Stabilizing Pre-Run-Time Schedules With the Help of GraceTime

  • Authors:
  • Antonio Pessoa Magalhães;João Gabriel Silva

  • Affiliations:
  • SAIC - DEMEGI Faculty of Engineering, University of Porto - PORTUGAL;GSC - DEI Faculty of Sciences and Technology, University of Coimbra - PORTUGAL

  • Venue:
  • Real-Time Systems
  • Year:
  • 1999

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Abstract

This paper discusses the stabilityof a feasible pre-run-time schedule for a transient overloadintroduced by processes re-execution during an error recoveryaction. It shows that the stability of a schedule strictly tunedto meet hard deadlines is very small, invalidating thus backwarderror recovery. However, the stability of the schedule alwaysincreases when a real-time process is considered as having anominal and a hard deadline separated by a non-zero grace time.This is true for sets of processes having arbitrary precedenceand exclusion constraints, and executed on a single or multiprocessorbased architecture. Grace time is not just the key element forthe realistic estimation of the timing constraints of real-timeerror processing techniques. It also allows backward error recoveryto be included in very efficient pre-run-time scheduled systemswhen the conditions stated in this paper are satisfied. Thisis a very important conclusion, as it shows that fault-toleranthard real-time systems do not have to be extremely expensiveand complex.