RegionTrack

Abstract

Atomicity is a correctness criterion to reason about isolated code regions in a multithreaded program when they are executed concurrently. However, dynamic instances of these code regions, called transactions , may fail to behave atomically, resulting in transactional atomicity violations. Existing dynamic online atomicity checkers incur either false positives or false negatives in detecting transactions experiencing transactional atomicity violations. This article proposes <monospace>RegionTrack</monospace>. <monospace>RegionTrack</monospace> tracks cross-thread dependences at the event, dynamic subregion, and transaction levels. It maintains both dynamic subregions within selected transactions and transactional happens-before relations through its novel timestamp propagation approach. We prove that <monospace>RegionTrack</monospace> is sound and complete in detecting both transactional atomicity violations and non-serializable traces. To the best of our knowledge, it is the first online technique that precisely captures the transitively closed set of happens-before relations over all conflicting events with respect to every running transaction for the above two kinds of issues. We have evaluated <monospace>RegionTrack</monospace> on 19 subjects of the DaCapo and the Java Grande Forum benchmarks. The empirical results confirm that <monospace>RegionTrack</monospace> precisely detected all those transactions which experienced transactional atomicity violations and identified all non-serializable traces. The overall results also show that <monospace>RegionTrack</monospace> incurred 1.10x and 1.08x lower memory and runtime overheads than <monospace>Velodrome</monospace> and 2.10x and 1.21x lower than <monospace>Aerodrome</monospace>, respectively. Moreover, it incurred 2.89x lower memory overhead than <monospace>DoubleChecker</monospace>. On average, <monospace>Velodrome</monospace> detected about 55% fewer violations than <monospace>RegionTrack</monospace>, which in turn reported about 3%–70% fewer violations than <monospace>DoubleChecker</monospace>.