Obstruction-Free Algorithms Can Be Practically Wait-Free

The obstruction-free progress condition is weaker than previous nonblocking progress conditions such as lock-freedom and waitfreedom, and admits simpler implementations that are faster in the uncontended case. Pragmatic contention management techniques appear to be effective at facilitating progress in practice, but, as far as we know, none guarantees progress. We present a transformation that converts any obstruction-free algorithm into one that is wait-free when analyzed in the unknown-bound semisynchronous model. Because all practical systems satisfy the assumptions of the unknown-bound model, our result implies that, for all practical purposes, obstruction-free implementations can provide progress guarantees equivalent to wait-freedom. Our transformation preserves the advantages of any pragmatic contention manager, while guaranteeing progress.