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    SubjectRe: [question] NR_IRQS in genirq
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    On Wed, Nov 24, 2010 at 9:18 PM, Thomas Gleixner <tglx@linutronix.de> wrote:
    > On Wed, 24 Nov 2010, Haojian Zhuang wrote:
    >
    >> Hi all,
    >>
    >> I'm using the latest kernel 2.6.37-rc1. Now I met some issues on genirq.
    >>
    >> 1. While SPARSE IRQ is enabled, nr_irqs may be larger than NR_IRQS.
    >> But the allocated_irqs bitmap (kernel/irq/irqdesc.c) is restricted in
    >> NR_IRQS. Is it an issue?
    >
    > Why can nr_irqs become larger? Is that a theoretical problem or did
    > you run into this ?
    >
    >

    Hi Thomas,

    My hardware environment is ARM. Each machine description can specify
    nr_irqs. In my implementation of PXA, NR_IRQS is fixed for SoC
    internal IRQs. And there's some additional board IRQs, we arrange them
    between NR_IRQS and nr_irqs. So nr_irqs will be larger than NR_IRQS if
    board IRQs exists.

    We use dynamic board IRQs since each machine has different
    requirement. And CONFIG_HARDIRQ_SW_RESEND is occasionally, I actually
    met issue in resend_irqs because of accessing bitmap memory out of
    bound.

    Do you mean that we shouldn't use SPARSE IRQ by this way?

    Best Regards
    Haojian


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