Lockheed Martin Space Operations At the Johnson Space Center

In most practical systems, periodic tasks commonly contribute to the major parts of application tasks in the systems. Under preemptive scheduling, priorities are assigned to the periodic tasks. Task priorities can be static, which remains constant, or dynamic, which will change, during the life of the system. A preemptive static priority scheduling algorithm possesses predictable behavior for which, given a set of periodic tasks, the schedulability can be well analyzed. In this paper, an exact schedulability analysis, called an exact execution time test, for a set of periodic tasks scheduled by a static priority scheduling algorithm will be introduced and investigated. 1