Re: unregister_netdevice: waiting for DEV to become free (2)

[Tetsuo Handa]

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.