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

[Simon McVittie]

On Tue, 29 Sep 2020 at 22:29:29 -0300, Leandro Cunha wrote:
> > * Is this a new installation, or have you been using this hardware with
> >   Linux for a while? If you've been using it previously, have you had
> >   other graphics- or freeze-related issues with it?
> 
> Only in version 3.36.3 onwards, if I'm not mistaken. But it is the first time.

Presumably you've also been upgrading other packages, like the kernel
and graphics drivers. Please try installing the kernel from Debian 10
(linux-image-4.19.0-11-amd64) and booting into that - you can have
multiple kernels available on the same system, so this is a lot easier
than switching between versions of user-space packages, which is why
I'm suggesting to try it first. Then see whether you still get this same
bug with the older kernel.

If you still see the bug, another thing to try would be to confirm which
user-space packages cause the regression. The best way to do this is
probably to set up a temporary parallel installation of Debian 10 on the
same hardware (maybe on an external USB disk if you can get a suitable one),
and gradually upgrade it towards current testing:

* reduce the size of a partition enough to fit a new partition for
  Debian 10, or use a USB disk (you'll need at least 10G for an
  installation with just gnome-session and its dependencies, 20G is safer)
* install Debian 10 with at least the gnome-session package
  (if you have enough space, using the GNOME desktop task in the installer
  will be easiest; if you don't have much space, just install gnome-session)
* upgrade to 3.34.4-1 from:
  deb [check-valid-until=no] https://snapshot.debian.org/archive/debian/20200226T030551Z sid main
* try to reproduce the bug
* upgrade to 3.36.2-1 from:
  deb [check-valid-until=no] https://snapshot.debian.org/archive/debian/20200501T154658Z sid main
* try to reproduce the bug
* upgrade to 3.36.3-1 from:
  deb [check-valid-until=no] https://snapshot.debian.org/archive/debian/20200604T025809Z sid main
* try to reproduce the bug
* if none of those show the bug, try upgrading to the latest version from
  testing

If your guess about 3.36.3 is right, then this must have been triggered by
something that changed between 3.36.2 and 3.36.3, and that's a much smaller
change to examine.

When doing that, it would be helpful if you can upgrade only gnome-shell
and the packages that it requires - try to avoid upgrading the kernel or
the Mesa graphics drivers, to reduce the number of things you're varying.

If none of that makes the bug appear, try the same process with the
Mesa graphics drivers: libgles2, libgl1, libglx-mesa0, libgl1-mesa-dri,
libegl1 and libegl-mesa0.

The apt logs in /var/log/apt will tell us exactly what was upgraded in the
apt transaction that triggered the regression.

> > What do you mean by "restored the original system settings"?
> 
> I delete the configuration file.

Which one?

> > What do you mean by "it would only start if [...]"? GNOME would only
> > start if you did that? The laptop would only boot up if you did that?
> > Something else?
> 
> The answer is yes. Somehow you can't log in to a section.

OK, this might give us more useful information: if you can't log
in, but the computer doesn't freeze and you are able to work around
it without rebooting, then we might be able to get a log with more
information. Please could you try this:

* make a note of the time: time before reproducing bug
* reproduce the bug
* recover by rebooting
* make a note of the time again: time after rebooting
* try to log in (which you say will fail)
* delete the configuration file
* note the time again: time before login
* log in successfully
* note the time again when login has finished: time after login
* send the log from that whole period, and the times that you noted

That will help to correlate log messages with what you observe.

> > I don't think we can necessarily treat GNOME freezing on
> > more-than-10-year-old hardware as release-critical
> 
> Gnome works well on this hardware that was on the market for years,
> devices from 2011 and 2012 were still sold with this hardware is the
> case with mine.

Obviously we'd like it to continue to work, but hardware-specific
failures are difficult (especially for people who don't have the hardware
in front of them). If we treated every hardware-specific failure as
a release-critical bug that prevented the next Debian release from
happening, then we'd never be able to make a new release, because there's
always at least one device that regresses.

I've configured my (Intel-based) laptop to have the animated background to
see whether I can reproduce anything similar, but it's had this
configuration for 24 hours now without problems.

    smcv