aoqi@0: /*
aoqi@0:  * Copyright (c) 2002, 2013, Oracle and/or its affiliates. All rights reserved.
aoqi@0:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
aoqi@0:  *
aoqi@0:  * This code is free software; you can redistribute it and/or modify it
aoqi@0:  * under the terms of the GNU General Public License version 2 only, as
aoqi@0:  * published by the Free Software Foundation.
aoqi@0:  *
aoqi@0:  * This code is distributed in the hope that it will be useful, but WITHOUT
aoqi@0:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
aoqi@0:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
aoqi@0:  * version 2 for more details (a copy is included in the LICENSE file that
aoqi@0:  * accompanied this code).
aoqi@0:  *
aoqi@0:  * You should have received a copy of the GNU General Public License version
aoqi@0:  * 2 along with this work; if not, write to the Free Software Foundation,
aoqi@0:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
aoqi@0:  *
aoqi@0:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
aoqi@0:  * or visit www.oracle.com if you need additional information or have any
aoqi@0:  * questions.
aoqi@0:  *
aoqi@0:  */
aoqi@0: 
aoqi@0: #ifndef SHARE_VM_UTILITIES_WORKGROUP_HPP
aoqi@0: #define SHARE_VM_UTILITIES_WORKGROUP_HPP
aoqi@0: 
aoqi@0: #include "runtime/thread.inline.hpp"
aoqi@0: #include "utilities/taskqueue.hpp"
aoqi@0: 
aoqi@0: // Task class hierarchy:
aoqi@0: //   AbstractGangTask
aoqi@0: //     AbstractGangTaskWOopQueues
aoqi@0: //
aoqi@0: // Gang/Group class hierarchy:
aoqi@0: //   AbstractWorkGang
aoqi@0: //     WorkGang
aoqi@0: //       FlexibleWorkGang
aoqi@0: //         YieldingFlexibleWorkGang (defined in another file)
aoqi@0: //
aoqi@0: // Worker class hierarchy:
aoqi@0: //   GangWorker (subclass of WorkerThread)
aoqi@0: //     YieldingFlexibleGangWorker   (defined in another file)
aoqi@0: 
aoqi@0: // Forward declarations of classes defined here
aoqi@0: 
aoqi@0: class WorkGang;
aoqi@0: class GangWorker;
aoqi@0: class YieldingFlexibleGangWorker;
aoqi@0: class YieldingFlexibleGangTask;
aoqi@0: class WorkData;
aoqi@0: class AbstractWorkGang;
aoqi@0: 
aoqi@0: // An abstract task to be worked on by a gang.
aoqi@0: // You subclass this to supply your own work() method
aoqi@0: class AbstractGangTask VALUE_OBJ_CLASS_SPEC {
aoqi@0: public:
aoqi@0:   // The abstract work method.
aoqi@0:   // The argument tells you which member of the gang you are.
aoqi@0:   virtual void work(uint worker_id) = 0;
aoqi@0: 
aoqi@0:   // This method configures the task for proper termination.
aoqi@0:   // Some tasks do not have any requirements on termination
aoqi@0:   // and may inherit this method that does nothing.  Some
aoqi@0:   // tasks do some coordination on termination and override
aoqi@0:   // this method to implement that coordination.
aoqi@0:   virtual void set_for_termination(int active_workers) {};
aoqi@0: 
aoqi@0:   // Debugging accessor for the name.
aoqi@0:   const char* name() const PRODUCT_RETURN_(return NULL;);
aoqi@0:   int counter() { return _counter; }
aoqi@0:   void set_counter(int value) { _counter = value; }
aoqi@0:   int *address_of_counter() { return &_counter; }
aoqi@0: 
aoqi@0:   // RTTI
aoqi@0:   NOT_PRODUCT(virtual bool is_YieldingFlexibleGang_task() const {
aoqi@0:     return false;
aoqi@0:   })
aoqi@0: 
aoqi@0: private:
aoqi@0:   NOT_PRODUCT(const char* _name;)
aoqi@0:   // ??? Should a task have a priority associated with it?
