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Message-ID: <1369787693.3301.586.camel@edumazet-glaptop>
Subject: Re: [PATCH v2] rcu: fix a race in hlist_nulls_for_each_entry_rcu
 macro
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Roman Gushchin <klamm@yandex-team.ru>,
        Jesper Dangaard Brouer <brouer@redhat.com>
Cc: paulmck@linux.vnet.ibm.com, Dipankar Sarma <dipankar@in.ibm.com>,
        zhmurov@yandex-team.ru, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
        Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
        James Morris <jmorris@namei.org>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        Patrick McHardy <kaber@trash.net>
Date: Tue, 28 May 2013 17:34:53 -0700
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On Tue, 2013-05-28 at 13:10 +0400, Roman Gushchin wrote:
> On 28.05.2013 04:12, Eric Dumazet wrote:

> > Adding a barrier() is probably what we want.
> 
> I agree, inserting barrier() is also a correct and working fix.

Yeah, but I can not find a clean way to put it inside the "for (;;)"

for (barrier();;)  ->

error: expected expression before ‘__asm__’

No user currently does :

if (condition)
	hlist_nulls_for_each_entry_rcu(tpos, pos, head, member)

But who knows...