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Date: Mon, 29 Aug 2011 19:11:57 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Anton Blanchard <anton@au1.ibm.com>, Avi Kivity <avi@redhat.com>,
        Ingo Molnar <mingo@elte.hu>, Lai Jiangshan <laijs@cn.fujitsu.com>,
        "Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
        Paul Menage <menage@google.com>,
        Stephen Hemminger <shemminger@vyatta.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Tim Pepper <lnxninja@linux.vnet.ibm.com>
Subject: Re: [PATCH 05/32] nohz: Move rcu dynticks idle mode handling to idle
 enter/exit APIs
Message-ID: <20110829171155.GD9748@somewhere.redhat.com>
References: <1313423549-27093-1-git-send-email-fweisbec@gmail.com>
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 <1314627922.2816.65.camel@twins>
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On Mon, Aug 29, 2011 at 04:25:22PM +0200, Peter Zijlstra wrote:
> On Mon, 2011-08-15 at 17:52 +0200, Frederic Weisbecker wrote:
> > To prepare for nohz / idle logic split, pull out the rcu dynticks
> > idle mode switching to strict idle entry/exit areas.
> > 
> > So we make the dyntick mode possible without always involving rcu
> > extended quiescent state. 
> 
> Why is this a good thing? I would be thinking that if we're a userspace
> bound task and we disable the tick rcu would be finished on this cpu and
> thus the extended quiescent state is just what we want?

But we can stop the tick from the kernel, not just userspace.