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/* $OpenBSD: slow_atomic_lock.c,v 1.4 2008/10/02 23:27:23 deraadt Exp $ */
/* David Leonard, <d@csee.uq.edu.au>. Public domain. */
#include <pthread.h>
#include "pthread_private.h"
#include "spinlock.h"
#include <signal.h>
/*
* uthread atomic lock:
* attempt to acquire a lock (by giving it a non-zero value).
* Return zero on success, or the lock's value on failure
* This uses signal masking to make sure that no other thread
* can modify the lock while processing, hence it is very slow.
*/
int
_thread_slow_atomic_lock(volatile _spinlock_lock_t *lock)
{
_spinlock_lock_t old;
sigset_t oldset, newset = (sigset_t)~0;
/* block signals - incurs a context switch */
if (_thread_sys_sigprocmask(SIG_SETMASK, &newset, &oldset) < 0)
PANIC("_atomic_lock block");
old = *lock;
if (old == _SPINLOCK_UNLOCKED)
*lock = _SPINLOCK_LOCKED;
/* restore signal mask to what it was */
if (_thread_sys_sigprocmask(SIG_SETMASK, &oldset, NULL) < 0)
PANIC("_atomic_lock restore");
return (old != _SPINLOCK_UNLOCKED);
}
int
_thread_slow_atomic_is_locked(volatile _spinlock_lock_t *lock)
{
return (*lock != _SPINLOCK_UNLOCKED);
}
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