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// Copyright (C) 2016 The Qt Company Ltd.
// Copyright (C) 2016 Intel Corporation.
// Copyright (C) 2012 Olivier Goffart <ogoffart@woboq.com>
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
#ifndef QMUTEX_P_H
#define QMUTEX_P_H
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists for the convenience of
// qmutex.cpp and qmutex_unix.cpp. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
#include <QtCore/private/qglobal_p.h>
#include <QtCore/qnamespace.h>
#include <QtCore/qmutex.h>
#include <QtCore/qatomic.h>
#include <QtCore/qdeadlinetimer.h>
#include "qplatformdefs.h" // _POSIX_VERSION
#if defined(Q_OS_DARWIN)
# include <mach/semaphore.h>
#elif defined(Q_OS_UNIX)
# include <semaphore.h>
#endif
struct timespec;
QT_BEGIN_NAMESPACE
// We manipulate the pointer to this class in inline, atomic code,
// so syncqt mustn't mark them as private, so ELFVERSION:ignore-next
class QMutexPrivate
{
public:
~QMutexPrivate();
QMutexPrivate();
bool wait(QDeadlineTimer timeout = QDeadlineTimer::Forever);
void wakeUp() noexcept;
// Control the lifetime of the privates
QAtomicInt refCount;
int id;
bool ref()
{
Q_ASSERT(refCount.loadRelaxed() >= 0);
int c;
do {
c = refCount.loadRelaxed();
if (c == 0)
return false;
} while (!refCount.testAndSetRelaxed(c, c + 1));
Q_ASSERT(refCount.loadRelaxed() >= 0);
return true;
}
void deref()
{
Q_ASSERT(refCount.loadRelaxed() >= 0);
if (!refCount.deref())
release();
Q_ASSERT(refCount.loadRelaxed() >= 0);
}
void release();
static QMutexPrivate *allocate();
QAtomicInt waiters; // Number of threads waiting on this mutex. (may be offset by -BigNumber)
QAtomicInt possiblyUnlocked; /* Boolean indicating that a timed wait timed out.
When it is true, a reference is held.
It is there to avoid a race that happens if unlock happens right
when the mutex is unlocked.
*/
enum { BigNumber = 0x100000 }; //Must be bigger than the possible number of waiters (number of threads)
void derefWaiters(int value) noexcept;
//platform specific stuff
#if defined(Q_OS_DARWIN)
semaphore_t mach_semaphore;
#elif defined(Q_OS_UNIX)
sem_t semaphore;
#endif
};
QT_END_NAMESPACE
#endif // QMUTEX_P_H
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