diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/hotspot/share/runtime/vmThread.hpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/runtime/vmThread.hpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,166 @@
+/*
+ * Copyright (c) 1998, 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_RUNTIME_VMTHREAD_HPP
+#define SHARE_VM_RUNTIME_VMTHREAD_HPP
+
+#include "runtime/perfData.hpp"
+#include "runtime/thread.hpp"
+#include "runtime/vm_operations.hpp"
+
+//
+// Prioritized queue of VM operations.
+//
+// Encapsulates both queue management and
+// and priority policy
+//
+class VMOperationQueue : public CHeapObj<mtInternal> {
+ private:
+  enum Priorities {
+     SafepointPriority, // Highest priority (operation executed at a safepoint)
+     MediumPriority,    // Medium priority
+     nof_priorities
+  };
+
+  // We maintain a doubled linked list, with explicit count.
+  int           _queue_length[nof_priorities];
+  int           _queue_counter;
+  VM_Operation* _queue       [nof_priorities];
+  // we also allow the vmThread to register the ops it has drained so we
+  // can scan them from oops_do
+  VM_Operation* _drain_list;
+
+  // Double-linked non-empty list insert.
+  void insert(VM_Operation* q,VM_Operation* n);
+  void unlink(VM_Operation* q);
+
+  // Basic queue manipulation
+  bool queue_empty                (int prio);
+  void queue_add_front            (int prio, VM_Operation *op);
+  void queue_add_back             (int prio, VM_Operation *op);
+  VM_Operation* queue_remove_front(int prio);
+  void queue_oops_do(int queue, OopClosure* f);
+  void drain_list_oops_do(OopClosure* f);
+  VM_Operation* queue_drain(int prio);
+  // lock-free query: may return the wrong answer but must not break
+  bool queue_peek(int prio) { return _queue_length[prio] > 0; }
+
+ public:
+  VMOperationQueue();
+
+  // Highlevel operations. Encapsulates policy
+  bool add(VM_Operation *op);
+  VM_Operation* remove_next();                        // Returns next or null
+  VM_Operation* remove_next_at_safepoint_priority()   { return queue_remove_front(SafepointPriority); }
+  VM_Operation* drain_at_safepoint_priority() { return queue_drain(SafepointPriority); }
+  void set_drain_list(VM_Operation* list) { _drain_list = list; }
+  bool peek_at_safepoint_priority() { return queue_peek(SafepointPriority); }
+
+  // GC support
+  void oops_do(OopClosure* f);
+
+  void verify_queue(int prio) PRODUCT_RETURN;
+};
+
+
+//
+// A single VMThread (the primordial thread) spawns all other threads
+// and is itself used by other threads to offload heavy vm operations
+// like scavenge, garbage_collect etc.
+//
+
+class VMThread: public NamedThread {
+ private:
+  static ThreadPriority _current_priority;
+
+  static bool _should_terminate;
+  static bool _terminated;
+  static Monitor * _terminate_lock;
+  static PerfCounter* _perf_accumulated_vm_operation_time;
+
+  static const char* _no_op_reason;
+
+  static bool no_op_safepoint_needed(bool check_time);
+
+  void evaluate_operation(VM_Operation* op);
+
+ public:
+  // Constructor
+  VMThread();
+
+  // No destruction allowed
+  ~VMThread() {
+    guarantee(false, "VMThread deletion must fix the race with VM termination");
+  }
+
+
+  // Tester
+  bool is_VM_thread() const                      { return true; }
+  bool is_GC_thread() const                      { return true; }
+
+  // The ever running loop for the VMThread
+  void loop();
+
+  // Called to stop the VM thread
+  static void wait_for_vm_thread_exit();
+  static bool should_terminate()                  { return _should_terminate; }
+  static bool is_terminated()                     { return _terminated == true; }
+
+  // Execution of vm operation
+  static void execute(VM_Operation* op);
+
+  // Returns the current vm operation if any.
+  static VM_Operation* vm_operation()             { return _cur_vm_operation; }
+
+  // Returns the current vm operation name or set reason
+  static const char* vm_safepoint_description()   { return _cur_vm_operation != NULL ? _cur_vm_operation->name() : _no_op_reason; };
+
+  // Returns the single instance of VMThread.
+  static VMThread* vm_thread()                    { return _vm_thread; }
+
+  // GC support
+  void oops_do(OopClosure* f, CodeBlobClosure* cf);
+
+  void verify();
+
+  // Performance measurement
+  static PerfCounter* perf_accumulated_vm_operation_time()               { return _perf_accumulated_vm_operation_time; }
+
+  // Entry for starting vm thread
+  virtual void run();
+
+  // Creations/Destructions
+  static void create();
+  static void destroy();
+
+ private:
+  // VM_Operation support
+  static VM_Operation*     _cur_vm_operation;   // Current VM operation
+  static VMOperationQueue* _vm_queue;           // Queue (w/ policy) of VM operations
+
+  // Pointer to single-instance of VM thread
+  static VMThread*     _vm_thread;
+};
+
+#endif // SHARE_VM_RUNTIME_VMTHREAD_HPP