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41 
42 #ifndef QMUTEX_P_H
43 #define QMUTEX_P_H
44 
45 //
46 //  W A R N I N G
47 //  -------------
48 //
49 // This file is not part of the Qt API.  It exists for the convenience
50 // of qmutex.cpp, qmutex_unix.cpp, and qmutex_win.cpp.  This header
51 // file may change from version to version without notice, or even be
52 // removed.
53 //
54 // We mean it.
55 //
56 
57 #include <QtCore/private/qglobal_p.h>
58 #include <QtCore/qnamespace.h>
59 #include <QtCore/qmutex.h>
60 #include <QtCore/qatomic.h>
61 #include <QtCore/qdeadlinetimer.h>
62 
63 #if defined(Q_OS_MAC)
64 # include <mach/semaphore.h>
65 #elif defined(Q_OS_LINUX) && !defined(QT_LINUXBASE)
66 // use Linux mutexes everywhere except for LSB builds
67 #  define QT_LINUX_FUTEX
68 #elif defined(Q_OS_UNIX)
69 # if _POSIX_VERSION-0 >= 200112L || _XOPEN_VERSION-0 >= 600
70 #  include <semaphore.h>
71 #  define QT_UNIX_SEMAPHORE
72 # endif
73 #endif
74 
75 struct timespec;
76 
77 QT_BEGIN_NAMESPACE
78 
79 class QMutexData
80 {
81 public:
82     bool recursive;
83     QMutexData(QMutex::RecursionMode mode = QMutex::NonRecursive)
84         : recursive(mode == QMutex::Recursive) {}
85 };
86 
87 #if !defined(QT_LINUX_FUTEX)
88 class QMutexPrivate : public QMutexData
89 {
90 public:
91     ~QMutexPrivate();
92     QMutexPrivate();
93 
94     bool wait(int timeout = -1);
95     void wakeUp() noexcept;
96 
97     // Control the lifetime of the privates
98     QAtomicInt refCount;
99     int id;
100 
ref()101     bool ref() {
102         Q_ASSERT(refCount.loadRelaxed() >= 0);
103         int c;
104         do {
105             c = refCount.loadRelaxed();
106             if (c == 0)
107                 return false;
108         } while (!refCount.testAndSetRelaxed(c, c + 1));
109         Q_ASSERT(refCount.loadRelaxed() >= 0);
110         return true;
111     }
deref()112     void deref() {
113         Q_ASSERT(refCount.loadRelaxed() >= 0);
114         if (!refCount.deref())
115             release();
116         Q_ASSERT(refCount.loadRelaxed() >= 0);
117     }
118     void release();
119     static QMutexPrivate *allocate();
120 
121     QAtomicInt waiters; // Number of threads waiting on this mutex. (may be offset by -BigNumber)
122     QAtomicInt possiblyUnlocked; /* Boolean indicating that a timed wait timed out.
123                                     When it is true, a reference is held.
124                                     It is there to avoid a race that happens if unlock happens right
125                                     when the mutex is unlocked.
126                                   */
127     enum { BigNumber = 0x100000 }; //Must be bigger than the possible number of waiters (number of threads)
128     void derefWaiters(int value) noexcept;
129 
130     //platform specific stuff
131 #if defined(Q_OS_MAC)
132     semaphore_t mach_semaphore;
133 #elif defined(QT_UNIX_SEMAPHORE)
134     sem_t semaphore;
135 #elif defined(Q_OS_UNIX)
136     bool wakeup;
137     pthread_mutex_t mutex;
138     pthread_cond_t cond;
139 #elif defined(Q_OS_WIN)
140     Qt::HANDLE event;
141 #endif
142 };
143 #endif //QT_LINUX_FUTEX
144 
145 
146 #ifdef Q_OS_UNIX
147 // helper functions for qmutex_unix.cpp and qwaitcondition_unix.cpp
148 // they are in qwaitcondition_unix.cpp actually
149 void qt_initialize_pthread_cond(pthread_cond_t *cond, const char *where);
150 void qt_abstime_for_timeout(struct timespec *ts, QDeadlineTimer deadline);
151 #endif
152 
153 QT_END_NAMESPACE
154 
155 #endif // QMUTEX_P_H
156