Abstract

Programming with Java monitors is recognized to be difficult, and potentially inefficient due to many useless context switches induced by the notifyAll primitive. This paper presents SOM, Sequential Object Monitors, as an alternative to programming with Java monitors. Reifying monitor method calls as requests, and providing full access to the pending request queue, gives rise to fully sequential monitors: the SOM programmer gets away from any code interleaving. Moreover, useless context switches are avoided. Finally, from a software engineering point of view, SOM promotes separation of concerns, by untangling the synchronization concern from the application logic. This paper illustrates SOM expressiveness with several classical concurrency problems, and high-level abstractions like guards and chords. Benchmarks of the implementation confirm the expected efficiency. © Springer-Verlag 2004.