A Modular Scheme for Deadlock Prevention in an Object-Oriented Programming Model

Despite the advancements of concurrency theory in the past decades, practical concurrent programming has remained a challenging activity. Fundamental problems such as data races and deadlocks still persist for programmers since available detection and prevention tools are unsound or have otherwise not been well adopted. In an alternative approach, programming models that exclude certain classes of errors by design can address concurrency problems at a language level. In this paper we review SCOOP, an existing race-free programming model for concurrent object-oriented programming, and extend it with a scheme for deadlock prevention based on locking orders. The scheme facilitates modular reasoning about deadlocks by associating annotations with the interfaces of routines. We prove deadlock-freedom of well-formed programs using a rigorous formalization of the locking semantics of the programming model. The scheme has been implemented and we demonstrate its usefulness by applying it to the example of a simple web server.