[LightDM] lightdm goes into tight loop trying to create greeter sessions and fills up logs

[Greg Klanderman]

>>>>> On April 28, 2020 Adam Nielsen <a.nielsen at shikadi.net> wrote:

>> I am seeing lightdm run fine for a couple days, then while there is
>> still an active user session on seat-1, it decides it needs to create
>> a greeter session on seat-1.  That fails repeatedly, with it
>> attempting to create the greeter session 30-50 times per second.  This
>> quickly fills up the log file to many Gb, and uses significant CPU.

> This isn't a LightDM problem.  What is happening is that your machine
> is configured to start a second seat (seat-1), which causes LightDM to
> load as the login handler for that seat.  In order to provide this it
> launches another X instance, which then complaints that it hasn't been
> set up with a display device - perhaps you only have one and it's in
> use by the existing seat.

Hi Adam, thanks for your reply.  Did you look at the logs I posted on
the debian bug report?  After being started, lightdm runs fine on both
seat0 (VT7) and seat-1.  The greeter remains running on seat0 (I am
logged in directly from the VT1 console terminal, where I started X
the old fashioned way) and my son has an active session on seat-1
where he logged in via lightdm/greeter.  About 2-3 *days* later, it
decided that it needed to start a greeter on seat-1, and went into a
tight loop failing repeatedly.  I included the complete lightdm log up
until it starts looping.  Have been through several cycles of this,
and it seems to reliably happen a few days after restarting lightdm.

thanks,
Greg


> To fix the problem, either configure your system to only have one seat,
> or configure X11 with appropriate devices so that it can bring up the
> second seat without error.

> Cheers,
> Adam.