Bug#1011523: systemd-logind: lightdm ignores keyboard input for the first 3 seconds

[Vincent Lefevre <vincent@vinc17.net>]

Control: reassign -1 systemd 251-2

On 2022-05-25 20:43:50 +0200, Yves-Alexis Perez wrote:
> I've quickly tried here and didn't have any issue, but if it's
> hardware- dependent it's likely the reason why neither Michael nor
> me have been able to reproduce (whether gdm3 or lightdm).

I'm reassigning the bug to systemd because after getting annoyed
too many times, I decided to install xdm, and I exactly have the
same issue with it.

I can't try with gdm3 unfortunately because it is uninstallable
due to a buggy strong dependency chain. Anyway:

> I'm not sure it's actually linked to the display manager

That's also what I think, and this would explain why both lightdm
and xdm are affected.

> (rather than systemd itself,

Note that the problem appeared just after the upgrade to systemd 251-2,
and while there was never any issue before, it is now 100% reproducible
after a reboot (but not just after a reboot).

It seems that after the systemd upgrade, the display manager is started
several seconds earlier, which may be related to this problem.

> or maybe something in the X stack), but maybe it might help if you
> could test with another DM (gdm3 or another one) just in case?

See above.

I've also compared the result with my laptop, where I do not have this
issue, and I can see a difference in the systemd-logind logs:

* On my laptop (no issues):

Jun 23 04:29:33 zira systemd-logind[846]: Watching system buttons on /dev/input/event9 (Power Button)
Jun 23 04:29:33 zira systemd-logind[846]: Watching system buttons on /dev/input/event8 (Lid Switch)
Jun 23 04:29:33 zira systemd-logind[846]: Watching system buttons on /dev/input/event7 (Sleep Button)
Jun 23 04:29:33 zira systemd-logind[846]: Watching system buttons on /dev/input/event3 (Apple, Inc Apple Keyboard)
Jun 23 04:29:33 zira systemd-logind[846]: Watching system buttons on /dev/input/event0 (AT Translated Set 2 keyboard)
Jun 23 04:29:33 zira systemd-logind[846]: Watching system buttons on /dev/input/event11 (HP WMI hotkeys)

only 1 second after the boot.

* On my desktop machine, which has the issue:

Jun 24 14:12:02 cventin systemd-logind[607]: Watching system buttons on /dev/input/event0 (Power Button)
Jun 24 14:12:02 cventin systemd-logind[607]: Watching system buttons on /dev/input/event1 (Power Button)
Jun 24 14:12:03 cventin systemd-logind[607]: Watching system buttons on /dev/input/event2 (DELL Dell USB Entry Keyboard)

9 seconds after the boot.

However, this much larger delay doesn't explain this issue,
as shown by an excerpt of the history on this machine:

