linux-kernel - Re: [PATCH net] net: phy: mscc: fix deadlock in phy_ethtool_{get,set}

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Message-ID: <0a017d9f-168e-4c6e-a061-68118e8e635e@lunn.ch>
Date:   Tue, 14 Mar 2023 17:52:55 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     netdev@...r.kernel.org, Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: phy: mscc: fix deadlock in
 phy_ethtool_{get,set}_wol()

On Tue, Mar 14, 2023 at 06:45:47PM +0200, Vladimir Oltean wrote:
> On Tue, Mar 14, 2023 at 05:31:45PM +0100, Andrew Lunn wrote:
> > [Goes and checks to see if the same problem exists for other PHY drivers]
> 
> Here's a call path I am not sure how to interpret (but doesn't look like
> there's anything preventing it).
> 
> linkstate_get_sqi()
> -> mutex_lock(&phydev->lock)
>    -> phydev->drv->get_sqi(phydev);
>       -> lan87xx_get_sqi()
>          -> access_ereg()
>             -> lan937x_dsp_workaround()
>                -> mutex_lock(&phydev->lock);
>                -> mutex_unlock(&phydev->lock);
> -> mutex_unlock(&phydev->lock)

I noticed access_ereg() as well. But i don't think there have been any
recent changes there. Lots loop in the Microchip developers.

       Andrew