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 "cds/dynamicArchive.hpp"
  28 #include "ci/ciEnv.hpp"
  29 #include "classfile/javaClasses.inline.hpp"
  30 #include "classfile/javaThreadStatus.hpp"
  31 #include "classfile/systemDictionary.hpp"
  32 #include "classfile/vmClasses.hpp"
  33 #include "classfile/vmSymbols.hpp"
  34 #include "code/codeCache.hpp"
  35 #include "code/scopeDesc.hpp"
  36 #include "compiler/compileTask.hpp"
  37 #include "compiler/compilerThread.hpp"
  38 #include "gc/shared/oopStorage.hpp"
  39 #include "gc/shared/oopStorageSet.hpp"
  40 #include "gc/shared/tlab_globals.hpp"
  41 #include "jfr/jfrEvents.hpp"
  42 #include "jvm.h"
  43 #include "jvmtifiles/jvmtiEnv.hpp"
  44 #include "logging/log.hpp"
  45 #include "logging/logAsyncWriter.hpp"
  46 #include "logging/logStream.hpp"
  47 #include "memory/allocation.inline.hpp"
  48 #include "memory/iterator.hpp"
  49 #include "memory/universe.hpp"
  50 #include "oops/access.inline.hpp"
  51 #include "oops/instanceKlass.hpp"
  52 #include "oops/klass.inline.hpp"
  53 #include "oops/oop.inline.hpp"
  54 #include "oops/oopHandle.inline.hpp"
  55 #include "oops/verifyOopClosure.hpp"
  56 #include "prims/jvm_misc.hpp"
  57 #include "prims/jvmtiDeferredUpdates.hpp"
  58 #include "prims/jvmtiExport.hpp"
  59 #include "prims/jvmtiThreadState.inline.hpp"
  60 #include "runtime/atomic.hpp"
  61 #include "runtime/continuation.hpp"
  62 #include "runtime/continuationEntry.inline.hpp"
  63 #include "runtime/continuationHelper.inline.hpp"
  64 #include "runtime/deoptimization.hpp"
  65 #include "runtime/frame.inline.hpp"
  66 #include "runtime/handles.inline.hpp"
  67 #include "runtime/handshake.hpp"
  68 #include "runtime/interfaceSupport.inline.hpp"
  69 #include "runtime/java.hpp"
  70 #include "runtime/javaCalls.hpp"
  71 #include "runtime/javaThread.inline.hpp"
  72 #include "runtime/jniHandles.inline.hpp"
  73 #include "runtime/mutexLocker.hpp"
  74 #include "runtime/orderAccess.hpp"
  75 #include "runtime/osThread.hpp"
  76 #include "runtime/safepoint.hpp"
  77 #include "runtime/safepointMechanism.inline.hpp"
  78 #include "runtime/safepointVerifiers.hpp"
  79 #include "runtime/serviceThread.hpp"
  80 #include "runtime/stackFrameStream.inline.hpp"
  81 #include "runtime/stackWatermarkSet.hpp"
  82 #include "runtime/synchronizer.hpp"
  83 #include "runtime/threadCritical.hpp"
  84 #include "runtime/threadSMR.inline.hpp"
  85 #include "runtime/threadStatisticalInfo.hpp"
  86 #include "runtime/threadWXSetters.inline.hpp"
  87 #include "runtime/timer.hpp"
  88 #include "runtime/timerTrace.hpp"
  89 #include "runtime/vframe.inline.hpp"
  90 #include "runtime/vframeArray.hpp"
  91 #include "runtime/vframe_hp.hpp"
  92 #include "runtime/vmThread.hpp"
  93 #include "runtime/vmOperations.hpp"
  94 #include "services/threadService.hpp"
  95 #include "utilities/copy.hpp"
  96 #include "utilities/defaultStream.hpp"
  97 #include "utilities/dtrace.hpp"
  98 #include "utilities/events.hpp"
  99 #include "utilities/macros.hpp"
 100 #include "utilities/preserveException.hpp"
 101 #include "utilities/spinYield.hpp"
 102 #include "utilities/vmError.hpp"
 103 #if INCLUDE_JVMCI
 104 #include "jvmci/jvmci.hpp"
 105 #include "jvmci/jvmciEnv.hpp"
 106 #endif
 107 #if INCLUDE_JFR
 108 #include "jfr/jfr.hpp"
 109 #endif
 110 
 111 // Set by os layer.
 112 size_t      JavaThread::_stack_size_at_create = 0;
 113 
 114 #ifdef DTRACE_ENABLED
 115 
 116 // Only bother with this argument setup if dtrace is available
 117 
 118   #define HOTSPOT_THREAD_PROBE_start HOTSPOT_THREAD_START
 119   #define HOTSPOT_THREAD_PROBE_stop HOTSPOT_THREAD_STOP
 120 
 121   #define DTRACE_THREAD_PROBE(probe, javathread)                           \
 122     {                                                                      \
 123       ResourceMark rm(this);                                               \
 124       int len = 0;                                                         \
 125       const char* name = (javathread)->name();                             \
 126       len = strlen(name);                                                  \
 127       HOTSPOT_THREAD_PROBE_##probe(/* probe = start, stop */               \
 128         (char *) name, len,                                                \
 129         java_lang_Thread::thread_id((javathread)->threadObj()),            \
 130         (uintptr_t) (javathread)->osthread()->thread_id(),                 \
 131         java_lang_Thread::is_daemon((javathread)->threadObj()));           \
 132     }
 133 
 134 #else //  ndef DTRACE_ENABLED
 135 
 136   #define DTRACE_THREAD_PROBE(probe, javathread)
 137 
 138 #endif // ndef DTRACE_ENABLED
 139 
 140 void JavaThread::smr_delete() {
 141   if (_on_thread_list) {
 142     ThreadsSMRSupport::smr_delete(this);
 143   } else {
 144     delete this;
 145   }
 146 }
 147 
 148 // Initialized by VMThread at vm_global_init
 149 OopStorage* JavaThread::_thread_oop_storage = nullptr;
 150 
 151 OopStorage* JavaThread::thread_oop_storage() {
 152   assert(_thread_oop_storage != nullptr, "not yet initialized");
 153   return _thread_oop_storage;
 154 }
 155 
 156 void JavaThread::set_threadOopHandles(oop p) {
 157   assert(_thread_oop_storage != nullptr, "not yet initialized");
 158   _threadObj   = OopHandle(_thread_oop_storage, p);
 159   _vthread     = OopHandle(_thread_oop_storage, p);
 160   _jvmti_vthread = OopHandle(_thread_oop_storage, p->is_a(vmClasses::BoundVirtualThread_klass()) ? p : nullptr);
 161   _scopedValueCache = OopHandle(_thread_oop_storage, nullptr);
 162 }
 163 
 164 oop JavaThread::threadObj() const {
 165   // Ideally we would verify the current thread is oop_safe when this is called, but as we can
 166   // be called from a signal handler we would have to use Thread::current_or_null_safe(). That
 167   // has overhead and also interacts poorly with GetLastError on Windows due to the use of TLS.
 168   // Instead callers must verify oop safe access.
 169   return _threadObj.resolve();
 170 }
 171 
 172 oop JavaThread::vthread() const {
 173   return _vthread.resolve();
 174 }
 175 
 176 void JavaThread::set_vthread(oop p) {
 177   assert(_thread_oop_storage != nullptr, "not yet initialized");
 178   _vthread.replace(p);
 179 }
 180 
 181 oop JavaThread::jvmti_vthread() const {
 182   return _jvmti_vthread.resolve();
 183 }
 184 
 185 void JavaThread::set_jvmti_vthread(oop p) {
 186   assert(_thread_oop_storage != nullptr, "not yet initialized");
 187   _jvmti_vthread.replace(p);
 188 }
 189 
 190 oop JavaThread::scopedValueCache() const {
 191   return _scopedValueCache.resolve();
 192 }
 193 
 194 void JavaThread::set_scopedValueCache(oop p) {
 195   if (_scopedValueCache.ptr_raw() != nullptr) { // i.e. if the OopHandle has been allocated
 196     _scopedValueCache.replace(p);
 197   } else {
 198     assert(p == nullptr, "not yet initialized");
 199   }
 200 }
 201 
 202 void JavaThread::clear_scopedValueBindings() {
 203   set_scopedValueCache(nullptr);
 204   oop vthread_oop = vthread();
 205   // vthread may be null here if we get a VM error during startup,
 206   // before the java.lang.Thread instance has been created.
 207   if (vthread_oop != nullptr) {
 208     java_lang_Thread::clear_scopedValueBindings(vthread_oop);
 209   }
 210 }
 211 
 212 void JavaThread::allocate_threadObj(Handle thread_group, const char* thread_name,
 213                                     bool daemon, TRAPS) {
 214   assert(thread_group.not_null(), "thread group should be specified");
 215   assert(threadObj() == nullptr, "should only create Java thread object once");
 216 
 217   InstanceKlass* ik = vmClasses::Thread_klass();
 218   assert(ik->is_initialized(), "must be");
 219   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK);
 220 
 221   // We are called from jni_AttachCurrentThread/jni_AttachCurrentThreadAsDaemon.
 222   // We cannot use JavaCalls::construct_new_instance because the java.lang.Thread
 223   // constructor calls Thread.current(), which must be set here.
 224   java_lang_Thread::set_thread(thread_oop(), this);
 225   set_threadOopHandles(thread_oop());
 226 
 227   JavaValue result(T_VOID);
 228   if (thread_name != nullptr) {
 229     Handle name = java_lang_String::create_from_str(thread_name, CHECK);
 230     // Thread gets assigned specified name and null target
 231     JavaCalls::call_special(&result,
 232                             thread_oop,
 233                             ik,
 234                             vmSymbols::object_initializer_name(),
 235                             vmSymbols::threadgroup_string_void_signature(),
 236                             thread_group,
 237                             name,
 238                             CHECK);
 239   } else {
 240     // Thread gets assigned name "Thread-nnn" and null target
 241     // (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
 242     JavaCalls::call_special(&result,
 243                             thread_oop,
 244                             ik,
 245                             vmSymbols::object_initializer_name(),
 246                             vmSymbols::threadgroup_runnable_void_signature(),
 247                             thread_group,
 248                             Handle(),
 249                             CHECK);
 250   }
 251   os::set_priority(this, NormPriority);
 252 
 253   if (daemon) {
 254     java_lang_Thread::set_daemon(thread_oop());
 255   }
 256 }
 257 
 258 // ======= JavaThread ========
 259 
 260 #if INCLUDE_JVMCI
 261 
 262 jlong* JavaThread::_jvmci_old_thread_counters;
 263 
 264 bool jvmci_counters_include(JavaThread* thread) {
 265   return !JVMCICountersExcludeCompiler || !thread->is_Compiler_thread();
 266 }
 267 
 268 void JavaThread::collect_counters(jlong* array, int length) {
 269   assert(length == JVMCICounterSize, "wrong value");
 270   for (int i = 0; i < length; i++) {
 271     array[i] = _jvmci_old_thread_counters[i];
 272   }
 273   for (JavaThread* tp : ThreadsListHandle()) {
 274     if (jvmci_counters_include(tp)) {
 275       for (int i = 0; i < length; i++) {
 276         array[i] += tp->_jvmci_counters[i];
 277       }
 278     }
 279   }
 280 }
 281 
 282 // Attempt to enlarge the array for per thread counters.
