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Date: Mon, 25 Jul 2011 09:21:33 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Paul Turner <pjt@google.com>, linux-kernel@vger.kernel.org,
        Bharata B Rao <bharata@linux.vnet.ibm.com>,
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        Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>,
        Ingo Molnar <mingo@elte.hu>, Pavel Emelyanov <xemul@openvz.org>,
        Jason Baron <jbaron@redhat.com>
Subject: Re: [patch 00/18] CFS Bandwidth Control v7.2
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On Mon, Jul 25, 2011 at 05:00:41PM +0200, Peter Zijlstra wrote:
> On Mon, 2011-07-25 at 16:58 +0200, Peter Zijlstra wrote:
> > +               rcu_read_lock();
> > +               ret = walk_tg_tree_from(tg, tg_set_cfs_period_down, NULL, &period);
> > +               rcu_read_unlock(); 
> 
> rcu over a mutex doesn't really work in mainline, bah.. 

SRCU can handle that situation, FWIW.  But yes, blocking in an RCU
read-side critical section is a no-no.

							Thanx, Paul