1 /*
2 * Copyright (c) 1997, 2025, 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 "cds/cdsConfig.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 "nmt/memTracker.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "runtime/atomic.hpp"
40 #include "runtime/handles.inline.hpp"
41 #include "runtime/javaThread.inline.hpp"
42 #include "runtime/nonJavaThread.hpp"
43 #include "runtime/orderAccess.hpp"
44 #include "runtime/osThread.hpp"
45 #include "runtime/safepoint.hpp"
46 #include "runtime/safepointMechanism.inline.hpp"
47 #include "runtime/thread.inline.hpp"
48 #include "runtime/threadSMR.inline.hpp"
49 #include "utilities/macros.hpp"
50 #include "utilities/spinYield.hpp"
51 #if INCLUDE_JFR
52 #include "jfr/jfr.hpp"
53 #endif
54
55 THREAD_LOCAL Thread* Thread::_thr_current = nullptr;
56
57 // ======= Thread ========
58 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
59 // JavaThread
60
61 Thread::Thread(MemTag mem_tag) {
62
63 DEBUG_ONLY(_run_state = PRE_CALL_RUN;)
64
65 // stack and get_thread
66 set_stack_base(nullptr);
67 set_stack_size(0);
68 set_lgrp_id(-1);
69 DEBUG_ONLY(clear_suspendible_thread();)
70 DEBUG_ONLY(clear_indirectly_suspendible_thread();)
71 DEBUG_ONLY(clear_indirectly_safepoint_thread();)
72
73 // allocated data structures
74 set_osthread(nullptr);
75 set_resource_area(new (mem_tag) ResourceArea(mem_tag));
76 DEBUG_ONLY(_current_resource_mark = nullptr;)
77 set_handle_area(new (mem_tag) HandleArea(mem_tag, nullptr));
78 set_metadata_handles(new (mtClass) GrowableArray<Metadata*>(30, mtClass));
79 set_last_handle_mark(nullptr);
80
81 // Initial value of zero ==> never claimed.
82 _threads_do_token = 0;
83 _threads_hazard_ptr = nullptr;
84 _threads_list_ptr = nullptr;
85 _nested_threads_hazard_ptr_cnt = 0;
86 _rcu_counter = 0;
87
88 // the handle mark links itself to last_handle_mark
89 new HandleMark(this);
90
91 // plain initialization
92 DEBUG_ONLY(_owned_locks = nullptr;)
93 NOT_PRODUCT(_skip_gcalot = false;)
94 _jvmti_env_iteration_count = 0;
95 set_allocated_bytes(0);
96 _current_pending_raw_monitor = nullptr;
97 _vm_error_callbacks = nullptr;
98
99 // thread-specific hashCode stream generator state - Marsaglia shift-xor form
100 // If we are dumping, keep ihashes constant. Note that during dumping we only
101 // ever run one java thread, and no other thread should generate ihashes either,
102 // so using a constant seed should work fine.
103 _hashStateX = CDSConfig::is_dumping_static_archive() ? 0x12345678 : os::random();
104 _hashStateY = 842502087;
105 _hashStateZ = 0x8767; // (int)(3579807591LL & 0xffff) ;
106 _hashStateW = 273326509;
107
108 // Many of the following fields are effectively final - immutable
109 // Note that nascent threads can't use the Native Monitor-Mutex
110 // construct until the _MutexEvent is initialized ...
111 // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
112 // we might instead use a stack of ParkEvents that we could provision on-demand.
113 // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
114 // and ::Release()
115 _ParkEvent = ParkEvent::Allocate(this);
116
117 #ifdef CHECK_UNHANDLED_OOPS
118 if (CheckUnhandledOops) {
119 _unhandled_oops = new UnhandledOops(this);
120 }
121 #endif // CHECK_UNHANDLED_OOPS
122
123 // Notify the barrier set that a thread is being created. The initial
124 // thread is created before the barrier set is available. The call to
125 // BarrierSet::on_thread_create() for this thread is therefore deferred
126 // to BarrierSet::set_barrier_set().
