Proving that non-blocking algorithms don't block

Abstract

A concurrent data-structure implementation is considered nonblocking if it meets one of three following liveness criteria: waitfreedom, lock-freedom,orobstruction-freedom. Developers of nonblocking algorithms aim to meet these criteria. However, to date their proofs for non-trivial algorithms have been only manual pencil-and-paper semi-formal proofs. This paper proposes the first fully automatic tool that allows developers to ensure that their algorithms are indeed non-blocking. Our tool uses rely-guarantee reasoning while overcoming the technical challenge of sound reasoning in the presence of interdependent liveness properties.