Re: [PATCH v2 00/26] genirq: fix use of irq_find_mapping outside of legal RCU context

From: Jason Cooper <jason@lakedaemon.net>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
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Subject: Re: [PATCH v2 00/26] genirq: fix use of irq_find_mapping outside of legal RCU context
Date: Wed, 3 Sep 2014 08:04:06 -0400	[thread overview]
Message-ID: <20140903120406.GK30467@titan.lakedaemon.net> (raw)
In-Reply-To: <87y4uap98n.fsf@approximate.cambridge.arm.com>

On Wed, Aug 27, 2014 at 10:33:44AM +0100, Marc Zyngier wrote:
> Hi Thomas,
> 
> On Tue, Aug 26 2014 at 10:34:51 pm BST, Thomas Gleixner <tglx@linutronix.de> wrote:
> > On Tue, 26 Aug 2014, Marc Zyngier wrote:
> >
> >> A number of irqchip drivers are directly calling irq_find_mapping,
> >> which may use a rcu_read_lock call when walking the radix tree.
> >> 
> >> Turns out that if you hit that point with CONFIG_PROVE_RCU enabled,
> >> the kernel will shout at you, as using RCU in this context may be
> >> illegal (specially if coming from the idle state, where RCU would be
> >> in a quiescent state).
> >> 
> >> A possible fix would be to wrap calls to irq_find_mapping into a
> >> RCU_NONIDLE macro, but that really looks ugly.
> >> 
> >> This patch series introduce another generic IRQ entry point
> >> (handle_domain_irq), which has the exact same behaviour as handle_IRQ
> >> (as defined on arm, arm64 and openrisc), except that it also takes a
> >> irq_domain pointer. This allows the logical IRQ lookup to be done
> >> inside the irq_{enter,exit} section, which contains a
> >> rcu_irq_{enter,exit}, making it safe.
> >
> > Looks good. Should this be routed to the genirq tree?
> 
> I'm happy for you to take this series, provided the architecture
> maintainers agree on it (I'm still to hear from the openrisc guys, and
> their mailing-list seems to positively hate my guts).

I think everyone's had a chance to look over it by now.  Thomas, shall I
take the series?

thx,

Jason.