--- old/src/hotspot/share/gc/z/zPage.inline.hpp	2019-11-21 11:57:55.447745302 +0100
+++ new/src/hotspot/share/gc/z/zPage.inline.hpp	2019-11-21 11:57:54.959737060 +0100
@@ -255,7 +255,7 @@
       return 0;
     }
 
-    const uintptr_t prev_top = Atomic::cmpxchg(new_top, &_top, addr);
+    const uintptr_t prev_top = Atomic::cmpxchg(&_top, addr, new_top);
     if (prev_top == addr) {
       // Success
       return ZAddress::good(addr);
@@ -299,7 +299,7 @@
       return false;
     }
 
-    const uintptr_t prev_top = Atomic::cmpxchg(new_top, &_top, old_top);
+    const uintptr_t prev_top = Atomic::cmpxchg(&_top, old_top, new_top);
     if (prev_top == old_top) {
       // Success
       return true;