On Execution-Based Formalization for Sequential Consistency Verification

Abstract The adequacy of execution based formalizations in modeling and verifying shared memory systems is discussed. It is argued that unclear sentence.... not comparable. We claim that the decidability problem of sequential consistency for finite-state systems is an open problem, in contrast with the result o

Toward a Decidable Notion of Sequential Consistency

A memory model specifies a correctness requirement for a distributed shared memory protocol. Sequential consistency (SC) is the most widely researched model; previous work [1] has shown that, in general, the SC verification problem is undecidable. We identify two aspects of the formulation found in [1] that we consider to be highly unnatural; we call these non-prefix-closedness and prophetic inheritance. We conjecture that preclusion of such behavior yields a decidable version of SC, which we call decisive sequential consistency (DSC). We also introduce a structure called a view window (VW), which retains information about a protocol's history, and we define the notion of a VW-bound, which essentially bounds the size of the VWs needed to maintain DSC. We prove that the class of DSC protocols with VW-bound k is decidable; left conjectured is the hypothesis that all DSC protocols have such a bound, and further that the bound is computable from the protocol description. This hypothesis is true for all real protocols known to us; we verify its truth for the Lazy Caching protocol [2]