1 /*
2 * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
3 * Copyright (c) 2021, Azul Systems, Inc. All rights reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 *
24 */
25
26 #include "precompiled.hpp"
27 #include "cds/cdsConfig.hpp"
28 #include "classfile/javaClasses.hpp"
29 #include "classfile/javaThreadStatus.hpp"
30 #include "gc/shared/barrierSet.hpp"
31 #include "jfr/jfrEvents.hpp"
32 #include "jvm.h"
33 #include "jvmtifiles/jvmtiEnv.hpp"
34 #include "logging/log.hpp"
35 #include "memory/allocation.inline.hpp"
36 #include "memory/iterator.hpp"
37 #include "memory/resourceArea.hpp"
38 #include "nmt/memTracker.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "runtime/atomic.hpp"
41 #include "runtime/handles.inline.hpp"
42 #include "runtime/javaThread.inline.hpp"
43 #include "runtime/nonJavaThread.hpp"
44 #include "runtime/orderAccess.hpp"
45 #include "runtime/osThread.hpp"
46 #include "runtime/safepoint.hpp"
47 #include "runtime/safepointMechanism.inline.hpp"
48 #include "runtime/thread.inline.hpp"
49 #include "runtime/threadSMR.inline.hpp"
50 #include "utilities/macros.hpp"
51 #include "utilities/spinYield.hpp"
52 #if INCLUDE_JFR
53 #include "jfr/jfr.hpp"
54 #endif
55
56 #ifndef USE_LIBRARY_BASED_TLS_ONLY
57 // Current thread is maintained as a thread-local variable
58 THREAD_LOCAL Thread* Thread::_thr_current = nullptr;
59 #endif
60
61 // ======= Thread ========
62 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
63 // JavaThread
64
65 DEBUG_ONLY(Thread* Thread::_starting_thread = nullptr;)
66
67 Thread::Thread() {
68
69 DEBUG_ONLY(_run_state = PRE_CALL_RUN;)
70
71 // stack and get_thread
72 set_stack_base(nullptr);
73 set_stack_size(0);
74 set_lgrp_id(-1);
75 DEBUG_ONLY(clear_suspendible_thread();)
76 DEBUG_ONLY(clear_indirectly_suspendible_thread();)
77 DEBUG_ONLY(clear_indirectly_safepoint_thread();)
78
79 // allocated data structures
80 set_osthread(nullptr);
81 set_resource_area(new (mtThread)ResourceArea());
82 DEBUG_ONLY(_current_resource_mark = nullptr;)
83 set_handle_area(new (mtThread) HandleArea(nullptr));
84 set_metadata_handles(new (mtClass) GrowableArray<Metadata*>(30, mtClass));
85 set_last_handle_mark(nullptr);
86 DEBUG_ONLY(_missed_ic_stub_refill_verifier = nullptr);
87
88 // Initial value of zero ==> never claimed.
89 _threads_do_token = 0;
90 _threads_hazard_ptr = nullptr;
91 _threads_list_ptr = nullptr;
92 _nested_threads_hazard_ptr_cnt = 0;
93 _rcu_counter = 0;
94
95 // the handle mark links itself to last_handle_mark
96 new HandleMark(this);
97
98 // plain initialization
99 debug_only(_owned_locks = nullptr;)
100 NOT_PRODUCT(_skip_gcalot = false;)
101 _jvmti_env_iteration_count = 0;
102 set_allocated_bytes(0);
103 _current_pending_raw_monitor = nullptr;
104 _vm_error_callbacks = nullptr;
105
106 // thread-specific hashCode stream generator state - Marsaglia shift-xor form
107 // If we are dumping, keep ihashes constant. Note that during dumping we only
108 // ever run one java thread, and no other thread should generate ihashes either,
109 // so using a constant seed should work fine.
110 _hashStateX = CDSConfig::is_dumping_static_archive() ? 0x12345678 : os::random();
111 _hashStateY = 842502087;
112 _hashStateZ = 0x8767; // (int)(3579807591LL & 0xffff) ;
113 _hashStateW = 273326509;
114
115 // Many of the following fields are effectively final - immutable
116 // Note that nascent threads can't use the Native Monitor-Mutex
117 // construct until the _MutexEvent is initialized ...
118 // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
119 // we might instead use a stack of ParkEvents that we could provision on-demand.
120 // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
121 // and ::Release()
122 _ParkEvent = ParkEvent::Allocate(this);
123
124 #ifdef CHECK_UNHANDLED_OOPS
125 if (CheckUnhandledOops) {
126 _unhandled_oops = new UnhandledOops(this);
127 }
128 #endif // CHECK_UNHANDLED_OOPS
129
130 // Notify the barrier set that a thread is being created. The initial
131 // thread is created before the barrier set is available. The call to
132 // BarrierSet::on_thread_create() for this thread is therefore deferred
133 // to BarrierSet::set_barrier_set().
