1612998 - Perma-checkerboarding after toggling WR debug overlays

Status: RESOLVED WORKSFORME

(Core :: Graphics: WebRender, defect, P3)

Description

[Markus Stange [:mstange]]

With WebRender, sometimes I get into a state where scrolling will no longer make new content available - you can only scroll into empty areas on the page and those empty areas never get filled.
Usually this happens after I toggled some kind of debug overlay, for example the WR profiler overlay or the picture caching overlay.
It behaves as if APZ gets stuck in a state where it stops informing the main thread about the new scroll position. In a profile I can see that the main thread is fully available; repainting works, it just repaints a display port that never moves.

Comment 1

[Nicolas Silva [:nical]]

Scary stuff. Do you have fission enabled? Do you think it's a recent recent regression?

Comment 2

[Daniel Bodea [:danibodea]]

I have attempted reproducing this issue on a MacBook Pro 2017 with mac OS 10.14.6, on Nightly v74.0a1 from 2020-02-07.
I have activated webrender, installed the firefox profiler add-on, started the profiler (https://profiler.firefox.com/) and then navigated through several websites (including www.sketchfab.com, www.facebook.com, www.youtube.com). No issues were observed.

Can you give me more details on the reproduction of the issue on your system?
Can you describe the process as I did above?

Thank you for your contribution!

Comment 3

[Jeff Muizelaar [:jrmuizel]]

You'll need to set gfx.webrender.all=true and gfx.webrender.picture-caching=true

Comment 4

[Jeff Muizelaar [:jrmuizel]]

You don't need to use the gecko profiler.

Comment 5

[Markus Stange [:mstange]]

(In reply to Bodea Daniel [:danibodea] from comment #2)

Can you give me more details on the reproduction of the issue on your system?

I haven't tried to reproduce it.
The "WR profiler overlay" is unrelated to the Firefox profiler. The WR profiler overlay is controlled by the pref gfx.webrender.debug.profiler. And the picture caching overlay is controlled by the pref gfx.webrender.debug.picture-caching.

Comment 6

[Daniel Bodea [:danibodea]]

I have attempted to reproduce this issue again with the information I got in comment 3, but I was again unsuccessful.
Please answer some questions that might help to troubleshoot it:

1. Can you tell me which Mac OS version are you using?
2. Which browser version reproduces this issue?
3. Also, please tell us which websites you scrolled to see this issue reproduce.

Thank you!

Comment 7

[Jeff Muizelaar [:jrmuizel]]

I also see this on Window 10 with Nightly on any basically any website after toggling gfx.webrender.debug.profiler.

Comment 9

[Daniel Bodea [:danibodea]]

This bug appears to be related to Mac OS and Windows 10, and the bug it was made duplicate of appears to be related to mobile (Fenix).
This being said, I think the status is not correct.

Jeff, can you provide some steps to reproduce so I can properly confirm it and find a regression window?
Thank you for your contribution!

Comment 10

[Kris Taeleman (:ktaeleman)]

Hi Bodea,

The issue on android had the same repro steps and the fix was not android specific. I was able to reproduce the issue on windows and was fixed by the patch, which is why I think it's the same issue.

This was introduced by the following change: https://hg.mozilla.org/mozilla-central/rev/eac17a862c29a52ae1a389c5e55c0a1cec0db7b6

STR are:

• Turn on webrender (gfx.webrender.all = true) and restart browser to take effect.
• Ensure webrender is enabled in about:support (Compositor: Webrender)
• Open a couple of tabs with various pages.
• Toggle gfx.webrender.debug.profiler in about:config (on/off, doesn't matter)
• continue browsing or switch to older tabs and scroll up/down and notice the page no longer being rendered.

Thanks for double checking!

Comment 11

[BugBot [:suhaib / :marco/ :calixte]]

Bugbug thinks this bug is a regression, but please revert this change in case of error.

Comment 12

[Daniel Bodea [:danibodea]]

I have attempted reproducing this issue on Windows 10, Nightly v73.0a1 from 2020-01-05 (a build before the regression and I could not reproduce it) and I could not, as expected.
Then, I have attempted reproducing this issue on Windows 10, Nightly v74.0a1 from 2020-01-15 (a build after the regression and before the fix) and it reproduced, as expected.
Then, I have attempted reproduction on Nightly v75.0a1 from 2020-02-28 (a build after the fix) and it appears fixed.
I have reproduced and verified while using the Reddit website.

I deem this bug verified and it confirms that the fix from bug 1615575 also fixed the build on the desktop platform.