linux-kernel - Re: [patch v2 1/2] sched: Use resched IPI to kick off the nohz idle balance

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Date:	Tue, 04 Oct 2011 11:05:21 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Venki Pallipadi <venki@...gle.com>,
	Ingo Molnar <mingo@...e.hu>,
	Prarit Bhargava <prarit@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	stable@...nel.org
Subject: Re: [patch v2 1/2] sched: Use resched IPI to kick off the nohz idle
 balance

On Mon, 2011-10-03 at 15:09 -0700, Suresh Siddha wrote:
> +               smp_mb();
> +               /*
> +                * Use smp_send_reschedule() instead of resched_cpu().
> +                * This way we generate a sched IPI on the target cpu which
> +                * is idle. And the softirq performing nohz idle load balance
> +                * will be run before returning from the IPI.
> +                */
> +               smp_send_reschedule(ilb_cpu); 

Now the only thing missing is where the matching barrier is, does
receiving an interrupt imply a mb? If so that wants mentioning
somewhere, otherwise people will wonder how we can ever read the right
value.


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