linux-kernel - Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1

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Message-ID: <CAEA6p_CxiwXzQHgLA_Oma0pfayYReGc5QmJkV=Td9M1Kdqwbzg@mail.gmail.com>
Date:   Fri, 11 Aug 2017 17:25:58 -0700
From:   Wei Wang <weiwan@...gle.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        John Stultz <john.stultz@...aro.org>,
        Martin KaFai Lau <kafai@...com>,
        lkml <linux-kernel@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>
Subject: Re: unregister_netdevice: waiting for eth0 to become free. Usage
 count = 1

On Fri, Aug 11, 2017 at 5:19 PM, David Ahern <dsahern@...il.com> wrote:
> On 8/11/17 6:10 PM, Wei Wang wrote:
>> I think we have a potential fix for this issue.
>> Martin and I found that when addrconf_dst_alloc() creates a rt6, it is
>> possible that rt6->dst.dev points to loopback device while
>> rt6->rt6i_idev->dev points to a real device.
>> When the real device goes down, the current fib6 clean up code only
>> checks for rt6->dst.dev and assumes rt6->rt6i_idev->dev is the same.
>> That leaves unreleased refcnt on the real device if rt6->dst.dev
>> points to loopback dev.
>
> Yes, host routes and anycast routes.
>
> I have a patch to fix that but it is held up on a few VRF test cases
> failing. Hopefully I can get that figured out next week. These unrelated
> routes against the loopback device have been a source of a number of
> problems (e.g. take down 'lo' and all of IPv6 networking stops for that
> namespace).

Thanks David.
By "a patch to fix that" do you mean after your patch, for every rt6,
rt6->rt6i_idev will be the same as rt6->dst.dev?