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Exact Fault-Sensitive Feasibility Analysis of Real-Time Tasks

Summary: Exact Fault-Sensitive Feasibility Analysis
of Real-Time Tasks
Hakan Aydin, Member, IEEE
Abstract--In this paper, we consider the problem of checking the feasibility of a set of n real-time tasks while provisioning for timely
recovery from (at most) k transient faults. We extend the well-known processor demand approach to take into account the extra
overhead that may be induced by potential recovery operations under Earliest-Deadline-First scheduling. We develop a necessary and
sufficient test using a dynamic programming technique. An improvement upon the previous solutions is to address and efficiently solve
the case where the recovery blocks associated with a given task do not necessarily have the same execution time. We also provide an
online version of the algorithm that does not require a priori knowledge of release times. The online algorithm runs in Om k2
where m is the number of ready tasks. We extend the framework to periodic execution settings: We derive a sufficient condition that
can be checked efficiently for the feasibility of periodic tasks in the presence of faults. Finally, we analyze the case where the recovery
blocks are to be executed nonpreemptively and we formally show that the problem becomes intractable under that assumption.
Index Terms--Real-time scheduling, real-time systems, fault tolerance, deadline-driven systems, recovery blocks, processor demand

IN real-time systems, timeliness is as important as the
correctness of the output. Thus, traditionally, hard real-
time scheduling theory has aimed at achieving predict-


Source: Aydin, Hakan - Department of Computer Science, George Mason University


Collections: Computer Technologies and Information Sciences; Engineering