1 /*
2 * Copyright (c) 2003, 2024, 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/heapInspection.hpp"
32 #include "memory/oopFactory.hpp"
33 #include "memory/resourceArea.hpp"
34 #include "memory/universe.hpp"
35 #include "nmt/memTag.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 }
468 } else {
469 if (concurrent_locks) {
470 if (waitingToLockBlocker->is_a(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass())) {
471 oop threadObj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(waitingToLockBlocker);
472 // This JavaThread (if there is one) is protected by the
473 // ThreadsListSetter in VM_FindDeadlocks::doit().
474 currentThread = threadObj != nullptr ? java_lang_Thread::thread(threadObj) : nullptr;
475 } else {
476 currentThread = nullptr;
477 }
478 }
479 }
480
481 if (currentThread == nullptr || is_virtual_or_carrier_thread(currentThread)) {
482 // No dependency on another thread
483 break;
484 }
485 if (currentThread->depth_first_number() < 0) {
486 // First visit to this thread
487 currentThread->set_depth_first_number(globalDfn++);
488 } else if (currentThread->depth_first_number() < thisDfn) {
489 // Thread already visited, and not on a (new) cycle
490 break;
491 } else if (currentThread == previousThread) {
492 // Self-loop, ignore
493 break;
494 } else {
495 // We have a (new) cycle
496 num_deadlocks++;
497
498 // add this cycle to the deadlocks list
499 if (deadlocks == nullptr) {
500 deadlocks = cycle;
501 } else {
502 last->set_next(cycle);
503 }
504 last = cycle;
505 cycle = new DeadlockCycle();
506 break;
507 }
508 previousThread = currentThread;
509 waitingToLockMonitor = (ObjectMonitor*)currentThread->current_pending_monitor();
510 if (concurrent_locks) {
511 waitingToLockBlocker = currentThread->current_park_blocker();
512 }
513 }
514
515 }
516 delete cycle;
517 return deadlocks;
518 }
519
520 ThreadDumpResult::ThreadDumpResult() : _num_threads(0), _num_snapshots(0), _snapshots(nullptr), _last(nullptr), _next(nullptr), _setter() {
521
522 // Create a new ThreadDumpResult object and append to the list.
523 // If GC happens before this function returns, Method*
524 // in the stack trace will be visited.
525 ThreadService::add_thread_dump(this);
526 }
527
528 ThreadDumpResult::ThreadDumpResult(int num_threads) : _num_threads(num_threads), _num_snapshots(0), _snapshots(nullptr), _last(nullptr), _next(nullptr), _setter() {
529 // Create a new ThreadDumpResult object and append to the list.
530 // If GC happens before this function returns, oops
531 // will be visited.
532 ThreadService::add_thread_dump(this);
533 }
534
535 ThreadDumpResult::~ThreadDumpResult() {
536 ThreadService::remove_thread_dump(this);
537
538 // free all the ThreadSnapshot objects created during
539 // the VM_ThreadDump operation
540 ThreadSnapshot* ts = _snapshots;
541 while (ts != nullptr) {
542 ThreadSnapshot* p = ts;
543 ts = ts->next();
544 delete p;
545 }
546 }
547
548 ThreadSnapshot* ThreadDumpResult::add_thread_snapshot() {
549 ThreadSnapshot* ts = new ThreadSnapshot();
550 link_thread_snapshot(ts);
551 return ts;
552 }
553
554 ThreadSnapshot* ThreadDumpResult::add_thread_snapshot(JavaThread* thread) {
555 ThreadSnapshot* ts = new ThreadSnapshot();
