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Subject: Re: [PATCH 2/3] sched: enforce per-cpu utilization limits on
 runtime balancing
From: Peter Zijlstra <peterz@infradead.org>
To: Fabio Checconi <fchecconi@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
       Paul Turner <pjt@google.com>,
       Dario Faggioli <faggioli@gandalf.sssup.it>,
       Michael Trimarchi <michael@evidence.eu.com>,
       Dhaval Giani <dhaval@retis.sssup.it>,
       Tommaso Cucinotta <t.cucinotta@sssup.it>, linux-kernel@vger.kernel.org,
       Fabio Checconi <fabio@gandalf.sssup.it>
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Date: Thu, 25 Feb 2010 21:28:22 +0100
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On Tue, 2010-02-23 at 19:56 +0100, Fabio Checconi wrote:
> +               /*
> +                * Make sure that before restarting balancing everyone
> +                * sees the new free bandwidth.
> +                */
> +               smp_wmb(); 

You cannot order something on its own, barriers come in pairs, where is
his?