spu_run(2) — Linux manual page


spu_run(2)                 System Calls Manual                spu_run(2)

NAME         top

       spu_run - execute an SPU context

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

       #include <sys/spu.h>          /* Definition of SPU_* constants */
       #include <sys/syscall.h>      /* Definition of SYS_* constants */
       #include <unistd.h>

       int syscall(SYS_spu_run, int fd, uint32_t *npc, uint32_t *event);

       Note: glibc provides no wrapper for spu_run(), necessitating the
       use of syscall(2).

DESCRIPTION         top

       The spu_run() system call is used on PowerPC machines that
       implement the Cell Broadband Engine Architecture in order to
       access Synergistic Processor Units (SPUs).  The fd argument is a
       file descriptor returned by spu_create(2) that refers to a
       specific SPU context.  When the context gets scheduled to a
       physical SPU, it starts execution at the instruction pointer
       passed in npc.

       Execution of SPU code happens synchronously, meaning that
       spu_run() blocks while the SPU is still running.  If there is a
       need to execute SPU code in parallel with other code on either
       the main CPU or other SPUs, a new thread of execution must be
       created first (e.g., using pthread_create(3)).

       When spu_run() returns, the current value of the SPU program
       counter is written to npc, so successive calls to spu_run() can
       use the same npc pointer.

       The event argument provides a buffer for an extended status code.
       If the SPU context was created with the SPU_CREATE_EVENTS_ENABLED
       flag, then this buffer is populated by the Linux kernel before
       spu_run() returns.

       The status code may be one (or more) of the following constants:

              A DMA alignment error occurred.

              An invalid MFC DMA command was attempted.

              A DMA storage error occurred.

              An illegal instruction was executed.

       NULL is a valid value for the event argument.  In this case, the
       events will not be reported to the calling process.

RETURN VALUE         top

       On success, spu_run() returns the value of the spu_status
       register.  On failure, it returns -1 and sets errno is set to
       indicate the error.

       The spu_status register value is a bit mask of status codes and
       optionally a 14-bit code returned from the stop-and-signal
       instruction on the SPU.  The bit masks for the status codes are:

       0x02   SPU was stopped by a stop-and-signal instruction.

       0x04   SPU was stopped by a halt instruction.

       0x08   SPU is waiting for a channel.

       0x10   SPU is in single-step mode.

       0x20   SPU has tried to execute an invalid instruction.

       0x40   SPU has tried to access an invalid channel.

              The bits masked with this value contain the code returned
              from a stop-and-signal instruction.  These bits are valid
              only if the 0x02 bit is set.

       If spu_run() has not returned an error, one or more bits among
       the lower eight ones are always set.

ERRORS         top

       EBADF  fd is not a valid file descriptor.

       EFAULT npc is not a valid pointer, or event is non-NULL and an
              invalid pointer.

       EINTR  A signal occurred while spu_run() was in progress; see
              signal(7).  The npc value has been updated to the new
              program counter value if necessary.

       EINVAL fd is not a valid file descriptor returned from

       ENOMEM There was not enough memory available to handle a page
              fault resulting from a Memory Flow Controller (MFC) direct
              memory access.

       ENOSYS The functionality is not provided by the current system,
              because either the hardware does not provide SPUs or the
              spufs module is not loaded.

STANDARDS         top

       Linux on PowerPC.

HISTORY         top

       Linux 2.6.16.

NOTES         top

       spu_run() is meant to be used from libraries that implement a
       more abstract interface to SPUs, not to be used from regular
       applications.  See 
       ⟨http://www.bsc.es/projects/deepcomputing/linuxoncell/⟩ for the
       recommended libraries.

EXAMPLES         top

       The following is an example of running a simple, one-instruction
       SPU program with the spu_run() system call.

       #include <err.h>
       #include <fcntl.h>
       #include <stdint.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <sys/types.h>
       #include <unistd.h>

       int main(void)
           int       context, fd, spu_status;
           uint32_t  instruction, npc;

           context = syscall(SYS_spu_create, "/spu/example-context", 0, 0755);
           if (context == -1)
               err(EXIT_FAILURE, "spu_create");

            * Write a 'stop 0x1234' instruction to the SPU's
            * local store memory.
           instruction = 0x00001234;

           fd = open("/spu/example-context/mem", O_RDWR);
           if (fd == -1)
               err(EXIT_FAILURE, "open");
           write(fd, &instruction, sizeof(instruction));

            * set npc to the starting instruction address of the
            * SPU program. Since we wrote the instruction at the
            * start of the mem file, the entry point will be 0x0.
           npc = 0;

           spu_status = syscall(SYS_spu_run, context, &npc, NULL);
           if (spu_status == -1)
               err(EXIT_FAILURE, "open");

            * We should see a status code of 0x12340002:
            *   0x00000002 (spu was stopped due to stop-and-signal)
            * | 0x12340000 (the stop-and-signal code)
           printf("SPU Status: %#08x\n", spu_status);


SEE ALSO         top

       close(2), spu_create(2), capabilities(7), spufs(7)

Linux man-pages (unreleased)     (date)                       spu_run(2)

Pages that refer to this page: spu_create(2)syscalls(2)spufs(7)