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    SubjectRe: [GIT PULL rcu/next] rcu commits for 2.6.40
    On Mon, May 16, 2011 at 02:23:29PM +0200, Ingo Molnar wrote:
    > * Ingo Molnar <> wrote:
    > > > In the meantime, would you be willing to try out the patch at
    > > > This patch helped out Yinghai in
    > > > several configurations.
    > >
    > > Wasn't this the one i tested - or is it a new iteration?
    > >
    > > I'll try it in any case.
    > oh, this was a new iteration, mea culpa!
    > And yes, it solves all problems for me as well. Mind pushing it as a fix? :-)


    Unfortunately, the only reason I can see that it works is (1) there
    is some obscure bug in my code or (2) someone somewhere is failing to
    call irq_exit() on some interrupt-exit path. Much as I might be tempted
    to paper this one over, I believe that we do need to find whatever the
    underlying bug is.

    Oh, yes, there is option (3) as well: maybe if an interrupt deschedules
    a process, the final irq_exit() is omitted in favor of rcu_enter_nohz()?
    But I couldn't see any evidence of this in my admittedly cursory scan
    of the x86 interrupt-handling code.

    So until I learn differently, I am assuming that each and every
    irq_enter() has a matching call to irq_exit(), and that rcu_enter_nohz()
    is called after the final irq_exit() of a given burst of interrupts.

    If my assumptions are mistaken, please do let me know!

    Thanx, Paul

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