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

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Message-ID: <54070B93.7040104@arm.com>
Date:	Wed, 03 Sep 2014 13:37:39 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Jason Cooper <jason@...edaemon.net>,
	"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 03/09/14 13:25, 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?

I have them in a separate branch that can be pushed out as required.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...
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