netdev - Re: Soft lockup in inet_put

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Date:   Thu, 8 Dec 2016 16:36:56 -0500
From:   Josef Bacik <jbacik@...com>
To:     Hannes Frederic Sowa <hannes@...essinduktion.org>
CC:     Tom Herbert <tom@...bertland.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: Soft lockup in inet_put_port on 4.6

On Thu, Dec 8, 2016 at 4:03 PM, Hannes Frederic Sowa 
<hannes@...essinduktion.org> wrote:
> Hello Tom,
> 
> On Wed, Dec 7, 2016, at 00:06, Tom Herbert wrote:
>>  We are seeing a fair number of machines getting into softlockup in 
>> 4.6
>>  kernel. As near as I can tell this is happening on the spinlock in
>>  bind hash bucket. When inet_csk_get_port exits and does 
>> spinunlock_bh
>>  the TCP timer runs and we hit lockup in inet_put_port (presumably on
>>  same lock). It seems like the locked isn't properly be unlocked
>>  somewhere but I don't readily see it.
>> 
>>  Any ideas?
> 
> Likewise we received reports that pretty much look the same on our
> heavily patched kernel. Did you have a chance to investigate or
> reproduce the problem?
> 
> I am wondering if you would be able to take a complete thread stack 
> dump
> if you can reproduce this to check if one of the user space processes 
> is
> looping inside finding a free port?

We can reproduce the problem at will, still trying to run down the 
problem.  I'll try and find one of the boxes that dumped a core and get 
a bt of everybody.  Thanks,

Josef