Schedulability Analysis of Hierarchical Systems with Arbitrary Scheduling in the Global Level

Abstract

Schedulability analysis of hierarchical real-time systems is based in the previous knowledge of the scheduling algorithms both in the local and the global levels.In a partitioned system with safety and security issues and certification assurance levels, the global scheduling is usually generated using a static table. Therefore, each partition must allocate task jobs only in the temporal windows reserved for that partition. Even if the static table can come originally from a periodic server or other scheduling policy, the final plan can suffer from modifications due to changes in the system requirements. As a consequence, the CPU assignment to a partition does not have to correspond to any known policy. In this case, it is not possible to use existing scheduling analysis for hierarchical systems. This paper provides a schedulability analysis when the global level policy is not known but provided as a set of arbitrary time windows. The paper also provides a method to determine the more restrictive CPU assignment for a task set, as a mean of stablishing minimum temporal requirements for the partition.