[systemd-devel] Ordering after udev applied rules to `/dev/dri/card0`

[Paul Menzel]

Dear Lennart,


Am 01.04.20 um 17:10 schrieb Lennart Poettering:
> On Mi, 01.04.20 14:23, Paul Menzel (pmenzel+systemd-devel at molgen.mpg.de) wrote:
> 
>>>> After=device should work. udev announces device after all rules have
>>>> been processed.
>>>
>>> After= only orders, but this doesn't pull the device unit into the job
>>> queue. To do that, you need to add Wants= on the device unit as well.
>>
>> Trying this,
>>
>>      After=dev-dri-card0.device
>>      Wants=dev-dri-card0.device
>>
>> the service times out waiting for the device.
>>
>>      $ journalctl -a
>>      […]
>>      Apr 01 14:15:42.672430 kodi systemd[1]: Reached target Multi-User System.
>>      […]
>>      Apr 01 14:17:09.805001 kodi systemd[1]: dev-dri-card0.device: Job dev-dri-card0.device/start timed out.
>>      Apr 01 14:17:09.805839 kodi systemd[1]: Timed out waiting for device /dev/dri/card0.
>>      Apr 01 14:17:09.806464 kodi systemd[1]: dev-dri-card0.device: Job dev-dri-card0.device/start failed with result 'timeout'.
>>      Apr 01 14:17:09.809847 kodi systemd[1]: Starting Weston, a Wayland compositor, as a system service...
>>      […]
>>      $ ls -l /dev/dri/card0
>>      crw-rw---- 1 root video 226, 0 Apr  1 14:15 /dev/dri/card0
> 
> DRM devices are currently not tagged with "systemd", and thus no
> .device units are syntesized for them in systemd. Add a udev rule that
> matches against them and sets the "systemd" tag and they will appear
> in systemd, so that you can order your stuff against it.

That did the trick. In `systemd-analyze critical-chain` the device shows 
up with three seconds. Quite a lot, but unfortunately the Linux drivers 
do not seem to be optimized for speed.

But my problem turned out to be something else. getty at tty1.service and 
Weston on tty1 were apparently conflicting causing the permission denied 
errors, and adding `Conflict=getty at tty1.service` seems to have fixed it.

I created merge/pull request #15307 for adding the tags anyway [1].


Kind regards,

Paul


[1]: https://github.com/systemd/systemd/pull/15307