Литература_1 / sys_arch
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QNX→ Neutrino→ RTOS
System Architecture
For release 6.4.0
♥ 2008, QNX Software Systems GmbH & Co. KG.
♥ 1996–2008, QNX Software Systems GmbH & Co. KG. All rights reserved.
Published under license by:
QNX Software Systems International Corporation
175 Terence Matthews Crescent Kanata, Ontario
K2M 1W8 Canada
Voice: +1 613 591-0931
Fax: +1 613 591-3579 Email: info@qnx.com
Web: http://www.qnx.com/
Electronic edition published 2008
QNX, Neutrino, Photon, Photon microGUI, Momentics, and Aviage are trademarks, registered in certain jurisdictions, of QNX Software Systems GmbH & Co. KG. and are used under license by QNX Software Systems International Corporation. All other trademarks belong to their respective owners.
Contents
About This Guide |
xiii |
What you’ll find in this guide |
xv |
Typographical conventions |
xvi |
Note to Windows users |
xvii |
Technical support xvii |
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1 The Philosophy of QNX Neutrino |
1 |
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Design goals |
3 |
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An embeddable POSIX OS? |
3 |
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Product scaling |
3 |
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Why POSIX for embedded systems? |
4 |
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Why QNX Neutrino for embedded systems? |
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Microkernel architecture |
6 |
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The OS as a team of processes |
8 |
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A true kernel |
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System processes |
9 |
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Interprocess communication |
10 |
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QNX Neutrino as a message-passing operating system 10 |
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Network distribution of kernels |
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Single-computer model |
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Flexible networking |
11 |
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2 The QNX Neutrino Microkernel |
13 |
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Introduction |
15 |
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The implementation of QNX Neutrino 16 |
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POSIX realtime and thread extensions |
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System services |
16 |
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Threads and processes |
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Thread attributes |
20 |
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Thread scheduling |
24 |
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When are scheduling decisions are made? |
24 |
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Scheduling priority |
24 |
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Scheduling algorithms |
26 |
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October 16, 2008 |
Contents iii |
♥ 2008, QNX Software Systems GmbH & Co. KG.
IPC issues |
31 |
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Thread complexity issues |
31 |
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Synchronization services |
32 |
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Mutexes: mutual exclusion locks |
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33 |
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Condvars: condition variables |
34 |
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Barriers |
35 |
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Sleepon locks |
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38 |
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Reader/writer locks |
38 |
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Semaphores |
38 |
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Synchronization via scheduling algorithm |
39 |
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Synchronization via message passing |
40 |
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Synchronization via atomic operations |
40 |
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Synchronization services implementation |
40 |
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Clock and timer services |
41 |
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Time correction |
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42 |
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Timers |
42 |
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Interrupt handling |
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44 |
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Interrupt latency |
45 |
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Scheduling latency |
45 |
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Nested interrupts |
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46 |
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Interrupt calls |
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47 |
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3 |
Interprocess Communication (IPC) |
51 |
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Synchronous message passing |
53 |
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MsgReply() vs MsgError() |
56 |
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Message copying |
56 |
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Simple messages 58 |
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Channels and connections |
59 |
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Pulses |
61 |
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Priority inheritance and messages |
61 |
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Message-passing API |
62 |
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Robust implementations with Send/Receive/Reply |
62 |
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Events |
64 |
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I/O notification |
65 |
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Signals |
66 |
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Special signals |
68 |
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Summary of signals |
69 |
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POSIX message queues |
70 |
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Why use POSIX message queues? |
71 |
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File-like interface |
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71 |
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Message-queue functions |
72 |
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iv |
Contents |
October 16, 2008 |
♥ 2008, QNX Software Systems GmbH & Co. KG.
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Shared memory |
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72 |
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Shared memory with message passing |
73 |
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Creating a shared-memory object |
74 |
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mmap() |
74 |
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Initializing allocated memory |
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Typed memory |
78 |
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Implementation-defined behavior |
79 |
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Practical examples |
83 |
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Pipes and FIFOs |
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84 |
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Pipes |
84 |
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FIFOs |
85 |
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The Instrumented Microkernel |
87 |
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Introduction |
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89 |
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Instrumentation at a glance |
89 |
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Event control |
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90 |
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Modes of emission |
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90 |
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Ring buffer |
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91 |
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Data interpretation |
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91 |
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System analysis with the IDE |
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92 |
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Proactive tracing |
93 |
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5 |
Multicore Processing |
95 |
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Introduction |
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Asymmetric multiprocessing (AMP) |
97 |
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Symmetric multiprocessing (SMP) |
98 |
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Neutrino’s microkernel approach |
99 |
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Booting an x86 SMP system |
100 |
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Booting a PowerPC SMP system |
100 |
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How the SMP microkernel works |
101 |
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Critical sections |
102 |
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Bound multiprocessing (BMP) |
103 |
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A viable migration strategy |
104 |
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Choosing between AMP, SMP, and BMP 104 |
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6 |
Process Manager |
107 |
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Introduction |
109 |
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Process management |
109 |
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Process primitives |
109 |
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Process loading |
114 |
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Memory management |
114 |
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October 16, 2008 |
Contents v |
♥ 2008, QNX Software Systems GmbH & Co. KG.
