On Tue, Dec 17, 2013 at 11:51:26PM +0100, Frederic Weisbecker wrote:
> We need the default timekeeping CPU to be able to receive IPIs sent
> from full dynticks CPUs when they wake up from full system idle state.
>
> Therefore we need an entrypoint from the scheduler IPI so that the
> need to poll on timekeeping duty is re-evaluated from irq_exit().
>
> In order to achieve this, lets take the scheduler IPI everytime as long
> as there is at least one full dynticks CPU around. Full dynticks CPUs
> are interested too in taking scheduler IPIs to reevaluate their tick.
>
> Signed-off-by: Frederic Weisbecker <fweis...@gmail.com>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Ingo Molnar <mi...@kernel.org>
> Cc: Peter Zijlstra <pet...@infradead.org>
> Cc: Steven Rostedt <rost...@goodmis.org>
> Cc: Paul E. McKenney <paul...@linux.vnet.ibm.com>
> Cc: John Stultz <john.stu...@linaro.org>
> Cc: Alex Shi <alex....@linaro.org>
> Cc: Kevin Hilman <khil...@linaro.org>
> ---
> kernel/sched/core.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index e85cda2..f46a7bc 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1502,9 +1502,9 @@ void scheduler_ipi(void)
> if (tif_need_resched())
> set_preempt_need_resched();
>
> - if (llist_empty(&this_rq()->wake_list)
> - && !tick_nohz_full_cpu(smp_processor_id())
> - && !got_nohz_idle_kick())
> + if (llist_empty(&this_rq()->wake_list) &&
> + !tick_nohz_full_enabled() &&
> + !got_nohz_idle_kick())
> return;
OK, this is what I was missing in my question about whether the
NO_HZ_FULL state was re-evaluated in the interrupt-return path.
Thanx, Paul
> /*
> --
> 1.8.3.1
>
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