netdev - Re: [PATCH net] net: phy: Fix lack of reference count on PHY driver

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Message-ID: <88fb901e-47e3-698b-d111-7e965ca6760a@gmail.com>
Date:   Fri, 3 Feb 2017 13:04:40 -0800
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Russell King - ARM Linux <linux@...linux.org.uk>,
        David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, andrew@...n.ch, maowenan@...wei.com
Subject: Re: [PATCH net] net: phy: Fix lack of reference count on PHY driver

On 02/03/2017 01:54 AM, Russell King - ARM Linux wrote:
> On Thu, Feb 02, 2017 at 09:54:07PM -0500, David Miller wrote:
>> Hot plugging PHYs and notifications and all of that business is
>> net-next material.
> 
> I was talking more about unbinding of the driver, which is something
> that can be done today, eg:
> 
> $ ls -l /sys/bus/mdio_bus/drivers/Atheros\ 8035\ ethernet/
> total 0
> lrwxrwxrwx 1 root root    0 Feb  3 09:49 2188000.ethernet:00 -> ../../../../devices/soc0/soc/2100000.aips-bus/2188000.ethernet/mdio_bus/2188000.ethernet/2188000.ethernet:00
> --w------- 1 root root 4096 Feb  3 09:49 bind
> --w------- 1 root root 4096 Feb  3 09:49 uevent
> --w------- 1 root root 4096 Feb  3 09:49 unbind
> $ echo 2188000.ethernet:00 > /sys/bus/mdio_bus/drivers/Atheros\ 8035\ ethernet/unbind
> 
> is all it takes, and the same oops will happen.  Try it on a box
> you don't care about crashing. :)
> 
> This is my point - locking the module into the kernel using
> try_module_get() doesn't actually fix the problem where drivers are
> concerned, it just has the illusion of being safe.

I have some patches for that too, along with making bind, unbind work
again, because the state machine seems to be hosed (another thing that
was very well tested...).
-- 
Florian