linux-kernel - Re: [patch 00/18] CFS Bandwidth Control v7.2

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Message-ID: <20110725162133.GI2327@linux.vnet.ibm.com>
Date:	Mon, 25 Jul 2011 09:21:33 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Paul Turner <pjt@...gle.com>, linux-kernel@...r.kernel.org,
	Bharata B Rao <bharata@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval.giani@...il.com>,
	Balbir Singh <bsingharora@...il.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>,
	Pavel Emelyanov <xemul@...nvz.org>,
	Jason Baron <jbaron@...hat.com>
Subject: Re: [patch 00/18] CFS Bandwidth Control v7.2

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
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