netdev - Re: [PATCH v2] ravb: Fixed the problem that rmmod can not be done

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Date:   Thu, 30 Jul 2020 19:24:17 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...il.com>
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        Yuusuke Ashizuka <ashiduka@...itsu.com>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v2] ravb: Fixed the problem that rmmod can not be done

Hello!

On 7/30/20 2:37 PM, Yoshihiro Shimoda wrote:

>> From: Yuusuke Ashizuka, Sent: Thursday, July 30, 2020 7:02 PM
>> Subject: [PATCH v2] ravb: Fixed the problem that rmmod can not be done
> 
> Thank you for the patch! I found a similar patch for another driver [1].

   It's not the same case -- that driver hadn't had the MDIO release code at all
before that patch.

> So, we should apply this patch to the ravb driver.

   I believe the driver is innocent. :-)

> [1]
> fd5f375c1628 ("net-next: ax88796: Attach MII bus only when open")
> 
>> ravb is a module driver, but I cannot rmmod it after insmod it.
> 
> I think "When this driver is a module, I cannot ..." is better.

   Perhaps "... is built as a module".

>> ravb does mdio_init() at the time of probe, and module->refcnt is incremented
> 
> I think "This is because that this driver calls ravb_mdio_init() ..." is better.

   Yep.

> According to scripts/checkpatch.pl, I think it's better to be a maximum
> 75 chars per line in the commit description.

   Yes.
   (Note that for the source code the new length limit is 100, not 80.)

>> by alloc_mdio_bitbang() called after that.
>> Therefore, even if ifup is not performed, the driver is in use and rmmod cannot
>> be performed.

   That's not really obvious...

>> $ lsmod
>> Module                  Size  Used by
>> ravb                   40960  1
>> $ rmmod ravb
>> rmmod: ERROR: Module ravb is in use

   Shouldn't the driver core call the remove() method for the affected devices
first, before checking the refcount? 

>> Fixed to execute mdio_init() at open and free_mdio() at close, thereby rmmod is
> 
> I think "Fixed to call ravb_mdio_init() at open and ravb_mdio_release() ..." is better.
> However, I'm not sure whether that Sergei who is the reviwer of this driver accepts
> the descriptions which I suggested though :)

   The language barrier isn't the only obstacle. :-)

> By the way, I think you have to send this patch to the following maintainers too:
> # We can get it by using scripts/get_maintainers.pl.
> David S. Miller <davem@...emloft.net> (maintainer:NETWORKING DRIVERS,commit_signer:8/8=100%)
> Jakub Kicinski <kuba@...nel.org> (maintainer:NETWORKING DRIVERS)
> 
> Best regards,
> Yoshihiro Shimoda

   For the future, please trim your reply before the patch starts as you
don't comment on the patch itself anyway...

>> possible in the ifdown state.
>>
>> Signed-off-by: Yuusuke Ashizuka <ashiduka@...itsu.com>

[...]

MBR, Sergei