Real - Time Scheduling in a Generic Fault - Tolerant

Previous ultra-dependable real-time computing archi-tectures have been specialised to meet the requirements of a particular application domain. Over the last two years, a consortium of European companies and academic institutions has been investigating the design and development of a Generic Upgrad-able Architecture for Real-time Dependable Systems (GUARDS). The architecture aims to be tolerant of permanent and temporary, internal and external, physical faults and should provide connnement or tolerance of software design faults. It is deened along three axes (C, M, and I): channels (C) provide the primary hardware fault containment regions { it is possible to con-gure instances of the architecture with 1 to 4 channels ; multiple resources (M) can be provided in each channel either for increased performance and/or for use as secondary fault containment regions; multiple integrity levels (I) allow critical software to be protected from residual design faults in less-critical components. GUARDS critical applications are intended to be replicated across the channels. In this paper, we present our approach to real-time scheduling of the GUARDS architecture. We use an extended response-time analysis to predict the timing properties of replicated real-time transactions. Consideration is also given to the scheduling of the inter-channel communications network.