1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/net/phy/mdio-mux.c b/drivers/net/phy/mdio-mux.c
index 39ea0674dcde..5c120189ec86 100644
--- a/drivers/net/phy/mdio-mux.c
+++ b/drivers/net/phy/mdio-mux.c
@@ -46,7 +46,13 @@ static int mdio_mux_read(struct mii_bus *bus, int phy_id, int regnum)
         struct mdio_mux_parent_bus *pb = cb->parent;
         int r;
 
-        mutex_lock(&pb->mii_bus->mdio_lock);
+        /* In theory multiple mdio_mux could be stacked, thus creating
+         * more than a single level of nesting.  But in practice,
+         * SINGLE_DEPTH_NESTING will cover the vast majority of use
+         * cases.  We use it, instead of trying to handle the general
+         * case.
+         */
+        mutex_lock_nested(&pb->mii_bus->mdio_lock, SINGLE_DEPTH_NESTING);
         r = pb->switch_fn(pb->current_child, cb->bus_number, pb->switch_data);
         if (r)
                 goto out;
@@ -71,7 +77,7 @@ static int mdio_mux_write(struct mii_bus *bus, int phy_id,
 
         int r;
 
-        mutex_lock(&pb->mii_bus->mdio_lock);
+        mutex_lock_nested(&pb->mii_bus->mdio_lock, SINGLE_DEPTH_NESTING);
         r = pb->switch_fn(pb->current_child, cb->bus_number, pb->switch_data);
         if (r)
                 goto out;