Index: includes/common.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/common.inc,v
retrieving revision 1.1138
diff -u -p -r1.1138 common.inc
--- includes/common.inc	28 Mar 2010 10:46:36 -0000	1.1138
+++ includes/common.inc	31 Mar 2010 15:41:05 -0000
@@ -6064,16 +6064,7 @@ function drupal_flush_all_caches() {
   registry_rebuild();
   drupal_clear_css_cache();
   drupal_clear_js_cache();
-
-  // If invoked from update.php, we must not update the theme information in the
-  // database, or this will result in all themes being disabled.
-  if (defined('MAINTENANCE_MODE') && MAINTENANCE_MODE == 'update') {
-    _system_rebuild_theme_data();
-  }
-  else {
-    system_rebuild_theme_data();
-  }
-
+  system_rebuild_theme_data();
   drupal_theme_rebuild();
   menu_rebuild();
   node_types_rebuild();
Index: includes/install.core.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/install.core.inc,v
retrieving revision 1.6
diff -u -p -r1.6 install.core.inc
--- includes/install.core.inc	26 Mar 2010 22:14:46 -0000	1.6
+++ includes/install.core.inc	31 Mar 2010 15:41:05 -0000
@@ -1472,10 +1472,7 @@ function install_finished(&$install_stat
   $output .= '<p>' . (isset($messages['error']) ? st('Review the messages above before visiting <a href="@url">your new site</a>.', array('@url' => url(''))) : st('<a href="@url">Visit your new site</a>.', array('@url' => url('')))) . '</p>';
 
   // Rebuild the module and theme data, in case any newly-installed modules
-  // need to modify it via hook_system_info_alter(). We need to clear the
-  // theme static cache first, to make sure that the theme data is actually
-  // rebuilt.
-  drupal_static_reset('_system_rebuild_theme_data');
+  // need to modify it via hook_system_info_alter().
   system_rebuild_module_data();
   system_rebuild_theme_data();
 
Index: includes/theme.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/theme.inc,v
retrieving revision 1.586
diff -u -p -r1.586 theme.inc
--- includes/theme.inc	26 Mar 2010 17:14:45 -0000	1.586
+++ includes/theme.inc	31 Mar 2010 15:41:05 -0000
@@ -2468,7 +2468,7 @@ function template_preprocess_maintenance
 
   global $theme;
   // Retrieve the theme data to list all available regions.
-  $theme_data = _system_rebuild_theme_data();
+  $theme_data = list_themes();
   $regions = $theme_data[$theme]->info['regions'];
 
   // Get all region content set with drupal_add_region_content().
Index: includes/update.inc
===================================================================
RCS file: /cvs/drupal/drupal/includes/update.inc,v
retrieving revision 1.40
diff -u -p -r1.40 update.inc
--- includes/update.inc	20 Mar 2010 15:06:51 -0000	1.40
+++ includes/update.inc	31 Mar 2010 15:41:05 -0000
@@ -36,7 +36,10 @@ function update_check_incompatibility($n
 
   // Store values of expensive functions for future use.
   if (empty($themes) || empty($modules)) {
-    $themes = _system_rebuild_theme_data();
+    // We need to do a full rebuild here to make sure the database reflects any
+    // code changes that were made in the filesystem before the update script
+    // was initiated.
+    $themes = system_rebuild_theme_data();
     $modules = system_rebuild_module_data();
   }
 
Index: modules/system/system.module
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.module,v
retrieving revision 1.914
diff -u -p -r1.914 system.module
--- modules/system/system.module	30 Mar 2010 07:17:19 -0000	1.914
+++ modules/system/system.module	31 Mar 2010 15:41:06 -0000
@@ -2304,118 +2304,112 @@ function _system_update_bootstrap_status
  *   An associative array of themes information.
  */
 function _system_rebuild_theme_data() {
-  $themes_info = &drupal_static(__FUNCTION__, array());
-
-  if (empty($themes_info)) {
-    // Find themes
-    $themes = drupal_system_listing('/\.info$/', 'themes');
-    // Find theme engines
-    $engines = drupal_system_listing('/\.engine$/', 'themes/engines');
-
-    // Set defaults for theme info.
-    $defaults = array(
-      'regions' => array(
-        'sidebar_first' => 'Left sidebar',
-        'sidebar_second' => 'Right sidebar',
-        'content' => 'Content',
-        'header' => 'Header',
-        'footer' => 'Footer',
-        'highlight' => 'Highlighted content',
-        'help' => 'Help',
-        'page_top' => 'Page top',
-        'page_bottom' => 'Page bottom',
-      ),
-      'description' => '',
-      'features' => _system_default_theme_features(),
-      'screenshot' => 'screenshot.png',
-      'php' => DRUPAL_MINIMUM_PHP,
-    );
-
-    $sub_themes = array();
-    // Read info files for each theme
-    foreach ($themes as $key => $theme) {
-      $themes[$key]->filename = $theme->uri;
-      $themes[$key]->info = drupal_parse_info_file($theme->uri) + $defaults;
-
-      // Invoke hook_system_info_alter() to give installed modules a chance to
-      // modify the data in the .info files if necessary.
-      $type = 'theme';
-      drupal_alter('system_info', $themes[$key]->info, $themes[$key], $type);
+  // Find themes
+  $themes = drupal_system_listing('/\.info$/', 'themes');
+  // Find theme engines
+  $engines = drupal_system_listing('/\.engine$/', 'themes/engines');
+
+  // Set defaults for theme info.
+  $defaults = array(
+    'regions' => array(
+      'sidebar_first' => 'Left sidebar',
+      'sidebar_second' => 'Right sidebar',
+      'content' => 'Content',
+      'header' => 'Header',
+      'footer' => 'Footer',
+      'highlight' => 'Highlighted content',
+      'help' => 'Help',
+      'page_top' => 'Page top',
+      'page_bottom' => 'Page bottom',
+    ),
+    'description' => '',
+    'features' => _system_default_theme_features(),
+    'screenshot' => 'screenshot.png',
+    'php' => DRUPAL_MINIMUM_PHP,
+  );
 
