Qt 4.8
qorderedmutexlocker_p.h
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41 
42 #ifndef QORDEREDMUTEXLOCKER_P_H
43 #define QORDEREDMUTEXLOCKER_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 purely as an
50 // implementation detail. This header file may change from version to
51 // version without notice, or even be removed.
52 //
53 // We mean it.
54 //
55 
56 #include <QtCore/qmutex.h>
57 
59 
60 /*
61  Locks 2 mutexes in a defined order, avoiding a recursive lock if
62  we're trying to lock the same mutex twice.
63 */
65 {
66 public:
68  : mtx1((m1 == m2) ? m1 : (m1 < m2 ? m1 : m2)),
69  mtx2((m1 == m2) ? 0 : (m1 < m2 ? m2 : m1)),
70  locked(false)
71  {
72  relock();
73  }
75  {
76  unlock();
77  }
78 
79  void relock()
80  {
81  if (!locked) {
82  if (mtx1) mtx1->lockInline();
83  if (mtx2) mtx2->lockInline();
84  locked = true;
85  }
86  }
87 
88  void unlock()
89  {
90  if (locked) {
91  if (mtx1) mtx1->unlockInline();
92  if (mtx2) mtx2->unlockInline();
93  locked = false;
94  }
95  }
96 
97  static bool relock(QMutex *mtx1, QMutex *mtx2)
98  {
99  // mtx1 is already locked, mtx2 not... do we need to unlock and relock?
100  if (mtx1 == mtx2)
101  return false;
102  if (mtx1 < mtx2) {
103  mtx2->lockInline();
104  return true;
105  }
106  if (!mtx2->tryLockInline()) {
107  mtx1->unlock();
108  mtx2->lock();
109  mtx1->lock();
110  }
111  return true;
112  }
113 
114 private:
116  bool locked;
117 };
118 
120 
121 #endif
#define QT_END_NAMESPACE
This macro expands to.
Definition: qglobal.h:90
void lock()
Locks the mutex.
Definition: qmutex.cpp:151
The QMutex class provides access serialization between threads.
Definition: qmutex.h:60
static bool relock(QMutex *mtx1, QMutex *mtx2)
#define QT_BEGIN_NAMESPACE
This macro expands to.
Definition: qglobal.h:89
void lockInline()
Definition: qmutex.h:198
void unlockInline()
Definition: qmutex.h:196
void unlock()
Unlocks the mutex.
Definition: qmutex.cpp:296
QOrderedMutexLocker(QMutex *m1, QMutex *m2)
bool tryLockInline()
Definition: qmutex.h:197