1 /*
2 * Copyright (c) 2003, 2025, 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 "classfile/javaClasses.inline.hpp"
26 #include "classfile/systemDictionary.hpp"
27 #include "classfile/vmClasses.hpp"
28 #include "classfile/vmSymbols.hpp"
29 #include "gc/shared/oopStorageSet.hpp"
30 #include "memory/heapInspection.hpp"
31 #include "memory/oopFactory.hpp"
32 #include "memory/resourceArea.hpp"
33 #include "memory/universe.hpp"
34 #include "nmt/memTag.hpp"
35 #include "oops/instanceKlass.hpp"
36 #include "oops/klass.inline.hpp"
37 #include "oops/objArrayKlass.hpp"
38 #include "oops/objArrayOop.inline.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "oops/oopHandle.inline.hpp"
41 #include "prims/jvmtiRawMonitor.hpp"
42 #include "runtime/atomic.hpp"
43 #include "runtime/handles.inline.hpp"
44 #include "runtime/init.hpp"
45 #include "runtime/javaThread.inline.hpp"
46 #include "runtime/objectMonitor.inline.hpp"
47 #include "runtime/synchronizer.hpp"
48 #include "runtime/thread.inline.hpp"
49 #include "runtime/threads.hpp"
50 #include "runtime/threadSMR.inline.hpp"
51 #include "runtime/vframe.hpp"
52 #include "runtime/vmThread.hpp"
53 #include "runtime/vmOperations.hpp"
54 #include "services/threadService.hpp"
55
56 // TODO: we need to define a naming convention for perf counters
57 // to distinguish counters for:
58 // - standard JSR174 use
59 // - Hotspot extension (public and committed)
60 // - Hotspot extension (private/internal and uncommitted)
61
62 // Default is disabled.
63 bool ThreadService::_thread_monitoring_contention_enabled = false;
64 bool ThreadService::_thread_cpu_time_enabled = false;
65 bool ThreadService::_thread_allocated_memory_enabled = false;
66
67 PerfCounter* ThreadService::_total_threads_count = nullptr;
68 PerfVariable* ThreadService::_live_threads_count = nullptr;
69 PerfVariable* ThreadService::_peak_threads_count = nullptr;
70 PerfVariable* ThreadService::_daemon_threads_count = nullptr;
71 volatile int ThreadService::_atomic_threads_count = 0;
72 volatile int ThreadService::_atomic_daemon_threads_count = 0;
73
74 volatile jlong ThreadService::_exited_allocated_bytes = 0;
75
76 ThreadDumpResult* ThreadService::_threaddump_list = nullptr;
77
78 static const int INITIAL_ARRAY_SIZE = 10;
79
80 // OopStorage for thread stack sampling
81 static OopStorage* _thread_service_storage = nullptr;
82
83 void ThreadService::init() {
84 EXCEPTION_MARK;
85
86 // These counters are for java.lang.management API support.
87 // They are created even if -XX:-UsePerfData is set and in
88 // that case, they will be allocated on C heap.
89
90 _total_threads_count =
91 PerfDataManager::create_counter(JAVA_THREADS, "started",
92 PerfData::U_Events, CHECK);
93
94 _live_threads_count =
95 PerfDataManager::create_variable(JAVA_THREADS, "live",
96 PerfData::U_None, CHECK);
97
98 _peak_threads_count =
99 PerfDataManager::create_variable(JAVA_THREADS, "livePeak",
100 PerfData::U_None, CHECK);
101
102 _daemon_threads_count =
103 PerfDataManager::create_variable(JAVA_THREADS, "daemon",
104 PerfData::U_None, CHECK);
105
106 if (os::is_thread_cpu_time_supported()) {
107 _thread_cpu_time_enabled = true;
108 }
109
110 _thread_allocated_memory_enabled = true; // Always on, so enable it
111
112 // Initialize OopStorage for thread stack sampling walking
113 _thread_service_storage = OopStorageSet::create_strong("ThreadService OopStorage",
114 mtServiceability);
115 }
116
117 void ThreadService::reset_peak_thread_count() {
118 // Acquire the lock to update the peak thread count
119 // to synchronize with thread addition and removal.
120 MutexLocker mu(Threads_lock);
121 _peak_threads_count->set_value(get_live_thread_count());
122 }
123
124 static bool is_hidden_thread(JavaThread *thread) {
125 // hide VM internal or JVMTI agent threads
126 return thread->is_hidden_from_external_view() || thread->is_jvmti_agent_thread();
127 }
128
129 void ThreadService::add_thread(JavaThread* thread, bool daemon) {
130 assert(Threads_lock->owned_by_self(), "must have threads lock");
131
132 // Do not count hidden threads
133 if (is_hidden_thread(thread)) {
134 return;
135 }
136
137 _total_threads_count->inc();
138 _live_threads_count->inc();
139 Atomic::inc(&_atomic_threads_count);
140 int count = _atomic_threads_count;
141
142 if (count > _peak_threads_count->get_value()) {
143 _peak_threads_count->set_value(count);
144 }
145
146 if (daemon) {
147 _daemon_threads_count->inc();
148 Atomic::inc(&_atomic_daemon_threads_count);
149 }
150 }
151
152 void ThreadService::decrement_thread_counts(JavaThread* jt, bool daemon) {
153 Atomic::dec(&_atomic_threads_count);
154
155 if (daemon) {
156 Atomic::dec(&_atomic_daemon_threads_count);
157 }
158 }
159
160 void ThreadService::remove_thread(JavaThread* thread, bool daemon) {
161 assert(Threads_lock->owned_by_self(), "must have threads lock");
162
163 // Include hidden thread allcations in exited_allocated_bytes
164 ThreadService::incr_exited_allocated_bytes(thread->cooked_allocated_bytes());
165
166 // Do not count hidden threads
167 if (is_hidden_thread(thread)) {
168 return;
169 }
170
171 assert(!thread->is_terminated(), "must not be terminated");
172 if (!thread->is_exiting()) {
173 // We did not get here via JavaThread::exit() so current_thread_exiting()
174 // was not called, e.g., JavaThread::cleanup_failed_attach_current_thread().
