1 /*
   2  * Copyright (c) 2012, 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 "classfile/protectionDomainCache.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "memory/universe.hpp"
  31 #include "runtime/handles.inline.hpp"
  32 #include "runtime/interfaceSupport.inline.hpp"
  33 #include "runtime/javaCalls.hpp"
  34 #include "runtime/jniHandles.hpp"
  35 #include "runtime/serviceThread.hpp"
  36 #include "runtime/mutexLocker.hpp"
  37 #include "runtime/os.hpp"
  38 #include "prims/jvmtiImpl.hpp"
  39 #include "prims/resolvedMethodTable.hpp"
  40 #include "services/diagnosticArgument.hpp"
  41 #include "services/diagnosticFramework.hpp"
  42 #include "services/gcNotifier.hpp"
  43 #include "services/lowMemoryDetector.hpp"
  44 
  45 ServiceThread* ServiceThread::_instance = NULL;
  46 
  47 void ServiceThread::initialize() {
  48   EXCEPTION_MARK;
  49 
  50   const char* name = "Service Thread";
  51   Handle string = java_lang_String::create_from_str(name, CHECK);
  52 
  53   // Initialize thread_oop to put it into the system threadGroup
  54   Handle thread_group (THREAD, Universe::system_thread_group());
  55   Handle thread_oop = JavaCalls::construct_new_instance(
  56                           SystemDictionary::Thread_klass(),
  57                           vmSymbols::threadgroup_string_void_signature(),
  58                           thread_group,
  59                           string,
  60                           CHECK);
  61 
  62   {
  63     MutexLocker mu(Threads_lock);
  64     ServiceThread* thread =  new ServiceThread(&service_thread_entry);
  65 
  66     // At this point it may be possible that no osthread was created for the
  67     // JavaThread due to lack of memory. We would have to throw an exception
  68     // in that case. However, since this must work and we do not allow
  69     // exceptions anyway, check and abort if this fails.
  70     if (thread == NULL || thread->osthread() == NULL) {
  71       vm_exit_during_initialization("java.lang.OutOfMemoryError",
  72                                     os::native_thread_creation_failed_msg());
  73     }
  74 
  75     java_lang_Thread::set_thread(thread_oop(), thread);
  76     java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
  77     java_lang_Thread::set_daemon(thread_oop());
  78     thread->set_threadObj(thread_oop());
  79     _instance = thread;
  80 
  81     Threads::add(thread);
  82     Thread::start(thread);
  83   }
  84 }
  85 
  86 static void cleanup_oopstorages(OopStorage* const* storages, size_t size) {
  87   for (size_t i = 0; i < size; ++i) {
  88     storages[i]->delete_empty_blocks();
  89   }
  90 }
  91 
  92 void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {
  93   OopStorage* const oopstorages[] = {
  94     JNIHandles::global_handles(),
  95     JNIHandles::weak_global_handles(),
  96     StringTable::weak_storage(),
  97     SystemDictionary::vm_weak_oop_storage()
  98   };
  99   const size_t oopstorage_count = ARRAY_SIZE(oopstorages);
 100 
 101   while (true) {
 102     bool sensors_changed = false;
 103     bool has_jvmti_events = false;
 104     bool has_gc_notification_event = false;
 105     bool has_dcmd_notification_event = false;
 106     bool stringtable_work = false;
 107     bool symboltable_work = false;
 108     bool resolved_method_table_work = false;
 109     bool protection_domain_table_work = false;
 110     bool oopstorage_work = false;
 111     bool deflate_idle_monitors = false;
 112     JvmtiDeferredEvent jvmti_event;
 113     {
 114       // Need state transition ThreadBlockInVM so that this thread
 115       // will be handled by safepoint correctly when this thread is
 116       // notified at a safepoint.
 117 
 118       // This ThreadBlockInVM object is not also considered to be
 119       // suspend-equivalent because ServiceThread is not visible to
 120       // external suspension.
