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Theodore P. Baker

Bio: Theodore P. Baker is an academic researcher from Florida State University. The author has contributed to research in topics: Earliest deadline first scheduling & Dynamic priority scheduling. The author has an hindex of 31, co-authored 101 publications receiving 5340 citations. Previous affiliations of Theodore P. Baker include University of Florida & Cornell University.


Papers
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Journal ArticleDOI
TL;DR: It is shown how to extend the Priority Ceiling Protocol to handle: multiunit resources, which subsume binary semaphores and reader-writer locks; dynamic priority schemes, such as earliest-deadline-first (EDF), that use static “preemption levels”; sharing of runtime stack space between jobs.
Abstract: The Priority Ceiling Protocol (PCP) of Sha, Rajkumar and Lehoczky is a policy for locking binary semaphores that bounds priority inversion (i.e., the blocking of a job while a lower priority job executes), and thereby improves schedulability under fixed priority preemptive scheduling. We show how to extend the PCP to handle: multiunit resources, which subsume binary semaphores and reader-writer locks; dynamic priority schemes, such as earliest-deadline-first (EDF), that use static “preemption levels”; sharing of runtime stack space between jobs. These extensions can be applied independently, or together. The Stack Resource Policy (SRP) is a variant of the SRP that incorporates the three extensions mentioned above, plus the conservative assumption that each job may require the use of a shared stack. This avoids unnecessary context switches and allows the SRP to be implemented very simply using a stack. We prove a schedulability result for EDF scheduling with the SRP that is tighter than the one proved previously for EDF with a dynamic version of the PCP. The Minimal SRP (MSRP) is a slightly more complex variant of the SRP, which has similar properties, but imposes less blocking. The MSRP is optimal for stack sharing systems, in the sense that it is the least restrictive policy that strictly bounds priority inversion and prevents deadlock for rate monotone (RM) and earliest-deadline-first (EDF) scheduling.

823 citations

Journal ArticleDOI
TL;DR: Relativized versions of the open question of whether every language accepted nondeterministically in polynomial time can be recognized deterministic in poynomial time are investigated.
Abstract: We investigate relativized versions of the open question of whether every language accepted nondeterministically in polynomial time can be recognized deterministically in polynomial time. For any set X, let $\mathcal{P}^X (\text{resp. }\mathcal{NP}^X )$ be the class of languages accepted in polynomial time by deterministic (resp. nondeterministic) query machines with oracle X. We construct a recursive set A such that $\mathcal{P}^A = \mathcal{NP}^A $. On the other hand, we construct a recursive set B such that $\mathcal{P}^B e \mathcal{NP}^B $. Oracles X are constructed to realize all consistent set inclusion relations between the relativized classes $\mathcal{P}^X $, $\mathcal{NP}^X $, and co $\mathcal{NP}^X $, the family of complements of languages in $\mathcal{NP}^X $. Several related open problems are described.

684 citations

Journal ArticleDOI
TL;DR: This 25th year anniversary paper for the IEEE Real Time Systems Symposium reviews the key results in real-time scheduling theory and the historical events that led to the establishment of the current real- time computing infrastructure.
Abstract: In this 25th year anniversary paper for the IEEE Real Time Systems Symposium, we review the key results in real-time scheduling theory and the historical events that led to the establishment of the current real-time computing infrastructure. We conclude this paper by looking at the challenges ahead of us.

636 citations

Proceedings ArticleDOI
03 Dec 2003
TL;DR: Schedulability tests are presented for preemptive earlier-deadline-first and deadline-monotonic scheduling of periodic or sporadic real-time tasks on a single-queue m-server system, in which the deadline may be less than or equal to the task period.
Abstract: Schedulability tests are presented for preemptive earlier-deadline-first and deadline-monotonic scheduling of periodic or sporadic real-time tasks on a single-queue m-server system, in which the deadline of a task may be less than or equal to the task period. These results subsume and generalize several known utilization-based multiprocessor schedulability tests, and are derived via an independent proof.

