[Intel-gfx] [PATCH] drm/i915: Rework GPU reset sequence to match driver load & thaw

[Chris Wilson]

On Mon, Jul 28, 2014 at 11:26:38AM +0200, Daniel Vetter wrote:
> Oh, I guess that's the tricky bit why the old approach never worked -
> because reset_in_progress is set we failed the context/ppgtt loading
> through the rings and screwed up.
> 
> Problem with your approach is that we want to bail out here if a reset is
> in progress, so we can't just eat the EAGAIN. If we do that we potentially
> deadlock or overflow the ring.
> 
> I think we need a different hack here, and a few layers down (i.e. at the
> place where we actually generate that offending -EAGAIN).
> 
> - Around the re-init sequence in the reset function we set
>   dev_priv->mm.reload_in_reset or similar. Since we hold dev->struct_mutex
>   no one will see that, as long as we never leak it out of the critical
>   section.
> 
> - In the ring_begin code that checks for gpu hangs we ignore
>   reset_in_progress if this bit is set.
> 
> - Both places need fairly big comments to explain what exactly is going
>   on.

This is going from bad to worse. I think you can do better if you looked
at the problem afresh.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre