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

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Date: Fri, 29 Mar 2024 16:43:06 +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>
Subject: Re: [PATCH v7 0/8] devm_led_classdev_register() usage problem

Hello Lee

On 3/22/24 13:43, Lee Jones wrote:
> On Fri, 22 Mar 2024, George Stark wrote:
> 
>> 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
> 
> No problem.  I'll wait for v6.9-rc1.
> 

Just checked the v7 patch series on released 6.9-rc1 and it's applied
cleanly. If anything i can help please let me know.

-- 
Best regards
George