diff options
Diffstat (limited to 'lib/libpthread/arch/amd64/_atomic_lock.c')
| -rw-r--r-- | lib/libpthread/arch/amd64/_atomic_lock.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/lib/libpthread/arch/amd64/_atomic_lock.c b/lib/libpthread/arch/amd64/_atomic_lock.c index 087186e2858..70bdb487381 100644 --- a/lib/libpthread/arch/amd64/_atomic_lock.c +++ b/lib/libpthread/arch/amd64/_atomic_lock.c @@ -1,5 +1,6 @@ +/* $OpenBSD: _atomic_lock.c,v 1.2 2004/02/25 03:48:36 deraadt Exp $ */ /* - * Atomic lock for amd64 + * Atomic lock for amd64 -- taken from i386 code. */ #include "spinlock.h" @@ -7,5 +8,16 @@ int _atomic_lock(volatile _spinlock_lock_t *lock) { - /* dummy for now */ + _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); } |