[Notebook N7x0WU] Random black flickers in gnome-shell Wayland sessions

[lotuspsychje]

Ubuntu 22.04 development branch up to date to latest @ 26/10/2021 kernel 5.13.0-19-generic

While working around on the desktop i'm getting short screen flashes like a screenshot style
i cant reproduce them, they seem to come on random like every few minutes
journal logs dont record anything while they occur

this only happens on wayland, tested a long session on xorg where they dont occur

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: gnome-shell 40.5-1ubuntu2
ProcVersionSignature: Ubuntu 5.13.0-19.19-generic 5.13.14
Uname: Linux 5.13.0-19-generic x86_64
ApportVersion: 2.20.11-0ubuntu70
Architecture: amd64
CasperMD5CheckResult: unknown
CurrentDesktop: ubuntu:GNOME
Date: Tue Oct 26 11:12:30 2021
DisplayManager: gdm3
RelatedPackageVersions: mutter-common 40.5-1ubuntu2
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)
mtime.conffile..etc.xdg.autostart.gnome-shell-overrides-migration.desktop: 2021-10-23T19:12:47.175230

[Daniel van Vugt (vanvugt)]

Thanks for the bug report. Are the flashes light or dark?

Next time it happens, please immediately run:

  journalctl -b0 > journal.txt
  lspci -kv > lspci.txt

and attach the resulting text files here.

[lotuspsychje (lotuspsychje)]

@ Daniel

its a bit hard to say wich colour, as the flashes go so fast, like a fast screenshot
when leaving a journalctl -f open i cant see any errors on the time of the flashes

[Daniel van Vugt (vanvugt)]

Thanks. Please try these fixes separately so we can see which one if any avoids the problem:

------------------------------------------------

1. Edit /etc/default/grub and change:

   GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

   to

   GRUB_CMDLINE_LINUX_DEFAULT="quiet splash i915.enable_psr=0"

2. Run: sudo update-grub

3. Reboot.

------------------------------------------------

1. Edit /etc/environment and add a line:

   MUTTER_DEBUG_ENABLE_ATOMIC_KMS=0

2. Reboot.

------------------------------------------------

[lotuspsychje (lotuspsychje)]

@Daniel i tested both fixes for several hours individualy
but the flashes seem to keep happening

is there some sort of wayland realtime debug command i could try
to see if i can trace on the time its happening, as in journal logs nothing shows?

[Daniel van Vugt (vanvugt)]

Wayland is only a communication protocol between the app and the server. The underlying screen updates are implemented by gnome-shell (via libmutter) using KMS. You can make it log LOTS of information by adding this to /etc/environment:

  MUTTER_DEBUG=kms

If you do that and then record a separate log each time a flash happens:

  journalctl -b0 > anotherflash.txt

then that might be useful.

[lotuspsychje (lotuspsychje)]

i had a screen flash around 10h58

logs in attachment

[Daniel van Vugt (vanvugt)]

The only error I can see around 10:58 is bug 1948589 so maybe we should eliminate that first.

[Daniel van Vugt (vanvugt)]

Please enable both the suggestions in comment #5, and then follow comment #7 again.

[lotuspsychje (lotuspsychje)]

i had a screen flash on 11h39

with:

quiet splash i915.enable_psr=0
MUTTER_DEBUG_ENABLE_ATOMIC_KMS=0
MUTTER_DEBUG=kms

enabled

[lotuspsychje (lotuspsychje)]

i tryed journalctl -f in realtime too with the kms logs running

and when a flash occurs i cant seem to pinpoint errors on the seconds it happens

[Daniel van Vugt (vanvugt)]

Again I can't see any KMS errors but it is suspicious that bug 1948589 occurred around the time you mention. I'm starting to think this isn't a KMS issue at all.

Can you please take a video of the issue using a camera or phone?

[Daniel van Vugt (vanvugt)]

Do you have your background wallpaper set to change automatically? If so then you might see this flash periodically: https://gitlab.gnome.org/GNOME/mutter/-/issues/1882

[lotuspsychje (lotuspsychje)]

The screen record of the glitch

[lotuspsychje (lotuspsychje)]

@Daniel #14

i have 1 wallpaper active, not automaticly changed

[lotuspsychje (lotuspsychje)]

I also tested quiet splash mitigations=off without luck

[Daniel van Vugt (vanvugt)]

Thanks for the video! That "flash" seems to be the whole screen flickering to black. It can happen if the Wayland backend fails to assign a buffer to the screen for a frame. But it can also happen with monitor connection issues that may be hardware or software (kernel) problems. That's less likely on a laptop but not impossible (I've seen it there too).

Let's assume it's a software bug in Mutter's Wayland backend, but I am out of ideas right now other than using 'Ubuntu on Xorg' as a workaround.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Daniel van Vugt (vanvugt)]

I've merged your old bug 1838644 into this one.

[lotuspsychje (lotuspsychje)]

I tried booting with quiet splash intel_idle.max_cstate=4 like my old flickering bug, but no luck the flashes seem to persist

[lotuspsychje (lotuspsychje)]

Not sure if this would be relevant to this bug
but i can seem to reproduce a glitch inside gnomes systemsettings
toggle enable/disable the dock autohiding makes it glitch inside the systemsettings window

[Jimmys (jimmys-dimitrakopoulos)]

https://gitlab.freedesktop.org/drm/intel/-/issues/5569
Could this also be related?
I got this on Xorg as well, so it could be different...

[lotuspsychje (lotuspsychje)]

@ Jimmy #23

thank you for your suggest, your bug looks very interesting
my flickering however is really bad, results in a full screen unworkable state
but it looks a lot like yours too

i had this bug on ubuntu 18.04 & 22.04, on 20.04 with kernel 5.4 series it did not occur for me