JDK14/Java14源码在线阅读

/*
 * Copyright (c) 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/universe.hpp"
#include "runtime/interfaceSupport.inline.hpp"
#include "runtime/javaCalls.hpp"
#include "runtime/notificationThread.hpp"
#include "services/diagnosticArgument.hpp"
#include "services/diagnosticFramework.hpp"
#include "services/gcNotifier.hpp"
#include "services/lowMemoryDetector.hpp"

NotificationThread* NotificationThread::_instance = NULL;

void NotificationThread::initialize() {
  EXCEPTION_MARK;

  const char* name = "Notification Thread";
  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());
  Handle thread_oop = JavaCalls::construct_new_instance(
                          SystemDictionary::Thread_klass(),
                          vmSymbols::threadgroup_string_void_signature(),
                          thread_group,
                          string,
                          CHECK);

  Klass* group = SystemDictionary::ThreadGroup_klass();
  JavaValue result(T_VOID);
  JavaCalls::call_special(&result,
                          thread_group,
                          group,
                          vmSymbols::add_method_name(),
                          vmSymbols::thread_void_signature(),
                          thread_oop,
                          THREAD);
  {
    MutexLocker mu(Threads_lock);
    NotificationThread* thread =  new NotificationThread(&notification_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",
                                    os::native_thread_creation_failed_msg());
    }

    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());
    _instance = thread;

    Threads::add(thread);
    Thread::start(thread);
  }
}



void NotificationThread::notification_thread_entry(JavaThread* jt, TRAPS) {
  while (true) {
    bool sensors_changed = false;
    bool has_dcmd_notification_event = false;
    bool has_gc_notification_event = false;
    {
      // Need state transition ThreadBlockInVM so that this thread
      // will be handled by safepoint correctly when this thread is
      // notified at a safepoint.

      ThreadBlockInVM tbivm(jt);

      MonitorLocker ml(Notification_lock, Mutex::_no_safepoint_check_flag);
      // Process all available work on each (outer) iteration, rather than
      // only the first recognized bit of work, to avoid frequently true early
      // tests from potentially starving later work.  Hence the use of
      // arithmetic-or to combine results; we don't want short-circuiting.
      while (((sensors_changed = LowMemoryDetector::has_pending_requests()) |
              (has_dcmd_notification_event = DCmdFactory::has_pending_jmx_notification()) |

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