linux-kernel - Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after soft remove event

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Message-ID: <20160921130428.2e7bprll64vs6h2r@pd.tnic>
Date:   Wed, 21 Sep 2016 15:04:29 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Prarit Bhargava <prarit@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Len Brown <len.brown@...el.com>,
        Andi Kleen <ak@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>,
        Juergen Gross <jgross@...e.com>
Subject: Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after
 soft remove event

On Wed, Sep 21, 2016 at 07:39:31AM -0400, Prarit Bhargava wrote:
> The information in /sys/devices/system/cpu/cpuX/topology
> directory is useful for userspace monitoring applications and in-tree
> utilities like cpupower & turbostat.
> 
> When down'ing a CPU the /sys/devices/system/cpu/cpuX/topology directory is
> removed during the CPU_DEAD hotplug callback in the kernel.  The problem
> with this model is that the CPU has not been physically removed and the
> data in the topology directory is still valid.  IOW, the cpu is still
> present but the kernel has removed the topology directory making it
> very difficult to determine exactly where the cpu is located.

So I'm afraid I still don't understand what the problem here is.

And the commit message of 2/2 doesn't make it any clearer. Can you
please give a concrete example what the problem is and what you're
trying to achieve.

Thanks.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--