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    SubjectRe: [PATCH] uio: uio_pdrv_genirq V2
    Hello Alan,

    Alan Cox wrote:
    > On Thu, 10 Jul 2008 12:30:36 +0200
    > Uwe Kleine-König <Uwe.Kleine-Koenig@digi.com> wrote:
    >
    > > Alan Cox wrote:
    > > >
    > > > > > + else if (!irq_on && !priv->irq_disabled)
    > > > > > + disable_irq(dev_info->irq);
    > > > > I'm not sure if this is a problem on SMP. Should you use
    > > > > disable_irq_nosync here, too? Probably it's OK.
    > > >
    > > > That one will also deadlock.
    > > Can you explain why? I think irqcontrol is only called in task context.
    > > I only see one possible deadlock and that's disable_irq being called
    > > while the irq is IRQ_INPROGRESS on the same cpu. I'm always willing to
    > > learn.
    >
    > CPU0 (UIO IRQ) CPU1 (irqcontrol)
    > take IRQ
    > take spin lock
    > spin on spinlock
    > disable_irq (blocks)
    Ah, OK, that's because uio_pdrv_genirq_handler and
    uio_pdrv_genirq_irqcontrol share the lock.

    Is this something that lockdep can detect?

    Best regards and thanks for clearifying
    Uwe

    --
    Uwe Kleine-König, Software Engineer
    Digi International GmbH Branch Breisach, Küferstrasse 8, 79206 Breisach, Germany
    Tax: 315/5781/0242 / VAT: DE153662976 / Reg. Amtsgericht Dortmund HRB 13962
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