Process scheduling, an important issue in the design and maintenance of hard real-time systems, is discussed. A pre-run-time scheduling algorithm that addresses the problem of process sequencing is presented. The algorithm is designed for multiprocessor applications with preemptable processes having release times, computation times, deadlines and arbitrary precedence and exclusion constraints. The algorithm uses a branch-and-bound implicit enumeration technique to generate a feasible schedule for each processor. The set of feasible schedules ensures that the timing specifications of the processes are observed and that all the precedence and exclusion constraints between pairs of processes are satisfied. the algorithm was tested using a model derived from the F-18 mission computer operational flight program.>

The development of pre-run-time schedulers for certain hard real-time applications is investigated. This scheduling scheme requires the modeling of the program as a set of processes with corresponding timing specifications, such as release times, computation times, and deadlines. The models must specify precedence and exclusion constraints between pairs of processes. It is processed by an offline pre-run-time scheduling algorithm that computes a schedule for use at run time, ensuring that all static timing constraints of the system are observed. The technique works best in cases in which most processes are periodic, which is true for the F-18. A modeling process for the M18 Mission Computer software that is designed to lead the application of pre-run-time scheduling to the software and is applicable to other such hard systems is described.>