A framework for deadlock detection in core ABS

We present a framework for statically detecting deadlocks in a concurrent object-oriented language with asynchronous method calls and cooperative scheduling of method activations. Since this language features recursion and dynamic resource creation, deadlock detection is extremely complex and state-of-the-art solutions either give imprecise answers or do not scale. In order to augment precision and scalability we propose a modular framework that allows several techniques to be combined. The basic component of the framework is a front-end inference algorithm that extracts abstract behavioural descriptions of methods, called contracts, which retain resource dependency information. This component is integrated with a number of possible different back-ends that analyse contracts and derive deadlock information. As a proof-of-concept, we discuss two such back-ends: (i) an evaluator that computes a fixpoint semantics and (ii) an evaluator using abstract model checking.Comment: Software and Systems Modeling, Springer Verlag, 201

Deadlock detection of Java Bytecode

This paper presents a technique for deadlock detection of Java programs. The technique uses typing rules for extracting infinite-state abstract models of the dependencies among the components of the Java intermediate language -- the Java bytecode. Models are subsequently analysed by means of an extension of a solver that we have defined for detecting deadlocks in process calculi. Our technique is complemented by a prototype verifier that also covers most of the Java features.Comment: Pre-proceedings paper presented at the 27th International Symposium on Logic-Based Program Synthesis and Transformation (LOPSTR 2017), Namur, Belgium, 10-12 October 2017 (arXiv:1708.07854

PLACES'10: The 3rd Workshop on Programmng Language Approaches to concurrency and Communication-Centric Software

Paphos, Cyprus. March 201

A technique for detecting wait-notify deadlocks in Java

Deadlock analysis of object-oriented programs that dynamically create threads and objects is complex, because these programs may have an infinite number of states. In this thesis, I analyze the correctness of wait - notify patterns (e.g. deadlock freedom) by using a newly introduced technique that consists in an analysis model that is a basic concurrent language with a formal semantic. I detect deadlocks by associating a Petri Net graph to each process of the input program. This model allows to check if a deadlock occur by analysing the reachability tree. The technique presented is a basic step of a more complex and complete project, since in my work I only consider programs with one object

Bounded LTL Model Checking with Stable Models

In this paper bounded model checking of asynchronous concurrent systems is introduced as a promising application area for answer set programming. As the model of asynchronous systems a generalisation of communicating automata, 1-safe Petri nets, are used. It is shown how a 1-safe Petri net and a requirement on the behaviour of the net can be translated into a logic program such that the bounded model checking problem for the net can be solved by computing stable models of the corresponding program. The use of the stable model semantics leads to compact encodings of bounded reachability and deadlock detection tasks as well as the more general problem of bounded model checking of linear temporal logic. Correctness proofs of the devised translations are given, and some experimental results using the translation and the Smodels system are presented.Comment: 32 pages, to appear in Theory and Practice of Logic Programmin

