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

    On Sun, Dec 04, 2011 at 09:09:32PM +0200, Ido Yariv wrote:
    > 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
    > implementation?

    Any thoughts on this?


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