Synthesis of Flexible Fault-Tolerant Schedules with Preemption for Mixed Soft and Hard Real-Time Systems

In this paper we present an approach for scheduling with preemption for fault-tolerant embedded systems composed of soft and hard real-time processes. We are interested to maximize the overall utility for average, most likely to happen, scenarios and to guarantee the deadlines for the hard processes in the worst case scenarios. In many applications, the worst-case execution times of processes can be much longer than their average execution times. Thus, designs for the worst-case can be overly pessimistic, i.e., result in low overall utility. We propose preemption of process executions as a method to generate flexible schedules that maximize the overall utility for the average case while guarantee timing constraints in the worst case. Our scheduling algorithms determine off-line when to preempt and when to resurrect processes. The experimental results show the superiority of our new scheduling approach compared to approaches without preemption.