Bug 231897 – GPU process occasionally crashes under `StreamConnectionWorkQueue::processStreams()` in layout tests

• Status: RESOLVED
• Resolution: FIXED
• Component: WebKit2

[Wenson Hsieh]

Seems to happen somewhat randomly on EWS.

[Wenson Hsieh]

Created attachment 441611 [details]
Crash log

[Wenson Hsieh]

I can intermittently reproduce by running the tests in `compositing` on 4 iOS 15 simulators in parallel for ~3-4 iterations.

[Wenson Hsieh]

Created attachment 441650 [details]
Fixes the tests

[Wenson Hsieh]

Comment on attachment 441650 [details]
Fixes the tests

Thanks for the review!

[EWS]

Committed r284427 (243191@main): <https://commits.webkit.org/243191@main>

All reviewed patches have been landed. Closing bug and clearing flags on attachment 441650 [details].

[Radar WebKit Bug Importer]

<rdar://problem/84398678>

[Kimmo Kinnunen]

Comment on attachment 441650 [details]
Fixes the tests

View in context: https://bugs.webkit.org/attachment.cgi?id=441650&action=review

> Source/WebKit/GPUProcess/graphics/RemoteRenderingBackend.cpp:102
> +    m_workQueue->stop();

Is there a reason to do the ref-related changes?
Wasn't the stop the only thing that was missing?
I don't think the ref made above lives longer than the stop.

[Wenson Hsieh]

(In reply to Kimmo Kinnunen from comment #7)
> Comment on attachment 441650 [details]
> Fixes the tests
> 
> View in context:
> https://bugs.webkit.org/attachment.cgi?id=441650&action=review
> 
> > Source/WebKit/GPUProcess/graphics/RemoteRenderingBackend.cpp:102
> > +    m_workQueue->stop();
> 
> Is there a reason to do the ref-related changes?
> Wasn't the stop the only thing that was missing?
> I don't think the ref made above lives longer than the stop.

It's true that this call to `stop()` was technically the only change required to avoid the crash.

However, given that StreamConnectionWorkQueue is ref-counted, it was also wrong to be storing `m_workQueue` directly as a member on RemoteRenderingBackend, rather than through some kind of Ref-counted template class (i.e. Ref or RefPtr).

This would be important if (for example) we were to make `stop()` non-blocking in the future.