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    SubjectRe: [PATCH] Extend mwait idle to optimize away CAL and RES interrupts to an idle CPU -v1
    On Fri, Feb 24, 2012 at 01:41:50PM +0800, Yong Zhang wrote:
    > On Thu, Feb 23, 2012 at 11:34:11AM -0800, Venki Pallipadi wrote:
    > > On Thu, Feb 23, 2012 at 1:30 AM, Peter Zijlstra <peterz@infradead.org> wrote:
    > > > Why not scheduler_ipi()?
    > >
    > > Was trying to avoid irq_enter/exit. As the work here is done in idle
    > > thread context, I though we could avoid enter/exit.
    >
    > It seems we could not.
    > At least RCU need it, see commit c5d753a55, otherwise we will get
    > warning like 'RCU used illegally from extended quiescent state!'

    If the use is tracing, then Steven Rostedt's patchset plus use of his
    _rcuidle() tracing variants handles this:

    https://lkml.org/lkml/2012/2/7/231

    If this is instead algorithmic use of RCU, a set of patches I have queued
    up for 3.4 will be required.

    Thanx, Paul



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