Re: [PATCH v2] counter: interrupt-cnt: use devm_mutex_init()

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 27 May 2026 15:56:31 +0900
William Breathitt Gray <wbg@kernel.org> wrote:

> On Mon, May 25, 2026 at 08:11:52PM +0500, Stepan Ionichev wrote:
> > interrupt_cnt_probe() calls mutex_init() but neither this driver
> > nor the counter core issues a matching mutex_destroy() on unbind,
> > which leaks the lock debug state when CONFIG_DEBUG_MUTEXES is
> > enabled.
> > 
> > Switch to devm_mutex_init() so the mutex is torn down in the same
> > devm scope it was set up in.
> > 
> > Fixes: a55ebd47f21f ("counter: add IRQ or GPIO based counter")  
> 
> The mutex_init() code was added in 7351312632e8 ("counter:
> interrupt-cnt: Protect enable/disable OPs with mutex"), so the Fixes tag
> should refer to that commit.
> 

Not a fix.   For a long time it was common to take the view that
mutex_destroy() was only useful if you had marginally complex lifetime
handling in a driver and it might help detect bugs.

Now devm_mutex_init() makes it easier to do, the barrier to deciding
to have that protection is reduced, so we apply it to more drivers
(for IIO I now ask for this always).  That doesn't make it a fix as such,
more of an update to modern approaches and definitely not suitable for
the backports that will likely cause.  So I'd drop the fixes tag.

Jonathan

> William Breathitt Gray
>