[PATCH 06/10] leds: class: Take the LED access lock when reading brightness_hw_changed

[Armin Wolf <W_Armin@gmx.de>]

Reading the brightness_hw_changed field needs to be guarded against
concurrent writes by led_classdev_notify_brightness_hw_changed().

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
---
 drivers/leds/led-class.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index e1f1b710536b..77a0fce03952 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -6,6 +6,7 @@
  * Copyright (C) 2005-2007 Richard Purdie <rpurdie@openedhand.com>
  */
 
+#include <linux/cleanup.h>
 #include <linux/ctype.h>
 #include <linux/device.h>
 #include <linux/err.h>
@@ -102,11 +103,15 @@ static ssize_t brightness_hw_changed_show(struct device *dev, const struct devic
 					  char *buf)
 {
 	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	unsigned int brightness_hw_changed;
 
-	if (led_cdev->brightness_hw_changed == -1)
+	scoped_guard(mutex, &led_cdev->led_access)
+		brightness_hw_changed = led_cdev->brightness_hw_changed;
+
+	if (brightness_hw_changed == -1)
 		return -ENODATA;
 
-	return sysfs_emit(buf, "%u\n", led_cdev->brightness_hw_changed);
+	return sysfs_emit(buf, "%u\n", brightness_hw_changed);
 }
 
 static const DEVICE_ATTR_RO(brightness_hw_changed);
-- 
2.56.0