netdev - Re: [Patch net] ipv6: only call ip6_route_dev_notify() once for NETDEV

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Message-Id: <20170622.110723.1095460318299544942.davem@davemloft.net>
Date:   Thu, 22 Jun 2017 11:07:23 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     unlisted-recipients:; (no To-header on input)
Cc:     netdev@...r.kernel.org, jeffy.chen@...k-chips.com,
        dsahern@...il.com
Subject: Re: [Patch net] ipv6: only call ip6_route_dev_notify() once for
 NETDEV_UNREGISTER

From: Cong Wang <xiyou.wangcong@...il.com>
Date: Tue, 20 Jun 2017 11:42:27 -0700

> In commit 242d3a49a2a1 ("ipv6: reorder ip6_route_dev_notifier after ipv6_dev_notf")
> I assumed NETDEV_REGISTER and NETDEV_UNREGISTER are paired,
> unfortunately, as reported by jeffy, netdev_wait_allrefs()
> could rebroadcast NETDEV_UNREGISTER event until all refs are
> gone.
> 
> We have to add an additional check to avoid this corner case.
> For netdev_wait_allrefs() dev->reg_state is NETREG_UNREGISTERED,
> for dev_change_net_namespace(), dev->reg_state is
> NETREG_REGISTERED. So check for dev->reg_state != NETREG_UNREGISTERED.
> 
> Fixes: 242d3a49a2a1 ("ipv6: reorder ip6_route_dev_notifier after ipv6_dev_notf")
> Reported-by: jeffy <jeffy.chen@...k-chips.com>
> Cc: David Ahern <dsahern@...il.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>

Applied.