kamg@2511: /*
kamg@2511:  * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
kamg@2511:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
kamg@2511:  *
kamg@2511:  * This code is free software; you can redistribute it and/or modify it
kamg@2511:  * under the terms of the GNU General Public License version 2 only, as
kamg@2511:  * published by the Free Software Foundation.
kamg@2511:  *
kamg@2511:  * This code is distributed in the hope that it will be useful, but WITHOUT
kamg@2511:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
kamg@2511:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
kamg@2511:  * version 2 for more details (a copy is included in the LICENSE file that
kamg@2511:  * accompanied this code).
kamg@2511:  *
kamg@2511:  * You should have received a copy of the GNU General Public License version
kamg@2511:  * 2 along with this work; if not, write to the Free Software Foundation,
kamg@2511:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
kamg@2511:  *
kamg@2511:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
kamg@2511:  * or visit www.oracle.com if you need additional information or have any
kamg@2511:  * questions.
kamg@2511:  *
kamg@2511:  */
kamg@2511: 
kamg@2511: #include "precompiled.hpp"
kamg@2511: #include "runtime/interfaceSupport.hpp"
kamg@2511: #include "runtime/javaCalls.hpp"
kamg@2511: #include "runtime/serviceThread.hpp"
kamg@2511: #include "runtime/mutexLocker.hpp"
kamg@2511: #include "prims/jvmtiImpl.hpp"
kamg@2511: 
kamg@2511: ServiceThread* ServiceThread::_instance = NULL;
kamg@2511: 
kamg@2511: void ServiceThread::initialize() {
kamg@2511:   EXCEPTION_MARK;
kamg@2511: 
kamg@2511:   instanceKlassHandle klass (THREAD,  SystemDictionary::Thread_klass());
kamg@2511:   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);
kamg@2511: 
kamg@2511:   const char* name = JDK_Version::is_gte_jdk17x_version() ?
kamg@2511:       "Service Thread" : "Low Memory Detector";
kamg@2511: 
kamg@2511:   Handle string = java_lang_String::create_from_str(name, CHECK);
kamg@2511: 
kamg@2511:   // Initialize thread_oop to put it into the system threadGroup
kamg@2511:   Handle thread_group (THREAD, Universe::system_thread_group());
kamg@2511:   JavaValue result(T_VOID);
kamg@2511:   JavaCalls::call_special(&result, thread_oop,
kamg@2511:                           klass,
kamg@2511:                           vmSymbols::object_initializer_name(),
kamg@2511:                           vmSymbols::threadgroup_string_void_signature(),
kamg@2511:                           thread_group,
kamg@2511:                           string,
kamg@2511:                           CHECK);
kamg@2511: 
kamg@2511:   {
kamg@2511:     MutexLocker mu(Threads_lock);
kamg@2511:     ServiceThread* thread =  new ServiceThread(&service_thread_entry);
kamg@2511: 
kamg@2511:     // At this point it may be possible that no osthread was created for the
kamg@2511:     // JavaThread due to lack of memory. We would have to throw an exception
kamg@2511:     // in that case. However, since this must work and we do not allow
kamg@2511:     // exceptions anyway, check and abort if this fails.
kamg@2511:     if (thread == NULL || thread->osthread() == NULL) {
kamg@2511:       vm_exit_during_initialization("java.lang.OutOfMemoryError",
kamg@2511:                                     "unable to create new native thread");
kamg@2511:     }
kamg@2511: 
kamg@2511:     java_lang_Thread::set_thread(thread_oop(), thread);
kamg@2511:     java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
kamg@2511:     java_lang_Thread::set_daemon(thread_oop());
kamg@2511:     thread->set_threadObj(thread_oop());
dcubed@2623:     _instance = thread;
kamg@2511: 
kamg@2511:     Threads::add(thread);
kamg@2511:     Thread::start(thread);
kamg@2511:   }
kamg@2511: }
kamg@2511: 
kamg@2511: void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {
kamg@2511:   while (true) {
kamg@2511:     bool sensors_changed = false;
kamg@2511:     bool has_jvmti_events = false;
kamg@2511:     JvmtiDeferredEvent jvmti_event;
kamg@2511:     {
kamg@2511:       // Need state transition ThreadBlockInVM so that this thread
kamg@2511:       // will be handled by safepoint correctly when this thread is
kamg@2511:       // notified at a safepoint.
kamg@2511: 
kamg@2511:       // This ThreadBlockInVM object is not also considered to be
kamg@2511:       // suspend-equivalent because ServiceThread is not visible to
kamg@2511:       // external suspension.
kamg@2511: 
kamg@2511:       ThreadBlockInVM tbivm(jt);
kamg@2511: 
kamg@2511:       MutexLockerEx ml(Service_lock, Mutex::_no_safepoint_check_flag);
kamg@2511:       while (!(sensors_changed = LowMemoryDetector::has_pending_requests()) &&
kamg@2511:              !(has_jvmti_events = JvmtiDeferredEventQueue::has_events())) {
kamg@2511:         // wait until one of the sensors has pending requests, or there is a
kamg@2511:         // pending JVMTI event to post
kamg@2511:         Service_lock->wait(Mutex::_no_safepoint_check_flag);
kamg@2511:       }
kamg@2511: 
kamg@2511:       if (has_jvmti_events) {
kamg@2511:         jvmti_event = JvmtiDeferredEventQueue::dequeue();
kamg@2511:       }
kamg@2511:     }
kamg@2511: 
kamg@2511:     if (has_jvmti_events) {
kamg@2511:       jvmti_event.post();
kamg@2511:     }
kamg@2511: 
kamg@2511:     if (sensors_changed) {
kamg@2511:       LowMemoryDetector::process_sensor_changes(jt);
kamg@2511:     }
kamg@2511:   }
kamg@2511: }
kamg@2511: 
kamg@2511: bool ServiceThread::is_service_thread(Thread* thread) {
kamg@2511:   return thread == _instance;
kamg@2511: }