diff --git a/core/includes/update.inc b/core/includes/update.inc
index 8a18ebb..9dd8456 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -578,11 +578,6 @@ function update_batch($start, $redirect = NULL, $url = NULL, $batch = array(), $
  * @see update_batch()
  */
 function update_finished($success, $results, $operations) {
-  // Unlock the module system to flush all caches.
-  module_list_reset();
-  // Load all modules, so data structures can be properly rebuilt.
-  module_load_all(FALSE, TRUE);
-
   // Clear the caches in case the data has been updated.
   drupal_flush_all_caches();
 
diff --git a/core/modules/field/modules/field_sql_storage/field_sql_storage.install b/core/modules/field/modules/field_sql_storage/field_sql_storage.install
index 0bbdc5a..2229ef4 100644
--- a/core/modules/field/modules/field_sql_storage/field_sql_storage.install
+++ b/core/modules/field/modules/field_sql_storage/field_sql_storage.install
@@ -111,9 +111,6 @@ function field_sql_storage_update_8000(&$sandbox) {
   // Retrieve field data.
   $fields = _update_7000_field_read_fields(array('storage_type' => 'field_sql_storage'));
 
-  // Load private table name helper functions in field_sql_storage.module.
-  drupal_load('module', 'field_sql_storage');
-
   // Update schema.
   foreach ($fields as $field) {
     $data_table = _field_sql_storage_tablename($field);
diff --git a/core/modules/user/user.install b/core/modules/user/user.install
index a22b2d8..67957da 100644
--- a/core/modules/user/user.install
+++ b/core/modules/user/user.install
@@ -351,11 +351,11 @@ function user_install() {
  * The 'Member for' extra field has moved one level up in the array.
  */
 function user_update_8000() {
-  $settings = update_variable_get('field_bundle_settings_user__user', array());
+  $settings = field_bundle_settings('user', 'user');
   if (isset($settings['extra_fields']['display']['summary'])) {
     $settings['extra_fields']['display']['member_for'] = $settings['extra_fields']['display']['summary'];
     unset($settings['extra_fields']['display']['summary']);
-    update_variable_set('field_bundle_settings_user__user', $settings);
+    field_bundle_settings('user', 'user', $settings);
   }
 }
 
diff --git a/core/update.php b/core/update.php
index 35b42b4..b8a726d 100644
--- a/core/update.php
+++ b/core/update.php
@@ -129,11 +129,6 @@ function update_script_selection_form($form, &$form_state) {
       '#links' => update_helpful_links(),
     );
 
-    // Unlock the module system to flush all caches.
-    module_list_reset();
-    // Load all modules, so data structures can be properly rebuilt.
-    module_load_all(FALSE, TRUE);
-
     // No updates to run, so caches won't get flushed later.  Clear them now.
     drupal_flush_all_caches();
   }
@@ -371,6 +366,10 @@ function update_check_requirements($skip_warnings = FALSE) {
   }
 }
 
+// Some unavoidable errors happen because the database is not yet up-to-date.
+// Our custom error handler is not yet installed, so we just suppress them.
+ini_set('display_errors', FALSE);
+
 // We prepare a minimal bootstrap for the update requirements check to avoid
 // reaching the PHP memory limit.
 require_once DRUPAL_ROOT . '/core/includes/bootstrap.inc';
@@ -379,23 +378,6 @@ function update_check_requirements($skip_warnings = FALSE) {
 require_once DRUPAL_ROOT . '/core/includes/file.inc';
 require_once DRUPAL_ROOT . '/core/includes/unicode.inc';
 require_once DRUPAL_ROOT . '/core/includes/schema.inc';
-
-// The module list must be limited to System module for almost all parts of the
-// update process to prevent module APIs and hooks from being invoked too early
-// (trying to act on data structures that are not updated yet).
-// This especially applies to early bootstrap preparations when upgrading to a
-// new major version of Drupal core. Unfortunately, however, the initial
-// information and update selection pages (and forms) need to be able to invoke
-// hook_requirements() in all modules and also access other APIs. Therefore, the
-// effective module list has to be switched back and forth multiple times during
-// the update.php process.
-include_once DRUPAL_ROOT . '/core/includes/module.inc';
-$module_list['system']['filename'] = 'core/modules/system/system.module';
-
-// Lock the module list for the update bootstrap and performing initial system
-// changes.
-module_list(NULL, $module_list);
-
 update_prepare_d8_bootstrap();
 
 // Determine if the current user has access to run update.php.
@@ -422,6 +404,9 @@ function update_check_requirements($skip_warnings = FALSE) {
   require_once DRUPAL_ROOT . '/core/modules/system/system.install';
 
   // Load module basics.
+  include_once DRUPAL_ROOT . '/core/includes/module.inc';
+  $module_list['system']['filename'] = 'core/modules/system/system.module';
+  module_list(NULL, $module_list);
   drupal_load('module', 'system');
 
   // Reset the module_implements() cache so that any new hook implementations
@@ -434,9 +419,6 @@ function update_check_requirements($skip_warnings = FALSE) {
   // Set up theme system for the maintenance page.
   drupal_maintenance_theme();
 
-  // Unlock the module system to perform update requirements checks.
-  module_list_reset();
-
   // Check the update requirements for Drupal. Only report on errors at this
   // stage, since the real requirements check happens further down.
   update_check_requirements(TRUE);
@@ -466,9 +448,6 @@ function update_check_requirements($skip_warnings = FALSE) {
 
   update_fix_compatibility();
 
-  // Unlock the module system to perform update requirements checks.
-  module_list_reset();
-
   // Check the update requirements for all modules. If there are warnings, but
   // no errors, skip reporting them if the user has provided a URL parameter
   // acknowledging the warnings and indicating a desire to continue anyway. See
@@ -477,9 +456,6 @@ function update_check_requirements($skip_warnings = FALSE) {
   $skip_warnings = !empty($continue);
   update_check_requirements($skip_warnings);
 
-  // Re-lock the module system.
-  module_list(NULL, $module_list);
-
   switch ($op) {
     // update.php ops.
 
@@ -507,11 +483,6 @@ function update_check_requirements($skip_warnings = FALSE) {
       break;
 
     case 'results':
-      // Unlock the module system after performing updates.
-      module_list_reset();
-      // Load all modules to flush all caches and rebuild data structures.
-      module_load_all(FALSE, TRUE);
-
       $output = update_results_page();
       break;