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

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Message-ID: <a2a0f380-3e49-8772-dde9-bcebd94cd7fd@gmail.com>
Date:   Fri, 11 Aug 2017 18:19:16 -0600
From:   David Ahern <dsahern@...il.com>
To:     Wei Wang <weiwan@...gle.com>, Cong Wang <xiyou.wangcong@...il.com>,
        John Stultz <john.stultz@...aro.org>,
        Martin KaFai Lau <kafai@...com>
Cc:     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 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).