linux-kernel - Re: [PATCH v2 09/33] x86/intel_rdt: Add L3 cache capacity bitmask management

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Message-ID: <alpine.DEB.2.20.1609081131400.5647@nanos>
Date:   Thu, 8 Sep 2016 11:40:17 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Fenghua Yu <fenghua.yu@...el.com>
cc:     "H. Peter Anvin" <h.peter.anvin@...el.com>,
        Ingo Molnar <mingo@...e.hu>, Tony Luck <tony.luck@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>, Borislav Petkov <bp@...e.de>,
        Stephane Eranian <eranian@...gle.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        David Carrillo-Cisneros <davidcc@...gle.com>,
        Shaohua Li <shli@...com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
        Sai Prakhya <sai.praneeth.prakhya@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v2 09/33] x86/intel_rdt: Add L3 cache capacity bitmask
 management

On Thu, 8 Sep 2016, Fenghua Yu wrote:
>  
> +	for_each_online_cpu(i)
> +		rdt_cpumask_update(i);

The only reason why this does not blow up in your face is that at this
point the secondary cpus have been brought up already and user space is not
yet running, so cpu hotplug cannot happen in parallel. Protection by chance
is never a good idea.

Thanks,

	tglx