Bug 307077 – [GTK] A few more crashes with hardware acceleration disabled and softGL after 306485@main, 306842@main and 306855@main

• Component: WebKitGTK
• Status: NEW

[Carlos Alberto Lopez Perez]

Created attachment 478258 [details]
GDB backtrace for the crash

This is related to bug 306993

306993@main introduced several issues on GTK with compositing mode disabled or with hardware acceleration disabled and softGL. Most of this issues were fixed by 306842@main and 306855@main
However there are still some remaining problems.

I'm having this crash with one PW test. I'm currently testing on commit 306865@main and I have tried to apply locally the patch from https://github.com/WebKit/WebKit/pull/57960 but still crashes.

Note: This test were all passing fine before 306993@main

I'm running the minibrowser with --hardware-acceleration-policy=never  on a gpu-less environment (on a Docker container with Xvfb)

I'm attaching the gdb backtrace for the crash

The crash happens because this assertion is hit at Source/WebKit/WebProcess/WebPage/CoordinatedGraphics/DrawingAreaCoordinatedGraphicsGLib.cpp:285
   283	GraphicsLayerFactory* DrawingAreaCoordinatedGraphics::graphicsLayerFactory()
   284	{
   285	    RELEASE_ASSERT(m_layerTreeHost);
   286	    return m_layerTreeHost->graphicsLayerFactory();
   287	}


I think the problematic call is at frame 11

#11 0x00007f26cdb36c92 in WebCore::RenderLayerCompositor::updateCompositingLayers (this=0x7f26ac154c60, updateType=WebCore::CompositingUpdateType::AfterLayout, updateRootArg=0x0) at ../../../Source/WebCore/rendering/RenderLayerCompositor.cpp:1087


  1085	
  1086	    if (!m_compositing && (m_forceCompositingMode || (isRootFrameCompositor() && page().pageOverlayController().overlayCount())))
  1087	        enableCompositingMode(true);
  1088	



Basically is calling "enableCompositingMode(true);" when hardware-acceleration-policy is set to never.

I'm not an expert on this part of the WebKit code, but that initially looks wrong to me. I tried to comment out that call and then the crash is gone and the tests all pass again back.

--- a/Source/WebCore/rendering/RenderLayerCompositor.cpp
+++ b/Source/WebCore/rendering/RenderLayerCompositor.cpp
@@ -1085,4 +1085,6 @@ bool RenderLayerCompositor::updateCompositingLayers(CompositingUpdateType update
 
+#if !PLATFORM(GTK)
     if (!m_compositing && (m_forceCompositingMode || (isRootFrameCompositor() && page().pageOverlayController().overlayCount())))
         enableCompositingMode(true);
+#endif

[Carlos Alberto Lopez Perez]

(In reply to Carlos Alberto Lopez Perez from comment #0)
> Created attachment 478258 [details]
> GDB backtrace for the crash
> 
> This is related to bug 306993
> 
> 306993@main introduced several issues on GTK with compositing mode disabled
> or with hardware acceleration disabled and softGL. Most of this issues were
> fixed by 306842@main and 306855@main
> However there are still some remaining problems.
[...]
> Note: This test were all passing fine before 306993@main
> 

Sorry for the typo, i wanted to say 306485@main instead of 306993@main  (confused the bug number with the commit id)