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 /*

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

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  * 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

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 #ifndef SHARE_VM_UTILITIES_YIELDINGWORKGROUP_HPP

 #define SHARE_VM_UTILITIES_YIELDINGWORKGROUP_HPP

 #include "utilities/macros.hpp"

 #include "utilities/workgroup.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_UTILITIES_YIELDINGWORKGROUP_HPP