Mainstream languages such as C/C++ (with Pthreads), Java, and .NET provide programmers with both static and dynamic barriers for synchronizing concurrent threads in fork/join programs. However, such barrier synchronization in fork/join programs is hard to verify since programmers must not only keep track of the dynamic number of participating threads, but also ensure that all participants proceed in correctly synchronized phases. As barriers are commonly used in practice, verifying correct synchronization of barriers can provide compilers and analysers with important phasing information for improving the precision of their analyses and optimizations. In this paper, we propose an approach for statically verifying correct synchronization of static and dynamic barriers in fork/join programs. We introduce the notions of bounded permissions and phase numbers for keeping track of the number of participating threads and barrier phases respectively. The approach has been proven sound, and a prototype of it (named VeriBSync) has been implemented for verifying barrier synchronization of realistic programs in the SPLASH-2 benchmark suite.
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