From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH RFC 1/2] netfilter: conntrack: remove RCU usage in
 conntrack notifier
Date: Fri, 27 Apr 2012 20:58:51 +0200
Message-ID: <1335553131.2775.252.camel@edumazet-glaptop>
References: <1335551333-6103-1-git-send-email-bpoirier@suse.de>
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Cc: netdev@vger.kernel.org, Pablo Neira Ayuso <pablo@netfilter.org>,
	Patrick McHardy <kaber@trash.net>,
	"David S. Miller" <davem@davemloft.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Mike Frysinger <vapier@gentoo.org>,
	Arun Sharma <asharma@fb.com>, netfilter-devel@vger.kernel.org,
	netfilter@vger.kernel.org, coreteam@netfilter.org,
	linux-kernel@vger.kernel.org,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Benjamin Poirier <bpoirier@suse.de>
Return-path: <netfilter-devel-owner@vger.kernel.org>
In-Reply-To: <1335551333-6103-1-git-send-email-bpoirier@suse.de>
Sender: netfilter-devel-owner@vger.kernel.org
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On Fri, 2012-04-27 at 14:28 -0400, Benjamin Poirier wrote:
> I think that the rcu usage in this code is pointless. It should either be
> removed or, if it was intended to protect against something, it ought to make
> that clear.
> 
> 1) The code does not make use of the deferred deletion/wait for completion rcu
> api (ie. synchronize_rcu(), call_rcu()).
> 2) It does not benefit from the barriers implied by the rcu primitives used.
> The code deals with callback pointers. There's no need to order writes to the
> function code (!) before writes to the function pointers here.
> ---

At a first glance, this seems pretty wrong.

code can disappear under you, thats for sure.

CONFIG_NF_CT_NETLINK=m

hint : module unload contains an rcu barrier.