1 /*
2 * Copyright (c) 2003, 2023, 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/javaClasses.inline.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "classfile/vmClasses.hpp"
29 #include "classfile/vmSymbols.hpp"
30 #include "gc/shared/oopStorageSet.hpp"
31 #include "memory/allocation.hpp"
32 #include "memory/heapInspection.hpp"
33 #include "memory/oopFactory.hpp"
34 #include "memory/resourceArea.hpp"
35 #include "memory/universe.hpp"
36 #include "oops/instanceKlass.hpp"
37 #include "oops/klass.inline.hpp"
38 #include "oops/objArrayKlass.hpp"
39 #include "oops/objArrayOop.inline.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "oops/oopHandle.inline.hpp"
42 #include "prims/jvmtiRawMonitor.hpp"
43 #include "runtime/atomic.hpp"
44 #include "runtime/handles.inline.hpp"
45 #include "runtime/init.hpp"
46 #include "runtime/javaThread.inline.hpp"
47 #include "runtime/objectMonitor.inline.hpp"
48 #include "runtime/synchronizer.hpp"
49 #include "runtime/thread.inline.hpp"
50 #include "runtime/threads.hpp"
51 #include "runtime/threadSMR.inline.hpp"
52 #include "runtime/vframe.hpp"
53 #include "runtime/vmThread.hpp"
54 #include "runtime/vmOperations.hpp"
55 #include "services/threadService.hpp"
56
57 // TODO: we need to define a naming convention for perf counters
58 // to distinguish counters for:
59 // - standard JSR174 use
60 // - Hotspot extension (public and committed)
61 // - Hotspot extension (private/internal and uncommitted)
62
63 // Default is disabled.
64 bool ThreadService::_thread_monitoring_contention_enabled = false;
65 bool ThreadService::_thread_cpu_time_enabled = false;
66 bool ThreadService::_thread_allocated_memory_enabled = false;
67
68 PerfCounter* ThreadService::_total_threads_count = nullptr;
69 PerfVariable* ThreadService::_live_threads_count = nullptr;
70 PerfVariable* ThreadService::_peak_threads_count = nullptr;
71 PerfVariable* ThreadService::_daemon_threads_count = nullptr;
72 volatile int ThreadService::_atomic_threads_count = 0;
73 volatile int ThreadService::_atomic_daemon_threads_count = 0;
74
75 volatile jlong ThreadService::_exited_allocated_bytes = 0;
76
77 ThreadDumpResult* ThreadService::_threaddump_list = nullptr;
78
79 static const int INITIAL_ARRAY_SIZE = 10;
80
81 // OopStorage for thread stack sampling
82 static OopStorage* _thread_service_storage = nullptr;
83
84 void ThreadService::init() {
85 EXCEPTION_MARK;
86
87 // These counters are for java.lang.management API support.
88 // They are created even if -XX:-UsePerfData is set and in
89 // that case, they will be allocated on C heap.
90
91 _total_threads_count =
92 PerfDataManager::create_counter(JAVA_THREADS, "started",
93 PerfData::U_Events, CHECK);
94
95 _live_threads_count =
96 PerfDataManager::create_variable(JAVA_THREADS, "live",
97 PerfData::U_None, CHECK);
98
99 _peak_threads_count =
100 PerfDataManager::create_variable(JAVA_THREADS, "livePeak",
101 PerfData::U_None, CHECK);
102
103 _daemon_threads_count =
104 PerfDataManager::create_variable(JAVA_THREADS, "daemon",
105 PerfData::U_None, CHECK);
106
107 if (os::is_thread_cpu_time_supported()) {
108 _thread_cpu_time_enabled = true;
109 }
110
111 _thread_allocated_memory_enabled = true; // Always on, so enable it
112
113 // Initialize OopStorage for thread stack sampling walking
114 _thread_service_storage = OopStorageSet::create_strong("ThreadService OopStorage",
115 mtServiceability);
116 }
117
118 void ThreadService::reset_peak_thread_count() {
119 // Acquire the lock to update the peak thread count
120 // to synchronize with thread addition and removal.
121 MutexLocker mu(Threads_lock);
122 _peak_threads_count->set_value(get_live_thread_count());
123 }
124
125 static bool is_hidden_thread(JavaThread *thread) {
126 // hide VM internal or JVMTI agent threads
127 return thread->is_hidden_from_external_view() || thread->is_jvmti_agent_thread();
128 }
129
130 void ThreadService::add_thread(JavaThread* thread, bool daemon) {
131 assert(Threads_lock->owned_by_self(), "must have threads lock");
132
133 // Do not count hidden threads
134 if (is_hidden_thread(thread)) {
135 return;
136 }
137
138 _total_threads_count->inc();
139 _live_threads_count->inc();
140 Atomic::inc(&_atomic_threads_count);
141 int count = _atomic_threads_count;
142
143 if (count > _peak_threads_count->get_value()) {
144 _peak_threads_count->set_value(count);
145 }
146
147 if (daemon) {
148 _daemon_threads_count->inc();
149 Atomic::inc(&_atomic_daemon_threads_count);
150 }
151 }
152
153 void ThreadService::decrement_thread_counts(JavaThread* jt, bool daemon) {
154 Atomic::dec(&_atomic_threads_count);
155
156 if (daemon) {
157 Atomic::dec(&_atomic_daemon_threads_count);
158 }
159 }
160
161 void ThreadService::remove_thread(JavaThread* thread, bool daemon) {
162 assert(Threads_lock->owned_by_self(), "must have threads lock");
163
164 // Include hidden thread allcations in exited_allocated_bytes
165 ThreadService::incr_exited_allocated_bytes(thread->cooked_allocated_bytes());
166
167 // Do not count hidden threads
168 if (is_hidden_thread(thread)) {
169 return;
170 }
171
172 assert(!thread->is_terminated(), "must not be terminated");
173 if (!thread->is_exiting()) {
174 // We did not get here via JavaThread::exit() so current_thread_exiting()
175 // was not called, e.g., JavaThread::cleanup_failed_attach_current_thread().
