diff --git a/modules/field/field.api.php b/modules/field/field.api.php
index 9c52d24..0790f0b 100644
--- a/modules/field/field.api.php
+++ b/modules/field/field.api.php
@@ -124,6 +124,10 @@ function hook_field_extra_fields_alter(&$info) {
 /**
  * Define Field API field types.
  *
+ * Note that fields and their instances should never be created in the same
+ * module that defines their field type, because disabling the module will mark
+ * the fields as inactive, preventing them from being removed on uninstall.
+ *
  * @return
  *   An array whose keys are field type names and whose values are arrays
  *   describing the field type, with the following key/value pairs:
diff --git a/modules/field/field.crud.inc b/modules/field/field.crud.inc
index 339e9c4..605564a 100644
--- a/modules/field/field.crud.inc
+++ b/modules/field/field.crud.inc
@@ -23,6 +23,10 @@
  * This function does not bind the field to any bundle; use
  * field_create_instance() for that.
  *
+ * Note that fields and their instances should never be created in the same
+ * module that defines their field type, because disabling the module will mark
+ * the fields as inactive, preventing them from being removed on uninstall.
+ *
  * @param $field
  *   A field definition array. The field_name and type properties are required.
  *   Other properties, if omitted, will be given the following default values:
@@ -415,6 +419,10 @@ function field_delete_field($field_name) {
 /**
  * Creates an instance of a field, binding it to a bundle.
  *
+ * Note that fields and their instances should never be created in the same
+ * module that defines their field type, because disabling the module will mark
+ * the fields as inactive, preventing them from being removed on uninstall.
+ *
  * @param $instance
  *   A field instance definition array. The field_name, entity_type and
  *   bundle properties are required. Other properties, if omitted,
diff --git a/modules/field/field.module b/modules/field/field.module
index 9e03c8d..290caca 100644
--- a/modules/field/field.module
+++ b/modules/field/field.module
@@ -306,13 +306,6 @@ define('FIELD_LOAD_REVISION', 'FIELD_LOAD_REVISION');
 class FieldUpdateForbiddenException extends FieldException {}
 
 /**
- * Implements hook_flush_caches().
- */
-function field_flush_caches() {
-  return array('cache_field');
-}
-
-/**
  * Implements hook_help().
  */
 function field_help($path, $arg) {
@@ -386,45 +379,74 @@ function field_modules_uninstalled($modules) {
 }
 
 /**
- * Implements hook_modules_enabled().
+ * Implements hook_system_info_alter().
+ *
+ * Goes through a list of all modules that provide a field type, and makes them
+ * required if there are any active fields of that type.
  */
-function field_modules_enabled($modules) {
-  foreach ($modules as $module) {
-    field_associate_fields($module);
+function field_system_info_alter(&$info, $file, $type) {
+  if ($type == 'module' && module_hook($file->name, 'field_info')) {
+    $fields = field_read_fields(array('module' => $file->name), array('include_deleted' => TRUE));
+    if ($fields) {
+      $info['required'] = TRUE;
+
+      // Provide an explanation message (only mention pending deletions if there
+      // remains no actual, non-deleted fields)
+      $non_deleted = FALSE;
+      foreach ($fields as $field) {
+        if (empty($field['deleted'])) {
+          $non_deleted = TRUE;
+          break;
+        }
+      }
+      if ($non_deleted) {
+        $explanation = t('Field type(s) in use - see !link', array('!link' => l(t('Field list'), 'admin/reports/fields')));
+      }
+      else {
+        $explanation = t('Fields pending deletion');
+      }
+      $info['explanation'] = $explanation;
+    }
   }
-  field_cache_clear();
 }
 