175 decrement_thread_counts(thread, daemon);
176 }
177
178 int daemon_count = _atomic_daemon_threads_count;
179 int count = _atomic_threads_count;
180
181 // Counts are incremented at the same time, but atomic counts are
182 // decremented earlier than perf counts.
183 assert(_live_threads_count->get_value() > count,
184 "thread count mismatch %d : %d",
185 (int)_live_threads_count->get_value(), count);
186
187 _live_threads_count->dec(1);
188 if (daemon) {
189 assert(_daemon_threads_count->get_value() > daemon_count,
190 "thread count mismatch %d : %d",
191 (int)_daemon_threads_count->get_value(), daemon_count);
192
193 _daemon_threads_count->dec(1);
194 }
195
196 // Counts are incremented at the same time, but atomic counts are
197 // decremented earlier than perf counts.
198 assert(_daemon_threads_count->get_value() >= daemon_count,
199 "thread count mismatch %d : %d",
200 (int)_daemon_threads_count->get_value(), daemon_count);
201 assert(_live_threads_count->get_value() >= count,
202 "thread count mismatch %d : %d",
203 (int)_live_threads_count->get_value(), count);
204 assert(_live_threads_count->get_value() > 0 ||
205 (_live_threads_count->get_value() == 0 && count == 0 &&
206 _daemon_threads_count->get_value() == 0 && daemon_count == 0),
207 "thread counts should reach 0 at the same time, live %d,%d daemon %d,%d",
208 (int)_live_threads_count->get_value(), count,
209 (int)_daemon_threads_count->get_value(), daemon_count);
210 assert(_daemon_threads_count->get_value() > 0 ||
211 (_daemon_threads_count->get_value() == 0 && daemon_count == 0),
212 "thread counts should reach 0 at the same time, daemon %d,%d",
213 (int)_daemon_threads_count->get_value(), daemon_count);
214 }
215
216 void ThreadService::current_thread_exiting(JavaThread* jt, bool daemon) {
217 // Do not count hidden threads
218 if (is_hidden_thread(jt)) {
219 return;
220 }
221
222 assert(jt == JavaThread::current(), "Called by current thread");
223 assert(!jt->is_terminated() && jt->is_exiting(), "must be exiting");
224
225 decrement_thread_counts(jt, daemon);
226 }
227
228 // FIXME: JVMTI should call this function
229 Handle ThreadService::get_current_contended_monitor(JavaThread* thread) {
230 assert(thread != nullptr, "should be non-null");
231 DEBUG_ONLY(Thread::check_for_dangling_thread_pointer(thread);)
232
233 // This function can be called on a target JavaThread that is not
234 // the caller and we are not at a safepoint. So it is possible for
235 // the waiting or pending condition to be over/stale and for the
236 // first stage of async deflation to clear the object field in
237 // the ObjectMonitor. It is also possible for the object to be
238 // inflated again and to be associated with a completely different
239 // ObjectMonitor by the time this object reference is processed
240 // by the caller.
241 ObjectMonitor *wait_obj = thread->current_waiting_monitor();
242
243 oop obj = nullptr;
244 if (wait_obj != nullptr) {
245 // thread is doing an Object.wait() call
246 obj = wait_obj->object();
247 } else {
248 ObjectMonitor *enter_obj = thread->current_pending_monitor();
249 if (enter_obj != nullptr) {
250 // thread is trying to enter() an ObjectMonitor.
251 obj = enter_obj->object();
252 }
253 }
254
255 Handle h(Thread::current(), obj);
256 return h;
257 }
258
259 bool ThreadService::set_thread_monitoring_contention(bool flag) {
260 MutexLocker m(Management_lock);
261
262 bool prev = _thread_monitoring_contention_enabled;
263 _thread_monitoring_contention_enabled = flag;
264
265 return prev;
266 }
267
268 bool ThreadService::set_thread_cpu_time_enabled(bool flag) {
269 MutexLocker m(Management_lock);
270
271 bool prev = _thread_cpu_time_enabled;
272 _thread_cpu_time_enabled = flag;
273
274 return prev;
275 }
276
277 bool ThreadService::set_thread_allocated_memory_enabled(bool flag) {
278 MutexLocker m(Management_lock);
279
280 bool prev = _thread_allocated_memory_enabled;
281 _thread_allocated_memory_enabled = flag;
282
283 return prev;
284 }
285
286 void ThreadService::metadata_do(void f(Metadata*)) {
287 for (ThreadDumpResult* dump = _threaddump_list; dump != nullptr; dump = dump->next()) {
288 dump->metadata_do(f);
289 }
290 }
291
292 void ThreadService::add_thread_dump(ThreadDumpResult* dump) {
293 MutexLocker ml(Management_lock);
294 if (_threaddump_list == nullptr) {
295 _threaddump_list = dump;
296 } else {
297 dump->set_next(_threaddump_list);
298 _threaddump_list = dump;
299 }
300 }
301
302 void ThreadService::remove_thread_dump(ThreadDumpResult* dump) {
303 MutexLocker ml(Management_lock);
304
305 ThreadDumpResult* prev = nullptr;
306 bool found = false;
307 for (ThreadDumpResult* d = _threaddump_list; d != nullptr; prev = d, d = d->next()) {
308 if (d == dump) {
309 if (prev == nullptr) {
310 _threaddump_list = dump->next();
311 } else {
312 prev->set_next(dump->next());
313 }
314 found = true;
315 break;
316 }
317 }
318 assert(found, "The threaddump result to be removed must exist.");
319 }
320
321 // Dump stack trace of threads specified in the given threads array.
