Screen unlocked after resume, black flickering

[Alex]

I have been experiencing an issue only since a week or so, which I have reportedly also heard from a colleague of mine (2018 Dell XPS 13) since much longer.
My hardware is a Lenovo Thinkpad L480 with i5-8250u.

When using stock ubuntu 18.04.1, sometimes and sporadically (1 out of 3 or so) after resuming from suspend, the screen would not be locked and flicker, switching between a fully black screen and the previously (before going to standby) displayed content, which I regard as a security issue. The GUI is not responsive, however I can workaround using ctrl-alt-F1 and login using my password to "semi"-restore functionality. The flickering is then gone, but e.g. the dock doesn't respond correctly and my notifications are missing, until I restart gnome-shell. This then leaves me with a fully functional system again, which is why I have not regarded my issue the same as other bug reports, which report a system freeze.

I have tried using gnome-session instead of ubuntu-session for the past day as of writing this report and have NOT yet experienced the issue again, so I assume it has something to do with ubuntu's theme or alike.

Please provide information which log files could be helpful and I am going to try and reproduce the issue on ubuntu-session.
---
ProblemType: Bug
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
DisplayManager: gdm3
DistroRelease: Ubuntu 18.04
InstallationDate: Installed on 2019-01-03 (20 days ago)
InstallationMedia: Ubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
Package: gnome-shell 3.28.3-0ubuntu0.18.04.4
PackageArchitecture: amd64
ProcVersionSignature: Ubuntu 4.15.0-43.46-generic 4.15.18
Tags: bionic
Uname: Linux 4.15.0-43-generic x86_64
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo
_MarkForUpload: True

[Daniel van Vugt (vanvugt)]

Please:

1. Run: apport-collect 1813139
   to automatically send information about the system.

2. Take a video of the problem if you can.

[Daniel van Vugt (vanvugt)]

Ah, maybe you haven't really unlocked...

Please try the proposed fix in bug 1769383.

Please also try re-locking (Super+L) and unlocking again (bug 1800475).

[Alex (darthead)]

apport information

[Alex (darthead)]

apport information

[Alex (darthead)]

apport information

[Alex (darthead)]

apport information

[Alex (darthead)]

I have now tried using the Adwaita theme with ubuntu-session and could still reproduce the behaviour. Again, it doesn't happen (didn't happen yet) with gnome-session.

Locking and unlocking does work similarly to ctrl-alt-F1, even better: the dock isn't glitched when using it. However, e.g. my notification icons are still gone when returning to the desktop.

[Alex (darthead)]

To clarify: This behaviour occurs after opening the lid of my notebook, which means I haven't actually unlocked the device. Upon opening, it greets me with the previously displayed content with intermittent black flickering.

However, when going to login screen (ctrl-alt-F1) or lockscreen (super+L) I can unlock and make the GUI responsive again.

[Daniel van Vugt (vanvugt)]

Please try this proposed fix (from bug 1769383):

https://launchpad.net/ubuntu/+source/gnome-shell-extension-ubuntu-dock/0.9.1ubuntu18.04.3/+build/16310198/+files/gnome-shell-extension-ubuntu-dock_0.9.1ubuntu18.04.3_all.deb

Also if "Locking and unlocking does work" then this sounds like a duplicate of bug 1800475. Do you suppose that might be accurate?

[Alex (darthead)]

I have now installed the proposed package and will return to report in a few days, if the error didn't occur again.
I feel like the behaviour in my case is a more severe bug, as it shows previously displayed content which is a security concern. However, as the reason and solution are so similar, it might be appropriate to call it a duplicate.

[Alex (darthead)]

So far, I have not experienced the problem again. Thank you for your help!

[Daniel van Vugt (vanvugt)]

OK. I will mark this as a duplicate of bug 1769383 until proven otherwise.