netdev - Re: [PATCH net v3] net: bridge: move vlan init/deinit to NETDEV

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Message-ID: <20190731155338.15ff34cb@hermes.lan>
Date:   Wed, 31 Jul 2019 15:53:38 -0700
From:   Stephen Hemminger <stephen@...workplumber.org>
To:     Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Cc:     netdev@...r.kernel.org, roopa@...ulusnetworks.com,
        davem@...emloft.net, bridge@...ts.linux-foundation.org,
        michael-dev <michael-dev@...i-braun.de>
Subject: Re: [PATCH net v3] net: bridge: move vlan init/deinit to
 NETDEV_REGISTER/UNREGISTER

  
> -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.