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Make futexes cancellable by pthreads

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This commit is contained in:
Justine Tunney 2022-11-04 18:19:05 -07:00
parent 2278327eba
commit 022536cab6
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GPG key ID: BE714B4575D6E328
101 changed files with 627 additions and 391 deletions
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19
libc/thread/sem_timedwait.c
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@ -24,6 +24,7 @@
#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) {
@ -51,11 +52,18 @@ static struct timespec *sem_timeout(struct timespec *memory,
}
}
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
@ -80,14 +88,16 @@ int sem_timedwait(sem_t *sem, const struct timespec *abstime) {
}
_unassert(atomic_fetch_add_explicit(&sem->sem_waiters, +1,
memory_order_acquire) >= 0);
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, sem->sem_pshared,
sem_timeout(&ts, abstime));
if (rc == -EINTR) {
rc = eintr();
if (rc == -EINTR || rc == -ECANCELED) {
errno = -rc;
rc = -1;
} else if (rc == -EAGAIN || rc == -EWOULDBLOCK) {
rc = 0;
} else if (rc == -ETIMEDOUT) {
@ -111,8 +121,7 @@ int sem_timedwait(sem_t *sem, const struct timespec *abstime) {
&sem->sem_value, &v, v - 1, memory_order_acquire,
memory_order_relaxed)));
_unassert(atomic_fetch_add_explicit(&sem->sem_waiters, -1,
memory_order_release) > 0);
pthread_cleanup_pop(1);
return rc;
}