1 /*
   2  * Copyright (c) 2019, 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 "memory/universe.hpp"
  27 #include "runtime/interfaceSupport.inline.hpp"
  28 #include "runtime/javaCalls.hpp"
  29 #include "runtime/notificationThread.hpp"
  30 #include "services/diagnosticArgument.hpp"
  31 #include "services/diagnosticFramework.hpp"
  32 #include "services/gcNotifier.hpp"
  33 #include "services/lowMemoryDetector.hpp"
  34 
  35 NotificationThread* NotificationThread::_instance = NULL;
  36 
  37 void NotificationThread::initialize() {
  38   EXCEPTION_MARK;
  39 
  40   const char* name = "Notification Thread";
  41   Handle string = java_lang_String::create_from_str(name, CHECK);
  42 
  43   // Initialize thread_oop to put it into the system threadGroup
  44   Handle thread_group (THREAD, Universe::system_thread_group());
  45   Handle thread_oop = JavaCalls::construct_new_instance(
  46                           SystemDictionary::Thread_klass(),
  47                           vmSymbols::threadgroup_string_void_signature(),
  48                           thread_group,
  49                           string,
  50                           CHECK);
  51   
  52   Klass* group = SystemDictionary::ThreadGroup_klass();
  53   JavaValue result(T_VOID);
  54   JavaCalls::call_special(&result,
  55                           thread_group,
  56                           group,
  57                           vmSymbols::add_method_name(),
  58                           vmSymbols::thread_void_signature(),
  59                           thread_oop,
  60                           THREAD);
  61   {
  62     MutexLocker mu(Threads_lock);
  63     NotificationThread* thread =  new NotificationThread(&notification_thread_entry);
  64 
  65     // At this point it may be possible that no osthread was created for the
  66     // JavaThread due to lack of memory. We would have to throw an exception
  67     // in that case. However, since this must work and we do not allow
  68     // exceptions anyway, check and abort if this fails.
  69     if (thread == NULL || thread->osthread() == NULL) {
  70       vm_exit_during_initialization("java.lang.OutOfMemoryError",
  71                                     os::native_thread_creation_failed_msg());
  72     }
  73 
  74     java_lang_Thread::set_thread(thread_oop(), thread);
  75     java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
  76     java_lang_Thread::set_daemon(thread_oop());
  77     thread->set_threadObj(thread_oop());
  78     _instance = thread;
  79 
  80     Threads::add(thread);
  81     Thread::start(thread);
  82   }
  83 }
  84 
  85 
  86 
  87 void NotificationThread::notification_thread_entry(JavaThread* jt, TRAPS) {
  88   while (true) {
  89     bool sensors_changed = false;
  90     bool has_dcmd_notification_event = false;
  91     bool has_gc_notification_event = false;
  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       ThreadBlockInVM tbivm(jt);
  98 
  99       MonitorLocker ml(Notification_lock, Mutex::_no_safepoint_check_flag);
 100       // Process all available work on each (outer) iteration, rather than
 101       // only the first recognized bit of work, to avoid frequently true early
 102       // tests from potentially starving later work.  Hence the use of
 103       // arithmetic-or to combine results; we don't want short-circuiting.
 104       while (((sensors_changed = LowMemoryDetector::has_pending_requests()) |
 105               (has_dcmd_notification_event = DCmdFactory::has_pending_jmx_notification()) |
 106               (has_gc_notification_event = GCNotifier::has_event()))
 107              == 0) {
 108         // Wait until notified that there is some work to do.
 109         ml.wait();
 110       }
 111 
 112     }
 113 
 114     if (sensors_changed) {
 115       LowMemoryDetector::process_sensor_changes(jt);
 116     }
 117         
 118     if(has_gc_notification_event) {
 119       GCNotifier::sendNotification(CHECK);
 120     }
 121     
 122     if(has_dcmd_notification_event) {
 123       DCmdFactory::send_notification(CHECK);
 124     }
 125 
 126   }
 127 }
 128