/* * Copyright (c) 2013, 2014, 2021, 2022 Jonas 'Sortie' Termansen. * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. * * pthread/pthread_mutex_unlock.c * Unlocks a mutex. */ #include #include #include #include static const int UNLOCKED = 0; static const int CONTENDED = 2; int pthread_mutex_unlock(pthread_mutex_t* mutex) { if ( mutex->type == PTHREAD_MUTEX_RECURSIVE && mutex->recursion ) { mutex->recursion--; return 0; } mutex->owner = 0; // TODO: Multiple threads could have caused the contention and this wakes // only one such thread, but then the mutex returns to normal and the // subsequent unlocks doesn't wake the other contended threads. Work // around this bug by waking all of them instead, but it's better to // instead count the number of waiting threads. if ( __atomic_exchange_n(&mutex->lock, UNLOCKED, __ATOMIC_SEQ_CST) == CONTENDED ) futex(&mutex->lock, FUTEX_WAKE, INT_MAX, NULL); return 0; }