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Date:	Thu, 22 May 2014 14:13:28 +0200
From:	Borislav Petkov <>
To:	"Srivatsa S. Bhat" <>
Cc:	Srinivas Pandruvada <>,
	Jacob Pan <>,
	LKML <>,
	Borislav Petkov <>, Ingo Molnar <>,
	"Rafael J. Wysocki" <>,
	Peter Zijlstra <>,
	Thomas Gleixner <>,
	"" <>,
	Oleg Nesterov <>
Subject: Re: [PATCH] intel_rapl: Correct hotplug correction

On Thu, May 22, 2014 at 05:24:33PM +0530, Srivatsa S. Bhat wrote:
> That was just me trying to explain the current mess, not justifying
> it! :-/

Yes, it is a mess - thanks for explaining it.

> I think Oleg had a proposed patch to use per-cpu rwsem in CPU hotplug to
> drastically simplify this whole locking scheme. I think we could look at
> that again.

And that is my question: why can't all be made to use a single dumb lock
allowing only one task and lock everything hotplug with it?

Maybe it is an oversimplification but why do I care about hotplug
operations scaling - they're not on the fastpath anyway.

And yes, we're trying to remove CPU_POST_DEAD - I have one user in
MCE which I'm testing a removal patch for - and then we can all use
get_/put_online_cpus() like we used to do and be happy.

Having 2 + 1 aliased hotplug sync APIs is beyond insane and is simply
not needed IMHO.


Sent from a fat crate under my desk. Formatting is fine.
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