/* $OpenBSD: _atomic_lock.c,v 1.3 2009/06/01 22:52:38 guenther Exp $ */ /* David Leonard, . Public domain. */ /* * Atomic lock for amd64 -- taken from i386 code. */ #include int _atomic_lock(volatile _spinlock_lock_t *lock) { _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,(%2)" : "=r" (old) : "0" (old), "r" (lock)); return (old != _SPINLOCK_UNLOCKED); }