diff --git a/core/includes/config.inc b/core/includes/config.inc
index aa7e3a8..7684ff4 100644
--- a/core/includes/config.inc
+++ b/core/includes/config.inc
@@ -5,8 +5,14 @@ use Drupal\Core\Config\FileStorage;
 use Drupal\Core\Config\ConfigException;
 
 /**
- * The value a module should return from hook_config_sync() to indicate that
- * it should be called again by the config system during this sync.
+ * Flag to indicate that synchronization of module configuration depends on other configuration.
+ *
+ * hook_config_sync() implementations should return this value to indicate that
+ * the configuration changes cannot be applied yet and the hook implementation
+ * should be called again later during the synchronization.
+ *
+ * @todo Find a better value, or possibly replace with simple Boolean return
+ *   value for hook_config_sync().
  */
 const CONFIG_DEFER_SYNC = 'CONFIG_DEFER_SYNC';
 
@@ -106,17 +112,20 @@ function config($name, $config_class = NULL, $storage_class = NULL) {
  * Synchronizes configuration from FileStorage to DatabaseStorage.
  */
 function config_sync() {
-  $config_changes = config_get_changes_from_disk();
+  $config_changes = config_sync_get_changes();
   if (empty($config_changes)) {
     return;
   }
 
-  $lock_name = __FUNCTION__;
-  if (!lock_acquire($lock_name)) {
+  if (!lock_acquire(__FUNCTION__)) {
     // Another request is synchronizing configuration. Wait for it to complete,
-    // then re-check for any remaining differences.
-    lock_wait($lock_name);
-    return config_sync();
+    // then return a negative result for UI purposes. We do not make a
+    // difference between an actual synchronization error and a failed lock,
+    // because a concurrent request synchronizing configuration is an edge-case
+    // in the first place and would mean that more than one developer or
+    // site builder attempts to do it without coordinating with others.
+    lock_wait(__FUNCTION__);
+    return FALSE;
   }
 
   try {
@@ -128,10 +137,10 @@ function config_sync() {
   catch (ConfigException $e) {
     watchdog_exception('config_sync', $e);
     config_sync_invoke_sync_error_hooks($config_changes);
-    lock_release($lock_name);
+    lock_release(__FUNCTION__);
     return FALSE;
   }
-  lock_release($lock_name);
+  lock_release(__FUNCTION__);
   return TRUE;
 }
 
@@ -261,13 +270,13 @@ function config_sync_sort_dependencies(array $modules) {
 }
 
 /**
- * Returns a list of changes on disk compared to the active store.
+ * Returns a list of differences between FileStorage and DatabaseStorage.
  *
  * @return array|bool
  *   The list of files changed on disk compared to the active store, or FALSE if
  *   there are no differences.
  */
-function config_get_changes_from_disk() {
+function config_sync_get_changes() {
   $disk_config_names = FileStorage::getNamesWithPrefix();
   $active_config_names = DatabaseStorage::getNamesWithPrefix();
   $config_changes = array(
diff --git a/core/modules/config/config.admin.inc b/core/modules/config/config.admin.inc
index 1169bc0..f63dcd3 100644
--- a/core/modules/config/config.admin.inc
+++ b/core/modules/config/config.admin.inc
@@ -11,11 +11,11 @@
  * @see config_admin_import_form_submit()
  */
 function config_admin_import_form($form, &$form_state) {
-  $config_changes = config_get_changes_from_disk();
+  $config_changes = config_sync_get_changes();
 
   if (empty($config_changes)) {
     $form['no_changes'] = array(
-      '#markup' => 'There are no changes on disk to reload.'
+      '#markup' => t('There are no configuration changes.'),
     );
     return $form;
   }
@@ -49,10 +49,10 @@ function config_admin_import_form($form, &$form_state) {
  */
 function config_admin_import_form_submit($form, &$form_state) {
   if (config_sync()) {
-    drupal_set_message('Configuration successfully reloaded from disk.');
+    drupal_set_message(t('The configuration was imported successfully.'));
   }
   else {
-    drupal_set_message('There was an error reloading configuration from disk.', 'error');
+    drupal_set_message(t('The import failed due to an error. Any errors have been logged.'), 'error');
   }
 }