linux-kernel - Re: [PATCH v2] rcu: fix a race in hlist_nulls_for_each_entry

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Message-Id: <20130602.202703.1059637861388689182.davem@davemloft.net>
Date:	Sun, 02 Jun 2013 20:27:03 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	klamm@...dex-team.ru, paulmck@...ux.vnet.ibm.com,
	brouer@...hat.com, dipankar@...ibm.com, zhmurov@...dex-team.ru,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
	kaber@...sh.net, David.Laight@...LAB.COM
Subject: Re: [PATCH v2] rcu: fix a race in hlist_nulls_for_each_entry_rcu
 macro

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Sun, 02 Jun 2013 20:12:49 -0700

> On Sun, 2013-06-02 at 19:58 -0700, David Miller wrote:
>> From: Eric Dumazet <eric.dumazet@...il.com>
>> Date: Sun, 02 Jun 2013 16:31:35 -0700
>> 
>> > On Thu, 2013-05-30 at 12:25 +0400, Roman Gushchin wrote:
>> >> On 29.05.2013 23:06, Eric Dumazet wrote:
>> >> > On Wed, 2013-05-29 at 14:09 +0400, Roman Gushchin wrote:
>> >> >
>> >> > True, these lookup functions are usually structured the same around the
>> >> > hlist_nulls_for_each_entry_rcu() loop.
>> >> >
>> >> > A barrier() right before the loop seems to be a benefit, the size of
>> >> > assembly code is reduced by 48 bytes.
>> >> >
>> >> > And its one of the documented way to handle this kind of problems
>> >> > (Documentation/atomic_ops.txt line 114)
>> >> >
>> >> > I guess we should amend this documentation, eventually.
>> >> >
>> >> > Thanks, please add you "Signed-off-by" if you agree with the patch.
>> >> >
>> >> 
>> >> Signed-off-by: Roman Gushchin <klamm@...dex-team.ru>
>> >> 
>> >> Many thanks to you, Paul E. McKenney and David Laight for your
>> >> patches, help and participation in this discussion.
>> > 
>> > Thanks to you !
>> > 
>> > David, is there any problem with the patch ?
>> > 
>> > http://patchwork.ozlabs.org/patch/247360/ says "Not applicable", please
>> > tell me what is needed to get it merged.
>> 
>> It's not a networking patch, it's a patch for generic RCU upstream.
>> So it either goes through Paul McKenney, or directly via Linus on
>> linux-kernel.
> 
> Well, whole discussion went on linux kernel, and you were the original
> committer of this patch five years ago.
> 
> http://git.kernel.org/cgit/linux/kernel/git/davem/net-next.git/commit/?id=bbaffaca4810de1a25e32ecaf836eeaacc7a3d11
> 
> So please Paul or David make sure the patch goes in.
> 
> My only concern is that Paul seems quite busy these days.

Ok I can take it then, no problem.
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