Non-Sharable Resource Freshness in Real Time Scheduling

We propose, DONUT, a real-time producers/consumers model, as an abstract model for developing real-time scheduling and resource allocation techniques in the domain of real-time network management. Under this model, we consider not only the availability but also the freshness of the consumed resources (i.e., “donuts”). Given a resource type <, two quantitative measures are defined to evaluate the freshness of the consumed type < resources: worst case freshness (WCF<) and average case freshness (ACF<). In this paper, we address the freshness problem when all tasks are periodic and all resources are non-sharable/nonreusable. We show generally how to find an allocation scheme to optimize bothWCF< and ACF< simultaneously. Finally, we apply our result to extend the priority ceiling protocol to work with general unbounded semaphores, where Wait and Signal operations need not be in pairs in one task.