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

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Message-ID: <aIuZt3asLeiYncH1@shell.armlinux.org.uk>
Date: Thu, 31 Jul 2025 17:28:39 +0100
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Mark Brown <broonie@...nel.org>
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 05:16:13PM +0100, Mark Brown wrote:
> 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.

As I said, I'm just going to disable lockdep to shut up the warning and
not pursue any further time on this. If someone else cares about it
(which I doubt) they can try to come up with a solution. I suspect
nested regmap-irq is extremely rare.

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