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https://github.com/jart/cosmopolitan.git
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a359de7893
This changes *NSYNC to allocate waiters on the stack so our locks don't need to depend on dynamic memory. This make our runtiem simpler, and it also fixes bugs with thread cancellation support.
81 lines
3.3 KiB
C
81 lines
3.3 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/calls/calls.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/kprintf.h"
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#include "libc/intrin/weaken.h"
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#include "libc/thread/thread.h"
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#include "libc/thread/tls.h"
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#include "third_party/nsync/mu.h"
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/**
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* Locks mutex if it isn't locked already.
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*
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* Unlike pthread_mutex_lock() this function won't block and instead
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* returns an error immediately if the lock couldn't be acquired.
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*
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* @return 0 on success, or errno on error
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* @raise EBUSY if lock is already held
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* @raise ENOTRECOVERABLE if `mutex` is corrupted
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*/
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errno_t pthread_mutex_trylock(pthread_mutex_t *mutex) {
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int t;
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if (__tls_enabled && //
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mutex->_type == PTHREAD_MUTEX_NORMAL && //
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mutex->_pshared == PTHREAD_PROCESS_PRIVATE && //
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_weaken(nsync_mu_trylock)) {
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if (_weaken(nsync_mu_trylock)((nsync_mu *)mutex)) {
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return 0;
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} else {
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return EBUSY;
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}
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}
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if (mutex->_type == PTHREAD_MUTEX_NORMAL) {
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if (!atomic_exchange_explicit(&mutex->_lock, 1, memory_order_acquire)) {
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return 0;
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} else {
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return EBUSY;
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}
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}
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t = gettid();
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if (mutex->_owner == t) {
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if (mutex->_type != PTHREAD_MUTEX_ERRORCHECK) {
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if (mutex->_depth < 63) {
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++mutex->_depth;
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return 0;
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} else {
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return EAGAIN;
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}
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} else {
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return EBUSY;
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}
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}
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if (!atomic_exchange_explicit(&mutex->_lock, 1, memory_order_acquire)) {
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mutex->_depth = 0;
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mutex->_owner = t;
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return 0;
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} else {
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return EBUSY;
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}
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}
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