linux-kernel - Re: [PATCH 2/2] net: macb: Unregister nedev before MDIO bus in remove

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Message-ID: <ZWNpnBX7SnyCC+Q1@shell.armlinux.org.uk>
Date:   Sun, 26 Nov 2023 15:51:56 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Claudiu Beznea <claudiu.beznea@...on.dev>
Cc:     nicolas.ferre@...rochip.com, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        andrew@...n.ch, hkallweit1@...il.com, jgarzik@...ox.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] net: macb: Unregister nedev before MDIO bus in remove

On Sun, Nov 26, 2023 at 04:10:46PM +0200, Claudiu Beznea wrote:
> unregister_netdev() calls the struct net_device_ops::ndo_stop function,
> which in the case of the macb driver is macb_close(). macb_close() calls,
> in turn, PHY-specific APIs (e.g., phy_detach()). The call trace is as
> follows:
> 
> macb_close() ->
>   phylink_disconnect_phy() ->
>     phy_disconnect() ->
>       phy_detach()
> 
> phy_detach() will remove associated sysfs files by calling
> kernfs_remove_by_name_ns(), which will hit
> "kernfs: cannot remove 'attached_dev', no directory" WARN(), which will
> throw a stack trace too.
> 
> To avoid this, call unregiser_netdev() before mdiobus_unregister() and
> mdiobus_free().

Definitely the correct fix, also to fix the issue in patch 1.
> 
> Fixes: 7897b071ac3b ("net: macb: convert to phylink")
> Signed-off-by: Claudiu Beznea <claudiu.beznea@...on.dev>

Reviewed-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>

Thanks!

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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