device: Ensure we have sysfs path before comparing.

[coling]

In some cases we do not have a udev device when setting up a unit
(certainly the code gracefully handles this). However, we do
then go on to compare the path via path_equal which will assert
if a null value is passed in.

See https://bugs.mageia.org/show_bug.cgi?id=17766

Not sure if this is the correct fix, but it avoids the crash

[evverx]

#7  0x000055fd15d0c28b in mount_load_proc_self_mountinfo (m=m@entry=0x55fd15f9a320, set_flags=set_flags@entry=true) at src/core/mount.c:1537

Seems like #2730 (comment)

#2730 (comment)

That said this looks a bit weird that a side effect of unit_add_dependency_by_name(u, ...) is to invalidate 'u'. Note sure that all callers are prepared to that...

[keszybz]

The change looks "obviously correct", so I merged the commit. I took the liberty though to change sysfs to dev in the condition, it is equivalent, but shows the intent more clearly for me.

[ghost]

Intermittently, I am getting a lot of time out errors, generated by Conky - thus:

Failed to retrieve unit: Connection timed out
Failed to get properties: Connection timed out
Failed to retrieve unit: Connection timed out
Failed to get properties: Connection timed out
Failed to retrieve unit: Connection timed out
Failed to get properties: Connection timed out
Failed to retrieve unit: Connection timed out
Failed to get properties: Connection timed out
Failed to retrieve unit: Connection timed out
Failed to get properties: Connection timed out
Failed to retrieve unit: Connection timed out
Failed to get properties: Connection timed out
Failed to retrieve unit: Connection timed out
Failed to get properties: Connection timed out
Failed to retrieve unit: Connection timed out
Failed to get properties: Connection timed out
Failed to retrieve unit: Connection timed out
Failed to get properties: Connection timed out

Should I open a new issue?

Mint 18.2 x64 Cinnamon

[keszybz]

Yes, please open a new issue.