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Message-ID: <1369143450.3301.217.camel@edumazet-glaptop>
Subject: Re: [PATCH] rcu: fix a race in hlist_nulls_for_each_entry_rcu macro
From: Eric Dumazet <eric.dumazet@gmail.com>
To: paulmck@linux.vnet.ibm.com
Cc: Roman Gushchin <klamm@yandex-team.ru>,
        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, 21 May 2013 06:37:30 -0700
In-Reply-To: <20130521120906.GD3578@linux.vnet.ibm.com>
References: <519B38EC.90401@yandex-team.ru>
	 <20130521120906.GD3578@linux.vnet.ibm.com>
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On Tue, 2013-05-21 at 05:09 -0700, Paul E. McKenney wrote:
> > 
> > -#define hlist_nulls_first_rcu(head) \
> > -	(*((struct hlist_nulls_node __rcu __force **)&(head)->first))
> > +#define hlist_nulls_first_rcu(head)			\
> > +	(*((struct hlist_nulls_node __rcu __force **)	\
> > +	   &((volatile typeof(*head) *)head)->first))
> 
> Why not use ACCESS_ONCE() or (better) rcu_dereference_raw() here?
> 

+1

Very good catch Roman !

Thanks !