/**************************************************************************** | |
** | |
** 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. | |
** | |
** $QT_BEGIN_LICENSE:LGPL$ | |
** GNU Lesser General Public License Usage | |
** 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. | |
** | |
** GNU General Public License Usage | |
** Alternatively, this file may be used under the terms of the GNU General | |
** Public License version 3.0 as published by the Free Software Foundation | |
** and appearing in the file LICENSE.GPL included in the packaging of this | |
** file. Please review the following information to ensure the GNU General | |
** Public License version 3.0 requirements will be met: | |
** http://www.gnu.org/copyleft/gpl.html. | |
** | |
** Other Usage | |
** Alternatively, this file may be used in accordance with the terms and | |
** conditions contained in a signed written agreement between you and Nokia. | |
** | |
** | |
** | |
** | |
** | |
** $QT_END_LICENSE$ | |
** | |
****************************************************************************/ | |
#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 | |
class QMutex; | |
/* | |
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->lock(); | |
if (mtx2) mtx2->lock(); | |
locked = true; | |
} | |
} | |
void unlock() | |
{ | |
if (locked) { | |
if (mtx1) mtx1->unlock(); | |
if (mtx2) mtx2->unlock(); | |
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->lock(); | |
return true; | |
} | |
if (!mtx2->tryLock()) { | |
mtx1->unlock(); | |
mtx2->lock(); | |
mtx1->lock(); | |
} | |
return true; | |
} | |
private: | |
QMutex *mtx1, *mtx2; | |
bool locked; | |
}; | |
QT_END_NAMESPACE | |
#endif |