet type to the packet For example Ethernet packets contain type fields For NIs that do not support ARP the packet type parameter can be ignored on transmission and set to IP for incoming packets 4 13 Memory Management As packets move across various protocol layers in the pNA component they are subject to several data manipulations including m Addition of protocol headers m Deletion of protocol headers m Fragmentation of packets m Reassembly of packets m Copying of packets The pNA component is designed with specialized memory management so that such manipulations can be done optimally and easily The pNA component allows configuration of its memory management data structures via the pNA Configuration Table These structures are pSOSystem System Concepts 4 31 Chapter 4 Network Programming 4 32 critical to its performance hence understanding the basics of pNA memory management is crucial to configuring your system optimally The basic unit of data used internally by the pNA component is called a message Messages are stored in message structures A message structure contains one or more message block triplets linked via a singly link
59. that are called xxxxOpen and xxxxClose are device specific However in general xxxxOpen will initialize a device while pSOSystem System Concepts Chapter 7 I O System xxxxClose will terminate I O operations such as flushing buffer contents For many devices these two routines may be null routines The PREPC library does not pass an IOPB when calling de_open and de_close The pREPC library calls de_read and de_write to transfer data to or from a device The I O parameter block IOPB looks like the following typedef struct unsigned long count no of bytes to read or write void address addr of pREPC data buffer iopb Recall that the IOPB is pointed to by the in_iopb member of the ioparms structure passed to the driver de_write results in a call to the driver function xxxxWrite which must transfer count bytes from the pREPC data buffer pointed to by address de_read causes xxxxRead to be invoked which transfers count bytes from the device to the pREPC buffer xxxxRead is usually coded so that characters are read until a delimiter is detected or count bytes are received Also a pPREPC xxxxRead driver routine usually implements backspace line erase and other line editing facilities xxxxRead and xxxxWrite must return the number of bytes successfully read or written 7 10 Loader Drivers The pSOSystem loader is capable of loading applications directly from a device d
60. the running task The first event bit 31 is sent to PNAD by the pNA component upon receipt of a packet when the pNA ANNOUNCE _ PACKET entry is called either by an ISR or ni_poll Based on the content of the packet PNAD takes different actions such as waking up a blocked task sending a reply packet or if this is a gateway node forwarding a packet The last action should be particularly noted that is ifa node is a gateway PNAD is responsible for forwarding packets If the execution of PNAD is inhibited or delayed packet routing will also be inhibited or delayed The second event bit 30 is sent every 100 milliseconds as a result of a pSOS tm_evevery system call When PNAD wakes up every 100ms it performs time specific processing for TCP that relies heavily on time related retries and timeouts After performing its time related processing PNAD calls ni_poll for each Network Interface that has its POLL flag set pSOSystem System Concepts 4 15 Chapter 4 Network Programming 4 6 The User Signal Handler The pNA component defines a set of signals which correspond to unusual conditions that might arise during normal execution The user can provide an optional signal handler which is called by the pNAt component when one of these unusual or unpredictable conditions occurs For example if urgent data is received or if a connection is broken the pNA component calls the user provided signal handler The address o
61. to buffer the flow of data between the user application and the device By caching data in the buffer the pREPC library avoids excessive I O activity when the application is reading or writing small data units When first opened a file has no buffer Normally a buffer is automatically assigned to the file the first time it is read or written The buffer size is defined by the entry LC_BUFSIZ in the pREPC Configuration Table The pREPC component allocates the buffer from pSOS region 0 If memory is not available the calling task may block based on the values in the pREPC configuration table entries LC_WAITOPT and LC_TIMEOPT If a buffer cannot be obtained an error is returned to the read or write operation Note that if the default buffer assigned by the pREPC library is not appropriate for a particular file a buffer may be supplied directly by calling the setbuf or setvbuf functions A special case arises when a file is assigned a buffer of length O This occurs if LC_BUFSIZ is zero and as an option to the setvbuf call In this case no buffer is assigned to the file and all I O is unbuffered That is every read or write operation through the pREPC library will result in a call to a pHILE device driver as the case may be Finally note that the three standard files stdin stdout and stderr are not affected by the value of LC_BUFSIZ See section 6 3 5 for a discussion of the default buffering of these three files pSOSys
62. to implement remote I O services as part of your application design for example with server tasks and standard pSOS system services 5 On some target processors I O service calls do not automatically preserve all registers Refer to the Assembly Language Information appendix of the pSOSystem Programmer s Reference for information on register usage by the I O subsystem pSOSystem System Concepts 7 9 Chapter 7 I O System 7 6 Device Auto Initialization The pSOS kernel provides a feature whereby it can invoke a device s initialization function during pSOS kernel startup This is needed in special cases where a device is accessed from a daemon task that starts executing before control comes to the ROOT task Examples are the timer and serial devices that can be accessed by pMONT daemons You control auto initialization of a device through the flags element of the device s pSOS_IO_J ump_Table structure You set flags to one of the following symbolic constants which are defined in lt psos h gt 10_AUTOINIT Driver is initialized by pSOS 10_NOAUTOINIT Driver is not initialized by pSOS For example if the variable JumpTable is a pointer to a pSOS_1O_J ump_Table structure and you want its driver to be initialized by pSOS you write the following line of code JumpTable gt flags IO_AUTOINIT When auto initialization is enabled for a device pSOS invokes the driver s dev_init routine and passes an ioparms str
63. unknown type can occur only when read_vol or write_vol is issued on a volume that was initialized with intermixed control and data blocks In this case the pHILE file system manager will be unable to determine the block type If read_vol or write_vol is used to transfer a group of blocks that cross a control block data block boundary these bits will indicate pSOSystem System Concepts 7 19 Chapter 7 I O System 7 11 2 7 11 3 7 20 the type of the first block b_blksize specifies the size in base 2 of blocks to read or write b_dsktype specifies the type of MS DOS disk involved It is set by the dktype parameter of pcinit_vol and is only valid when PHILE calls the driver as a result of a call to pcinit_vol During all other system calls this value is undefined pcinit_vol is described in section 5 2 and in pSOSystem System Calls The remaining fields are for system use only The contents of the buffer header should not be modified by a driver It is strictly a read only data structure I O Transaction Sequencing pHILE drivers must execute transaction i e read and write requests that refer to common physical blocks in the order in which they are received For example if a request to write blocks 3 7 comes before a request to read blocks 7 10 then because both requests involve block 7 the first request must be executed first If a pSOS semaphore is used to control access to a driver then that sema
64. use of absolute time specifications might require additional time manipulations Wakeups Versus Alarms There are two distinct ways a task can respond to timing The first way is to go to sleep i e block and wake up at the desired time This synchronous method is supported by the tm_wkafter and tm_wkwhen calls The second way is to set an alarm timer and then continue running This asynchronous method is supported by tm_evafter and tm_evwhen When the alarm timer goes off the pSOS kernel will internally call ev_send to send the designated events to the task Of course the task must call ev_receive in order to test or wait for the scheduled event Alarm timers offer several interesting features First the calling task can execute while the timer is counting down Second a task can arm more than one alarm timer each set to go off at different times corresponding to multiple expected conditions This multiple alarm capability is especially useful in implementing nested timers a common requirement pSOSystem System Concepts 2 35 Chapter 2 pSOS Real Time Kernel 2 11 6 2 12 2 36 in more sophisticated communications systems Third alarm timers can be canceled using the tm_cancel call In essence the wakeup mechanism is useful only in timing an entire task The alarm mechanism can be used to time transactions within a task Timeslice If the running task s mode word see section 2 4 3 Task Mode Word has its
65. volume_size above that Using SCSI Commands to Format a Floppy Disk for pHILE Volumes l In your application use the SCSI driver command de_cntrl function SCSI_CTL_FORMAT This function performs a physical format of the floppy disk A code example using SCSI_CTL_FORMAT follows include lt drv_intf h gt define DEVICE MAJ OR MINOR PARTITION MAJ OR lt lt 16 PARTITION lt lt 8 MINOR UINT err_code For system calls struct scsi_ctl_iopb iopb For de_cntrl ULONG retval iopb function SCSI_CTL_FORMAT NOTE Partition must be zero err_code de_cntrl DEVICE 4 5 0 amp iopb amp retval if err_code 0 Error handling Use the pSOSystem system call init_vol to initialize the volumes in pHILE format Follow the example on page 5 7 but use a smaller volume_size number of blocks A 1 44 megabyte 3 1 2 floppy disk has 2 880 sectors per disk so init_vol cannot have a volume_size above that pSOSystem System Concepts 5 3 5 3 1 5 3 2 Chapter 5 pHILE File System Manager Working With Volumes The following sections discuss how to access the pHILE file system manager and all types of volumes what naming conventions are used and volume formatting differences Mounting And Unmounting Volumes Before a volume can be accessed it must be mounted The table below shows which system call is used to mount each kind of file system pSOSystem System
66. write_f operations involving small numbers of bytes 5 6 5 3 Delayed Write Mode When a volume has been mounted with delayed write mode the pHILE file system manager flushes memory resident data only when required by normal operation File Control Blocks are flushed only when a file is closed or a volume is synchronized Cache buffers are flushed only when they are reused a volume is synchronized or a volume is unmounted The delayed write mode is the most efficient of the three modes because it minimizes I O When using this mode however a system failure may leave a volume with inconsistent system data structures and old user data Delayed write mode is a reasonable choice when high throughput is required Normally using the sync_vol system call periodically is sufficient to maintain a consistent volume 5 6 5 4 Read Only Mode This mode prevents writing to the volume Only system calls that do not write to the volume are allowed All supported system calls that write to the volume abort and return the E_RO error Unsupported system calls still return their usual error code This synchronization mode is the only one supported on CD ROM volumes However it can be used on any local volume sync_vol The sync_vol system call copies the contents of the cache buffers and all in memory system data structures to a volume sync_vol is automatically executed when a volume is unmounted It is not needed for a volume if the volum
67. 00001 re ioctl s SIOCSIFDSTADDR char amp ifr pSOSystem System Concepts 4 27 Chapter 4 Network Programming 4 12 4 28 change the status of the interface number 1 to down this must be done in 2 steps get the current interface flags turn the UP flag off and set the interface flags ifr ifr_ifno 1 re ioctl s SIOCGIFFLAGS char amp ifr ifr ifr_ifno 1 ifr ifr_flags amp IFF_UP re ioctl s SIOCSIFFLAGS char amp ifr close the socket close s Address Resolution and ARP Every NI has two addresses associated with it an internet address and a hardware address The IP layer uses the internet address while the network driver uses the hardware address The process by which an internet address is mapped to a hardware address is called address resolution In many systems address resolution is performed by the network driver The address resolution process however can be difficult to implement Therefore to simplify the design of network drivers the pNA component provides the capability of resolving addresses internally To provide maximum flexibility this feature can be optionally turned on or off so that if necessary address resolution can still be handled at the driver level The pNA component goes through the following steps when performing address resolution 1 The pNA component examines the NI flags see section 4 11 3 to determine if it sho
68. 1000 0 Drop a group membership on the default interface defined above ipmreq imr_mcastaddr s_addr htonl1 0xe0000040 ipmreq imr_interface s_addr htonl INADDR_ANY setsockopt s IPPROTO_IP IP_DROP_MEMBERSHIP char amp ipmreq sizeof struct ip_mreq 4 22 pSOSystem System Concepts Chapter 4 Network Programming 4 10 Unnumbered Serial Links pNA supports unnumbered serial links as specified in RFC 1716 Assigning a unique IP address to each serial line connected to a host or router can cause an inefficient use of the scarce IP address space The unnumbered serial line concept has been proposed to solve this problem An unnumbered serial line does not have a unique IP address All unnumbered serial lines connected to a host or router share one IP address This single IP address is termed in pNA as the Network Node ID This is equivalent to the RFC s term of Router ID If unnumbered links are to be used then the pNA Network Node ID must be set either at configuration time or by the ioctI system call For PPP and SLIP this implies that the source IP address is fixed to be the Network Node ID pNA will then internally assign the IP address of the serial line to be the Network Node ID All IP packets transmitted over this serial line will contain the Network Node ID as the source address of the packet An NI is configured as an unnumbered link if the IFF_UNNUMBERED flag is set in ifr_flags 4 11 Ne
69. 4 The disk drivers supplied with pSOSystem support the following partitioning scheme The driver reads logical sector O 512 bytes of the disk and checks for a Master Boot Record signature in bytes 510 and 511 The signature expected is 0x55 in byte 510 and OxAA in byte 511 If the signature is correct the driver assumes the record is a Master Boot Record and stores the partition information contained in the record ina static table This table is called the driver s Partition Table The driver s Partition Table contains entries for each partition found on the disk drive Each entry contains the beginning logical block address of the partition the size of the partition and a write protect flag byte The driver uses the beginning block address to offset all reads and writes to the partition It uses the size of the partition to ensure the block to be read or written is in the range of the partition You can set the write protect byte through an I O control call to the driver The driver checks this byte whenever a write is attempted on the partition If the write protect byte is set it doesn t perform the write and returns an error to indicate the partition is write protected If the driver finds a Master Boot Record it expects the disk s partition table to start at byte 446 The driver expects the disk s partition table to have four entries each with the following structure struct ide part unsigned char boot_ind Boot in
70. 6 and Super Hitachi processors used is an obsolete field that is present only to maintain compatibility with older versions of pSOSystem On entry to the driver tid contains the task ID of the calling task It should not be changed by the driver pSOSystem System Concepts 7 7 Chapter 7 I O System 7 5 7 8 On entry to the driver in_dev contains dev as provided by the calling task that is the 32 bit device number It should not be changed by the driver status is no longer used On entry to the driver in_iopb points to the iopb provided by the calling task It should not be changed by the driver io_data_area is no longer used err is used by the driver to return an error code or 0 if the operation was successful See section 7 3 for a discussion on error codes out_retval is used by the driver to return an unsigned long value to the calling task s retval variable The contents of out_retval is copied into the variable pointed to by the service call input parameter retval Device Driver Exec ution Environment Logically a device driver executes as a subroutine to the calling task Note that device drivers always execute in the supervisor state Other characteristics of a task s mode remain unchanged by calling a device driver Therefore if a task is preemptible prior to calling a device driver it remains preemptible while executing the driver If a driver wants to disable preemption it should use t_mode
71. 6 7 storage management services 2 20 stream sockets 4 8 1 7 Index streams 6 8 binary 6 8 text 6 8 subnets 4 6 synchronization 2 24 synchronous I O 7 13 synchronous RSC 3 7 system architecture 1 2 T task 2 3 2 4 ASR 2 33 control block 2 15 creation 2 14 management 2 14 memory 2 18 mode word 2 16 preemption 2 2 priority 2 2 2 9 scheduling 2 9 stacks 2 17 states 2 6 termination 2 18 task to task communication 2 24 TCB 2 15 TCP 4 3 text streams 6 8 time and date 2 35 time management 2 34 time unit 2 35 timeout facility 2 35 timeslicing 2 10 2 37 timeslice quantum 2 10 timing absolute 2 36 relative 2 36 token semaphore 2 32 transport layer 4 3 U UDP 4 3 unnumbered serial links 4 23 V variable length message queue 2 28 volume initialization 5 4 volume parameter record 5 6 volume definition of 5 2 W wakeups 2 37 pSOSystem System Concepts integrated systems Document Title pSOSystem System Concepts Part Number 000 5115 001B Revision Date August 1996
72. 7 A task uses the recv call to receive data recv accepts as input a socket descriptor specifying the communication endpoint the address and length of a buffer to receive the data and a set of flags A flag can be set to indicate that the recv is for data that has been marked by the sender as out of band only A second flag allows recv to peek at the message that is the data is returned to the caller but not consumed If the requested data is not available at the socket and the socket has not been marked as non blocking recv causes the caller to block until the data is received On return from the recv call the server task will find the data copied into the specified buffer Connectionless Sockets While connection based communication is the most widely used paradigm connectionless communication is also supported via datagram or raw sockets When using datagram sockets there is no requirement for connection establishment Instead the destination address i e the address of the foreign socket is given at the time of each data transfer To send data the sendto system call is used sendto s buf buflen flags to tolen The s buf buflen and flags parameters are the same as those in send The to and tolen values are used to indicate the address of the foreign socket that will receive the data The recvfrom system call is used to receive data recvfrom s buf buflen flags to tolen The address
73. A component allocates a data block for every buffer configured in the system The pNA memory configuration is critical to its performance Configuring too few buffers or wrong sizes leads to reduced performance Configuring too many buffers wastes memory Optimal performance can be achieved empirically by tuning the following configurable elements Number of message blocks m Buffer configuration m MTU size buffers m 128 byte buffers m Zero size buffers The following sections give general configuration guidelines Buffer C onfiguration Buffer configuration is specified via the nc_bcfg element in the pNA Configuration Table See the Configuration Tables section of the pSOSystem Programmer s Reference It allows you to configure application specific buffer sizes into the system Two attributes are associated with a buffer configuration buffer size and the number of buffers The pNA component copies data into its internal buffers via two interfaces It copies data from the user buffers to its internal buffers during send sendto and sendmsg service calls It copies data from the NI buffers to its internal buffers during Announce Packet calls The pNA component allows buffers of multiple sizes to be configured into the system In order to allocate a buffer to copy data it first selects the buffer size using the following best fit algorithm 1 The pNA component first tries to find an exact match for
74. Asynchronous I O is generally more complex especially when error recovery must be considered The main advantage it has over synchronous I O is that it allows the calling task to overlap execution with the I O potentially optimizing throughput on a task basis The effect that this has at the system level is less clear because multitasking ensures overlap even in the case of synchronous I O by giving the CPU to another task For this reason synchronous I O should be used unless special considerations require asynchronous implementation Note that if Type 1 mutual exclusion is required it is normally taken care of by the asynchronous mechanism without the need for extra code A simple one level asynchronous driver can be implemented using just one message queue The device s init service creates the queue rdy and sends one message to it When a task calls read or write the driver first calls q_receive to get a message from the queue rdy starts the I O transaction and then immediately returns The device s ISR upon transaction completion uses q_send to post a message to the queue rdy This indicates that the device is again ready If this or another task calls the same device service before the last I O transaction is done then the q_receive puts it into the wait queue to wait until the ISR sends its completion message The pseudo code is as follows ASYNC_OP DEV_ISR Begin Begin q_ receive rdy wait transfer
75. Calls provides detailed descriptions of these system calls File System Mount system call pHILE mount_vol MS DOS pcmount_vol CD ROM cdmount_vol NFS nfsmount_vol The pHILE file system manager maintains a mounted volume table whose entries track and control mounted volumes in a system The size of the mounted volume table and hence the maximum number of volumes that can be mounted contemporaneously is determined by the parameter fc_nmount in the pHILE Configuration Table When a volume is no longer needed it should be unmounted by using the unmount_vol system call When a volume is unmounted its entry in the mounted volume table is removed Any task can unmount a volume It does not have to be the same task that originally mounted the volume A volume cannot be unmounted if it has any open files Volume Names and Device Numbers When a volume is mounted the caller provides a 32 bit pSOS logical device number This logical device number serves as the volume s name while it is mounted A logical device number consists of two fields a 16 bit major device number followed by a 16 bit minor device number pSOSystem System Concepts 5 11 Chapter 5 pHILE File System Manager By convention if a device is partitioned must be a hard disk the minor device number itself consists of two fields the partition number in the most significant 8 bits and the minor device number in the least significant 8 bits For more infor
76. Configuration Table The pNA Configuration Table entry NC_CFGTAB points to a subcomponent table which in turn contains a pointer to the pRPC Configuration Table pRPC shares the pNA error code space for both fatal and nonfatal errors A pNA nonfatal error code has the form O0x50XX where XX is the error value A pRPC nonfatal error code has the form 0x51XX where XX is the error value pSOSystem System Concepts Chapter 4 Network Programming A pNA fatal error code has the form Ox5FXX where XX is the fatal error value A set of 32 fatal errors from the pNA fatal error space is allocated for pRPC beginning at Ox80 See the error code appendix of pSOSystem System Calls for a complete listing of fatal and nonfatal pNA error codes 4 20 2 pRPC Architecture The pRPC subcomponent depends on the services of pSOSystem components other than the pNA component Figure 4 5 on page 4 53 illustrates the relationship between the pRPC subcomponent and the other parts of pSOSystem stdio Streams TCP UDP Devices Disk Drivers Network Drivers Communication Drivers Figure 4 5 pRPC Dependencies pSOSystem System Concepts 4 53 Chapter 4 Network Programming 4 20 3 4 54 RPC packets use the TCP or UDP protocols for network transport The pNA component provides the TCP UDP network interface to the pRPC subcomponent Direct access to XDR facilities bypassing RPC is supported by using memory buff
77. D ROM volumes MS DOS volumes and NFS Network File System volumes The pREPC library does not distinguish between the underlying volume types and therefore works equally well with all four volume types However there are a number of small differences between the various volumes that may affect the results of certain pREPC functions Function descriptions indicate those cases where the volume type may affect function results and how those functions would be affected I O devices correspond to pSOS logical devices and are usually associated with devices such as terminals or printers From an application s standpoint their main difference from disk files is that they have no position indicator Data being read from or written to an I O device can be thought of as a continuous stream When reading and writing disk files the pREPC library calls the pHILE file system manager which in turn calls the pSOS I O Supervisor When reading and writing I O devices the pREPC library calls the psOS I O Supervisor directly Before a file a disk file or an I O device can be read or written it must be opened using fopen One of the fopen function s input parameters is a name that specifies the file to open Disk files are designated by pHILE pathnames while I O devices are identified by pSOS logical device numbers Examples 3 2 designates an I O device with logical device number 3 2 3 2 abcd designates a disk file stored on logica
78. E gt B A running task E becomes blocked when pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel Figure 2 2 Task State Transitions 1 It requests a message q_receive q_vreceive with wait from an empty message queue or 2 It waits for an event condition ev_receive with wait enabled that is not presently pending or 3 It requests a semaphore token Sm_p with wait that is not presently available or 4 It requests memory rn_getseg with wait that is not presently available or 5 It pauses for a time interval tm_wkafter or until a particular time tm_wkwhen B gt R A blocked task B becomes ready when l A message arrives at the message queue q_send q_vsend q_urgent q_vurgent q_broadcast q_vbroadcast where B has been waiting and B is first in that wait queue or 2 An event is sent to B ev_send fulfilling the event condition it has been waiting for or 3 A semaphore token is returned Sm_v and B is first in that wait queue or 4 Memory returned to the region rn_retseg now allows a memory segment that to be allocated to B or pSOSystem System Concepts 2 7 Chapter 2 pSOS Real Time Kernel 5 B has been waiting with a timeout option for events a message a semaphore or a memory segment and that timeout interval expires or 6 B has been delayed and its delay interval expires or its wakeup time arrives or 7 Bis waiting at a message queue semaphore or memory region a
79. ILE file system manager manages and organizes data as sets of files on storage devices and in turn does all of the actual I O The pHILE I O path depends on the type of volume mounted and is described in detail in Chapter 5 pHILE File System Manager PHILE services such as open_f and write_f can be called directly However if you use the pREPC file I O functions which in turn call the pHILE file system manager your application code will be more portable The pREPC direct I O and character I O functions read and write sequences of characters The formatted I O functions perform transformations on the input and output and include the familiar printf and scanf functions Files Disk Files and I O Devices Under the pREPC library all I O is directed to and from files The PREPC library divides files into two categories I O devices and disk files They are treated as similarly as possible but there are intrinsic differences between the two Disk files are part of a true file system managed by the pHILE file system manager There is a file position indicator associated with each disk file which marks the current location within the file It is advanced whenever data is read from or written to the file In addition it can be changed via system calls pSOSystem System Concepts Chapter 6 pREPC ANSI C Library The pHILE file system manager manages four types of volumes These are pHILE formatted volumes C
80. INTEGRATED SYSTEMS PSOSYSTEM SYSTEM CONCEPTS integrated systems a Copyright 1996 Integrated Systems Inc All rights reserved Printed in U S A systems Document Title pSOSystem System Concepts Part Number 000 5115 001B Revision Date August 1996 Integrated Systems Inc 201 Moffett Park Drive Sunnyvale CA 94089 1322 Corporate pSOS Support MATRIX Support Phone 408 542 1500 408 542 1925 1 800 458 7767 408 542 1930 1 800 958 8885 Fax 408 542 1950 408 542 1951 408 542 1951 E mail ideas isi com psos_support isi com mx_support isi com Home Page http www isi com LICENSED SOFTWARE CONFIDENTIAL PROPRIETARY This document and the associated software contain information proprietary to Integrated Systems Inc or its licensors and may be used only in accordance with the Integrated Systems license agreement under which this package is provided No part of this document may be copied reproduced transmitted translated or reduced to any electronic medium or machine readable form without the prior written consent of Integrated Systems Integrated Systems makes no representation with respect to the contents and assumes no responsibility for any errors that might appear in this document Integrated Systems specifically disclaims any implied warranties of merchantability or fitness for a particular purpose This publication and the contents hereof are subject to change without notice
81. Membership Protocol IGMP 4 20 pSOSystem System Concepts Chapter 4 Network Programming The NI driver must of course support multicast The driver must be configured with the IFF_MULTICAST flag set IP Multicast support allows a host to declare interest to participate in a host group The host group is defined as a set of O or more hosts that are identified by a multicast IP address A host may join and leave groups at its will A host does not need to be a member of a group to send datagrams to the group But it needs to join a group to receive datagrams addressed to the group The reliability of sending multicast IP packets is equal to that of sending unicast IP packets No guarantees of packet delivery are made Multicast IP addresses are in the class D range i e those that fall in the range 224 0 0 0 to 239 255 255 255 There exists a list of well known groups identified in the internet For example the group address 224 0 0 1 is used to address all IP hosts on a directly connected network The NI driver must support multicast For each interface capable of multicast pNA adds the ALL_HOSTS multicast group 224 0 0 1 It is possible that the group may not be added because not enough memberships have been configured by the user This is not an error pNA supports IP multicast only through the RAW IP socket interface The setsockopt system call should be used to add delete memberships and set multicasting options for a particular s
82. Multiprocessing Kernel Usage Within pSOS dn Services Any address in a dual ported zone used as input to the pSOS m kernel or entered in a Configuration Table must be an internal address to the local node Similarly when a pSOS m system call outputs an address that is in a dual ported zone it will always be an internal address to the node from which the call is made Consider in particular a partition created in a dual ported zone and exported to enable shared usage by two or more nodes A pt_getbuf call to this partition automatically returns the internal address of the allocated buffer In other words the pSOS m kernel always returns the address that the calling program can use to access the buffer If the calling node is tied to the zone s p port then the returned internal address will be the p port address If the calling node is tied to the s port then the returned internal address will be the s port address Usage Outside pSOS Often operations in dual ported zones fall outside the context of the pSOS kernel For example the address of a partition buffer or a user structure may be passed from one node to another within the user s application code If this address is in a dual ported zone then the two system calls m_int2ext and m_ext2int may need to be used to perform a necessary address conversion Observe the following rule When an address within a dual port zone must be passed from one node to another then pass the
83. SCII name is user assigned and passed to the pSOS kernel as input to an Obj_CREATE e g t_create system call The pSOS kernel in turn generates and assigns a unique 32 bit object ID e g Tid to the new object Except for Obj_IDENT e g q_ident calls all system calls that reference an object must use its ID For example a task is suspended using its Tid a message is sent to a message queue using its Qid and so forth pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel The run time ID of an object is of course known to its creator task it is returned by the Obj_CREATE system call Any other task that knows an object only by its user assigned name can obtain its ID in one of two ways 1 Use the system call Obj_IDENT once with the object s name as input the pSOS kernel returns the object s ID which can then be saved away 2 Or the object ID can be obtained from the parent task in one of several ways For example the parent can store away the object s ID in a global variable the Tid for task ABCD can be saved in a global variable with a name like ABCD_TID for access by all other tasks An object s ID contains implicitly the location even in a multiprocessor distributed system of the object s control block e g TCB or QCB a structure used by the pSOS kernel to manage and operate on the abstract object Objects are truly dynamic the binding of a named object to its reference handle is de
84. SOS Multiprocessing Kernel 3 8 Upon notification of a node failure the master does the following 1 First if notification did not come from the failed node the master sends a shutdown packet to the failed node If the failed node receives it that is it has not completely failed yet it performs the shutdown procedure as described in Chapter 2 pSOS Real Time Kernel 2 Second it sends a failure notification packet to all remaining slave nodes 3 Lastly it removes all global objects created by the failed node from its global object table The pSOS m kernel on all nodes including the master perform the next 4 steps after receiving notification of a node failure 1 The pSOS m kernel calls the Kernel Interface KI service ki_roster to notify the KI that a node has left the system 2 The pSOS m kernel calls the user provided routine pointed to by the Multiprocessor Configuration Table entry mc_roster to notify the application that a node has left the system 3 All agents waiting on behalf of the failed node are recovered 4 All tasks waiting for RSC reply packets from the failed node are awakened and given error ERR_NDKLD indicating that the node failed while the call was in progress After all of the above steps are completed unless notified by your mc_roster routine it is possible that your application code may still use object IDs for objects that were on the failed node If this happens the pSOS m ker
85. System A real time system s most time critical area tends to be I O Therefore a device driver should be customized and crafted to optimize throughput and response A driver should not have to be designed to meet the specifications of any externally imposed generalized or performance robbing protocols In keeping with this concept the pSOS kernel does not impose any restrictions on the construction or operation of an I O device driver A driver can choose among the set of pSOS system services to implement queueing waiting wakeup buffering and other mechanisms in a way that best fits the particular driver s data and control characteristics The pSOS kernel includes an I O supervisor whose purpose is to furnish a device independent standard method both for integrating drivers into the system and for calling these drivers from the user s application I O can be done completely outside of the pSOS kernel For instance an application may elect to request and service some or all I O directly from tasks We recommend however that device drivers be incorporated under the pSOS I O supervisor pREPC and pHILEt drivers are always called via the I O supervisor pSOSystem System Concepts 7 1 Chapter 7 I O System 7 1 7 2 I O System Overview Figure 7 1 illustrates the relationship between a device driver the pSOS I O system and tasks using I O services Application Task pSOS I O System Device Driver Figur
