Análise de ferramentas de teste no contexto de aprendizado de programação concorrente

Programas com múltiplos fluxos de execução são chamados programas concorrentes. Estes programas, devido às inúmeras possibilidades de intercalações destes fluxos e necessidade de sincronização entre eles, estão suscetíveis a diversos problemas não presentes na programação sequencial, como corridas de dados, deadlocks, e violações de atomicidade e ordem. Este não-determinismo traz um grande desafio tanto no desenvolvimento de sistemas concorrentes, quanto no aprendizado de conceitos de concorrência, principalmente para alunos iniciantes na área. Considerando esta dificuldade, este trabalho buscou encontrar ferramentas didáticas para realização de testes em programas concorrentes, analisando diversas abordagens propostas de teste e selecionando as ferramentas mais adequadas para o propósito acadêmico. As ferramentas FastTrack, RVPredict e Atomizer foram estudadas com maior detalhamento e experimentadas com programas clássicos de concorrência, como produtor-consumidor, avaliando problemas de corrida de dados e violação de atomicidade. Na avaliação de cada ferramenta, foram considerados sua usabilidade, facilidade de entendimento da saída apresentada, limitações de uso e acurácia. Dentre as técnicas estudadas, o FastTrack apresentou falsos positivos em seus resultados, mas obteve resultados acurados em programas que utilizam a primitiva de sincronização synchronized. O Atomizer apresentou falsos negativos, porém, tem o diferencial de explorar o problema de violação de atomicidade, que é pouco abordado por outras ferramentas. Já o RVPredict obteve resultados acurados, mas não é compatível com programas que possuem muitos laços, ou ramificações. Assim, é recomendado um uso complementar destas ferramentas, avaliando as necessidades do programa a ser testado

Exposing concurrency failures: a comprehensive survey of the state of the art and a novel approach to reproduce field failures

With the rapid advance of multi-core and distributed architectures, concurrent systems are becoming more and more popular. Concurrent systems are extremely hard to develop and validate, as their overall behavior depends on the non-deterministic interleaving of the execution flows that comprise the system. Wrong and unexpected interleavings may lead to concurrency faults that are extremely hard to avoid, detect, and fix due to their non-deterministic nature. This thesis addresses the problem of exposing concurrency failures. Exposing concurrency failures is a crucial activity to locate and fix the related fault and amounts to determine both a test case and an interleaving that trigger the failure. Given the high cost of manually identifying a failure-inducing test case and interleaving among the infinite number of inputs and interleavings of the system, the problem of automatically exposing concurrency failures has been studied by researchers since the late seventies and is still a hot research topic. This thesis advances the research in exposing concurrency failures by proposing two main contributions. The first contribution is a comprehensive survey and taxonomy of the state-of-the-art techniques for exposing concurrency failures. The taxonomy and survey provide a framework that captures the key features of the existing techniques, identify a set of classification criteria to review and compare them, and highlight their strengths and weaknesses, leading to a thorough assessment of the field and paving the road for future progresses. The second contribution of this thesis is a technique to automatically expose and reproduce concurrency field failure. One of the main findings of our survey is that automatically reproducing concurrency field failures is still an open problem, as the few techniques that have been proposed rely on information that may be hard to collect, and identify failure-inducing interleavings but do not synthesize failure-inducing test cases. We propose a technique that advances over state- of-the-art approaches by relying on information that is easily obtainable and by automatically identifying both a failure- inducing test case and interleaving. We empirically demonstrate the effectiveness of our approach on a benchmark of real concurrency failures taken from different popular code bases

Computer Aided Verification

The open access two-volume set LNCS 11561 and 11562 constitutes the refereed proceedings of the 31st International Conference on Computer Aided Verification, CAV 2019, held in New York City, USA, in July 2019. The 52 full papers presented together with 13 tool papers and 2 case studies, were carefully reviewed and selected from 258 submissions. The papers were organized in the following topical sections: Part I: automata and timed systems; security and hyperproperties; synthesis; model checking; cyber-physical systems and machine learning; probabilistic systems, runtime techniques; dynamical, hybrid, and reactive systems; Part II: logics, decision procedures; and solvers; numerical programs; verification; distributed systems and networks; verification and invariants; and concurrency

Computer Aided Verification

The open access two-volume set LNCS 11561 and 11562 constitutes the refereed proceedings of the 31st International Conference on Computer Aided Verification, CAV 2019, held in New York City, USA, in July 2019. The 52 full papers presented together with 13 tool papers and 2 case studies, were carefully reviewed and selected from 258 submissions. The papers were organized in the following topical sections: Part I: automata and timed systems; security and hyperproperties; synthesis; model checking; cyber-physical systems and machine learning; probabilistic systems, runtime techniques; dynamical, hybrid, and reactive systems; Part II: logics, decision procedures; and solvers; numerical programs; verification; distributed systems and networks; verification and invariants; and concurrency