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    SubjectRe: [RFC] genirq: Flush the irq thread on synchronization
    Hi Thomas,

    On Sat, Dec 03, 2011 at 12:21:46AM +0100, Thomas Gleixner wrote:
    > I can see your problem, but this might lead to threads_active leaks
    > under certain conditions. desc->threads_active was only meant to deal
    > with shared interrupts.
    > We explicitely allow a design where the primary handler can leave the
    > device interrupt enabled and allow further interrupts to occur while
    > the handler is running. We only have a single bit to note that the
    > thread should run, but your wakeup would up the threads_active count
    > in that scenario several times w/o a counterpart which decrements it.
    > The solution for this is to keep the current threads_active semantics
    > and make the wait function different. Instead of waiting for
    > threads_active to become 0 it should wait for threads_active == 0 and
    > the IRQTF_RUNTHREAD for all actions to be cleared. To avoid looping
    > over the actions, we can take a similar approach as we take with the
    > desc->threads_oneshot bitfield.

    Thanks for reviewing this.

    I might be missing something, but I don't see any potential
    threads_active leaks in this approach. We wont increase threads_active
    if IRQTF_RUNTHREAD was already set beforehand (as test_and_set_bit()
    will return 1).

    If irq_wake_thread is called multiple times before irq_thread has had a
    chance to run, threads_active will only be increased once and decreased
    back when IRQTF_RUNTHREAD is cleared.

    Am I missing something? If not, do you see any other issues with this


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