A simple local-spin group mutual exclusion algorithm

This paper presents a new solution to the group mutual exclusion problem re cently Posed by Joung. In this problem, processes repeatedly request access to various "sessions." It is required that distinct processes are not in d ifferent sessions concurrently, that multiple processes may be in the same session concurrently, and that each process that tries to enter a session i s eventually able to do so. This problem is a generalization of the mutual exclusion and readers-writers problems. Our algorithm and its correctness p roof are substantially simpler than Joung's. This simplicity is achieved by building upon known solutions to the more specific mutual exclusion proble m. Our algorithm also has various advantages over Joung's, depending on the choice of mutual exclusion algorithm used. These advantages include admitt ing a process to its session in constant time in the absence of contention, spinning locally in Cache Coherent (CC) and Nonuniform Memory Access (NUMA ) systems, and improvements in the complexity measures proposed by Joung.