Automated Analysis of Parametric Timing-Based Mutual Exclusion Algorithms

Deadlock-free algorithms that ensure mutual exclusion crucially depend on timing assumptions. In this paper, we describe our experience in automatically verifying mutual-exclusion and deadlock-freedom of the Fischer and Lynch-Shavit algorithms, using the model checker modulo theories mcmt. First, we explain how to specify timing-based algorithms in the mcmt input language as symbolic transition systems. Then, we show how the tool can verify all the safety properties used by Lynch and Shavit to establish mutual-exclusion, regardless of the number of processes in the system. Finally, we verify deadlock-freedom by following a reduction to "safety problems with lemmata synthesis" and using acceleration to avoid divergence. We also show how to automatically synthesize the bounds on the waiting time of a process to enter the critical section.