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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

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 * published by the Free Software Foundation.

 *

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 * 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.

 *

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#ifndef SHARE_VM_GC_SHARED_WORKGROUP_HPP

#define SHARE_VM_GC_SHARED_WORKGROUP_HPP

#include "memory/allocation.hpp"

#include "runtime/globals.hpp"

#include "runtime/thread.hpp"

#include "gc/shared/gcId.hpp"

#include "logging/log.hpp"

#include "utilities/debug.hpp"

#include "utilities/globalDefinitions.hpp"

// Task class hierarchy:

//   AbstractGangTask

//

// Gang/Group class hierarchy:

//   AbstractWorkGang

//     WorkGang

//     YieldingFlexibleWorkGang (defined in another file)

//

// Worker class hierarchy:

//   AbstractGangWorker (subclass of WorkerThread)

//     GangWorker

//     YieldingFlexibleGangWorker   (defined in another file)

// Forward declarations of classes defined here

class AbstractGangWorker;

class Semaphore;

class WorkGang;

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

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

class AbstractGangTask {

  const char* _name;

  const uint _gc_id;

 public:

  explicit AbstractGangTask(const char* name) :

    _name(name),

    _gc_id(GCId::current_or_undefined())

  {}

  // The abstract work method.

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

  virtual void work(uint worker_id) = 0;

  // Debugging accessor for the name.

  const char* name() const { return _name; }

  const uint gc_id() const { return _gc_id; }

};

struct WorkData {

  AbstractGangTask* _task;

  uint              _worker_id;

  WorkData(AbstractGangTask* task, uint worker_id) : _task(task), _worker_id(worker_id) {}

};

// Interface to handle the synchronization between the coordinator thread and the worker threads,

// when a task is dispatched out to the worker threads.

class GangTaskDispatcher : public CHeapObj<mtGC> {

 public:

  virtual ~GangTaskDispatcher() {}

  // Coordinator API.

  // Distributes the task out to num_workers workers.

  // Returns when the task has been completed by all workers.

  virtual void coordinator_execute_on_workers(AbstractGangTask* task, uint num_workers) = 0;

  // Worker API.

  // Waits for a task to become available to the worker.

  // Returns when the worker has been assigned a task.

  virtual WorkData worker_wait_for_task() = 0;

  // Signal to the coordinator that the worker is done with the assigned task.

  virtual void     worker_done_with_task() = 0;

};

// The work gang is the collection of workers to execute tasks.

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

// while "_total_workers" is the number of available of workers.

class AbstractWorkGang : public CHeapObj<mtInternal> {

 protected:

  // The array of worker threads for this gang.

  AbstractGangWorker** _workers;

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

  uint _total_workers;

  // The currently active workers in this gang.

  uint _active_workers;

  // The count of created workers in the gang.

  uint _created_workers;

  // Printing support.

  const char* _name;

  ~AbstractWorkGang() {}

 private:

  // Initialize only instance data.

  const bool _are_GC_task_threads;

  const bool _are_ConcurrentGC_threads;

  void set_thread(uint worker_id, AbstractGangWorker* worker) {

    _workers[worker_id] = worker;

  }

 public:

  AbstractWorkGang(const char* name, uint workers, bool are_GC_task_threads, bool are_ConcurrentGC_threads) :

      _total_workers(workers),

      _active_workers(UseDynamicNumberOfGCThreads ? 1U : workers),

      _created_workers(0),

      _are_GC_task_threads(are_GC_task_threads),

      _are_ConcurrentGC_threads(are_ConcurrentGC_threads)

  { }

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

  void initialize_workers();

  bool are_GC_task_threads()      const { return _are_GC_task_threads; }

  bool are_ConcurrentGC_threads() const { return _are_ConcurrentGC_threads; }

  uint total_workers() const { return _total_workers; }

  uint created_workers() const {

    return _created_workers;

  }

  virtual uint active_workers() const {

    assert(_active_workers <= _total_workers,

           "_active_workers: %u > _total_workers: %u", _active_workers, _total_workers);

    assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,

           "Unless dynamic should use total workers");

    return _active_workers;

  }

  uint update_active_workers(uint v) {

    assert(v <= _total_workers,

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

    _active_workers = MIN2(v, _total_workers);

    add_workers(false /* exit_on_failure */);

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

    log_trace(gc, task)("%s: using %d out of %d workers", name(), _active_workers, _total_workers);

    return _active_workers;

  }

  // Add GC workers as needed.

  void add_workers(bool initializing);

  // Add GC workers as needed to reach the specified number of workers.

  void add_workers(uint active_workers, bool initializing);

  // Return the Ith worker.

  AbstractGangWorker* worker(uint i) const;

  // Base name (without worker id #) of threads.

  const char* group_name() { return name(); }

  void threads_do(ThreadClosure* tc) const;

  // Create a GC worker and install it into the work gang.

  virtual AbstractGangWorker* install_worker(uint which);

  // Debugging.

  const char* name() const { return _name; }

  // Printing

  void print_worker_threads_on(outputStream *st) const;

  void print_worker_threads() const {

    print_worker_threads_on(tty);

  }

 protected:

  virtual AbstractGangWorker* allocate_worker(uint which) = 0;

};

// An class representing a gang of workers.

class WorkGang: public AbstractWorkGang {

  // To get access to the GangTaskDispatcher instance.

  friend class GangWorker;

  GangTaskDispatcher* const _dispatcher;

  GangTaskDispatcher* dispatcher() const {

    return _dispatcher;

  }

public:

  WorkGang(const char* name,

           uint workers,

           bool are_GC_task_threads,

           bool are_ConcurrentGC_threads);

  ~WorkGang();

  // Run a task using the current active number of workers, returns when the task is done.

  virtual void run_task(AbstractGangTask* task);

  // Run a task with the given number of workers, returns

  // when the task is done. The number of workers must be at most the number of

  // active workers.  Additional workers may be created if an insufficient

  // number currently exists.

  void run_task(AbstractGangTask* task, uint num_workers);

protected:

  virtual AbstractGangWorker* allocate_worker(uint which);

};

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

class AbstractGangWorker: public WorkerThread {

public:

  AbstractGangWorker(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() = 0;

  AbstractWorkGang* gang() const { return _gang; }

};

class GangWorker: public AbstractGangWorker {

public:

  GangWorker(WorkGang* gang, uint id) : AbstractGangWorker(gang, id) {}

protected:

  virtual void loop();

private:

  WorkData wait_for_task();

  void run_task(WorkData work);

  void signal_task_done();

  WorkGang* gang() const { return (WorkGang*)_gang; }

};

// 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;

  bool    _aborted;

  Monitor* monitor()        { return &_monitor; }

  uint     n_workers()      { return _n_workers; }

  uint     n_completed()    { return _n_completed; }

  bool     should_reset()   { return _should_reset; }

  bool     aborted()        { return _aborted; }

  void     zero_completed() { _n_completed = 0; }

  void     inc_completed()  { _n_completed++; }

  void     set_aborted()    { _aborted = true; }

  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 or the barrier is aborted.

  // Returns false if the barrier was aborted.

  bool enter();

  // Aborts the barrier and wakes up any threads waiting for

  // the barrier to complete. The barrier will remain in the

  // aborted state until the next call to set_n_workers().

  void abort();

};

// 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> {

  volatile uint* _tasks;

  uint _n_tasks;

  volatile 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();

  // 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.)

  //

  // n_threads - Number of threads executing the sub-tasks.

  void all_tasks_completed(uint n_threads);

  // 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.

  volatile 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.

  volatile 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();

};

#endif // SHARE_VM_GC_SHARED_WORKGROUP_HPP