 121 
 122       ThreadBlockInVM tbivm(jt);
 123 
 124       MonitorLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
 125       // Process all available work on each (outer) iteration, rather than
 126       // only the first recognized bit of work, to avoid frequently true early
 127       // tests from potentially starving later work.  Hence the use of
 128       // arithmetic-or to combine results; we don't want short-circuiting.
 129       while (((sensors_changed = LowMemoryDetector::has_pending_requests()) |
 130               (has_jvmti_events = JvmtiDeferredEventQueue::has_events()) |
 131               (has_gc_notification_event = GCNotifier::has_event()) |
 132               (has_dcmd_notification_event = DCmdFactory::has_pending_jmx_notification()) |
 133               (stringtable_work = StringTable::has_work()) |
 134               (symboltable_work = SymbolTable::has_work()) |
 135               (resolved_method_table_work = ResolvedMethodTable::has_work()) |
 136               (protection_domain_table_work = SystemDictionary::pd_cache_table()->has_work()) |
 137               (oopstorage_work = OopStorage::has_cleanup_work_and_reset()) |
 138               (deflate_idle_monitors = ObjectSynchronizer::is_async_deflation_needed())
 139              ) == 0) {
 140         // Wait until notified that there is some work to do.
 141         // If AsyncDeflateIdleMonitors, then we wait for
 142         // GuaranteedSafepointInterval so that is_async_deflation_needed()
 143         // is checked at the same interval.
 144         ml.wait(AsyncDeflateIdleMonitors ? GuaranteedSafepointInterval : 0);
 145       }
 146 
 147       if (has_jvmti_events) {
 148         jvmti_event = JvmtiDeferredEventQueue::dequeue();
 149       }
 150     }
 151 
 152     if (stringtable_work) {
 153       StringTable::do_concurrent_work(jt);
 154     }
 155 
 156     if (symboltable_work) {
 157       SymbolTable::do_concurrent_work(jt);
 158     }
 159 
 160     if (has_jvmti_events) {
 161       jvmti_event.post();
 162     }
 163 
 164     if (sensors_changed) {
 165       LowMemoryDetector::process_sensor_changes(jt);
 166     }
 167 
 168     if(has_gc_notification_event) {
 169       GCNotifier::sendNotification(CHECK);
 170     }
 171 
 172     if(has_dcmd_notification_event) {
 173       DCmdFactory::send_notification(CHECK);
 174     }
 175 
 176     if (resolved_method_table_work) {
 177       ResolvedMethodTable::do_concurrent_work(jt);
 178     }
 179 
 180     if (protection_domain_table_work) {
 181       SystemDictionary::pd_cache_table()->unlink();
 182     }
 183 
 184     if (oopstorage_work) {
 185       cleanup_oopstorages(oopstorages, oopstorage_count);
 186     }
 187 
 188     if (deflate_idle_monitors) {
 189       // Deflate any global idle monitors.
 190       ObjectSynchronizer::deflate_global_idle_monitors_using_JT();
 191 
 192       // deflate_per_thread_idle_monitors_using_JT() is called by
 193       // each JavaThread from ObjectSynchronizer::omAlloc() as needed.
 194       int count = 0;
 195       for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
 196         if (jt->omInUseCount > 0) {
 197           // This JavaThread is using monitors so mark it.
 198           jt->omShouldDeflateIdleMonitors = true;
 199           count++;
 200         }
 201       }
 202       if (count > 0) {
 203         log_debug(monitorinflation)("requesting async deflation of idle monitors for %d thread(s).", count);
 204       }
 205       // The ServiceThread's async deflation request has been processed.
 206       ObjectSynchronizer::set_is_async_deflation_requested(false);
 207 
 208       // The global in-use list was handled above, but the request won't
 209       // be complete until the JavaThreads have handled their in-use
 210       // lists. This is the nature of an async deflation request.
 211     }
 212   }
 213 }
 214 
 215 bool ServiceThread::is_service_thread(Thread* thread) {
 216   return thread == _instance;
 217 }