[Intel-wired-lan] [PATCH 18/19] igc: Change adapter->nfc_rule_lock to mutex

[Andre Guedes <andre.guedes@intel.com>]

This patch changes adapter->nfc_rule_lock type from spin_lock to mutex
so we avoid unnecessary busy waiting on lock contention.

A closer look at the execution context of NFC rule API users shows that
all of them run in process context. The API users are: ethtool ops,
igc_configure(), called when interface is brought up by user or reset
workequeue thread, igc_down(), called when interface is brought down,
and igc_remove(), called when driver is unloaded.

Signed-off-by: Andre Guedes <andre.guedes@intel.com>
---
Note that checkpatch.pl reports an issue with this patch. The issue is a false
positive. There is a comment right above that line referring to the lock.

Here is the report:

CHECK: struct mutex definition without comment
#31: FILE: drivers/net/ethernet/intel/igc/igc.h:193:
+       struct mutex nfc_rule_lock;
---
 drivers/net/ethernet/intel/igc/igc.h         |  2 +-
 drivers/net/ethernet/intel/igc/igc_ethtool.c | 24 ++++++++++----------
 drivers/net/ethernet/intel/igc/igc_main.c    | 14 ++++++------
 3 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc.h b/drivers/net/ethernet/intel/igc/igc.h
index a484b328268b..14f9edaaaf83 100644
--- a/drivers/net/ethernet/intel/igc/igc.h
+++ b/drivers/net/ethernet/intel/igc/igc.h
@@ -190,7 +190,7 @@ struct igc_adapter {
 	/* Any access to elements in nfc_rule_list is protected by the
 	 * nfc_rule_lock.
 	 */
-	spinlock_t nfc_rule_lock;
+	struct mutex nfc_rule_lock;
 	struct list_head nfc_rule_list;
 	unsigned int nfc_rule_count;
 
diff --git a/drivers/net/ethernet/intel/igc/igc_ethtool.c b/drivers/net/ethernet/intel/igc/igc_ethtool.c
index 32bc77af71dd..db42dc046403 100644
--- a/drivers/net/ethernet/intel/igc/igc_ethtool.c
+++ b/drivers/net/ethernet/intel/igc/igc_ethtool.c
@@ -939,7 +939,7 @@ static int igc_ethtool_get_nfc_rule(struct igc_adapter *adapter,
 
 	cmd->data = IGC_MAX_RXNFC_RULES;
 
-	spin_lock(&adapter->nfc_rule_lock);
+	mutex_lock(&adapter->nfc_rule_lock);
 
 	rule = igc_get_nfc_rule(adapter, fsp->location);
 	if (!rule)
@@ -971,11 +971,11 @@ static int igc_ethtool_get_nfc_rule(struct igc_adapter *adapter,
 		eth_broadcast_addr(fsp->m_u.ether_spec.h_source);
 	}
 
-	spin_unlock(&adapter->nfc_rule_lock);
+	mutex_unlock(&adapter->nfc_rule_lock);
 	return 0;
 
 out:
-	spin_unlock(&adapter->nfc_rule_lock);
+	mutex_unlock(&adapter->nfc_rule_lock);
 	return -EINVAL;
 }
 
@@ -988,18 +988,18 @@ static int igc_ethtool_get_nfc_rules(struct igc_adapter *adapter,
 
 	cmd->data = IGC_MAX_RXNFC_RULES;
 
-	spin_lock(&adapter->nfc_rule_lock);
+	mutex_lock(&adapter->nfc_rule_lock);
 
 	list_for_each_entry(rule, &adapter->nfc_rule_list, list) {
 		if (cnt == cmd->rule_cnt) {
-			spin_unlock(&adapter->nfc_rule_lock);
+			mutex_unlock(&adapter->nfc_rule_lock);
 			return -EMSGSIZE;
 		}
 		rule_locs[cnt] = rule->location;
 		cnt++;
 	}
 
-	spin_unlock(&adapter->nfc_rule_lock);
+	mutex_unlock(&adapter->nfc_rule_lock);
 
 	cmd->rule_cnt = cnt;
 