+
 /**
- * Implements hook_modules_disabled().
+ * Implements hook_flush_caches().
  */
-function field_modules_disabled($modules) {
-  // Track fields whose field type is being disabled.
+function field_flush_caches() {
+  // Refresh the 'active' and 'storage_active' columns according to the current
+  // set of enabled modules.
+  $all_modules = system_rebuild_module_data();
+  $modules = array();
+  foreach ($all_modules as $module_name => $module) {
+    if ($module->status) {
+      $modules[] = $module_name;
+      field_associate_fields($module_name);
+    }
+  }
   db_update('field_config')
     ->fields(array('active' => 0))
-    ->condition('module', $modules, 'IN')
+    ->condition('module', $modules, 'NOT IN')
     ->execute();
-
-  // Track fields whose storage backend is being disabled.
   db_update('field_config')
     ->fields(array('storage_active' => 0))
-    ->condition('storage_module', $modules, 'IN')
+    ->condition('storage_module', $modules, 'NOT IN')
     ->execute();
 
-  field_cache_clear();
+  return array('cache_field');
 }
 
 /**
  * Allows a module to update the database for fields and columns it controls.
  *
- * @param string $module
+ * @param $module
  *   The name of the module to update on.
  */
 function field_associate_fields($module) {
   // Associate field types.
-  $field_types =(array) module_invoke($module, 'field_info');
+  $field_types = (array) module_invoke($module, 'field_info');
   foreach ($field_types as $name => $field_info) {
-    watchdog('field', 'Updating field type %type with module %module.', array('%type' => $name, '%module' => $module));
     db_update('field_config')
       ->fields(array('module' => $module, 'active' => 1))
       ->condition('type', $name)
@@ -433,7 +455,6 @@ function field_associate_fields($module) {
   // Associate storage backends.
   $storage_types = (array) module_invoke($module, 'field_storage_info');
   foreach ($storage_types as $name => $storage_info) {
-    watchdog('field', 'Updating field storage %type with module %module.', array('%type' => $name, '%module' => $module));
     db_update('field_config')
       ->fields(array('storage_module' => $module, 'storage_active' => 1))
       ->condition('storage_type', $name)
diff --git a/modules/field/tests/field.test b/modules/field/tests/field.test
index 9281273..8a24fc1 100644
--- a/modules/field/tests/field.test
+++ b/modules/field/tests/field.test
@@ -2356,6 +2356,7 @@ class FieldCrudTestCase extends FieldTestCase {
     $this->assertTrue($field_definition <= $field, t('The field was properly read.'));
 
     module_disable($modules, FALSE);
+    drupal_flush_all_caches();
 
     $fields = field_read_fields(array('field_name' => $field_name), array('include_inactive' => TRUE));
     $this->assertTrue(isset($fields[$field_name]) && $field_definition < $field, t('The field is properly read when explicitly fetching inactive fields.'));
@@ -2368,6 +2369,7 @@ class FieldCrudTestCase extends FieldTestCase {
 
       $module = array_shift($modules);
       module_enable(array($module), FALSE);
+      drupal_flush_all_caches();
     }
 
