Port away from QMutexLocker in public headers

We can't use qt_scoped_lock/qt_unique_lock here, so port to
std::unique_lock and std::lock_guard for now.

This is in preparation of deprecating QMutexLocker in favor
of std::unique_lock and std::scoped_lock.

In QFutureInterface, change the return type of mutex() from
QMutex* to QMutex&, so we don't need to deref when passing
to std::lock_guard. We need to keep the old method around
for BC reasons, so the new one needs an artificial function
argument for disambiguation. This will vanish come Qt 6.

Change-Id: I1a0f0205952a249512ec2dbd3f0f48dd209b1636
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/concurrent/qtconcurrentreducekernel.h

@@ -52,6 +52,8 @@
 #include <QtCore/qthreadpool.h>
 #include <QtCore/qvector.h>
 
+#include <mutex>
+
 QT_BEGIN_NAMESPACE
 
 
@@ -147,7 +149,7 @@ public:
                    ReduceResultType &r,
                    const IntermediateResults<T> &result)
     {
-        QMutexLocker locker(&mutex);
+        std::unique_lock<QMutex> locker(mutex);
         if (!canReduce(result.begin)) {
             ++resultsMapSize;
             resultsMap.insert(result.begin, result);
@@ -161,7 +163,7 @@ public:
             // reduce this result
             locker.unlock();
             reduceResult(reduce, r, result);
-            locker.relock();
+            locker.lock();
 
             // reduce all stored results as well
             while (!resultsMap.isEmpty()) {
@@ -170,7 +172,7 @@ public:
 
                 locker.unlock();
                 reduceResults(reduce, r, resultsMapCopy);
-                locker.relock();
+                locker.lock();
 
                 resultsMapSize -= resultsMapCopy.size();
             }
@@ -180,7 +182,7 @@ public:
             // reduce this result
             locker.unlock();
             reduceResult(reduce, r, result);
-            locker.relock();
+            locker.lock();
 
             // OrderedReduce
             progress += result.end - result.begin;
@@ -193,7 +195,7 @@ public:
 
                 locker.unlock();
                 reduceResult(reduce, r, it.value());
-                locker.relock();
+                locker.lock();
 
                 --resultsMapSize;
                 progress += it.value().end - it.value().begin;

src/corelib/global/qglobalstatic.h

@@ -98,6 +98,7 @@ enum GuardValues {
 
 QT_END_NAMESPACE
 #include <QtCore/qmutex.h>
+#include <mutex>
 QT_BEGIN_NAMESPACE
 
 #define Q_GLOBAL_STATIC_INTERNAL(ARGS)                                  \
@@ -107,7 +108,7 @@ QT_BEGIN_NAMESPACE
         static QBasicMutex mutex;                                       \
         int x = guard.loadAcquire();                                    \
         if (Q_UNLIKELY(x >= QtGlobalStatic::Uninitialized)) {           \
-            QMutexLocker locker(&mutex);                                \
+            const std::lock_guard<QBasicMutex> locker(mutex);           \
             if (guard.loadRelaxed() == QtGlobalStatic::Uninitialized) {        \
                 d = new Type ARGS;                                      \
                 static struct Cleanup {                                 \

src/corelib/thread/qfutureinterface.cpp

@@ -429,6 +429,11 @@ QMutex *QFutureInterfaceBase::mutex() const
     return &d->m_mutex;
 }
 
+QMutex &QFutureInterfaceBase::mutex(int) const
+{
+    return d->m_mutex;
+}
+
 QtPrivate::ExceptionStore &QFutureInterfaceBase::exceptionStore()
 {
     return d->m_exceptionStore;

src/corelib/thread/qfutureinterface.h

@@ -45,6 +45,8 @@
 #include <QtCore/qexception.h>
 #include <QtCore/qresultstore.h>
 
+#include <mutex>
+
 QT_REQUIRE_CONFIG(future);
 
 QT_BEGIN_NAMESPACE
@@ -118,6 +120,7 @@ public:
     void waitForResume();
 
     QMutex *mutex() const;
+    QMutex &mutex(int) const;
     QtPrivate::ExceptionStore &exceptionStore();
     QtPrivate::ResultStoreBase &resultStoreBase();
     const QtPrivate::ResultStoreBase &resultStoreBase() const;
@@ -188,7 +191,7 @@ public:
 template <typename T>
 inline void QFutureInterface<T>::reportResult(const T *result, int index)
 {
-    QMutexLocker locker(mutex());
+    std::lock_guard<QMutex> locker(mutex(0));
     if (this->queryState(Canceled) || this->queryState(Finished)) {
         return;
     }
@@ -214,7 +217,7 @@ inline void QFutureInterface<T>::reportResult(const T &result, int index)
 template <typename T>
 inline void QFutureInterface<T>::reportResults(const QVector<T> &_results, int beginIndex, int count)
 {
-    QMutexLocker locker(mutex());
+    std::lock_guard<QMutex> locker(mutex(0));
     if (this->queryState(Canceled) || this->queryState(Finished)) {
         return;
     }
@@ -242,14 +245,14 @@ inline void QFutureInterface<T>::reportFinished(const T *result)
 template <typename T>
 inline const T &QFutureInterface<T>::resultReference(int index) const
 {
-    QMutexLocker lock(mutex());
+    std::lock_guard<QMutex> locker(mutex(0));
     return resultStoreBase().resultAt(index).template value<T>();
 }
 
 template <typename T>
 inline const T *QFutureInterface<T>::resultPointer(int index) const
 {
-    QMutexLocker lock(mutex());
+    std::lock_guard<QMutex> locker(mutex(0));
     return resultStoreBase().resultAt(index).template pointer<T>();
 }
 
@@ -263,7 +266,7 @@ inline QList<T> QFutureInterface<T>::results()
     QFutureInterfaceBase::waitForResult(-1);
 
     QList<T> res;
-    QMutexLocker lock(mutex());
+    std::lock_guard<QMutex> locker(mutex(0));
 
     QtPrivate::ResultIteratorBase it = resultStoreBase().begin();
     while (it != resultStoreBase().end()) {