MIME-Version: 1.0
In-Reply-To: <CALAqxLX=GP5FMXfoEGuSwUuZp0cTyUCzh+ntSdknevjJioM0hg@mail.gmail.com>
References: <CALAqxLWVYgnTnwAwm7uNQ6P_Z8xFd96NQ+G_j1qT+h5F6habag@mail.gmail.com>
 <CALAqxLXG8X2nkLEHM63oiY=M17vcpU2+-ec7x_aBWDCqrj4U-Q@mail.gmail.com>
 <CAM_iQpW2=aKKUmWanbuhqXdZGxr_TqB5pQ+U+A0+=optuGX5-Q@mail.gmail.com>
 <CALAqxLXv60ReJu26omM6p=ZboEm-Z-3w+q0JcxLXDqqK5ohNoQ@mail.gmail.com>
 <CAEA6p_AL8uUghtZgp4OmqygcFs-Jiy286P5r6tRd+yeSWxR3KA@mail.gmail.com>
 <CALAqxLXY-kE2N__eDq514cLycR0-QRpyOCMWpdttO6fgovE2rg@mail.gmail.com>
 <CAEA6p_C_rEYkJhcniyy6HUHgNxWFoxWzZ-WHsaSmNDwx4D+RXQ@mail.gmail.com>
 <CAEA6p_AOcNkAWPc7NFBnr8QWi3eHdJiQ2=8D_DB_XthwSDL2+Q@mail.gmail.com>
 <CALAqxLUoV6EQvofTEv9whW1_QMPBPU7eJBhRFUjaSs7CGeRFww@mail.gmail.com>
 <CAM_iQpWMWg5ytDq2Y9p9uet1zowGuCX+eksyiyxu9vQ18WoPxQ@mail.gmail.com>
 <CAEA6p_CooRGNOQN3fosF0JLqmd9aOTuNHKNPE8cbrzDH6c176w@mail.gmail.com>
 <CAEA6p_COwXWP97wSHvzokmm8ckQ2QEd7=dfNH04ttDPm_z3bcg@mail.gmail.com>
 <CALAqxLV-e=Uz_zG6VYcKSTG0+qJdpPOv0_vagnGx4bABgzO4tg@mail.gmail.com> <CALAqxLX=GP5FMXfoEGuSwUuZp0cTyUCzh+ntSdknevjJioM0hg@mail.gmail.com>
From: Wei Wang <weiwan@google.com>
Date: Sat, 12 Aug 2017 12:28:21 -0700
Message-ID: <CAEA6p_AY=rk_x_HoaBoxR+499E+jHqdUFgYyni6nTaCSfqDs8Q@mail.gmail.com>
Subject: Re: unregister_netdevice: waiting for eth0 to become free. Usage
 count = 1
To: John Stultz <john.stultz@linaro.org>
Cc: Cong Wang <xiyou.wangcong@gmail.com>, Martin KaFai Lau <kafai@fb.com>,
        lkml <linux-kernel@vger.kernel.org>,
        Network Development <netdev@vger.kernel.org>,
        Linux USB List <linux-usb@vger.kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Felipe Balbi <felipe.balbi@linux.intel.com>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1713
Lines: 43

On Fri, Aug 11, 2017 at 8:07 PM, John Stultz <john.stultz@linaro.org> wrote:
> On Fri, Aug 11, 2017 at 5:31 PM, John Stultz <john.stultz@linaro.org> wrote:
>> On Fri, Aug 11, 2017 at 5:10 PM, Wei Wang <weiwan@google.com> wrote:
>>>> If after Cong's fix, the issue still happens, could you help try the
>>>> patch attached and collect all logs when you try the reproduce the
>>>> issue? It would be great to have logs for both success case and the
>>>> failure case.
>>>>
>>>> Thanks so much for your help.
>>>>
>>>
>>> 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.
>>>
>>> The attached potential fix is tested by Martin and made sure it fixes his issue.
>>>
>>> John,
>>> It will be great if you can also give it a try and see if it fixes the
>>> issue on your side before I submit an official patch.
>>
>> So yes, sorry I haven't been able to get back quicker on the other
>> patches sent, was mucking about in other work.
>>
>> So yea, this patch  (potential fix for unregister_netdevice()) seems
>> to avoid the issue.
>>
>> I'm going to do some further testing, but its looking good so far.
>
> Looks good so far! I've not hit the issue yet.
>
> Thanks so much for sorting out a fix!
>
> If its useful:
> Tested-by: John Stultz <john.stultz@linaro.org>
>
> thanks again
> -john