From: Eric Dumazet <eric.dumazet@gmail.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
David Ahern <dsahern@gmail.com>,
"David S. Miller" <davem@davemloft.net>
Cc: Julian Anastasov <ja@ssi.bg>,
Cong Wang <xiyou.wangcong@gmail.com>,
syzbot <syzbot+30209ea299c09d8785c9@syzkaller.appspotmail.com>,
ddstreet@ieee.org, dvyukov@google.com,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
syzkaller-bugs@googlegroups.com
Subject: Re: unregister_netdevice: waiting for DEV to become free (2)
Date: Sun, 28 Apr 2019 08:04:18 -0700 [thread overview]
Message-ID: <a9075b87-4f02-fe78-e86d-34f67bdf8b2a@gmail.com> (raw)
In-Reply-To: <6e57bc11-1603-0898-dfd4-0f091901b422@i-love.sakura.ne.jp>
On 4/27/19 9:22 PM, Tetsuo Handa wrote:
> 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.
>
This is the design yes. We can not let a dst having a pointer to some garbage memory.
(since we are going to free it very soon)
dst can be long lived objects. netdev (but loopback) are not.
> 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?
You'll have to study all the netdev notifiers to answer this question.
They are many of them, and they have a priority to let them run in a given order.
>
> Since I'm not a netdev person, I appreciate if you can explain
> that shutdown sequence using a flow chart.
I am a netdev person, but I have no time to explain this at this moment.
next prev parent reply other threads:[~2019-04-28 15:04 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-15 18:50 unregister_netdevice: waiting for DEV to become free (2) syzbot
2018-08-15 20:28 ` syzbot
2018-08-15 20:41 ` Dmitry Vyukov
2018-08-20 4:31 ` syzbot
2018-08-20 12:55 ` Julian Anastasov
2018-08-21 5:40 ` Cong Wang
2018-08-22 4:11 ` Julian Anastasov
2019-04-15 13:36 ` Tetsuo Handa
2019-04-15 15:35 ` David Ahern
2019-04-21 20:41 ` Stephen Suryaputra
2019-04-22 14:58 ` David Ahern
2019-04-22 16:04 ` Eric Dumazet
2019-04-22 16:09 ` Eric Dumazet
2019-04-16 14:00 ` Tetsuo Handa
2019-04-26 13:43 ` Tetsuo Handa
2019-04-27 17:16 ` David Ahern
2019-04-27 22:33 ` Tetsuo Handa
2019-04-27 23:52 ` Eric Dumazet
2019-04-28 4:22 ` Tetsuo Handa
2019-04-28 15:04 ` Eric Dumazet [this message]
2019-04-29 18:34 ` David Ahern
2019-04-29 18:43 ` David Ahern
2019-05-01 13:38 ` Tetsuo Handa
2019-05-01 14:52 ` David Ahern
2019-05-01 16:16 ` Tetsuo Handa
2019-05-04 14:52 ` [PATCH] ipv4: Delete uncached routes upon unregistration of loopback device Tetsuo Handa
2019-05-04 15:56 ` Eric Dumazet
2019-05-04 17:09 ` Tetsuo Handa
2019-05-04 17:24 ` Eric Dumazet
2019-05-04 20:13 ` Julian Anastasov
2019-11-28 9:56 ` unregister_netdevice: waiting for DEV to become free (2) Tetsuo Handa
2019-11-29 5:54 ` Lukas Bulwahn
2019-11-29 6:51 ` Jouni Högander
2019-12-05 10:00 ` Jouni Högander
2019-12-05 11:00 ` Tetsuo Handa
2019-12-16 11:12 ` Tetsuo Handa
2019-12-17 7:08 ` Jouni Högander
2019-10-11 10:14 ` Tetsuo Handa
2019-10-11 15:12 ` Alexei Starovoitov
2019-10-16 10:34 ` Toke Høiland-Jørgensen
2019-11-15 9:43 ` Tetsuo Handa
2019-11-21 11:36 ` Toke Høiland-Jørgensen
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