| The reachability analysis of recursive programs that communicate over asynchronous and reliable Fifo channels calls for restrictions to ensure decidability. We extend here a model proposed by La Torre, Madhusudan and Parlato [LMP08], based on communicating pushdown systems that can dequeue with empty stack only. Our extension adds the dual modality, which allows to dequeue with non-empty stack, thus modelling interrupts for working threads. We study (possibly cyclic) network architectures under a semantic assumption (mutex communication) that ensures the decidability of reachability for finite state systems. Sub- sequently, 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 [LMP08] for bounded context analysis to our symmetric queueing policy. We provide here a direct (and simpler) proof |
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