linux-kernel - Re: [GIT PULL] RCU changes for v3.3

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Date:	Tue, 24 Jan 2012 15:54:37 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] RCU changes for v3.3

On Wed, Jan 25, 2012 at 12:46:49AM +0100, Eric Dumazet wrote:
> Le mardi 24 janvier 2012 à 15:29 -0800, Paul E. McKenney a écrit :
> 
> > And here is another version of the patch.
> > 
> > 							Thanx, Paul
> > 
> > ------------------------------------------------------------------------
> > 
> > x86: Avoid invoking RCU when CPU is idle
> > 
> > The idle loop is a quiscent state for RCU, which means that RCU ignores
> > CPUs that have told RCU that they are idle via rcu_idle_enter().  There
> > are nevertheless quite a few places where idle CPUs use RCU, most commonly
> > indirectly via tracing.  This patch fixes these problems for x86.
> > 
> > Many of these bugs have been in the kernel for quite some time, but
> > Frederic's recent change now gives warnings.
> > 
> > This patch takes the straightforward approach of pushing the
> > rcu_idle_enter()/rcu_idle_exit() pair further down into the core
> > of the idle loop.
> > 
> > Signed-off-by: Paul E. McKenney <paul.mckenney@...aro.org>
> > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > 
> 
> Oh well, just when I decided to sleep a bit, you send a new patch :)

;-)  ;-)  ;-)

> This seems to remove the warnings at least on my x86_64 server, thanks !
> 
> Tested-by: Eric Dumazet <eric.dumazet@...il.com>

Good to hear!  Thank you!!!  I have added your Reported-by and
Tested-by.

							Thanx, Paul

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