Nonatomic mutual exclusion with local spinning

  • Authors:
  • James H. Anderson;Yong-Jik Kim

  • Affiliations:
  • University of North Carolina at Chapel Hill;University of North Carolina at Chapel Hill

  • Venue:
  • Proceedings of the twenty-first annual symposium on Principles of distributed computing
  • Year:
  • 2002

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Abstract

We present an N-process local-spin mutual exclusion algorithm, based on nonatomic reads and writes, in which each process performs Θ(log N) remote memory references to enter and exit its critical section. No atomic read/write algorithm with better asymptotic worst-case time complexity is currently known. This suggests that atomic memory is not fundamentally required if one is interested in worst-case time complexity. The same cannot be said if one is interested in fast-path or adaptive algorithms. We show that such algorithms fundamentally require memory accesses to be atomic. In particular, we show that for any N-process nonatomic algorithm, there exists a single-process execution in which the lone competing process executes Ω(log N/log log N) remote operations to enter its critical section. Moreover, these operations must access Ω(√log N/log log N) distinct variables.