From Java to real-time Java : A model-driven methodology with automated toolchain

Real-time systems are receiving increasing attention with the emerging application scenarios that are safety-critical, complex in functionality, high on timing-related performance requirements, and cost-sensitive, such as autonomous vehicles. Development of real-time systems is error-prone and highly dependent on the sophisticated domain expertise, making it a costly process. There is a trend of the existing software without the real-time notion being re-developed to realise real-time features, e.g., in the big data technology. This paper utilises the principles of model-driven engineering (MDE) and proposes the first methodology that automatically converts standard time-sharing Java applications to real-time Java applications. It opens up a new research direction on development automation of real-time programming languages and inspires many research questions that can be jointly investigated by the embedded systems, programming languages as well as MDE communities

Simulation of multi-core scheduling in real-time embedded systems

In real-time systems the correctness of a system depends not only on the logical correctness of the running program but also on the time at which the logically correct output is produced. Therefore, in such a system it is necessary to provide the right computational result within a strict time limit called the deadline of a task. In hard real-time systems the deadline of a task must not be missed, whereas in soft real-time systems it can be missed occasionally. In recent years the trend has been observed which shows a shift from single-core to multi-core architectures for real-time systems. The main point of this thesis is to study a few promising multi-core scheduling algorithms both from the partitioned and the global approaches to multi-core scheduling and implement some of them into the existing simulation software. To represent the partitioned approach, Partitioned EDF has been implemented with the capability of specification of a resource access protocol for each core. The partitioned approach requires heuristics for task partitioning, the problem known to be NP-hard in the strong sense. For this reason, the implementation of Partitioned EDF requires manual task partitioning of the system in order to be able to utilize the maximum processing power. Proportionate Fair abbreviated as Pfair is the only known optimal way to schedule a set of periodic tasks on multi-core systems that falls into the global approach of multi-core scheduling. Therefore, to represent the global approach, several variants of Pfair scheduling algorithm have been selected for the implementation into the existing system. To be truly useful in practice, a real-time multi-core scheduling algorithm should support access to shared resources using some resource access protocol. For this reason, the Flexible Multiprocessor Locking Protocol abbreviated as FMLP has been studied and implemented to simulate shared resource access on multi-core systems. This resource access protocol can be used by scheduling algorithms representing both the partitioned and global approaches, but it only supports such variants of those algorithms which allow non-preemptive execution. A variant of Global EDF termed Global Suspendable Non-preemptive EDF was implemented prior to implementing FMLP. The existing simulator provided a set of single-core and some basic multi-core scheduling algorithms for scheduling real-time task sets. No schedulability analysis was implemented in the previous work. So, as part of this thesis, the schedulability analysis for single core scheduling algorithms has been implemented. A schedulability analysis for the partitioned approach of multi-core scheduling has also been provided for systems where a single-core scheduling algorithm runs on each partition. The updated simulation software also supports self-suspension of tasks for a specified duration

Logic programming in the context of multiparadigm programming: the Oz experience

Oz is a multiparadigm language that supports logic programming as one of its major paradigms. A multiparadigm language is designed to support different programming paradigms (logic, functional, constraint, object-oriented, sequential, concurrent, etc.) with equal ease. This article has two goals: to give a tutorial of logic programming in Oz and to show how logic programming fits naturally into the wider context of multiparadigm programming. Our experience shows that there are two classes of problems, which we call algorithmic and search problems, for which logic programming can help formulate practical solutions. Algorithmic problems have known efficient algorithms. Search problems do not have known efficient algorithms but can be solved with search. The Oz support for logic programming targets these two problem classes specifically, using the concepts needed for each. This is in contrast to the Prolog approach, which targets both classes with one set of concepts, which results in less than optimal support for each class. To explain the essential difference between algorithmic and search programs, we define the Oz execution model. This model subsumes both concurrent logic programming (committed-choice-style) and search-based logic programming (Prolog-style). Instead of Horn clause syntax, Oz has a simple, fully compositional, higher-order syntax that accommodates the abilities of the language. We conclude with lessons learned from this work, a brief history of Oz, and many entry points into the Oz literature.Comment: 48 pages, to appear in the journal "Theory and Practice of Logic Programming

Abstraction and Verification of Properties of a Real-Time Java

International audienceWe present a tool for analysing resource sharing conflicts in multithreaded Java programs. Java programs are translated to timed automata models verified afterwards by the Uppaal model checker. Analysed programs are annotated with timing information indicating the execution duration of a particular statement. Based on the timing information, the analysis of execution paths is performed, which gives an answer whether resource sharing conflicts are possible in a multithreaded Java program. If the analysis succeeds, resource locks may be eliminated from the Java program

Embedded System Design

A unique feature of this open access textbook is to provide a comprehensive introduction to the fundamental knowledge in embedded systems, with applications in cyber-physical systems and the Internet of things. It starts with an introduction to the field and a survey of specification models and languages for embedded and cyber-physical systems. It provides a brief overview of hardware devices used for such systems and presents the essentials of system software for embedded systems, including real-time operating systems. The author also discusses evaluation and validation techniques for embedded systems and provides an overview of techniques for mapping applications to execution platforms, including multi-core platforms. Embedded systems have to operate under tight constraints and, hence, the book also contains a selected set of optimization techniques, including software optimization techniques. The book closes with a brief survey on testing. This fourth edition has been updated and revised to reflect new trends and technologies, such as the importance of cyber-physical systems (CPS) and the Internet of things (IoT), the evolution of single-core processors to multi-core processors, and the increased importance of energy efficiency and thermal issues

Patterns for Providing Real-Time Guarantees in DOC Middleware - Doctoral Dissertation, May 2002

The advent of open and widely adopted standards such as Common Object Request Broker Architecture (CORBA) [47] has simplified and standardized the development of distributed applications. For applications with real-time constraints, including avionics, manufacturing, and defense systems, these standards are evolving to include Quality-of-Service (QoS) specifications. Operating systems such as Real-time Linux [60] have responded with interfaces and algorithms to guarantee real-time response; similarly, languages such as Real-time Java [59] include mechanisms for specifying real-time properties for threads. However, the middleware upon which large distributed applications are based has not yet addressed end-to-end guarantees of QoS specifications. Unless this challenge can be met, developers must resort to ad hoc solutions that may not scale or migrate well among different platforms. This thesis provides two contributions to the study of real-time Distributed Object Computing (DOC) middleware. First, it identifies potential bottlenecks and problems with respect to guaranteeing real-time performance in contemporary middleware. Experimental results illustrate how these problems lead to incorrect real-time behavior in contemporary middleware platforms. Second, this thesis presents designs and techniques for providing real-time QoS guarantees in DOC middleware in the context of TAO [6], an open-source and widely adopted implementation of real-time CORBA. Architectural solutions presented here are coupled with empirical evaluations of end-to-end real-time behavior. Analysis of the problems, forces, solutions, and consequences are presented in terms of patterns and frame-works, so that solutions obtained for TAO can be appropriately applied to other real-time systems