Priority-free conditionally-preemptive scheduling of modular sporadic real-time systems

For a real-time system (RTS) processing both sporadic and (multiple-period) periodic tasks, this study presents a novel modular modeling framework to describe the parameters of tasks, conforming to the pertinent concepts and techniques of discrete-event systems (DES). A task is represented by an automaton synchronized by the modular models corresponding to its parameters. As a consequence, a DES model depicting the RTS is synchronized by the DES representing these tasks. Based on supervisory control theory, priority-free conditionally-preemptive (PFCP) real-time scheduling is solved by finding all the safe execution sequences. Finally, the PFCP scheduling is illustrated by real-world examples.