Fair scheduling of dynamic task systems on multiprocessors

In dynamic real-time task systems, tasks that are subject to deadlines are al-lowed to join and leave the system. In previous work, Stoica et al. and Baruah et al.presented conditions under which such joins and leaves may occur in fair-scheduleduniprocessor systems without causing missed deadlines. In this paper, we extendtheir work by considering fair-scheduled multiprocessors. We show that their con-ditions are sufficient on M processors, under any deadline-based Pfair schedulingalgorithm, if the utilization of every subset of M − 1 tasks is at most one. Further,for the general case in which task utilizations are not restricted in this way, wederive sufficient join/leave conditions for the PD2 Pfair algorithm. We also showthat, in general, these conditions cannot be improved upon without causing misseddeadlines.