SDDM spuriously auto-restarts when starting Plasma Wayland session

[roccodev]

I'm using SDDM to launch a Plasma Wayland session on Fedora 40. I'm using the NVIDIA proprietary driver (550.67), if it matters.

Many times it works fine, but sometimes starting the KDE session takes longer than expected (after login, around 30 seconds). When this happens, after 2 minutes or so, SDDM restarts, switches to tty1, but does not log me out. I can switch to tty2 and get back to the logged in session just fine. This isn't a dealbreaker, though it is annoying.

I've also noticed that when the issue occurs, shutting down (from the Plasma menu) just logs me out of tty2, I then need to shutdown from the new SDDM instance on tty1.

Here's the output of journalctl -u sddm when the issue occurs (SDDM exits with Auth: sddm-helper exited with 2):

apr 27 16:41:09 cavanich systemd[1]: Started sddm.service - Simple Desktop Display Manager.
apr 27 16:41:09 cavanich sddm-helper[1866]: Detected locale "C" with character encoding "ANSI_X3.4-1968", which is not UTF-8.
                                            Qt depends on a UTF-8 locale, and has switched to "C.UTF-8" instead.
                                            If this causes problems, reconfigure your locale. See the locale(1) manual
                                            for more information.
apr 27 16:41:09 cavanich sddm-helper[1866]: pam_unix(sddm-greeter:session): session opened for user sddm(uid=984) by (uid=0)
apr 27 16:41:54 cavanich sddm-helper[2091]: Detected locale "C" with character encoding "ANSI_X3.4-1968", which is not UTF-8.
                                            Qt depends on a UTF-8 locale, and has switched to "C.UTF-8" instead.
                                            If this causes problems, reconfigure your locale. See the locale(1) manual
                                            for more information.
apr 27 16:41:54 cavanich sddm-helper[2091]: gkr-pam: unable to locate daemon control file
apr 27 16:41:54 cavanich sddm-helper[2091]: gkr-pam: stashed password to try later in open session
apr 27 16:41:54 cavanich sddm-helper[2091]: pam_kwallet5(sddm:auth): pam_kwallet5: pam_sm_authenticate
apr 27 16:41:54 cavanich sddm-helper[2091]: pam_kwallet5(sddm:setcred): pam_kwallet5: pam_sm_setcred
apr 27 16:41:54 cavanich sddm-helper[2091]: pam_unix(sddm:session): session opened for user rocco(uid=1000) by rocco(uid=0)
apr 27 16:41:54 cavanich sddm-helper[2091]: gkr-pam: gnome-keyring-daemon started properly and unlocked keyring
apr 27 16:41:54 cavanich sddm-helper[2091]: pam_kwallet5(sddm:session): pam_kwallet5: pam_sm_open_session
apr 27 16:41:54 cavanich sddm-helper[2091]: Starting Wayland user session: "/etc/sddm/wayland-session" "/usr/libexec/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland"
apr 27 16:43:24 cavanich sddm[1854]: Auth: sddm-helper exited with 2
apr 27 16:43:24 cavanich sddm-helper[4149]: Detected locale "C" with character encoding "ANSI_X3.4-1968", which is not UTF-8.
                                            Qt depends on a UTF-8 locale, and has switched to "C.UTF-8" instead.
                                            If this causes problems, reconfigure your locale. See the locale(1) manual
                                            for more information.
apr 27 16:43:24 cavanich sddm-helper[4149]: pam_unix(sddm-greeter:session): session opened for user sddm(uid=984) by (uid=0)

while this is the log from a working attempt:

apr 26 16:02:11 cavanich systemd[1]: Started sddm.service - Simple Desktop Display Manager.
apr 26 16:02:11 cavanich sddm-helper[1878]: Detected locale "C" with character encoding "ANSI_X3.4-1968", which is not UTF-8.
                                            Qt depends on a UTF-8 locale, and has switched to "C.UTF-8" instead.
                                            If this causes problems, reconfigure your locale. See the locale(1) manual
                                            for more information.
apr 26 16:02:11 cavanich sddm-helper[1878]: pam_unix(sddm-greeter:session): session opened for user sddm(uid=984) by (uid=0)
apr 26 16:02:20 cavanich sddm-helper[2091]: Detected locale "C" with character encoding "ANSI_X3.4-1968", which is not UTF-8.
                                            Qt depends on a UTF-8 locale, and has switched to "C.UTF-8" instead.
                                            If this causes problems, reconfigure your locale. See the locale(1) manual
                                            for more information.
apr 26 16:02:20 cavanich sddm-helper[2091]: gkr-pam: unable to locate daemon control file
apr 26 16:02:20 cavanich sddm-helper[2091]: gkr-pam: stashed password to try later in open session
apr 26 16:02:20 cavanich sddm-helper[2091]: pam_kwallet5(sddm:auth): pam_kwallet5: pam_sm_authenticate
apr 26 16:02:20 cavanich sddm-helper[2091]: pam_kwallet5(sddm:setcred): pam_kwallet5: pam_sm_setcred
apr 26 16:02:21 cavanich sddm-helper[2091]: pam_unix(sddm:session): session opened for user rocco(uid=1000) by rocco(uid=0)
apr 26 16:02:21 cavanich sddm-helper[2091]: gkr-pam: gnome-keyring-daemon started properly and unlocked keyring
apr 26 16:02:21 cavanich sddm-helper[2091]: pam_kwallet5(sddm:session): pam_kwallet5: pam_sm_open_session
apr 26 16:02:21 cavanich sddm-helper[2091]: Starting Wayland user session: "/etc/sddm/wayland-session" "/usr/libexec/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland"

If you know any log files that could be useful, I'd be happy to share them.

[WerySkok]

Also got the same problem after enabling custom sound scheme in Plasma with system-ready or system-shutdown sounds (I saw these names in naming spec, that's why I gave them a try, but they didn't work). After switching back to default sound scheme, I got rid of this issue

[roccodev]

Interesting, I did notice that with Plasma 6 it began to play a sound during login. I'm also running some Pipewire modules you don't see on every setup (namely pulse tunnels, zeroconf discover) which may delay audio activation for a while.

I'll try disabling the sound (System Settings > Notifications > Configure Application Settings > Plasma Workspace > Login) and report back.