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Add posix semaphores support

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There's still some bugs to work out on Windows and OpenBSD.
This commit is contained in:
Justine Tunney 2022-10-14 08:25:47 -07:00
parent f52f65b2e3
commit 8111462789
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36 changed files with 779 additions and 59 deletions
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42
libc/thread/sem_trywait.c Normal file
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/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or 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. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/errno.h"
#include "libc/intrin/atomic.h"
#include "libc/sysv/errfuns.h"
#include "libc/thread/semaphore.h"
/**
* Locks semaphore only if it's currently not locked.
*
* @return 0 on success, or -1 w/ errno
* @raise EAGAIN if semaphore is locked
* @raise EDEADLK if deadlock was detected
* @raise EINVAL if `sem` is invalid
*/
int sem_trywait(sem_t *sem) {
int v;
v = atomic_load_explicit(&sem->sem_value, memory_order_relaxed);
do {
if (!v) return eagain();
if (v < 0) return einval();
} while (!atomic_compare_exchange_weak_explicit(
&sem->sem_value, &v, v - 1, memory_order_acquire, memory_order_relaxed));
return 0;
}