linux-kernel - [PATCH] [175/223] backlight: grab ops

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Date:	Mon, 13 Dec 2010 00:48:00 +0100 (CET)
From:	Andi Kleen <andi@...stfloor.org>
To:	u.kleine-koenig@...gutronix.de, u.kleine-koenig@...gutronix.de,
	u.kleine-koenig@...gutronix.de, rpurdie@...ux.intel.com,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	gregkh@...e.de, ak@...ux.intel.com, linux-kernel@...r.kernel.org,
	stable@...nel.org
Subject: [PATCH] [175/223] backlight: grab ops_lock before testing bd->ops

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= <u.kleine-koenig@...gutronix.de>

commit d1d73578e053b981c3611e5a211534290d24a5eb upstream.

According to the comment describing ops_lock in the definition of struct
backlight_device and when comparing with other functions in backlight.c
the mutex must be hold when checking ops to be non-NULL.

Fixes a problem added by c835ee7f4154992e6 ("backlight: Add suspend/resume
support to the backlight core") in Jan 2009.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Acked-by: Richard Purdie <rpurdie@...ux.intel.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

---
 drivers/video/backlight/backlight.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Index: linux/drivers/video/backlight/backlight.c
===================================================================
--- linux.orig/drivers/video/backlight/backlight.c
+++ linux/drivers/video/backlight/backlight.c
@@ -197,12 +197,12 @@ static int backlight_suspend(struct devi
 {
 	struct backlight_device *bd = to_backlight_device(dev);
 
-	if (bd->ops->options & BL_CORE_SUSPENDRESUME) {
-		mutex_lock(&bd->ops_lock);
+	mutex_lock(&bd->ops_lock);
+	if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
 		bd->props.state |= BL_CORE_SUSPENDED;
 		backlight_update_status(bd);
-		mutex_unlock(&bd->ops_lock);
 	}
+	mutex_unlock(&bd->ops_lock);
 
 	return 0;
 }
@@ -211,12 +211,12 @@ static int backlight_resume(struct devic
 {
 	struct backlight_device *bd = to_backlight_device(dev);
 
-	if (bd->ops->options & BL_CORE_SUSPENDRESUME) {
-		mutex_lock(&bd->ops_lock);
+	mutex_lock(&bd->ops_lock);
+	if (bd->ops && bd->ops->options & BL_CORE_SUSPENDRESUME) {
 		bd->props.state &= ~BL_CORE_SUSPENDED;
 		backlight_update_status(bd);
-		mutex_unlock(&bd->ops_lock);
 	}
+	mutex_unlock(&bd->ops_lock);
 
 	return 0;
 }
--
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