Bug 75000 – [Qt][WK2] Crash in ~WebGraphicsLayer when running fast/multicol/pagination-* tests

• Component: WebKit2
• Status: RESOLVED INVALID

[Balazs Kelemen]

WebKitTestRunner LayoutTests/fast/multicol/pagination-*.html
It's not clear which test will crash. Running them separately does not reproduce it.
We also have an assertion with these tests but is seems like a different bug: https://bugs.webkit.org/show_bug.cgi?id=74999
I did a debug build with ASSERT_DISABLED to avoid hitting the assert.
Backtrace:

#0  0x00007ffff5a32db5 in WebCore::WebGraphicsLayer::~WebGraphicsLayer (this=0x6ad6c0, __in_chrg=<optimized out>)
    at /home/balazs/WebKitGit/Source/WebKit2/WebProcess/WebCoreSupport/WebGraphicsLayer.cpp:100
#1  0x00007ffff5a32f12 in WebCore::WebGraphicsLayer::~WebGraphicsLayer (this=0x6ad6c0, __in_chrg=<optimized out>)
    at /home/balazs/WebKitGit/Source/WebKit2/WebProcess/WebCoreSupport/WebGraphicsLayer.cpp:101
#2  0x00007ffff58847b2 in WTF::deleteOwnedPtr<WebCore::GraphicsLayer> (ptr=0x6ad6c0)
    at /home/balazs/WebKitGit/Source/JavaScriptCore/wtf/OwnPtrCommon.h:53
#3  0x00007ffff5a65140 in WTF::OwnPtr<WebCore::GraphicsLayer>::clear (this=0x7268d8)
    at /home/balazs/WebKitGit/Source/JavaScriptCore/wtf/OwnPtr.h:100
#4  0x00007ffff5a64b76 in WTF::OwnPtr<WebCore::GraphicsLayer>::operator= (this=0x7268d8)
    at /home/balazs/WebKitGit/Source/JavaScriptCore/wtf/OwnPtr.h:73
#5  0x00007ffff6317625 in WebCore::RenderLayerBacking::destroyGraphicsLayers (this=0x7268c0)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderLayerBacking.cpp:162
#6  0x00007ffff631719c in WebCore::RenderLayerBacking::~RenderLayerBacking (this=0x7268c0, __in_chrg=<optimized out>)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderLayerBacking.cpp:117
#7  0x00007ffff631732a in WebCore::RenderLayerBacking::~RenderLayerBacking (this=0x7268c0, __in_chrg=<optimized out>)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderLayerBacking.cpp:118
#8  0x00007ffff63130ce in WTF::deleteOwnedPtr<WebCore::RenderLayerBacking> (ptr=0x7268c0)
    at /home/balazs/WebKitGit/Source/JavaScriptCore/wtf/OwnPtrCommon.h:53
#9  0x00007ffff6312d5a in WTF::OwnPtr<WebCore::RenderLayerBacking>::clear (this=0x755188)
    at /home/balazs/WebKitGit/Source/JavaScriptCore/wtf/OwnPtr.h:100
#10 0x00007ffff630f718 in WebCore::RenderLayer::clearBacking (this=0x755068)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderLayer.cpp:3936
#11 0x00007ffff62fea2e in WebCore::RenderLayer::~RenderLayer (this=0x755068, __in_chrg=<optimized out>)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderLayer.cpp:224
#12 0x00007ffff62feba8 in WebCore::RenderLayer::~RenderLayer (this=0x755068, __in_chrg=<optimized out>)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderLayer.cpp:234
#13 0x00007ffff6301a9e in WebCore::RenderLayer::destroy (this=0x755068, renderArena=0x75c5a0)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderLayer.cpp:1088
#14 0x00007ffff62b4f66 in WebCore::RenderBoxModelObject::destroyLayer (this=0x6e2888)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderBoxModelObject.cpp:273
#15 0x00007ffff6340c6d in WebCore::RenderObject::willBeDestroyed (this=0x6e2888)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderObject.cpp:2237
#16 0x00007ffff62b4fa9 in WebCore::RenderBoxModelObject::willBeDestroyed (this=0x6e2888)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderBoxModelObject.cpp:287
#17 0x00007ffff62a2252 in WebCore::RenderBox::willBeDestroyed (this=0x6e2888)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderBox.cpp:267
#18 0x00007ffff6255e5d in WebCore::RenderBlock::willBeDestroyed (this=0x6e2888)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderBlock.cpp:204
#19 0x00007ffff6340c99 in WebCore::RenderObject::destroy (this=0x6e2888)
    at /home/balazs/WebKitGit/Source/WebCore/rendering/RenderObject.cpp:2243
#20 0x00007ffff5d32a75 in WebCore::Document::detach (this=0x76c530) at /home/balazs/WebKitGit/Source/WebCore/dom/Document.cpp:1870

Well, it's a bit confusing (for example ~RenderLayerBacking seems to call itself which cannot happen in reality). But at least it is sure that smg is not ok with the WebGraphicsLayer object's m_layerTreeTileClient member:
(gdb) p *m_layerTreeTileClient
$12 = {
  _vptr.WebLayerTreeTileClient = 0x4545454545454545
}

Does this pattern say something to you?

[Balazs Kelemen]

*** Bug 74511 has been marked as a duplicate of this bug. ***

[Balazs Kelemen]

Created attachment 120186 [details]
Patch

[Balazs Kelemen]

It's a freed object dereferencing bug.

[Balazs Kelemen]

Created attachment 120187 [details]
Patch

Ergh, I forgot that these tests are still asserting in debug (but this is another issue, see bug 42408).

[Balazs Kelemen]

> Ergh, I forgot that these tests are still asserting in debug (but this is another issue, see bug 42408).

D'oh, it is bug 74999.

[Noam Rosenthal]

I think this should be fixed in r107236.

[Balazs Kelemen]

(In reply to comment #6)
> I think this should be fixed in r107236.

Sorry, I forgot to mention that I landed this.

[Balazs Kelemen]

(In reply to comment #7)
> (In reply to comment #6)
> > I think this should be fixed in r107236.
> 
> Sorry, I forgot to mention that I landed this.

Which caused a memory leak fixed in http://trac.webkit.org/changeset/104370.