[Intel-gfx] [PATCH 31/38] drm/i915: Track the pinned kernel contexts on each engine

[Chris Wilson]

Quoting Tvrtko Ursulin (2019-03-05 18:07:39)
> >       /*
> >        * Similarly the preempt context must always be available so that
> > -      * we can interrupt the engine at any time.
> > +      * we can interrupt the engine at any time. However, as preemption
> > +      * is optional, we allow it to fail.
> >        */
> > -     if (i915->preempt_context) {
> > -             ce = intel_context_pin(i915->preempt_context, engine);
> > -             if (IS_ERR(ce)) {
> > -                     ret = PTR_ERR(ce);
> > -                     goto err_unpin_kernel;
> > -             }
> > -     }
> > +     if (i915->preempt_context)
> > +             pin_context(i915->preempt_context, engine,
> > +                         &engine->preempt_context);
> 
> You lost the failure path here. I suspect deliberately? But I am not 
> convinced we want to silently lose preemption when keeping the failure 
> path is so easy.

The failure path kills the module. Whereas we can quite happily survive
without preemption.
-Chris