/*

 * Copyright (c) 2002, 2010, 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.

 *

 */

// Forward declarations of classes defined here

class WorkGang;

class GangWorker;

class YieldingFlexibleGangWorker;

class YieldingFlexibleGangTask;

class WorkData;

class AbstractWorkGang;

// An abstract task to be worked on by a gang.

// You subclass this to supply your own work() method

class AbstractGangTask VALUE_OBJ_CLASS_SPEC {

public:

  // The abstract work method.

  // The argument tells you which member of the gang you are.

  virtual void work(int i) = 0;

  // This method configures the task for proper termination.

  // Some tasks do not have any requirements on termination

  // and may inherit this method that does nothing.  Some

  // tasks do some coordination on termination and override

  // this method to implement that coordination.

  virtual void set_for_termination(int active_workers) {};

  // Debugging accessor for the name.

  const char* name() const PRODUCT_RETURN_(return NULL;);

  int counter() { return _counter; }

  void set_counter(int value) { _counter = value; }

  int *address_of_counter() { return &_counter; }

  // RTTI

  NOT_PRODUCT(virtual bool is_YieldingFlexibleGang_task() const {

    return false;

  })

private:

  NOT_PRODUCT(const char* _name;)

  // ??? Should a task have a priority associated with it?

  // ??? Or can the run method adjust priority as needed?

  int _counter;

protected:

  // Constructor and desctructor: only construct subclasses.

  AbstractGangTask(const char* name) {

    NOT_PRODUCT(_name = name);

    _counter = 0;

  }

  virtual ~AbstractGangTask() { }

};

class AbstractGangTaskWOopQueues : public AbstractGangTask {

  OopTaskQueueSet*       _queues;

  ParallelTaskTerminator _terminator;

 public:

  AbstractGangTaskWOopQueues(const char* name, OopTaskQueueSet* queues) :

    AbstractGangTask(name), _queues(queues), _terminator(0, _queues) {}

  ParallelTaskTerminator* terminator() { return &_terminator; }

  virtual void set_for_termination(int active_workers) {

    terminator()->reset_for_reuse(active_workers);

  }

  OopTaskQueueSet* queues() { return _queues; }

};

// Class AbstractWorkGang:

// An abstract class representing a gang of workers.

// You subclass this to supply an implementation of run_task().

class AbstractWorkGang: public CHeapObj {

  // Here's the public interface to this class.

public:

  // Constructor and destructor.

  AbstractWorkGang(const char* name, bool are_GC_task_threads,

                   bool are_ConcurrentGC_threads);

  ~AbstractWorkGang();

  // Run a task, returns when the task is done (or terminated).

  virtual void run_task(AbstractGangTask* task) = 0;

  // Stop and terminate all workers.

  virtual void stop();

public:

  // Debugging.

  const char* name() const;

protected:

  // Initialize only instance data.

  const bool _are_GC_task_threads;

  const bool _are_ConcurrentGC_threads;

  // Printing support.

  const char* _name;

  // The monitor which protects these data,

  // and notifies of changes in it.

  Monitor*  _monitor;

  // The count of the number of workers in the gang.

  int _total_workers;

  // Whether the workers should terminate.

  bool _terminate;

  // The array of worker threads for this gang.

  // This is only needed for cleaning up.

  GangWorker** _gang_workers;

  // The task for this gang.

  AbstractGangTask* _task;

  // A sequence number for the current task.

  int _sequence_number;

  // The number of started workers.

  int _started_workers;

  // The number of finished workers.

  int _finished_workers;

public:

  // Accessors for fields

  Monitor* monitor() const {

    return _monitor;

  }

  int total_workers() const {

    return _total_workers;

  }

  virtual int active_workers() const {

    return _total_workers;

  }

  bool terminate() const {

    return _terminate;

  }

  GangWorker** gang_workers() const {

    return _gang_workers;

  }

  AbstractGangTask* task() const {

    return _task;

  }

  int sequence_number() const {

    return _sequence_number;

  }

  int started_workers() const {

    return _started_workers;

  }

  int finished_workers() const {

    return _finished_workers;

  }

  bool are_GC_task_threads() const {

    return _are_GC_task_threads;

  }

  bool are_ConcurrentGC_threads() const {

    return _are_ConcurrentGC_threads;

  }

  // Predicates.

  bool is_idle() const {

    return (task() == NULL);

  }

  // Return the Ith gang worker.

