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Date: Tue, 21 Dec 2010 00:52:03 +0100
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: LKML <linux-kernel@vger.kernel.org>, Thomas Gleixner <tglx@linutronix.de>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
        Lai Jiangshan <laijs@cn.fujitsu.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Anton Blanchard <anton@au1.ibm.com>,
        Tim Pepper <lnxninja@linux.vnet.ibm.com>
Subject: Re: [RFC PATCH 07/15] nohz_task: Restart tick when RCU forces nohz
 task cpu quiescent state
Message-ID: <20101220235158.GE1715@nowhere>
References: <1292858662-5650-1-git-send-email-fweisbec@gmail.com>
 <1292858662-5650-8-git-send-email-fweisbec@gmail.com>
 <1292860929.5021.16.camel@laptop>
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On Mon, Dec 20, 2010 at 05:02:09PM +0100, Peter Zijlstra wrote:
> On Mon, 2010-12-20 at 16:24 +0100, Frederic Weisbecker wrote:
> > If a cpu is in nohz mode due to a nohz task running, then
> > it is not able to notify quiescent states requested by other
> > CPUs.
> > 
> > Then restart the tick to remotely force the quiescent states on the
> > nohz task cpus.
> 
> -ENOPARSE.. if its in NOHZ state, it couldn't possibly need to
> participate in the quiescent state machine because the cpu is in a
> quiescent state and has 0 RCU activity.


But it can be in nohz state in the kernel in which case it can have
any RCU activity.
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