[Libdlo] GDM black screen / user and count meaning

[Alexander Todorov]

Hi all,
from time to time I have the issue that when in multiseat configuration GDM will 
start but show black screen. All log and exit codes from the gdmdynamic commands 
don't show any errors.


In udlbf.c there's the following comment:
     889 /*
     890  * It's common for several clients to have framebuffer open simultaneously.
     891  * e.g. both fbcon and X. Makes things interesting.
     892  * Assumes caller is holding info->lock (for open and release at least)
     893  */

This applies to  dlfb_ops_open() and dlfb_ops_release() functions.

What I think might be happening is that when Xorg starts something is holding 
the lock so that the screen goes black instead of showing the login screen. 
After 10 minutes the poweroff/screen saver kicks in and after that the black 
screen can be used again - i.e. it shows the GDM login screen after screensaver 
is cancelled.

What is the meaning of user and fb_count variables in the:

dl_warn("released /dev/fb%d user=%d count=%d\n", info->node, user, dev->fb_count);

In the above mentioned functions?

I'm trying to understand how this works and why does it break sometimes.

Regards,
Alexander.