Deterministic platform software for hard real-time systems using multi-core COTS

Future generations of avionic equipments are expected to embed multi-core processors. Using Components Off-The-Shelf (COTS) processors is considered both by the industrial and academic communities, as well as certification authorities. However, in the safety-critical domain, a common issue with COTS multi-core processors is their lack of predictability, directly linked to the difficulty to foresee and manage inter-core interferences due to shared hardware resources. A possible solution consists in defining a Usage Domain that constrains the use of shared resources down to a level for which interference situations are known and their impact on software execution time is acceptable. Nevertheless, COTS processors have not been designed to see their behavior restricted by such usage domains, and do not provide dedicated mechanisms for that purpose. Hence the usage domains are enforced by more complex mechanisms implemented in dedicated pieces of software running below the applicative level. We call them Deterministic Platform Software (DPS). The objective of this paper is to propose an overview of existing DPS solutions, and propose criteria leading to a uniform classification. Additionally, we propose a mapping of these solutions to a selection of avionic use cases.