-      if (!empty($themes[$key]->info['base theme'])) {
-        $sub_themes[] = $key;
-      }
-      if (empty($themes[$key]->info['engine'])) {
-        $filename = dirname($themes[$key]->uri) . '/' . $themes[$key]->name . '.theme';
-        if (file_exists($filename)) {
-          $themes[$key]->owner = $filename;
-          $themes[$key]->prefix = $key;
-        }
+  $sub_themes = array();
+  // Read info files for each theme
+  foreach ($themes as $key => $theme) {
+    $themes[$key]->filename = $theme->uri;
+    $themes[$key]->info = drupal_parse_info_file($theme->uri) + $defaults;
+
+    // Invoke hook_system_info_alter() to give installed modules a chance to
+    // modify the data in the .info files if necessary.
+    $type = 'theme';
+    drupal_alter('system_info', $themes[$key]->info, $themes[$key], $type);
+
+    if (!empty($themes[$key]->info['base theme'])) {
+      $sub_themes[] = $key;
+    }
+    if (empty($themes[$key]->info['engine'])) {
+      $filename = dirname($themes[$key]->uri) . '/' . $themes[$key]->name . '.theme';
+      if (file_exists($filename)) {
+        $themes[$key]->owner = $filename;
+        $themes[$key]->prefix = $key;
       }
-      else {
-        $engine = $themes[$key]->info['engine'];
-        if (isset($engines[$engine])) {
-          $themes[$key]->owner = $engines[$engine]->uri;
-          $themes[$key]->prefix = $engines[$engine]->name;
-          $themes[$key]->template = TRUE;
-        }
+    }
+    else {
+      $engine = $themes[$key]->info['engine'];
+      if (isset($engines[$engine])) {
+        $themes[$key]->owner = $engines[$engine]->uri;
+        $themes[$key]->prefix = $engines[$engine]->name;
+        $themes[$key]->template = TRUE;
       }
+    }
 
-      // Give the stylesheets proper path information.
-      $pathed_stylesheets = array();
-      if (isset($themes[$key]->info['stylesheets'])) {
-        foreach ($themes[$key]->info['stylesheets'] as $media => $stylesheets) {
-          foreach ($stylesheets as $stylesheet) {
-            $pathed_stylesheets[$media][$stylesheet] = dirname($themes[$key]->uri) . '/' . $stylesheet;
-          }
+    // Give the stylesheets proper path information.
+    $pathed_stylesheets = array();
+    if (isset($themes[$key]->info['stylesheets'])) {
+      foreach ($themes[$key]->info['stylesheets'] as $media => $stylesheets) {
+        foreach ($stylesheets as $stylesheet) {
+          $pathed_stylesheets[$media][$stylesheet] = dirname($themes[$key]->uri) . '/' . $stylesheet;
         }
       }
-      $themes[$key]->info['stylesheets'] = $pathed_stylesheets;
+    }
+    $themes[$key]->info['stylesheets'] = $pathed_stylesheets;
 
-      // Give the scripts proper path information.
-      $scripts = array();
-      if (isset($themes[$key]->info['scripts'])) {
-        foreach ($themes[$key]->info['scripts'] as $script) {
-          $scripts[$script] = dirname($themes[$key]->uri) . '/' . $script;
-        }
-      }
-      $themes[$key]->info['scripts'] = $scripts;
-      // Give the screenshot proper path information.
-      if (!empty($themes[$key]->info['screenshot'])) {
-        $themes[$key]->info['screenshot'] = dirname($themes[$key]->uri) . '/' . $themes[$key]->info['screenshot'];
+    // Give the scripts proper path information.
+    $scripts = array();
+    if (isset($themes[$key]->info['scripts'])) {
+      foreach ($themes[$key]->info['scripts'] as $script) {
+        $scripts[$script] = dirname($themes[$key]->uri) . '/' . $script;
       }
     }
+    $themes[$key]->info['scripts'] = $scripts;
+    // Give the screenshot proper path information.
+    if (!empty($themes[$key]->info['screenshot'])) {
+      $themes[$key]->info['screenshot'] = dirname($themes[$key]->uri) . '/' . $themes[$key]->info['screenshot'];
+    }
+  }
 
