[Intel-gfx] [PATCH 08/33] drm/i915: Move setting of request->batch into its single callsite

[Chris Wilson]

On Tue, Aug 09, 2016 at 06:53:16PM +0300, Mika Kuoppala wrote:
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> 
> > request->batch_obj is only set by execbuffer for the convenience of
> > debugging hangs. By moving that operation to the callsite, we can
> > simplify all other callers and future patches. We also move the
> > complications of reference handling of the request->batch_obj next to
> > where the active tracking is set up for the request.
> >
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >  drivers/gpu/drm/i915/i915_gem_execbuffer.c | 10 +++++++++-
> >  drivers/gpu/drm/i915/i915_gem_request.c    | 12 +-----------
> >  drivers/gpu/drm/i915/i915_gem_request.h    |  8 +++-----
> >  3 files changed, 13 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > index c494b79ded20..c8d13fea4b25 100644
> > --- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > +++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
> > @@ -1702,6 +1702,14 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
> >  		goto err_batch_unpin;
> >  	}
> >  
> > +	/* Whilst this request exists, batch_obj will be on the
> > +	 * active_list, and so will hold the active reference. Only when this
> > +	 * request is retired will the the batch_obj be moved onto the
> > +	 * inactive_list and lose its active reference. Hence we do not need
> > +	 * to explicitly hold another reference here.
> > +	 */
> 
> The comment here might or might not need revisiting. I can't say yet.

That's still true. Active objects have a reference that prevents them
from being freed whilst in use by the GPU - currently managed by
i915_gem_object_retire__read() iirc.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre