netdev - Re: [PATCH net-next] net: phy: replace mutex_is_locked with lockdep_assert

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Message-ID: <X/Y8D2TgQDBumfvO@lunn.ch>
Date:   Wed, 6 Jan 2021 23:39:11 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Russell King - ARM Linux <linux@...linux.org.uk>,
        Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] net: phy: replace mutex_is_locked with
 lockdep_assert_held in phylib

On Wed, Jan 06, 2021 at 02:03:40PM +0100, Heiner Kallweit wrote:
> Switch to lockdep_assert_held(_once), similar to what is being done
> in other subsystems. One advantage is that there's zero runtime
> overhead if lockdep support isn't enabled.

Hi Heiner

I'm not sure we are bothered about performance here. MDIO operations
are slow, a mutex check is fast relative to that.

I wonder how many do development work with lockdep enabled? I think i
prefer catching hard to find locking bugs earlier, verses a tiny
performance overhead.

       Andrew