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https://github.com/jart/cosmopolitan.git
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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
54 lines
2.9 KiB
C
54 lines
2.9 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/calls/calls.h"
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#include "libc/dce.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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#include "third_party/nsync/mu_semaphore.h"
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/**
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* Initializes unnamed semaphore.
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*
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* Calling sem_init() on an already initialized semaphore is undefined.
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*
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* @param sem should make its way to sem_destroy() if this succeeds
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* @param pshared if semaphore may be shared between processes, provided
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* `sem` is backed by `mmap(MAP_ANONYMOUS | MAP_SHARED)` memory
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* @param value is initial count of semaphore
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* @return 0 on success, or -1 w/ errno
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* @raise EINVAL if `value` exceeds `SEM_VALUE_MAX`
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*/
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int sem_init(sem_t *sem, int pshared, unsigned value) {
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int rc;
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if (value > SEM_VALUE_MAX) {
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rc = einval();
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} else {
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sem->sem_magic = SEM_MAGIC_UNNAMED;
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atomic_store_explicit(&sem->sem_value, value, memory_order_relaxed);
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sem->sem_pshared = !!pshared;
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sem->sem_pid = getpid();
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sem->sem_waiters = 0;
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rc = 0;
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}
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STRACE("sem_init(%p, %hhhd, %u) → %d% m", sem, pshared, value, rc);
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return rc;
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}
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