https://bugzilla.kernel.org/show_bug.cgi?id=78221
--- Comment #14 from t3st3r@mail.ru --- Nono, v3.15 (release) is okay on my GPU in regard to this bug. That what makes testing patch tricky.
Bug has been here since unknown. I can tell for sure it plagued all 3.15RCs (maybe earlier versions as well). But between 3.15rc8 and 3.15 release, bunch of last-minute DRM fixes landed (0a4ae727d6aa459247b027387edb6ff99f657792). Except everything else, it corrected this GPU deadlock problem. So v3.15 (the one and the only) does not exposes that bug.
When I gave a try to v3.16rc1, I figured out bug re-appeared. Hence, looked like regression in 3.16RCs.