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Date: Sat, 26 Dec 2020 17:37:20 +0100
From: Ali Abdallah <ali.abdallah@suse.com>
To: freebsd-stable@freebsd.org
Cc: freebsd-current@freebsd.org
Subject: MII media status race condition causing fictitious link down
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Hello,

As I've sent a couple of patches to add support for Thinkpad USB-C gen2
to if_ure(4), I came across a very strange link random state change,
causing dhclient to think the link went effectively down, which is not
the case.

First I thought that if_ure(4) doesn't play well with the new chip of the
dock, but after lot of debugging, it turns out to be a nasty race
condition in mii bus code [1].

I'm sending this mail to raise awareness about this issue. Apparently it
exists since long time (I even remember having had this issue in the
past on my older Thinkpad).

[1] https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=252165

Regards,

-- 
Ali Abdallah | SUSE L3 Engineer
GPG fingerprint: 51A0 F4A0 C8CF C98F 842E  A9A8 B945 56F8 1C85 D0D5