Radius aware probabilistic testing of deadlocks with guarantees

Concurrency bugs only occur under certain interleaving. Existing randomized techniques are usually ineffective. PCT innovatively generates scheduling, before executing a program, based on pri-orities and priority change points. Hence, it provides a probabilis-tic guarantee to trigger concurrency bugs. PCT randomly selects priority change points among all events, which might be effective for non-deadlock concurrency bugs. However, deadlocks usually involve two or more threads and locks, and require more ordering constraints to be triggered. We interestingly observe that, every two events of a deadlock usually occur within a short range. We generally formulate this range as the bug Radius, to denote the max distance of every two events of a concurrency bug. Based on the bug radius, we propose RP_ro (Radius aware Probabilistic testing) for triggering deadlocks. Unlike PCT , RP_ro selects priori-ty change points within the radius of the targeted deadlocks but not among all events. Hence, it guarantees larger probabilities to trigger deadlocks. We have implemented RP_ro and PCT and eval-uated them on a set of real-world benchmarks containing 10 unique deadlocks. The experimental results show that RP_ro trig-gered all deadlocks with higher probabilities (i.e., 7.7x times larger on average) than that by PCT . We also evaluated RP_ro with radius varying from 1 to 150 (or 300). The result shows that the radius of a deadlock is much smaller (i.e., from 2 to 114 in our experiment) than the number of all events. This further confirms our observation and makes RP_ro meaningful in practice.