[Intel-gfx] [PATCH 02/10] drm/i915/userptr: Make gup errors stickier

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> Keep any error reported by the gup_worker until we are notified that the
> arena has changed (via the mmu-notifier). This has the importance of
> making two consecutive calls to i915_gem_object_get_pages() reporting
> the same error, and curtailing an loop of detecting a fault and requeueing
> a gup_worker.
>
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>  drivers/gpu/drm/i915/i915_gem_userptr.c | 17 +++++++----------
>  1 file changed, 7 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_userptr.c b/drivers/gpu/drm/i915/i915_gem_userptr.c
> index 57218cca7e05..be54825ef3e8 100644
> --- a/drivers/gpu/drm/i915/i915_gem_userptr.c
> +++ b/drivers/gpu/drm/i915/i915_gem_userptr.c
> @@ -542,8 +542,6 @@ __i915_gem_userptr_get_pages_worker(struct work_struct *_work)
>  			}
>  		}
>  		obj->userptr.work = ERR_PTR(ret);
> -		if (ret)
> -			__i915_gem_userptr_set_active(obj, false);
>  	}
>  
>  	obj->userptr.workers--;
> @@ -628,15 +626,14 @@ i915_gem_userptr_get_pages(struct drm_i915_gem_object *obj)
>  	 * to the vma (discard or cloning) which should prevent the more
>  	 * egregious cases from causing harm.
>  	 */
> -	if (IS_ERR(obj->userptr.work)) {
> -		/* active flag will have been dropped already by the worker */
> -		ret = PTR_ERR(obj->userptr.work);
> -		obj->userptr.work = NULL;
> -		return ret;
> -	}
> -	if (obj->userptr.work)
> +
> +	if (obj->userptr.work) {
>  		/* active flag should still be held for the pending work */
> -		return -EAGAIN;
> +		if (IS_ERR(obj->userptr.work))
> +			return PTR_ERR(obj->userptr.work);

Previously you did set the work to null before returning error,
now you dont.

Is it the responsibility of cancel_userptr now, through mm notifier,
that clears the pointer?

-Mika


> +		else
> +			return -EAGAIN;
> +	}
>  
>  	/* Let the mmu-notifier know that we have begun and need cancellation */
>  	ret = __i915_gem_userptr_set_active(obj, true);
> -- 
> 2.8.1
>
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