** Description changed: Regression from Ubuntu 24.04 (Noble). In 24.04, bug #2063143 was fixed by adding systemd-udev-settle.service as a startup dependency of SDDM (package sddm 0.20.0-2ubuntu4.2). This fix is missing in the Ubuntu 26.04 package. - Problem: + 1) Release of Ubuntu: + $ lsb_release -rd + Description: Ubuntu 26.04 LTS + Release: 26.04 - On cold boot, SDDM starts before the AMDGPU DRM driver has finished - initializing. The greeter crashes with HELPER_TTY_ERROR and enters a - rapid restart loop, resulting in a black screen with lit backlight. This - happens on approximately 50-75% of cold boots. + 2) Package version: + $ apt-cache policy sddm + sddm: + Installed: 0.21.0+git20250502.4fe234b-2ubuntu3 + Candidate: 0.21.0+git20250502.4fe234b-2ubuntu3 + Version table: + *** 0.21.0+git20250502.4fe234b-2ubuntu3 500 + 500 http://archive.ubuntu.com/ubuntu resolute/universe amd64 Packages + 100 /var/lib/dpkg/status - System: - - OS: Kubuntu 26.04 (Resolute) - - Kernel: 7.0.0-15-generic - - SDDM: 0.21.0+git20250502.4fe234b-2ubuntu3 - - Mesa: 26.0.3-1ubuntu1 - - GPU: AMD Radeon + 3) Expected to happen: + SDDM should wait for DRM drivers to be ready before starting, as it did in Ubuntu 24.04. - Evidence: + 4) What happened instead: + On cold boot, SDDM starts before the AMDGPU DRM driver has finished initializing. The greeter crashes with HELPER_TTY_ERROR and enters a rapid restart loop, resulting in a black screen with lit backlight. This happens on approximately 50-75% of cold boots. + + Evidence from journalctl (previous boot): + May 09 13:56:13 mr sddm[1938]: Adding new display... + [repeats in a tight loop with HELPER_TTY_ERROR] The 24.04 fix added these lines to sddm.service: After=systemd-udev-settle.service Wants=systemd-udev-settle.service The 26.04 sddm.service does not contain these lines. Verified by inspecting /usr/lib/systemd/system/sddm.service. Workaround: - Adding a systemd override works around the race condition: sudo mkdir -p /etc/systemd/system/sddm.service.d sudo tee /etc/systemd/system/sddm.service.d/udev-settle.conf << 'EOF' [Unit] After=systemd-udev-settle.service Wants=systemd-udev-settle.service EOF sudo systemctl daemon-reload - Expected behavior: - - SDDM should wait for DRM drivers to be ready before starting, as it did - in Ubuntu 24.04. - Related bugs: - #2063143 (24.04, Fix Released) - #2066275 (24.04 SRU) - sddm/sddm#1917 (upstream, still open)
** Tags added: amdgpu kubuntu resolute -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/2152106 Title: SDDM black screen on boot - missing systemd-udev-settle dependency (regression from 24.04) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/sddm/+bug/2152106/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
