Real-Time Systems and Programming Languages

Transcription

1 Real-Time Systems and Programming Languages Ada, Real-Time Java and C/Real-Time POSIX Fourth Edition Alan Burns and Andy Wellings University of York * ADDISON-WESLEY An imprint of Pearson Education Harlow, England London New York Boston San Francisco Toronto Sydney Singapore - Hong Kong Tokyo Seoul Taipei New Delhi Cape Town Madrid Mexico City Amsterdam Munich Paris Milan

2 Contents Preface xiii 1 Introduction to real-time systems Definition of a real-time system Examples of real-time systems Characteristics of real-time systems Development cycle for real-time systems Languages for programming real-time systems 20 Summary 23 Further reading 25 Exercises 26 2 Reliability and fault tolerance Reliability, failure and faults Failure modes Fault prevention and fault tolerance ^-version programming Software dynamic redundancy The recovery block approach to software fault tolerance A comparison between N-version programming and recovery blocks Dynamic redundancy and exceptions Measuring and predicting the reliability of software Safety, reliability and dependability 53 Summary 55 Further reading 56 Exercises 57 3 Exceptions and exception handling Exception handling in older real-time languages Modern exception handling Exception handling in Ada, Java and С Recovery blocks and exceptions 85 v

3 vi CONTENTS Summary 88 Further reading 89 Exercises 89 4 Concurrent programming Processes and tasks/threads Concurrent execution Task representation Concurrent execution in Ada Concurrent execution in Java Ill 4.6 Concurrent execution in C/Real-Time POSIX Multiprocessor and distributed systems A simple embedded system Language-supported versus operating-system-supported concurrency 131 Summary 132 Further reading 133 Exercises Shared variable-based synchronization and communication Mutual exclusion and condition synchronization Busy waiting Suspend and resume Semaphores Conditional critical regions Monitors Mutexes and condition variables in C/Real-Time POSIX Protected objects in Ada Synchronized methods in Java Shared memory multiprocessors Simple embedded system revisited 183 Summary 185 Further reading 186 Exercises Message-based synchronization and communication Process synchronization Task naming and message structure Message passing in Ada Selective waiting The Ada select statement Non-determinism, selective waiting and synchronization primitives C/Real-Time POSIX message queues Distributed systems Simple embedded system revisited 219 Summary 220 Further reading 221 Exercises 222

4 CONTENTS Vll 7 Atomic actions, concurrent tasks and reliability Atomic actions Atomic actions in C/Real-Time POSIX, Ada and Real-Time Java Recoverable atomic actions Asynchronous notification Asynchronous notification in C/Real-Time POSIX Asynchronous notification in Ada Asynchronous notification in Real-Time Java 266 Summary 278 Further reading 280 Exercises Resource control Resource control and atomic actions Resource management Expressive power and ease of use The requeue facility Asymmetric naming and security Resource usage Deadlock 304 Summary 304 Further reading 305 Exercises Real-time facilities The notion of time Access to a clock Delaying a task Programming timeouts Specifying timing requirements Temporal scopes 328 Summary 332 Further reading 333 Exercises Programming real-time abstractions Real-time tasks Programming periodic activities Programming aperiodic and sporadic activities The role of real-time events and their handlers Controlling input and output jitter Other approaches for supporting temporal scopes 356 Summary 363 Further reading 364 Exercises 364

5 Vlii CONTENTS 11 Scheduling real-time systems The cyclic executive approach Task-based scheduling Fixed-priority scheduling (FPS) Utilization-based schedulability tests for FPS Response time analysis (RTA) for FPS Sporadic and aperiodic tasks Task systems with D < T Task interactions and blocking Priority ceiling protocols An extendible task model for FPS Earliest deadline first (EDF) scheduling Dynamic systems and online analysis Worst-case execution time Multiprocessor scheduling Scheduling for power-aware systems Incorporating system overheads 414 Summary 419 Further reading 420 Exercises Programming schedulable systems Programming cyclic executives Programming preemptive priority-based systems Ada and fixed-priority scheduling The Ada Ravenscar profile Dynamic priorities and other Ada facilities C/Real-Time POSIX and fixed-priority scheduling Real-Time Java and fixed-priority scheduling Programming EDF systems Mixed scheduling 453 Summary 454 Further reading 454 Exercises Tolerating timing faults Dynamic redundancy and timing faults Deadline miss detection Overrun of worst-case execution time Overrun of sporadic events Overrun of resource usage Damage confinement Error recovery 485 Summary 492 Further reading 493 Exercises 493

6 CONTENTS IX 14 Low-level programming Hardware input/output mechanisms Language requirements Ada Real-Time Java С and older real-time languages Scheduling device drivers Memory management 521 Summary 527 Further reading 528 Exercises Mine control case study Mine drainage The HRT-HOOD design method The logical architecture design The physical architecture design Translation to Ada Translation to Real-Time Java Fault tolerance and distribution 570 Summary 572 Further reading 572 Exercises Conclusions 575 References 579 Index 587 Supporting resources Visit to find valuable online resources For instructors Solutions to exercises Example examination questions Code fragments PowerPoint slides For more information please contact your local Pearson Education sales representative or visit