aoqi@0:   // ??? Or can the run method adjust priority as needed?
aoqi@0:   int _counter;
aoqi@0: 
aoqi@0: protected:
aoqi@0:   // Constructor and desctructor: only construct subclasses.
aoqi@0:   AbstractGangTask(const char* name)
aoqi@0:   {
aoqi@0:     NOT_PRODUCT(_name = name);
aoqi@0:     _counter = 0;
aoqi@0:   }
aoqi@0:   ~AbstractGangTask() { }
aoqi@0: 
aoqi@0: public:
aoqi@0: };
aoqi@0: 
aoqi@0: class AbstractGangTaskWOopQueues : public AbstractGangTask {
aoqi@0:   OopTaskQueueSet*       _queues;
aoqi@0:   ParallelTaskTerminator _terminator;
aoqi@0:  public:
aoqi@0:   AbstractGangTaskWOopQueues(const char* name, OopTaskQueueSet* queues) :
aoqi@0:     AbstractGangTask(name), _queues(queues), _terminator(0, _queues) {}
aoqi@0:   ParallelTaskTerminator* terminator() { return &_terminator; }
aoqi@0:   virtual void set_for_termination(int active_workers) {
aoqi@0:     terminator()->reset_for_reuse(active_workers);
aoqi@0:   }
aoqi@0:   OopTaskQueueSet* queues() { return _queues; }
aoqi@0: };
aoqi@0: 
aoqi@0: 
aoqi@0: // Class AbstractWorkGang:
aoqi@0: // An abstract class representing a gang of workers.
aoqi@0: // You subclass this to supply an implementation of run_task().
aoqi@0: class AbstractWorkGang: public CHeapObj<mtInternal> {
aoqi@0:   // Here's the public interface to this class.
aoqi@0: public:
aoqi@0:   // Constructor and destructor.
aoqi@0:   AbstractWorkGang(const char* name, bool are_GC_task_threads,
aoqi@0:                    bool are_ConcurrentGC_threads);
aoqi@0:   ~AbstractWorkGang();
aoqi@0:   // Run a task, returns when the task is done (or terminated).
aoqi@0:   virtual void run_task(AbstractGangTask* task) = 0;
aoqi@0:   // Stop and terminate all workers.
aoqi@0:   virtual void stop();
aoqi@0:   // Return true if more workers should be applied to the task.
aoqi@0:   virtual bool needs_more_workers() const { return true; }
aoqi@0: public:
aoqi@0:   // Debugging.
aoqi@0:   const char* name() const;
aoqi@0: protected:
aoqi@0:   // Initialize only instance data.
aoqi@0:   const bool _are_GC_task_threads;
aoqi@0:   const bool _are_ConcurrentGC_threads;
aoqi@0:   // Printing support.
aoqi@0:   const char* _name;
aoqi@0:   // The monitor which protects these data,
aoqi@0:   // and notifies of changes in it.
aoqi@0:   Monitor*  _monitor;
aoqi@0:   // The count of the number of workers in the gang.
aoqi@0:   uint _total_workers;
aoqi@0:   // Whether the workers should terminate.
aoqi@0:   bool _terminate;
aoqi@0:   // The array of worker threads for this gang.
aoqi@0:   // This is only needed for cleaning up.
aoqi@0:   GangWorker** _gang_workers;
aoqi@0:   // The task for this gang.
aoqi@0:   AbstractGangTask* _task;
aoqi@0:   // A sequence number for the current task.
aoqi@0:   int _sequence_number;
aoqi@0:   // The number of started workers.
aoqi@0:   uint _started_workers;
aoqi@0:   // The number of finished workers.
