On preemptive scheduling of periodic, real-time tasks on one processor

  • Sanjoy K. Baruah
  • Rodney R. Howell
  • Louis E. Rosier
Part of the Lecture Notes in Computer Science book series (LNCS, volume 452)


We investigate the preemptive scheduling of periodic, real-time task systems on one processor. We present three major results. First, we show that the Simultaneous Congruences Problem is NP-complete in the strong sense. Although this result is included primarily as a lemma for showing our next major theorem, it is important in its own right, answering a question that has been open for ten years. Our second major result is perhaps the most important in the paper — that deciding whether a given task system is feasible on one processor is co-NP-complete in the strong sense. Our fourth major result is that for incomplete task systems, i.e., task systems in which the start times are not specified, the feasibility problem is Ω 2 P -complete. Several other results involving cases in which all tasks are initially released at the same time, or in which there are a fixed number of distinct types of tasks, can be derived from these three theorems.


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Copyright information

© Springer-Verlag Berlin Heidelberg 1990

Authors and Affiliations

  • Sanjoy K. Baruah
    • 1
  • Rodney R. Howell
    • 2
  • Louis E. Rosier
    • 1
  1. 1.Dept. of Computer SciencesThe University of Texas at AustinAustinU.S.A.
  2. 2.Dept. of Computing and Information SciencesKansas State UniversityManhattanU.S.A.

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