https://bugs.freedesktop.org/show_bug.cgi?id=99275
--- Comment #26 from Reimar Imhof tuxuser@quantentunnel.de --- According comment #15: Things are properly tested.
Together with comment #24 there is a render bug in kernel 4.8 that shows up at 100% cpu load. With kernel 4.9 this same bug shows up at 0% / idle cpu load.
With af79ad2b1f337a00aa150b993635b10bc68dc842 Merge branch 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip it changed from "bug shows at 100% load" to "bug shows at 0% load". And the change is something about the scheduler. To me this seems likely.
In summery the word "regression" might be wrong.