     // Check that the field is active again after all modules have been
diff --git a/modules/field_ui/field_ui.admin.inc b/modules/field_ui/field_ui.admin.inc
index 96beb13..db31004 100644
--- a/modules/field_ui/field_ui.admin.inc
+++ b/modules/field_ui/field_ui.admin.inc
@@ -12,17 +12,27 @@ function field_ui_fields_list() {
   $instances = field_info_instances();
   $field_types = field_info_field_types();
   $bundles = field_info_bundles();
+
+  $modules = system_rebuild_module_data();
+
   $header = array(t('Field name'), t('Field type'), t('Used in'));
   $rows = array();
   foreach ($instances as $entity_type => $type_bundles) {
     foreach ($type_bundles as $bundle => $bundle_instances) {
       foreach ($bundle_instances as $field_name => $instance) {
         $field = field_info_field($field_name);
+
+        // Initialize the row if we encounter the field for the first time.
+        if (!isset($rows[$field_name])) {
+          $rows[$field_name]['class'] = $field['locked'] ? array('menu-disabled') : array('');
+          $rows[$field_name]['data'][0] = $field['locked'] ? t('@field_name (Locked)', array('@field_name' => $field_name)) : $field_name;
+          $module_name = $field_types[$field['type']]['module'];
+          $rows[$field_name]['data'][1] = $field_types[$field['type']]['label'] . ' ' . t('(module: !module)', array('!module' => $modules[$module_name]->info['name']));
+        }
+
+        // Add the current instance.
         $admin_path = _field_ui_bundle_admin_path($entity_type, $bundle);
-        $rows[$field_name]['data'][0] = $field['locked'] ? t('@field_name (Locked)', array('@field_name' => $field_name)) : $field_name;
-        $rows[$field_name]['data'][1] = $field_types[$field['type']]['label'];
         $rows[$field_name]['data'][2][] = $admin_path ? l($bundles[$entity_type][$bundle]['label'], $admin_path . '/fields') : $bundles[$entity_type][$bundle]['label'];
-        $rows[$field_name]['class'] = $field['locked'] ? array('menu-disabled') : array('');
       }
     }
   }
diff --git a/modules/forum/forum.test b/modules/forum/forum.test
index 1dc45c6..d59ed44 100644
--- a/modules/forum/forum.test
+++ b/modules/forum/forum.test
@@ -31,6 +31,7 @@ class ForumTestCase extends DrupalWebTestCase {
     // Create users.
     $this->admin_user = $this->drupalCreateUser(array(
       'access administration pages',
+      'administer modules',
       'administer blocks',
       'administer forums',
       'administer menu',
@@ -52,6 +53,30 @@ class ForumTestCase extends DrupalWebTestCase {
   }
 
   /**
+   * Tests disabling and re-enabling forum.
+   */
+  function testEnableForumField() {
+    $this->drupalLogin($this->admin_user);
+    
+    // Disable the forum module.
+    $edit = array();
+    $edit['modules[Core][forum][enable]'] = FALSE;
+    $this->drupalPost('admin/modules', $edit, t('Save configuration'));
+    $this->assertText(t('The configuration options have been saved.'), t('Modules status has been updated.'));
+    module_list(TRUE);
+    $this->assertFalse(module_exists('forum'), t('Forum module is not enabled.'));
+
+    // Attempt to re-enable the forum module and ensure it does not try to
+    // recreate the taxonomy_forums field.
+    $edit = array();
+    $edit['modules[Core][forum][enable]'] = 'forum';
+    $this->drupalPost('admin/modules', $edit, t('Save configuration'));
+    $this->assertText(t('The configuration options have been saved.'), t('Modules status has been updated.'));
+    module_list(TRUE);
+    $this->assertTrue(module_exists('forum'), t('Forum module is enabled.'));
+  }
+
+  /**
    * Login users, create forum nodes, and test forum functionality through the admin and user interfaces.
    */
   function testForum() {
diff --git a/modules/system/system.admin.inc b/modules/system/system.admin.inc
index 9e7d69d..abb796c 100644
--- a/modules/system/system.admin.inc
+++ b/modules/system/system.admin.inc
@@ -799,7 +799,7 @@ function system_modules($form, $form_state = array()) {
     $extra['enabled'] = (bool) $module->status;
     if (!empty($module->info['required'] )) {
       $extra['disabled'] = TRUE;
-      $extra['required_by'][] = $distribution_name;
+      $extra['required_by'][] = $distribution_name . (!empty($module->info['explanation']) ? ' ('. $module->info['explanation'] .')' : '');
     }
 
     // If this module requires other modules, add them to the array.
diff --git a/modules/system/system.test b/modules/system/system.test
index be4e366..d5bbcff 100644
--- a/modules/system/system.test
+++ b/modules/system/system.test
@@ -294,39 +294,6 @@ class ModuleDependencyTestCase extends ModuleTestCase {
   }
 
