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FUTEX_WAKE(2const) — Linux manual page

FUTEX_WAKE(2const)FUTEX_WAKE(2const)

NAME        top

       FUTEX_WAKE - wake waiters that are inside FUTEX_WAIT

LIBRARY        top

       Standard C library (libc,-lc)

SYNOPSIS        top

#include <linux/futex.h>/* Definition ofFUTEX_*constants */#include <sys/syscall.h>/* Definition ofSYS_*constants */#include <unistd.h>long syscall(SYS_futex, uint32_t *uaddr, FUTEX_WAKE, uint32_tval);

DESCRIPTION        top

       This operation wakes at mostval of the waiters that are waiting       (e.g., insideFUTEX_WAIT(2const)) on the futex word at the addressuaddr.       Most commonly,val is specified as either 1 (wake up a single       waiter) orINT_MAX(wake up all waiters).       No guarantee is provided about which waiters are awoken (e.g., a       waiter with a higher scheduling priority is not guaranteed to be       awoken in preference to a waiter with a lower priority).

RETURN VALUE        top

       On error, -1 is returned, anderrno is set to indicate the error.       On success,FUTEX_WAKEreturns the number of waiters that were       woken up.

ERRORS        top

       Seefutex(2).EINVALThe kernel detected an inconsistency between the user-space              state atuaddr and the kernel state—that is, it detected a              waiter which waits inFUTEX_LOCK_PI(2const) orFUTEX_LOCK_PI2(2const) onuaddr.

STANDARDS        top

       Linux.

HISTORY        top

       Linux 2.6.0.

SEE ALSO        top

futex(2)

COLOPHON        top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-30FUTEX_WAKE(2const)

Pages that refer to this page:futex(2), FUTEX_CMP_REQUEUE(2const), FUTEX_FD(2const), FUTEX_WAIT(2const), FUTEX_WAIT_BITSET(2const), FUTEX_WAIT_REQUEUE_PI(2const)

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