Created attachment 100490 [details]
/sys/class/drm/card0/error

I have Ubuntu Trusty (actually Mint based on it), running Mate and Compiz:
uname -a
Linux kolya-laptop 3.13.0-27-generic #50-Ubuntu SMP Thu May 15 18:06:16 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor Graphics Controller (rev 09)

I get this in dmesg from time to time:
[176923.802692] [drm] stuck on render ring
[176923.802696] [drm] GPU crash dump saved to /sys/class/drm/card0/error
[176923.802697] [drm] GPU hangs can indicate a bug anywhere in the entire gfx stack, including userspace.
[176923.802698] [drm] Please file a _new_ bug report on bugs.freedesktop.org against DRI -> DRM/Intel
[176923.802699] [drm] drm/i915 developers can then reassign to the right component if it's not a kernel issue.
[176923.802699] [drm] The gpu crash dump is required to analyze gpu hangs, so please always attach it.

Machine freezes for a bit when this happens. Sometimes some letters on the screen got garbled - i.e. one particular letter on every window gets rendered in broken way.

Error contents attached.

Please let me know if I can provide any other information.

Thanks.