--- a/src/hotspot/share/gc/z/zMarkStackAllocator.cpp	Mon Nov 25 12:32:40 2019 +0100
+++ b/src/hotspot/share/gc/z/zMarkStackAllocator.cpp	Mon Nov 25 12:33:15 2019 +0100
@@ -70,7 +70,7 @@
       return 0;
     }
 
-    const uintptr_t prev_top = Atomic::cmpxchg(new_top, &_top, top);
+    const uintptr_t prev_top = Atomic::cmpxchg(&_top, top, new_top);
     if (prev_top == top) {
       // Success
       return top;