/*

 * Copyright (c) 1997, 2019, 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.

 *

 */

#include "precompiled.hpp"

#include "memory/allocation.hpp"

#include "runtime/init.hpp"

#include "runtime/task.hpp"

#include "runtime/thread.inline.hpp"

#include "runtime/timer.hpp"

int PeriodicTask::_num_tasks = 0;

PeriodicTask* PeriodicTask::_tasks[PeriodicTask::max_tasks];

void PeriodicTask::real_time_tick(int delay_time) {

  assert(Thread::current()->is_Watcher_thread(), "must be WatcherThread");

  // The WatcherThread does not participate in the safepoint protocol

  // for the PeriodicTask_lock because it is not a JavaThread.

  MutexLocker ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);

  int orig_num_tasks = _num_tasks;

  for(int index = 0; index < _num_tasks; index++) {

    _tasks[index]->execute_if_pending(delay_time);

    if (_num_tasks < orig_num_tasks) { // task dis-enrolled itself

      index--;  // re-do current slot as it has changed

      orig_num_tasks = _num_tasks;

    }

  }

}

int PeriodicTask::time_to_wait() {

  assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");

  if (_num_tasks == 0) {

    return 0; // sleep until shutdown or a task is enrolled

  }

  int delay = _tasks[0]->time_to_next_interval();

  for (int index = 1; index < _num_tasks; index++) {

    delay = MIN2(delay, _tasks[index]->time_to_next_interval());

  }

  return delay;

}

PeriodicTask::PeriodicTask(size_t interval_time) :

  _counter(0), _interval((int) interval_time) {

  // Sanity check the interval time

  assert(_interval >= PeriodicTask::min_interval &&

         _interval %  PeriodicTask::interval_gran == 0,

              "improper PeriodicTask interval time");

}

PeriodicTask::~PeriodicTask() {

  // This PeriodicTask may have already been disenrolled by a call

  // to disenroll() before the PeriodicTask was deleted.

  disenroll();

}

// enroll the current PeriodicTask

void PeriodicTask::enroll() {

  // Follow normal safepoint aware lock enter protocol if the caller does

  // not already own the PeriodicTask_lock. Otherwise, we don't try to

  // enter it again because VM internal Mutexes do not support recursion.

  //

  MutexLocker ml(PeriodicTask_lock->owned_by_self() ? NULL : PeriodicTask_lock);

  if (_num_tasks == PeriodicTask::max_tasks) {

    fatal("Overflow in PeriodicTask table");

  } else {

    _tasks[_num_tasks++] = this;

  }

  WatcherThread* thread = WatcherThread::watcher_thread();

  if (thread != NULL) {

    thread->unpark();

  } else {

    WatcherThread::start();

  }

}

// disenroll the current PeriodicTask

void PeriodicTask::disenroll() {

  // Follow normal safepoint aware lock enter protocol if the caller does

  // not already own the PeriodicTask_lock. Otherwise, we don't try to

  // enter it again because VM internal Mutexes do not support recursion.

  //

  MutexLocker ml(PeriodicTask_lock->owned_by_self() ? NULL : PeriodicTask_lock);

  int index;

  for(index = 0; index < _num_tasks && _tasks[index] != this; index++)

    ;

  if (index == _num_tasks) {

    return;

  }

  _num_tasks--;

  for (; index < _num_tasks; index++) {

    _tasks[index] = _tasks[index+1];

  }

}