Omen+: a precise dynamic deadlock detector for multithreaded Java libraries

Designing thread-safe libraries without concurrency defects can be a challenging task. Detecting deadlocks while invoking methods in these libraries concurrently is hard due to the possible number of method invocation combinations, the object assignments to the parameters and the associated thread interleavings. In this paper, we describe the design and implementation of OMEN+ that takes a multithreaded library as the input and detects true deadlocks in a scalable manner. We achieve this by automatically synthesizing relevant multithreaded tests and analyze the associated execution traces using a precise deadlock detector. We validate the usefulness of OMEN+ by applying it on many multithreaded Java libraries and detect a number of deadlocks even in documented thread-safe libraries. The tool is available for free download at http://www.csa.iisc.ernet.in/~sss/tool/omenplus.html.