Comment 71 for bug 1384342

This bug should be fixed on Haswell with linux-3.19 or later, or Ivy Bridge with linux-3.17 or later
(or an earlier version of linux that has incorporated the patch above "...else if (IS_IVYBRIDGE(dev) || IS_HASWELL(dev))...")

If you can still reproduce it after that, then note from dri-devel list:

"If you can reproduce this somehow, please boot with drm.debug=0xe and
attach the complete dmesg up to the WARNING. We seem to loose track of
pageflips under obscure circumstances sometimes. We have more band-aids
queued up, but fixing the underlying issue would be better ofc."

- http://permalink.gmane.org/gmane.comp.video.dri.devel/112025