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Date: Sun, 28 Apr 2019 13:22:49 +0900 From: Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp> To: Eric Dumazet <eric.dumazet@...il.com>, David Ahern <dsahern@...il.com>, "David S. Miller" <davem@...emloft.net> Cc: Julian Anastasov <ja@....bg>, Cong Wang <xiyou.wangcong@...il.com>, syzbot <syzbot+30209ea299c09d8785c9@...kaller.appspotmail.com>, ddstreet@...e.org, dvyukov@...gle.com, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, syzkaller-bugs@...glegroups.com Subject: Re: unregister_netdevice: waiting for DEV to become free (2) On 2019/04/28 8:52, Eric Dumazet wrote: > On 4/27/19 3:33 PM, Tetsuo Handa wrote: >> >> I'm waiting for davem why it is safe to move the dst entry from >> "a device to unregister" to "a loopback device in that namespace". >> I'm waiting for an explanation how the dst entry which was moved to >> "a loopback device in that namespace" is released (i.e. what the >> expected shutdown sequence is). > > The most probable explanation is that we make sure the loopback device > is the last one to be dismantled at netns deletion, > and this would obviously happen after all dst have been released. > rt_flush_dev() becomes a no-op if "dev" == "a loopback device in that namespace". And according to debug printk(), rt_flush_dev() is called on "a loopback device in that namespace" itself. If "a loopback device in that namespace" is the last "one" (== "a network device in that namespace" ?), which shutdown sequence should have called dev_put("a loopback device in that namespace") before unregistration of "a loopback device in that namespace" starts? Since I'm not a netdev person, I appreciate if you can explain that shutdown sequence using a flow chart.
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