Comment 16 for bug 1795637

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Iain Lane (laney) wrote : Re: No login screen when booting Cosmic

I think the dupe indicated in comment #12 is probably correct.

I didn't manage to make this happen when not using plymouth (removing "splash" from the kernel commandline). I also installed bionic-release's version of plymouth, to eliminate whether or not the patches applied there are bad. The bug still happens with that version, too.

I'll attach some logs. When the bug happens, we get EPERM when calling drmModeObjectSetProperty() and other things:

Oct 09 17:40:46 marshmallow gnome-shell[764]: Failed to apply DRM plane transform 0: Permission denied

and of course GDM can't start up.

It's some kind of race, since apparently (I didn't actually confirm this myself, but others have said so) switching VTs or restarting GDM manually makes it work. The first one isn't that surprising, since GDM is dynamically starting & stopping its greeter when the active VT changes. Also adding a sleep apparently works around the problem - maybe also not surprising if we're waiting for something to relinquish the DRM device.