Quoting Tvrtko Ursulin (2018-02-07 10:40:46)
>
> On 06/02/2018 09:46, Chris Wilson wrote:
> > When a request is preempted, it is unsubmitted from the HW queue and
> > removed from the active list of breadcrumbs. In the process, this
> > however triggers the signaler and it may see the clear rbtree with the
> > old, and still valid, seqno. This confuses the signaler into action and
> > signaling the fence.
> >
> > Fixes: d6a2289d9d6b ("drm/i915: Remove the preempted request from the execution queue")
> > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>
> > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> > Cc: <stable@xxxxxxxxxxxxxxx> # v4.12+
> > ---
> Looks OK. But I can't say it's straightforward to understand it.
But I hope the GEM_BUG_ON() was nice icing on the cake :)
> Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Thanks, added your explanation to the changelog and pushed.
-Chris