 283 jlong* resize_counters_array(jlong* old_counters, int current_size, int new_size) {
 284   jlong* new_counters = NEW_C_HEAP_ARRAY_RETURN_NULL(jlong, new_size, mtJVMCI);
 285   if (new_counters == nullptr) {
 286     return nullptr;
 287   }
 288   if (old_counters == nullptr) {
 289     old_counters = new_counters;
 290     memset(old_counters, 0, sizeof(jlong) * new_size);
 291   } else {
 292     for (int i = 0; i < MIN2((int) current_size, new_size); i++) {
 293       new_counters[i] = old_counters[i];
 294     }
 295     if (new_size > current_size) {
 296       memset(new_counters + current_size, 0, sizeof(jlong) * (new_size - current_size));
 297     }
 298     FREE_C_HEAP_ARRAY(jlong, old_counters);
 299   }
 300   return new_counters;
 301 }
 302 
 303 // Attempt to enlarge the array for per thread counters.
 304 bool JavaThread::resize_counters(int current_size, int new_size) {
 305   jlong* new_counters = resize_counters_array(_jvmci_counters, current_size, new_size);
 306   if (new_counters == nullptr) {
 307     return false;
 308   } else {
 309     _jvmci_counters = new_counters;
 310     return true;
 311   }
 312 }
 313 
 314 class VM_JVMCIResizeCounters : public VM_Operation {
 315  private:
 316   int _new_size;
 317   bool _failed;
 318 
 319  public:
 320   VM_JVMCIResizeCounters(int new_size) : _new_size(new_size), _failed(false) { }
 321   VMOp_Type type()                  const        { return VMOp_JVMCIResizeCounters; }
 322   bool allow_nested_vm_operations() const        { return true; }
 323   void doit() {
 324     // Resize the old thread counters array
 325     jlong* new_counters = resize_counters_array(JavaThread::_jvmci_old_thread_counters, JVMCICounterSize, _new_size);
 326     if (new_counters == nullptr) {
 327       _failed = true;
 328       return;
 329     } else {
 330       JavaThread::_jvmci_old_thread_counters = new_counters;
 331     }
 332 
 333     // Now resize each threads array
 334     for (JavaThread* tp : ThreadsListHandle()) {
 335       if (!tp->resize_counters(JVMCICounterSize, _new_size)) {
 336         _failed = true;
 337         break;
 338       }
 339     }
 340     if (!_failed) {
 341       JVMCICounterSize = _new_size;
 342     }
 343   }
 344 
 345   bool failed() { return _failed; }
 346 };
 347 
 348 bool JavaThread::resize_all_jvmci_counters(int new_size) {
 349   VM_JVMCIResizeCounters op(new_size);
 350   VMThread::execute(&op);
 351   return !op.failed();
 352 }
 353 
 354 #endif // INCLUDE_JVMCI
 355 
 356 #ifdef ASSERT
 357 // Checks safepoint allowed and clears unhandled oops at potential safepoints.
 358 void JavaThread::check_possible_safepoint() {
 359   if (_no_safepoint_count > 0) {
 360     print_owned_locks();
 361     assert(false, "Possible safepoint reached by thread that does not allow it");
 362   }
 363 #ifdef CHECK_UNHANDLED_OOPS
 364   // Clear unhandled oops in JavaThreads so we get a crash right away.
 365   clear_unhandled_oops();
 366 #endif // CHECK_UNHANDLED_OOPS
 367 
 368   // Macos/aarch64 should be in the right state for safepoint (e.g.
 369   // deoptimization needs WXWrite).  Crashes caused by the wrong state rarely
 370   // happens in practice, making such issues hard to find and reproduce.
 371 #if defined(__APPLE__) && defined(AARCH64)
 372   if (AssertWXAtThreadSync) {
 373     assert_wx_state(WXWrite);
 374   }
 375 #endif
 376 }
 377 
 378 void JavaThread::check_for_valid_safepoint_state() {
 379   // Don't complain if running a debugging command.
 380   if (DebuggingContext::is_enabled()) return;
 381 
 382   // Check NoSafepointVerifier, which is implied by locks taken that can be
 383   // shared with the VM thread.  This makes sure that no locks with allow_vm_block
 384   // are held.
 385   check_possible_safepoint();
 386 
 387   if (thread_state() != _thread_in_vm) {
 388     fatal("LEAF method calling lock?");
 389   }
 390 
 391   if (GCALotAtAllSafepoints) {
 392     // We could enter a safepoint here and thus have a gc
 393     InterfaceSupport::check_gc_alot();
 394   }
 395 }
 396 #endif // ASSERT
 397 
 398 // A JavaThread is a normal Java thread
 399 
 400 JavaThread::JavaThread() :
 401   // Initialize fields
 402 
 403   _on_thread_list(false),
 404   DEBUG_ONLY(_java_call_counter(0) COMMA)
 405   _entry_point(nullptr),
 406   _deopt_mark(nullptr),
 407   _deopt_nmethod(nullptr),
 408   _vframe_array_head(nullptr),
 409   _vframe_array_last(nullptr),
 410   _jvmti_deferred_updates(nullptr),
 411   _callee_target(nullptr),
 412   _vm_result(nullptr),
 413   _vm_result_2(nullptr),
 414 
 415   _current_pending_monitor(nullptr),
 416   _current_pending_monitor_is_from_java(true),
 417   _current_waiting_monitor(nullptr),
 418   _active_handles(nullptr),
 419   _free_handle_block(nullptr),
 420   _Stalled(0),
 421 
 422   _monitor_chunks(nullptr),
 423 
 424   _suspend_flags(0),
 425 
 426   _thread_state(_thread_new),
 427   _saved_exception_pc(nullptr),
 428 #ifdef ASSERT
 429   _no_safepoint_count(0),
 430   _visited_for_critical_count(false),
 431 #endif
 432 
 433   _terminated(_not_terminated),
 434   _in_deopt_handler(0),
 435   _doing_unsafe_access(false),
 436   _do_not_unlock_if_synchronized(false),
 437 #if INCLUDE_JVMTI
 438   _carrier_thread_suspended(false),
 439   _is_in_VTMS_transition(false),
 440   _is_in_tmp_VTMS_transition(false),
 441 #ifdef ASSERT
 442   _is_VTMS_transition_disabler(false),
 443 #endif
 444 #endif
 445   _jni_attach_state(_not_attaching_via_jni),
 446 #if INCLUDE_JVMCI
 447   _pending_deoptimization(-1),
 448   _pending_monitorenter(false),
 449   _pending_transfer_to_interpreter(false),
 450   _in_retryable_allocation(false),
 451   _pending_failed_speculation(0),
 452   _jvmci{nullptr},
 453   _libjvmci_runtime(nullptr),
 454   _jvmci_counters(nullptr),
 455   _jvmci_reserved0(0),
 456   _jvmci_reserved1(0),
 457   _jvmci_reserved_oop0(nullptr),
 458 #endif // INCLUDE_JVMCI
 459 
 460   _exception_oop(oop()),
 461   _exception_pc(0),
 462   _exception_handler_pc(0),
 463   _is_method_handle_return(0),
 464 
 465   _jni_active_critical(0),
 466   _pending_jni_exception_check_fn(nullptr),
 467   _depth_first_number(0),
 468 
 469   // JVMTI PopFrame support
 470   _popframe_condition(popframe_inactive),
 471   _frames_to_pop_failed_realloc(0),
 472 
 473   _cont_entry(nullptr),
 474   _cont_fastpath(0),
 475   _cont_fastpath_thread_state(1),
 476   _held_monitor_count(0),
 477   _jni_monitor_count(0),
 478 
 479   _handshake(this),
 480 
 481   _popframe_preserved_args(nullptr),
 482   _popframe_preserved_args_size(0),
 483 
 484   _jvmti_thread_state(nullptr),
 485   _interp_only_mode(0),
 486   _should_post_on_exceptions_flag(JNI_FALSE),
 487   _thread_stat(new ThreadStatistics()),
 488 
 489   _parker(),
 490 
 491   _class_to_be_initialized(nullptr),
 492 
 493   _SleepEvent(ParkEvent::Allocate(this))
 494 {
 495   set_jni_functions(jni_functions());
 496 
 497 #if INCLUDE_JVMCI
 498   assert(_jvmci._implicit_exception_pc == nullptr, "must be");
 499   if (JVMCICounterSize > 0) {
 500     resize_counters(0, (int) JVMCICounterSize);
 501   }
 502 #endif // INCLUDE_JVMCI
 503 
 504   // Setup safepoint state info for this thread
 505   ThreadSafepointState::create(this);
 506 
 507   SafepointMechanism::initialize_header(this);
 508 
 509   set_requires_cross_modify_fence(false);
 510 
 511   pd_initialize();
 512   assert(deferred_card_mark().is_empty(), "Default MemRegion ctor");
 513 }
 514 
 515 JavaThread::JavaThread(bool is_attaching_via_jni) : JavaThread() {
 516   if (is_attaching_via_jni) {
 517     _jni_attach_state = _attaching_via_jni;
 518   }
 519 }
 520 
 521 
 522 // interrupt support
 523 
 524 void JavaThread::interrupt() {
 525   // All callers should have 'this' thread protected by a
 526   // ThreadsListHandle so that it cannot terminate and deallocate
 527   // itself.
 528   debug_only(check_for_dangling_thread_pointer(this);)
 529 
 530   // For Windows _interrupt_event
 531   WINDOWS_ONLY(osthread()->set_interrupted(true);)
 532 
 533   // For Thread.sleep
 534   _SleepEvent->unpark();
 535 
 536   // For JSR166 LockSupport.park
 537   parker()->unpark();
 538 
 539   // For ObjectMonitor and JvmtiRawMonitor
 540   _ParkEvent->unpark();
 541 }
 542 
 543 
 544 bool JavaThread::is_interrupted(bool clear_interrupted) {
 545   debug_only(check_for_dangling_thread_pointer(this);)
 546 
 547   if (_threadObj.peek() == nullptr) {
 548     // If there is no j.l.Thread then it is impossible to have
 549     // been interrupted. We can find null during VM initialization
 550     // or when a JNI thread is still in the process of attaching.
 551     // In such cases this must be the current thread.
 552     assert(this == Thread::current(), "invariant");
 553     return false;
 554   }
 555 
 556   bool interrupted = java_lang_Thread::interrupted(threadObj());
 557 
 558   // NOTE that since there is no "lock" around the interrupt and
 559   // is_interrupted operations, there is the possibility that the
 560   // interrupted flag will be "false" but that the
 561   // low-level events will be in the signaled state. This is
 562   // intentional. The effect of this is that Object.wait() and
 563   // LockSupport.park() will appear to have a spurious wakeup, which
 564   // is allowed and not harmful, and the possibility is so rare that
 565   // it is not worth the added complexity to add yet another lock.
 566   // For the sleep event an explicit reset is performed on entry
 567   // to JavaThread::sleep, so there is no early return. It has also been
 568   // recommended not to put the interrupted flag into the "event"
 569   // structure because it hides the issue.
