| [556] | 1 | /****************************************************************************
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| 2 | **
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| [846] | 3 | ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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| [556] | 4 | ** All rights reserved.
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| 5 | ** Contact: Nokia Corporation ([email protected])
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| 6 | **
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| 7 | ** This file is part of the documentation of the Qt Toolkit.
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| 8 | **
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| [846] | 9 | ** $QT_BEGIN_LICENSE:FDL$
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| [556] | 10 | ** Commercial Usage
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| 11 | ** Licensees holding valid Qt Commercial licenses may use this file in
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| 12 | ** accordance with the Qt Commercial License Agreement provided with the
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| [846] | 13 | ** Software or, alternatively, in accordance with the terms contained in a
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| 14 | ** written agreement between you and Nokia.
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| [556] | 15 | **
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| [846] | 16 | ** GNU Free Documentation License
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| 17 | ** Alternatively, this file may be used under the terms of the GNU Free
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| 18 | ** Documentation License version 1.3 as published by the Free Software
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| 19 | ** Foundation and appearing in the file included in the packaging of this
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| 20 | ** file.
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| [556] | 21 | **
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| 22 | ** If you have questions regarding the use of this file, please contact
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| 23 | ** Nokia at [email protected].
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| 24 | ** $QT_END_LICENSE$
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| 25 | **
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| 26 | ****************************************************************************/
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| 27 |
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| 28 | /*!
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| 29 | \page atomic-operations.html
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| 30 | \title Implementing Atomic Operations
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| 31 | \brief A guide to implementing atomic operations on new architectures.
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| 32 |
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| 33 | \ingroup best-practices
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| 34 | \ingroup qt-embedded-linux
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| 35 |
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| 36 | Qt uses an optimization called \l {Implicitly Shared
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| 37 | Classes}{implicit sharing} for many of its value classes.
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| 38 |
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| 39 | Starting with Qt 4, all of Qt's implicitly shared classes can
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| 40 | safely be copied across threads like any other value classes,
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| 41 | i.e., they are fully \l {Reentrancy and Thread-Safety}{reentrant}.
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| 42 | This is accomplished by implementing reference counting
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| 43 | operations using atomic hardware instructions on all the
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| 44 | different platforms supported by Qt.
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| 45 |
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| 46 | To support a new architecture, it is important to ensure that
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| 47 | these platform-specific atomic operations are implemented in a
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| 48 | corresponding header file (\c qatomic_ARCH.h), and that this file
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| 49 | is located in Qt's \c src/corelib/arch directory. For example, the
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| 50 | Intel 80386 implementation is located in \c
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| 51 | src/corelib/arch/qatomic_i386.h.
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| 52 |
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