On the Efficient Scheduling of Non-Periodic Tasks in Hard Real-Time Systems

This paper1 presents linear time, on-line algorithms which guarantee and jointly schedule firm aperiodic, hard sporadic and periodic tasks in fixedpriority real-time systems. We develop and capitalize on a methodology which computes the spare capacity Z(a; b) exactly in time (n), for arbitrary schedule intervals [a; b), which, to the best of our knowledge, is the first linear time algorithm reported in the literature. Previous state of the art methods incur pseudopolynomial time to guarantee on-line a single aperiodic and incur continuous overhead for slack maintenance. Our method guarantees and schedules firm tasks to receive FIFO or EDF service, incurring a one-time linear cost, of (n) and (n + k), respectively, where k is the number of pending firm tasks.