Hierarchical scheduling of complex embedded real-time systems

For most of today’s embedded software systems, correct operation requires not only correct function, they must additionally satisfy specific extra-functional properties, in particular related to timing. System development (including software development) is substantially facilitated if the system parts can be developed and verified in isolation, and if the correctness of the system can be inferred from the correctness of its parts. Such modular and compositional design of software system has for a long time been considered the holy-grail of system design, and is unfortunately only possible in selected scenarios. This paper deals with one such scenario: using hierarchical scheduling to provide predictable timing and temporal isolation of embedded software. During the past years we have worked on various issues on hierarchical scheduling, and this paper presents an overview of selected research results, focusing on issues related to synchronization among software modules