--- /dev/null	2020-01-17 11:46:19.065201212 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahSATBMarkQueue.hpp	2020-01-17 17:10:36.420129029 +0100
@@ -0,0 +1,135 @@
+/*
+ * Copyright (c) 2001, 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_GC_SHENANDOAH_SATBMARKQUEUE_HPP
+#define SHARE_VM_GC_SHENANDOAH_SATBMARKQUEUE_HPP
+
+#include "gc/g1/ptrQueue.hpp"
+#include "memory/allocation.hpp"
+
+class JavaThread;
+class ShenandoahSATBMarkQueueSet;
+
+// Base class for processing the contents of a SATB buffer.
+class ShenandoahSATBBufferClosure : public StackObj {
+protected:
+  ~ShenandoahSATBBufferClosure() { }
+
+public:
+  // Process the SATB entries in the designated buffer range.
+  virtual void do_buffer(void** buffer, size_t size) = 0;
+};
+
+// A PtrQueue whose elements are (possibly stale) pointers to object heads.
+class ShenandoahSATBMarkQueue: public PtrQueue {
+  friend class ShenandoahSATBMarkQueueSet;
+
+private:
+  // Filter out unwanted entries from the buffer.
+  void filter();
+
+  template <class HeapType>
+  void filter_impl();
+
+public:
+  ShenandoahSATBMarkQueue(ShenandoahSATBMarkQueueSet* qset, bool permanent = false);
+
+  // Process queue entries and free resources.
+  void flush();
+
+  // Apply cl to the active part of the buffer.
+  // Prerequisite: Must be at a safepoint.
+  void apply_closure_and_empty(ShenandoahSATBBufferClosure* cl);
+
+  // Overrides PtrQueue::should_enqueue_buffer(). See the method's
+  // definition for more information.
+  virtual bool should_enqueue_buffer();
+
+#ifndef PRODUCT
+  // Helpful for debugging
+  void print(const char* name);
+#endif // PRODUCT
+
+  // Compiler support.
+  static ByteSize byte_offset_of_index() {
+    return PtrQueue::byte_offset_of_index<ShenandoahSATBMarkQueue>();
+  }
+  using PtrQueue::byte_width_of_index;
+
+  static ByteSize byte_offset_of_buf() {
+    return PtrQueue::byte_offset_of_buf<ShenandoahSATBMarkQueue>();
+  }
+  using PtrQueue::byte_width_of_buf;
+
+  static ByteSize byte_offset_of_active() {
+    return PtrQueue::byte_offset_of_active<ShenandoahSATBMarkQueue>();
+  }
+  using PtrQueue::byte_width_of_active;
+
+};
+
+class ShenandoahSATBMarkQueueSet: public PtrQueueSet {
+  ShenandoahSATBMarkQueue _shared_satb_queue;
+
+#ifdef ASSERT
+  void dump_active_states(bool expected_active);
+  void verify_active_states(bool expected_active);
+#endif // ASSERT
+
+public:
+  ShenandoahSATBMarkQueueSet();
+
+  void initialize(Monitor* cbl_mon, Mutex* fl_lock,
+                  int process_completed_threshold,
+                  Mutex* lock);
+
+  ShenandoahSATBMarkQueue& satb_queue_for_thread(Thread* t);
+
+  // Apply "set_active(active)" to all SATB queues in the set. It should be
+  // called only with the world stopped. The method will assert that the
+  // SATB queues of all threads it visits, as well as the SATB queue
+  // set itself, has an active value same as expected_active.
+  void set_active_all_threads(bool active, bool expected_active);
+
+  // Filter all the currently-active SATB buffers.
+  void filter_thread_buffers();
+
+  // If there exists some completed buffer, pop and process it, and
+  // return true.  Otherwise return false.  Processing a buffer
+  // consists of applying the closure to the active range of the
+  // buffer; the leading entries may be excluded due to filtering.
+  bool apply_closure_to_completed_buffer(ShenandoahSATBBufferClosure* cl);
+
+#ifndef PRODUCT
+  // Helpful for debugging
+  void print_all(const char* msg);
+#endif // PRODUCT
+
+  ShenandoahSATBMarkQueue* shared_satb_queue() { return &_shared_satb_queue; }
+
+  // If a marking is being abandoned, reset any unprocessed log buffers.
+  void abandon_partial_marking();
+};
+
+#endif // SHARE_VM_GC_SHENANDOAH_SATBMARKQUEUE_HPP