--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/shared/preservedMarks.hpp	Tue Feb 23 10:44:05 2016 +0100
@@ -0,0 +1,111 @@
+/*
+ * Copyright (c) 2016, 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_GC_SHARED_PRESERVEDMARKS_HPP
+#define SHARE_VM_GC_SHARED_PRESERVEDMARKS_HPP
+
+#include "memory/allocation.hpp"
+#include "memory/padded.hpp"
+#include "oops/oop.hpp"
+#include "utilities/stack.hpp"
+
+class OopAndMarkOop {
+private:
+  oop _o;
+  markOop _m;
+
+public:
+  OopAndMarkOop(oop obj, markOop m) : _o(obj), _m(m) { }
+
+  void set_mark() const {
+    _o->set_mark(_m);
+  }
+};
+typedef Stack<OopAndMarkOop, mtGC> OopAndMarkOopStack;
+
+class PreservedMarks VALUE_OBJ_CLASS_SPEC {
+private:
+  OopAndMarkOopStack _stack;
+
+  inline bool should_preserve_mark(oop obj, markOop m) const;
+  inline void push(oop obj, markOop m);
+
+public:
+  bool is_empty() const { return _stack.is_empty(); }
+  inline void push_if_necessary(oop obj, markOop m);
+  // Iterate over the stack, restore the preserved marks, then reclaim
+  // the memory taken up by stack chunks.
+  void restore();
+  ~PreservedMarks() { assert(is_empty(), "should have been cleared"); }
+};
+
+class RemoveForwardedPointerClosure: public ObjectClosure {
+public:
+  virtual void do_object(oop obj);
+};
+
+class PreservedMarksSet VALUE_OBJ_CLASS_SPEC {
+private:
+  // true -> _stacks will be allocated in the C heap
+  // false -> _stacks will be allocated in the resource arena
+  const bool _in_c_heap;
+
+  // Number of stacks we have allocated (typically, one stack per GC worker).
+  // This should be >= 1 if the stacks have been initialized,
+  // or == 0 if they have not.
+  uint _num;
+
+  // Stack array (typically, one stack per GC worker) of length _num.
+  // This should be != NULL if the stacks have been initialized,
+  // or == NULL if they have not.
+  Padded<PreservedMarks>* _stacks;
+
+public:
+  // Return the i'th stack.
+  PreservedMarks* get(uint i = 0) const {
+    assert(_num > 0 && _stacks != NULL, "stacks should have been initialized");
+    assert(i < _num, "pre-condition");
+    return (_stacks + i);
+  }
+
+  // Allocate stack array.
+  void init(uint num);
+  // Iterate over all stacks, restore all preserved marks, then
+  // reclaim the memory taken up by stack chunks.
+  void restore();
+  // Reclaim stack array.
+  void reclaim();
+
+  // Assert all the stacks are empty.
+  void assert_empty() PRODUCT_RETURN;
+
+  PreservedMarksSet(bool in_c_heap)
+      : _in_c_heap(in_c_heap), _num(0), _stacks(NULL) { }
+
+  ~PreservedMarksSet() {
+    assert(_stacks == NULL && _num == 0, "stacks should have been reclaimed");
+  }
+};
+
+#endif // SHARE_VM_GC_SHARED_PRESERVEDMARKS_HPP