Greg Klanderman
2020-Apr-29 17:52 UTC
[LightDM] lightdm goes into tight loop trying to create greeter sessions and fills up logs
>>>>> 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.
Adam Nielsen
2020-Apr-29 23:32 UTC
[LightDM] lightdm goes into tight loop trying to create greeter sessions and fills up logs
> 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.I can't see any X logs for the successful sessions, only one X log where it complains that there's no display device and terminates, which causes LightDM to try to restart X, which leads to the loop you mentioned.> 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.I think I can see this in the logs, and it looks like seat-1 logs out and back in once, successfully.> 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.It looks like something is triggering LightDM to run again on seat-1. This itself isn't a problem, as you can run `dm-tool switch-to-greeter` to start multiple sessions on the same seat (they each start on a different VT and you can switch between them like any other VTs). I am wondering whether something is causing this to happen in your case? What happens if you use dmtool like this to start another session, do you get another one running on that seat, or does it trigger a similar loop? I presume you have configured the seats manually in the X config files. I am wondering why it is trying a whole bunch of display drivers (ati, amdgpu, modesetting, vesa, etc, etc.) before complaining that it can't find a valid display. This normally only happens if you haven't specified a device in xorg.conf. It's telling you to specify the BusID in xorg.conf but if you've manually configured the seats I would've expected you to already have done this. Cheers, Adam.