556 link_thread_snapshot(ts);
557 ts->initialize(t_list(), thread);
558 return ts;
559 }
560
561 void ThreadDumpResult::link_thread_snapshot(ThreadSnapshot* ts) {
562 assert(_num_threads == 0 || _num_snapshots < _num_threads,
563 "_num_snapshots must be less than _num_threads");
564 _num_snapshots++;
565 if (_snapshots == nullptr) {
566 _snapshots = ts;
567 } else {
568 _last->set_next(ts);
569 }
570 _last = ts;
571 }
572
573 void ThreadDumpResult::metadata_do(void f(Metadata*)) {
574 for (ThreadSnapshot* ts = _snapshots; ts != nullptr; ts = ts->next()) {
575 ts->metadata_do(f);
576 }
577 }
578
579 ThreadsList* ThreadDumpResult::t_list() {
580 return _setter.list();
581 }
582
583 StackFrameInfo::StackFrameInfo(javaVFrame* jvf, bool with_lock_info) {
584 _method = jvf->method();
585 _bci = jvf->bci();
586 _class_holder = OopHandle(_thread_service_storage, _method->method_holder()->klass_holder());
587 _locked_monitors = nullptr;
588 if (with_lock_info) {
589 Thread* current_thread = Thread::current();
590 ResourceMark rm(current_thread);
591 HandleMark hm(current_thread);
592 GrowableArray<MonitorInfo*>* list = jvf->locked_monitors();
593 int length = list->length();
594 if (length > 0) {
595 _locked_monitors = new (mtServiceability) GrowableArray<OopHandle>(length, mtServiceability);
596 for (int i = 0; i < length; i++) {
597 MonitorInfo* monitor = list->at(i);
598 assert(monitor->owner() != nullptr, "This monitor must have an owning object");
599 _locked_monitors->append(OopHandle(_thread_service_storage, monitor->owner()));
600 }
601 }
602 }
603 }
604
605 StackFrameInfo::~StackFrameInfo() {
606 if (_locked_monitors != nullptr) {
607 for (int i = 0; i < _locked_monitors->length(); i++) {
608 _locked_monitors->at(i).release(_thread_service_storage);
609 }
610 delete _locked_monitors;
611 }
612 _class_holder.release(_thread_service_storage);
613 }
614
615 void StackFrameInfo::metadata_do(void f(Metadata*)) {
616 f(_method);
617 }
618
619 void StackFrameInfo::print_on(outputStream* st) const {
620 ResourceMark rm;
621 java_lang_Throwable::print_stack_element(st, method(), bci());
622 int len = (_locked_monitors != nullptr ? _locked_monitors->length() : 0);
623 for (int i = 0; i < len; i++) {
624 oop o = _locked_monitors->at(i).resolve();
625 st->print_cr("\t- locked <" INTPTR_FORMAT "> (a %s)", p2i(o), o->klass()->external_name());
626 }
627 }
628
629 // Iterate through monitor cache to find JNI locked monitors
630 class InflatedMonitorsClosure: public MonitorClosure {
631 private:
632 ThreadStackTrace* _stack_trace;
633 public:
634 InflatedMonitorsClosure(ThreadStackTrace* st) {
635 _stack_trace = st;
636 }
637 void do_monitor(ObjectMonitor* mid) {
638 oop object = mid->object();
639 if (!_stack_trace->is_owned_monitor_on_stack(object)) {
640 _stack_trace->add_jni_locked_monitor(object);
641 }
642 }
643 };
644
645 ThreadStackTrace::ThreadStackTrace(JavaThread* t, bool with_locked_monitors) {
646 _thread = t;
647 _frames = new (mtServiceability) GrowableArray<StackFrameInfo*>(INITIAL_ARRAY_SIZE, mtServiceability);
648 _depth = 0;
649 _with_locked_monitors = with_locked_monitors;
650 if (_with_locked_monitors) {
651 _jni_locked_monitors = new (mtServiceability) GrowableArray<OopHandle>(INITIAL_ARRAY_SIZE, mtServiceability);
