1 /*
   2  * Copyright (c) 2012, 2017, 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   InstanceKlass* klass = SystemDictionary::Thread_klass();
  43   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);
  44 
  45   const char* name = "Service Thread";
  46 
  47   Handle string = java_lang_String::create_from_str(name, CHECK);
  48 
  49   // Initialize thread_oop to put it into the system threadGroup
  50   Handle thread_group (THREAD, Universe::system_thread_group());
  51   JavaValue result(T_VOID);
  52   JavaCalls::call_special(&result, thread_oop,
  53                           klass,
  54                           vmSymbols::object_initializer_name(),
  55                           vmSymbols::threadgroup_string_void_signature(),
  56                           thread_group,
  57                           string,
  58                           CHECK);
  59 
  60   {
  61     MutexLocker mu(Threads_lock);
  62     ServiceThread* thread =  new ServiceThread(&service_thread_entry);
  63 
  64     // At this point it may be possible that no osthread was created for the
  65     // JavaThread due to lack of memory. We would have to throw an exception
  66     // in that case. However, since this must work and we do not allow
  67     // exceptions anyway, check and abort if this fails.
  68     if (thread == NULL || thread->osthread() == NULL) {
  69       vm_exit_during_initialization("java.lang.OutOfMemoryError",
  70                                     os::native_thread_creation_failed_msg());
  71     }
  72 
  73     java_lang_Thread::set_thread(thread_oop(), thread);
  74     java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
  75     java_lang_Thread::set_daemon(thread_oop());
  76     thread->set_threadObj(thread_oop());
  77     _instance = thread;
  78 
  79     Threads::add(thread);
  80     Thread::start(thread);
  81   }
  82 }
  83 
  84 void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {
  85   while (true) {
  86     bool sensors_changed = false;
  87     bool has_jvmti_events = false;
  88     bool has_gc_notification_event = false;
  89     bool has_dcmd_notification_event = false;
  90     bool acs_notify = false;
  91     JvmtiDeferredEvent jvmti_event;
  92     {
  93       // Need state transition ThreadBlockInVM so that this thread
  94       // will be handled by safepoint correctly when this thread is
  95       // notified at a safepoint.
  96 
  97       // This ThreadBlockInVM object is not also considered to be
  98       // suspend-equivalent because ServiceThread is not visible to
  99       // external suspension.
 100 
 101       ThreadBlockInVM tbivm(jt);
 102 
 103       MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
 104       while (!(sensors_changed = LowMemoryDetector::has_pending_requests()) &&
 105              !(has_jvmti_events = JvmtiDeferredEventQueue::has_events()) &&
 106               !(has_gc_notification_event = GCNotifier::has_event()) &&
 107               !(has_dcmd_notification_event = DCmdFactory::has_pending_jmx_notification())) {
 108         // wait until one of the sensors has pending requests, or there is a
 109         // pending JVMTI event or JMX GC notification to post
 110         Service_lock->wait(Mutex::_no_safepoint_check_flag);
 111       }
 112 
 113       if (has_jvmti_events) {
 114         jvmti_event = JvmtiDeferredEventQueue::dequeue();
 115       }
 116     }
 117 
 118     if (has_jvmti_events) {
 119       jvmti_event.post();
 120     }
 121 
 122     if (sensors_changed) {
 123       LowMemoryDetector::process_sensor_changes(jt);
 124     }
 125 
 126     if(has_gc_notification_event) {
 127         GCNotifier::sendNotification(CHECK);
 128     }
 129 
 130     if(has_dcmd_notification_event) {
 131       DCmdFactory::send_notification(CHECK);
 132     }
 133   }
 134 }
 135 
 136 bool ServiceThread::is_service_thread(Thread* thread) {
 137   return thread == _instance;
 138 }