Two-enqueuer queue in Common2

TL;DR

This paper introduces the first wait-free algorithm for a queue with two enqueuers and multiple dequeuers within the Common2 class, addressing a longstanding open problem in concurrent object implementation.

Contribution

It provides the first known implementation of a two-enqueuer queue in Common2, expanding the understanding of shared object capabilities with consensus number 2.

Findings

First Common2 queue algorithm with two enqueuers

Supports any number of dequeuers

Advances theoretical understanding of wait-free concurrent objects

Abstract

The question of whether all shared objects with consensus number 2 belong to Common2, the set of objects that can be implemented in a wait-free manner by any type of consensus number 2, was first posed by Herlihy. In the absence of general results, several researchers have obtained implementations for restricted-concurrency versions of FIFO queues. We present the first Common2 algorithm for a queue with two enqueuers and any number of dequeuers.