Message-ID: <1364302242.5053.19.camel@laptop>
Subject: Re: [RFC PATCH v3 4/6] sched: secure access to other CPU statistics
From: Peter Zijlstra <peterz@infradead.org>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linaro-kernel@lists.linaro.org, mingo@kernel.org,
        linux@arm.linux.org.uk, pjt@google.com, santosh.shilimkar@ti.com,
        morten.rasmussen@arm.com, chander.kashyap@linaro.org,
        cmetcalf@tilera.com, tony.luck@intel.com, alex.shi@intel.com,
        preeti@linux.vnet.ibm.com, paulmck@linux.vnet.ibm.com,
        tglx@linutronix.de, len.brown@intel.com, arjan@linux.intel.com,
        amit.kucheria@linaro.org, corbet@lwn.net
Date: Tue, 26 Mar 2013 13:50:42 +0100
In-Reply-To: <1363955155-18382-5-git-send-email-vincent.guittot@linaro.org>
References: <1363955155-18382-1-git-send-email-vincent.guittot@linaro.org>
	 <1363955155-18382-5-git-send-email-vincent.guittot@linaro.org>
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On Fri, 2013-03-22 at 13:25 +0100, Vincent Guittot wrote:
> @@ -3364,13 +3364,16 @@ done:
>  static bool is_buddy_busy(int cpu)
>  {
>         struct rq *rq = cpu_rq(cpu);
> +       u32 sum = rq->avg.runnable_avg_sum;
> +       u32 period = rq->avg.runnable_avg_period;
> +
> +       sum = min(sum, period);

OK this makes sense; use a simple sanity constraint instead of going
overboard on serialization -- however, why is this a separate patch?

That is, this could easily be part of the patch that introduces
is_buddy_busy(); also you likely want part of this patch's changelog
to become a comment that goes right above this min() :-)

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