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Research On Real-time Scheduling Algorithms And Implementation And Designing Of Sharing Model Resource

Posted on:2008-07-10Degree:MasterType:Thesis
Country:ChinaCandidate:F M WangFull Text:PDF
GTID:2178360248452089Subject:Computer software and theory
Abstract/Summary:PDF Full Text Request
Real-time system not only needs to satisfy function demand of application, but also needs to satisfy real-time requirement put-forward by the application. However, real-time requirement of various real-time tasks are different. Real-time application system may be composed of disjoint task subsets, which need layered scheduling mechanism provided by operating system. Aiming at this problem, in this paper, through to analysisμC/OS- II real-time kernel with open code and scheduling strategies of preemptive priority. Though analyzing task scheduling algorithm and resource distribution state of this real-time system, a scheme of adding fixed time assignment scheme inμC/OS-II real-time kernel is proposed to realize two layers scheduling strategies. Sub-modular is scheduled rotate by time-ship, but tasks are scheduled according to preemptive priority in sub-modular. Resources control protocol is needed to design and define again. It can inhibit priority inverting and deadlock phenomenon in two layers scheduling system.Firstly, kernel task-control-block (TCB) data structure is expanded in layers algorithm. A parameter that used for indicating which sub-modular created task belonging to is added in TCB, and this parameter provide layered control information for scheduling algorithm. Then, two-stage index tables are created to realize layered cascade search. Ceiling protocol rules is modify and redefine based on layers algorithm, it provide adding control lock for sub-modular, when a resource is occupied in a sub-modular, it cannot been applied by other sub-modular though preempting priority, it can realize inner task to distribute resource in sub-modular though layer ceiling protocol. Ceiling protocol rules set priority for task and resource separately in redefine protocol rule, it is a resource control protocol can realize homology priority task. This protocol can guarantee task scheduling constrained condition in layer sub-modular before deadline, which realizes aim of resource distribution seasonally in disjoint task subsets. Theoretical analysis and experimental results indicate that through reconstruct structure ofμC/OS- II kernel and improve scheduler, reachμC/OS- II support two layers scheduling aim, the scheduling function is extended and enhanced. It lays foundation forμC/OS-II kernel ability of support complicated application in real time system. Layer control protocol can inhibit priority inverting and deadlock phenomenon in two layers scheduling system, strengthening its control ability to resource in real-time application.
Keywords/Search Tags:Real-time System, Layer Scheduling Algorithm, Fixed-rotates, μC/OS- II, Layer Protocol
PDF Full Text Request
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