322 // Returns StackTraceElement[][] each element is the stack trace of a thread in
323 // the corresponding entry in the given threads array
324 Handle ThreadService::dump_stack_traces(GrowableArray<instanceHandle>* threads,
325 int num_threads,
326 TRAPS) {
327 assert(num_threads > 0, "just checking");
328
329 ThreadDumpResult dump_result;
330 VM_ThreadDump op(&dump_result,
331 threads,
332 num_threads,
333 -1, /* entire stack */
334 false, /* with locked monitors */
335 false /* with locked synchronizers */);
336 VMThread::execute(&op);
337
338 // Allocate the resulting StackTraceElement[][] object
339
340 ResourceMark rm(THREAD);
341 Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_StackTraceElement_array(), true, CHECK_NH);
342 ObjArrayKlass* ik = ObjArrayKlass::cast(k);
343 objArrayOop r = oopFactory::new_objArray(ik, num_threads, CHECK_NH);
344 objArrayHandle result_obj(THREAD, r);
345
346 int num_snapshots = dump_result.num_snapshots();
347 assert(num_snapshots == num_threads, "Must have num_threads thread snapshots");
348 assert(num_snapshots == 0 || dump_result.t_list_has_been_set(), "ThreadsList must have been set if we have a snapshot");
349 int i = 0;
350 for (ThreadSnapshot* ts = dump_result.snapshots(); ts != nullptr; i++, ts = ts->next()) {
351 ThreadStackTrace* stacktrace = ts->get_stack_trace();
352 if (stacktrace == nullptr) {
353 // No stack trace
354 result_obj->obj_at_put(i, nullptr);
355 } else {
356 // Construct an array of java/lang/StackTraceElement object
357 Handle backtrace_h = stacktrace->allocate_fill_stack_trace_element_array(CHECK_NH);
358 result_obj->obj_at_put(i, backtrace_h());
359 }
360 }
361
362 return result_obj;
363 }
364
365 void ThreadService::reset_contention_count_stat(JavaThread* thread) {
366 ThreadStatistics* stat = thread->get_thread_stat();
367 if (stat != nullptr) {
368 stat->reset_count_stat();
369 }
370 }
371
372 void ThreadService::reset_contention_time_stat(JavaThread* thread) {
373 ThreadStatistics* stat = thread->get_thread_stat();
374 if (stat != nullptr) {
375 stat->reset_time_stat();
376 }
377 }
378
379 bool ThreadService::is_virtual_or_carrier_thread(JavaThread* jt) {
380 oop threadObj = jt->threadObj();
381 if (threadObj != nullptr && threadObj->is_a(vmClasses::BaseVirtualThread_klass())) {
382 // a virtual thread backed by JavaThread
383 return true;
384 }
385 if (jt->is_vthread_mounted()) {
386 // carrier thread
387 return true;
388 }
389 return false;
390 }
391
392 // Find deadlocks involving raw monitors, object monitors and concurrent locks
393 // if concurrent_locks is true.
394 // We skip virtual thread carriers under the assumption that the current scheduler, ForkJoinPool,
395 // doesn't hold any locks while mounting a virtual thread, so any owned monitor (or j.u.c., lock for that matter)
396 // on that JavaThread must be owned by the virtual thread, and we don't support deadlock detection for virtual threads.
397 DeadlockCycle* ThreadService::find_deadlocks_at_safepoint(ThreadsList * t_list, bool concurrent_locks) {
398 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
399
400 // This code was modified from the original Threads::find_deadlocks code.
401 int globalDfn = 0, thisDfn;
402 ObjectMonitor* waitingToLockMonitor = nullptr;
403 JvmtiRawMonitor* waitingToLockRawMonitor = nullptr;
404 oop waitingToLockBlocker = nullptr;
405 bool blocked_on_monitor = false;
406 JavaThread *currentThread, *previousThread;
407 int num_deadlocks = 0;
408
409 // Initialize the depth-first-number for each JavaThread.
410 JavaThreadIterator jti(t_list);
411 for (JavaThread* jt = jti.first(); jt != nullptr; jt = jti.next()) {
412 if (!is_virtual_or_carrier_thread(jt)) {
413 jt->set_depth_first_number(-1);
414 }
415 }
416
417 DeadlockCycle* deadlocks = nullptr;
418 DeadlockCycle* last = nullptr;
419 DeadlockCycle* cycle = new DeadlockCycle();
420 for (JavaThread* jt = jti.first(); jt != nullptr; jt = jti.next()) {
421 if (is_virtual_or_carrier_thread(jt)) {
422 // skip virtual and carrier threads
423 continue;
424 }
425 if (jt->depth_first_number() >= 0) {
426 // this thread was already visited
427 continue;
428 }
429
430 thisDfn = globalDfn;
431 jt->set_depth_first_number(globalDfn++);
432 previousThread = jt;
433 currentThread = jt;
434
435 cycle->reset();
436
437 // The ObjectMonitor* can't be async deflated since we are at a safepoint.
438 // When there is a deadlock, all the monitors involved in the dependency
439 // cycle must be contended and heavyweight. So we only care about the
440 // heavyweight monitor a thread is waiting to lock.
441 waitingToLockMonitor = jt->current_pending_monitor();
442 // JVM TI raw monitors can also be involved in deadlocks, and we can be
443 // waiting to lock both a raw monitor and ObjectMonitor at the same time.
444 // It isn't clear how to make deadlock detection work correctly if that
445 // happens.
