After reinstalling my notebook (ThinkPad X201) from CD with a new SSD, I encountered random stops of the graphical system. I could still use open windows, but the window bars were not usable anymore. I could not close them or open new ones. I could switch to a console with Strg-Alt-Fx though. dmesg tells:
[10875.259009] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
[10875.259018] [drm] capturing error event; look for more information in /debug/dri/0/i915_error_state
[10877.255560] [drm:i915_hangcheck_hung] *ERROR* Hangcheck timer elapsed... GPU hung
[10877.255775] [drm:i915_reset] *ERROR* GPU hanging too fast, declaring wedged!
[10877.255779] [drm:i915_reset] *ERROR* Failed to reset chip.
I never had this error before, so I figured it is either connected to the SSD or a kernel update that I installed on the way. After deactivating an energy saving feature of the graphic chip, the problem does not occur anymore:
- Add i915.i915_enable_rc6=0 to /etc/default/grub at GRUB_CMDLINE_LINUX_DEFAULT=
- run update-grub
UPDATE 01/31: After several days without hangs, they came back. dmesg provides the same output messages. Grub still has the RC6 energy saving feature deactivated. I noticed that the problem is only occuring when I have browsers (Chromium and Firefox) open with websites showing Flash videos. I deactivated hardware acceleration in both browsers and see what happens.
UPDATE 02/03: Again, it happened. This time, there was no Flash involved. I am using the Mono-based Tomboy program for making notes. The display driver hangs reproducible when I open one note...
UPDATE 02/07: I switched off hardware acceleration within Flash as well. I had one week without crashes - until now: The crash happened again when opening a PDF file in evince. I noticed that the window decoration (title bar etc.) vanishes after every crash. This decoration is rendered by compiz, which uses 3D rendering with hardware acceleration. Hardware acceleration cannot be turned off for compiz, but it is possible to use metacity instead of compiz. Metacity does not make use of the 3D stuff at all. It can be enabled from the command line by typing "metacity --replace", but this can have some side effects. It is better to choose "Ubuntu 2D" at the login screen: There is a dropdown selection if you click on the Ubuntu logo next to the login name. Let's see if it works now.
UPDATE 03/02: There are no crashes any more with Ubuntu 2D. The only thing that occasionally disappears is the left sidebar. It can easily be recovered by "metacity --replace".