127 BarrierSet* const barrier_set = BarrierSet::barrier_set();
128 if (barrier_set != nullptr) {
129 barrier_set->on_thread_create(this);
130 } else {
131 // Only the main thread should be created before the barrier set
132 // and that happens just before Thread::current is set. No other thread
133 // can attach as the VM is not created yet, so they can't execute this code.
134 // If the main thread creates other threads before the barrier set that is an error.
135 assert(Thread::current_or_null() == nullptr, "creating thread before barrier set");
136 }
137
138 MACOS_AARCH64_ONLY(DEBUG_ONLY(_wx_init = false));
139
140 _profile_vm_locks = false;
141 _profile_vm_calls = false;
142 _profile_vm_ops = false;
143 _profile_rt_calls = false;
144 _profile_upcalls = false;
145
146 _all_bc_counter_value = 0;
147 _clinit_bc_counter_value = 0;
148
149 _current_rt_call_timer = nullptr;
150 }
151
152 #ifdef ASSERT
153 address Thread::stack_base() const {
154 // Note: can't report Thread::name() here as that can require a ResourceMark which we
155 // can't use because this gets called too early in the thread initialization.
156 assert(_stack_base != nullptr, "Stack base not yet set for thread id:%d (0 if not set)",
157 osthread() != nullptr ? osthread()->thread_id() : 0);
158 return _stack_base;
159 }
160 #endif
161
162 void Thread::initialize_tlab() {
163 if (UseTLAB) {
164 tlab().initialize();
165 }
166 }
167
168 void Thread::retire_tlab(ThreadLocalAllocStats* stats) {
169 // Sampling and serviceability support
170 if (tlab().end() != nullptr) {
171 incr_allocated_bytes(tlab().used_bytes());
172 heap_sampler().retire_tlab(tlab().top());
173 }
174
175 // Retire the TLAB
176 tlab().retire(stats);
177 }
178
179 void Thread::fill_tlab(HeapWord* start, size_t pre_reserved, size_t new_size) {
180 // Thread allocation sampling support
181 heap_sampler().set_tlab_top_at_sample_start(start);
182
183 // Fill the TLAB
184 tlab().fill(start, start + pre_reserved, new_size);
185 }
186
187 void Thread::initialize_thread_current() {
188 assert(_thr_current == nullptr, "Thread::current already initialized");
189 _thr_current = this;
190 assert(ThreadLocalStorage::thread() == nullptr, "ThreadLocalStorage::thread already initialized");
191 ThreadLocalStorage::set_thread(this);
192 assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
193 }
194
195 void Thread::clear_thread_current() {
196 assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
197 _thr_current = nullptr;
198 ThreadLocalStorage::set_thread(nullptr);
199 }
200
201 void Thread::record_stack_base_and_size() {
202 // Note: at this point, Thread object is not yet initialized. Do not rely on
203 // any members being initialized. Do not rely on Thread::current() being set.
204 // If possible, refrain from doing anything which may crash or assert since
205 // quite probably those crash dumps will be useless.
206 address base;
207 size_t size;
208 os::current_stack_base_and_size(&base, &size);
209 set_stack_base(base);
210 set_stack_size(size);
211
212 // Set stack limits after thread is initialized.
213 if (is_Java_thread()) {
214 JavaThread::cast(this)->stack_overflow_state()->initialize(stack_base(), stack_end());
215 }
216 }
217
218 void Thread::register_thread_stack_with_NMT() {
219 MemTracker::record_thread_stack(stack_end(), stack_size());
220 }
221
222 void Thread::unregister_thread_stack_with_NMT() {
223 MemTracker::release_thread_stack(stack_end(), stack_size());
224 }
225
226 void Thread::call_run() {
227 DEBUG_ONLY(_run_state = CALL_RUN;)
228
229 // At this point, Thread object should be fully initialized and
230 // Thread::current() should be set.
