LOCK_UNLOCKED
LOCK_UNLOCKED, LOCK_LOCKED) == LOCK_LOCKED)) {
old = atomic_swap_32(&busmem->shm_lock, LOCK_UNLOCKED);
LOCK_UNLOCKED, LOCK_LOCKED) == LOCK_LOCKED)) {
old = atomic_swap_32(&busmem->shm_lock, LOCK_UNLOCKED);