linux-kernel - Re: [patch V2 12/13] cpufreq/sparc-us2e: Replace racy task affinity logic

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Date:   Thu, 13 Apr 2017 10:50:54 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     tglx@...utronix.de
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        mingo@...nel.org, bigeasy@...utronix.de, benh@...nel.crashing.org,
        fenghua.yu@...el.com, herbert@...dor.apana.org.au,
        jiangshanlai@...il.com, lenb@...nel.org, mpe@...erman.id.au,
        rjw@...ysocki.net, tj@...nel.org, tony.luck@...el.com,
        viresh.kumar@...aro.org, linux-pm@...r.kernel.org
Subject: Re: [patch V2 12/13] cpufreq/sparc-us2e: Replace racy task
 affinity logic

From: Thomas Gleixner <tglx@...utronix.de>
Date: Thu, 13 Apr 2017 10:19:07 +0200 (CEST)

> spu_queue_register() needs to invoke setup functions on a particular
> 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 using work_on_cpu_safe() which guarantees to run the code on
> the requested CPU or to fail in case the CPU is offline.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Acked-by: Herbert Xu <herbert@...dor.apana.org.au>

Acked-by: David S. Miller <davem@...emloft.net>