rem: mutex_lock(&locking->mutex);
add: acquire_sem(locking->lock);
context: get_advisory_locking(struct vnode *vnode){	mutex_lock(&sVnodeMutex);	struct advisory_locking *locking = vnode->advisory_locking;	if (locking != NULL)		mutex_lock(&locking->mutex);	mutex_unlock(&sVnodeMutex);	return locking;}