Extending a HSF-enabled open-source real-time operating system with resource sharing

Hierarchical scheduling frameworks (HSFs) provide means for composing complex real-time systems from well-defined, independently analyzed subsystems. To support resource sharing within two-level, fixed priority scheduled HSFs, two synchronization protocols based on the stack resource policy (SRP) have recently been presented, i.e. HSRP [1] and SIRAP [2]. This paper describes an implementation to provide such HSFs with SRP-based synchronization protocols. We base our implementations on the commercially available real-time operating system µC/OS-II, extended with proprietary support for periodic tasks, idling periodic servers and two-level fixed priority preemptive scheduling. Specifically, we show the implementation of SRP as a local synchronization protocol, and present the implementation of both HSRP and SIRAP. Moreover, we investigate the system overhead induced by the synchronization primitives of each protocol. Our aim is that these protocols can be used side-by-side within the same HSF, so that their primitives can be selected based on the protocol’s relative strengths