Analysis of Hierarchical EDF Pre-emptive Scheduling

This paper focuses on scheduling different hard real-time applications on a uniprocessor when the earliest deadline first algorithm is used as the local scheduler, and the global scheduler of the system could be fixed priority (FP) or earliest deadline first (EDF). Each application task could be periodic or sporadic, bound or unbound, with arbitrary relative deadline which could be less than, equal to or greater than its period. A number of different server types are considered. This paper presents an exact and efficient schedulability test for the application tasks based on the capacity demand criterion when the global scheduler could be FP or EDF, in some cases, it is necessary and sufficient. Schedulability tests which are necessary and sufficient for several types of dynamic servers are presented when the global scheduler is EDF.