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 void ServiceThread::initialize() { 33 EXCEPTION_MARK; 34 35 instanceKlassHandle klass (THREAD, SystemDictionary::Thread_klass()); 36 instanceHandle thread_oop = klass->allocate_instance_handle(CHECK); 37 38 const char thread_name[] = "Service Thread"; 39 Handle string = java_lang_String::create_from_str(thread_name, CHECK); 40 41 // Initialize thread_oop to put it into the system threadGroup 42 Handle thread_group (THREAD, Universe::system_thread_group()); 43 JavaValue result(T_VOID); 44 JavaCalls::call_special(&result, thread_oop, 45 klass, 46 vmSymbolHandles::object_initializer_name(), 47 vmSymbolHandles::threadgroup_string_void_signature(), 48 thread_group, 49 string, 50 CHECK); 51 52 { 53 MutexLocker mu(Threads_lock); 54 ServiceThread* thread = new ServiceThread(&service_thread_entry); 55 56 // At this point it may be possible that no osthread was created for the 57 // JavaThread due to lack of memory. We would have to throw an exception 58 // in that case. However, since this must work and we do not allow 59 // exceptions anyway, check and abort if this fails. 60 if (thread == NULL || thread->osthread() == NULL) { 61 vm_exit_during_initialization("java.lang.OutOfMemoryError", 62 "unable to create new native thread"); 63 } 64 65 java_lang_Thread::set_thread(thread_oop(), thread); 66 java_lang_Thread::set_priority(thread_oop(), NearMaxPriority); 67 java_lang_Thread::set_daemon(thread_oop()); 68 thread->set_threadObj(thread_oop()); 69 70 Threads::add(thread); 71 Thread::start(thread); 72 } 73 } 74 75 void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) { 76 while (true) { 77 bool sensors_changed = false; 78 bool has_jvmti_events = false; 79 JvmtiDeferredEvent jvmti_event = JvmtiDeferredEvent::null_event(); 80 { 81 // _no_safepoint_check_flag is used here as Service_lock is a 82 // special lock and the VMThread may acquire this lock at safepoint. 83 // Need state transition ThreadBlockInVM so that this thread 84 // will be handled by safepoint correctly when this thread is 85 // notified at a safepoint. 86 87 // This ThreadBlockInVM object is not also considered to be 88 // suspend-equivalent because ServiceThread is not visible to 89 // external suspension. 90 91 ThreadBlockInVM tbivm(jt); 92 93 MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag); 94 while (!(sensors_changed = LowMemoryDetector::has_pending_requests()) && 95 !(has_jvmti_events = JvmtiDeferredEventQueue::has_events())) { 96 // wait until one of the sensors has pending requests, or there is a 97 // pending JVMTI event to post 98 Service_lock->wait(Mutex::_no_safepoint_check_flag); 99 } 100 101 if (has_jvmti_events) { 102 // We dequeue the event here while holding Service_lock but post it 103 // after releasing the lock. 104 jvmti_event = JvmtiDeferredEventQueue::dequeue(); 105 } 106 } 107 108 if (sensors_changed) { 109 LowMemoryDetector::process_sensor_changes(jt); 110 } 111 112 if (has_jvmti_events) { 113 jvmti_event.post(); 114 } 115 } 116 }