Implementing a Flexible Scheduler in Ada

  • Guillem Bernat
  • Alan Burns
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 2043)


Much of the research on flexible scheduling schemes is prevented from being used in practice by the lack of implementations that provide the necessary abstractions. In this paper we show how Ada’s tasking facilities do enable such schedulers to be constructed. A case example is given that shows that the combination of existing language features is sufficient to program the required functionality. Only the lack of budget time management causes difficulty.


Schedule Scheme Admission Policy Spare Capacity Sporadic Task Short Deadline 
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  1. 1.
    S. Baruah, G. Koren, D. Mao, B. Mishra, A. Raghunathan, L. Rosier, D. Shasha, and F. Wang. On the competitiveness of online real-time task scheduling. Real-Time Systems, 4(2):124–144, 1992.CrossRefGoogle Scholar
  2. 2.
    G. Bernat and A. Burns. Combining (n m)-hard deadlines with dual priority scheduling. In Proceedings of 18th IEEE Real-Time systems symposium. San Francisco, CA, December 1997.Google Scholar
  3. 3.
    S. Biyabani, J.A. Stankovic, and K. Ramamritham. The integration of criticalness and deadlines in scheduling real-time tasks. In Proceedings of the 9th IEEE Real-Time Systems Symposium, pages 152–169, 1988.Google Scholar
  4. 4.
    G. Buttazzo, M. Spuri, and F. Sensini. Value vs. deadline scheduling in overload conditions. In Proceedings of the IEEE Real-Time Systems Symposium, 1995.Google Scholar
  5. 5.
    G. Buttazzo and J. Stankovic. RED: A robust earliest deadline scheduling algorithm. In Proceedings of the 3rd International Workshop on Responsive Computer Systems, Austin, 1993.Google Scholar
  6. 6.
    R.I. Davis and A. J. Wellings. Dual priority scheduling. In Proceedings Real-Time Systems Symposium, pages 100–109, 1995.Google Scholar
  7. 7.
    T.L. Dean and M. Boddy. An analysis of time-dependent planning. In Proceedings of the Seventh National Conference on Artificial Intelligence, pages 49–54, 1988.Google Scholar
  8. 8.
    E.D. Jensen, C.D. Locke, and H. Tokuda. A time driven scheduling model for real-time operating systems. In Proceedings IEEE Real-Time Sytems Symposium, pages 112–122, 1985.Google Scholar
  9. 9.
    Y.S. Kim. An optimal scheduling algorithm for preemptive real-time tasks. Information Processing Letters, 50(1):43–48, 1994.zbMATHCrossRefGoogle Scholar
  10. 10.
    J.W.S. Liu, K.J. Lin, W.K. Shih, A.C.S. Yu, J.Y. Chung, and W. Zhao. Algorithms for scheduling imprecise computations. IEEE Computer, pages 58–68, 1991.Google Scholar
  11. 11.
    C.D. Locke. Best-effort decision making for real-time scheduling. CMU-CS-86-134 (PhD Thesis), Computer Science Department, CMU, 1986.Google Scholar
  12. 12.
    R. Oliveira and J. Fraga. Scheduling imprecise computation tasks with intra-task/inter-task dependence. In Proceedings of the 21st IFAC/IFIP Workshop on Real-Time Programming, WRTP’96, pages 51–56, 1996.Google Scholar
  13. 13.
    S.J. Russell and S. Zilberstein. Composinng real-time systems. In Proceedings of the Twelfth International Joint Conference on Artificial Intelligence, pages 212–217, 1991.Google Scholar
  14. 14.
    K. Schwan and H. Zhou. Dynamic scheduling of hard real-time tasks and real-time threads. IEEE Transactions on Software Engineering, 18(8):736–748, 1992.CrossRefGoogle Scholar
  15. 15.
    W. K. Shih, J. W. S. Liu, and J. Y. Chung. Algorithms for scheduling imprecise computations with timing constraints. In Proc. IEEE Real-Time Systems Symposium, 1989.Google Scholar
  16. 16.
    M. Silly, H. Chetto, and N. Elyounsi. An optimal algorithm for guaranteeing sporadic tasks in hard real-time systems. In Proceedings 2nd IEEE Symposium on Parallel and Distributed Systems, pages 578–585, 1990.Google Scholar
  17. 17.
    H. Tokuda, J.W. Wendorf, and H.Y. Wang. Implementation of a time-driven scheduler for real-time operating systems. In Proceedings of IEEE Real-Time Systems Symposium, pages 271–280, 1987.Google Scholar
  18. 18.
    J.W. Wendorf. Implementation and evaluation of a time-driven scheduling processor. In Proceedings of IEEE Real-Time Systems Symposium, pages 172–180, 1988.Google Scholar
  19. 19.
    S. Zilberstein. Resource-bounded sensing and planning in autonomous systems. Autonomous Robots, 3:31–48, 1996.CrossRefGoogle Scholar
  20. 20.
    S. Zilberstein. Using anytime algorithms in intelligent systems. AI Magazine, 17(3):73–83, 1996.Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2001

Authors and Affiliations

  • Guillem Bernat
    • 1
  • Alan Burns
    • 1
  1. 1.Real-Time Systems Research Group Department of Computer ScienceUniversity of YorkUK

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