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462ba6909e
When sem_wait() used its futexes it would always use process shared mode which can be problematic on platforms like Windows, where that causes it to use the slow futex polyfill. Now when sem_init() is called in private mode that'll be passed along so we can use a faster WaitOnAddress() call
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 et 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/intrin/atomic.h"
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#include "libc/intrin/strace.h"
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#include "libc/limits.h"
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#include "libc/sysv/errfuns.h"
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#include "libc/thread/semaphore.h"
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/**
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* Destroys unnamed semaphore.
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*
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* If `sem` was successfully initialized by sem_init() then
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* sem_destroy() may be called multiple times, before it may be
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* reinitialized again by calling sem_init().
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*
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* Calling sem_destroy() on a semaphore created by sem_open() has
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* undefined behavior. Using `sem` after calling sem_destroy() is
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* undefined behavior that will cause semaphore APIs to either crash or
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* raise `EINVAL` until `sem` is passed to sem_init() again.
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*
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* @param sem was created by sem_init()
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* @return 0 on success, or -1 w/ errno
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* @raise EINVAL if `sem` wasn't valid
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* @raise EBUSY if `sem` has waiters
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*/
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int sem_destroy(sem_t *sem) {
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int rc, waiters;
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npassert(sem->sem_magic != SEM_MAGIC_NAMED);
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if (sem->sem_magic != SEM_MAGIC_UNNAMED) {
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rc = einval();
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} else {
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waiters = atomic_load_explicit(&sem->sem_waiters, memory_order_relaxed);
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unassert(waiters >= 0);
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if (waiters) {
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rc = ebusy();
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} else {
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atomic_store_explicit(&sem->sem_value, INT_MIN, memory_order_relaxed);
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rc = 0;
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}
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}
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STRACE("sem_destroy(%p) → %d% m", sem, rc);
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return rc;
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}
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