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/* $OpenBSD: _atomic_lock.c,v 1.1 2005/12/03 18:16:19 tedu Exp $ */
/* David Leonard, <d@csee.uq.edu.au>. Public domain. */
/*
* Atomic lock for i386
*/
#include <machine/spinlock.h>
int
_atomic_lock(register volatile _spinlock_lock_t *lock)
{
register _spinlock_lock_t old;
/*
* Use the eXCHanGe instruction to swap the lock value with
* a local variable containing the locked state.
*/
old = _SPINLOCK_LOCKED;
__asm__("xchg %0,%1"
: "=r" (old), "=m" (*lock)
: "0" (old), "1" (*lock));
return (old != _SPINLOCK_UNLOCKED);
}
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