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

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Message-ID: <1370229169.24311.119.camel@edumazet-glaptop>
Date:	Sun, 02 Jun 2013 20:12:49 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
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

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.

Thanks


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