--- old/src/hotspot/share/gc/z/zMarkStackAllocator.cpp	2019-11-21 11:57:51.639680988 +0100
+++ new/src/hotspot/share/gc/z/zMarkStackAllocator.cpp	2019-11-21 11:57:51.211673759 +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;
@@ -110,8 +110,8 @@
 
   // Increment top before end to make sure another
   // thread can't steal out newly expanded space.
-  addr = Atomic::add(size, &_top) - size;
-  Atomic::add(expand_size, &_end);
+  addr = Atomic::add(&_top, size) - size;
+  Atomic::add(&_end, expand_size);
 
   return addr;
 }