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

Thomas Gleixner
2014-09-03T12:25:23Z

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?