@@ -1303,7 +1303,7 @@ static int igc_ethtool_add_nfc_rule(struct igc_adapter *adapter,
 
 	igc_ethtool_init_nfc_rule(rule, fsp);
 
-	spin_lock(&adapter->nfc_rule_lock);
+	mutex_lock(&adapter->nfc_rule_lock);
 
 	err = igc_ethtool_check_nfc_rule(adapter, rule);
 	if (err)
@@ -1317,11 +1317,11 @@ static int igc_ethtool_add_nfc_rule(struct igc_adapter *adapter,
 	if (err)
 		goto err;
 
-	spin_unlock(&adapter->nfc_rule_lock);
+	mutex_unlock(&adapter->nfc_rule_lock);
 	return 0;
 
 err:
-	spin_unlock(&adapter->nfc_rule_lock);
+	mutex_unlock(&adapter->nfc_rule_lock);
 	kfree(rule);
 	return err;
 }
@@ -1333,17 +1333,17 @@ static int igc_ethtool_del_nfc_rule(struct igc_adapter *adapter,
 		(struct ethtool_rx_flow_spec *)&cmd->fs;
 	struct igc_nfc_rule *rule;
 
-	spin_lock(&adapter->nfc_rule_lock);
+	mutex_lock(&adapter->nfc_rule_lock);
 
 	rule = igc_get_nfc_rule(adapter, fsp->location);
 	if (!rule) {
-		spin_unlock(&adapter->nfc_rule_lock);
+		mutex_unlock(&adapter->nfc_rule_lock);
 		return -EINVAL;
 	}
 
 	igc_del_nfc_rule(adapter, rule);
 
-	spin_unlock(&adapter->nfc_rule_lock);
+	mutex_unlock(&adapter->nfc_rule_lock);
 	return 0;
 }
 
diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 134523064fe9..38327d9ec385 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -2540,12 +2540,12 @@ static void igc_flush_nfc_rules(struct igc_adapter *adapter)
 {
 	struct igc_nfc_rule *rule, *tmp;
 
-	spin_lock(&adapter->nfc_rule_lock);
+	mutex_lock(&adapter->nfc_rule_lock);
 
 	list_for_each_entry_safe(rule, tmp, &adapter->nfc_rule_list, list)
 		igc_del_nfc_rule(adapter, rule);
 
-	spin_unlock(&adapter->nfc_rule_lock);
+	mutex_unlock(&adapter->nfc_rule_lock);
 }
 
 /**
@@ -2584,24 +2584,24 @@ static void igc_restore_nfc_rules(struct igc_adapter *adapter)
 {
 	struct igc_nfc_rule *rule;
 
-	spin_lock(&adapter->nfc_rule_lock);
+	mutex_lock(&adapter->nfc_rule_lock);
 
 	list_for_each_entry_reverse(rule, &adapter->nfc_rule_list, list)
 		igc_enable_nfc_rule(adapter, rule);
 
-	spin_unlock(&adapter->nfc_rule_lock);
+	mutex_unlock(&adapter->nfc_rule_lock);
 }
 
 static void igc_nfc_rule_exit(struct igc_adapter *adapter)
 {
 	struct igc_nfc_rule *rule;
 
-	spin_lock(&adapter->nfc_rule_lock);
+	mutex_lock(&adapter->nfc_rule_lock);
 
 	list_for_each_entry(rule, &adapter->nfc_rule_list, list)
 		igc_disable_nfc_rule(adapter, rule);
 
-	spin_unlock(&adapter->nfc_rule_lock);
+	mutex_unlock(&adapter->nfc_rule_lock);
 }
 
 static int igc_uc_sync(struct net_device *netdev, const unsigned char *addr)
@@ -3574,7 +3574,7 @@ static int igc_sw_init(struct igc_adapter *adapter)
 				VLAN_HLEN;
 	adapter->min_frame_size = ETH_ZLEN + ETH_FCS_LEN;
 
-	spin_lock_init(&adapter->nfc_rule_lock);
+	mutex_init(&adapter->nfc_rule_lock);
 	INIT_LIST_HEAD(&adapter->nfc_rule_list);
 	adapter->nfc_rule_count = 0;
 
-- 
2.26.0