Making lock-free data structures verifiable with artificial transactions

Abstract

Among all classes of parallel programming abstractions, lock-free data structures are considered one of the most scalable and efficient thanks to their fine-grained style of synchronization. However, they are also challenging for developers and tools to verify because of the huge number of possible interleavings that result from fine-grained synchronizations. This paper addresses this fundamental problem between performance and verifiability of lock-free data structure implementations. We present Txit, a system that greatly reduces the set of possible interleavings by inserting transactions into the implementation of a lock-free data structure. We leverage hardware transactional memory support from Intel Haswell processors to enforce these artificial transactions. Evaluation on six popular lock-free data structure libraries shows that Txit makes it easy to verify lock-free data structures while incurring acceptable runtime overhead. Further analysis shows that two inefficiencies in Haswell are the largest contributors to this overhead.