Towards hierarchical scheduling in AUTOSAR
ABSTRACT AUTOSAR is a partnership between automotive manufactures and suppliers. It aims at standardizing the automotive software architecture and separating software and hardware. This approach makes software more independent, maintainable, reuseable, etc. Still there is much work to do in order for this standard to be usable. This paper focus on automotive software integration in AUTOSAR, with the use of hierarchical scheduling as an enabling technology. At this point, AUTOSAR components do not have any timing relation with its tasks. This causes an unpredictive runtime behavior which can only be analyzed and verified after integration phase. We discuss how integration can be done in AUTOSAR, with runtime temporal isolation of components. This enable schedulability analysis at the level of components rather than at the level of tasks.
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ABSTRACT: The selection of task attributes for empirical evaluations of multiprocessor scheduling algorithms and associated schedulability analyses can greatly affect the results of experiments. Taskset generation algorithms should meet three requirements: efficiency, parameter independence, and lack of bias. Satisfying these requirements enables tasksets to be generated in a moderate amount of time, allows effects of specific parameters to be explored without the problem of confounding variables, and ensures fairness in comparisons between different schedulability analysis techniques. For the uniprocessor case, they are met by the UUniFast algorithm but for multiprocessor systems, where the total desired utilisation is greater than one, UUniFast can produce invalid tasksets. This paper outlines an algorithm, Randfixedsum, for the underlying mathematical problem of efficiently generating uniformly distributed random points whose components have constant sum. This algorithm has been available via a MatLab forum for a number of years; however, this is the first time it has been formally published. This algorithm has direct application to multiprocessor taskset generation. The importance of period generation to experimental evaluation of schedulability tests is also covered.
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ABSTRACT: With the advent of the integrated architecture paradigm promoted by AUTOSAR, the automotive domain needs a standard temporal isolation policy. In this paper, we review the different approaches proposed so far and we discuss their applicability to forthcoming systems.1st Workshop on Critical Automotive Applications: Robustness & Safety, CARS 2010 (EDCC Workshop), Valencia, Spain, 27 April 2010; 04/2010
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ABSTRACT: In hierarchical scheduling, a system is organized into multiple levels of individually scheduled subsystems (hierarchical scheduling tree), which provides several benefits for developers including possibilities for parallel development of subsystems. In this paper, we study how the model of task automata and the Times tool can be applied to provide support for rapid and early prototyping of hierarchically scheduled embedded systems. As a main result, we show how a single node, in an arbitrary level in a hierarchical scheduling tree (scheduled with fixed-priority preemptive scheduling), can easily be analyzed in Times by replacing all interfering nodes with a small set of higher priority (dummy) tasks. We show with an algorithm how these dummy tasks are generated (including task-parameters such as period, offset etc.). Further, we generate executable source code, with the Times code-generator, that emulates the scheduling environment (with our dummy tasks), i.e., the hierarchical scheduling tree and all of its preemptions, of a small example system. Yet another contribution is that we transform the generated (brickOS) source code to run on an industrial oriented platform (VxWorks), and conduct an performance evaluation.