1 /*
   2  * Copyright (c) 1997, 2024, Oracle and/or its affiliates. All rights reserved.
   3  * Copyright (c) 2021, Azul Systems, Inc. All rights reserved.
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This code is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 only, as
   8  * published by the Free Software Foundation.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  *
  24  */
  25 
  26 #include "precompiled.hpp"
  27 #include "cds/cds_globals.hpp"
  28 #include "cds/cdsConfig.hpp"
  29 #include "cds/metaspaceShared.hpp"
  30 #include "classfile/classLoader.hpp"
  31 #include "classfile/javaClasses.hpp"
  32 #include "classfile/javaThreadStatus.hpp"
  33 #include "classfile/systemDictionary.hpp"
  34 #include "classfile/vmClasses.hpp"
  35 #include "classfile/vmSymbols.hpp"
  36 #include "compiler/compileBroker.hpp"
  37 #include "compiler/compileTask.hpp"
  38 #include "compiler/compilerThread.hpp"
  39 #include "gc/shared/barrierSet.hpp"
  40 #include "gc/shared/barrierSetNMethod.hpp"
  41 #include "gc/shared/gcVMOperations.hpp"
  42 #include "gc/shared/oopStorage.hpp"
  43 #include "gc/shared/oopStorageSet.hpp"
  44 #include "gc/shared/stringdedup/stringDedup.hpp"
  45 #include "jfr/jfrEvents.hpp"
  46 #include "jvm.h"
  47 #include "jvmtifiles/jvmtiEnv.hpp"
  48 #include "logging/log.hpp"
  49 #include "logging/logAsyncWriter.hpp"
  50 #include "logging/logConfiguration.hpp"
  51 #include "memory/allocation.inline.hpp"
  52 #include "memory/iterator.hpp"
  53 #include "memory/oopFactory.hpp"
  54 #include "memory/resourceArea.hpp"
  55 #include "memory/universe.hpp"
  56 #include "nmt/memTracker.hpp"
  57 #include "oops/instanceKlass.hpp"
  58 #include "oops/klass.inline.hpp"
  59 #include "oops/oop.inline.hpp"
  60 #include "oops/symbol.hpp"
  61 #include "prims/jvm_misc.hpp"
  62 #include "prims/jvmtiAgentList.hpp"
  63 #include "runtime/arguments.hpp"
  64 #include "runtime/fieldDescriptor.inline.hpp"
  65 #include "runtime/flags/jvmFlagLimit.hpp"
  66 #include "runtime/globals.hpp"
  67 #include "runtime/handles.inline.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/jniPeriodicChecker.hpp"
  74 #include "runtime/lockStack.inline.hpp"
  75 #include "runtime/monitorDeflationThread.hpp"
  76 #include "runtime/mutexLocker.hpp"
  77 #include "runtime/nonJavaThread.hpp"
  78 #include "runtime/objectMonitor.inline.hpp"
  79 #include "runtime/osThread.hpp"
  80 #include "runtime/safepoint.hpp"
  81 #include "runtime/safepointMechanism.inline.hpp"
  82 #include "runtime/safepointVerifiers.hpp"
  83 #include "runtime/serviceThread.hpp"
  84 #include "runtime/sharedRuntime.hpp"
  85 #include "runtime/stackWatermarkSet.inline.hpp"
  86 #include "runtime/statSampler.hpp"
  87 #include "runtime/stubCodeGenerator.hpp"
  88 #include "runtime/thread.inline.hpp"
  89 #include "runtime/threadSMR.inline.hpp"
  90 #include "runtime/threads.hpp"
  91 #include "runtime/timer.hpp"
  92 #include "runtime/timerTrace.hpp"
  93 #include "runtime/trimNativeHeap.hpp"
  94 #include "runtime/vmOperations.hpp"
  95 #include "runtime/vm_version.hpp"
  96 #include "services/attachListener.hpp"
  97 #include "services/management.hpp"
  98 #include "services/threadIdTable.hpp"
  99 #include "services/threadService.hpp"
 100 #include "utilities/dtrace.hpp"
 101 #include "utilities/events.hpp"
 102 #include "utilities/macros.hpp"
 103 #include "utilities/vmError.hpp"
 104 #if INCLUDE_JVMCI
 105 #include "jvmci/jvmci.hpp"
 106 #include "jvmci/jvmciEnv.hpp"
 107 #endif
 108 #ifdef COMPILER2
 109 #include "opto/idealGraphPrinter.hpp"
 110 #endif
 111 #if INCLUDE_RTM_OPT
 112 #include "runtime/rtmLocking.hpp"
 113 #endif
 114 #if INCLUDE_JFR
 115 #include "jfr/jfr.hpp"
 116 #endif
 117 
 118 // Initialization after module runtime initialization
 119 void universe_post_module_init();  // must happen after call_initPhase2
 120 
 121 
 122 static void initialize_class(Symbol* class_name, TRAPS) {
 123   Klass* klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
 124   InstanceKlass::cast(klass)->initialize(CHECK);
 125 }
 126 
 127 
 128 // Creates the initial ThreadGroup
 129 static Handle create_initial_thread_group(TRAPS) {
 130   Handle system_instance = JavaCalls::construct_new_instance(
 131                             vmClasses::ThreadGroup_klass(),
 132                             vmSymbols::void_method_signature(),
 133                             CHECK_NH);
 134   Universe::set_system_thread_group(system_instance());
 135 
 136   Handle string = java_lang_String::create_from_str("main", CHECK_NH);
 137   Handle main_instance = JavaCalls::construct_new_instance(
 138                             vmClasses::ThreadGroup_klass(),
 139                             vmSymbols::threadgroup_string_void_signature(),
 140                             system_instance,
 141                             string,
 142                             CHECK_NH);
 143   return main_instance;
 144 }
 145 
 146 // Creates the initial Thread, and sets it to running.
 147 static void create_initial_thread(Handle thread_group, JavaThread* thread,
 148                                  TRAPS) {
 149   InstanceKlass* ik = vmClasses::Thread_klass();
 150   assert(ik->is_initialized(), "must be");
 151   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK);
 152 
 153   // Cannot use JavaCalls::construct_new_instance because the java.lang.Thread
 154   // constructor calls Thread.current(), which must be set here for the
 155   // initial thread.
 156   java_lang_Thread::set_thread(thread_oop(), thread);
 157   thread->set_threadOopHandles(thread_oop());
 158 
 159   Handle string = java_lang_String::create_from_str("main", CHECK);
 160 
 161   JavaValue result(T_VOID);
 162   JavaCalls::call_special(&result, thread_oop,
 163                           ik,
 164                           vmSymbols::object_initializer_name(),
 165                           vmSymbols::threadgroup_string_void_signature(),
 166                           thread_group,
 167                           string,
 168                           CHECK);
 169 
 170   assert(thread->lock_id() == ThreadIdentifier::initial(), "invariant");
 171 
 172   // Set thread status to running since main thread has
 173   // been started and running.
 174   java_lang_Thread::set_thread_status(thread_oop(),
 175                                       JavaThreadStatus::RUNNABLE);
 176 }
 177 
 178 // Extract version and vendor specific information from
 179 // java.lang.VersionProps fields.
 180 // Returned char* is allocated in the thread's resource area
 181 // so must be copied for permanency.
