--- wp-cron.php
+++ wp-cron.php
@@ -64,7 +64,9 @@
 if ( isset($keys[0]) && $keys[0] > $gmt_time )
 	die();
 
-$doing_cron_transient = get_transient( 'doing_cron');
+
+// The cron lock: a unix timestamp from when the cron was spawned.
+$doing_cron_transient = get_transient( 'doing_cron' );
 
 // Use global $doing_wp_cron lock otherwise use the GET lock. If no lock, trying grabbing a new lock.
 if ( empty( $doing_wp_cron ) ) {
@@ -79,7 +81,10 @@
 	}
 }
 
-// Check lock
+/*
+ * The cron lock (a unix timestamp set when the cron was spawned),
+ * must match $doing_wp_cron (the "key").
+ */
 if ( $doing_cron_transient != $doing_wp_cron )
 	return;