aoqi@0:   uint _finished_workers;
aoqi@0: public:
aoqi@0:   // Accessors for fields
aoqi@0:   Monitor* monitor() const {
aoqi@0:     return _monitor;
aoqi@0:   }
aoqi@0:   uint total_workers() const {
aoqi@0:     return _total_workers;
aoqi@0:   }
aoqi@0:   virtual uint active_workers() const {
aoqi@0:     return _total_workers;
aoqi@0:   }
aoqi@0:   bool terminate() const {
aoqi@0:     return _terminate;
aoqi@0:   }
aoqi@0:   GangWorker** gang_workers() const {
aoqi@0:     return _gang_workers;
aoqi@0:   }
aoqi@0:   AbstractGangTask* task() const {
aoqi@0:     return _task;
aoqi@0:   }
aoqi@0:   int sequence_number() const {
aoqi@0:     return _sequence_number;
aoqi@0:   }
aoqi@0:   uint started_workers() const {
aoqi@0:     return _started_workers;
aoqi@0:   }
aoqi@0:   uint finished_workers() const {
aoqi@0:     return _finished_workers;
aoqi@0:   }
aoqi@0:   bool are_GC_task_threads() const {
aoqi@0:     return _are_GC_task_threads;
aoqi@0:   }
aoqi@0:   bool are_ConcurrentGC_threads() const {
aoqi@0:     return _are_ConcurrentGC_threads;
aoqi@0:   }
aoqi@0:   // Predicates.
aoqi@0:   bool is_idle() const {
aoqi@0:     return (task() == NULL);
aoqi@0:   }
aoqi@0:   // Return the Ith gang worker.
aoqi@0:   GangWorker* gang_worker(uint i) const;
aoqi@0: 
aoqi@0:   void threads_do(ThreadClosure* tc) const;
aoqi@0: 
aoqi@0:   // Printing
aoqi@0:   void print_worker_threads_on(outputStream *st) const;
aoqi@0:   void print_worker_threads() const {
aoqi@0:     print_worker_threads_on(tty);
aoqi@0:   }
aoqi@0: 
aoqi@0: protected:
aoqi@0:   friend class GangWorker;
aoqi@0:   friend class YieldingFlexibleGangWorker;
aoqi@0:   // Note activation and deactivation of workers.
aoqi@0:   // These methods should only be called with the mutex held.
aoqi@0:   void internal_worker_poll(WorkData* data) const;
aoqi@0:   void internal_note_start();
aoqi@0:   void internal_note_finish();
aoqi@0: };
aoqi@0: 
aoqi@0: class WorkData: public StackObj {
aoqi@0:   // This would be a struct, but I want accessor methods.
aoqi@0: private:
aoqi@0:   bool              _terminate;
aoqi@0:   AbstractGangTask* _task;
aoqi@0:   int               _sequence_number;
aoqi@0: public:
aoqi@0:   // Constructor and destructor
aoqi@0:   WorkData() {
aoqi@0:     _terminate       = false;
aoqi@0:     _task            = NULL;
aoqi@0:     _sequence_number = 0;
aoqi@0:   }
aoqi@0:   ~WorkData() {
aoqi@0:   }
aoqi@0:   // Accessors and modifiers
aoqi@0:   bool terminate()                       const { return _terminate;  }
aoqi@0:   void set_terminate(bool value)               { _terminate = value; }
aoqi@0:   AbstractGangTask* task()               const { return _task; }
aoqi@0:   void set_task(AbstractGangTask* value)       { _task = value; }
aoqi@0:   int sequence_number()                  const { return _sequence_number; }
aoqi@0:   void set_sequence_number(int value)          { _sequence_number = value; }
aoqi@0: 
aoqi@0:   YieldingFlexibleGangTask* yf_task()    const {
aoqi@0:     return (YieldingFlexibleGangTask*)_task;
aoqi@0:   }
aoqi@0: };
aoqi@0: 
aoqi@0: // Class WorkGang:
aoqi@0: class WorkGang: public AbstractWorkGang {
aoqi@0: public:
aoqi@0:   // Constructor
aoqi@0:   WorkGang(const char* name, uint workers,
aoqi@0:            bool are_GC_task_threads, bool are_ConcurrentGC_threads);
aoqi@0:   // Run a task, returns when the task is done (or terminated).