231
232 assert(Thread::current_or_null() != nullptr, "current thread is unset");
233 assert(Thread::current_or_null() == this, "current thread is wrong");
234
235 // Perform common initialization actions
236
237 MACOS_AARCH64_ONLY(this->init_wx());
238
239 register_thread_stack_with_NMT();
240
241 JFR_ONLY(Jfr::on_thread_start(this);)
242
243 log_debug(os, thread)("Thread %zu stack dimensions: "
244 PTR_FORMAT "-" PTR_FORMAT " (%zuk).",
245 os::current_thread_id(), p2i(stack_end()),
246 p2i(stack_base()), stack_size()/1024);
247
248 // Perform <ChildClass> initialization actions
249 DEBUG_ONLY(_run_state = PRE_RUN;)
250 this->pre_run();
251
252 // Invoke <ChildClass>::run()
253 DEBUG_ONLY(_run_state = RUN;)
254 this->run();
255 // Returned from <ChildClass>::run(). Thread finished.
256
257 // Perform common tear-down actions
258
259 assert(Thread::current_or_null() != nullptr, "current thread is unset");
260 assert(Thread::current_or_null() == this, "current thread is wrong");
261
262 // Perform <ChildClass> tear-down actions
263 DEBUG_ONLY(_run_state = POST_RUN;)
264 this->post_run();
265
266 // Note: at this point the thread object may already have deleted itself,
267 // so from here on do not dereference *this*. Not all thread types currently
268 // delete themselves when they terminate. But no thread should ever be deleted
269 // asynchronously with respect to its termination - that is what _run_state can
270 // be used to check.
271
272 // Logically we should do this->unregister_thread_stack_with_NMT() here, but we
273 // had to move that into post_run() because of the `this` deletion issue.
274
275 assert(Thread::current_or_null() == nullptr, "current thread still present");
276 }
277
278 Thread::~Thread() {
279
280 // Attached threads will remain in PRE_CALL_RUN, as will threads that don't actually
281 // get started due to errors etc. Any active thread should at least reach post_run
282 // before it is deleted (usually in post_run()).
283 assert(_run_state == PRE_CALL_RUN ||
284 _run_state == POST_RUN, "Active Thread deleted before post_run(): "
285 "_run_state=%d", (int)_run_state);
286
287 // Notify the barrier set that a thread is being destroyed. Note that a barrier
288 // set might not be available if we encountered errors during bootstrapping.
289 BarrierSet* const barrier_set = BarrierSet::barrier_set();
290 if (barrier_set != nullptr) {
291 barrier_set->on_thread_destroy(this);
292 }
293
294 // deallocate data structures
295 delete resource_area();
296 // since the handle marks are using the handle area, we have to deallocated the root
297 // handle mark before deallocating the thread's handle area,
298 assert(last_handle_mark() != nullptr, "check we have an element");
299 delete last_handle_mark();
300 assert(last_handle_mark() == nullptr, "check we have reached the end");
301
302 ParkEvent::Release(_ParkEvent);
303 // Set to null as a termination indicator for has_terminated().
304 Atomic::store(&_ParkEvent, (ParkEvent*)nullptr);
305
306 delete handle_area();
307 delete metadata_handles();
308
309 // osthread() can be null, if creation of thread failed.
310 if (osthread() != nullptr) os::free_thread(osthread());
311
312 // Clear Thread::current if thread is deleting itself and it has not
313 // already been done. This must be done before the memory is deallocated.
314 // Needed to ensure JNI correctly detects non-attached threads.
315 if (this == Thread::current_or_null()) {
316 Thread::clear_thread_current();
317 }
318
319 CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
320 }
321
322 #ifdef ASSERT
323 // A JavaThread is considered dangling if it not handshake-safe with respect to
324 // the current thread, it is not on a ThreadsList, or not at safepoint.
325 void Thread::check_for_dangling_thread_pointer(Thread *thread) {
326 assert(!thread->is_Java_thread() ||
327 JavaThread::cast(thread)->is_handshake_safe_for(Thread::current()) ||
328 !JavaThread::cast(thread)->on_thread_list() ||
329 SafepointSynchronize::is_at_safepoint() ||
330 ThreadsSMRSupport::is_a_protected_JavaThread_with_lock(JavaThread::cast(thread)),
331 "possibility of dangling Thread pointer");
332 }
333 #endif
334
335 // Is the target JavaThread protected by the calling Thread or by some other
336 // mechanism?
