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Date: Wed, 2 Apr 2008 06:37:15 -0700
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Jens Axboe <jens.axboe@oracle.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@elte.hu>,
       Pekka J Enberg <penberg@cs.helsinki.fi>,
       Vegard Nossum <vegard.nossum@gmail.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: kmemcheck caught read from freed memory (cfq_free_io_context)
Message-ID: <20080402133715.GA5327@linux.vnet.ibm.com>
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References: <20080402072456.GI12774@kernel.dk> <20080402072846.GA16454@elte.hu> <20080402105539.GA5610@linux.vnet.ibm.com> <1207133961.8514.768.camel@twins> <20080402113327.GC41073@gandalf.sssup.it> <20080402114338.GA12774@kernel.dk> <20080402123620.GH12774@kernel.dk> <20080402123639.GI12774@kernel.dk> <20080402125530.GF41073@gandalf.sssup.it> <20080402125819.GO12774@kernel.dk>
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On Wed, Apr 02, 2008 at 02:58:19PM +0200, Jens Axboe wrote:
> On Wed, Apr 02 2008, Fabio Checconi wrote:
> > > From: Jens Axboe <jens.axboe@oracle.com>
> > > Date: Wed, Apr 02, 2008 02:36:39PM +0200
> > >
> > > > Looks good and tests fine as well. I've applied it, on top of the
> > > > hlist_for_each_entry_safe_rcu() fix.
> > > > 
> > > > http://git.kernel.dk/?p=linux-2.6-block.git;a=commit;h=436151ad32b4a59e0d36165a7d6312545f126661
> > > > 
> > 
> > ok, thanks.  anyway I don't think the hlist_for_each_entry_safe_rcu()
> > is needed at this point, since the pos->next pointer is still valid
> > (at least) until the next rcu_read_unlock().  am I wrong?
> 
> it isn't, but it's still clearer. so either that or a nice comment, I
> just stuck with what I had already committed.

Given Peter's comment, would you be willing to drop the
hlist_for_each_entry_safe_rcu()?  People tend to read too much into
the "safe" sometimes.  ;-)

							Thanx, Paul