2018-11-16  4.18.0-2-amd64  systemd 239       2 seconds
2019-01-03  4.18.0-3-amd64  systemd 240       2 seconds
2019-02-19  4.19.0-3-amd64  systemd 240       1 second
2019-02-22  4.19.0-3-amd64  systemd 241       2 seconds
2019-05-09  4.19.0-5-amd64  systemd 241       1 second
2019-05-27  4.19.0-5-amd64  systemd 241       2 seconds
2019-06-19  4.19.0-5-amd64  systemd 241       3 seconds
2019-07-19  4.19.0-5-amd64  systemd 241       3 seconds
2019-08-07  4.19.0-5-amd64  systemd 241       3 seconds
2019-08-19  5.2.0-2-amd64   systemd 241       5 seconds
2019-08-21  5.2.0-2-amd64   systemd 241       5 seconds
2019-08-22  5.2.0-2-amd64   systemd 242       6 seconds
2019-08-30  5.2.0-2-amd64   systemd 242       4 seconds
2019-09-06  5.2.0-2-amd64   systemd 242       5 seconds
2019-09-23  5.2.0-2-amd64   systemd 242       5 seconds
2019-09-30  5.2.0-3-amd64   systemd 242       5 seconds
2019-10-11  5.2.0-3-amd64   systemd 242       5 seconds
2019-10-21  5.3.0-1-amd64   systemd 242       7 seconds
2019-11-04  5.3.0-1-amd64   systemd 242       7 seconds
2019-11-12  5.3.0-2-amd64   systemd 243-5     8 seconds
2019-11-13  5.3.0-2-amd64   systemd 243-5    12 seconds
2019-11-15  5.3.0-2-amd64   systemd 243-6    11 seconds
2019-11-18  5.3.0-2-amd64   systemd 243-7    11 seconds
2019-11-20  5.3.0-2-amd64   systemd 243-8    11 seconds
2019-12-02  5.3.0-2-amd64   systemd 243-9    11 seconds
2019-12-03  5.3.0-2-amd64   systemd 244-3    12 seconds
2019-12-09  5.3.0-3-amd64   systemd 244-3    12 seconds
2020-01-06  5.4.0-1-amd64   systemd 244-3    13 seconds
2020-01-07  5.4.0-2-amd64   systemd 244-3    10 seconds
2020-01-21  5.4.0-3-amd64   systemd 244-3    12 seconds
2020-01-28  5.4.0-3-amd64   systemd 244.1-1  11 seconds
2020-02-10  5.4.0-3-amd64   systemd 244.2-1  11 seconds
2020-02-18  5.4.0-4-amd64   systemd 244.3-1  12 seconds
2020-03-13  5.4.0-4-amd64   systemd 245-2    11 seconds
2020-07-01  5.4.0-4-amd64   systemd 245.6-1  12 seconds
2020-07-17  5.7.0-1-amd64   systemd 245.6-3  11 seconds
2020-08-17  5.7.0-1-amd64   systemd 246.1-1  10 seconds
2020-08-21  5.7.0-1-amd64   systemd 246.2-1  10 seconds
2020-09-08  5.7.0-3-amd64   systemd 246.4-1  12 seconds
2020-09-21  5.8.0-2-amd64   systemd 246.5-1  10 seconds
2020-09-22  5.8.0-2-amd64   systemd 246.6-1  10 seconds
2020-10-13  5.8.0-3-amd64   systemd 246.6-1  12 seconds
2020-10-28  5.9.0-1-amd64   systemd 246.6-2  12 seconds
2020-10-26  5.9.0-3-amd64   systemd 246.6-5  11 seconds
2021-01-06  5.10.0-1-amd64  systemd 247.1-3  10 seconds
2021-01-07  5.10.0-1-amd64  systemd 247.2-4  10 seconds
2021-06-01  5.10.0-7-amd64  systemd 247.3-5  10 seconds
2021-07-22  5.10.0-8-amd64  systemd 247.3-6  10 seconds
2021-08-16  5.10.0-8-amd64  systemd 247.9-1  10 seconds
2021-09-22  5.14.0-1-amd64  systemd 247.9-1   9 seconds
2021-09-29  5.14.0-1-amd64  systemd 247.9-3  10 seconds
2021-10-04  5.14.0-1-amd64  systemd 247.9-4  10 seconds
2021-10-06  5.14.0-2-amd64  systemd 247.9-4  10 seconds
2021-10-20  5.14.0-2-amd64  systemd 249.5-1  11 seconds
2021-11-09  5.14.0-4-amd64  systemd 249.5-2  11 seconds
2021-11-23  5.15.0-1-amd64  systemd 249.7-1  10 seconds
2022-01-12  5.15.0-2-amd64  systemd 250.2-1   9 seconds
2022-01-18  5.15.0-2-amd64  systemd 250.2-3   8 seconds
2022-01-21  5.15.0-3-amd64  systemd 250.3-1   9 seconds
2022-02-09  5.16.0-1-amd64  systemd 250.3-2   9 seconds
2022-03-17  5.16.0-5-amd64  systemd 250.4-1   8 seconds
2022-05-05  5.17.0-1-amd64  systemd 250.4-1   8 seconds
2022-05-13  5.17.0-2-amd64  systemd 250.4-1   8 seconds
2022-05-16  5.17.0-2-amd64  systemd 250.4-1   8 seconds
2022-05-24  5.17.0-2-amd64  systemd 251-2    10 seconds
2022-06-07  5.17.0-2-amd64  systemd 251-2     9 seconds
2022-06-13  5.17.0-3-amd64  systemd 251.2-5  10 seconds
2022-06-20  5.17.0-3-amd64  systemd 251.2-5  10 seconds
2022-06-23  5.18.0-2-amd64  systemd 251.2-5  10 seconds

I recall that the issue suddenly started to occur after the upgrade
to systemd 251-2.

> I don't think there's really code in the display manager to specifically
> handle keyboards, I'd assume it's in the X part, but I might be wrong.

The issue could also be in the X server, e.g. in case of a race condition
whose effects appeared after the upgrade to systemd 251-2.

There are log messages related to the keyboard in /var/log/Xorg.0.log, but
timestamps are relative to some unknown point. So I can't compare with the
systemd logs. This is really silly!

> And it might be possible that the DM is starting “too soon” on your box, but
> delaying likely won't fix the keyboard delay itself, it's just that the UI
> will be available later (maybe it's better for consistency though).

This would be a poor workaround to the real issue. There are
absolutely no reasons why the keyboard wouldn't work earlier
(it is working without any issue in grub).

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)