The CI Bug Log issue associated to this bug has been updated.

### New filters associated

* SKL GLK: igt@gem_persistent_relocs@forked-interruptible-thrashing -timeout - Received signal SIGQUIT
  - https://intel-gfx-ci.01.org/tree/drm-tip/Trybot_4242/shard-skl9/igt@gem_persistent_relocs@forked-interruptible-thrashing.html
  - https://intel-gfx-ci.01.org/tree/drm-tip/Patchwork_12955/shard-glk7/igt@gem_persistent_relocs@forked-interruptible-thrashing.html

My guess for the symptom here is the uninterruptible wait for flush_work in i915_drop_caches_set(DROP_IDLE). Exactly why it wasn't able to idle, unknown as we have no debug logs. However, I've been poking at the same code to avoid the uninterruptible lockup, and so present

commit 3970564940ba0322bcefce7fd8fd35c2b85846bf
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Tue May 7 13:11:08 2019 +0100

    drm/i915: Stop spinning for DROP_IDLE (debugfs/i915_drop_caches)
    
    If the user is racing a call to debugfs/i915_drop_caches with ongoing
    submission from another thread/process, we may never end up idling the
    GPU and be uninterruptibly spinning in debugfs/i915_drop_caches trying
    to catch an idle moment.
    
    Just flush the work once, that should be enough to park the system under
    correct conditions. Outside of those we either have a driver bug or the
    user is racing themselves. Sadly, because the user may be provoking the
    unwanted situation we can't put a warn here to attract attention to a
    probable bug.
    
    Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
    Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
    Link: https://patchwork.freedesktop.org/patch/msgid/20190507121108.18377-4-chris@chris-wilson.co.uk

*** Bug 110646 has been marked as a duplicate of this bug. ***

A CI Bug Log filter associated to this bug has been updated:

{- SKL GLK: igt@gem_persistent_relocs@forked-interruptible-thrashing -timeout - Received signal SIGQUIT -}
{+ BDW SKL GLK: igt@gem_persistent_relocs@forked-*-thrashing -timeout - Received signal SIGQUIT +}

New failures caught by the filter:

  * https://intel-gfx-ci.01.org/tree/drm-tip/drmtip_279/fi-bdw-gvtdvm/igt@gem_persistent_relocs@forked-thrashing.html

This issue occurred only once on drmtip_279 (5 months, 3 weeks old).
Closing and archiving the issue.

The CI Bug Log issue associated to this bug has been archived.

New failures matching the above filters will not be associated to this bug anymore.