 182 static const char* get_java_version_info(InstanceKlass* ik,
 183                                          Symbol* field_name) {
 184   fieldDescriptor fd;
 185   bool found = ik != nullptr &&
 186                ik->find_local_field(field_name,
 187                                     vmSymbols::string_signature(), &fd);
 188   if (found) {
 189     oop name_oop = ik->java_mirror()->obj_field(fd.offset());
 190     if (name_oop == nullptr) {
 191       return nullptr;
 192     }
 193     const char* name = java_lang_String::as_utf8_string(name_oop);
 194     return name;
 195   } else {
 196     return nullptr;
 197   }
 198 }
 199 
 200 // ======= Threads ========
 201 
 202 // The Threads class links together all active threads, and provides
 203 // operations over all threads. It is protected by the Threads_lock,
 204 // which is also used in other global contexts like safepointing.
 205 // ThreadsListHandles are used to safely perform operations on one
 206 // or more threads without the risk of the thread exiting during the
 207 // operation.
 208 //
 209 // Note: The Threads_lock is currently more widely used than we
 210 // would like. We are actively migrating Threads_lock uses to other
 211 // mechanisms in order to reduce Threads_lock contention.
 212 
 213 int         Threads::_number_of_threads = 0;
 214 int         Threads::_number_of_non_daemon_threads = 0;
 215 int         Threads::_return_code = 0;
 216 uintx       Threads::_thread_claim_token = 1; // Never zero.
 217 
 218 #ifdef ASSERT
 219 bool        Threads::_vm_complete = false;
 220 #endif
 221 
 222 // General purpose hook into Java code, run once when the VM is initialized.
 223 // The Java library method itself may be changed independently from the VM.
 224 static void call_postVMInitHook(TRAPS) {
 225   Klass* klass = SystemDictionary::resolve_or_null(vmSymbols::jdk_internal_vm_PostVMInitHook(), THREAD);
 226   if (klass != nullptr) {
 227     JavaValue result(T_VOID);
 228     JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
 229                            vmSymbols::void_method_signature(),
 230                            CHECK);
 231   }
 232 }
 233 
 234 // All NonJavaThreads (i.e., every non-JavaThread in the system).
 235 void Threads::non_java_threads_do(ThreadClosure* tc) {
 236   NoSafepointVerifier nsv;
 237   for (NonJavaThread::Iterator njti; !njti.end(); njti.step()) {
 238     tc->do_thread(njti.current());
 239   }
 240 }
 241 
 242 // All JavaThreads
 243 #define ALL_JAVA_THREADS(X) \
 244   for (JavaThread* X : *ThreadsSMRSupport::get_java_thread_list())
 245 
 246 // All JavaThreads
 247 void Threads::java_threads_do(ThreadClosure* tc) {
 248   assert_locked_or_safepoint(Threads_lock);
 249   // ALL_JAVA_THREADS iterates through all JavaThreads.
 250   ALL_JAVA_THREADS(p) {
 251     tc->do_thread(p);
 252   }
 253 }
 254 
 255 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system).
 256 void Threads::threads_do(ThreadClosure* tc) {
 257   assert_locked_or_safepoint(Threads_lock);
 258   java_threads_do(tc);
 259   non_java_threads_do(tc);
 260 }
 261 
 262 void Threads::possibly_parallel_threads_do(bool is_par, ThreadClosure* tc) {
 263   assert_at_safepoint();
 264 
 265   uintx claim_token = Threads::thread_claim_token();
 266   ALL_JAVA_THREADS(p) {
 267     if (p->claim_threads_do(is_par, claim_token)) {
 268       tc->do_thread(p);
 269     }
 270   }
 271   for (NonJavaThread::Iterator njti; !njti.end(); njti.step()) {
 272     Thread* current = njti.current();
 273     if (current->claim_threads_do(is_par, claim_token)) {
 274       tc->do_thread(current);
 275     }
 276   }
 277 }
 278 
 279 // The system initialization in the library has three phases.
 280 //
 281 // Phase 1: java.lang.System class initialization
 282 //     java.lang.System is a primordial class loaded and initialized
 283 //     by the VM early during startup.  java.lang.System.<clinit>
 284 //     only does registerNatives and keeps the rest of the class
 285 //     initialization work later until thread initialization completes.
 286 //
 287 //     System.initPhase1 initializes the system properties, the static
 288 //     fields in, out, and err. Set up java signal handlers, OS-specific
 289 //     system settings, and thread group of the main thread.
 290 static void call_initPhase1(TRAPS) {
 291   Klass* klass = vmClasses::System_klass();
 292   JavaValue result(T_VOID);
 293   JavaCalls::call_static(&result, klass, vmSymbols::initPhase1_name(),
 294                                          vmSymbols::void_method_signature(), CHECK);
 295 }
 296 
 297 // Phase 2. Module system initialization
 298 //     This will initialize the module system.  Only java.base classes
 299 //     can be loaded until phase 2 completes.
 300 //
 301 //     Call System.initPhase2 after the compiler initialization and jsr292
 302 //     classes get initialized because module initialization runs a lot of java
 303 //     code, that for performance reasons, should be compiled.  Also, this will
 304 //     enable the startup code to use lambda and other language features in this
 305 //     phase and onward.
 306 //
 307 //     After phase 2, The VM will begin search classes from -Xbootclasspath/a.
 308 static void call_initPhase2(TRAPS) {
 309   TraceTime timer("Initialize module system", TRACETIME_LOG(Info, startuptime));
 310 
 311   Klass* klass = vmClasses::System_klass();
 312 
 313   JavaValue result(T_INT);
 314   JavaCallArguments args;
 315   args.push_int(DisplayVMOutputToStderr);
 316   args.push_int(log_is_enabled(Debug, init)); // print stack trace if exception thrown
 317   JavaCalls::call_static(&result, klass, vmSymbols::initPhase2_name(),
 318                                          vmSymbols::boolean_boolean_int_signature(), &args, CHECK);
 319   if (result.get_jint() != JNI_OK) {
 320     vm_exit_during_initialization(); // no message or exception
 321   }
 322 
 323   universe_post_module_init();
 324 }
 325 
 326 // Phase 3. final setup - set security manager, system class loader and TCCL
 327 //
 328 //     This will instantiate and set the security manager, set the system class
 329 //     loader as well as the thread context class loader.  The security manager
 330 //     and system class loader may be a custom class loaded from -Xbootclasspath/a,
 331 //     other modules or the application's classpath.
 332 static void call_initPhase3(TRAPS) {
 333   Klass* klass = vmClasses::System_klass();
 334   JavaValue result(T_VOID);
 335   JavaCalls::call_static(&result, klass, vmSymbols::initPhase3_name(),
 336                                          vmSymbols::void_method_signature(), CHECK);
 337 }
 338 
 339 void Threads::initialize_java_lang_classes(JavaThread* main_thread, TRAPS) {
 340   TraceTime timer("Initialize java.lang classes", TRACETIME_LOG(Info, startuptime));
 341 
 342   initialize_class(vmSymbols::java_lang_String(), CHECK);
 343 
 344   // Inject CompactStrings value after the static initializers for String ran.
 345   java_lang_String::set_compact_strings(CompactStrings);
 346 
 347   // Initialize java_lang.System (needed before creating the thread)
 348   initialize_class(vmSymbols::java_lang_System(), CHECK);
 349   // The VM creates & returns objects of this class. Make sure it's initialized.
 350   initialize_class(vmSymbols::java_lang_Class(), CHECK);
 351   initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK);
 352   Handle thread_group = create_initial_thread_group(CHECK);
 353   Universe::set_main_thread_group(thread_group());
 354   initialize_class(vmSymbols::java_lang_Thread(), CHECK);
 355   create_initial_thread(thread_group, main_thread, CHECK);
 356 
 357   // The VM creates objects of this class.
