linux-kernel - Re: [PATCH] gpio: sysfs: add missing mutex

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Message-ID: <aCdutI4J6r5kjCNs@hovoldconsulting.com>
Date: Fri, 16 May 2025 18:58:28 +0200
From: Johan Hovold <johan@...nel.org>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Linus Walleij <linus.walleij@...aro.org>, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	stable@...r.kernel.org
Subject: Re: [PATCH] gpio: sysfs: add missing mutex_destroy()

On Fri, May 16, 2025 at 02:32:54PM +0200, Bartosz Golaszewski wrote:
> On Fri, May 16, 2025 at 1:42 PM Johan Hovold <johan@...nel.org> wrote:
> >
> > On Fri, May 16, 2025 at 12:40:23PM +0200, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > >
> > > We initialize the data->mutex in gpiod_export() but lack the
> > > corresponding mutex_destroy() in gpiod_unexport() causing a resource
> > > leak with mutex debugging enabled. Add the call right before kfreeing
> > > the GPIO data.
> >
> > No, there's no resource leak and it's perfectly fine not to call
> > mutex_destroy().
> 
> No, there's no leak but with lock debugging it still warns if the
> mutex is locked when it's being destroyed so the change still makes
> sense with a modified commit message.
> 
> > You can't just make shit up and then pretend to fix it...
> 
> There's no need for this kind of comment. You made your point clear in
> the first sentence.

Your claim that there's "a resource leak with mutex debugging enabled"
is is quite specific. Now I had to go check that no one had changed
something in ways they shouldn't have recently. But mutex_destroy()
still works as it always has, which you should have verified yourself
before sending a "fix" tagged for stable backport based on a hunch.

Johan