Bug#971343: Animated background/wallpaper (changing over time) causes system freeze on Nouveau

[Simon McVittie]

On Wed, 30 Sep 2020 at 12:31:06 -0300, Leandro Cunha wrote:
> I did this test and there was no crash, but see the attached
> screenshot to see how the wallpaper.

Hmm, interesting failure mode. I think there was a bug fixed recently
where the animated background draws one frame at the wrong brightness
before adjusting correctly to the time of day - this might mean your Shell
is actually showing half of one frame and half of another or something?

> In the bug attached see from 10:29 when I started testing with Kernel
> 4.19, until 10:44 that appears in the screen capture that shows both
> wallpapers side by side. Normally the interface stopped responding,
> but what I do is run su -c "cat /var/log/syslog > log" on tty to
> check.

To confirm, are you saying that the log entries from Sep 30 10:29 to
10:44 are with the 4.19 kernel from Debian 10, but with everything else
(including Mesa and GNOME) taken from unstable?

> What calls attention that the screen is black, but the interface does
> not freeze with this version of Kernel, being that I ran the tests on
> Xorg where I had the best performance so far.

This looks interesting:

> Sep 30 10:29:36 debian-pc gnome-shell[1707]: nouveau: kernel rejected pushbuf: Não foi possível alocar memória
> Sep 30 10:29:36 debian-pc kernel: [ 1520.979894] nouveau 0000:01:00.0: Xorg[1558]: fail ttm_validate
> Sep 30 10:29:36 debian-pc kernel: [ 1520.979904] nouveau 0000:01:00.0: Xorg[1558]: validating bo list
> Sep 30 10:29:36 debian-pc kernel: [ 1520.979915] nouveau 0000:01:00.0: Xorg[1558]: validate: -12
> Sep 30 10:29:36 debian-pc gnome-shell[1707]: nouveau: ch7: krec 0 pushes 1 bufs 13 relocs 0

This also looks maybe bad:

> Sep 30 10:44:10 debian-pc kernel: [ 2395.486040] nouveau 0000:01:00.0: fb: trapped read at 00473a4200 on channel 3 [1fa20000 Xorg[1558]] engine 00 [PGRAPH] client 0a [TEXTURE] subclient 00 [] reason 00000002 [PAGE_NOT_PRESENT]
> Sep 30 10:44:10 debian-pc kernel: [ 2395.493226] nouveau 0000:01:00.0: fb: trapped read at 0047913d00 on channel 3 [1fa20000 Xorg[1558]] engine 00 [PGRAPH] client 0a [TEXTURE] subclient 00 [] reason 00000002 [PAGE_NOT_PRESENT]

which I think indicates a bug in the nouveau kernel-side driver? But I
might be wrong.

> Sep 30 10:30:59 debian-pc gnome-shell[1707]: JS ERROR: TypeError: this._dialog is null#012_onFocusChanged at resource:///org/gnome/shell/ui/closeDialog.js:135:9#012reset at resource:///org/gnome/shell/ui/viewSelector.js:452:26#012show at resource:///org/gnome/shell/ui/viewSelector.js:275:14#012_animateVisible at resource:///org/gnome/shell/ui/overview.js:580:27#012show at resource:///org/gnome/shell/ui/overview.js:566:14#012_onShowAppsButtonToggled@/usr/share/gnome-shell/extensions/dash-to-dock at micxgx.gmail.com/docking.js:1908:31

It's probably best if you disable extensions like dash-to-dock while
testing this.

    smcv