86. System Concepts 4 19 4 MIB II fables Chapter 4 Network Programming This section presents the MIB II tables supported by the pNA component and their corresponding C language representations 4 19 4 1 Interfaces Table Structure and Elements MIB IT Object Type struct mib_ifentry ie_iindex ie_descr ie_type ie_mtu ie_speed ie_physaddress ie_adminstatus ie_operstatus ie_lastchange ie_inoctets ie_inucastpkts ie_nucastpkts ie_indiscards ie_inerrors ie_inunknownprotos ie_outoctets ie_outucastpkts ie_outnucastpkts ie_outdiscards ie_outerrors ie_outqlen ie_specific pSOSystem System Concepts ifIndex index ifDescr ifType default ifMtu ifSpeed ifPhysAddress ifAdminStatus ifOperStatus ifLastChange ifInOctets ifInUcastPkts ifInNUcastPkts ifInDiscards ifInErrors ifInUnknownProtos ifOutOctets ifOutUCastPkts ifOutNUcastPkts ifOutDiscards ifOutErrors ifOutQLen ifSpecific 4 49 Chapter 4 Network Programming 4 19 4 2 IP Address Table Structure and Elements struct mib_ipaddrreq ia_iaddr ia_ifindex ia_netmask ia_bcastaddr ia_reasmmaxsize 4 19 4 3 IP Route Table Structure and Elements struct mib_iproutereq ir_idest ir_ifindex ir_nexthop ir_type ir_proto ir_mask MIB IT Object Type ipAdEntAddr index ipAdEnt IfIndex default ipAdEntNetMask ipAdEntBcastAddr ipAdEntReasmMaxSize MIB IT Object Type ipRouteDest index ipRouteIfIndex ipRouteNextHop default
87. a filename in lower case but the system maps them to upper case The maximum length for a filename is 31 characters The CD ROM file system treats a pathname that begins with a digit as absolute if the path component is a valid currently mounted pSOSystem logical device name see section 5 3 2 Otherwise the system treats the pathname as relative As a special case the file name _VOLUME Y in the root directory is used to read the primary volume descriptor which is the starting point for locating all information on the volume For a detailed description of _VOLUME Y refer to the open_f system call description in pSOSystem System Calls Basic Services for All Volumes This section describes basic services that can be used with all types of volumes For detailed descriptions of the system calls discussed in this section see the system calls reference Opening and Closing Files Before a file can be read or written it must be opened with the open_f system call open_f accepts as input a pathname that specifies a file and a mode parameter which has meaning only when opening files pSOSystem System Concepts 5 19 Chapter 5 pHILE File System Manager 5 20 located on NFS volumes open_f returns a small integer called a file ID FID that is used by all other system calls that reference the file A file may be opened by more than one task at the same time Each time a file is opened a new FID is returned When a fi
88. a_area err_code de_open dev iopb amp retval err_code de_close dev iopb amp retval err_code de_read dev iopb amp retval err_code de_write dev iopb amp retval err_code de_cntrl dev iopb amp retval The first parameter dev is a 32 bit device number that selects a specific device The most significant 16 bits of the device number is the major device number which is used by the pSOS kernel to route control to the proper driver The least significant 16 bits is the minor device number which is ignored by the pSOS kernel and passed to the driver The minor device number is used to select among several units serviced by one driver Drivers that support only one unit can ignore it The second parameter iopb is the address of an I O parameter block This structure is used to exchange device specific input and output parameters between the calling task and the driver The length and contents of this I O parameter block are driver specific The third parameter retval is the address of a variable that receives an optional 32 bit return value from the driver for example a byte count on a read operation Use of retval by the driver is optional because values can always be returned via iopb However using retval is normally more convenient when only a single scalar value need be returned de_init takes a fourth parameter data_area This parameter is no longer used but remains for compatibility with older driv
89. ach partition on the disk Partitioning can be redone to change the partition boundaries However this destroys all data in any partition that is changed 3 Writing the Volume Parameter Record Just as the partition table provides information about each partition on a hard disk a volume parameter record in the first sector of each volume partition or floppy disk describes the geometry of that volume which is information such as volume size and the starting location of data structures on the volume On MS DOS format volumes the volume parameter record is called the boot record On pHILE format volumes the volume parameter record is called the root block You are responsible for executing the commands that write the volume parameter record The way in which it is written is described below 4 Creating an Empty File System Within Each Disk Partition Each volume must be initialized to contain either an MS DOS ora pHILE format file system You are responsible for executing the intitialization commands You use the system call init_vol to initialize pHILE format volumes Note that init_vol also writes the volume parameter record You use the format command to initialize MS DOS format volumes Once it is intialized you can use the system call pcinit_vol to re initialize it pcinit_vol leaves the volume parameter record alone However the re initialization destroys all data stored in any existing file system and writes
90. adecimal numbers 0x401 are preceded by Ox Symbol Conventions The symbol of a processor located to the left of text identifies processor specific information this example identifies 68K specific information 68K Support Customers in the United States can contact Integrated Systems Technical Support as described below International customers can contact m The local Integrated Systems branch office m The local pSOS distributor m Integrated Systems Technical Support as described below Before contacting Integrated Systems Technical Support please gather the information called for in Table 1 The detailed description in Table 1 should include the following pSOSystem System Concepts About This Manual m The procedure you followed to build the code Include components used by the application A complete record of any error messages as seen on the screen useful for tracking problems by error code Acomplete test case if applicable Attach all include or startup files as well as a sequence of commands that will reproduce the problem Contacting Integrated Systems Support To contact Integrated Systems Technical Support use one of the following methods m Call 408 542 1925 US and international countries m Send a fax to 408 542 1950 m Send e mail to psos_support isi com Integrated Systems actively seeks suggestions and comments about our software documentation customer support and training Please
91. ained on an erasable media while data blocks are written on a write once device After the data partition of a volume is filled the information from the control blocks that had been on erasable media can be transferred to the write once device where it is permanently recorded Intermixing control and data blocks means that your data and pHILE data structures will be written randomly on a device The manner in which control and data blocks are organized on a volume is determined when the volume is initialized One of the input parameters to init_vol specifies the starting block number of the volume s data blocks If O is specified then the data and control blocks are intermixed Otherwise data blocks begin at the specified block The starting data block number must be divisible by eight For example if a data block starting number of 200 is specified on a volume containing 5000 blocks then blocks 2 199 recall blocks O and 1 are not used by the pHILE file system manager are control blocks and blocks 200 4999 are data blocks How Files Are Organized A file is a collection of blocks that contain data a file descriptor that contains control information and an entry in a parent directory file The following sections outline how files are constructed and how data in them is used 5 7 2 1 The Fle Number Externally a file is specified by its pathname Internally the pHILE file system manager converts this pathname into a corr
92. am elements m Tasks m I O Device Drivers m Interrupt Service Routines ISRs Tasks their virtual environment and ISRs are the primary topics of discussion in this chapter The I O system and device drivers are discussed in Chapter 7 I O System pSOSystem System Concepts 2 1 Chapter 2 pSOS Real Time Kernel 2 2 2 2 Additional issues and considerations introduced by multiprocessor configurations are covered in Chapter 3 pSOS m Multiprocessing Kernel Multitasking Implementation A multitasked system is dynamic because task switching is driven by temporal events In a multitasking system while tasks are internally synchronous different tasks can execute asynchronously Figure 2 1 illustrates the multitasking kernel A task can be stopped to allow execution to pass to another task at any time In a very general way Figure 2 1 illustrates multitasking and how it allows interrupt handlers to directly trigger tasks that can trigger other tasks pSOS Figure 2 1 Multitasking Approach pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel Thus a multitasked implementation closely parallels the real world which is mainly asynchronous and or cyclical as far as real time systems apply Application software for multitasking systems is likely to be far more structured race free maintainable and re usable Several pSOS kernel attributes help solve the problems inherent in real time software d
93. an also be accessed directly by application developers who have their own unique requirements This section describes how this MIB can be accessed Background RFC 1213 groups MIB II objects into the following categories m System m Interfaces m Address Translation a IP m ICMP m TCP m UDP m EGP m Transmission SNMP The pNA component contains built in support for the IP ICMP TCP and UDP groups The Interfaces group is supported by pNA NIs The pSOSystem SNMP library provides support for the System and SNMP pSOSystem System Concepts 4 43 Chapter 4 Network Programming 4 19 2 4 44 groups The Address Translation group is being phased out of the MIB II specification Its functionality is provided via the IP group The Transmission group is not yet defined and the pNA component does not include EGP so neither of these groups are supported MIB II objects regardless of which category they fall into can be classified as simple variables or tables Simple variables are types such as integers or character strings In general the pNA component maintains one instance of each simple variable For example ipInReceives is a MIB II object used to keep track of the number of datagrams received Tables correspond to one dimensional arrays Each element in an array that is each entry in a table has multiple fields For example MIB II includes an IP Route Table where each entry in the table consists of the followin
94. an integral part of IP It is required to be implemented by hosts conforming to level 2 of the IP multicasting specification in RFC 1112 See Section 4 17 Internet Group Management Protocol IGMP ARP is used to map internet addresses to physical network addresses it is described in Section 4 12 2 Address Resolution Protocol ARP The Intemet Model pNA operates in an internet environment An internet is an interconnected set of networks Each constituent network supports communication among a number of attached devices or nodes In addition networks are connected by nodes that are called gateways Gateways provide a communication path so that data can be exchanged between nodes on different networks Nodes communicate by exchanging packets Every packet in transit through an internet has a destination internet address which identifies the packet s final destination The source and destination nodes can be on the same network i e connected or they can be on different networks i e indirectly connected If they are on different networks the packet must pass through one or more gateways Intemet Addresses Each node in an internet has at least one unique internet IP address An internet address is a 32 bit number that begins with a network number followed by a node number There are three formats or classes of internet addresses The different classes are distinguished by their high order bits The three classes ar
95. an synchronize its actions to the occurrence of a hardware interrupt by using either a message queue events flag semaphores or ASR pSOSystem System Concepts 2 12 1 2 12 2 Chapter 2 pSOS Real Time Kernel Interrupt Entry Sel oes On Coldfire PowerPC MIPS and x86 processors interrupts should be directly vectored to the user supplied ISRs As early as possible the ISR should call the I_ENTER entry in MPS el the pSOS kernel I_ENTER sets an internal flag to indicate that an interrupt is being serviced and then returns to the ISR Synchronizing With Tasks An ISR usually communicates with one or more tasks either directly or indirectly as part of its input output transactions The nature of this communication is usually to drive a task forcing it to run and handle the interrupting condition This is similar to the task to task type of communication or synchronization with two important differences First an ISR is usually a communication synchronization source it often needs to return a semaphore or send a message or an event toa task An ISR is rarely a communication sink it cannot wait for a message or an event Second a system call made from an ISR will always return immediately to the ISR without going through the normal pSOS dispatch For example even if an ISR sends a message and wakes up a high priority task the pSOS kernel must nevertheless return first to the ISR This d
96. anagement cccccccccececcececee eee ete a aE E E Ead 4 31 Memory Configuration eseese iieii eae a i i iE 4 34 4 14 1 Buffer Configuration 2 0 0 nieas aana AA AAEE EE a 4 35 4 14 1 1 MTU Size Buffers 2 0 0 cece ccc eceeeeneneeeen es 4 36 4 14 1 2 Service Call Size Buffers ccc eeceeeee eens 4 36 4 14 1 3 128 Byte Buffers cee ee cece eee eeeeeees 4 37 4 14 1 4 Zero Size Buffers 2 0 ccc cee eee eeeeeeeneeeeeenes 4 37 4 142 Message BIOCKS ii ieit naio e a Hat ead esavedens eda es 4 37 4 14 3 Tuning the pNAt Component cece cee c eee eee eee ee 4 38 Zero COPY OPUONS e223 262 AEE A ROA OAAR septa EA AASR 4 38 4 15 1 Socket Extensions aicsin dee dae ii e i ioiii ih 4 39 4 15 2 Network Interface Option ssssssssesssesesreseeeseseeseseserressss 4 40 Internet Control Message Protocol ICMP ce ceeeceeese eee eee eee ee 4 40 Internet Group Management Protocol IGMP cececeeeee eee eee ee 4 4 NES SUPPOUL isceeieaecac ae soe er EEEE EEEE Win eies sate E A E E 4 42 MIB SUpport ainiaan a IAOEE EEE TTAR 4 43 K T9 T BACKSTOUNGE oroarea tee a a aaa A acaba he 4 43 4 19 2 Accessing Simple Variables cece cece tee eee eens 4 44 419 32 Accessing Va Dl Sitti seccdstecayeatesbicas heshucoc seb seas ce a A E A EAT 4 46 4 19 4 MIB Tables iniciei ieie doa en te dae sedan EE R E 4 49 4 19 4 1 Interfaces Table ssneeseeseesseesssesesesessessressees 4 49 4 19 4 2 IP Address Table
97. apter 1 Product Overview L3 1 4 In addition to these core components pSOSystem includes the following m Networking protocols including SNMP FTP Telnet TFTP NFS and STREAMS m Run time loader m User application shell Support for C applications Boot ROMs m Pre configured versions of pSOSystem for popular commercial hardware m psSOSystem templates for custom configurations m Chip level device drivers m Sample applications This manual focuses on explaining pSOSystem core components Other parts of the pSOSystem environment are described in the pSOSystem Programmer s Reference and in the pSOSystem Getting Started manual Integrated Development Environment The pSOSystem integrated cross development environment can reside on a UNIX or DOS based computer It includes C and C optimizing compilers a target CPU simulator a pSOS OS simulator and a cross debug solution that supports source and system level debugging The pSOSystem debugging environment centers on the pROBE system level debugger and optional high level debugger The high level debugger executes on your host computer and works in conjunction with the PROBE system level debugger which runs on a target system pSOSystem System Concepts Chapter 1 Product Overview The combination of the pROBE debugger and optional host debugger provides a multitasking debug solution that features A sophisticated mouse and window user interface Auto
98. aret dollar sign tilde exclamation point number sign percent sign amp ampersand hyphen braces at sign single quotation mark apostrophe Q parentheses When a pathname is specified the volume directory and filenames all are separated by either a forward slash or a backward slash The following examples show permissible pathnames for files located on MS DOS formatted volumes 0 1 fruit apples O apples new apples The MS DOS file system treats a pathname that begins with a digit as absolute if the path component is a valid currently mounted pSOSystem logical device name see section 5 3 2 Otherwise the system treats the pathname as relative pSOSystem System Concepts 5 4 3 5 4 4 5 5 5 5 1 Chapter 5 pHILE File System Manager Naming Files on NFS Volumes On NFS volumes a file is named by a sequence of up to 64 characters All characters except backslash and null are allowed Filenames and directory names are separated in pathnames by forward slashes If the pHILE file system manager encounters a symbolic link while traversing an NFS pathname it recursively expands the link up to three levels of nesting Naming Filles on CD ROM Volumes A filename on a CD ROM volume consists of characters from the following set 0 9 A Z amp 3 4507 On a CD ROM volume letters are upper case You can specify names for
99. arnings from any of them pSOSystem System Concepts 3 1 3 pSOSHn Multiprocessing Kemel The pSOS tm real time multiprocessing operating system kernel is the multiprocessing version of the pSOS real time multitasking operating system kernel It extends many of the pSOS system calls to operate seamlessly across multiple processing nodes This chapter is designed to supplement the information provided in Chapter 2 It covers those areas in which the functionality of the pSOS m kernel differs from that of the pSOS kernel System Overview The pSOS m kernel is designed so that tasks that make up an application can reside on several processor nodes and still exchange data communicate and synchronize exactly as if they are running ona single processor To support this the pSOS m kernel allows system calls to operate across processor boundaries system wide Processing nodes can be connected via any type of connection for example shared memory message based buses or custom links to name a few The pSOS m kernel is designed for functionally divided multiprocessing systems This is the best model for most real time applications given the dedicated nature of such applications and their need for deterministic behavior Each processor executes and manages a separate often pSOSystem System Concepts 3 1 Chapter 3 pSOS Multiprocessing Kernel 3 2 3 2 distinct set of functions Typically the decomposition and assignment
100. ask can be defined for each Network Interface NI installed in your system Routes that are added to the pNA IP forwarding table can include IP subnet masks A default value of the mask is computed internally based on the address class if the subnet mask is not explicitly specified Broadc ast Addresses The pNA component provides an optional broadcast capability if the underlying network supports it An internet address with a node number i e host part consisting of either all ones or all zeros is designated a broadcast address A broadcast address is used to refer to all of the nodes on a given network For example you can broadcast a packet to all of the nodes on the Class B network 128 1 by sending a packet to address 128 1 255 255 Similarly the broadcast address of a node with IP address 128 1 200 1 and netmask of Oxffffff00 is 128 1 200 255 A Sample Intemet 4 3 4 depicts an internet consisting of two networks Note that because node B is on both networks it has two internet addresses and serves as a gateway between networks 90 and 100 For example if node A wants to send a packet to node D it sends the packet to node B which in turn sends it to node D The Soc ket Layer The socket layer is the programmer s interface to the pNA component It is based on the notion of sockets and designed to be syntactically and semantically compatible with UNIX 4 3 BSD networking services This section is intended to provide a br
101. at can be connected to the pNA component Entries can be added to the NI Table in one of two ways pSOSystem System Concepts Chapter 4 Network Programming 1 The pNA Configuration Table entry NC_INI contains a pointer to an Initial NI Table The contents of the Initial NI Table are copied to the actual NI Table during pNA initialization 2 The pNA system call add_ni can be used to add an entry to the NI Table dynamically after the pNA component has been initialized The following code segment illustrates some NI related ioctl operations define satosin sa struct sockaddr_in sa define MAX BUF 1024 int s rc struct ifconf ifc struct ifreq ifr char buffer MAX_BUF create any type of socket s socket AF_INET SOCK_DGRAM 0 get the interface configuration list ifc ifc_len MAX _ BUF ifc ifc_buf buffer re ioctl s SIOCGIFCONF char amp ifc change the IP address of the pNA interface 1 to 192 0 0 1 ifr ifr_ifno 1 satosin amp ifr ifr_addr gt sin_family AF_INET satosin amp ifr ifr_addr gt sin_addr s_addr hton1 0xc0000001 re ioctl s SIOCSIFADDR char amp ifr change the destination IP address of a point point interface pNA interface 2 such as a PPP line to 192 0 0 1 ifr ifr_ifno 2 satosin amp ifr ifr_addr gt sin_family AF_INET satosin amp ifr ifr_dstaddr gt sin_addr s_addr htonl1 0xc00
102. ble length message queues 2 28 D data blocks 4 32 datagram sockets 4 8 deblocking 5 26 decomposition criteria 2 4 decomposition of an application 2 4 default gateway 4 18 deletion of message queues 2 25 of partitions 2 23 of regions 2 21 of semaphores 2 31 of tasks 2 42 of variable length message queues 2 22 2 28 2 29 dependent action 2 4 destination Internet address 4 5 device auto initialization 7 4 7 10 device drivers environment 7 8 pHILE 7 18 pREPC 7 16 dispatch criteria 2 12 dual ported memory 3 17 E end of file flag 6 10 error flag 6 10 error handling 4 17 errors fatal 2 40 events 2 29 operations 2 30 versus messages 2 30 expansion unit 5 37 extent 5 37 extent map 5 38 external address 3 18 F failed nodes 3 13 fatal error handler 2 41 fatal errors 2 40 FC_LOGBSIZE 5 13 5 26 FC_NBUF 5 26 FC_NCFILE 5 20 FC_NFCB 5 20 filesystem manager 1 3 flags NI 4 25 FLIST 5 34 fully buffered 6 7 G gateways 4 5 Global Object Table 3 5 pSOSystem System Concepts global objects 3 4 global shutdown 3 16 H hardware addresses 4 25 heap management algorithm 2 22 hosts 4 6 l 1 0 7 1 asynchronous 7 13 block translation 7 20 buffer header 7 18 mutual exclusion 7 12 pREPC 7 16 switch table 7 3 synchronous 7 13 system overview 7 2 transaction sequencing 7 20 I_RETURN entry 2 12 ICMP 4 4 4 40 message types 4 40 idle tasks 2 19 IGMP 4 41 initialization 5 4 internal address 3 18
103. bnets As mentioned above an internet address consists of a network part and a host part To provide additional flexibility in the area of network addressing the notion of subnet addressing has become popular and is supported by the pNA component Conceptually subnet addressing allows you to divide a single network into multiple sub networks Instead of dividing a 32 bit internet address into a network part and host part subnetting divides an address into a network part and a local part The local part is then sub divided into a sub net part and a host part The sub division of the host part of the internet address is transparent to nodes on other networks Sub net addressing is implemented by extending the network portion of an internet address to include some of the bits that are normally considered part of the host part The specification as to which bits are to be interpreted as the network address is called the network mask The network mask is a 32 bit value with ones in all bit positions that are to be interpreted as the network portion For example consider a pNA node with an address equal to 128 9 01 01 This address defines a Class B network with a network pSOSystem System Concepts 4 3 3 4 3 4 4 4 Chapter 4 Network Programming address equal to 128 9 If the network is assigned a network mask equal to Oxffffff00 then from the perspective of the pNA component the node resides on network 128 9 01 A network m
104. buffers must always be pNA configured to function Zero size buffers are used to create message block triplets with externally specified data buffers See Section 4 15 Zero Copy Options and the pna_esballoc call description in pSOSystem System Calls 4 14 11 MTU Size Buffers When a non zero copy NI is pNA configured data is copied from the NI buffers to pNA internal buffers Hence it is optimal to have MTU size buffers configured in the system The number of buffers that should be configured depends on the incoming network traffic on that NI 4 14 12 Service Call Size Buffers Data is copied from user buffers to pNA internal data buffers during send sendto and sendmsg service calls For optimal performance the pNA component should be configured with buffer sizes specified in pSOSystem System Concepts 4 14 2 Chapter 4 Network Programming the service calls The optimal number of buffers depends on the buffer size of the socket 4 14 1 3 128 Byte Buffers The pNA component uses 128 byte buffers to store protocol headers and addresses The number of protocol headers allocated at any given time depends on the number of packets sent or received simultaneously by the protocol layers in the pNA component The number of packets sent or received by the pNA component varies with the number of active sockets and with socket buffer size The number of packets that can exist per active socket is the socket buffer
105. ca ee a EN EA dade dekcentanes 3 16 3 10 The Node R ster sie 8 es Felice ee aaah ae ceodin elds E AN 3 16 3 11 Dual Ported Memory Considerations cece see eee eee eeee een enee 3 17 SIEL P PortianG S Port v3 eis eis aa ea aes ccd teen cvs sedadeuideacstdeae 3 17 3 11 2 Internal and External Address cc cece eee ee eeeeeeeneeees 3 18 3 11 3 Usage Within pSOStm Services 2 0 cece eee eee eeee eee eees 3 19 5 11 4 Usage Outside pSOSP nen n cee sete cee ceases aawet egos dlets 3 19 Network Programming 4 1 Overview of Networking Facilities 0c eeeceeeeeceeceeeeen een eeneenees 4 1 4 2 pNA Software Architecture osoro Aa seekar rasata aKa Ka Kasaat 4 3 4 3 The Internet Model sersriend ea a a ts 4 5 43 1 Internet Addresses iniri AE TE EE EE EER ERES 4 5 A Dm O UDNES ini EE R EE E OEE OEA AO 4 6 4 3 3 Broadcast AddrESS Suuirerar o AEA A iE 4 7 43 4 ASample Internet eien ena a e heehee ethan a 4 7 4 The Socket Layer oe i a a E a E a N 4 7 AA BASICS k ea A A A E E E E A ONS 4 8 4 4 2 Socket Creation eiriaa TA AEE AERE E O E EEEE 4 9 44 3 Socket AddTESSES airoiioisriioi idi iTA A EEEE EERS 4 9 4 4 4 Connection Establishment ssssssssssessssessrsseseesersersresee 4 10 4 4 5 Data Transtetoeicsiso sisiiiri tiid eiis i haves EE EEEa 4 11 4 4 6 Comnnectionless Sockets ccecececececeeeeneeeeeeeeeeseeeeeees 4 12 4AT Discarding Sockets pei St beh ee eet eee i aa 4 12 4 4 8 Socket Opuons
106. can communicate with a target over a serial or TCP IP network connection pSOSystem System Concepts 1 1 Chapter 1 Product Overview 1 2 1 2 System Architecture The pSOSystem software employs a modular architecture It is built around the pSOS real time multi tasking kernel and a collection of companion software components Software components are standard building blocks delivered as absolute position independent code modules They are standard parts in the sense that they are unchanged from one application to another This black box technique eliminates maintenance by the user and assures reliability because hundreds of applications execute the same identical code Unlike most system software a software component is not wired down to a piece of hardware It makes no assumptions about the execution target environment Each software component utilizes a user supplied configuration table that contains application and hardware related parameters to configure itself at startup Every component implements a logical collection of system calls To the application developer system calls appear as re entrant C functions callable from an application Any combination of components can be incorporated into a system to match your real time design requirements The pSOSystem components are listed below NOTE Certain components may not yet be available on all target processors Check the release notes to see which pSOSystem components are
107. ce disk terminal etc Figure 6 1 I O Structure of the pREPC Library The pREPC I O functions provide a uniform method for handling all types of I O They mask the underlying layers and allow application programs to be hardware and device independent A user application can however call any of the layers directly depending on its requirements The lowest most primitive way of doing I O is by directly accessing the hardware device involved for example a serial channel or a disk pSOSystem System Concepts 6 3 Chapter 6 pREPC ANSI C Library 6 3 1 6 4 controller Programming at this level involves detailed knowledge of the device s control registers etc Although all I O eventually reaches this level it is almost never part of the application program as it is too machine dependent The next step up from the actual device is to call a device driver Under the pSOS kernel all device drivers are called in a similar fashion via the pSOS I O Supervisor which is explained in Chapter 7 I O System For reading and writing data all that is generally required is a pointer to the buffer to read into or write from a byte count and a way to identify the device being used The pSOS I O Supervisor provides the fastest most direct route for getting a piece of data to a device In some cases this is the best way Generally however it is better to use the pREPC direct character or formatted I O services The pH
108. contiguous block allocation pHILE format volumes can be a wide range of devices from floppy disks to write once optical disks as described below o Hard disks IDE Up to 31 5 gigabytes the maximum IDE CHS size SCSI Up to 2 048 gigabytes the maximum SCSI size o Floppy disks Any size a Optical disks 124 4 Mbyte Fuji M2511A OMEM MS DOS Volumes These are devices that are formatted and managed according to MS DOS FAT file system conventions and specifications pHILE supports both FAT12 and FAT16 MS DOS volumes offer a convenient method for exchanging data between a pSOS system and a PC running the MS DOS operating system Because of their internal organization MS DOS volumes are much less efficient than pHILE volumes Hence they should be used only when data interchange is desired see section 5 2 1 The pHILE file system pSOSystem System Concepts Chapter 5 pHILE File System Manager manager supports the MS DOS hard disk and floppy disk formats and storage capacities listed below o Hard disks IDE interchangeable with DOS Capacity up to 528 megabytes IDE accessible only to pHILE Capacity up to 2 gigabytes SCSI interchangeable with DOS Capacity up to 2 gigabytes o Floppy disks 360 kilobytes 5 1 4 DD double density 720 kilobytes 3 1 2 DD double density 1 2 megabytes 5 1 4 DH high density 1 2 megabytes 5 1 4 NEC 1 44 megabytes 3 1 2 DH high density 2 88
109. d The table search order may be modified using the node input parameter to the Object Ident system calls In particular 1 If node equals O the pSOS m kernel first searches the Local Object Table and then the Global Object Table on the caller s node If the object is not found a request is posted to the master node which searches its Global Object Table beginning with objects exported by node number 1 then node 2 and so on 2 If node equals the local node s node number then the pSOS m kernel searches the Global Object Table on the local node only 3 If node is not equal to the local node number a request is posted to the master node which searches its Global Object Table for objects created and exported by the specified node Typically object binding is a one time only non time critical operation executed as part of setting up the application or when adding a new object Remote Service Calls When the pSOS m kernel receives a system call whose target object ID indicates that the object does not reside on the node from which the call is made the pSOS m kernel will process the system call as a remote service call RSC In general an RSC involves two nodes The source node is the node from which the system call is made The destination node is the node on which the object of the system call resides To complete an RSC the pSOS m kernels on both the source and destination nodes must carry out a sequence of well coordina
110. d and bound to it In order to complete the connection the server must issue the accept system call specifying the descriptor of the socket that was specified in the prior listen call The accept call does not connect the initial socket however Instead it creates a new socket with the same properties as the initial one This new socket is connected to the client s socket and its descriptor is returned to the server The initial socket is thereby left free for other clients that might want to use connect to request a connection with the server If a connection request is pending at the socket when the accept call is issued a connection is established If the socket does not have any pending connections the server task blocks unless the socket has been pSOSystem System Concepts Chapter 4 Network Programming marked as non blocking see section 4 4 9 until such time as a client initiates a connection by issuing a connect call directed at the socket Although not usually necessary either the client or the server can optionally use the getpeername call to obtain the address of the peer socket that is the socket on the other end of the connection The following illustrates the steps described above SERVER CLIENT socket domain type protocol socket domain type protocol bind s addr addrlen listen s backlog connect s addr addrlen accept s addr addrlen 4 4 5 Data Transfer After a
111. d by pNA when calling the user provided signal handler pSOSystem System Concepts Chapter 4 Network Programming 4 7 Enor Handling The pNA component uses the UNIX BSD 4 3 socket level error reporting mechanisms When UNIX detects an error condition it stores an error code into the internal variable errno and returns 1 to the caller To get the error code the calling task reads errno prior to making another system call errno is defined in psos h 4 8 Packet Routing The pNA component includes complete routing facilities This means that in addition to providing end to end communication between two network nodes a pNA node forwards packets in an internet environment When the pNA component receives a packet addressed to some other node it attempts to forward the packet toward its destination The pNA component forwards packets based on routes that define the connectivity between nodes A route provides reachability information by defining a mapping between a destination address and a next hop within a physically attached network Routes can be classified as either direct or indirect A direct route defines a path to a directly connected node Packets destined for that node are sent directly to the final destination node An indirect route defines a path to an indirectly connected node see section 4 3 Packets addressed to an indirectly connected node are routed through an intermediate gateway node Routes can be classifi
112. data translation itself Authentication The RPC protocol allows client authentication by RPC servers When authentication is being employed servers can identify the client task that made a specific request Clients are identified by credentials included with each RPC request they make Servers may refuse requests based upon the contents of their credentials The representation of credentials is operating system specific because different operating systems identify tasks differently Consequently the pSOSystem System Concepts Chapter 4 Network Programming RPC definition allows the use of custom credentials in addition to specifying a format for UNIX task credentials In order to facilitate porting of UNIX clients to pSOSystem and interoperability between pSOSystem clients and UNIX servers pRPC fully supports the generation of UNIX style credentials The content of UNIX credentials are defined by the following data structure struct authunix_parms u_long aup_time credential s creation time char aup_machname hostname of client int aup_uid client s UNIX effective uid int aup_gid client s UNIX effective gid u_int aup_len element length of aup_gids int aup_gids array of groups user is in The pRPC subcomponent supports the standard RPC routines for manipulating UNIX compatible credentials These routines are authunix_create and authunix_create_default Both routine
113. detail and present recommended methods for performing these operations 2 14 1 Deleting Tasks That Use Components To avoid permanent loss of component resources the pSOS kernel does not allow deletion of a task that is holding any such resource Instead t_delete returns an error code which indicates that the task to be deleted holds one or more resources The exact conditions under which components hold resources are complex In general any task that has made a component service call might be holding resources But all components provide a facility for returning all of their task related resources via a single service call We recommend that these calls be made prior to calling t_delete pHILE pNA and pREPC components can hold resources that must be returned before a task can be deleted These resources are returned by calling close_f 0 close O and fclose 0 and free 1 respectively Because the pREPC component calls the pHILE component and the pHILE component calls the pNA component if NFS is in use these services must be called in the correct order Below is a sample code fragment that a task can use to delete itself fclose 0 close pREPC files close_f 0 return pHILE resources close 0 return pNA resources free void 1 return pREPC resources t_delete 0 and commit suicide Obviously calls to components not in use should be omitted Because only the task to be deleted
