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 /*

  * Copyright (c) 2001, 2011, 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.

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  */

 #include "precompiled.hpp"

 #include "memory/allocation.hpp"

 #include "memory/allocation.inline.hpp"

 #include "runtime/os.hpp"

 #include "utilities/workgroup.hpp"

 // Definitions of WorkGang methods.

 AbstractWorkGang::AbstractWorkGang(const char* name,

                                    bool  are_GC_task_threads,

                                    bool  are_ConcurrentGC_threads) :

   _name(name),

   _are_GC_task_threads(are_GC_task_threads),

   _are_ConcurrentGC_threads(are_ConcurrentGC_threads) {

   assert(!(are_GC_task_threads && are_ConcurrentGC_threads),

          "They cannot both be STW GC and Concurrent threads" );

   // Other initialization.

   _monitor = new Monitor(/* priority */       Mutex::leaf,

                          /* name */           "WorkGroup monitor",

                          /* allow_vm_block */ are_GC_task_threads);

   assert(monitor() != NULL, "Failed to allocate monitor");

   _terminate = false;

   _task = NULL;

   _sequence_number = 0;

   _started_workers = 0;

   _finished_workers = 0;

 }

 WorkGang::WorkGang(const char* name,

                    uint        workers,

                    bool        are_GC_task_threads,

                    bool        are_ConcurrentGC_threads) :

   AbstractWorkGang(name, are_GC_task_threads, are_ConcurrentGC_threads) {

   _total_workers = workers;

 }

 GangWorker* WorkGang::allocate_worker(uint which) {

   GangWorker* new_worker = new GangWorker(this, which);

   return new_worker;

 }

 // The current implementation will exit if the allocation

 // of any worker fails.  Still, return a boolean so that

 // a future implementation can possibly do a partial

 // initialization of the workers and report such to the

 // caller.

 bool WorkGang::initialize_workers() {

   if (TraceWorkGang) {

     tty->print_cr("Constructing work gang %s with %d threads",

                   name(),

                   total_workers());

   }

   _gang_workers = NEW_C_HEAP_ARRAY(GangWorker*, total_workers());

   if (gang_workers() == NULL) {

     vm_exit_out_of_memory(0, "Cannot create GangWorker array.");

     return false;

   }

   os::ThreadType worker_type;

   if (are_ConcurrentGC_threads()) {

     worker_type = os::cgc_thread;

   } else {

     worker_type = os::pgc_thread;

   }

   for (uint worker = 0; worker < total_workers(); worker += 1) {

     GangWorker* new_worker = allocate_worker(worker);

     assert(new_worker != NULL, "Failed to allocate GangWorker");

     _gang_workers[worker] = new_worker;

     if (new_worker == NULL || !os::create_thread(new_worker, worker_type)) {

       vm_exit_out_of_memory(0, "Cannot create worker GC thread. Out of system resources.");

       return false;

     }

     if (!DisableStartThread) {

       os::start_thread(new_worker);

     }

   }

   return true;

 }

 AbstractWorkGang::~AbstractWorkGang() {

   if (TraceWorkGang) {

     tty->print_cr("Destructing work gang %s", name());

   }

   stop();   // stop all the workers

   for (uint worker = 0; worker < total_workers(); worker += 1) {

     delete gang_worker(worker);

   }

   delete gang_workers();

   delete monitor();

 }

 GangWorker* AbstractWorkGang::gang_worker(uint i) const {

   // Array index bounds checking.

   GangWorker* result = NULL;

   assert(gang_workers() != NULL, "No workers for indexing");

   assert(((i >= 0) && (i < total_workers())), "Worker index out of bounds");

   result = _gang_workers[i];

   assert(result != NULL, "Indexing to null worker");

   return result;

 }

 void WorkGang::run_task(AbstractGangTask* task) {

   run_task(task, total_workers());

 }

 void WorkGang::run_task(AbstractGangTask* task, uint no_of_parallel_workers) {

   task->set_for_termination(no_of_parallel_workers);

   // This thread is executed by the VM thread which does not block

   // on ordinary MutexLocker's.

   MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);

   if (TraceWorkGang) {

     tty->print_cr("Running work gang %s task %s", name(), task->name());

   }

   // Tell all the workers to run a task.

   assert(task != NULL, "Running a null task");

   // Initialize.

   _task = task;

   _sequence_number += 1;

   _started_workers = 0;

   _finished_workers = 0;

   // Tell the workers to get to work.

   monitor()->notify_all();

   // Wait for them to be finished

   while (finished_workers() < no_of_parallel_workers) {

     if (TraceWorkGang) {

       tty->print_cr("Waiting in work gang %s: %d/%d finished sequence %d",

                     name(), finished_workers(), no_of_parallel_workers,

                     _sequence_number);

     }

     monitor()->wait(/* no_safepoint_check */ true);

   }

   _task = NULL;

   if (TraceWorkGang) {

     tty->print_cr("\nFinished work gang %s: %d/%d sequence %d",

                   name(), finished_workers(), no_of_parallel_workers,

                   _sequence_number);

     Thread* me = Thread::current();

     tty->print_cr("  T: 0x%x  VM_thread: %d", me, me->is_VM_thread());

   }

 }

 void FlexibleWorkGang::run_task(AbstractGangTask* task) {

   // If active_workers() is passed, _finished_workers

   // must only be incremented for workers that find non_null

   // work (as opposed to all those that just check that the

   // task is not null).

   WorkGang::run_task(task, (uint) active_workers());

 }

 void AbstractWorkGang::stop() {

   // Tell all workers to terminate, then wait for them to become inactive.

   MutexLockerEx ml(monitor(), Mutex::_no_safepoint_check_flag);

   if (TraceWorkGang) {

     tty->print_cr("Stopping work gang %s task %s", name(), task()->name());

   }

   _task = NULL;

   _terminate = true;

   monitor()->notify_all();

   while (finished_workers() < active_workers()) {

     if (TraceWorkGang) {

       tty->print_cr("Waiting in work gang %s: %d/%d finished",

                     name(), finished_workers(), active_workers());

     }

     monitor()->wait(/* no_safepoint_check */ true);

   }

 }

 void AbstractWorkGang::internal_worker_poll(WorkData* data) const {

   assert(monitor()->owned_by_self(), "worker_poll is an internal method");

   assert(data != NULL, "worker data is null");

   data->set_terminate(terminate());

   data->set_task(task());

   data->set_sequence_number(sequence_number());

 }

 void AbstractWorkGang::internal_note_start() {

   assert(monitor()->owned_by_self(), "note_finish is an internal method");

   _started_workers += 1;

 }

 void AbstractWorkGang::internal_note_finish() {

   assert(monitor()->owned_by_self(), "note_finish is an internal method");

   _finished_workers += 1;

 }

 void AbstractWorkGang::print_worker_threads_on(outputStream* st) const {

   uint    num_thr = total_workers();

   for (uint i = 0; i < num_thr; i++) {

     gang_worker(i)->print_on(st);

     st->cr();

   }

 }

 void AbstractWorkGang::threads_do(ThreadClosure* tc) const {

   assert(tc != NULL, "Null ThreadClosure");

   uint num_thr = total_workers();

   for (uint i = 0; i < num_thr; i++) {

     tc->do_thread(gang_worker(i));

   }

 }

 // GangWorker methods.

 GangWorker::GangWorker(AbstractWorkGang* gang, uint id) {

   _gang = gang;

   set_id(id);

   set_name("Gang worker#%d (%s)", id, gang->name());

 }

 void GangWorker::run() {

   initialize();

   loop();

 }

 void GangWorker::initialize() {

   this->initialize_thread_local_storage();

   assert(_gang != NULL, "No gang to run in");

   os::set_priority(this, NearMaxPriority);

   if (TraceWorkGang) {

     tty->print_cr("Running gang worker for gang %s id %d",

                   gang()->name(), id());

   }

   // The VM thread should not execute here because MutexLocker's are used

   // as (opposed to MutexLockerEx's).

   assert(!Thread::current()->is_VM_thread(), "VM thread should not be part"

          " of a work gang");

 }

 void GangWorker::loop() {

   int previous_sequence_number = 0;

   Monitor* gang_monitor = gang()->monitor();

   for ( ; /* !terminate() */; ) {

     WorkData data;

     int part;  // Initialized below.

