From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Wed, 22 Jun 2016 07:46:12 +0000 (+0100)
Subject: drm/fb-helper: Reduce READ_ONCE(master) to lockless_dereference
X-Git-Tag: v4.8-rc1~62^2~34^2~1
X-Git-Url: http://git.cascardo.eti.br/?a=commitdiff_plain;h=fa7d81bb3c269;hp=366e292df678caed1fb3644989e6b5ae2333808c;p=cascardo%2Flinux.git

drm/fb-helper: Reduce READ_ONCE(master) to lockless_dereference

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@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Julia Lawall <julia.lawall@lip6.fr>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1466581572-16608-1-git-send-email-chris@chris-wilson.co.uk
---

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) {