Memory Management Units (MMUs) 115
Memory protection at run time 116
Quality control 117
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Full-protection model |
118 |
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Variable page size |
118 |
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Pathname management |
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119 |
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Domains of authority |
119 |
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Resolving pathnames |
119 |
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Symbolic prefixes |
123 |
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File descriptor namespace 125 |
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7 |
Dynamic Linking |
129 |
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Shared objects 131 |
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Statically linked |
131 |
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Dynamically linked |
131 |
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Augmenting code at runtime 132 |
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How shared objects are used |
132 |
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ELF format |
132 |
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ELF without COFF |
133 |
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The process |
133 |
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Runtime linker |
134 |
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Loading a shared library at runtime 135 |
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Symbol name resolution |
136 |
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8 |
Resource Managers |
137 |
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Introduction 139 |
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What is a resource manager? |
139 |
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Why write a resource manager? |
139 |
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The types of resource managers |
141 |
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Communication via native IPC |
142 |
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Resource manager architecture |
143 |
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Message types |
143 |
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The resource manager shared library |
144 |
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Summary |
148 |
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9 |
Filesystems |
149 |
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Introduction |
151 |
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Filesystems and pathname resolution |
151 |
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Filesystem classes |
152 |
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Filesystems as shared libraries |
152 |
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io-blk |
153 |
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vi |
Contents |
October 16, 2008 |
♥ 2008, QNX Software Systems GmbH & Co. KG.
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Filesystem limitations |
156 |
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Image filesystem |
156 |
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RAM “filesystem” |
157 |
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Embedded transaction filesystem (ETFS) |
157 |
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Inside a transaction |
158 |
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Types of storage media |
158 |
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Reliability features |
159 |
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QNX 4 filesystem |
161 |
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Power-Safe filesystem |
161 |
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Problems with existing disk filesystems |
161 |
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Copy-on-write filesystem |
162 |
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Performance |
164 |
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DOS Filesystem |
166 |
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CD-ROM filesystem |
168 |
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FFS3 filesystem |
168 |
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Customization |
169 |
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Organization |
169 |
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Features |
170 |
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Utilities |
172 |
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System calls |
172 |
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NFS filesystem 172 |
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CIFS filesystem |
172 |
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Linux Ext2 filesystem |
173 |
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Universal Disk Format (UDF) filesystem |
173 |
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Virtual filesystems |
173 |
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10 |
Character I/O 175 |
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Introduction |
177 |
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Driver/io-char communication |
178 |
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Device control |
179 |
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Input modes |
180 |
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Device subsystem performance |
183 |
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Console devices |
183 |
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Terminal emulation |
183 |
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Serial devices |
183 |
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Parallel devices |
184 |
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Pseudo terminal devices (ptys) |
184 |
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11 |
Networking Architecture |
187 |
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Introduction |
189 |
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Network manager (io-pkt*) |
189 |
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October 16, 2008 |
Contents vii |
♥ 2008, QNX Software Systems GmbH & Co. KG.
Threading model |
191 |
Protocol module |
192 |
Driver module |
193 |
Loading and unloading a driver 193
12 Native Networking (Qnet) 195
QNX Neutrino distributed |
197 |
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Name resolution and lookup |
198 |
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File descriptor (connection ID) |
199 |
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Behind a simple open() |
199 |
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Global Name Service (GNS) |
201 |
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Network naming 201 |
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Redundant Qnet: Quality of Service (QoS) and multiple paths 202
QoS policies 202
Specifying QoS policies 205
Symbolic links 205
Examples 206 |
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Local networks |
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Remote networks |
206 |
Custom device drivers |
207 |
13 TCP/IP Networking 209
Introduction 211
Stack configurations 211
Structure of the TCP/IP manager 212
Socket API 212
Database routines |
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Multiple stacks 214 |
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IP filtering and NAT |
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NTP 214 |
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Dynamic host configuration 215
AutoIP 215 |
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PPP over Ethernet |
215 |
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/etc/autoconnect |
216 |
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Embedded web server |
216 |
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CGI method |
216 |
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SSI method |
217 |
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14 High Availability 219
What is High Availability? 221
An OS for HA 221
viii |
Contents |
October 16, 2008 |
♥ 2008, QNX Software Systems GmbH & Co. KG.
Custom hardware support |
222 |
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Client library |
222 |
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Recovery example |
223 |
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High Availability Manager |
224 |
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HAM and the Guardian |
225 |
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HAM hierarchy 225 |
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Publishing autonomously detected conditions 229 |
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Subscribing to autonomously published conditions 229 |
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HAM as a “filesystem” |
230 |
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Multistage recovery |
230 |
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HAM API |
231 |
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15 |
Adaptive Partitioning |
235 |
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What are partitions? |
237 |
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Because adaptive partitions are not “boxes” what are they? 238 |
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Why adaptive? |
238 |
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Benefits of adaptive partitioning |
239 |
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Engineering product performance |
239 |
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Dealing with design complexity |
240 |
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Providing security |
241 |
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Debugging |
242 |
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Adaptive partitioning thread scheduler 242
16 |
The Photon microGUI 245 |
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A graphical microkernel |
247 |
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The Photon event space |
248 |
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Regions |
249 |
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Events 250 |
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Graphics drivers |
251 |
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Multiple graphics drivers |
252 |
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Color model |
252 |
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Font support |
253 |
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Stroke-based fonts |
253 |
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Unicode multilingual support |
253 |
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UTF-8 encoding 253 |
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Animation support |
254 |
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Printing support |
254 |
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The Photon Window Manager |
255 |
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Widget library |
255 |
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Fundamental widgets 256 |
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Container widgets |
258 |
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October 16, 2008 |
Contents ix |
♥ 2008, QNX Software Systems GmbH & Co. KG.
Advanced widgets 260
Convenience functions |
265 |
Driver development kits |
267 |
Summary 268 |
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17 Multimedia 269
Overview |
271 |
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MME functional areas |
272 |
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The MME interface |
273 |
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Component-based architecture 274 |
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The MME resource managers 274 |
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Glossary 277 |
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Index |
295 |
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x |
Contents |
October 16, 2008 |