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  * accompanied this code).

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 #ifndef SHARE_VM_UTILITIES_WORKGROUP_HPP

 #define SHARE_VM_UTILITIES_WORKGROUP_HPP

 #include "runtime/thread.inline.hpp"

 #include "utilities/taskqueue.hpp"

 // Task class hierarchy:

 //   AbstractGangTask

 //     AbstractGangTaskWOopQueues

 //

 // Gang/Group class hierarchy:

 //   AbstractWorkGang

 //     WorkGang

 //       FlexibleWorkGang

 //         YieldingFlexibleWorkGang (defined in another file)

 //

 // Worker class hierarchy:

 //   GangWorker (subclass of WorkerThread)

 //     YieldingFlexibleGangWorker   (defined in another file)

 // 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(uint worker_id) = 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;

   }

   ~AbstractGangTask() { }

 public:

 };

 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<mtInternal> {

   // 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();

   // Return true if more workers should be applied to the task.

   virtual bool needs_more_workers() const { return true; }

 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.

   uint _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.

   uint _started_workers;

   // The number of finished workers.

   uint _finished_workers;

 public:

   // Accessors for fields

   Monitor* monitor() const {

     return _monitor;

   }

   uint total_workers() const {

     return _total_workers;

   }

   virtual uint 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;

   }

   uint started_workers() const {

     return _started_workers;

   }

   uint 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(uint 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, uint 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(uint 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; }

 };

 // Dynamic number of worker threads

 //

 // This type of work gang is used to run different numbers of

 // worker threads at different times.  The

 // number of workers run for a task is "_active_workers"

 // instead of "_total_workers" in a WorkGang.  The method

 // "needs_more_workers()" returns true until "_active_workers"

 // have been started and returns false afterwards.  The

 // implementation of "needs_more_workers()" in WorkGang always

 // returns true so that all workers are started.  The method

 // "loop()" in GangWorker was modified to ask "needs_more_workers()"

 // in its loop to decide if it should start working on a task.

 // A worker in "loop()" waits for notification on the WorkGang

 // monitor and execution of each worker as it checks for work

 // is serialized via the same monitor.  The "needs_more_workers()"

 // call is serialized and additionally the calculation for the

 // "part" (effectively the worker id for executing the task) is

 // serialized to give each worker a unique "part".  Workers that

 // are not needed for this tasks (i.e., "_active_workers" have

 // been started before it, continue to wait for work.

 class FlexibleWorkGang: public WorkGang {

   // The currently active workers in this gang.

   // This is a number that is dynamically adjusted

   // and checked in the run_task() method at each invocation.

   // As described above _active_workers determines the number

   // of threads started on a task.  It must also be used to

   // determine completion.

  protected:

   uint _active_workers;

  public:

   // Constructor and destructor.

   // Initialize active_workers to a minimum value.  Setting it to

   // the parameter "workers" will initialize it to a maximum

   // value which is not desirable.

   FlexibleWorkGang(const char* name, uint workers,

                    bool are_GC_task_threads,

                    bool  are_ConcurrentGC_threads) :

     WorkGang(name, workers, are_GC_task_threads, are_ConcurrentGC_threads),

     _active_workers(UseDynamicNumberOfGCThreads ? 1U : ParallelGCThreads) {}

   // Accessors for fields

   virtual uint active_workers() const { return _active_workers; }

   void set_active_workers(uint v) {

     assert(v <= _total_workers,

            "Trying to set more workers active than there are");

     _active_workers = MIN2(v, _total_workers);

     assert(v != 0, "Trying to set active workers to 0");

     _active_workers = MAX2(1U, _active_workers);

     assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,

            "Unless dynamic should use total workers");

   }

   virtual void run_task(AbstractGangTask* task);

   virtual bool needs_more_workers() const {

     return _started_workers < _active_workers;

   }

 };

 // 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;

   uint     _n_workers;

   uint     _n_completed;

   bool    _should_reset;

   Monitor* monitor()        { return &_monitor; }

   uint     n_workers()      { return _n_workers; }

   uint     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(uint 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(uint 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<mtInternal> {

   uint* _tasks;

   uint _n_tasks;

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

   // It does not control how many threads will execute the subtask

   // but must be initialized to the number that do execute the task

   // in order to correctly decide when the subtask is done (all the

   // threads working on the task have finished).

   uint _n_threads;

   uint _threads_completed;

 #ifdef ASSERT

   volatile uint _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(uint 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.

   uint n_threads() { return _n_threads; }

   void set_n_threads(uint 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(uint 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:

   uint _n_tasks;     // Total number of tasks available.

   uint _n_claimed;   // Number of tasks claimed.

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

   // See comments on SubTasksDone::_n_threads

   uint _n_threads;   // Total number of parallel threads.

   uint _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

   uint 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.

   uint n_threads() { return _n_threads; }

   void set_n_threads(uint 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(uint 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(uint& 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 : public CHeapObj<mtInternal> {

   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);

 };

 #endif // SHARE_VM_UTILITIES_WORKGROUP_HPP