linux-kernel - Re: [BUG] 6.16-rc7: lockdep failure with max77620-gpio/max77686-rtc

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Message-ID: <14c68c29-68d8-4119-8f70-616c07397dc4@sirena.org.uk>
Date: Thu, 31 Jul 2025 17:16:13 +0100
From: Mark Brown <broonie@...nel.org>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: Krzysztof Kozlowski <krzk@...nel.org>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>, linux-gpio@...r.kernel.org,
	linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
	Thierry Reding <treding@...dia.com>
Subject: Re: [BUG] 6.16-rc7: lockdep failure with max77620-gpio/max77686-rtc

On Thu, Jul 31, 2025 at 04:57:42PM +0100, Russell King (Oracle) wrote:
> On Thu, Jul 31, 2025 at 02:18:24PM +0100, Mark Brown wrote:

> > I *think* mutex_lock_nested() is what we're looking for here, with the
> > depth information from the irq_desc but I'm also not super familiar with
> > this stuff.

> I'm not sure about that, because the irq_desc locks don't nest:

>         raw_spin_lock_init(&desc->lock);
>         lockdep_set_class(&desc->lock, &irq_desc_lock_class);

> What saves irq_desc lock nesting in this case is that
> __irq_put_desc_unlock() unlocks desc->lock calling the
> irq_bus_sync_unlock() method. So, I don't think we have anything at
> the irq_desc level which deals with lock-nesting.

Yeah, and that's all internals which we're not super encouraged to peer
at.  There should be something that'll give us a nesting level
somewhere...  

Lockdep's handling of nesting is generally fun.

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