  GangWorker* gang_worker(int i) const;

  void threads_do(ThreadClosure* tc) const;

  // Printing

  void print_worker_threads_on(outputStream *st) const;

  void print_worker_threads() const {

    print_worker_threads_on(tty);

  }

protected:

  friend class GangWorker;

  friend class YieldingFlexibleGangWorker;

  // Note activation and deactivation of workers.

  // These methods should only be called with the mutex held.

  void internal_worker_poll(WorkData* data) const;

  void internal_note_start();

  void internal_note_finish();

};

class WorkData: public StackObj {

  // This would be a struct, but I want accessor methods.

private:

  bool              _terminate;

  AbstractGangTask* _task;

  int               _sequence_number;

public:

  // Constructor and destructor

  WorkData() {

    _terminate       = false;

    _task            = NULL;

    _sequence_number = 0;

  }

  ~WorkData() {

  }

  // Accessors and modifiers

  bool terminate()                       const { return _terminate;  }

  void set_terminate(bool value)               { _terminate = value; }

  AbstractGangTask* task()               const { return _task; }

  void set_task(AbstractGangTask* value)       { _task = value; }

  int sequence_number()                  const { return _sequence_number; }

  void set_sequence_number(int value)          { _sequence_number = value; }

  YieldingFlexibleGangTask* yf_task()    const {

    return (YieldingFlexibleGangTask*)_task;

  }

};

// Class WorkGang:

class WorkGang: public AbstractWorkGang {

public:

  // Constructor

  WorkGang(const char* name, int workers,

           bool are_GC_task_threads, bool are_ConcurrentGC_threads);

  // Run a task, returns when the task is done (or terminated).

  virtual void run_task(AbstractGangTask* task);

  void run_task(AbstractGangTask* task, uint no_of_parallel_workers);

  // Allocate a worker and return a pointer to it.

  virtual GangWorker* allocate_worker(int which);

  // Initialize workers in the gang.  Return true if initialization

  // succeeded. The type of the worker can be overridden in a derived

  // class with the appropriate implementation of allocate_worker().

  bool initialize_workers();

};

// Class GangWorker:

//   Several instances of this class run in parallel as workers for a gang.

class GangWorker: public WorkerThread {

public:

  // Constructors and destructor.

  GangWorker(AbstractWorkGang* gang, uint id);

  // The only real method: run a task for the gang.

  virtual void run();

  // Predicate for Thread

  virtual bool is_GC_task_thread() const;

  virtual bool is_ConcurrentGC_thread() const;

  // Printing

  void print_on(outputStream* st) const;

  virtual void print() const { print_on(tty); }

protected:

  AbstractWorkGang* _gang;

  virtual void initialize();

  virtual void loop();

public:

  AbstractWorkGang* gang() const { return _gang; }

};

class FlexibleWorkGang: public WorkGang {

 protected:

  int _active_workers;

 public:

  // Constructor and destructor.

  FlexibleWorkGang(const char* name, int workers,

                   bool are_GC_task_threads,

                   bool  are_ConcurrentGC_threads) :

    WorkGang(name, workers, are_GC_task_threads, are_ConcurrentGC_threads) {

    _active_workers = ParallelGCThreads;

  };

  // Accessors for fields

  virtual int active_workers() const { return _active_workers; }

  void set_active_workers(int v) { _active_workers = v; }

};

// Work gangs in garbage collectors: 2009-06-10

//

// SharedHeap - work gang for stop-the-world parallel collection.

//   Used by

//     ParNewGeneration

//     CMSParRemarkTask

//     CMSRefProcTaskExecutor

//     G1CollectedHeap

//     G1ParFinalCountTask

// ConcurrentMark

// CMSCollector

// A class that acts as a synchronisation barrier. Workers enter

// the barrier and must wait until all other workers have entered

// before any of them may leave.

class WorkGangBarrierSync : public StackObj {

protected:

  Monitor _monitor;

  int     _n_workers;

  int     _n_completed;

  bool    _should_reset;

  Monitor* monitor()        { return &_monitor; }

  int      n_workers()      { return _n_workers; }

  int      n_completed()    { return _n_completed; }

  bool     should_reset()   { return _should_reset; }

  void     zero_completed() { _n_completed = 0; }

  void     inc_completed()  { _n_completed++; }

  void     set_should_reset(bool v) { _should_reset = v; }

public:

  WorkGangBarrierSync();

  WorkGangBarrierSync(int n_workers, const char* name);

  // Set the number of workers that will use the barrier.

