Predictable Synchronization Mechanisms for Multiprocessor

Predictability is of paramount concern for hard real-time systems. In one approach to predictability, every aspect of a real-time system and every primitive provided by the underlying operating system must be bounded and predictable in order to achieve overall predictability. In this paper, we describe several concurrency control synchronization mechanisms developed for a next generation multiprocessor real-time kernel, the Spring Kernel. The important features of these mechanisms include semaphore support for mutual exclusion with linear waiting and bounded resource usage, termed strong semaphores. Three, more e cient, strong semaphore solutions are proposed in this paper. Two of them are based on the main theorem of the paper, the Deferred Bus theorem. These two solutions can either be implemented in hardware or software. The third solution, a pure software solution, is an extension to the existing Burns' algorithm. A performance comparison and a complexity analysis in terms of time, space and bus tra c are presented. This work is part of the Spring Project directed by Prof. Krithi Ramamritham and Prof. John A. Stankovic at the University of Massachusetts and is funded in part by the O ce of Naval Research under contract N00014-85-K-0398 and by the National Science Foundation under grant DCR-8500332.