Research And Implementation Of Priority Inversion In μC/OS-Ⅱ

Real-Time Operating System (RTOS) generally has characteristics of multitasking and real-time. Multitasking means each of tasks can be executed concurrently. Because of multitasking executes concurrently will lead to multiple tasks sharing resource. RTOS generally adopt Mutual Exclusion Semaphore or lock to manage shared resources, any task must have the right of the shared resource before trying to operate shared resources, if not, it have to wait until the other task release the shared resource. Real-time means the response time of the system must be determined in a certain period of time. As the sharing resource, it tends to appear that the task which has higher priority is blockd by lower priority task, and the task which has medium priority will be executed before the higher priority task. It is called priority inversion.Along with the application domain of embedded application has obtained more and more widespread application, and the theories and technical problems related with Embedded Operating System have also become hot spot of research and development. Especially, to ensure real-time characteristics as well as resources effective management in Embedded Operating System have become the most mportant and the most active research topic in Operating System research domain. Preemptive and multitasking Real-Time Operating System can’t avoided the danger of priority inversion, if we do not take effective measures, infinite priority inversion may occur, application will collapse and the unpredictable mistakes. Therefore, it is crucial toalleviate priority inversion on Real-Time Operating System when analyzing and designing Embedded Real-Time System.In the thesis, μC/OS-Ⅱ, a free code, preemptive and multitasking real-time operating system has been selected as study object to solve the priority inversion in vehicle navigation system. The reason and the influence produced by priority inversion phenomena have been analyzed detailed. Design models (priority inheritance protocol and priority ceiling protocol) which used to solve priority inversion are researched and analyzed deeply. According to the demand of the vehicle navigation system, this paper extends data structure and makes correction on the relevant function concerning about the data structure, thereby solves this problem, makes the system to be simplify design and improves stability of the system. Through the transplantation of μC/OS-II verifies the feasibility and effectiveness of the method on virtual platform of Windows.