diff --git a/core/authorize.php b/core/authorize.php
index fe374fa..f1921cb 100644
--- a/core/authorize.php
+++ b/core/authorize.php
@@ -182,7 +182,7 @@ function authorize_access_allowed(Request $request) {
 }
 
 $bare_html_page_renderer = \Drupal::service('bare_html_page_renderer');
-$response = $bare_html_page_renderer->renderBarePage($content, $page_title, 'maintenance_page', array(
+$response = $bare_html_page_renderer->renderBarePage($content, $page_title, 'page__maintenance', array(
   '#show_messages' => $show_messages,
 ));
 if (!$is_allowed) {
diff --git a/core/includes/batch.inc b/core/includes/batch.inc
index 0958c3a..d273929 100644
--- a/core/includes/batch.inc
+++ b/core/includes/batch.inc
@@ -138,7 +138,7 @@ function _batch_progress_page() {
     // it. While this causes invalid HTML, the same would be true if we didn't,
     // as content is not allowed to appear after </html> anyway.
     $bare_html_page_renderer = \Drupal::service('bare_html_page_renderer');
-    $response = $bare_html_page_renderer->renderBarePage(['#markup' => $fallback], $current_set['title'], 'maintenance_page', array(
+    $response = $bare_html_page_renderer->renderBarePage(['#markup' => $fallback], $current_set['title'], 'page__maintenance', array(
       '#show_messages' => FALSE,
     ));
 
diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 36612ecf..0407647 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -984,7 +984,7 @@ function install_display_output($output, $install_state) {
   }
 
   $bare_html_page_renderer = \Drupal::service('bare_html_page_renderer');
-  $response = $bare_html_page_renderer->renderBarePage($output, $output['#title'], 'install_page', $regions);
+  $response = $bare_html_page_renderer->renderBarePage($output, $output['#title'], 'page__maintenance__install', $regions);
   $default_headers = array(
     'Expires' => 'Sun, 19 Nov 1978 05:00:00 GMT',
     'Last-Modified' => gmdate(DATE_RFC1123, REQUEST_TIME),
diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index 2947eb9..a5f17f7 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -1137,7 +1137,7 @@ function template_preprocess_maintenance_task_list(&$variables) {
  * See the @link themeable Default theme implementations topic @endlink for
  * details.
  */
-function template_preprocess(&$variables, $context) {
+function template_preprocess(&$variables, $hook, $info) {
   // Merge in variables that don't depend on hook and don't change during a
   // single page request.
   // Use the advanced drupal_static() pattern, since this is called very often.
@@ -1153,8 +1153,8 @@ function template_preprocess(&$variables, $context) {
 
   // When theming a render element, merge its #attributes into
   // $variables['attributes'].
-  if (isset($context['info']['render element'])) {
-    $key = $context['info']['render element'];
+  if (isset($info['render element'])) {
+    $key = $info['render element'];
     if (isset($variables[$key]['#attributes'])) {
       $variables['attributes'] = NestedArray::mergeDeep($variables['attributes'], $variables[$key]['#attributes']);
     }
@@ -1292,7 +1292,7 @@ function template_preprocess_html(&$variables) {
  * inside "modules/system/page.html.twig". Look in there for the full list of
  * variables.
  */
-function template_preprocess_page(&$variables, $context) {
+function template_preprocess_page(&$variables) {
   $language_interface = \Drupal::languageManager()->getCurrentLanguage();
   $site_config = \Drupal::config('system.site');
 
@@ -1334,11 +1334,6 @@ function template_preprocess_page(&$variables, $context) {
   if ($node = \Drupal::routeMatch()->getParameter('node')) {
     $variables['node'] = $node;
   }
-
-  // @todo Remove once https://drupal.org/node/939462 is fixed.
-  if ($context['suggestion'] !== 'page' && function_exists($function = 'template_preprocess_' . $context['suggestion'])) {
-    $function($variables, $context);
-  }
 }
 
 /**
@@ -1477,7 +1472,7 @@ function template_preprocess_region(&$variables) {
  *   - attributes: A string containing the attributes for the wrapping div.
  *   - title_attributes: A string containing the attributes for the title.
  */
-function template_preprocess_field(&$variables) {
+function template_preprocess_field(&$variables, $hook) {
   $element = $variables['element'];
 