 358   initialize_class(vmSymbols::java_lang_Module(), CHECK);
 359 
 360 #ifdef ASSERT
 361   InstanceKlass *k = vmClasses::UnsafeConstants_klass();
 362   assert(k->is_not_initialized(), "UnsafeConstants should not already be initialized");
 363 #endif
 364 
 365   // initialize the hardware-specific constants needed by Unsafe
 366   initialize_class(vmSymbols::jdk_internal_misc_UnsafeConstants(), CHECK);
 367   jdk_internal_misc_UnsafeConstants::set_unsafe_constants();
 368 
 369   // The VM preresolves methods to these classes. Make sure that they get initialized
 370   initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK);
 371   initialize_class(vmSymbols::java_lang_ref_Finalizer(), CHECK);
 372 
 373   // Phase 1 of the system initialization in the library, java.lang.System class initialization
 374   call_initPhase1(CHECK);
 375 
 376   // Get the Java runtime name, version, and vendor info after java.lang.System is initialized.
 377   // Some values are actually configure-time constants but some can be set via the jlink tool and
 378   // so must be read dynamically. We treat them all the same.
 379   InstanceKlass* ik = SystemDictionary::find_instance_klass(THREAD, vmSymbols::java_lang_VersionProps(),
 380                                                             Handle(), Handle());
 381   {
 382     ResourceMark rm(main_thread);
 383     JDK_Version::set_java_version(get_java_version_info(ik, vmSymbols::java_version_name()));
 384 
 385     JDK_Version::set_runtime_name(get_java_version_info(ik, vmSymbols::java_runtime_name_name()));
 386 
 387     JDK_Version::set_runtime_version(get_java_version_info(ik, vmSymbols::java_runtime_version_name()));
 388 
 389     JDK_Version::set_runtime_vendor_version(get_java_version_info(ik, vmSymbols::java_runtime_vendor_version_name()));
 390 
 391     JDK_Version::set_runtime_vendor_vm_bug_url(get_java_version_info(ik, vmSymbols::java_runtime_vendor_vm_bug_url_name()));
 392   }
 393 
 394   // an instance of OutOfMemory exception has been allocated earlier
 395   initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK);
 396   initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK);
 397   initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK);
 398   initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK);
 399   initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK);
 400   initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK);
 401   initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK);
 402   initialize_class(vmSymbols::java_lang_IllegalArgumentException(), CHECK);
 403 }
 404 
 405 void Threads::initialize_jsr292_core_classes(TRAPS) {
 406   TraceTime timer("Initialize java.lang.invoke classes", TRACETIME_LOG(Info, startuptime));
 407 
 408   initialize_class(vmSymbols::java_lang_invoke_MethodHandle(), CHECK);
 409   initialize_class(vmSymbols::java_lang_invoke_ResolvedMethodName(), CHECK);
 410   initialize_class(vmSymbols::java_lang_invoke_MemberName(), CHECK);
 411   initialize_class(vmSymbols::java_lang_invoke_MethodHandleNatives(), CHECK);
 412 }
 413 
 414 jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
 415   extern void JDK_Version_init();
 416 
 417   // Preinitialize version info.
 418   VM_Version::early_initialize();
 419 
 420   // Check version
 421   if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
 422 
 423   // Initialize library-based TLS
 424   ThreadLocalStorage::init();
 425 
 426   // Initialize the output stream module
 427   ostream_init();
 428 
 429   // Process java launcher properties.
 430   Arguments::process_sun_java_launcher_properties(args);
 431 
 432   // Initialize the os module
 433   os::init();
 434 
 435   MACOS_AARCH64_ONLY(os::current_thread_enable_wx(WXWrite));
 436 
 437   // Record VM creation timing statistics
 438   TraceVmCreationTime create_vm_timer;
 439   create_vm_timer.start();
 440 
 441   // Initialize system properties.
 442   Arguments::init_system_properties();
 443 
 444   // So that JDK version can be used as a discriminator when parsing arguments
 445   JDK_Version_init();
 446 
 447   // Update/Initialize System properties after JDK version number is known
 448   Arguments::init_version_specific_system_properties();
 449 
 450   // Make sure to initialize log configuration *before* parsing arguments
 451   LogConfiguration::initialize(create_vm_timer.begin_time());
 452 
 453   // Parse arguments
 454   // Note: this internally calls os::init_container_support()
 455   jint parse_result = Arguments::parse(args);
 456   if (parse_result != JNI_OK) return parse_result;
 457 
 458   // Initialize NMT right after argument parsing to keep the pre-NMT-init window small.
 459   MemTracker::initialize();
 460 
 461   os::init_before_ergo();
 462 
 463   jint ergo_result = Arguments::apply_ergo();
 464   if (ergo_result != JNI_OK) return ergo_result;
 465 
 466   // Final check of all ranges after ergonomics which may change values.
 467   if (!JVMFlagLimit::check_all_ranges()) {
 468     return JNI_EINVAL;
 469   }
 470 
 471   // Final check of all 'AfterErgo' constraints after ergonomics which may change values.
 472   bool constraint_result = JVMFlagLimit::check_all_constraints(JVMFlagConstraintPhase::AfterErgo);
 473   if (!constraint_result) {
 474     return JNI_EINVAL;
 475   }
 476 
 477   if (PauseAtStartup) {
 478     os::pause();
 479   }
 480 
 481   HOTSPOT_VM_INIT_BEGIN();
 482 
 483   // Timing (must come after argument parsing)
 484   TraceTime timer("Create VM", TRACETIME_LOG(Info, startuptime));
 485 
 486   // Initialize the os module after parsing the args
 487   jint os_init_2_result = os::init_2();
 488   if (os_init_2_result != JNI_OK) return os_init_2_result;
 489 
 490 #ifdef CAN_SHOW_REGISTERS_ON_ASSERT
 491   // Initialize assert poison page mechanism.
 492   if (ShowRegistersOnAssert) {
 493     initialize_assert_poison();
 494   }
 495 #endif // CAN_SHOW_REGISTERS_ON_ASSERT
 496 
 497   SafepointMechanism::initialize();
 498 
 499   jint adjust_after_os_result = Arguments::adjust_after_os();
 500   if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;
 501 
 502   // Initialize output stream logging
 503   ostream_init_log();
 504 
 505   // Launch -agentlib/-agentpath and converted -Xrun agents
 506   JvmtiAgentList::load_agents();
 507 
 508   // Initialize Threads state
 509   _number_of_threads = 0;
 510   _number_of_non_daemon_threads = 0;
 511 
 512   // Initialize global data structures and create system classes in heap
 513   vm_init_globals();
 514 
 515 #if INCLUDE_JVMCI
 516   if (JVMCICounterSize > 0) {
 517     JavaThread::_jvmci_old_thread_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtJVMCI);
 518     memset(JavaThread::_jvmci_old_thread_counters, 0, sizeof(jlong) * JVMCICounterSize);
 519   } else {
 520     JavaThread::_jvmci_old_thread_counters = nullptr;
 521   }
 522 #endif // INCLUDE_JVMCI
 523 
 524   // Initialize OopStorage for threadObj
 525   JavaThread::_thread_oop_storage = OopStorageSet::create_strong("Thread OopStorage", mtThread);
 526 
 527   // Attach the main thread to this os thread
 528   JavaThread* main_thread = new JavaThread();
 529   main_thread->set_thread_state(_thread_in_vm);
 530   main_thread->initialize_thread_current();
 531   // must do this before set_active_handles
 532   main_thread->record_stack_base_and_size();
 533   main_thread->register_thread_stack_with_NMT();
 534   main_thread->set_active_handles(JNIHandleBlock::allocate_block());
 535   MACOS_AARCH64_ONLY(main_thread->init_wx());
 536 
 537   // Set the lock_id now since we will run Java code before the Thread instance
 538   // is even created. The same value will be assigned to the Thread instance on init.