aoqi@0:   virtual void run_task(AbstractGangTask* task);
aoqi@0:   void run_task(AbstractGangTask* task, uint no_of_parallel_workers);
aoqi@0:   // Allocate a worker and return a pointer to it.
aoqi@0:   virtual GangWorker* allocate_worker(uint which);
aoqi@0:   // Initialize workers in the gang.  Return true if initialization
aoqi@0:   // succeeded. The type of the worker can be overridden in a derived
aoqi@0:   // class with the appropriate implementation of allocate_worker().
aoqi@0:   bool initialize_workers();
aoqi@0: };
aoqi@0: 
aoqi@0: // Class GangWorker:
aoqi@0: //   Several instances of this class run in parallel as workers for a gang.
aoqi@0: class GangWorker: public WorkerThread {
aoqi@0: public:
aoqi@0:   // Constructors and destructor.
aoqi@0:   GangWorker(AbstractWorkGang* gang, uint id);
aoqi@0: 
aoqi@0:   // The only real method: run a task for the gang.
aoqi@0:   virtual void run();
aoqi@0:   // Predicate for Thread
aoqi@0:   virtual bool is_GC_task_thread() const;
aoqi@0:   virtual bool is_ConcurrentGC_thread() const;
aoqi@0:   // Printing
aoqi@0:   void print_on(outputStream* st) const;
aoqi@0:   virtual void print() const { print_on(tty); }
aoqi@0: protected:
aoqi@0:   AbstractWorkGang* _gang;
aoqi@0: 
aoqi@0:   virtual void initialize();
aoqi@0:   virtual void loop();
aoqi@0: 
aoqi@0: public:
aoqi@0:   AbstractWorkGang* gang() const { return _gang; }
aoqi@0: };
aoqi@0: 
aoqi@0: // Dynamic number of worker threads
aoqi@0: //
aoqi@0: // This type of work gang is used to run different numbers of
aoqi@0: // worker threads at different times.  The
aoqi@0: // number of workers run for a task is "_active_workers"
aoqi@0: // instead of "_total_workers" in a WorkGang.  The method
aoqi@0: // "needs_more_workers()" returns true until "_active_workers"
aoqi@0: // have been started and returns false afterwards.  The
aoqi@0: // implementation of "needs_more_workers()" in WorkGang always
aoqi@0: // returns true so that all workers are started.  The method
aoqi@0: // "loop()" in GangWorker was modified to ask "needs_more_workers()"
aoqi@0: // in its loop to decide if it should start working on a task.
aoqi@0: // A worker in "loop()" waits for notification on the WorkGang
aoqi@0: // monitor and execution of each worker as it checks for work
aoqi@0: // is serialized via the same monitor.  The "needs_more_workers()"
aoqi@0: // call is serialized and additionally the calculation for the
aoqi@0: // "part" (effectively the worker id for executing the task) is
aoqi@0: // serialized to give each worker a unique "part".  Workers that
aoqi@0: // are not needed for this tasks (i.e., "_active_workers" have
aoqi@0: // been started before it, continue to wait for work.
aoqi@0: 
aoqi@0: class FlexibleWorkGang: public WorkGang {
aoqi@0:   // The currently active workers in this gang.
aoqi@0:   // This is a number that is dynamically adjusted
aoqi@0:   // and checked in the run_task() method at each invocation.
aoqi@0:   // As described above _active_workers determines the number
aoqi@0:   // of threads started on a task.  It must also be used to
aoqi@0:   // determine completion.
aoqi@0: 
aoqi@0:  protected:
aoqi@0:   uint _active_workers;
aoqi@0:  public:
aoqi@0:   // Constructor and destructor.
