From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Tue, 23 Jun 2020 17:47:23 +0100
Subject: net: phylink: fix ethtool -A with attached PHYs
Patch-mainline: v5.8-rc3
Git-commit: c718af2d00a37587b09e5958d142da7569f3d55b
References: bsc#1176447

Fix a phylink's ethtool set_pauseparam support deadlock caused by phylib
interacting with phylink: we must not hold the state lock while calling
phylib functions that may call into phylink_phy_change().

Fixes: f904f15ea9b5 ("net: phylink: allow ethtool -A to change flow control advertisement")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/phy/phylink.c |   21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -1437,20 +1437,23 @@ int phylink_ethtool_set_pauseparam(struc
 	linkmode_set_pause(config->advertising, pause->tx_pause,
 			   pause->rx_pause);
 
-	/* If we have a PHY, phylib will call our link state function if the
-	 * mode has changed, which will trigger a resolve and update the MAC
-	 * configuration.
-	 */
-	if (pl->phydev) {
-		phy_set_asym_pause(pl->phydev, pause->rx_pause,
-				   pause->tx_pause);
-	} else if (!test_bit(PHYLINK_DISABLE_STOPPED,
-			     &pl->phylink_disable_state)) {
+	if (!pl->phydev && !test_bit(PHYLINK_DISABLE_STOPPED,
+				     &pl->phylink_disable_state)) {
 		phylink_mac_config(pl, &pl->link_config);
 		phylink_mac_an_restart(pl);
 	}
+
 	mutex_unlock(&pl->state_mutex);
 
+	/* If we have a PHY, a change of the pause frame advertisement will
+	 * cause phylib to renegotiate (if AN is enabled) which will in turn
+	 * call our phylink_phy_change() and trigger a resolve.  Note that
+	 * we can't hold our state mutex while calling phy_set_asym_pause().
+	 */
+	if (pl->phydev)
+		phy_set_asym_pause(pl->phydev, pause->rx_pause,
+				   pause->tx_pause);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(phylink_ethtool_set_pauseparam);