linux-kernel - Re: Weird rcu lockdep warning

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Message-ID: <20100415194758.GQ2471@linux.vnet.ibm.com>
Date:	Thu, 15 Apr 2010 12:47:58 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Lai Jiangshan <laijs@...fujitsu.com>,
	David Miller <davem@...emloft.net>, a.p.zijlstra@...llo.nl,
	mingo@...e.hu, sparclinux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Weird rcu lockdep warning

On Thu, Apr 15, 2010 at 08:57:05PM +0200, Frederic Weisbecker wrote:
> On Wed, Apr 14, 2010 at 09:24:26PM -0700, Paul E. McKenney wrote:
> > On Wed, Apr 14, 2010 at 09:00:57AM -0700, Paul E. McKenney wrote:
> > > On Wed, Apr 14, 2010 at 05:51:11PM +0200, Frederic Weisbecker wrote:
> > 
> > [ . . .]
> > 
> > > > Note I just tested the patch the previous one and it looks fine now.
> > > > You can then safely consider the "general idea" fixes the problem :)
> > > 
> > > Thank you, Frederic!!!
> > 
> > And here is what I hope is the official fix.
> > 
> > Could you please test it?
> > 
> > 							Thanx, Paul
> > 
> > ------------------------------------------------------------------------
> > 
> > commit 9be39c445a41e458d53cf9a57d25dbfa4b74c970
> > Author: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> > Date:   Tue Apr 13 18:45:51 2010 -0700
> > 
> >     rcu: Make RCU lockdep check the lockdep_recursion variable
> >     
> >     The lockdep facility temporarily disables lockdep checking by incrementing
> >     the current->lockdep_recursion variable.  Such disabling happens in NMIs
> >     and in other situations where lockdep might expect to recurse on itself.
> >     This patch therefore checks current->lockdep_recursion, disabling RCU
> >     lockdep splats when this variable is non-zero.  In addition, this patch
> >     removes the "likely()", as suggested by Lai Jiangshan.
> >     
> >     Reported-by: Frederic Weisbecker <fweisbec@...il.com>
> >     Reported-by: David Miller <davem@...emloft.net>
> >     Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 
> Tested-by: Frederic Weisbecker <fweisbec@...il.com>

Thank you, Frederic!

							Thanx, Paul
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