FUTEX_UNLOCK_PI(2const)                                FUTEX_UNLOCK_PI(2const)

NAME
       FUTEX_UNLOCK_PI - unlock a priority-inheritance 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_UNLOCK_PI);

DESCRIPTION
       This operation wakes the top priority waiter that is waiting in
       FUTEX_LOCK_PI(2const) or FUTEX_LOCK_PI2(2const) on the futex address
       provided by the uaddr argument.

       This is called when the user-space value at uaddr cannot be changed
       atomically from a TID (of the owner) to 0.

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

       On success, FUTEX_UNLOCK_PI returns 0 if the futex was successfully
       unlocked.

ERRORS
       See futex(2).

       EINVAL The kernel detected an inconsistency between the user-space
              state at uaddr and the kernel state.  This indicates either
              state corruption or that the kernel found a waiter on uaddr
              which is waiting via FUTEX_WAIT(2const) or
              FUTEX_WAIT_BITSET(2const).

       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.

       EPERM  The caller does not own the lock represented by the futex word.

STANDARDS
       Linux.

HISTORY
       Linux 2.6.18.

SEE ALSO
       futex(2)

Linux man-pages 6.16              2025-05-30           FUTEX_UNLOCK_PI(2const)