mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 19:43:32 +00:00
90460ceb3c
While we have always licked glibc and musl libc on gnu/systemd sadly the Apple Libc implementation of pthread_mutex_t is better than ours. It may be due to how the XNU kernel and M2 microprocessor are in league when it comes to scheduling processes and the NSYNC behavior is being penalized. We can solve this by leaning more heavily on ulock using Drepper's algo. It's kind of ironic that Linux's official mutexes work terribly on Linux but almost as good as Apple Libc if used on MacOS.
58 lines
3 KiB
C
58 lines
3 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
|
|
│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
|
|
╞══════════════════════════════════════════════════════════════════════════════╡
|
|
│ Copyright 2022 Justine Alexandra Roberts Tunney │
|
|
│ │
|
|
│ Permission to use, copy, modify, and/or distribute this software for │
|
|
│ any purpose with or without fee is hereby granted, provided that the │
|
|
│ above copyright notice and this permission notice appear in all copies. │
|
|
│ │
|
|
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
|
|
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
|
|
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
|
|
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
|
|
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
|
|
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
|
|
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
|
|
│ PERFORMANCE OF THIS SOFTWARE. │
|
|
╚─────────────────────────────────────────────────────────────────────────────*/
|
|
#include "libc/dce.h"
|
|
#include "libc/intrin/atomic.h"
|
|
#include "libc/thread/thread.h"
|
|
#include "third_party/nsync/cv.h"
|
|
#include "third_party/nsync/futex.internal.h"
|
|
|
|
/**
|
|
* Wakes at least one thread waiting on condition, e.g.
|
|
*
|
|
* pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
|
|
* pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
|
|
* // ...
|
|
* pthread_mutex_lock(&lock);
|
|
* pthread_cond_signal(&cond);
|
|
* pthread_mutex_unlock(&lock);
|
|
*
|
|
* This function has no effect if there aren't any threads currently
|
|
* waiting on the condition.
|
|
*
|
|
* @return 0 on success, or errno on error
|
|
* @see pthread_cond_broadcast
|
|
* @see pthread_cond_wait
|
|
*/
|
|
errno_t pthread_cond_signal(pthread_cond_t *cond) {
|
|
|
|
#if PTHREAD_USE_NSYNC
|
|
// favor *NSYNC if this is a process private condition variable
|
|
// if using Mike Burrows' code isn't possible, use a naive impl
|
|
if (!cond->_pshared && !IsXnuSilicon()) {
|
|
nsync_cv_signal((nsync_cv *)cond);
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
// roll forward the monotonic sequence
|
|
atomic_fetch_add_explicit(&cond->_sequence, 1, memory_order_acq_rel);
|
|
if (atomic_load_explicit(&cond->_waiters, memory_order_acquire))
|
|
nsync_futex_wake_((atomic_int *)&cond->_sequence, 1, cond->_pshared);
|
|
return 0;
|
|
}
|