WinRT: Read data in callback to prevent deadlock

When playing mp3 with QMediaPlayer and seeking is performed (IMFMediaEngineEx::SetCurrentTime)
and also IMFByteStream::BeginRead is already done (actual data has not
been read yet) but IMFByteStream::EndRead is not called.
There would be a possibility to get a deadlock when the playback gets stuck.

Possible problem call flow:
1. BeginRead is called
2. Queue finishRead and postpone it
3. SetCurrentTime to new position (is called on event loop)
4. finishRead is called
5. EndRead is called

As a result MF_MEDIA_ENGINE_EVENT_SEEKING is received but
MF_MEDIA_ENGINE_EVENT_SEEKED is never received.

Proposing to read data directly from BeginRead callback and avoid
possibility to seek when data is not read yet.

Task-number: QTBUG-67614
Change-Id: I809e5df1c05de8014ebd0a48fd008a291f39433c
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

2 files changed, 1 insertions, 9 deletions

diff --git a/src/plugins/winrt/qwinrtmediaplayercontrol.cpp b/src/plugins/winrt/qwinrtmediaplayercontrol.cpp
index de6b3418e..fae8e6bf0 100644
--- a/src/plugins/winrt/qwinrtmediaplayercontrol.cpp
+++ b/src/plugins/winrt/qwinrtmediaplayercontrol.cpp
@@ -423,7 +423,7 @@ public:
         HRESULT hr;
         hr = MFCreateAsyncResult(readResult.Get(), callback, state, &asyncResult);
         RETURN_HR_IF_FAILED("Failed to create read callback result");
-        QMetaObject::invokeMethod(q, "finishRead", Qt::QueuedConnection);
+        finishRead();
         return S_OK;
     }
 
@@ -906,10 +906,4 @@ QVideoRendererControl *QWinRTMediaPlayerControl::videoRendererControl()
     return d->videoRenderer;
 }
 
-void QWinRTMediaPlayerControl::finishRead()
-{
-    Q_D(QWinRTMediaPlayerControl);
-    d->streamProvider->finishRead();
-}
-
 QT_END_NAMESPACE
diff --git a/src/plugins/winrt/qwinrtmediaplayercontrol.h b/src/plugins/winrt/qwinrtmediaplayercontrol.h
index 1e854f5bb..174ba664b 100644
--- a/src/plugins/winrt/qwinrtmediaplayercontrol.h
+++ b/src/plugins/winrt/qwinrtmediaplayercontrol.h
@@ -93,8 +93,6 @@ public:
     QVideoRendererControl *videoRendererControl();
 
 private:
-    Q_INVOKABLE void finishRead();
-
     QScopedPointer<QWinRTMediaPlayerControlPrivate, QWinRTMediaPlayerControlPrivate> d_ptr;
     Q_DECLARE_PRIVATE(QWinRTMediaPlayerControl)
 };