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    SubjectRe: [Ksummit-2008-discuss] Delayed interrupt work, thread pools
    Hello,

    (including linux-rt-users in the CC:, irqthreads are on-topic there)

    On Wed, Jul 2, 2008 at 1:02 PM, Andi Kleen <andi@firstfloor.org> wrote:
    > Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
    >
    >>> how much of this would be obsoleted if we had irqthreads ?
    >>
    >> I'm not sure irqthreads is what I want...
    >>
    > I also think interrupts threads are a bad idea in many cases because
    > their whole "advantage" over classical interrupts is that they can
    > block. Now blocking can be usually take a unbounded potentially long
    > time.
    >
    > What do you do when there are more interrupts in that unbounded time?
    >
    If by irqthreads the -rt implementation is meant, isn't this what happens:

    irq kernel handler masks the source interrupt
    irq handler awakes the matching irqthread (they always are present)
    irqthread is scheduled, does work and returns
    irq kernel unmasks the source interrupt

    > Create more interrupt threads? At some point you'll have hundreds
    > of threads doing nothing when you're unlucky.
    >
    Each irqthread handles one irq.
    So now new irq thread would spawn for any interrupt.

    Regards,
    --
    Leon


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