 570   // Also, because there is no lock, we must only clear the interrupt
 571   // state if we are going to report that we were interrupted; otherwise
 572   // an interrupt that happens just after we read the field would be lost.
 573   if (interrupted && clear_interrupted) {
 574     assert(this == Thread::current(), "only the current thread can clear");
 575     java_lang_Thread::set_interrupted(threadObj(), false);
 576     WINDOWS_ONLY(osthread()->set_interrupted(false);)
 577   }
 578 
 579   return interrupted;
 580 }
 581 
 582 void JavaThread::block_if_vm_exited() {
 583   if (_terminated == _vm_exited) {
 584     // _vm_exited is set at safepoint, and Threads_lock is never released
 585     // so we will block here forever.
 586     // Here we can be doing a jump from a safe state to an unsafe state without
 587     // proper transition, but it happens after the final safepoint has begun so
 588     // this jump won't cause any safepoint problems.
 589     set_thread_state(_thread_in_vm);
 590     Threads_lock->lock();
 591     ShouldNotReachHere();
 592   }
 593 }
 594 
 595 JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) : JavaThread() {
 596   _jni_attach_state = _not_attaching_via_jni;
 597   set_entry_point(entry_point);
 598   // Create the native thread itself.
 599   // %note runtime_23
 600   os::ThreadType thr_type = os::java_thread;
 601   thr_type = entry_point == &CompilerThread::thread_entry ? os::compiler_thread :
 602                                                             os::java_thread;
 603   os::create_thread(this, thr_type, stack_sz);
 604   // The _osthread may be null here because we ran out of memory (too many threads active).
 605   // We need to throw and OutOfMemoryError - however we cannot do this here because the caller
 606   // may hold a lock and all locks must be unlocked before throwing the exception (throwing
 607   // the exception consists of creating the exception object & initializing it, initialization
 608   // will leave the VM via a JavaCall and then all locks must be unlocked).
 609   //
 610   // The thread is still suspended when we reach here. Thread must be explicit started
 611   // by creator! Furthermore, the thread must also explicitly be added to the Threads list
 612   // by calling Threads:add. The reason why this is not done here, is because the thread
 613   // object must be fully initialized (take a look at JVM_Start)
 614 }
 615 
 616 JavaThread::~JavaThread() {
 617 
 618   // Enqueue OopHandles for release by the service thread.
 619   add_oop_handles_for_release();
 620 
 621   // Return the sleep event to the free list
 622   ParkEvent::Release(_SleepEvent);
 623   _SleepEvent = nullptr;
 624 
 625   // Free any remaining  previous UnrollBlock
 626   vframeArray* old_array = vframe_array_last();
 627 
 628   if (old_array != nullptr) {
 629     Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
 630     old_array->set_unroll_block(nullptr);
 631     delete old_info;
 632     delete old_array;
 633   }
 634 
 635   JvmtiDeferredUpdates* updates = deferred_updates();
 636   if (updates != nullptr) {
 637     // This can only happen if thread is destroyed before deoptimization occurs.
 638     assert(updates->count() > 0, "Updates holder not deleted");
 639     // free deferred updates.
 640     delete updates;
 641     set_deferred_updates(nullptr);
 642   }
 643 
 644   // All Java related clean up happens in exit
 645   ThreadSafepointState::destroy(this);
 646   if (_thread_stat != nullptr) delete _thread_stat;
 647 
 648 #if INCLUDE_JVMCI
 649   if (JVMCICounterSize > 0) {
 650     FREE_C_HEAP_ARRAY(jlong, _jvmci_counters);
 651   }
 652 #endif // INCLUDE_JVMCI
 653 }
 654 
 655 
 656 // First JavaThread specific code executed by a new Java thread.
 657 void JavaThread::pre_run() {
 658   // empty - see comments in run()
 659 }
 660 
 661 // The main routine called by a new Java thread. This isn't overridden
 662 // by subclasses, instead different subclasses define a different "entry_point"
 663 // which defines the actual logic for that kind of thread.
 664 void JavaThread::run() {
 665   // initialize thread-local alloc buffer related fields
 666   initialize_tlab();
 667 
 668   _stack_overflow_state.create_stack_guard_pages();
 669 
 670   cache_global_variables();
 671 
 672   // Thread is now sufficiently initialized to be handled by the safepoint code as being
 673   // in the VM. Change thread state from _thread_new to _thread_in_vm
 674   assert(this->thread_state() == _thread_new, "wrong thread state");
 675   set_thread_state(_thread_in_vm);
 676 
 677   // Before a thread is on the threads list it is always safe, so after leaving the
 678   // _thread_new we should emit a instruction barrier. The distance to modified code
 679   // from here is probably far enough, but this is consistent and safe.
 680   OrderAccess::cross_modify_fence();
 681 
 682   assert(JavaThread::current() == this, "sanity check");
 683   assert(!Thread::current()->owns_locks(), "sanity check");
 684 
 685   DTRACE_THREAD_PROBE(start, this);
 686 
 687   // This operation might block. We call that after all safepoint checks for a new thread has
 688   // been completed.
 689   set_active_handles(JNIHandleBlock::allocate_block());
 690 
 691   if (JvmtiExport::should_post_thread_life()) {
 692     JvmtiExport::post_thread_start(this);
 693 
 694   }
 695 
 696   if (AlwaysPreTouchStacks) {
 697     pretouch_stack();
 698   }
 699 
 700   // We call another function to do the rest so we are sure that the stack addresses used
 701   // from there will be lower than the stack base just computed.
 702   thread_main_inner();
 703 }
 704 
 705 void JavaThread::thread_main_inner() {
 706   assert(JavaThread::current() == this, "sanity check");
 707   assert(_threadObj.peek() != nullptr, "just checking");
 708 
 709   // Execute thread entry point unless this thread has a pending exception.
 710   // Note: Due to JVMTI StopThread we can have pending exceptions already!
 711   if (!this->has_pending_exception()) {
 712     {
 713       ResourceMark rm(this);
 714       this->set_native_thread_name(this->name());
 715     }
 716     HandleMark hm(this);
 717     this->entry_point()(this, this);
 718   }
 719 
 720   DTRACE_THREAD_PROBE(stop, this);
 721 
 722   // Cleanup is handled in post_run()
 723 }
 724 
 725 // Shared teardown for all JavaThreads
 726 void JavaThread::post_run() {
 727   this->exit(false);
 728   this->unregister_thread_stack_with_NMT();
 729   // Defer deletion to here to ensure 'this' is still referenceable in call_run
 730   // for any shared tear-down.
 731   this->smr_delete();
 732 }
 733 
 734 static void ensure_join(JavaThread* thread) {
 735   // We do not need to grab the Threads_lock, since we are operating on ourself.
 736   Handle threadObj(thread, thread->threadObj());
 737   assert(threadObj.not_null(), "java thread object must exist");
 738   ObjectLocker lock(threadObj, thread);
 739   // Thread is exiting. So set thread_status field in  java.lang.Thread class to TERMINATED.
 740   java_lang_Thread::set_thread_status(threadObj(), JavaThreadStatus::TERMINATED);
 741   // Clear the native thread instance - this makes isAlive return false and allows the join()
 742   // to complete once we've done the notify_all below. Needs a release() to obey Java Memory Model
 743   // requirements.
 744   OrderAccess::release();
 745   java_lang_Thread::set_thread(threadObj(), nullptr);
 746   lock.notify_all(thread);
 747   // Ignore pending exception, since we are exiting anyway
 748   thread->clear_pending_exception();
 749 }
 750 
 751 static bool is_daemon(oop threadObj) {
 752   return (threadObj != nullptr && java_lang_Thread::is_daemon(threadObj));
 753 }
 754 
 755 // For any new cleanup additions, please check to see if they need to be applied to
 756 // cleanup_failed_attach_current_thread as well.
 757 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
 758   assert(this == JavaThread::current(), "thread consistency check");
 759   assert(!is_exiting(), "should not be exiting or terminated already");
 760 
 761   elapsedTimer _timer_exit_phase1;
 762   elapsedTimer _timer_exit_phase2;
 763   elapsedTimer _timer_exit_phase3;
 764   elapsedTimer _timer_exit_phase4;
 765 
 766   if (log_is_enabled(Debug, os, thread, timer)) {
 767     _timer_exit_phase1.start();
 768   }
 769 
 770   HandleMark hm(this);
 771   Handle uncaught_exception(this, this->pending_exception());
 772   this->clear_pending_exception();
 773   Handle threadObj(this, this->threadObj());
 774   assert(threadObj.not_null(), "Java thread object should be created");
 775 
 776   if (!destroy_vm) {
 777     if (uncaught_exception.not_null()) {
 778       EXCEPTION_MARK;
 779       // Call method Thread.dispatchUncaughtException().
 780       Klass* thread_klass = vmClasses::Thread_klass();
 781       JavaValue result(T_VOID);
 782       JavaCalls::call_virtual(&result,
 783                               threadObj, thread_klass,
 784                               vmSymbols::dispatchUncaughtException_name(),
 785                               vmSymbols::throwable_void_signature(),
 786                               uncaught_exception,
 787                               THREAD);
 788       if (HAS_PENDING_EXCEPTION) {
 789         ResourceMark rm(this);
 790         jio_fprintf(defaultStream::error_stream(),
 791                     "\nException: %s thrown from the UncaughtExceptionHandler"
 792                     " in thread \"%s\"\n",
 793                     pending_exception()->klass()->external_name(),
 794                     name());
 795         CLEAR_PENDING_EXCEPTION;
 796       }
 797     }
 798 
 799     if (!is_Compiler_thread()) {
 800       // We have finished executing user-defined Java code and now have to do the
 801       // implementation specific clean-up by calling Thread.exit(). We prevent any
 802       // asynchronous exceptions from being delivered while in Thread.exit()
 803       // to ensure the clean-up is not corrupted.
 804       NoAsyncExceptionDeliveryMark _no_async(this);
 805 
 806       EXCEPTION_MARK;
 807       JavaValue result(T_VOID);
 808       Klass* thread_klass = vmClasses::Thread_klass();
 809       JavaCalls::call_virtual(&result,
 810                               threadObj, thread_klass,
 811                               vmSymbols::exit_method_name(),
 812                               vmSymbols::void_method_signature(),
 813                               THREAD);
 814       CLEAR_PENDING_EXCEPTION;
 815     }
 816 
 817     // notify JVMTI
 818     if (JvmtiExport::should_post_thread_life()) {
 819       JvmtiExport::post_thread_end(this);
 820     }
 821   } else {
 822     // before_exit() has already posted JVMTI THREAD_END events
 823   }
 824 
 825   // Cleanup any pending async exception now since we cannot access oops after
 826   // BarrierSet::barrier_set()->on_thread_detach() has been executed.
 827   if (has_async_exception_condition()) {
 828     handshake_state()->clean_async_exception_operation();
 829   }
 830 
 831   // The careful dance between thread suspension and exit is handled here.
 832   // Since we are in thread_in_vm state and suspension is done with handshakes,
 833   // we can just put in the exiting state and it will be correctly handled.
 834   // Also, no more async exceptions will be added to the queue after this point.