134 BarrierSet* const barrier_set = BarrierSet::barrier_set();
135 if (barrier_set != nullptr) {
136 barrier_set->on_thread_create(this);
137 } else {
138 // Only the main thread should be created before the barrier set
139 // and that happens just before Thread::current is set. No other thread
140 // can attach as the VM is not created yet, so they can't execute this code.
141 // If the main thread creates other threads before the barrier set that is an error.
142 assert(Thread::current_or_null() == nullptr, "creating thread before barrier set");
143 }
144
145 MACOS_AARCH64_ONLY(DEBUG_ONLY(_wx_init = false));
146 }
147
148 void Thread::initialize_tlab() {
149 if (UseTLAB) {
150 tlab().initialize();
151 }
152 }
153
154 void Thread::initialize_thread_current() {
155 #ifndef USE_LIBRARY_BASED_TLS_ONLY
156 assert(_thr_current == nullptr, "Thread::current already initialized");
157 _thr_current = this;
158 #endif
159 assert(ThreadLocalStorage::thread() == nullptr, "ThreadLocalStorage::thread already initialized");
160 ThreadLocalStorage::set_thread(this);
161 assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
162 }
163
164 void Thread::clear_thread_current() {
165 assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
166 #ifndef USE_LIBRARY_BASED_TLS_ONLY
167 _thr_current = nullptr;
168 #endif
169 ThreadLocalStorage::set_thread(nullptr);
170 }
171
172 void Thread::record_stack_base_and_size() {
173 // Note: at this point, Thread object is not yet initialized. Do not rely on
174 // any members being initialized. Do not rely on Thread::current() being set.
175 // If possible, refrain from doing anything which may crash or assert since
176 // quite probably those crash dumps will be useless.
177 address base;
178 size_t size;
179 os::current_stack_base_and_size(&base, &size);
180 set_stack_base(base);
181 set_stack_size(size);
182
183 // Set stack limits after thread is initialized.
184 if (is_Java_thread()) {
185 JavaThread::cast(this)->stack_overflow_state()->initialize(stack_base(), stack_end());
186 }
187 }
188
189 void Thread::register_thread_stack_with_NMT() {
190 MemTracker::record_thread_stack(stack_end(), stack_size());
191 }
192
193 void Thread::unregister_thread_stack_with_NMT() {
194 MemTracker::release_thread_stack(stack_end(), stack_size());
195 }
196
197 void Thread::call_run() {
198 DEBUG_ONLY(_run_state = CALL_RUN;)
199
200 // At this point, Thread object should be fully initialized and
201 // Thread::current() should be set.
202
203 assert(Thread::current_or_null() != nullptr, "current thread is unset");
204 assert(Thread::current_or_null() == this, "current thread is wrong");
205
206 // Perform common initialization actions
207
208 MACOS_AARCH64_ONLY(this->init_wx());
209
210 register_thread_stack_with_NMT();
211
212 JFR_ONLY(Jfr::on_thread_start(this);)
213
214 log_debug(os, thread)("Thread " UINTX_FORMAT " stack dimensions: "
215 PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT "k).",
216 os::current_thread_id(), p2i(stack_end()),
217 p2i(stack_base()), stack_size()/1024);
218
219 // Perform <ChildClass> initialization actions
220 DEBUG_ONLY(_run_state = PRE_RUN;)
221 this->pre_run();
222
223 // Invoke <ChildClass>::run()
224 DEBUG_ONLY(_run_state = RUN;)
225 this->run();
226 // Returned from <ChildClass>::run(). Thread finished.
227
228 // Perform common tear-down actions
229
230 assert(Thread::current_or_null() != nullptr, "current thread is unset");
231 assert(Thread::current_or_null() == this, "current thread is wrong");
232
233 // Perform <ChildClass> tear-down actions
234 DEBUG_ONLY(_run_state = POST_RUN;)
235 this->post_run();
236
237 // Note: at this point the thread object may already have deleted itself,
238 // so from here on do not dereference *this*. Not all thread types currently
239 // delete themselves when they terminate. But no thread should ever be deleted
240 // asynchronously with respect to its termination - that is what _run_state can
241 // be used to check.
242
243 assert(Thread::current_or_null() == nullptr, "current thread still present");
244 }
245
246 Thread::~Thread() {
247
248 // Attached threads will remain in PRE_CALL_RUN, as will threads that don't actually
249 // get started due to errors etc. Any active thread should at least reach post_run
250 // before it is deleted (usually in post_run()).
