Research on Resource Access Control Protocol Based on Layered Scheduling Algorithm

Complicated real-time application needs operating system providing layered scheduling mechanism to realize two layers scheduling for disjoint tasks subset. For satisfying the running predictability of real-time task under circumstance of layered scheduling, operating system should have corresponding resource access control protocol to avoid infinite priority inversion and deadlock phenomenon while multi-task sharing resource. Aiming at the problems, a new resource access control protocol based on layered scheduling algorithm is proposed. The protocol expands and redefines the priority inheritance protocol and the priority ceiling protocol, distributes resource control lock for each sub-modules, cross-sub-module resource contention is prohibited. Inside a sub-module, priority of task and priority of resource are set respectively, and priority ceiling protocol is realized by dual priority control approach. This protocol controls layered multi-task accessing critical resource effectively and reasonably, meet the demand of schedulable constraint condition for real-time task in layered sub-module situation, improves real-time performance of layered scheduling algorithm. Theoretical analysis and experimental results indicate that layered resource access control protocol has the ability of inhibiting priority inversion and avoiding deadlock phenomenon effectively, enhanced resource access control ability while supporting real-time application.