iwlwifi: enable serialization of synchronous commands

Until now it was only possible to have one synchronous command running at
any time. If a synchronous command is in progress when a second request
arrives then the second command will fail. Create a new mutex specific for
this purpose to only allow one synchronous command at a time, but enable
other commands to wait instead of fail if a synchronous command is in
progress.

Signed-off-by: Reinette Chatre <reinette.chatre@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/iwlwifi/iwl-hcmd.c b/drivers/net/wireless/iwlwifi/iwl-hcmd.c
index 86783c2..73681c4 100644
--- a/drivers/net/wireless/iwlwifi/iwl-hcmd.c
+++ b/drivers/net/wireless/iwlwifi/iwl-hcmd.c
@@ -164,15 +164,13 @@
 	 /* A synchronous command can not have a callback set. */
 	BUG_ON(cmd->callback);
 
-	if (test_and_set_bit(STATUS_HCMD_SYNC_ACTIVE, &priv->status)) {
-		IWL_ERR(priv,
-			"Error sending %s: Already sending a host command\n",
+	IWL_DEBUG_INFO(priv, "Attempting to send sync command %s\n",
 			get_cmd_string(cmd->id));
-		ret = -EBUSY;
-		goto out;
-	}
+	mutex_lock(&priv->sync_cmd_mutex);
 
 	set_bit(STATUS_HCMD_ACTIVE, &priv->status);
+	IWL_DEBUG_INFO(priv, "Setting HCMD_ACTIVE for command %s \n",
+			get_cmd_string(cmd->id));
 
 	cmd_idx = iwl_enqueue_hcmd(priv, cmd);
 	if (cmd_idx < 0) {
@@ -193,6 +191,8 @@
 				jiffies_to_msecs(HOST_COMPLETE_TIMEOUT));
 
 			clear_bit(STATUS_HCMD_ACTIVE, &priv->status);
+			IWL_DEBUG_INFO(priv, "Clearing HCMD_ACTIVE for command %s \n",
+				       get_cmd_string(cmd->id));
 			ret = -ETIMEDOUT;
 			goto cancel;
 		}
@@ -237,7 +237,7 @@
 		cmd->reply_page = 0;
 	}
 out:
-	clear_bit(STATUS_HCMD_SYNC_ACTIVE, &priv->status);
+	mutex_unlock(&priv->sync_cmd_mutex);
 	return ret;
 }
 EXPORT_SYMBOL(iwl_send_cmd_sync);