Real-Time Systems

, Volume 4, Issue 1, pp 37–53 | Cite as

Software architecture for hard real-time applications: Cyclic executives vs. fixed priority executives

  • C. Douglass Locke


We contrast the software architecture of a hard real-time application using a fixed priority task structure against the software architecture of the same system using a cyclic executive structure to satisfy hard real-time deadlines in response to a set of embedded system requirements. We identify the perceived and actual advantages and disadvantages of both approaches, consider the types of applications which can take advantage of these approaches, and make recommendations related to the attributes of such applications that might be needed with both approaches. We conclude that the fixed priority approach, when priorities are assigned using rate monotonic priorities, generally dominates the cyclic executive approach for hard real-time systems.


Operating System Embed System Software Architecture Computing Methodology System Requirement 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    T. P.Baker and A.Shaw. 1989. The Cyclic Executive Model and Ada. Real-Time Systems: The International Journal of Time-Critical Computing Systems 1, (1):7–25.Google Scholar
  2. 2.
    J.P. Lehoczky and L. Sha. 1986. The Average Case Behavior of the Rate-Monotonic Scheduling Algorithm, School of Computer Science, Technical Report, Carnegie Mellon University.Google Scholar
  3. 3.
    J.P. Lehoczky, L. Sha, and Y. Ding. 1989. The Rate Monotonic Scheduling Algorithm-Exact Characterization and Average Case Behavior. Proceedings of the Real-Time Systems Symposium, Santa Monica, CA. USA: pp. 166–171, IEEE, December.Google Scholar
  4. 4.
    J.P. Lehoczky, L. Sha, and H.K. Strosnider. 1987. Enhanced Aperiodic Responsiveness in Hard Real-Time Environments. Proceedings of the Eighth Real-Time Systems Symposium, pp. 261–270, IEEE, December.Google Scholar
  5. 5.
    C.L.Liu and J.W.Layland. 1973. Scheduling Algorithms for Multiprogramming in A Hard-Real-Time Environment. Journal of the Association for Computing Machinery, 20(1): 46–61.Google Scholar
  6. 6.
    L.Sha and J.B.Goodenough. 1990. Real-Time Scheduling Theory and Ada. IEEE Computer, 23(4): 53–62, April.Google Scholar
  7. 7.
    L. Sha, J.P. Lehoczky, and R. Rajkumar. 1986. Solutions for Some Practical Problems in Prioritized Preemptive Scheduling. Proceedings of the Seventh Real-Time Systems Symposium, pp. 181–191, IEEE, December 1986.Google Scholar
  8. 8.
    L. Sha, R. Rajkumar, and J.P. Lehoczky. 1990. Priority Inheritance Protocols—An Approach to Real-Time Synchronization, IEEE Transactions on Computers, 39(9), September.Google Scholar

Copyright information

© Kluwer Academic Publishers 1992

Authors and Affiliations

  • C. Douglass Locke
    • 1
  1. 1.International Business MachinesBethesdaUSA

Personalised recommendations