114. dge a priori or acquired regarding an object s node of residence pSOSystem System Concepts 3 4 3 3 4 4 Chapter 3 pSOS Multiprocessing Kernel Global Object ables Every node running the pSOS kernel or the pSOS m kernel has a Local Object Table that contains entries for local objects In a multiprocessor system every node also has a Global Object Table A slave node s Global Object Table contains entries for objects that are resident on the slave node and exported for use by other nodes The master node s global object table contains entries for every exported object in the system regardless of its node of residence On a slave node when an object is created with the XX_GLOBAL option the pSOS m kernel enters its name and ID in the Global Object Table on the object s node of residence In addition the pSOS m kernel passes the object s name and ID to the master node for entry in the master node s Global Object Table Thus every global object located on a slave node has entries in two Global Object Tables the one on its node of residence and the one on the master node On the master node when an object is created with the XX_GLOBAL option the global object s name and ID are simply entered in the master node s Global Object Table Similar operations occur when a global object is deleted When a global object is deleted it is removed from the master node s Global Object Table and its own node s Global
115. dication 80h active unsigned char start_head Starting head number unsigned char start_sect Starting sector and cyl hi unsigned char start_cyl Starting cylinder low unsigned char sys_ind System Indicator unsigned char end_head Ending head unsigned char end_sect Ending sector and cyl high unsigned char end_cyl Ending cylinder low unsigned long start_rsect Starting relative sector unsigned long nsects Number of sectors in partition The driver computes the starting relative sector and size of each partition table entry If the driver is an IDE driver it computes these values from the cylinder head and sector fields start_head through end_cyl If the driver is a SCSI driver it computes these values from the Starting Relative Sector start_rsect and Number of Sector nsects fields pSOSystem System Concepts Chapter 7 I O System The driver checks the System Indicator sys_ind element of the first entry If the System Indicator is 0 the driver considers the entry to be empty and goes on to the next entry If the System Indicator is 0x05 the driver considers the entry to be an extended partition entry that contains information on an extended partition table If the System Indicator is any other value the driver considers the entry to be a valid entry that contains information on a partition on the disk The driver then stores the computed starting relative
116. e RPC library and its existence and use are transparent to application programmers At system initialization time the pRPC subcomponent automatically creates a port mapper task with the pSOS name pmap The pmap task is started with a priority of 254 An application may change the priority of pmap via the standard pSOS service call t_setpri Global Variable psOSystem tasks all run in the same address space Consequently global variables are accessible to and shared by every task running on the same processor Whenever multiple tasks use the same global variable they must synchronize access to it to prevent its value from being changed by one task while it is being used by another task Synchronization can be achieved by using a mutex lock implemented with a semaphore or disabling task preemption around the regions of code which access the variable The pRPC subcomponent eliminates the need to use custom synchronization in RPC XDR applications by replacing global variables with task specific equivalents Subroutines are provided in the pRPC subcomponent to provide access to the task specific variables pSOSystem System Concepts Chapter 4 Network Programming The following global variables are replaced by local variables in the pRPC subcomponent Global Variable Service Call Description svc_fdset get_fdset Bit mask of used TCP IP socket IDs rpc_createerr rpc_getcreateerr Reason for RPC client handle creation failu
117. e send and sendto system calls To receive out of band data the MSG _OOB flag is used when calling recv and recvfrom The SIOCATMARK option in the ioctl system call can be used to determine if out of band data is currently ready to be read Socket Data Structures The pNA component uses two data structures to manage sockets socket control blocks and open socket tables A socket control block SCB is a system data structure used by the pNA component to maintain state information about a socket During initialization the pNA component creates a fixed number of SCBs An SCB is allocated for a socket when it is created via the socket call Every task has an open socket table associated with it This table is used to store the addresses of the socket control blocks for the sockets that can be referenced by the task A socket descriptor is actually an index into an open socket table Because each task has its own open socket table you can see that one socket might be referenced by more than one socket descriptor New socket descriptors for a given socket can be obtained with the shr_socket system call see section 4 4 2 The pNA Daemon Task When pNA system calls are made there are three possible outcomes 1 The pNA component executes the requested service and returns to the caller 2 The system call cannot be completed immediately but it does not require the caller to wait In this case the pNA component schedu
118. e shared priority is often used to prevent mutual preemption among certain tasks such as those that share non reentrant critical regions In such cases roundrobin should be left disabled for all such related tasks in order to prevent the pSOS kernel from switching tasks in the midst of such a region To maximize efficiency a task s roundrobin should be left disabled if 1 it has a priority level to itself or 2 it shares its priority level with one or more other tasks but roundrobin by timeslice among them is not necessary 2 3 6 Manual Roundrobin For certain applications automatic roundrobin by timeslice might not be suitable However there might still be a need to perform roundrobin manually that is the running task might need to explicitly give up the CPU to other ready tasks of the same priority The pSOS kernel supports manual roundrobin via the tm_wkafter system call with a zero interval If the running task is the only ready task pSOSystem System Concepts 2 11 Chapter 2 pSOS Real Time Kernel 2 3 7 2 3 8 at that priority level then the call simply returns to it If there are one or more ready tasks at the same priority then the pSOS kernel will take the calling task from the running state into the ready state thereby putting it behind all ready tasks of that priority This forces the pSOS kernel to switch from that last running task to another task of the same priority now at the head of the ready
119. e the volume name must include a partition The filenumber follows the partition separated by a dot If a filenumber is not given the complete path starts at the volume s root directory pSOSystem System Concepts 5 15 Chapter 5 pHILE File System Manager A relative pathname identifies a file or directory by specifying a path relative to a predefined directory on a predefined volume together called the current directory The current directory is unique for each task It can be set and changed with the change_dir system call For examples of absolute pathnames consider the following MS DOS file system For illustration assume that the filenumber of the root directory is Ox10000 or 65536 the filenumber of directory sports is Ox1 or 1 the filenumber of file agenda is 0x2 or 2 and the filenumber of file baseball is Ox20003 or 131075 The get_fn system call is used to determine the actual filenumber Root Directory sports agenda l baseball This file system is on the example partitioned SCSI hard disk of section 5 3 2 The SCSI adapter device number is 4 The SCSI ID of the disk drive is 3 The file system is on partition 2 Some of the different ways of writing absolute pathnames of the two files and the two directories are described below File Absolute Pathname Components Root 4 3 2 Volume including partition Filename Root 4 3 2 Volume including partition Filename Root 4 3 2 65536 Volume including partition
120. e 5 21 shows the relationship between the system data structures discussed in this section pSOSystem System Concepts 5 5 2 Chapter 5 pHILE File System Manager Data Structures Data Structures in Memory ona Device Task A FID 1 Pointer 1 gt Fie 1 FCB i FID 2 Pointer 2 FID 3 UNUSED Task B FCB j FID 1 Pointer 1 a FID 2 Pointer 2 gt File 3 FCB k File Open file File Control IDs tables Blocks Figure 5 2 The Relationship Among a File ID a File Control Block and a File Reading And Writing Once a file is open it may be read or written with the read_f and write_f system calls respectively read_f accepts as input an FID identifying the file to read the address of a user data buffer to receive the data and the number of bytes to read Data transfer begins at the byte indicated by the position pointer as explained in the next section read_f returns the number of bytes transferred from the file to the user s buffer If this value is less than the number requested and the return code does not indicate that an error occurred then the end of file has been reached Attempting to read beyond the end of file is not considered an error pSOSystem System Concepts 5 21 Chapter 5 pHILE File System Manager 5 5 3 5 22 The write_f system call is used to write data to a file write_f is similar to read_f It accepts as input an FID to identify a file th
121. e 7 1 I O System Organization As shown an I O operation begins when an application task calls the pSOS I O system The pSOS kernel examines the call parameters and passes control to the appropriate device driver The device driver performs the requested I O service and then returns control to the pSOS kernel which in turn returns control back to the calling task Because device drivers are hardware dependent the exact services offered by a device driver are determined by the driver implementation However the pSOS kernel defines a standard set of six I O services that a device driver may support These services are de_init de_open de_close de_read de_write and de_cntrl A driver may support any or all six of these services depending on the driver design The pSOS kernel does not impose any restrictions or make any assumptions about the services provided by the driver However in general the following conventions apply de_init is normally called once from the ROOT task to initialize the device It should be called before any other I O services are directed to the driver pSOSystem System Concepts Chapter 7 I O System de_read and de_write perform the obvious functions de_open and de_close are used for duties that are not directly related to data transfer or device operations For example a device driver may use de_open and de_close to enforce exclusive use of the device spanning several read
122. e NI is a point to point interface pSOSystem System Concepts 4 25 Chapter 4 Network Programming 4 11 4 4 115 4 11 6 4 26 RAWMEM If this is set the pNA component passes packets in the form of mblk message block linked lists see Section 4 13 Memory Management Similarly the driver announces packets by passing a pointer to the message block UNNUMBERED If this is set the NI is an unnumbered point to point link pNA assigns the network node ID as the IP address of the link see Section 4 10 Unnumbered Serial Links UP If this is set the initial mode of the NI is up Note that if the ARP flag is enabled the BROADCAST flag must also be set see section 4 12 Network Subnet Mask A network can have a network mask associated with it to support subnet addressing The network mask is a 32 bit value with ones in all bit positions that are to be interpreted as the network portion See section 4 3 2 for a discussion on subnet addressing Destination Address In point to point networks two hosts are joined on opposite ends of a network interface The destination address of the companion host is specified in the pNA NI Table entry DSTIPADDR for point to point networks The NI fable The pNA component stores the parameters described above for each NI in the NI Table The size of the NI Table is determined by the pNA Configuration Table entry NC_NNI which defines the maximum number of networks th
123. e address of a user data buffer containing data and the number of bytes to transfer Data transfer begins at the byte indicated by the position pointer as explained in the next section write_f always transfers the number of bytes requested unless the target volume runs out of space or an error occurs Positioning Within Files From the user s point of view a file is a numbered sequence of bytes For example if a file contains 210 bytes they are numbered 0 through 209 For every connection established by open_f the pHILE file system manager maintains a position pointer that marks the next byte to read or write The position pointer is a 32 bit unsigned integer and is initialized to O by open_f Every read or write call advances the position pointer by the number of bytes transferred by that operation In this way a file can be read or written sequentially The position pointer will be equal to the number of bytes in the file when the end of file is reached In the example cited above the position marker will be 210 after the last byte is read The Iseek_f system call can be used to relocate a position pointer Iseek_f accepts three input parameters The first parameter is an FID used to specify a file The second parameter is an offset that specifies the number of bytes by which the position pointer should be moved The third parameter specifies that the move should be relative to one of the following m The beginn
124. e defined as A B and C with high order bits of O 10 and 110 They use 8 16 and 24 bits respectively for the network part of the address Each class has fewer bits for the node part of the address and thus supports fewer nodes than the higher classes pSOSystem System Concepts 4 5 Chapter 4 Network Programming 4 3 2 4 6 IP multicast groups are identified by Class D IP addresses i e those with four high order bits 1110 The group addresses range from 224 0 0 0 to 239 255 255 255 Class E IP addresses i e those with 1111 as their high order four bits are reserved for future addressing needs Externally an internet address is represented as a string of four 8 bit values separated by dots Internally an internet address is represented as a 32 bit value For example the internet address 90 0 0 1 is internally represented as 0x5a000001 This address identifies node 1 on network 90 Network 90 is a class A network In the networking literature nodes are sometimes called hosts However in real time systems the term host is normally used to refer to a development system or workstation as opposed to a target system Therefore we choose to use the term node rather than host Note that a node can have more than one internet address A gateway node for example is attached to at least two physical networks and therefore has at least two internet addresses Each internet address corresponds to one node network connection Su
125. e is mounted with immediate write mode pSOSystem System Concepts Chapter 5 pHILE File System Manager 5 7 pHILE Format Volumes This section discusses how pHILE format volumes are organized and the special system calls available only for pHILE format volumes 5 7 1 How pHILE Format Volumes Are Organized As mentioned in Section 5 6 3 Blocking Deblocking a pHILE format volume consists of a sequence of logical blocks Several blocks per volume are dedicated to hold management information for the volume These blocks are accessed directly by the pHILE file system manager without going through normal file operations The management blocks are defined as follows BOOTLOAD ROOTBLOCK ROOTDIR BITMAP FLIST pSOSystem System Concepts The first and second blocks O and 1 are never used by the pHILE file system manager They are reserved in case a bootstrap loader is needed for the volume Block 2 is always used as the root block for a volume This block contains all information needed by the pHILE file system manager to locate other vital information on the volume Block 3 is always used to hold the first block of the root directory for the volume As the root directory grows additional blocks are allocated dynamically as required This contiguous sequence of blocks is used to hold the bitmap for the volume which uses bits to indicate what blocks are free Its size and location are determined by parame
126. e master boot sector Information about the encoding of partition numbers is explained in section 7 11 4 MS DOS Hard Drive Considerations Sector Size and Partitions This section describes special considerations required when using MS DOS hard drives with the pHILE file system manager You must provide a driver that performs partition table block translation if your hard disk contains multiple partitions pHILE itself places no restrictions on the number of types of partitions supported on a hard disk It merely passes the partition number to the hard disk driver without interpreting it The partition number and drive number are encoded in the 16 bit minor device number The upper eight bits are the partition number The lower eight bits are the drive number Table 7 2 shows the mapping of minor device number to drive number and partition number for drive number zero Table 7 2 Minor Number to Drive Partition Mapping Minor Number Drive Partition 256 0x100 0 1 512 0x200 0 2 768 0x300 0 3 1024 0x400 0 4 1280 0x500 0 5 1536 0x600 0 6 NOTE Use only devices with a 512 byte sector size which is standard for MS DOS file systems Although the pHILE file system manager allows you to initialize an MS DOS partition file system on devices with other sector sizes if you connect such devices to an MS DOS system it will not be able to read them pSOSystem System Concepts 7 23 Chapter 7 I O System 7 2
127. e name is given to the pHILE file system manager as a string of two or three numbers separated by dots Each number is decimal or hexadecimal Hexadecimal numbers are preceded by Ox If two numbers are given they are the 16 bit major device number followed by the 16 bit minor device number If three are given they are in order the 16 bit major device number the 8 bit minor device number and the 8 bit partition number In this case an equivalent 16 bit minor device number is constructed with the partition number in the most significant 8 bits and the given minor device number in the least significant 8 bits For a volume name example consider partition 2 of a partitioned SCSI hard disk The SCSI adapter device driver number is 4 The SCSI ID of pSOSystem System Concepts Chapter 5 pHILE File System Manager the disk drive is 3 Some of the different ways of writing the same volume name are given below Name Components 4 3 2 Major device number Minor device number Partition 0x4 0x3 0x2 Major device number Minor device number Partition 4 515 Major device number Minor device number 4 0x203 Major device number Minor device number 5 3 3 Local Volumes CD ROM MS DOS and pHILE Format Volumes Internally the pHILE file system manager treats local file system volumes differently than NFS volumes Each local volume consists of a sequence of logical blocks and a file is a named collection of blocks In this model a logical block
128. e system exactly and as easily as if they are all running on a single CPU Global Objects On every object creation system call there is a flag parameter XX_GLOBAL which can be used to declare that the object will be known globally to all other nodes in the system XX is short for the actual object For example task message queue and semaphore objects can be declared as global by using T_ GLOBAL Q GLOBAL and SM_GLOBAL respectively Memory partitions can also be declared as global although this is useful only in a shared memory multiprocessor system where the partition is contained in an area addressable by multiple nodes Memory region objects can only be local An object should be exported only if it will be referenced by a node other than its node of residence because an exported i e global object requires management and storage not only on the resident node but also on the master node Object ID Each object local or global is known system wide by two identities a user assigned 32 bit name and a unique pSOS assigned 32 bit run time ID This ID when used as input on system calls is used by the pSOS m kernel to locate the object s node of residence as well as its control structure on that node This notion of a system wide object ID is a critical element that enables pSOS m system calls to be effective system wide that is transparently across nodes The application program never needs to possess any explicit knowle
129. ecessary conditions for combining two tasks into one task though this might result in a loss of efficiency or clarity By the same token a task can always be split into two though perhaps with some loss of efficiency Terminology In this discussion a job is defined as a group of one or more tasks and a task is defined as a group of one or more actions An action act is a locus of instruction execution often a loop A dependent action dact is an action containing one and only one dependent condition this condition requires the action to wait until the condition is true but the condition can only be made true by another dact Decomposition Criteria Given a task with actions A and B if any one of the following criteria are satisfied then actions A and B should be in separate tasks Time dact A and dact B are dependent on cyclical conditions that have different frequencies or phases Asynchrony dact A and dact B are dependent on conditions that have no temporal relationships to each other pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel Priority dact A and dact B are dependent on conditions that require a different priority of attention Clarity Maintainability act A and act B are either functionally or logically removed from each other The pSOS kernel imposes essentially no limit on the number of tasks that can coexist in an application You simply specify in the pSOS Configurati
130. ecuting pHILE code task A is preempted by task B 3 Task B then restarts task A In such situations the pHILE file system manager correctly returns resources as required However a pHILE or MS DOS file system volume may be left in an inconsistent state For example if t_restart interrupts a create_f operation a file descriptor FD may have been allocated but not the directory entry As a result an FD may be permanently lost t_restart detects potential corruption and returns the warning code pSOSystem System Concepts Chapter 5 pHILE File System Manager OxOD When this warning code is received verify_vol should be used on all pHILE format volumes to detect and correct any resulting volume inconsistencies 5 8 1 2 Deleting Tasks That Use the pHILE File System Manager To avoid permanent loss of pHILE resources the pSOS kernel does not allow deletion of a task that is holding any pHILE resource Instead t_delete returns error code 0x18 which indicates that the task to be deleted holds pHILE resources The exact conditions under which the pHILE file system manager holds resources are complex In general any task that has made a pHILE service call may hold pHILE resources close_f 0 which returns all pHILE resources held by the calling task should be used prior to calling t_delete The pNA and pREPC components also hold resources which must be returned before a task can be deleted These resources a
131. ed from your application program They are linked with the code you develop when you build your application However when you attempt to use these libraries in a real time embedded system they encounter one or more of the following problems m It is the user s responsibility to integrate library I O functions into the target environment a time consuming task m The library functions are not reentrant and therefore do not work in a multitasking environment m The library functions are not compatible with a published standard resulting in application code that is not portable The pREPC ANSI C Library solves all of the above problems First it is designed to work with the pSOS Real Time Multitasking Kernel and the pHILE file system manager so all operating system dependent issues have been addressed and resolved Second it is designed to operate ina multitasking environment and finally it complies with the C Standard Library specified by the American National Standards Institute pSOSystem System Concepts 6 1 Chapter 6 pREPC ANSI C Library 6 2 6 2 Functions Summary The pREPC library provides more than 115 run time functions Following the conventions used in the ANSI X3J11 standard these functions can be separated into 4 categories m Character Handling Functions m String Handling Functions m General Utilities m Input Output Functions The Character Handling Functions provide facilities for testing characte
132. ed further as either host or network A host route specifies a path to a particular destination node based on the complete destination node s IP address A network route specifies a path to a destination node based only on the network portion of the destination node s IP address That is a network route specifies a path to an entire destination network rather than to a particular node in the network Direct routes provide a mapping between a destination address and a Network Interface NI They are added during NI initialization When an NI is added into the system see section 4 11 6 pNA adds a direct route for that NI If the network is a point to point network a pNA node is connected to a single node see section 4 11 5 and the route is a host route Otherwise it is a network route pSOSystem System Concepts 4 17 Chapter 4 Network Programming Indirect routes provide a mapping between a destination address and a gateway address Unlike direct routes indirect routes are not created automatically by the pNA component Indirect routes are created explicitly either by entries in the pNA Configuration Table or by using the pNA system call ioctl The pNA component supports one final routing mechanism a default gateway which can be specified in the pNA configuration table The default gateway specifies the address to which all packets are forwarded when no other route for the packet can be found In fact in most pNA
133. ed list Each message block triplet contains a contiguous block of memory defining part of a message A complete message is formed by linking such message block triplets in a singly linked list Each message block triplet contains a Message Block a Data Block and a Buffer Figure 4 3 illustrates the message block triplet Message Block Bm Next Message mblk_t Data Block dblk_t Data Buffer Figure 4 3 Message Block Triplet A message block contains the characteristics of the partial message defined by the message block triplet A data block contains the characteristics of the buffer to which it points A buffer is a contiguous block of memory containing data A data block may be contained in several message block triplets However there is a one to one correspondence between data blocks and buffers The C language definitions of the data structures for message blocks and data blocks are in the header file lt pna h gt Figure 4 4 on page 4 33 illustrates a complete message formed by a linked list of message block triplets pSOSystem System Concepts Message Block 1 Chapter 4 Network Programming Message Block 2 Message Block 3 Figure 4 4 Message Block Linkage pSOSystem System Concepts b_cont B b_cont __ b_rptr b_rptr mblk_t mblk_
134. eferred dispatching is necessary because the ISR must be allowed to complete The pSOS kernel allows an ISR to make any of the synchronization sourcing system calls including q_send q_urgent and q_broadcast to post messages to message queues Sm_v to return a semaphore and ev_send to send events to tasks A typical system implementation for example can use a message queue for this ISR to task communication A task requests and waits for a message at the queue An ISR sends a message to the queue thereby unblocking the task and making it ready to run The ISR then exits using the I_RETURN entry into the pSOS kernel Among other things I RETURN causes the pSOS kernel to dispatch to run the highest priority task which can be the interrupted running task or the task just awakened by the ISR The message as usual can be used to carry data or pointers to data or for synchronization pSOSystem System Concepts 2 37 Chapter 2 pSOS Real Time Kernel 2 12 3 2 38 In some applications an ISR might additionally have the need to dequeue messages from a message queue For example a message queue might be used to hold a chain of commands Tasks needing service will send command messages to the queue When an ISR finishes one command it checks to see if the command chain is now empty If not then it will dequeue the next command in the chain and start it To support this type of implementation the pSOS kernel allows an ISR to make
135. ence a message queue totally eliminates the need to search for its control structure A QCB is allocated to a message queue when it is created and reclaimed for re use when it is deleted This structure contains the queue s name and ID wait queueing method and message queue length and limit Memory considerations for Q CBs are given in the Memory Usage section of the pSOSystem Programmer s Reference pSOSystem System Concepts 2 23 Chapter 2 pSOS Real Time Kernel 2 7 2 2 7 3 2 24 Queue Operations A queue usually has two types of users sources and sinks A source posts messages and can be a task or an ISR A sink consumes messages and can be another task or with certain restrictions an ISR There are three different ways to post a message q_send q_urgent and q_broadcast When a message arrives at a queue and there is no task waiting it is copied into a message buffer taken from either the shared or if it has one the queue s private free buffer pool The message buffer is then entered into the message queue A q_send call puts a message at the end of the message queue q_urgent inserts a message at the front of the message queue When a message arrives at a queue and there are one or more tasks already waiting there then the message will be given to the first task in the wait queue No message buffer will be used That task then leaves the queue and becomes ready to run The q_broadcast sy
136. eoradi e a shan ves A 7 18 7 11 2 I O Transaction Sequencing eeeessesseesesesererrerererrerereses 7 20 7 11 3 Logical to Physical Block Translation 0 cceee eens 7 20 7 11 3 1 pHILE Format Volumes 7 20 7 11 3 2 MS DOS Floppy Disk Format seere 7 21 7 11 3 3 Partitioned Hard Disk Format Standard MS DOS cccceececec eee eeeeeeeneeeees 7 22 7 11 4 MS DOS Hard Drive Considerations Sector Size and Partition S sorio eei se se e eE EE Len es dei dda stones EET O 7 23 Index pSOSystem System Concepts xi Contents pSOSystem System Concepts About This Manual Purpose This manual is part of a documentation set that describes pSOSystem the modular high performance real time operating system environment from Integrated Systems This manual provides theoretical information about the operation of the pSOSystem environment Read this manual to gain a conceptual understanding of pSOSystem and to understand how the various software components in pSOSystem can be combined to create an environment suited to your particular needs More detailed technical information on pSOSystem can be found in the other manuals of the pSOSystem basic documentation set which include the pSOSystem Installation Guide pSOSystem Getting Started pSOSystem System Calls the pSOSystem Programmer s Reference and the pROBE User s Manual Audience This manual is targeted primarily for embedded application developers who want
137. er s Guide describes how to use the Integrated Systems Point to Point Protocol PPP driver SNMP User s Manual describes the internal structure and operation of pSOSystem SNMP Simple Network Management Protocol product This manual also describes how to install and use the SNMP MIB Management Information Base Compiler TCP IP for OpEN User s Guide describes how to use the pSOSystem Streams based TCP IP for OpEN product X 25 User s Guide describes the interfaces provided by the X 25 for OpEN multiplexing driver that implements the packet level protocol defined by the CCITT Other manuals also accompany your host system development tool kit Refer to the pSOSystem Release Notes for a complete listing pSOSystem System Concepts XV About This Manual Notation Conventions The following notation conventions are used in this manual Function names q_receive filenames pdefs h keywords int and operators that must be typed exactly as shown are presented in bold m Italics indicate that a user defined value or name drive pathname can be substituted for the italicized word s shown Italics also indicate emphasis such as when important terms are introduced m Keynames Enter are shown within square brackets Keynames separated by hyphens are typed together For example to type Ctrl Shift E hold down the Ctrl and Shift keys and type the letter E m Code examples are shown in constant width m Hex
138. erein aana ode A ATE NARAN EAS 2 30 2 8 2 Events Versus Messages sssssssessrrrsrereerereerereressereeee 2 30 DEMAPHOLES oignon Ne aienea sead a ie pa E A ANa LE aR 2 31 2 9 1 The Semaphore Control BlocK sesssessesseessresessrsererereeses 2 31 2 9 2 Semaphore OperationS ssssssssssssssrsresresereoreresrseesesee 2 32 pSOSystem System Concepts Contents 2 10 Asynchronous Signals sasssa aena a n i 2 32 RIAT THE ASR heroini i O AT O OO E 2 33 2 10 2 Asynchronous Signal Operations sssssssesesessssesesesssere 2 33 2 10 3 Signals Versus Events veridi iir a AE AR A 2 34 2T Time Management noaea a e a a e aa a a a aaa TA 2 34 2 045 1 The Time Unike AA E RA 2 35 ZT Time and Date nissen e a e A A A AAE 2 35 2 IE Se TIME OUUS aE E EEEE E AEA N A SERA 2 35 2 11 4 Absolute Versus Relative Timing 0 cece eee eee eee ee 2 36 2 11 5 Wakeups Versus Alarms ccceeeeeee eee ee eee eeeeeseneenen ones 2 36 2 116 Times hce aone e tents int arias she ENEO ANENE E 2 37 2 12 Interrupt Service ROUtINES coe decenta iniiae a aa E 2 37 2 12 1 Interrupt EN S e ie a sak e a e e e E A aa 2 38 2 12 2 Synchronizing With Tasks esssssesesesssseseseresesesseseseses 2 38 2 12 3 System Calls Allowed From an ISR ssssssssesesesssesessssesese 2 39 2 13 Fatal Errors and the Shutdown Procedure eeseeeesseeeeeesrerrerereses 2 40 2 14 Tasks Using Other Components sessssesseessrsseesersr
139. ererrere 5 11 5 3 2 Volume Names and Device Numbers eeccscesererrererercree 5 11 5 3 3 Local Volumes CD ROM MS DOS and pHILE Format Vol umes5 13 p34 NES Volumes ercren i rra A A E 5 13 Files Directories and Pathnames seesssessesserssseerererreresererereseese 5 15 5 4 1 Naming Files on pHILE Format Volumes 0 005 5 18 5 4 2 Naming Files on MS DOS Volumes sssssesssesererssressresese 5 18 5 4 3 Naming Files on NFS Volumes sssssssssesessrseseresssessesesere 5 19 5 4 4 Naming Files on CD ROM Volumes ssssssssseseresssresesssees 5 19 Basic Services for All VOLUMES cece eeeeeeceecee eee eeeeeeeeeneceeeeeens 5 19 5 5 1 Opening and Closing Files eee ees eeeeeeeeeeeneeees 5 19 5 5 2 Reading And Writing seein ine a ai 5 21 5 5 3 Positioning Within Files 00 0 cece eeeee eee eeeeeeeeees 5 22 5 5 4 Creating Files and Directories cece eee ee eee ee eee eees 5 23 5 5 5 Changing Directories 2 0 0 cee cee scence ee E E S 5 23 5 5 6 Moving and Renaming Files cee eeeeeeeee eee eeeeeeeeees 5 23 5 0 7 Deleting Piles tics niesieni e cede e ds cleanest EE E iE E 5 24 pSOSystem System Concepts Contents 5 6 Special Services for Local Volume TypeS ceeeeeceeeeeeeeeeeeeeees 5 24 DOA Setii OPEN Daini e hs ANE hana near E 5 24 5 6 2 Direct Volume Ovriciscasaccecicceaiede ss E E E AE Aaa 5 25 5 6 3 Blocking Deblocking asnrieneninioi oia
140. ernal implementation issues that are relevant only for local volumes that is not NFS volumes Understanding the material in these sections can help you improve the performance of your system get fn open_fn Each time a file is opened the pathname must be parsed and the directories searched If the pathname traverses many levels of the directory tree or if any directory in the path contains a large numbers of files then a directory search can be time consuming Most applications open files infrequently and the directory search time in such cases is unimportant However if the same file must be frequently opened and closed the parsing and searching overhead can be substantial On pHILE CD ROM and MS_DOS formatted volumes an alternate method of opening a file open_fn bypasses all parsing and directory searching Rather than providing a pathname the calling task can provide the file number The get_fn call is used to obtain the file number get_fn accepts a pathname as input and returns the file number of the corresponding file get_fn followed by an open_fn is functionally equivalent to an open_f call If the file is to be opened many times it is more efficient to call get_fn once and then use open_fn whenever the file must be opened A second and less obvious advantage of get_fn and open_fn involves reusing pathnames Often a pathname must be saved so a file can be reopened later If a file is deeply nested i
