A conflict-resilient lock-free linearizable calendar queue

In the last two decades, great attention has been devoted to the design of non-blocking and linearizable data structures, which enable exploiting the scaled-up degree of parallelism in off-the-shelf shared-memory multi-core machines. In this context, priority queues are highly challenging. Indeed, concurrent attempts to extract the highest-priority item are prone to create detrimental thread conflicts that lead to abort/retry of the operations. In this article, we present the first priority queue that jointly provides: (i) lock-freedom and linearizability; (ii) conflict resiliency against concurrent extractions; (iii) adaptiveness to different contention profiles; and (iv) amortized constant-time access for both insertions and extractions. Beyond presenting our solution, we also provide proof of its correctness based on an assertional approach. Also, we present an experimental study on a 64-CPU machine, showing that our proposal provides performance improvements over state-of-the-art non-blocking priority queues.