176 decrement_thread_counts(thread, daemon);
177 }
178
179 int daemon_count = _atomic_daemon_threads_count;
180 int count = _atomic_threads_count;
181
182 // Counts are incremented at the same time, but atomic counts are
183 // decremented earlier than perf counts.
184 assert(_live_threads_count->get_value() > count,
185 "thread count mismatch %d : %d",
186 (int)_live_threads_count->get_value(), count);
187
188 _live_threads_count->dec(1);
189 if (daemon) {
190 assert(_daemon_threads_count->get_value() > daemon_count,
191 "thread count mismatch %d : %d",
192 (int)_daemon_threads_count->get_value(), daemon_count);
193
194 _daemon_threads_count->dec(1);
195 }
196
197 // Counts are incremented at the same time, but atomic counts are
198 // decremented earlier than perf counts.
199 assert(_daemon_threads_count->get_value() >= daemon_count,
200 "thread count mismatch %d : %d",
201 (int)_daemon_threads_count->get_value(), daemon_count);
202 assert(_live_threads_count->get_value() >= count,
203 "thread count mismatch %d : %d",
204 (int)_live_threads_count->get_value(), count);
205 assert(_live_threads_count->get_value() > 0 ||
206 (_live_threads_count->get_value() == 0 && count == 0 &&
207 _daemon_threads_count->get_value() == 0 && daemon_count == 0),
208 "thread counts should reach 0 at the same time, live %d,%d daemon %d,%d",
209 (int)_live_threads_count->get_value(), count,
210 (int)_daemon_threads_count->get_value(), daemon_count);
211 assert(_daemon_threads_count->get_value() > 0 ||
212 (_daemon_threads_count->get_value() == 0 && daemon_count == 0),
213 "thread counts should reach 0 at the same time, daemon %d,%d",
214 (int)_daemon_threads_count->get_value(), daemon_count);
215 }
216
217 void ThreadService::current_thread_exiting(JavaThread* jt, bool daemon) {
218 // Do not count hidden threads
219 if (is_hidden_thread(jt)) {
220 return;
221 }
222
223 assert(jt == JavaThread::current(), "Called by current thread");
224 assert(!jt->is_terminated() && jt->is_exiting(), "must be exiting");
225
226 decrement_thread_counts(jt, daemon);
227 }
228
229 // FIXME: JVMTI should call this function
230 Handle ThreadService::get_current_contended_monitor(JavaThread* thread) {
231 assert(thread != nullptr, "should be non-null");
232 debug_only(Thread::check_for_dangling_thread_pointer(thread);)
233
234 // This function can be called on a target JavaThread that is not
235 // the caller and we are not at a safepoint. So it is possible for
236 // the waiting or pending condition to be over/stale and for the
237 // first stage of async deflation to clear the object field in
238 // the ObjectMonitor. It is also possible for the object to be
239 // inflated again and to be associated with a completely different
240 // ObjectMonitor by the time this object reference is processed
241 // by the caller.
242 ObjectMonitor *wait_obj = thread->current_waiting_monitor();
243
244 oop obj = nullptr;
245 if (wait_obj != nullptr) {
246 // thread is doing an Object.wait() call
247 obj = wait_obj->object();
248 } else {
249 ObjectMonitor *enter_obj = thread->current_pending_monitor();
250 if (enter_obj != nullptr) {
251 // thread is trying to enter() an ObjectMonitor.
252 obj = enter_obj->object();
253 }
254 }
255
256 Handle h(Thread::current(), obj);
257 return h;
258 }
259
260 bool ThreadService::set_thread_monitoring_contention(bool flag) {
261 MutexLocker m(Management_lock);
262
263 bool prev = _thread_monitoring_contention_enabled;
264 _thread_monitoring_contention_enabled = flag;
265
266 return prev;
267 }
268
269 bool ThreadService::set_thread_cpu_time_enabled(bool flag) {
270 MutexLocker m(Management_lock);
271
272 bool prev = _thread_cpu_time_enabled;
273 _thread_cpu_time_enabled = flag;
274
275 return prev;
276 }
277
278 bool ThreadService::set_thread_allocated_memory_enabled(bool flag) {
279 MutexLocker m(Management_lock);
280
281 bool prev = _thread_allocated_memory_enabled;
282 _thread_allocated_memory_enabled = flag;
283
284 return prev;
285 }
286
287 void ThreadService::metadata_do(void f(Metadata*)) {
288 for (ThreadDumpResult* dump = _threaddump_list; dump != nullptr; dump = dump->next()) {
289 dump->metadata_do(f);
290 }
291 }
292
293 void ThreadService::add_thread_dump(ThreadDumpResult* dump) {
294 MutexLocker ml(Management_lock);
295 if (_threaddump_list == nullptr) {
296 _threaddump_list = dump;
297 } else {
298 dump->set_next(_threaddump_list);
299 _threaddump_list = dump;
300 }
301 }
302
303 void ThreadService::remove_thread_dump(ThreadDumpResult* dump) {
304 MutexLocker ml(Management_lock);
305
306 ThreadDumpResult* prev = nullptr;
307 bool found = false;
308 for (ThreadDumpResult* d = _threaddump_list; d != nullptr; prev = d, d = d->next()) {
309 if (d == dump) {
310 if (prev == nullptr) {
311 _threaddump_list = dump->next();
312 } else {
313 prev->set_next(dump->next());
314 }
315 found = true;
316 break;
317 }
318 }
319 assert(found, "The threaddump result to be removed must exist.");
320 }
321
322 // Dump stack trace of threads specified in the given threads array.
