[Intel-gfx] [PATCH v4 20/61] drm/i915: Rework clflush to work correctly without obj->mm.lock.

[Thomas Hellström]

On 10/16/20 12:44 PM, Maarten Lankhorst wrote:
> Pin in the caller, not in the work itself. This should also
> work better for dma-fence annotations.
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> ---
>   drivers/gpu/drm/i915/gem/i915_gem_clflush.c | 15 +++++++--------
>   1 file changed, 7 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_clflush.c b/drivers/gpu/drm/i915/gem/i915_gem_clflush.c
> index bc0223716906..daf9284ef1f5 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_clflush.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_clflush.c
> @@ -27,15 +27,8 @@ static void __do_clflush(struct drm_i915_gem_object *obj)
>   static int clflush_work(struct dma_fence_work *base)
>   {
>   	struct clflush *clflush = container_of(base, typeof(*clflush), base);
> -	struct drm_i915_gem_object *obj = clflush->obj;
> -	int err;
>   
> -	err = i915_gem_object_pin_pages(obj);
> -	if (err)
> -		return err;
> -
> -	__do_clflush(obj);
> -	i915_gem_object_unpin_pages(obj);
> +	__do_clflush(clflush->obj);
>   
>   	return 0;
>   }
> @@ -44,6 +37,7 @@ static void clflush_release(struct dma_fence_work *base)
>   {
>   	struct clflush *clflush = container_of(base, typeof(*clflush), base);
>   
> +	i915_gem_object_unpin_pages(clflush->obj);

Hmm, Could we do without pinning here? Pages present are protected first 
by the object lock, then by the fence?

/Thomas