--- a/src/hotspot/share/gc/z/zReferenceProcessor.cpp	Mon Nov 25 12:32:07 2019 +0100
+++ b/src/hotspot/share/gc/z/zReferenceProcessor.cpp	Mon Nov 25 12:32:40 2019 +0100
@@ -316,7 +316,7 @@
 
   // Prepend discovered references to internal pending list
   if (*list != NULL) {
-    *p = Atomic::xchg(*list, _pending_list.addr());
+    *p = Atomic::xchg(_pending_list.addr(), *list);
     if (*p == NULL) {
       // First to prepend to list, record tail
       _pending_list_tail = p;