323 // Returns StackTraceElement[][] each element is the stack trace of a thread in
324 // the corresponding entry in the given threads array
325 Handle ThreadService::dump_stack_traces(GrowableArray<instanceHandle>* threads,
326 int num_threads,
327 TRAPS) {
328 assert(num_threads > 0, "just checking");
329
330 ThreadDumpResult dump_result;
331 VM_ThreadDump op(&dump_result,
332 threads,
333 num_threads,
334 -1, /* entire stack */
335 false, /* with locked monitors */
336 false /* with locked synchronizers */);
337 VMThread::execute(&op);
338
339 // Allocate the resulting StackTraceElement[][] object
340
341 ResourceMark rm(THREAD);
342 Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_StackTraceElement_array(), true, CHECK_NH);
343 ObjArrayKlass* ik = ObjArrayKlass::cast(k);
344 objArrayOop r = oopFactory::new_objArray(ik, num_threads, CHECK_NH);
345 objArrayHandle result_obj(THREAD, r);
346
347 int num_snapshots = dump_result.num_snapshots();
348 assert(num_snapshots == num_threads, "Must have num_threads thread snapshots");
349 assert(num_snapshots == 0 || dump_result.t_list_has_been_set(), "ThreadsList must have been set if we have a snapshot");
350 int i = 0;
351 for (ThreadSnapshot* ts = dump_result.snapshots(); ts != nullptr; i++, ts = ts->next()) {
352 ThreadStackTrace* stacktrace = ts->get_stack_trace();
353 if (stacktrace == nullptr) {
354 // No stack trace
355 result_obj->obj_at_put(i, nullptr);
356 } else {
357 // Construct an array of java/lang/StackTraceElement object
358 Handle backtrace_h = stacktrace->allocate_fill_stack_trace_element_array(CHECK_NH);
359 result_obj->obj_at_put(i, backtrace_h());
360 }
361 }
362
363 return result_obj;
364 }
365
366 void ThreadService::reset_contention_count_stat(JavaThread* thread) {
367 ThreadStatistics* stat = thread->get_thread_stat();
368 if (stat != nullptr) {
369 stat->reset_count_stat();
370 }
371 }
372
373 void ThreadService::reset_contention_time_stat(JavaThread* thread) {
374 ThreadStatistics* stat = thread->get_thread_stat();
375 if (stat != nullptr) {
376 stat->reset_time_stat();
377 }
378 }
379
380 bool ThreadService::is_virtual_or_carrier_thread(JavaThread* jt) {
381 oop threadObj = jt->threadObj();
382 if (threadObj != nullptr && threadObj->is_a(vmClasses::BaseVirtualThread_klass())) {
383 // a virtual thread backed by JavaThread
384 return true;
385 }
386 if (jt->is_vthread_mounted()) {
387 // carrier thread
388 return true;
389 }
390 return false;
391 }
392
393 // Find deadlocks involving raw monitors, object monitors and concurrent locks
394 // if concurrent_locks is true.
395 // We skip virtual thread carriers under the assumption that the current scheduler, ForkJoinPool,
396 // doesn't hold any locks while mounting a virtual thread, so any owned monitor (or j.u.c., lock for that matter)
397 // on that JavaThread must be owned by the virtual thread, and we don't support deadlock detection for virtual threads.
398 DeadlockCycle* ThreadService::find_deadlocks_at_safepoint(ThreadsList * t_list, bool concurrent_locks) {
399 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
400
401 // This code was modified from the original Threads::find_deadlocks code.
402 int globalDfn = 0, thisDfn;
403 ObjectMonitor* waitingToLockMonitor = nullptr;
404 JvmtiRawMonitor* waitingToLockRawMonitor = nullptr;
405 oop waitingToLockBlocker = nullptr;
406 bool blocked_on_monitor = false;
407 JavaThread *currentThread, *previousThread;
408 int num_deadlocks = 0;
409
410 // Initialize the depth-first-number for each JavaThread.
411 JavaThreadIterator jti(t_list);
412 for (JavaThread* jt = jti.first(); jt != nullptr; jt = jti.next()) {
413 if (!is_virtual_or_carrier_thread(jt)) {
414 jt->set_depth_first_number(-1);
415 }
416 }
417
418 DeadlockCycle* deadlocks = nullptr;
419 DeadlockCycle* last = nullptr;
420 DeadlockCycle* cycle = new DeadlockCycle();
421 for (JavaThread* jt = jti.first(); jt != nullptr; jt = jti.next()) {
422 if (is_virtual_or_carrier_thread(jt)) {
423 // skip virtual and carrier threads
424 continue;
425 }
426 if (jt->depth_first_number() >= 0) {
427 // this thread was already visited
428 continue;
429 }
430
431 thisDfn = globalDfn;
432 jt->set_depth_first_number(globalDfn++);
433 previousThread = jt;
434 currentThread = jt;
435
436 cycle->reset();
437
438 // The ObjectMonitor* can't be async deflated since we are at a safepoint.
439 // When there is a deadlock, all the monitors involved in the dependency
440 // cycle must be contended and heavyweight. So we only care about the
441 // heavyweight monitor a thread is waiting to lock.
442 waitingToLockMonitor = jt->current_pending_monitor();
443 // JVM TI raw monitors can also be involved in deadlocks, and we can be
444 // waiting to lock both a raw monitor and ObjectMonitor at the same time.
445 // It isn't clear how to make deadlock detection work correctly if that
446 // happens.
