Fix deadlock when a new url is set in loading state

Setting a new url while QMediaPlayer is in loading state
can result in a deadlock between the GUI and worker thread.

Because main thread is waiting when worker realeses m_graph
but worker cleared all pending tasks and is waiting for new tasks
from main thread.

Task-number: QTBUG-53534
Change-Id: I296ecdf866c5d85efc7121d3e7936334d6b700fd
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@qt.io>
Reviewed-by: Christian Stromme <christian.stromme@qt.io>

2 files changed, 11 insertions, 3 deletions

diff --git a/src/plugins/directshow/player/directshowplayerservice.cpp b/src/plugins/directshow/player/directshowplayerservice.cpp
index 9cbb62969..8ee5d67a1 100644
--- a/src/plugins/directshow/player/directshowplayerservice.cpp
+++ b/src/plugins/directshow/player/directshowplayerservice.cpp
@@ -402,7 +402,6 @@ void DirectShowPlayerService::doSetUrlSource(QMutexLocker *locker)
     } else if (!m_resources.isEmpty()) {
         m_pendingTasks |= SetUrlSource;
     } else {
-        m_pendingTasks = 0;
         m_graphStatus = InvalidMedia;
 
         switch (hr) {
@@ -1688,8 +1687,6 @@ void DirectShowPlayerService::run()
     QMutexLocker locker(&m_mutex);
 
     for (;;) {
-        ::ResetEvent(m_taskHandle);
-
         while (m_pendingTasks == 0) {
             DWORD result = 0;
 
diff --git a/tests/auto/integration/qmediaplayerbackend/tst_qmediaplayerbackend.cpp b/tests/auto/integration/qmediaplayerbackend/tst_qmediaplayerbackend.cpp
index 5a703f2e1..9fe0a39ec 100644
--- a/tests/auto/integration/qmediaplayerbackend/tst_qmediaplayerbackend.cpp
+++ b/tests/auto/integration/qmediaplayerbackend/tst_qmediaplayerbackend.cpp
@@ -59,6 +59,7 @@ private slots:
     void construction();
     void loadMedia();
     void unloadMedia();
+    void loadMediaInLoadingState();
     void playPauseStop();
     void processEOS();
     void deleteLaterAtEOS();
@@ -325,6 +326,16 @@ void tst_QMediaPlayerBackend::unloadMedia()
     QVERIFY(!positionSpy.isEmpty());
 }
 
+void tst_QMediaPlayerBackend::loadMediaInLoadingState()
+{
+    const QUrl url("http://unavailable.media/");
+    QMediaPlayer player;
+    player.setMedia(QMediaContent(url));
+    player.play();
+    // Sets new media while old has not been finished.
+    player.setMedia(QMediaContent(url));
+    QTRY_COMPARE(player.mediaStatus(), QMediaPlayer::InvalidMedia);
+}
 
 void tst_QMediaPlayerBackend::playPauseStop()
 {