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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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 */

#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(), mtInternal);

  if (gang_workers() == NULL) {

    vm_exit_out_of_memory(0, OOM_MALLOC_ERROR, "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, OOM_MALLOC_ERROR,

              "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();

  this->record_stack_base_and_size();

  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, mtInternal);

  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, mtInternal);

}

// *** 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;