I should also add that based on the mailing list discussion, it seems that this has exposed some overall bad logic in the code, and that while this is a hotfix, it's not a good overall solution. They mentioned revisiting the code for drm-next (which at this point would be 4.5 I think). So the patch should still hold for 4.4, but won't be valid at some point in the not-too-distant future.