1 /*
2 * Copyright (c) 2003, 2009, 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 class OopClosure;
26 class ThreadDumpResult;
27 class ThreadStackTrace;
28 class ThreadSnapshot;
29 class StackFrameInfo;
30 class ThreadConcurrentLocks;
31 class DeadlockCycle;
32
33 // VM monitoring and management support for the thread and
34 // synchronization subsystem
35 //
36 // Thread contention monitoring is disabled by default.
37 // When enabled, the VM will begin measuring the accumulated
38 // elapsed time a thread blocked on synchronization.
39 //
40 class ThreadService : public AllStatic {
41 private:
42 // These counters could be moved to Threads class
43 static PerfCounter* _total_threads_count;
44 static PerfVariable* _live_threads_count;
45 static PerfVariable* _peak_threads_count;
46 static PerfVariable* _daemon_threads_count;
47
48 // These 2 counters are atomically incremented once the thread is exiting.
49 // They will be atomically decremented when ThreadService::remove_thread is called.
50 static volatile int _exiting_threads_count;
51 static volatile int _exiting_daemon_threads_count;
52
53 static bool _thread_monitoring_contention_enabled;
54 static bool _thread_cpu_time_enabled;
55
56 // Need to keep the list of thread dump result that
57 // keep references to methodOop since thread dump can be
58 // requested by multiple threads concurrently.
59 static ThreadDumpResult* _threaddump_list;
60
61 public:
62 static void init();
63 static void add_thread(JavaThread* thread, bool daemon);
64 static void remove_thread(JavaThread* thread, bool daemon);
65 static void current_thread_exiting(JavaThread* jt);
66
67 static bool set_thread_monitoring_contention(bool flag);
68 static bool is_thread_monitoring_contention() { return _thread_monitoring_contention_enabled; }
69
70 static bool set_thread_cpu_time_enabled(bool flag);
71 static bool is_thread_cpu_time_enabled() { return _thread_cpu_time_enabled; }
72
73 static jlong get_total_thread_count() { return _total_threads_count->get_value(); }
74 static jlong get_peak_thread_count() { return _peak_threads_count->get_value(); }
75 static jlong get_live_thread_count() { return _live_threads_count->get_value() - _exiting_threads_count; }
76 static jlong get_daemon_thread_count() { return _daemon_threads_count->get_value() - _exiting_daemon_threads_count; }
77
78 static int exiting_threads_count() { return _exiting_threads_count; }
79 static int exiting_daemon_threads_count() { return _exiting_daemon_threads_count; }
80
81 // Support for thread dump
82 static void add_thread_dump(ThreadDumpResult* dump);
83 static void remove_thread_dump(ThreadDumpResult* dump);
84
85 static Handle get_current_contended_monitor(JavaThread* thread);
86
87 // This function is called by JVM_DumpThreads.
88 static Handle dump_stack_traces(GrowableArray<instanceHandle>* threads,
89 int num_threads, TRAPS);
90
91 static void reset_peak_thread_count();
92 static void reset_contention_count_stat(JavaThread* thread);
93 static void reset_contention_time_stat(JavaThread* thread);
94
95 static DeadlockCycle* find_deadlocks_at_safepoint(bool object_monitors_only);
96
97 // GC support
98 static void oops_do(OopClosure* f);
99 };
100
101 // Per-thread Statistics for synchronization
102 class ThreadStatistics : public CHeapObj {
103 private:
104 // The following contention statistics are only updated by
105 // the thread owning these statistics when contention occurs.
106
107 jlong _contended_enter_count;
108 elapsedTimer _contended_enter_timer;
109 jlong _monitor_wait_count;
110 elapsedTimer _monitor_wait_timer;
111 jlong _sleep_count;
112 elapsedTimer _sleep_timer;
113
114
115 // These two reset flags are set to true when another thread
116 // requests to reset the statistics. The actual statistics
117 // are reset when the thread contention occurs and attempts
118 // to update the statistics.
