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Date: Thu, 10 Oct 2013 12:36:31 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@kernel.org>,
        "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
        Peter Zijlstra <peterz@infradead.org>,
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        Andrea Arcangeli <aarcange@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/6] Optimize the cpu hotplug locking -v2
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On Thu, 10 Oct 2013 09:00:44 -0700
Andrew Morton <akpm@linux-foundation.org> wrote:

> It's been ages since I looked at this stuff :( Although it isn't used
> much, memory hotplug manages to use stop_machine() on the add/remove
> (ie, "writer") side and nothing at all on the "reader" side.  Is there
> anything which fundamentally prevents cpu hotplug from doing the same?


I would think that memory hotplug may require stop machine as all CPUs
may touch that memory. But we would like to remove stomp machine from
CPU hotplug. Why prevent all CPUs from running when we want to remove
one?

-- Steve