251 assert(_run_state == PRE_CALL_RUN ||
252 _run_state == POST_RUN, "Active Thread deleted before post_run(): "
253 "_run_state=%d", (int)_run_state);
254
255 // Notify the barrier set that a thread is being destroyed. Note that a barrier
256 // set might not be available if we encountered errors during bootstrapping.
257 BarrierSet* const barrier_set = BarrierSet::barrier_set();
258 if (barrier_set != nullptr) {
259 barrier_set->on_thread_destroy(this);
260 }
261
262 // deallocate data structures
263 delete resource_area();
264 // since the handle marks are using the handle area, we have to deallocated the root
265 // handle mark before deallocating the thread's handle area,
266 assert(last_handle_mark() != nullptr, "check we have an element");
267 delete last_handle_mark();
268 assert(last_handle_mark() == nullptr, "check we have reached the end");
269
270 ParkEvent::Release(_ParkEvent);
271 // Set to null as a termination indicator for has_terminated().
272 Atomic::store(&_ParkEvent, (ParkEvent*)nullptr);
273
274 delete handle_area();
275 delete metadata_handles();
276
277 // osthread() can be null, if creation of thread failed.
278 if (osthread() != nullptr) os::free_thread(osthread());
279
280 // Clear Thread::current if thread is deleting itself and it has not
281 // already been done. This must be done before the memory is deallocated.
282 // Needed to ensure JNI correctly detects non-attached threads.
283 if (this == Thread::current_or_null()) {
284 Thread::clear_thread_current();
285 }
286
287 CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
288 }
289
290 #ifdef ASSERT
291 // A JavaThread is considered dangling if it not handshake-safe with respect to
292 // the current thread, it is not on a ThreadsList, or not at safepoint.
293 void Thread::check_for_dangling_thread_pointer(Thread *thread) {
294 assert(!thread->is_Java_thread() ||
295 JavaThread::cast(thread)->is_handshake_safe_for(Thread::current()) ||
296 !JavaThread::cast(thread)->on_thread_list() ||
297 SafepointSynchronize::is_at_safepoint() ||
298 ThreadsSMRSupport::is_a_protected_JavaThread_with_lock(JavaThread::cast(thread)),
299 "possibility of dangling Thread pointer");
300 }
301 #endif
302
303 // Is the target JavaThread protected by the calling Thread or by some other
304 // mechanism?
305 //
306 bool Thread::is_JavaThread_protected(const JavaThread* target) {
307 Thread* current_thread = Thread::current();
308
309 // Do the simplest check first:
310 if (SafepointSynchronize::is_at_safepoint()) {
311 // The target is protected since JavaThreads cannot exit
312 // while we're at a safepoint.
313 return true;
314 }
315
316 // If the target hasn't been started yet then it is trivially
317 // "protected". We assume the caller is the thread that will do
318 // the starting.
319 if (target->osthread() == nullptr || target->osthread()->get_state() <= INITIALIZED) {
320 return true;
321 }
322
323 // Now make the simple checks based on who the caller is:
324 if (current_thread == target || Threads_lock->owner() == current_thread) {
325 // Target JavaThread is self or calling thread owns the Threads_lock.
326 // Second check is the same as Threads_lock->owner_is_self(),
327 // but we already have the current thread so check directly.
328 return true;
329 }
330
331 // Check the ThreadsLists associated with the calling thread (if any)
332 // to see if one of them protects the target JavaThread:
333 if (is_JavaThread_protected_by_TLH(target)) {
334 return true;
335 }
336
337 // Use this debug code with -XX:+UseNewCode to diagnose locations that
338 // are missing a ThreadsListHandle or other protection mechanism:
339 // guarantee(!UseNewCode, "current_thread=" INTPTR_FORMAT " is not protecting target="
340 // INTPTR_FORMAT, p2i(current_thread), p2i(target));
341
342 // Note: Since 'target' isn't protected by a TLH, the call to
343 // target->is_handshake_safe_for() may crash, but we have debug bits so
344 // we'll be able to figure out what protection mechanism is missing.
345 assert(target->is_handshake_safe_for(current_thread), "JavaThread=" INTPTR_FORMAT
346 " is not protected and not handshake safe.", p2i(target));
347
348 // The target JavaThread is not protected so it is not safe to query:
349 return false;
350 }
351
352 // Is the target JavaThread protected by a ThreadsListHandle (TLH) associated
353 // with the calling Thread?
