Thread-Modular Static Analysis for Relaxed Memory Models

We propose a memory-model-aware static program analysis method for accurately analyzing the behavior of concurrent software running on processors with weak consistency models such as x86-TSO, SPARC-PSO, and SPARC-RMO. At the center of our method is a unified framework for deciding the feasibility of inter-thread interferences to avoid propagating spurious data flows during static analysis and thus boost the performance of the static analyzer. We formulate the checking of interference feasibility as a set of Datalog rules which are both efficiently solvable and general enough to capture a range of hardware-level memory models. Compared to existing techniques, our method can significantly reduce the number of bogus alarms as well as unsound proofs. We implemented the method and evaluated it on a large set of multithreaded C programs. Our experiments showthe method significantly outperforms state-of-the-art techniques in terms of accuracy with only moderate run-time overhead.Comment: revised version of the ESEC/FSE 2017 pape

Event Stream Processing with Multiple Threads

Current runtime verification tools seldom make use of multi-threading to speed up the evaluation of a property on a large event trace. In this paper, we present an extension to the BeepBeep 3 event stream engine that allows the use of multiple threads during the evaluation of a query. Various parallelization strategies are presented and described on simple examples. The implementation of these strategies is then evaluated empirically on a sample of problems. Compared to the previous, single-threaded version of the BeepBeep engine, the allocation of just a few threads to specific portions of a query provides dramatic improvement in terms of running time

McMini: A Programmable DPOR-based Model Checker for Multithreaded Programs

Model checking has become a key tool for gaining confidence in correctness of multi-threaded programs. Unit tests and functional tests do not suffice because of race conditions that are not discovered by those tests. McMini is an extensible model checker based on DPOR (Dynamic Partial Order Reduction). A mechanism was invented to declare to McMini new, primitive thread operations, typically in 100~lines or less of C~code. The mechanism was extended to also allow the end user to declare alternative thread wakeup policies, including spurious wakeups from condition variables. One declares: (I) under what conditions an operation is enabled; (ii) which thread operations are independent of each other; and (iii) when two operations can be considered as co-enabled. An optional wakeup policy is implemented by defining when a wait operation (on a semaphore, condition variable, etc.) is enabled. A new enqueue thread operation is described, allowing a user to declare alternative wakeup policies. McMini was first confirmed to operate correctly and efficiently as a traditional, but extensible model checker for mutex, semaphore, condition variable, and reader-writer. McMini's extensibility was then tested on novel primitive operations, representing other useful paradigms for multithreaded operations. An example is readers-and-two-writers. The speed of model checking was found to be five times faster and more, as compared to traditional implementations on top of condition variables. Alternative wakeup policies (e.g., FIFO, LIFO, arbitrary, etc.) were then tested using an enqueue operation. Finally, spurious wakeups were tested with a program that exposes a bug only in the presence of a spurious wakeup.Comment: 24 pages, 1 figur