447 waitingToLockRawMonitor = jt->current_pending_raw_monitor();
448
449 if (concurrent_locks) {
450 waitingToLockBlocker = jt->current_park_blocker();
451 }
452
453 while (waitingToLockMonitor != nullptr ||
454 waitingToLockRawMonitor != nullptr ||
455 waitingToLockBlocker != nullptr) {
456 cycle->add_thread(currentThread);
457 // Give preference to the raw monitor
458 if (waitingToLockRawMonitor != nullptr) {
459 Thread* owner = waitingToLockRawMonitor->owner();
460 if (owner != nullptr && // the raw monitor could be released at any time
461 owner->is_Java_thread()) {
462 currentThread = JavaThread::cast(owner);
463 }
464 } else if (waitingToLockMonitor != nullptr) {
465 if (waitingToLockMonitor->has_owner()) {
466 currentThread = Threads::owning_thread_from_monitor(t_list, waitingToLockMonitor);
467 if (currentThread == nullptr) {
468 // This function is called at a safepoint so the JavaThread
469 // that owns waitingToLockMonitor should be findable, but
470 // if it is not findable, then the previous currentThread is
471 // blocked permanently. We record this as a deadlock.
472 num_deadlocks++;
473
474 // add this cycle to the deadlocks list
475 if (deadlocks == nullptr) {
476 deadlocks = cycle;
477 } else {
478 last->set_next(cycle);
479 }
480 last = cycle;
481 cycle = new DeadlockCycle();
482 break;
483 }
484 }
485 } else {
486 if (concurrent_locks) {
487 if (waitingToLockBlocker->is_a(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass())) {
488 oop threadObj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(waitingToLockBlocker);
489 // This JavaThread (if there is one) is protected by the
490 // ThreadsListSetter in VM_FindDeadlocks::doit().
491 currentThread = threadObj != nullptr ? java_lang_Thread::thread(threadObj) : nullptr;
492 } else {
493 currentThread = nullptr;
494 }
495 }
496 }
497
498 if (currentThread == nullptr || is_virtual_or_carrier_thread(currentThread)) {
499 // No dependency on another thread
500 break;
501 }
502 if (currentThread->depth_first_number() < 0) {
503 // First visit to this thread
504 currentThread->set_depth_first_number(globalDfn++);
505 } else if (currentThread->depth_first_number() < thisDfn) {
506 // Thread already visited, and not on a (new) cycle
507 break;
508 } else if (currentThread == previousThread) {
509 // Self-loop, ignore
510 break;
511 } else {
512 // We have a (new) cycle
513 num_deadlocks++;
514
515 // add this cycle to the deadlocks list
516 if (deadlocks == nullptr) {
517 deadlocks = cycle;
518 } else {
519 last->set_next(cycle);
520 }
521 last = cycle;
522 cycle = new DeadlockCycle();
523 break;
524 }
525 previousThread = currentThread;
526 waitingToLockMonitor = (ObjectMonitor*)currentThread->current_pending_monitor();
527 if (concurrent_locks) {
528 waitingToLockBlocker = currentThread->current_park_blocker();
529 }
530 }
531
532 }
533 delete cycle;
534 return deadlocks;
535 }
536
537 ThreadDumpResult::ThreadDumpResult() : _num_threads(0), _num_snapshots(0), _snapshots(nullptr), _last(nullptr), _next(nullptr), _setter() {
538
539 // Create a new ThreadDumpResult object and append to the list.
540 // If GC happens before this function returns, Method*
541 // in the stack trace will be visited.
542 ThreadService::add_thread_dump(this);
543 }
544
545 ThreadDumpResult::ThreadDumpResult(int num_threads) : _num_threads(num_threads), _num_snapshots(0), _snapshots(nullptr), _last(nullptr), _next(nullptr), _setter() {
546 // Create a new ThreadDumpResult object and append to the list.
547 // If GC happens before this function returns, oops
548 // will be visited.
549 ThreadService::add_thread_dump(this);
550 }
551
552 ThreadDumpResult::~ThreadDumpResult() {
553 ThreadService::remove_thread_dump(this);
554
555 // free all the ThreadSnapshot objects created during
556 // the VM_ThreadDump operation
557 ThreadSnapshot* ts = _snapshots;
558 while (ts != nullptr) {
559 ThreadSnapshot* p = ts;
560 ts = ts->next();
561 delete p;
562 }
563 }
564
565 ThreadSnapshot* ThreadDumpResult::add_thread_snapshot() {
566 ThreadSnapshot* ts = new ThreadSnapshot();
567 link_thread_snapshot(ts);
568 return ts;
569 }
570
571 ThreadSnapshot* ThreadDumpResult::add_thread_snapshot(JavaThread* thread) {
572 ThreadSnapshot* ts = new ThreadSnapshot();
573 link_thread_snapshot(ts);
574 ts->initialize(t_list(), thread);
575 return ts;
576 }
577
578 void ThreadDumpResult::link_thread_snapshot(ThreadSnapshot* ts) {
579 assert(_num_threads == 0 || _num_snapshots < _num_threads,
580 "_num_snapshots must be less than _num_threads");
581 _num_snapshots++;
582 if (_snapshots == nullptr) {
583 _snapshots = ts;
584 } else {
585 _last->set_next(ts);
586 }
587 _last = ts;
588 }
589
590 void ThreadDumpResult::metadata_do(void f(Metadata*)) {
591 for (ThreadSnapshot* ts = _snapshots; ts != nullptr; ts = ts->next()) {
592 ts->metadata_do(f);
593 }
594 }
595
596 ThreadsList* ThreadDumpResult::t_list() {
597 return _setter.list();
598 }
599
600 StackFrameInfo::StackFrameInfo(javaVFrame* jvf, bool with_lock_info) {
601 _method = jvf->method();
602 _bci = jvf->bci();
603 _class_holder = OopHandle(_thread_service_storage, _method->method_holder()->klass_holder());
