Index: src/wp-includes/post.php
===================================================================
--- src/wp-includes/post.php	(revision 40052)
+++ src/wp-includes/post.php	(working copy)
@@ -5932,7 +5932,9 @@
 		add_post_meta( $post_id, '_pingme', '1' );
 	add_post_meta( $post_id, '_encloseme', '1' );
 
-	wp_schedule_single_event(time(), 'do_pings');
+	if ( false === wp_next_scheduled( 'do_pings' ) ) {
+		wp_schedule_single_event( time(), 'do_pings' );
+	}
 }
 
 /**