Re: [PATCH v5 5/5] dma-buf/sync_file: only enable fence signalling on poll()

[Chris Wilson]

On Thu, Aug 04, 2016 at 11:24:14PM -0300, Gustavo Padovan wrote:
> From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> 
> Signalling doesn't need to be enabled at sync_file creation, it is only
> required if userspace waiting the fence to signal through poll().
> 
> Thus we delay fence_add_callback() until poll is called. It only adds the
> callback the first time poll() is called. This avoid re-adding the same
> callback multiple times.
> 
> v2: rebase and update to work with new fence support for sync_file
> 
> v3: use atomic operation to set enabled and protect fence_add_callback()
> 
> v4: use user bit from fence flags (comment from Chris Wilson)
> 
> Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxxxx>
> ---
> +	if (!test_and_set_bit(POLL_ENABLED, &sync_file->fence->flags)) {
> +		if (fence_add_callback(sync_file->fence, &sync_file->cb,
> +				   fence_check_cb_func) < 0)
> +			wake_up_all(&sync_file->wq);
> +	}
> +
>  	status = fence_is_signaled(sync_file->fence);

status can only be true/false here.
	return fence_is_signaled(sync_file->fence) ? POLLIN : 0;

Reviwed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre