Detection Of Atomicity Violations Research Articles

Davida: A Decentralization Approach to Localizing Transaction Sequences for Debugging Transactional Atomicity Violations

Atomicity is a desirable property for multithreaded programs. In such programs, a transaction is an execution of an atomic code region that may contain memory accesses on an arbitrary number of shared variables. When transactions are not conflicting with one another in a trace, they greatly simplify the reasoning of the program correctness. If a transaction incurs an atomicity violation in a trace, developers have to debug the code, but this is challenging. To achieve practical runtime performances, existing dynamic techniques for detecting such atomicity violations face a challenge: They are designed for either detecting all such atomicity violations without the capability of localizing the corresponding cross-thread transaction sequences or deliberately missing some atomicity violations in the trade of localizing some of them to support their atomicity violation detection. In this article, we propose Davida, a novel technique to address this problem. Davida efficiently tracks selective transactions and cross-thread dependency sequences over transactions reachable from the currently active transactions of all the threads in a decentralized manner. We prove that Davida precisely accomplishes every atomicity violation in a trace with an actual sequence of transactions triggering the violation. The experimental results on 15 subjects showed that Davida outperformed Velodrome, the previous graph-based state-of-the-art technique, in both performance and completeness.

Atomicity Violation in Multithreaded Applications and Its Detection in Static Code Analysis Process

This paper is a contribution to the field of research dealing with the parallel computing, which is used in multithreaded applications. The paper discusses the characteristics of atomicity violation in multithreaded applications and develops a new definition of atomicity violation based on previously defined relationships between operations, that can be used to atomicity violation detection. A method of detection of conflicts causing atomicity violation was also developed using the source code model of multithreaded applications that predicts errors in the software.

AVPredictor: Comprehensive prediction and detection of atomicity violations

SummaryConcurrency bugs, such as atomicity‐violation bugs, are difficult to detect due to the uncertainty of thread‐scheduling. It is particularly difficult to conduct a thorough bug fix when an atomicity‐violation bug can be triggered by different buggy interleavings. This paper proposes a prediction‐based approach to comprehensively detect atomicity‐violation bugs. A bug fix can be incomplete when the developer cannot have all the buggy interleavings. Based on the candidate interleavings, this approach can predict unmanifested atomicity‐violation bugs from a non‐buggy execution and comprehensively display all the buggy interleavings for the same bug to assist a thorough fix. We use a monitored execution to record execution traces and predict potential buggy interleavings based on the candidate interleavings identified from the trace. Then, we use controlled executions to verify the predicted buggy interleavings by controlling the thread‐scheduling. We implemented a prototype tool called AVPredictor and evaluated it with real‐world tests. Experiments show that AVPredictor can effectively find all the known atomicity‐violation bugs as well as a previously unknown bug together with all the buggy interleavings for each bug. The runtime overhead is 13x for the monitored execution and 18x for the controlled execution.

Efficient detection and validation of atomicity violations in concurrent programs

Atomicity violations are a major source of bugs in concurrent programs. Empirical studies have shown that the majority of atomicity violations are instances of the three-access pattern, where two accesses to a shared variable by a thread are interleaved by an access to the same variable by another thread. This article describes two advancements in atomicity violation detection. First, we describe a new technique that directs the execution of a dynamic analysis tool towards three-access pattern (TAP) instances. The directed search is based on constraint solving and concolic execution. We implemented this technique in a tool called AtomChase. Using 27 benchmarks comprising 5.4 million lines of Java, we compared AtomChase to five other tools. AtomChase found 20% more TAP instances than all five tools combined. Second, we show that not all TAP instances are atomicity violations and present a formally grounded approach to validating the non-atomicity of TAP instances. This approach, called HyperCV, prevents the inclusion of false positives in results presented to users. HyperCV uses a set of provably sufficient conditions for non-atomicity to efficiently validate TAP instances. Using the same benchmarks, HyperCV validated 79% of TAP instances in linear rather than exponential execution time.

