Scheduling sporadic tasks with shared resources in hard-real-timesystems

摘要

The problem of scheduling a set of sporadic tasks that share a setof serially reusable, single unit software resources on a singleprocessor is considered. The correctness conditions are that: eachinvocation of each task completes execution at or before a well-defineddeadline; and a resource is never accessed by more than one tasksimultaneously. An optimal online algorithm for scheduling a set ofsporadic tasks is presented. The algorithm results from the integrationof a synchronization scheme for access to shared resources with theearliest deadline first algorithm. A set of relations on task parametersthat are necessary and sufficient for a set of tasks to be schedulableis also derived. The proposed model for the analysis of processorscheduling policies is novel in that it incorporates minimum as well asmaximum processing time requirements of tasks. The scheduling algorithmand the sporadic tasking model have been incorporated into an operatingsystem kernel and used to implement several real-time systems