Local Rely-Guarantee Reasoning


Xinyu Feng


Rely-Guarantee reasoning is a well-known method for verification of shared-variable concurrent programs. However, it is difficult for users to define rely/guarantee conditions, which specify threads' behaviors over the whole program state. Recent efforts to combine Separation Logic with Rely-Guarantee reasoning have made it possible to hide thread-local resources, but the shared resources still need to be globally known and specified. This greatly limits the reuse of verified program modules.

In this talk, I present LRG, a new Rely-Guarantee-based logic that brings local reasoning and information hiding to concurrency verification. The logic, for the first time, supports a frame rule over rely/guarantee conditions so that specifications of program modules only need to talk about the resources used locally, and the verified modules can be reused in different threads without redoing the proof. Moreover, I introduce a new hiding rule to hide the resources shared by a subset of threads from the rest in the system. The support of information hiding not only improves the modularity of Rely-Guarantee reasoning, but also enables the sharing of dynamically allocated resources, which requires adjustment of rely/guarantee conditions.

The paper about this work is available at http://ttic.uchicago.edu/~feng/research/publications/LRG.html