mirror of
https://github.com/jart/cosmopolitan.git
synced 2025-01-31 19:43:32 +00:00
298ba74a45
Python triggered the undefined behavior previously since it appears to be posting to a semaphore owned by a different process that wasn't set to process shared mode. The performance loss to process shared futexes is so low and semaphores are generally used for this purpose, so it'll be much simpler to simply not impose undefined behavior here.
109 lines
4.3 KiB
C
109 lines
4.3 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
|
|
│vi: set net 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/assert.h"
|
|
#include "libc/calls/cp.internal.h"
|
|
#include "libc/calls/struct/timespec.h"
|
|
#include "libc/calls/struct/timespec.internal.h"
|
|
#include "libc/errno.h"
|
|
#include "libc/intrin/atomic.h"
|
|
#include "libc/limits.h"
|
|
#include "libc/sysv/errfuns.h"
|
|
#include "libc/thread/semaphore.h"
|
|
#include "libc/thread/thread.h"
|
|
#include "third_party/nsync/futex.internal.h"
|
|
|
|
static void sem_delay(int n) {
|
|
volatile int i;
|
|
for (i = 0; i != 1 << n; i++) donothing;
|
|
}
|
|
|
|
static void sem_timedwait_cleanup(void *arg) {
|
|
sem_t *sem = arg;
|
|
_unassert(atomic_fetch_add_explicit(&sem->sem_waiters, -1,
|
|
memory_order_acq_rel) > 0);
|
|
}
|
|
|
|
/**
|
|
* Locks semaphore w/ deadline.
|
|
*
|
|
* @param abstime is absolute deadline or null to wait forever
|
|
* @return 0 on success, or -1 w/ errno
|
|
* @raise ECANCELED if calling thread was cancelled in masked mode
|
|
* @raise EINTR if signal was delivered instead
|
|
* @raise EDEADLK if deadlock was detected
|
|
* @raise ETIMEDOUT if deadline expired
|
|
* @raise EINVAL if `sem` is invalid
|
|
* @cancellationpoint
|
|
*/
|
|
int sem_timedwait(sem_t *sem, const struct timespec *abstime) {
|
|
int e, i, v, rc;
|
|
struct timespec ts;
|
|
|
|
e = errno;
|
|
for (i = 0; i < 7; ++i) {
|
|
rc = sem_trywait(sem);
|
|
if (!rc) {
|
|
return rc;
|
|
} else if (errno == EAGAIN) {
|
|
errno = e;
|
|
sem_delay(i);
|
|
} else {
|
|
return rc;
|
|
}
|
|
}
|
|
|
|
BEGIN_CANCELLATION_POINT;
|
|
_unassert(atomic_fetch_add_explicit(&sem->sem_waiters, +1,
|
|
memory_order_acq_rel) >= 0);
|
|
pthread_cleanup_push(sem_timedwait_cleanup, sem);
|
|
|
|
do {
|
|
if (!(v = atomic_load_explicit(&sem->sem_value, memory_order_relaxed))) {
|
|
rc = nsync_futex_wait_(&sem->sem_value, v, true, abstime);
|
|
if (rc == -EINTR || rc == -ECANCELED) {
|
|
errno = -rc;
|
|
rc = -1;
|
|
} else if (rc == -EAGAIN || rc == -EWOULDBLOCK) {
|
|
rc = 0;
|
|
} else if (rc == -ETIMEDOUT) {
|
|
_npassert(abstime);
|
|
if (timespec_cmp(*abstime, timespec_real()) <= 0) {
|
|
rc = etimedout();
|
|
} else {
|
|
rc = 0;
|
|
}
|
|
} else {
|
|
_npassert(!rc);
|
|
rc = 0;
|
|
}
|
|
} else if (v > 0) {
|
|
rc = 0;
|
|
} else {
|
|
_unassert(v > INT_MIN);
|
|
rc = einval();
|
|
}
|
|
} while (!rc && (!v || !atomic_compare_exchange_weak_explicit(
|
|
&sem->sem_value, &v, v - 1, memory_order_acquire,
|
|
memory_order_relaxed)));
|
|
|
|
pthread_cleanup_pop(1);
|
|
END_CANCELLATION_POINT;
|
|
|
|
return rc;
|
|
}
|