446 waitingToLockRawMonitor = jt->current_pending_raw_monitor();
447
448 if (concurrent_locks) {
449 waitingToLockBlocker = jt->current_park_blocker();
450 }
451
452 while (waitingToLockMonitor != nullptr ||
453 waitingToLockRawMonitor != nullptr ||
454 waitingToLockBlocker != nullptr) {
455 cycle->add_thread(currentThread);
456 // Give preference to the raw monitor
457 if (waitingToLockRawMonitor != nullptr) {
458 Thread* owner = waitingToLockRawMonitor->owner();
459 if (owner != nullptr && // the raw monitor could be released at any time
460 owner->is_Java_thread()) {
461 currentThread = JavaThread::cast(owner);
462 }
463 } else if (waitingToLockMonitor != nullptr) {
464 if (waitingToLockMonitor->has_owner()) {
465 currentThread = Threads::owning_thread_from_monitor(t_list, waitingToLockMonitor);
466 // If currentThread is null we would like to know if the owner
467 // is an unmounted vthread (no JavaThread*), because if it's not,
468 // it would mean the previous currentThread is blocked permanently
469 // and we should record this as a deadlock. Since there is currently
470 // no fast way to determine if the owner is indeed an unmounted
471 // vthread we never record this as a deadlock. Note: unless there
472 // is a bug in the VM, or a thread exits without releasing monitors
473 // acquired through JNI, null should imply an unmounted vthread owner.
474 }
475 } else {
476 if (concurrent_locks) {
477 if (waitingToLockBlocker->is_a(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass())) {
478 oop threadObj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(waitingToLockBlocker);
479 // This JavaThread (if there is one) is protected by the
480 // ThreadsListSetter in VM_FindDeadlocks::doit().
481 currentThread = threadObj != nullptr ? java_lang_Thread::thread(threadObj) : nullptr;
482 } else {
483 currentThread = nullptr;
484 }
485 }
486 }
487
488 if (currentThread == nullptr || is_virtual_or_carrier_thread(currentThread)) {
489 // No dependency on another thread
490 break;
491 }
492 if (currentThread->depth_first_number() < 0) {
493 // First visit to this thread
494 currentThread->set_depth_first_number(globalDfn++);
495 } else if (currentThread->depth_first_number() < thisDfn) {
496 // Thread already visited, and not on a (new) cycle
497 break;
498 } else if (currentThread == previousThread) {
499 // Self-loop, ignore
500 break;
501 } else {
502 // We have a (new) cycle
503 num_deadlocks++;
504
505 // add this cycle to the deadlocks list
506 if (deadlocks == nullptr) {
507 deadlocks = cycle;
508 } else {
509 last->set_next(cycle);
510 }
511 last = cycle;
512 cycle = new DeadlockCycle();
513 break;
514 }
515 previousThread = currentThread;
516 waitingToLockMonitor = (ObjectMonitor*)currentThread->current_pending_monitor();
517 if (concurrent_locks) {
518 waitingToLockBlocker = currentThread->current_park_blocker();
519 }
520 }
521
522 }
523 delete cycle;
524 return deadlocks;
525 }
526
527 ThreadDumpResult::ThreadDumpResult() : _num_threads(0), _num_snapshots(0), _snapshots(nullptr), _last(nullptr), _next(nullptr), _setter() {
528
529 // Create a new ThreadDumpResult object and append to the list.
530 // If GC happens before this function returns, Method*
531 // in the stack trace will be visited.
532 ThreadService::add_thread_dump(this);
533 }
534
535 ThreadDumpResult::ThreadDumpResult(int num_threads) : _num_threads(num_threads), _num_snapshots(0), _snapshots(nullptr), _last(nullptr), _next(nullptr), _setter() {
536 // Create a new ThreadDumpResult object and append to the list.
537 // If GC happens before this function returns, oops
538 // will be visited.
539 ThreadService::add_thread_dump(this);
540 }
541
542 ThreadDumpResult::~ThreadDumpResult() {
543 ThreadService::remove_thread_dump(this);
544
545 // free all the ThreadSnapshot objects created during
546 // the VM_ThreadDump operation
547 ThreadSnapshot* ts = _snapshots;
548 while (ts != nullptr) {
549 ThreadSnapshot* p = ts;
550 ts = ts->next();
551 delete p;
552 }
553 }
554
555 ThreadSnapshot* ThreadDumpResult::add_thread_snapshot() {
556 ThreadSnapshot* ts = new ThreadSnapshot();
557 link_thread_snapshot(ts);
558 return ts;
559 }
560
561 ThreadSnapshot* ThreadDumpResult::add_thread_snapshot(JavaThread* thread) {
562 ThreadSnapshot* ts = new ThreadSnapshot();
563 link_thread_snapshot(ts);
564 ts->initialize(t_list(), thread);
565 return ts;
566 }
567
568 void ThreadDumpResult::link_thread_snapshot(ThreadSnapshot* ts) {
569 assert(_num_threads == 0 || _num_snapshots < _num_threads,
570 "_num_snapshots must be less than _num_threads");
571 _num_snapshots++;
572 if (_snapshots == nullptr) {
573 _snapshots = ts;
574 } else {
575 _last->set_next(ts);
576 }
577 _last = ts;
578 }
579
580 void ThreadDumpResult::metadata_do(void f(Metadata*)) {
581 for (ThreadSnapshot* ts = _snapshots; ts != nullptr; ts = ts->next()) {
582 ts->metadata_do(f);
583 }
584 }
585
586 ThreadsList* ThreadDumpResult::t_list() {
587 return _setter.list();
588 }
589
590 StackFrameInfo::StackFrameInfo(javaVFrame* jvf, bool with_lock_info) {
591 _method = jvf->method();
592 _bci = jvf->bci();
593 _class_holder = OopHandle(_thread_service_storage, _method->method_holder()->klass_holder());
