--- old/src/hotspot/share/gc/serial/serialHeap.cpp	2020-04-27 10:20:15.747836682 +0200
+++ new/src/hotspot/share/gc/serial/serialHeap.cpp	2020-04-27 10:20:15.555833557 +0200
@@ -90,3 +90,8 @@
   memory_pools.append(_old_pool);
   return memory_pools;
 }
+
+// No workGang for SerialHeap, work serially with thread 0.
+void SerialHeap::run_task(AbstractGangTask* task) {
+  task->work(0);
+}