aoqi@0:   // Initialize active_workers to a minimum value.  Setting it to
aoqi@0:   // the parameter "workers" will initialize it to a maximum
aoqi@0:   // value which is not desirable.
aoqi@0:   FlexibleWorkGang(const char* name, uint workers,
aoqi@0:                    bool are_GC_task_threads,
aoqi@0:                    bool  are_ConcurrentGC_threads) :
aoqi@0:     WorkGang(name, workers, are_GC_task_threads, are_ConcurrentGC_threads),
aoqi@0:     _active_workers(UseDynamicNumberOfGCThreads ? 1U : ParallelGCThreads) {}
aoqi@0:   // Accessors for fields
aoqi@0:   virtual uint active_workers() const { return _active_workers; }
aoqi@0:   void set_active_workers(uint v) {
aoqi@0:     assert(v <= _total_workers,
aoqi@0:            "Trying to set more workers active than there are");
aoqi@0:     _active_workers = MIN2(v, _total_workers);
aoqi@0:     assert(v != 0, "Trying to set active workers to 0");
aoqi@0:     _active_workers = MAX2(1U, _active_workers);
aoqi@0:     assert(UseDynamicNumberOfGCThreads || _active_workers == _total_workers,
aoqi@0:            "Unless dynamic should use total workers");
aoqi@0:   }
aoqi@0:   virtual void run_task(AbstractGangTask* task);
aoqi@0:   virtual bool needs_more_workers() const {
aoqi@0:     return _started_workers < _active_workers;
aoqi@0:   }
aoqi@0: };
aoqi@0: 
aoqi@0: // Work gangs in garbage collectors: 2009-06-10
aoqi@0: //
aoqi@0: // SharedHeap - work gang for stop-the-world parallel collection.
aoqi@0: //   Used by
aoqi@0: //     ParNewGeneration
aoqi@0: //     CMSParRemarkTask
aoqi@0: //     CMSRefProcTaskExecutor
aoqi@0: //     G1CollectedHeap
aoqi@0: //     G1ParFinalCountTask
aoqi@0: // ConcurrentMark
aoqi@0: // CMSCollector
aoqi@0: 
aoqi@0: // A class that acts as a synchronisation barrier. Workers enter
aoqi@0: // the barrier and must wait until all other workers have entered
aoqi@0: // before any of them may leave.
aoqi@0: 
aoqi@0: class WorkGangBarrierSync : public StackObj {
aoqi@0: protected:
aoqi@0:   Monitor _monitor;
aoqi@0:   uint    _n_workers;
aoqi@0:   uint    _n_completed;
aoqi@0:   bool    _should_reset;
aoqi@0:   bool    _aborted;
aoqi@0: 
aoqi@0:   Monitor* monitor()        { return &_monitor; }
aoqi@0:   uint     n_workers()      { return _n_workers; }
aoqi@0:   uint     n_completed()    { return _n_completed; }
aoqi@0:   bool     should_reset()   { return _should_reset; }
aoqi@0:   bool     aborted()        { return _aborted; }
aoqi@0: 
aoqi@0:   void     zero_completed() { _n_completed = 0; }
aoqi@0:   void     inc_completed()  { _n_completed++; }
aoqi@0:   void     set_aborted()    { _aborted = true; }
aoqi@0:   void     set_should_reset(bool v) { _should_reset = v; }
aoqi@0: 
aoqi@0: public:
aoqi@0:   WorkGangBarrierSync();
aoqi@0:   WorkGangBarrierSync(uint n_workers, const char* name);
aoqi@0: 
aoqi@0:   // Set the number of workers that will use the barrier.
aoqi@0:   // Must be called before any of the workers start running.
aoqi@0:   void set_n_workers(uint n_workers);
aoqi@0: 
aoqi@0:   // Enter the barrier. A worker that enters the barrier will
aoqi@0:   // not be allowed to leave until all other threads have
aoqi@0:   // also entered the barrier or the barrier is aborted.