 835   set_terminated(_thread_exiting);
 836   ThreadService::current_thread_exiting(this, is_daemon(threadObj()));
 837 
 838   if (log_is_enabled(Debug, os, thread, timer)) {
 839     _timer_exit_phase1.stop();
 840     _timer_exit_phase2.start();
 841   }
 842 
 843   // Capture daemon status before the thread is marked as terminated.
 844   bool daemon = is_daemon(threadObj());
 845 
 846   // Notify waiters on thread object. This has to be done after exit() is called
 847   // on the thread (if the thread is the last thread in a daemon ThreadGroup the
 848   // group should have the destroyed bit set before waiters are notified).
 849   ensure_join(this);
 850   assert(!this->has_pending_exception(), "ensure_join should have cleared");
 851 
 852   if (log_is_enabled(Debug, os, thread, timer)) {
 853     _timer_exit_phase2.stop();
 854     _timer_exit_phase3.start();
 855   }
 856   // 6282335 JNI DetachCurrentThread spec states that all Java monitors
 857   // held by this thread must be released. The spec does not distinguish
 858   // between JNI-acquired and regular Java monitors. We can only see
 859   // regular Java monitors here if monitor enter-exit matching is broken.
 860   //
 861   // ensure_join() ignores IllegalThreadStateExceptions, and so does
 862   // ObjectSynchronizer::release_monitors_owned_by_thread().
 863   if (exit_type == jni_detach) {
 864     // Sanity check even though JNI DetachCurrentThread() would have
 865     // returned JNI_ERR if there was a Java frame. JavaThread exit
 866     // should be done executing Java code by the time we get here.
 867     assert(!this->has_last_Java_frame(),
 868            "should not have a Java frame when detaching or exiting");
 869     ObjectSynchronizer::release_monitors_owned_by_thread(this);
 870     assert(!this->has_pending_exception(), "release_monitors should have cleared");
 871   }
 872 
 873   // Since above code may not release JNI monitors and if someone forgot to do an
 874   // JNI monitorexit, held count should be equal jni count.
 875   // Consider scan all object monitor for this owner if JNI count > 0 (at least on detach).
 876   assert(this->held_monitor_count() == this->jni_monitor_count(),
 877          "held monitor count should be equal to jni: " INT64_FORMAT " != " INT64_FORMAT,
 878          (int64_t)this->held_monitor_count(), (int64_t)this->jni_monitor_count());
 879   if (CheckJNICalls && this->jni_monitor_count() > 0) {
 880     // We would like a fatal here, but due to we never checked this before there
 881     // is a lot of tests which breaks, even with an error log.
 882     log_debug(jni)("JavaThread %s (tid: " UINTX_FORMAT ") with Objects still locked by JNI MonitorEnter.",
 883       exit_type == JavaThread::normal_exit ? "exiting" : "detaching", os::current_thread_id());
 884   }
 885 
 886   // These things needs to be done while we are still a Java Thread. Make sure that thread
 887   // is in a consistent state, in case GC happens
 888   JFR_ONLY(Jfr::on_thread_exit(this);)
 889 
 890   if (active_handles() != nullptr) {
 891     JNIHandleBlock* block = active_handles();
 892     set_active_handles(nullptr);
 893     JNIHandleBlock::release_block(block);
 894   }
 895 
 896   if (free_handle_block() != nullptr) {
 897     JNIHandleBlock* block = free_handle_block();
 898     set_free_handle_block(nullptr);
 899     JNIHandleBlock::release_block(block);
 900   }
 901 
 902   // These have to be removed while this is still a valid thread.
 903   _stack_overflow_state.remove_stack_guard_pages();
 904 
 905   if (UseTLAB) {
 906     tlab().retire();
 907   }
 908 
 909   if (JvmtiEnv::environments_might_exist()) {
 910     JvmtiExport::cleanup_thread(this);
 911   }
 912 
 913   // We need to cache the thread name for logging purposes below as once
 914   // we have called on_thread_detach this thread must not access any oops.
 915   char* thread_name = nullptr;
 916   if (log_is_enabled(Debug, os, thread, timer)) {
 917     ResourceMark rm(this);
 918     thread_name = os::strdup(name());
 919   }
 920 
 921   log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").",
 922     exit_type == JavaThread::normal_exit ? "exiting" : "detaching",
 923     os::current_thread_id());
 924 
 925   if (log_is_enabled(Debug, os, thread, timer)) {
 926     _timer_exit_phase3.stop();
 927     _timer_exit_phase4.start();
 928   }
 929 
 930 #if INCLUDE_JVMCI
 931   if (JVMCICounterSize > 0) {
 932     if (jvmci_counters_include(this)) {
 933       for (int i = 0; i < JVMCICounterSize; i++) {
 934         _jvmci_old_thread_counters[i] += _jvmci_counters[i];
 935       }
 936     }
 937   }
 938 #endif // INCLUDE_JVMCI
 939 
 940   // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread.
 941   // We call BarrierSet::barrier_set()->on_thread_detach() here so no touching of oops after this point.
 942   Threads::remove(this, daemon);
 943 
 944   if (log_is_enabled(Debug, os, thread, timer)) {
 945     _timer_exit_phase4.stop();
 946     log_debug(os, thread, timer)("name='%s'"
 947                                  ", exit-phase1=" JLONG_FORMAT
 948                                  ", exit-phase2=" JLONG_FORMAT
 949                                  ", exit-phase3=" JLONG_FORMAT
 950                                  ", exit-phase4=" JLONG_FORMAT,
 951                                  thread_name,
 952                                  _timer_exit_phase1.milliseconds(),
 953                                  _timer_exit_phase2.milliseconds(),
 954                                  _timer_exit_phase3.milliseconds(),
 955                                  _timer_exit_phase4.milliseconds());
 956     os::free(thread_name);
 957   }
 958 }
 959 
 960 void JavaThread::cleanup_failed_attach_current_thread(bool is_daemon) {
 961   if (active_handles() != nullptr) {
 962     JNIHandleBlock* block = active_handles();
 963     set_active_handles(nullptr);
 964     JNIHandleBlock::release_block(block);
 965   }
 966 
 967   if (free_handle_block() != nullptr) {
 968     JNIHandleBlock* block = free_handle_block();
 969     set_free_handle_block(nullptr);
 970     JNIHandleBlock::release_block(block);
 971   }
 972 
 973   // These have to be removed while this is still a valid thread.
 974   _stack_overflow_state.remove_stack_guard_pages();
 975 
 976   if (UseTLAB) {
 977     tlab().retire();
 978   }
 979 
 980   Threads::remove(this, is_daemon);
 981   this->smr_delete();
 982 }
 983 
 984 JavaThread* JavaThread::active() {
 985   Thread* thread = Thread::current();
 986   if (thread->is_Java_thread()) {
 987     return JavaThread::cast(thread);
 988   } else {
 989     assert(thread->is_VM_thread(), "this must be a vm thread");
 990     VM_Operation* op = ((VMThread*) thread)->vm_operation();
 991     JavaThread *ret = op == nullptr ? nullptr : JavaThread::cast(op->calling_thread());
 992     return ret;
 993   }
 994 }
 995 
 996 bool JavaThread::is_lock_owned(address adr) const {
 997   if (Thread::is_lock_owned(adr)) return true;
 998 
 999   for (MonitorChunk* chunk = monitor_chunks(); chunk != nullptr; chunk = chunk->next()) {
1000     if (chunk->contains(adr)) return true;
1001   }
1002 
1003   return false;
1004 }
1005 
1006 oop JavaThread::exception_oop() const {
1007   return Atomic::load(&_exception_oop);
1008 }
1009 
1010 void JavaThread::set_exception_oop(oop o) {
1011   Atomic::store(&_exception_oop, o);
1012 }
1013 
1014 void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
1015   chunk->set_next(monitor_chunks());
1016   set_monitor_chunks(chunk);
1017 }
1018 
1019 void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
1020   guarantee(monitor_chunks() != nullptr, "must be non empty");
1021   if (monitor_chunks() == chunk) {
1022     set_monitor_chunks(chunk->next());
1023   } else {
1024     MonitorChunk* prev = monitor_chunks();
1025     while (prev->next() != chunk) prev = prev->next();
1026     prev->set_next(chunk->next());
1027   }
1028 }
1029 
1030 void JavaThread::handle_special_runtime_exit_condition() {
1031   if (is_obj_deopt_suspend()) {
1032     frame_anchor()->make_walkable();
1033     wait_for_object_deoptimization();
1034   }
1035   JFR_ONLY(SUSPEND_THREAD_CONDITIONAL(this);)
1036 }
1037 
1038 
1039 // Asynchronous exceptions support
1040 //
1041 void JavaThread::handle_async_exception(oop java_throwable) {
1042   assert(java_throwable != nullptr, "should have an _async_exception to throw");
1043   assert(!is_at_poll_safepoint(), "should have never called this method");
1044 
1045   if (has_last_Java_frame()) {
1046     frame f = last_frame();
1047     if (f.is_runtime_frame()) {
1048       // If the topmost frame is a runtime stub, then we are calling into
1049       // OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
1050       // must deoptimize the caller before continuing, as the compiled exception
1051       // handler table may not be valid.
1052       RegisterMap reg_map(this,
1053                           RegisterMap::UpdateMap::skip,
1054                           RegisterMap::ProcessFrames::include,
1055                           RegisterMap::WalkContinuation::skip);
1056       frame compiled_frame = f.sender(&reg_map);
1057       if (!StressCompiledExceptionHandlers && compiled_frame.can_be_deoptimized()) {
1058         Deoptimization::deoptimize(this, compiled_frame);
1059       }
1060     }
1061   }
1062 
1063   // We cannot call Exceptions::_throw(...) here because we cannot block
1064   set_pending_exception(java_throwable, __FILE__, __LINE__);
1065 
1066   clear_scopedValueBindings();
1067 
1068   LogTarget(Info, exceptions) lt;
1069   if (lt.is_enabled()) {
1070     ResourceMark rm;
1071     LogStream ls(lt);
1072     ls.print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", p2i(this));
1073     if (has_last_Java_frame()) {
1074       frame f = last_frame();
1075       ls.print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", p2i(f.pc()), p2i(f.sp()));
1076     }
1077     ls.print_cr(" of type: %s", java_throwable->klass()->external_name());
1078   }
1079 }
1080 
1081 void JavaThread::install_async_exception(AsyncExceptionHandshake* aeh) {
1082   // Do not throw asynchronous exceptions against the compiler thread
1083   // or if the thread is already exiting.
1084   if (!can_call_java() || is_exiting()) {
1085     delete aeh;
1086     return;
1087   }
1088 
1089   oop exception = aeh->exception();
1090   Handshake::execute(aeh, this);  // Install asynchronous handshake
1091 
1092   ResourceMark rm;
1093   if (log_is_enabled(Info, exceptions)) {
1094     log_info(exceptions)("Pending Async. exception installed of type: %s",
1095                          InstanceKlass::cast(exception->klass())->external_name());
1096   }
1097   // for AbortVMOnException flag
1098   Exceptions::debug_check_abort(exception->klass()->external_name());
1099 
1100   // Interrupt thread so it will wake up from a potential wait()/sleep()/park()
1101   java_lang_Thread::set_interrupted(threadObj(), true);
1102   this->interrupt();
1103 }
1104 
1105 class InstallAsyncExceptionHandshake : public HandshakeClosure {
1106   AsyncExceptionHandshake* _aeh;
1107 public:
1108   InstallAsyncExceptionHandshake(AsyncExceptionHandshake* aeh) :
1109     HandshakeClosure("InstallAsyncException"), _aeh(aeh) {}
1110   ~InstallAsyncExceptionHandshake() {
1111     // If InstallAsyncExceptionHandshake was never executed we need to clean up _aeh.
