The Distributed Deadline Synchronization Protocol for real-time systems scheduled by EDF

Many distributed and multiprocessor real-time applications consist of pipelines of tasks that must complete before their end-to-end deadlines. Different schedulability analyses have been proposed for both Fixed Priority and Earliest Deadline First scheduling. All the schedulability analyses proposed so far assume that a global clock synchronization protocol is used to synchronize the deadlines of jobs allocated on different processors. This assumption may limit the applicability of EDF to such systems. In this paper, we propose the Distributed Deadline Synchronization Protocol (DDSP) for computing the absolute deadlines of jobs. The protocol is a non-trivial extension of the Release Guard Protocol proposed for fixed priority systems. DDSP does not require a global clock synchronization, yet existing schedulability analyses are valid for schedules generated by DDSP.