[PATCH net-next v20 06/15] net: phylink: make phylink_validate state locked

[Christian Marangi <ansuelsmth@gmail.com>]

In preparation for support for PCS release/late attach, rework the
phylink_validate functions to be locked under the state mutex.

With the introduction of a notifier that can be called concurrently while a
phylink_create is called or an interface mode validation is being run, on
recalculating the supported interface and capabilities, an inconsistency
can be introduced with 2 validation run at the same time.

To handle this, make the phylink_validate lock under the phylink state
mutex, add lockless variant for phylink_validate_mask and phylink_validate
and add lockdep check to make sure the mutex is held in the inner
validate functions.

Function that already run phylink_validate under state mutex, are updated
to use the lockless variant.

Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
---
 drivers/net/phy/phylink.c | 53 ++++++++++++++++++++++++++++++++-------
 1 file changed, 44 insertions(+), 9 deletions(-)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index e2e0b313fd61..a7ec4feb950a 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -9,6 +9,7 @@
 #include <linux/ethtool.h>
 #include <linux/export.h>
 #include <linux/gpio/consumer.h>
+#include <linux/lockdep.h>
 #include <linux/netdevice.h>
 #include <linux/of.h>
 #include <linux/of_mdio.h>
@@ -550,6 +551,8 @@ static int phylink_validate_mac_and_pcs(struct phylink *pl,
 	unsigned long capabilities;
 	int ret;
 
+	lockdep_assert_held(&pl->state_mutex);
+
 	/* Get the PCS for this interface mode */
 	if (pl->mac_ops->mac_select_pcs) {
 		pcs = pl->mac_ops->mac_select_pcs(pl->config, state->interface);
@@ -628,6 +631,8 @@ static void phylink_validate_one(struct phylink *pl, struct phy_device *phy,
 	__ETHTOOL_DECLARE_LINK_MODE_MASK(tmp_supported);
 	struct phylink_link_state tmp_state;
 
+	lockdep_assert_held(&pl->state_mutex);
+
 	linkmode_copy(tmp_supported, supported);
 
 	tmp_state = *state;
@@ -648,15 +653,17 @@ static void phylink_validate_one(struct phylink *pl, struct phy_device *phy,
 	}
 }
 
-static int phylink_validate_mask(struct phylink *pl, struct phy_device *phy,
-				 unsigned long *supported,
-				 struct phylink_link_state *state,
-				 const unsigned long *interfaces)
+static int __phylink_validate_mask(struct phylink *pl, struct phy_device *phy,
+				   unsigned long *supported,
+				   struct phylink_link_state *state,
+				   const unsigned long *interfaces)
 {
 	__ETHTOOL_DECLARE_LINK_MODE_MASK(all_adv) = { 0, };
 	__ETHTOOL_DECLARE_LINK_MODE_MASK(all_s) = { 0, };
 	int interface;
 
+	lockdep_assert_held(&pl->state_mutex);
+
 	for_each_set_bit(interface, interfaces, PHY_INTERFACE_MODE_MAX)
 		phylink_validate_one(pl, phy, supported, state, interface,
 				     all_s, all_adv);
@@ -667,14 +674,30 @@ static int phylink_validate_mask(struct phylink *pl, struct phy_device *phy,
 	return phylink_is_empty_linkmode(supported) ? -EINVAL : 0;
 }
 
-static int phylink_validate(struct phylink *pl, unsigned long *supported,
-			    struct phylink_link_state *state)
+static int phylink_validate_mask(struct phylink *pl, struct phy_device *phy,
+				 unsigned long *supported,
+				 struct phylink_link_state *state,
+				 const unsigned long *interfaces)
+{
+	int ret;
+
+	mutex_lock(&pl->state_mutex);
+	ret = __phylink_validate_mask(pl, phy, supported, state, interfaces);
+	mutex_unlock(&pl->state_mutex);
+
+	return ret;
+}
+
+static int __phylink_validate(struct phylink *pl, unsigned long *supported,
+			      struct phylink_link_state *state)
 {
 	const unsigned long *interfaces = pl->supported_interfaces;
 
+	lockdep_assert_held(&pl->state_mutex);
+
 	if (state->interface == PHY_INTERFACE_MODE_NA)
-		return phylink_validate_mask(pl, NULL, supported, state,
-					     interfaces);
+		return __phylink_validate_mask(pl, NULL, supported, state,
+					       interfaces);
 
 	if (!test_bit(state->interface, interfaces))
 		return -EINVAL;
@@ -682,6 +705,18 @@ static int phylink_validate(struct phylink *pl, unsigned long *supported,
 	return phylink_validate_mac_and_pcs(pl, supported, state);
 }
 
+static int phylink_validate(struct phylink *pl, unsigned long *supported,
+			    struct phylink_link_state *state)
+{
+	int ret;
+
+	mutex_lock(&pl->state_mutex);
+	ret = __phylink_validate(pl, supported, state);
+	mutex_unlock(&pl->state_mutex);
+
+	return ret;
+}
+
 static void phylink_fill_fixedlink_supported(unsigned long *supported)
 {
 	linkmode_set_bit(ETHTOOL_LINK_MODE_Pause_BIT, supported);
@@ -2117,7 +2152,7 @@ void phylink_update_mac_pause_capabilities(struct phylink *pl, unsigned long mac
 	else if (pl->sfp_bus)
 		linkmode_and(pl->supported, pl->supported, pl->sfp_support);
 
-	phylink_validate(pl, pl->supported, config);
+	__phylink_validate(pl, pl->supported, config);
 
 	pause_state = config->pause;
 
-- 
2.55.0