652 } else {
653 _jni_locked_monitors = nullptr;
654 }
655 }
656
657 void ThreadStackTrace::add_jni_locked_monitor(oop object) {
658 _jni_locked_monitors->append(OopHandle(_thread_service_storage, object));
659 }
660
661 ThreadStackTrace::~ThreadStackTrace() {
662 for (int i = 0; i < _frames->length(); i++) {
663 delete _frames->at(i);
664 }
665 delete _frames;
666 if (_jni_locked_monitors != nullptr) {
667 for (int i = 0; i < _jni_locked_monitors->length(); i++) {
668 _jni_locked_monitors->at(i).release(_thread_service_storage);
669 }
670 delete _jni_locked_monitors;
671 }
672 }
673
674 void ThreadStackTrace::dump_stack_at_safepoint(int maxDepth, ObjectMonitorsView* monitors, bool full) {
675 assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
676
677 if (_thread->has_last_Java_frame()) {
678 RegisterMap reg_map(_thread,
679 RegisterMap::UpdateMap::include,
680 RegisterMap::ProcessFrames::include,
681 RegisterMap::WalkContinuation::skip);
682 ResourceMark rm(VMThread::vm_thread());
683 // If full, we want to print both vthread and carrier frames
684 vframe* start_vf = !full && _thread->is_vthread_mounted()
685 ? _thread->carrier_last_java_vframe(®_map)
686 : _thread->last_java_vframe(®_map);
687 int count = 0;
688 for (vframe* f = start_vf; f; f = f->sender() ) {
689 if (maxDepth >= 0 && count == maxDepth) {
690 // Skip frames if more than maxDepth
691 break;
692 }
693 if (!full && f->is_vthread_entry()) {
694 break;
695 }
696 if (f->is_java_frame()) {
697 javaVFrame* jvf = javaVFrame::cast(f);
698 add_stack_frame(jvf);
699 count++;
700 } else {
701 // Ignore non-Java frames
702 }
703 }
704 }
705
706 if (_with_locked_monitors) {
707 // Iterate inflated monitors and find monitors locked by this thread
708 // that are not found in the stack, e.g. JNI locked monitors:
709 InflatedMonitorsClosure imc(this);
710 monitors->visit(&imc, _thread);
711 }
712 }
713
714
715 bool ThreadStackTrace::is_owned_monitor_on_stack(oop object) {
716 assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
717
718 bool found = false;
719 int num_frames = get_stack_depth();
720 for (int depth = 0; depth < num_frames; depth++) {
721 StackFrameInfo* frame = stack_frame_at(depth);
722 int len = frame->num_locked_monitors();
723 GrowableArray<OopHandle>* locked_monitors = frame->locked_monitors();
724 for (int j = 0; j < len; j++) {
725 oop monitor = locked_monitors->at(j).resolve();
726 assert(monitor != nullptr, "must be a Java object");
727 if (monitor == object) {
728 found = true;
729 break;
730 }
731 }
732 }
733 return found;
734 }
735
736 Handle ThreadStackTrace::allocate_fill_stack_trace_element_array(TRAPS) {
737 InstanceKlass* ik = vmClasses::StackTraceElement_klass();
738 assert(ik != nullptr, "must be loaded in 1.4+");
739
740 // Allocate an array of java/lang/StackTraceElement object
741 objArrayOop ste = oopFactory::new_objArray(ik, _depth, CHECK_NH);
742 objArrayHandle backtrace(THREAD, ste);
743 for (int j = 0; j < _depth; j++) {
744 StackFrameInfo* frame = _frames->at(j);
745 methodHandle mh(THREAD, frame->method());
746 oop element = java_lang_StackTraceElement::create(mh, frame->bci(), CHECK_NH);
747 backtrace->obj_at_put(j, element);
748 }
749 return backtrace;