   /**
-   * Tests re-enabling forum with taxonomy disabled.
-   */
-  function testEnableForumTaxonomyFieldDependency() {
-    // Enable the forum module.
-    $edit = array();
-    $edit['modules[Core][forum][enable]'] = 'forum';
-    $this->drupalPost('admin/modules', $edit, t('Save configuration'));
-    $this->assertModules(array('forum'), TRUE);
-
-    // Disable the forum module.
-    $edit = array();
-    $edit['modules[Core][forum][enable]'] = FALSE;
-    $this->drupalPost('admin/modules', $edit, t('Save configuration'));
-    $this->assertModules(array('forum'), FALSE);
-
-    // Disable the taxonomy module.
-    $edit = array();
-    $edit['modules[Core][taxonomy][enable]'] = FALSE;
-    $this->drupalPost('admin/modules', $edit, t('Save configuration'));
-    $this->assertModules(array('taxonomy'), FALSE);
-
-    // Attempt to re-enable the forum module with taxonomy disabled and ensure
-    // forum does not try to recreate the taxonomy_forums field.
-    $edit = array();
-    $edit['modules[Core][forum][enable]'] = 'forum';
-    $this->drupalPost('admin/modules', $edit, t('Save configuration'));
-    $this->assertText(t('Some required modules must be enabled'), t('Dependency required.'));
-    $this->drupalPost(NULL, NULL, t('Continue'));
-    $this->assertText(t('The configuration options have been saved.'), t('Modules status has been updated.'));
-    $this->assertModules(array('taxonomy', 'forum'), TRUE);
-  }
-
-  /**
    * Tests that module dependencies are enabled in the correct order via the
    * UI. Dependencies should be enabled before their dependents.
    */
@@ -364,18 +331,18 @@ class ModuleDependencyTestCase extends ModuleTestCase {
     $this->drupalPost('admin/modules', $edit, t('Save configuration'));
     $this->assertModules(array('forum'), TRUE);
 
-    // Disable forum and taxonomy. Both should now be installed but disabled.
+    // Disable forum and comment. Both should now be installed but disabled.
     $edit = array('modules[Core][forum][enable]' => FALSE);
     $this->drupalPost('admin/modules', $edit, t('Save configuration'));
     $this->assertModules(array('forum'), FALSE);
-    $edit = array('modules[Core][taxonomy][enable]' => FALSE);
+    $edit = array('modules[Core][comment][enable]' => FALSE);
     $this->drupalPost('admin/modules', $edit, t('Save configuration'));
-    $this->assertModules(array('taxonomy'), FALSE);
+    $this->assertModules(array('comment'), FALSE);
 
     // Check that the taxonomy module cannot be uninstalled.
     $this->drupalGet('admin/modules/uninstall');
-    $checkbox = $this->xpath('//input[@type="checkbox" and @disabled="disabled" and @name="uninstall[taxonomy]"]');
-    $this->assert(count($checkbox) == 1, t('Checkbox for uninstalling the taxonomy module is disabled.'));
+    $checkbox = $this->xpath('//input[@type="checkbox" and @disabled="disabled" and @name="uninstall[comment]"]');
+    $this->assert(count($checkbox) == 1, t('Checkbox for uninstalling the comment module is disabled.'));
 
     // Uninstall the forum module, and check that taxonomy now can also be
     // uninstalled.
@@ -383,7 +350,7 @@ class ModuleDependencyTestCase extends ModuleTestCase {
     $this->drupalPost('admin/modules/uninstall', $edit, t('Uninstall'));
     $this->drupalPost(NULL, NULL, t('Uninstall'));
     $this->assertText(t('The selected modules have been uninstalled.'), t('Modules status has been updated.'));
-    $edit = array('uninstall[taxonomy]' => 'taxonomy');
+    $edit = array('uninstall[comment]' => 'comment');
     $this->drupalPost('admin/modules/uninstall', $edit, t('Uninstall'));
     $this->drupalPost(NULL, NULL, t('Uninstall'));
     $this->assertText(t('The selected modules have been uninstalled.'), t('Modules status has been updated.'));