iwlwifi: serialize station management actions

We are seeing some race conditions between incoming station management
requests (station add/remove) and the internal unassoc RXON command that
modifies station table. Modify these flows to require the mutex to be held
and thus serializing them.

This fixes http://bugzilla.intellinuxwireless.org/show_bug.cgi?id=2207

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-sta.c b/drivers/net/wireless/iwlwifi/iwl-sta.c
index 83a2636..c27c13f 100644
--- a/drivers/net/wireless/iwlwifi/iwl-sta.c
+++ b/drivers/net/wireless/iwlwifi/iwl-sta.c
@@ -1373,10 +1373,14 @@
 
 	IWL_DEBUG_INFO(priv, "received request to remove station %pM\n",
 			sta->addr);
+	mutex_lock(&priv->mutex);
+	IWL_DEBUG_INFO(priv, "proceeding to remove station %pM\n",
+			sta->addr);
 	ret = iwl_remove_station(priv, sta_common->sta_id, sta->addr);
 	if (ret)
 		IWL_ERR(priv, "Error removing station %pM\n",
 			sta->addr);
+	mutex_unlock(&priv->mutex);
 	return ret;
 }
 EXPORT_SYMBOL(iwl_mac_sta_remove);