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

Marc Zyngier
2014-09-03T12:37:39Z

On 03/09/14 13:25, Thomas Gleixner wrote:
> On Wed, 3 Sep 2014, Marc Zyngier wrote:
>> [Dropping linux@openrisc.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@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?
>>>
>>> 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...