Randomized mutual exclusion in O(log N / log log N) RMRs

Danny Hendler, Philipp Woelfel

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

7 Scopus citations


Mutual exclusion is a fundamental distributed coordination problem. Shared-memory mutual exclusion research focuses on local-spin algorithms and uses the remote memory references (RMRs) metric. A recent proof [9] established an Ω(log N) lower bound on the number of RMRs incurred by processes as they enter and exit the critical section, matching an upper bound by Yang and Anderson [18]. Both these bounds apply for algorithms that only use read and write operations. The lower bound of [9] only holds for deterministic algorithms, however; the question of whether randomized mutual exclusion algorithms, using reads and writes only, can achieve sub-logarithmic expected RMR complexity remained open. This paper answers this question in the affirmative. We present two strong-adversary [8] randomized local-spin mutual exclusion algorithms. In both algorithms, processes incur O(log N / log log N) expected RMRs per passage in every execution. Our first algorithm has sub-optimal worst-case RMR complexity of O(log N/ log log N) 2). Our second algorithm is a variant of the first that can be combined with a deterministic algorithm, such as [18], to obtain O(log N) worst-case RMR complexity. The combined algorithm thus achieves sub-logarithmic expected RMR complexity while maintaining optimal worst-case RMR complexity. Our upper bounds apply for both the cache coherent (CC) and the distributed shared memory (DSM) models.

Original languageEnglish
Title of host publicationPODC'09 - Proceedings of the 2009 ACM Symposium on Principles of Distributed Computing
Number of pages10
StatePublished - 9 Nov 2009
Event2009 ACM Symposium on Principles of Distributed Computing, PODC'09 - Calgary, AB, Canada
Duration: 10 Aug 200912 Aug 2009


Conference2009 ACM Symposium on Principles of Distributed Computing, PODC'09
CityCalgary, AB


  • Mutual exclusion
  • Remote memory references (RMRs)


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