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    SubjectRe: bisected: 'perf top' causing soft lockups under Xen
    On Wed, Feb 15, 2012 at 10:25:44AM +0100, Peter Zijlstra wrote:
    > On Wed, 2012-02-15 at 00:57 -0800, Steven Noonan wrote:
    > > It seems to me that there are two options for fixing this, but I'm
    > > probably lacking the necessary context (or experience with Xen). Either:
    > >
    > > - The patch provided by Ben needs to have additional work to specially
    > > handle IRQ_WORK_VECTOR, since it seems to be a special case where
    > > there's no event channel attached for it. Perhaps adding an event
    > > channel for this is the fix? Seems high-overhead, but I lack a good
    > > understanding of how interrupts are handled in Xen.
    > So that's a self-IPI, is Xen failing to implement this?

    It does have self-IPIs.
    > > or
    > >
    > > - Perf needs to be "enlightened" about Xen and avoid sending an IPI in
    > > the first place.
    > Uhm, no. If anything Xen should simply not implement
    > arch_irq_work_raise(). The callbacks are then ran from the timer
    > interrupt.

    Looks like that wouldn't be too difficult - meaning implement a similar
    form of IRQ_WORKER that would call


    .. along with the rest of the stuff from Ben's patch. Let me see if I can
    prep a patch.

     \ /
      Last update: 2012-02-15 17:23    [W:0.021 / U:3.944 seconds]
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