Subject: Re: mmotm 2010-11-23 + autogroups -> inconsistent lock state
From: Mike Galbraith <efault@gmx.de>
To: paulmck@linux.vnet.ibm.com
Cc: Valdis.Kletnieks@vt.edu, akpm@linux-foundation.org,
        Ingo Molnar <mingo@elte.hu>, mm-commits@vger.kernel.org,
        linux-kernel@vger.kernel.org
In-Reply-To: <20101202181658.GG2085@linux.vnet.ibm.com>
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	 <20101202181658.GG2085@linux.vnet.ibm.com>
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Date: Fri, 03 Dec 2010 04:58:22 +0100
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On Thu, 2010-12-02 at 10:16 -0800, Paul E. McKenney wrote:
> On Wed, Nov 24, 2010 at 01:25:25PM -0700, Mike Galbraith wrote:
>  
> > Despite task groups being freed via rcu, update_shares_cup() hits freed
> > memory and explodes, and nothing I've tried has been able to stop it.
> > The only thing I haven't tried (aside from the right thing;) is to take
> > rcu out of the picture entirely.
> 
> Is your new autogroup structure retaining a pointer to memory that
> is freed by RCU?

That turned out to be a typo that left freed cfs_rq registered.  No dark
elves (memory ordering), just a defenseless little typo.

	-Mike

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