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Speed up unnamed POSIX semaphores

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When sem_wait() used its futexes it would always use process shared mode
which can be problematic on platforms like Windows, where that causes it
to use the slow futex polyfill. Now when sem_init() is called in private
mode that'll be passed along so we can use a faster WaitOnAddress() call
This commit is contained in:
Justine Tunney 2024-09-13 06:25:27 -07:00
parent b5fcb59a85
commit 462ba6909e
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GPG key ID: BE714B4575D6E328
5 changed files with 76 additions and 30 deletions
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25
libc/thread/sem_destroy.c
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@ -18,6 +18,7 @@
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/intrin/atomic.h"
#include "libc/intrin/strace.h"
#include "libc/limits.h"
#include "libc/sysv/errfuns.h"
#include "libc/thread/semaphore.h"
@ -40,14 +41,20 @@
* @raise EBUSY if `sem` has waiters
*/
int sem_destroy(sem_t *sem) {
int waiters;
int rc, waiters;
npassert(sem->sem_magic != SEM_MAGIC_NAMED);
if (sem->sem_magic != SEM_MAGIC_UNNAMED)
return einval();
waiters = atomic_load_explicit(&sem->sem_waiters, memory_order_relaxed);
unassert(waiters >= 0);
if (waiters)
return ebusy();
atomic_store_explicit(&sem->sem_value, INT_MIN, memory_order_relaxed);
return 0;
if (sem->sem_magic != SEM_MAGIC_UNNAMED) {
rc = einval();
} else {
waiters = atomic_load_explicit(&sem->sem_waiters, memory_order_relaxed);
unassert(waiters >= 0);
if (waiters) {
rc = ebusy();
} else {
atomic_store_explicit(&sem->sem_value, INT_MIN, memory_order_relaxed);
rc = 0;
}
}
STRACE("sem_destroy(%p) → %d% m", sem, rc);
return rc;
}