Fix crash in scene2d at shutdownv5.10.1

The resource manager policy for scene2d nodes has been changed so the
scene2d constructor gets called multiple times at startup. That in turn
increments render thread user counter every time. The cleanup code gets
called for each instanciated QScene2D node so at shutdown the counter
never reaches zero and the render thread is not closed properly. Change
the implementation so that the counter gets incremented only when the
render thread has been properly initialized.

Task-number: QTBUG-66003
Change-Id: I33a5b1f407e65329776bcabe0b66ff049581a435
Reviewed-by: Svenn-Arne Dragly <svenn-arne.dragly@qt.io>
Reviewed-by: Miikka Heikkinen <miikka.heikkinen@qt.io>
Reviewed-by: Paul Lemire <paul.lemire@kdab.com>
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>
(cherry picked from commit 564dfd87c5b1317dcf9fbc4d1c8d858c72513421)
Reviewed-by: Antti Määttä <antti.maatta@qt.io>

1 files changed, 8 insertions, 5 deletions

diff --git a/src/quick3d/quick3dscene2d/items/scene2d.cpp b/src/quick3d/quick3dscene2d/items/scene2d.cpp
index 4abc7cf42..1147abf68 100644
--- a/src/quick3d/quick3dscene2d/items/scene2d.cpp
+++ b/src/quick3d/quick3dscene2d/items/scene2d.cpp
@@ -123,7 +123,7 @@ Scene2D::Scene2D()
     , m_mouseEnabled(true)
     , m_renderPolicy(Qt3DRender::Quick::QScene2D::Continuous)
 {
-    renderThreadClientCount->fetchAndAddAcquire(1);
+
 }
 
 Scene2D::~Scene2D()
@@ -146,6 +146,8 @@ void Scene2D::initializeSharedObject()
             return;
         }
 
+        renderThreadClientCount->fetchAndAddAcquire(1);
+
         renderThread->setObjectName(QStringLiteral("Scene2D::renderThread"));
         m_renderThread = renderThread;
         m_sharedObject->m_renderThread = m_renderThread;
@@ -413,10 +415,11 @@ void Scene2D::cleanup()
         m_sharedObject->wake();
         m_sharedObject = nullptr;
     }
-
-    renderThreadClientCount->fetchAndSubAcquire(1);
-    if (renderThreadClientCount->load() == 0)
-        renderThread->quit();
+    if (m_renderThread) {
+        renderThreadClientCount->fetchAndSubAcquire(1);
+        if (renderThreadClientCount->load() == 0)
+            renderThread->quit();
+    }
 }