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    SubjectRe: [KVM-RFC PATCH 1/2] eventfd: add an explicit srcu based notifier interface
    Davide Libenzi wrote:
    > On Thu, 18 Jun 2009, Gregory Haskins wrote:
    >
    >
    >> Davide Libenzi wrote:
    >>
    >>> On Thu, 18 Jun 2009, Gregory Haskins wrote:
    >>>
    >>>
    >>>
    >>>> Actually there is only one (the tx-thread) aside from the eventfd
    >>>> imposed workqueue one. Incidentally, I would love to get rid of the
    >>>> other thread too, so I am not just picking on eventfd ;). The other is
    >>>> a lot harder since it has to update the virtio-ring and may need to page
    >>>> in guest memory to do so.
    >>>>
    >>>>
    >>> No, there is the interface rx softirq too, that makes two.
    >>>
    >> Actually, I believe you are mistaken. It normally executes the softirq
    >> in interrupt context, not a thread.
    >>
    >> But I digress. Lets just shelve the SRCU conversation for another day.
    >> It was my bad for introducing it now prematurely to solve a mostly
    >> unrelated problem: the module-reference thing. I didn't realize the
    >> SRCU change would be so controversial, and I didn't think to split
    >> things apart as I have done today.
    >>
    >> But the fact is: I do not see any way to actually use your referenceless
    >> POLLHUP release code in a race free way without doing something like I
    >> propose in 3/4, 4/4. Lets keep the discussion focused on that for now,
    >> if we could.
    >>
    >
    > OK, since I got literally swamped by the amount of talks and patches over
    > this theoretically simple topic, would you mind 1) posting the global
    > patch over eventfd 2) describe exactly what races are you talking about
    > 3) explain why this should be any concern of eventfd at all?
    >
    >
    >
    Yes, I can do that. Thanks Davide,

    -Greg


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