mirror of
https://github.com/jart/cosmopolitan.git
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60 lines
3.1 KiB
C
60 lines
3.1 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/dce.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/futex.internal.h"
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#include "libc/intrin/intrin.h"
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#include "libc/intrin/pthread.h"
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/**
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* Unlocks read-write lock.
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*
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* @return 0 on success, or errno on error
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* @raise EINVAL if lock is in a bad state
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*/
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int pthread_rwlock_unlock(pthread_rwlock_t *rwlock) {
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int old, waits;
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for (;;) {
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old = atomic_load_explicit(&rwlock->lock, memory_order_relaxed);
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if (!old || old < -1) {
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assert(!"badlock");
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return EINVAL;
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} else if (old == -1 || old == 1) {
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waits = atomic_load_explicit(&rwlock->waits, memory_order_relaxed);
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if (atomic_compare_exchange_weak_explicit(&rwlock->lock, &old, 0,
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memory_order_acquire,
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memory_order_relaxed)) {
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if (waits && (IsLinux() || IsOpenbsd())) {
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if (rwlock->attr == PTHREAD_PROCESS_SHARED) {
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_futex_wake_public(&rwlock->lock, 1);
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} else {
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_futex_wake_private(&rwlock->lock, 1);
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}
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}
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return 0;
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}
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} else if (atomic_compare_exchange_weak_explicit(
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&rwlock->lock, &old, old - 1, memory_order_acquire,
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memory_order_relaxed)) {
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return 0;
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}
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}
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}
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