--- /dev/null	2018-11-30 10:10:44.238550338 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahWorkGroup.hpp	2018-11-30 21:09:24.192674373 +0100
@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2017, 2018, Red Hat, Inc. All rights reserved.
+ *
+ * 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_SHENANDOAHWORKGROUP_HPP
+#define SHARE_VM_GC_SHENANDOAH_SHENANDOAHWORKGROUP_HPP
+
+#include "gc/shared/workgroup.hpp"
+#include "gc/shenandoah/shenandoahTaskqueue.hpp"
+#include "memory/allocation.hpp"
+
+class ShenandoahObjToScanQueueSet;
+
+class ShenandoahWorkerScope : public StackObj {
+private:
+  uint      _n_workers;
+  WorkGang* _workers;
+public:
+  ShenandoahWorkerScope(WorkGang* workers, uint nworkers, const char* msg, bool do_check = true);
+  ~ShenandoahWorkerScope();
+};
+
+class ShenandoahPushWorkerScope : StackObj {
+protected:
+  uint      _n_workers;
+  uint      _old_workers;
+  WorkGang* _workers;
+
+public:
+  ShenandoahPushWorkerScope(WorkGang* workers, uint nworkers, bool do_check = true);
+  ~ShenandoahPushWorkerScope();
+};
+
+class ShenandoahPushWorkerQueuesScope : public ShenandoahPushWorkerScope {
+private:
+  ShenandoahObjToScanQueueSet* _queues;
+
+public:
+  ShenandoahPushWorkerQueuesScope(WorkGang* workers, ShenandoahObjToScanQueueSet* queues, uint nworkers, bool do_check = true);
+  ~ShenandoahPushWorkerQueuesScope();
+};
+
+class ShenandoahWorkGang : public WorkGang {
+private:
+  bool     _initialize_gclab;
+public:
+  ShenandoahWorkGang(const char* name,
+           uint workers,
+           bool are_GC_task_threads,
+           bool are_ConcurrentGC_threads) :
+    WorkGang(name, workers, are_GC_task_threads, are_ConcurrentGC_threads), _initialize_gclab(false) {
+    }
+
+  // Create a GC worker and install it into the work gang.
+  // We need to initialize gclab for dynamic allocated workers
+  AbstractGangWorker* install_worker(uint which);
+
+  // We allow _active_workers < _total_workers when UseDynamicNumberOfGCThreads is off.
+  // We use the same WorkGang for concurrent and parallel processing, and honor
+  // ConcGCThreads and ParallelGCThreads settings
+  virtual uint active_workers() const {
+    assert(_active_workers > 0, "no active worker");
+    assert(_active_workers <= _total_workers,
+           "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers);
+    return _active_workers;
+  }
+
+  void set_initialize_gclab() { assert(!_initialize_gclab, "Can only enable once"); _initialize_gclab = true; }
+};
+
+#endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHWORKGROUP_HPP