ASP: Abstraction Subspace Partitioning for Detection of Atomicity Violations with an Empirical Study

Dynamic concurrency bug detectors predict and then examine suspicious instances of atomicity violations from executions of multithreaded programs. Only few predicted instances are real bugs. Prioritizing such instances can make the examinations cost-effective, but is there any design factor exhibiting significant influence? This work presents the first controlled experiment that studies two design factors, abstraction level and subspace, in partitioning such instances through 35 resultant partition-based techniques on 10 benchmarks with known vulnerability-related bugs. The empirical analysis reveals significant findings. First, partition-based prioritization can significantly improve the fault detection rate. Second, coarse-grained techniques are more effective than fine-grained ones, and using some one-dimensional subspaces is more effective than using other dimensional subspaces. Third, eight previously unknown techniques can be more effective than the technique modeled after a state-of-the-art dynamic detector.

ColorSafe

In this paper, we propose ColorSafe, an architecture that detects and dynamically avoids single- and multi-variable atomicity violation bugs. The key idea is to group related data into colors and then monitor access interleavings in the "color space". This enables detection of atomicity violations involving any data of the same color. We leverage support for meta-data to maintain color information, and signatures to efficiently keep recent color access histories. ColorSafe dynamically avoids atomicity violations by inserting ephemeral transactions that prevent erroneous interleavings. ColorSafe has two modes of operation: (1) debugging mode makes detection more precise, producing fewer false positives and collecting more information; and, (2) deployment mode provides robust, efficient dynamic bug avoidance with less precise detection. This makes ColorSafe useful throughout the lifetime of programs, not just during development. Our results show that, in deployment mode, ColorSafe is able to successfully avoid the majority of multi-variable atomicity violations in bug kernels, as well as in large applications (Apache and MySQL). In debugging mode, ColorSafe detects bugs with few false positives.

Runtime analysis of atomicity for multithreaded programs

Atomicity is a correctness condition for concurrent systems. Informally, atomicity is the property that every concurrent execution of a set of transactions is equivalent to some serial execution of the same transactions. In multithreaded programs, executions of procedures (or methods) can be regarded as transactions. Correctness in the presence of concurrency typically requires atomicity of these transactions. Tools that automatically detect atomicity violations can uncover subtle errors that are hard to find with traditional debugging and testing techniques. This paper describes two algorithms for runtime detection of atomicity violations and compares their cost and effectiveness. The reduction-based algorithm checks atomicity based on commutativity properties of events in a trace; the block-based algorithm efficiently represents the relevant information about a trace as a set of blocks (i.e., pairs of events plus associated synchronizations) and checks atomicity by comparing each block with other blocks. To improve the efficiency and accuracy of both algorithms, we incorporate a multilockset algorithm for checking data races, dynamic escape analysis, and happen-before analysis. Experiments show that both algorithms are effective in finding atomicity violations. The block-based algorithm is more accurate but more expensive than the reduction-based algorithm.

Static Detection of Atomicity Violations in Object-Oriented Programs.

Violations of atomicity are possible sources of errors in parallel programs. A violation occurs if the effect of a method execution depends on the execution of concurrent threads that operate on the same or overlapping parts of a shared data structure. All accesses to shared data are assumed to be ordered through synchronization, hence common techniques for data race and deadlock detection are not able to find such errors. We have developed a static analysis that infers atomicity constraints and identifies potential violations. The analysis is based on an abstract model of threads and data. A symbolic execution tracks object locking and access and provides information that is finally used to determine potential violations of atomicity. We provide a detailed evaluation of our algorithm for a number of Java benchmarks. Although the algorithm does not guarantee to find all violations of atomicity, our experience shows that our method is efficient and effective in determining several known synchronization problems in a set of application programs and the Java library. The problem of overreporting that is commonly encountered due to conservatism in static analyses is moderate.