Bug 596303

Created attachment 416865 [details]
Randr configuration file causing hangs

Description of problem:

I am using RHEL6 on laptop in docking station with external monitor.

Today after opening of partially closed laptop (still in docking station, with monitor attached to docking station, not sleeping - being in screensaver and waiting for password) strange thing happened. Position of laptop-screen to monitor-screen swapped - from laptop left and monitor right to vice versa.

So I entered password to screensaver and click gnome-display-settings applet to change it back. There was some warning telling me there is a probem with monitor settings (I am sorry for not having screenshot). Anyway, I switched position back and - X server hanged.

After logging via ssh and doing reboot -f (shutdown -r now did not work), this hang repeatedly happens every time I log into Gnome with same user. With new user it does not happen.

I tracked the problem down to ~/.config/monitors.xml (and monitors.xml.backup).
Without these files, logging for this particular user works again. Putting these files back makes the problem appear again. I will attach these.

Also, there are such errors in messages:
kernel: INFO: task i915:152 blocked for more than 120 seconds.
kernel: INFO: task Xorg:2641 blocked for more than 120 seconds.
(see attachments for full error messages)

So it seems some situation caused gnome-display-settings to generate possibly invalid configuration, libgnomedesktop RRandr code tries to apply it and Xorg server hangs.

Version-Release number of selected component (if applicable):

gnome-desktop-2.28.2-6.el6.x86_64
xorg-x11-server-Xorg-1.7.6-5.el6.x86_64
xorg-x11-drv-intel-2.11.0-4.el6.x86_64
libXrandr-1.3.0-4.el6.x86_64

How reproducible:

Always on my desktop when using attached monitors.xml

Steps to Reproduce:
1. useradd -m testuser
2. put monitors.xml into /home/testuser/.config/ (owner testuser)
3. try to log in via gdm as this testuser
  
Actual results:

X server hangs, computer gets unusable locally.
Ssh access is possible, but Xorg cannot be killed and even shutdown -r does not work (reboot -f works).

Expected results:

No hangs! Perhaps a warning or sanitization if monitors.xml is really broken.
And if it is broken, it would be nice to find out why it was crippled by gnome-display-settings applet.

Additional info:

RandR code in libgnomedesktop is responsible for handling monitors.xml. It is nicely documented: http://live.gnome.org/RandR