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Date: Wed, 31 Jul 2019 15:53:38 -0700
From: Stephen Hemminger <stephen@networkplumber.org>
Message-ID: <20190731155338.15ff34cb@hermes.lan>
In-Reply-To: <20190731224955.10908-1-nikolay@cumulusnetworks.com>
References: <319fda43-195d-2b92-7f62-7e273c084a29@cumulusnetworks.com>
	<20190731224955.10908-1-nikolay@cumulusnetworks.com>
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Subject: Re: [Bridge] [PATCH net v3] net: bridge: move vlan init/deinit to
 NETDEV_REGISTER/UNREGISTER
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To: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Cc: netdev@vger.kernel.org, roopa@cumulusnetworks.com, bridge@lists.linux-foundation.org, davem@davemloft.net, michael-dev <michael-dev@fami-braun.de>

  
> -int br_vlan_init(struct net_bridge *br)
> +static int br_vlan_init(struct net_bridge *br)
>  {
>  	struct net_bridge_vlan_group *vg;
>  	int ret = -ENOMEM;
> @@ -1083,6 +1085,8 @@ int br_vlan_init(struct net_bridge *br)
>  	return ret;
>  
>  err_vlan_add:
> +	RCU_INIT_POINTER(br->vlgrp, NULL);
> +	synchronize_rcu();

Calling sychronize_rcu is expensive. And the callback for
notifier is always called with rtnl_head. 

Why not just keep the pointer initialization back in the
code where bridge is created, it was safe there.