[Intel-gfx] [PATCH 10/15] drm/i915: Assert that machine is wedged for nop_submit_request

[Chris Wilson]

Quoting Michel Thierry (2017-07-18 01:15:00)
> On 17/07/17 02:11, Chris Wilson wrote:
> > We should only ever do nop_submit_request when the machine is wedged, so
> > assert it is so.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > ---
> >   drivers/gpu/drm/i915/i915_gem.c | 1 +
> >   1 file changed, 1 insertion(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index ca7a56ff3904..5517373c1bea 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -3089,6 +3089,7 @@ void i915_gem_reset_finish(struct drm_i915_private *dev_priv)
> >   
> >   static void nop_submit_request(struct drm_i915_gem_request *request)
> >   {
> > +     GEM_BUG_ON(!i915_terminally_wedged(&request->i915->gpu_error));
> >       dma_fence_set_error(&request->fence, -EIO);
> >       i915_gem_request_submit(request);
> >       intel_engine_init_global_seqno(request->engine, request->global_seqno);
> > 
> 
> Not sure about this, your patch before this one, ("[PATCH 09/15] 
> drm/i915: Wake up waiters after setting the WEDGED bit"), is moving the 
> set_bit after engine_set_wedged:

But we are inside a stop_machine()...

> @@ -3157,10 +3157,12 @@ static int __i915_gem_set_wedged_BKL(void *data)
>         struct intel_engine_cs *engine;
>         enum intel_engine_id id;
> 
> -       set_bit(I915_WEDGED, &i915->gpu_error.flags);
>         for_each_engine(engine, i915, id)
>                 engine_set_wedged(engine);
> 
> +       set_bit(I915_WEDGED, &i915->gpu_error.flags);
> +       wake_up_all(&i915->gpu_error.reset_queue);
> +
>         return 0;
>   }
> 
> I don't think it won't hit the BUG_ON because i915_gem_set_wedged is 
> already protected by stop_machine. Anyway it looks odd.

Ah, I did consider it in passing, then rationalised it away because the
stop_machine() gives us the guarantee that we won't run
nop_submit_request() until after the wedging.
-Chris