From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH v2 9/9] netfilter: Replace smp_read_barrier_depends()
 with lockless_dereference()
Date: Fri, 21 Nov 2014 16:05:03 -0800
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Cc: Pablo Neira Ayuso <pablo@netfilter.org>,
	Patrick McHardy <kaber@trash.net>,
	Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>,
	"David S. Miller" <davem@davemloft.net>,
	Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
	James Morris <jmorris@namei.org>,
	Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
	netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
	"open list:NETWORKING [IPv4/..." <netdev@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>
To: Pranith Kumar <bobby.prani@gmail.com>
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On Fri, 2014-11-21 at 16:57 -0500, Pranith Kumar wrote:

> Hi Eric,
> 
> Thanks for looking at this patch.
> 
> I've been scratching my head since morning trying to find out what was
> so obviously wrong with this patch. Alas, I don't see what you do.
> 
> Could you point it out and show me how incompetent I am, please?
> 
> Thanks!

Well, even it the code is _not_ broken, I don't see any value with this
patch.

If I use git blame on current code, line containing
smp_read_barrier_depends() exactly points to the relevant commit [1]

After your change, it will point to some cleanup, which makes little
sense to me, considering you did not change the smp_wmb() in
xt_replace_table().

I, as a netfilter contributor would like to keep current code as is,
because it is how I feel safe with it.

We have a proliferation of interfaces, but this does not help to
understand the issues and code maintenance.

smp_read_barrier_depends() better documents the read barrier than 
lockless_dereference().

The point of having a lock or not is irrelevant here.

[1]
http://git.kernel.org/cgit/linux/kernel/git/davem/net.git/commit/?id=b416c144f46af1a30ddfa4e4319a8f077381ad63