     {

       // Grab the gang mutex.

       MutexLocker ml(gang_monitor);

       // Wait for something to do.

       // Polling outside the while { wait } avoids missed notifies

       // in the outer loop.

       gang()->internal_worker_poll(&data);

       if (TraceWorkGang) {

         tty->print("Polled outside for work in gang %s worker %d",

                    gang()->name(), id());

         tty->print("  terminate: %s",

                    data.terminate() ? "true" : "false");

         tty->print("  sequence: %d (prev: %d)",

                    data.sequence_number(), previous_sequence_number);

         if (data.task() != NULL) {

           tty->print("  task: %s", data.task()->name());

         } else {

           tty->print("  task: NULL");

         }

         tty->cr();

       }

       for ( ; /* break or return */; ) {

         // Terminate if requested.

         if (data.terminate()) {

           gang()->internal_note_finish();

           gang_monitor->notify_all();

           return;

         }

         // Check for new work.

         if ((data.task() != NULL) &&

             (data.sequence_number() != previous_sequence_number)) {

           if (gang()->needs_more_workers()) {

             gang()->internal_note_start();

             gang_monitor->notify_all();

             part = gang()->started_workers() - 1;

             break;

           }

         }

         // Nothing to do.

         gang_monitor->wait(/* no_safepoint_check */ true);

         gang()->internal_worker_poll(&data);

         if (TraceWorkGang) {

           tty->print("Polled inside for work in gang %s worker %d",

                      gang()->name(), id());

           tty->print("  terminate: %s",

                      data.terminate() ? "true" : "false");

           tty->print("  sequence: %d (prev: %d)",

                      data.sequence_number(), previous_sequence_number);

           if (data.task() != NULL) {

             tty->print("  task: %s", data.task()->name());

           } else {

             tty->print("  task: NULL");

           }

           tty->cr();

         }

       }

       // Drop gang mutex.

     }

     if (TraceWorkGang) {

       tty->print("Work for work gang %s id %d task %s part %d",

                  gang()->name(), id(), data.task()->name(), part);

     }

     assert(data.task() != NULL, "Got null task");

     data.task()->work(part);

     {

       if (TraceWorkGang) {

         tty->print("Finish for work gang %s id %d task %s part %d",

                    gang()->name(), id(), data.task()->name(), part);

       }

       // Grab the gang mutex.

       MutexLocker ml(gang_monitor);

       gang()->internal_note_finish();

       // Tell the gang you are done.

       gang_monitor->notify_all();

       // Drop the gang mutex.

     }

     previous_sequence_number = data.sequence_number();

   }

 }

 bool GangWorker::is_GC_task_thread() const {

   return gang()->are_GC_task_threads();

 }

 bool GangWorker::is_ConcurrentGC_thread() const {

   return gang()->are_ConcurrentGC_threads();

 }

 void GangWorker::print_on(outputStream* st) const {

   st->print("\"%s\" ", name());

   Thread::print_on(st);

   st->cr();

 }

 // Printing methods

 const char* AbstractWorkGang::name() const {

   return _name;

 }

 #ifndef PRODUCT

 const char* AbstractGangTask::name() const {

   return _name;

 }

 #endif /* PRODUCT */

 // FlexibleWorkGang

 // *** WorkGangBarrierSync

 WorkGangBarrierSync::WorkGangBarrierSync()

   : _monitor(Mutex::safepoint, "work gang barrier sync", true),

     _n_workers(0), _n_completed(0), _should_reset(false) {

 }

 WorkGangBarrierSync::WorkGangBarrierSync(uint n_workers, const char* name)

   : _monitor(Mutex::safepoint, name, true),

     _n_workers(n_workers), _n_completed(0), _should_reset(false) {

 }

 void WorkGangBarrierSync::set_n_workers(uint n_workers) {

   _n_workers   = n_workers;