119 bool _count_pending_reset;
120 bool _timer_pending_reset;
121
122 // Keep accurate times for potentially recursive class operations
123 int _perf_recursion_counts[6];
124 elapsedTimer _perf_timers[6];
125
126 // utility functions
127 void check_and_reset_count() {
128 if (!_count_pending_reset) return;
129 _contended_enter_count = 0;
130 _monitor_wait_count = 0;
131 _sleep_count = 0;
132 _count_pending_reset = 0;
133 }
134 void check_and_reset_timer() {
135 if (!_timer_pending_reset) return;
136 _contended_enter_timer.reset();
137 _monitor_wait_timer.reset();
138 _sleep_timer.reset();
139 _timer_pending_reset = 0;
140 }
141
142 public:
143 ThreadStatistics();
144
145 jlong contended_enter_count() { return (_count_pending_reset ? 0 : _contended_enter_count); }
146 jlong contended_enter_ticks() { return (_timer_pending_reset ? 0 : _contended_enter_timer.active_ticks()); }
147 jlong monitor_wait_count() { return (_count_pending_reset ? 0 : _monitor_wait_count); }
148 jlong monitor_wait_ticks() { return (_timer_pending_reset ? 0 : _monitor_wait_timer.active_ticks()); }
149 jlong sleep_count() { return (_count_pending_reset ? 0 : _sleep_count); }
150 jlong sleep_ticks() { return (_timer_pending_reset ? 0 : _sleep_timer.active_ticks()); }
151
152 void monitor_wait() { check_and_reset_count(); _monitor_wait_count++; }
153 void monitor_wait_begin() { check_and_reset_timer(); _monitor_wait_timer.start(); }
154 void monitor_wait_end() { _monitor_wait_timer.stop(); check_and_reset_timer(); }
155
156 void thread_sleep() { check_and_reset_count(); _sleep_count++; }
157 void thread_sleep_begin() { check_and_reset_timer(); _sleep_timer.start(); }
158 void thread_sleep_end() { _sleep_timer.stop(); check_and_reset_timer(); }
159
160 void contended_enter() { check_and_reset_count(); _contended_enter_count++; }
161 void contended_enter_begin() { check_and_reset_timer(); _contended_enter_timer.start(); }
162 void contended_enter_end() { _contended_enter_timer.stop(); check_and_reset_timer(); }
163
164 void reset_count_stat() { _count_pending_reset = true; }
165 void reset_time_stat() { _timer_pending_reset = true; }
166
167 int* perf_recursion_counts_addr() { return _perf_recursion_counts; }
168 elapsedTimer* perf_timers_addr() { return _perf_timers; }
169 };
170
171 // Thread snapshot to represent the thread state and statistics
172 class ThreadSnapshot : public CHeapObj {
173 private:
174 JavaThread* _thread;
175 oop _threadObj;
176 java_lang_Thread::ThreadStatus _thread_status;
177
178 bool _is_ext_suspended;
179 bool _is_in_native;
180
181 jlong _contended_enter_ticks;
182 jlong _contended_enter_count;
183 jlong _monitor_wait_ticks;
184 jlong _monitor_wait_count;
185 jlong _sleep_ticks;
186 jlong _sleep_count;
187 oop _blocker_object;
188 oop _blocker_object_owner;
189
190 ThreadStackTrace* _stack_trace;
191 ThreadConcurrentLocks* _concurrent_locks;
192 ThreadSnapshot* _next;
193
194 public:
195 // Dummy snapshot
196 ThreadSnapshot() : _thread(NULL), _threadObj(NULL), _stack_trace(NULL), _concurrent_locks(NULL), _next(NULL),
197 _blocker_object(NULL), _blocker_object_owner(NULL) {};
198 ThreadSnapshot(JavaThread* thread);
199 ~ThreadSnapshot();
200
201 java_lang_Thread::ThreadStatus thread_status() { return _thread_status; }
202
203 oop threadObj() const { return _threadObj; }
204
205 void set_next(ThreadSnapshot* n) { _next = n; }
206
207 bool is_ext_suspended() { return _is_ext_suspended; }
208 bool is_in_native() { return _is_in_native; }
209
210 jlong contended_enter_count() { return _contended_enter_count; }
211 jlong contended_enter_ticks() { return _contended_enter_ticks; }
212 jlong monitor_wait_count() { return _monitor_wait_count; }
213 jlong monitor_wait_ticks() { return _monitor_wait_ticks; }
214 jlong sleep_count() { return _sleep_count; }
