Identifying future field accesses in exhaustive state space traversal

Abstract

Abstract-One popular approach to detect errors in multithreaded programs is to systematically explore all possible interleavings. A common algorithmic strategy is to construct the program state space on-the-fly and perform thread scheduling choices at any instruction that could have effects visible to other threads. Existing tools do not look ahead in the code to be executed, and thus their decisions are too conservative. They create unnecessary thread scheduling choices at instructions that do not actually influence other threads, which implies exploring exponentially greater numbers of interleavings.In this paper we describe how information about field accesses that may occur in the future can be used to identify and eliminate unnecessary thread choices. This reduces the number of states that must be processed to explore all possible behaviors and therefore improves the performance of exhaustive state space traversal. We have applied this technique to Java PathFinder, using the WALA library for static analysis. Experiments on several Java programs show big performance gains. In particular, it is now possible to check with Java PathFinder more complex programs than before in reasonable time.

Approximating happens-before order: interplay between static analysis and state space traversal

“…Results of our experiments show that combination of the field access analysis with the mayhappen-before analysis yields a significant improvement over the standalone field access analysis [17] in terms of the number of eliminated redundant interleavings and thread scheduling choices.…”

“…In the experiments, we use the fully context-sensitive field access analysis, which is the most precise variant proposed in [17]. JPF traverses the whole state space in the case of every benchmark program, as none of the programs contain any error that JPF can detect.…”

“…Many redundant thread interleavings were avoided in this way, as shown by the experimental results published in [17]. The field access analysis combines static analysis with knowledge of the dynamic program state (thread call stacks) that is maintained by JPF during the state space traversal.…”

“…Our approach to the design of hybrid analyses, described here, was originally proposed in [17] for the field access analysis.…”

“…In prior work [17], we designed a hybrid field access analysis, which provides information about fields possibly accessed during the program execution, and used its results in JPF for more precise identification of globally-relevant and thread-local statements. Many redundant thread interleavings were avoided in this way, as shown by the experimental results published in [17].…”