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Subject: Re: [PATCH net-next-2.6] igmp: RCU conversion of in_dev->mc_list
From: Eric Dumazet <eric.dumazet@gmail.com>
To: =?ISO-8859-1?Q?Am=E9rico?= Wang <xiyou.wangcong@gmail.com>
Cc: Cypher Wu <cypher.w@gmail.com>, linux-kernel@vger.kernel.org,
        netdev <netdev@vger.kernel.org>, David Miller <davem@davemloft.net>
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Content-Type: text/plain; charset="UTF-8"
Date: Fri, 12 Nov 2010 15:26:14 +0100
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Le vendredi 12 novembre 2010 à 14:34 +0100, Eric Dumazet a écrit :
> Le vendredi 12 novembre 2010 à 10:22 +0100, Eric Dumazet a écrit :
> > Le vendredi 12 novembre 2010 à 16:19 +0800, Américo Wang a écrit :
> > > On Fri, Nov 12, 2010 at 08:27:54AM +0100, Eric Dumazet wrote:
> > 
> > > >A RCU conversion is far more complex.
> > > >
> > > 
> > > Yup.
> > 
> > 
> > Well, actually this is easy in this case.
> > 
> > I'll post a patch to do this RCU conversion.
> > 
> > 
> 
> Note : compile tested only, I'll appreciate if someone can test it ;)
> 
> Note: one patch from net-2.6 is not yet included in net-next-2.6, so
> please make sure you have it before testing ;)
> 
> ( http://git.kernel.org/?p=linux/kernel/git/davem/net-2.6.git;a=commitdiff;h=18943d292facbc70e6a36fc62399ae833f64671b )
> 
> 
> Thanks
> 
> [PATCH net-next-2.6] igmp: RCU conversion of in_dev->mc_list
> 
> in_dev->mc_list is protected by one rwlock (in_dev->mc_list_lock).
> 
> This can easily be converted to a RCU protection.
> 
> Writers hold RTNL, so mc_list_lock is removed, not replaced by a
> spinlock.
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
> Cc: Cypher Wu <cypher.w@gmail.com>
> Cc: Américo Wang <xiyou.wangcong@gmail.com>
> ---

...

>  void ip_mc_up(struct in_device *in_dev)
>  {
> -	struct ip_mc_list *i;
> +	struct ip_mc_list *pmc;
>  
>  	ASSERT_RTNL();
>  
>  	ip_mc_inc_group(in_dev, IGMP_ALL_HOSTS);
>  
> -	for (i=in_dev->mc_list; i; i=i->next)
> -		igmp_group_added(i);
> +	for_each_pmc_rtnl(in_dev, pmc);
> +		igmp_group_added(pmc);
>  }


Oops there is an extra ; after the for_each_pmc_rtnl(in_dev, pmc)

should be

	for_each_pmc_rtnl(in_dev, pmc)
		igmp_group_added(pmc);


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