Search

We present a proof calculus and method for the static verification of assertions and procedure specifications in shared-memory concurrent programs. The key idea in our approach is to use atomicity as a proof tool and to simplify the verification of assertions by rewriting programs to consist of larger atomic actions. We propose a novel, iterative proof style in which alternating use of abstraction and reduction is exploited to compute larger atomic code blocks in a sound manner. This makes possible the verification of assertions in the transformed program by simple sequential reasoning within atomic blocks, or significantly simplified application of existing concurrent program verification techniques such as the Owicki-Gries or rely-guarantee methods. Our method facilitates a clean separation of concerns where at each phase of the proof, the user worries only about only either the sequential properties or the concurrency control mechanisms in the program. We implemented our method in a tool called QED. We demonstrate the simplicity and effectiveness of our approach on a number of benchmarks including ones with intricate concurrency protocols.

This paper explores the notion of an atomic action as a method of process structuring. This notion, first introduced explicitly by Eswaren et al [6] in the context of data base systems, reduces the problem of coping with many processes to that of coping with a single process within the atomic action . A form of process synchronization, the await statement, is adapted to work naturally with atomic actions. System recovery is also considered and we show how atomic actions can be used to isolate recovery action to a single process. Explicit control of recovery is provided by a reset procedure that permits information from rejected control paths to be passed to subsequent alternative paths.