Timing-Based Mutual Exclusion with Local Spinning

We consider the time complexity of shared-memory mutual exclusion algorithms based on reads, writes, and comparison primitives under the remotememory-reference (RMR) time measure. For asynchronous systems, a lower bound of Ω(log N/ log log N) RMRs per critical-section entry has been established in previous work, where N is the number of processes. In this paper, we show that lower RMR time complexity is attainable in semi-synchronous systems in which processes may execute delay statements. When assessing the time complexity of delay-based algorithms, the question of whether delays should be counted arises. We consider both possibilities. Also of relevance is whether delay durations are upper-bounded. (They are lower-bounded by de£nition.) Again, we consider both possibilities. For each of these possibilities, we present an algorithm with either Θ(1) or Θ(log log N) time complexity. For the cases in which a Θ(log log N) algorithm is given, we establish matching Ω(log logN) lower bounds.