Return to search

Models and Complexity Results in Real-Time Scheduling Theory

When designing real-time systems, we want to prove that they will satisfy given timing constraints at run time. The main objective of real-time scheduling theory is to analyze properties of mathematical models that capture the temporal behaviors of such systems. These models typically consist of a collection of computational tasks, each of which generates an infinite sequence of task activations. In this thesis we study different classes of models and their corresponding analysis problems. First, we consider models of mixed-criticality systems. The timing constraints of these systems state that all tasks must meet their deadlines for the run-time scenarios fulfilling certain assumptions, for example on execution times. For the other scenarios, only the most important tasks must meet their deadlines. We study both tasks with sporadic activation patterns and tasks with complicated activation patterns described by arbitrary directed graphs. We present sufficient schedulability tests, i.e., methods used to prove that a given collection of tasks will meet their timing constraints under a particular scheduling algorithm. Second, we consider models where tasks can lock mutually exclusive resources and have activation patterns described by directed cycle graphs. We present an optimal scheduling algorithm and an exact schedulability test. Third, we address a pair of longstanding open problems in real-time scheduling theory. These concern the computational complexity of deciding whether a collection of sporadic tasks are schedulable on a uniprocessor. We show that this decision problem is strongly coNP-complete in the general case. In the case where the asymptotic resource utilization of the tasks is bounded by a constant smaller than 1, we show that it is weakly coNP-complete.

Identiferoai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-267017
Date January 2015
CreatorsEkberg, Pontus
PublisherUppsala universitet, Avdelningen för datorteknik, Uppsala universitet, Datorteknik, Uppsala
Source SetsDiVA Archive at Upsalla University
LanguageEnglish
Detected LanguageEnglish
TypeDoctoral thesis, comprehensive summary, info:eu-repo/semantics/doctoralThesis, text
Formatapplication/pdf
Rightsinfo:eu-repo/semantics/openAccess
RelationDigital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 ; 1324

Page generated in 0.0027 seconds