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led: core: Use atomic bit-field for the blink-flags 

All the LED_BLINK* flags are accessed read-modify-write from e.g.
led_set_brightness and led_blink_set_oneshot while both
set_brightness_work and the blink_timer may be running.

If these race then the modify step done by one of them may be lost,
switch the LED_BLINK* flags to a new atomic work_flags bit-field
to avoid this race.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>
This commit is contained in:
Hans de Goede 2016-11-08 14:38:46 +01:00 committed by Jacek Anaszewski
parent 8338eab50f
commit a9c6ce57ec
3 changed files with 42 additions and 35 deletions
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1
drivers/leds/led-class.c
View File

@ -204,6 +204,7 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
dev_warn(parent, "Led %s renamed to %s due to name collision",
led_cdev->name, dev_name(led_cdev->dev));
led_cdev->work_flags = 0;
#ifdef CONFIG_LEDS_TRIGGERS
init_rwsem(&led_cdev->trigger_lock);
#endif

52
drivers/leds/led-core.c
View File

@ -53,12 +53,13 @@ static void led_timer_function(unsigned long data)
if (!led_cdev->blink_delay_on || !led_cdev->blink_delay_off) {
led_set_brightness_nosleep(led_cdev, LED_OFF);
led_cdev->flags &= ~LED_BLINK_SW;
clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
return;
}
if (led_cdev->flags & LED_BLINK_ONESHOT_STOP) {
led_cdev->flags &= ~(LED_BLINK_ONESHOT_STOP | LED_BLINK_SW);
if (test_and_clear_bit(LED_BLINK_ONESHOT_STOP,
&led_cdev->work_flags)) {
clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
return;
}
@ -73,10 +74,9 @@ static void led_timer_function(unsigned long data)
* Do it only if there is no pending blink brightness
* change, to avoid overwriting the new value.
*/
if (!(led_cdev->flags & LED_BLINK_BRIGHTNESS_CHANGE))
if (!test_and_clear_bit(LED_BLINK_BRIGHTNESS_CHANGE,
&led_cdev->work_flags))
led_cdev->blink_brightness = brightness;
else
led_cdev->flags &= ~LED_BLINK_BRIGHTNESS_CHANGE;
brightness = LED_OFF;
delay = led_cdev->blink_delay_off;
}
@ -87,13 +87,15 @@ static void led_timer_function(unsigned long data)
* the final blink state so that the led is toggled each delay_on +
* delay_off milliseconds in worst case.
*/
if (led_cdev->flags & LED_BLINK_ONESHOT) {
if (led_cdev->flags & LED_BLINK_INVERT) {
if (test_bit(LED_BLINK_ONESHOT, &led_cdev->work_flags)) {
if (test_bit(LED_BLINK_INVERT, &led_cdev->work_flags)) {
if (brightness)
led_cdev->flags |= LED_BLINK_ONESHOT_STOP;
set_bit(LED_BLINK_ONESHOT_STOP,
&led_cdev->work_flags);
} else {
if (!brightness)
led_cdev->flags |= LED_BLINK_ONESHOT_STOP;
set_bit(LED_BLINK_ONESHOT_STOP,
&led_cdev->work_flags);
}
}
@ -106,10 +108,9 @@ static void set_brightness_delayed(struct work_struct *ws)
container_of(ws, struct led_classdev, set_brightness_work);
int ret = 0;
if (led_cdev->flags & LED_BLINK_DISABLE) {
if (test_and_clear_bit(LED_BLINK_DISABLE, &led_cdev->work_flags)) {
led_cdev->delayed_set_value = LED_OFF;
led_stop_software_blink(led_cdev);
led_cdev->flags &= ~LED_BLINK_DISABLE;
}
ret = __led_set_brightness(led_cdev, led_cdev->delayed_set_value);
@ -152,7 +153,7 @@ static void led_set_software_blink(struct led_classdev *led_cdev,
return;
}
led_cdev->flags |= LED_BLINK_SW;
set_bit(LED_BLINK_SW, &led_cdev->work_flags);
mod_timer(&led_cdev->blink_timer, jiffies + 1);
}
@ -161,7 +162,7 @@ static void led_blink_setup(struct led_classdev *led_cdev,
unsigned long *delay_on,
unsigned long *delay_off)
{
if (!(led_cdev->flags & LED_BLINK_ONESHOT) &&
if (!test_bit(LED_BLINK_ONESHOT, &led_cdev->work_flags) &&
led_cdev->blink_set &&
!led_cdev->blink_set(led_cdev, delay_on, delay_off))
return;
@ -188,8 +189,8 @@ void led_blink_set(struct led_classdev *led_cdev,
{
del_timer_sync(&led_cdev->blink_timer);
led_cdev->flags &= ~LED_BLINK_ONESHOT;
led_cdev->flags &= ~LED_BLINK_ONESHOT_STOP;
clear_bit(LED_BLINK_ONESHOT, &led_cdev->work_flags);
clear_bit(LED_BLINK_ONESHOT_STOP, &led_cdev->work_flags);
led_blink_setup(led_cdev, delay_on, delay_off);
}
@ -200,17 +201,17 @@ void led_blink_set_oneshot(struct led_classdev *led_cdev,
unsigned long *delay_off,
int invert)
{
if ((led_cdev->flags & LED_BLINK_ONESHOT) &&
if (test_bit(LED_BLINK_ONESHOT, &led_cdev->work_flags) &&
timer_pending(&led_cdev->blink_timer))
return;
led_cdev->flags |= LED_BLINK_ONESHOT;
led_cdev->flags &= ~LED_BLINK_ONESHOT_STOP;
set_bit(LED_BLINK_ONESHOT, &led_cdev->work_flags);
clear_bit(LED_BLINK_ONESHOT_STOP, &led_cdev->work_flags);
if (invert)
led_cdev->flags |= LED_BLINK_INVERT;
set_bit(LED_BLINK_INVERT, &led_cdev->work_flags);
else
led_cdev->flags &= ~LED_BLINK_INVERT;
clear_bit(LED_BLINK_INVERT, &led_cdev->work_flags);
led_blink_setup(led_cdev, delay_on, delay_off);
}
@ -221,7 +222,7 @@ void led_stop_software_blink(struct led_classdev *led_cdev)
del_timer_sync(&led_cdev->blink_timer);
led_cdev->blink_delay_on = 0;
led_cdev->blink_delay_off = 0;
led_cdev->flags &= ~LED_BLINK_SW;
clear_bit(LED_BLINK_SW, &led_cdev->work_flags);
}
EXPORT_SYMBOL_GPL(led_stop_software_blink);
@ -232,17 +233,18 @@ void led_set_brightness(struct led_classdev *led_cdev,
* If software blink is active, delay brightness setting
* until the next timer tick.
*/
if (led_cdev->flags & LED_BLINK_SW) {
if (test_bit(LED_BLINK_SW, &led_cdev->work_flags)) {
/*
* If we need to disable soft blinking delegate this to the
* work queue task to avoid problems in case we are called
* from hard irq context.
*/
if (brightness == LED_OFF) {
led_cdev->flags |= LED_BLINK_DISABLE;
set_bit(LED_BLINK_DISABLE, &led_cdev->work_flags);
schedule_work(&led_cdev->set_brightness_work);
} else {
led_cdev->flags |= LED_BLINK_BRIGHTNESS_CHANGE;
set_bit(LED_BLINK_BRIGHTNESS_CHANGE,
&led_cdev->work_flags);
led_cdev->blink_brightness = brightness;
}
return;

