A Review of Priority Assignment in Real-Time Systems

Robert Ian Davis, Liliana Cucu-Grosjean, Marko Bertogna, Alan Burns

Research output: Contribution to journalArticlepeer-review


It is over 40 years since the first seminal work on
priority assignment for real-time systems using fixed priority
scheduling. Since then, huge progress has been made in the
field of real-time scheduling with more complex models and
schedulability analysis techniques developed to better
represent and analyse real systems. This tutorial style review
provides an in-depth assessment of priority assignment
techniques for hard real-time systems scheduled using fixed
priorities. It examines the role and importance of priority in
fixed priority scheduling in all of its guises, including: preemptive
and non-pre-emptive scheduling; covering single- and
multi-processor systems, and networks. A categorisation of
optimal priority assignment techniques is given, along with the
conditions on their applicability. We examine the extension of
these techniques via sensitivity analysis to form robust priority
assignment policies that can be used even when there is only
partial information available about the system. The review
covers priority assignment in a wide variety of settings
including: mixed-criticality systems, systems with deferred
pre-emption, and probabilistic real-time systems with worstcase
execution times described by random variables. It
concludes with a discussion of open problems in the area of
priority assignment.
Original languageEnglish
Pages (from-to)64-82
JournalJournal of systems architecture
Publication statusPublished - 14 Apr 2016

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© 2016, Elsevier B.V. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details


  • real-time

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