linux-kernel - Re: kmemcheck caught read from freed memory (cfq_free_io

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Message-ID: <20080402122814.GF12774@kernel.dk>
Date:	Wed, 2 Apr 2008 14:28:15 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Pekka Enberg <penberg@...helsinki.fi>, paulmck@...ux.vnet.ibm.com,
	Ingo Molnar <mingo@...e.hu>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Randy Dunlap <randy.dunlap@...cle.com>
Subject: Re: kmemcheck caught read from freed memory (cfq_free_io_context)

On Wed, Apr 02 2008, Peter Zijlstra wrote:
> On Wed, 2008-04-02 at 13:53 +0200, Jens Axboe wrote:
> 
> > > Yeah, SLAB_DESTROY_BY_RCU should have a _HUGE_ comment explaining it,
> > > I'm sure this is not the first (nor the last) time people get that
> > > wrong.
> > 
> > It should, SLAB_DESTROY_BY_RCU is definitely useful, but it is expected
> > to be an 'easier' way of doing the call_rcu() manually. So it definitely
> > needs more documentation.
> > 
> 
> Ok I gave it a go, how bad is this text?

I think it looks good. The key point is this:

"This delays freeing the SLAB page by a grace period, it does _NOT_ delay
object freeing."

which is right in the front of the text and with sample validation
below. So you can add my acked-by to that, if you want.

-- 
Jens Axboe

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