1 /*
2 * Copyright (c) 2012, 2021, 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/classLoaderDataGraph.inline.hpp"
27 #include "classfile/javaClasses.hpp"
28 #include "classfile/protectionDomainCache.hpp"
29 #include "classfile/stringTable.hpp"
30 #include "classfile/symbolTable.hpp"
31 #include "classfile/systemDictionary.hpp"
32 #include "classfile/vmClasses.hpp"
33 #include "gc/shared/oopStorage.hpp"
34 #include "gc/shared/oopStorageSet.hpp"
35 #include "memory/universe.hpp"
36 #include "oops/oopHandle.inline.hpp"
37 #include "runtime/handles.inline.hpp"
38 #include "runtime/interfaceSupport.inline.hpp"
39 #include "runtime/java.hpp"
40 #include "runtime/javaCalls.hpp"
41 #include "runtime/jniHandles.hpp"
42 #include "runtime/serviceThread.hpp"
43 #include "runtime/mutexLocker.hpp"
44 #include "runtime/os.hpp"
45 #include "prims/jvmtiImpl.hpp"
46 #include "prims/jvmtiTagMap.hpp"
47 #include "prims/resolvedMethodTable.hpp"
48 #include "services/diagnosticArgument.hpp"
49 #include "services/diagnosticFramework.hpp"
50 #include "services/gcNotifier.hpp"
51 #include "services/lowMemoryDetector.hpp"
52 #include "services/threadIdTable.hpp"
53
54 ServiceThread* ServiceThread::_instance = NULL;
55 JvmtiDeferredEvent* ServiceThread::_jvmti_event = NULL;
56 // The service thread has it's own static deferred event queue.
57 // Events can be posted before JVMTI vm_start, so it's too early to call JvmtiThreadState::state_for
58 // to add this field to the per-JavaThread event queue. TODO: fix this sometime later
59 JvmtiDeferredEventQueue ServiceThread::_jvmti_service_queue;
60
61 // Defer releasing JavaThread OopHandle to the ServiceThread
62 class OopHandleList : public CHeapObj<mtInternal> {
63 OopHandle _handle;
64 OopHandleList* _next;
65 public:
OopHandleList(OopHandle h,OopHandleList * next)66 OopHandleList(OopHandle h, OopHandleList* next) : _handle(h), _next(next) {}
~OopHandleList()67 ~OopHandleList() {
68 _handle.release(JavaThread::thread_oop_storage());
69 }
next() const70 OopHandleList* next() const { return _next; }
71 };
72
73 static OopHandleList* _oop_handle_list = NULL;
74
release_oop_handles()75 static void release_oop_handles() {
76 OopHandleList* list;
77 {
78 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
79 list = _oop_handle_list;
80 _oop_handle_list = NULL;
81 }
82 assert(!SafepointSynchronize::is_at_safepoint(), "cannot be called at a safepoint");
83
84 while (list != NULL) {
85 OopHandleList* l = list;
86 list = l->next();
87 delete l;
88 }
89 }
90
initialize()91 void ServiceThread::initialize() {
92 EXCEPTION_MARK;
93
94 const char* name = "Service Thread";
95 Handle string = java_lang_String::create_from_str(name, CHECK);
96
97 // Initialize thread_oop to put it into the system threadGroup
98 Handle thread_group (THREAD, Universe::system_thread_group());
99 Handle thread_oop = JavaCalls::construct_new_instance(
100 vmClasses::Thread_klass(),
101 vmSymbols::threadgroup_string_void_signature(),
102 thread_group,
103 string,
104 CHECK);
105
106 {
107 MutexLocker mu(THREAD, Threads_lock);
108 ServiceThread* thread = new ServiceThread(&service_thread_entry);
109
110 // At this point it may be possible that no osthread was created for the
111 // JavaThread due to lack of memory. We would have to throw an exception
112 // in that case. However, since this must work and we do not allow
113 // exceptions anyway, check and abort if this fails.
114 if (thread == NULL || thread->osthread() == NULL) {
115 vm_exit_during_initialization("java.lang.OutOfMemoryError",
116 os::native_thread_creation_failed_msg());
117 }
118
119 java_lang_Thread::set_thread(thread_oop(), thread);
120 java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
121 java_lang_Thread::set_daemon(thread_oop());
122 thread->set_threadObj(thread_oop());
123 _instance = thread;
124
125 Threads::add(thread);
126 Thread::start(thread);
127 }
128 }
129
cleanup_oopstorages()130 static void cleanup_oopstorages() {
131 for (OopStorage* storage : OopStorageSet::Range<OopStorageSet::Id>()) {
132 storage->delete_empty_blocks();
133 }
134 }
135
service_thread_entry(JavaThread * jt,TRAPS)136 void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {
137 while (true) {
138 bool sensors_changed = false;
139 bool has_jvmti_events = false;
140 bool has_gc_notification_event = false;
141 bool has_dcmd_notification_event = false;
142 bool stringtable_work = false;
143 bool symboltable_work = false;
144 bool resolved_method_table_work = false;
145 bool thread_id_table_work = false;
146 bool protection_domain_table_work = false;
147 bool oopstorage_work = false;
148 JvmtiDeferredEvent jvmti_event;
149 bool oop_handles_to_release = false;
150 bool cldg_cleanup_work = false;
151 bool jvmti_tagmap_work = false;
152 {
153 // Need state transition ThreadBlockInVM so that this thread
154 // will be handled by safepoint correctly when this thread is
155 // notified at a safepoint.