   _n_completed = 0;

   _should_reset = false;

 }

 void WorkGangBarrierSync::enter() {

   MutexLockerEx x(monitor(), Mutex::_no_safepoint_check_flag);

   if (should_reset()) {

     // The should_reset() was set and we are the first worker to enter

     // the sync barrier. We will zero the n_completed() count which

     // effectively resets the barrier.

     zero_completed();

     set_should_reset(false);

   }

   inc_completed();

   if (n_completed() == n_workers()) {

     // At this point we would like to reset the barrier to be ready in

     // case it is used again. However, we cannot set n_completed() to

     // 0, even after the notify_all(), given that some other workers

     // might still be waiting for n_completed() to become ==

     // n_workers(). So, if we set n_completed() to 0, those workers

     // will get stuck (as they will wake up, see that n_completed() !=

     // n_workers() and go back to sleep). Instead, we raise the

     // should_reset() flag and the barrier will be reset the first

     // time a worker enters it again.

     set_should_reset(true);

     monitor()->notify_all();

   } else {

     while (n_completed() != n_workers()) {

       monitor()->wait(/* no_safepoint_check */ true);

     }

   }

 }

 // SubTasksDone functions.

 SubTasksDone::SubTasksDone(uint n) :

   _n_tasks(n), _n_threads(1), _tasks(NULL) {

   _tasks = NEW_C_HEAP_ARRAY(uint, n);

   guarantee(_tasks != NULL, "alloc failure");

   clear();

 }

 bool SubTasksDone::valid() {

   return _tasks != NULL;

 }

 void SubTasksDone::set_n_threads(uint t) {

   assert(_claimed == 0 || _threads_completed == _n_threads,

          "should not be called while tasks are being processed!");

   _n_threads = (t == 0 ? 1 : t);

 }

 void SubTasksDone::clear() {

   for (uint i = 0; i < _n_tasks; i++) {

     _tasks[i] = 0;

   }

   _threads_completed = 0;

 #ifdef ASSERT

   _claimed = 0;

 #endif

 }

 bool SubTasksDone::is_task_claimed(uint t) {

   assert(0 <= t && t < _n_tasks, "bad task id.");

   uint old = _tasks[t];

   if (old == 0) {

     old = Atomic::cmpxchg(1, &_tasks[t], 0);

   }

   assert(_tasks[t] == 1, "What else?");

   bool res = old != 0;

 #ifdef ASSERT

   if (!res) {

     assert(_claimed < _n_tasks, "Too many tasks claimed; missing clear?");

     Atomic::inc((volatile jint*) &_claimed);

   }

 #endif

   return res;

 }

 void SubTasksDone::all_tasks_completed() {

   jint observed = _threads_completed;

   jint old;

   do {

     old = observed;

     observed = Atomic::cmpxchg(old+1, &_threads_completed, old);

   } while (observed != old);

   // If this was the last thread checking in, clear the tasks.

   if (observed+1 == (jint)_n_threads) clear();

 }

 SubTasksDone::~SubTasksDone() {

   if (_tasks != NULL) FREE_C_HEAP_ARRAY(jint, _tasks);

 }

 // *** SequentialSubTasksDone

 void SequentialSubTasksDone::clear() {

   _n_tasks   = _n_claimed   = 0;

   _n_threads = _n_completed = 0;

 }

 bool SequentialSubTasksDone::valid() {

   return _n_threads > 0;

 }

 bool SequentialSubTasksDone::is_task_claimed(uint& t) {

   uint* n_claimed_ptr = &_n_claimed;

   t = *n_claimed_ptr;

   while (t < _n_tasks) {

     jint res = Atomic::cmpxchg(t+1, n_claimed_ptr, t);

     if (res == (jint)t) {

       return false;

     }

     t = *n_claimed_ptr;

   }

   return true;

