Dear Linux folks,
On a Dell Precision 3540/0M14W7 with Debian sid/unstable restoring the
keyboard backlight takes over 100 ms according to `systemd-analyze
critical-chain` [1].
```
$ systemd-analyze critical-chain
[…]
└─sysinit.target @887ms
└─systemd-backlight@leds:dell::kbd_backlight.service
@1.295s +114ms
└─system-systemd\x2dbacklight.slice @1.294s
└─system.slice @291ms
└─-.slice @291ms
```
I have to run the program [2] under strace to know for sure, that the
delay is caused by accessing the backlight device. Unfortunately, the
device is already in use by somebody else, so debugging is not easy.
Maybe you have some hint, how to approach analysis from the Linux kernel
side.
Kind regards,
Paul
[1]: https://github.com/systemd/systemd/issues/17885
[2]:
https://github.com/systemd/systemd/blob/5acd143259068c8959d7823b178ffbca3269db30/src/backlight/backlight.c
