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

On September 26, 2017 8:13:21 AM PDT, Eric Dumazet [off-list ref] wrote:

On Tue, Sep 26, 2017 at 8:04 AM, Tariq Toukan [off-list ref]
wrote:

quoted

On 26/09/2017 3:51 PM, Eric Dumazet wrote:

quoted

On Tue, Sep 26, 2017 at 4:21 AM, Tariq Toukan [off-list ref]

wrote:

quoted

quoted

quoted

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.

quoted

quoted

quoted

Bug is that mlx4 driver restart fails, because mlx4_core is still

in use.

quoted

quoted

quoted

According to module dependencies, both mlx4_en and mlx4_ib should

have

quoted

quoted

quoted

been
unloaded at this point
Please see log below.

This looks to be some kind of a race, as the repro is not

deterministic.

quoted

quoted

quoted

Probably the en/ib modules are now mistakenly reloaded.

Any idea what could this be?

Regards,
Tariq


[root@reg-l-vrt-41016-009 ~]# /etc/init.d/openibd stop
Unloading HCA driver:                                      [  OK  ]
[root@reg-l-vrt-41016-009 ~]# /etc/init.d/openibd start
Loading HCA driver and Access Layer:                       [  OK  ]
[root@reg-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

quoted

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