337 //
338 bool Thread::is_JavaThread_protected(const JavaThread* target) {
339 Thread* current_thread = Thread::current();
340
341 // Do the simplest check first:
342 if (SafepointSynchronize::is_at_safepoint()) {
343 // The target is protected since JavaThreads cannot exit
344 // while we're at a safepoint.
345 return true;
346 }
347
348 // If the target hasn't been started yet then it is trivially
349 // "protected". We assume the caller is the thread that will do
350 // the starting.
351 if (target->osthread() == nullptr || target->osthread()->get_state() <= INITIALIZED) {
352 return true;
353 }
354
355 // Now make the simple checks based on who the caller is:
356 if (current_thread == target || Threads_lock->owner() == current_thread) {
357 // Target JavaThread is self or calling thread owns the Threads_lock.
358 // Second check is the same as Threads_lock->owner_is_self(),
359 // but we already have the current thread so check directly.
360 return true;
361 }
362
363 // Check the ThreadsLists associated with the calling thread (if any)
364 // to see if one of them protects the target JavaThread:
365 if (is_JavaThread_protected_by_TLH(target)) {
366 return true;
367 }
368
369 // Use this debug code with -XX:+UseNewCode to diagnose locations that
370 // are missing a ThreadsListHandle or other protection mechanism:
371 // guarantee(!UseNewCode, "current_thread=" INTPTR_FORMAT " is not protecting target="
372 // INTPTR_FORMAT, p2i(current_thread), p2i(target));
373
374 // Note: Since 'target' isn't protected by a TLH, the call to
375 // target->is_handshake_safe_for() may crash, but we have debug bits so
376 // we'll be able to figure out what protection mechanism is missing.
377 assert(target->is_handshake_safe_for(current_thread), "JavaThread=" INTPTR_FORMAT
378 " is not protected and not handshake safe.", p2i(target));
379
380 // The target JavaThread is not protected so it is not safe to query:
381 return false;
382 }
383
384 // Is the target JavaThread protected by a ThreadsListHandle (TLH) associated
385 // with the calling Thread?
386 //
387 bool Thread::is_JavaThread_protected_by_TLH(const JavaThread* target) {
388 Thread* current_thread = Thread::current();
389
390 // Check the ThreadsLists associated with the calling thread (if any)
391 // to see if one of them protects the target JavaThread:
392 for (SafeThreadsListPtr* stlp = current_thread->_threads_list_ptr;
393 stlp != nullptr; stlp = stlp->previous()) {
394 if (stlp->list()->includes(target)) {
395 // The target JavaThread is protected by this ThreadsList:
396 return true;
397 }
398 }
399
400 // The target JavaThread is not protected by a TLH so it is not safe to query:
401 return false;
402 }
403
404 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
405 DEBUG_ONLY(check_for_dangling_thread_pointer(thread);)
406 // Can return an error!
407 (void)os::set_priority(thread, priority);
408 }
409
410
411 void Thread::start(Thread* thread) {
412 // Start is different from resume in that its safety is guaranteed by context or
413 // being called from a Java method synchronized on the Thread object.
414 if (thread->is_Java_thread()) {
415 // Initialize the thread state to RUNNABLE before starting this thread.
416 // Can not set it after the thread started because we do not know the
417 // exact thread state at that time. It could be in MONITOR_WAIT or
418 // in SLEEPING or some other state.