1112     delete _aeh;
1113   }
1114   void do_thread(Thread* thr) {
1115     JavaThread* target = JavaThread::cast(thr);
1116     target->install_async_exception(_aeh);
1117     _aeh = nullptr;
1118   }
1119 };
1120 
1121 void JavaThread::send_async_exception(JavaThread* target, oop java_throwable) {
1122   OopHandle e(Universe::vm_global(), java_throwable);
1123   InstallAsyncExceptionHandshake iaeh(new AsyncExceptionHandshake(e));
1124   Handshake::execute(&iaeh, target);
1125 }
1126 
1127 #if INCLUDE_JVMTI
1128 void JavaThread::set_is_in_VTMS_transition(bool val) {
1129   _is_in_VTMS_transition = val;
1130 }
1131 
1132 #ifdef ASSERT
1133 void JavaThread::set_is_VTMS_transition_disabler(bool val) {
1134   _is_VTMS_transition_disabler = val;
1135 }
1136 #endif
1137 #endif
1138 
1139 // External suspension mechanism.
1140 //
1141 // Guarantees on return (for a valid target thread):
1142 //   - Target thread will not execute any new bytecode.
1143 //   - Target thread will not enter any new monitors.
1144 //
1145 bool JavaThread::java_suspend() {
1146 #if INCLUDE_JVMTI
1147   // Suspending a JavaThread in VTMS transition or disabling VTMS transitions can cause deadlocks.
1148   assert(!is_in_VTMS_transition(), "no suspend allowed in VTMS transition");
1149   assert(!is_VTMS_transition_disabler(), "no suspend allowed for VTMS transition disablers");
1150 #endif
1151 
1152   guarantee(Thread::is_JavaThread_protected(/* target */ this),
1153             "target JavaThread is not protected in calling context.");
1154   return this->handshake_state()->suspend();
1155 }
1156 
1157 bool JavaThread::java_resume() {
1158   guarantee(Thread::is_JavaThread_protected_by_TLH(/* target */ this),
1159             "missing ThreadsListHandle in calling context.");
1160   return this->handshake_state()->resume();
1161 }
1162 
1163 // Wait for another thread to perform object reallocation and relocking on behalf of
1164 // this thread. The current thread is required to change to _thread_blocked in order
1165 // to be seen to be safepoint/handshake safe whilst suspended and only after becoming
1166 // handshake safe, the other thread can complete the handshake used to synchronize
1167 // with this thread and then perform the reallocation and relocking.
1168 // See EscapeBarrier::sync_and_suspend_*()
1169 
1170 void JavaThread::wait_for_object_deoptimization() {
1171   assert(!has_last_Java_frame() || frame_anchor()->walkable(), "should have walkable stack");
1172   assert(this == Thread::current(), "invariant");
1173 
1174   bool spin_wait = os::is_MP();
1175   do {
1176     ThreadBlockInVM tbivm(this, true /* allow_suspend */);
1177     // Wait for object deoptimization if requested.
1178     if (spin_wait) {
1179       // A single deoptimization is typically very short. Microbenchmarks
1180       // showed 5% better performance when spinning.
1181       const uint spin_limit = 10 * SpinYield::default_spin_limit;
1182       SpinYield spin(spin_limit);
1183       for (uint i = 0; is_obj_deopt_suspend() && i < spin_limit; i++) {
1184         spin.wait();
1185       }
1186       // Spin just once
1187       spin_wait = false;
1188     } else {
1189       MonitorLocker ml(this, EscapeBarrier_lock, Monitor::_no_safepoint_check_flag);
1190       if (is_obj_deopt_suspend()) {
1191         ml.wait();
1192       }
1193     }
1194     // A handshake for obj. deoptimization suspend could have been processed so
1195     // we must check after processing.
1196   } while (is_obj_deopt_suspend());
1197 }
1198 
1199 #ifdef ASSERT
1200 // Verify the JavaThread has not yet been published in the Threads::list, and
1201 // hence doesn't need protection from concurrent access at this stage.
1202 void JavaThread::verify_not_published() {
1203   // Cannot create a ThreadsListHandle here and check !tlh.includes(this)
1204   // since an unpublished JavaThread doesn't participate in the
1205   // Thread-SMR protocol for keeping a ThreadsList alive.
1206   assert(!on_thread_list(), "JavaThread shouldn't have been published yet!");
1207 }
1208 #endif
1209 
1210 // Slow path when the native==>Java barriers detect a safepoint/handshake is
1211 // pending, when _suspend_flags is non-zero or when we need to process a stack
1212 // watermark. Also check for pending async exceptions (except unsafe access error).
1213 // Note only the native==>Java barriers can call this function when thread state
1214 // is _thread_in_native_trans.
1215 void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
1216   assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
1217   assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "Unwalkable stack in native->Java transition");
1218 
1219   thread->set_thread_state(_thread_in_vm);
1220 
1221   // Enable WXWrite: called directly from interpreter native wrapper.
1222   MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXWrite, thread));
1223 
1224   SafepointMechanism::process_if_requested_with_exit_check(thread, true /* check asyncs */);
1225 
1226   // After returning from native, it could be that the stack frames are not
1227   // yet safe to use. We catch such situations in the subsequent stack watermark
1228   // barrier, which will trap unsafe stack frames.
1229   StackWatermarkSet::before_unwind(thread);
1230 }
1231 
1232 #ifndef PRODUCT
1233 // Deoptimization
1234 // Function for testing deoptimization
1235 void JavaThread::deoptimize() {
1236   StackFrameStream fst(this, false /* update */, true /* process_frames */);
1237   bool deopt = false;           // Dump stack only if a deopt actually happens.
1238   bool only_at = strlen(DeoptimizeOnlyAt) > 0;
1239   // Iterate over all frames in the thread and deoptimize
1240   for (; !fst.is_done(); fst.next()) {
1241     if (fst.current()->can_be_deoptimized()) {
1242 
1243       if (only_at) {
1244         // Deoptimize only at particular bcis.  DeoptimizeOnlyAt
1245         // consists of comma or carriage return separated numbers so
1246         // search for the current bci in that string.
1247         address pc = fst.current()->pc();
1248         nmethod* nm =  (nmethod*) fst.current()->cb();
1249         ScopeDesc* sd = nm->scope_desc_at(pc);
1250         char buffer[8];
1251         jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
1252         size_t len = strlen(buffer);
1253         const char * found = strstr(DeoptimizeOnlyAt, buffer);
1254         while (found != nullptr) {
1255           if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
1256               (found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
1257             // Check that the bci found is bracketed by terminators.
1258             break;
1259           }
1260           found = strstr(found + 1, buffer);
1261         }
1262         if (!found) {
1263           continue;
1264         }
1265       }
1266 
1267       if (DebugDeoptimization && !deopt) {
1268         deopt = true; // One-time only print before deopt
1269         tty->print_cr("[BEFORE Deoptimization]");
1270         trace_frames();
1271         trace_stack();
1272       }
1273       Deoptimization::deoptimize(this, *fst.current());
1274     }
1275   }
1276 
1277   if (DebugDeoptimization && deopt) {
1278     tty->print_cr("[AFTER Deoptimization]");
1279     trace_frames();
1280   }
1281 }
1282 
1283 
1284 // Make zombies
1285 void JavaThread::make_zombies() {
1286   for (StackFrameStream fst(this, true /* update */, true /* process_frames */); !fst.is_done(); fst.next()) {
1287     if (fst.current()->can_be_deoptimized()) {
1288       // it is a Java nmethod
1289       nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
1290       nm->make_not_entrant();
1291     }
1292   }
1293 }
1294 #endif // PRODUCT
1295 
1296 
1297 void JavaThread::deoptimize_marked_methods() {
1298   if (!has_last_Java_frame()) return;
1299   StackFrameStream fst(this, false /* update */, true /* process_frames */);
1300   for (; !fst.is_done(); fst.next()) {
1301     if (fst.current()->should_be_deoptimized()) {
1302       Deoptimization::deoptimize(this, *fst.current());
1303     }
1304   }
1305 }
1306 
1307 #ifdef ASSERT
1308 void JavaThread::verify_frame_info() {
1309   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
1310          (has_last_Java_frame() && java_call_counter() > 0),
1311          "unexpected frame info: has_last_frame=%s, java_call_counter=%d",
1312          has_last_Java_frame() ? "true" : "false", java_call_counter());
1313 }
1314 #endif
1315 
1316 // Push on a new block of JNI handles.
1317 void JavaThread::push_jni_handle_block() {
1318   // Allocate a new block for JNI handles.
1319   // Inlined code from jni_PushLocalFrame()
1320   JNIHandleBlock* old_handles = active_handles();
1321   JNIHandleBlock* new_handles = JNIHandleBlock::allocate_block(this);
1322   assert(old_handles != nullptr && new_handles != nullptr, "should not be null");
1323   new_handles->set_pop_frame_link(old_handles);  // make sure java handles get gc'd.
1324   set_active_handles(new_handles);
1325 }
1326 
1327 // Pop off the current block of JNI handles.
1328 void JavaThread::pop_jni_handle_block() {
1329   // Release our JNI handle block
1330   JNIHandleBlock* old_handles = active_handles();
1331   JNIHandleBlock* new_handles = old_handles->pop_frame_link();
1332   assert(new_handles != nullptr, "should never set active handles to null");
1333   set_active_handles(new_handles);
1334   old_handles->set_pop_frame_link(nullptr);
1335   JNIHandleBlock::release_block(old_handles, this);
1336 }
1337 
1338 void JavaThread::oops_do_no_frames(OopClosure* f, CodeBlobClosure* cf) {
1339   // Verify that the deferred card marks have been flushed.
1340   assert(deferred_card_mark().is_empty(), "Should be empty during GC");
1341 
1342   // Traverse the GCHandles
1343   Thread::oops_do_no_frames(f, cf);
1344 
1345   if (active_handles() != nullptr) {
1346     active_handles()->oops_do(f);
1347   }
1348 
1349   DEBUG_ONLY(verify_frame_info();)
1350 
1351   if (has_last_Java_frame()) {
1352     // Traverse the monitor chunks
1353     for (MonitorChunk* chunk = monitor_chunks(); chunk != nullptr; chunk = chunk->next()) {
1354       chunk->oops_do(f);
1355     }
1356   }
1357 
1358   assert(vframe_array_head() == nullptr, "deopt in progress at a safepoint!");
1359   // If we have deferred set_locals there might be oops waiting to be
1360   // written
1361   GrowableArray<jvmtiDeferredLocalVariableSet*>* list = JvmtiDeferredUpdates::deferred_locals(this);
1362   if (list != nullptr) {
1363     for (int i = 0; i < list->length(); i++) {
1364       list->at(i)->oops_do(f);
1365     }
1366   }
1367 
1368   // Traverse instance variables at the end since the GC may be moving things
1369   // around using this function
1370   f->do_oop((oop*) &_vm_result);
1371   f->do_oop((oop*) &_exception_oop);
1372 #if INCLUDE_JVMCI
1373   f->do_oop((oop*) &_jvmci_reserved_oop0);
1374 #endif
1375 
1376   if (jvmti_thread_state() != nullptr) {
1377     jvmti_thread_state()->oops_do(f, cf);
1378   }
1379 
1380   // The continuation oops are really on the stack. But there is typically at most
1381   // one of those per thread, so we handle them here in the oops_do_no_frames part
1382   // so that we don't have to sprinkle as many stack watermark checks where these
1383   // oops are used. We just need to make sure the thread has started processing.