354 //
355 bool Thread::is_JavaThread_protected_by_TLH(const JavaThread* target) {
356 Thread* current_thread = Thread::current();
357
358 // Check the ThreadsLists associated with the calling thread (if any)
359 // to see if one of them protects the target JavaThread:
360 for (SafeThreadsListPtr* stlp = current_thread->_threads_list_ptr;
361 stlp != nullptr; stlp = stlp->previous()) {
362 if (stlp->list()->includes(target)) {
363 // The target JavaThread is protected by this ThreadsList:
364 return true;
365 }
366 }
367
368 // The target JavaThread is not protected by a TLH so it is not safe to query:
369 return false;
370 }
371
372 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
373 debug_only(check_for_dangling_thread_pointer(thread);)
374 // Can return an error!
375 (void)os::set_priority(thread, priority);
376 }
377
378
379 void Thread::start(Thread* thread) {
380 // Start is different from resume in that its safety is guaranteed by context or
381 // being called from a Java method synchronized on the Thread object.
382 if (thread->is_Java_thread()) {
383 // Initialize the thread state to RUNNABLE before starting this thread.
384 // Can not set it after the thread started because we do not know the
385 // exact thread state at that time. It could be in MONITOR_WAIT or
386 // in SLEEPING or some other state.
387 java_lang_Thread::set_thread_status(JavaThread::cast(thread)->threadObj(),
388 JavaThreadStatus::RUNNABLE);
389 }
390 os::start_thread(thread);
391 }
392
393 // GC Support
394 bool Thread::claim_par_threads_do(uintx claim_token) {
395 uintx token = _threads_do_token;
396 if (token != claim_token) {
397 uintx res = Atomic::cmpxchg(&_threads_do_token, token, claim_token);
398 if (res == token) {
399 return true;
400 }
401 guarantee(res == claim_token, "invariant");
402 }
403 return false;
404 }
405
406 void Thread::oops_do_no_frames(OopClosure* f, NMethodClosure* cf) {
407 // Do oop for ThreadShadow
408 f->do_oop((oop*)&_pending_exception);
409 handle_area()->oops_do(f);
410 }
411
412 // If the caller is a NamedThread, then remember, in the current scope,
413 // the given JavaThread in its _processed_thread field.
414 class RememberProcessedThread: public StackObj {
415 NamedThread* _cur_thr;
416 public:
417 RememberProcessedThread(Thread* thread) {
418 Thread* self = Thread::current();
419 if (self->is_Named_thread()) {
420 _cur_thr = (NamedThread *)self;
421 assert(_cur_thr->processed_thread() == nullptr, "nesting not supported");
422 _cur_thr->set_processed_thread(thread);
423 } else {
424 _cur_thr = nullptr;
425 }
426 }
427
428 ~RememberProcessedThread() {
429 if (_cur_thr) {
430 assert(_cur_thr->processed_thread() != nullptr, "nesting not supported");
431 _cur_thr->set_processed_thread(nullptr);
432 }
433 }
434 };
435
436 void Thread::oops_do(OopClosure* f, NMethodClosure* cf) {
437 // Record JavaThread to GC thread
438 RememberProcessedThread rpt(this);
439 oops_do_no_frames(f, cf);
440 oops_do_frames(f, cf);
441 }
442
443 void Thread::metadata_handles_do(void f(Metadata*)) {
444 // Only walk the Handles in Thread.
445 if (metadata_handles() != nullptr) {
446 for (int i = 0; i< metadata_handles()->length(); i++) {
447 f(metadata_handles()->at(i));
448 }
449 }
450 }
451
452 void Thread::print_on(outputStream* st, bool print_extended_info) const {
453 // get_priority assumes osthread initialized
454 if (osthread() != nullptr) {
455 int os_prio;
456 if (os::get_native_priority(this, &os_prio) == OS_OK) {
457 st->print("os_prio=%d ", os_prio);
458 }
459
460 st->print("cpu=%.2fms ",
461 (double)os::thread_cpu_time(const_cast<Thread*>(this), true) / 1000000.0
462 );
463 st->print("elapsed=%.2fs ",
464 (double)_statistical_info.getElapsedTime() / 1000.0
465 );
466 if (is_Java_thread() && (PrintExtendedThreadInfo || print_extended_info)) {
467 size_t allocated_bytes = (size_t) const_cast<Thread*>(this)->cooked_allocated_bytes();
468 st->print("allocated=" SIZE_FORMAT "%s ",
469 byte_size_in_proper_unit(allocated_bytes),
470 proper_unit_for_byte_size(allocated_bytes)
471 );
472 st->print("defined_classes=" INT64_FORMAT " ", _statistical_info.getDefineClassCount());
473 }
474
475 st->print("tid=" INTPTR_FORMAT " ", p2i(this));
476 if (!is_Java_thread() || !JavaThread::cast(this)->is_vthread_mounted()) {
477 osthread()->print_on(st);
478 }
479 }
480 ThreadsSMRSupport::print_info_on(this, st);
481 st->print(" ");
482 debug_only(if (WizardMode) print_owned_locks_on(st);)
483 }
484
485 void Thread::print() const { print_on(tty); }
486
487 // Thread::print_on_error() is called by fatal error handler. Don't use
488 // any lock or allocate memory.
