Schedulability Analysis of Timed Regular Tasks by Under-Approximation on WCET
Schedulability analysis is one of the most important issues in developing and analyzing real-time systems. Given a task system where each task is characterized by a worst-case execution time (WCET) and a relative deadline, the schedulability analysis is decidable. However in reality, it is difficult to calculate the WCET of a complex task, even after it is abstracted to a formal model, e.g., timed automata (TAs). This paper proposes a schedulability analysis method without the information of the WCET, by introducing a model named timed regular task automata (TRTAs). Each task is described by a TA, a starting point with a clock valuation, a status and a relative deadline. A test is performed on each TA for an under-approximation of the WCET. The system may still be unschedulable under the approximation. A further schedulability checking is then performed by encoding to the reachability problem of nested timed automata (NeTAs). The methodology is thus sound and complete.
KeywordsTask Type Parallel Composition Task System Early Deadline First Schedulability Analysis
This work is supported by National Natural Science Foundation of China with grant No. 61472240, 61672340, 61472238, and the NSFC-JSPS bilateral joint research project with grant No. 61511140100.
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