linux-kernel - Re: [PATCH] backlight: led_bl: Hold led_access lock when calling led_sysfs

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Message-ID: <20250207143003.1c518df3@bootlin.com>
Date: Fri, 7 Feb 2025 14:30:03 +0100
From: Herve Codina <herve.codina@...tlin.com>
To: Lee Jones <lee@...nel.org>, Daniel Thompson <danielt@...nel.org>, Jingoo
 Han <jingoohan1@...il.com>, Helge Deller <deller@....de>, Tony Lindgren
 <tony@...mide.com>, Pavel Machek <pavel@....cz>, Tomi Valkeinen
 <tomi.valkeinen@...com>, Jean-Jacques Hiblot <jjhiblot@...com>
Cc: Daniel Thompson <daniel.thompson@...aro.org>,
 dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, Luca Ceresoli <luca.ceresoli@...tlin.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, stable@...r.kernel.org
Subject: Re: [PATCH] backlight: led_bl: Hold led_access lock when calling
 led_sysfs_disable()

Hi Lee, Daniel, Jingoo,

On Wed, 22 Jan 2025 10:19:14 +0100
Herve Codina <herve.codina@...tlin.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@...r.kernel.org
> Signed-off-by: Herve Codina <herve.codina@...tlin.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