netdev - Re: 4.6.3, pppoe + shaper workload, skb_panic / skb_push / ppp_start

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Date:	Wed, 17 Aug 2016 14:54:37 +0300
From:	Denys Fedoryshchenko <nuclearcat@...learcat.com>
To:	Guillaume Nault <g.nault@...halink.fr>
Cc:	Cong Wang <xiyou.wangcong@...il.com>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	netdev-owner@...r.kernel.org
Subject: Re: 4.6.3, pppoe + shaper workload, skb_panic / skb_push /
 ppp_start_xmit

On 2016-08-09 00:05, Guillaume Nault wrote:
> On Mon, Aug 08, 2016 at 02:25:00PM +0300, Denys Fedoryshchenko wrote:
>> On 2016-08-01 23:59, Guillaume Nault wrote:
>> > Do you still have the vmlinux file with debug symbols that generated
>> > this panic?
>> Sorry for delay, i didn't had same image on all servers and probably i 
>> found
>> cause of panic, but still testing on several servers.
>> If i remove SFQ qdisc from ppp shapers, servers not rebooting anymore.
>> 
> Thanks for the feedback. I wonder which interactions between SFQ and
> PPP can lead to this problem. I'll take a look.
> 
>> But still i need around 2 days to make sure that's the reason.
>> 
> Okay, just let me know if you can confirm that removing SFQ really
> solves the problem.
After long testing, i can confirm removing sfq from rules decreased 
panic reboot greatly, tested on many different servers.
I will try today to do some stress tests, to apply on live system at 
night sfq qdiscs, then remove them.
Then i will try also to disconnect all users with sfq qdiscs attached.
Not sure it will help to reproduce the bug, but worth to try.

Still i am hitting once per week some different conntrack bug, sand 
thats why i was confused, i was getting clearly panics in conntrack and 
then something else, i was not sure if it is different bugs, hardware 
glitch or something else.