750 }
751
752 void ThreadStackTrace::add_stack_frame(javaVFrame* jvf) {
753 StackFrameInfo* frame = new StackFrameInfo(jvf, _with_locked_monitors);
754 _frames->append(frame);
755 _depth++;
756 }
757
758 void ThreadStackTrace::metadata_do(void f(Metadata*)) {
759 int length = _frames->length();
760 for (int i = 0; i < length; i++) {
761 _frames->at(i)->metadata_do(f);
762 }
763 }
764
765
766 ConcurrentLocksDump::~ConcurrentLocksDump() {
767 if (_retain_map_on_free) {
768 return;
769 }
770
771 for (ThreadConcurrentLocks* t = _map; t != nullptr;) {
772 ThreadConcurrentLocks* tcl = t;
773 t = t->next();
774 delete tcl;
775 }
776 }
777
778 void ConcurrentLocksDump::dump_at_safepoint() {
779 // dump all locked concurrent locks
780 assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
781
782 GrowableArray<oop>* aos_objects = new (mtServiceability) GrowableArray<oop>(INITIAL_ARRAY_SIZE, mtServiceability);
783
784 // Find all instances of AbstractOwnableSynchronizer
785 HeapInspection::find_instances_at_safepoint(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass(),
786 aos_objects);
787 // Build a map of thread to its owned AQS locks
788 build_map(aos_objects);
789
790 delete aos_objects;
791 }
792
793
794 // build a map of JavaThread to all its owned AbstractOwnableSynchronizer
795 void ConcurrentLocksDump::build_map(GrowableArray<oop>* aos_objects) {
796 int length = aos_objects->length();
797 for (int i = 0; i < length; i++) {
798 oop o = aos_objects->at(i);
799 oop owner_thread_obj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(o);
800 if (owner_thread_obj != nullptr) {
801 // See comments in ThreadConcurrentLocks to see how this
802 // JavaThread* is protected.
803 JavaThread* thread = java_lang_Thread::thread(owner_thread_obj);
804 assert(o->is_instance(), "Must be an instanceOop");
805 add_lock(thread, (instanceOop) o);
806 }
807 }
808 }
809
810 void ConcurrentLocksDump::add_lock(JavaThread* thread, instanceOop o) {
811 ThreadConcurrentLocks* tcl = thread_concurrent_locks(thread);
812 if (tcl != nullptr) {
813 tcl->add_lock(o);
814 return;
815 }
816
817 // First owned lock found for this thread
818 tcl = new ThreadConcurrentLocks(thread);
819 tcl->add_lock(o);
820 if (_map == nullptr) {
821 _map = tcl;
822 } else {
823 _last->set_next(tcl);
824 }
825 _last = tcl;
826 }
827
828 ThreadConcurrentLocks* ConcurrentLocksDump::thread_concurrent_locks(JavaThread* thread) {
829 for (ThreadConcurrentLocks* tcl = _map; tcl != nullptr; tcl = tcl->next()) {
830 if (tcl->java_thread() == thread) {
831 return tcl;
832 }
833 }
834 return nullptr;
835 }
836
837 void ConcurrentLocksDump::print_locks_on(JavaThread* t, outputStream* st) {
838 st->print_cr(" Locked ownable synchronizers:");
839 ThreadConcurrentLocks* tcl = thread_concurrent_locks(t);
840 GrowableArray<OopHandle>* locks = (tcl != nullptr ? tcl->owned_locks() : nullptr);
841 if (locks == nullptr || locks->is_empty()) {
842 st->print_cr("\t- None");
843 st->cr();
844 return;
845 }
846
847 for (int i = 0; i < locks->length(); i++) {
848 oop obj = locks->at(i).resolve();
849 st->print_cr("\t- <" INTPTR_FORMAT "> (a %s)", p2i(obj), obj->klass()->external_name());
850 }
851 st->cr();
852 }
853
