From: Grazvydas Ignotas <notasas@gmail.com>
Date: Sat, 19 Mar 2016 01:28:14 +0000 (+0200)
Subject: leds-twl4030-pwm: fix another race
X-Git-Tag: sz_175~46
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=01f551de7fa4a384027f3f8d9119c45ca9d0fd1a

leds-twl4030-pwm: fix another race

This is a race between twl4030_pwmled_work() reading led->new_brightness
vs twl4030_pwmled_brightness() writing to it. Probably needs a proper
lock, but we want twl4030_pwmled_brightness() to not block and assume
work items come from single queue and should not race each other.
---

diff --git a/drivers/leds/leds-twl4030-pwm.c b/drivers/leds/leds-twl4030-pwm.c
index f6d656ed414d..66f431d46d03 100644
--- a/drivers/leds/leds-twl4030-pwm.c
+++ b/drivers/leds/leds-twl4030-pwm.c
@@ -99,18 +99,20 @@ static void twl4030_enable_pwm01(enum twl4030_led led, bool enable)
 
 static void twl4030_pwmled_work(struct work_struct *work)
 {
+	enum led_brightness new_brightness;
 	struct twl4030_pwmled *led;
 	int val;
 
 	led = container_of(work, struct twl4030_pwmled, work);
 
-	if (led->new_brightness == LED_OFF) {
+	new_brightness = ACCESS_ONCE(led->new_brightness);
+	if (new_brightness == LED_OFF) {
 		if (led->old_brightness != LED_OFF)
 			led->enable(led->id, 0);
 		goto out;
 	}
 
-	val = led->new_brightness * 0x7f / LED_FULL;
+	val = new_brightness * 0x7f / LED_FULL;
 	/* avoid 0: on = off = 0 means full brightness */
 	if (val == 0)
 		val = 1;
@@ -121,7 +123,7 @@ static void twl4030_pwmled_work(struct work_struct *work)
 		led->enable(led->id, 1);
 
 out:
-	led->old_brightness = led->new_brightness;
+	led->old_brightness = new_brightness;
 }
 
 static void twl4030_pwmled_brightness(struct led_classdev *cdev,