net: phy: add locking to phy_read_mmd_indirect()/phy_write_mmd_indirect()

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.

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")
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
index 1e1fbb0..34fe339 100644 (file)
--- 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);
        }