1 /*
2 * Copyright (c) 1997, 2023, 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 "classfile/javaClasses.hpp"
28 #include "classfile/javaThreadStatus.hpp"
29 #include "gc/shared/barrierSet.hpp"
30 #include "jfr/jfrEvents.hpp"
31 #include "jvm.h"
32 #include "jvmtifiles/jvmtiEnv.hpp"
33 #include "logging/log.hpp"
34 #include "memory/allocation.inline.hpp"
35 #include "memory/iterator.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "runtime/atomic.hpp"
39 #include "runtime/handles.inline.hpp"
40 #include "runtime/javaThread.inline.hpp"
41 #include "runtime/nonJavaThread.hpp"
42 #include "runtime/orderAccess.hpp"
43 #include "runtime/osThread.hpp"
44 #include "runtime/safepoint.hpp"
45 #include "runtime/safepointMechanism.inline.hpp"
46 #include "runtime/thread.inline.hpp"
47 #include "runtime/threadSMR.inline.hpp"
48 #include "services/memTracker.hpp"
49 #include "utilities/macros.hpp"
50 #include "utilities/spinYield.hpp"
51 #if INCLUDE_JFR
52 #include "jfr/jfr.hpp"
53 #endif
54
55 #ifndef USE_LIBRARY_BASED_TLS_ONLY
56 // Current thread is maintained as a thread-local variable
57 THREAD_LOCAL Thread* Thread::_thr_current = nullptr;
58 #endif
59
60 // ======= Thread ========
61 void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
62 return throw_excpt ? AllocateHeap(size, flags, CURRENT_PC)
63 : AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
64 }
65
66 void Thread::operator delete(void* p) {
67 FreeHeap(p);
68 }
69
70 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
71 // JavaThread
72
73 DEBUG_ONLY(Thread* Thread::_starting_thread = nullptr;)
74
75 Thread::Thread() {
76
77 DEBUG_ONLY(_run_state = PRE_CALL_RUN;)
78
79 // stack and get_thread
80 set_stack_base(nullptr);
81 set_stack_size(0);
82 set_lgrp_id(-1);
83 DEBUG_ONLY(clear_suspendible_thread();)
84
85 // allocated data structures
86 set_osthread(nullptr);
87 set_resource_area(new (mtThread)ResourceArea());
88 DEBUG_ONLY(_current_resource_mark = nullptr;)
89 set_handle_area(new (mtThread) HandleArea(nullptr));
90 set_metadata_handles(new (mtClass) GrowableArray<Metadata*>(30, mtClass));
91 set_last_handle_mark(nullptr);
92 DEBUG_ONLY(_missed_ic_stub_refill_verifier = nullptr);
93
94 // Initial value of zero ==> never claimed.
95 _threads_do_token = 0;
96 _threads_hazard_ptr = nullptr;
97 _threads_list_ptr = nullptr;
98 _nested_threads_hazard_ptr_cnt = 0;
99 _rcu_counter = 0;
100
101 // the handle mark links itself to last_handle_mark
102 new HandleMark(this);
103
104 // plain initialization
105 debug_only(_owned_locks = nullptr;)
106 NOT_PRODUCT(_skip_gcalot = false;)
107 _jvmti_env_iteration_count = 0;
108 set_allocated_bytes(0);
109 _current_pending_raw_monitor = nullptr;
110
111 // thread-specific hashCode stream generator state - Marsaglia shift-xor form
112 _hashStateX = os::random();
113 _hashStateY = 842502087;
114 _hashStateZ = 0x8767; // (int)(3579807591LL & 0xffff) ;
115 _hashStateW = 273326509;
116
117 // Many of the following fields are effectively final - immutable
118 // Note that nascent threads can't use the Native Monitor-Mutex
119 // construct until the _MutexEvent is initialized ...
120 // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
121 // we might instead use a stack of ParkEvents that we could provision on-demand.
122 // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
123 // and ::Release()
124 _ParkEvent = ParkEvent::Allocate(this);
125
126 #ifdef CHECK_UNHANDLED_OOPS
127 if (CheckUnhandledOops) {
128 _unhandled_oops = new UnhandledOops(this);
129 }
130 #endif // CHECK_UNHANDLED_OOPS
131
132 // Notify the barrier set that a thread is being created. The initial
133 // thread is created before the barrier set is available. The call to
134 // BarrierSet::on_thread_create() for this thread is therefore deferred
135 // to BarrierSet::set_barrier_set().
