BarrierFinder: recognizing ad hoc barriers

Abstract

Ad hoc synchronizations are pervasive in multi-threaded programs. Due to their diversity and complexity, understanding the enforced synchronization relationships of ad hoc synchronizations is challenging but crucial to multi-threaded program development and maintenance. Existing techniques can partially detect primitive ad hoc synchronizations, but they cannot recognize complete implementations or infer the enforced synchronization relationships. In this paper, we propose a framework to automatically identify complex ad hoc synchronizations in full and infer their synchronization relationships. We instantiate the framework with a tool called BarrierFinder, which features various techniques, including program slicing and bounded symbolic execution, to efficiently explore the interleaving space of ad hoc synchronizations within multi-threaded programs and collect execution traces. BarrierFinder then uses these traces to characterize ad hoc synchronizations into different types with a focus on recognizing barriers. Our evaluation shows that BarrierFinder is both effective and efficient in doing this, and BarrierFinder is also helpful for programmers to understand the correctness of their implemented ad hoc synchronizations.