list_empty atomic?

Hello, I have a list that is manipulated by several threads. Insert, remove and iteration are protected by a lock. Is the locking necessary too just for checking if the list is empty, i.e., is list_empty() atomic/safe to call without the lock held or not? thanks -- Filipe David Manana, "Reasonable men adapt themselves to the world. Unreasonable men adapt the world to themselves. That's why all progress depends on unreasonable men."