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

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Message-ID: <CANn89iJ4io_gX-V8A4hE04cH=czGZYs8WGBOpaiBpWMMHOgVVw@mail.gmail.com>
Date:   Tue, 26 Sep 2017 08:13:21 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Tariq Toukan <tariqt@...lanox.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "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 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.

Thanks.