215 jlong sleep_ticks() { return _sleep_ticks; }
216
217
218 oop blocker_object() { return _blocker_object; }
219 oop blocker_object_owner() { return _blocker_object_owner; }
220
221 ThreadSnapshot* next() const { return _next; }
222 ThreadStackTrace* get_stack_trace() { return _stack_trace; }
223 ThreadConcurrentLocks* get_concurrent_locks() { return _concurrent_locks; }
224
225 void dump_stack_at_safepoint(int max_depth, bool with_locked_monitors);
226 void set_concurrent_locks(ThreadConcurrentLocks* l) { _concurrent_locks = l; }
227 void oops_do(OopClosure* f);
228 };
229
230 class ThreadStackTrace : public CHeapObj {
231 private:
232 JavaThread* _thread;
233 int _depth; // number of stack frames added
234 bool _with_locked_monitors;
235 GrowableArray<StackFrameInfo*>* _frames;
236 GrowableArray<oop>* _jni_locked_monitors;
237
238 public:
239
240 ThreadStackTrace(JavaThread* thread, bool with_locked_monitors);
241 ~ThreadStackTrace();
242
243 JavaThread* thread() { return _thread; }
244 StackFrameInfo* stack_frame_at(int i) { return _frames->at(i); }
245 int get_stack_depth() { return _depth; }
246
247 void add_stack_frame(javaVFrame* jvf);
248 void dump_stack_at_safepoint(int max_depth);
249 Handle allocate_fill_stack_trace_element_array(TRAPS);
250 void oops_do(OopClosure* f);
251 GrowableArray<oop>* jni_locked_monitors() { return _jni_locked_monitors; }
252 int num_jni_locked_monitors() { return (_jni_locked_monitors != NULL ? _jni_locked_monitors->length() : 0); }
253
254 bool is_owned_monitor_on_stack(oop object);
255 void add_jni_locked_monitor(oop object) { _jni_locked_monitors->append(object); }
256 };
257
258 // StackFrameInfo for keeping methodOop and bci during
259 // stack walking for later construction of StackTraceElement[]
260 // Java instances
261 class StackFrameInfo : public CHeapObj {
262 private:
263 methodOop _method;
264 int _bci;
265 GrowableArray<oop>* _locked_monitors; // list of object monitors locked by this frame
266
267 public:
268
269 StackFrameInfo(javaVFrame* jvf, bool with_locked_monitors);
270 ~StackFrameInfo() {
271 if (_locked_monitors != NULL) {
272 delete _locked_monitors;
273 }
274 };
275 methodOop method() const { return _method; }
276 int bci() const { return _bci; }
277 void oops_do(OopClosure* f);
278
279 int num_locked_monitors() { return (_locked_monitors != NULL ? _locked_monitors->length() : 0); }
280 GrowableArray<oop>* locked_monitors() { return _locked_monitors; }
281
282 void print_on(outputStream* st) const;
283 };
284
285 class ThreadConcurrentLocks : public CHeapObj {
286 private:
287 GrowableArray<instanceOop>* _owned_locks;
288 ThreadConcurrentLocks* _next;
289 JavaThread* _thread;
290 public:
291 ThreadConcurrentLocks(JavaThread* thread);
292 ~ThreadConcurrentLocks();
293
294 void add_lock(instanceOop o);
295 void set_next(ThreadConcurrentLocks* n) { _next = n; }
296 ThreadConcurrentLocks* next() { return _next; }
297 JavaThread* java_thread() { return _thread; }
298 GrowableArray<instanceOop>* owned_locks() { return _owned_locks; }
299 void oops_do(OopClosure* f);
300 };
301
302 class ConcurrentLocksDump : public StackObj {
303 private:
304 ThreadConcurrentLocks* _map;
305 ThreadConcurrentLocks* _last; // Last ThreadConcurrentLocks in the map
306 bool _retain_map_on_free;
307
308 void build_map(GrowableArray<oop>* aos_objects);
309 void add_lock(JavaThread* thread, instanceOop o);
310
311 public:
312 ConcurrentLocksDump(bool retain_map_on_free) : _map(NULL), _last(NULL), _retain_map_on_free(retain_map_on_free) {};
313 ConcurrentLocksDump() : _map(NULL), _last(NULL), _retain_map_on_free(false) {};
314 ~ConcurrentLocksDump();
315
316 void dump_at_safepoint();
317 ThreadConcurrentLocks* thread_concurrent_locks(JavaThread* thread);
318 void print_locks_on(JavaThread* t, outputStream* st);
319 };
320
