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    SubjectRe: [RFC patch 2/3] genirq: Add buslock support for irq chips on slow busses
    On Fri, 14 Aug 2009, Peter Zijlstra wrote:
    > On Thu, 2009-08-13 at 19:40 +0000, Thomas Gleixner wrote:
    > >
    > > +/**
    > > + * disable_slowbus_irq - disable an slowbus irq and wait for completion
    > > + * @irq: Interrupt to disable
    > > + *
    > > + * Disable the selected interrupt line. Enables and Disables are
    > > + * nested.
    > > + * This function waits for any pending IRQ handlers for this interrupt
    > > + * to complete before returning. If you use this function while
    > > + * holding a resource the IRQ handler may need you will deadlock.
    > > + *
    > > + * This function must not be called from IRQ context.
    > > + */
    > > +void disable_slowbus_irq(unsigned int irq)
    > > +{
    > > + struct irq_desc *desc = irq_to_desc(irq);
    > > +
    > > + if (!desc || !desc->chip || !desc->chip->bus_lock)
    > > + return;
    > > +
    > > + desc->chip->bus_lock(irq);
    > > + disable_irq_nosync(irq);
    > > + if (desc->action)
    > > + synchronize_irq(irq);
    > > + desc->chip->bus_sync_unlock(irq);
    > > +}
    > > +EXPORT_SYMBOL(disable_slowbus_irq);
    >
    > Should we also not check that desc->chip->bus_lock is not set for the
    > regular function disable_irq()?
    >
    > It seems to me mixing disable_irq() and disable_slowbus_irq() is a
    > recipe for disaster.
    >
    > Same for the other slowbus functions of course.

    Yeah, that's what I wanted to avoid with the first version, which did
    the conditional locking and did not require a separate API, but Ingo
    frowned upon the conditional lock.

    Thanks,

    tglx



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