24
include/linux/leds.h
View File

@ -42,16 +42,20 @@ struct led_classdev {
#define LED_UNREGISTERING (1 << 1)
/* Upper 16 bits reflect control information */
#define LED_CORE_SUSPENDRESUME (1 << 16)
#define LED_BLINK_SW (1 << 17)
#define LED_BLINK_ONESHOT (1 << 18)
#define LED_BLINK_ONESHOT_STOP (1 << 19)
#define LED_BLINK_INVERT (1 << 20)
#define LED_BLINK_BRIGHTNESS_CHANGE (1 << 21)
#define LED_BLINK_DISABLE (1 << 22)
#define LED_SYSFS_DISABLE (1 << 23)
#define LED_DEV_CAP_FLASH (1 << 24)
#define LED_HW_PLUGGABLE (1 << 25)
#define LED_PANIC_INDICATOR (1 << 26)
#define LED_SYSFS_DISABLE (1 << 17)
#define LED_DEV_CAP_FLASH (1 << 18)
#define LED_HW_PLUGGABLE (1 << 19)
#define LED_PANIC_INDICATOR (1 << 20)
/* set_brightness_work / blink_timer flags, atomic, private. */
unsigned long work_flags;
#define LED_BLINK_SW 0
#define LED_BLINK_ONESHOT 1
#define LED_BLINK_ONESHOT_STOP 2
#define LED_BLINK_INVERT 3
#define LED_BLINK_BRIGHTNESS_CHANGE 4
#define LED_BLINK_DISABLE 5
/* Set LED brightness level
* Must not sleep. Use brightness_set_blocking for drivers