View-based axiomatic reasoning for the weak memory models PSO and SRA

Abstract

Weak memory models describe the semantics of concurrent programs in modern multicore architectures. As these semantics deviate from the commonly assumed model of sequential consistency, reasoning techniques like Owicki-Gries-style proof calculi need to be adapted to specific memory models. To avoid having to design a new proof calculus for every new memory model, a uniform approach for axiomatic reasoning has recently been proposed. This approach bases reasoning on memory-model independent axioms about thread views and how they are changed by program actions like reads and writes. It allows to prove program correctness based on axioms only. Such proofs are valid for all memory models instantiating the axioms.

In this paper, we study instantiations of the axioms for two memory models, the Partial Store Order (PSO) and the Strong Release Acquire (SRA) model. We see that both models fulfil all but one axiom, a different one though. For PSO, the missing axiom refers to message-passing abilities of memory models; for SRA, the missing axiom refers to the independence of actions on executing threads. We discuss the consequences of these missing axioms and illustrate the reasoning technique on a specific litmus test.