mirror of
https://github.com/jart/cosmopolitan.git
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44 lines
2.4 KiB
C
44 lines
2.4 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2022 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/assert.h"
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#include "libc/errno.h"
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#include "libc/intrin/atomic.h"
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#include "libc/intrin/strace.internal.h"
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#include "libc/sysv/errfuns.h"
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#include "libc/thread/semaphore.h"
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#include "third_party/nsync/futex.internal.h"
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/**
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* Unlocks semaphore.
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*
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* @return 0 on success, or -1 w/ errno
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* @raise EINVAL if `sem` isn't valid
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*/
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int sem_post(sem_t *sem) {
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int rc;
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int old = atomic_fetch_add_explicit(&sem->sem_value, 1, memory_order_relaxed);
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if (old >= 0) {
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_npassert(nsync_futex_wake_(&sem->sem_value, 1, sem->sem_pshared) >= 0);
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rc = 0;
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} else {
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rc = einval();
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}
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STRACE("sem_post(%p) → %d% m", sem, rc);
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return rc;
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}
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