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In this paper, we compare and survey different ways to model the scheduling delays corresponding to non-preemptive critical sections being executed by the tasks of different components that ultimately need to share one processor. We focus on the performance of compositional timing analyses for systems and we compare different protocols for the arbitration of tasks that wish to execute critical sections. Such analysis methods support timing predictable composition of independently validated components. This validation consists of analyzing the worst-case impact of critical sections on the schedules of the component's tasks. Finally, we evaluate the performance of the analysis methods by means of a simulation study.

Various approaches can be utilized upon resource locking for mutually exclusive resource access in multiprocessor platforms. So far two conventional approaches exist for dealing with tasks that are blocked on a global resource in a multi-processor platform. Either the blocked task performs a busy wait, i.e. spins, at the highest priority level until the resource is released, or it is suspended. Although both approaches provide mutually exclusive access to resources, they can introduce long blocking delays to tasks, which may be unacceptable for many industrial applications. In this paper, we propose a general spin-based model for resource sharing in multiprocessor platforms in which the priority of the blocked tasks during spinning can be selected arbitrarily. Moreover, we provide the analysis for two selected spin-lock priorities and we show by means of a general comparison as well as specific examples that these solutions may provide a better performance for higher priority tasks.

Hierarchical scheduling frameworks (HSFs) provide means for composing complex real-time systems from well-defined independently developed and analyzed subsystems. To support shared logical resources requiring mutual exclusive access in two-level HSFs, overrun without payback has been proposed as a mechanism to prevent budget depletion during resource access arbitrated by the stack resource policy (SRP). In this paper, we revisit the global schedulability analysis of synchronization protocols based on SRP and overrun without payback for fixed-priority scheduled HSFs. We derive a new global schedulability analysis based on the observation that the overrun budget is merely meant to prevent budget depletion during global resource access. The deadline of a subsystem therefore only needs to hold for its normal budget rather than the sum of the normal and overrun budget. Our novel analysis is considerably simpler than an earlier, initially improved analysis, which improved both the original local and global schedulability analyses. We evaluate the new analysis based on an extensive simulation study and compare the results with the existing analysis. Our simplified analysis does not significantly affect schedulability compared to the initially improved analysis. It is therefore proposed as a preferable engineering approach to synchronization protocols for compositional real-time systems. We accordingly present the implementation of our improvement in an OSEK-compliant real-time operating system to sketch its applicability in today's industrial automotive standards. Both implementation and run-time overheads are discussed providing measured results1. © 2011 IEEE.