Static detection of error of double locking of mutex

Abstract

This paper describes algorithm for static search for error of double locking of mutex. The algorithm allows emitting warnings with low level of false positives. We considered finding errors for abstract library containing functions of mutex lock, unlock and conditional locking. We defined a set of regular languages, which models locks and unlocks during concrete execution of a program. We have defined a domain approximated set of regular languages. The algorithm is implemented in terms of data flow analysis. In the analysis elements of the domain are used as the data flow properties. The algorithm is described for a program that has only one mutex and does not contain any aliases. In that case every emitted warning will correspond to a real error which may occur during program execution. The algorithm is implemented in system of static analysis Svace developed in Institute for System Programming of the Russian Academy of Sciences. Svace performs alias analysis and matching of formal and actual function parameters. This makes it possible to apply the algorithm to search for double locking of a program containing only one mutex, and the rest of the work will be executed by Svace. The search algorithm of the double lock implemented in Svace can emit some number of false positives because Svace performs nonconservative analysis.