594 _locked_monitors = nullptr;
595 if (with_lock_info) {
596 Thread* current_thread = Thread::current();
597 ResourceMark rm(current_thread);
598 HandleMark hm(current_thread);
599 GrowableArray<MonitorInfo*>* list = jvf->locked_monitors();
600 int length = list->length();
601 if (length > 0) {
602 _locked_monitors = new (mtServiceability) GrowableArray<OopHandle>(length, mtServiceability);
603 for (int i = 0; i < length; i++) {
604 MonitorInfo* monitor = list->at(i);
605 assert(monitor->owner() != nullptr, "This monitor must have an owning object");
606 _locked_monitors->append(OopHandle(_thread_service_storage, monitor->owner()));
607 }
608 }
609 }
610 }
611
612 StackFrameInfo::~StackFrameInfo() {
613 if (_locked_monitors != nullptr) {
614 for (int i = 0; i < _locked_monitors->length(); i++) {
615 _locked_monitors->at(i).release(_thread_service_storage);
616 }
617 delete _locked_monitors;
618 }
619 _class_holder.release(_thread_service_storage);
620 }
621
622 void StackFrameInfo::metadata_do(void f(Metadata*)) {
623 f(_method);
624 }
625
626 void StackFrameInfo::print_on(outputStream* st) const {
627 ResourceMark rm;
628 java_lang_Throwable::print_stack_element(st, method(), bci());
629 int len = (_locked_monitors != nullptr ? _locked_monitors->length() : 0);
630 for (int i = 0; i < len; i++) {
631 oop o = _locked_monitors->at(i).resolve();
632 st->print_cr("\t- locked <" INTPTR_FORMAT "> (a %s)", p2i(o), o->klass()->external_name());
633 }
634 }
635
636 // Iterate through monitor cache to find JNI locked monitors
637 class InflatedMonitorsClosure: public MonitorClosure {
638 private:
639 ThreadStackTrace* _stack_trace;
640 public:
641 InflatedMonitorsClosure(ThreadStackTrace* st) {
642 _stack_trace = st;
643 }
644 void do_monitor(ObjectMonitor* mid) {
645 oop object = mid->object();
646 if (!_stack_trace->is_owned_monitor_on_stack(object)) {
647 _stack_trace->add_jni_locked_monitor(object);
648 }
649 }
650 };
651
652 ThreadStackTrace::ThreadStackTrace(JavaThread* t, bool with_locked_monitors) {
653 _thread = t;
654 _frames = new (mtServiceability) GrowableArray<StackFrameInfo*>(INITIAL_ARRAY_SIZE, mtServiceability);
655 _depth = 0;
656 _with_locked_monitors = with_locked_monitors;
657 if (_with_locked_monitors) {
658 _jni_locked_monitors = new (mtServiceability) GrowableArray<OopHandle>(INITIAL_ARRAY_SIZE, mtServiceability);
659 } else {
660 _jni_locked_monitors = nullptr;
661 }
662 }
663
664 void ThreadStackTrace::add_jni_locked_monitor(oop object) {
665 _jni_locked_monitors->append(OopHandle(_thread_service_storage, object));
666 }
667
668 ThreadStackTrace::~ThreadStackTrace() {
669 for (int i = 0; i < _frames->length(); i++) {
670 delete _frames->at(i);
671 }
672 delete _frames;
673 if (_jni_locked_monitors != nullptr) {
674 for (int i = 0; i < _jni_locked_monitors->length(); i++) {
675 _jni_locked_monitors->at(i).release(_thread_service_storage);
676 }
677 delete _jni_locked_monitors;
678 }
679 }
680
681 void ThreadStackTrace::dump_stack_at_safepoint(int maxDepth, ObjectMonitorsView* monitors, bool full) {
682 assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
683
684 if (_thread->has_last_Java_frame()) {
685 RegisterMap reg_map(_thread,
686 RegisterMap::UpdateMap::include,
687 RegisterMap::ProcessFrames::include,
688 RegisterMap::WalkContinuation::skip);
689 ResourceMark rm(VMThread::vm_thread());
690 // If full, we want to print both vthread and carrier frames
691 vframe* start_vf = !full && _thread->is_vthread_mounted()
692 ? _thread->carrier_last_java_vframe(®_map)
693 : _thread->last_java_vframe(®_map);
694 int count = 0;
695 for (vframe* f = start_vf; f; f = f->sender() ) {
696 if (maxDepth >= 0 && count == maxDepth) {
697 // Skip frames if more than maxDepth
698 break;
699 }
700 if (!full && f->is_vthread_entry()) {
701 break;
702 }
703 if (f->is_java_frame()) {
704 javaVFrame* jvf = javaVFrame::cast(f);
705 add_stack_frame(jvf);
706 count++;
707 } else {
708 // Ignore non-Java frames
709 }
710 }
711 }
712
713 if (_with_locked_monitors) {
714 // Iterate inflated monitors and find monitors locked by this thread
715 // that are not found in the stack, e.g. JNI locked monitors:
716 InflatedMonitorsClosure imc(this);
717 monitors->visit(&imc, _thread);
718 }
719 }
720
721
722 bool ThreadStackTrace::is_owned_monitor_on_stack(oop object) {
723 assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
724
725 bool found = false;
726 int num_frames = get_stack_depth();
727 for (int depth = 0; depth < num_frames; depth++) {
728 StackFrameInfo* frame = stack_frame_at(depth);
729 int len = frame->num_locked_monitors();
730 GrowableArray<OopHandle>* locked_monitors = frame->locked_monitors();
731 for (int j = 0; j < len; j++) {
732 oop monitor = locked_monitors->at(j).resolve();
733 assert(monitor != nullptr, "must be a Java object");
734 if (monitor == object) {
735 found = true;
736 break;
737 }
738 }
739 }
740 return found;
741 }
742
743 Handle ThreadStackTrace::allocate_fill_stack_trace_element_array(TRAPS) {
744 InstanceKlass* ik = vmClasses::StackTraceElement_klass();
745 assert(ik != nullptr, "must be loaded in 1.4+");
746
747 // Allocate an array of java/lang/StackTraceElement object