419 java_lang_Thread::set_thread_status(JavaThread::cast(thread)->threadObj(),
420 JavaThreadStatus::RUNNABLE);
421 }
422 os::start_thread(thread);
423 }
424
425 // GC Support
426 bool Thread::claim_par_threads_do(uintx claim_token) {
427 uintx token = _threads_do_token;
428 if (token != claim_token) {
429 uintx res = Atomic::cmpxchg(&_threads_do_token, token, claim_token);
430 if (res == token) {
431 return true;
432 }
433 guarantee(res == claim_token, "invariant");
434 }
435 return false;
436 }
437
438 void Thread::oops_do_no_frames(OopClosure* f, NMethodClosure* cf) {
439 // Do oop for ThreadShadow
440 f->do_oop((oop*)&_pending_exception);
441 handle_area()->oops_do(f);
442 }
443
444 // If the caller is a NamedThread, then remember, in the current scope,
445 // the given JavaThread in its _processed_thread field.
446 class RememberProcessedThread: public StackObj {
447 NamedThread* _cur_thr;
448 public:
449 RememberProcessedThread(Thread* thread) {
450 Thread* self = Thread::current();
451 if (self->is_Named_thread()) {
452 _cur_thr = (NamedThread *)self;
453 assert(_cur_thr->processed_thread() == nullptr, "nesting not supported");
454 _cur_thr->set_processed_thread(thread);
455 } else {
456 _cur_thr = nullptr;
457 }
458 }
459
460 ~RememberProcessedThread() {
461 if (_cur_thr) {
462 assert(_cur_thr->processed_thread() != nullptr, "nesting not supported");
463 _cur_thr->set_processed_thread(nullptr);
464 }
465 }
466 };
467
468 void Thread::oops_do(OopClosure* f, NMethodClosure* cf) {
469 // Record JavaThread to GC thread
470 RememberProcessedThread rpt(this);
471 oops_do_no_frames(f, cf);
472 oops_do_frames(f, cf);
473 }
474
475 void Thread::metadata_handles_do(void f(Metadata*)) {
476 // Only walk the Handles in Thread.
477 if (metadata_handles() != nullptr) {
478 for (int i = 0; i< metadata_handles()->length(); i++) {
479 f(metadata_handles()->at(i));
480 }
481 }
482 }
483
484 void Thread::print_on(outputStream* st, bool print_extended_info) const {
485 // get_priority assumes osthread initialized
486 if (osthread() != nullptr) {
487 int os_prio;
488 if (os::get_native_priority(this, &os_prio) == OS_OK) {
489 st->print("os_prio=%d ", os_prio);
490 }
491
492 st->print("cpu=%.2fms ",
493 (double)os::thread_cpu_time(const_cast<Thread*>(this), true) / 1000000.0
494 );
495 st->print("elapsed=%.2fs ",
496 (double)_statistical_info.getElapsedTime() / 1000.0
497 );
498 if (is_Java_thread() && (PrintExtendedThreadInfo || print_extended_info)) {
499 size_t allocated_bytes = (size_t) const_cast<Thread*>(this)->cooked_allocated_bytes();
500 st->print("allocated=%zu%s ",
501 byte_size_in_proper_unit(allocated_bytes),
502 proper_unit_for_byte_size(allocated_bytes)
503 );
504 st->print("defined_classes=" INT64_FORMAT " ", _statistical_info.getDefineClassCount());
505 }
506
507 st->print("tid=" INTPTR_FORMAT " ", p2i(this));
508 if (!is_Java_thread() || !JavaThread::cast(this)->is_vthread_mounted()) {
509 osthread()->print_on(st);
510 }
511 }
512 ThreadsSMRSupport::print_info_on(this, st);
513 st->print(" ");
514 DEBUG_ONLY(if (WizardMode) print_owned_locks_on(st);)
515 }
516
517 void Thread::print() const { print_on(tty); }
518
519 // Thread::print_on_error() is called by fatal error handler. Don't use
520 // any lock or allocate memory.
521 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
522 assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
523
524 st->print("%s \"%s\"", type_name(), name());
525
526 OSThread* os_thr = osthread();
527 if (os_thr != nullptr) {
528 st->fill_to(67);
529 if (os_thr->get_state() != ZOMBIE) {
530 // Use raw field members for stack base/size as this could be
531 // called before a thread has run enough to initialize them.
