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

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Date:	Tue, 21 May 2013 06:37:30 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	paulmck@...ux.vnet.ibm.com
Cc:	Roman Gushchin <klamm@...dex-team.ru>,
	Dipankar Sarma <dipankar@...ibm.com>, zhmurov@...dex-team.ru,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH] rcu: fix a race in hlist_nulls_for_each_entry_rcu macro

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 !


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