Schedulability analysis of the fault-tolerant hard real-time tasks with limited priority levels

In this paper, we consider fixed priority scheduling of fault-tolerant hard real-time tasks in which the priority level of the system is insufficient. This paper extends necessary and sufficient conditions for the purposed of limited priority levels on fault-tolerant hard real-time systems which takes into account the effect of temporary faults. The major contribution of our approach is to consider the recovery of tasks running with higher system priorities for the case of limited priority levels. This characteristic is very useful since the available slack time of higher system priority tasks can be make use of for recovering the faulty tasks of lower system priorities. Due to its flexibility and simplicity, the proposed approach provides an effective schedulability analysis, where the schedulability utilization of the system can be improved.