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

Thomas Gleixner
2014-08-26T21:35:00Z

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?

Thanks,

tglx