AVIO

Abstract

Concurrency bugs are among the most difficult to test and diagnose of all software bugs. The multicore technology trend worsens this problem. Most previous concurrency bug detection work focuses on one bug subclass, data races, and neglects many other important ones such as atomicity violations , which will soon become increasingly important due to the emerging trend of transactional memory models.This paper proposes an innovative, comprehensive, invariantbased approach called AVIO to detect atomicity violations. Our idea is based on a novel observation called access interleaving invariant , which is a good indication of programmers' assumptions about the atomicity of certain code regions. By automatically extracting such invariants and detecting violations of these invariants at run time, AVIO can detect a variety of atomicity violations.Based on this idea, we have designed and built two implementations of AVIO and evaluated the trade-offs between them. The first implementation, AVIO-S, is purely in software, while the second, AVIO-H, requires some simple extensions to the cache coherence hardware. AVIO-S is cheaper and more accurate but incurs much higher overhead and thus more run-time perturbation than AVIOH. Therefore, AVIO-S is more suitable for in-house bug detection and postmortem bug diagnosis, while AVIO-H can be used for bug detection during production runs.We evaluate both implementations of AVIO using large realworld server applications (Apache and MySQL) with six representative real atomicity violation bugs, and SPLASH-2 benchmarks. Our results show that AVIO detects more tested atomicity violations of various types and has 25 times fewer false positives than previous solutions on average.