A fair and space-efficient mutual exclusion

For shared memory systems with time and resource constraints such as embedded real-time systems, mutual exclusion mechanism that is both fair and space-efficient can be very useful. In this paper, we present a bounded-bypass algorithm using only two shared variables, regardless of the number of contending processes, by operation fetch&store as well as atomic read/write. To achieve the same level of fairness, we show that, by the same set of operations, two shared variables are necessary, and therefore our algorithm is space-optimal.