Precedence constraints in hard real-time distributed systems

Hard real-time multitask-multiprocessor systems are one of the more important species of the taxonomic genus of distributed systems. The assignment of m preemptible periodic tasks to be executed in a set of n processors (interconnected through a communications network) is a NP-complete problem that must meet several constraints: time, allocation, resources, communication and precedence. The first three are processor-dependent and the fourth is network-dependent, but all of them can be verified as the assignment process goes on. Precedence constraints, instead, can be best verified when a tentative assignment, meeting the first four constraints, is obtained. In this paper, a formally proved method is presented to validate tentative assignments. In order to solve the problem of jitter in data arrivals, timed release counters are proposed.

[1]  R. Obenza,et al.  Rate monotonic analysis for real-time systems , 1993, Computer.

[2]  Jorge Santos,et al.  Rate Monotonic Scheduling in Hard Real-Time Systems , 1993, Inf. Process. Lett..

[3]  Mathai Joseph,et al.  Finding Response Times in a Real-Time System , 1986, Comput. J..

[4]  Chung Laung Liu,et al.  Scheduling Algorithms for Multiprogramming in a Hard-Real-Time Environment , 1989, JACM.

[5]  David Lorge Parnas,et al.  Scheduling Processes with Release Times, Deadlines, Precedence, and Exclusion Relations , 1990, IEEE Trans. Software Eng..

[6]  Krithi Ramamritham,et al.  Allocation and scheduling of complex periodic tasks , 1990, Proceedings.,10th International Conference on Distributed Computing Systems.

[7]  Ricardo Cayssials,et al.  Design of a learning fuzzy production system to solve an NP-hard real-time assignment problem , 1996, Proceedings of the Eighth Euromicro Workshop on Real-Time Systems.

[8]  John P. Lehoczky,et al.  The rate monotonic scheduling algorithm: exact characterization and average case behavior , 1989, [1989] Proceedings. Real-Time Systems Symposium.