1 /*
   2  * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "runtime/interfaceSupport.inline.hpp"
  27 #include "runtime/javaCalls.hpp"
  28 #include "runtime/serviceThread.hpp"
  29 #include "runtime/mutexLocker.hpp"
  30 #include "runtime/os.hpp"
  31 #include "prims/jvmtiImpl.hpp"
  32 #include "services/diagnosticArgument.hpp"
  33 #include "services/diagnosticFramework.hpp"
  34 #include "services/gcNotifier.hpp"
  35 #include "services/lowMemoryDetector.hpp"
  36 
  37 ServiceThread* ServiceThread::_instance = NULL;
  38 
  39 void ServiceThread::initialize() {
  40   EXCEPTION_MARK;
  41 
  42   const char* name = "Service Thread";
  43   Handle string = java_lang_String::create_from_str(name, CHECK);
  44 
  45   // Initialize thread_oop to put it into the system threadGroup
  46   Handle thread_group (THREAD, Universe::system_thread_group());
  47   Handle thread_oop = JavaCalls::construct_new_instance(
  48                           SystemDictionary::Thread_klass(),
  49                           vmSymbols::threadgroup_string_void_signature(),
  50                           thread_group,
  51                           string,
  52                           CHECK);
  53 
  54   {
  55     MutexLocker mu(Threads_lock);
  56     ServiceThread* thread =  new ServiceThread(&service_thread_entry);
  57 
  58     // At this point it may be possible that no osthread was created for the
  59     // JavaThread due to lack of memory. We would have to throw an exception
  60     // in that case. However, since this must work and we do not allow
  61     // exceptions anyway, check and abort if this fails.
  62     if (thread == NULL || thread->osthread() == NULL) {
  63       vm_exit_during_initialization("java.lang.OutOfMemoryError",
  64                                     os::native_thread_creation_failed_msg());
  65     }
  66 
  67     java_lang_Thread::set_thread(thread_oop(), thread);
  68     java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
  69     java_lang_Thread::set_daemon(thread_oop());
  70     thread->set_threadObj(thread_oop());
  71     _instance = thread;
  72 
  73     Threads::add(thread);
  74     Thread::start(thread);
  75   }
  76 }
  77 
  78 void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {
  79   while (true) {
  80     bool sensors_changed = false;
  81     bool has_jvmti_events = false;
  82     bool has_gc_notification_event = false;
  83     bool has_dcmd_notification_event = false;
  84     bool acs_notify = false;
  85     JvmtiDeferredEvent jvmti_event;
  86     {
  87       // Need state transition ThreadBlockInVM so that this thread
  88       // will be handled by safepoint correctly when this thread is
  89       // notified at a safepoint.
  90 
  91       // This ThreadBlockInVM object is not also considered to be
  92       // suspend-equivalent because ServiceThread is not visible to
  93       // external suspension.
  94 
  95       ThreadBlockInVM tbivm(jt);
  96 
  97       MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
  98       while (!(sensors_changed = LowMemoryDetector::has_pending_requests()) &&
  99              !(has_jvmti_events = JvmtiDeferredEventQueue::has_events()) &&
 100               !(has_gc_notification_event = GCNotifier::has_event()) &&
 101               !(has_dcmd_notification_event = DCmdFactory::has_pending_jmx_notification())) {
 102         // wait until one of the sensors has pending requests, or there is a
 103         // pending JVMTI event or JMX GC notification to post
 104         Service_lock->wait(Mutex::_no_safepoint_check_flag);
 105       }
 106 
 107       if (has_jvmti_events) {
 108         jvmti_event = JvmtiDeferredEventQueue::dequeue();
 109       }
 110     }
 111 
 112     if (has_jvmti_events) {
 113       jvmti_event.post();
 114     }
 115 
 116     if (sensors_changed) {
 117       LowMemoryDetector::process_sensor_changes(jt);
 118     }
 119 
 120     if(has_gc_notification_event) {
 121         GCNotifier::sendNotification(CHECK);
 122     }
 123 
 124     if(has_dcmd_notification_event) {
 125       DCmdFactory::send_notification(CHECK);
 126     }
 127   }
 128 }
 129 
 130 bool ServiceThread::is_service_thread(Thread* thread) {
 131   return thread == _instance;
 132 }