Dynamic acceptance of aperiodic tasks with periodic tasks under resource sharing constraints

Abstract

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A real-time system is considered in which a set of periodic tasks are scheduled on an earliest-deadline-first basis and exclusively access critical sections through a dynamic priority ceiling protocol. An optimal online acceptance test is described for hard deadline aperiodic tasks. Aperiodic tasks are accepted only if all deadlines can be met. Here, optimality means that the algorithm is able to answer ‘yes’ to the question of the acceptance of a newly occurring task each time it is possible. The time complexity of the test is O(⌈R/p⌉.n+m) where n is the number of periodic tasks, R is the longest deadline, p is the shortest period and m is the number of aperiodic tasks that have previously been accepted but not completed.