1// Copyright (C) 2016 The Qt Company Ltd.
2// Copyright (C) 2016 Intel Corporation.
3// Copyright (C) 2012 Olivier Goffart <ogoffart@woboq.com>
4// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
5// Qt-Security score:significant reason:default
6
7#ifndef QMUTEX_P_H
8#define QMUTEX_P_H
9
10//
11// W A R N I N G
12// -------------
13//
14// This file is not part of the Qt API. It exists for the convenience of
15// qmutex.cpp and qmutex_unix.cpp. This header file may change from version to
16// version without notice, or even be removed.
17//
18// We mean it.
19//
20
21#include <QtCore/private/qglobal_p.h>
22#include <QtCore/qnamespace.h>
23#include <QtCore/qmutex.h>
24#include <QtCore/qatomic.h>
25#include <QtCore/qdeadlinetimer.h>
26
27#include "qplatformdefs.h" // _POSIX_VERSION
28
29#if defined(Q_OS_DARWIN)
30# include <mach/semaphore.h>
31#elif defined(Q_OS_UNIX)
32# include <semaphore.h>
33#endif
34
35struct timespec;
36
37QT_BEGIN_NAMESPACE
38
39// ### Qt7 remove this comment block
40// We manipulate the pointer to this class in inline, atomic code,
41// so syncqt mustn't mark them as private, so ELFVERSION:ignore-next
42class QMutexPrivate
43{
44public:
45 ~QMutexPrivate();
46 QMutexPrivate();
47
48 bool wait(QDeadlineTimer timeout = QDeadlineTimer::Forever);
49 void wakeUp() noexcept;
50
51 // Control the lifetime of the privates
52 QAtomicInt refCount;
53 int id;
54
55 bool ref()
56 {
57 Q_ASSERT(refCount.loadRelaxed() >= 0);
58 int c;
59 do {
60 c = refCount.loadRelaxed();
61 if (c == 0)
62 return false;
63 } while (!refCount.testAndSetRelaxed(expectedValue: c, newValue: c + 1));
64 Q_ASSERT(refCount.loadRelaxed() >= 0);
65 return true;
66 }
67 void deref()
68 {
69 Q_ASSERT(refCount.loadRelaxed() >= 0);
70 if (!refCount.deref())
71 release();
72 Q_ASSERT(refCount.loadRelaxed() >= 0);
73 }
74 void release();
75 static QMutexPrivate *allocate();
76
77 QAtomicInt waiters; // Number of threads waiting on this mutex. (may be offset by -BigNumber)
78 QAtomicInt possiblyUnlocked; /* Boolean indicating that a timed wait timed out.
79 When it is true, a reference is held.
80 It is there to avoid a race that happens if unlock happens right
81 when the mutex is unlocked.
82 */
83 enum { BigNumber = 0x100000 }; //Must be bigger than the possible number of waiters (number of threads)
84 void derefWaiters(int value) noexcept;
85
86 //platform specific stuff
87#if defined(Q_OS_DARWIN)
88 semaphore_t mach_semaphore;
89#elif defined(Q_OS_UNIX)
90 sem_t semaphore;
91#endif
92};
93
94QT_END_NAMESPACE
95
96#endif // QMUTEX_P_H
97

source code of qtbase/src/corelib/thread/qmutex_p.h