Skip to main content
Log in

Improvement in feasibility testing for real-time tasks

  • Published:
Real-Time Systems Aims and scope Submit manuscript


Scheduling analysis in real-time systems require an off-line feasibility (schedulability) test to guarantee the response time of critical tasks. There are fast and efficient tests for static schedulers. However, when a dynamic scheduler is required, the available tests are not as feast and efficient as static ones. In this paper, two different characterizations of feasible task sets are presented. These characterizations lead to an new feasibility algorithm. The proposed algorithm has an worst-case exponential complexity, but experimental results indicated that it runs on pseudo-polynomial time for a very large percentage of task sets. The algorithm also provides a sufficient condition for feasible asynchronous task sets. One of the main contributions of this work is the theoretical approach used to obtain the new feasibility test. The results of a large number of simulations, as well as, the theoretical demonstrations point out the improvements reached over previous tests.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Similar content being viewed by others


  • AudsleyN. C., BurnsA., DavidR. I., TindellK. W. and WellingsA. J. “Fixed Priority Pre-emptive Scheduling: An Historical Prespective”, Real-Time Systems, Vol 8(2/3), Mar/May 1995, pp. 173–198.

    Google Scholar 

  • AudsleyN. C., BurnsA., RichardsonM., TindellK.W. and WellingsA. J. “Applying New Scheduling Theory to Static Priority Pre-emptive Scheduling”, Software Engineering Journal, Vol. 8(5) Sept 1993 pp. 284–292.

    Google Scholar 

  • Baruah, S., Mok, A., and Rosier, L. “Preemptively Scheduling Hard-Real-Time Sporadic Tasks on One periodic”, 11th Real-Time Systems Symposium, Dec 1990, pp. 182–190.

  • Baruah, S., Rosier, L. and Howell, R. R. “Algorithms and Complexity Concerning the Preemptive Scheduling of Periodic, Real-Time Tasks on One Processor”, Real-Time Systems, Dec 1990, pp. 301–324.

  • Bihari, T., and Schwan, K. “Dynamic adaptation of Real-Time software”, ACM Trans. Computer Syst. and Software, May 1991.

  • Burns, A., Wellings, A. J., Bailey, C. M. and Fyfe, E. “The Olympus Attitude and Orbital Control System: A Case Study in Hard Real-Time System Design and Implementation”, Department of Computer Science, University of York, report YCS 190 1993.

  • Chetto, H. and Chetto, M. “Some results of the Earliest Deadline Scheduling Algorithm”, IEEE Transactions Software Engineering, Oct 1989.

  • Dertouzos, M. “Control robotics: the procedural control of physical processors”, Proceedings of the IFIP Congress, 1974, pp. 807–813.

  • Garey, M. R., and Johnson, D. S. “Computer And Intractability, A Guide to the Theory of NP-Completeness”, Ed: W. H. Freeman And Company, 1979.

  • KnuthD. “The art of computer programming”, Vol. 2, 1969, pp. 293–304.

    Google Scholar 

  • LiuC. and LaylandJ. “Scheduling algorithms for multiprogramming in a hard Real-Time environment”, Journal of the ACM, Vol. 20(1) 1973, pp. 46–61.

    Google Scholar 

  • Lehoczky, J. P. “Fixed priority scheduling of periodic task sets with arbitrary deadlines”, Proceedings of the 11th IEEE Real-Time Systems Symposium, Dec 1990, pp. 201–209.

  • LeungJ. and MerrillM. “A note on the preemptive scheduling of periodic, Real-Time tasks” Information Processing Letters, Vol. 11, 1980, pp. 115–118.

    Google Scholar 

  • LeungJ. and WhiteheadJ. “On the complexity of fixed-priority scheduling of periodic, Real-Time tasks”, Performance Evaluation, Vol. 2(4), Dec 1982, pp. 237–250.

    Google Scholar 

  • Mok, A. “Fundamental Design Problems of Distributed Systems for the Hard Real-Time Environment”, PhD Thesis, MIT Laboratory for Computer Science, May 1983.

  • SRL90 ShaL., RajkumarR. and LehoczkyJ. P. “Priority inheritance protocols: An approach to real-time synchronization”, IEEE Transactions on Computers, Vol. 93, Sep 1990, pp. 1175–1185.

    Google Scholar 

Download references

Author information

Authors and Affiliations


Additional information

This work has been partially supported by a grant of CICYT No. TAP94-0511 of the Spanish Government

Rights and permissions

Reprints and permissions

About this article

Cite this article

Ripoll, I., Crespo, A. & Mok, A.K. Improvement in feasibility testing for real-time tasks. Real-Time Systems 11, 19–39 (1996).

Download citation

  • Issue Date:

  • DOI: