Hierarchical scheduling frameworks (HSFs) have been extensively investigated as a paradigm for facilitating temporal isolation between components that need to be integrated on a single shared processor. 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]. In the presence of shared resources, however, temporal isolation may break when one of the accessing components executes longer than specified during global resource access. As a solution we propose a SRP-based synchronization protocol for HSFs, named Basic Hierarchical Synchronization protocol with Temporal Protection (B-HSTP). The schedulability of those components that are independent of the unavailable resource is unaffected.
This paper describes an implementation to provide HSFs, accompanied by SRP-based synchronization protocols, with means for temporal isolation. We base our implementations on the commercially available real-time operating system μC/OS-II, extended with proprietary support for two-level fixed priority preemptive scheduling. We specifically show the implementation of B-HSTP and we investigate the system overhead induced by its synchronization primitives in combination with HSRP and SIRAP. By supporting both protocols in our HSF, their primitives can be selected based on the protocol’s relative strengths.