spu_create(2)

Purpose

spu_create() created a logical context for one of the Cell Broadband Engine’s Synergistic Processor Units: it created a new context directory at path under the spufs filesystem and returned a file descriptor bound to that context (spu_create.2, DESCRIPTION). The returned fd’s only legal uses were spu_run(2), the *at() family as dirfd, or close (spu_create.2, DESCRIPTION) – an early example of the “syscall returns an fd, everything else goes through file operations” design.

Synopsis

#include <sys/spu.h>   /* SPU_* constants */
#include <sys/syscall.h>
#include <unistd.h>
int syscall(SYS_spu_create, const char *path, unsigned int flags,
            mode_t mode, int neighbor_fd);

Arguments and behavior

path had to name a nonexistent directory inside the spufs mount point; on success the kernel creates it and populates it with the spufs(7) file set (spu_create.2, DESCRIPTION). flags included SPU_CREATE_EVENTS_ENABLED (event reporting through spu_run’s event out-param) and SPU_CREATE_GANG (attach to a gang for group scheduling, via neighbor_fd); an isolated (protected) context required SPU_CREATE_ISOLATED and hardware support – ENODEV when unsupported, EPERM when the isolation flag was misused (spu_create.2, DESCRIPTION/ERRORS). Contexts were destroyed when the last fd closed (spu_create.2, DESCRIPTION).

Return value and errors

New file descriptor on success; -1 with errno (spu_create.2, RETURN VALUE). Errors include: EACCES (no write access to the spufs mount), EEXIST (path taken), EFAULT, EINVAL (path not in spufs; bad flags), EMFILE/ENFILE (fd limits), ENOSPC (SPU resources or per-user context limit), ENOSYS (no SPUs or spufs module unloaded), EPERM (isolation misuse), plus the usual path-resolution set (spu_create.2, ERRORS).

Flags and constants

SPU_CREATE_EVENTS_ENABLED, SPU_CREATE_GANG, SPU_CREATE_ISOLATED (<sys/spu.h>).

Security and notes

Access control was the spufs mount’s permission bits – root-configurable, typically delegated to a Cell compute group. The man page’s NOTES point out the call “is meant to be used from libraries that implement a more abstract interface to SPUs, not to be used from regular applications” (spu_create.2, NOTES). The Cell’s decline retired the whole pair; the design DNA (fd-scoped accelerator contexts) lives on in GPU/accelerator frameworks. Cross-reference: spu_run, perf_event_open.

References

• https://man7.org/linux/man-pages/man2/spu_create.2.html
• man-pages syscalls(2) (2.6.16)