1 /* 2 * Copyright (c) 2011, 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.hpp" 27 #include "runtime/javaCalls.hpp" 28 #include "runtime/serviceThread.hpp" 29 #include "runtime/mutexLocker.hpp" 30 #include "prims/jvmtiImpl.hpp" 31 32 ServiceThread* ServiceThread::_instance = NULL; 33 34 void ServiceThread::initialize() { 35 EXCEPTION_MARK; 36 37 instanceKlassHandle klass (THREAD, SystemDictionary::Thread_klass()); 38 instanceHandle thread_oop = klass->allocate_instance_handle(CHECK); 39 40 const char* name = JDK_Version::is_gte_jdk17x_version() ? 41 "Service Thread" : "Low Memory Detector"; 42 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 JavaValue result(T_VOID); 48 JavaCalls::call_special(&result, thread_oop, 49 klass, 50 vmSymbols::object_initializer_name(), 51 vmSymbols::threadgroup_string_void_signature(), 52 thread_group, 53 string, 54 CHECK); 55 56 { 57 MutexLocker mu(Threads_lock); 58 ServiceThread* thread = new ServiceThread(&service_thread_entry); 59 60 // At this point it may be possible that no osthread was created for the 61 // JavaThread due to lack of memory. We would have to throw an exception 62 // in that case. However, since this must work and we do not allow 63 // exceptions anyway, check and abort if this fails. 64 if (thread == NULL || thread->osthread() == NULL) { 65 vm_exit_during_initialization("java.lang.OutOfMemoryError", 66 "unable to create new native thread"); 67 } 68 69 java_lang_Thread::set_thread(thread_oop(), thread); 70 java_lang_Thread::set_priority(thread_oop(), NearMaxPriority); 71 java_lang_Thread::set_daemon(thread_oop()); 72 thread->set_threadObj(thread_oop()); 73 74 Threads::add(thread); 75 Thread::start(thread); 76 77 _instance = thread; 78 } 79 } 80 81 void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) { 82 while (true) { 83 bool sensors_changed = false; 84 bool has_jvmti_events = 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 // wait until one of the sensors has pending requests, or there is a 101 // pending JVMTI event to post 102 Service_lock->wait(Mutex::_no_safepoint_check_flag); 103 } 104 105 if (has_jvmti_events) { 106 jvmti_event = JvmtiDeferredEventQueue::dequeue(); 107 } 108 } 109 110 if (has_jvmti_events) { 111 jvmti_event.post(); 112 } 113 114 if (sensors_changed) { 115 LowMemoryDetector::process_sensor_changes(jt); 116 } 117 } 118 } 119 120 bool ServiceThread::is_service_thread(Thread* thread) { 121 return thread == _instance; 122 }