854 ThreadConcurrentLocks::ThreadConcurrentLocks(JavaThread* thread) {
855 _thread = thread;
856 _owned_locks = new (mtServiceability) GrowableArray<OopHandle>(INITIAL_ARRAY_SIZE, mtServiceability);
857 _next = nullptr;
858 }
859
860 ThreadConcurrentLocks::~ThreadConcurrentLocks() {
861 for (int i = 0; i < _owned_locks->length(); i++) {
862 _owned_locks->at(i).release(_thread_service_storage);
863 }
864 delete _owned_locks;
865 }
866
867 void ThreadConcurrentLocks::add_lock(instanceOop o) {
868 _owned_locks->append(OopHandle(_thread_service_storage, o));
869 }
870
871 ThreadStatistics::ThreadStatistics() {
872 _contended_enter_count = 0;
873 _monitor_wait_count = 0;
874 _sleep_count = 0;
875 _count_pending_reset = false;
876 _timer_pending_reset = false;
877 memset((void*) _perf_recursion_counts, 0, sizeof(_perf_recursion_counts));
878 }
879
880 oop ThreadSnapshot::threadObj() const { return _threadObj.resolve(); }
881
882 void ThreadSnapshot::initialize(ThreadsList * t_list, JavaThread* thread) {
883 _thread = thread;
884 oop threadObj = thread->threadObj();
885 _threadObj = OopHandle(_thread_service_storage, threadObj);
886
887 ThreadStatistics* stat = thread->get_thread_stat();
888 _contended_enter_ticks = stat->contended_enter_ticks();
889 _contended_enter_count = stat->contended_enter_count();
890 _monitor_wait_ticks = stat->monitor_wait_ticks();
891 _monitor_wait_count = stat->monitor_wait_count();
892 _sleep_ticks = stat->sleep_ticks();
893 _sleep_count = stat->sleep_count();
894
895 // If thread is still attaching then threadObj will be null.
896 _thread_status = threadObj == nullptr ? JavaThreadStatus::NEW
897 : java_lang_Thread::get_thread_status(threadObj);
898
899 _is_suspended = thread->is_suspended();
900 _is_in_native = (thread->thread_state() == _thread_in_native);
901
902 Handle obj = ThreadService::get_current_contended_monitor(thread);
903
904 oop blocker_object = nullptr;
905 oop blocker_object_owner = nullptr;
906
907 if (thread->is_vthread_mounted() && thread->vthread() != threadObj) { // ThreadSnapshot only captures platform threads
908 _thread_status = JavaThreadStatus::IN_OBJECT_WAIT;
909 oop vthread = thread->vthread();
910 assert(vthread != nullptr, "");
911 blocker_object = vthread;
912 blocker_object_owner = vthread;
913 } else if (_thread_status == JavaThreadStatus::BLOCKED_ON_MONITOR_ENTER ||
914 _thread_status == JavaThreadStatus::IN_OBJECT_WAIT ||
915 _thread_status == JavaThreadStatus::IN_OBJECT_WAIT_TIMED) {
916
917 if (obj() == nullptr) {
918 // monitor no longer exists; thread is not blocked
919 _thread_status = JavaThreadStatus::RUNNABLE;
920 } else {
921 blocker_object = obj();
922 JavaThread* owner = ObjectSynchronizer::get_lock_owner(t_list, obj);
923 if ((owner == nullptr && _thread_status == JavaThreadStatus::BLOCKED_ON_MONITOR_ENTER)
924 || (owner != nullptr && owner->is_attaching_via_jni())) {
925 // ownership information of the monitor is not available
926 // (may no longer be owned or releasing to some other thread)
927 // make this thread in RUNNABLE state.
928 // And when the owner thread is in attaching state, the java thread
929 // is not completely initialized. For example thread name and id
930 // and may not be set, so hide the attaching thread.
