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    On Thu, 27 May 2010, Milton Miller wrote:

    >
    > [Hmm, why did this not appear in patchwork.kernel.org? Now
    > I have to guess a CC list.]
    >
    > On Wed, 26 May 2010 around 22:43:50 -0400 (EDT), Len Brown wrote:
    > > From: Len Brown <len.brown@intel.com>
    > >
    > > TS_POLLING set tells the scheduler a task will poll
    > > need_resched() to look for work.
    > >
    >
    > True
    >
    > > TS_POLLING clear tells resched_task() and wake_up_idle_cpu()
    > > that the remote CPU is sleeping in idle, and thus requires
    > > a reschedule interrupt to wake them to notice work.
    >
    > No, that only applies to the idle task.
    >
    >
    > >
    > > Update the description of TS_POLLING to reflect how it works.
    > > "cleared when sleeping in idle, requiring reschedule interrupt"
    >
    > That would imply its set for every normal task that is not in some
    > kind of sleep state.

    you're right, just the idle task sets this flag.

    > > Signed-off-by: Len Brown <len.brown@intel.com>
    > > Acked-by: Peter Zijlstra <peterz@infradead.org>
    >
    > > -#define TS_POLLING 0x0004 /* true if in idle loop
    > > - and not sleeping */
    > > +#define TS_POLLING 0x0004 /* clear when sleeping in idle
    > > + requiring reschedule interrupt */
    >
    > How about "idle task polling need_resched, skip sending interrupt"?

    I think that is an improvement over my wording.

    Though technically we're not polling need_resched in the case
    I have in mind. The hardware is snooping any write to the thread flags
    via MONITOR/MWAIT trigger address.

    cheers,
    -Len Brown, Intel Open Source Technology Center






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