OFF-LINE SCHEDULING OF REAL TIME APPLICATIONS WITH VARIABLE DURATION TASKS

摘要

We propose a model oriented scheduling methodology for highly coupled real time applications. We show that variations in the computation times of tasks may hazard the safeness of the controlled process. For the sake of reliability we take conditional instructions of tasks' code explicitly into account, in order to reduce the potential failures. We fisrt adapt the task's temporal model to this context, then we model applications using autonomous Petri nets which run under the earliest firing rule with terminal marking set. We define two concepts of schedulability: the local schedulability and the global one and we define the concept of scheduling graph. Finally, we show how to obtain a scheduling graph from the graph of global schedulability.