linux-kernel - Re: [PATCH RESEND] mfd: arizona: Fix lockdep recursion warning on set_irq

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Message-ID: <20160324153525.GM1490@localhost.localdomain>
Date:	Thu, 24 Mar 2016 15:35:25 +0000
From:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Lee Jones <lee.jones@...aro.org>, <linux-kernel@...r.kernel.org>,
	<patches@...nsource.wolfsonmicro.com>
Subject: Re: [PATCH RESEND] mfd: arizona: Fix lockdep recursion warning on
 set_irq_wake

On Thu, Mar 24, 2016 at 01:56:52PM +0100, Thomas Gleixner wrote:
> On Thu, 24 Mar 2016, Lee Jones wrote:
> 
> > FAO Thomas
> > 
> > > Lockdep explicitly sets all the irq_desc locks as a single lock-class,
> > > which causes a "possible recursive locking detected" warning when we
> > > attempt to propagate the IRQ wake to our parent IRQ in
> > > arizona_irq_set_wake. Although this appears to be a false positive
> > > because an IRQ is unlikely to be its own parent, this was clearly
> > > intentionally prohibited.
> > > 
> > > To avoid this lockdep warning, take a cue from the regmap-irq system,
> > > and add bus lock callbacks on the IRQ chip and propagate the wake in
> > > the bus unlock which will happen after the desc lock has been released
> > > and thus avoid the issue.
> > 
> > This looks like a hack to me.  I'd like Thomas (Cc'ed) to look it over.
> 
> irq_set_lockdep_class() exists for a reason. See kernel/irq/generic-chip.c or
> drivers/gpio/gpiolib.c for examples.

Apologies for missing that. Thanks guys I will have a look and
respin the patch.

Thanks,
Charles