Ticket #32478: 32478.diff

src/wp-cron.php

@@ -64 +64 @@
 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 ) ) {
         if ( empty( $_GET[ 'doing_wp_cron' ] ) ) {
@@ -79 +81 @@
         }
 }
 
-// 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;
 

src/wp-includes/cron.php

@@ -225 +225 @@
                 return;
 
         /*
-        * multiple processes on multiple web servers can run this code concurrently
-        * try to make this as atomic as possible by setting doing_cron switch
-        */
+         * A unix timestamp of when the last cron was spawned and has not finished running.
+         *
+         * Multiple processes on multiple web servers can run this code concurrently,
+         * this lock attempts to make spawning as atomic as possible.
+         */
         $lock = get_transient('doing_cron');
 
         if ( $lock > $gmt_time + 10 * MINUTE_IN_SECONDS )
@@ -266 +268 @@
                 return;
         }
 
+        // Set the cron lock with the current unix timestamp, when the cron is being spawned.
         $doing_wp_cron = sprintf( '%.22F', $gmt_time );
         set_transient( 'doing_cron', $doing_wp_cron );