Deprecate QMutex in recursive mode

Use QRecursiveMutex instead.

Pick-to: 5.15
Change-Id: I862fc2b3143deeb5c96dc8d445be5f9fa2535670
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/corelib/thread/qmutex.cpp

@@ -152,6 +152,7 @@ public:
 
 /*!
     \enum QMutex::RecursionMode
+    \obsolete Use QRecursiveMutex to create a recursive mutex.
 
     \value Recursive  In this mode, a thread can lock the same mutex
                       multiple times and the mutex won't be unlocked
@@ -173,6 +174,7 @@ public:
 
 /*!
     Constructs a new mutex. The mutex is created in an unlocked state.
+    \obsolete Use QRecursiveMutex to create a recursive mutex.
 
     If \a mode is QMutex::Recursive, a thread can lock the same mutex
     multiple times and the mutex won't be unlocked until a
@@ -197,7 +199,7 @@ QMutex::QMutex(RecursionMode mode)
 QMutex::~QMutex()
 {
     QMutexData *d = d_ptr.loadRelaxed();
-    if (isRecursive()) {
+    if (QBasicMutex::isRecursive()) {
         delete static_cast<QRecursiveMutexPrivate *>(d);
     } else if (d) {
 #ifndef QT_LINUX_FUTEX

src/corelib/thread/qmutex.h

@@ -132,8 +132,16 @@ public:
 #else
     QMutex() { d_ptr.storeRelaxed(nullptr); }
 #endif
+#if QT_DEPRECATED_SINCE(5,15)
     enum RecursionMode { NonRecursive, Recursive };
+    QT_DEPRECATED_VERSION_X(5, 15, "Use QRecursiveMutex instead of a recursive QMutex")
     explicit QMutex(RecursionMode mode);
+
+    QT_DEPRECATED_VERSION_X(5, 15, "Use QRecursiveMutex instead of a recursive QMutex")
+    bool isRecursive() const noexcept
+    { return QBasicMutex::isRecursive(); }
+#endif
+
     ~QMutex();
 
     // BasicLockable concept
@@ -164,9 +172,6 @@ public:
     }
 #endif
 
-    bool isRecursive() const noexcept
-    { return QBasicMutex::isRecursive(); }
-
 private:
     Q_DISABLE_COPY(QMutex)
     friend class QMutexLocker;

src/corelib/thread/qwaitcondition_unix.cpp

@@ -213,7 +213,7 @@ bool QWaitCondition::wait(QMutex *mutex, QDeadlineTimer deadline)
 {
     if (! mutex)
         return false;
-    if (mutex->isRecursive()) {
+    if (static_cast<QBasicMutex *>(mutex)->isRecursive()) {
         qWarning("QWaitCondition: cannot wait on recursive mutexes");
         return false;
     }