604 _locked_monitors = nullptr;
605 if (with_lock_info) {
606 Thread* current_thread = Thread::current();
607 ResourceMark rm(current_thread);
608 HandleMark hm(current_thread);
609 GrowableArray<MonitorInfo*>* list = jvf->locked_monitors();
610 int length = list->length();
611 if (length > 0) {
612 _locked_monitors = new (mtServiceability) GrowableArray<OopHandle>(length, mtServiceability);
613 for (int i = 0; i < length; i++) {
614 MonitorInfo* monitor = list->at(i);
615 assert(monitor->owner() != nullptr, "This monitor must have an owning object");
616 _locked_monitors->append(OopHandle(_thread_service_storage, monitor->owner()));
617 }
618 }
619 }
620 }
621
622 StackFrameInfo::~StackFrameInfo() {
623 if (_locked_monitors != nullptr) {
624 for (int i = 0; i < _locked_monitors->length(); i++) {
625 _locked_monitors->at(i).release(_thread_service_storage);
626 }
627 delete _locked_monitors;
628 }
629 _class_holder.release(_thread_service_storage);
630 }
631
632 void StackFrameInfo::metadata_do(void f(Metadata*)) {
633 f(_method);
634 }
635
636 void StackFrameInfo::print_on(outputStream* st) const {
637 ResourceMark rm;
638 java_lang_Throwable::print_stack_element(st, method(), bci());
639 int len = (_locked_monitors != nullptr ? _locked_monitors->length() : 0);
640 for (int i = 0; i < len; i++) {
641 oop o = _locked_monitors->at(i).resolve();
642 st->print_cr("\t- locked <" INTPTR_FORMAT "> (a %s)", p2i(o), o->klass()->external_name());
643 }
644 }
645
646 // Iterate through monitor cache to find JNI locked monitors
647 class InflatedMonitorsClosure: public MonitorClosure {
648 private:
649 ThreadStackTrace* _stack_trace;
650 public:
651 InflatedMonitorsClosure(ThreadStackTrace* st) {
652 _stack_trace = st;
653 }
654 void do_monitor(ObjectMonitor* mid) {
655 oop object = mid->object();
656 if (!_stack_trace->is_owned_monitor_on_stack(object)) {
657 _stack_trace->add_jni_locked_monitor(object);
658 }
659 }
660 };
661
662 ThreadStackTrace::ThreadStackTrace(JavaThread* t, bool with_locked_monitors) {
663 _thread = t;
664 _frames = new (mtServiceability) GrowableArray<StackFrameInfo*>(INITIAL_ARRAY_SIZE, mtServiceability);
665 _depth = 0;
666 _with_locked_monitors = with_locked_monitors;
667 if (_with_locked_monitors) {
668 _jni_locked_monitors = new (mtServiceability) GrowableArray<OopHandle>(INITIAL_ARRAY_SIZE, mtServiceability);
669 } else {
670 _jni_locked_monitors = nullptr;
671 }
672 }
673
674 void ThreadStackTrace::add_jni_locked_monitor(oop object) {
675 _jni_locked_monitors->append(OopHandle(_thread_service_storage, object));
676 }
677
678 ThreadStackTrace::~ThreadStackTrace() {
679 for (int i = 0; i < _frames->length(); i++) {
680 delete _frames->at(i);
681 }
682 delete _frames;
683 if (_jni_locked_monitors != nullptr) {
684 for (int i = 0; i < _jni_locked_monitors->length(); i++) {
685 _jni_locked_monitors->at(i).release(_thread_service_storage);
686 }
687 delete _jni_locked_monitors;
688 }
689 }
690
691 void ThreadStackTrace::dump_stack_at_safepoint(int maxDepth, ObjectMonitorsView* monitors, bool full) {
692 assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
693
694 if (_thread->has_last_Java_frame()) {
695 RegisterMap reg_map(_thread,
696 RegisterMap::UpdateMap::include,
697 RegisterMap::ProcessFrames::include,
698 RegisterMap::WalkContinuation::skip);
699 ResourceMark rm(VMThread::vm_thread());
700 // If full, we want to print both vthread and carrier frames
701 vframe* start_vf = !full && _thread->is_vthread_mounted()
702 ? _thread->carrier_last_java_vframe(®_map)
703 : _thread->last_java_vframe(®_map);
704 int count = 0;
705 for (vframe* f = start_vf; f; f = f->sender() ) {
706 if (maxDepth >= 0 && count == maxDepth) {
707 // Skip frames if more than maxDepth
708 break;
709 }
710 if (!full && f->is_vthread_entry()) {
711 break;
712 }
713 if (f->is_java_frame()) {
714 javaVFrame* jvf = javaVFrame::cast(f);
715 add_stack_frame(jvf);
716 count++;
717 } else {
718 // Ignore non-Java frames
719 }
720 }
721 }
722
723 if (_with_locked_monitors) {
724 // Iterate inflated monitors and find monitors locked by this thread
725 // that are not found in the stack, e.g. JNI locked monitors:
726 InflatedMonitorsClosure imc(this);
727 monitors->visit(&imc, _thread);
728 }
729 }
730
731
732 bool ThreadStackTrace::is_owned_monitor_on_stack(oop object) {
733 assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
734
735 bool found = false;
736 int num_frames = get_stack_depth();
737 for (int depth = 0; depth < num_frames; depth++) {
738 StackFrameInfo* frame = stack_frame_at(depth);
739 int len = frame->num_locked_monitors();
740 GrowableArray<OopHandle>* locked_monitors = frame->locked_monitors();
741 for (int j = 0; j < len; j++) {
742 oop monitor = locked_monitors->at(j).resolve();
743 assert(monitor != nullptr, "must be a Java object");
744 if (monitor == object) {
745 found = true;
746 break;
747 }
748 }
749 }
750 return found;
751 }
752
753 Handle ThreadStackTrace::allocate_fill_stack_trace_element_array(TRAPS) {
754 InstanceKlass* ik = vmClasses::StackTraceElement_klass();
755 assert(ik != nullptr, "must be loaded in 1.4+");
756
757 // Allocate an array of java/lang/StackTraceElement object
