linux-kernel - Re: [patch 12/13] cpufreq/sparc-us2e: Replace racy task affinity logic

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Message-ID: <20170413025057.GL5910@vireshk-i7>
Date:   Thu, 13 Apr 2017 08:20:57 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "David S. Miller" <davem@...emloft.net>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Len Brown <lenb@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, Tejun Heo <tj@...nel.org>,
        Tony Luck <tony.luck@...el.com>, linux-pm@...r.kernel.org
Subject: Re: [patch 12/13] cpufreq/sparc-us2e: Replace racy task affinity
 logic

On 12-04-17, 22:07, Thomas Gleixner wrote:
> The access to the HBIRD_ESTAR_MODE register in the cpu frequency control
> functions must happen on the target CPU. This is achieved by temporarily
> setting the affinity of the calling user space thread to the requested CPU
> and reset it to the original affinity afterwards.
> 
> That's racy vs. CPU hotplug and concurrent affinity settings for that
> thread resulting in code executing on the wrong CPU and overwriting the
> new affinity setting.
> 
> Replace it by a straight forward smp function call. 
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Cc: linux-pm@...r.kernel.org
> ---
>  drivers/cpufreq/sparc-us2e-cpufreq.c |   45 ++++++++++++++++-------------------
>  1 file changed, 21 insertions(+), 24 deletions(-)

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh