Scheduling periodic hard real-time tasks with arbitrary deadlines on multiprocessors

Pfair scheduling has usually been applied in the context of scheduling periodic tasks with coinciding periods and deadlines. This paper addresses the problem of scheduling hard real-time tasks characterized by arbitrary deadlines in a pfair manner on multiprocessor systems. We prove fundamental properties of the weight functions of such tasks and show that when such tasks are scheduled in a pfair manner every job of every task meets its deadline. We also present RRM (rational rate-monotonic), a static-priority scheme to schedule a set of such tasks, and derive demand-based sufficient conditions for determining the pfair schedulability of hard real-time tasks with arbitrary deadlines on multiprocessors under the RRM scheme. We also address the problem of accounting for interrupt-handling overheads in pfair systems and present a technique for implementing the priority ceiling protocol on pfair systems by modifying task weight functions.