Scheduling Fault-Tolerant Distributed Hard Real-Time Tasks Independently of the Replication Strategies

Replication is a well-know fault-tolerance technique, and several replication strategies exist (e.g. active, passive, and semi-active replication). To be used in hard real-time systems, the presence of replication must be dealt with in scheduling algorithms, and more particularly in the feasibility tests in charge of testing whether deadlines will be met or not. So far, existing solutions to integrate replicated tasks in scheduling algorithms were specific to a given replication strategy or to its implementation on a given architecture. This paper is devoted to the description of a framework for taking into account the replicated tasks in scheduling algorithms that is largely independent of the replication technique. We show on an example that the same scheduling algorithm can be used whatever replication strategy is selected, even if several replication strategies are simultaneously used.