Hmm, yes, this was why that hangcheck -> stuck rings markup was in the idle worker. That code had an inherent race condition, just need to find a better means of flagging this failure -- less of a concern as the test is explicitly trying to break the driver.

Created attachment 125520 [details]
IVB-kms_setmode__clone_exclusive_crtc-kern.log

Created attachment 125521 [details]
KBLU-drv_missed_irq-kern.log

Created attachment 125522 [details]
KBLU-drv_missed_irq-output

Reproduced on KBL-U.

KBL-U
Hardware
Platform: KABY LAKE-U
CPU : Intel(R) Core(TM) @ 2.60GHz
MCP : KBL-U G0 2+2
QDF : QYQ8
Chipset PCH: SPT-LP C1
CRB : KABY LAKE U DDR3L RVP7 CRB FAB1

Software
BIOS: 38_07 KBLSE2R1.R00.X038.P07.1606200632 from https://ubit-artifactory-ba.intel.com/artifactory/simple/one-windows-local/Submissions/ifwi/KBL_PURPLE_IFWI_2016_WW26_1_00_HR'16/IFWI-KBL_PURPLE_IFWI_2016_WW26_1_00_HR'16-R.7z
ME FW: 11.5.0.1058
EC FW: 1.19
Ksc (EC FW): 1.20
Linux distribution: Ubuntu 16.04 64 bits
Kernel: 4.7.0 6f87e85 from http://cgit.freedesktop.org/drm-intel/
   commit 6f87e85fa302ffdb4cb9f4cd712691165923c7a2
 Author: Chris Wilson <chris@chris-wilson.co.uk>
  Date:   Mon Aug 1 15:53:41 2016 +0100
  drm-intel-nightly: 2016y-08m-01d-14h-53m-17s UTC integration manifest
drm: libdrm-2.4.70 f19cd3a from git://anongit.freedesktop.org/mesa/drm
mesa: mesa-11.2.2 3a9f628from git://anongit.freedesktop.org/mesa/mesa
cairo: 1.15.2 db8a7f1 from git://anongit.freedesktop.org/cairo
xserver: xorg-server-1.18.0-502 c833c08 from git://git.freedesktop.org/git/xorg/xserver
xf86-video-intel: 2.99.917-688 49daf5d from git://git.freedesktop.org/git/xorg/driver/xf86-video-intel
libva: libva-1.7.0-40 f7e2263 from git://git.freedesktop.org/git/vaapi/libva
vaapi-intel-driver: 1.7.0-64 1cd6795 from git://git.freedesktop.org/git/vaapi/intel-driver
GuC 9.14 from http://rdvivi-hillsboro.jf.intel.com/firmware/kbl_guc_ver9_14.tar.bz2 
DMC 1.01 from: https://01.org/linuxgraphics/downloads/kabylake-dmc-1.01 
Intel-Gpu-Tools 1.15-188 53b4dfdfrom http://anongit.freedesktop.org/git/xorg/app/intel-gpu-tools.git

In my tree, I have moved the kicking from hangcheck to intel_breadcrumbs.c which prevents this problem. I'll try and get that polished up...

Christophe, please try with Chris' patch: https://patchwork.freedesktop.org/series/10711/

Had some fun with the test case as well. It appears that on execlists (at least) we could get spurious interrupts due to the IIR bit being set for the user interrupt and a second context-switch interrupt causing processing of the wakeup.

commit 83348ba84ee0d5d4d982e5382bfbc8b2a2d05e75
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Tue Aug 9 17:47:51 2016 +0100

    drm/i915: Move missed interrupt detection from hangcheck to breadcrumbs
    
    In commit 2529d57050af ("drm/i915: Drop racy markup of missed-irqs from
    idle-worker") the racy detection of missed interrupts was removed when
    we went idle. This however opened up the issue that the stuck waiters
    were not being reported, causing a test case failure. If we move the
    stuck waiter detection out of hangcheck and into the breadcrumb
    mechanims (i.e. the waiter) itself, we can avoid this issue entirely.
    This leaves hangcheck looking for a stuck GPU (inspecting for request
    advancement and HEAD motion), and breadcrumbs looking for a stuck
    waiter - hopefully make both easier to understand by their segregation.