[Intel-gfx] [PATCH 2/6] drm/i915: Initialise basic fence before acquiring seqno

[Chris Wilson]

Quoting Tvrtko Ursulin (2020-02-03 10:55:52)
> 
> On 03/02/2020 09:41, Chris Wilson wrote:
> > Inside the intel_timeline_get_seqno(), we currently track the retirement
> > of the old cachelines by listening to the new request. This requires
> > that the new request is ready to be used and so requires a minimum bit
> > of initialisation prior to getting the new seqno.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > Cc: Matthew Auld <matthew.auld at intel.com>
> > ---
> >   drivers/gpu/drm/i915/i915_request.c | 21 ++++++++++++++-------
> >   1 file changed, 14 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> > index 78a5f5d3c070..f56b046a32de 100644
> > --- a/drivers/gpu/drm/i915/i915_request.c
> > +++ b/drivers/gpu/drm/i915/i915_request.c
> > @@ -595,6 +595,8 @@ static void __i915_request_ctor(void *arg)
> >       i915_sw_fence_init(&rq->submit, submit_notify);
> >       i915_sw_fence_init(&rq->semaphore, semaphore_notify);
> >   
> > +     dma_fence_init(&rq->fence, &i915_fence_ops, &rq->lock, 0, 0);
> > +
> >       rq->file_priv = NULL;
> >       rq->capture_list = NULL;
> >   
> > @@ -653,25 +655,30 @@ __i915_request_create(struct intel_context *ce, gfp_t gfp)
> >               }
> >       }
> >   
> > -     ret = intel_timeline_get_seqno(tl, rq, &seqno);
> > -     if (ret)
> > -             goto err_free;
> > -
> >       rq->i915 = ce->engine->i915;
> >       rq->context = ce;
> >       rq->engine = ce->engine;
> >       rq->ring = ce->ring;
> >       rq->execution_mask = ce->engine->mask;
> >   
> > +     kref_init(&rq->fence.refcount);
> > +     rq->fence.flags = 0;
> > +     rq->fence.error = 0;
> > +     INIT_LIST_HEAD(&rq->fence.cb_list);
> 
> One of these fields the previous user leaves in a non-empty state?

Yes, we don't reset cb_list after signaling, error and flags hold
residuals, but refcount is known to be 0!
-Chris