1 files changed, 42 insertions, 5 deletions

diff --git a/upgrade.php b/upgrade.php
index f60f57707..d07b2a1da 100644
--- a/upgrade.php
+++ b/upgrade.php
@@ -9,22 +9,59 @@
  * new version of the script. Deleting the script is not a requirement and
  * leaving it behind does not affect the security of the site.
  *
+ * Upgrades use a table {db_prefix}upgrade_lock as a mutex to prevent concurrent upgrades.
+ *
  * @package Elgg.Core
  * @subpackage Upgrade
  */
 
+// we want to know if an error occurs
+ini_set('display_errors', 1);
+
 define('UPGRADING', 'upgrading');
 require_once(dirname(__FILE__) . "/engine/start.php");
 
 if (get_input('upgrade') == 'upgrade') {
-	if (version_upgrade_check()) {
+	// prevent someone from running the upgrade script in parallel (see #4643)
+	if (!_elgg_upgrade_lock()) {
+		register_error(elgg_echo('upgrade:locked'));
+		forward();
+	}
+	
+	// disable the system log for upgrades to avoid exceptions when the schema changes.
+	elgg_unregister_event_handler('log', 'systemlog', 'system_log_default_logger');
+	elgg_unregister_event_handler('all', 'all', 'system_log_listener');
+	
+	if (elgg_get_unprocessed_upgrades()) {
 		version_upgrade();
 	}
-	elgg_view_regenerate_simplecache();
-	elgg_filepath_cache_reset();
+
+	// turn off time limit so plugins that have upgrade scripts aren't interrupted
+	set_time_limit(0);
+	elgg_trigger_event('upgrade', 'system', null);
+	elgg_invalidate_simplecache();
+	elgg_reset_system_cache();
+	
+	_elgg_upgrade_unlock();
+	
 } else {
-	echo elgg_view_page(elgg_echo('upgrade'), '', 'upgrade');
+	// if upgrading from < 1.8.0, check for the core view 'welcome' and bail if it's found.
+	// see https://github.com/elgg/elgg/issues/3064
+	// we're not checking the view itself because it's likely themes will override this view.
+	// we're only concerned with core files.
+	$welcome = dirname(__FILE__) . '/views/default/welcome.php';
+	if (file_exists($welcome)) {
+		elgg_set_viewtype('failsafe');
+		// can't have pretty messages because we don't know the state of the views.
+		$content = elgg_echo('upgrade:unable_to_upgrade_info');
+		$title = elgg_echo('upgrade:unable_to_upgrade');
+		
+		echo elgg_view_page($title, $content);
+		exit;
+	}
+
+	echo elgg_view_page(elgg_echo('upgrading'), '', 'upgrade');
 	exit;
 }
 
-forward();
\ No newline at end of file
+forward();