Schedulability Analysis and Priority Assignment for Segmented Self-Suspending Tasks
Lea Schönberger, Wen-Hung Huang, Georg von der Brüggen, Kuan-Hsun Chen, Jian-Jia Chen · 2018
Self-suspending behavior in real-time embedded systems can have a major and non-trivial negative impact on timing predictability. In this work, we investigate how to analyze the schedulability of segmented self-suspending task systems under a fixed-priority assignment. For this purpose, we introduce the multi-segment workload function as well as the maximum workload function in order to quantify the maximum interference from the higher-priority tasks when constructing our (sufficient) schedulability test. Moreover, we derive an optimal priority assignment with respect to our schedulability test since it is compatible with Audsley's Optimal Priority Assignment (OPA). We show by means of comprehensive evaluations that our approach is highly effective concerning the number of schedulable task sets. Furthermore, one set of results reveals a rather non-intuitive observation, namely, that the worst-case suspension time of a computation segment should also be respected to improve the schedulability even if the suspension may finish earlier.