[Libdlo] GDM black screen / user and count meaning

[Bernie Thompson]

Hi Alexander,

On Sun, Nov 7, 2010 at 4:04 AM, Alexander Todorov <atodorov at otb.bg> wrote:
> 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.

That behavior is unlikely to do with udlfb counting clients with the
framebuffer open (so it can know when the last client has released).

But it does seem like someone is errantly blanking the screen, or the
original modeset failed.  Since it's intermittent, some kind of race.

Unfortunately, I don't have udlfb printing anything to the logs in
dlfb_ops_blank(), or else I'd ask you to check dmesg if someone was
errantly blanking the screen in that case.  If you wanted to add a
dl_notice in that function, you could get more clues.

But another way -- when the problem happens again, we can you try writing 0 to

/sys/class/graphics/fb1/blank

(for the appropriate framebufer fbX)

And see if the screen comes back?  If it does, that would confirm the
blanking theory. Then we'd need to track down who's doing it.

Thanks,
Bernie