From: Eric Dumazet <eric.dumazet@gmail.com>
To: Pranith Kumar <bobby.prani@gmail.com>
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>
Subject: Re: [PATCH v2 9/9] netfilter: Replace smp_read_barrier_depends() with lockless_dereference()
Date: Fri, 21 Nov 2014 16:05:03 -0800 [thread overview]
Message-ID: <1416614703.20938.0.camel@edumazet-glaptop2.roam.corp.google.com> (raw)
In-Reply-To: <CAJhHMCCCSU7PbWdgPouefbLJBcoxR8nmsS8dg_=BcuqVJZbDew@mail.gmail.com>
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
next prev parent reply other threads:[~2014-11-22 0:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1416582363-20661-1-git-send-email-bobby.prani@gmail.com>
2014-11-21 15:06 ` [PATCH v2 9/9] netfilter: Replace smp_read_barrier_depends() with lockless_dereference() Pranith Kumar
2014-11-21 16:12 ` Eric Dumazet
2014-11-21 21:57 ` Pranith Kumar
2014-11-22 0:05 ` Eric Dumazet [this message]
2014-11-22 1:23 ` Pranith Kumar
2014-11-22 0:24 ` Andres Freund
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