1384   ContinuationEntry* entry = _cont_entry;
1385   while (entry != nullptr) {
1386     f->do_oop((oop*)entry->cont_addr());
1387     f->do_oop((oop*)entry->chunk_addr());
1388     entry = entry->parent();
1389   }
1390 }
1391 
1392 void JavaThread::oops_do_frames(OopClosure* f, CodeBlobClosure* cf) {
1393   if (!has_last_Java_frame()) {
1394     return;
1395   }
1396   // Finish any pending lazy GC activity for the frames
1397   StackWatermarkSet::finish_processing(this, nullptr /* context */, StackWatermarkKind::gc);
1398   // Traverse the execution stack
1399   for (StackFrameStream fst(this, true /* update */, false /* process_frames */); !fst.is_done(); fst.next()) {
1400     fst.current()->oops_do(f, cf, fst.register_map());
1401   }
1402 }
1403 
1404 #ifdef ASSERT
1405 void JavaThread::verify_states_for_handshake() {
1406   // This checks that the thread has a correct frame state during a handshake.
1407   verify_frame_info();
1408 }
1409 #endif
1410 
1411 void JavaThread::nmethods_do(CodeBlobClosure* cf) {
1412   DEBUG_ONLY(verify_frame_info();)
1413   MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXWrite, Thread::current());)
1414 
1415   if (has_last_Java_frame()) {
1416     // Traverse the execution stack
1417     for (StackFrameStream fst(this, true /* update */, true /* process_frames */); !fst.is_done(); fst.next()) {
1418       fst.current()->nmethods_do(cf);
1419     }
1420   }
1421 
1422   if (jvmti_thread_state() != nullptr) {
1423     jvmti_thread_state()->nmethods_do(cf);
1424   }
1425 }
1426 
1427 void JavaThread::metadata_do(MetadataClosure* f) {
1428   if (has_last_Java_frame()) {
1429     // Traverse the execution stack to call f() on the methods in the stack
1430     for (StackFrameStream fst(this, true /* update */, true /* process_frames */); !fst.is_done(); fst.next()) {
1431       fst.current()->metadata_do(f);
1432     }
1433   } else if (is_Compiler_thread()) {
1434     // need to walk ciMetadata in current compile tasks to keep alive.
1435     CompilerThread* ct = (CompilerThread*)this;
1436     if (ct->env() != nullptr) {
1437       ct->env()->metadata_do(f);
1438     }
1439     CompileTask* task = ct->task();
1440     if (task != nullptr) {
1441       task->metadata_do(f);
1442     }
1443   }
1444 }
1445 
1446 // Printing
1447 const char* _get_thread_state_name(JavaThreadState _thread_state) {
1448   switch (_thread_state) {
1449   case _thread_uninitialized:     return "_thread_uninitialized";
1450   case _thread_new:               return "_thread_new";
1451   case _thread_new_trans:         return "_thread_new_trans";
1452   case _thread_in_native:         return "_thread_in_native";
1453   case _thread_in_native_trans:   return "_thread_in_native_trans";
1454   case _thread_in_vm:             return "_thread_in_vm";
1455   case _thread_in_vm_trans:       return "_thread_in_vm_trans";
1456   case _thread_in_Java:           return "_thread_in_Java";
1457   case _thread_in_Java_trans:     return "_thread_in_Java_trans";
1458   case _thread_blocked:           return "_thread_blocked";
1459   case _thread_blocked_trans:     return "_thread_blocked_trans";
1460   default:                        return "unknown thread state";
1461   }
1462 }
1463 
1464 void JavaThread::print_thread_state_on(outputStream *st) const {
1465   st->print_cr("   JavaThread state: %s", _get_thread_state_name(_thread_state));
1466 }
1467 
1468 // Called by Threads::print() for VM_PrintThreads operation
1469 void JavaThread::print_on(outputStream *st, bool print_extended_info) const {
1470   st->print_raw("\"");
1471   st->print_raw(name());
1472   st->print_raw("\" ");
1473   oop thread_oop = threadObj();
1474   if (thread_oop != nullptr) {
1475     st->print("#" INT64_FORMAT " [%ld] ", (int64_t)java_lang_Thread::thread_id(thread_oop), (long) osthread()->thread_id());
1476     if (java_lang_Thread::is_daemon(thread_oop))  st->print("daemon ");
1477     st->print("prio=%d ", java_lang_Thread::priority(thread_oop));
1478   }
1479   Thread::print_on(st, print_extended_info);
1480   // print guess for valid stack memory region (assume 4K pages); helps lock debugging
1481   st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
1482   if (thread_oop != nullptr) {
1483     if (is_vthread_mounted()) {
1484       oop vt = vthread();
1485       assert(vt != nullptr, "");
1486       st->print_cr("   Carrying virtual thread #" INT64_FORMAT, (int64_t)java_lang_Thread::thread_id(vt));
1487     } else {
1488       st->print_cr("   java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
1489     }
1490   }
1491 #ifndef PRODUCT
1492   _safepoint_state->print_on(st);
1493 #endif // PRODUCT
1494   if (is_Compiler_thread()) {
1495     CompileTask *task = ((CompilerThread*)this)->task();
1496     if (task != nullptr) {
1497       st->print("   Compiling: ");
1498       task->print(st, nullptr, true, false);
1499     } else {
1500       st->print("   No compile task");
1501     }
1502     st->cr();
1503   }
1504 }
1505 
1506 void JavaThread::print() const { print_on(tty); }
1507 
1508 void JavaThread::print_name_on_error(outputStream* st, char *buf, int buflen) const {
1509   st->print("%s", get_thread_name_string(buf, buflen));
1510 }
1511 
1512 // Called by fatal error handler. The difference between this and
1513 // JavaThread::print() is that we can't grab lock or allocate memory.
1514 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
1515   st->print("%s \"%s\"", type_name(), get_thread_name_string(buf, buflen));
1516   Thread* current = Thread::current_or_null_safe();
1517   assert(current != nullptr, "cannot be called by a detached thread");
1518   if (!current->is_Java_thread() || JavaThread::cast(current)->is_oop_safe()) {
1519     // Only access threadObj() if current thread is not a JavaThread
1520     // or if it is a JavaThread that can safely access oops.
1521     oop thread_obj = threadObj();
1522     if (thread_obj != nullptr) {
1523       if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
1524     }
1525   }
1526   st->print(" [");
1527   st->print("%s", _get_thread_state_name(_thread_state));
1528   if (osthread()) {
1529     st->print(", id=%d", osthread()->thread_id());
1530   }
1531   st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
1532             p2i(stack_end()), p2i(stack_base()));
1533   st->print("]");
1534 
1535   ThreadsSMRSupport::print_info_on(this, st);
1536   return;
1537 }
1538 
1539 
1540 // Verification
1541 
1542 void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
1543   // ignore if there is no stack
1544   if (!has_last_Java_frame()) return;
1545   // traverse the stack frames. Starts from top frame.
1546   for (StackFrameStream fst(this, true /* update_map */, true /* process_frames */, false /* walk_cont */); !fst.is_done(); fst.next()) {
1547     frame* fr = fst.current();
1548     f(fr, fst.register_map());
1549   }
1550 }
1551 
1552 static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
1553 
1554 void JavaThread::verify() {
1555   // Verify oops in the thread.
1556   oops_do(&VerifyOopClosure::verify_oop, nullptr);
1557 
1558   // Verify the stack frames.
1559   frames_do(frame_verify);
1560 }
1561 
1562 // CR 6300358 (sub-CR 2137150)
1563 // Most callers of this method assume that it can't return null but a
1564 // thread may not have a name whilst it is in the process of attaching to
1565 // the VM - see CR 6412693, and there are places where a JavaThread can be
1566 // seen prior to having its threadObj set (e.g., JNI attaching threads and
1567 // if vm exit occurs during initialization). These cases can all be accounted
1568 // for such that this method never returns null.
1569 const char* JavaThread::name() const  {
1570   if (Thread::is_JavaThread_protected(/* target */ this)) {
1571     // The target JavaThread is protected so get_thread_name_string() is safe:
1572     return get_thread_name_string();
1573   }
1574 
1575   // The target JavaThread is not protected so we return the default:
1576   return Thread::name();
1577 }
1578 
1579 // Returns a non-null representation of this thread's name, or a suitable
1580 // descriptive string if there is no set name.
1581 const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
1582   const char* name_str;
1583 #ifdef ASSERT
1584   Thread* current = Thread::current_or_null_safe();
1585   assert(current != nullptr, "cannot be called by a detached thread");
1586   if (!current->is_Java_thread() || JavaThread::cast(current)->is_oop_safe()) {
1587     // Only access threadObj() if current thread is not a JavaThread
1588     // or if it is a JavaThread that can safely access oops.
1589 #endif
1590     oop thread_obj = threadObj();
1591     if (thread_obj != nullptr) {
1592       oop name = java_lang_Thread::name(thread_obj);
1593       if (name != nullptr) {
1594         if (buf == nullptr) {
1595           name_str = java_lang_String::as_utf8_string(name);
1596         } else {
1597           name_str = java_lang_String::as_utf8_string(name, buf, buflen);
1598         }
1599       } else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
1600         name_str = "<no-name - thread is attaching>";
1601       } else {
1602         name_str = "<un-named>";
1603       }
1604     } else {
1605       name_str = Thread::name();
1606     }
1607 #ifdef ASSERT
1608   } else {
1609     // Current JavaThread has exited...
1610     if (current == this) {
1611       // ... and is asking about itself:
1612       name_str = "<no-name - current JavaThread has exited>";
1613     } else {
1614       // ... and it can't safely determine this JavaThread's name so
1615       // use the default thread name.
1616       name_str = Thread::name();
1617     }
1618   }
1619 #endif
1620   assert(name_str != nullptr, "unexpected null thread name");
1621   return name_str;
1622 }
1623 
1624 // Helper to extract the name from the thread oop for logging.
1625 const char* JavaThread::name_for(oop thread_obj) {
1626   assert(thread_obj != nullptr, "precondition");
1627   oop name = java_lang_Thread::name(thread_obj);
1628   const char* name_str;
1629   if (name != nullptr) {
1630     name_str = java_lang_String::as_utf8_string(name);
1631   } else {
1632     name_str = "<un-named>";
1633   }
1634   return name_str;
1635 }
1636 
1637 void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
1638 
1639   assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
1640   assert(NoPriority <= prio && prio <= MaxPriority, "sanity check");
1641   // Link Java Thread object <-> C++ Thread
1642 
1643   // Get the C++ thread object (an oop) from the JNI handle (a jthread)
1644   // and put it into a new Handle.  The Handle "thread_oop" can then
1645   // be used to pass the C++ thread object to other methods.