287 citations

Proceedings ArticleDOI
05 Dec 1990
TL;DR: The stack resource policy is at least as good as the PCP in reducing maximum priority inversion and supports a stronger schedulability test with EDF scheduling.
Abstract: The stack resource policy (SRP) is a resource allocation policy which permits processes with different priorities to share a single runtime stack. It is a refinement of the priority ceiling protocol (PCP), which strictly bounds priority inversion and permits simple schedulability tests. With or without stack sharing, the SRP offers the following improvements over the PCP: (1) it unifies the treatment of stack, reader-writer, multiunit resources, and binary semaphores; (2) it applies directly to some dynamic scheduling policies, including earliest deadline first (EDF), as well as to static priority policies; (3) with EDF scheduling, it supports a stronger schedulability test; and (4) it reduces the maximum number of context switches for a job execution request by a factor of two. It is at least as good as the PCP in reducing maximum priority inversion. >

286 citations


Cited by
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Journal ArticleDOI
Larry J. Stockmeyer1
TL;DR: The problem of deciding validity in the theory of equality is shown to be complete in polynomial-space, and close upper and lower bounds on the space complexity of this problem are established.

1,402 citations

Journal ArticleDOI
TL;DR: In this article, the first occurrence of a string X as a consecutive block within a text Y is found by using a randomized algorithm. But the algorithm requires a constant number of storage locations, and essentially runs in real time.
Abstract: We present randomized algorithms to solve the following string-matching problem and some of its generalizations: Given a string X of length n (the pattern) and a string Y (the text), find the first occurrence of X as a consecutive block within Y. The algorithms represent strings of length n by much shorter strings called fingerprints, and achieve their efficiency by manipulating fingerprints instead of longer strings. The algorithms require a constant number of storage locations, and essentially run in real time. They are conceptually simple and easy to implement. The method readily generalizes to higher-dimensional patternmatching problems.

1,400 citations

Journal ArticleDOI
Neil Audsley1, Alan Burns1, Mike M. Richardson1, Ken Tindell1, Andy Wellings1 
TL;DR: The paper presents exact schedulability analyses for real-time systems scheduled at runtime with a static priority pre-emptive dispatcher and the predictions that follow are seen to be in close agreement with the behaviour exhibited during simulation studies.
Abstract: The paper presents exact schedulability analyses for real-time systems scheduled at runtime with a static priority pre-emptive dispatcher. The tasks to be scheduled are allowed to experience internal blocking (from other tasks with which they share resources) and (with certain restrictions) to release jitter, such as waiting for a message to arrive. The analysis presented is more general than that previously published and subsumes, for example, techniques based on the Rate Monotonic approach. In addition to presenting the relevant theory, an existing avionics case study is described and analysed. The predictions that follow from this analysis are seen to be in close agreement with the behaviour exhibited during simulation studies.

1,168 citations

Book
15 Jan 2000
TL;DR: RTSJ's features and the thinking behind the specification's design are explained, which aims to provide a platform-a Java execution environment and application program interface (API) that lets programmers correctly reason about the temporal behavior of executing software.
Abstract: New languages, programming disciplines, operating systems, and software engineering techniques sometimes hold considerable potential for real-time software developers. A promising area of interest-but one fairly new to the real-time community-is object-oriented programming. Java, for example, draws heavily from object orientation and is highly suitable for extension to real-time and embedded systems. Recognizing this fit between Java and real-time software development, the Real-Time for Java Experts Group (RTJEG) began developing the real-time specification for Java (RTSJ) in March 1999 under the Java Community Process. This article explains RTSJ's features and the thinking behind the specification's design. The goal of the RTJEG, of which the authors are both members, was to provide a platform-a Java execution environment and application program interface (API)-that lets programmers correctly reason about the temporal behavior of executing software.

1,094 citations

Book
23 Jan 2013
TL;DR: This book takes a cyber-physical approach to embedded systems, introducing the engineering concepts underlying embedded systems as a technology and as a subject of study.
Abstract: The most visible use of computers and software is processing information for human consumption. The vast majority of computers in use, however, are much less visible. They run the engine, brakes, seatbelts, airbag, and audio system in your car. They digitally encode your voice and construct a radio signal to send it from your cell phone to a base station. They command robots on a factory floor, power generation in a power plant, processes in a chemical plant, and traffic lights in a city. These less visible computers are called embedded systems, and the software they run is called embedded software. The principal challenges in designing and analyzing embedded systems stem from their interaction with physical processes. This book takes a cyber-physical approach to embedded systems, introducing the engineering concepts underlying embedded systems as a technology and as a subject of study. The focus is on modeling, design, and analysis of cyber-physical systems, which integrate computation, networking, and physical processes. The second edition offers two new chapters, several new exercises, and other improvements. The book can be used as a textbook at the advanced undergraduate or introductory graduate level and as a professional reference for practicing engineers and computer scientists. Readers should have some familiarity with machine structures, computer programming, basic discrete mathematics and algorithms, and signals and systems.

1,017 citations