diff -r 2c3cc4b01880 -r c16ac7a2eba4 src/hotspot/share/jfr/recorder/checkpoint/types/traceid/jfrTraceIdEpoch.cpp
--- a/src/hotspot/share/jfr/recorder/checkpoint/types/traceid/jfrTraceIdEpoch.cpp	Wed Oct 30 16:14:56 2019 +0100
+++ b/src/hotspot/share/jfr/recorder/checkpoint/types/traceid/jfrTraceIdEpoch.cpp	Wed Oct 30 19:43:52 2019 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -25,15 +25,13 @@
 #include "precompiled.hpp"
 #include "jfr/recorder/checkpoint/types/traceid/jfrTraceIdEpoch.hpp"
 #include "runtime/safepoint.hpp"
-#include "runtime/orderAccess.hpp"
 
 // Alternating epochs on each rotation allow for concurrent tagging.
-// The regular epoch shift happens only during a safepoint.
-// The fence is there only for the emergency dump case which happens outside of safepoint.
+// The epoch shift happens only during a safepoint.
 bool JfrTraceIdEpoch::_epoch_state = false;
+bool volatile JfrTraceIdEpoch::_tag_state = false;
+
 void JfrTraceIdEpoch::shift_epoch() {
+  assert(SafepointSynchronize::is_at_safepoint(), "invariant");
   _epoch_state = !_epoch_state;
-  if (!SafepointSynchronize::is_at_safepoint()) {
-    OrderAccess::fence();
-  }
 }