1646 
1647   // Set the Java level thread object (jthread) field of the
1648   // new thread (a JavaThread *) to C++ thread object using the
1649   // "thread_oop" handle.
1650 
1651   // Set the thread field (a JavaThread *) of the
1652   // oop representing the java_lang_Thread to the new thread (a JavaThread *).
1653 
1654   Handle thread_oop(Thread::current(),
1655                     JNIHandles::resolve_non_null(jni_thread));
1656   assert(InstanceKlass::cast(thread_oop->klass())->is_linked(),
1657          "must be initialized");
1658   set_threadOopHandles(thread_oop());
1659   java_lang_Thread::set_thread(thread_oop(), this);
1660 
1661   if (prio == NoPriority) {
1662     prio = java_lang_Thread::priority(thread_oop());
1663     assert(prio != NoPriority, "A valid priority should be present");
1664   }
1665 
1666   // Push the Java priority down to the native thread; needs Threads_lock
1667   Thread::set_priority(this, prio);
1668 
1669   // Add the new thread to the Threads list and set it in motion.
1670   // We must have threads lock in order to call Threads::add.
1671   // It is crucial that we do not block before the thread is
1672   // added to the Threads list for if a GC happens, then the java_thread oop
1673   // will not be visited by GC.
1674   Threads::add(this);
1675 }
1676 
1677 oop JavaThread::current_park_blocker() {
1678   // Support for JSR-166 locks
1679   oop thread_oop = threadObj();
1680   if (thread_oop != nullptr) {
1681     return java_lang_Thread::park_blocker(thread_oop);
1682   }
1683   return nullptr;
1684 }
1685 
1686 // Print current stack trace for checked JNI warnings and JNI fatal errors.
1687 // This is the external format, selecting the platform or vthread
1688 // as applicable, and allowing for a native-only stack.
1689 void JavaThread::print_jni_stack() {
1690   assert(this == JavaThread::current(), "Can't print stack of other threads");
1691   if (!has_last_Java_frame()) {
1692     ResourceMark rm(this);
1693     char* buf = NEW_RESOURCE_ARRAY_RETURN_NULL(char, O_BUFLEN);
1694     if (buf == nullptr) {
1695       tty->print_cr("Unable to print native stack - out of memory");
1696       return;
1697     }
1698     frame f = os::current_frame();
1699     VMError::print_native_stack(tty, f, this, true /*print_source_info */,
1700                                 -1 /* max stack */, buf, O_BUFLEN);
1701   } else {
1702     print_active_stack_on(tty);
1703   }
1704 }
1705 
1706 void JavaThread::print_stack_on(outputStream* st) {
1707   if (!has_last_Java_frame()) return;
1708 
1709   Thread* current_thread = Thread::current();
1710   ResourceMark rm(current_thread);
1711   HandleMark hm(current_thread);
1712 
1713   RegisterMap reg_map(this,
1714                       RegisterMap::UpdateMap::include,
1715                       RegisterMap::ProcessFrames::include,
1716                       RegisterMap::WalkContinuation::skip);
1717   vframe* start_vf = platform_thread_last_java_vframe(&reg_map);
1718   int count = 0;
1719   for (vframe* f = start_vf; f != nullptr; f = f->sender()) {
1720     if (f->is_java_frame()) {
1721       javaVFrame* jvf = javaVFrame::cast(f);
1722       java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
1723 
1724       // Print out lock information
1725       if (JavaMonitorsInStackTrace) {
1726         jvf->print_lock_info_on(st, count);
1727       }
1728     } else {
1729       // Ignore non-Java frames
1730     }
1731 
1732     // Bail-out case for too deep stacks if MaxJavaStackTraceDepth > 0
1733     count++;
1734     if (MaxJavaStackTraceDepth > 0 && MaxJavaStackTraceDepth == count) return;
1735   }
1736 }
1737 
1738 void JavaThread::print_vthread_stack_on(outputStream* st) {
1739   assert(is_vthread_mounted(), "Caller should have checked this");
1740   assert(has_last_Java_frame(), "must be");
1741 
1742   Thread* current_thread = Thread::current();
1743   ResourceMark rm(current_thread);
1744   HandleMark hm(current_thread);
1745 
1746   RegisterMap reg_map(this,
1747                       RegisterMap::UpdateMap::include,
1748                       RegisterMap::ProcessFrames::include,
1749                       RegisterMap::WalkContinuation::include);
1750   ContinuationEntry* cont_entry = last_continuation();
1751   vframe* start_vf = last_java_vframe(&reg_map);
1752   int count = 0;
1753   for (vframe* f = start_vf; f != nullptr; f = f->sender()) {
1754     // Watch for end of vthread stack
1755     if (Continuation::is_continuation_enterSpecial(f->fr())) {
1756       assert(cont_entry == Continuation::get_continuation_entry_for_entry_frame(this, f->fr()), "");
1757       if (cont_entry->is_virtual_thread()) {
1758         break;
1759       }
1760       cont_entry = cont_entry->parent();
1761     }
1762     if (f->is_java_frame()) {
1763       javaVFrame* jvf = javaVFrame::cast(f);
1764       java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
1765 
1766       // Print out lock information
1767       if (JavaMonitorsInStackTrace) {
1768         jvf->print_lock_info_on(st, count);
1769       }
1770     } else {
1771       // Ignore non-Java frames
1772     }
1773 
1774     // Bail-out case for too deep stacks if MaxJavaStackTraceDepth > 0
1775     count++;
1776     if (MaxJavaStackTraceDepth > 0 && MaxJavaStackTraceDepth == count) return;
1777   }
1778 }
1779 
1780 void JavaThread::print_active_stack_on(outputStream* st) {
1781   if (is_vthread_mounted()) {
1782     print_vthread_stack_on(st);
1783   } else {
1784     print_stack_on(st);
1785   }
1786 }
1787 
1788 #if INCLUDE_JVMTI
1789 // Rebind JVMTI thread state from carrier to virtual or from virtual to carrier.
1790 JvmtiThreadState* JavaThread::rebind_to_jvmti_thread_state_of(oop thread_oop) {
1791   set_jvmti_vthread(thread_oop);
1792 
1793   // unbind current JvmtiThreadState from JavaThread
1794   JvmtiThreadState::unbind_from(jvmti_thread_state(), this);
1795 
1796   // bind new JvmtiThreadState to JavaThread
1797   JvmtiThreadState::bind_to(java_lang_Thread::jvmti_thread_state(thread_oop), this);
1798 
1799   return jvmti_thread_state();
1800 }
1801 #endif
1802 
1803 // JVMTI PopFrame support
1804 void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
1805   assert(_popframe_preserved_args == nullptr, "should not wipe out old PopFrame preserved arguments");
1806   if (in_bytes(size_in_bytes) != 0) {
1807     _popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes), mtThread);
1808     _popframe_preserved_args_size = in_bytes(size_in_bytes);
1809     Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
1810   }
1811 }
1812 
1813 void* JavaThread::popframe_preserved_args() {
1814   return _popframe_preserved_args;
1815 }
1816 
1817 ByteSize JavaThread::popframe_preserved_args_size() {
1818   return in_ByteSize(_popframe_preserved_args_size);
1819 }
1820 
1821 WordSize JavaThread::popframe_preserved_args_size_in_words() {
1822   int sz = in_bytes(popframe_preserved_args_size());
1823   assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
1824   return in_WordSize(sz / wordSize);
1825 }
1826 
1827 void JavaThread::popframe_free_preserved_args() {
1828   assert(_popframe_preserved_args != nullptr, "should not free PopFrame preserved arguments twice");
1829   FREE_C_HEAP_ARRAY(char, (char*)_popframe_preserved_args);
1830   _popframe_preserved_args = nullptr;
1831   _popframe_preserved_args_size = 0;
1832 }
1833 
1834 #ifndef PRODUCT
1835 
1836 void JavaThread::trace_frames() {
1837   tty->print_cr("[Describe stack]");
1838   int frame_no = 1;
1839   for (StackFrameStream fst(this, true /* update */, true /* process_frames */); !fst.is_done(); fst.next()) {
1840     tty->print("  %d. ", frame_no++);
1841     fst.current()->print_value_on(tty, this);
1842     tty->cr();
1843   }
1844 }
1845 
1846 class PrintAndVerifyOopClosure: public OopClosure {
1847  protected:
1848   template <class T> inline void do_oop_work(T* p) {
1849     oop obj = RawAccess<>::oop_load(p);
1850     if (obj == nullptr) return;
1851     tty->print(INTPTR_FORMAT ": ", p2i(p));
1852     if (oopDesc::is_oop_or_null(obj)) {
1853       if (obj->is_objArray()) {
1854         tty->print_cr("valid objArray: " INTPTR_FORMAT, p2i(obj));
1855       } else {
1856         obj->print();
1857       }
1858     } else {
1859       tty->print_cr("invalid oop: " INTPTR_FORMAT, p2i(obj));
1860     }
1861     tty->cr();
1862   }
1863  public:
1864   virtual void do_oop(oop* p) { do_oop_work(p); }
1865   virtual void do_oop(narrowOop* p)  { do_oop_work(p); }
1866 };
1867 
1868 #ifdef ASSERT
1869 // Print or validate the layout of stack frames
1870 void JavaThread::print_frame_layout(int depth, bool validate_only) {
1871   ResourceMark rm;
1872   PreserveExceptionMark pm(this);
1873   FrameValues values;
1874   int frame_no = 0;
1875   for (StackFrameStream fst(this, true, true, true); !fst.is_done(); fst.next()) {
1876     fst.current()->describe(values, ++frame_no, fst.register_map());
1877     if (depth == frame_no) break;
1878   }
1879   Continuation::describe(values);
1880   if (validate_only) {
1881     values.validate();
1882   } else {
1883     tty->print_cr("[Describe stack layout]");
1884     values.print(this);
1885   }
1886 }
1887 #endif
1888 
1889 void JavaThread::trace_stack_from(vframe* start_vf) {
1890   ResourceMark rm;
1891   int vframe_no = 1;
1892   for (vframe* f = start_vf; f; f = f->sender()) {
1893     if (f->is_java_frame()) {
1894       javaVFrame::cast(f)->print_activation(vframe_no++);
1895     } else {
1896       f->print();
1897     }
1898     if (vframe_no > StackPrintLimit) {
1899       tty->print_cr("...<more frames>...");
1900       return;
1901     }
1902   }
1903 }
1904 
1905 
1906 void JavaThread::trace_stack() {
1907   if (!has_last_Java_frame()) return;
1908   Thread* current_thread = Thread::current();
1909   ResourceMark rm(current_thread);
1910   HandleMark hm(current_thread);
1911   RegisterMap reg_map(this,
1912                       RegisterMap::UpdateMap::include,
1913                       RegisterMap::ProcessFrames::include,
1914                       RegisterMap::WalkContinuation::skip);
1915   trace_stack_from(last_java_vframe(&reg_map));
1916 }
1917 
1918 
1919 #endif // PRODUCT
1920 
1921 void JavaThread::inc_held_monitor_count(int i, bool jni) {
1922 #ifdef SUPPORT_MONITOR_COUNT
1923   assert(_held_monitor_count >= 0, "Must always be greater than 0: " INT64_FORMAT, (int64_t)_held_monitor_count);
1924   _held_monitor_count += i;
1925   if (jni) {
1926     assert(_jni_monitor_count >= 0, "Must always be greater than 0: " INT64_FORMAT, (int64_t)_jni_monitor_count);
1927     _jni_monitor_count += i;
1928   }
1929 #endif
1930 }
1931 
1932 void JavaThread::dec_held_monitor_count(int i, bool jni) {
1933 #ifdef SUPPORT_MONITOR_COUNT
1934   _held_monitor_count -= i;
1935   assert(_held_monitor_count >= 0, "Must always be greater than 0: " INT64_FORMAT, (int64_t)_held_monitor_count);
1936   if (jni) {
1937     _jni_monitor_count -= i;
1938     assert(_jni_monitor_count >= 0, "Must always be greater than 0: " INT64_FORMAT, (int64_t)_jni_monitor_count);
1939   }
1940 #endif
1941 }
1942 
1943 frame JavaThread::vthread_last_frame() {
1944   assert (is_vthread_mounted(), "Virtual thread not mounted");
1945   return last_frame();
1946 }
1947 
1948 frame JavaThread::carrier_last_frame(RegisterMap* reg_map) {
1949   const ContinuationEntry* entry = vthread_continuation();
1950   guarantee (entry != nullptr, "Not a carrier thread");
1951   frame f = entry->to_frame();
1952   if (reg_map->process_frames()) {
1953     entry->flush_stack_processing(this);
1954   }
1955   entry->update_register_map(reg_map);
1956   return f.sender(reg_map);
1957 }
1958 
1959 frame JavaThread::platform_thread_last_frame(RegisterMap* reg_map) {
1960   return is_vthread_mounted() ? carrier_last_frame(reg_map) : last_frame();
1961 }
1962 
1963 javaVFrame* JavaThread::last_java_vframe(const frame f, RegisterMap *reg_map) {
1964   assert(reg_map != nullptr, "a map must be given");
1965   for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender()) {
1966     if (vf->is_java_frame()) return javaVFrame::cast(vf);
1967   }
1968   return nullptr;
1969 }
1970 
1971 Klass* JavaThread::security_get_caller_class(int depth) {
1972   ResetNoHandleMark rnhm;
1973   HandleMark hm(Thread::current());
1974 
1975   vframeStream vfst(this);
1976   vfst.security_get_caller_frame(depth);
1977   if (!vfst.at_end()) {
1978     return vfst.method()->method_holder();
1979   }
1980   return nullptr;
1981 }
1982 
1983 // java.lang.Thread.sleep support
1984 // Returns true if sleep time elapsed as expected, and false
1985 // if the thread was interrupted.
