[Intel-gfx] [PATCH] drm/fb-helper: Reduce READ_ONCE(master) to lockless_dereference

[Daniel Vetter]

On Wed, Jun 22, 2016 at 08:46:12AM +0100, Chris Wilson wrote:
> We are only documenting that the read is outside of the lock, and do not
> require strict ordering on the operation. In this case the more relaxed
> lockless_dereference() will suffice.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniel Vetter <daniel.vetter at intel.com>
> Cc: Julia Lawall <julia.lawall at lip6.fr>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Emil Velikov <emil.l.velikov at gmail.com>

Applied to drm-misc.
-Daniel

> ---
>  drivers/gpu/drm/drm_fb_helper.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 0a06f9120b5a..ce54e985d91b 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -464,7 +464,7 @@ static bool drm_fb_helper_is_bound(struct drm_fb_helper *fb_helper)
>  
>  	/* Sometimes user space wants everything disabled, so don't steal the
>  	 * display if there's a master. */
> -	if (READ_ONCE(dev->master))
> +	if (lockless_dereference(dev->master))
>  		return false;
>  
>  	drm_for_each_crtc(crtc, dev) {
> -- 
> 2.8.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch