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    SubjectRe: Threaded interrupt handlers broken?
    On Sun, 16 Aug 2009, Michael Buesch wrote:
    > On Sunday 16 August 2009 15:22:29 Thomas Gleixner wrote:
    >
    > > > + if (0&&unlikely(desc->status & IRQ_DISABLED)) {
    > >
    > > So the interrupt is marked disabled. How do you setup the handler
    > > ? And what does the primary handler do ? Can you post your driver
    > > code please?
    >
    > This patch converts the b43 driver to threaded interrupts:
    > http://bu3sch.de/patches/wireless-testing/20090816-1535/patches/002-b43-threaded-irq-handler.patch

    On the first glance this looks not too bad. the unlocked access to the
    irq status registers looks a bit scary, but that is not relevant for
    the problem at hand.

    > It kind of works with this hack applied to kernel/irq/manage.c

    Hmm. Is the interrupt of the device shared ? If yes, what's the other
    device on that interrupt line ? what puzzles me is the fact that the
    IRQ_DISABLED flag is set. Is there anything unusual in dmesg ?

    > > So you wake when the thread counter is != 0 after the decrement.
    > >
    > > #define atomic_dec_and_test(v) (atomic_sub_return(1, (v)) == 0)
    >
    > Yeah, isn't that what we want to do? I read the test as "wake other threads,
    > if there are other threads" or something like that.

    No, it's for synchronize_irq(). When there are threaded handlers in
    progress, then sychronize_irq() waits on the waitqueue until they are
    finished. So we wake the queue when the last threaded handler of this
    irq line returns from thread_fn.

    Thanks,

    tglx


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