Non-premptive Fixed Priority schedulingwith FIFO arbitration:uniprocessor and distributed cases

In this paper, we focus on non-preemptive Fixed Priority scheduling. We are interested in the worst case response time of flows, both in uniprocessor and distributed cases. On a processor, the number of available priorities is generally limited. If this number is less than the number of flows to be considered, several flows have to share the same priority. Such flows are assumed to be scheduled arbitrarily in the classical approach. We assume in this paper that these flows are scheduled FIFO. This assumption leads us to revisit classical results in the uniprocessor case. As we obtain response times less than or equal to the classical results, any flow set feasible with the classical approach is feasible with our approach. The converse is false, as shown by an example. Moreover, we determine the conditions leading to shorter response times. We then establish new results in a distributed context. We show how to compute an upper bound on the end-to-end response time of any flow. For this, we use a worst case analysis based on the trajectory approach.