led: core: Fix blink_brightness setting race

All 3 of led_timer_func, led_set_brightness and led_set_software_blink
set blink_brightness. If led_timer_func or led_set_software_blink race
with led_set_brightness they may end up overwriting the new
blink_brightness. The new atomic work_flags does not protect against
this as it just protects the flags and not blink_brightness.

This commit introduces a new new_blink_brightness value which gets
set by led_set_brightness and read by led_timer_func on LED on, fixing
this.

Dealing with the new brightness at LED on time, makes the new
brightness apply sooner, which also fixes a led_set_brightness which
happens while a oneshot blink which ends in LED on is running not
getting applied.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>

diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index bd6bb4d44f054b1739ec5cb16b9c95471d6cf044..ef13604454133e4d3c5acb7ab2bb3c492cec490c 100644 (file)
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -66,17 +66,17 @@ static void led_timer_function(unsigned long data)
        brightness = led_get_brightness(led_cdev);
        if (!brightness) {
                /* Time to switch the LED on. */
-               brightness = led_cdev->blink_brightness;
+               if (test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE,
+                                       &led_cdev->work_flags))
+                       brightness = led_cdev->new_blink_brightness;
+               else
+                       brightness = led_cdev->blink_brightness;
                delay = led_cdev->blink_delay_on;
        } else {
                /* Store the current brightness value to be able
                 * to restore it when the delay_off period is over.
-                * Do it only if there is no pending blink brightness
-                * change, to avoid overwriting the new value.
                 */
-               if (!test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE,
-                                       &led_cdev->work_flags))
-                       led_cdev->blink_brightness = brightness;
+               led_cdev->blink_brightness = brightness;
                brightness = LED_OFF;
                delay = led_cdev->blink_delay_off;
        }
@@ -245,7 +245,7 @@ void led_set_brightness(struct led_classdev *led_cdev,
                } else {
                        set_bit(LED_BLINK_BRIGHTNESS_CHANGE,
                                &led_cdev->work_flags);
-                       led_cdev->blink_brightness = brightness;
+                       led_cdev->new_blink_brightness = brightness;
                }
                return;
        }

diff --git a/include/linux/leds.h b/include/linux/leds.h
index 21c598b366f834d5044ac319bbe26c00b3d19a98..569cb531094c20a9aa2db478aaa6f348d2afd7f4 100644 (file)
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -93,6 +93,7 @@ struct led_classdev {
        unsigned long            blink_delay_on, blink_delay_off;
        struct timer_list        blink_timer;
        int                      blink_brightness;
+       int                      new_blink_brightness;
        void                    (*flash_resume)(struct led_classdev *led_cdev);
 
        struct work_struct      set_brightness_work;