aoqi@0:   // Returns false if the barrier was aborted.
aoqi@0:   bool enter();
aoqi@0: 
aoqi@0:   // Aborts the barrier and wakes up any threads waiting for
aoqi@0:   // the barrier to complete. The barrier will remain in the
aoqi@0:   // aborted state until the next call to set_n_workers().
aoqi@0:   void abort();
aoqi@0: };
aoqi@0: 
aoqi@0: // A class to manage claiming of subtasks within a group of tasks.  The
aoqi@0: // subtasks will be identified by integer indices, usually elements of an
aoqi@0: // enumeration type.
aoqi@0: 
aoqi@0: class SubTasksDone: public CHeapObj<mtInternal> {
aoqi@0:   uint* _tasks;
aoqi@0:   uint _n_tasks;
aoqi@0:   // _n_threads is used to determine when a sub task is done.
aoqi@0:   // It does not control how many threads will execute the subtask
aoqi@0:   // but must be initialized to the number that do execute the task
aoqi@0:   // in order to correctly decide when the subtask is done (all the
aoqi@0:   // threads working on the task have finished).
aoqi@0:   uint _n_threads;
aoqi@0:   uint _threads_completed;
aoqi@0: #ifdef ASSERT
aoqi@0:   volatile uint _claimed;
aoqi@0: #endif
aoqi@0: 
aoqi@0:   // Set all tasks to unclaimed.
aoqi@0:   void clear();
aoqi@0: 
aoqi@0: public:
aoqi@0:   // Initializes "this" to a state in which there are "n" tasks to be
aoqi@0:   // processed, none of the which are originally claimed.  The number of
aoqi@0:   // threads doing the tasks is initialized 1.
aoqi@0:   SubTasksDone(uint n);
aoqi@0: 
aoqi@0:   // True iff the object is in a valid state.
aoqi@0:   bool valid();
aoqi@0: 
aoqi@0:   // Get/set the number of parallel threads doing the tasks to "t".  Can only
aoqi@0:   // be called before tasks start or after they are complete.
aoqi@0:   uint n_threads() { return _n_threads; }
aoqi@0:   void set_n_threads(uint t);
aoqi@0: 
aoqi@0:   // Returns "false" if the task "t" is unclaimed, and ensures that task is
aoqi@0:   // claimed.  The task "t" is required to be within the range of "this".
aoqi@0:   bool is_task_claimed(uint t);
aoqi@0: 
aoqi@0:   // The calling thread asserts that it has attempted to claim all the
aoqi@0:   // tasks that it will try to claim.  Every thread in the parallel task
aoqi@0:   // must execute this.  (When the last thread does so, the task array is
aoqi@0:   // cleared.)
aoqi@0:   void all_tasks_completed();
aoqi@0: 
aoqi@0:   // Destructor.
aoqi@0:   ~SubTasksDone();
aoqi@0: };
aoqi@0: 
aoqi@0: // As above, but for sequential tasks, i.e. instead of claiming
aoqi@0: // sub-tasks from a set (possibly an enumeration), claim sub-tasks
aoqi@0: // in sequential order. This is ideal for claiming dynamically
aoqi@0: // partitioned tasks (like striding in the parallel remembered
aoqi@0: // set scanning). Note that unlike the above class this is
aoqi@0: // a stack object - is there any reason for it not to be?
aoqi@0: 
aoqi@0: class SequentialSubTasksDone : public StackObj {
aoqi@0: protected:
aoqi@0:   uint _n_tasks;     // Total number of tasks available.
aoqi@0:   uint _n_claimed;   // Number of tasks claimed.
aoqi@0:   // _n_threads is used to determine when a sub task is done.
aoqi@0:   // See comments on SubTasksDone::_n_threads
aoqi@0:   uint _n_threads;   // Total number of parallel threads.
aoqi@0:   uint _n_completed; // Number of completed threads.
