[Intel-gfx] [PATCH] drm/i915: Move assert of page pin vs bind count into i915_vma_unbind

[Daniel Vetter]

On Fri, Dec 30, 2016 at 05:33:14PM +0000, Chris Wilson wrote:
> The read of the page pin count and the bind count are unordered,
> presenting races in the assert and it firing off incorrectly. Prevent
> this by restricting the assert to the vma bind/unbind routines where we
> have local cpu ordering between the two.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>

Fun.

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>
> ---
>  drivers/gpu/drm/i915/i915_drv.h | 1 -
>  drivers/gpu/drm/i915/i915_vma.c | 1 +
>  2 files changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 00ecbb4da25e..1aa33444115a 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -3291,7 +3291,6 @@ __i915_gem_object_unpin_pages(struct drm_i915_gem_object *obj)
>  	GEM_BUG_ON(!obj->mm.pages);
>  
>  	atomic_dec(&obj->mm.pages_pin_count);
> -	GEM_BUG_ON(atomic_read(&obj->mm.pages_pin_count) < obj->bind_count);
>  }
>  
>  static inline void
> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
> index 414f0f7f5059..d48c68214611 100644
> --- a/drivers/gpu/drm/i915/i915_vma.c
> +++ b/drivers/gpu/drm/i915/i915_vma.c
> @@ -640,6 +640,7 @@ int i915_vma_unbind(struct i915_vma *vma)
>  	 * reaped by the shrinker.
>  	 */
>  	i915_gem_object_unpin_pages(obj);
> +	GEM_BUG_ON(atomic_read(&obj->mm.pages_pin_count) < obj->bind_count);
>  
>  destroy:
>  	if (unlikely(i915_vma_is_closed(vma)))
> -- 
> 2.11.0
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch