Research Of Real-Time Middleware Priority Scheduling Mechanisms

As the application of distributed real-time systems is becoming more and more popular, the scheduling mechanism faces new requirements and challenges because of the coexistence of different kinds of time-constraint tasks. To date, available real-time middleware scheduling modals aim at some aspect of scheduling and do not apply to this problem. Based on the research into real-time middleware and relative scheduling theoretic, this thesis implements a Real-Time CORBA Integrated Scheduling Service modal, by extending the scheduling service of TAO. In the Integrated Scheduling Service, hard periodic tasks are scheduled off-line to meet their real-time requirements, and each soft aperiodic task request is assigned a suitable deadline to enhance the aperiodic responsiveness. Scheduling guarantees of hard periodic tasks are preserved through the on-line schedulability analysis. The sharing of critical section resources between the tasks is also considered in the Integrated Scheduling Service's schedulability analysis, and bounded blocking for accessing the critical section resource is achieved by introducing the Priority Ceiling Protocol. By treating tasks differently according to their time constraints, the static off-line scheduling and the dynamic on-line scheduling are integrated, and the scheduling requirements are satisfied.