Reachability Analysis of Communicating Pushdown Systems
Résumé
The reachability analysis of recursive programs that commu- nicate asynchronously over reliable Fifo channels calls for restrictions to ensure decidability. We extend here a model proposed by [La Torre et al. 2008], based on communicating pushdown sys- tems that can dequeue with empty stack only. Our extension adds the dual modality, which allows to dequeue with non-empty stack, and thus models interrupts for working threads. We study (possibly cyclic) net- work architectures under a semantic assumption on communication that ensures the decidability of reachability for finite state systems. Subse- quently, we determine precisely how pushdowns can be added to this setting while preserving the decidability; in the positive case we obtain exponential time as the exact complexity bound of reachability. A sec- ond result is a generalization of the doubly exponential time algorithm of [La Torre et al. 2008] for bounded context analysis to our symmetric queueing policy. We provide here a direct and simpler algorithm.