-    // Now that we've established all our master themes, go back and fill in
-    // data for subthemes.
-    foreach ($sub_themes as $key) {
-      $themes[$key]->base_themes = system_find_base_themes($themes, $key);
-      // Don't proceed if there was a problem with the root base theme.
-      if (!current($themes[$key]->base_themes)) {
-        continue;
-      }
-      $base_key = key($themes[$key]->base_themes);
-      foreach (array_keys($themes[$key]->base_themes) as $base_theme) {
-        $themes[$base_theme]->sub_themes[$key] = $themes[$key]->info['name'];
+  // Now that we've established all our master themes, go back and fill in data
+  // for subthemes.
+  foreach ($sub_themes as $key) {
+    $themes[$key]->base_themes = system_find_base_themes($themes, $key);
+    // Don't proceed if there was a problem with the root base theme.
+    if (!current($themes[$key]->base_themes)) {
+      continue;
+    }
+    $base_key = key($themes[$key]->base_themes);
+    foreach (array_keys($themes[$key]->base_themes) as $base_theme) {
+      $themes[$base_theme]->sub_themes[$key] = $themes[$key]->info['name'];
+    }
+    // Copy the 'owner' and 'engine' over if the top level theme uses a theme
+    // engine.
+    if (isset($themes[$base_key]->owner)) {
+      if (isset($themes[$base_key]->info['engine'])) {
+        $themes[$key]->info['engine'] = $themes[$base_key]->info['engine'];
+        $themes[$key]->owner = $themes[$base_key]->owner;
+        $themes[$key]->prefix = $themes[$base_key]->prefix;
       }
-      // Copy the 'owner' and 'engine' over if the top level theme uses a
-      // theme engine.
-      if (isset($themes[$base_key]->owner)) {
-        if (isset($themes[$base_key]->info['engine'])) {
-          $themes[$key]->info['engine'] = $themes[$base_key]->info['engine'];
-          $themes[$key]->owner = $themes[$base_key]->owner;
-          $themes[$key]->prefix = $themes[$base_key]->prefix;
-        }
-        else {
-          $themes[$key]->prefix = $key;
-        }
+      else {
+        $themes[$key]->prefix = $key;
       }
     }
-
-    $themes_info = $themes;
   }
 
-  return $themes_info;
+  return $themes;
 }
 
 /**
Index: modules/system/system.test
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.test,v
retrieving revision 1.117
diff -u -p -r1.117 system.test
--- modules/system/system.test	12 Mar 2010 14:33:02 -0000	1.117
+++ modules/system/system.test	31 Mar 2010 15:41:06 -0000
@@ -1604,6 +1604,20 @@ class UpdateScriptFunctionalTest extends
     $this->drupalGet($this->update_url, array('external' => TRUE));
     $this->assertResponse(200);
   }
+
+  /**
+   * Tests the effect of using the update script on the theme system.
+   */
+  function testThemeSystem() {
+    // Since visiting update.php triggers a rebuild of the theme system from an
+    // unusual maintenance mode environment, we check that this rebuild did not
+    // put any incorrect information about the themes into the database.
+    $original_theme_data = db_query("SELECT * FROM {system} WHERE type = 'theme' ORDER BY name")->fetchAll();
+    $this->drupalLogin($this->update_user);
+    $this->drupalGet($this->update_url, array('external' => TRUE));
+    $final_theme_data = db_query("SELECT * FROM {system} WHERE type = 'theme' ORDER BY name")->fetchAll();
+    $this->assertEqual($original_theme_data, $final_theme_data, t('Visiting update.php does not alter the information about themes stored in the database.'));
+  }
 }
 
 /**
Index: modules/system/system.updater.inc
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.updater.inc,v
retrieving revision 1.5
diff -u -p -r1.5 system.updater.inc
--- modules/system/system.updater.inc	30 Jan 2010 07:59:25 -0000	1.5
+++ modules/system/system.updater.inc	31 Mar 2010 15:41:06 -0000
@@ -135,8 +135,7 @@ class ThemeUpdater extends Updater imple
   public function postInstall() {
     // Update the system table.
     clearstatcache();
-    drupal_static_reset('_system_rebuild_theme_data');
-    _system_rebuild_theme_data();
+    system_rebuild_theme_data();
 
     // Active the theme
     db_update('system')