931 _thread_status = JavaThreadStatus::RUNNABLE;
932 blocker_object = nullptr;
933 } else if (owner != nullptr) {
934 blocker_object_owner = owner->threadObj();
935 }
936 }
937 } else if (_thread_status == JavaThreadStatus::PARKED || _thread_status == JavaThreadStatus::PARKED_TIMED) {
938 blocker_object = thread->current_park_blocker();
939 if (blocker_object != nullptr && blocker_object->is_a(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass())) {
940 blocker_object_owner = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(blocker_object);
941 }
942 }
943
944 if (blocker_object != nullptr) {
945 _blocker_object = OopHandle(_thread_service_storage, blocker_object);
946 }
947 if (blocker_object_owner != nullptr) {
948 _blocker_object_owner = OopHandle(_thread_service_storage, blocker_object_owner);
949 }
950 }
951
952 oop ThreadSnapshot::blocker_object() const { return _blocker_object.resolve(); }
953 oop ThreadSnapshot::blocker_object_owner() const { return _blocker_object_owner.resolve(); }
954
955 ThreadSnapshot::~ThreadSnapshot() {
956 _blocker_object.release(_thread_service_storage);
957 _blocker_object_owner.release(_thread_service_storage);
958 _threadObj.release(_thread_service_storage);
959
960 delete _stack_trace;
961 delete _concurrent_locks;
962 }
963
964 void ThreadSnapshot::dump_stack_at_safepoint(int max_depth, bool with_locked_monitors,
965 ObjectMonitorsView* monitors, bool full) {
966 _stack_trace = new ThreadStackTrace(_thread, with_locked_monitors);
967 _stack_trace->dump_stack_at_safepoint(max_depth, monitors, full);
968 }
969
970
971 void ThreadSnapshot::metadata_do(void f(Metadata*)) {
972 if (_stack_trace != nullptr) {
973 _stack_trace->metadata_do(f);
974 }
975 }
976
977
978 DeadlockCycle::DeadlockCycle() {
979 _threads = new (mtServiceability) GrowableArray<JavaThread*>(INITIAL_ARRAY_SIZE, mtServiceability);
980 _next = nullptr;
981 }
982
983 DeadlockCycle::~DeadlockCycle() {
984 delete _threads;
985 }
986
987 void DeadlockCycle::print_on_with(ThreadsList * t_list, outputStream* st) const {
988 st->cr();
989 st->print_cr("Found one Java-level deadlock:");
990 st->print("=============================");
991
992 JavaThread* currentThread;
993 JvmtiRawMonitor* waitingToLockRawMonitor;
994 oop waitingToLockBlocker;
995 int len = _threads->length();
996 for (int i = 0; i < len; i++) {
997 currentThread = _threads->at(i);
998 // The ObjectMonitor* can't be async deflated since we are at a safepoint.
999 ObjectMonitor* waitingToLockMonitor = currentThread->current_pending_monitor();
1000 waitingToLockRawMonitor = currentThread->current_pending_raw_monitor();
1001 waitingToLockBlocker = currentThread->current_park_blocker();
1002 st->cr();
1003 st->print_cr("\"%s\":", currentThread->name());
1004 const char* owner_desc = ",\n which is held by";
1005
1006 // Note: As the JVM TI "monitor contended enter" event callback is executed after ObjectMonitor
1007 // sets the current pending monitor, it is possible to then see a pending raw monitor as well.
1008 if (waitingToLockRawMonitor != nullptr) {
1009 st->print(" waiting to lock JVM TI raw monitor " INTPTR_FORMAT, p2i(waitingToLockRawMonitor));
1010 Thread* owner = waitingToLockRawMonitor->owner();
1011 // Could be null as the raw monitor could be released at any time if held by non-JavaThread
1012 if (owner != nullptr) {
1013 if (owner->is_Java_thread()) {
1014 currentThread = JavaThread::cast(owner);
1015 st->print_cr("%s \"%s\"", owner_desc, currentThread->name());
1016 } else {
1017 st->print_cr(",\n which has now been released");
1018 }
1019 } else {
1020 st->print_cr("%s non-Java thread=" PTR_FORMAT, owner_desc, p2i(owner));
1021 }
1022 }
1023
1024 if (waitingToLockMonitor != nullptr) {
1025 st->print(" waiting to lock monitor " INTPTR_FORMAT, p2i(waitingToLockMonitor));
1026 oop obj = waitingToLockMonitor->object();
1027 st->print(" (object " INTPTR_FORMAT ", a %s)", p2i(obj),
1028 obj->klass()->external_name());
1029
1030 if (!currentThread->current_pending_monitor_is_from_java()) {
1031 owner_desc = "\n in JNI, which is held by";
1032 }
1033 currentThread = Threads::owning_thread_from_monitor(t_list, waitingToLockMonitor);
1034 if (currentThread == nullptr) {
1035 // The deadlock was detected at a safepoint so the JavaThread
1036 // that owns waitingToLockMonitor should be findable, but
1037 // if it is not findable, then the previous currentThread is
1038 // blocked permanently.
