winrt: Proper guarding by readMutex

Commented its purpose and the guarded members for
readMutex.

Fixed places where guarded members were accessed without
using the mutex.

Use QMutexLocker instead of manually (un-)locking the
mutex.

Task-number: QTBUG-44357
Change-Id: I0d46f9592d5a9d1b52e73df961785a6f6c9e80be
Reviewed-by: David Faure <david.faure@kdab.com>

2 files changed, 19 insertions, 6 deletions

diff --git a/src/network/socket/qnativesocketengine_winrt.cpp b/src/network/socket/qnativesocketengine_winrt.cpp
index f8e92d3f50..f710f6b142 100644
--- a/src/network/socket/qnativesocketengine_winrt.cpp
+++ b/src/network/socket/qnativesocketengine_winrt.cpp
@@ -659,6 +659,7 @@ qint64 QNativeSocketEngine::read(char *data, qint64 maxlen)
     if (d->socketType != QAbstractSocket::TcpSocket)
         return -1;
 
+    QMutexLocker mutexLocker(&d->readMutex);
     // There will be a read notification when the socket was closed by the remote host. If that
     // happens and there isn't anything left in the buffer, we have to return -1 in order to signal
     // the closing of the socket.
@@ -667,7 +668,6 @@ qint64 QNativeSocketEngine::read(char *data, qint64 maxlen)
         return -1;
     }
 
-    QMutexLocker mutexLocker(&d->readMutex);
     qint64 b = d->readBytes.read(data, maxlen);
     d->bytesAvailable = d->readBytes.size() - d->readBytes.pos();
     return b;
@@ -701,7 +701,7 @@ qint64 QNativeSocketEngine::readDatagram(char *data, qint64 maxlen, QIpPacketHea
 {
 #ifndef QT_NO_UDPSOCKET
     Q_D(QNativeSocketEngine);
-    d->readMutex.lock();
+    QMutexLocker locker(&d->readMutex);
     if (d->socketType != QAbstractSocket::UdpSocket || d->pendingDatagrams.isEmpty()) {
         if (header)
             header->clear();
@@ -721,7 +721,7 @@ qint64 QNativeSocketEngine::readDatagram(char *data, qint64 maxlen, QIpPacketHea
     } else {
         readOrigin = datagram.data;
     }
-    d->readMutex.unlock();
+    locker.unlock();
     memcpy(data, readOrigin, qMin(maxlen, qint64(datagram.data.length())));
     return readOrigin.length();
 #else
@@ -772,12 +772,14 @@ qint64 QNativeSocketEngine::writeDatagram(const char *data, qint64 len, const QI
 bool QNativeSocketEngine::hasPendingDatagrams() const
 {
     Q_D(const QNativeSocketEngine);
+    QMutexLocker locker(&d->readMutex);
     return d->pendingDatagrams.length() > 0;
 }
 
 qint64 QNativeSocketEngine::pendingDatagramSize() const
 {
     Q_D(const QNativeSocketEngine);
+    QMutexLocker locker(&d->readMutex);
     if (d->pendingDatagrams.isEmpty())
         return -1;
 
@@ -1465,7 +1467,7 @@ HRESULT QNativeSocketEnginePrivate::handleReadyRead(IAsyncBufferOperation *async
     hr = byteArrayAccess->Buffer(&data);
     Q_ASSERT_SUCCEEDED(hr);
 
-    readMutex.lock();
+    QMutexLocker readLocker(&readMutex);
     if (readBytes.atEnd()) // Everything has been read; the buffer is safe to reset
         readBytes.close();
     if (!readBytes.isOpen())
@@ -1476,7 +1478,7 @@ HRESULT QNativeSocketEnginePrivate::handleReadyRead(IAsyncBufferOperation *async
     readBytes.write(reinterpret_cast<const char*>(data), qint64(bufferLength));
     readBytes.seek(readPos);
     bytesAvailable = readBytes.size() - readBytes.pos();
-    readMutex.unlock();
+    readLocker.unlock();
 
     if (notifyOnRead)
         emit q->readReady();
diff --git a/src/network/socket/qnativesocketengine_winrt_p.h b/src/network/socket/qnativesocketengine_winrt_p.h
index 79530d57f1..c9a67ca5f4 100644
--- a/src/network/socket/qnativesocketengine_winrt_p.h
+++ b/src/network/socket/qnativesocketengine_winrt_p.h
@@ -215,12 +215,23 @@ private:
     Microsoft::WRL::ComPtr<ABI::Windows::Networking::Sockets::IStreamSocketListener> tcpListener;
     Microsoft::WRL::ComPtr<ABI::Windows::Foundation::IAsyncAction> connectOp;
     QVector<Microsoft::WRL::ComPtr<ABI::Windows::Foundation::IAsyncOperationWithProgress<ABI::Windows::Storage::Streams::IBuffer *, UINT32>>> pendingReadOps;
+
+    // Protected by readMutex. Written in handleReadyRead (native callback)
     QBuffer readBytes;
-    QMutex readMutex;
+
+    // In case of TCP readMutex protects readBytes and bytesAvailable. In case of UDP it is
+    // pendingDatagrams. They are written inside native callbacks (handleReadyRead and
+    // handleNewDatagrams/putIntoPendingDatagramsList)
+    mutable QMutex readMutex;
+
     bool emitOnNewDatagram;
+
+    // Protected by readMutex. Written in handleReadyRead (native callback)
     QAtomicInteger<int> bytesAvailable;
 
+    // Protected by readMutex. Written in handleNewDatagrams/putIntoPendingDatagramsList
     QList<WinRtDatagram> pendingDatagrams;
+
     QList<ABI::Windows::Networking::Sockets::IStreamSocket *> pendingConnections;
     QList<ABI::Windows::Networking::Sockets::IStreamSocket *> currentConnections;
     QEventLoop eventLoop;