Schedulability of event-driven code blocks in real-time embedded systems

Many real-time embedded systems involve a collection of independently executing event-driven code blocks, having hard real-time constraints. Tasks in many such systems, like network processors, are either not preemptable or have restrictions on the number of preemptions allowed. All the previous work on the schedulability analysis of such systems either have exponential complexity, or allow unbounded number of preemptions and are usually based on heuristics. In this paper we present the exact necessary and sufficient conditions under EDF, for the schedulability of such a collection of code blocks in a non-preemptive environment, and give efficient algorithms for testing them. We validate our analytical results with experiments and show that the schedulability analysis problem in such systems can be exactly and efficiently solved in practice.