141. ernel the arrival of a clock tick it is normally called from the real time clock ISR on each timer interrupt The frequency of tm_tick determines the granularity of the system time base Obviously the higher the frequency the higher the time resolution for timeouts etc On the other hand processing each clock tick takes a small amount of system overhead You can specify this clock tick frequency in the pSOS Configuration Table as kc_ticks2sec For example if this value is specified as 100 the system time manager will interpret 100 tm_tick system calls to be one second real time Time and Date The pSOS kernel maintains true calendar time and date including perpetual leap year compensation Two pSOS system calls tm_set and tm_get allow you to set and obtain the date and time of day Time resolution is accurate to system time ticks No elapsed tick counter is included because this can be easily maintained by your own code For example your real time clock ISR can in addition to calling tm_tick on each clock interrupt increment a 32 bit global counter variable Timeouts Implicitly the pSOS kernel uses the time manager to provide a timeout facility to other system calls e g q_receive q_vreceive ev_receive sm_p and rn_getseg The pSOS kernel uses a proprietary timing structure and algorithm which in addition to being efficient guarantees constant time operations Both task entry into and removal from the timeo
142. ernel automatically reclaims the segment and returns it to Region 0 Like any memory region your application can make rn_getseg and rn_retseg system calls to Region O to dynamically allocate and return variable sized memory segments Region 0 by default queues any tasks waiting there for segment allocation by FIFO order Allocation Algorithm The pSOS kernel takes a piece at the beginning of the input memory area to use as the region s control block RNCB The size of the RNCB varies depending on the region size and its unit_size parameter described below A formula giving the size of an RNCB is given in the Memory Usage section of the pSOSystem Programmer s Reference Each memory region has a unit_size parameter specified as an input to rn_create This region specific parameter is the region s smallest unit of allocation This unit must be a power of 2 but greater than or equal to 16 bytes Any segment allocated by rn_getseg is always a size equal to the nearest multiple of unit_size For example if a region s unit_size is 32 bytes and an rn_getseg call requests 130 bytes then a segment with 5 units or 160 bytes will be allocated A region s length cannot be greater than 32 767 times the unit_size of the region pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel The unit_size specification has a significant impact on 1 the efficiency of the allocation algorithm and 2 the size of the region s RNCB
143. ers and or pSOS application code Each service call returns zero if the operation is successful or an error code if an error occurred A few of the error codes are returned by pSOS and these codes are defined in lt psos h gt Error codes returned by Integrated Systems drivers are defined in lt drv_intf h gt Error codes from other drivers of course are not defined by Integrated Systems pSOSystem System Concepts 7 5 Chapter 7 I O System 7 4 7 6 With the following exceptions error codes are driver specific m Ifthe entry in the I O Switch Table called by the pSOS kernel is 1 then the pSOS kernel returns a value of ERR_NODR indicating that the driver with the requested major number is not configured a If an illegal major device number is input the pSOS kernel returns ERR_IODN Note that although the pSOS kernel does not define all of them error codes below 0x10000 are reserved for use by pSOSystem components and should not be used by the drivers Finally note that if a switch table entry is null the pSOS kernel returns 0 pSOS Kemel to Driver Interface The pSOS kernel calls a device driver using the following syntax xxxxFunction struct ioparms xxxxFunction is the driver entry point for the corresponding service called by the application By convention Function is the service name while xxxx identifies the driver being called For example a console driver might consist of six functions called
144. ers or stdio streams as a translation source or destination I O streams are managed by pREPC Streams may refer to pHILE managed files or directly to devices The pHILE component accesses remote NFS files by using network RPCs utilizing both the pRPC subcomponent and the pNA component In addition to the communication paths shown on the diagram the pRPC subcomponent also relies on pREPC for support of standard dynamic memory allocation Consequently XDR memory allocation within the pRPC subcomponent uses the same policy when insufficient memory is available as is used by applications that use the pREPC ANSI standard interface directly The pRPC subcomponent uses services provided directly by the pREPC and PNA components Installation of those components is prerequisite to the use of the pRPC subcomponent The pHILE component is only required if the ability to store XDR encoded data on local or remote disk files is desired The pRPC subcomponent must be installed in any system that will use the pHILE component for NFS regardless of whether custom RPC XDR code will be used or not This is necessary because NFS is implemented using RPC XDR XDR is useful in conjunction with NFS for sharing raw data files between hosts that use different native representations of that data Using XDR to write data files guarantees they can be correctly read by all hosts NFS has no knowledge of file contents or structure so it cannot perform any
145. esident target queue If the q_send call is successful then the pSOS m kernel uses the packet buffer it received in Step 5 to build a reply packet and calls KI to send the packet to the source node pSOSystem System Concepts 3 7 Chapter 3 pSOS Multiprocessing Kernel 3 8 7 If the KI delivers the reply packet successfully the pSOS m kernel simply executes a normal dispatch to return to the user s application 8 Back on the source node its KI senses an incoming packet typically from an ISR and calls the pSOS m Announce Packet entry 9 When the KI ISR exits the pSOS m kernel calls the KI to receive the packet deciphers its contents recognizes that it is a normal conclusion of an RSC returns the packet buffer unblocks the calling task and executes a normal dispatch to return to the application This example shows a completely normal operation If there is any error or abnormal condition at any level the results may vary from a system shutdown to an error code being returned to the caller Certain pSOS m system calls are not supported as RSCs Most of these are excluded because they can never be RSCs for instance calls that can only be self directed at the calling task for example t_mode ev_receive and tm_wkafter tm_set and tm_get are not supported because they affect resources in this case time that are otherwise strictly local resources Some calls are excluded because their implementation as RSCs wo
146. esponding file number which is indexed With this file number the pHILE file system manager accesses a file descriptor and uses its content to perform the necessary operations on the file You normally do not use the file number externally as a file ID A call such as create_f for example returns an external file ID not the internal proprietary file number However file numbers are used in the get_fn read_dir and open_fn system calls pSOSystem System Concepts 5 35 Chapter 5 pHILE File System Manager 5 36 5 7 2 2 The File Descriptor Each file descriptor is 128 bytes and contains the following information m The logical file size in bytes m The physical file size in blocks m The file type directory or ordinary system or data m The time of last modification m The file s expansion unit m The file s extent map 5 7 2 3 File Types There are two type attributes associated with a file A file may be an ordinary or a directory file and it may be a system file or a data file Ordinary and directory files were discussed above System files are created by the pHILE file system manager when a volume is initialized There are three system files per volume BITMAP SYS The volume s bitmap FLIST SYS The volume s FLIST The volume s root directory Because system files contain vital data structures they are protected against user removal and modification Reading however is allowed 5 7 2 4 Time of
147. eu E TE TAIANA AAA AA A a 6 8 6 4 Memory Allocation aa E E ARAK TREA 6 9 6 5 Error Handling eres meni nat ee eraen siea iaaa a ae EE Ea aE aaa 6 9 6 6 Restarting Tasks That Use the pREPC Library sssssssssesesesseses 6 10 6 7 Deleting Tasks That Use the pREPC Library essssesesessesesesseses 6 10 6 8 Deleting Tasks With exit or abort eesssesesssesssresssesersrsererereresee 6 11 7 VO System 7 1 T O2SY StL OVETVIEW merere ir E a E a eed conten E steeds 7 2 7 2 T OsSwiteh Tables sissies a e a bite c cdatieds Ghseds aide dtapitaeade sedeua ven 7 3 7 3 Application to pSOS Interface iirin iiA E 7 5 7 4 pSOS Kernel to Driver Interface 2 0 0 eee ceeeeeeeeeeeeeeeeeeneeeeneens 7 6 7 5 Device Driver Execution Environment cccceccececcec enc eeeeneeeenees 7 8 7 6 Device Auto Initialization seseeseesessesseeseesesserorsessesseesereeseeses 7 10 Til Mutual Exclusioniisioacciesis stat acacia da asada neta estes cai ea E MO Es 7 12 TB NTO MOEIS awcsvsevaceinectitce eke vas 6s oa dais ST le adn Pe vbr EEA 7 13 RBA Synchronous Ove sels ewe cd aies eine e E se 7 13 7 9 2 Asynchronous I O ati r e eae davon dbcgdadasdaes dogs 7 14 CY IPREPCFDrIVET S aain ails oaa E EAEE ETE a EINES 7 16 pSOSystem System Concepts Contents 710 LOAGER DIVERS eiriaa oiii otis vais aed Gace N Sucdesdandevdasasvess 7 17 Gell P PHILEF Drivers si scccdesedauddedaedders canker TANER O E EEES 7 18 7 111 The Buffer Header m
148. eue local queue sm_p Acquire a semaphore no wait and local semaphore sm_v Return a semaphore local semaphore t_getreg Get a task s software register local task t_resume Resume a suspended task local task t_setreg Set a task s software register local task tm_get Get time and date tm_set Set time and date tm_tick Announce a clock tick to the pSOS kernel As noted earlier because an ISR cannot block a q_receive q_vreceive or sm_p call from an ISR must use the no wait i e unconditional return option Also because remote service calls block the above services can only be called from an ISR if the referenced object is local All other pSOS system calls are either not meaningful in the context of an ISR or can be functionally served by another system call Making calls not listed above from an ISR will lead to dangerous race conditions and unpredictable results 2 13 Fatal Erors and the Shutdown Procedure Most error conditions resulting from system calls for example parametric and temporary resource exhaustion errors are non fatal These are reported back to the caller A few error conditions prevent continued operation This class of errors known as fatal errors include startup configuration defects internal resource exhaustion conditions and various other non recoverable conditions In addition your application software can at any time generate a fatal error by making the system call k_fatal
149. eue control block 2 25 queues operations 2 25 R raw sockets 4 9 ready task state 2 6 receiving a message 2 26 receiving an event 2 30 Region 0 2 21 region control block 2 22 region manager 2 22 regions 2 20 rejoin latency requirements 3 16 pSOSystem System Concepts remote service calls 3 6 restarting nodes 3 14 RNCB 2 22 root block 5 6 roundrobin criteria for disabling 2 11 roundrobin bit 2 10 roundrobin scheduling automatic 2 10 manual 2 12 routes 4 17 direct 4 17 host 4 17 indirect 4 17 network 4 17 routing facilities 4 17 RPC library 1 2 RSC 3 6 RSC overhead 3 11 running task state 2 6 S SCB 4 14 scheduling 2 9 modification of 2 16 segments 2 21 semaphore control block 2 31 semaphores 2 31 operations 2 31 2 32 sending a message 2 25 sending an event 2 30 sequence numbers 3 15 server 4 10 pSOSystem System Concepts Index shutdown global 3 16 shutdown procedure 2 41 signal handler 4 16 signals 4 16 signals versus events 2 34 slave node 3 2 SMCB 2 31 SNMP 4 43 agents 4 51 socket control blocks 4 14 socket descriptor 4 9 socket layer 4 3 4 7 sockets 4 8 addresses 4 9 connection 4 10 connectionless 4 12 creation 4 9 data structures 4 14 data transfer 4 11 datagram 4 8 foreign 4 11 local 4 11 non blocking 4 13 options 4 13 out of band data 4 13 raw 4 9 socket extensions 4 39 stream 4 8 termination 4 12 s port 3 17 stale IDs 3 15 state transitions 2 6 stdin stdout stderr
150. evelopment They include m Partitioning of actions into multiple tasks each capable of executing in parallel overlapping with other tasks the pSOS kernel switches on cue between tasks thus enabling applications to act asynchronously in response to the outside world m Task prioritization The pSOS kernel always executes the highest priority task that can run m Task preemption If an action is in progress and a higher priority external event occurs the event s associated action takes over immediately m Powerful race free synchronization mechanisms available to applications which include message queues semaphores multiple wait events and asynchronous signals m Timing functions such as wakeup alarm timers and timeouts for servicing cyclical external events 2 2 1 Conceptofa Task From the system s perspective a task is the smallest unit of execution that can compete on its own for system resources A task lives in a virtual insulated environment furnished by the pSOS kernel Within this space a task can use system resources or wait for them to become available if necessary without explicit concern for other tasks Resources include the CPU I O devices memory space and so on Conceptually a task can execute concurrently with and independent of other tasks The pSOS kernel simply switches between different tasks on cue The cues come by way of system calls to the pSOS kernel For example a system cal
151. f the user provided signal handler is provided in the pNA Configuration Table entry NC_SIGNAL When called by the pNA component the handler receives as input the signal type i e the reason the handler is being called the socket descriptor of the affected socket and the TID of the task that owns the affected socket When a socket is first created it has no owner it must be assigned one using the ioctl system call It is up to the user to decide how to handle the signal For example the handler can call the pSOS as_send system call to modify the execution path of the owner A user signal handler is not required The user can choose to ignore signals generated by the pNA component by setting NC_SIGNAL equal to zero In addition if the socket has no owner the signals are dropped The signals are provided to the user so that the application can respond to these unpredictable conditions if it chooses to do so The following is a list of the signals that can be generated by the pNA component SIGIO 0x40000000 I O activity on the socket SIGPIPE 0x20000000 Connection has been disconnected SIGURG 0x10000000 Urgent data has been received SIGINTF 0x08000000 Change in interface status occurred The socket descriptor is replaced by the interface number and the TID is set to O The description of NC_SIGNAL in the Configuration Tables section of the pSOSystem Programmer s Reference describes the calling conventions use
152. ferred to runtime By analogy the pSOS kernel treats objects like files A file is created by name But to avoid searching read and write operations use the file s ID returned by create or open Thus t_create is analogous to File_Create and t_ident to File Open As noted above an object s name can be any 32 bit integer However it is customary to use four character ASCII names because ASCII names are more easily remembered and pSOSystem debug tools will display an object name in ASCII if possible 2 4 Task Management In general task management provides dynamic creation and deletion of tasks and control over task attributes The available system calls in this group are t_create Create a new task t_ident Get the ID of a task t_start Start a new task t_restart Restart a task t_delete Delete a task t_suspend Suspend a task pSOSystem System Concepts 2 13 Chapter 2 pSOS Real Time Kernel 2 4 1 t_resume Resume a suspended task t_setpri Change a task s priority t_mode Change calling task s mode bits t_setreg Set a task s notepad register t_getreg Get a task s notepad register Creation ofa Task Task creation refers to two operations The first is the actual creation of the task by the t_create call The second is making the task ready to run by the t_start call These two calls work in conjunction so the pSOS kernel can schedule the task for execution and allow the task to compete for other system
153. g fields ipAdEntAddr ipAdEntlflndex ipAdEntNetMask ipAdEntBcastAddr ipAdEntReasmMaxSize Accessing Simple Variables All MIB II objects regardless of type are accessed by using the pNA ioctl int s int command int arg system call The parameter S can be any valid socket descriptor The command argument specifies an MIB II object and the operation to be performed on that object Per the SNMP standard two operations are allowed You can set the value of an MIB II object Set command or retrieve an object s value Get command A valid command parameter is an uppercase string equal to the name of a MIB II object prepended by either SIOCG or SIOCS for Get and Set operations respectively A complete list of permissible commands is provided in the ioctl call description in pSOSystem System Calls The way ioctl is used differs depending on whether you are accessing simple variables or tables For simple variables arg is a pointer to a variable used either to input a value for Set operations or receive a value for Get operations arg must be typecast based on the MIB II object type pSOSystem System Concepts Chapter 4 Network Programming The following table shows the C language types used by the pNA component to represent different types of MIB II objects MIB II Object Type pNA Representation INTEGER long OBJ ECT IDENTIFIER char as an ASCII string IpAddress struct in_addr defined in pna h Counter
154. gion 0O The pSOS kernel requires at least one region in order to function This special region s name is RN 0 and its id is zero 0 The start address and length of this region are specified in the pSOS Configuration Table During pSOS startup the pSOS kernel first carves a Data Segment from the beginning of Region O for its own data area and control pSOSystem System Concepts 2 19 Chapter 2 pSOS Real Time Kernel 2 5 3 2 20 structures such as TCBs etc A formula to calculate the exact size of this pSOS Data Segment is given in the Memory Usage section of the pSOSystem Programmer s Reference manual The remaining block of Region O is used for task stacks as well as any user rn_getseg calls The pSOS kernel pre allocates memory for its own use That is after startup the pSOS kernel makes no dynamic demands for memory However when the t_create system call is used to create a new task the pSOS kernel will internally generate an rn_getseg call to obtain a segment from Region O to use as the task s stack or stacks in the case of certain processors Similarly when q_vcreate is used to create a variable length message queue the pSOS kernel allocates a segment from Region O to store messages pending at the queue Note that the pSOS kernel keeps track of each task s stack segment and each variable length message queue s message storage segment When a task or variable length queue is deleted the pSOS k
155. hapter 4 Network Programming 4 14 3 4 15 4 38 configured in the system In most cases it is sufficient to configure the total number of message blocks to be twice the total number of buffers configured in the system Tuning the pNA Component The pNA component also provides statistics for buffer and message block usage via the ioctI service call The SIOCGDBSTAT command can be used to return buffer usage and SIOCGMBSTAT can be used to get message block usage These commands provide information on the number of times tasks waited for a buffer the number of times a buffer was unavailable the number of free buffers and the total number of buffers configured in the system You can use this information to tweak the message block and data buffer configuration Zero Copy Options Copying data is an expensive operation in any networking system Hence eliminating it is critical to optimal performance The pNA component performs data copy at its two interfaces It copies data from the user buffer to pNA internal buffers during send sendto and sendmsg service calls and vice versa during recv recvfrom and recvmsg calls A data copy is performed between the NI and pNA buffers when data is exchanged Because the pNA memory manager is highly optimized to eliminate data copy data is copied only at the interfaces during data transfers In order to maximize performance the pNA component provides options to elimina
156. he following code segment illustrates how to add delete or modify routing entries stored in the pNA internal routing table define satosin sa struct sockaddr_in sa int s rc struct rtentry rte bzero char amp rte sizeof rte create any type of socket s socket AF_INET SOCK_DGRAM 0 add a host route to 192 0 0 1 through gateway 128 0 0 1 satosin amp rte rt_dst gt sin_family AF_INET satosin amp rte rt_dst gt sin_addr s_addr htonl 0xc0000001 satosin amp rte rt_gateway gt sin_family AF_INET satosin amp rte rt_gateway gt sin_addr s_addr htonl1 0x80000001 rte rt_flags RTF_HOST RTF_GATEWAY re ioctl s SIOCADDRT char amp rte add a route to the network 192 0 0 0 through gateway 128 0 0 1 pNA uses the class C network mask 255 255 255 0 associated with the network 192 0 0 0 satosin amp rte rt_dst gt sin_family AF_INET satosin amp rte rt_dst gt sin_addr s_addr htonl 0xc0000001 satosin amp rte rt_gateway gt sin_family AF_INET satosin amp rte rt_gateway gt sin_addr s_addr htonl1 0x80000001 rte rt_flags RTF_GATEWAY re ioctl s SIOCADDRT char amp rte add a route to the sub network 128 10 10 0 through gateway 23 0 0 1 The sub network mask is 255 255 255 0 pSOSystem System Concepts 4 19 Chapter 4 Network Programming satosin amp rte rt_dst gt s
157. hich are performed by you The following definitions describe the entire formatting process 1 Physical format or Low level format A physical format puts markings on the storage medium typically a magnetic surface that delineate basic storage units usually sectors or blocks On hard disks physical formatting is purely a hardware operation and is almost always done at the factory Instructions for physically formatting hard disks are not provided in this manual On floppy disks you normally perform the physical formatting Instructions for doing this are provided below Physical formatting very rarely needs to be redone If it is redone it destroys all data on the disk 2 Partitioning Hard Disks Only A hard disk can be divided into one or more partitions which are separate physical sections of the disk Each partition is treated as a logically distinct unit that must be separately formatted and mounted Each partition can contain only one volume The partitions on a disk can contain volumes of different types That is some partitions can contain MS DOS volumes while others contain pHILE volumes You are responsible for executing the commands that partition the hard disk When a hard disk is divided into partitions a partition table is also written on the disk The partition table is located in pSOSystem System Concepts 5 5 Chapter 5 pHILE File System Manager the first sector of the disk and provides the address of e
158. iable length message queues These services are as follows q_vcreate Create a variable length message queue q_vident Get the ID of a variable length message queue q_vdelete Delete a variable length message queue q_vreceive Get or wait for message from a variable length message queue q_vsend Post a message at end of a variable length message queue q_vurgent Put a message at head of a variable length message queue q_vbroadcast Broadcast a message to a variable length message queue A variable length queue is created with the q_vcreate service call In addition to name and flags the caller provides two additional input parameters The first specifies the queue s maximum message length A message of any length up to this maximum can be sent to the queue Any attempt to send a message larger than a queue s maximum message pSOSystem System Concepts 2 27 Chapter 2 pSOS Real Time Kernel 2 8 2 28 length results in an error The second parameter specifies the queue s maximum message queue length This is the maximum number of messages that can be waiting at the queue simultaneously Unlike ordinary queues which use buffers from the system wide buffer pool for message storage variable length queues always store messages in buffers that are allocated from region O when the queue is created These buffers are then available for the exclusive use of the queue They are never shared with other queues and they are only returned to
159. ice However the pHILE file system manager keeps track of the length of a file in bytes Unless the length of a file is an exact multiple of the block size the last block of the file will be partially used There are therefore two sizes associated with every file a logical size and a physical size The logical size of a file is the number of data bytes within the file that you can access This size automatically increases whenever data is appended to the file but never decreases The physical size of a file corresponds to the number of blocks currently allocated to the file Thus the logical and physical sizes of a file are generally different unless a file s logical size happens to exactly fill the number of physical blocks allocated to the file As with its logical size a file s physical size never decreases except when it is deleted or truncated to less than the physical size System Calls Unique to pHILE Format This section discusses those services available after you create a pHILE format volume These services are not available with any other file system format 5 7 7 1 annex f write_f operations will automatically add new blocks to a file as required but the blocks added often are not contiguous This situation can be partially controlled on pHILE format volumes by using a larger file expansion unit For even more efficient contiguous grouping the annex _f function may be used to manually allocate or expand a file
160. ied in the system call The buffer cache will be bypassed The following example illustrates how the pHILE file system manager utilizes the buffer cache The pHILE file system manager receives a write_f request for a sequence of bytes that covers 6 blocks as follows see Figure 5 3 on page 5 28 m The operation starts in middle of block 24 which is not in a cache A cache buffer is obtained and block 24 is read into it via a physical read operation Then the respective bytes are copied from the user buffer into the cache buffer m Blocks 25 and 26 are not in a cache Because they are contiguous a single physical write operation is used to write the bytes from the user buffer to blocks on the volume m Block 27 is in a cache buffer so bytes are transferred to it overwriting its old data m Block 28 is not in a cache so a physical write operation is used to write the bytes to the block on the volume pSOSystem System Concepts 5 27 Chapter 5 pHILE File System Manager 5 6 5 5 28 m Block 29 is in a cache buffer so the respective bytes are copied into it Physic al Block 24 25 26 27 28 29 30 In Cache No No No Yes No Yes Figure 5 3 Blocking Factorsand Cache Buffering Synchronization Modes Because of the buffer cache a pHILE or MS DOS format volume might not always contain the most recent data The data in a cache buffer might have been modified but not written to disk If a hardware failure occurs bef
161. ief overview of sockets and how they are used pSOSystem System Concepts 4 7 Chapter 4 Network Programming 4 4 1 4 8 Network 100 100 0 0 3 100 0 0 4 Node A Node B Node C 90 0 0 1 90 0 0 2 Network 90 Figure 4 2 A Sample Intemet Basics A socketis an endpoint of communication It is the basic building block for communication Tasks communicate by sending and receiving data through sockets Sockets are typed according to the characteristics of the communication they support The pNA component provides three types of sockets supporting three different types of service m Stream sockets use the Transmission Control Protocol TCP and provide a connection based communication service Before data is transmitted between stream sockets a connection is established between them m Datagram sockets use the User Datagram Protocol UDP and provide a connectionless communication service Datagram sockets allow tasks to exchange data with a minimum of protocol overhead However reliable delivery of data is not guaranteed pSOSystem System Concepts 4 4 2 4 4 3 Chapter 4 Network Programming m Raw sockets provide user level access to the IP ICMP see section 4 16 and IGMP see section 4 17 layers This enables you to implement transport protocols other than TCP UDP over the IP layer They provide connectionless and datagram communication service Socket Creation Sockets are created via the socket sys
162. ight can be used for any application specific purpose The Idle Task At startup the pSOS kernel automatically creates and starts an idle task named IDLE whose sole purpose in life is to soak up CPU time when no other task can run IDLE runs at priority O with a stack allocated from Region O whose size is equal to kc_rootsst On most processors IDLE executes only an infinite loop On some processors pSOS can be configured to call a user defined routine when IDLE is executed This user defined routine can be used for purposes such as power conservation See pSOS and pSOS m Configuration Table Parameters in pSOSystem Getting Started for more details Though simple IDLE is an important task It must not be tampered with via t_delete t_suspend t_setpri or t_mode unless you have provided an equivalent task to fulfill this necessary idling function Storage Allocation pSOS storage management services provide dynamic allocation of both variable size segments and fixed size buffers The system calls are rn_create Create a memory region rn_ident Get the ID of a memory region rn_delete Delete a memory region rn_getseg Allocate a segment from a region pSOSystem System Concepts 2 5 1 2 5 2 Chapter 2 pSOS Real Time Kernel rn_retseg Return a segment to a region pt_create Create a partition of buffers pt_ident Get the ID of a partition pt_delete Delete a partition of buffers pt_getbuf Get a buffer from a parti
163. in_family AF_INET satosin amp rte rt_dst gt sin_addr s_addr htonl 0x800a0a00 satosin amp rte rt_gateway gt sin_family AF_INET satosin amp rte rt_gateway gt sin_addr s_addr htonl 0x17000001 rte rt_netmask hton1 0xffffff00 rte rt_flags RTF_GATEWAY RTF_MASK re ioctl s SIOCADDRT char amp rte modify the above route to go through a different gateway 23 0 0 2 satosin amp rte rt_dst gt sin_family AF_INET satosin amp rte rt_dst gt sin_addr s_addr htonl 0x800a0a00 satosin amp rte rt_gateway gt sin_family AF_INET satosin amp rte rt_gateway gt sin_addr s_addr htonl1 0x17000002 rte rt_netmask htonl OxffffFf00 rte rt_flags RTF_GATEWAY RTF_MASK re ioctl s SIOCMODRT char amp rte delete the route modified above satosin amp rte rt_dst gt sin_family AF_INET satosin amp rte rt_dst gt sin_addr s_addr htonl 0x800a0a00 satosin amp rte rt_gateway gt sin_family AF_INET satosin amp rte rt_gateway gt sin_addr s_addr htonl 0x17000002 rte rt_netmask htonl 0OxffffFf00 rte rt_flags RTF_GATEWAY RTF_MASK re ioctl s SIOCDELRT char amp rte close the socket close s 49 IP Multicast pNA provides level 2 IP multicast capability as defined by RFC 1112 This implies support for sending and receiving IP multicast packets and an implementation of the Internet Group
164. ing then it gets the semaphore and therefore the device In summary a shared device may be protected by bracketing its operations with sm_p and sm_v system calls Where should these calls take place The two possibilities referred to later as Type 1 and Type 2 are as follows 1 sm_p is put at the front of the read and write operation and sm_v at the end 2 sm_p is put in de_open and sm_v in de_close To read or write a task must first open the device When it is finished using the device the device must be closed Type 2 allows a task to own a device across multiple read write operations whereas with Type 1 a task may lose control of the device after each operation In a real time application most devices are not shared and therefore do not require mutual exclusion Even for devices that are shared Type 1 is usually sufficient pSOSystem System Concepts Chapter 7 I O System 7 8 I O Models Two fundamental methods of servicing I O requests are known they are termed synchronous and asynchronous Synchronous I O blocks the calling task until the I O transaction is completed so that the I O overlaps with the execution of other tasks Asynchronous I O does not block the calling task thus allowing I O to overlap with this as well as other tasks The pSOS kernel supports both methods The following sections present models of synchronous and asynchronous device drivers The models are highly simplified
165. ing of file m The end of file m The current position The pHILE file system manager does not allow positioning beyond the end of a file Any attempt to do so results in an error code being returned The position pointer is left unchanged pSOSystem System Concepts 5 5 4 5 5 5 5 5 6 Chapter 5 pHILE File System Manager Creating Files and Directories Because of the differences between ordinary files and directory files separate system calls are provided for creating files and directories The create _f system call is used to create an ordinary file make_dir is used to create directories When an ordinary file is created an entry for it is added to its parent directory Both ordinary and directory files are initially empty When creating an ordinary file on a pHILE format volume you must specify an expansion unit This parameter controls the incremental growth of the file Details on this parameter can be found in section 5 7 2 5 Because of the read only operation of CD ROM volumes the CD ROM file system does not support creation of files and directories Changing Directories The current directory for a task can be set and altered using the change_dir system call change_dir accepts as input a pathname specifying the new directory This pathname can be either an absolute or relative pathname Once the new directory is set all subsequent relative pathnames are interpreted with respect to the new current directo
166. installations a default route is the only routing information ever needed In summary the pNA component uses the following algorithm to determine a packet route 1 The pNA component first looks for a host route using the destination node s complete IP address If one exists and is a direct route the packet is sent directly to the destination node If it is an indirect route the packet is forwarded to the gateway specified in the route 2 If a host route does not exist the pNA component looks for a network route using the network portion of the destination node s IP address If one exists and is a direct route the packet is sent directly to the destination node If it is an indirect route the packet is forwarded to the gateway specified in the route 3 Ifa network route does not exist the pNA component forwards the packet to the default gateway if one has been provided 4 Otherwise the packet is dropped Routes can be configured into the pNA component during initialization The configuration table entry NC_LIROUTE contains a pointer to an Initial Routing Table see the Configuration Tables section of the pSOSystem Programmer s Reference They can also be added or altered dynamically using the pNA system call ioctl For simplicity most systems use a default gateway node A default gateway is specified by the configuration table entry NC_DEFGN pSOSystem System Concepts Chapter 4 Network Programming T
167. internet 4 5 Internet address 4 5 Internet Control Message Protocol 4 40 interrupt service routines 2 37 IOPB parameter block 7 18 IP 4 3 4 5 pSOSystem System Concepts Index IP multicast 4 20 ISR 2 37 2 39 returning from 2 12 ISR to task communication 2 24 job 2 4 K kernel 1 2 2 1 Kernel Interface 3 2 KI 3 2 L LC_BUFSIZ 6 6 LC_TIMEOPT 6 6 LC_WAITOPT 6 6 line buffered 6 7 link field 2 26 loader drivers 7 17 Local Object Table 3 5 local volumes 5 13 5 24 M major device number 7 3 7 5 manual roundrobin scheduling 2 12 master node 3 2 maximum transmission unit 4 24 memory buffers 2 23 I 3 Index dual ported 3 17 heap management algorithm 2 22 partitions 2 23 Region 0 2 21 regions 2 20 segments 2 21 memory management services 2 20 message block triplet 4 32 message blocks 4 32 4 37 message queues 2 24 ordinary 2 26 variable length 2 28 messages 2 26 4 32 broadcasting 2 26 buffers 2 26 contents of 2 26 length 2 28 queue length 2 29 receiving 2 26 sending 2 25 synchronization of 2 27 versus events 2 30 MIB II accessing tables 4 46 object categories 4 43 object types 4 45 tables 4 49 MIB II support 4 43 minor device number 7 5 MPCT 3 2 MS DOS volumes 5 13 5 24 floppy disk format 7 21 hard disk format 7 22 hard drive considerations 7 23 initializing 5 4 naming files on 5 18 MTU 4 24 multicast 4 20 Multiprocessor Configuration Table 3 2 multitasking 2 2 mutual exc
168. l device 3 2 abcd designates a disk file in the current directory When fopen opens a disk file it generates a pHILE open_f system call When it opens an I O device fopen calls the pSOS de_open service Regardless of whether fopen opens an I O device or a disk file it allocates a FILE data structure which is discussed in section 6 3 2 6 3 2 File Data Structure As mentioned in the previous section when a file is opened it is allocated a data structure of type FILE In the pREPC library this is a 32 bit address of a pREPC file structure fopen returns a pointer to this pSOSystem System Concepts 6 5 Chapter 6 pREPC ANSI C Library 6 3 3 6 6 allocated data structure All file operations require the pointer to this structure as an input parameter to identify the file If it is not explicitly given it is implied as in the case of functions which always use the standard input or output device See section 6 3 4 The FILE data structure is used to store control information for the open file Some of the more important members of this structure include the address of the file s buffer the current position in the file an end of file EOF flag and an error flag In addition there is a flag that indicates whether the file is a disk file or an I O device Some of these fields have no meaning for I O devices such as the position indicator Buffers Open files normally have an associated buffer that is used
