An almost non-blocking stack

• Authors: Hans-J. Boehm
• Venue: Proceedings of the twenty-third annual ACM symposium on Principles of distributed computing
• Year: 2004

Non-blocking data structure implementations can be useful for performance and fault-tolerance reasons. And they are far easier to use correctly in a signal- or interrupt-handler context.We describe a weaker class of "almost non-blocking" data structures, which block only if more than some number N of threads attempt to simultaneously access the same data structure. We argue that this gives much of the benefit of fully non-blocking data structures, particularly for signal or interrupt handlers.We present an almost non-blocking linked stack implementation which is efficiently implementable even on hardware providing a single word compare-and-swap operation, while potentially providing the same interface as a well-known fully non-blocking solution, which relies on a double-width compare-and-swap instruction. By making a platform-dependent choice between these, we can implement a signal-handler-safe stack or free-list abstraction that is both portable and exhibits uniformly high performance with any flavor of compare-and-swap instruction.