1986 bool JavaThread::sleep(jlong millis) {
1987   assert(this == Thread::current(),  "thread consistency check");
1988 
1989   ParkEvent * const slp = this->_SleepEvent;
1990   // Because there can be races with thread interruption sending an unpark()
1991   // to the event, we explicitly reset it here to avoid an immediate return.
1992   // The actual interrupt state will be checked before we park().
1993   slp->reset();
1994   // Thread interruption establishes a happens-before ordering in the
1995   // Java Memory Model, so we need to ensure we synchronize with the
1996   // interrupt state.
1997   OrderAccess::fence();
1998 
1999   jlong prevtime = os::javaTimeNanos();
2000 
2001   for (;;) {
2002     // interruption has precedence over timing out
2003     if (this->is_interrupted(true)) {
2004       return false;
2005     }
2006 
2007     if (millis <= 0) {
2008       return true;
2009     }
2010 
2011     {
2012       ThreadBlockInVM tbivm(this);
2013       OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
2014       slp->park(millis);
2015     }
2016 
2017     // Update elapsed time tracking
2018     jlong newtime = os::javaTimeNanos();
2019     if (newtime - prevtime < 0) {
2020       // time moving backwards, should only happen if no monotonic clock
2021       // not a guarantee() because JVM should not abort on kernel/glibc bugs
2022       assert(false,
2023              "unexpected time moving backwards detected in JavaThread::sleep()");
2024     } else {
2025       millis -= (newtime - prevtime) / NANOSECS_PER_MILLISEC;
2026     }
2027     prevtime = newtime;
2028   }
2029 }
2030 
2031 // Last thread running calls java.lang.Shutdown.shutdown()
2032 void JavaThread::invoke_shutdown_hooks() {
2033   HandleMark hm(this);
2034 
2035   // We could get here with a pending exception, if so clear it now.
2036   if (this->has_pending_exception()) {
2037     this->clear_pending_exception();
2038   }
2039 
2040   EXCEPTION_MARK;
2041   Klass* shutdown_klass =
2042     SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
2043                                       THREAD);
2044   if (shutdown_klass != nullptr) {
2045     // SystemDictionary::resolve_or_null will return null if there was
2046     // an exception.  If we cannot load the Shutdown class, just don't
2047     // call Shutdown.shutdown() at all.  This will mean the shutdown hooks
2048     // won't be run.  Note that if a shutdown hook was registered,
2049     // the Shutdown class would have already been loaded
2050     // (Runtime.addShutdownHook will load it).
2051     JavaValue result(T_VOID);
2052     JavaCalls::call_static(&result,
2053                            shutdown_klass,
2054                            vmSymbols::shutdown_name(),
2055                            vmSymbols::void_method_signature(),
2056                            THREAD);
2057   }
2058   CLEAR_PENDING_EXCEPTION;
2059 }
2060 
2061 #ifndef PRODUCT
2062 void JavaThread::verify_cross_modify_fence_failure(JavaThread *thread) {
2063    report_vm_error(__FILE__, __LINE__, "Cross modify fence failure", "%p", thread);
2064 }
2065 #endif
2066 
2067 // Helper function to create the java.lang.Thread object for a
2068 // VM-internal thread. The thread will have the given name, and be
2069 // a member of the "system" ThreadGroup.
2070 Handle JavaThread::create_system_thread_object(const char* name, TRAPS) {
2071   Handle string = java_lang_String::create_from_str(name, CHECK_NH);
2072 
2073   // Initialize thread_oop to put it into the system threadGroup.
2074   // This is done by calling the Thread(ThreadGroup group, String name) constructor.
2075   Handle thread_group(THREAD, Universe::system_thread_group());
2076   Handle thread_oop =
2077     JavaCalls::construct_new_instance(vmClasses::Thread_klass(),
2078                                       vmSymbols::threadgroup_string_void_signature(),
2079                                       thread_group,
2080                                       string,
2081                                       CHECK_NH);
2082 
2083   return thread_oop;
2084 }
2085 
2086 // Starts the target JavaThread as a daemon of the given priority, and
2087 // bound to the given java.lang.Thread instance.
2088 // The Threads_lock is held for the duration.
2089 void JavaThread::start_internal_daemon(JavaThread* current, JavaThread* target,
2090                                        Handle thread_oop, ThreadPriority prio) {
2091 
2092   assert(target->osthread() != nullptr, "target thread is not properly initialized");
2093 
2094   MutexLocker mu(current, Threads_lock);
2095 
2096   // Initialize the fields of the thread_oop first.
2097 
2098   java_lang_Thread::set_thread(thread_oop(), target); // isAlive == true now
2099 
2100   if (prio != NoPriority) {
2101     java_lang_Thread::set_priority(thread_oop(), prio);
2102     // Note: we don't call os::set_priority here. Possibly we should,
2103     // else all threads should call it themselves when they first run.
2104   }
2105 
2106   java_lang_Thread::set_daemon(thread_oop());
2107 
2108   // Now bind the thread_oop to the target JavaThread.
2109   target->set_threadOopHandles(thread_oop());
2110 
2111   Threads::add(target); // target is now visible for safepoint/handshake
2112   Thread::start(target);
2113 }
2114 
2115 void JavaThread::vm_exit_on_osthread_failure(JavaThread* thread) {
2116   // At this point it may be possible that no osthread was created for the
2117   // JavaThread due to lack of resources. However, since this must work
2118   // for critical system threads just check and abort if this fails.
2119   if (thread->osthread() == nullptr) {
2120     // This isn't really an OOM condition, but historically this is what
2121     // we report.
2122     vm_exit_during_initialization("java.lang.OutOfMemoryError",
2123                                   os::native_thread_creation_failed_msg());
2124   }
2125 }
2126 
2127 void JavaThread::pretouch_stack() {
2128   // Given an established java thread stack with usable area followed by
2129   // shadow zone and reserved/yellow/red zone, pretouch the usable area ranging
2130   // from the current frame down to the start of the shadow zone.
2131   const address end = _stack_overflow_state.shadow_zone_safe_limit();
2132   if (is_in_full_stack(end)) {
2133     char* p1 = (char*) alloca(1);
2134     address here = (address) &p1;
2135     if (is_in_full_stack(here) && here > end) {
2136       size_t to_alloc = here - end;
2137       char* p2 = (char*) alloca(to_alloc);
2138       log_trace(os, thread)("Pretouching thread stack from " PTR_FORMAT " to " PTR_FORMAT ".",
2139                             p2i(p2), p2i(end));
2140       os::pretouch_memory(p2, p2 + to_alloc,
2141                           NOT_AIX(os::vm_page_size()) AIX_ONLY(4096));
2142     }
2143   }
2144 }
2145 
2146 // Deferred OopHandle release support.
2147 
2148 class OopHandleList : public CHeapObj<mtInternal> {
2149   static const int _count = 4;
2150   OopHandle _handles[_count];
2151   OopHandleList* _next;
2152   int _index;
2153  public:
2154   OopHandleList(OopHandleList* next) : _next(next), _index(0) {}
2155   void add(OopHandle h) {
2156     assert(_index < _count, "too many additions");
2157     _handles[_index++] = h;
2158   }
2159   ~OopHandleList() {
2160     assert(_index == _count, "usage error");
2161     for (int i = 0; i < _index; i++) {
2162       _handles[i].release(JavaThread::thread_oop_storage());
2163     }
2164   }
2165   OopHandleList* next() const { return _next; }
2166 };
2167 
2168 OopHandleList* JavaThread::_oop_handle_list = nullptr;
2169 
2170 // Called by the ServiceThread to do the work of releasing
2171 // the OopHandles.
2172 void JavaThread::release_oop_handles() {
2173   OopHandleList* list;
2174   {
2175     MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
2176     list = _oop_handle_list;
2177     _oop_handle_list = nullptr;
2178   }
2179   assert(!SafepointSynchronize::is_at_safepoint(), "cannot be called at a safepoint");
2180 
2181   while (list != nullptr) {
2182     OopHandleList* l = list;
2183     list = l->next();
2184     delete l;
2185   }
2186 }
2187 
2188 // Add our OopHandles for later release.
2189 void JavaThread::add_oop_handles_for_release() {
2190   MutexLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
2191   OopHandleList* new_head = new OopHandleList(_oop_handle_list);
2192   new_head->add(_threadObj);
2193   new_head->add(_vthread);
2194   new_head->add(_jvmti_vthread);
2195   new_head->add(_scopedValueCache);
2196   _oop_handle_list = new_head;
2197   Service_lock->notify_all();
2198 }