Fault-Tolerant Rate-Monotonic Scheduling

Due to the critical nature of the tasks in hard real-time systems, it is essential that faults be tolerated. Several studies have shown that space applications, which have very high reliability requirements, have also very high transient faults frequency. Therefore, tolerance to this type of faults is essential in such applications. In this paper, we present a scheme which can be used to tolerate faults during the execution of preemptive real-time tasks. We describe a recovery scheme which can be used to re-execute tasks in the event of single and multiple transient faults and discuss conditions that must be met by any such recovery scheme. We then extend the Rate Monotonic Scheduling (RMS) scheme to provide tolerance for single and multiple transient faults. We derive schedulability bounds for sets of real-time tasks given the desired level of fault tolerance for each task or subset of tasks. Finally, we analyze and compare the bounds derived as a function of the amount of processing ..