489 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
490 assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
491
492 st->print("%s \"%s\"", type_name(), name());
493
494 OSThread* os_thr = osthread();
495 if (os_thr != nullptr) {
496 st->fill_to(67);
497 if (os_thr->get_state() != ZOMBIE) {
498 // Use raw field members for stack base/size as this could be
499 // called before a thread has run enough to initialize them.
500 st->print(" [id=%d, stack(" PTR_FORMAT "," PTR_FORMAT ") (" PROPERFMT ")]",
501 osthread()->thread_id(), p2i(_stack_base - _stack_size), p2i(_stack_base),
502 PROPERFMTARGS(_stack_size));
503 } else {
504 st->print(" terminated");
505 }
506 } else {
507 st->print(" unknown state (no osThread)");
508 }
509 ThreadsSMRSupport::print_info_on(this, st);
510 }
511
512 void Thread::print_value_on(outputStream* st) const {
513 if (is_Named_thread()) {
514 st->print(" \"%s\" ", name());
515 }
516 st->print(INTPTR_FORMAT, p2i(this)); // print address
517 }
518
519 #ifdef ASSERT
520 void Thread::print_owned_locks_on(outputStream* st) const {
521 Mutex* cur = _owned_locks;
522 if (cur == nullptr) {
523 st->print(" (no locks) ");
524 } else {
525 st->print_cr(" Locks owned:");
526 while (cur) {
527 cur->print_on(st);
528 cur = cur->next();
529 }
530 }
531 }
532 #endif // ASSERT
533
534 bool Thread::set_as_starting_thread() {
535 assert(_starting_thread == nullptr, "already initialized: "
536 "_starting_thread=" INTPTR_FORMAT, p2i(_starting_thread));
537 // NOTE: this must be called inside the main thread.
538 DEBUG_ONLY(_starting_thread = this;)
539 return os::create_main_thread(JavaThread::cast(this));
540 }
541
542 // Ad-hoc mutual exclusion primitives: SpinLock
543 //
544 // We employ SpinLocks _only for low-contention, fixed-length
545 // short-duration critical sections where we're concerned
546 // about native mutex_t or HotSpot Mutex:: latency.
547 //
548 // TODO-FIXME: ListLock should be of type SpinLock.
549 // We should make this a 1st-class type, integrated into the lock
550 // hierarchy as leaf-locks. Critically, the SpinLock structure
551 // should have sufficient padding to avoid false-sharing and excessive
552 // cache-coherency traffic.
553
554
555 typedef volatile int SpinLockT;
556
557 void Thread::SpinAcquire(volatile int * adr, const char * LockName) {
558 if (Atomic::cmpxchg(adr, 0, 1) == 0) {
559 return; // normal fast-path return
560 }
561
562 // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
563 int ctr = 0;
564 int Yields = 0;
565 for (;;) {
566 while (*adr != 0) {
567 ++ctr;
568 if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
569 if (Yields > 5) {
570 os::naked_short_sleep(1);
571 } else {
572 os::naked_yield();
573 ++Yields;
574 }
575 } else {
576 SpinPause();
577 }
578 }
579 if (Atomic::cmpxchg(adr, 0, 1) == 0) return;
580 }
581 }
582
583 void Thread::SpinRelease(volatile int * adr) {
584 assert(*adr != 0, "invariant");
585 OrderAccess::fence(); // guarantee at least release consistency.
586 // Roach-motel semantics.
587 // It's safe if subsequent LDs and STs float "up" into the critical section,
588 // but prior LDs and STs within the critical section can't be allowed
589 // to reorder or float past the ST that releases the lock.
590 // Loads and stores in the critical section - which appear in program
591 // order before the store that releases the lock - must also appear
592 // before the store that releases the lock in memory visibility order.
593 // Conceptually we need a #loadstore|#storestore "release" MEMBAR before
594 // the ST of 0 into the lock-word which releases the lock, so fence
595 // more than covers this on all platforms.
596 *adr = 0;
597 }