jPredictor

jPredictor is a tool for detecting concurrency errors in Java programs. The Java program is instrumented to emit property-relevant events at runtime and then executed. The resulting execution trace is collected and analyzed by Predictor, which extracts a causality relation sliced using static analysis and refined with lock-atomicity information. The resulting abstract model, a hybrid of a partial order and atomic blocks, is then exhaustively analyzed against the property and errors with counter-examples are reported to the user. Thus, jPredictor can "predict" errors that did not happen in the observed execution, but which could have happened under a different thread scheduling. The analysis technique employed in jPredictor is fully automatic, generic (works for any trace property), sound (produces no false alarms) but it is incomplete may miss errors). Two common types of errors are investigated in this paper: dataraces and atomicity violations. Experiments show that jPredictor is precise (in its predictions), effective and efficient. After the code producing them was executed only once, jPredictor found all the errors reported by other tools. It also found errors missed by other tools, including static race detectors, as well as unknown errors in popular systems like Tomcat and the Apache FTP server.