[SOLVED] SDDM does not start unless GDM has run first

brenns10 · 2017-10-05 05:57:52

Recently, I did a rather large package upgrade (for context, my kernel went from 4.12.5 to 4.13.3). Durnig this upgrade, my SDDM version went from 0.14.0-2 to 0.15.0-2. After rebooting, I found that my display manager would not load, leaving me at a black screen at the end of my boot process. The computer is totally unresponsive, not even letting me switch TTY.

I booted into single user mode, disabled sddm, and started toying around. I installed gdm, simply to have an alternative display manager to try out. Strangely, GDM worked just fine, and after doing "systemctl start gdm" and "systemctl stop gdm", I was able to "systemctl start sddm" without any problem! I installed lightdm nad the GTK greeter, and found that, similar to SDDM, it would not run on boot, but it would run after GDM has been started and stopped!

This feels very much like some sort of graphics driver issue, but it is a bit beyond me at the moment. The laptop is a Thinkpad T450s with Intel graphics:

$ lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation HD Graphics 5500 (rev 09)

If anyone has any ideas, I'd love to hear them!

Last edited by brenns10 (2017-10-06 04:09:53)

jasonwryan · 2017-10-05 06:12:27

Read your journal/log for a failed session...

Moving to NC.

seth · 2017-10-05 08:36:04

Did you try simply starting sddm "later", ie. boot into the multi-user.target, login, wait. wait. wait. start sddm?

brenns10 · 2017-10-06 02:08:04

Sorry for the rather brief post earlier, I was already tired from a a full night of debugging.

Did you try simply starting sddm "later", ie. boot into the multi-user.target, login, wait. wait. wait. start sddm?

I had tried that a couple times indirectly and it didn't help. It seems that only after GDM runs does SDDM or LightDM seem happy running.

Read your journal/log for a failed session...

Looked through several old boots and found the following which occurred if I left the computer up long enough waiting for the DM to show up:

[Oct 5 18:52] DMAR: DRHD: handling fault status reg 2
[  +0.000006] DMAR: [DMA Write] Request device [00:02.0] fault addr c20000 [fault reason 23] Unknown
[  +3.830887] [drm:fw_domains_get [i915]] *ERROR* render: timed out waiting for forcewake ack to clear.
[  +0.050060] [drm:fw_domains_get [i915]] *ERROR* render: timed out waiting for forcewake ack to clear.
[  +0.050027] [drm:fw_domains_get [i915]] *ERROR* render: timed out waiting for forcewake ack to clear.

Looks to be kernel related. I downgraded the kernel back to 4.12.5 and the issue went away! Now I guess the next step is to go kernel changelogs looking for anything that might cause the above. Some cursory googling suggests this might be related, which is linked to this discussion and patch.

brenns10 · 2017-10-06 02:36:24

Downloaded each version of the kernel between 4.12.5 and 4.13.3 on archive.archlinux.org and tested booting into each one:

4.12.5  works!
4.12.6  works!
4.12.7  works!
4.12.8  works!
4.12.10 works!
4.12.12 works!
4.12.13 works!

4.13.1  broken!
4.13.2  broken!
4.13.3  broken!
4.13.4  broken!

Not exactly surprising. Time to dive into the 4.13 changes.

brenns10 · 2017-10-06 04:09:14

After more investigation, it looks like I'm late to the party and ran into this issue. The fix described there:

intel_iommu=off

works for me. Will watch the bug to see if the underlying issue is fixed.

Arch Linux

#1 2017-10-05 05:57:52

[SOLVED] SDDM does not start unless GDM has run first

#2 2017-10-05 06:12:27

Re: [SOLVED] SDDM does not start unless GDM has run first

#3 2017-10-05 08:36:04

Re: [SOLVED] SDDM does not start unless GDM has run first

#4 2017-10-06 02:08:04

Re: [SOLVED] SDDM does not start unless GDM has run first

#5 2017-10-06 02:36:24

Re: [SOLVED] SDDM does not start unless GDM has run first

#6 2017-10-06 04:09:14

Re: [SOLVED] SDDM does not start unless GDM has run first

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