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Date:   Wed, 30 Nov 2022 17:33:15 +0000
From:   "Russell King (Oracle)" <linux@armlinux.org.uk>
To:     Andrew Lunn <andrew@lunn.ch>
Cc:     Frank <Frank.Sae@motor-comm.com>, Peter Geis <pgwipeout@gmail.com>,
        Heiner Kallweit <hkallweit1@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>, yinghong.zhang@motor-comm.com,
        fei.zhang@motor-comm.com, hua.sun@motor-comm.com,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next] net: phy: Add driver for Motorcomm yt8531
 gigabit ethernet phy
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References: <20221130094928.14557-1-Frank.Sae@motor-comm.com>
 <Y4copjAzKpGSeunB@shell.armlinux.org.uk>
 <Y4eOkiaRywaUJa9n@lunn.ch>
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Sender: Russell King (Oracle) <linux@armlinux.org.uk>
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Hi Andrew,

On Wed, Nov 30, 2022 at 06:10:42PM +0100, Andrew Lunn wrote:
> This is not the first time Russell has pointed out your locking is
> wrong.
> 
> How about adding a check in functions which should be called with the
> lock taken really do have the lock taken?

They already do:

        lockdep_assert_held_once(&bus->mdio_lock);

but I guess people just aren't testing their code with lockdep enabled.

The only other thing I can think of trying is to use mutex_trylock():

	if (WARN_ON_ONCE(mutex_trylock(&bus->mdio_lock)))
		mutex_unlock(&bus->mdio_lock);

scattered throughout.

However, if the author does have lockdep enabled but ignores the
warnings, that isn't going to help.

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