Automatic detection and resolution of deadlocks in Go programs

The Go programming language is acquiring momentum in the development of concurrent software. Even though Go supports the shared-memory model, the message-passing alternative is the favoured idiomatic approach. Naturally, this practice is not exempt of the usual difficulties: programs may deadlock and the language run-time has only very basic support for deadlock detection. Previous research on deadlock detection mainly focused on shared-memory concurrency models. For mainstream languages, tools and approaches specific to the message-passing paradigm are scarce and incipient. There is however a large body of work on models of concurrency that only recently started to be applied to languages like Go. Since the Go run-time lets many deadlocks pass unnoticed, and the existing solutions provided by third party tools detect many deadlocks but only try to fix a limited set of specific patterns, imposing severe conditions to do so, there is a clear need for more general deadlock resolution strategies, going beyond prevention and avoidance. To gain insight on real-world deadlock bugs, we first built and categorized a collection of bugs sourced from high-profile open-source Go projects. Next, we extended and implemented an algorithm that takes an abstraction of the communication behaviour of the program and, when all the communication operations on channels necessary for progress are present, but a deadlock is possible, presents the problem and offers a possible resolution for the error. The extensions allows our approach to analyse a much wider range of real world programs. We conclude with an evaluation, comparing with two other state-of-the-art solutions.A linguagem de programação Go tem ganhado tração no desenvolvimento de software concorrente. Apesar de o Go suportar o modelo de partilha de memória, o modelo alternativo de partilha de mensagens é a abordagem idiomática. Naturalmente, esta prática não está isenta das dificuldades usuais: os programas podem bloquear e o runtime da linguagem só possui um suporte muito básico para a deteção destes bloqueios. Investigação anterior na deteção de bloqueios focou principalmente no modelo de partilha de memória. Para linguagens convencionais, ferramentas e abordagens dedicadas ao paradigma de passagem de mensagens são escassas e incipientes. No entanto, existe um grande conjunto de trabalhos sobre modelos de concorrência que só recentemente começou a ser aplicado em linguagens como o Go. Visto que o run-time do Go deixa muitos bloqueios passar despercebidos e as soluções existentes detetam muitos bloqueios, mas só tentam resolver um conjunto muito pequeno de padrões. De modo a ganhar conhecimento sobre erros de bloqueio reais, nós começámos por construir e categorizar uma coleção de erros obtidos a partir de projetos Go open-source de alto perfil. De seguida, nós estendemos e implementámos um algoritmo que recebe uma abstração do comportamento da comunicação de um programa e quando todas as operações de comunicação nos canais necessários para o progresso estão presentes, mas um bloqueio é possível, apresenta o erro e oferece uma possível resolução do erro. A nossa extensão permite analisar um conjunto muito maior de programas reais. Concluímos com uma avaliação, comparando com duas outras soluções do estado da arte

Recursive Decomposition of Progress Graphs

Search of a state transition system is traditionally how deadlock detection for concurrent programs has been accomplished. This paper examines an approach to deadlock detection that uses geometric semantics involving the topo-logical notion of dihomotopy to partition the state space into components; after that the reduced state space is exhaustively searched. Prior work partitioned the state space inductively. in this paper we show that a recursive technique provides greater reduction of the size of the state transition system and therefore more efficient deadlock detection. If the preprocessing can be done efficiently, then for large problems we expect to see more efficient deadlock detection and eventually more efficient verification of some temporal properties. © 2009 IEEE

A Graph-Based Semantics Workbench for Concurrent Asynchronous Programs

A number of novel programming languages and libraries have been proposed that offer simpler-to-use models of concurrency than threads. It is challenging, however, to devise execution models that successfully realise their abstractions without forfeiting performance or introducing unintended behaviours. This is exemplified by SCOOP---a concurrent object-oriented message-passing language---which has seen multiple semantics proposed and implemented over its evolution. We propose a "semantics workbench" with fully and semi-automatic tools for SCOOP, that can be used to analyse and compare programs with respect to different execution models. We demonstrate its use in checking the consistency of semantics by applying it to a set of representative programs, and highlighting a deadlock-related discrepancy between the principal execution models of the language. Our workbench is based on a modular and parameterisable graph transformation semantics implemented in the GROOVE tool. We discuss how graph transformations are leveraged to atomically model intricate language abstractions, and how the visual yet algebraic nature of the model can be used to ascertain soundness.Comment: Accepted for publication in the proceedings of FASE 2016 (to appear

Deadlock Analysis of Wait-Notify Coordination

International audienceDeadlock analysis of concurrent programs that contain coordination primitives (wait, notify and notifyAll) is notoriously challenging. Not only these primitives affect the scheduling of processes, but also notifications unmatched by a corresponding wait are silently lost. We design a behavioral type system for a core calculus featuring shared objects and Java-like coordination primitives. The type system is based on a simple language of object protocols-called usages-to determine whether objects are used reliably, so as to guarantee deadlock freedom