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Date: Thu, 11 Apr 2024 14:45:14 +0100
From: Lee Jones <lee@kernel.org>
To: George Stark <gnstark@salutedevices.com>
Cc: andy.shevchenko@gmail.com, pavel@ucw.cz, vadimp@nvidia.com,
	christophe.leroy@csgroup.eu, hdegoede@redhat.com,
	mazziesaccount@gmail.com, peterz@infradead.org, mingo@redhat.com,
	will@kernel.org, longman@redhat.com, boqun.feng@gmail.com,
	nikitos.tr@gmail.com, marek.behun@nic.cz, kabel@kernel.org,
	linux-leds@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v7 0/8] devm_led_classdev_register() usage problem
Message-ID: <20240411134514.GK1980182@google.com>
References: <20240314201856.1991899-1-gnstark@salutedevices.com>
 <20240321181133.GG13211@google.com>
 <9bfd0ccc-a5d8-446c-a08c-bbc36a4d66eb@salutedevices.com>
 <20240322104303.GN13211@google.com>
 <e3dd3ed1-02dc-447c-9fdd-9d8193a25e5f@salutedevices.com>
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In-Reply-To: <e3dd3ed1-02dc-447c-9fdd-9d8193a25e5f@salutedevices.com>

On Fri, 29 Mar 2024, George Stark wrote:

> 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.

It applies, but doesn't seem to build:

make --silent --keep-going --jobs=8 O=../build ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- CROSS_COMPILE_COMPAT=arm-linux-gnueabihf- 'CC=sccache aarch64-linux-gnu-gcc' 'HOSTCC=sccache gcc' allmodconfig
make --silent --keep-going --jobs=8 O=../build ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- CROSS_COMPILE_COMPAT=arm-linux-gnueabihf- 'CC=sccache aarch64-linux-gnu-gcc' 'HOSTCC=sccache gcc'
ERROR: modpost: "__devm_mutex_init" [drivers/leds/leds-an30259a.ko] undefined!
ERROR: modpost: "__devm_mutex_init" [drivers/leds/leds-aw200xx.ko] undefined!
ERROR: modpost: "__devm_mutex_init" [drivers/leds/leds-aw2013.ko] undefined!
ERROR: modpost: "__devm_mutex_init" [drivers/leds/leds-lm3532.ko] undefined!
ERROR: modpost: "__devm_mutex_init" [drivers/leds/leds-mlxreg.ko] undefined!
make[3]: *** [/builds/linux/scripts/Makefile.modpost:145: Module.symvers] Error 1

Did you forget to export it?

-- 
Lee Jones [李琼斯]