Verification of a Hierarchical Generic Mutual Exclusion Algorithm

In distributed environments, the shared resources access control by mutual exclusion paradigm is a recurrent key problem. To cope with the new constraints implied by recently developed large scale distributed systems like grids, mutual exclusion algorithms become more and more complex and thus much harder to prove and/or verify. In this article, we propose the formal modeling and the verification of a new generic hierarchical approach. This approach is based on the composition of classical already proof checked distributed algorithms. It overcomes some limitations of these classical algorithms by taking into account the network topology latencies and have a high scalability where centralized ones don’t. We also have formalized the properties of the mutual exclusion paradigm in order to verify them against our solution. We prove that our compositional approach preserves theses properties under the assumption that all used plain algorithms assert them. This verification by formal method checkers was eased by the efficient use of already proved mutual exclusion algorithms and the reduction of state spaces by exploiting the symmetries. keywords: distributed algorithm, composition, mutual exclusion, grid computing, colored Petri nets, model checking.