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From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH 2/2] udp: RCU handling for Unicast packets.
Date: Sat, 01 Nov 2008 21:19:31 -0700 (PDT)
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From: Eric Dumazet <dada1@cosmosbay.com>
Date: Thu, 30 Oct 2008 06:50:07 +0100

> [PATCH] udp: add a missing smp_wmb() in udp_lib_get_port()
> 
> Corey Minyard spotted a missing memory barrier in udp_lib_get_port()
> 
> We need to make sure a reader cannot read the new 'sk->sk_next' value
> and previous value of 'sk->sk_hash'. Or else, an item could be deleted
> from a chain, and inserted into another chain. If new chain was empty
> before the move, 'next' pointer is NULL, and lockless reader can
> not detect it missed following items in original chain.
> 
> This patch is temporary, since we expect an upcoming patch
> to introduce another way of handling the problem.
> 
> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>

I've applied this to net-next-2.6