Schedule Table Generation for Time-Triggered Mixed Criticality Systems

Recent research in real-time scheduling for mixed criticality systems has centered on an event-triggered/prioritydriven approach to scheduling. Current practice in many safetycritical domains, however, favors a time-triggered approach. We present here an effective and flexible approach for applying mode changes for time-triggered systems to handle mixed criticality job sets. It is based on a heuristic search algorithm for constructing schedule tables for the different criticalities: a change of criticality levels results in a change in the schedule table that is being used. The sequence of steps in case of a change of criticality level is known beforehand. We present a search-tree based framework for our heuristic search, and derive a heuristic function for guiding the search that significantly reduces the search space for backtracking by swapping search decisions over several levels in the search tree.