Protocol-transparent resource sharing in hierarchically scheduled real-time systems

Abstract

Hierarchical scheduling frameworks (HSFs) provide means for composing complex real-time systems from welldefined, independently analyzed subsystems. To support resource sharing within two-level HSFs, three synchronization protocols based on the stack resource policy (SRP) have recently been presented, i.e. HSRP [1], SIRAP [2] and BROE [3]. This paper describes the first implementation presenting these three SRPbased synchronization protocols side-by-side in a HSF-enabled real-time operating system. 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 preemptive scheduling. Moreover, we investigate the system overhead of the synchronization primitives of each protocol. Transparent interfaces allow a protocol to be selected during integration time based on its relative strengths 1 .

An engineering approach to synchronization based on overrun for compositional real-time systems

“…Finally, we evaluate an implementation of the overrun mechanism in an OSEK-compliant operating system that adheres to the new schedulability analysis. This marginally affects the implementation complexity and runtime overheads compared to our implementation in [9] which complies to both the original and initially improved analysis.…”

Dependable Resource Sharing for Compositional Real-Time Systems

“…We have recently extended a commercial real-time microkernel, µC/OS-II [28], with an HSF and synchronization support by means of SIRAP, HSRP and BROE [16]. In this section we investigate the complexity and overheads of the synchronization primitives of HSTP within our framework.…”

“…it is not canceled before expiration, then it executes a handler which implements HSTP's unlock policy and marks the resource busy. Based on our measurements, the timer manipulations triple the execution times of the lock and unlock operations compared to the implementations of these primitives in [16]. However, this is the price for preventing the propagation of temporal faults to resource-independent components.…”

“…Although HSRP [3] originally does not integrate into HSFs due to the lacking support for independent analysis of components, Behnam et al [15] lifted this limitation. However, these three protocols, including their implementations in [16], [17], assume that components respect their timing contract with respect to global resource sharing. In this paper we smooth and limit the unpredictable interferences caused by contract violations to the components that share the global resource.…”

Grasp: Visualizing the behavior of hierarchical multiprocessor real-time systems

“…The usage of Grasp has also been reported in [1], [2], [3] where it was used to gain insights into new approaches for hierarchical scheduling in Linux and VxWorks operating systems.…”