netdev - Re: [Patch net 00/16] net_sched: fix races with RCU callbacks

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Date:   Tue, 31 Oct 2017 14:55:40 -0400
From:   Lucas Bates <lucasb@...atatu.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>
Cc:     Cong Wang <xiyou.wangcong@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Chris Mi <chrism@...lanox.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jiri Pirko <jiri@...nulli.us>,
        John Fastabend <john.fastabend@...il.com>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [Patch net 00/16] net_sched: fix races with RCU callbacks

On Tue, Oct 31, 2017 at 7:00 AM, Jamal Hadi Salim <jhs@...atatu.com> wrote:
> On 17-10-31 01:44 AM, Cong Wang wrote:
>>
>> Can you try this patch? From your stack trace it is not clear where
>> the cause is, but we know that the crash is in __tcf_idr_release(),
>> this is how I came up with the following patch:
>>
>>
>> diff --git a/include/net/act_api.h b/include/net/act_api.h
>> index b944e0eb93be..5072446d5f06 100644
>> --- a/include/net/act_api.h
>> +++ b/include/net/act_api.h
>> @@ -122,7 +122,9 @@ void tcf_idrinfo_destroy(const struct tc_action_ops
>> *ops,
>>
>>   static inline void tc_action_net_exit(struct tc_action_net *tn)
>>   {
>> +       rtnl_lock();
>>          tcf_idrinfo_destroy(tn->ops, tn->idrinfo);
>> +       rtnl_unlock();
>>          kfree(tn->idrinfo);
>>   }
>>
>>
>
> Looks like an excellent bet;-> tdc kills the container at the end of the
> test.

Unfortunately it doesn't seem to have had any effect, I'm still seeing
the same bug as yesterday. At Jamal's suggestion I put in a delay
after tdc completed running the tests but before it deleted the
container - and I didn't run into the bug after many runs. I had no
luck getting serial console access on any of our other systems so I
have another stack trace photo which I'll send to you directly.