[Intel-gfx] [PATCH] drm/i915: use kref_put_mutex in i915_gem_request_unreference__unlocked

[Daniel Vetter]

On Tue, Apr 07, 2015 at 11:32:02AM +0200, Maarten Lankhorst wrote:
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> ---
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index b13c5526a73b..7aaf8eddf19c 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -2146,14 +2146,14 @@ i915_gem_request_unreference(struct drm_i915_gem_request *req)
>  static inline void
>  i915_gem_request_unreference__unlocked(struct drm_i915_gem_request *req)
>  {
> -	if (req && !atomic_add_unless(&req->ref.refcount, -1, 1)) {
> -		struct drm_device *dev = req->ring->dev;
> +	struct drm_device *dev;
> +
> +	if (!req)
> +		return;
>  
> -		mutex_lock(&dev->struct_mutex);
> -		if (likely(atomic_dec_and_test(&req->ref.refcount)))
> -			i915_gem_request_free(&req->ref);
> +	dev = req->ring->dev;
> +	if (kref_put_mutex(&req->ref, i915_gem_request_free, &dev->struct_mutex))
>  		mutex_unlock(&dev->struct_mutex);

We don't need this conditional unlock here since that's only possible if
you have a weak reference somewhere (i.e. using kref_get_unless_zero). If
the object only has strong references and you're dropping the last one it
can't magically get resurrected somehow.

And drm_gem_object_unreference_unlocked wants the same patch I think.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch