netdev - Re: Latest net-next from GIT panic

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Date:   Wed, 20 Sep 2017 19:58:51 +0200
From:   Paweł Staszewski <pstaszewski@...are.pl>
To:     Wei Wang <weiwan@...gle.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: Latest net-next from GIT panic



W dniu 2017-09-20 o 19:46, Wei Wang pisze:
>>> This is why I suggested to replace the BUG() in another mail
>>>
>>> So :
>>>
>>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>>> index
>>> f535779d9dc1dfe36934c2abba4e43d053ac5d6f..220cd12456754876edf2d3ef13195e82d70d5c74
>>> 100644
>>> --- a/include/linux/netdevice.h
>>> +++ b/include/linux/netdevice.h
>>> @@ -3331,7 +3331,15 @@ void netdev_run_todo(void);
>>>     */
>>>    static inline void dev_put(struct net_device *dev)
>>>    {
>>> -       this_cpu_dec(*dev->pcpu_refcnt);
>>> +       int __percpu *pref = READ_ONCE(dev->pcpu_refcnt);
>>> +
>>> +       if (!pref) {
>>> +               pr_err("no pcpu_refcnt on dev %p(%s) state %d dismantle
>>> %d\n",
>>> +                      dev, dev->name, dev->reg_state, dev->dismantle);
>>> +               for (;;)
>>> +                       cpu_relax();
>>> +       }
>>> +       this_cpu_dec(*pref);
>>>    }
>>>      /**
>>>
> Thanks a lot Eric for the debug patch.
>
> Pawel,
>
> I want to confirm with you about the last good commit when you did bisection.
> You mentioned:
>
>> And the last one
>>
>> git bisect good
>> Bisecting: 1 revision left to test after this (roughly 1 step)
>> [1cfb71eeb12047bcdbd3e6730ffed66e810a0855] ipv6: take dst->__refcnt for
>> insertion into fib6 tree
>>
>> With this have kernel panic same as always
>>
>> git bisect bad
>> Bisecting: 0 revisions left to test after this (roughly 0 steps)
>> [b838d5e1c5b6e57b10ec8af2268824041e3ea911] ipv4: mark DST_NOGC and
>> remove the operation of dst_free()
>
> So it breaks right at:
> [b838d5e1c5b6e57b10ec8af2268824041e3ea911] ipv4: mark DST_NOGC and
> remove the operation of dst_free()
> Right?
> If you sync the image to one commit before the above one:
> [9df16efadd2a8a82731dc76ff656c771e261827f] ipv4: call dst_hold_safe() properly
> Does it crash?
Later today i will repeat last three steps - in about next 3 hours after 
rush hours of internet traffic - now i cant touch backup router  :)

>
> And could you confirm that your config does not have any IPv6
> addresses or routes configured?
There is ipv6 enabled
And yes there are some ipv6 ip's
One interface have ipv6 enabled with one static route

  but no ipv6 bgp sessions - so nt many ipv6 prefixes and ipv6 fib is 
almost empty

ip -6 r ls | wc -l
57


>
> Thanks.
> Wei
>
>
> 6:03 +0200, Paweł Staszewski wrote:
>>>> Nit much more after adding this patch
>>>>
>>>> https://bugzilla.kernel.org/attachment.cgi?id=258529
>>>>
>>> This is why I suggested to replace the BUG() in another mail
>>>
>>> So :
>>>
>>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>>> index
>>> f535779d9dc1dfe36934c2abba4e43d053ac5d6f..220cd12456754876edf2d3ef13195e82d70d5c74
>>> 100644
>>> --- a/include/linux/netdevice.h
>>> +++ b/include/linux/netdevice.h
>>> @@ -3331,7 +3331,15 @@ void netdev_run_todo(void);
>>>     */
>>>    static inline void dev_put(struct net_device *dev)
>>>    {
>>> -       this_cpu_dec(*dev->pcpu_refcnt);
>>> +       int __percpu *pref = READ_ONCE(dev->pcpu_refcnt);
>>> +
>>> +       if (!pref) {
>>> +               pr_err("no pcpu_refcnt on dev %p(%s) state %d dismantle
>>> %d\n",
>>> +                      dev, dev->name, dev->reg_state, dev->dismantle);
>>> +               for (;;)
>>> +                       cpu_relax();
>>> +       }
>>> +       this_cpu_dec(*pref);
>>>    }
>>>      /**
>>>
>>>
>>>
>> Full panic
>>
>> https://bugzilla.kernel.org/attachment.cgi?id=258531
>>
>>
>> I will change patch and apply but later today cause now cant use backup
>> router as testlab - Internet rush hours if something happens this will be
>> bed when second router will have bugged kernel :)
>>
>>