1039 st->print_cr("%s UNKNOWN_owner_addr=" PTR_FORMAT, owner_desc,
1040 p2i(waitingToLockMonitor->owner()));
1041 continue;
1042 }
1043 } else {
1044 st->print(" waiting for ownable synchronizer " INTPTR_FORMAT ", (a %s)",
1045 p2i(waitingToLockBlocker),
1046 waitingToLockBlocker->klass()->external_name());
1047 assert(waitingToLockBlocker->is_a(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass()),
1048 "Must be an AbstractOwnableSynchronizer");
1049 oop ownerObj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(waitingToLockBlocker);
1050 currentThread = java_lang_Thread::thread(ownerObj);
1051 assert(currentThread != nullptr, "AbstractOwnableSynchronizer owning thread is unexpectedly null");
1052 }
1053 st->print_cr("%s \"%s\"", owner_desc, currentThread->name());
1054 }
1055
1056 st->cr();
1057
1058 // Print stack traces
1059 bool oldJavaMonitorsInStackTrace = JavaMonitorsInStackTrace;
1060 JavaMonitorsInStackTrace = true;
1061 st->print_cr("Java stack information for the threads listed above:");
1062 st->print_cr("===================================================");
1063 for (int j = 0; j < len; j++) {
1064 currentThread = _threads->at(j);
1065 st->print_cr("\"%s\":", currentThread->name());
1066 currentThread->print_stack_on(st);
1067 }
1068 JavaMonitorsInStackTrace = oldJavaMonitorsInStackTrace;
1069 }
1070
1071 ThreadsListEnumerator::ThreadsListEnumerator(Thread* cur_thread,
1072 bool include_jvmti_agent_threads,
1073 bool include_jni_attaching_threads,
1074 bool include_bound_virtual_threads) {
1075 assert(cur_thread == Thread::current(), "Check current thread");
1076
1077 int init_size = ThreadService::get_live_thread_count();
1078 _threads_array = new GrowableArray<instanceHandle>(init_size);
1079
1080 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
1081 // skips JavaThreads in the process of exiting
1082 // and also skips VM internal JavaThreads
1083 // Threads in _thread_new or _thread_new_trans state are included.
1084 // i.e. threads have been started but not yet running.
1085 if (jt->threadObj() == nullptr ||
1086 jt->is_exiting() ||
1087 !java_lang_Thread::is_alive(jt->threadObj()) ||
1088 jt->is_hidden_from_external_view()) {
1089 continue;
1090 }
1091
1092 // skip agent threads
1093 if (!include_jvmti_agent_threads && jt->is_jvmti_agent_thread()) {
1094 continue;
1095 }
1096
1097 // skip jni threads in the process of attaching
1098 if (!include_jni_attaching_threads && jt->is_attaching_via_jni()) {
1099 continue;
1100 }
1101
1102 // skip instances of BoundVirtualThread
1103 if (!include_bound_virtual_threads && jt->threadObj()->is_a(vmClasses::BoundVirtualThread_klass())) {
1104 continue;
1105 }
1106
1107 instanceHandle h(cur_thread, (instanceOop) jt->threadObj());
1108 _threads_array->append(h);
1109 }
1110 }