From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Andrew Lunn <andrew@lunn.ch>
Cc: Michael Walle <michael@walle.cc>,
bcm-kernel-feedback-list@broadcom.com, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org,
Florian Fainelli <f.fainelli@gmail.com>,
Heiner Kallweit <hkallweit1@gmail.com>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>
Subject: Re: [PATCH net-next] net: phy: introduce phydev->port
Date: Wed, 10 Feb 2021 11:01:49 +0000 [thread overview]
Message-ID: <20210210110148.GT1463@shell.armlinux.org.uk> (raw)
In-Reply-To: <YCM8JiO4FfKx5ECo@lunn.ch>
On Wed, Feb 10, 2021 at 02:51:34AM +0100, Andrew Lunn wrote:
> This is a general comment, not a problem specific to this patch.
>
> There is some interesting race conditions here. The marvell driver
> first checks the fibre page and gets the status of the fiber port. As
> you can see from the hunk above, it clears out pause, duplex, speed,
> sets port to PORT_FIBRE, and then reads the PHY registers to set these
> values. If link is not detected on the fibre, it swaps page and does
> it all again, but for the copper port. So once per second,
> phydev->port is going to flip flop PORT_FIBER->PORT_TP, if copper has
> link.
>
> Now, the read_status() call into the driver should be performed while
> holding the phydev->lock. So to the PHY state machine, this flip/flop
> does not matter, it is atomic with respect to the lock. But
> phy_ethtool_ksettings_get() is not talking the lock. It could see
> speed, duplex, and port while they have _UNKNOWN values, or port is
> part way through a flip flop. I think we need to take the lock here.
> phy_ethtool_ksettings_set() should also probably take the lock.
phy_ethtool_ksettings_get() needs to take the lock, otherwise it could
read the phy_device members in the middle of an update. This is likely
a long-standing phylib bug.
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!
next prev parent reply other threads:[~2021-02-10 11:05 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-09 16:38 [PATCH net-next] net: phy: introduce phydev->port Michael Walle
2021-02-09 23:01 ` Florian Fainelli
2021-02-10 1:51 ` Andrew Lunn
2021-02-10 11:01 ` Russell King - ARM Linux admin [this message]
2021-02-10 1:53 ` Andrew Lunn
2021-02-10 11:20 ` Michael Walle
2021-02-10 11:54 ` Russell King - ARM Linux admin
2021-02-10 12:10 ` Michael Walle
2021-02-10 18:34 ` Florian Fainelli
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