758 objArrayOop ste = oopFactory::new_objArray(ik, _depth, CHECK_NH);
759 objArrayHandle backtrace(THREAD, ste);
760 for (int j = 0; j < _depth; j++) {
761 StackFrameInfo* frame = _frames->at(j);
762 methodHandle mh(THREAD, frame->method());
763 oop element = java_lang_StackTraceElement::create(mh, frame->bci(), CHECK_NH);
764 backtrace->obj_at_put(j, element);
765 }
766 return backtrace;
767 }
768
769 void ThreadStackTrace::add_stack_frame(javaVFrame* jvf) {
770 StackFrameInfo* frame = new StackFrameInfo(jvf, _with_locked_monitors);
771 _frames->append(frame);
772 _depth++;
773 }
774
775 void ThreadStackTrace::metadata_do(void f(Metadata*)) {
776 int length = _frames->length();
777 for (int i = 0; i < length; i++) {
778 _frames->at(i)->metadata_do(f);
779 }
780 }
781
782
783 ConcurrentLocksDump::~ConcurrentLocksDump() {
784 if (_retain_map_on_free) {
785 return;
786 }
787
788 for (ThreadConcurrentLocks* t = _map; t != nullptr;) {
789 ThreadConcurrentLocks* tcl = t;
790 t = t->next();
791 delete tcl;
792 }
793 }
794
795 void ConcurrentLocksDump::dump_at_safepoint() {
796 // dump all locked concurrent locks
797 assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
798
799 GrowableArray<oop>* aos_objects = new (mtServiceability) GrowableArray<oop>(INITIAL_ARRAY_SIZE, mtServiceability);
800
801 // Find all instances of AbstractOwnableSynchronizer
802 HeapInspection::find_instances_at_safepoint(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass(),
803 aos_objects);
804 // Build a map of thread to its owned AQS locks
805 build_map(aos_objects);
806
807 delete aos_objects;
808 }
809
810
811 // build a map of JavaThread to all its owned AbstractOwnableSynchronizer
812 void ConcurrentLocksDump::build_map(GrowableArray<oop>* aos_objects) {
813 int length = aos_objects->length();
814 for (int i = 0; i < length; i++) {
815 oop o = aos_objects->at(i);
816 oop owner_thread_obj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(o);
817 if (owner_thread_obj != nullptr) {
818 // See comments in ThreadConcurrentLocks to see how this
819 // JavaThread* is protected.
820 JavaThread* thread = java_lang_Thread::thread(owner_thread_obj);
821 assert(o->is_instance(), "Must be an instanceOop");
822 add_lock(thread, (instanceOop) o);
823 }
824 }
825 }
826
827 void ConcurrentLocksDump::add_lock(JavaThread* thread, instanceOop o) {
828 ThreadConcurrentLocks* tcl = thread_concurrent_locks(thread);
829 if (tcl != nullptr) {
830 tcl->add_lock(o);
831 return;
832 }
833
834 // First owned lock found for this thread
835 tcl = new ThreadConcurrentLocks(thread);
836 tcl->add_lock(o);
837 if (_map == nullptr) {
838 _map = tcl;
839 } else {
840 _last->set_next(tcl);
841 }
842 _last = tcl;
843 }
844
845 ThreadConcurrentLocks* ConcurrentLocksDump::thread_concurrent_locks(JavaThread* thread) {
846 for (ThreadConcurrentLocks* tcl = _map; tcl != nullptr; tcl = tcl->next()) {
847 if (tcl->java_thread() == thread) {
848 return tcl;
849 }
850 }
851 return nullptr;
852 }
853
854 void ConcurrentLocksDump::print_locks_on(JavaThread* t, outputStream* st) {
855 st->print_cr(" Locked ownable synchronizers:");
856 ThreadConcurrentLocks* tcl = thread_concurrent_locks(t);
857 GrowableArray<OopHandle>* locks = (tcl != nullptr ? tcl->owned_locks() : nullptr);
858 if (locks == nullptr || locks->is_empty()) {
859 st->print_cr("\t- None");
860 st->cr();
861 return;
862 }
863
864 for (int i = 0; i < locks->length(); i++) {
865 oop obj = locks->at(i).resolve();
866 st->print_cr("\t- <" INTPTR_FORMAT "> (a %s)", p2i(obj), obj->klass()->external_name());
867 }
868 st->cr();
869 }
870
871 ThreadConcurrentLocks::ThreadConcurrentLocks(JavaThread* thread) {
872 _thread = thread;
873 _owned_locks = new (mtServiceability) GrowableArray<OopHandle>(INITIAL_ARRAY_SIZE, mtServiceability);
874 _next = nullptr;
875 }
876
877 ThreadConcurrentLocks::~ThreadConcurrentLocks() {
878 for (int i = 0; i < _owned_locks->length(); i++) {
879 _owned_locks->at(i).release(_thread_service_storage);
880 }
881 delete _owned_locks;
882 }
883
884 void ThreadConcurrentLocks::add_lock(instanceOop o) {
885 _owned_locks->append(OopHandle(_thread_service_storage, o));
886 }
887
888 ThreadStatistics::ThreadStatistics() {
889 _contended_enter_count = 0;
890 _monitor_wait_count = 0;
891 _sleep_count = 0;
892 _count_pending_reset = false;
893 _timer_pending_reset = false;
894 memset((void*) _perf_recursion_counts, 0, sizeof(_perf_recursion_counts));
895 }
896
897 oop ThreadSnapshot::threadObj() const { return _threadObj.resolve(); }
898
899 void ThreadSnapshot::initialize(ThreadsList * t_list, JavaThread* thread) {
900 _thread = thread;
901 oop threadObj = thread->threadObj();
902 _threadObj = OopHandle(_thread_service_storage, threadObj);
903
904 ThreadStatistics* stat = thread->get_thread_stat();
905 _contended_enter_ticks = stat->contended_enter_ticks();
906 _contended_enter_count = stat->contended_enter_count();
907 _monitor_wait_ticks = stat->monitor_wait_ticks();
908 _monitor_wait_count = stat->monitor_wait_count();
909 _sleep_ticks = stat->sleep_ticks();
910 _sleep_count = stat->sleep_count();
911
912 // If thread is still attaching then threadObj will be null.