 539   main_thread->set_lock_id(ThreadIdentifier::next());
 540   assert(main_thread->lock_id() == ThreadIdentifier::initial(), "invariant");
 541 
 542   if (!main_thread->set_as_starting_thread()) {
 543     vm_shutdown_during_initialization(
 544                                       "Failed necessary internal allocation. Out of swap space");
 545     main_thread->smr_delete();
 546     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
 547     return JNI_ENOMEM;
 548   }
 549 
 550   // Enable guard page *after* os::create_main_thread(), otherwise it would
 551   // crash Linux VM, see notes in os_linux.cpp.
 552   main_thread->stack_overflow_state()->create_stack_guard_pages();
 553 
 554   // Initialize Java-Level synchronization subsystem
 555   ObjectMonitor::Initialize();
 556   ObjectSynchronizer::initialize();
 557 
 558   // Initialize global modules
 559   jint status = init_globals();
 560   if (status != JNI_OK) {
 561     main_thread->smr_delete();
 562     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
 563     return status;
 564   }
 565 
 566   // Create WatcherThread as soon as we can since we need it in case
 567   // of hangs during error reporting.
 568   WatcherThread::start();
 569 
 570   // Add main_thread to threads list to finish barrier setup with
 571   // on_thread_attach.  Should be before starting to build Java objects in
 572   // init_globals2, which invokes barriers.
 573   {
 574     MutexLocker mu(Threads_lock);
 575     Threads::add(main_thread);
 576   }
 577 
 578   status = init_globals2();
 579   if (status != JNI_OK) {
 580     Threads::remove(main_thread, false);
 581     // It is possible that we managed to fully initialize Universe but have then
 582     // failed by throwing an exception. In that case our caller JNI_CreateJavaVM
 583     // will want to report it, so we can't delete the main thread.
 584     if (!main_thread->has_pending_exception()) {
 585       main_thread->smr_delete();
 586     }
 587     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
 588     return status;
 589   }
 590 
 591   ObjectMonitor::Initialize2();
 592 
 593   JFR_ONLY(Jfr::on_create_vm_1();)
 594 
 595   // Should be done after the heap is fully created
 596   main_thread->cache_global_variables();
 597 
 598   // Any JVMTI raw monitors entered in onload will transition into
 599   // real raw monitor. VM is setup enough here for raw monitor enter.
 600   JvmtiExport::transition_pending_onload_raw_monitors();
 601 
 602   // Create the VMThread
 603   { TraceTime timer("Start VMThread", TRACETIME_LOG(Info, startuptime));
 604 
 605     VMThread::create();
 606     VMThread* vmthread = VMThread::vm_thread();
 607 
 608     if (!os::create_thread(vmthread, os::vm_thread)) {
 609       vm_exit_during_initialization("Cannot create VM thread. "
 610                                     "Out of system resources.");
 611     }
 612 
 613     // Wait for the VM thread to become ready, and VMThread::run to initialize
 614     // Monitors can have spurious returns, must always check another state flag
 615     {
 616       MonitorLocker ml(Notify_lock);
 617       os::start_thread(vmthread);
 618       while (!vmthread->is_running()) {
 619         ml.wait();
 620       }
 621     }
 622   }
 623 
 624   assert(Universe::is_fully_initialized(), "not initialized");
 625   if (VerifyDuringStartup) {
 626     // Make sure we're starting with a clean slate.
 627     VM_Verify verify_op;
 628     VMThread::execute(&verify_op);
 629   }
 630 
 631   // We need this to update the java.vm.info property in case any flags used
 632   // to initially define it have been changed. This is needed for both CDS
 633   // since UseSharedSpaces may be changed after java.vm.info
 634   // is initially computed. See Abstract_VM_Version::vm_info_string().
 635   // This update must happen before we initialize the java classes, but
 636   // after any initialization logic that might modify the flags.
 637   Arguments::update_vm_info_property(VM_Version::vm_info_string());
 638 
 639   JavaThread* THREAD = JavaThread::current(); // For exception macros.
 640   HandleMark hm(THREAD);
 641 
 642   // Always call even when there are not JVMTI environments yet, since environments
 643   // may be attached late and JVMTI must track phases of VM execution
 644   JvmtiExport::enter_early_start_phase();
 645 
 646   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
 647   JvmtiExport::post_early_vm_start();
 648 
 649   // Launch -Xrun agents early if EagerXrunInit is set
 650   if (EagerXrunInit) {
 651     JvmtiAgentList::load_xrun_agents();
 652   }
 653 
 654   initialize_java_lang_classes(main_thread, CHECK_JNI_ERR);
 655 
 656   quicken_jni_functions();
 657 
 658   // No more stub generation allowed after that point.
 659   StubCodeDesc::freeze();
 660 
 661   // Set flag that basic initialization has completed. Used by exceptions and various
 662   // debug stuff, that does not work until all basic classes have been initialized.
 663   set_init_completed();
 664 
 665   LogConfiguration::post_initialize();
 666   Metaspace::post_initialize();
 667   MutexLockerImpl::post_initialize();
 668 
 669   HOTSPOT_VM_INIT_END();
 670 
 671   // record VM initialization completion time
 672 #if INCLUDE_MANAGEMENT
 673   Management::record_vm_init_completed();
 674 #endif // INCLUDE_MANAGEMENT
 675 
 676   log_info(os)("Initialized VM with process ID %d", os::current_process_id());
 677 
 678   // Signal Dispatcher needs to be started before VMInit event is posted
 679   os::initialize_jdk_signal_support(CHECK_JNI_ERR);
 680 
 681   // Start Attach Listener if +StartAttachListener or it can't be started lazily
 682   if (!DisableAttachMechanism) {
 683     AttachListener::vm_start();
 684     if (StartAttachListener || AttachListener::init_at_startup()) {
 685       AttachListener::init();
 686     }
 687   }
 688 
 689   // Launch -Xrun agents if EagerXrunInit is not set.
 690   if (!EagerXrunInit) {
 691     JvmtiAgentList::load_xrun_agents();
 692   }
 693 
 694   Arena::start_chunk_pool_cleaner_task();
 695 
 696   // Start the service thread
 697   // The service thread enqueues JVMTI deferred events and does various hashtable
 698   // and other cleanups.  Needs to start before the compilers start posting events.
 699   ServiceThread::initialize();
 700 
 701   // Start the monitor deflation thread:
 702   MonitorDeflationThread::initialize();
 703 
 704   // initialize compiler(s)
 705 #if defined(COMPILER1) || COMPILER2_OR_JVMCI
 706   bool init_compilation = true;
 707 #if INCLUDE_JVMCI
 708   bool force_JVMCI_initialization = false;
 709   if (EnableJVMCI) {
 710     // Initialize JVMCI eagerly when it is explicitly requested.
 711     // Or when JVMCILibDumpJNIConfig or JVMCIPrintProperties is enabled.
 712     force_JVMCI_initialization = EagerJVMCI || JVMCIPrintProperties || JVMCILibDumpJNIConfig;
 713     if (!force_JVMCI_initialization && UseJVMCICompiler && !UseJVMCINativeLibrary && (!UseInterpreter || !BackgroundCompilation)) {
 714       // Force initialization of jarjvmci otherwise requests for blocking
 715       // compilations will not actually block until jarjvmci is initialized.