748 objArrayOop ste = oopFactory::new_objArray(ik, _depth, CHECK_NH);
749 objArrayHandle backtrace(THREAD, ste);
750 for (int j = 0; j < _depth; j++) {
751 StackFrameInfo* frame = _frames->at(j);
752 methodHandle mh(THREAD, frame->method());
753 oop element = java_lang_StackTraceElement::create(mh, frame->bci(), CHECK_NH);
754 backtrace->obj_at_put(j, element);
755 }
756 return backtrace;
757 }
758
759 void ThreadStackTrace::add_stack_frame(javaVFrame* jvf) {
760 StackFrameInfo* frame = new StackFrameInfo(jvf, _with_locked_monitors);
761 _frames->append(frame);
762 _depth++;
763 }
764
765 void ThreadStackTrace::metadata_do(void f(Metadata*)) {
766 int length = _frames->length();
767 for (int i = 0; i < length; i++) {
768 _frames->at(i)->metadata_do(f);
769 }
770 }
771
772
773 ConcurrentLocksDump::~ConcurrentLocksDump() {
774 if (_retain_map_on_free) {
775 return;
776 }
777
778 for (ThreadConcurrentLocks* t = _map; t != nullptr;) {
779 ThreadConcurrentLocks* tcl = t;
780 t = t->next();
781 delete tcl;
782 }
783 }
784
785 void ConcurrentLocksDump::dump_at_safepoint() {
786 // dump all locked concurrent locks
787 assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
788
789 GrowableArray<oop>* aos_objects = new (mtServiceability) GrowableArray<oop>(INITIAL_ARRAY_SIZE, mtServiceability);
790
791 // Find all instances of AbstractOwnableSynchronizer
792 HeapInspection::find_instances_at_safepoint(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass(),
793 aos_objects);
794 // Build a map of thread to its owned AQS locks
795 build_map(aos_objects);
796
797 delete aos_objects;
798 }
799
800
801 // build a map of JavaThread to all its owned AbstractOwnableSynchronizer
802 void ConcurrentLocksDump::build_map(GrowableArray<oop>* aos_objects) {
803 int length = aos_objects->length();
804 for (int i = 0; i < length; i++) {
805 oop o = aos_objects->at(i);
806 oop owner_thread_obj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(o);
807 if (owner_thread_obj != nullptr) {
808 // See comments in ThreadConcurrentLocks to see how this
809 // JavaThread* is protected.
810 JavaThread* thread = java_lang_Thread::thread(owner_thread_obj);
811 assert(o->is_instance(), "Must be an instanceOop");
812 add_lock(thread, (instanceOop) o);
813 }
814 }
815 }
816
817 void ConcurrentLocksDump::add_lock(JavaThread* thread, instanceOop o) {
818 ThreadConcurrentLocks* tcl = thread_concurrent_locks(thread);
819 if (tcl != nullptr) {
820 tcl->add_lock(o);
821 return;
822 }
823
824 // First owned lock found for this thread
825 tcl = new ThreadConcurrentLocks(thread);
826 tcl->add_lock(o);
827 if (_map == nullptr) {
828 _map = tcl;
829 } else {
830 _last->set_next(tcl);
831 }
832 _last = tcl;
833 }
834
835 ThreadConcurrentLocks* ConcurrentLocksDump::thread_concurrent_locks(JavaThread* thread) {
836 for (ThreadConcurrentLocks* tcl = _map; tcl != nullptr; tcl = tcl->next()) {
837 if (tcl->java_thread() == thread) {
838 return tcl;
839 }
840 }
841 return nullptr;
842 }
843
844 void ConcurrentLocksDump::print_locks_on(JavaThread* t, outputStream* st) {
845 st->print_cr(" Locked ownable synchronizers:");
846 ThreadConcurrentLocks* tcl = thread_concurrent_locks(t);
847 GrowableArray<OopHandle>* locks = (tcl != nullptr ? tcl->owned_locks() : nullptr);
848 if (locks == nullptr || locks->is_empty()) {
849 st->print_cr("\t- None");
850 st->cr();
851 return;
852 }
853
854 for (int i = 0; i < locks->length(); i++) {
855 oop obj = locks->at(i).resolve();
856 st->print_cr("\t- <" INTPTR_FORMAT "> (a %s)", p2i(obj), obj->klass()->external_name());
857 }
858 st->cr();
859 }
860
861 ThreadConcurrentLocks::ThreadConcurrentLocks(JavaThread* thread) {
862 _thread = thread;
863 _owned_locks = new (mtServiceability) GrowableArray<OopHandle>(INITIAL_ARRAY_SIZE, mtServiceability);
864 _next = nullptr;
865 }
866
867 ThreadConcurrentLocks::~ThreadConcurrentLocks() {
868 for (int i = 0; i < _owned_locks->length(); i++) {
869 _owned_locks->at(i).release(_thread_service_storage);
870 }
871 delete _owned_locks;
872 }
873
874 void ThreadConcurrentLocks::add_lock(instanceOop o) {
875 _owned_locks->append(OopHandle(_thread_service_storage, o));
876 }
877
878 ThreadStatistics::ThreadStatistics() {
879 _contended_enter_count = 0;
880 _monitor_wait_count = 0;
881 _sleep_count = 0;
882 _count_pending_reset = false;
883 _timer_pending_reset = false;
884 memset((void*) _perf_recursion_counts, 0, sizeof(_perf_recursion_counts));
885 }
886
887 oop ThreadSnapshot::threadObj() const { return _threadObj.resolve(); }
888
889 void ThreadSnapshot::initialize(ThreadsList * t_list, JavaThread* thread) {
890 _thread = thread;
891 oop threadObj = thread->threadObj();
892 _threadObj = OopHandle(_thread_service_storage, threadObj);
893
894 ThreadStatistics* stat = thread->get_thread_stat();
895 _contended_enter_ticks = stat->contended_enter_ticks();
896 _contended_enter_count = stat->contended_enter_count();
897 _monitor_wait_ticks = stat->monitor_wait_ticks();
898 _monitor_wait_count = stat->monitor_wait_count();
899 _sleep_ticks = stat->sleep_ticks();
900 _sleep_count = stat->sleep_count();
901
902 // If thread is still attaching then threadObj will be null.
