The information structure of distributed mutual exclusion algorithms

Reviewer: Hikyu Lee

The major contribution of this paper is the presentation of a formal model to describe a generalized mutual exclusion problem in distributed systems. The presentation of the proposed information structure and generalized algorithms, with a proof of necessary and sufficient conditions to achieve a deadlock-free mutual exclusion, is self-contained and well organized. The paper also gives a good list of references for past work done in this area. The performance analysis section of this paper is rather weak. It gives lower and upper bounds on message exchanges for critical section entry. However, the bounds may not be tight enough for practical evaluation of different algorithms. The paper also lacks a comparative analysis of performance that ties the number of message exchanges for critical section entry to the overall efficiency of the algorithm. Although optimization of a particular algorithm may be strongly dependent upon the topology of a network and certain implementation constraints, the performance metric described in this paper does not seem to provide a meaningful guideline. The author discusses dynamic information structures toward the end of the paper by citing an example in the literature. The proposed information structure will be more practical if algorithms are developed that utilize dynamic information structure to achieve an optimized performance.