netdev - Re: [PATCH] net: phy: add locking to phy_read_mmd_indirect()/phy_write_mmd

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Date:	Tue, 25 Aug 2015 07:08:24 -0700
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Russell King <rmk+kernel@....linux.org.uk>,
	"David S. Miller" <davem@...emloft.net>
CC:	netdev@...r.kernel.org
Subject: Re: [PATCH] net: phy: add locking to phy_read_mmd_indirect()/phy_write_mmd_indirect()

Le 08/25/15 01:49, Russell King a écrit :
> The phy layer is missing locking for the above two functions - it
> has been observed that two threads (userspace and the phy worker
> thread) can race, entering the bus ->write or ->read functions
> simultaneously.
> 
> This causes the FEC driver to initialise a completion while another
> thread is waiting on it or while the interrupt is calling complete()
> on it, which causes spinlock unlock-without-lock, spinlock lockups,
> and completion timeouts.
> 
> Signed-off-by: Russell King <rmk+kernel@....linux.org.uk>

Acked-by: Florian Fainelli <f.fainelli@...il.com>
Fixes: a59a4d192 ("phy: add the EEE support and the way to access to the
MMD registers.")
Fixes: 0c1d77dfb ("net: libphy: Add phy specific function to access mmd
phy registers")

Thanks!

> ---
>  drivers/net/phy/phy.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
> index 1e1fbb049ec6..34fe339f4e80 100644
> --- a/drivers/net/phy/phy.c
> +++ b/drivers/net/phy/phy.c
> @@ -1038,10 +1038,14 @@ int phy_read_mmd_indirect(struct phy_device *phydev, int prtad,
>  	int value = -1;
>  
>  	if (phydrv->read_mmd_indirect == NULL) {
> -		mmd_phy_indirect(phydev->bus, prtad, devad, addr);
> +		struct mii_bus *bus = phydev->bus;
> +
> +		mutex_lock(&bus->mdio_lock);
> +		mmd_phy_indirect(bus, prtad, devad, addr);
>  
>  		/* Read the content of the MMD's selected register */
> -		value = phydev->bus->read(phydev->bus, addr, MII_MMD_DATA);
> +		value = bus->read(bus, addr, MII_MMD_DATA);
> +		mutex_unlock(&bus->mdio_lock);
>  	} else {
>  		value = phydrv->read_mmd_indirect(phydev, prtad, devad, addr);
>  	}
> @@ -1071,10 +1075,14 @@ void phy_write_mmd_indirect(struct phy_device *phydev, int prtad,
>  	struct phy_driver *phydrv = phydev->drv;
>  
>  	if (phydrv->write_mmd_indirect == NULL) {
> -		mmd_phy_indirect(phydev->bus, prtad, devad, addr);
> +		struct mii_bus *bus = phydev->bus;
> +
> +		mutex_lock(&bus->mdio_lock);
> +		mmd_phy_indirect(bus, prtad, devad, addr);
>  
>  		/* Write the data into MMD's selected register */
> -		phydev->bus->write(phydev->bus, addr, MII_MMD_DATA, data);
> +		bus->write(bus, addr, MII_MMD_DATA, data);
> +		mutex_unlock(&bus->mdio_lock);
>  	} else {
>  		phydrv->write_mmd_indirect(phydev, prtad, devad, addr, data);
>  	}
> 


-- 
Florian
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