  // Must be called before any of the workers start running.

  void set_n_workers(int n_workers);

  // Enter the barrier. A worker that enters the barrier will

  // not be allowed to leave until all other threads have

  // also entered the barrier.

  void enter();

};

// A class to manage claiming of subtasks within a group of tasks.  The

// subtasks will be identified by integer indices, usually elements of an

// enumeration type.

class SubTasksDone: public CHeapObj {

  jint* _tasks;

  int _n_tasks;

  int _n_threads;

  jint _threads_completed;

#ifdef ASSERT

  volatile jint _claimed;

#endif

  // Set all tasks to unclaimed.

  void clear();

public:

  // Initializes "this" to a state in which there are "n" tasks to be

  // processed, none of the which are originally claimed.  The number of

  // threads doing the tasks is initialized 1.

  SubTasksDone(int n);

  // True iff the object is in a valid state.

  bool valid();

  // Get/set the number of parallel threads doing the tasks to "t".  Can only

  // be called before tasks start or after they are complete.

  int n_threads() { return _n_threads; }

  void set_n_threads(int t);

  // Returns "false" if the task "t" is unclaimed, and ensures that task is

  // claimed.  The task "t" is required to be within the range of "this".

  bool is_task_claimed(int t);

  // The calling thread asserts that it has attempted to claim all the

  // tasks that it will try to claim.  Every thread in the parallel task

  // must execute this.  (When the last thread does so, the task array is

  // cleared.)

  void all_tasks_completed();

  // Destructor.

  ~SubTasksDone();

};

// As above, but for sequential tasks, i.e. instead of claiming

// sub-tasks from a set (possibly an enumeration), claim sub-tasks

// in sequential order. This is ideal for claiming dynamically

// partitioned tasks (like striding in the parallel remembered

// set scanning). Note that unlike the above class this is

// a stack object - is there any reason for it not to be?

class SequentialSubTasksDone : public StackObj {

protected:

  jint _n_tasks;     // Total number of tasks available.

  jint _n_claimed;   // Number of tasks claimed.

  // _n_threads is used to determine when a sub task is done.

  // See comments on SubTasksDone::_n_threads

  jint _n_threads;   // Total number of parallel threads.

  jint _n_completed; // Number of completed threads.

  void clear();

public:

  SequentialSubTasksDone() {

    clear();

  }

  ~SequentialSubTasksDone() {}

  // True iff the object is in a valid state.

  bool valid();

  // number of tasks

  jint n_tasks() const { return _n_tasks; }

  // Get/set the number of parallel threads doing the tasks to t.

  // Should be called before the task starts but it is safe

  // to call this once a task is running provided that all

  // threads agree on the number of threads.

  int n_threads() { return _n_threads; }

  void set_n_threads(int t) { _n_threads = t; }

  // Set the number of tasks to be claimed to t. As above,

  // should be called before the tasks start but it is safe

  // to call this once a task is running provided all threads

  // agree on the number of tasks.

  void set_n_tasks(int t) { _n_tasks = t; }

  // Returns false if the next task in the sequence is unclaimed,

  // and ensures that it is claimed. Will set t to be the index

  // of the claimed task in the sequence. Will return true if

  // the task cannot be claimed and there are none left to claim.

  bool is_task_claimed(int& t);

  // The calling thread asserts that it has attempted to claim

  // all the tasks it possibly can in the sequence. Every thread

  // claiming tasks must promise call this. Returns true if this

  // is the last thread to complete so that the thread can perform

  // cleanup if necessary.

  bool all_tasks_completed();

};

// Represents a set of free small integer ids.

class FreeIdSet {

  enum {

    end_of_list = -1,

    claimed = -2

  };

  int _sz;

  Monitor* _mon;

  int* _ids;

  int _hd;

  int _waiters;

  int _claimed;

  static bool _safepoint;

  typedef FreeIdSet* FreeIdSetPtr;

  static const int NSets = 10;

  static FreeIdSetPtr _sets[NSets];

  static bool _stat_init;

  int _index;

public:

  FreeIdSet(int sz, Monitor* mon);

  ~FreeIdSet();

  static void set_safepoint(bool b);

  // Attempt to claim the given id permanently.  Returns "true" iff

  // successful.

  bool claim_perm_id(int i);

  // Returns an unclaimed parallel id (waiting for one to be released if

  // necessary).  Returns "-1" if a GC wakes up a wait for an id.

  int claim_par_id();

  void release_par_id(int id);

};