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Atomicity is a fundamental correctness property in multithreaded programs. A method is atomic if, for every execution, there is an equivalent serial execution in which the actions of the method are not interleaved with actions of other threads. Atomic methods are amenable to sequential reasoning, which significantly facilitates subsequent analysis and verification. This article presents a type system for specifying and verifying the atomicity of methods in multithreaded Java programs using a synthesis of Lipton's theory of reduction and type systems for race detection. The type system supports guarded, write-guarded, and unguarded fields, as well as thread-local data, parameterized classes and methods, and protected locks. We also present an algorithm for verifying atomicity via type inference. We have applied our type checker and type inference tools to a number of commonly used Java library classes and programs. These tools were able to verify the vast majority of methods in these benchmarks as atomic, indicating that atomicity is a widespread methodology for multithreaded programming. In addition, reported atomicity violations revealed some subtle errors in the synchronization disciplines of these programs.

This article presents a static race-detection analysis for multithreaded shared-memory programs, focusing on the Java programming language. The analysis is based on a type system that captures many common synchronization patterns. It supports classes with internal synchronization, classes that require client-side synchronization, and thread-local classes. In order to demonstrate the effectiveness of the type system, we have implemented it in a checker and applied it to over 40,000 lines of hand-annotated Java code. We found a number of race conditions in the standard Java libraries and other test programs. The checker required fewer than 20 additional type annotations per 1,000 lines of code. This article also describes two improvements that facilitate checking much larger programs: an algorithm for annotation inference and a user interface that clarifies warnings generated by the checker. These extensions have enabled us to use the checker for identifying race conditions in large-scale software systems with up to 500,000 lines of code.