136 BarrierSet* const barrier_set = BarrierSet::barrier_set();
137 if (barrier_set != nullptr) {
138 barrier_set->on_thread_create(this);
139 } else {
140 // Only the main thread should be created before the barrier set
141 // and that happens just before Thread::current is set. No other thread
142 // can attach as the VM is not created yet, so they can't execute this code.
143 // If the main thread creates other threads before the barrier set that is an error.
144 assert(Thread::current_or_null() == nullptr, "creating thread before barrier set");
145 }
146
147 MACOS_AARCH64_ONLY(DEBUG_ONLY(_wx_init = false));
148 }
149
150 void Thread::initialize_tlab() {
151 if (UseTLAB) {
152 tlab().initialize();
153 }
154 }
155
156 void Thread::initialize_thread_current() {
157 #ifndef USE_LIBRARY_BASED_TLS_ONLY
158 assert(_thr_current == nullptr, "Thread::current already initialized");
159 _thr_current = this;
160 #endif
161 assert(ThreadLocalStorage::thread() == nullptr, "ThreadLocalStorage::thread already initialized");
162 ThreadLocalStorage::set_thread(this);
163 assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
164 }
165
166 void Thread::clear_thread_current() {
167 assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
168 #ifndef USE_LIBRARY_BASED_TLS_ONLY
169 _thr_current = nullptr;
170 #endif
171 ThreadLocalStorage::set_thread(nullptr);
172 }
173
174 void Thread::record_stack_base_and_size() {
175 // Note: at this point, Thread object is not yet initialized. Do not rely on
176 // any members being initialized. Do not rely on Thread::current() being set.
177 // If possible, refrain from doing anything which may crash or assert since
178 // quite probably those crash dumps will be useless.
179 set_stack_base(os::current_stack_base());
180 set_stack_size(os::current_stack_size());
181
182 // Set stack limits after thread is initialized.
183 if (is_Java_thread()) {
184 JavaThread::cast(this)->stack_overflow_state()->initialize(stack_base(), stack_end());
185 }
186 }
187
188 void Thread::register_thread_stack_with_NMT() {
189 MemTracker::record_thread_stack(stack_end(), stack_size());
190 }
191
192 void Thread::unregister_thread_stack_with_NMT() {
193 MemTracker::release_thread_stack(stack_end(), stack_size());
194 }
195
196 void Thread::call_run() {
197 DEBUG_ONLY(_run_state = CALL_RUN;)
198
199 // At this point, Thread object should be fully initialized and
200 // Thread::current() should be set.
201
202 assert(Thread::current_or_null() != nullptr, "current thread is unset");
203 assert(Thread::current_or_null() == this, "current thread is wrong");
204
205 // Perform common initialization actions
206
207 MACOS_AARCH64_ONLY(this->init_wx());
208
209 register_thread_stack_with_NMT();
210
211 JFR_ONLY(Jfr::on_thread_start(this);)
212
213 log_debug(os, thread)("Thread " UINTX_FORMAT " stack dimensions: "
214 PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT "k).",
215 os::current_thread_id(), p2i(stack_end()),
216 p2i(stack_base()), stack_size()/1024);
217
218 // Perform <ChildClass> initialization actions
219 DEBUG_ONLY(_run_state = PRE_RUN;)
220 this->pre_run();
221
222 // Invoke <ChildClass>::run()
223 DEBUG_ONLY(_run_state = RUN;)
224 this->run();
225 // Returned from <ChildClass>::run(). Thread finished.
226
227 // Perform common tear-down actions
228
229 assert(Thread::current_or_null() != nullptr, "current thread is unset");
230 assert(Thread::current_or_null() == this, "current thread is wrong");
231
232 // Perform <ChildClass> tear-down actions
233 DEBUG_ONLY(_run_state = POST_RUN;)
234 this->post_run();
235
236 // Note: at this point the thread object may already have deleted itself,
237 // so from here on do not dereference *this*. Not all thread types currently
238 // delete themselves when they terminate. But no thread should ever be deleted
239 // asynchronously with respect to its termination - that is what _run_state can
240 // be used to check.
241
242 assert(Thread::current_or_null() == nullptr, "current thread still present");
243 }
244
245 Thread::~Thread() {
246
247 // Attached threads will remain in PRE_CALL_RUN, as will threads that don't actually
248 // get started due to errors etc. Any active thread should at least reach post_run
249 // before it is deleted (usually in post_run()).
