Testing deadline misses for real-time systems using constraint optimization techniques

Safety-critical real-time applications are typically subject to stringent timing constraints which are dictated by the surrounding physical environments. Specifically, tasks in these applications need to finish their execution before given deadlines, otherwise the system is deemed unsafe. It is therefore important to test real-time systems for deadline misses. In this paper, we present a strategy for testing real-time applications that aim sat finding test scenarios in which deadline misses become more likely. We identify such test scenarios by searching the possible ways that a set of real-time tasks can be executed according to the scheduling policy of the operating system on which they are running. We formulate this search problem using a constraint optimization model that includes (1) a set of constraints capturing how a given set of tasks with real-time constraints are executed according to a particular scheduling policy, and (2) a cost function that estimates how likely the given tasks are to miss their deadlines. We implement our constraint optimization model in ILOG SOLVER, apply our model to several examples, and report on the performance results.