FUTEX_WAIT_REQUEUE_PI(2const)

NAME

FUTEX_WAIT_REQUEUE_PI - wait on a non-PI futex, and potentially be requeued onto a PI futex

LIBRARY

Standard C library (libc, -lc)

SYNOPSIS

#include <linux/futex.h>  /* Definition of FUTEX_* constants */
#include <sys/syscall.h>  /* Definition of SYS_* constants */
#include <unistd.h>

long syscall(SYS_futex, uint32_t *uaddr, FUTEX_WAIT_REQUEUE_PI,
             uint32_t val,
             const struct timespec *timeout,
             uint32_t *uaddr2);

DESCRIPTION

Wait on a non-PI futex at uaddr and potentially be requeued (via a FUTEX_CMP_REQUEUE_PI(2const) operation in another task) onto a PI futex at uaddr2. The wait operation on uaddr is the same as for FUTEX_WAIT(2const).

The waiter can be removed from the wait on uaddr without requeueing on uaddr2 via a FUTEX_WAKE(2const) operation in another task. In this case, the FUTEX_WAIT_REQUEUE_PI operation fails with the error EAGAIN.

If timeout is not NULL, the structure it points to specifies an absolute timeout for the wait operation. If timeout is NULL, the operation can block indefinitely.

RETURN VALUE

On error, -1 is returned, and errno is set to indicate the error.

On success, FUTEX_WAIT_REQUEUE_PI returns 0 if the caller was successfully requeued to the futex for the futex word at uaddr2.

ERRORS

See futex(2).

EAGAIN: The value pointed to by uaddr was not equal to the expected value val at the time of the call.

: Note: on Linux, the symbolic names EAGAIN and EWOULDBLOCK (both of which appear in different parts of the kernel futex code) have the same value.

EFAULT: uaddr2 or timeout did not point to a valid user-space address.
EINVAL: The supplied timeout argument was invalid (tv_sec was less than zero, or tv_nsec was not less than 1,000,000,000).
EINVAL: uaddr2 does not point to a valid object—that is, the address is not four-byte-aligned.
ENOSYS: A run-time check determined that the operation is not available. The PI-futex operations are not implemented on all architectures and are not supported on some CPU variants.
ETIMEDOUT: The timeout expired before the operation completed.

STANDARDS

Linux.

HISTORY

Linux 2.6.31.