An increasing number of modern real-time systems and the nowadays ubiquitous multicore architectures demand the application of programming techniques for reliable and efficient concurrent synchronization. Some recentl...
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An increasing number of modern real-time systems and the nowadays ubiquitous multicore architectures demand the application of programming techniques for reliable and efficient concurrent synchronization. Some recently developed Compare-And-Swap (CAS) based nonblocking techniques hold the promise of delivering practical and safer concurrency. The ABA problem is a fundamental problem to many CAS-based designs. Its significance has increased with the suggested use of CAS as a core atomic primitive for the implementation of portable lock-free algorithms. The ABA problem's occurrence is due to the intricate and complex interactions of the application's concurrent operations and, if not remedied, ABA can significantly corrupt the semantics of a nonblocking algorithm. The current state of the art leaves the elimination of the ABA hazards to the ingenuity of the software designer. In this work we provide the first systematic and detailed analysis of the ABA problem in lock-free Descriptor-based designs. We study the semantics of Descriptor-based lock-free data structures and propose a classification of their operations that helps us better understand the ABA problem and subsequently derive an effective ABA prevention scheme. Our ABA prevention approach outperforms by a large factor the use of the alternative CAS-based ABA prevention schemes. It offers speeds comparable to the use of the architecture-specific CAS2 instruction used for version counting. We demonstrate our ABA prevention scheme by integrating it into an advanced nonblocking data structure, a lock-free dynamically resizable array.
The increase of computational power in embedded systems has allowed integrating together hard real-time tasks and rich applications. Complex SW infrastructures containing both RTOS and GPOS are required to handle this...
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The increase of computational power in embedded systems has allowed integrating together hard real-time tasks and rich applications. Complex SW infrastructures containing both RTOS and GPOS are required to handle this complexity. To optimally map system functionality to the hard-RT SW domain, to the general purpose SW domain or to HW peripherals, early performance evaluations at the first steps of the design process are required. Approximate timed co-simulation has been proposed as a fast solution for system modeling at early design steps. This co-simulation technique allows simulating systems at speed close to functional execution, while considering timing effects. As a consequence, system performance estimations can be obtained early, allowing efficient design space exploration and system refinement. To achieve fast simulation speed, the SW code is pre-annotated with time information. The annotated code is then natively executed, performing what is called native-based co-simulation. Previous native-based simulation environments are not prepared to model multi-OS systems, so the performance evaluation of the different SW domains is not possible. This paper proposes a new embedded system modeling solution considering dual RTOS/GPOS systems. A real Linux-based infrastructure has been modeled an integrated into a state-of-the-art co-simulation environment. The resulting solution is capable of modeling and evaluating all HW and SW system components providing the designer with valuable information for early system optimization and design space exploration.
Many emerging embedded systems consist of multiple embedded nodes, which are connected through an internal small area network. In such systems, the synchronization between the embedded nodes is essential to provide re...
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ISBN:
(纸本)9780769535739
Many emerging embedded systems consist of multiple embedded nodes, which are connected through an internal small area network. In such systems, the synchronization between the embedded nodes is essential to provide real-time cooperation environment. On small area networks, the severe obstacle for achieving real-time synchronization is the unpredictable overhead of the system software running on the embedded nodes. This is true especially if a traditional operating system has been installed. Despite of these drawbacks, it is quite common to run traditional operating systems on some of the embedded nodes to utilize various existing applications. In this paper, we propose a novel design of communication primitives called RTDiP-Sync for real-timedistributed synchronization over small area networks. Experiment results show that the suggested design can minimize the communication overhead and provide better overhead prediction.
Modular component-based robot systems require not only an infrastructure for component management, but also scalability as well as real-time properties. Robot Technology (RT)-Middleware is a software platform for such...
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ISBN:
(纸本)9780769535739
Modular component-based robot systems require not only an infrastructure for component management, but also scalability as well as real-time properties. Robot Technology (RT)-Middleware is a software platform for such component-based robot systems. Each component in the RT-Middleware, so-called "RT-component" supporting particular robot functions, is based on Common object Request Broker Architecture (CORBA). Unfortunately, the RT-Middleware lacks the mechanism for real-time control. In this paper, we extend the framework of the RT-components to take care of timing constraints. We first enable tasks to have different periods within each RT-component. We then modify the packet format of the General Inter-ORB Protocol (GIOP) to transfer the information of timing constraints over RT-components. The performance evaluation on ART-Linux shows that the extended RT-component framework improves the schedulability of distributedreal-time tasks, without causing critical overheads in unmarshaling the modified GIOP packets.
We present an architectural framework that provides the foundation for building smart object systems and uses a document centric approach utilizing a profile based artefact framework and a task based application frame...