 }

 bool SequentialSubTasksDone::all_tasks_completed() {

   uint* n_completed_ptr = &_n_completed;

   uint  complete        = *n_completed_ptr;

   while (true) {

     uint res = Atomic::cmpxchg(complete+1, n_completed_ptr, complete);

     if (res == complete) {

       break;

     }

     complete = res;

   }

   if (complete+1 == _n_threads) {

     clear();

     return true;

   }

   return false;

 }

 bool FreeIdSet::_stat_init = false;

 FreeIdSet* FreeIdSet::_sets[NSets];

 bool FreeIdSet::_safepoint;

 FreeIdSet::FreeIdSet(int sz, Monitor* mon) :

   _sz(sz), _mon(mon), _hd(0), _waiters(0), _index(-1), _claimed(0)

 {

   _ids = new int[sz];

   for (int i = 0; i < sz; i++) _ids[i] = i+1;

   _ids[sz-1] = end_of_list; // end of list.

   if (_stat_init) {

     for (int j = 0; j < NSets; j++) _sets[j] = NULL;

     _stat_init = true;

   }

   // Add to sets.  (This should happen while the system is still single-threaded.)

   for (int j = 0; j < NSets; j++) {

     if (_sets[j] == NULL) {

       _sets[j] = this;

       _index = j;

       break;

     }

   }

   guarantee(_index != -1, "Too many FreeIdSets in use!");

 }

 FreeIdSet::~FreeIdSet() {

   _sets[_index] = NULL;

 }

 void FreeIdSet::set_safepoint(bool b) {

   _safepoint = b;

   if (b) {

     for (int j = 0; j < NSets; j++) {

       if (_sets[j] != NULL && _sets[j]->_waiters > 0) {

         Monitor* mon = _sets[j]->_mon;

         mon->lock_without_safepoint_check();

         mon->notify_all();

         mon->unlock();

       }

     }

   }

 }

 #define FID_STATS 0

 int FreeIdSet::claim_par_id() {

 #if FID_STATS

   thread_t tslf = thr_self();

   tty->print("claim_par_id[%d]: sz = %d, claimed = %d\n", tslf, _sz, _claimed);

 #endif

   MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);

   while (!_safepoint && _hd == end_of_list) {

     _waiters++;

 #if FID_STATS

     if (_waiters > 5) {

       tty->print("claim_par_id waiting[%d]: %d waiters, %d claimed.\n",

                  tslf, _waiters, _claimed);

     }

 #endif

     _mon->wait(Mutex::_no_safepoint_check_flag);

     _waiters--;

   }

   if (_hd == end_of_list) {

 #if FID_STATS

     tty->print("claim_par_id[%d]: returning EOL.\n", tslf);

 #endif

     return -1;

   } else {

     int res = _hd;

     _hd = _ids[res];

     _ids[res] = claimed;  // For debugging.

     _claimed++;

 #if FID_STATS

     tty->print("claim_par_id[%d]: returning %d, claimed = %d.\n",

                tslf, res, _claimed);

 #endif

     return res;

   }

 }

 bool FreeIdSet::claim_perm_id(int i) {

   assert(0 <= i && i < _sz, "Out of range.");

   MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);

   int prev = end_of_list;

   int cur = _hd;

   while (cur != end_of_list) {

     if (cur == i) {

       if (prev == end_of_list) {

         _hd = _ids[cur];

       } else {

         _ids[prev] = _ids[cur];

       }

       _ids[cur] = claimed;

       _claimed++;

       return true;

     } else {

       prev = cur;

       cur = _ids[cur];

     }

   }

   return false;

 }

 void FreeIdSet::release_par_id(int id) {

   MutexLockerEx x(_mon, Mutex::_no_safepoint_check_flag);

   assert(_ids[id] == claimed, "Precondition.");

   _ids[id] = _hd;

   _hd = id;

   _claimed--;

 #if FID_STATS

   tty->print("[%d] release_par_id(%d), waiters =%d,  claimed = %d.\n",

              thr_self(), id, _waiters, _claimed);

 #endif

   if (_waiters > 0)

     // Notify all would be safer, but this is OK, right?

     _mon->notify_all();

 }