lightdm crashes and cannot start graphical session

[yuwata]

Submission type

• Bug report

systemd version the issue has been seen with

f62c9e5 (#6099). Its parent f9ce1a4 works fine.

Used distribution

fedora 26 x86_64

In case of bug report: Expected behaviour you didn't see

lightdm works fine and user can login graphically.

In case of bug report: Unexpected behaviour you saw

lightdm starts but no keyboard input is accepted, mouse cursor is not shown does not move. So, I cannot change console neither shutdown system by mouse.

In case of bug report: Steps to reproduce the problem

Boot the system with lightdm.

[yuwata]

I am not sure, but I guess the commit eca2995 (#6210) cause this problem.

[yuwata]

Sorry the commit is not related. This bug is caused by f62c9e5 (#6099). Its parent f9ce1a4 works fine.

[whot]

do you have any logs from lightdm that could hint at what's going on here?

[yuwata]

@whot Unfortunately, all lightdm related log files are size 0. I guess that logs and journal are not flushed to disk because system crashes soon after lightdm starts.
Do you have any idea to get logs?

[hramrach]

You can also bisect the commits of pr #6099 to get an idea what change broke lightdm. Personally I am not aware of any change visible outside udev that would happen unless you add custom configuration.

Also what version of lightdm do you use? lightdm 1.22.0 works for me even with the patched systemd.

[yuwata]

@hramrach I've bisected the commits of PR #6099. The result is the following:

• 1b83323 Use same script to build key list in Makefile and meson: OK
• c6dce24 hwdb: support pressing buttons on a keyboard: OK
• 3ee4e61 hwdb: fix help text in 60-keyboard.hwdb: OK
• 38887d1 rules: move input_id rule to a separate file: CRASH!!!

Note that I do not customize udev configuration.

[yuwata]

The current master HEAD 980cb55 with reverting 38887d1 works fine.

[yuwata]

Note that 38887d1 does not break CUI sessions, that is, booting systemd with the kernel command option 3 works fine.

[hramrach]

Presumably what can happen is that some keyboard properties are added to non-keyboard evdev device handled by atkbd driver (does such thing exist?), lightdm assumes the device is a keyboard based on that property and crashes because of that. There is nothing else that should change as a result of 38887d1

[yuwata]

@hramrach Do you have any idea to check whether such thing actually happens or not?

[hramrach]

Yes, if you build with meson you will not get 60-input-id.rules

Which would mean lightdm crashes without input devices.

[yuwata]

Fixed by #6222. Thank you.