On 20/01/2020 17:57, Chris Wilson wrote:
Keep the rq->fence.flags consistent with the status of the
rq->sched.link, and clear the associated bits when decoupling the link
on retirement (as we may wish to inspect those flags independent of
other state).

Fixes: 32ff621fd744 ("drm/i915/gt: Allow temporary suspension of inflight 
requests")
References: https://gitlab.freedesktop.org/drm/intel/issues/997
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
---
  drivers/gpu/drm/i915/i915_request.c | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_request.c 
b/drivers/gpu/drm/i915/i915_request.c
index 9ed0d3bc7249..78a5f5d3c070 100644
--- a/drivers/gpu/drm/i915/i915_request.c
+++ b/drivers/gpu/drm/i915/i915_request.c
@@ -221,6 +221,8 @@ static void remove_from_engine(struct i915_request *rq)
                locked = engine;
        }
        list_del_init(&rq->sched.link);
+       clear_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);

This one I think can not be set in retirement. Or there is a path?

[comes back after writing the comment below]

Race between completion to hold puts the request on hold, then request completes just as it is un-held? It needs retire to happen at the right time, driven by ...? Is this it?

+       clear_bit(I915_FENCE_FLAG_HOLD, &rq->fence.flags);

This one I think indeed can race with completion.

Regards,

Tvrtko

        spin_unlock_irq(&locked->active.lock);
  }
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