linux-kernel - Re: [PATCH v2 00/26] genirq: fix use of irq_find

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Date:	Wed, 3 Sep 2014 08:37:29 -0400
From:	Jason Cooper <jason@...edaemon.net>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Marc Zyngier <marc.zyngier@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"shawn.guo@...escale.com" <shawn.guo@...escale.com>,
	"kernel@...gutronix.de" <kernel@...gutronix.de>,
	"tony@...mide.com" <tony@...mide.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	"jonas@...thpole.se" <jonas@...thpole.se>,
	"shc_work@...l.ru" <shc_work@...l.ru>,
	"baohua@...nel.org" <baohua@...nel.org>,
	"maxime.ripard@...e-electrons.com" <maxime.ripard@...e-electrons.com>,
	"khilman@...aro.org" <khilman@...aro.org>,
	"sboyd@...eaurora.org" <sboyd@...eaurora.org>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	"larry.bassel@...aro.org" <larry.bassel@...aro.org>,
	Mark Rutland <Mark.Rutland@....com>,
	Sudeep Holla <Sudeep.Holla@....com>,
	"stefan.kristiansson@...nalahti.fi" 
	<stefan.kristiansson@...nalahti.fi>,
	"vkale@....com" <vkale@....com>,
	"schwidefsky@...ibm.com" <schwidefsky@...ibm.com>
Subject: Re: [PATCH v2 00/26] genirq: fix use of irq_find_mapping outside
 of legal RCU context

On Wed, Sep 03, 2014 at 02:25:09PM +0200, Thomas Gleixner wrote:
> On Wed, 3 Sep 2014, Marc Zyngier wrote:
> > [Dropping linux@...nrisc.net from the CC list]
> > 
> > On 03/09/14 13:09, Thomas Gleixner wrote:
> > > On Wed, 3 Sep 2014, Jason Cooper wrote:
> > > 
> > >> 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@...utronix.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?
> > > 
> > > Yes please.
> > 
> > Do you want a pull request? Or are you picking up the patches from the ML?
> 
> Did you pick up the Acked/Reviewed/Ignored-by tags?

Marc, unless you've already done it, I'll pull from the ml, since I need
to apply the Acked-bys and tweak the subject lines.

thx,

Jason.
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