#798317 xserver-xorg-video-radeon: Strange interaction of radeon config, screenshot and x11vnc

Package:
xserver-xorg-video-radeon
Source:
xserver-xorg-video-ati
Description:
X.Org X server -- AMD/ATI Radeon display driver
Submitter:
Luis Mochan
Date:
2015-09-17 18:24:03 UTC
Severity:
normal
#798317#5
Date:
2015-09-08 00:58:27 UTC
From:
To:
For some time I have found a strange behavior in the behavior of my radeon
under X. After a fresh bootstrap I can start an X session without problem,
except that if I make a screen shot it turns out completely black and if I
access my computer by running x11vnc locally and vncviewer remotely, the screen
is also completely black and unusable from the remote location. If I logout and
login again, the behavior doesn't change.

If I uncomment the line
  #       Option  "EXAPixmaps"            "on"
in the configuration file
  /etc/X11/xorg.conf.d/20-radeon.conf
and restart my display manager (lightdm) X tries to run repeatedly and
unsuccesfully. Thus, it seems that option doesn't work with my card. The
strange behavior is the following. When I comment back that line, I recover X
and furthermore, screenshot and magically x11vnc start working normally!

Thus, it seems that something good happens irreversibly after I turn on the
invalid option and then turn it off. Whatever happens, should have happened
normally without me having to perform this magic, accidentaly discovered step.

Please let me know what additional information I can provide that may prove
useful.
#798317#10
Date:
2015-09-08 06:20:24 UTC
From:
To:
[...]

I don't know what the problem is, but FWIW you shouldn't enable Option
"RenderAccel", because RENDER acceleration uses the 3D engine, which
isn't validated on RN100 GPUs. That might explain at least the issue
with Option "EXAPixmaps" enabled.
#798317#15
Date:
2015-09-08 13:47:55 UTC
From:
To:
Dear Michel,
Thanks. I'll try later to disable RenderAccel and test enabling
EXAPixmaps again. I must confess that I copied the configuration
file from somewhere and, without much understanding, commented and
uncommented lines until I the black screen problem was solved, but at
the next boot it came back.
Regards,
Luis
#798317#20
Date:
2015-09-08 16:35:57 UTC
From:
To:
I turned off RenderAccel, turned on EXAPixmaps and
rebooted. Everything seems to work fine now; I got into X and
screenshot captures correctly the screen images and x11vnc displays
the screen correctly.
Thanks,
Luis
#798317#25
Date:
2015-09-09 02:34:20 UTC
From:
To:
Is there still a problem without Option "EXAPixmaps"?
#798317#30
Date:
2015-09-09 02:46:15 UTC
From:
To:
I haven´t rebooted without that option, but it seems it runs faster without it (I turned it off and restarted X).
Regards
#798317#35
Date:
2015-09-09 03:51:22 UTC
From:
To:
The EXAPixmaps option was specifically introduced to be disabled on GPUs
like yours for this reason. :)
#798317#40
Date:
2015-09-16 02:26:28 UTC
From:
To:
Finally I had the opportunity. If I reboot without RenderAccel and
EXAPixmaps, then, again, x11vnc and screenshot produce only a black
rectangle. If I then turn RenderAccel on and restart lightdm the
system starts without problem. If I then turn it off and restart
lightdm again everything is fine, including screenshot and
x11vnc. Could it be some required module that is only loaded when I turn on
RendeerAccel and then remains loaded after I turn it off?
Best regards,
Luis
#798317#45
Date:
2015-09-17 15:30:40 UTC
From:
To:
What if you just restart lightdm without any configuration changes? Does
that make it work properly as well?
#798317#50
Date:
2015-09-17 18:20:48 UTC
From:
To:
It is possible that I made a mistake and that the line I
commented/uncommented above was AccelMethod and not RenderAccel
(otherwise, I couldn't reproduce today what I described above).
No. I just tried. It didn't't work properly until I turned EXAPixmaps on
and then turned it off.

Regards,
Luis