netdev - Re:Re: [drivers/net/vxlan]Why rcu_read_lock is not obtained before rculist travelling

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Date:   Wed, 1 Mar 2017 20:40:16 +0800 (CST)
From:   "Xiaobo Yan" <yanxb123@....com>
To:     "Cong Wang" <xiyou.wangcong@...il.com>
Cc:     "Stephen Hemminger" <stephen@...workplumber.org>,
        "Linux Kernel Network Developers" <netdev@...r.kernel.org>
Subject: Re:Re: [drivers/net/vxlan]Why rcu_read_lock is not obtained before
 rculist travelling


Hi Cong,

Thanks very much for your reply.  It's indeeded acquired by upper layer.

Thanks

At 2017-03-01 05:29:17, "Cong Wang" <xiyou.wangcong@...il.com> wrote:
>On Tue, Feb 28, 2017 at 6:03 AM, Xiaobo Yan <yanxb123@....com> wrote:
>> But I don’t find any rcu_read_lock invoked before travelling fdb_head list.  In vxlan_xmit and vxlan_snoop function, vxlan_find_mac function is called to search the vxlan_fdb of the dst_mac or src_mac. Then information in vxlan_fdb  is used for further process.  But as no rcu_read_lock is obtained before the list travelling, I am wondering if it is possible that vxlan_fdb is freed when it is being used.
>>
>
>In both RX and TX paths, rcu read lock is acquired by upper layer.
>Check __dev_queue_xmit() and process_backlog().