 716       force_JVMCI_initialization = true;
 717     }
 718     if (JVMCIPrintProperties || JVMCILibDumpJNIConfig) {
 719       // Both JVMCILibDumpJNIConfig and JVMCIPrintProperties exit the VM
 720       // so compilation should be disabled. This prevents dumping or
 721       // printing from happening more than once.
 722       init_compilation = false;
 723     }
 724   }
 725 #endif
 726   if (init_compilation) {
 727     CompileBroker::compilation_init(CHECK_JNI_ERR);
 728   }
 729 #endif
 730 
 731   // Start string deduplication thread if requested.
 732   if (StringDedup::is_enabled()) {
 733     StringDedup::start();
 734   }
 735 
 736   // Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
 737   // It is done after compilers are initialized, because otherwise compilations of
 738   // signature polymorphic MH intrinsics can be missed
 739   // (see SystemDictionary::find_method_handle_intrinsic).
 740   initialize_jsr292_core_classes(CHECK_JNI_ERR);
 741 
 742   // This will initialize the module system.  Only java.base classes can be
 743   // loaded until phase 2 completes
 744   call_initPhase2(CHECK_JNI_ERR);
 745 
 746   JFR_ONLY(Jfr::on_create_vm_2();)
 747 
 748   // Always call even when there are not JVMTI environments yet, since environments
 749   // may be attached late and JVMTI must track phases of VM execution
 750   JvmtiExport::enter_start_phase();
 751 
 752   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
 753   JvmtiExport::post_vm_start();
 754 
 755   // Final system initialization including security manager and system class loader
 756   call_initPhase3(CHECK_JNI_ERR);
 757 
 758   // cache the system and platform class loaders
 759   SystemDictionary::compute_java_loaders(CHECK_JNI_ERR);
 760 
 761   if (Continuations::enabled()) {
 762     // Initialize Continuation class now so that failure to create enterSpecial/doYield
 763     // special nmethods due to limited CodeCache size can be treated as a fatal error at
 764     // startup with the proper message that CodeCache size is too small.
 765     initialize_class(vmSymbols::jdk_internal_vm_Continuation(), CHECK_JNI_ERR);
 766   }
 767 
 768 #if INCLUDE_CDS
 769   // capture the module path info from the ModuleEntryTable
 770   ClassLoader::initialize_module_path(THREAD);
 771   if (HAS_PENDING_EXCEPTION) {
 772     java_lang_Throwable::print(PENDING_EXCEPTION, tty);
 773     vm_exit_during_initialization("ClassLoader::initialize_module_path() failed unexpectedly");
 774   }
 775 #endif
 776 
 777 #if INCLUDE_JVMCI
 778   if (force_JVMCI_initialization) {
 779     JVMCI::initialize_compiler(CHECK_JNI_ERR);
 780   }
 781 #endif
 782 
 783   if (NativeHeapTrimmer::enabled()) {
 784     NativeHeapTrimmer::initialize();
 785   }
 786 
 787   // Always call even when there are not JVMTI environments yet, since environments
 788   // may be attached late and JVMTI must track phases of VM execution
 789   JvmtiExport::enter_live_phase();
 790 
 791   // Make perfmemory accessible
 792   PerfMemory::set_accessible(true);
 793 
 794   // Notify JVMTI agents that VM initialization is complete - nop if no agents.
 795   JvmtiExport::post_vm_initialized();
 796 
 797   JFR_ONLY(Jfr::on_create_vm_3();)
 798 
 799 #if INCLUDE_MANAGEMENT
 800   Management::initialize(THREAD);
 801 
 802   if (HAS_PENDING_EXCEPTION) {
 803     // management agent fails to start possibly due to
 804     // configuration problem and is responsible for printing
 805     // stack trace if appropriate. Simply exit VM.
 806     vm_exit(1);
 807   }
 808 #endif // INCLUDE_MANAGEMENT
 809 
 810   StatSampler::engage();
 811   if (CheckJNICalls)                  JniPeriodicChecker::engage();
 812 
 813 #if INCLUDE_RTM_OPT
 814   RTMLockingCounters::init();
 815 #endif
 816 
 817   call_postVMInitHook(THREAD);
 818   // The Java side of PostVMInitHook.run must deal with all
 819   // exceptions and provide means of diagnosis.
 820   if (HAS_PENDING_EXCEPTION) {
 821     CLEAR_PENDING_EXCEPTION;
 822   }
 823 
 824   // Let WatcherThread run all registered periodic tasks now.
 825   // NOTE:  All PeriodicTasks should be registered by now. If they
 826   //   aren't, late joiners might appear to start slowly (we might
 827   //   take a while to process their first tick).
 828   WatcherThread::run_all_tasks();
 829 
 830   create_vm_timer.end();
 831 #ifdef ASSERT
 832   _vm_complete = true;
 833 #endif
 834 
 835   if (CDSConfig::is_dumping_static_archive()) {
 836     MetaspaceShared::preload_and_dump();
 837   }
 838 
 839   return JNI_OK;
 840 }
 841 
 842 // Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
 843 // the program falls off the end of main(). Another VM exit path is through
 844 // vm_exit() when the program calls System.exit() to return a value or when
 845 // there is a serious error in VM. The two shutdown paths are not exactly
 846 // the same, but they share Shutdown.shutdown() at Java level and before_exit()
 847 // and VM_Exit op at VM level.
 848 //
 849 // Shutdown sequence:
 850 //   + Shutdown native memory tracking if it is on
 851 //   + Wait until we are the last non-daemon thread to execute
 852 //     <-- every thing is still working at this moment -->
 853 //   + Call java.lang.Shutdown.shutdown(), which will invoke Java level
 854 //        shutdown hooks
 855 //   + Call before_exit(), prepare for VM exit
 856 //      > run VM level shutdown hooks (they are registered through JVM_OnExit(),
 857 //        currently the only user of this mechanism is File.deleteOnExit())
 858 //      > stop StatSampler, watcher thread,
 859 //        post thread end and vm death events to JVMTI,
 860 //        stop signal thread
 861 //   + Call JavaThread::exit(), it will:
 862 //      > release JNI handle blocks, remove stack guard pages
 863 //      > remove this thread from Threads list
 864 //     <-- no more Java code from this thread after this point -->
 865 //   + Stop VM thread, it will bring the remaining VM to a safepoint and stop
 866 //     the compiler threads at safepoint
 867 //     <-- do not use anything that could get blocked by Safepoint -->
 868 //   + Disable tracing at JNI/JVM barriers
 869 //   + Set _vm_exited flag for threads that are still running native code
 870 //   + Call exit_globals()
 871 //      > deletes tty
 872 //      > deletes PerfMemory resources
 873 //   + Delete this thread
 874 //   + Return to caller
 875 
 876 void Threads::destroy_vm() {
 877   JavaThread* thread = JavaThread::current();
 878 
 879 #ifdef ASSERT
 880   _vm_complete = false;
 881 #endif
 882   // Wait until we are the last non-daemon thread to execute, or
 883   // if we are a daemon then wait until the last non-daemon thread has
 884   // executed.
 885   bool daemon = java_lang_Thread::is_daemon(thread->threadObj());
 886   int expected = daemon ? 0 : 1;
 887   {
 888     MonitorLocker nu(Threads_lock);
 889     while (Threads::number_of_non_daemon_threads() > expected)
 890       // This wait should make safepoint checks, wait without a timeout.
