iwlagn: warn about nested SYNC commands

Since there is no protection around SYNC host command mechanism, at least WARN
when collision happens between two SYNC host comamnds. I am not sure there is a
real  issue (beyond the HCMD_ACTIVE flag maintenance) with having two SYNC host
commands at the same time, but at least now, we will know about it.
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>

drivers/net/wireless/iwlwifi/iwl-dev.h

@@ -1300,6 +1300,7 @@ struct iwl_priv {
 
 	/* command queue number */
 	u8 cmd_queue;
+	u8 last_sync_cmd_id;
 
 	/* max number of station keys */
 	u8 sta_key_max_num;

drivers/net/wireless/iwlwifi/iwl-hcmd.c

@@ -181,7 +181,16 @@ int iwl_send_cmd_sync(struct iwl_priv *priv, struct iwl_host_cmd *cmd)
 	IWL_DEBUG_INFO(priv, "Attempting to send sync command %s\n",
 			get_cmd_string(cmd->id));
 
-	set_bit(STATUS_HCMD_ACTIVE, &priv->status);
+	if (test_and_set_bit(STATUS_HCMD_ACTIVE, &priv->status)) {
+		IWL_ERR(priv, "STATUS_HCMD_ACTIVE already set while sending %s"
+			      ". Previous SYNC cmdn is %s\n",
+			get_cmd_string(cmd->id),
+			get_cmd_string(priv->last_sync_cmd_id));
+		WARN_ON(1);
+	} else {
+		priv->last_sync_cmd_id = cmd->id;
+	}
+
 	IWL_DEBUG_INFO(priv, "Setting HCMD_ACTIVE for command %s\n",
 			get_cmd_string(cmd->id));