903 _thread_status = threadObj == nullptr ? JavaThreadStatus::NEW
904 : java_lang_Thread::get_thread_status(threadObj);
905
906 _is_suspended = thread->is_suspended();
907 _is_in_native = (thread->thread_state() == _thread_in_native);
908
909 Handle obj = ThreadService::get_current_contended_monitor(thread);
910
911 oop blocker_object = nullptr;
912 oop blocker_object_owner = nullptr;
913
914 if (thread->is_vthread_mounted() && thread->vthread() != threadObj) { // ThreadSnapshot only captures platform threads
915 _thread_status = JavaThreadStatus::IN_OBJECT_WAIT;
916 oop vthread = thread->vthread();
917 assert(vthread != nullptr, "");
918 blocker_object = vthread;
919 blocker_object_owner = vthread;
920 } else if (_thread_status == JavaThreadStatus::BLOCKED_ON_MONITOR_ENTER ||
921 _thread_status == JavaThreadStatus::IN_OBJECT_WAIT ||
922 _thread_status == JavaThreadStatus::IN_OBJECT_WAIT_TIMED) {
923
924 if (obj() == nullptr) {
925 // monitor no longer exists; thread is not blocked
926 _thread_status = JavaThreadStatus::RUNNABLE;
927 } else {
928 blocker_object = obj();
929 JavaThread* owner = ObjectSynchronizer::get_lock_owner(t_list, obj);
930 if ((owner == nullptr && _thread_status == JavaThreadStatus::BLOCKED_ON_MONITOR_ENTER)
931 || (owner != nullptr && owner->is_attaching_via_jni())) {
932 // ownership information of the monitor is not available
933 // (may no longer be owned or releasing to some other thread)
934 // make this thread in RUNNABLE state.
935 // And when the owner thread is in attaching state, the java thread
936 // is not completely initialized. For example thread name and id
937 // and may not be set, so hide the attaching thread.
938 _thread_status = JavaThreadStatus::RUNNABLE;
939 blocker_object = nullptr;
940 } else if (owner != nullptr) {
941 blocker_object_owner = owner->threadObj();
942 }
943 }
944 } else if (_thread_status == JavaThreadStatus::PARKED || _thread_status == JavaThreadStatus::PARKED_TIMED) {
945 blocker_object = thread->current_park_blocker();
946 if (blocker_object != nullptr && blocker_object->is_a(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass())) {
947 blocker_object_owner = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(blocker_object);
948 }
949 }
950
951 if (blocker_object != nullptr) {
952 _blocker_object = OopHandle(_thread_service_storage, blocker_object);
953 }
954 if (blocker_object_owner != nullptr) {
955 _blocker_object_owner = OopHandle(_thread_service_storage, blocker_object_owner);
956 }
957 }
958
959 oop ThreadSnapshot::blocker_object() const { return _blocker_object.resolve(); }
960 oop ThreadSnapshot::blocker_object_owner() const { return _blocker_object_owner.resolve(); }
961
962 ThreadSnapshot::~ThreadSnapshot() {
963 _blocker_object.release(_thread_service_storage);
964 _blocker_object_owner.release(_thread_service_storage);
965 _threadObj.release(_thread_service_storage);
966
967 delete _stack_trace;
968 delete _concurrent_locks;
969 }
970
971 void ThreadSnapshot::dump_stack_at_safepoint(int max_depth, bool with_locked_monitors,
972 ObjectMonitorsView* monitors, bool full) {
973 _stack_trace = new ThreadStackTrace(_thread, with_locked_monitors);
974 _stack_trace->dump_stack_at_safepoint(max_depth, monitors, full);
975 }
976
977
978 void ThreadSnapshot::metadata_do(void f(Metadata*)) {
979 if (_stack_trace != nullptr) {
980 _stack_trace->metadata_do(f);
981 }
982 }
983
984
985 DeadlockCycle::DeadlockCycle() {
986 _threads = new (mtServiceability) GrowableArray<JavaThread*>(INITIAL_ARRAY_SIZE, mtServiceability);
987 _next = nullptr;
988 }
989
990 DeadlockCycle::~DeadlockCycle() {
991 delete _threads;
992 }
993
994 void DeadlockCycle::print_on_with(ThreadsList * t_list, outputStream* st) const {
995 st->cr();
996 st->print_cr("Found one Java-level deadlock:");
997 st->print("=============================");
998
999 JavaThread* currentThread;
1000 JvmtiRawMonitor* waitingToLockRawMonitor;
1001 oop waitingToLockBlocker;
1002 int len = _threads->length();
1003 for (int i = 0; i < len; i++) {
1004 currentThread = _threads->at(i);
1005 // The ObjectMonitor* can't be async deflated since we are at a safepoint.
