mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-02-07 15:03:34 +00:00
63 lines
3.4 KiB
C
63 lines
3.4 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/intrin/atomic.h"
|
|
#include "libc/intrin/strace.h"
|
|
#include "libc/thread/thread.h"
|
|
|
|
/**
|
|
* Acquires spin lock, e.g.
|
|
*
|
|
* pthread_spinlock_t lock;
|
|
* pthread_spin_init(&lock, PTHREAD_PROCESS_PRIVATE);
|
|
* pthread_spin_lock(&lock);
|
|
* // do work...
|
|
* pthread_spin_unlock(&lock);
|
|
* pthread_spin_destroy(&lock);
|
|
*
|
|
* This function has undefined behavior when `spin` wasn't intialized or
|
|
* was destroyed, and if the lock is already held by the calling thread.
|
|
*
|
|
* You can debug locks the acquisition of locks by building your program
|
|
* with `cosmocc -mdbg` and passing the `--strace` flag to your program.
|
|
* This will cause a line to be logged each time a mutex or spin lock is
|
|
* locked or unlocked. When locking, this is printed after the lock gets
|
|
* acquired. The entry to the lock operation will be logged too but only
|
|
* if the lock couldn't be immediately acquired. Lock logging works best
|
|
* when `mutex` refers to a static variable, in which case its name will
|
|
* be printed in the log.
|
|
*
|
|
* @return 0 on success, or errno on error
|
|
* @see pthread_spin_trylock
|
|
* @see pthread_spin_unlock
|
|
* @see pthread_spin_init
|
|
*/
|
|
errno_t pthread_spin_lock(pthread_spinlock_t *spin) {
|
|
if (atomic_exchange_explicit(&spin->_lock, 1, memory_order_acquire)) {
|
|
LOCKTRACE("acquiring pthread_spin_lock(%t)...", spin);
|
|
for (;;) {
|
|
for (;;)
|
|
if (!atomic_load_explicit(&spin->_lock, memory_order_relaxed))
|
|
break;
|
|
if (!atomic_exchange_explicit(&spin->_lock, 1, memory_order_acquire))
|
|
break;
|
|
}
|
|
}
|
|
LOCKTRACE("pthread_spin_lock(%t)", spin);
|
|
return 0;
|
|
}
|