Cannot start a new session (switch user)

[dreaming-augustin]

On tty7, I can start a regular session (Plasma) normally.

However, I cannot start a parallel session. In KDE, I select "Switch user", confirm it in the dialog overlay,
but then nothing happens and I am back to the current session.
/var/log/sddm.log shows nothing but when I tail the following file, the given 2 lines appear when the bug occurs:

tail -f  /home/user/.local/share/sddm/xorg-session.log
ktp-kded-module: 
QXcbConnection: XCB error: 3 (BadWindow), sequence: 11372, resource id: 10485780, major code: 18 (ChangeProperty), minor code: 0

[dreaming-augustin]

I use X11 / Gentoo / open-rc with sddm 0.17.0.

[dreaming-augustin]

But then, sddm does not log all errors, so it's more difficult to understand what is going on. See:
#770

[raryelcostasouza]

Seems similar to the bug (https://bugzilla.redhat.com/show_bug.cgi?id=1591107) I reported for Fedora 28 Kde Spin. I also had the same problem on Kubuntu 18.04.

[ohallot]

Confirming comment by @raryelcostasouza on Kubuntu 18.04.

Here is the output of "grep sddm /var/log/syslog":

Jun 14 13:50:59 olivier-ntbk sddm[1096]: Adding new display on vt 2 ...
Jun 14 13:50:59 olivier-ntbk sddm[1096]: Loading theme configuration from ""
Jun 14 13:50:59 olivier-ntbk sddm[1096]: Display server starting...
Jun 14 13:50:59 olivier-ntbk sddm[1096]: Running: /usr/bin/X -nolisten tcp -auth /var/run/sddm/{f4e33d1d-567a-428a-ac0e-94c6315ca229} -background none -noreset -displayfd 19 -seat seat0 vt2
Jun 14 13:51:00 olivier-ntbk sddm[1096]: Display server failed to start. Exiting
Jun 14 13:51:01 olivier-ntbk systemd[1]: sddm.service: Main process exited, code=dumped, status=6/ABRT
Jun 14 13:51:01 olivier-ntbk sddm[1096]: kwalletd5: Checking for pam module
Jun 14 13:51:01 olivier-ntbk sddm[1096]: kwalletd5: Got pam-login param
Jun 14 13:51:01 olivier-ntbk sddm[1096]: kwalletd5: Waiting for hash on 15-
Jun 14 13:51:01 olivier-ntbk sddm[1096]: kwalletd5: waitingForEnvironment on: 19
Jun 14 13:51:01 olivier-ntbk sddm[1096]: kwalletd5: client connected
Jun 14 13:51:01 olivier-ntbk sddm[1096]: kwalletd5: client disconnected
Jun 14 13:51:01 olivier-ntbk sddm-helper[1305]: [PAM] Closing session
Jun 14 13:51:01 olivier-ntbk sddm-helper[1305]: [PAM] Ended.
Jun 14 13:51:02 olivier-ntbk systemd[1]: sddm.service: Failed with result 'core-dump'.
Jun 14 13:51:02 olivier-ntbk systemd[1]: sddm.service: Triggering OnFailure= dependencies.
Jun 14 13:51:03 olivier-ntbk systemd[1]: sddm.service: Service hold-off time over, scheduling restart.
Jun 14 13:51:03 olivier-ntbk systemd[1]: sddm.service: Scheduled restart job, restart counter is at 1.
Jun 14 13:51:03 olivier-ntbk sddm[5776]: Initializing...
Jun 14 13:51:03 olivier-ntbk sddm[5776]: Logind interface found
Jun 14 13:51:03 olivier-ntbk sddm[5776]: Starting...
Jun 14 13:51:03 olivier-ntbk sddm[5776]: Adding new display on vt 1 ...
Jun 14 13:51:03 olivier-ntbk sddm[5776]: Loading theme configuration from ""
Jun 14 13:51:03 olivier-ntbk sddm[5776]: Display server starting...
Jun 14 13:51:03 olivier-ntbk sddm[5776]: Running: /usr/bin/X -nolisten tcp -auth /var/run/sddm/{cd61689e-ded8-4d1d-8129-a273b84689d1} -background none -noreset -displayfd 18 -seat seat0 vt1

You'll notice that sddm or X tries to start a session in VT2 but fails. Then it restarts in VT1 from scratch. The existing session in VT1 is killed, and sddm manages to awake at VT1.

The bug prevents opening more than one session in the machine.

Some extra info: Dell Vostro 3560, 8GB mem, 500GB SSD (samsung), Kubuntu 18.4 installed from scratch.

[raryelcostasouza]

I just tried downgrading the sddm package on Fedora 28 to the version 0.15.0-1.fc27.x86_64.rpm (https://koji.fedoraproject.org/koji/buildinfo?buildID=965774)... and now the user switching works fine.

[raryelcostasouza]

In Kubuntu 18.04 I tried reverting to the default version for artful (0.14.0-4ubuntu1 https://packages.ubuntu.com/artful/sddm) and the also to the debian version (0.15.0-1 https://snapshot.debian.org/package/sddm/0.15.0-1/) but no success... the problem happens as usual...

[xardasjhh]

Just in case that somebody else looks for a solution... I had a similar bug with Kubuntu 18.04, the switch user function also failed to open a session at VT2 (same output in /var/log/syslog). But in contrast to your description it just logged me out.

In my case I had an active Nouveau and Intel driver. After I blacklisted the Nouveau like here https://askubuntu.com/questions/841876/how-to-disable-nouveau-kernel-driver, everything worked fine again.

[ohallot]

I second @xardasjhh workaround. In my case I blacklisted the radeon driver.

So, follow blacklisting instructions indicated by @xardasjhh but change "nouveau" to "radeon" if it is the case.

Looks like sddm don't like laptops with dual graphic chips.

[ohallot]

Adding more information and workaround.

On disabling the radeon driver with a blacklist in modprobe.d/ , I noticed that my laptop was getting hot , around 90 degrees C, even with no CPU load (the laptop has a throttling feature that lowers the clock when temperature is high).

Then I found this page on hybrid graphics laptops: https://help.ubuntu.com/community/HybridGraphics

1. removed the blacklist-radeon.conf I put before in modprobe.d
2. I followed the instructions in section "Enabling vga_switcheroo " in full. No need to go further. AFAIK this will only enable the kernel to handle the radeon chip and prevent sddm to crash
3. Reboot laptop to let the kernel handle

I hope this helps to narrow the issue

[int-ua]

Disabling radeon driver is a subpar solution IMO. I had everything working perfectly on 4.15 kernel but it started failing after upgrade to 5.0. I've tested it and the only thing that leads to this failure is booting into a different kernel, here is a relevant report for Kubuntu: https://bugs.launchpad.net/ubuntu/+source/linux-signed-hwe/+bug/1845924

[arthurtse]

Confirming @ohallot on Kubuntu 20.04 with Lenovo IdeaPad 320s-13IKB. However this bug doesn't happen when I try to reproduce it with the Kubuntu live CD. I initially observed it after I installed Kubuntu and performed a dist-upgrade. So perhaps it was introduced in some update.

[bonkmaykrQ]

Confirmed that this bug still occurs on Arch Linux with KDE Plasma 5 and Linux kernel version 5 on the HP Envy x360 Convertible

Sys info page:

[ohallot]

Latest SDDM release (0.19.0-2ubuntu2.3) seems to have fixed the issue.

sddm (0.19.0-2ubuntu2.3) jammy; urgency=medium

• Patch Xsetup script to use bash (LP: #2009074)
  • Allows previous patch to actually run as it
    requires arrays