 891       nu.wait(0);
 892   }
 893 
 894   EventShutdown e;
 895   if (e.should_commit()) {
 896     e.set_reason("No remaining non-daemon Java threads");
 897     e.commit();
 898   }
 899 
 900   // Hang forever on exit if we are reporting an error.
 901   if (ShowMessageBoxOnError && VMError::is_error_reported()) {
 902     os::infinite_sleep();
 903   }
 904   os::wait_for_keypress_at_exit();
 905 
 906   // run Java level shutdown hooks
 907   thread->invoke_shutdown_hooks();
 908 
 909   before_exit(thread);
 910 
 911   thread->exit(true);
 912 
 913   // We are no longer on the main thread list but could still be in a
 914   // secondary list where another thread may try to interact with us.
 915   // So wait until all such interactions are complete before we bring
 916   // the VM to the termination safepoint. Normally this would be done
 917   // using thread->smr_delete() below where we delete the thread, but
 918   // we can't call that after the termination safepoint is active as
 919   // we will deadlock on the Threads_lock. Once all interactions are
 920   // complete it is safe to directly delete the thread at any time.
 921   ThreadsSMRSupport::wait_until_not_protected(thread);
 922 
 923   // Stop VM thread.
 924   {
 925     // 4945125 The vm thread comes to a safepoint during exit.
 926     // GC vm_operations can get caught at the safepoint, and the
 927     // heap is unparseable if they are caught. Grab the Heap_lock
 928     // to prevent this. The GC vm_operations will not be able to
 929     // queue until after the vm thread is dead. After this point,
 930     // we'll never emerge out of the safepoint before the VM exits.
 931     // Assert that the thread is terminated so that acquiring the
 932     // Heap_lock doesn't cause the terminated thread to participate in
 933     // the safepoint protocol.
 934 
 935     assert(thread->is_terminated(), "must be terminated here");
 936     MutexLocker ml(Heap_lock);
 937 
 938     VMThread::wait_for_vm_thread_exit();
 939     assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
 940     VMThread::destroy();
 941   }
 942 
 943   // Now, all Java threads are gone except daemon threads. Daemon threads
 944   // running Java code or in VM are stopped by the Safepoint. However,
 945   // daemon threads executing native code are still running.  But they
 946   // will be stopped at native=>Java/VM barriers. Note that we can't
 947   // simply kill or suspend them, as it is inherently deadlock-prone.
 948 
 949   VM_Exit::set_vm_exited();
 950 
 951   // Clean up ideal graph printers after the VMThread has started
 952   // the final safepoint which will block all the Compiler threads.
 953   // Note that this Thread has already logically exited so the
 954   // clean_up() function's use of a JavaThreadIteratorWithHandle
 955   // would be a problem except set_vm_exited() has remembered the
 956   // shutdown thread which is granted a policy exception.
 957 #if defined(COMPILER2) && !defined(PRODUCT)
 958   IdealGraphPrinter::clean_up();
 959 #endif
 960 
 961   notify_vm_shutdown();
 962 
 963   // exit_globals() will delete tty
 964   exit_globals();
 965 
 966   // Deleting the shutdown thread here is safe. See comment on
 967   // wait_until_not_protected() above.
 968   delete thread;
 969 
 970 #if INCLUDE_JVMCI
 971   if (JVMCICounterSize > 0) {
 972     FREE_C_HEAP_ARRAY(jlong, JavaThread::_jvmci_old_thread_counters);
 973   }
 974 #endif
 975 
 976   LogConfiguration::finalize();
 977 }
 978 
 979 
 980 jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
 981   if (version == JNI_VERSION_1_1) return JNI_TRUE;
 982   return is_supported_jni_version(version);
 983 }
 984 
 985 
 986 jboolean Threads::is_supported_jni_version(jint version) {
 987   if (version == JNI_VERSION_1_2) return JNI_TRUE;
 988   if (version == JNI_VERSION_1_4) return JNI_TRUE;
 989   if (version == JNI_VERSION_1_6) return JNI_TRUE;
 990   if (version == JNI_VERSION_1_8) return JNI_TRUE;
 991   if (version == JNI_VERSION_9) return JNI_TRUE;
 992   if (version == JNI_VERSION_10) return JNI_TRUE;
 993   if (version == JNI_VERSION_19) return JNI_TRUE;
 994   if (version == JNI_VERSION_20) return JNI_TRUE;
 995   if (version == JNI_VERSION_21) return JNI_TRUE;
 996   return JNI_FALSE;
 997 }
 998 
 999 void Threads::add(JavaThread* p, bool force_daemon) {
1000   // The threads lock must be owned at this point
1001   assert(Threads_lock->owned_by_self(), "must have threads lock");
1002 
1003   BarrierSet::barrier_set()->on_thread_attach(p);
1004 
1005   // Once a JavaThread is added to the Threads list, smr_delete() has
1006   // to be used to delete it. Otherwise we can just delete it directly.
1007   p->set_on_thread_list();
1008 
1009   _number_of_threads++;
1010   oop threadObj = p->threadObj();
1011   bool daemon = true;
1012   // Bootstrapping problem: threadObj can be null for initial
1013   // JavaThread (or for threads attached via JNI)
1014   if (!force_daemon &&
1015       (threadObj == nullptr || !java_lang_Thread::is_daemon(threadObj))) {
1016     _number_of_non_daemon_threads++;
1017     daemon = false;
1018   }
1019 
1020   ThreadService::add_thread(p, daemon);
1021 
1022   // Maintain fast thread list
1023   ThreadsSMRSupport::add_thread(p);
1024 
1025   // Increase the ObjectMonitor ceiling for the new thread.
1026   ObjectSynchronizer::inc_in_use_list_ceiling();
1027 
1028   // Possible GC point.
1029   Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p));
1030 
1031   // Make new thread known to active EscapeBarrier
1032   EscapeBarrier::thread_added(p);
1033 }
1034 
1035 void Threads::remove(JavaThread* p, bool is_daemon) {
1036   // Extra scope needed for Thread_lock, so we can check
1037   // that we do not remove thread without safepoint code notice
1038   { MonitorLocker ml(Threads_lock);
1039 
1040     if (ThreadIdTable::is_initialized()) {
1041       // This cleanup must be done before the current thread's GC barrier
1042       // is detached since we need to touch the threadObj oop.
1043       jlong tid = SharedRuntime::get_java_tid(p);
1044       ThreadIdTable::remove_thread(tid);
1045     }
1046 
1047     // BarrierSet state must be destroyed after the last thread transition
1048     // before the thread terminates. Thread transitions result in calls to
1049     // StackWatermarkSet::on_safepoint(), which performs GC processing,
1050     // requiring the GC state to be alive.
1051     BarrierSet::barrier_set()->on_thread_detach(p);
1052     if (p->is_exiting()) {
1053       // If we got here via JavaThread::exit(), then we remember that the
1054       // thread's GC barrier has been detached. We don't do this when we get
1055       // here from another path, e.g., cleanup_failed_attach_current_thread().
1056       p->set_terminated(JavaThread::_thread_gc_barrier_detached);
1057     }
1058 
1059     assert(ThreadsSMRSupport::get_java_thread_list()->includes(p), "p must be present");
1060 
1061     // Maintain fast thread list
1062     ThreadsSMRSupport::remove_thread(p);
1063 
1064     _number_of_threads--;
1065     if (!is_daemon) {
1066       _number_of_non_daemon_threads--;
1067 
1068       // If this is the last non-daemon thread then we need to do
1069       // a notify on the Threads_lock so a thread waiting
1070       // on destroy_vm will wake up. But that thread could be a daemon
1071       // or non-daemon, so we notify for both the 0 and 1 case.
