netdev - Re: [NET] ROUTE: fix rcu_dereference() uses in /proc/net/rt

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Message-ID: <20080111000020.GB22040@gondor.apana.org.au>
Date:	Fri, 11 Jan 2008 11:00:20 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	Eric Dumazet <dada1@...mosbay.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	davem@...emloft.net, dipankar@...ibm.com, netdev@...r.kernel.org
Subject: Re: [NET] ROUTE: fix rcu_dereference() uses in /proc/net/rt_cache

On Fri, Jan 11, 2008 at 12:10:42AM +0100, Jarek Poplawski wrote:
>
> It seems this optimization could've a side effect: if during such a
> loop updates are done, and r is seen !NULL during while() check, but
> NULL after rcu_dereference(), the listing/counting could stop too
> soon. So, IMHO, probably the first version of this patch is more
> reliable. (Or alternatively additional check is needed before return.)

No, while the value of r->u.dst.rt_next can change between two readings,
the value of r cannot.

Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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