Display freezes randomly - high CPU usage

[Tristan Boureau]

Randomly, system freezes with high CPU usage (cooling fan goes high when the problem happens) since update to Ubuntu 20.04.1 LTS.

Same problem with X11 and Wayland.

Display freezes and keyboard or mouse inputs won't change anything.
Caps and num lock won't react either.

Ctrl+alt+anything doesn't solve the issue.

Only possibility is then to force reboot using power button.

After reboot, I could find in logs :
gnome-shell
libinput error: client bug: timer event6 debounce short: scheduled expiry is in the past (-15ms), your system is too slow

Problem happens in any situation, for example while videoconferencing with any software, or using LibreOffice Writer, sometimes with Firefox.

The only common fact seems to be that Firefox is always opened.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: mutter 3.36.7+git20201123-0.20.04.1
ProcVersionSignature: Ubuntu 5.8.0-38.43~20.04.1-generic 5.8.18
Uname: Linux 5.8.0-38-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.14
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Wed Jan 20 10:27:48 2021
InstallationDate: Installed on 2020-11-15 (65 days ago)
InstallationMedia: Ubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=fr_FR.UTF-8
 SHELL=/bin/bash
SourcePackage: mutter
UpgradeStatus: No upgrade log present (probably fresh install)

[Daniel van Vugt (vanvugt)]

Would you say the problem occurs when entering/leaving fullscreen in Firefox? Sounds like bug 1749779.

[Daniel van Vugt (vanvugt)]

Also, please open the 'Extensions' app and try disabling any extensions you might have installed. We need to check that as a first priority because so many bugs are caused by extensions.

[Tristan Boureau (hackerouvert)]

I never use fullscreen function under Firefox, so the problem is not related to the mentioned bug.

Do you mean Firefox, or gnome-shell extensions ?

[Daniel van Vugt (vanvugt)]

I mean gnome-shell extensions. In your list of apps you will find one called 'Extensions'.

[Tristan Boureau (hackerouvert)]

I have those manually installed extensions :
- hibernate-status@dromi
- <email address hidden>

I disabled them as required, so as to test if problem persists.

In case it does, I will tell you here in a new comment.

In case it solves the issue, I can't tell after how much time we can consider the problem fixed, as it has happened three times some days, and in december it only happened one time in total, it's totally random.
I can just tell that it didn't happen with the two previous LTS releases.
And that it persists after a complete OS re-install.

How should we process in case the problem doesn't happen for weeks ?

[Daniel van Vugt (vanvugt)]

We can often tell exactly what caused a freeze after rebooting and looking at the log of the previous boot where the freeze occurred.

Next time the freeze happens, please reboot and then in a Terminal window run:

  journalctl -b-1 > prevboot.txt

and attach the resulting text file here.

[Tristan Boureau (hackerouvert)]

Problem happened again.
Here enclosed, you will find the result of a journalctl for last boot

[Daniel van Vugt (vanvugt)]

Thanks. I can't see a problem in that log... Next time a freeze happens, please try waiting for 10 seconds, the reboot and again run:

  journalctl -b-1 > prevboot.txt

and attach the resulting text file here.

[Daniel van Vugt (vanvugt)]

In case the freeze is actually some part of the shell or display server crashing, please also follow these instructions:

https://wiki.ubuntu.com/Bugs/Responses#Missing_a_crash_report_or_having_a_.crash_attachment

[Tristan Boureau (hackerouvert)]

Problem happened again, this time using Firefox (last time was while using FreeCAD).
I waited a minute before rebooting (as each time, so as to be sure the system is really frozen).

I have no file under /var/crash, sorry.

[Daniel van Vugt (vanvugt)]

Thanks. Unfortunately the most recent messages in that log show gnome-shell had NOT frozen for more than 0.019 seconds. So that's not the issue...

Please ensure you still don't have any usual extensions enabled like:
- hibernate-status@dromi
- <email address hidden>

Please also confirm which process is using high CPU when the problem happens. To do that you will need to install 'openssh-server' and log in from a different machine, then run 'top'.

[Tristan Boureau (hackerouvert)]

Thanks for your kind help Daniel.
Six weeks ago, I migrated to Debian 10, default install with Gnome and Wayland.
Since then, I didn't encounter any problem working with the same programs.

This bug can be closed, as I won't be able to help finding what the exact issue was.