[Interest] Crash in QSGOpaqueTextureMaterial::compare

[Gunnar Sletta]

Hi Jani,

If you have a dangling texture pointer in one of the nodes, then this will most likely not crash during updatePaintNode() but rather during rendering when the texture is taken into use. So I suggest you look at your nodes and textures. The important bit is that no node is referencing a texture after that texture has been deleted. 

A tool such as valgrind or similar memory debugger will greatly help you to pinpoint the source of the deleted texture.

cheers,
Gunnar

> On 12 Dec 2016, at 08:39, Jani Tykka <jtykka at broadsoft.com> wrote:
> 
> Actually QSGSimpleTextureNode is used. Just that crashes does rarely
> or never occur when that part of code is being executed. They might
> occur much later when that code has been already executed and deleted
> or then the code is not related at all (really unsure about the steps
> that produces the crash).
> 
> Here is the code which is used in QQuickItem. Do you see anything
> suspicious here? Thanks.
> 
> QSGNode * VideoItem::updatePaintNode( QSGNode * node,
> UpdatePaintNodeData * /*data*/ )
> {
> QSGSimpleTextureNode * n = static_cast< QSGSimpleTextureNode* >( node );
> if ( !n )
>   n = new QSGSimpleTextureNode;
> n->setRect( 0, 0, width(), height() );
> 
> delete m_Texture;
> m_Texture = window()->createTextureFromImage( m_Renderer->getImage() );
> n->setTexture( m_Texture );
> n->markDirty( QSGNode::DirtyGeometry );
> 
> return n;
> }
> 
> On Fri, Dec 9, 2016 at 8:17 PM, Gunnar Sletta <gunnar at sletta.org <mailto:gunnar at sletta.org>> wrote:
>> Is the application using QSGSimpleTextureNode and QSGTexture or is this a plain QML application? If so, are you deleting textures at the right time and updating nodes accordingly?
>> 
>> We did have issues with textures being deleted out of turn on the render thread, but that was fixed back in 5.1-days or so and I haven't seen backtraces like this since then.
>> 
>> cheers,
>> Gunnar
>> 
>>> On 09 Dec 2016, at 12:16, Jani Tykka <jtykka at broadsoft.com> wrote:
>>> 
>>> Hi,
>>> 
>>> I'm experiencing a crash that is quite common, but no idea about steps
>>> how to reproduce it (I have never been able to reproduce it myself,
>>> but various users sees it time after time). I think it's not directly
>>> a Qt bug, instead it might be something I do incorrectly. The crash
>>> seems to be most common after the application had been idling for a
>>> while or the computer is resumed from the sleep mode. Basically when
>>> the scene needs to be rendered again. I'd appreciate any hints that
>>> would help me to track this issue. See clipped crash stack traces
>>> below (Qt 5.6.2 on Windows), thanks.
>>> 
>>> Case 1
>>> QSGOpaqueTextureMaterial::compare
>>> qt5\qtdeclarative\src\quick\scenegraph\util\qsgtexturematerial.cpp:295
>>> QSGBatchRenderer::Renderer::prepareOpaqueBatches
>>> qt5\qtdeclarative\src\quick\scenegraph\coreapi\qsgbatchrenderer.cpp:1520
>>> Qt5Core.dll Qt5Core.dll at 0x1afb0
>>> Qt5Quick.dll QSGBatchRenderer::Renderer::render
>>> qt5\qtdeclarative\src\quick\scenegraph\coreapi\qsgbatchrenderer.cpp:2615
>>> Qt5Quick.dll QSGRenderer::renderScene
>>> qt5\qtdeclarative\src\quick\scenegraph\coreapi\qsgrenderer.cpp:217
>>> Qt5Quick.dll QSGRenderer::renderScene
>>> qt5\qtdeclarative\src\quick\scenegraph\coreapi\qsgrenderer.cpp:177
>>> Qt5Quick.dll QSGRenderContext::renderNextFrame
>>> qt5\qtdeclarative\src\quick\scenegraph\qsgcontext.cpp:555
>>> Qt5Quick.dll QQuickWindowPrivate::renderSceneGraph
>>> qt5\qtdeclarative\src\quick\items\qquickwindow.cpp:424
>>> Qt5Quick.dll QSGWindowsRenderLoop::renderWindow
>>> qt5\qtdeclarative\src\quick\scenegraph\qsgwindowsrenderloop.cpp:452
>>> Qt5Quick.dll QSGWindowsRenderLoop::render
>>> qt5\qtdeclarative\src\quick\scenegraph\qsgwindowsrenderloop.cpp:371
>>> Qt5Quick.dll QSGWindowsRenderLoop::event
>>> qt5\qtdeclarative\src\quick\scenegraph\qsgwindowsrenderloop.cpp:350
>>> Qt5Widgets.dll QApplicationPrivate::notify_helper
>>> qt5\qtbase\src\widgets\kernel\qapplication.cpp:3804
>>> ....
>>> 
>>> Case 2
>>> Qt5Quick.dll QSGOpaqueTextureMaterial::compare
>>> qt5\qtdeclarative\src\quick\scenegraph\util\qsgtexturematerial.cpp:295
>>> Qt5Quick.dll QSGBatchRenderer::Batch::isMaterialCompatible
>>> qt5\qtdeclarative\src\quick\scenegraph\coreapi\qsgbatchrenderer.cpp:620
>>> Qt5Quick.dll QSGBatchRenderer::Renderer::nodeChanged
>>> qt5\qtdeclarative\src\quick\scenegraph\coreapi\qsgbatchrenderer.cpp:1212
>>> Qt5Quick.dll QSGNode::markDirty
>>> qt5\qtdeclarative\src\quick\scenegraph\coreapi\qsgnode.cpp:672
>>> Qt5Quick.dll QSGDefaultImageNode::setTexture
>>> qt5\qtdeclarative\src\quick\scenegraph\qsgdefaultimagenode.cpp:244
>>> Qt5Quick.dll QQuickImage::updatePaintNode
>>> qt5\qtdeclarative\src\quick\items\qquickimage.cpp:724
>>> Qt5Quick.dll QQuickWindowPrivate::updateDirtyNode
>>> qt5\qtdeclarative\src\quick\items\qquickwindow.cpp:3061
>>> Qt5Quick.dll QQuickWindowPrivate::updateDirtyNodes
>>> qt5\qtdeclarative\src\quick\items\qquickwindow.cpp:2806
>>> Qt5Quick.dll QQuickWindowPrivate::syncSceneGraph
>>> qt5\qtdeclarative\src\quick\items\qquickwindow.cpp:379
>>> Qt5Quick.dll QSGWindowsRenderLoop::renderWindow
>>> qt5\qtdeclarative\src\quick\scenegraph\qsgwindowsrenderloop.cpp:448
>>> Qt5Quick.dll QSGWindowsRenderLoop::render
>>> qt5\qtdeclarative\src\quick\scenegraph\qsgwindowsrenderloop.cpp:371
>>> Qt5Quick.dll QSGWindowsRenderLoop::exposureChanged
>>> qt5\qtdeclarative\src\quick\scenegraph\qsgwindowsrenderloop.cpp:286
>>> ...
>>> 
>>> --
>>> 
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>> 
> 
> 
> 
> -- 
> Jani Tykkä
> Development Manager | BroadSoft, Inc. | +358 44 596 0587 | jtykka at broadsoft.com <mailto:jtykka at broadsoft.com>
> 
> -- 
> 
> 
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