532 st->print(" [id=%d, stack(" PTR_FORMAT "," PTR_FORMAT ") (" PROPERFMT ")]",
533 osthread()->thread_id(), p2i(_stack_base - _stack_size), p2i(_stack_base),
534 PROPERFMTARGS(_stack_size));
535 } else {
536 st->print(" terminated");
537 }
538 } else {
539 st->print(" unknown state (no osThread)");
540 }
541 ThreadsSMRSupport::print_info_on(this, st);
542 }
543
544 void Thread::print_value_on(outputStream* st) const {
545 if (is_Named_thread()) {
546 st->print(" \"%s\" ", name());
547 }
548 st->print(INTPTR_FORMAT, p2i(this)); // print address
549 }
550
551 #ifdef ASSERT
552 void Thread::print_owned_locks_on(outputStream* st) const {
553 Mutex* cur = _owned_locks;
554 if (cur == nullptr) {
555 st->print(" (no locks) ");
556 } else {
557 st->print_cr(" Locks owned:");
558 while (cur) {
559 cur->print_on(st);
560 cur = cur->next();
561 }
562 }
563 }
564
565 Thread* Thread::_starting_thread = nullptr;
566
567 bool Thread::is_starting_thread(const Thread* t) {
568 assert(_starting_thread != nullptr, "invariant");
569 return t == _starting_thread;
570 }
571 #endif // ASSERT
572
573 bool Thread::set_as_starting_thread(JavaThread* jt) {
574 assert(jt != nullptr, "invariant");
575 assert(_starting_thread == nullptr, "already initialized: "
576 "_starting_thread=" INTPTR_FORMAT, p2i(_starting_thread));
577 // NOTE: this must be called from Threads::create_vm().
578 DEBUG_ONLY(_starting_thread = jt;)
579 return os::create_main_thread(jt);
580 }
581
582 // Ad-hoc mutual exclusion primitive: spin lock
583 //
584 // We employ a spin lock _only for low-contention, fixed-length
585 // short-duration critical sections where we're concerned
586 // about native mutex_t or HotSpot Mutex:: latency.
587
588 void Thread::SpinAcquire(volatile int * adr) {
589 if (Atomic::cmpxchg(adr, 0, 1) == 0) {
590 return; // normal fast-path return
591 }
592
593 // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
594 int ctr = 0;
595 int Yields = 0;
596 for (;;) {
597 while (*adr != 0) {
598 ++ctr;
599 if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
600 if (Yields > 5) {
601 os::naked_short_sleep(1);
602 } else {
603 os::naked_yield();
604 ++Yields;
605 }
606 } else {
607 SpinPause();
608 }
609 }
610 if (Atomic::cmpxchg(adr, 0, 1) == 0) return;
611 }
612 }
613
614 void Thread::SpinRelease(volatile int * adr) {
615 assert(*adr != 0, "invariant");
616 OrderAccess::fence(); // guarantee at least release consistency.
617 // Roach-motel semantics.
618 // It's safe if subsequent LDs and STs float "up" into the critical section,
619 // but prior LDs and STs within the critical section can't be allowed
620 // to reorder or float past the ST that releases the lock.
621 // Loads and stores in the critical section - which appear in program
622 // order before the store that releases the lock - must also appear
623 // before the store that releases the lock in memory visibility order.
624 // Conceptually we need a #loadstore|#storestore "release" MEMBAR before
625 // the ST of 0 into the lock-word which releases the lock, so fence
626 // more than covers this on all platforms.
627 *adr = 0;
628 }
629
630 const char* ProfileVMCallContext::name(PerfTraceTime* t) {
631 return t->name();
632 }
633
634 int ProfileVMCallContext::_perf_nested_runtime_calls_count = 0;
635
636 void ProfileVMCallContext::notify_nested_rt_call(PerfTraceTime* outer_timer, PerfTraceTime* inner_timer) {
637 log_debug(init)("Nested runtime call: inner=%s outer=%s", inner_timer->name(), outer_timer->name());
638 Atomic::inc(&ProfileVMCallContext::_perf_nested_runtime_calls_count);
639 }
640