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 "classfile/stringTable.hpp"
  27 #include "runtime/interfaceSupport.inline.hpp"
  28 #include "runtime/javaCalls.hpp"
  29 #include "runtime/serviceThread.hpp"
  30 #include "runtime/mutexLocker.hpp"
  31 #include "runtime/os.hpp"
  32 #include "prims/jvmtiImpl.hpp"
  33 #include "services/diagnosticArgument.hpp"
  34 #include "services/diagnosticFramework.hpp"
  35 #include "services/gcNotifier.hpp"
  36 #include "services/lowMemoryDetector.hpp"
  37 
  38 ServiceThread* ServiceThread::_instance = NULL;
  39 
  40 void ServiceThread::initialize() {
  41   EXCEPTION_MARK;
  42 
  43   const char* name = "Service Thread";
  44   Handle string = java_lang_String::create_from_str(name, CHECK);
  45 
  46   // Initialize thread_oop to put it into the system threadGroup
  47   Handle thread_group (THREAD, Universe::system_thread_group());
  48   Handle thread_oop = JavaCalls::construct_new_instance(
  49                           SystemDictionary::Thread_klass(),
  50                           vmSymbols::threadgroup_string_void_signature(),
  51                           thread_group,
  52                           string,
  53                           CHECK);
  54 
  55   {
  56     MutexLocker mu(Threads_lock);
  57     ServiceThread* thread =  new ServiceThread(&service_thread_entry);
  58 
  59     // At this point it may be possible that no osthread was created for the
  60     // JavaThread due to lack of memory. We would have to throw an exception
  61     // in that case. However, since this must work and we do not allow
  62     // exceptions anyway, check and abort if this fails.
  63     if (thread == NULL || thread->osthread() == NULL) {
  64       vm_exit_during_initialization("java.lang.OutOfMemoryError",
  65                                     os::native_thread_creation_failed_msg());
  66     }
  67 
  68     java_lang_Thread::set_thread(thread_oop(), thread);
  69     java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
  70     java_lang_Thread::set_daemon(thread_oop());
  71     thread->set_threadObj(thread_oop());
  72     _instance = thread;
  73 
  74     Threads::add(thread);
  75     Thread::start(thread);
  76   }
  77 }
  78 
  79 void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {
  80   while (true) {
  81     bool sensors_changed = false;
  82     bool has_jvmti_events = false;
  83     bool has_gc_notification_event = false;
  84     bool has_dcmd_notification_event = false;
  85     bool acs_notify = false;
  86     bool stringtable_work = false;
  87     JvmtiDeferredEvent jvmti_event;
  88     {
  89       // Need state transition ThreadBlockInVM so that this thread
  90       // will be handled by safepoint correctly when this thread is
  91       // notified at a safepoint.
  92 
  93       // This ThreadBlockInVM object is not also considered to be
  94       // suspend-equivalent because ServiceThread is not visible to
  95       // external suspension.
  96 
  97       ThreadBlockInVM tbivm(jt);
  98 
  99       MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
 100       while (!(sensors_changed = LowMemoryDetector::has_pending_requests()) &&
 101              !(has_jvmti_events = JvmtiDeferredEventQueue::has_events()) &&
 102               !(has_gc_notification_event = GCNotifier::has_event()) &&
 103               !(has_dcmd_notification_event = DCmdFactory::has_pending_jmx_notification()) &&
 104               !(stringtable_work = StringTable::has_work())) {
 105         // wait until one of the sensors has pending requests, or there is a
 106         // pending JVMTI event or JMX GC notification to post
 107         Service_lock->wait(Mutex::_no_safepoint_check_flag);
 108       }
 109 
 110       if (has_jvmti_events) {
 111         jvmti_event = JvmtiDeferredEventQueue::dequeue();
 112       }
 113     }
 114 
 115     if (stringtable_work) {
 116       StringTable::do_concurrent_work(jt);
 117     }
 118 
 119     if (has_jvmti_events) {
 120       jvmti_event.post();
 121     }
 122 
 123     if (sensors_changed) {
 124       LowMemoryDetector::process_sensor_changes(jt);
 125     }
 126 
 127     if(has_gc_notification_event) {
 128         GCNotifier::sendNotification(CHECK);
 129     }
 130 
 131     if(has_dcmd_notification_event) {
 132       DCmdFactory::send_notification(CHECK);
 133     }
 134   }
 135 }
 136 
 137 bool ServiceThread::is_service_thread(Thread* thread) {
 138   return thread == _instance;
 139 }