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

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Date:	Thu, 24 Mar 2016 13:56:52 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Lee Jones <lee.jones@...aro.org>
cc:	Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>,
	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, 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.