321 class ThreadDumpResult : public StackObj {
322 private:
323 int _num_threads;
324 int _num_snapshots;
325 ThreadSnapshot* _snapshots;
326 ThreadSnapshot* _last;
327 ThreadDumpResult* _next;
328 public:
329 ThreadDumpResult();
330 ThreadDumpResult(int num_threads);
331 ~ThreadDumpResult();
332
333 void add_thread_snapshot(ThreadSnapshot* ts);
334 void set_next(ThreadDumpResult* next) { _next = next; }
335 ThreadDumpResult* next() { return _next; }
336 int num_threads() { return _num_threads; }
337 int num_snapshots() { return _num_snapshots; }
338 ThreadSnapshot* snapshots() { return _snapshots; }
339 void oops_do(OopClosure* f);
340 };
341
342 class DeadlockCycle : public CHeapObj {
343 private:
344 bool _is_deadlock;
345 GrowableArray<JavaThread*>* _threads;
346 DeadlockCycle* _next;
347 public:
348 DeadlockCycle();
349 ~DeadlockCycle();
350
351 DeadlockCycle* next() { return _next; }
352 void set_next(DeadlockCycle* d) { _next = d; }
353 void add_thread(JavaThread* t) { _threads->append(t); }
354 void reset() { _is_deadlock = false; _threads->clear(); }
355 void set_deadlock(bool value) { _is_deadlock = value; }
356 bool is_deadlock() { return _is_deadlock; }
357 int num_threads() { return _threads->length(); }
358 GrowableArray<JavaThread*>* threads() { return _threads; }
359 void print_on(outputStream* st) const;
360 };
361
362 // Utility class to get list of java threads.
363 class ThreadsListEnumerator : public StackObj {
364 private:
365 GrowableArray<instanceHandle>* _threads_array;
366 public:
367 ThreadsListEnumerator(Thread* cur_thread,
368 bool include_jvmti_agent_threads = false,
369 bool include_jni_attaching_threads = true);
370 int num_threads() { return _threads_array->length(); }
371 instanceHandle get_threadObj(int index) { return _threads_array->at(index); }
372 };
373
374
375 // abstract utility class to set new thread states, and restore previous after the block exits
376 class JavaThreadStatusChanger : public StackObj {
377 private:
378 java_lang_Thread::ThreadStatus _old_state;
379 JavaThread* _java_thread;
380 bool _is_alive;
381
382 void save_old_state(JavaThread* java_thread) {
383 _java_thread = java_thread;
384 _is_alive = is_alive(java_thread);
385 if (is_alive()) {
386 _old_state = java_lang_Thread::get_thread_status(_java_thread->threadObj());
387 }
388 }
389
390 public:
391 static void set_thread_status(JavaThread* java_thread,
392 java_lang_Thread::ThreadStatus state) {
393 java_lang_Thread::set_thread_status(java_thread->threadObj(), state);
394 }
395
396 void set_thread_status(java_lang_Thread::ThreadStatus state) {
397 if (is_alive()) {
398 set_thread_status(_java_thread, state);
399 }
400 }
401
402 JavaThreadStatusChanger(JavaThread* java_thread,
403 java_lang_Thread::ThreadStatus state) {
404 save_old_state(java_thread);
405 set_thread_status(state);
406 }
407
408 JavaThreadStatusChanger(JavaThread* java_thread) {
409 save_old_state(java_thread);
410 }
411
412 ~JavaThreadStatusChanger() {
413 set_thread_status(_old_state);
414 }
415
416 static bool is_alive(JavaThread* java_thread) {
417 return java_thread != NULL && java_thread->threadObj() != NULL;
418 }
419
420 bool is_alive() {
421 return _is_alive;
422 }
423 };
424
425 // Change status to waiting on an object (timed or indefinite)
426 class JavaThreadInObjectWaitState : public JavaThreadStatusChanger {
427 private:
428 ThreadStatistics* _stat;
429 bool _active;
430
431 public:
432 JavaThreadInObjectWaitState(JavaThread *java_thread, bool timed) :
433 JavaThreadStatusChanger(java_thread,
434 timed ? java_lang_Thread::IN_OBJECT_WAIT_TIMED : java_lang_Thread::IN_OBJECT_WAIT) {
435 if (is_alive()) {
436 _stat = java_thread->get_thread_stat();
437 _active = ThreadService::is_thread_monitoring_contention();
438 _stat->monitor_wait();
439 if (_active) {
