diff -r 2c3cc4b01880 -r c16ac7a2eba4 src/hotspot/share/jfr/recorder/checkpoint/types/traceid/jfrTraceIdEpoch.hpp
--- a/src/hotspot/share/jfr/recorder/checkpoint/types/traceid/jfrTraceIdEpoch.hpp	Wed Oct 30 16:14:56 2019 +0100
+++ b/src/hotspot/share/jfr/recorder/checkpoint/types/traceid/jfrTraceIdEpoch.hpp	Wed Oct 30 19:43:52 2019 +0100
@@ -25,18 +25,19 @@
 #ifndef SHARE_JFR_RECORDER_CHECKPOINT_TYPES_TRACEID_JFRTRACEIDEPOCH_HPP
 #define SHARE_JFR_RECORDER_CHECKPOINT_TYPES_TRACEID_JFRTRACEIDEPOCH_HPP
 
+#include "jfr/utilities/jfrTypes.hpp"
 #include "memory/allocation.hpp"
-#include "jfr/utilities/jfrTypes.hpp"
+#include "runtime/orderAccess.hpp"
 
-#define USED_BIT 1
-#define METHOD_USED_BIT (USED_BIT << 2)
-#define EPOCH_1_SHIFT 0
-#define EPOCH_2_SHIFT 1
-#define USED_EPOCH_1_BIT (USED_BIT << EPOCH_1_SHIFT)
-#define USED_EPOCH_2_BIT (USED_BIT << EPOCH_2_SHIFT)
-#define METHOD_USED_EPOCH_1_BIT (METHOD_USED_BIT << EPOCH_1_SHIFT)
-#define METHOD_USED_EPOCH_2_BIT (METHOD_USED_BIT << EPOCH_2_SHIFT)
-#define METHOD_AND_CLASS_IN_USE_BITS (METHOD_USED_BIT | USED_BIT)
+#define USED_BIT                             1
+#define METHOD_USED_BIT                      (USED_BIT << 2)
+#define EPOCH_1_SHIFT                        0
+#define EPOCH_2_SHIFT                        1
+#define USED_EPOCH_1_BIT                     (USED_BIT << EPOCH_1_SHIFT)
+#define USED_EPOCH_2_BIT                     (USED_BIT << EPOCH_2_SHIFT)
+#define METHOD_USED_EPOCH_1_BIT              (METHOD_USED_BIT << EPOCH_1_SHIFT)
+#define METHOD_USED_EPOCH_2_BIT              (METHOD_USED_BIT << EPOCH_2_SHIFT)
+#define METHOD_AND_CLASS_IN_USE_BITS         (METHOD_USED_BIT | USED_BIT)
 #define METHOD_AND_CLASS_IN_USE_EPOCH_1_BITS (METHOD_AND_CLASS_IN_USE_BITS << EPOCH_1_SHIFT)
 #define METHOD_AND_CLASS_IN_USE_EPOCH_2_BITS (METHOD_AND_CLASS_IN_USE_BITS << EPOCH_2_SHIFT)
 
@@ -44,6 +45,8 @@
   friend class JfrCheckpointManager;
  private:
   static bool _epoch_state;
+  static bool volatile _tag_state;
+
   static void shift_epoch();
 
  public:
@@ -86,6 +89,20 @@
   static traceid method_and_class_in_use_prev_epoch_bits() {
     return _epoch_state ? METHOD_AND_CLASS_IN_USE_EPOCH_1_BITS :  METHOD_AND_CLASS_IN_USE_EPOCH_2_BITS;
   }
+
+  static bool has_changed_tag_state() {
+    if (OrderAccess::load_acquire(&_tag_state)) {
+      OrderAccess::release_store(&_tag_state, false);
+      return true;
+    }
+    return false;
+  }
+
+  static void set_changed_tag_state() {
+    if (!OrderAccess::load_acquire(&_tag_state)) {
+      OrderAccess::release_store(&_tag_state, true);
+    }
+  }
 };
 
 #endif // SHARE_JFR_RECORDER_CHECKPOINT_TYPES_TRACEID_JFRTRACEIDEPOCH_HPP