Resource Synchronization in Hierarchically Scheduled Real-Time Systems Using Preemptive Critical Sections

In this paper we outline a novel approach for accessing mutually exclusive resources in hierarchically scheduled real-time systems. Our method known as the Resource Access Control Protocol with Preemption (RACPwP) is an improved resource allocation protocol which utilizes preemptive critical sections to provide guaranteed determinism for hard real-time tasks and comparable response times for soft real-time tasks. Our experiments demonstrated that RACPwP outperforms other state-of-the-art resource access control protocols used in hierarchically scheduled systems. RACPwP was implemented as part of VxWorks and evaluated in an actual embedded application used in the aerospace industry. As a result, the response times for hard real-time tasks were improved over a traditional resource synchronization protocol.