linux-kernel - Re: [PATCH v4 00/10] devm_led_classdev

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Date: Fri, 9 Feb 2024 19:11:01 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Lee Jones <lee@...nel.org>
Cc: George Stark <gnstark@...utedevices.com>, pavel@....cz,
	vadimp@...dia.com, mpe@...erman.id.au, npiggin@...il.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, linux-leds@...r.kernel.org,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	kernel@...utedevices.com
Subject: Re: [PATCH v4 00/10] devm_led_classdev_register() usage problem

On Thu, Dec 21, 2023 at 03:11:11PM +0000, Lee Jones wrote:
> On Thu, 14 Dec 2023, 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 subsytem 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.
> > 
> > [1] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/
> > [2] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/#mc132b9b350fa51931b4fcfe14705d9f06e91421f
> > [3] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/#mdbf572a85c33f869a553caf986b6228bb65c8383

..

> FYI: I'll conduct my review once the locking side is settled.

To reduce burden can you apply the first one? It's a fix.

-- 
With Best Regards,
Andy Shevchenko