--- a/src/hotspot/share/gc/shared/taskqueue.inline.hpp	Thu Oct 17 20:27:44 2019 +0100
+++ b/src/hotspot/share/gc/shared/taskqueue.inline.hpp	Thu Oct 17 20:53:35 2019 +0100
@@ -184,6 +184,11 @@
   } else {
     // Otherwise, the queue contained exactly one element; we take the slow
     // path.
+
+    // The barrier is required to prevent reordering the two reads of _age:
+    // one is the _age.get() below, and the other is _age.top() above the if-stmt.
+    // The algorithm may fail if _age.get() reads an older value than _age.top().
+    OrderAccess::loadload();
     return pop_local_slow(localBot, _age.get());
   }
 }
@@ -202,7 +207,7 @@
   // Architectures with weak memory model require a barrier here
   // to guarantee that bottom is not older than age,
   // which is crucial for the correctness of the algorithm.
-#if !(defined SPARC || defined IA32 || defined AMD64)
+#ifndef CPU_MULTI_COPY_ATOMIC
   OrderAccess::fence();
 #endif
   uint localBot = OrderAccess::load_acquire(&_bottom);