EDF Schedulability Analysis on Mixed-Criticality Systems with Permitted Failure Probability

Many safety critical real-time systems are considered certified when they meet failure probability requirements with respect to the maximum permitted incidences of failure per hour. In this paper, the mixed-criticality task model with multiple worst case execution time (WCET) estimations is extended to incorporate such system-level certification restrictions. A new parameter is added to each task, characterizing the distribution of the WCET estimations -- the likelihood of all jobs of a task finishing their executions within the less pessimistic WCET estimate. An efficient algorithm named LFF-Clustering is derived for scheduling mixed-criticality systems represented by this model. Experimental analyses show our new model and algorithm out-perform current state-of-the-art mixed-criticality scheduling algorithms.