netdev - Re: Repeatable inet6_dump_fib crash in stock 4.12.0-rc4+

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Date:   Tue, 20 Jun 2017 14:41:23 -0700
From:   Ben Greear <greearb@...delatech.com>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     David Ahern <dsahern@...il.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        netdev <netdev@...r.kernel.org>
Subject: Re: Repeatable inet6_dump_fib crash in stock 4.12.0-rc4+

On 06/20/2017 11:05 AM, Michal Kubecek wrote:
> On Tue, Jun 20, 2017 at 07:12:27AM -0700, Ben Greear wrote:
>> On 06/14/2017 03:25 PM, David Ahern wrote:
>>> On 6/14/17 4:23 PM, Ben Greear wrote:
>>>> On 06/13/2017 07:27 PM, David Ahern wrote:
>>>>
>>>>> Let's try a targeted debug patch. See attached
>>>>
>>>> I had to change it to pr_err so it would go to our serial console
>>>> since the system locked hard on crash,
>>>> and that appears to be enough to change the timing where we can no longer
>>>> reproduce the problem.
>>>
>>>
>>> ok, let's figure out which one is doing that. There are 3 debug
>>> statements. I suspect fib6_del_route is the one setting the state to
>>> FWS_U. Can you remove the debug prints in fib6_repair_tree and
>>> fib6_walk_continue and try again?
>>
>> We cannot reproduce with just that one printf in the kernel either.  It
>> must change the timing too much to trigger the bug.
>
> You might try trace_printk() which should have less impact (don't forget
> to enable /proc/sys/kernel/ftrace_dump_on_oops).

We cannot reproduce with trace_printk() either.

Thanks,
Ben

>
> Michal Kubecek
>


-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com