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Date:   Fri, 26 Oct 2018 21:26:12 +0200
From:   Oleksandr Natalenko <oleksandr@natalenko.name>
To:     =?UTF-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
Cc:     Dave Taht <dave.taht@gmail.com>,
        "David S. Miller" <davem@davemloft.net>,
        Jamal Hadi Salim <jhs@mojatatu.com>,
        Cong Wang <xiyou.wangcong@gmail.com>,
        Jiri Pirko <jiri@resnulli.us>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: CAKE and r8169 cause panic on upload in v4.19
Message-ID: <61d09f0db41f269cc9ee13dd68a5c285@natalenko.name>
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Hello.

I was excited regarding the fact that v4.19 introduced CAKE, so I've 
deployed it on my home router.

I used this script of mine [1]:

# bufferbloat enp3s0.100 20 20

to do its job on the VLAN interface, where 20/20 ISP link is switched 
from the home switch. Basically, it just follows [2] with simple 
bandwidth restriction and egress mirroring using ifb.

Then I thought it would be nice to run speedtest-cli on one of the 
computer in the home LAN, connected to this router. Download stage went 
fine, but immediately after upload started I've got a panic on the 
router: [3] (sorry, it is a photo, netconsole didn't work because, I 
assume, the panic happened in the networking code). I rebooted the 
router and tried once more, and got the same result, again during upload 
stage. Then I rebooted again, replaced CAKE script with my former HTB 
script, and after running speedtest-cli a couple of times there's no 
panic.

Before running speedtest-cli I was using CAKE for a couple of days 
without generating much traffic just fine. It seems it crashes only if 
lots of traffic is generated with tools like this.

My sysctl: [4] and ethtool -k: [5]

So far, I've found something similar only here: [6] [7]. The common 
thing is r8169 driver in use, so, maybe, it is a driver issue, and CAKE 
is just happy to reveal it.

If it is something known, please point me to a possible fix. If it is 
something new, I'm open to provide more info on your request, try 
patches etc (as usual).

Thanks.

-- 
   Oleksandr Natalenko (post-factum)

[1] https://gist.github.com/4b27c49a7f9b4d775e2e38ba23d3f13c
[2] https://www.bufferbloat.net/projects/codel/wiki/Cake
[3] https://bit.ly/2SlUl7R
[4] https://gist.github.com/pfactum/bdad2594b151578f460857cacd94c689
[5] https://gist.github.com/pfactum/cad2cc5d1512b31fbc76d821b3e63dbf
[6] https://boards.4chan.org/g/thread/68171835#p68188019
[7] https://i.4cdn.org/g/1540307271879.jpg