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Diffstat (limited to 'src/corelib/thread/qorderedmutexlocker_p.h')
-rw-r--r-- | src/corelib/thread/qorderedmutexlocker_p.h | 121 |
1 files changed, 121 insertions, 0 deletions
diff --git a/src/corelib/thread/qorderedmutexlocker_p.h b/src/corelib/thread/qorderedmutexlocker_p.h new file mode 100644 index 0000000000..ddabfb7977 --- /dev/null +++ b/src/corelib/thread/qorderedmutexlocker_p.h @@ -0,0 +1,121 @@ +/**************************************************************************** +** +** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies). +** All rights reserved. +** Contact: Nokia Corporation (qt-info@nokia.com) +** +** This file is part of the QtCore module of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the Technology Preview License Agreement accompanying +** this package. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 2.1 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 2.1 requirements +** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. +** +** In addition, as a special exception, Nokia gives you certain additional +** rights. These rights are described in the Nokia Qt LGPL Exception +** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. +** +** If you have questions regarding the use of this file, please contact +** Nokia at qt-info@nokia.com. +** +** +** +** +** +** +** +** +** $QT_END_LICENSE$ +** +****************************************************************************/ + +#ifndef QORDEREDMUTEXLOCKER_P_H +#define QORDEREDMUTEXLOCKER_P_H + +// +// W A R N I N G +// ------------- +// +// This file is not part of the Qt API. It exists purely as an +// implementation detail. This header file may change from version to +// version without notice, or even be removed. +// +// We mean it. +// + +QT_BEGIN_NAMESPACE + +#include <QtCore/qmutex.h> + +/* + Locks 2 mutexes in a defined order, avoiding a recursive lock if + we're trying to lock the same mutex twice. +*/ +class QOrderedMutexLocker +{ +public: + QOrderedMutexLocker(QMutex *m1, QMutex *m2) + : mtx1((m1 == m2) ? m1 : (m1 < m2 ? m1 : m2)), + mtx2((m1 == m2) ? 0 : (m1 < m2 ? m2 : m1)), + locked(false) + { + relock(); + } + ~QOrderedMutexLocker() + { + unlock(); + } + + void relock() + { + if (!locked) { + if (mtx1) mtx1->lockInline(); + if (mtx2) mtx2->lockInline(); + locked = true; + } + } + + void unlock() + { + if (locked) { + if (mtx1) mtx1->unlockInline(); + if (mtx2) mtx2->unlockInline(); + locked = false; + } + } + + static bool relock(QMutex *mtx1, QMutex *mtx2) + { + // mtx1 is already locked, mtx2 not... do we need to unlock and relock? + if (mtx1 == mtx2) + return false; + if (mtx1 < mtx2) { + mtx2->lockInline(); + return true; + } + if (!mtx2->tryLockInline()) { + mtx1->unlock(); + mtx2->lock(); + mtx1->lock(); + } + return true; + } + +private: + QMutex *mtx1, *mtx2; + bool locked; +}; + +QT_END_NAMESPACE + +#endif |