1006 ObjectMonitor* waitingToLockMonitor = currentThread->current_pending_monitor();
1007 waitingToLockRawMonitor = currentThread->current_pending_raw_monitor();
1008 waitingToLockBlocker = currentThread->current_park_blocker();
1009 st->cr();
1010 st->print_cr("\"%s\":", currentThread->name());
1011 const char* owner_desc = ",\n which is held by";
1012
1013 // Note: As the JVM TI "monitor contended enter" event callback is executed after ObjectMonitor
1014 // sets the current pending monitor, it is possible to then see a pending raw monitor as well.
1015 if (waitingToLockRawMonitor != nullptr) {
1016 st->print(" waiting to lock JVM TI raw monitor " INTPTR_FORMAT, p2i(waitingToLockRawMonitor));
1017 Thread* owner = waitingToLockRawMonitor->owner();
1018 // Could be null as the raw monitor could be released at any time if held by non-JavaThread
1019 if (owner != nullptr) {
1020 if (owner->is_Java_thread()) {
1021 currentThread = JavaThread::cast(owner);
1022 st->print_cr("%s \"%s\"", owner_desc, currentThread->name());
1023 } else {
1024 st->print_cr(",\n which has now been released");
1025 }
1026 } else {
1027 st->print_cr("%s non-Java thread=" PTR_FORMAT, owner_desc, p2i(owner));
1028 }
1029 }
1030
1031 if (waitingToLockMonitor != nullptr) {
1032 st->print(" waiting to lock monitor " INTPTR_FORMAT, p2i(waitingToLockMonitor));
1033 oop obj = waitingToLockMonitor->object();
1034 st->print(" (object " INTPTR_FORMAT ", a %s)", p2i(obj),
1035 obj->klass()->external_name());
1036
1037 if (!currentThread->current_pending_monitor_is_from_java()) {
1038 owner_desc = "\n in JNI, which is held by";
1039 }
1040 currentThread = Threads::owning_thread_from_monitor(t_list, waitingToLockMonitor);
1041 if (currentThread == nullptr) {
1042 // The deadlock was detected at a safepoint so the JavaThread
1043 // that owns waitingToLockMonitor should be findable, but
1044 // if it is not findable, then the previous currentThread is
1045 // blocked permanently.
1046 st->print_cr("%s UNKNOWN_owner_addr=" INT64_FORMAT, owner_desc,
1047 waitingToLockMonitor->owner());
1048 continue;
1049 }
1050 } else {
1051 st->print(" waiting for ownable synchronizer " INTPTR_FORMAT ", (a %s)",
1052 p2i(waitingToLockBlocker),
1053 waitingToLockBlocker->klass()->external_name());
1054 assert(waitingToLockBlocker->is_a(vmClasses::java_util_concurrent_locks_AbstractOwnableSynchronizer_klass()),
1055 "Must be an AbstractOwnableSynchronizer");
1056 oop ownerObj = java_util_concurrent_locks_AbstractOwnableSynchronizer::get_owner_threadObj(waitingToLockBlocker);
1057 currentThread = java_lang_Thread::thread(ownerObj);
1058 assert(currentThread != nullptr, "AbstractOwnableSynchronizer owning thread is unexpectedly null");
1059 }
1060 st->print_cr("%s \"%s\"", owner_desc, currentThread->name());
1061 }
1062
1063 st->cr();
1064
1065 // Print stack traces
1066 bool oldJavaMonitorsInStackTrace = JavaMonitorsInStackTrace;
1067 JavaMonitorsInStackTrace = true;
1068 st->print_cr("Java stack information for the threads listed above:");
1069 st->print_cr("===================================================");
1070 for (int j = 0; j < len; j++) {
1071 currentThread = _threads->at(j);
1072 st->print_cr("\"%s\":", currentThread->name());
1073 currentThread->print_stack_on(st);
1074 }
1075 JavaMonitorsInStackTrace = oldJavaMonitorsInStackTrace;
1076 }
1077
1078 ThreadsListEnumerator::ThreadsListEnumerator(Thread* cur_thread,
1079 bool include_jvmti_agent_threads,
1080 bool include_jni_attaching_threads,
1081 bool include_bound_virtual_threads) {
1082 assert(cur_thread == Thread::current(), "Check current thread");
1083
1084 int init_size = ThreadService::get_live_thread_count();
1085 _threads_array = new GrowableArray<instanceHandle>(init_size);
1086
1087 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
1088 // skips JavaThreads in the process of exiting
1089 // and also skips VM internal JavaThreads
1090 // Threads in _thread_new or _thread_new_trans state are included.
1091 // i.e. threads have been started but not yet running.
1092 if (jt->threadObj() == nullptr ||
1093 jt->is_exiting() ||
1094 !java_lang_Thread::is_alive(jt->threadObj()) ||
1095 jt->is_hidden_from_external_view()) {
1096 continue;
1097 }
1098
1099 // skip agent threads
1100 if (!include_jvmti_agent_threads && jt->is_jvmti_agent_thread()) {
1101 continue;
1102 }
1103
1104 // skip jni threads in the process of attaching
1105 if (!include_jni_attaching_threads && jt->is_attaching_via_jni()) {
1106 continue;
1107 }
1108
1109 // skip instances of BoundVirtualThread
1110 if (!include_bound_virtual_threads && jt->threadObj()->is_a(vmClasses::BoundVirtualThread_klass())) {
1111 continue;
1112 }
1113
1114 instanceHandle h(cur_thread, (instanceOop) jt->threadObj());
1115 _threads_array->append(h);
1116 }
1117 }