netdev - Re: [PATCH 1/5] 8021q: Vlan driver should use rcu_barrier() on unload instead of syncronize

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Message-ID: <20090608155446.GB6961@linux.vnet.ibm.com>
Date:	Mon, 8 Jun 2009 08:54:46 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Jesper Dangaard Brouer <hawk@...x.dk>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, urs.thuermann@...kswagen.de,
	oliver.hartkopp@...kswagen.de, wg@...ndegger.com,
	vladislav.yasevich@...com, sri@...ibm.com,
	linux-sctp@...r.kernel.org, Trond.Myklebust@...app.com,
	linux-nfs@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH 1/5] 8021q: Vlan driver should use rcu_barrier() on
	unload instead of syncronize_net()

On Mon, Jun 08, 2009 at 03:11:28PM +0200, Jesper Dangaard Brouer wrote:
> The VLAN 8021q driver needs to call rcu_barrier() when unloading the module,
> instead of syncronize_net().  This is needed to make sure that outstanding
> call_rcu() callbacks have completed, before the callback function code is
> removed on module unload.

Looks good!  And thank you for checking up on this!!!

Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> Signed-off-by: Jesper Dangaard Brouer <hawk@...x.dk>
> ---
> 
>  net/8021q/vlan.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/net/8021q/vlan.c b/net/8021q/vlan.c
> index 714e1c3..fe64908 100644
> --- a/net/8021q/vlan.c
> +++ b/net/8021q/vlan.c
> @@ -758,7 +758,7 @@ static void __exit vlan_cleanup_module(void)
>  		BUG_ON(!hlist_empty(&vlan_group_hash[i]));
> 
>  	unregister_pernet_gen_device(vlan_net_id, &vlan_net_ops);
> -	synchronize_net();
> +	rcu_barrier(); /* Wait for completion of call_rcu()'s */
> 
>  	vlan_gvrp_uninit();
>  }
> 
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