** Description changed:
+ [ Impact ]
+
+ Since around about kernel 6.9, gdm3 fails to wait for a proper DRM
+ kernel driver to load. So if your kernel driver is particularly slow
+ (like dual AMD GPU systems in this case) then the login screen is
+ displayed using simpledrm and software rendering. That wouldn't be a
+ problem by itself except that a second or two later, the kernel
+ "hotplugs" the old graphics card out and replaces it with the proper
+ one. Mutter/GNOME currently cannot handle GPU hotplugging well and will
+ usually freeze.
+
+ [ Test Plan ]
+
+ Ideally this should be executed by someone who experienced the issue in
+ the first place (dual AMD GPU machines). Otherwise the login process
+ should just be verified for robustness and the steps are the same:
+
+ 1. Reboot the machine.
+ 2. Expect the login screen to appear.
+ 3. Log in immediately.
+ 4. Expect the desktop appears.
+ 5. Press Super or Super+A and expect the screen to animate.
+ 6. Reboot the machine again.
+ 7. Expect the login screen to appear.
+ 8. Wait at least 20 seconds before logging in.
+ 9. Expect the desktop appears.
+ 10. Press Super or Super+A and expect the screen to animate.
+
+ [ Where problems could occur ]
+
+ Since the loop gating the start of the login screen itself is being
+ modified, there is a risk that some part of the login experience could
+ become broken or delayed.
+
+ [ Other Info (original report) ]
+
After upgrading to Ubuntu 25.04 my laptop fails to properly start the
gnome login shell. During boot I see the graphical splash screen as
expected, but once the login screen should show, one of the below things
happen:
- Nothing, I keep seeing the boot splash screen.
- The login screen is rendered, but only a single frame. Moving the mouse or
pressing keys has no effect.
- The login screen is rendered and the mouse cursor moves, but none of the
widgets respond to clicks or pressing keys.
To recover, I have to Ctrl+Alt+F2 and login on the terminal interface.
Then I can do a `sudo systemctl restart user-120.slice` after which I
can go back to the GUI login screen and it works.
ProblemType: Bug
DistroRelease: Ubuntu 25.04
Package: gnome-shell 48.0-1ubuntu1
ProcVersionSignature: Ubuntu 6.14.0-22.22-generic 6.14.5
Uname: Linux 6.14.0-22-generic x86_64
ApportVersion: 2.32.0-0ubuntu5.2
Architecture: amd64
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Thu Jun 26 22:21:40 2025
DisplayManager: gdm3
InstallationDate: Installed on 2024-12-25 (183 days ago)
InstallationMedia: Ubuntu 24.10 "Oracular Oriole" - Release amd64 (20241009.4)
RelatedPackageVersions: mutter-common 48.1-1ubuntu3
SourcePackage: gnome-shell
UpgradeStatus: Upgraded to plucky on 2025-06-15 (11 days ago)
** Changed in: gdm3 (Ubuntu Plucky)
Status: Triaged => In Progress
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https://bugs.launchpad.net/bugs/2115451
Title:
Since kernel 6.9, the login screen starts with simpledrm and switches
to amdgpu one second later, causing freezes
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