   // Creating variables for the template.
@@ -1673,13 +1668,9 @@ function drupal_common_theme() {
     ),
     'page__maintenance' => array(
       'base hook' => 'page',
-      'render element' => 'page',
-      'template' => 'page--maintenance',
     ),
     'page__maintenance__install' => array(
       'base hook' => 'page',
-      'render element' => 'page',
-      'template' => 'page--maintenance--install',
     ),
     'region' => array(
       'render element' => 'elements',
diff --git a/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
index 92071da..bb2a215 100644
--- a/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/MaintenanceModeSubscriber.php
@@ -106,7 +106,7 @@ public function onKernelRequestMaintenance(GetResponseEvent $event) {
         $content = Xss::filterAdmin(SafeMarkup::format($this->config->get('system.maintenance')->get('message'), array(
           '@site' => $this->config->get('system.site')->get('name'),
         )));
-        $response = $this->bareHtmlPageRenderer->renderBarePage(['#markup' => $content], $this->t('Site under maintenance'), 'maintenance_page');
+        $response = $this->bareHtmlPageRenderer->renderBarePage(['#markup' => $content], $this->t('Site under maintenance'), 'page__maintenance');
         $response->setStatusCode(503);
         $event->setResponse($response);
       }
diff --git a/core/lib/Drupal/Core/Render/BareHtmlPageRendererInterface.php b/core/lib/Drupal/Core/Render/BareHtmlPageRendererInterface.php
index 9e1f8ee..7a85e64 100644
--- a/core/lib/Drupal/Core/Render/BareHtmlPageRendererInterface.php
+++ b/core/lib/Drupal/Core/Render/BareHtmlPageRendererInterface.php
@@ -38,9 +38,9 @@
  * in a limited environment).
  *
  * Currently, there are two types of bare pages available:
- * - Install (hook_preprocess_install_page(), install-page.html.twig).
- * - Maintenance (hook_preprocess_maintenance_page(),
- *   maintenance-page.html.twig).
+ * - Install (hook_preprocess__page__maintenance__install(), page--maintenance--install.html.twig).
+ * - Maintenance (hook_preprocess_page__maintenance(),
+ *   page--maintenance.html.twig).
  *
  * @see \Drupal\Core\Render\MainContent\HtmlRenderer
  */
diff --git a/core/lib/Drupal/Core/Render/theme.api.php b/core/lib/Drupal/Core/Render/theme.api.php
index 7e00e38..e9144cf 100644
--- a/core/lib/Drupal/Core/Render/theme.api.php
+++ b/core/lib/Drupal/Core/Render/theme.api.php
@@ -483,32 +483,29 @@ function hook_form_system_theme_settings_alter(&$form, \Drupal\Core\Form\FormSta
  *
  * @param $variables
  *   The variables array (modify in place).
- * @param $context
- *   The context for which this preprocess function is running. This includes:
- *   - hook:
- *     @todo Document this after figuring out what it is. It's not necessarily
- *       the same as what was passed to _theme() as $hook, nor is it
- *       necessarily the same as 'suggestion'. What is it?
- *   - suggestions: The array of theme hook suggestions that were searched in
- *     order to find one that was implemented via a template or function.
- *   - suggestion: The theme hook suggestion that was found and therefore
- *     will be rendered after variable processing is complete.
- *   - info: The theme registry information for the matching hook/suggestion.
-*/
-function hook_preprocess(&$variables, $context) {
+ * @param $hook
+ *   The name of the theme hook.
+ */
+function hook_preprocess(&$variables, $hook) {
+ static $hooks;
+
   // Add contextual links to the variables, if the user has permission.
 
   if (!\Drupal::currentUser()->hasPermission('access contextual links')) {
     return;
   }
 
