drm/i915/guc: Fix the fix for reset lock confusion

The previous fix for the circlular lock splat about the busyness
worker wasn't quite complete. Even though the reset-in-progress flag
is cleared at the start of intel_uc_reset_finish, the entire function
is still inside the reset mutex lock. Not sure why the patch appeared
to fix the issue both locally and in CI. However, it is now back
again.

There is a further complication that the wedge code path within
intel_gt_reset() jumps around so much that it results in nested
reset_prepare/_finish calls. That is, the call sequence is:
  intel_gt_reset
  | reset_prepare
  | __intel_gt_set_wedged
  | | reset_prepare
  | | reset_finish
  | reset_finish

The nested finish means that even if the clear of the in-progress flag
was moved to the end of _finish, it would still be clear for the
entire second call. Surprisingly, this does not seem to be causing any
other problems at present.

As an aside, a wedge on fini does not call the finish functions at
all. The reset_in_progress flag is left set (twice).

So instead of trying to cancel the worker anywhere at all in the reset
path, just add a cancel to intel_guc_submission_fini instead. Note
that it is not a problem if the worker is still active during a reset.
Either it will run before the reset path starts locking things and
will simply block the reset code for a tiny amount of time. Or it will
run after the locks have been acquired and will early exit due to the
try-lock.

Also, do not use the reset-in-progress flag to decide whether a
synchronous cancel is safe (from a lockdep perspective) or not.
Instead, use the actual reset mutex state (both the genuine one and
the custom rolled BACKOFF one).

Fixes: 0e00a8814eec ("drm/i915/guc: Avoid circular locking issue on busyness flush")
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Cc: Zhanjun Dong <zhanjun.dong@intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: Andi Shyti <andi.shyti@linux.intel.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Nirmoy Das <nirmoy.das@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Jonathan Cavitt <jonathan.cavitt@intel.com>
Cc: Prathap Kumar Valsan <prathap.kumar.valsan@intel.com>
Cc: Alan Previn <alan.previn.teres.alexis@intel.com>
Cc: Madhumitha Tolakanahalli Pradeep <madhumitha.tolakanahalli.pradeep@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Ashutosh Dixit <ashutosh.dixit@intel.com>
Cc: Dnyaneshwar Bhadane <dnyaneshwar.bhadane@intel.com>
Reviewed-by: Nirmoy Das <nirmoy.das@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240329235306.1559639-1-John.C.Harrison@Intel.com
(cherry picked from commit 3563d855312acedcd445a3767f0cb07906f1c26f)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

0 files changed, 0 insertions, 0 deletions