1072       if (number_of_non_daemon_threads() <= 1) {
1073         ml.notify_all();
1074       }
1075     }
1076     ThreadService::remove_thread(p, is_daemon);
1077 
1078     // Make sure that safepoint code disregard this thread. This is needed since
1079     // the thread might mess around with locks after this point. This can cause it
1080     // to do callbacks into the safepoint code. However, the safepoint code is not aware
1081     // of this thread since it is removed from the queue.
1082     p->set_terminated(JavaThread::_thread_terminated);
1083 
1084     // Notify threads waiting in EscapeBarriers
1085     EscapeBarrier::thread_removed(p);
1086   } // unlock Threads_lock
1087 
1088   // Reduce the ObjectMonitor ceiling for the exiting thread.
1089   ObjectSynchronizer::dec_in_use_list_ceiling();
1090 
1091   // Since Events::log uses a lock, we grab it outside the Threads_lock
1092   Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p));
1093 }
1094 
1095 // Operations on the Threads list for GC.  These are not explicitly locked,
1096 // but the garbage collector must provide a safe context for them to run.
1097 // In particular, these things should never be called when the Threads_lock
1098 // is held by some other thread. (Note: the Safepoint abstraction also
1099 // uses the Threads_lock to guarantee this property. It also makes sure that
1100 // all threads gets blocked when exiting or starting).
1101 
1102 void Threads::oops_do(OopClosure* f, CodeBlobClosure* cf) {
1103   ALL_JAVA_THREADS(p) {
1104     p->oops_do(f, cf);
1105   }
1106   VMThread::vm_thread()->oops_do(f, cf);
1107 }
1108 
1109 void Threads::change_thread_claim_token() {
1110   if (++_thread_claim_token == 0) {
1111     // On overflow of the token counter, there is a risk of future
1112     // collisions between a new global token value and a stale token
1113     // for a thread, because not all iterations visit all threads.
1114     // (Though it's pretty much a theoretical concern for non-trivial
1115     // token counter sizes.)  To deal with the possibility, reset all
1116     // the thread tokens to zero on global token overflow.
1117     struct ResetClaims : public ThreadClosure {
1118       virtual void do_thread(Thread* t) {
1119         t->claim_threads_do(false, 0);
1120       }
1121     } reset_claims;
1122     Threads::threads_do(&reset_claims);
1123     // On overflow, update the global token to non-zero, to
1124     // avoid the special "never claimed" initial thread value.
1125     _thread_claim_token = 1;
1126   }
1127 }
1128 
1129 #ifdef ASSERT
1130 static void assert_thread_claimed(const char* kind, Thread* t, uintx expected) {
1131   const uintx token = t->threads_do_token();
1132   assert(token == expected,
1133          "%s " PTR_FORMAT " has incorrect value " UINTX_FORMAT " != "
1134          UINTX_FORMAT, kind, p2i(t), token, expected);
1135 }
1136 
1137 void Threads::assert_all_threads_claimed() {
1138   ALL_JAVA_THREADS(p) {
1139     assert_thread_claimed("JavaThread", p, _thread_claim_token);
1140   }
1141 
1142   struct NJTClaimedVerifierClosure : public ThreadClosure {
1143     uintx _thread_claim_token;
1144 
1145     NJTClaimedVerifierClosure(uintx thread_claim_token) : ThreadClosure(), _thread_claim_token(thread_claim_token) { }
1146 
1147     virtual void do_thread(Thread* thread) override {
1148       assert_thread_claimed("Non-JavaThread", VMThread::vm_thread(), _thread_claim_token);
1149     }
1150   } tc(_thread_claim_token);
1151 
1152   non_java_threads_do(&tc);
1153 }
1154 #endif // ASSERT
1155 
1156 class ParallelOopsDoThreadClosure : public ThreadClosure {
1157 private:
1158   OopClosure* _f;
1159   CodeBlobClosure* _cf;
1160 public:
1161   ParallelOopsDoThreadClosure(OopClosure* f, CodeBlobClosure* cf) : _f(f), _cf(cf) {}
1162   void do_thread(Thread* t) {
1163     t->oops_do(_f, _cf);
1164   }
1165 };
1166 
1167 void Threads::possibly_parallel_oops_do(bool is_par, OopClosure* f, CodeBlobClosure* cf) {
1168   ParallelOopsDoThreadClosure tc(f, cf);
1169   possibly_parallel_threads_do(is_par, &tc);
1170 }
1171 
1172 void Threads::metadata_do(MetadataClosure* f) {
1173   ALL_JAVA_THREADS(p) {
1174     p->metadata_do(f);
1175   }
1176 }
1177 
1178 class ThreadHandlesClosure : public ThreadClosure {
1179   void (*_f)(Metadata*);
1180  public:
1181   ThreadHandlesClosure(void f(Metadata*)) : _f(f) {}
1182   virtual void do_thread(Thread* thread) {
1183     thread->metadata_handles_do(_f);
1184   }
1185 };
1186 
1187 void Threads::metadata_handles_do(void f(Metadata*)) {
1188   // Only walk the Handles in Thread.
1189   ThreadHandlesClosure handles_closure(f);
1190   threads_do(&handles_closure);
1191 }
1192 
1193 // Get count Java threads that are waiting to enter the specified monitor.
1194 GrowableArray<JavaThread*>* Threads::get_pending_threads(ThreadsList * t_list,
1195                                                          int count,
1196                                                          address monitor) {
1197   GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
1198 
1199   int i = 0;
1200   for (JavaThread* p : *t_list) {
1201     if (!p->can_call_java()) continue;
1202 
1203     // The first stage of async deflation does not affect any field
1204     // used by this comparison so the ObjectMonitor* is usable here.
1205     address pending = (address)p->current_pending_monitor();
1206     if (pending == monitor) {             // found a match
1207       if (i < count) result->append(p);   // save the first count matches
1208       i++;
1209     }
1210   }
1211 
1212   return result;
1213 }
1214 
1215 
1216 JavaThread *Threads::owning_thread_from_stacklock(ThreadsList * t_list, address basicLock) {
1217   assert(LockingMode == LM_LEGACY, "Not with new lightweight locking");
1218 
1219   JavaThread* the_owner = nullptr;
1220   for (JavaThread* q : *t_list) {
1221     if (q->is_lock_owned(basicLock)) {
1222       the_owner = q;
1223       break;
1224     }
1225   }
1226   return the_owner;
1227 }
1228 
1229 JavaThread* Threads::owning_thread_from_object(ThreadsList * t_list, oop obj) {
1230   assert(LockingMode == LM_LIGHTWEIGHT, "Only with new lightweight locking");
1231   for (JavaThread* q : *t_list) {
1232     // Need to start processing before accessing oops in the thread.
