netdev - Re: [PATCH v2 net-next 0/7] net: speedup netns create/delete time

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Date:   Tue, 26 Sep 2017 08:22:39 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>,
        Tariq Toukan <tariqt@...lanox.com>
CC:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Majd Dibbiny <majd@...lanox.com>,
        Yonatan Cohen <yonatanc@...lanox.com>,
        Eran Ben Elisha <eranbe@...lanox.com>
Subject: Re: [PATCH v2 net-next 0/7] net: speedup netns create/delete time

On September 26, 2017 8:13:21 AM PDT, Eric Dumazet <edumazet@...gle.com> wrote:
>On Tue, Sep 26, 2017 at 8:04 AM, Tariq Toukan <tariqt@...lanox.com>
>wrote:
>>
>>
>> On 26/09/2017 3:51 PM, Eric Dumazet wrote:
>>>
>>> On Tue, Sep 26, 2017 at 4:21 AM, Tariq Toukan <tariqt@...lanox.com>
>wrote:
>>>>
>>>>
>>>> Hi Eric,
>>>>
>>>> We see a regression introduced in this series, specifically in the
>>>> patches
>>>> touching lib/kobject_uevent.c.
>>>> We tried to figure out what is wrong there, but couldn't point it
>out.
>>>>
>>>> Bug is that mlx4 driver restart fails, because mlx4_core is still
>in use.
>>>> According to module dependencies, both mlx4_en and mlx4_ib should
>have
>>>> been
>>>> unloaded at this point
>>>> Please see log below.
>>>>
>>>> This looks to be some kind of a race, as the repro is not
>deterministic.
>>>> Probably the en/ib modules are now mistakenly reloaded.
>>>>
>>>> Any idea what could this be?
>>>>
>>>> Regards,
>>>> Tariq
>>>>
>>>>
>>>> [root@...-l-vrt-41016-009 ~]# /etc/init.d/openibd stop
>>>> Unloading HCA driver:                                      [  OK  ]
>>>> [root@...-l-vrt-41016-009 ~]# /etc/init.d/openibd start
>>>> Loading HCA driver and Access Layer:                       [  OK  ]
>>>> [root@...-l-vrt-41016-009 ~]# /etc/init.d/openibd stop
>>>> Unloading mlx4_core                                        [FAILED]
>>>> rmmod: ERROR: Module mlx4_core is in use
>>>
>>> I have absolutely no idea. Please bisect.
>>
>> We previously saw a similar issue, that was reported in mailing list.
>> Dmitry Torokhov suggested the following fix:
>> https://lkml.org/lkml/2017/9/12/523
>>
>> And indeed, it solved the issue.
>>
>> We kept the suggested patch in our internal branch, and rebased.
>> Issue appeared again once your series was accepted.
>>
>> By bisecting, we see that the issue re-appears in this patch:
>> 4a336a23d619 kobject: copy env blob in one go
>>
>>>
>>> Are you really using netns in the first place ?
>>
>> No. But seems like it still affects the modules load/unload.
>>
>> Regards,
>> Tariq
>
>Ah this makes sense now.
>
>Dmitry Torokhov hack breaks the assumption I used in my patch.
>
>Since it is not upstream yet, I believe that it will need more work
>before being in a proper state.

It is in Greg's tree where all kobject patches should go through as far as I know.


Thanks.

-- 
Dmitry