169. l ev_receive call Response to signals is asynchronous it can happen at any point in the task s execution Note that while this involuntary response behavior is by design it can be modified to some extent by using t_mode to disable i e postpone asynchronous signal processing Time Management Time management provides the following functions Maintain calendar time and date Timeout optional a task that is waiting for messages semaphores events or segments Wake up or send an alarm to a task after a designated interval or at an appointed time Track the running task s timeslice and mechanize roundrobin scheduling These functions depend on periodic timer interrupts and will not work in the absence of a real time clock or timer hardware The explicit time management system calls are tm_tick Inform the pSOS kernel of clock tick arrival tm_set Set time and date tm_get Get time and date tm_wkafter Wakeup task after interval tm_wkwhen Wakeup task at appointed time tm_evafter Send events to task after interval tm_evevery Send events to calling task at periodic intervals pSOSystem System Concepts 2 33 Chapter 2 pSOS Real Time Kernel 2 11 1 2 11 2 2 11 3 2 34 tm_evwhen Send events to task at appointed time tm_cancel Cancel an alarm timer The Time Unit The system time unit is a clock tick defined as the interval between tm_tick system calls This call is used to announce to the pSOS k
170. l might cause the kernel to stop one task in mid stream and continue another from the last stopping point Although each task is a logically separate set of actions it must coordinate and synchronize itself with actions in other tasks or with ISRs by calling pSOS system services pSOSystem System Concepts 2 3 Chapter 2 pSOS Real Time Kernel 2 2 2 2 4 Decomposition Criteria The decomposition of a complex application into a set of tasks and ISRs is a matter of balance and trade offs but one which obviously impacts the degree of parallelism and therefore efficiency that can be achieved Excessive decomposition exacts an inordinate amount of overhead activity required in switching between the virtual environments of different tasks Insufficient decomposition reduces throughput because actions in each task proceed serially whether they need to or not There are no fixed rules for partitioning an application the strategy used depends on the nature of the application First of all if an application involves multiple independent main jobs for example control of N independent robots then each job should have one or more tasks to itself Within each job however the partitioning into multiple cooperating tasks requires much more analysis and experience The following discussion presents a set of reasonably sufficient criteria whereby a job with multiple actions can be divided into separate tasks Note that there are no n
171. le translation on accesses in partition 0 Assuming your driver follows these guidelines prepare and make use of DOS hard drives in the pHILE environment as described in Section 5 2 Formatting and Initializing Disks pSOSystem System Concepts 7 25 Chapter 7 I O System 7 26 pSOSystem System Concepts Index A action 2 4 address broadcast 4 7 external 3 18 internal 3 18 Internet 4 5 address resolution 4 28 Address Resolution Protocol 4 30 addresses hardware 4 25 Agents 3 10 alarms 2 36 ANSI C standard library 1 3 application to pSOS interface 7 5 architecture 1 2 ARP 4 5 4 30 ARP Table 4 29 ASR 2 32 ASR operations 2 34 asynchronous I O 7 14 asynchronous RSC 3 9 asynchronous signals 2 32 pSOSystem System Concepts Index asynchrony 2 5 auto initialization 7 4 7 10 automatic roundrobin scheduling 2 10 binary streams 6 8 blocked task state 2 6 blocking 5 26 boot record 5 6 broadcast address 4 7 broadcasting a message 2 26 buffer header 7 18 buffers 2 23 4 32 128 byte 4 37 zero size 4 37 C CD ROM volumes 5 3 5 13 5 24 naming files on 5 19 client 4 10 client authentication 4 54 clock tick 2 35 coherency checks 3 11 control blocks partition PTCB 2 23 queue QCB 2 25 region RNCB 2 22 semaphore SMCB 2 31 task TCB 2 15 conventions XV creation of message queues 2 24 I 1 Index of partitions 2 23 of regions 2 20 of semaphores 2 31 of tasks 2 14 of varia
172. le is opened for the first time the pHILE file system manager allocates a data structure for it in memory called a file control block FCB The FCB is used by the pHILE file system manager to manage file operations and is initialized with system information retrieved from the volume on which the file resides All subsequent open calls on the file use the same FCB it remains in use until the last connection to the file is closed At that time the FCB is reclaimed for reuse The close_f system call is used to terminate a connection to a file it should be used whenever a file connection is no longer needed At pHILE startup a fixed number of FCBs are created reflecting the maximum number of permissible concurrently open files specified in the pHILE Configuration Table entry fc_nfcb In addition to the FCB the pHILE file system manager uses a system data structure called an open file table to manage open files Every task has its own open file table which is used by the pHILE file system manager to store information about all of the files that have been opened by that task Each entry in an open file table controls one connection to a file The FID mentioned above is actually used to index into a task s Open File Table The size of these open file tables is specified in the pHILE Configuration Table entry fc_ncfile This parameter sets a limit on the number of files which a task can have open at the same time Figure 5 2 on pag
173. les the necessary operations and returns control to the caller For example the send system call copies data from the pSOSystem System Concepts Chapter 4 Network Programming user s buffer to an internal buffer The data might not actually be transmitted until later but control returns to the calling task which continues to run 3 The system call cannot be completed immediately and the caller must wait For example the user might attempt to read data that is not yet available In this case the pNA component blocks the calling task The blocked task is eventually rescheduled by subsequent asynchronous activity As the above indicates the internet protocols are not always synchronous That is not all pNA activities are initiated directly by a call from an application task Rather certain generic processing activities are triggered in response to external events such as incoming packets and timer expirations To handle asynchronous operations the pNA component creates a daemon task called PNAD PNAD is created during pNA initialization It is created with a priority of 255 to assure its prompt execution The priority of PNAD can be lowered with the pSOS t_setpri call However its priority must be higher than the priority of any task calling the pNA component PNAD is normally blocked waiting for one of two events encoded in bits 30 and 31 When PNAD receives either of these two events it is unblocked and preempts
174. lled by the task to be deleted prior to calling t_delete pNA and pHILE components also hold resources that must be returned before a task can be deleted These resources are returned by calling close O and close_f 0 respectively Because the pREPC library calls the pHILE file system manager and the pREPC library calls the pNA component if NFS is in use these services must be called in the correct order Below is a sample code fragment which a task can use to delete itself fclose 0 close pREPC files close_f 0 return pHILE resources close 0 return pNA resources free void 1 return pREPC resources t_delete 0 and commit suicide Obviously close calls to components not in use should be omitted Because only the task to be deleted can make the necessary close calls the simplest way to delete a task is to restart the task and pass arguments requesting self deletion Of course the task being deleted must contain code to handle this condition 6 8 Deleting Tasks With exit orabort The exit and abort calls are implemented in the pREPC library as macros that are defined in the header file prepc h These macros which the user needs to modify depending on which components are present in the system can be used to return all system resources and delete the task pSOSystem System Concepts 6 11 Chapter 6 pREPC ANSI C Library 6 12 pSOSystem System Concepts 7 VO
175. lls respectively The nfsmount_vol system call also has some unique features When mounting an NFS volume you must specify the IP address of an NFS server and the name of a directory on that server which will act as the volume s root directory 5 4 Files Directories and Pathna mes The pHILE file system manager defines two types of files ordinary files and directory files An ordinary file contains user managed data A directory file contains information necessary for accessing ordinary and or other sub directory files under this directory Every volume contains at least one directory file called the ROOT directory From it can emanate a tree structure of directories and ordinary files to an arbitrary depth Of course the ROOT directory might contain only ordinary files yielding a common one level structure Files may not cross over volumes and therefore cannot be larger than the volumes on which they reside Every file is uniquely identified by using a pathname A pathname specifies a path through a directory structure that terminates on a target file or directory Pathnames are either absolute or relative An absolute pathname always begins with a volume name and specifies a complete path through the directory tree leading to a file or directory On local volumes a filenumber can be used to start the complete path at any file or directory on the volume For more information on filenumbers see section 5 7 1 2 In this cas
176. lusion 2 24 7 12 N NC_CFGTAB 4 52 NC_DEFGID 4 42 NC_DEFGN 4 18 NC_DEFUID 4 42 NC_HOSTNAME 4 42 NC_INI 4 27 NC_IROUTE 4 18 NC_NNI 4 26 NC_SIGNAL 4 16 Network Interface 4 4 4 23 network manager 1 2 network mask 4 6 networking facilities 4 1 NFS 4 42 NFS volumes 5 3 5 13 naming files on 5 19 NI 4 4 4 23 flags 4 25 NI Table 4 26 node failure 3 13 node numbers 3 3 node restart 3 14 node roster 3 16 nodes 4 5 4 6 master 3 2 slave 3 2 pSOSystem System Concepts notation conventions XV notepad registers 2 19 O object classes 2 12 Object Create system calls 2 13 object ID 2 13 3 4 Object Ident system calls 2 13 3 5 object name 2 13 objects 3 4 global 3 4 stale 3 15 open socket tables 4 14 out of band data 4 13 P packet type 4 31 packets 4 5 4 17 4 34 partition control block 2 23 partition table 5 5 partitions 2 23 pHILE 5 1 basic services 5 19 blocking and deblocking 5 26 cache buffers 5 26 deleting tasks 5 47 direct volume I O 5 25 drivers 7 18 file types 5 15 formatted volumes 5 13 5 31 NFS services 5 13 pathnames 5 15 restarting tasks 5 46 synchronization modes 5 28 pSOSystem System Concepts Index volume names and device numbers 5 11 volume operations 5 11 volume types 5 2 pHILE driver 7 16 pHILE format volumes 5 13 5 24 7 20 block allocation 5 41 data address mapping 5 39 expansion unit 5 37 extent 5 37 extent map 5 38 file block types 5 34 file descripto
177. ly retrieved from a device pSOSystem System Concepts Chapter 5 pHILE File System Manager When the pHILE file system manager needs to access a logical block it first checks to see if an image of the block is contained in a cache buffer If yes the pHILE file system manager simply works with the cache buffer in memory There is no need for a physical I O operation thus improving performance Buffers in the cache are maintained using a _ least recently used algorithm This means that if the pHILE file system manager needs to use a buffer and they are all in use then the buffer that has been untouched the longest regardless of volume is reused Before reusing a buffer the pHILE file system manager must test to see if the data in the buffer has been modified e g because of a write_f operation If the data has been changed then the pHILE file system manager must call your driver to transfer the buffer s data to the volume before it can be reused If the buffer has not been modified for example the data was only read then the data on the volume is identical to that in the buffer and the buffer can be reused It is worth noting that the pHILE file system manager bypasses the buffer cache if possible to increase performance If a read or write call involves all of the bytes within a block then the pHILE file system manager requests your driver to transfer the data directly between the volume and the user buffer specif
178. m An application interface to provide functions such as open_f and close _f The application interface is provided by the pHILE file system manager m XDR services to put the data in a format that can be generally recognized and Remote Procedure Calls to pass requests for NFS service to a server The pRPC component provides RPC and XDR services m On the transport level a socket interface that observes the User Datagram Protocol and the Internet Protocol to carry the Remote Procedure Calls as UDP IP messages for the server pNA provides a UDP IP transport for communication with a server For the most part you treat remote and local files the same way There are some differences however which you must understand when using NFS volumes 5 14 pSOSystem System Concepts Chapter 5 pHILE File System Manager When an NFS client for example the pHILE file system manager requests services from an NFS server it must identify itself by supplying a user ID group ID and hostname These items are used by the server to accept or reject client requests How these parameters are used depends on the server The hostname is a string of up to 31 characters and must be supplied in the pNA Configuration Table The user ID and group ID are 32 bit numbers Default values for these quantities are supplied in the pNA Configuration Table They may also be examined and set for individual tasks by using the pNA get_id and set_id system ca
179. m Concepts 3 15 Chapter 3 pSOS Multiprocessing Kernel 3 8 2 3 9 3 10 Rejoin Latency Requirements When a node fails considerable activity occurs on every node in the system to ensure that the node is gracefully removed from the system If the node should rejoin too soon after failing certain inter nodal activities by the new instantiation of the node may be mistakenly rejected as relics of the old instantiation of the node To avoid such errors a failed node must not rejoin until all remaining nodes have been notified of the failure and have completed the steps described in section 3 7 In addition there must be no packets remaining in transit in the KI either to or from the failed node or reporting failure of the node or awaiting processing at any node This is usually accomplished by inserting a small delay in the node s initialization code For most systems communicating through shared memory a delay of 1 second should be more than adequate Global Shutdown A global shutdown is a process whereby all nodes stop operating at the same time It can be caused for two reasons 1 A fatal error occurred on the master node 2 A k_fatal call was made with the K_GLOBAL attribute set In this case the node where the call was made notifies the master node In either case the master node then sends every slave node a shutdown packet All nodes then perform the normal pSOS m kernel shutdown procedure The Node Roster
180. m_create accepts as input a_user assigned name an initial count and several characteristics including whether tasks waiting for the semaphore will wait first in first out or by task priority The initial count parameter should reflect the number of available tokens at the semaphore sm_create assigns a unique ID the SMid to each semaphore The number of semaphores in your system is limited by the kc_nsema4 specification in the pSOS Configuration Table A semaphore can be deleted using the sm_delete system call If one or more tasks are waiting there they will be removed from the wait queue and returned to the ready state When they run each task will have returned from its respective sm_p call with an error code Semaphore Deleted The Semaphore Contol Block Like a Qid a semaphore s SMid carries the location of the semaphore control block SMCB even in a multiprocessor configuration This is an important notion because using the SMid to reference a semaphore eliminates completely the need to search for its control structure An SMCB is allocated to a semaphore when it is created and reclaimed for re use when it is deleted This structure contains the semaphore s pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel name and ID the token count and wait queueing method It also contains the head and tail of a doubly linked task wait queue Memory considerations for SMCBs are given in the Memory Usage
181. matic tracking of program execution through source code files Traces and breaks on high level language statements Breaks on task state changes and operating system calls Monitoring of language variables and system level objects such as tasks queues and semaphores Profiling for performance tuning and analysis System and task debug modes The ability to debug optimized code The pROBE debugger in addition to acting as a back end for a high level debugger on the host can function as a standalone target resident debugger that can accompany the final product to provide a field maintenance capability The pROBE debugger and other pSOSystem development tools are described in other manuals See Related Documentation in About This Manual pSOSystem System Concepts 1 5 Chapter 1 Product Overview 1 6 pSOSystem System Concepts 2 pSOS Real Time Kemel 2 1 Overview Discussions in this chapter focus primarily on concepts relevant to a single processor system The pSOS kernel is a real time multitasking operating system kernel As such it acts as a nucleus of supervisory software that m Performs services on demand m Schedules manages and allocates resources m Generally coordinates multiple asynchronous activities The pSOS kernel maintains a highly simplified view of application software irrespective of the application s inner complexities To the pSOS kernel applications consist of three classes of progr
182. mation on hard disk partitions see Section 7 11 3 3 Partitioned Hard Disk Format Standard MS DOS The interpretation of the device number by the pHILE file system manager depends on the type of volume For local volumes the major device number identifies a user supplied device driver associated with the volume When the pHILE file system manager needs to read or write a volume it makes a pSOS I O system call specifying the volume s major device number The pSOS kernel uses the major device number to find the device driver through its I O Switch Table The minor device number is simply passed to the driver Refer to Chapter 7 I O System for a discussion of pSOS I O and pHILE drivers NFS volumes do not have device drivers per se I O requests directed to NFS volumes are routed through the pRPC and pNA components rather than standard pSOS I O mechanisms The volume name is used only to identify the volume while it is mounted The interpretation of the minor device number of local volumes is determined by the device driver A few typical uses are to select the device if the driver controls multiple devices or to select the device operating mode For example the Integrated Systems SCSI hard disk drivers conform with the partition convention above They divide the 16 bit minor device number into two fields the partition number in the most significant 8 bits and the SCSI ID number in the least significant 8 bits A volum
183. megabytes 3 1 2 DQ high density a Optical disks 124 4 megabytes Fuji M2511A OMEM NFS Volumes NFS volumes allow you to access files on remote systems as a Network File System NFS client Files located on an NFS server will be treated exactly as though they were on a local disk Since NFS is a protocol not a file system format you can access pHILE MS DOS or CD ROM format files a CD ROM Volumes These are devices that are formatted and managed according to ISO 9660 CD ROM file system specifications pHILE does not pSOSystem System Concepts 5 3 Chapter 5 pHILE File System Manager 5 2 5 2 1 5 4 support the following CD ROM volume attributes o Multi volume sets o Interleaved files o CD ROMs with logical block size not equal to 2048 o Multi extent files o Files with extended attribute records o Record format files Formatting and Initializing Disks If your pSOSystem application writes data you need to take special care in preparing the data storage medium it uses either hard disk or floppy disks In pHILE you can write data to either MS DOS format volumes or pHILE format volumes The volume type chosen for the application determines the procedure you use to format and initialize the hard disk or floppy disks This section m discusses how to choose the volume type for your application m defines the stages of disk formatting and initialization and m provides instructions for formatti
184. messages at its own pace The second example uses two queues to close the synchronization loop and provide interlocked communication A task that is a message sink to one queue is a message source to the other and vice versa Task A sends a message to queue X and does not continue until it receives a message from queue Y Task B synchronizes itself to the arrival of a message to 2 26 pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel queue X and responds by sending an acknowledgment message to queue Y The result is that tasks A and B interact in an interlocked coroutine like fashion 2 7 5 Variable Length Message Queues Recall that ordinary message queues use fixed length 16 byte messages While 16 bytes is adequate for most purposes in some cases it is convenient to use messages of differing sizes particularly larger messages The pSOS kernel supports a special type of message queue called a variable length message queue A variable length message queue can accept messages of any length up to a maximum specified when the queue is created Internally the pSOS kernel implements variable length message queues as a special type of ordinary queue That is ordinary and variable length message queues are not different objects but rather different forms of the same object Although they are implemented using the same underlying object the pSOS kernel provides a complete family of services to create manage and use var
185. meters The first is the position of the first byte to lock The second is the number of bytes to lock A lock may start and or end beyond both the physical or logical end of a file This allows a lock to anticipate future expansion of a file Thus lock_f can be used to prevent all other connections to the file from m Modifying or appending any data in the locked region of the file and m Reading any data in or being appended to the locked region of the file When a lock is in place the locked region can be accessed only by the task that placed the lock and then only via the file ID with which the lock was placed Each connection to a file may lock only one region of a file at any time If a task needs to lock two different parts of a file simultaneously then it must open the file twice to obtain a second connection via a different file ID If a lock_f call is issued through a connection that has an existing lock then the existing lock is automatically removed and replaced by the new lock This lock replacement takes place as an atomic operation That is the existing lock is removed and the new lock is set in a single operation This precludes in the case that the old and new regions overlap any opportunity for another task to access or even worse lock the overlapped region during the replacement window pSOSystem System Concepts 5 45 Chapter 5 pHILE File System Manager 5 8 5 8 1 5 46 To remove an e
186. n or not The q_send system call is used to enqueue an I O command The q_receive system call is used to dequeue the next I O command The clause cmd empty actually represents the test for queue empty as returned by q_receive Calling t_mode to disable preemption is necessary to prevent a race condition on the flag variable In this example it is not necessary to disable interrupts along with preemption pSOSystem System Concepts 7 15 Chapter 7 I O System 7 9 pREPC Drivers As described in Chapter 6 pREPC ANSI C Library pREPC I O can be directed to either disk files or physical devices Disk file I O is always routed via the pHILE file system manager while device I O goes directly to the pSOS I O Supervisor An I O device driver that is called by the PREPC library directly via the pSOS kernel is called a pREPC driver while a disk driver is called a pHILE driver as illustrated in Figure 7 4 PREPC Driver Figure 7 4 pHILE and pREPC Drivers This section discusses pREPC drivers section 7 11 covers pHILE drivers The pREPC library uses four pSOS I O calls de_open de_close de_read and de_write Therefore a pREPC driver must supply four corresponding functions e g xxxxOpen xxxxClose xxxxRead xxxxWrite The pREPC library calls de_open and de_close when fopen and fclose are called respectively by your application The corresponding driver functions
187. name and user and group IDs are used when accessing NFS servers Every task that uses NFS services must have a user ID and a group ID These values are used by an NFS server to recognize a client task and grant or deny services based on its identity Refer to your host system NFS server documentation for a further discussion of NFS protection mechanisms The pNA Configuration Table entry NC_LHOSTNAME is used to define the host name This entry points to a null terminated string of up to 32 characters which contains the host name for the node The pNA Configuration Table entries NC_DEFUID and NC_DEFGID can be used to define default values for a task s user ID and group ID respectively Subsequent to task creation the system calls set_id and pSOSystem System Concepts 4 19 4 19 1 Chapter 4 Network Programming get_id can be used to change or examine a task s user and group ID Note that similar system calls setid_u Q and getid_u are provided by the pHILE component Integrated Systems recommends however that you use the set_id and get_id system calls provided in the pNA component for future compatibility MIB II Support The pNA component supports a TCP IP Management Information Base commonly known as MIB II as defined in the internet standard RFC 1213 The pSOSystem optional SNMP Simple Network Management Protocol package uses this MIB II to provide complete turnkey SNMP agent functionality pNA MIB II c
188. nd that queue semaphore or region is deleted by another task B gt E A blocked task B becomes the running task when 1 Any one of the B gt R conditions occurs B has higher priority than the last running task and the last running task has preemption enabled R gt E A ready task R becomes running when the last running task E 1 Blocks or Re enables preemption and R has higher priority than E or Has preemption enabled and E changes its own or R s priority so that R now has higher priority than E and all other ready tasks or 4 Runs out of its timeslice its roundrobin mode is enabled and R has the same priority as E E gt R The running task E becomes a ready task when 1 Any one of the B gt E conditions occurs for a blocked task B as a result of a system call by E or an ISR or 2 Any one of the conditions 2 4 of R gt E occurs A fourth but secondary state is the suspended state A suspended task cannot run until it is explicitly resumed Suspension is very similar to blocking but there are fundamental differences First a task can block only itself but it can suspend other tasks as well as itself Second a blocked task can also be suspended In this case the effects are additive that task must be both unblocked and resumed the order being irrelevant before the task can become ready or running 2 8 pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel NOTE The task s
189. nd hence its data An extent is a sequence of physically contiguous blocks An extent consists of one or more blocks similarly a file with data consists of one or more extents A file can acquire an extent in one of two ways During a write _f operation when a file is expanded or m During an annex _f operation These operations also might not produce a new extent because the pHILE file system manager may merge the newly allocated blocks into an existing extent logically the last extent if the new blocks are contiguous with that extent An extent is described by an extent descriptor lt starting block number number of blocks gt which identifies the physical address of the blocks that make up the extent pSOSystem System Concepts 5 37 Chapter 5 pHILE File System Manager 5 38 5 7 2 7 The Extent Map The extent map for a file is a list of its extent descriptors For reasons of efficiency this map is organized by layers of indirection The first 10 extent descriptors are located in the file s file descriptor Additional extent descriptors when needed are stored in indirect blocks Each indirect block is a physical block that contains up to n extent descriptors Because an extent descriptor is 8 bytes the number n of extent descriptors that can be held in an indirect block is blocksize 8 For example if blocksize is 1 Kbyte then nis 128 Indirect blocks are allocated as needed for each file Each i
190. nd on synchronous services such as messages or events which even if possible suffer a great loss in efficiency There are three related system calls as_catch Establish a task s ASR as_send Send signals to a task as_return Return from an ASR pSOSystem System Concepts 2 31 Chapter 2 pSOS Real Time Kernel 2 10 1 2 10 2 2 32 An asynchronous signal is a user defined condition Each task has 32 signals encoded bit wise in a long word To receive signals a task must establish an ASR using the as_catch call The as_send call can be used to send one or more asynchronous signals to a task thereby forcing the task the next time it is dispatched to first go to its ASR At the end of an ASR a call to as_return allows the pSOS kernel to return the task to its original point of execution The ASR A task can have only one active ASR established using the as_catch call A task s ASR executes in the task s context from the outside it is not possible to discern whether a task is executing in its main code body or its ASR The as_catch call supplies both the ASR s starting address and its initial mode of execution This mode replaces the mode of the task s main code body see section 2 4 3 Task Mode Word as long as the ASR is executing It is used to control the ASR s execution behavior including whether it is preemptible and whether or not further asynchronous signals are accepted Typically ASRs e
191. ndirect block is addressed via an indirect block descriptor which is also a pair of words lt starting block number last logical block number 1 gt where the first item is a physical block number and the second item is the logical number 1 of the last block contained in this indirect block of extent descriptors This last number is useful for quickly determining whether an indirect block needs to be searched while locating a particular logical block within a file The indirect block descriptor for the first indirect block if needed is held in a file descriptor If more than one indirect block is needed as in the case of rather large and scattered files then the second through n 1 th indirect block descriptors are held in an index block If allocated this index block will contain up to n indirect block descriptors Again because each indirect block descriptor is 8 bytes long the number n of indirect block descriptors in the index block is equal to blocksize 8 For example if blocksize is 1 Kbyte then this number will be 128 The physical block address of the index block is contained in a file descriptor A file can have only one index block The structure of the extent map ensures that in the worst case no more than two block accesses are needed to locate an extent descriptor Moreover the cache buffers will tend to retain frequently used index and indirect blocks This extent map structure clearly favors file contig
192. nel returns the error ERR_STALEID Slave Node Restart A node that has failed may subsequently restart and rejoin the system The pSOS m kernel treats a rejoining node exactly like a newly joining node that is as described in section 3 6 In fact internally the pSOS m kernel does not distinguish between the two cases However a rejoining node introduces some special considerations that are discussed in the following subsections pSOSystem System Concepts 3 8 1 Chapter 3 pSOS Multiprocessing Kernel Stale Objects and Node Sequence Numbers Recall from section 3 7 that when a node exits the system IDs for objects on the node may still be held by task level code Such IDs are called stale IDs So long as the failed node does not rejoin detection of stale IDs is trivial because the node is known not to be in the system However should the failed node rejoin then in the absence of other protection mechanisms a stale ID could again become valid This might lead to improper program execution To guard against use of stale IDs after a failed node has rejoined every node is assigned a sequence number The master node is responsible for assigning and maintaining sequence numbers A newly joining node is assigned sequence number 1 and the sequence number is incremented thereafter each time the node rejoins All object IDs contain both the node number and sequence number of the object s node of residence Therefore a stale ID is ea
193. net host address 128 0 0 1 satosin amp ar arp_ pa gt sin_ satosin amp ar arp_pa gt sin_ AF_UNSPEC ar arp_ha sa_family re ioctl s SIOCDARP close the socket close s AF_INET htonl1 0x80000001 family addr s_addr char amp ar The pNA component uses the Address Resolution Protocol ARP to determine the hardware address of a node dynamically given its internet 1 A sender wishing to learn the hardware address of a destination node prepares and broadcasts an ARP packet containing the 4 12 2 Address Resolution Protocol ARP address ARP operates as follows destination internet address 4 30 pSOSystem System Concepts Chapter 4 Network Programming 2 Every node on the network receives the packet and compares its own internet address to the address specified in the broadcasted packet 3 Ifa receiving node has a matching internet address it prepares and transmits to the sending node an ARP reply packet containing its hardware address ARP can be used only if all nodes on the network support it If your network consists only of pNA nodes this requirement is of course satisfied Otherwise you must make sure that the non pNA nodes support ARP ARP was originally developed for Ethernet networks and is usually supported by Ethernet drivers Networks based on other media might or might not support ARP The pNA component treats internet packets differently
194. ng and initializing hard or floppy disks to use either MS DOS or pHILE format volumes Throughout this section the word formatting refers to the entire process of preparing a hard or floppy disk for use The word initialization refers to the last stage of formatting which is creating the file systems to hold MS DOS or pHILE format files NOTE Considerations for writing device drivers that access MS DOS and pHILE volumes can be found in Section 7 11 pHILE Drivers Which Volume Type Should I Use You should use pHILE volumes whenever possible because they are faster and more efficient than MS DOS volumes However you must use MS DOS volumes if you are setting up a data interchange scenario pSOSystem System Concepts Chapter 5 pHILE File System Manager involving a PC that is if the data will be written on the target but read later on a PC An example of such a scenario is an application on a satellite that collects data in space When the satellite comes back to earth the disk is loaded onto a PC and the data is read there If using MS DOS volumes you must format the disk s using DOS commands on a PC If using pHILE volumes you can format the disk s using either DOS commands or the I O control commands of a SCSI driver Specific formatting procedures are provided later in this section 5 2 2 Format Definitions Formatting a disk requires several steps some of which are performed at the factory and some of w
195. ning extent in the appropriate region If the calling function is annex _f the number of blocks actually allocated is returned to the caller If a write_f is executed a new allocation size is calculated depending on the number of blocks not yet allocated and the operation is repeated That way one write_f call can add several extents to a file 3 The volume is full no free blocks In this case a volume full error is returned to the calling task The time to read and write to a file depends on how fragmented the file is A file fragmented into many small and scattered extents will take more time to access than a file consisting of fewer and larger extents If a file can be compacted into 10 or fewer extents then all of the file s data blocks can be identified using an extent map stored in the File Control Block This is the optimal case If a file has more than 10 extents indirect blocks or index blocks must be used which reduces access times pSOSystem System Concepts Chapter 5 pHILE File System Manager Some attention should be given to a file s expansion unit specification which is described in section 5 7 2 5 A larger expansion unit results in higher throughput but may waste disk space because some blocks may not be used On the other hand a smaller expansion unit uses disk space more efficiently but may cause fragmentation This fragmentation will be a function of m The average number of bytes written
