Scheduling Fixed-Priority Hard Real-Time Tasks in the Presence of Faults

We describe an approach to scheduling hard real-time tasks taking into account fault scenarios. All tasks are scheduled at run-time according to their fixed priorities, which are determined off-line. Upon error-detection, special tasks are released to perform error-recovery actions. We allow error-recovery actions to be executed at higher priority levels so that the fault resilience of the task set can be increased. To do so, we extend the well known response time analysis technique and describe a non-standard priority assignment policy. Results from simulation indicate that the fault resilience of the task sets can be significantly increased by using the proposed approach.