Scheduling of hard-aperiodic requests in dynamic priority systems

In this paper, we discuss the problem of jointly scheduling both hard deadline of periodic and aperiodic tasks in dynamic priority systems. The proposed scheduling scheme has extended the APS (Alternative Priority Scheduling) algorithm which is developed by the authors. The APS algorithm has a simple slack calculation method which in consequence makes it be practical. The paper develops an efficient acceptance test method for hard-aperiodic requests. The on-line acceptance test performs to determine whether the timing requirements of the arriving hard aperiodic tasks can be met while guaranteeing all the deadlines of periodic tasks and any already accepted but not yet completed aperiodic tasks.