196. nk field links one message buffer to another At startup the pSOS kernel allocates a shared pool of free message buffers The size of this pool is equal to the kc_nmsgbuf entry in the pSOS Configuration Table A message queue can be created to use either a pool of buffers shared among many queues or its own private pool of buffers In the first case messages arriving at the queue will use free buffers from the shared pool on an as needed basis In the second case a number of free buffers equal to the queue s maximum length are taken from the shared pool and set aside for the private use of the message queue pSOSystem System Concepts 2 25 Chapter 2 pSOS Real Time Kernel 2 7 4 Two Examples of Queue Usage The examples cited below and depicted in Figure 2 3 illustrate the ways in which the message queue facility can be used to implement various synchronization requirements TASK A TASK B Q_ SEND Q_RECV TASK A TASK B Q_ SEND Q_RECV E E E E Q_ ND Figure 2 3 One Way and Two Way Queue Synchronization The first example typifies the straightforward use of a message queue as a FIFO queue between one or more message sources and one or more message sinks Synchronization provided by a single queue is one way and non interlocked That is a message sink synchronizes its activities to the arrival of a message to the queue but a message source does not synchronize to any queue or sink condition it can elect to produce
197. nt to obtain a subnet address mask 4 17 Intemet Group Management Protocol IGMP IGMP is used by IP nodes to report their host group memberships to any immediately neighboring multicast routers Like ICMP IGMP is an pSOSystem System Concepts 4 41 Chapter 4 Network Programming 4 18 4 42 integral part of IP It is implemented by all nodes conforming to the Level 2 IP Multicasting specification in RFC 1112 IGMP messages are encapsulated in IP datagrams with an IP protocol number of 2 IGMP can be accessed through the RAW IP socket facility Two types of IGMP messages are of concern to nodes TYPE DESCRIPTION 1 HOST MEMBERSHIP QUERY Multicast routers send Host Membership Query messages to discover which host groups have members on their attached local networks Queries are addressed to the ALL_HOSTS group address 224 0 0 1 2 HOST MEMBERSHIP REPORT Hosts respond to a Query by generating Host Membership Reports reporting each host group to which they belong on the network interface from which the Query was received A Report is sent with an IP destination address equal to the host group address being reported and with an IP time to live of 1 NFS Support The pNA component can be used in conjunction with the pHILE component and the pRPC subcomponent to offer NFS support To support NFS the pNA component allows you to assign a host name to your pNA system and a user ID and group ID to each task The host
198. ntains a message block and a data block allocated by the pNA component The data buffer in the triplet is passed in as a parameter to the call Network Interface Option The pNA network interface definition supports data exchange between the pNA component and an NI via message block triplets If the RAWMEM flag is set in the NI flags it indicates that the interface supports the zero copy operation and the exchange of data between NI and the pNA component is in the form of message block triplets The pointers to the pna_alloch pna_freeb pna_freemsg and pna_esballoc functions are passed to the NI driver during its ni_init function call See Section 4 11 Network Interfaces These functions are used by the NI to gain access to pNA memory management routines Intemet Control Message Protocol IC MP ICMP is a control and error message protocol for IP It is layered above IP for input and output but it is really part of IP ICMP can be accessed through the raw socket facility The pNA component processes and generates ICMP messages in response to ICMP messages it receives ICMP can be used to determine if the pNA component is accessible on a network For example some workstations such as SUN provide a utility program called ping which generates ICMP echo requests and then waits for corresponding replies and displays them when received The pNA component responds to the ICMP messages sent by ping ICMP support
199. o run otherwise the wait continues for the remaining events 2 8 2 Events Versus Messages Events differ from messages in the following sense m An event can be used to synchronize with a task but it cannot directly carry any information m Topologically events are sent point to point That is they explicitly identify the receiving task A message on the other hand is sent to a message queue In a multireceiver case a message sender does not necessarily know which task will receive the message m One ev_receive call can condition the caller to wait for multiple events q_receive on the other hand can only wait for one message from one queue m Messages are automatically buffered and queued Events are neither counted nor queued If an event is already pending when a pSOSystem System Concepts 2 29 Chapter 2 pSOS Real Time Kernel 2 9 2 9 1 2 30 second identical one is sent to the same task the second event will have no effect Sema phores The pSOS kernel provides a set of familiar semaphore operations In general they are most useful as resource tokens in implementing mutual exclusion The related system calls are listed below sm_create Create a semaphore sm_ident Get the ID of a semaphore sm_delete Delete a semaphore sm_p Get wait for a semaphore token sm_v Return a semaphore token Like a message queue a semaphore is an abstract object created dynamically using the sm_create system call s
200. o store socket addresses during pNA service calls As the messages pass through the protocol layers they are subjected to various data manipulations copying fragmentation and reassembly For instance when preparing a packet for transmission the TCP layer makes a copy of the packet from the socket buffer tags a TCP header and passes the packet to the IP layer Similarly the IP layer fragments packets it receives from the transport layer TCP UDP to fit the MTU of the outgoing Network Interface pNA memory management is optimized to perform such operations efficiently and maximize performance by avoiding physical copying of data For instance copying of message block triplets is achieved by allocating a new message block associating it with the original data block and increasing the reference count to the original data block This avoids costly data copy operations Memory Configuration During the initialization of the pNA component various memory structures are created and initialized The initialization sequence creates message blocks data blocks and data buffers of multiple sizes The pSOSystem System Concepts 4 14 1 Chapter 4 Network Programming number of each is configurable in the pNA Configuration Table the pNA component provides entries in the configuration table to specify the number of message blocks and data buffers Because there is a one to one relationship between data blocks and data buffers the pN
201. ocket Example code below shows how multicasting can be done a multicast interface IP address 128 0 0 1 define MY _IP_ADDR 0x80000001 int s char loop struct ip_mreq ipmreq struct rtentry rt struct sockaddr_in sin char Buffer 1000 define satosin sa struct sockaddr_in sa open a RAW IP socket s socket AF_INET SOCK_RAW 100 pSOSystem System Concepts 4 21 Chapter 4 Network Programming Add a default Multicast Route for Transmission satosin amp rt rt_dst gt sin_family AF_INET satosin amp rt rt_dst gt sin_addr s_addr htonl1 0xe0000000 satosin amp rt rt_gateway gt sin_family AF_INET satosin amp rt rt_gateway gt sin_addr s_addr htonl MY_IP_ADDR rt rt_netmask htonl 0xf 000000 rt rt_flags RTF_MASK ioctl s SIOCADDRT char amp rt Add a group membership on the default interface defined above ipmreq imr_mcastaddr s_addr htonl1 0xe0000040 ipmreq imr_interface s_addr htonl INADDR_ANY setsockopt s IPPROTO_IP IP_ADD MEMBERSHIP char amp ipmreq sizeof struct ip_mreq Disable loopback of multicast packets loop 0 setsockopt s IPPROTO_IP IP_MULTICAST_LOOP char amp loop sizeof char Send a multicast packet sin sin_addr s_addr htonl 0xe00000 0 sin sin_family AF_INET sendto s Buffer 1000 0 amp sin sizeof sin Receive a multicast packet recv s Buffer
202. of functions is done prior to runtime and is thus permanent as opposed to task reassignment or load balancing The latest version of the pSOS m kernel incorporates facilities that support the following Soft Fail A processing node can suffer a hardware or software failure and other nodes will continue running Hot Swap New nodes can be inserted or removed from a system without shutting down Software Arc hitec ture The pSOS m kernel implements a master slave architecture As shown in Figure 3 1 every pSOSt m system must have exactly one node called the master node which manages the system and coordinates the activities of all other nodes called slave nodes The master node must be present when the system is initialized and must remain in the system at all times In addition to the master a system may have anywhere between zero and 16382 slave nodes Unlike the master node slave nodes may join exit and rejoin the system at any time The pSOS m kernel itself is entirely hardware independent It makes no assumptions about the physical media connecting the processing nodes or the topology of the connection This interconnect medium can be a memory bus a network a custom link or a combination of the above To perform interprocessor communication the pSOS m kernel calls a user provided communication layer called the Kernel Interface KI The interface between the pSOS m kernel and the KI is standard and independent of the inte
203. of multiple instances of the entries shown The pNA component allows you to access any field in any entry add table entries and delete entries The key to understanding how to manipulate tables is to recognize that MIB II table entries are not referenced by simple integers like normal programming arrays Rather one or more fields are defined to be index fields and entries are identified by specifying values for the index fields The index fields were selected so that they identify a unique table entry The index fields are indicated in the MIB II tables shown This raises the question of how you determine the valid indices at any time You obtain them with ioctl the following way First declare a variable of type mib_args this structure is defined in lt pna_mib h gt using the following syntax struct mib_args long len bytes pointed to by buffer char buffer ptr to table specific struct array buffer points to an array of structures with a type corresponding to the table you want to access len is the number of bytes reserved for buffer The buffer should be large enough to hold the maximum possible size of the particular table being accessed Call ioctl with command equal to the MIB II object corresponding to the name of the table argis a pointer to the mib_args variable Upon return from ioctl the array pointed to by arg will have all of its index fields set with valid values In addition there will be
204. of the data s sender is returned to the caller via the to parameter Disc arding Sockets Once a socket is no longer needed its socket descriptor can be discarded by using the close system call If this is the last socket descriptor associated with the socket then close de allocates the socket control block see section 4 4 11 and unless the LINGER option is set see section 4 4 8 discards any queued data As a special case close 0 pSOSystem System Concepts 4 4 8 4 4 9 4 4 10 Chapter 4 Network Programming closes all socket descriptors that have been allocated to the calling task This is particularly useful when a task is to be deleted Socket Options The setsockopt system call allows a socket s creator to associate a number of options with the socket These options modify the behavior of the socket in a number of ways such as whether messages sent to this socket should be routed to networks that are not directly connected to this node the DONTROUTE option whether sockets should be deleted immediately if their queues still contain data the LINGER option whether packet broadcasting is permitted via this socket the BROADCAST option and so forth Multicasting related options may also be set through this call A detailed description of these options and their effects is given in the setsockopt call description in pSOSystem System Calls Options associated with a socket can be checked via the getsockop
205. oid b_devforw system use only void b_devback system use only void b_avlflow system use only pSOSystem System Concepts Chapter 7 I O System void b_avlback system use only void b_bufptr address of data buffer void b_bufwaitf system use only void b_bufwaitb system use only void b_volptr system use only unsigned short b_blksize size of blocks in base 2 unsigned short b_dsktype type of disk BUFFER_HEADER A pHILE driver uses only six of the parameters in the buffer header They are the following b_blockno specifies the starting block number to read or write b bcount specifies the number of consecutive blocks to read or write For more information on these parameters see section 7 11 3 b _bufptr supplies the address of a data area it is either the address of a pHILE cache buffer or a user data area During a read operation data is transferred from the device to this data area Data flows in the opposite direction during a write operation b_flags contains a number of flags most of which are for system use only However the low order two bits of this field indicate the block type as follows Bit 1 Bit O Explanation 0 0 Unknown block type 0 1 Data block 1 0 Control block b flags is used by more sophisticated drivers that take special action when control blocks are read or written Most drivers will ignore b flags b flags low bits 00
206. on Table the maximum number of tasks expected to be active contemporaneously and the pSOS kernel allocates sufficient memory for the requisite system data structures to manage that many tasks 2 3 Overview of System Operations pSOS kernel services can be separated into the following categories m Task Management m Storage Allocation m Message Queue Services m Event and Asynchronous Signal Services m Semaphore Services m Time Management and Timer Services m Interrupt Completion Service m Error Handling Service m Multiprocessor Support Services Detailed descriptions of each system call are provided in pSOSystem System Calls The remainder of this chapter provides more details on the principles of pSOS kernel operation and is highly recommended reading for first time users of the pSOS kernel 2 3 1 Task States A task can be in one of several execution states A task s state can change only as result of a system call made to the pSOS kernel by the task itself or by another task or ISR From a macroscopic perspective a multitasked application moves along by virtue of system calls into pSOS forcing the pSOS kernel to then change the states of affected tasks and possibly as a result switch from running one task to running pSOSystem System Concepts 2 5 Chapter 2 pSOS Real Time Kernel 2 3 2 2 6 another Therefore gaining a complete understanding of task states and state transitions is an important step towards using the
207. one that executes during device auto initialization and another that executes when the device initialization routine is explicitly invoked by the application from within the context of a pSOS task The tid field of the ioparms structure can be checked by the device initialization procedure to identify whether the call originated in device auto initialization or was made by a task Note that under pSOSystem every task has a non zero tid whereas the tid passed during auto initialization is zero pSOSystem System Concepts 7 11 Chapter 7 I O System 7 7 Mutual Exclusion If a device may be used by more than one task then its device driver must provide some mechanism to ensure that no more than one task at a time will use it When the device is in use any task requesting its service must be made to wait This exclusion and wait mechanism may be implemented using a message queue or semaphore In the case of semaphores the driver s init service would call sm_create to create a semaphore and set an initial count typically 1 This semaphore represents a resource token To request a device service say de_read a task must first acquire the semaphore using the system call sm_p with SM_WAIT attribute If the semaphore is available then so is the device Otherwise the pSOS kernel puts the task into the semaphore wait queue When a task is done with the device it must return the semaphore using sm_v If another task is already wait
208. ore the disk is updated the data will be lost A similar situation can arise with the system data structures used by the pHILE file system manager to manage a volume for example FCBs FATs bit maps and so forth To reduce the number of disk accesses required during normal operation copies of certain system data structures normally residing on volumes are maintained in memory In this case if a hardware failure occurs before the pHILE file system manager updates a volume then the volume will be corrupted To deal with these situations and at the same time to accommodate different application requirements for security and performance the pHILE file system manager provides three synchronization modes that dictate when a volume is updated A fourth synchronization mode is also provided Read Only which does not dictate when a volume is updated The synchronization mode is selected when a volume is mounted The four possible modes are described in Table 5 2 pSOSystem System Concepts Chapter 5 pHILE File System Manager Table 5 2 Possible Modes for Synchronization Mode Mnemonic Effect Trade Off Immediate Write All changed datais High security SM_IMMED_WRITE flushed low performance immediately Control Write Flush only control Medium security SM_CONTROL_WRITE data that changed medium performance Delayed Write Flush data only as Low security SM_DELAYED_WRITE required high performance Read Only Writes to the N
209. ork The process by which internet addresses are mapped to hardware addresses is called address resolution and is discussed in section 4 12 Unlike an internet address which is four bytes long the length of a hardware address varies depending on the type of network For example an Ethernet address is 6 bytes while a shared memory address is usually 4 bytes The pNA component can support hardware addresses up to 14 bytes in length The length of a NI s hardware address must be specified Contol Hags Each NI has a set of flags that define optional capabilities as follows ARP This is used to enable or disable address resolution see section 4 12 BROADCAST This is used to tell the pNA component if the NI supports broadcasting If you attempt to broadcast a packet on a network with this flag disabled the pNA component returns an error EXTLOOPBACK If this is disabled the pNA component loops back packets addressed to itself That is if you send a packet to yourself the pNA component does not call the NI but the packet is processed as if it were received externally If this flag is enabled the pNA component calls the NI MULTICAST If this is set the NI is capable of doing multicast see Section 4 9 IP Multicast POLL If this is set the ni_poll service is called by the pSOS daemon task PNAD This flag is normally used in conjunction with PpROBE and SpOTLIGHT debuggers POINTTOPOINT If this is set th
210. ort of a dual ported zone then three entries in its pSOS m Multiprocessor Configuration Table must be used to describe the zone mc_dprext and mc_dprint specify the starting address of the zone as seen from the s port and the p port respectively mc_dprlen specifies the size of the zone in bytes In effect these entries define a special window on the node s address space The pSOS m kernel uses these windows to perform transparent address conversions for the user s application If a node is not connected to any dual ported zone or accesses dual ported zones only through their s ports then the three configuration table entries should be set to O Notice that the number of zones a processor node can be connected to via the p port is limited to one NOTE A structure user or pSOSHn must begin and end in a dual port zone Itmustnot staddle a boundary between single and dual ported memory Intemal and Extemal Address When a node is connected to a dual ported zone any structure it references in that zone whether it is created by the user s application code or by the pSOS kernel e g a partition buffer is defined to have two addresses 1 The internal address is defined as the address used by the node to access the structure Depending on the node this may be the p port or the s port address for the zone 2 The external address is always the s port address pSOSystem System Concepts 3 113 3 11 4 Chapter 3 pSOS
211. oth as their value Get as its value Set Get Get An SNMP agent should return O as the value of this object 4 51 Chapter 4 Network Programming 4 19 6 4 20 4 20 1 4 52 Network Interfaces Objects defined by the Interfaces group are maintained by the Network Interfaces configured in your system These objects are accessed via the ni_ioctl system call pNA uses ni_ioctl when necessary to access Interfaces objects ni_ioctl is described in the pSOSystem Programmer s Reference pRPC Subc omponent The pNA component can be extended by adding the pRPC subcomponent which implements remote procedure calls pRPC provides a complete implementation of the Open Network Computing ONC Remote Procedure Call RPC and eXternal Data Representation XDR specifications The pRPC subcomponent is designed to be source code compatible with Sun Microsystems RPC and XDR libraries Sections 4 20 2 through 4 20 5 describe those aspects of pRPC that are unique to the Integrated Systems implementation Whatis a Subc omponent A pNA subcomponent is a block of code that extends the feature set of the pNA component A subcomponent is similar to all other components with the caveat that it relies on the pNA component for resources and services pNA initializes pRPC after it completes its own initialization sequence Like any component pRPC requires RAM which can be allocated from Region 0 or defined in a
212. partitions are dynamic abstract objects managed by the pSOS kernel A partition is created using the pt_create call with the following inputs its user assigned name starting address and length and buffer_size The system call pt_create returns a partition ID PTid assigned by the pSOS kernel to the caller For any other task that knows a partition only by name the pt_ident call can be used to obtain a named partition s PTid The pSOS kernel takes a small piece at the beginning of the input memory area to use as the partition s control block PTCB The rest of the partition is organized as a pool of equal sized buffers Because of this simple organization the pt_getbuf and pt_retbuf system calls are highly efficient pSOSystem System Concepts 2 21 Chapter 2 pSOS Real Time Kernel 2 6 2 7 2 22 A partition has the following limits it must start on a long word boundary and its buffer size must be a power of 2 but greater than or equal to 4 bytes Partitions can be deleted although this is rarely done in a typical application For one thing deletion must be carefully considered and is allowed by the pSOS kernel only if there are no outstanding buffers allocated from it Partitions can be used in a tightly coupled multiprocessor configuration for efficient data exchange between processor nodes For a complete discussion of shared partitions see Chapter 3 pSOS m Multiprocessing Kernel Communication
213. pecified is 100 the FLIST occupies 12800 bytes or 13 blocks if the block size is 1 Kbyte Note that if the number of file descriptors on a volume is specified as n then the maximum number of user created files that can exist on the volume is n The number of file descriptors created will actually be n 4 because four internal system files are always present the root directory BITMAP SYS FLIST SYS and a reserved null file These system files are write protected and cannot be written to directly or deleted 5 7 1 5 Contol and Data Block Regions pHILE format volumes recognize two types of file blocks control blocks and data blocks Control blocks contain pHILE data structures such as m The bootload blocks O and 1 m The root block block 2 m The bitmap m The FLIST m All directory file blocks m Indirect and index blocks Indirect and index blocks are used with extent maps and are explained in section 5 7 2 7 Data and control blocks can be either intermixed or partitioned Partitioning control and data blocks is a unique feature of pHILE format volumes and makes the pHILE file system manager capable of working with write once devices When a partition is used the logical address space of a volume is divided into two regions one for control blocks and pSOSystem System Concepts 5 7 2 Chapter 5 pHILE File System Manager one for data blocks Using this method control blocks can be temporarily maint
214. per write_f m The number of annex_f calls used and m Concurrent file activity that is how many tasks are using the volume at the same time When the pHILE file system manager needs to add blocks to a file it always checks to see if the new blocks can be merged into the last extent used 5 7 5 How Directories Are Organized Directories implement the hierarchical file structure of the pHILE file system manager A volume s directory tree structure is built on top of but also out of the basic data file structure That is directory files are treated in almost all respects as ordinary data files Directory files hold data about their children and the parent of a directory will hold data about the directory A directory file contains an array of entries Each entry describes a file in the directory An entry is nothing more than a 2 tuple as follows Entry lt _filenumber filename gt filenumber is the number of the file and filename is its name Each directory entry uses 16 bytes so if the block size is 1 Kbyte one block can store 64 entries When a file is created the pHILE file system manager assigns it a file descriptor in the volume s FLIST described below and makes an entry in the directory file to which it belongs pSOSystem System Concepts 5 43 Chapter 5 pHILE File System Manager 5 7 6 5 7 7 5 44 Logical and Physical File Sizes Files occupy an integral number of storage blocks on the dev
215. performs various coherency checks to see if the node should be allowed to join see below and if so grants admission to pSOSystem System Concepts 3 11 Chapter 3 pSOS Multiprocessing Kernel 3 12 the new node Finally it notifies other nodes in the system that the new node has joined For a multiprocessor pSOS m system to operate correctly the system must be coherent That is certain Multiprocessor Configuration Table parameters must have the same value on every node in the system In addition the pSOS m kernel versions on each node must be compatible There are four important coherency checks that are performed whenever a slave node joins 1 The pSOS m kernel version on each slave node must be compatible with the master node 2 The maximum number of nodes in the system as specified in the Multiprocessor Configuration Table entry mc_nnode must match the value specified on the master node 3 The maximum number of global objects on the node as specified by the Multiprocessor Configuration Table entry mc_nglbobj must match the value specified on the master node 4 The maximum packet size that can be transmitted by the KI as specified by the Multiprocessor Configuration Table entry mc_kimaxbuf must match the value specified on the master node All of the above conditions are checked by the master node when a slave node attempts to join If any condition is not met the slave node will not be allowed to join The slave node
216. phore must be created with FIFO queuing of tasks Otherwise requests posted to the driver might not be processed in the order in which they arrive Logic al to Physic al Block Translation The b_blockno and b count parameters together specify a sequence of logical blocks that must be read or written by the driver However most physical devices are not organized as a linear sequence of blocks They are divided into sectors tracks cylinders heads and so forth A pHILE driver must therefore translate logical block numbers provided by the pHILE file system manager into physical block addresses on the device How this is done depends on the type of device being accessed 7 11 3 1 pHILE Format Volumes For pHILE format volumes a driver may implement any translation scheme that maps each logical block to a unique physical block However the pHILE file system manager operates at maximum pSOSystem System Concepts Chapter 7 I O System efficiency if blocks that are logically contiguous are also physically contiguous Because of track to track transitions and other such boundaries this usually is not entirely feasible but a pHILE driver should minimize discontinuities 7 11 3 2 MS DOS Hoppy Disk Format For MS DOS volumes a driver must implement the same mapping used by MS DOS otherwise your diskette will not be MS DOS compatible This section describes the required block mapping for each of the five MS DOS floppy di
217. pter 5 pHILE File System Manager Detailed information on SNMP is available in the SNMP User s Manual and STREAMS is documented in the OPEN User s Guide which describes the pSOSystem OPEN Open Protocol Embedded Networking product 4 2 pNA Software Architecture pNA is organized into four layers Figure 4 1 illustrates the architecture and how the protocols fit into it The socket layer provides the application programming interface This layer provides services callable as re entrant procedures which your application uses to access internet protocols it conforms to industry standard UNIX 4 3 BSD socket syntax and semantics In addition this layer contains enhancements specifically for embedded real time applications The transport layer supports the two Internet Transport protocols Transmission Control Protocol TCP and User Datagram Protocol UDP These protocols provide network independent transport services They are built on top of the Internet Protocol IP TCP provides reliable full duplex task to task data stream connections It is based on the internet layer but adds reliability flow control multiplexing and connections to the capabilities provided by the lower layers pSOSystem System Concepts 4 3 Chapter 4 Network Programming 4 4 Application Soc ket Layer Network Interfaces Figure 4 1 pNA Architecture UDP provides a datagram mode of packet switched communication It
218. q_receive system calls to obtain messages from a queue and sm_Pp calls to acquire a semaphore Note however that these calls must use the no wait option so that the call will return whether or not a message or semaphore is available System Calls Allowed From an ISR The restricted subset of pSOS system calls that can be issued from an ISR are as follows Conditions necessary for the call to be issued from an ISR are in parentheses as_send Send asynchronous signals to a task local task ev_send Send events to a task local task k_fatal Abort and enter fatal error handler k_terminate Terminate a failed node pSOS m component only pt_getbuf Get a buffer from a partition local partition pt_retbuf Return a buffer to a partition local partition q_broadcast Broadcast a message to an ordinary queue local queue q_receive Get a message from an ordinary message queue no wait and local queue q_send Post a message to end of an ordinary message queue local queue q_urgent Post a message at head of an ordinary message queue local queue q_vbroadcast Broadcast a variable length message to queue local queue q_vreceive Get a message from a variable length message queue no wait and local queue pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel q_vsend Post a message to end of a variable length message queue local queue q_vurgent Post a message at head of a variable length message qu
219. quests 100 bytes starting at byte number 7000 the request is processed by the pHILE file system manager as follows 1 Byte 7000 divided by 1024 6 remainder 856 2 Logical file block 6 is needed because blocks are numbered from 0 3 According to extent map block 6 is the 2nd block in the extent 789 2 4 The pHILE file system manager calls your driver to read volume block 790 5 The pHILE file system manager extracts bytes 856 to 955 from the 1024 bytes that were read in pSOSystem System Concepts 5 39 Chapter 5 Extent 0 Size Extent 9 Size Index File Descriptor IndirectO pHILE File System Manager Extent 10 Size Extent n 9 Size Indirect Block 0 Indirect 1 Extent n 10 Last block 1 Size Indirect n Extent 2n 9 Last block 1 Size Index Block Indirect Block 1 Extent n n 10 Size Extent n 1 n 9 Size Indirect Block n Figure 5 4 The Layout of an Extent Map pSOSystem System Concepts Chapter 5 pHILE File System Manager 5 7 4 Block Allocation Methods Because blocks are the basic unit of the pHILE volume block allocation algorithms are extremely important to system throughput Blocks must be allocated whenever m A write _f extends the logical size of a file beyond the file s physical size m An anne
220. queue Dispatch Criteria Dispatch refers to the exit stage of the pSOS kernel where it must decide which task to run upon exit that is whether it should continue with the running task or switch to run another ready task If the pSOS kernel is entered because of a system call from a task then the pSOS kernel will always exit through the dispatcher in order to catch up with any state transitions that might have been caused by the system call For example the calling task might have blocked itself or made a higher priority blocked task ready On the other hand if the pSOS kernel is entered because of a system call by an ISR then the pSOS kernel will not dispatch but will instead return directly to the calling ISR to allow the ISR to finish its duties Because a system call from an ISR might have caused a state transition such as readying a blocked task a dispatch must be forced at some point This is the reason for the I RETURN entry into the pSOS kernel which is used by an ISR to exit the interrupt service and at the same time allow the pSOS kernel to execute a dispatch Objects Names and IDs The pSOS kernel is an object oriented operating system kernel Object classes include tasks memory regions memory partitions message queues and semaphores Each object is created at runtime and known throughout the system by two identities a pre assigned name and a run time ID An object s 32 bit 4 characters if A
221. r 5 36 file descriptor list 5 34 file number 5 35 file structure 5 43 naming files on 5 18 organization 5 31 root block 5 32 root directory 5 33 volume bitmap 5 33 pHILE volumes initializing 5 4 pNA 4 3 address resolution 4 28 architecture 4 3 ARP Table 4 29 buffer configuration 4 35 daemon task 4 14 environment 4 5 error handling 4 17 ICMP 4 40 IGMP 4 41 IP multicast 4 20 memory configuration 4 35 MIB II support 4 43 network interface 4 23 I 5 Index NFS support 4 42 NI attributes 4 24 NI Table 4 26 packet routing 4 17 signal handling 4 16 socket layer 4 7 subcomponents 4 52 unnumbered serial links 4 23 zero copy operations 4 38 pNAD 4 15 p port 3 17 preemption bit 2 10 pREPC 6 1 buffers 6 6 deleting tasks 6 10 environment 6 3 error handling 6 9 file structure 6 5 files 6 4 functions 6 2 1 0 7 16 memory allocation 6 9 restarting tasks 6 10 streams 6 8 pREPC drivers 7 16 pROBE debugger 1 4 pRPC 4 52 architecture 4 53 client authentication 4 54 global variables 4 56 port mapper 4 56 pSOS attributes 2 2 kernel 2 1 region manager 2 22 services 2 5 pSOS t m 3 1 architecture 3 2 coherency checks 3 12 overview 3 1 startup 3 11 pSOS to driver interface 7 6 psOSsystem ANSI C standard library 1 3 architecture 1 2 components 1 2 debug environment 1 4 facilities 1 4 filesystem manager 1 3 kernel 1 2 2 1 network manager 1 2 overview 1 1 RPC library 1 2 PTCB 2 23 Q QCB 2 25 qu
222. rconnect medium In addition to the KI and the standard pSOS Configuration Table pSOS m requires a user supplied Multiprocessor Configuration Table MPCT that defines application specific parameters pSOSystem System Concepts Chapter 3 pSOS Multiprocessing Kernel APPLICATION Figure 3 1 pSOS m Layered Approach 3 3 Node Numbers Every node is identified by a user assigned node number A node number must be unique that is no two nodes can have the same number Node numbers must be greater than or equal to 1 and less than or equal to the maximum node number specified in the Multiprocessor Configuration Table entry mc_nnode Because node numbers must be unique mc_nnode also determines the maximum number of nodes that can be in the system its value should be greater than 1 and less than or equal to 16383 However a system may have less than mc_nnode nodes if not all node numbers are in use Node number 1 designates the master node All other nodes are slave nodes One node in your system must be assigned node number 1 pSOSystem System Concepts 3 3 Chapter 3 pSOS Multiprocessing Kernel 3 4 3 4 1 3 4 2 3 4 Objects pSOS is an object oriented kernel Object classes include tasks memory regions memory partitions message queues and semaphores In a pSOS m multiprocessor system the notion of objects transcends node boundaries Objects e g a task or queue can be reached or referenced from any node in th
223. re Use of these pRPC subroutines is described in pSOSystem System Calls pSOSystem System Concepts 4 57 Chapter 4 Network Programming 4 58 pSOSystem System Concepts 5 pHILE File System Manager This chapter describes the pSOSystem file management option the pHILE file system manager The following topics are discussed m Volume types How to mount and access volumes Conventions for files directories and pathnames m Basic services for all volume types m Special services for local volume types m Blocking and deblocking m Cache buffers m Synchronization modes m Organization of pHILE format volumes m Special considerations pSOSystem System Concepts 5 1 Chapter 5 pHILE File System Manager 5 1 5 2 Volume Types From the point of view of the pHILE file system manager a file system consists of a set of files and a volume is a container for one file system Avolume can be a single device such as a floppy disk a partition within a device such as a section of a hard disk or a remote directory tree such as a file system exported by an NFS server The pHILE file system manager recognizes the following four types of volumes pHILE Format Volumes These are devices that are formatted and managed by using proprietary data structures and algorithms optimized for real time performance pHILE format volumes offer high throughput data locking selectable cache write through and
