diff -r 2c3cc4b01880 -r c16ac7a2eba4 src/hotspot/share/jfr/utilities/jfrThreadIterator.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/jfr/utilities/jfrThreadIterator.hpp	Wed Oct 30 19:43:52 2019 +0100
@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_JFR_UTILITIES_JFRTHREADITERATOR_HPP
+#define SHARE_VM_JFR_UTILITIES_JFRTHREADITERATOR_HPP
+
+#include "memory/allocation.hpp"
+#include "runtime/thread.hpp"
+#include "runtime/threadSMR.hpp"
+
+template <typename Adapter, typename AP = StackObj>
+class JfrThreadIterator : public AP {
+ private:
+  Adapter _adapter;
+ public:
+  JfrThreadIterator() : _adapter() {}
+  typename Adapter::Type* next() {
+    assert(has_next(), "invariant");
+    return _adapter.next();
+  }
+  bool has_next() const {
+    return _adapter.has_next();
+  }
+};
+
+class JfrJavaThreadIteratorAdapter {
+ private:
+  JavaThreadIteratorWithHandle _iter;
+  JavaThread* _next;
+ public:
+  typedef JavaThread Type;
+  JfrJavaThreadIteratorAdapter();
+  bool has_next() const {
+    return _next != NULL;
+  }
+  Type* next();
+};
+
+class JfrNonJavaThreadIteratorAdapter {
+ private:
+  NonJavaThread::Iterator _iter;
+  NonJavaThread* _next;
+ public:
+  typedef NonJavaThread Type;
+  JfrNonJavaThreadIteratorAdapter();
+  bool has_next() const;
+  Type* next();
+};
+
+typedef JfrThreadIterator<JfrJavaThreadIteratorAdapter, StackObj> JfrJavaThreadIterator;
+typedef JfrThreadIterator<JfrNonJavaThreadIteratorAdapter, StackObj> JfrNonJavaThreadIterator;
+
+#endif // SHARE_VM_JFR_UTILITIES_JFRTHREADITERATOR_HPP