156
157 // This ThreadBlockInVM object is not also considered to be
158 // suspend-equivalent because ServiceThread is not visible to
159 // external suspension.
160
161 ThreadBlockInVM tbivm(jt);
162
163 MonitorLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
164 // Process all available work on each (outer) iteration, rather than
165 // only the first recognized bit of work, to avoid frequently true early
166 // tests from potentially starving later work. Hence the use of
167 // arithmetic-or to combine results; we don't want short-circuiting.
168 while (((sensors_changed = (!UseNotificationThread && LowMemoryDetector::has_pending_requests())) |
169 (has_jvmti_events = _jvmti_service_queue.has_events()) |
170 (has_gc_notification_event = (!UseNotificationThread && GCNotifier::has_event())) |
171 (has_dcmd_notification_event = (!UseNotificationThread && DCmdFactory::has_pending_jmx_notification())) |
172 (stringtable_work = StringTable::has_work()) |
173 (symboltable_work = SymbolTable::has_work()) |
174 (resolved_method_table_work = ResolvedMethodTable::has_work()) |
175 (thread_id_table_work = ThreadIdTable::has_work()) |
176 (protection_domain_table_work = SystemDictionary::pd_cache_table()->has_work()) |
177 (oopstorage_work = OopStorage::has_cleanup_work_and_reset()) |
178 (oop_handles_to_release = (_oop_handle_list != NULL)) |
179 (cldg_cleanup_work = ClassLoaderDataGraph::should_clean_metaspaces_and_reset()) |
180 (jvmti_tagmap_work = JvmtiTagMap::has_object_free_events_and_reset())
181 ) == 0) {
182 // Wait until notified that there is some work to do.
183 ml.wait();
184 }
185
186 if (has_jvmti_events) {
187 // Get the event under the Service_lock
188 jvmti_event = _jvmti_service_queue.dequeue();
189 _jvmti_event = &jvmti_event;
190 }
191 }
192
193 if (stringtable_work) {
194 StringTable::do_concurrent_work(jt);
195 }
196
197 if (symboltable_work) {
198 SymbolTable::do_concurrent_work(jt);
199 }
200
201 if (has_jvmti_events) {
202 _jvmti_event->post();
203 _jvmti_event = NULL; // reset
204 }
205
206 if (!UseNotificationThread) {
207 if (sensors_changed) {
208 LowMemoryDetector::process_sensor_changes(jt);
209 }
210
211 if(has_gc_notification_event) {
212 GCNotifier::sendNotification(CHECK);
213 }
214
215 if(has_dcmd_notification_event) {
216 DCmdFactory::send_notification(CHECK);
217 }
218 }
219
220 if (resolved_method_table_work) {
221 ResolvedMethodTable::do_concurrent_work(jt);
222 }
223
224 if (thread_id_table_work) {
225 ThreadIdTable::do_concurrent_work(jt);
226 }
227
228 if (protection_domain_table_work) {
229 SystemDictionary::pd_cache_table()->unlink();
230 }
231
232 if (oopstorage_work) {
233 cleanup_oopstorages();
234 }
235
236 if (oop_handles_to_release) {
237 release_oop_handles();
238 }
239
240 if (cldg_cleanup_work) {
241 ClassLoaderDataGraph::safepoint_and_clean_metaspaces();
242 }
243
244 if (jvmti_tagmap_work) {
245 JvmtiTagMap::flush_all_object_free_events();
246 }
247 }
248 }
249
enqueue_deferred_event(JvmtiDeferredEvent * event)250 void ServiceThread::enqueue_deferred_event(JvmtiDeferredEvent* event) {
251 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
252 // If you enqueue events before the service thread runs, gc and the sweeper
253 // cannot keep the nmethod alive. This could be restricted to compiled method
254 // load and unload events, if we wanted to be picky.
255 assert(_instance != NULL, "cannot enqueue events before the service thread runs");
256 _jvmti_service_queue.enqueue(*event);
257 Service_lock->notify_all();
258 }
259
oops_do_no_frames(OopClosure * f,CodeBlobClosure * cf)260 void ServiceThread::oops_do_no_frames(OopClosure* f, CodeBlobClosure* cf) {
261 JavaThread::oops_do_no_frames(f, cf);
262 // The ServiceThread "owns" the JVMTI Deferred events, scan them here
263 // to keep them alive until they are processed.
264 if (_jvmti_event != NULL) {
265 _jvmti_event->oops_do(f, cf);
266 }
267 // Requires a lock, because threads can be adding to this queue.
268 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
269 _jvmti_service_queue.oops_do(f, cf);
270 }
271
nmethods_do(CodeBlobClosure * cf)272 void ServiceThread::nmethods_do(CodeBlobClosure* cf) {
273 JavaThread::nmethods_do(cf);
274 if (cf != NULL) {
275 if (_jvmti_event != NULL) {
276 _jvmti_event->nmethods_do(cf);
277 }
278 // Requires a lock, because threads can be adding to this queue.
279 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
280 _jvmti_service_queue.nmethods_do(cf);
281 }
282 }
283
add_oop_handle_release(OopHandle handle)284 void ServiceThread::add_oop_handle_release(OopHandle handle) {
285 MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
286 OopHandleList* new_head = new OopHandleList(handle, _oop_handle_list);
287 _oop_handle_list = new_head;
288 Service_lock->notify_all();
289 }
290