224. re returned by calling close O and fclose O respectively Because the pREPC component calls the pHILE file system manager and the pHILE file system manager calls the pNA component if NFS is in use these services must be called in the correct order Below is a sample code fragment that a task can use to delete itself if SC _PREPC YES fclose 0 return pREPC resources endif if SC _PHILE YES close_f 0 return pHILE resources endif if SC_PNA YES close 0 return pNA resources endif if SC_PSE YES pse_close 0 return pSE resources endif if SC _PREPC YES free 1 return pREPC memory endif t_delete 0 and commit suicide pSOSystem System Concepts 5 47 Chapter 5 pHILE File System Manager 5 48 The conditionals prevent calls to components that are not included You can omit the conditionals if you also omit the calls to components that are not included or not in use Because only the task to be deleted can make the necessary close calls the simplest way to delete a task is to restart the task and pass arguments requesting self deletion Of course the task being deleted must contain code to handle this condition pSOSystem System Concepts 6 1 6 pREPC ANSIC Library Intoduction Most C compilers are delivered with some sort of run time library These run time libraries contain a collection of pre defined functions that can be call
225. rererererereereresee 2 42 2 14 1 Deleting Tasks That Use Components eeeeccseereeeereses 2 42 2 14 2 Restarting Tasks That Use Components sseseessseese 2 43 3 pSOS m Multiprocessing Kemel Ball e Systemi OVETVIEW eerie eoe E EEE AEAEE E A E E an deeee 3 1 Ta Solare Architecte niena a A RENATA EEEO a 3 2 3 amp 8 Node Numbers esnan n en a a a A ah ai DE dead vee 3 3 o E O oI e E E aaa ere eee 3 4 3 4 1 Global ODjects 4 e a en a e a a a aair 3 4 3427 ODJSCE Dea n e eana a AE VES 3 4 3 4 3 Global Object Tables aee e A aat 3 5 3 4 4 Ident Operations on Global Objects seesesseeseeesresersereses 3 5 3 0 Remote Servico Calls isiasissa arrana a a e a e ia 3 6 3 5 1 Synchronous Remote Service Calls 2 00 cece eee eee eens 3 7 3 5 2 Asynchronous Remote Service Calls cece eeeeee eee ees 3 9 ODIO AFONSA sinensis ved cca kteed ia E antes Wate dauceeeat 3 10 3 0 4 RSC Overhead sis hcckiteccaneetotenia eins eis a a a a 3 11 3 6 System Startup and Coherency cee eee eee eee cesses eeeeeeeenenees 3 11 Sif Node Failures naana n e a E tebbec essa ce be ta S anes 3 13 pSOSystem System Concepts v Contents vi 3 8 Slave Node RESlartscvesesi ex descses eerie s a rea tbuy ys eas ga yeas EEEE canes 3 14 3 8 1 Stale Objects and Node Sequence Numberts 3 15 3 8 2 Rejoin Latency Requirements cc eee eee esse seen eeeeees 3 16 39 Global SHUtKHOWN e erena a ae E ca id
226. reserved for its private use A queue is not explicitly bound to any task Logically one or more tasks can send messages to a queue and one or more tasks can request messages from it A message queue therefore serves as a many to many communication switching station Consider this many to 1 communication example A server task can use a message queue as its input request queue Several client tasks independently send request messages to this queue The server task waits at this queue for input requests processes them and goes back for more a single queue single server implementation The number of message queues in your system is limited by the kc_nqueue specification in the pSOS Configuration Table A message queue can be deleted using the q_delete system call If one or more tasks are waiting there they will be removed from the wait queue and returned to the ready state When they run each task will have returned from their respective q_receive call with an error code Queue Deleted On the other hand if there are messages posted at the queue then the pSOS kernel will reclaim the message buffers and all message contents are lost Message buffers are covered in section 2 7 3 Messages and Message Buffers The Queue Contol Block Like a Tid a message queue s Qid carries the location of the queue s control block QCB even in a multiprocessor configuration This is an important notion because using the Qid to refer
227. river The driver must comply with the requirements mentioned in Section 7 9 pREPC Drivers The loader invokes only the de_read function internally Drivers that work with a loader must satisfy an additional requirement The loader can call the device read function with the address field of the I O parameter block IOPB set to NULL On receiving a request with address set to NULL the driver must read count bytes from the device and discard them This enables the loader to skip huge sections of object files that it does not need to load With some devices this can be accomplished by skipping count bytes without actually reading them An example of a loader compatible device driver is the TFTP pseudo device driver supplied with pSOSystem pSOSystem System Concepts 7 17 Chapter 7 I O System 7 11 7 11 1 pHILE Drivers Except for NFS volumes the pHILE file system manager accesses a volume by calling a device driver via the pSOS I O supervisor A driver invoked by the pHILE file system manager is called a pHILE driver When the pHILE file system manager needs to read or write data it calls the driver corresponding to the major minor device number specified when the volume was mounted The pHILE file system manager uses only two of the six standard I O system calls de_read and de_write Therefore a pHILE driver only has to supply two functions xxxxRead and xxxxWrite In practice most pHILE drivers also pro
228. roblems to the software any data structure in dual ported memory has two addresses one for each port Consider the problem when one processor node passes the address of a data structure to a second node If the data structure is in dual ported memory the address may have to be translated before it can be used by the target node depending on whether or not the target node accesses this memory through the same port as the sender node To overcome this confusion over the duality of address and minimize its impact on user application code the pSOS m kernel includes facilities that perform address conversions But first a few terminology definitions 3 11 1 P Portand S Port A zone is a piece of contiguously addressable memory which can be single or dual ported The two ports of a dual ported zone are named the p port and the s port The private p port is distinguishable in that it is typically reserved for one processor node only The system s port is normally open to one or more processor nodes pSOSystem System Concepts 3 17 Chapter 3 pSOS Multiprocessing Kernel 3 11 2 In a typical pSOS m configuration the multiple nodes are tied via a system bus e g VME or Multibus In this case each dual ported zone s s port would be interfaced to the system bus and each p port would be connected to one processor node via a private bus that is usually but not necessarily on the same circuit board If a node is connected to the p p
229. rs for example is a character a digit and mapping characters for example convert an ASCII character from lowercase to uppercase The String Handling Functions perform operations on strings With these functions you can copy one string to another string append one string to another string compare two strings and search a string for a substring The General Utilities provide a variety of miscellaneous functions including allocating and deallocating memory converting strings to numbers searching and sorting arrays and generating random numbers I O is the largest and most complex area of support The I O Functions include character direct and formatted I O functions I O is discussed in Section 6 3 I O Overview Detailed descriptions of each function are provided in pSOSystem System Calls NOTE The pREPC ANSI C library opens all files in binary mode regardless of the mode parameter passed to the fopen call This includes text files on MS DOS file systems pSOSystem System Concepts 6 3 Chapter 6 pREPC ANSI C Library I O Overview There are several different levels of I O supported by the pREPC pSOS pHILE environment providing different amounts of buffering formatting and so forth This results in a layered approach to I O because the higher levels call the lower levels The main levels are shown in Figure 6 1 pREPC Input Output f C Application j Program pSOS I O Supervisor Devi
230. ry The pHILE file system manager does not assume a default current directory for any task If a task intends to use relative pathnames then it must call change_dir at least once On pHILE format volumes the current directory may be deleted The results of using a relative pathname after the current directory has been deleted is unpredictable and should never be attempted Moving and Renaming Files The move_f system call allows a volume s directory tree structure to be modified by moving a file from one directory to another On MS DOS volumes only ordinary files may be moved On pHILE format volumes and NFS volumes ordinary and directory files may be moved CD ROM files cannot be moved or renamed When a directory is moved all of the files and subdirectories are also moved pSOSystem System Concepts 5 23 Chapter 5 pHILE File System Manager 5 5 7 5 6 5 6 1 5 24 move_f can be used to rename a file by moving it within the same directory Actually move_f is a misnomer because move _f never really moves data it only manipulates directory entries Files may not be moved between volumes Deleting Files Ordinary and directory files may be deleted removed by using the remove _f system call A file may not be removed if it is open or if it is a non empty directory file On a CD ROM file system a file cannot be deleted Special Services for Local Volume Types This section discusses some int
231. s automatically set the value of the aup_time element The authunix_create routine takes as arguments the values of the remaining fields The authunix_create_default routine sets the values of the authunix_parms structure members from their pNA equivalents The pNA configuration parameters are fully documented in the Configuration Tables section of the pSOSystem Programmer s Reference authunix_parms member Value set by authunix_create_default aup_machine PNA configuration parameter NC_HOSTNAME aup_uid PNA configuration parameter NC_DEFUID may be changed on a per task basis by the pNA call set_id aup_gid pNA configuration parameter NC_DEFGID may be changed on a per task basis by the pNA call set_id pSOSystem System Concepts 4 55 Chapter 4 Network Programming 4 20 4 4 20 5 4 56 aup_len aup_gids aup_len is always 0 so aup_gids is always empty Port Mapper RPC supports the use of the networking protocols TCP and UDP for message transport Because RPC and TCP UDP use different task addressing schemes clients must translate servers RPC addresses to TCP UDP addresses prior to making remote procedure calls RPC uses a port mapper task running on each host to perform address translation for local servers Prior to making a remote procedure call clients contact the server s port mapper to determine the appropriate TCP UDP destination address The port mapper protocol is handled within th
232. s physical size in anticipation of new data Call annex_f by passing the number of contiguous blocks you wish to add to a file known by a file ID the call will return the number of blocks added annex_f does nothing however to the logical size of the file see the cautions in the description of the call If a file s final size can be estimated in advance then annex_f may be used to allocate a single contiguous extent for the file immediately after its creation So long as subsequent write operations do not extend past this size the file will be truly contiguous If the file must be expanded then this may be left pSOSystem System Concepts Chapter 5 pHILE File System Manager implicitly to write_f or performed explicitly using additional annex_f operations 5 7 7 2 lock f The pHILE file system manager allows a single file to be opened and accessed by more than one task simultaneously Concurrent read access is generally quite safe however if one or more tasks perform write operations concurrent update then it may be necessary for such tasks to secure exclusive access to all or part of the file The lock_f function allows a task to lock a specified region of a file As long as the lock is in effect the pHILE file system manager will prevent all other file connections from reading writing or locking that region of the file thus providing exclusive access to a single connection lock_f requires two para
233. s soon as the call returns the buffer can be reused or de allocated by its owner The pNA component has copied the data into its internal buffers When the zero copy option is used control of the buffer triplet passes to the pNA component When the pNA component finishes using the message block triplet the triplet is freed Similarly on a recv call control of the buffer passes to the application which is responsible for freeing the message block triplet When zero copy is used with non blocking sockets there is a possibility that a send call may return after sending a part of the whole message In this case the user may resend the remaining part of the buffer on the next send call using the same message block triplet The message block points to the remaining part of the message Internally pNA keeps a reference to the buffer until the data is sent Four service calls are provided to access pNA memory management They are as follows pna_allocb allocates a message block triplet that contains a data buffer of the size passed in as a parameter The data buffer is internal to the pNA component pna_freeb frees a single message block triplet pna_freemsg frees a message pna_esballoc associates a message block and a data block with an externally specified buffer pna_esballoc returns a pSOSystem System Concepts 4 39 Chapter 4 Network Programming 4 15 2 4 16 4 40 pointer to a message block triplet that co
234. s 7 unique message types with each reserved to designate specific IP packet or network status characteristics as follows TYPE DESCRIPTION 1 ECHO REQUEST AND REPLY This type is used to test verify that the destination is reachable and responding The ping utility relies on this ICMP message type 2 DESTINATION UNREACHABLE This message type is generated when an IP datagram cannot be delivered by a pSOSystem System Concepts Chapter 4 Network Programming node This type is further delineated by ancillary codes defined as follows CODE EXPLANATION Network unreachable Host unreachable Protocol unreachable Port unreachable Fragmentation needed and DF is set Source route failed Destination network unknown Destination host unknown Source isolated OMAN DAP WBN FY O Communication with destination network is administratively prohibited jo Communication with destination host is administratively unknown 11 Network unreachable for type of service 12 Host unreachable for type of service 3 SOURCE QUENCH This type is generated when buffers are exhausted at an intermediary gateway or end host REDIRECT This type is generated for a change of route TIME EXCEEDED FOR DATAGRAM This type is generated when the datagram s time to live field has exceeded its limit 6 TIMESTAMP REQUEST AND REPLY This type is generated to request a timestamp 7 ADDRESS MASK REQUEST AND REPLY This type is se
235. sidered as an error condition If zero characters are returned the pREPC library treats this as an EOF condition Note that the buffering provided by the pREPC library adds a layer of buffering on top of the buffering implemented by the pHILE file system manager 6 3 5 stdin stdout stderr Three files are opened automatically for every task that calls the pREPC library They are referred to as the standard input device stdin the standard output device stdout and the standard error device stderr They can be disk files or I O devices and are defined by entries in the PREPC Configuration Table stdin stdout and stderr are implicitly referenced by certain input output functions For example printf always writes to stdout and scanf always reads from stdin pSOSystem System Concepts 6 7 Chapter 6 pREPC ANSI C Library 6 3 6 6 8 stdout and stderr are opened in mode w while stdin is opened in mode r Modes are discussed in the fopen description given in the system calls reference Each file is assigned a 256 byte buffer LC_BUFSIZ has no effect on the buffer size of these three files The buffering characteristics for stdin and stdout depend on the type of files specified for these devices In the case of an I O device they are line buffered For a disk file they are fully buffered stderr is an exception Regardless of whether stderr is attached to a disk file or an I O device it is fully buffered Like any
236. sily detected by comparing the sequence number in the ID to the current sequence number for the node Object IDs are 32 bit unsigned integers Because only 32 bits are available in a node number the number of bits used to encode the sequence number depends on the maximum number of nodes in the system as specified in the Multiprocessor Configuration Table entry mc_nnode If mc_nnode is less than 256 then 8 bits are used to encode the sequence number and the maximum sequence number is 255 If mc_nnode is greater than or equal to 256 then the number of bits used to encode the sequence number is given by the formula 16 ceil log gt mc_nnode 1 For example in a system with 800 nodes 6 bits would be available for the sequence number and the maximum sequence number would therefore be 63 In the largest possible system recall mc_nnode may not exceed 16383 there would be 2 bits available to encode the sequence number Once a node s sequence number reaches the maximum allowable value the next time the node attempts to rejoin the action taken by the pSOS m kernel depends on the value of the Multiprocessor Configuration Table entry mc_flags on the rejoining slave node If the SEQWRAP bit is not set then the node will not be allowed to rejoin However if SEQWRAP is set then the sequence number will wrap around to one Because this could theoretically allow a stale ID to be reused this option should be used with caution pSOSystem Syste
237. size divided by the MTU of the outgoing NI pNA service calls also use 128 byte buffers for temporary purposes they use a maximum of three buffers per call 4 14 1 4 Zero Size Buffers Zero size buffers are used during pna_esballoc service calls to attach externally supplied user buffers to a message block and a data block When zero size buffers are specified the pNA component allocates only a data block that is the associated buffer is not allocated The optimal number of zero size buffers to be configured depends on the number of externally specified buffers that can attached to pNA message blocks that is the number of times pna_esballoc is used For more details see Section 4 15 Zero Copy Options Message Blocks The pNA memory manager is highly optimized for data copy and fragmentation During these operations the pNA component allocates an additional message block and reuses the original data block and buffer The number of pNA copy or fragmentation operations per buffer depends on the size of the buffer and on the MTU size of the NI s configured in the system The maximum number of fragments for buffers of sizes less than the smallest MTU is two and the maximum number of fragments for all other buffers is the buffer size divided by the MTU The number of message blocks configured in the system should equal the total number of fragments that can be formed from the buffers pSOSystem System Concepts 4 37 C
238. sk formats MS DOS floppy disks have two sides side O and side 1 On each side there are T tracks numbered O to T 1 Each track contains S sectors numbered 1 to S A sector is 512 bytes and maps directly to a pHILE block A diskette thus contains 2 T S sectors The characteristics of each MS DOS diskette are shown in Table 7 1 Table 7 1 Characteristics of MS DOS Diskettes Capacity Track Number Sectors per Track 360 Kbyte 40 9 1 2 Mbyte 80 15 720 Kbyte 80 9 1 4 Mbyte 80 18 2 8 Mbyte 80 36 A block is mapped to a sector head track sector by the following rules 1 The track number is first determined by dividing the block number by 2 S The remainder R1 is saved for Step 2 2 R1 is divided by S to obtain the side O or 1 The remainder R2 is saved for Step 3 3 One is added to R2 to obtain the sector number These rules are summarized by the following equations Track Block 2 S remainder R1 Side R1 S remainder R2 Sector R2 1 pSOSystem System Concepts 7 21 Chapter 7 I O System 7 22 An example On a 360 Kbyte diskette T 40 and S 9 Block 425 is mapped as follows Track 425 2 9 23 remainder 11 Side 11 9 1 remainder 2 Sector 2 1 3 Thus on a 360 Kbyte floppy logical block 425 maps to Side 1 Track 23 Sector 3 7 11 3 3 Partitioned Hard Disk Format Standard MS DOS The following equations apply to hard disks Cylinder block
239. ss hardware address gt tuple in the ARP Table This is the normal way that the ARP Table is updated The next section explains how ARP operates 3 ARP Table entries can be added dynamically by using ioctl The following code segment illustrates the usage of the various ARP ioctl calls define satosin sa struct sockaddr_in sa int s rc struct arpreq ar char ha create any type of socket s socket AF_INET SOCK_DGRAM 0 get the arp entry corresponding to the internet host address 128 0 0 1 satosin amp ar arp_pa gt sin_family AF_INET satosin amp ar arp_pa gt sin_addr s_addr htonl1 0x80000001 pSOSystem System Concepts 4 29 Chapter 4 Network Programming ar arp_ha sa_family AF_UNSPEC re ioctl s SIOCGARP char amp ar set a permanent but not publishable arp entry corresponding to the internet host address 128 0 0 1 If the entry exists it will be modified Set the ethernet address to aa bb cc dd ee ff satosin amp ar arp_ pa gt sin_ satosin amp ar arp_pa gt sin_addr s_addr AF_INET htonl1 0x80000001 family ar arp_ha sa_family AF_UNSPEC bzero ar arp_ha sa_data 14 ha ar arp_ha sa_data ha 0 Oxaa ha 1 Oxbb ha 2 Oxcc ha 3 Oxdd ha 4 Oxee ha 5 Oxff ar arp_flags ATF_PERM re ioctl s SIOCSARP char amp ar delete the arp entry corresponding to the inter
240. start the calling task send an ASR or event to the calling task or ignore the error altogether If an mc_asyncerr routine is not provided mc_asyncerr 0 pSOS m generates an internal fatal error Note that an asynchronous service may operate on a local object In this case the call is performed synchronously because all relevant data structures are readily available Nonetheless should an error occur it is handled as if the object were remote Thus mc_asyncerr is invoked and no error indication is returned to the caller This provides consistent behavior regardless of the location of the referenced object Asynchronous calls are only supported in the pSOS m kernel If called when using the pSOS kernel the single processor version an error is returned Agents Certain RSCs require waiting at an object on a remote node For example q_receive and sm_p may require the calling task to wait for a message or semaphore respectively If the message queue or semaphore is local then the pSOS m kernel simply enqueues the calling task s TCB to wait at the object What if the object is not local Suppose the example in section 3 5 1 involves a q_receive not a q_send call The transaction sequence is identical up to when the destination node s pSOS m kernel deciphers the received packet and recognizes the q_receive The pSOS m kernel uses a pseudo object called an Agent to generate the q_receive call to the target queue If the que
241. stem call broadcasts a message to all tasks waiting at a queue This provides an efficient method to wake up multiple tasks with a single system call There is only one way to request a message from a queue the q_receive system call If no message is pending the task can elect to wait wait with timeout or return unconditionally If a task elects to wait it will either be by first in first out or by task priority order depending on the specifications given when the queue was created If the message queue is non empty then the first message in the queue will be returned to the caller The message buffer that held that message is then released back to the shared or the queue s private free buffer pool Messages and Message Buffers Messages are fixed length consisting of four long words A message s content is entirely dependent on the application It can be used to carry data pointer to data data size the sender s Tid a response queue Qid or some combination of the above In the degenerate case where a message is used purely for synchronization it might carry no information at all pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel When a message arrives at a message queue and no task is waiting the message must be copied into a message buffer that is then entered into the message queue A pSOS message buffer consists of five long words Four of the long words are the message and one is a link field The li
242. t system call Non Bloc king Sockets Many socket operations cannot be completed immediately For instance a task might attempt to read data that is not yet available at a socket In the normal case this would cause the calling task to block until the data became available A socket can be marked as non blocking through use of the ioctl system call If a socket has been marked as non blocking an operation request that cannot be completed without blocking does not execute and an error is returned to the caller The select system call can be used to check the status of a socket so that a system call will not be made that would cause the caller to block Out of Band Data Stream sockets support the notion of out of band data Out of band data is a logically independent transmission channel associated with each pair of connected sockets The user has the choice of receiving out of band data either in sequence with the normal data or independently of the normal sequence It is also possible to peek at out of band data pSOSystem System Concepts 4 13 Chapter 4 Network Programming 4 4 11 45 A logical mark is placed in the data stream to indicate the point at which out of band data was sent If multiple sockets might have out of band data awaiting delivery for exceptional conditions select can be used to determine those sockets with such data pending To send out of band data the MSG_OOB flag should be set with th
243. t mblk_t b_rptr b_wptr b_wptr b_wptr b_datap b_datap b_datap Data Block 1 Data Block 2 db_base db_base dblk_t dblk_t db_lim db_lim Data Buffer Data Buffer p a lt _ PE a a 4 33 Chapter 4 Network Programming 4 14 4 34 The basic unit of transmission used by protocol layers in the pNA component is a packet A packet contains a protocol header and the data it encapsulates Each protocol layer tags a header to the packet and passes it to the lower layer for transmission The lower layer in turn uses the packet as encapsulated data and tags its protocol header and passes it to its lower layer Packets are stored in the form of messages The buffers in the pNA component are used to store data protocol headers and addresses Data is passed into the pNA component via two interfaces At the user level data is passed via the send sendto and sendmsg service calls At the NI interface data is passed via the Announce Packet call See Section 4 11 Network Interfaces The pNA component allocates a message block triplet and copies data from the external buffer to the buffer associated with the triplet The message is then passed to the protocol layers for further manipulation As the data passes through various protocol layers additional message block triplets are allocated to store the protocol headers and are linked to the message The pNA component also allocates temporary message block triplets t
244. t be assigned to each task when it is created There are 256 priority levels 255 is the highest O the lowest Certain priority levels are reserved for use by special pSOSystem tasks Level O is reserved for the IDLE daemon task furnished by the pSOS kernel Levels 240 255 are reserved for a variety of high priority tasks including the pSOS ROOT A task s priority including that of system tasks can be changed at runtime by calling the t_setpri system call When a task enters the ready state the pSOS kernel puts it into an indexed ready queue behind tasks of higher or equal priority All ready queue operations including insertions and removals are achieved in fast constant time No search loop is needed pSOSystem System Concepts 2 9 Chapter 2 pSOS Real Time Kernel 2 3 5 During dispatch when it is about to exit and return to the application code the pSOS kernel will normally run the task with the highest priority in the ready queue If this is the same task that was last running then the pSOS kernel simply returns to it Otherwise the last running task must have either blocked or one or more ready tasks now have higher priority In the first blocked case the pSOS kernel will always switch to run the task currently at the top of the indexed ready queue In the second case technically known as preemption the pSOS kernel will also perform a task switch unless the last running task has its preemption mode disabled
245. taliasiedaltas A tolaaieinvedeue sistas ste veaade te xvi 1 Product Overview Tel What Isi pSOSystem ioneina E EEEE e dues 1 1 V2 SySte m Architecture ii3c53 26 Hs ie Higlek elaeitae teats aged ea aa Meee 1 2 1 3 Integrated Development Environment c cece eee ee eee eee ee enee 1 4 2 pSOS Real Time Kemel 2e YQVECTVICW oc doses sos so EE ae Sat EA T EE A eh ves eed ven AAE ue E EEA 2 1 2 2 Multitasking Implementation cece ec ee eee ee eee neeeeneaeeenens 2 2 2 2 1 Concept ofa Task vi dia diusistiies dendes lade E N A 2 3 2 2 2 Decomposition Criteria ee eee cece eee eeeeeeeeeeeeneneeeeees 2 4 2 3 Overview of System Operations ccc ec eee eeceteceaeeeeeeneeeeeenes 2 5 2 3 1 Task SES ere tdenss e E a 2 6 pSOSystem System Concepts iii Contents 2 4 2 5 2 6 2 7 2 8 2 9 iv 2 3 2 SEALE Transitions i ahssan ses ved cele wiee a SUS veces daed ews 2 6 2 9 9 Task Scheduling roo coea eae wees ea dul a EEEE EN e i Ei 2 9 2 9 4 Task Priority iced iee Gs lee cade die dain dew E E alli das AERE EE 2 9 2 3 5 Roundrobin by Timeslicing c cece eee eee eeeeeee eee eens 2 10 2 3 6 Manual Roundrobin cece ee eee eee eee ee eee eeesenensaees 2 12 2 3 7 Dispatch Criteria red scdcedcee tates avin is ian de SEEE A 2 12 2 3 8 Objects Names and IDS cece en scene ee neeeenenees 2 12 Task Managemen onirin ns asia eas EEE A EAS 2 14 2AF Creation f
246. tarting block number of data space See section 5 7 1 5 In addition the root block contains the following information about the volume INIT_TIME The time and date of volume initialization VOLUME_NAME The volume label VOLUME_ SIZE The volume size in blocks NUMBEROF FD The number of file descriptors that is the FLIST size VALIDATE KEY Volume initialization successful pSOSystem System Concepts Chapter 5 pHILE File System Manager 5 7 1 2 The Root Directory The volume s root directory is a directory file that forms the starting point from which the pHILE file system manager locates all other files on a volume From the root directory emanates the tree structure of sub directories and ordinary files In the simplest case the root directory contains only ordinary files thus yielding a one level directory structure common in less sophisticated file systems Immediately after a volume has been initialized its root directory contains two files FLIST SYS which is the volume s list of file descriptors and BITMAP SYS which is the volume s map of occupied blocks As with any user file ordinary or directory the root directory is expanded automatically by the pHILE file system manager as required For directory files such expansion occurs one block at a time and the blocks are generally not contiguous Contiguous expansion of directory files can be achieved using the annex_f system call described in pSOSystem S
247. tates discussed above should not be confused with user and supervisor program states that exist on some processors The latter are hardware states of privilege 2 3 3 Task Scheduling The pSOS kernel employs a priority based preemptive scheduling algorithm In general the pSOS kernel ensures that at any point in time the running task is the one with the highest priority among all ready to run tasks in the system However you can modify pSOS scheduling behavior by selectively enabling and disabling preemption or time slicing for one or more tasks Each task has a mode word see section 2 4 3 Task Mode Word with two settable bits that can affect scheduling One bit controls the task s preemptibility If disabled then once the task enters the running state it will stay running even if other tasks of higher priority enter the ready state A task switch will occur only if the running task blocks or if it re enables preemption A second mode bit controls timeslicing If the running task s timeslice bit is enabled the pSOS kernel automatically tracks how long the task has been running When the task exceeds the predetermined timeslice and other tasks with the same priority are ready to run the pSOS kernel switches to run one of those tasks Timeslicing only affects scheduling among equal priority tasks For more details on timeslicing see section 2 3 5 Roundrobin by Timeslicing 2 3 4 Task Priority A priority mus
248. te data copy at its interfaces as well These options are referred to as zero copy operations The pNA component extends the standard Berkeley socket interface at the user level and provides an option at the NI level to support zero copy operations Zero copy is achieved in the pNA component by providing a means of exchanging data at interfaces via message block triplets and by enabling access to its memory management The zero copy operations provided at the interfaces are independent of each other that is an application can choose either one or both In most cases the NI interface is optimized to pSOSystem System Concepts 4 15 1 Chapter 4 Network Programming perform zero copy while retaining the standard interface at the socket level Socket Extensions The sendto send recv and recvfrom service calls are extended to support the zero copy option An option is provided in the calls allowing data to be exchanged via message block triplets An additional flag MSG_RAWMEM is provided in these service calls When the flags parameter in these service calls is set to MSG_RAWMEM the buf parameter contains a pointer to a message block triplet See these service call descriptions in pSOSystem System Calls When the zero copy option is not used a buffer always remains in the control of its owner For example during a send call the address of the buffer containing data to be sent is passed to the pNA component A
249. ted actions and exchange a number of internode packets There are two types of RSC synchronous and asynchronous Each is described in the following sections pSOSystem System Concepts Chapter 3 pSOS Multiprocessing Kernel 3 5 1 Synchronous Remote Service Calls A synchronous RSC occurs whenever any of the following pSOS m service calls are directed to an object that does not reside on the local node as_send ev_send q_broadcast q_vbroadcast q_receive q_vreceive q_send q_vsend q_urgent q_vurgent pt_getbuf pt_retbuf sm_p sm_v t_getreg t_setreg t_resume t_suspend t_setpri Consider what happens when a task calls q_send to send a message to a queue on another node l On the source node the pSOS m kernel receives the call deciphers the QID and determines that this requires an RSC The pSOS m kernel calls the Kernel Interface KI to get a packet buffer loads the buffer with the q_send information and calls the KI to send the packet to the destination node If the KI delivers the packet successfully the pSOS m kernel blocks the calling task and then switches to run another task Meanwhile on the destination node its KI senses an incoming packet typically from an ISR and calls the pSOS m Announce Packet entry When the KI s ISR exits pSOS m calls the KI to receive the packet deciphers its contents and generates an internal q_send call to deliver the message to the r
250. tem System Concepts Chapter 6 pREPC ANSI C Library 6 3 4 Buffering Techniques This section describes the buffering techniques used by the pREPC library There are two cases to consider writing and reading On output data is sent to the file s buffer and subsequently transferred or flushed to the I O device or disk file by calling a pSOS device driver for an I O device or the pHILE file system manager for a disk file The time at which a buffer is flushed depends on whether the file is line buffered or fully buffered If line buffered the buffer is flushed when either the buffer is full or a new line character is detected If fully buffered the buffer is flushed only when it is full In addition data can be manually flushed or forced from a buffer at any time by calling the fflush function By default I O devices are line buffered whereas disk files are fully buffered This can be changed after a file is opened by using the setbuf or setvbuf functions When reading the pREPC library retrieves data from a file s buffer When attempting to read from an empty buffer the pREPC library calls either a pSOS driver or the pHILE file system manager to replenish its contents When attempting to replenish its internal buffer the pREPC library reads sufficient characters to fill the buffer The pSOS driver or the pHILE file system manager may return fewer characters than requested This is not necessarily con
251. tem call The type of the socket stream datagram or raw is given as an input parameter to the call A socket descriptor is returned which is then used by the creator to access the socket An example of socket used to create a stream socket is as follows s socket AF_INET SOCK_STREAM 0 The returned socket descriptor can only be used by the socket s creator However the shr_socket system call can be used to allow other tasks to reference the socket ns shr_socket s tid The parameter S is a socket descriptor used by the calling task to reference an existing socket S is normally a socket descriptor returned by socket The parameter tid is the task ID of another task that wants to access the same socket shr_socket returns a new socket descriptor ns which can be used by tid to reference the socket This system call is useful when designing UNIX style server programs Socket Addresses Sockets are created without addresses Until an address is assigned or bound to a socket it cannot be used to receive data A socket address consists of a user defined 16 bit port number and a 32 bit internet address The socket address functions as a name that is used by other entities such as tasks residing on other nodes within the internet to reference the socket pSOSystem System Concepts 4 9 Chapter 4 Network Programming 4 4 4 The bind system call is used to bind a socket address to a socket bind takes as inp
