backlight: led_bl: Hold led_access lock when calling led_sysfs_disable()

[PATCH] backlight: led_bl: Hold led_access lock when calling led_sysfs_disable()

Posted by Herve Codina 11 months ago

Lockdep detects the following issue on led-backlight removal:
  [  142.315935] ------------[ cut here ]------------
  [  142.315954] WARNING: CPU: 2 PID: 292 at drivers/leds/led-core.c:455 led_sysfs_enable+0x54/0x80
  ...
  [  142.500725] Call trace:
  [  142.503176]  led_sysfs_enable+0x54/0x80 (P)
  [  142.507370]  led_bl_remove+0x80/0xa8 [led_bl]
  [  142.511742]  platform_remove+0x30/0x58
  [  142.515501]  device_remove+0x54/0x90
  ...

Indeed, led_sysfs_enable() has to be called with the led_access
lock held.

Hold the lock when calling led_sysfs_disable().

Fixes: ae232e45acf9 ("backlight: add led-backlight driver")
Cc: stable@vger.kernel.org
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
 drivers/video/backlight/led_bl.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c
index ae34d1ecbfbe..d2db157b2c29 100644
--- a/drivers/video/backlight/led_bl.c
+++ b/drivers/video/backlight/led_bl.c
@@ -229,8 +229,11 @@ static void led_bl_remove(struct platform_device *pdev)
 	backlight_device_unregister(bl);
 
 	led_bl_power_off(priv);
-	for (i = 0; i < priv->nb_leds; i++)
+	for (i = 0; i < priv->nb_leds; i++) {
+		mutex_lock(&priv->leds[i]->led_access);
 		led_sysfs_enable(priv->leds[i]);
+		mutex_unlock(&priv->leds[i]->led_access);
+	}
 }
 
 static const struct of_device_id led_bl_of_match[] = {
-- 
2.47.1

Re: (subset) [PATCH] backlight: led_bl: Hold led_access lock when calling led_sysfs_disable()

Posted by Lee Jones 10 months, 1 week ago

On Wed, 22 Jan 2025 10:19:14 +0100, Herve Codina wrote:
> Lockdep detects the following issue on led-backlight removal:
>   [  142.315935] ------------[ cut here ]------------
>   [  142.315954] WARNING: CPU: 2 PID: 292 at drivers/leds/led-core.c:455 led_sysfs_enable+0x54/0x80
>   ...
>   [  142.500725] Call trace:
>   [  142.503176]  led_sysfs_enable+0x54/0x80 (P)
>   [  142.507370]  led_bl_remove+0x80/0xa8 [led_bl]
>   [  142.511742]  platform_remove+0x30/0x58
>   [  142.515501]  device_remove+0x54/0x90
>   ...
> 
> [...]

Applied, thanks!

[1/1] backlight: led_bl: Hold led_access lock when calling led_sysfs_disable()
      commit: 276822a00db3c1061382b41e72cafc09d6a0ec30

--
Lee Jones [李琼斯]

Re: [PATCH] backlight: led_bl: Hold led_access lock when calling led_sysfs_disable()

Posted by Herve Codina 10 months, 2 weeks ago

Hi Lee, Daniel, Jingoo,

On Wed, 22 Jan 2025 10:19:14 +0100
Herve Codina <herve.codina@bootlin.com> wrote:

> Lockdep detects the following issue on led-backlight removal:
>   [  142.315935] ------------[ cut here ]------------
>   [  142.315954] WARNING: CPU: 2 PID: 292 at drivers/leds/led-core.c:455 led_sysfs_enable+0x54/0x80
>   ...
>   [  142.500725] Call trace:
>   [  142.503176]  led_sysfs_enable+0x54/0x80 (P)
>   [  142.507370]  led_bl_remove+0x80/0xa8 [led_bl]
>   [  142.511742]  platform_remove+0x30/0x58
>   [  142.515501]  device_remove+0x54/0x90
>   ...
> 
> Indeed, led_sysfs_enable() has to be called with the led_access
> lock held.
> 
> Hold the lock when calling led_sysfs_disable().
> 
> Fixes: ae232e45acf9 ("backlight: add led-backlight driver")
> Cc: stable@vger.kernel.org
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>

I didn't receive any feedback.

v6.14-rc1 has been released since the patch was sent but the patch applies on
top of v6.14-rc1 without any issue.

Of course if really needed, I can resend the patch. Just tell me.

Best regards,
Hervé