913 _thread_status = threadObj == nullptr ? JavaThreadStatus::NEW
914 : java_lang_Thread::get_thread_status(threadObj);
915
916 _is_suspended = thread->is_suspended();
917 _is_in_native = (thread->thread_state() == _thread_in_native);
918
919 Handle obj = ThreadService::get_current_contended_monitor(thread);
920
921 oop blocker_object = nullptr;
922 oop blocker_object_owner = nullptr;
923
924 if (thread->is_vthread_mounted() && thread->vthread() != threadObj) { // ThreadSnapshot only captures platform threads
925 _thread_status = JavaThreadStatus::IN_OBJECT_WAIT;
926 oop vthread = thread->vthread();
927 assert(vthread != nullptr, "");
928 blocker_object = vthread;
929 blocker_object_owner = vthread;
930 } else if (_thread_status == JavaThreadStatus::BLOCKED_ON_MONITOR_ENTER ||
931 _thread_status == JavaThreadStatus::IN_OBJECT_WAIT ||
932 _thread_status == JavaThreadStatus::IN_OBJECT_WAIT_TIMED) {
933
934 if (obj() == nullptr) {
935 // monitor no longer exists; thread is not blocked
936 _thread_status = JavaThreadStatus::RUNNABLE;
937 } else {
938 blocker_object = obj();
939 JavaThread* owner = ObjectSynchronizer::get_lock_owner(t_list, obj);
940 if ((owner == nullptr && _thread_status == JavaThreadStatus::BLOCKED_ON_MONITOR_ENTER)
941 || (owner != nullptr && owner->is_attaching_via_jni())) {
942 // ownership information of the monitor is not available
943 // (may no longer be owned or releasing to some other thread)
944 // make this thread in RUNNABLE state.
945 // And when the owner thread is in attaching state, the java thread
946 // is not completely initialized. For example thread name and id
947 // and may not be set, so hide the attaching thread.
948 _thread_status = JavaThreadStatus::RUNNABLE;
949 blocker_object = nullptr;
950 } else if (owner != nullptr) {
951 blocker_object_owner = owner->threadObj();
952 }
953 }
954 } else if (_thread_status == JavaThreadStatus::PARKED || _thread_status == JavaThreadStatus::PARKED_TIMED) {
955 blocker_object = thread->current_park_blocker();
956 if (blocker_object != nullptr && blocker_object->is_a(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass())) {
957 blocker_object_owner = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(blocker_object);
958 }
959 }
960
961 if (blocker_object != nullptr) {
962 _blocker_object = OopHandle(_thread_service_storage, blocker_object);
963 }
964 if (blocker_object_owner != nullptr) {
965 _blocker_object_owner = OopHandle(_thread_service_storage, blocker_object_owner);
966 }
967 }
968
969 oop ThreadSnapshot::blocker_object() const { return _blocker_object.resolve(); }
970 oop ThreadSnapshot::blocker_object_owner() const { return _blocker_object_owner.resolve(); }
971
972 ThreadSnapshot::~ThreadSnapshot() {
973 _blocker_object.release(_thread_service_storage);
974 _blocker_object_owner.release(_thread_service_storage);
975 _threadObj.release(_thread_service_storage);
976
977 delete _stack_trace;
978 delete _concurrent_locks;
979 }
980
981 void ThreadSnapshot::dump_stack_at_safepoint(int max_depth, bool with_locked_monitors,
982 ObjectMonitorsView* monitors, bool full) {
983 _stack_trace = new ThreadStackTrace(_thread, with_locked_monitors);
984 _stack_trace->dump_stack_at_safepoint(max_depth, monitors, full);
985 }
986
987
988 void ThreadSnapshot::metadata_do(void f(Metadata*)) {
989 if (_stack_trace != nullptr) {
990 _stack_trace->metadata_do(f);
991 }
992 }
993
994
995 DeadlockCycle::DeadlockCycle() {
996 _threads = new (mtServiceability) GrowableArray<JavaThread*>(INITIAL_ARRAY_SIZE, mtServiceability);
997 _next = nullptr;
998 }
999
1000 DeadlockCycle::~DeadlockCycle() {
1001 delete _threads;
1002 }
1003
1004 void DeadlockCycle::print_on_with(ThreadsList * t_list, outputStream* st) const {
1005 st->cr();
1006 st->print_cr("Found one Java-level deadlock:");
1007 st->print("=============================");
1008
1009 JavaThread* currentThread;
1010 JvmtiRawMonitor* waitingToLockRawMonitor;
1011 oop waitingToLockBlocker;
1012 int len = _threads->length();
1013 for (int i = 0; i < len; i++) {
1014 currentThread = _threads->at(i);
1015 // The ObjectMonitor* can't be async deflated since we are at a safepoint.