250 assert(_run_state == PRE_CALL_RUN ||
251 _run_state == POST_RUN, "Active Thread deleted before post_run(): "
252 "_run_state=%d", (int)_run_state);
253
254 // Notify the barrier set that a thread is being destroyed. Note that a barrier
255 // set might not be available if we encountered errors during bootstrapping.
256 BarrierSet* const barrier_set = BarrierSet::barrier_set();
257 if (barrier_set != nullptr) {
258 barrier_set->on_thread_destroy(this);
259 }
260
261 // deallocate data structures
262 delete resource_area();
263 // since the handle marks are using the handle area, we have to deallocated the root
264 // handle mark before deallocating the thread's handle area,
265 assert(last_handle_mark() != nullptr, "check we have an element");
266 delete last_handle_mark();
267 assert(last_handle_mark() == nullptr, "check we have reached the end");
268
269 ParkEvent::Release(_ParkEvent);
270 // Set to null as a termination indicator for has_terminated().
271 Atomic::store(&_ParkEvent, (ParkEvent*)nullptr);
272
273 delete handle_area();
274 delete metadata_handles();
275
276 // osthread() can be nullptr, if creation of thread failed.
277 if (osthread() != nullptr) os::free_thread(osthread());
278
279 // Clear Thread::current if thread is deleting itself and it has not
280 // already been done. This must be done before the memory is deallocated.
281 // Needed to ensure JNI correctly detects non-attached threads.
282 if (this == Thread::current_or_null()) {
283 Thread::clear_thread_current();
284 }
285
286 CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
287 }
288
289 #ifdef ASSERT
290 // A JavaThread is considered dangling if it not handshake-safe with respect to
291 // the current thread, it is not on a ThreadsList, or not at safepoint.
292 void Thread::check_for_dangling_thread_pointer(Thread *thread) {
293 assert(!thread->is_Java_thread() ||
294 JavaThread::cast(thread)->is_handshake_safe_for(Thread::current()) ||
295 !JavaThread::cast(thread)->on_thread_list() ||
296 SafepointSynchronize::is_at_safepoint() ||
297 ThreadsSMRSupport::is_a_protected_JavaThread_with_lock(JavaThread::cast(thread)),
298 "possibility of dangling Thread pointer");
299 }
300 #endif
301
302 // Is the target JavaThread protected by the calling Thread or by some other
303 // mechanism?
304 //
305 bool Thread::is_JavaThread_protected(const JavaThread* target) {
306 Thread* current_thread = Thread::current();
307
308 // Do the simplest check first:
309 if (SafepointSynchronize::is_at_safepoint()) {
310 // The target is protected since JavaThreads cannot exit
311 // while we're at a safepoint.
312 return true;
313 }
314
315 // If the target hasn't been started yet then it is trivially
316 // "protected". We assume the caller is the thread that will do
317 // the starting.
318 if (target->osthread() == nullptr || target->osthread()->get_state() <= INITIALIZED) {
319 return true;
320 }
321
322 // Now make the simple checks based on who the caller is:
323 if (current_thread == target || Threads_lock->owner() == current_thread) {
324 // Target JavaThread is self or calling thread owns the Threads_lock.
325 // Second check is the same as Threads_lock->owner_is_self(),
326 // but we already have the current thread so check directly.
327 return true;
328 }
329
330 // Check the ThreadsLists associated with the calling thread (if any)
331 // to see if one of them protects the target JavaThread:
332 if (is_JavaThread_protected_by_TLH(target)) {
333 return true;
334 }
335
336 // Use this debug code with -XX:+UseNewCode to diagnose locations that
337 // are missing a ThreadsListHandle or other protection mechanism:
338 // guarantee(!UseNewCode, "current_thread=" INTPTR_FORMAT " is not protecting target="
339 // INTPTR_FORMAT, p2i(current_thread), p2i(target));
340
341 // Note: Since 'target' isn't protected by a TLH, the call to
342 // target->is_handshake_safe_for() may crash, but we have debug bits so
343 // we'll be able to figure out what protection mechanism is missing.
344 assert(target->is_handshake_safe_for(current_thread), "JavaThread=" INTPTR_FORMAT
345 " is not protected and not handshake safe.", p2i(target));
346
347 // The target JavaThread is not protected so it is not safe to query:
348 return false;
349 }
350
351 // Is the target JavaThread protected by a ThreadsListHandle (TLH) associated
352 // with the calling Thread?
