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Subject: Re: CPU Hotplug rework
From: Steven Rostedt <rostedt@goodmis.org>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rusty Russell <rusty@rustcorp.com.au>, paulmck@linux.vnet.ibm.com,
        "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>,
        Arjan van de Ven <arjan@infradead.org>,
        "Rafael J. Wysocki" <rjw@sisk.pl>,
        Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
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        Milton Miller <miltonm@bga.com>, "mingo@elte.hu" <mingo@elte.hu>,
        Tejun Heo <tj@kernel.org>, KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
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Date: Mon, 26 Mar 2012 09:09:46 -0400
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On Mon, 2012-03-26 at 10:02 +0200, Peter Zijlstra wrote:
> On Mon, 2012-03-26 at 11:11 +1030, Rusty Russell wrote:
> > Obviously, having callbacks hanging around until the CPU comes back is
> > not viable, nor is blocking preempt during the callbacks.  Calling
> > get_online_cpus() is too heavy. 
> 
> -rt has patches (albeit somewhat ugly) to make get_online_cpus() a br
> style rw-lock. 

Unfortunately, -rt still has broken cpu hotplug.

-- Steve