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ISBN:
(纸本)9780769535739
We present an architectural framework that provides the foundation for building smart object systems and uses a document centric approach utilizing a profile based artefact framework and a task based application framework. Our artefact framework represents an instrumented physical smart objects as a collection of service profiles and expresses these services in generic documents. Applications for smart objects are expressed as a collection of functional tasks (independent of the implementation.) in a corresponding document. A runtimecomponent provides the foundation for mapping these tasks to the corresponding service provider smart objects. There are three primary advantages of our approach- firstly, it allows developers to write applications in a generic way without prior knowledge of the smart objects that could be used by the applications. Secondly;smart object management (locating/accessing/etc.) issues are completely handled by the infrastructure thus application development becomes rapid and simple. Finally;the programming abstraction used in the framework allows extension of functionalities of smart objects and applications very easily. We describe an. implemented prototype of our framework and show examples of its use in a real life scenario to illustrate its feasibility.
Sensor webs are often composed of servers connected to distributedreal-time embedded (DRE) systems that operate in open environments where operating conditions, workload, resource availability, and connectivity canno...
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ISBN:
(纸本)9780769535739
Sensor webs are often composed of servers connected to distributedreal-time embedded (DRE) systems that operate in open environments where operating conditions, workload, resource availability, and connectivity cannot be accurately characterized a priori. The South East Alaska MOnitoring Network for Science, Telecommunications, Education, and Research (SEAMONSTER) project exhibits many common system management and dynamic operation challenges for effective, autonomous system adaptation in a representative sensor web. These challenges cover both field operation (e.g., power management through system sleep/wake cycles and reaction to local environmental changes) and server operation (e.g., system adaptation for new/modified goals, resource allocation for a changing set of applications, and configuration changes for fluctuating workload). This paper presents the results of integrating and applying quality-of-service (QoS)-enabled component middle-ware, dynamic resource management, and autonomous agent technologies to address these challenges in SEAMONSTER.
General-purpose middleware, by definition, cannot readily support domain-specific semantics without significant manual efforts in specializing the middleware. This paper presents GRAFT (GeneRative Aspects for Fault To...
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ISBN:
(纸本)9780769535739
General-purpose middleware, by definition, cannot readily support domain-specific semantics without significant manual efforts in specializing the middleware. This paper presents GRAFT (GeneRative Aspects for Fault Tolerance), which is a model-driven, automated, and aspects-based approach for specializing general-purpose middleware with failure handling and recovery semantics imposed by a domain. Model-driven techniques are used to specify the special fault tolerance requirements, which are then transformed into middleware-level code artifacts using generative programming. Since the resulting fault tolerance semantics often crosscut the middleware architecture, GRAFT uses aspect-oriented programming to weave them into the original fabric of the general-purpose middleware. We evaluate the capabilities of GRAFT using a representative case study.
Network Enabled Capability (NEC) is the U.K. Ministry of Defence's response to the quickly changing conflict environment in which its forces must operate. In NEC, systems need to be integrated in context, to assis...
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ISBN:
(纸本)9780769535739
Network Enabled Capability (NEC) is the U.K. Ministry of Defence's response to the quickly changing conflict environment in which its forces must operate. In NEC, systems need to be integrated in context, to assist in human activity and provide dependable inter-operation. In order to provide reliable and sustainable military capability, fast paced changes must be conducted without halting the operation of a capability. In this paper we present the concept of evolutionary service-oriented architecture for delivering sustainable capability. The reliability of the architecture is evaluated by simulations using a computer-based model. The simulation results indicate that the evolutionary service-oriented architecture can provide higher reliability and sustainability in the provision of capability in a dynamic environment.
Multiprocessor embedded software presents major challenges including the increased complexity and stringent performance requirements raised by parallel processing capability. Although component-based approaches can gr...
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ISBN:
(纸本)9780769535739
Multiprocessor embedded software presents major challenges including the increased complexity and stringent performance requirements raised by parallel processing capability. Although component-based approaches can greatly alleviate the complexity problem, traditional approaches do not provide adequate support for performance requirements on multiprocessors. In this paper, we extend component-based approaches for performance-aware design and analysis of multiprocessor embedded software. The proposed approach begins with a component model that is able to capture concurrent and performance-critical behavior based on UML activity diagrams. It then identifies and exploits potential sources of concurrency within components to produce a multithreaded software design targeted at multiprocessors. We also provide a schedulability analysis that can be used for validating multithreaded software design from a temporal perspective.
Quality of service adaptability refers to the ability of components/services to adapt in run-time the quality exhibited. A composition study from a quality point of view would investigate how these adaptable elements ...
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ISBN:
(纸本)9780769535739
Quality of service adaptability refers to the ability of components/services to adapt in run-time the quality exhibited. A composition study from a quality point of view would investigate how these adaptable elements could be combined to meet system's quality requirements. Enclosing quality properties with architectural models has been typically used to improve system understanding. Nevertheless these properties along with some supplementary information about quality adaptation would allow us to carry out a composition study during the design phase and even to predict some features of the adaptability behavior of the system. Existing modeling languages and tools lack enough mechanisms to cope with adaptability, e.g. to describe system elements that may offer/require several quality levels. This paper shows how we reuse existing modeling languages and tools, combine them and create new ones to tackle the problem of quality of service adaptability and composition. The final goal of this work is to evaluate architectural models to predict system's QoS behavior before it is implemented.
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