Function do_sem_wake

freebsd/kern/kern_umtx.c:3231–3265

* Signal a userland semaphore. */

 * Signal a userland semaphore.
 */
static int
do_sem_wake(struct thread *td, struct _usem *sem)
{
	struct umtx_key key;
	int error, cnt;
	uint32_t flags;

	error = fueword32(&sem->_flags, &flags);
	if (error == -1)
		return (EFAULT);
	if ((error = umtx_key_get(sem, TYPE_SEM, GET_SHARE(flags), &key)) != 0)
		return (error);
	umtxq_lock(&key);
	umtxq_busy(&key);
	cnt = umtxq_count(&key);
	if (cnt > 0) {
		/*
		 * Check if count is greater than 0, this means the memory is
		 * still being referenced by user code, so we can safely
		 * update _has_waiters flag.
		 */
		if (cnt == 1) {
			umtxq_unlock(&key);
			error = suword32(&sem->_has_waiters, 0);
			umtxq_lock(&key);
			if (error == -1)
				error = EFAULT;
		}
		umtxq_signal(&key, 1);
	}
	umtxq_unbusy(&key);
	umtxq_unlock(&key);
	umtx_key_release(&key);
	return (error);
}
#endif

static int