Quorum Based Mutual Exclusion in Asynchronous Systems with Unreliable Failure Detectors

This paper defines the quorum-based fault-tolerant mutual exclusion problem in a message-passing asynchronous system and determines a failure detector to solve the problem. This failure detector, which we call the modal failure detector star, and which we denote by M*, is strictly weaker than the perfect failure detector P but strictly stronger than the eventually perfect failure detector ◇P. The paper shows that at any environment, the problem is solvable with M*.