+  if (!isset($hooks)) {
+    $hooks = theme_get_registry();
+  }
+
   // Determine the primary theme function argument.
-  if (isset($context['info']['variables'])) {
-    $keys = array_keys($context['info']['variables']);
+  if (isset($hooks[$hook]['variables'])) {
+    $keys = array_keys($hooks[$hook]['variables']);
     $key = $keys[0];
   }
   else {
-    $key = $context['info']['render element'];
+    $key = $hooks[$hook]['render element'];
   }
 
   if (isset($variables[$key])) {
diff --git a/core/lib/Drupal/Core/Theme/ThemeManager.php b/core/lib/Drupal/Core/Theme/ThemeManager.php
index c2b76fe..9958b56 100644
--- a/core/lib/Drupal/Core/Theme/ThemeManager.php
+++ b/core/lib/Drupal/Core/Theme/ThemeManager.php
@@ -287,15 +287,9 @@ public function render($hook, array $variables) {
       }
     }
     if (isset($info['preprocess functions'])) {
-      $context = array(
-        'hook' => $hook,
-        'suggestions' => $suggestions,
-        'suggestion' => isset($suggestion) ? $suggestion : NULL,
-        'info' => $info,
-      );
       foreach ($info['preprocess functions'] as $preprocessor_function) {
         if (function_exists($preprocessor_function)) {
-          $preprocessor_function($variables, $context);
+          $preprocessor_function($variables, $hook, $info);
         }
       }
       // Allow theme preprocess functions to set $variables['#attached'] and
@@ -359,13 +353,7 @@ public function render($hook, array $variables) {
       // adding some new variable to track that.
       if (!isset($variables['directory'])) {
         $default_template_variables = array();
-        $context = array(
-          'hook' => $hook,
-          'suggestions' => $suggestions,
-          'suggestion' => isset($suggestion) ? $suggestion : NULL,
-          'info' => $info,
-        );
-        template_preprocess($default_template_variables, $context);
+        template_preprocess($default_template_variables, $hook, $info);
         $variables += $default_template_variables;
       }
       if (!isset($default_attributes)) {
diff --git a/core/modules/contextual/contextual.module b/core/modules/contextual/contextual.module
index 088b998..a672e4e 100644
--- a/core/modules/contextual/contextual.module
+++ b/core/modules/contextual/contextual.module
@@ -101,14 +101,14 @@ function contextual_help($route_name, RouteMatchInterface $route_match) {
  * @see contextual_page_attachments()
  * @see \Drupal\contextual\ContextualController::render()
  */
-function contextual_preprocess(&$variables, $context) {
+function contextual_preprocess(&$variables, $hook, $info) {
   // Determine the primary theme function argument.
-  if (!empty($context['info']['variables'])) {
-    $keys = array_keys($context['info']['variables']);
+  if (!empty($info['variables'])) {
+    $keys = array_keys($info['variables']);
     $key = $keys[0];
   }
-  elseif (!empty($context['info']['render element'])) {
-    $key = $context['info']['render element'];
+  elseif (!empty($info['render element'])) {
+    $key = $info['render element'];
   }
   if (!empty($key) && isset($variables[$key])) {
     $element = $variables[$key];
diff --git a/core/modules/system/src/Controller/DbUpdateController.php b/core/modules/system/src/Controller/DbUpdateController.php
index fa8104d..10f66b7 100644
--- a/core/modules/system/src/Controller/DbUpdateController.php
+++ b/core/modules/system/src/Controller/DbUpdateController.php
@@ -186,7 +186,7 @@ public function handle($op, Request $request) {
     }
     $title = isset($output['#title']) ? $output['#title'] : $this->t('Drupal database update');
 
-    return $this->bareHtmlPageRenderer->renderBarePage($output, $title, 'maintenance_page', $regions);
+    return $this->bareHtmlPageRenderer->renderBarePage($output, $title, 'page__maintenance', $regions);
   }
 
