Parallel, Hardware-Supported Interrupt Handling in an Event-Triggered Real-Time Operating System

A common problem in event-triggered real-time systems is caused by low-priority tasks that are implemented as interrupt handlers interrupting and disturbing high-priority tasks that are implemented as threads. This problem is termed rate-monotonic priority inversion, and current software-based solutions are restricted in terms of more sophisticated scheduler features as demanded for instance by the AUTOSAR embedded-operating-system specification. We propose a hardware-based approach that makes use of a coprocessor to eliminate the potential priority inversion. By evaluating a prototypical implementation, we show that our approach both overcomes the restrictions of software approaches and introduces only a slight processing overhead in exchange for increased predictability.