353 //
354 bool Thread::is_JavaThread_protected_by_TLH(const JavaThread* target) {
355 Thread* current_thread = Thread::current();
356
357 // Check the ThreadsLists associated with the calling thread (if any)
358 // to see if one of them protects the target JavaThread:
359 for (SafeThreadsListPtr* stlp = current_thread->_threads_list_ptr;
360 stlp != nullptr; stlp = stlp->previous()) {
361 if (stlp->list()->includes(target)) {
362 // The target JavaThread is protected by this ThreadsList:
363 return true;
364 }
365 }
366
367 // The target JavaThread is not protected by a TLH so it is not safe to query:
368 return false;
369 }
370
371 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
372 debug_only(check_for_dangling_thread_pointer(thread);)
373 // Can return an error!
374 (void)os::set_priority(thread, priority);
375 }
376
377
378 void Thread::start(Thread* thread) {
379 // Start is different from resume in that its safety is guaranteed by context or
380 // being called from a Java method synchronized on the Thread object.
381 if (thread->is_Java_thread()) {
382 // Initialize the thread state to RUNNABLE before starting this thread.
383 // Can not set it after the thread started because we do not know the
384 // exact thread state at that time. It could be in MONITOR_WAIT or
385 // in SLEEPING or some other state.
386 java_lang_Thread::set_thread_status(JavaThread::cast(thread)->threadObj(),
387 JavaThreadStatus::RUNNABLE);
388 }
389 os::start_thread(thread);
390 }
391
392 // GC Support
393 bool Thread::claim_par_threads_do(uintx claim_token) {
394 uintx token = _threads_do_token;
395 if (token != claim_token) {
396 uintx res = Atomic::cmpxchg(&_threads_do_token, token, claim_token);
397 if (res == token) {
398 return true;
399 }
400 guarantee(res == claim_token, "invariant");
401 }
402 return false;
403 }
404
405 void Thread::oops_do_no_frames(OopClosure* f, CodeBlobClosure* cf) {
406 // Do oop for ThreadShadow
407 f->do_oop((oop*)&_pending_exception);
408 handle_area()->oops_do(f);
409 }
410
411 // If the caller is a NamedThread, then remember, in the current scope,
412 // the given JavaThread in its _processed_thread field.
413 class RememberProcessedThread: public StackObj {
414 NamedThread* _cur_thr;
415 public:
416 RememberProcessedThread(Thread* thread) {
417 Thread* self = Thread::current();
418 if (self->is_Named_thread()) {
419 _cur_thr = (NamedThread *)self;
420 assert(_cur_thr->processed_thread() == nullptr, "nesting not supported");
421 _cur_thr->set_processed_thread(thread);
422 } else {
423 _cur_thr = nullptr;
424 }
425 }
426
427 ~RememberProcessedThread() {
428 if (_cur_thr) {
429 assert(_cur_thr->processed_thread() != nullptr, "nesting not supported");
430 _cur_thr->set_processed_thread(nullptr);
431 }
432 }
433 };
434
435 void Thread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
436 // Record JavaThread to GC thread
437 RememberProcessedThread rpt(this);
438 oops_do_no_frames(f, cf);
439 oops_do_frames(f, cf);
440 }
441
442 void Thread::metadata_handles_do(void f(Metadata*)) {
443 // Only walk the Handles in Thread.
444 if (metadata_handles() != nullptr) {
445 for (int i = 0; i< metadata_handles()->length(); i++) {
446 f(metadata_handles()->at(i));
447 }
448 }
449 }
450
451 void Thread::print_on(outputStream* st, bool print_extended_info) const {
452 // get_priority assumes osthread initialized
453 if (osthread() != nullptr) {
454 int os_prio;
455 if (os::get_native_priority(this, &os_prio) == OS_OK) {
456 st->print("os_prio=%d ", os_prio);
457 }
458
459 st->print("cpu=%.2fms ",
460 os::thread_cpu_time(const_cast<Thread*>(this), true) / 1000000.0
461 );
462 st->print("elapsed=%.2fs ",
463 _statistical_info.getElapsedTime() / 1000.0
464 );
465 if (is_Java_thread() && (PrintExtendedThreadInfo || print_extended_info)) {
466 size_t allocated_bytes = (size_t) const_cast<Thread*>(this)->cooked_allocated_bytes();
467 st->print("allocated=" SIZE_FORMAT "%s ",
468 byte_size_in_proper_unit(allocated_bytes),
469 proper_unit_for_byte_size(allocated_bytes)
470 );
471 st->print("defined_classes=" INT64_FORMAT " ", _statistical_info.getDefineClassCount());
472 }
473
474 st->print("tid=" INTPTR_FORMAT " ", p2i(this));
475 if (!is_Java_thread() || !JavaThread::cast(this)->is_vthread_mounted()) {
476 osthread()->print_on(st);
477 }
478 }
479 ThreadsSMRSupport::print_info_on(this, st);
480 st->print(" ");
481 debug_only(if (WizardMode) print_owned_locks_on(st);)
482 }
483
484 void Thread::print() const { print_on(tty); }
485
486 // Thread::print_on_error() is called by fatal error handler. Don't use
487 // any lock or allocate memory.
