__ARCH_SPIN_LOCK_UNLOCKED__
#define arch_spin_is_locked(x) ((x)->slock != __ARCH_SPIN_LOCK_UNLOCKED__)
return (val == __ARCH_SPIN_LOCK_UNLOCKED__);
unsigned int val = __ARCH_SPIN_LOCK_UNLOCKED__;
WRITE_ONCE(lock->slock, __ARCH_SPIN_LOCK_UNLOCKED__);
#define __ARCH_SPIN_LOCK_UNLOCKED { __ARCH_SPIN_LOCK_UNLOCKED__ }