Merge branch 'topic/next' into for-next

1 files changed, 8 insertions, 2 deletions

diff --git a/drivers/net/phy/mdio-mux.c b/drivers/net/phy/mdio-mux.c
index 39ea0674dcd..5c120189ec8 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;