But the concern with a shared integer is correctness under inc/dec. If you have a multi-processor and you don't LOCK then the value can be anything because it'

But the concern with a shared integer is correctness under inc/dec. If you have a multi-processor and you don't LOCK then the value can be anything because it's racy. With multiple threads there is still correctness when multiple threads access the atomic and the flags returned are correct without the need to "lock the bus". The article just explains why the return value uses the flags - for correctness. If you have a sequence of instructions then (potentially) you don't have correctness either with multiple threads on the same core or across cores. EDIT: if your point was that you can't return the value using either LOCK INC or INC and either on a single core or multiple cores then your point is correct. I sort of read it as INC itself (the x86 instruction) is racy under multi-threading.