Ceiling Priority for Synchronous Communication in Real-Time Systems

Software complexity has increased in real-time systems such as automotive electronic control units (ECUs), as many functions are required for such systems. As software complexity has increased, component-based development has been broadly used to decouple software components for reusability, modifiability, and extensibility. Synchronous communication is frequently used between components in component-based development such as AUTomotive Open System ARchitecture (AUTOSAR). Previous studies on scheduling algorithms did not investigate the blocking and priority inversion problem in synchronous communication between tasks. We have observed that synchronous communication has same problem with resources sharing such as critical sections and semaphores, which have been investigated in many studies. The priority inversion also exists in synchronous communication between tasks since all consumer tasks communicating with the same provider tasks must wait until the provider tasks respond. We propose Ceiling Priority for Synchronous Communication (CPSC) for priority assignment and schedulability analysis based on rate-monotonic scheduling. The proposed algorithm was used for automotive battery management system (BMS) based on AUTOSAR and a multiprocessor in multi-criticality real-time systems.