440 _stat->monitor_wait_begin();
441 }
442 } else {
443 _active = false;
444 }
445 }
446
447 ~JavaThreadInObjectWaitState() {
448 if (_active) {
449 _stat->monitor_wait_end();
450 }
451 }
452 };
453
454 // Change status to parked (timed or indefinite)
455 class JavaThreadParkedState : public JavaThreadStatusChanger {
456 private:
457 ThreadStatistics* _stat;
458 bool _active;
459
460 public:
461 JavaThreadParkedState(JavaThread *java_thread, bool timed) :
462 JavaThreadStatusChanger(java_thread,
463 timed ? java_lang_Thread::PARKED_TIMED : java_lang_Thread::PARKED) {
464 if (is_alive()) {
465 _stat = java_thread->get_thread_stat();
466 _active = ThreadService::is_thread_monitoring_contention();
467 _stat->monitor_wait();
468 if (_active) {
469 _stat->monitor_wait_begin();
470 }
471 } else {
472 _active = false;
473 }
474 }
475
476 ~JavaThreadParkedState() {
477 if (_active) {
478 _stat->monitor_wait_end();
479 }
480 }
481 };
482
483 // Change status to blocked on (re-)entering a synchronization block
484 class JavaThreadBlockedOnMonitorEnterState : public JavaThreadStatusChanger {
485 private:
486 ThreadStatistics* _stat;
487 bool _active;
488
489 static bool contended_enter_begin(JavaThread *java_thread) {
490 set_thread_status(java_thread, java_lang_Thread::BLOCKED_ON_MONITOR_ENTER);
491 ThreadStatistics* stat = java_thread->get_thread_stat();
492 stat->contended_enter();
493 bool active = ThreadService::is_thread_monitoring_contention();
494 if (active) {
495 stat->contended_enter_begin();
496 }
497 return active;
498 }
499
500 public:
501 // java_thread is waiting thread being blocked on monitor reenter.
502 // Current thread is the notifying thread which holds the monitor.
503 static bool wait_reenter_begin(JavaThread *java_thread, ObjectMonitor *obj_m) {
504 assert((java_thread != NULL), "Java thread should not be null here");
505 bool active = false;
506 if (is_alive(java_thread) && ServiceUtil::visible_oop((oop)obj_m->object())) {
507 active = contended_enter_begin(java_thread);
508 }
509 return active;
510 }
511
512 static void wait_reenter_end(JavaThread *java_thread, bool active) {
513 if (active) {
514 java_thread->get_thread_stat()->contended_enter_end();
515 }
516 set_thread_status(java_thread, java_lang_Thread::RUNNABLE);
517 }
518
519 JavaThreadBlockedOnMonitorEnterState(JavaThread *java_thread, ObjectMonitor *obj_m) :
520 JavaThreadStatusChanger(java_thread) {
521 assert((java_thread != NULL), "Java thread should not be null here");
522 // Change thread status and collect contended enter stats for monitor contended
523 // enter done for external java world objects and it is contended. All other cases
524 // like for vm internal objects and for external objects which are not contended
525 // thread status is not changed and contended enter stat is not collected.
526 _active = false;
527 if (is_alive() && ServiceUtil::visible_oop((oop)obj_m->object()) && obj_m->contentions() > 0) {
528 _stat = java_thread->get_thread_stat();
529 _active = contended_enter_begin(java_thread);
530 }
531 }
532
533 ~JavaThreadBlockedOnMonitorEnterState() {
534 if (_active) {
535 _stat->contended_enter_end();
536 }
537 }
538 };
539
540 // Change status to sleeping
541 class JavaThreadSleepState : public JavaThreadStatusChanger {
542 private:
543 ThreadStatistics* _stat;
544 bool _active;
545 public:
546 JavaThreadSleepState(JavaThread *java_thread) :
547 JavaThreadStatusChanger(java_thread, java_lang_Thread::SLEEPING) {
548 if (is_alive()) {
549 _stat = java_thread->get_thread_stat();
550 _active = ThreadService::is_thread_monitoring_contention();
551 _stat->thread_sleep();
552 if (_active) {
553 _stat->thread_sleep_begin();
554 }
555 } else {
556 _active = false;
557 }
558 }
559
560 ~JavaThreadSleepState() {
561 if (_active) {
562 _stat->thread_sleep_end();
563 }
564 }
565 };