/*

 * Copyright (c) 2014, 2015, 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 "gc/g1/suspendibleThreadSet.hpp"

#include "runtime/mutexLocker.hpp"

#include "runtime/thread.inline.hpp"

uint   SuspendibleThreadSet::_nthreads          = 0;

uint   SuspendibleThreadSet::_nthreads_stopped  = 0;

bool   SuspendibleThreadSet::_suspend_all       = false;

double SuspendibleThreadSet::_suspend_all_start = 0.0;

void SuspendibleThreadSet::join() {

  assert(!Thread::current()->is_suspendible_thread(), "Thread already joined");

  MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);

  while (_suspend_all) {

    ml.wait(Mutex::_no_safepoint_check_flag);

  }

  _nthreads++;

  DEBUG_ONLY(Thread::current()->set_suspendible_thread();)

}

void SuspendibleThreadSet::leave() {

  assert(Thread::current()->is_suspendible_thread(), "Thread not joined");

  MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);

  assert(_nthreads > 0, "Invalid");

  DEBUG_ONLY(Thread::current()->clear_suspendible_thread();)

  _nthreads--;

  if (_suspend_all) {

    ml.notify_all();

  }

}

void SuspendibleThreadSet::yield() {

  assert(Thread::current()->is_suspendible_thread(), "Must have joined");

  if (_suspend_all) {

    MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);

    if (_suspend_all) {

      _nthreads_stopped++;

      if (_nthreads_stopped == _nthreads) {

        if (ConcGCYieldTimeout > 0) {

          double now = os::elapsedTime();

          guarantee((now - _suspend_all_start) * 1000.0 < (double)ConcGCYieldTimeout, "Long delay");

        }

      }

      ml.notify_all();

      while (_suspend_all) {

        ml.wait(Mutex::_no_safepoint_check_flag);

      }

      assert(_nthreads_stopped > 0, "Invalid");

      _nthreads_stopped--;

      ml.notify_all();

    }

  }

}

void SuspendibleThreadSet::synchronize() {

  assert(Thread::current()->is_VM_thread(), "Must be the VM thread");

  if (ConcGCYieldTimeout > 0) {

    _suspend_all_start = os::elapsedTime();

  }

  MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);

  assert(!_suspend_all, "Only one at a time");

  _suspend_all = true;

  while (_nthreads_stopped < _nthreads) {

    ml.wait(Mutex::_no_safepoint_check_flag);

  }

}

void SuspendibleThreadSet::desynchronize() {

  assert(Thread::current()->is_VM_thread(), "Must be the VM thread");

  MonitorLockerEx ml(STS_lock, Mutex::_no_safepoint_check_flag);

  assert(_nthreads_stopped == _nthreads, "Invalid");

  _suspend_all = false;

  ml.notify_all();

}