Randomized Two-Process Wait-Free Test-and-Set

TL;DR

This paper introduces a simple, explicit randomized algorithm for 2-process wait-free test-and-set, achieving efficient expected steps with minimal atomic variables, and provides a finite-state analysis for correctness and performance.

Contribution

It presents the first explicit, simple randomized 2-process wait-free test-and-set algorithm using minimal atomic variables and a finite-state analysis for correctness and efficiency.

Findings

Test-and-set takes at most 11 expected steps

Reset operation takes exactly 1 step

Finite-state analysis confirms correctness and performance

Abstract

We present the first explicit, and currently simplest, randomized algorithm for 2-process wait-free test-and-set. It is implemented with two 4-valued single writer single reader atomic variables. A test-and-set takes at most 11 expected elementary steps, while a reset takes exactly 1 elementary step. Based on a finite-state analysis, the proofs of correctness and expected length are compressed into one table.