252. ters that you supply when you initialize the volume This contiguous sequence of blocks is used to hold the file descriptors for the volume It is positioned immediately following the bitmap Its size is determined by parameters you supply when you initialize a volume 5 31 Chapter 5 pHILE File System Manager 5 32 Thus a volume has four initial data structures containing vital internal management data Before a volume can be used it must be initialized using the init_vol call described in the system calls reference init_vol builds the root block the root directory the bitmap and the FLIST structures on the volume See the init_vol call description in pSOSystem System Calls for C language definitions of these data structures The bitmap can be placed anywhere on a volume and it is always followed by the FLIST They need not be contiguous with the root block root directory or any other data structure on the volume Because the bitmap is used during write operations and FLIST is used extensively during all file creation and connection overall volume access can be improved by careful placement of these structures 5 7 1 1 The Root Block The root block is the starting point from which the pHILE file system manager locates all other data on the volume For this purpose it contains the BITMAP_ADDRESS The starting block number of the volume bitmap FLIST_ADDRESS The starting block number of FLIST DATA_ADDRESS The s
253. the data buffer pSOSystem System Concepts 4 35 Chapter 4 Network Programming 4 36 2 If there is no such buffer size available the pNA component searches for the smallest sized buffer that can contain the requested size 3 If there is none the pNA component selects the maximum buffer size configured Once a size is selected the pNA component checks for a free buffer from the selected size s buffer list If none are available the pNA component blocks the caller on a blocking call or returns null on a non blocking call If the size of the buffer is not sufficient to copy all of the data the pNA component copies the data into multiple buffers For optimal configuration the pNA component should always find an exact match when doing buffer size selection Thus the configuration should have buffer sizes equal to the MTU of the NI s configured in the pNA component to satisfy the requirement at the NI interface and buffer sizes equal to the user buffer sizes specified in the send sendto and sendmsg service calls to satisfy user interface requirements The number of buffers to be configured for each size depends on the socket buffer size and incoming network traffic pNA flexible memory configuration provides multiple buffer sizes However 128 byte and zero size buffers have special meanings 128 byte buffers are used internally by the pNA component for storing protocol headers and for temporary usage These
254. then aborts with a fatal error Joining nodes must observe one important timing limitation In networks with widely varying transmission times between nodes it is possible for a node to join the system obtain the ID of an object on a remote node and post an RSC to that object all before the object s node of residence has been notified that the new node has joined When this occurs the destination node simply ignores the RSC This may cause the calling task to hang or if the call was asynchronous to proceed believing the call was successful To prevent such a condition a newly joining node must not post an RSC to a remote node until a sufficient amount of time has elapsed to ensure the remote node has received notification of the new node s existence In systems with similar transmission times between all master and slave nodes no special precautions are required because all slaves would be pSOSystem System Concepts Chapter 3 pSOS Multiprocessing Kernel informed of the new node well before the new node could successfully IDENT the remote object and post an RSC In systems with dissimilar transmission times an adequate delay should be introduced in the ROOT task The delay should be roughly equal to the worst case transmission time from the master to a slave node 3 7 Node Failures As mentioned before the master node must never fail In contrast slave nodes may exit a system at any time Although a node may exit for any
255. tion pt_retbuf Return a buffer to a partition Regions and Segments A memory region is a user defined physically contiguous block of memory Regions can possess distinctive implicit attributes For example one can reside in strictly local RAM another in system wide accessible RAM Regions must be mutually disjoint and can otherwise be positioned on any long word boundary Like tasks regions are dynamic abstract objects managed by the pSOS kernel A region is created using the rn_create call with the following inputs its user assigned name starting address and length and unit_size The pSOS system call rn_create returns a region ID RNid to the caller For any other task that knows a region only by name the rn_ident call can be used to obtain a named region s RNid A segment is a variable sized piece of memory from a memory region allocated by the pSOS kernel on the rn_getseg system call Inputs to rn_getseg include a region ID a segment size that might be anything and an option to wait until there is sufficient free memory in the region The rn_retseg call reclaims an allocated segment and returns it to a region A region can be deleted although this is rarely used in a typical application For one thing deletion must be carefully considered and is allowed by the pSOS kernel only if there are no outstanding segments allocated from it or if the delete override option was used when the region was created Special Re
256. to do so being careful to restore the task s original mode before exiting Similar caveats apply to Asynchronous Service Routines ASRs pSOSystem System Concepts Chapter 7 I O System Because a device driver executes as a subroutine to the calling task it can use any pSOS system call The following system services are commonly used by drivers Function System Call Waiting q_receive ev_receive sm_p Wakeup q_send ev_send sm_v Queueing q_receive q_send Timing tm_tick Timeout parameters on Waits Mutual exclusion sm_p sm_v Buffer management pt_getbuf pt_retbuf Storage allocation rn_getseg rn_retseg In addition a device driver usually has an ISR which performs wakeup queueing and buffer management functions For a complete list of system calls allowed from an ISR see Chapter 2 pSOS Real Time Kernel Note the following caveats regarding driver usage 1 You must account for device driver supervisor stack usage when determining the stack sizes for tasks that perform I O I O calls can never be made from the pSOS task creation task deletion or context switch callouts 2 I O calls can never be made from the pSOS task creation task deletion or context switch callouts I O calls can never be made from an ISR In multiprocessor systems I O service calls can only be directed at the local node The pSOS kernel does not support remote I O calls However it is possible
257. to gain an overall understanding of pSOSystem components Basic familiarity with UNIX terms and concepts is assumed A secondary audience includes those seeking an introduction to pSOSystem features pSOSystem System Concepts xiii About This Manual Organization This manual is organized as follows Chapter 1 Product Overview presents a brief introduction to pSOSystem software including the standard components Chapter 2 pSOS Real Time Kernel describes the pSOS real time multitasking kernel the heart of pSOSystem software Chapter 3 pSOS m Multiprocessing Kernel describes the extensions offered by the pSOS m multitasking multiprocessing kernel Chapter 4 Network Programming provides a summary of pSOSystem networking services and describes in detail the pNA TCP IP Manager component Chapter 5 pHILE File System Manager describes the pSOSystem file management component Chapter 6 pREPC ANSI C Library describes the pSOSystem ANSI C run time library Chapter 7 I O System discusses the pSOSystem I O system and explains how device drivers are incorporated into a system Related Documentation When using the pSOSystem software you might want to have on hand the other manuals of the basic documentation set m pSOSystem Installation Guide provides installation instructions for workstation and PC hosts m pSOSystem Getting Started explains how to create and bring up pSOSystem based applications This manual also
258. ts pathname can be quite long pSOSystem System Concepts Chapter 5 pHILE File System Manager and may consequently require a significant amount of memory for storage Even worse if a saved pathname is expressed relative to a current directory and the current directory changes before the file is reopened the operation will fail or the wrong file will be opened In these cases the pathname can instead be converted into a file number The file can be re opened at a later time independently of the current directory 5 6 2 Direct Volume I O While a volume s data is usually accessed through the directory organization provided by the pHILE file system manager certain applications may need to access data via its logical address on the volume Two pHILE system calls read_vol and write_vol allow you to access data on a local volume by block address Any number of bytes may be accessed beginning at any byte within any logical block on a volume These calls provide two advantages compared to calling the appropriate device driver directly which bypasses the pHILE file system manager entirely First if the volume has been mounted with some synchronization mode other than immediate write data recently written to the volume may still be memory resident not having yet been flushed to the device Calling the driver directly would not read the latest copy of such data Worse data written directly to the volume could be overwritten by
259. twork Interfaces The pNA component accesses a network by calling a user provided layer of software called the Network Interface NI The interface between the pNA component and the NI is standard and independent of the network s physical media or topology it isolates the pNA component from the network s physical characteristics The NI is essentially a device driver that provides access to a transmission medium The terms network interface NI and network driver are all used interchangeably in this manual A detailed description of the interface between the pNA component and the NI is given in the Interfaces and Drivers section of the pSOSystem Programmer s Reference There must be one NI for each network connected to a pNA node In the simplest case a node is connected to just one network and will have just one NI However a node can be connected to several networks simultaneously and therefore have several network interfaces Each NI is assigned a unique IP address pSOSystem System Concepts 4 23 Chapter 4 Network Programming 4 11 1 4 24 Each network connection NI has a number of attributes associated with it They are as follows m The address of the NI entry point m The IP address m The maximum transmission unit m The length of its hardware address Control flags m The network mask m Destination IP address point to point links The pNA component stores these attributes for all of the net
260. ucture that is initialized as follows m The higher order 16 bits of the device number in_dev are set to the device major number the lower sixteen bits are set to 0 m The calling task s ID tid and the used field are set to O m The pointer to the IOPB in_iopb and data area io_data_area are set to NULL The auto initialization occurs just after pSOS initializes itself and all the components configured in the system and just before it transfers control to the highest priority task in the system During auto initialization no task context is available This places certain restrictions on the device initialization functions that can be called during auto initialization Follow these guidelines when writing a device initialization function that you intend to use for auto initialization m Use only system calls that are callable from an ISR m Do not use pSOS system calls that block pSOSystem System Concepts Chapter 7 I O System m You can create or delete global objects but do not make other calls to global objects residing on a remote node because they can block Note that system calls that are non blocking if made locally are blocking if made across node boundaries Do not use system calls from components other than the pSOS kernel as they require a task context These restrictions are not severe for a routine that simply initializes devices A device initialization function can be divided into two parts
261. ue is empty then the Agent s Control Block which resembles a mini TCB will be queued at the message wait queue The destination node then executes a normal dispatch and returns to the application Later when a message is posted to the target queue the Agent is dequeued from the message wait queue The pSOS m kernel uses the original RSC packet buffer to hold a reply packet containing among other things the received message it then calls the KI to send the reply packet back to the source node The Agent is released to the free Agent pool and all remaining transactions are again identical to that for q_send In summary Agents are used to wait for messages or semaphores on behalf of the task that made the RSC They are needed because the pSOSystem System Concepts Chapter 3 pSOS Multiprocessing Kernel calling tasks are not resident on the destination node and thus not available to perform any waiting function The Multiprocessor Configuration Table entry mc_nagent specifies the number of Agents that the pSOS m kernel will allocate for that node Because one Agent is used for every RSC that requires waiting on the destination node this parameter must be large enough to support the expected worst case number of such RSCs 3 5 4 RSC Overhead In comparison to a system call whose target object is resident on the node from which the call is made an RSC requires several hidden transactions between the pSOS m kernel and the KI both
262. uity For example ifa file can be covered in fewer than 10 extents then access to any of its data can be accomplished via the file descriptor alone pSOSystem System Concepts Chapter 5 pHILE File System Manager The extent map will hold up to n n 1 10 extents where n is blocksize 8 as above For example if blocksize is 1 Kbyte then the maximum number of extents per file is 128 129 10 or 16522 In the worst case of 1 block per extent a file can contain 16522 blocks or 16 megabytes of data However because the pHILE file system manager contains both implicit and explicit features to cluster many blocks into a single extent the number of extents required to map a file is usually very much smaller In fact even for a very large file the number of extents needed to map the file rarely exceeds 100 Figure 5 4 on page 5 40 illustrates an example of an extent map layout 5 7 3 Data Address Mapping The pHILE file system manager allows you to access file content down to individual bytes For each file access the pHILE file system manager performs a number of address translations that convert or map your stretch of data into a volume block or blocks As an example of file content access consider a file with three extents Assume its file descriptor s extent map looks like the following 060 5 789 2 556 1 That is the file has 8 blocks Assume that block size is 1 Kbyte If a read call re
263. ularly true for dynamic applications wherein parts of the system can be shutdown and or regenerated on demand In general t_delete should only be used to perform self deletion The reason is simple When used to forcibly delete another task t_delete denies that task a chance to perform any necessary cleanup work A preferable method is to use the t_restart call which forces a task back to its initial entry point Because t_restart can pass an optional argument list the target task can use this to distinguish between a t_start a meaningful t_restart or a request for self deletion In the latter case the task can return any allocated resources execute any necessary cleanup code and then gracefully call t_delete to delete itself pSOSystem System Concepts 2 17 Chapter 2 pSOS Real Time Kernel 2 4 7 2 4 8 2 5 A deleted task ceases to exist insofar as the pSOS kernel is concerned and any references to it whether by name or by Tid will evoke an error return Notepad Registers Each task has 16 software notepad 32 bit registers They are carried in a task s TCB and can be set and read using the t_setreg and t_getreg calls respectively The purpose of these registers is to provide to each task in a standard system wide manner a set of named variables that can be set and read by other tasks including by remote tasks on other processor nodes Eight of these notepad registers are reserved for system use The remaining e
264. uld have meant compromises in other important respects At present object creation and deletion calls are not supported for performance and robustness reasons Notice that every system call that may be useful for communication synchronization and state control is included Furthermore note that RSCs are supported only if they are called from tasks Calls from ISRs are illegal because the overhead associated with internode communication makes it unacceptable for use from an ISR In summary in the event of an RSC the pSOS m kernel on the source and destination nodes use their respective KI to exchange packets which in a manner completely transparent to the user s application bridge the gap between the two nodes pSOSystem System Concepts Chapter 3 pSOS Multiprocessing Kernel 3 5 2 Asynchronous Remote Service Calls When a task makes a synchronous remote service call the task is blocked until a reply is received from the destination node This allows errors and return values to be returned to the calling task and is essential to transparent operation across nodes However some service calls such as q_send return only an error code and if the caller knows an error is not possible then waiting for a reply needlessly delays execution of the calling task and consumes CPU resources with the processing of two context switches as the task blocks and then unblocks For faster operation in these cases the pSOS m kernel offers
265. uld handle address resolution internally If not i e the ARP flag is disabled the pNA component passes the internet address to the network driver 2 If the ARP flag is enabled the pNA component searches its ARP Table see section 4 12 1 for an entry containing the internet address If an entry is found the corresponding hardware address is passed to the NI pSOSystem System Concepts Chapter 4 Network Programming 3 If the internet address is not found in the ARP Table the pNA component uses the Address Resolution Protocol see section 4 12 2 to obtain the hardware address dynamically 4 12 1 The ARP Table The pNA component maintains a table called the ARP Table for obtaining a hardware address given an internet address This table consists of lt internet address hardware address gt tuples The ARP Table is created during pNA initialization the pNA Configuration Table entry NC_NARP specifies its size Entries can be added to the ARP Table in one of three ways 1 An Initial ARP Table can be supplied The pNA Configuration Table entry NC_IARP contains a pointer to an Initial ARP Table The contents of the Initial ARP Table are copied to the actual ARP Table during pNA initialization 2 Internet to hardware address associations can be determined dynamically by the ARP protocol When the pNA component uses ARP to dynamically determine an internet to hardware address mapping it stores the new lt internet addre
266. unsigned long Gauge unsigned long TimeTicks unsigned long DisplayString char PhysAddress struct sockaddr defined in pna h The following code fragments demonstrate how to set and get the objects ipInReceives and ipForwarding respectively Get the value of ipInReceives long s unsigned long ip_input_pkts socket type in following call is irrelevant s socket AF_INET SOCK STREAM 0 ioctl s SIOCGIPINRECEIVES amp ip_input_pkts close s print lu IP datagrams recvd n ip_input_pkts Set the value of ipForwarding int s already open socket descriptor long forwarding get current status first ioctl s SIOCGIPFORWARDING amp forwarding if forwarding 1 puts Forwarding was on else forwarding 2 puts Forwarding was off forwarding 2 corresponds to not forwarding ioctl s SIOCSIPFORWARDING amp forwarding puts Forwarding turned off pSOSystem System Concepts 4 45 Chapter 4 Network Programming 4 19 3 4 46 Accessing Tables Accessing information stored in tables is more complicated than accessing simple variables The complexity is primarily due to the SNMP specification and the fact that table sizes vary over time based on the state of your system The pNA component defines C data structures for each MIB II table These definitions are contained in lt pna_mib h gt and are shown in section 4 19 4 A table usually consists
267. ut a socket descriptor and a socket address and creates an association between the socket and the address specified An example using bind is as follows bind s addr addrlen Connection Establishment When two tasks wish to communicate the first step is for each task to create a socket The next step depends on the type of sockets that were created Most often stream sockets are used in which case a connection must be established between them Connection establishment is usually asymmetric with one task acting as a client and the other task a server The server binds an address i e a 32 bit internet address and a 16 bit port number to its socket as described above and then uses the listen system call to set up the socket so that it can accept connection requests from clients The listen call takes as input a socket descriptor and a backlog parameter backlog specifies a limit to the number of connection requests that can be queued for acceptance at the socket A client task can now initiate a connection to the server task by issuing the connect system call connect takes a socket address and a socket descriptor as input The socket address is the address of the socket at which the server is listening The socket descriptor identifies a socket that constitutes the client s endpoint for the client server connection If the client s socket is unbound at the time of the connect call an address is automatically selecte
268. ut state are performed in constant time no search loops are required If a task is waiting say for message q_receive with timeout and the message arrives in time then the task is simply removed from the timing pSOSystem System Concepts 2 11 4 2 115 Chapter 2 pSOS Real Time Kernel structure given the message and made ready to run If the message does not arrive before the time interval expires then the task will be given an error code indicating timeout and made ready to run Timeout is measured in ticks If kc_ticks2sec is 100 and an interval of 50 milliseconds is required then a value of 5 should be specified Timeout intervals are 32 bits wide allowing a maximum of 2 ticks A timeout value of n will expire on the nth forthcoming tick Because the system call can happen anywhere between two ticks this implies that the real time interval will be between n 1 and n ticks Absolute Versus Relative Timing There are two ways a task can specify timing relative or absolute Relative timing is specified as an interval measured in ticks Absolute timing is specified as an appointed calendar date and time The system calls tm_wkafter and tm_evafter accept relative timing specifications The system calls tm_wkwhen and tm_evwhen accept absolute time specifications Note that absolute timing is affected by any tm_set calls that change the calendar date and time whereas relative timings are not affected In addition
269. vide an xxxxlnit service even though it is not called by the pHILE file system manager It must be called independently by your application via de_init prior to mounting the volume corresponding to the device Similarly even though de_open de_close and de_cntrl are not used by the pHILE file system manager a driver can implement these operations for physical I O error sensing formatting and so forth Like all drivers called by the pSOS I O supervisor pHILE drivers receive an ioparms parameter on input Before a pHILE driver exits it must store an error code indicating the success or failure of the call in ioparms err A value of zero indicates the call was successful Any other value indicates an error condition In this case the pHILE file system manager aborts the current operation and returns the error code back to the calling application Error code values are driver defined Check the error code appendix of psOSystem System Calls for the error code values available to drivers The Buffer Header When dealing with pHILE drivers the IOPB parameter block pointed to by ioparms in_iopb is called a buffer header A buffer header has the following structure typedef struct buffer_header unsigned long b_device device major minor number unsigned long b_blockno starting block number unsigned short b_flags block_type data or control unsigned short b_bcount number of blocks to transfer v
270. vironment offers both Network File System NFS client and NFS server support NFS server allows remote systems to access files stored on pHILE managed devices NFS client facilities are part of the pHILE component and allow your application to transparently access files stored on remote storage devices STREAMS is an extremely flexible facility for developing system communication services It can be used to implement services ranging from complete networking protocol suites to individual device drivers Many modern networking protocols including Windows NT and UNIX System V Release 4 2 networking services are implemented in a STREAMS environment pSOSystem offers a complete System V Release 4 2 compatible STREAMS environment called OpEN Open Protocol Embedded Networking 4 2 pSOSystem System Concepts Chapter 4 Network Programming The following documents published by Prentice Hall provide more detailed information on UNIX System V Release 4 2 m Operating System API Reference ISBN 0 13 017658 3 m STREAMS Modules and Drivers ISBN O 13 066879 6 a Network Programming Interfaces ISBN 0 13 017641 9 m Device Driver Reference ISBN 0 13 042631 8 This chapter describes the pNA and pRPC network components The FTP Telnet pSH TFTP and NFS server facilities are documented in the System Services section of the pSOSystem Programmer s Reference NFS client services are described along with the pHILE component in Cha
271. work interfaces installed in your system in the NI Table discussed in Section 4 11 6 The NI Table NI attributes can be modified using ioctl The first two attributes are self explanatory Maximum transmission units hardware addresses control flags network subnet mask and destination IP address are discussed in the following subsections Maximum Transmission Units MTU Most networks are limited in the number of bytes that can be physically transmitted in a single transaction Each NI therefore has an associated maximum transmission unit MTU which is the maximum packet size that can be sent or received If the size of a packet exceeds the network s MTU the IP layer fragments the packet for transmission Similarly the IP layer on the receiving node reassembles the fragments into the original packet The minimum MTU allowed by the pNA component is 64 bytes There is no maximum limit A larger MTU leads to less fragmentation of packets but usually increases the internal memory requirements of the NI Generally an MTU between 512 bytes and 2K bytes is reasonable For example the MTU for Ethernet is 1500 pSOSystem System Concepts 4 11 2 4 11 3 Chapter 4 Network Programming Hardware Addresses In addition to its internet address every NI has a hardware address The internet address is used by the IP layer while the hardware address is used by the network driver when physically transferring packets on the netw
272. x f call is made m A new block must be added to a directory to accommodate a new entry This can happen on a create_f make_dir or move _f call m An indirect or index block must be added when a new extent is added to a file This can happen whenever blocks are allocated for whatever reason When more blocks are needed the pHILE file system manager first determines the allocation size This is the ideal size of the extent to be allocated The allocation size for each case above is determined as follows Case 1 write_f Extends a File When extending an ordinary file to write data from a write_f call the allocation size is the larger of the number of blocks needed for the data and the expansion unit that you specified when the file was created For example assume that a write_f call requires two blocks If the file was created with an expansion unit of five blocks then the allocation size will be five blocks On the other hand if the file s expansion unit is one then the allocation size will be two blocks Case 2 annex_f Extends a File The allocation size is a parameter of the annex_f call and is thus provided by the calling task Case 3 A New Entry Extends A Directory File Directories have the following properties m They grow one entry at a time m Each entry is 16 bytes long and m There is no expansion unit associated with a directory For all of these reasons the directory allocation size is
273. xecute with asynchronous signals disabled Otherwise the ASR must be programmed to handle re entrancy The details of how an ASR gains control are processor specific this information can be found in the description of as_catch in pSOSystem System Calls A task can disable and enable its ASR selectively by calling t_mode Any signals received while a task s ASR is disabled are left pending When re enabled an ASR will receive control if there are any pending signals Asynchronous Signal Operations The as_send call makes the specified signals pending at the target task without affecting its state or when it will run If the target task is not the running task its ASR takes over only when it is next dispatched to run If the target is the running task which is possible only if the signals are sent by the task itself or more likely by an ISR then the running task s course changes immediately to the ASR pSOSystem System Concepts 2 10 3 2 11 Chapter 2 pSOS Real Time Kernel Signals Versus Events Despite their resemblance asynchronous signals are fundamentally different from events as follows To synchronize to an event a task must explicitly call ev_receive ev_send by itself has no effect on the receiving task s state By contrast as_send can unilaterally force the receiving task to execute its ASR From the perspective of the receiving task response to events is synchronous it occurs only after a successfu
274. xecutes an illegal instruction to cause a deliberate illegal instruction exception The illegal instruction hopefully causes control to pass to a ROM monitor or other low level debug tool The illegal instruction executed is processor specific on most processors it is a divide by zero instruction In all cases the pSOS kernel makes certain information regarding the nature of the failure available to the entity receiving control Refer to the error code appendix of pSOSystem System Calls for a detailed description of this information Tasks Using Other Components Integrated Systems offers many other system components that can be used in systems with the pSOS kernel While these components are easy to install and use they require special consideration with respect to their internal resources and multitasking pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel During normal operation components internally allocate and hold resources on behalf of calling tasks Some resources are held only during execution of a service call Others are held indefinitely and this depends on the state of the task In the pHILE component for example control information is kept whenever files are open The pSOS service calls t_restart and t_delete asynchronously alter the execution path of a task and present special problems relative to management of these resources The subsections that follow discuss deletion and restart related issues in
275. xisting lock replace it with a new lock of length zero using the same file ID A lock prevents offending read_f write_f and lock_f operations only It does not prevent another task from adding blocks to a file with the annex_f call Nor does it prevent access to the file s data via the read_vol and write_vol calls Special Considerations Restarting and Deleting Tasks That Use the pHILE File System Manager During normal operation the pHILE file system manager internally allocates and holds resources on behalf of calling tasks Some resources are held only during execution of a service call while others are held indefinitely based on the state of the task for example when files are open The pSOS service calls t_restart and t_delete asynchronously alter the execution path of a task and present special problems relative to management of these resources This section discusses delete related and restart related issues in detail and presents recommended ways to perform these operations 5 8 1 1 Restarting Tasks That Use the pHILE File System Manager The pSOS kernel allows a task to be restarted regardless of its current state The restart operation has no effect on currently opened files All files remain open and their L_ptr s are unchanged It is possible to restart a task while the task is executing code within the pHILE component Consider the following example 1 Task A makes a pHILE call 2 While ex
276. you should avoid direct modification of the CPU control status register Use t_mode for such purposes so that the pSOS kernel is correctly informed of such changes pSOSystem System Concepts Chapter 2 pSOS Real Time Kernel 2 4 4 Task Stacks Each task must have its own stack or stacks You declare the size of the stack s when you create the task using t_create Details regarding processor specific use of stacks are provided in the t_create call description of pSOSystem System Calls Additional information on stacks is provided in the Memory Usage section of the pSOSystem Programmer s Reference 2 4 5 Task Memory The pSOS kernel allocates and maintains a task s stack s but it has no explicit knowledge of a task s code or data areas For most applications application code is memory resident prior to system startup being either ROM resident or bootloaded For some systems a task can be brought into memory just before it is created or started in which case memory allocation and or location sensitivity should be considered 2 4 6 Death ofa Task A task can terminate itself or another task The t_delete pSOS Service removes a created task by reclaiming its TCB and returning the stack memory segment to Region 0 The TCB is marked as free and can be reused by a new task The proper reclamation of resources such as segments buffers or semaphores should be an important part of task deletion This is partic
277. ystem Calls 5 7 1 3 The Volume Bitmap A volume s bitmap is actually a system file It is read only it performs the critical function of tracking the usage of each block on the volume One bit is used to tag each block in the volume If a block is allocated to a file then the corresponding bit is set to 1 If a block is free the corresponding bit is 0 The size of the bitmap is determined by the size of the volume Thus for example if the volume has 32K blocks then the bitmap uses 32K bits or 4 Kbytes If block size is 1 Kbyte then 4 blocks are allocated for this bitmap Immediately after a volume has been initialized its bitmap shows blocks used by the bootloader the root block the bitmap itself and FLIST SYS The bitmap can be read as lt volume gt BITMAP SYS This file is write protected and hence cannot be written to directly or deleted pSOSystem System Concepts 5 33 Chapter 5 pHILE File System Manager 5 34 5 7 1 4 The File Descriptor List Every file whether it is an ordinary or directory file requires a control structure called a file descriptor FD Each volume contains its own list of file descriptors called the FLIST which is stored in a contiguous sequence of blocks More details about file descriptors are in section 5 7 2 2 You specify the number of file descriptors in the FLIST when you initialize a volume Each file descriptor is 128 bytes long Therefore if the number of file descriptors s
278. ystem within the partition Below is a code example using init_vol pSOSystem System Concepts 5 7 Chapter 5 pHILE File System Manager include sys _conf h FC_LOGBSIZE UINT err_code For system calls char scratchbuf 1 lt lt FC_LOGBSIZE For init_vol const INIT_VOL_PARAMS init_vol_params For init_vol SAMPLE volume label 100000 32 volume_size Number of blocks 1000 num_of_file_descriptors Number of files on the volume 4 starting_bitmap_block_number Must be gt 4 o starting_data_block_number Intermix control and data blocks err_code init_vol 4 5 1 init_vol_params scratchbuf if err_code 0 Error handling Using SCSI Commands to Format a Hard Disk for pHILE Volumes l 5 8 In your application use the SCSI driver command de_cntrl function SCSI_CTL_PARTITION This function partitions the disk into up to four primary partitions It cannot create extended partitions or logical partitions A code example using SCSI_CTL_PARTITION follows include lt drv_intf h gt NOTES There must be some reserved space before the first partition There must be an extra entry with size 0 to mark the end of the list define DEVICE MAJ OR MINOR PARTITION MAJ OR lt lt 16 PARTITION lt lt 8 MINOR const PARTITION_ENTRY parts 4 1 At most 4 partitions Each entry is begin size

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