/*

 * Copyright (c) 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.

 *

 */

#include "precompiled.hpp"

#include "runtime/interfaceSupport.hpp"

#include "runtime/javaCalls.hpp"

#include "runtime/serviceThread.hpp"

#include "runtime/mutexLocker.hpp"

#include "prims/jvmtiImpl.hpp"

ServiceThread* ServiceThread::_instance = NULL;

void ServiceThread::initialize() {

  EXCEPTION_MARK;

  instanceKlassHandle klass (THREAD,  SystemDictionary::Thread_klass());

  instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);

  const char* name = JDK_Version::is_gte_jdk17x_version() ?

      "Service Thread" : "Low Memory Detector";

  Handle string = java_lang_String::create_from_str(name, CHECK);

  // Initialize thread_oop to put it into the system threadGroup

  Handle thread_group (THREAD, Universe::system_thread_group());

  JavaValue result(T_VOID);

  JavaCalls::call_special(&result, thread_oop,

                          klass,

                          vmSymbols::object_initializer_name(),

                          vmSymbols::threadgroup_string_void_signature(),

                          thread_group,

                          string,

                          CHECK);

  {

    MutexLocker mu(Threads_lock);

    ServiceThread* thread =  new ServiceThread(&service_thread_entry);

    // At this point it may be possible that no osthread was created for the

    // JavaThread due to lack of memory. We would have to throw an exception

    // in that case. However, since this must work and we do not allow

    // exceptions anyway, check and abort if this fails.

    if (thread == NULL || thread->osthread() == NULL) {

      vm_exit_during_initialization("java.lang.OutOfMemoryError",

                                    "unable to create new native thread");

    }

    java_lang_Thread::set_thread(thread_oop(), thread);

    java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);

    java_lang_Thread::set_daemon(thread_oop());

    thread->set_threadObj(thread_oop());

    Threads::add(thread);

    Thread::start(thread);

    _instance = thread;

  }

}

void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {

  while (true) {

    bool sensors_changed = false;

    bool has_jvmti_events = false;

    JvmtiDeferredEvent jvmti_event;

    {

      // Need state transition ThreadBlockInVM so that this thread

      // will be handled by safepoint correctly when this thread is

      // notified at a safepoint.

      // This ThreadBlockInVM object is not also considered to be

      // suspend-equivalent because ServiceThread is not visible to

      // external suspension.

      ThreadBlockInVM tbivm(jt);

      MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);

      while (!(sensors_changed = LowMemoryDetector::has_pending_requests()) &&

             !(has_jvmti_events = JvmtiDeferredEventQueue::has_events())) {

        // wait until one of the sensors has pending requests, or there is a

        // pending JVMTI event to post

        Service_lock->wait(Mutex::_no_safepoint_check_flag);

      }

      if (has_jvmti_events) {

        jvmti_event = JvmtiDeferredEventQueue::dequeue();

      }

    }

    if (has_jvmti_events) {

      jvmti_event.post();

    }

    if (sensors_changed) {

      LowMemoryDetector::process_sensor_changes(jt);

    }

  }

}

bool ServiceThread::is_service_thread(Thread* thread) {

  return thread == _instance;

}