THE NON-OPTIMALITY OF THE MONOTONIC PRIORITY ASSIGNMENTS FOR HARD REAL-TIME OFFSET FREE SYSTEMS

In this paper, we study the problem of scheduling hard real-time perio dic tasks with static priority pre-emptive algorithms. We consider tas ks which are characterized by a period, a hard deadline, a computation time and an offset (the time of the first request), where the offsets may be chosen by the scheduling algorithm, hence the denomination off set free systems. We study the rate monotonic and the deadline monoton ic priority assignments for this kind of system and we compare the off set free systems and the asynchronous systems in terms of priority ass ignment. Hence, we show that the rate and the deadline monotonic prior ity assignments are not optimal for offset free systems.