A UNIFIED METHOD OF MUTUAL EXCLUSION IN PARALLEL AND DISTRIBUTED SYSTEMS

This paper proposes a mutual exclusion method that is unified for the parallel and distributed systems. The method partially serializes requ ests into partial queues of requests, which are next totally serialize d into a main queue. A request in the main queue is authorized to ente r the critical section (CS) when the request receives the privilege to ken from the previous request in the queue. In the distributed system of N sites that each is a parallel system, mutual exclusion is perform ed by cooperation of two algorithms based on the same method. The algo rithm for the distributed system works on a logical network (that is a directed tree) of S (less than or equal to N) sites. The algorithm fo r each site produces a local-main queue of requests. The chunk of re q uests in the local queue is concatenated at a time to the partial queu e of the distributed system. Then the cost of mutual exclusion - the n umber of intersite messages required per CS entry - is reduced to O(1) (between O and 3).