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

Marc Zyngier
2014-09-03T12:40:28Z

On 03/09/14 13:37, Jason Cooper wrote:
> On Wed, Sep 03, 2014 at 02:25:09PM +0200, 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?
>
> 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.

If you're going to repaint the subject lines, then I'll leave you to it! ;-)

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