Comment # 1 on bug 1000433 from Takashi Iwai

Hrm, this warning comes from a code path specific to AVIVO ASIC that is older
than DCE6.  I'm not sure whether the GPU hang is directly related with this,
though.

And the warning is WARN_ON_ONCE(), hence it appears only once at each boot.
Maybe that's the reason you saw the stack trace rarely.

I prepared a test radeon KMP containing a debug patch showing the drm error
message instead of kernel warning, but not only once.  Could you give it a try?
 The package is being built at OBS home:tiwai:bnc1000433 repo.  It's for the
latest TW kernel.
   http://download.opensuse.org/repositories/home:/tiwai:/bnc1000433/

Once after installing radeon-kmp and rebuildinig initrd, reboot, then try to
reproduce the bug.  If this code path is relevant, it must happen when you
moving the cursor outside the left-upper corner (0, 0) somehow.