488 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
489 assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
490
491 st->print("%s \"%s\"", type_name(), name());
492
493 OSThread* os_thr = osthread();
494 if (os_thr != nullptr) {
495 if (os_thr->get_state() != ZOMBIE) {
496 st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
497 p2i(stack_end()), p2i(stack_base()));
498 st->print(" [id=%d]", osthread()->thread_id());
499 } else {
500 st->print(" terminated");
501 }
502 } else {
503 st->print(" unknown state (no osThread)");
504 }
505 ThreadsSMRSupport::print_info_on(this, st);
506 }
507
508 void Thread::print_value_on(outputStream* st) const {
509 if (is_Named_thread()) {
510 st->print(" \"%s\" ", name());
511 }
512 st->print(INTPTR_FORMAT, p2i(this)); // print address
513 }
514
515 #ifdef ASSERT
516 void Thread::print_owned_locks_on(outputStream* st) const {
517 Mutex* cur = _owned_locks;
518 if (cur == nullptr) {
519 st->print(" (no locks) ");
520 } else {
521 st->print_cr(" Locks owned:");
522 while (cur) {
523 cur->print_on(st);
524 cur = cur->next();
525 }
526 }
527 }
528 #endif // ASSERT
529
530 // We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
531 // However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
532 // used for compilation in the future. If that change is made, the need for these methods
533 // should be revisited, and they should be removed if possible.
534
535 bool Thread::is_lock_owned(address adr) const {
536 return is_in_full_stack(adr);
537 }
538
539 bool Thread::set_as_starting_thread() {
540 assert(_starting_thread == nullptr, "already initialized: "
541 "_starting_thread=" INTPTR_FORMAT, p2i(_starting_thread));
542 // NOTE: this must be called inside the main thread.
543 DEBUG_ONLY(_starting_thread = this;)
544 return os::create_main_thread(JavaThread::cast(this));
545 }
546
547 // Ad-hoc mutual exclusion primitives: SpinLock
548 //
549 // We employ SpinLocks _only for low-contention, fixed-length
550 // short-duration critical sections where we're concerned
551 // about native mutex_t or HotSpot Mutex:: latency.
552 //
553 // TODO-FIXME: ListLock should be of type SpinLock.
554 // We should make this a 1st-class type, integrated into the lock
555 // hierarchy as leaf-locks. Critically, the SpinLock structure
556 // should have sufficient padding to avoid false-sharing and excessive
557 // cache-coherency traffic.
558
559
560 typedef volatile int SpinLockT;
561
562 void Thread::SpinAcquire(volatile int * adr, const char * LockName) {
563 if (Atomic::cmpxchg(adr, 0, 1) == 0) {
564 return; // normal fast-path return
565 }
566
567 // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
568 int ctr = 0;
569 int Yields = 0;
570 for (;;) {
571 while (*adr != 0) {
572 ++ctr;
573 if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
574 if (Yields > 5) {
575 os::naked_short_sleep(1);
576 } else {
577 os::naked_yield();
578 ++Yields;
579 }
580 } else {
581 SpinPause();
582 }
583 }
584 if (Atomic::cmpxchg(adr, 0, 1) == 0) return;
585 }
586 }
587
588 void Thread::SpinRelease(volatile int * adr) {
589 assert(*adr != 0, "invariant");
590 OrderAccess::fence(); // guarantee at least release consistency.
591 // Roach-motel semantics.
592 // It's safe if subsequent LDs and STs float "up" into the critical section,
593 // but prior LDs and STs within the critical section can't be allowed
594 // to reorder or float past the ST that releases the lock.
595 // Loads and stores in the critical section - which appear in program
596 // order before the store that releases the lock - must also appear
597 // before the store that releases the lock in memory visibility order.
598 // Conceptually we need a #loadstore|#storestore "release" MEMBAR before
599 // the ST of 0 into the lock-word which releases the lock, so fence
600 // more than covers this on all platforms.
601 *adr = 0;
602 }