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Date: Mon, 30 Mar 2015 16:01:31 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>,
        Preeti U Murthy <preeti@linux.vnet.ibm.com>,
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Subject: Re: [PATCH V2] sched: Improve load balancing in the presence of idle
 CPUs
Message-ID: <20150330140131.GZ23123@twins.programming.kicks-ass.net>
References: <20150326130014.21532.17158.stgit@preeti.in.ibm.com>
 <20150327143839.GO18994@e105550-lin.cambridge.arm.com>
 <55158966.4050300@linux.vnet.ibm.com>
 <20150327175651.GR18994@e105550-lin.cambridge.arm.com>
 <20150330110632.GT23123@twins.programming.kicks-ass.net>
 <20150330120302.GT18994@e105550-lin.cambridge.arm.com>
 <20150330122449.GH21418@twins.programming.kicks-ass.net>
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On Mon, Mar 30, 2015 at 03:29:09PM +0200, Vincent Guittot wrote:
> On 30 March 2015 at 14:24, Peter Zijlstra <peterz@infradead.org> wrote:
> > @@ -7647,6 +7648,8 @@ static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)
> >                         break;
> >
> >                 rq = cpu_rq(balance_cpu);
> > +               if (rq == this_rq)
> > +                       done = true;
> 
> AFAICT, this can't happen because we start the for_each _cpu loop with:
> if (balance_cpu == this_cpu || !idle_cpu(balance_cpu))
> continue;

Oh hey, look at me being blind ;-)