aoqi@0: 
aoqi@0:   void clear();
aoqi@0: 
aoqi@0: public:
aoqi@0:   SequentialSubTasksDone() {
aoqi@0:     clear();
aoqi@0:   }
aoqi@0:   ~SequentialSubTasksDone() {}
aoqi@0: 
aoqi@0:   // True iff the object is in a valid state.
aoqi@0:   bool valid();
aoqi@0: 
aoqi@0:   // number of tasks
aoqi@0:   uint n_tasks() const { return _n_tasks; }
aoqi@0: 
aoqi@0:   // Get/set the number of parallel threads doing the tasks to t.
aoqi@0:   // Should be called before the task starts but it is safe
aoqi@0:   // to call this once a task is running provided that all
aoqi@0:   // threads agree on the number of threads.
aoqi@0:   uint n_threads() { return _n_threads; }
aoqi@0:   void set_n_threads(uint t) { _n_threads = t; }
aoqi@0: 
aoqi@0:   // Set the number of tasks to be claimed to t. As above,
aoqi@0:   // should be called before the tasks start but it is safe
aoqi@0:   // to call this once a task is running provided all threads
aoqi@0:   // agree on the number of tasks.
aoqi@0:   void set_n_tasks(uint t) { _n_tasks = t; }
aoqi@0: 
aoqi@0:   // Returns false if the next task in the sequence is unclaimed,
aoqi@0:   // and ensures that it is claimed. Will set t to be the index
aoqi@0:   // of the claimed task in the sequence. Will return true if
aoqi@0:   // the task cannot be claimed and there are none left to claim.
aoqi@0:   bool is_task_claimed(uint& t);
aoqi@0: 
aoqi@0:   // The calling thread asserts that it has attempted to claim
aoqi@0:   // all the tasks it possibly can in the sequence. Every thread
aoqi@0:   // claiming tasks must promise call this. Returns true if this
aoqi@0:   // is the last thread to complete so that the thread can perform
aoqi@0:   // cleanup if necessary.
aoqi@0:   bool all_tasks_completed();
aoqi@0: };
aoqi@0: 
aoqi@0: // Represents a set of free small integer ids.
aoqi@0: class FreeIdSet : public CHeapObj<mtInternal> {
aoqi@0:   enum {
aoqi@0:     end_of_list = -1,
aoqi@0:     claimed = -2
aoqi@0:   };
aoqi@0: 
aoqi@0:   int _sz;
aoqi@0:   Monitor* _mon;
aoqi@0: 
aoqi@0:   int* _ids;
aoqi@0:   int _hd;
aoqi@0:   int _waiters;
aoqi@0:   int _claimed;
aoqi@0: 
aoqi@0:   static bool _safepoint;
aoqi@0:   typedef FreeIdSet* FreeIdSetPtr;
aoqi@0:   static const int NSets = 10;
aoqi@0:   static FreeIdSetPtr _sets[NSets];
aoqi@0:   static bool _stat_init;
aoqi@0:   int _index;
aoqi@0: 
aoqi@0: public:
aoqi@0:   FreeIdSet(int sz, Monitor* mon);
aoqi@0:   ~FreeIdSet();
aoqi@0: 
aoqi@0:   static void set_safepoint(bool b);
aoqi@0: 
aoqi@0:   // Attempt to claim the given id permanently.  Returns "true" iff
aoqi@0:   // successful.
aoqi@0:   bool claim_perm_id(int i);
aoqi@0: 
aoqi@0:   // Returns an unclaimed parallel id (waiting for one to be released if
aoqi@0:   // necessary).  Returns "-1" if a GC wakes up a wait for an id.
aoqi@0:   int claim_par_id();
aoqi@0: 
aoqi@0:   void release_par_id(int id);
aoqi@0: };
aoqi@0: 
aoqi@0: #endif // SHARE_VM_UTILITIES_WORKGROUP_HPP