Real-Time Systems Modeling and Scheduling With Hyperperiodic Tasks

Hard real-time systems refer to computer systems that have stringent deadlines. A failure to satisfy timing constraints may result in catastrophic consequences. Real-time applications include temperature control of a nuclear reactor core, air traffic control, and telemetry. In this paper, we propose to model a real-time system using a combination of hyperperiodic, periodic, and aperiodic tasks. A hyperperiodic task is one that can be scheduled more frequently when there is a light load on the system, but always recurs at least as frequently as its given hyperperiod. We provide several results on the schedulability of hyperperiodic tasks on a single processor system. We also describe a scheduling algorithm for hyperperiodic tasks. We then analyze the combined scheduling of hyperperiodic tasks with aperiodic tasks and periodic tasks. Key-Words: Real-time and embedded systems, periodic and hyperperiodic tasks, real-time scheduling.