   /**
diff --git a/core/modules/system/templates/page--maintenance--install.html.twig b/core/modules/system/templates/page--maintenance--install.html.twig
index 1d0e479..964821e 100644
--- a/core/modules/system/templates/page--maintenance--install.html.twig
+++ b/core/modules/system/templates/page--maintenance--install.html.twig
@@ -6,7 +6,7 @@
  * All available variables are mirrored in page.html.twig.
  * Some may be blank but they are provided for consistency.
  *
- * @see template_preprocess_install_page()
+ * @see template_preprocess_page__maintenance__install()
  *
  * @ingroup themeable
  */
diff --git a/core/modules/system/templates/page--maintenance.html.twig b/core/modules/system/templates/page--maintenance.html.twig
index 748ed5a..6ca60fd 100644
--- a/core/modules/system/templates/page--maintenance.html.twig
+++ b/core/modules/system/templates/page--maintenance.html.twig
@@ -6,7 +6,7 @@
  * All available variables are mirrored in page.html.twig.
  * Some may be blank but they are provided for consistency.
  *
- * @see template_preprocess_maintenance_page()
+ * @see template_preprocess_page__maintenance()
  *
  * @ingroup themeable
  */
diff --git a/core/themes/bartik/bartik.theme b/core/themes/bartik/bartik.theme
index 759e193..7baf9ad 100644
--- a/core/themes/bartik/bartik.theme
+++ b/core/themes/bartik/bartik.theme
@@ -39,7 +39,7 @@ function bartik_preprocess_html(&$variables) {
 /**
  * Implements hook_preprocess_HOOK() for page templates.
  */
-function bartik_preprocess_page(&$variables, $context) {
+function bartik_preprocess_page(&$variables) {
   // Set the options that apply to both page and maintenance page.
   _bartik_process_page($variables);
 
@@ -59,11 +59,6 @@ function bartik_preprocess_page(&$variables, $context) {
     // Make sure the shortcut link is the first item in title_suffix.
     $variables['title_suffix']['add_or_remove_shortcut']['#weight'] = -100;
   }
-
-  // @todo Remove once https://drupal.org/node/939462 is fixed.
-  if ($context['suggestion'] !== 'page' && function_exists($function = 'bartik_preprocess_' . $context['suggestion'])) {
-    $function($variables, $context);
-  }
 }
 
 /**
@@ -73,7 +68,7 @@ function bartik_preprocess_page__maintenance(&$variables) {
   // By default, site_name is set to Drupal if no db connection is available
   // or during site installation. Setting site_name to an empty string makes
   // the site and update pages look cleaner.
-  // @see template_preprocess_maintenance_page
+  // @see template_preprocess_page__maintenance
   if (!$variables['db_is_active']) {
     $variables['site_name'] = '';
   }
diff --git a/core/themes/bartik/templates/page--maintenance.html.twig b/core/themes/bartik/templates/page--maintenance.html.twig
index 3cd787b..f414e47 100644
--- a/core/themes/bartik/templates/page--maintenance.html.twig
+++ b/core/themes/bartik/templates/page--maintenance.html.twig
@@ -5,7 +5,7 @@
  *
  * All available variables are mirrored in page.html.twig.
  *
- * @see template_preprocess_maintenance_page()
+ * @see template_preprocess_page__maintenance()
  */
  #}
 <div id="page-wrapper">
diff --git a/core/themes/seven/seven.theme b/core/themes/seven/seven.theme
index b0f559b..b10be99 100644
--- a/core/themes/seven/seven.theme
+++ b/core/themes/seven/seven.theme
@@ -26,18 +26,13 @@ function seven_preprocess_html(&$variables) {
 /**
  * Implements hook_preprocess_HOOK() for page templates.
  */
-function seven_preprocess_page(&$variables, $context) {
+function seven_preprocess_page(&$variables) {
   $variables['primary_local_tasks'] = $variables['tabs'];
   unset($variables['primary_local_tasks']['#secondary']);
   $variables['secondary_local_tasks'] = array(
     '#theme' => 'menu_local_tasks',
     '#secondary' => isset($variables['tabs']['#secondary']) ? $variables['tabs']['#secondary'] : '',
   );
-
-  // @todo Remove once https://drupal.org/node/939462 is fixed.
-  if ($context['suggestion'] !== 'page' && function_exists($function = 'seven_preprocess_' . $context['suggestion'])) {
-    $function($variables, $context);
-  }
 }
 
 /**
diff --git a/core/themes/seven/templates/page--maintenance--install.html.twig b/core/themes/seven/templates/page--maintenance--install.html.twig
index b501fb8..d8e28fa 100644
--- a/core/themes/seven/templates/page--maintenance--install.html.twig
+++ b/core/themes/seven/templates/page--maintenance--install.html.twig
@@ -6,7 +6,7 @@
  * All available variables are mirrored in page.html.twig.
  * Some may be blank but they are provided for consistency.
  *
- * @see template_preprocess_install_page()
+ * @see template_preprocess_page__maintenance__install()
  */
 #}
 <div class="layout-container">