linux-kernel - Re: [PATCH v7 0/8] devm_led_classdev

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Date: Fri, 22 Mar 2024 13:19:59 +0300
From: George Stark <gnstark@...utedevices.com>
To: Lee Jones <lee@...nel.org>
CC: <andy.shevchenko@...il.com>, <pavel@....cz>, <vadimp@...dia.com>,
	<christophe.leroy@...roup.eu>, <hdegoede@...hat.com>,
	<mazziesaccount@...il.com>, <peterz@...radead.org>, <mingo@...hat.com>,
	<will@...nel.org>, <longman@...hat.com>, <boqun.feng@...il.com>,
	<nikitos.tr@...il.com>, <marek.behun@....cz>, <kabel@...nel.org>,
	<linux-leds@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<kernel@...utedevices.com>
Subject: Re: [PATCH v7 0/8] devm_led_classdev_register() usage problem

Hello Lee

On 3/21/24 21:11, Lee Jones wrote:
> On Thu, 14 Mar 2024, George Stark wrote:
> 
>> This patch series fixes the problem of devm_led_classdev_register misusing.
>>
>> The basic problem is described in [1]. Shortly when devm_led_classdev_register()
>> is used then led_classdev_unregister() called after driver's remove() callback.
>> led_classdev_unregister() calls driver's brightness_set callback and that callback
>> may use resources which were destroyed already in driver's remove().
>>
>> After discussion with maintainers [2] [3] we decided:
>> 1) don't touch led subsystem core code and don't remove led_set_brightness() from it
>> but fix drivers
>> 2) don't use devm_led_classdev_unregister
>>
>> So the solution is to use devm wrappers for all resources
>> driver's brightness_set() depends on. And introduce dedicated devm wrapper
>> for mutex as it's often used resource.

..

>>    locking/mutex: introduce devm_mutex_init()
>>    leds: aw2013: use devm API to cleanup module's resources
>>    leds: aw200xx: use devm API to cleanup module's resources
>>    leds: lp3952: use devm API to cleanup module's resources
>>    leds: lm3532: use devm API to cleanup module's resources
>>    leds: nic78bx: use devm API to cleanup module's resources
>>    leds: mlxreg: use devm_mutex_init() for mutex initialization
>>    leds: an30259a: use devm_mutex_init() for mutex initialization
>>
>>   drivers/leds/leds-an30259a.c | 14 ++++----------
>>   drivers/leds/leds-aw200xx.c  | 32 +++++++++++++++++++++-----------
>>   drivers/leds/leds-aw2013.c   | 25 +++++++++++++------------
>>   drivers/leds/leds-lm3532.c   | 29 +++++++++++++++++------------
>>   drivers/leds/leds-lp3952.c   | 21 +++++++++++----------
>>   drivers/leds/leds-mlxreg.c   | 14 +++++---------
>>   drivers/leds/leds-nic78bx.c  | 23 +++++++++++++----------
>>   include/linux/mutex.h        | 27 +++++++++++++++++++++++++++
>>   kernel/locking/mutex-debug.c | 11 +++++++++++
>>   9 files changed, 122 insertions(+), 74 deletions(-)
> 
> Doesn't apply to v6.8.
> 
> What base was used for this?

I've just pulled git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
and v7 was applied cleanly. linux-next is ok too.

v6.8 is lack of recent patch 6969d0a2ba1adc9ba6a49b9805f24080896c255c
v7's patch #2 depends on it

-- 
Best regards
George