1233     StackWatermark* watermark = StackWatermarkSet::get(q, StackWatermarkKind::gc);
1234     if (watermark != nullptr) {
1235       watermark->start_processing();
1236     }
1237 
1238     if (q->lock_stack().contains(obj)) {
1239       return q;
1240     }
1241   }
1242   return nullptr;
1243 }
1244 
1245 JavaThread* Threads::owning_thread_from_monitor(ThreadsList* t_list, ObjectMonitor* monitor) {
1246   if (monitor->is_owner_anonymous()) {
1247     if (LockingMode == LM_LIGHTWEIGHT) {
1248       return owning_thread_from_object(t_list, monitor->object());
1249     } else {
1250       assert(LockingMode == LM_LEGACY, "invariant");
1251       return owning_thread_from_stacklock(t_list, (address)monitor->stack_locker());
1252     }
1253   } else {
1254     JavaThread* the_owner = nullptr;
1255     int64_t owner_tid = (int64_t)monitor->owner();
1256     for (JavaThread* q : *t_list) {
1257       if (monitor->is_owner(q)) {
1258         the_owner = q;
1259         break;
1260       }
1261     }
1262     return the_owner;
1263   }
1264 }
1265 
1266 class PrintOnClosure : public ThreadClosure {
1267 private:
1268   outputStream* _st;
1269 
1270 public:
1271   PrintOnClosure(outputStream* st) :
1272       _st(st) {}
1273 
1274   virtual void do_thread(Thread* thread) {
1275     if (thread != nullptr) {
1276       thread->print_on(_st);
1277       _st->cr();
1278     }
1279   }
1280 };
1281 
1282 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
1283 void Threads::print_on(outputStream* st, bool print_stacks,
1284                        bool internal_format, bool print_concurrent_locks,
1285                        bool print_extended_info) {
1286   char buf[32];
1287   st->print_raw_cr(os::local_time_string(buf, sizeof(buf)));
1288 
1289   st->print_cr("Full thread dump %s (%s %s):",
1290                VM_Version::vm_name(),
1291                VM_Version::vm_release(),
1292                VM_Version::vm_info_string());
1293   st->cr();
1294 
1295 #if INCLUDE_SERVICES
1296   // Dump concurrent locks
1297   ConcurrentLocksDump concurrent_locks;
1298   if (print_concurrent_locks) {
1299     concurrent_locks.dump_at_safepoint();
1300   }
1301 #endif // INCLUDE_SERVICES
1302 
1303   ThreadsSMRSupport::print_info_on(st);
1304   st->cr();
1305 
1306   ALL_JAVA_THREADS(p) {
1307     ResourceMark rm;
1308     p->print_on(st, print_extended_info);
1309     if (print_stacks) {
1310       if (internal_format) {
1311         p->trace_stack();
1312       } else {
1313         p->print_stack_on(st);
1314       }
1315     }
1316     st->cr();
1317 #if INCLUDE_SERVICES
1318     if (print_concurrent_locks) {
1319       concurrent_locks.print_locks_on(p, st);
1320     }
1321 #endif // INCLUDE_SERVICES
1322   }
1323 
1324   PrintOnClosure cl(st);
1325   cl.do_thread(VMThread::vm_thread());
1326   Universe::heap()->gc_threads_do(&cl);
1327   cl.do_thread(WatcherThread::watcher_thread());
1328   cl.do_thread(AsyncLogWriter::instance());
1329 
1330   st->flush();
1331 }
1332 
1333 void Threads::print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf,
1334                              int buflen, bool* found_current) {
1335   if (this_thread != nullptr) {
1336     bool is_current = (current == this_thread);
1337     *found_current = *found_current || is_current;
1338     st->print("%s", is_current ? "=>" : "  ");
1339 
1340     st->print(PTR_FORMAT, p2i(this_thread));
1341     st->print(" ");
1342     this_thread->print_on_error(st, buf, buflen);
1343     st->cr();
1344   }
1345 }
1346 
1347 class PrintOnErrorClosure : public ThreadClosure {
1348   outputStream* _st;
1349   Thread* _current;
1350   char* _buf;
1351   int _buflen;
1352   bool* _found_current;
1353   unsigned _num_printed;
1354  public:
1355   PrintOnErrorClosure(outputStream* st, Thread* current, char* buf,
1356                       int buflen, bool* found_current) :
1357    _st(st), _current(current), _buf(buf), _buflen(buflen), _found_current(found_current),
1358    _num_printed(0) {}
1359 
1360   virtual void do_thread(Thread* thread) {
1361     _num_printed++;
1362     Threads::print_on_error(thread, _st, _current, _buf, _buflen, _found_current);
1363   }
1364 
1365   unsigned num_printed() const { return _num_printed; }
1366 };
1367 
1368 // Threads::print_on_error() is called by fatal error handler. It's possible
1369 // that VM is not at safepoint and/or current thread is inside signal handler.
1370 // Don't print stack trace, as the stack may not be walkable. Don't allocate
1371 // memory (even in resource area), it might deadlock the error handler.
1372 void Threads::print_on_error(outputStream* st, Thread* current, char* buf,
1373                              int buflen) {
1374   ThreadsSMRSupport::print_info_on(st);
1375   st->cr();
1376 
1377   bool found_current = false;
1378   st->print_cr("Java Threads: ( => current thread )");
1379   unsigned num_java = 0;
1380   ALL_JAVA_THREADS(thread) {
1381     print_on_error(thread, st, current, buf, buflen, &found_current);
1382     num_java++;
1383   }
1384   st->print_cr("Total: %u", num_java);
1385   st->cr();
1386 
1387   st->print_cr("Other Threads:");
1388   unsigned num_other = ((VMThread::vm_thread() != nullptr) ? 1 : 0) +
1389       ((WatcherThread::watcher_thread() != nullptr) ? 1 : 0) +
1390       ((AsyncLogWriter::instance() != nullptr)  ? 1 : 0);
1391   print_on_error(VMThread::vm_thread(), st, current, buf, buflen, &found_current);
1392   print_on_error(WatcherThread::watcher_thread(), st, current, buf, buflen, &found_current);
1393   print_on_error(AsyncLogWriter::instance(), st, current, buf, buflen, &found_current);
1394 
1395   if (Universe::heap() != nullptr) {
1396     PrintOnErrorClosure print_closure(st, current, buf, buflen, &found_current);
1397     Universe::heap()->gc_threads_do(&print_closure);
1398     num_other += print_closure.num_printed();
1399   }
1400 
1401   if (!found_current) {
1402     st->cr();
1403     st->print("=>" PTR_FORMAT " (exited) ", p2i(current));
1404     current->print_on_error(st, buf, buflen);
1405     num_other++;
1406     st->cr();
1407   }
1408   st->print_cr("Total: %u", num_other);
1409   st->cr();
1410 
1411   st->print_cr("Threads with active compile tasks:");
1412   unsigned num = print_threads_compiling(st, buf, buflen);
1413   st->print_cr("Total: %u", num);
1414 }
1415 
1416 unsigned Threads::print_threads_compiling(outputStream* st, char* buf, int buflen, bool short_form) {
1417   unsigned num = 0;
1418   ALL_JAVA_THREADS(thread) {
1419     if (thread->is_Compiler_thread()) {
1420       CompilerThread* ct = (CompilerThread*) thread;
1421 
1422       // Keep task in local variable for null check.
1423       // ct->_task might be set to null by concurring compiler thread
1424       // because it completed the compilation. The task is never freed,
1425       // though, just returned to a free list.
1426       CompileTask* task = ct->task();
1427       if (task != nullptr) {
1428         thread->print_name_on_error(st, buf, buflen);
1429         st->print("  ");
1430         task->print(st, nullptr, short_form, true);
1431         num++;
1432       }
1433     }
1434   }
1435   return num;
1436 }
1437 
1438 void Threads::verify() {
1439   ALL_JAVA_THREADS(p) {
1440     p->verify();
1441   }
1442   VMThread* thread = VMThread::vm_thread();
1443   if (thread != nullptr) thread->verify();
1444 }