Comment by RossBencina

Agreed. But you make it sound like the worst case is necessarily fatal. It depends on the use-case. The workable cmpxchg algorithms will make progress on at least one core each round. In a push or pop operation one of the cmpxchg must have succeeded for another to fail. The atomic xchg algorithms that I know of have other undesirable pathologies (e.g. a suspended producer can stall the consumer).