--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc/cms/yieldingWorkgroup.hpp	Wed May 13 15:16:06 2015 +0200
@@ -0,0 +1,214 @@
+/*
+ * Copyright (c) 2005, 2015, 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_CMS_YIELDINGWORKGROUP_HPP
+#define SHARE_VM_GC_CMS_YIELDINGWORKGROUP_HPP
+
+#include "gc/shared/workgroup.hpp"
+#include "utilities/macros.hpp"
+
+// Forward declarations
+class YieldingFlexibleWorkGang;
+
+// Status of tasks
+enum Status {
+    INACTIVE,
+    ACTIVE,
+    YIELDING,
+    YIELDED,
+    ABORTING,
+    ABORTED,
+    COMPLETING,
+    COMPLETED
+};
+
+// Class YieldingFlexibleGangWorker:
+//   Several instances of this class run in parallel as workers for a gang.
+class YieldingFlexibleGangWorker: public GangWorker {
+public:
+  // Ctor
+  YieldingFlexibleGangWorker(AbstractWorkGang* gang, int id) :
+    GangWorker(gang, id) { }
+
+public:
+  YieldingFlexibleWorkGang* yf_gang() const
+    { return (YieldingFlexibleWorkGang*)gang(); }
+
+protected: // Override from parent class
+  virtual void loop();
+};
+
+class FlexibleGangTask: public AbstractGangTask {
+  int _actual_size;                      // size of gang obtained
+protected:
+  int _requested_size;                   // size of gang requested
+public:
+ FlexibleGangTask(const char* name): AbstractGangTask(name),
+    _requested_size(0) {}
+
+  // The abstract work method.
+  // The argument tells you which member of the gang you are.
+  virtual void work(uint worker_id) = 0;
+
+  int requested_size() const { return _requested_size; }
+  int actual_size()    const { return _actual_size; }
+
+  void set_requested_size(int sz) { _requested_size = sz; }
+  void set_actual_size(int sz)    { _actual_size    = sz; }
+};
+
+// An abstract task to be worked on by a flexible work gang,
+// and where the workers will periodically yield, usually
+// in response to some condition that is signalled by means
+// that are specific to the task at hand.
+// You subclass this to supply your own work() method.
+// A second feature of this kind of work gang is that
+// it allows for the signalling of certain exceptional
+// conditions that may be encountered during the performance
+// of the task and that may require the task at hand to be
+// `aborted' forthwith. Finally, these gangs are `flexible'
+// in that they can operate at partial capacity with some
+// gang workers waiting on the bench; in other words, the
+// size of the active worker pool can flex (up to an apriori
+// maximum) in response to task requests at certain points.
+// The last part (the flexible part) has not yet been fully
+// fleshed out and is a work in progress.
+class YieldingFlexibleGangTask: public FlexibleGangTask {
+  Status _status;
+  YieldingFlexibleWorkGang* _gang;
+
+protected:
+  // Constructor and desctructor: only construct subclasses.
+  YieldingFlexibleGangTask(const char* name): FlexibleGangTask(name),
+    _status(INACTIVE),
+    _gang(NULL) { }
+
+  ~YieldingFlexibleGangTask() { }
+
+  friend class YieldingFlexibleWorkGang;
+  friend class YieldingFlexibleGangWorker;
+  NOT_PRODUCT(virtual bool is_YieldingFlexibleGang_task() const {
+    return true;
+  })
+
+  void set_status(Status s) {
+    _status = s;
+  }
+  YieldingFlexibleWorkGang* gang() {
+    return _gang;
+  }
+  void set_gang(YieldingFlexibleWorkGang* gang) {
+    assert(_gang == NULL || gang == NULL, "Clobber without intermediate reset?");
+    _gang = gang;
+  }
+
+public:
+  // The abstract work method.
+  // The argument tells you which member of the gang you are.
+  virtual void work(uint worker_id) = 0;
+
+  // Subclasses should call the parent's yield() method
+  // after having done any work specific to the subclass.
+  virtual void yield();
+
+  // An abstract method supplied by
+  // a concrete sub-class which is used by the coordinator
+  // to do any "central yielding" work.
+  virtual void coordinator_yield() = 0;
+
+  // Subclasses should call the parent's abort() method
+  // after having done any work specific to the sunbclass.
+  virtual void abort();
+
+  Status status()  const { return _status; }
+  bool yielding()  const { return _status == YIELDING; }
+  bool yielded()   const { return _status == YIELDED; }
+  bool completed() const { return _status == COMPLETED; }
+  bool aborted()   const { return _status == ABORTED; }
+  bool active()    const { return _status == ACTIVE; }
+};
+// Class YieldingWorkGang: A subclass of WorkGang.
+// In particular, a YieldingWorkGang is made up of
+// YieldingGangWorkers, and provides infrastructure
+// supporting yielding to the "GangOverseer",
+// being the thread that orchestrates the WorkGang via run_task().
+class YieldingFlexibleWorkGang: public FlexibleWorkGang {
+  // Here's the public interface to this class.
+public:
+  // Constructor and destructor.
+  YieldingFlexibleWorkGang(const char* name, uint workers,
+                           bool are_GC_task_threads);
+
+  YieldingFlexibleGangTask* yielding_task() const {
+    assert(task() == NULL || task()->is_YieldingFlexibleGang_task(),
+           "Incorrect cast");
+    return (YieldingFlexibleGangTask*)task();
+  }
+  // Allocate a worker and return a pointer to it.
+  GangWorker* allocate_worker(uint which);
+
+  // Run a task; returns when the task is done, or the workers yield,
+  // or the task is aborted, or the work gang is terminated via stop().
+  // A task that has been yielded can be continued via this same interface
+  // by using the same task repeatedly as the argument to the call.
+  // It is expected that the YieldingFlexibleGangTask carries the appropriate
+  // continuation information used by workers to continue the task
+  // from its last yield point. Thus, a completed task will return
+  // immediately with no actual work having been done by the workers.
+  void run_task(AbstractGangTask* task) {
+    guarantee(false, "Use start_task instead");
+  }
+  void start_task(YieldingFlexibleGangTask* new_task);
+  void continue_task(YieldingFlexibleGangTask* gang_task);
+
+  // Abort a currently running task, if any; returns when all the workers
+  // have stopped working on the current task and have returned to their
+  // waiting stations.
+  void abort_task();
+
+  // Yield: workers wait at their current working stations
+  // until signalled to proceed by the overseer.
+  void yield();
+
+  // Abort: workers are expected to return to their waiting
+  // stations, whence they are ready for the next task dispatched
+  // by the overseer.
+  void abort();
+
+private:
+  uint _yielded_workers;
+  void wait_for_gang();
+
+public:
+  // Accessors for fields
+  uint yielded_workers() const {
+    return _yielded_workers;
+  }
+
+private:
+  friend class YieldingFlexibleGangWorker;
+  void reset(); // NYI
+};
+
+#endif // SHARE_VM_GC_CMS_YIELDINGWORKGROUP_HPP