1016 ObjectMonitor* waitingToLockMonitor = currentThread->current_pending_monitor();
1017 waitingToLockRawMonitor = currentThread->current_pending_raw_monitor();
1018 waitingToLockBlocker = currentThread->current_park_blocker();
1019 st->cr();
1020 st->print_cr("\"%s\":", currentThread->name());
1021 const char* owner_desc = ",\n which is held by";
1022
1023 // Note: As the JVM TI "monitor contended enter" event callback is executed after ObjectMonitor
1024 // sets the current pending monitor, it is possible to then see a pending raw monitor as well.
1025 if (waitingToLockRawMonitor != nullptr) {
1026 st->print(" waiting to lock JVM TI raw monitor " INTPTR_FORMAT, p2i(waitingToLockRawMonitor));
1027 Thread* owner = waitingToLockRawMonitor->owner();
1028 // Could be null as the raw monitor could be released at any time if held by non-JavaThread
1029 if (owner != nullptr) {
1030 if (owner->is_Java_thread()) {
1031 currentThread = JavaThread::cast(owner);
1032 st->print_cr("%s \"%s\"", owner_desc, currentThread->name());
1033 } else {
1034 st->print_cr(",\n which has now been released");
1035 }
1036 } else {
1037 st->print_cr("%s non-Java thread=" PTR_FORMAT, owner_desc, p2i(owner));
1038 }
1039 }
1040
1041 if (waitingToLockMonitor != nullptr) {
1042 st->print(" waiting to lock monitor " INTPTR_FORMAT, p2i(waitingToLockMonitor));
1043 oop obj = waitingToLockMonitor->object();
1044 st->print(" (object " INTPTR_FORMAT ", a %s)", p2i(obj),
1045 obj->klass()->external_name());
1046
1047 if (!currentThread->current_pending_monitor_is_from_java()) {
1048 owner_desc = "\n in JNI, which is held by";
1049 }
1050 currentThread = Threads::owning_thread_from_monitor(t_list, waitingToLockMonitor);
1051 if (currentThread == nullptr) {
1052 // The deadlock was detected at a safepoint so the JavaThread
1053 // that owns waitingToLockMonitor should be findable, but
1054 // if it is not findable, then the previous currentThread is
1055 // blocked permanently.
1056 st->print_cr("%s UNKNOWN_owner_addr=" PTR_FORMAT, owner_desc,
1057 p2i(waitingToLockMonitor->owner()));
1058 continue;
1059 }
1060 } else {
1061 st->print(" waiting for ownable synchronizer " INTPTR_FORMAT ", (a %s)",
1062 p2i(waitingToLockBlocker),
1063 waitingToLockBlocker->klass()->external_name());
1064 assert(waitingToLockBlocker->is_a(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass()),
1065 "Must be an AbstractOwnableSynchronizer");
1066 oop ownerObj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(waitingToLockBlocker);
1067 currentThread = java_lang_Thread::thread(ownerObj);
1068 assert(currentThread != nullptr, "AbstractOwnableSynchronizer owning thread is unexpectedly null");
1069 }
1070 st->print_cr("%s \"%s\"", owner_desc, currentThread->name());
1071 }
1072
1073 st->cr();
1074
1075 // Print stack traces
1076 bool oldJavaMonitorsInStackTrace = JavaMonitorsInStackTrace;
1077 JavaMonitorsInStackTrace = true;
1078 st->print_cr("Java stack information for the threads listed above:");
1079 st->print_cr("===================================================");
1080 for (int j = 0; j < len; j++) {
1081 currentThread = _threads->at(j);
1082 st->print_cr("\"%s\":", currentThread->name());
1083 currentThread->print_stack_on(st);
1084 }
1085 JavaMonitorsInStackTrace = oldJavaMonitorsInStackTrace;
1086 }
1087
1088 ThreadsListEnumerator::ThreadsListEnumerator(Thread* cur_thread,
1089 bool include_jvmti_agent_threads,
1090 bool include_jni_attaching_threads,
1091 bool include_bound_virtual_threads) {
1092 assert(cur_thread == Thread::current(), "Check current thread");
1093
1094 int init_size = ThreadService::get_live_thread_count();
1095 _threads_array = new GrowableArray<instanceHandle>(init_size);
1096
1097 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
1098 // skips JavaThreads in the process of exiting
1099 // and also skips VM internal JavaThreads
1100 // Threads in _thread_new or _thread_new_trans state are included.
1101 // i.e. threads have been started but not yet running.
1102 if (jt->threadObj() == nullptr ||
1103 jt->is_exiting() ||
1104 !java_lang_Thread::is_alive(jt->threadObj()) ||
1105 jt->is_hidden_from_external_view()) {
1106 continue;
1107 }
1108
1109 // skip agent threads
1110 if (!include_jvmti_agent_threads && jt->is_jvmti_agent_thread()) {
1111 continue;
1112 }
1113
1114 // skip jni threads in the process of attaching
1115 if (!include_jni_attaching_threads && jt->is_attaching_via_jni()) {
1116 continue;
1117 }
1118
1119 // skip instances of BoundVirtualThread
1120 if (!include_bound_virtual_threads && jt->threadObj()->is_a(vmClasses::BoundVirtualThread_klass())) {
1121 continue;
1122 }
1123
1124 instanceHandle h(cur_thread, (instanceOop) jt->threadObj());
1125 _threads_array->append(h);
1126 }
1127 }