netdev - Re: ordering of call to unbind() in usbnet

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Message-ID: <a363a053-ee8b-c7d4-5ba5-57187d1b4651@suse.com>
Date:   Thu, 17 Mar 2022 16:53:34 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Oleksij Rempel <o.rempel@...gutronix.de>
CC:     Lukas Wunner <lukas@...ner.de>, Oliver Neukum <oneukum@...e.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: ordering of call to unbind() in usbnet_disconnect



On 15.03.22 14:28, Andrew Lunn wrote:
>>>> It was linked to unregistered/freed
>>>> netdev. This is why my patch changing the order to call phy_disconnect()
>>>> first and then unregister_netdev().
>>> Unregistered yes, but freed no.  Here's the order before 2c9d6c2b871d:
>>>
>>>   usbnet_disconnect()
>>>     unregister_netdev()
>>>     ax88772_unbind()
>>>       phy_disconnect()
>>>     free_netdev()
>>>
>>> Is it illegal to disconnect a PHY from an unregistered, but not yet freed
>>> net_device?
> There are drivers which unregistering and then calling
> phy_disconnect. In general that should be a valid pattern. But more
> MAC drivers actually connect the PHY on open and disconnect it on
> close. So it is less well used.
Hi,

this is an interesting discussion, but what practical conclusion
do we draw from it? Is it necessary to provide both orders
of notifying the subdriver, or isn't it?

    Regards
        Oliver