1 /*
   2  * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "jvm.h"
  27 #include "classfile/classLoader.hpp"
  28 #include "classfile/javaClasses.hpp"
  29 #include "classfile/moduleEntry.hpp"
  30 #include "classfile/systemDictionary.hpp"
  31 #include "classfile/vmSymbols.hpp"
  32 #include "code/codeCache.hpp"
  33 #include "code/scopeDesc.hpp"
  34 #include "compiler/compileBroker.hpp"
  35 #include "compiler/compileTask.hpp"
  36 #include "gc/shared/gcId.hpp"
  37 #include "gc/shared/gcLocker.inline.hpp"
  38 #include "gc/shared/workgroup.hpp"
  39 #include "interpreter/interpreter.hpp"
  40 #include "interpreter/linkResolver.hpp"
  41 #include "interpreter/oopMapCache.hpp"
  42 #include "jvmtifiles/jvmtiEnv.hpp"
  43 #include "logging/log.hpp"
  44 #include "logging/logConfiguration.hpp"
  45 #include "logging/logStream.hpp"
  46 #include "memory/metaspaceShared.hpp"
  47 #include "memory/oopFactory.hpp"
  48 #include "memory/resourceArea.hpp"
  49 #include "memory/universe.inline.hpp"
  50 #include "oops/instanceKlass.hpp"
  51 #include "oops/objArrayOop.hpp"
  52 #include "oops/oop.inline.hpp"
  53 #include "oops/symbol.hpp"
  54 #include "oops/verifyOopClosure.hpp"
  55 #include "prims/jvm_misc.hpp"
  56 #include "prims/jvmtiExport.hpp"
  57 #include "prims/jvmtiThreadState.hpp"
  58 #include "prims/privilegedStack.hpp"
  59 #include "runtime/arguments.hpp"
  60 #include "runtime/atomic.hpp"
  61 #include "runtime/biasedLocking.hpp"
  62 #include "runtime/commandLineFlagConstraintList.hpp"
  63 #include "runtime/commandLineFlagWriteableList.hpp"
  64 #include "runtime/commandLineFlagRangeList.hpp"
  65 #include "runtime/deoptimization.hpp"
  66 #include "runtime/frame.inline.hpp"
  67 #include "runtime/globals.hpp"
  68 #include "runtime/handshake.hpp"
  69 #include "runtime/init.hpp"
  70 #include "runtime/interfaceSupport.hpp"
  71 #include "runtime/java.hpp"
  72 #include "runtime/javaCalls.hpp"
  73 #include "runtime/jniPeriodicChecker.hpp"
  74 #include "runtime/memprofiler.hpp"
  75 #include "runtime/mutexLocker.hpp"
  76 #include "runtime/objectMonitor.hpp"
  77 #include "runtime/orderAccess.inline.hpp"
  78 #include "runtime/osThread.hpp"
  79 #include "runtime/prefetch.inline.hpp"
  80 #include "runtime/safepoint.hpp"
  81 #include "runtime/safepointMechanism.inline.hpp"
  82 #include "runtime/sharedRuntime.hpp"
  83 #include "runtime/statSampler.hpp"
  84 #include "runtime/stubRoutines.hpp"
  85 #include "runtime/sweeper.hpp"
  86 #include "runtime/task.hpp"
  87 #include "runtime/thread.inline.hpp"
  88 #include "runtime/threadCritical.hpp"
  89 #include "runtime/threadSMR.inline.hpp"
  90 #include "runtime/timer.hpp"
  91 #include "runtime/timerTrace.hpp"
  92 #include "runtime/vframe.hpp"
  93 #include "runtime/vframeArray.hpp"
  94 #include "runtime/vframe_hp.hpp"
  95 #include "runtime/vmThread.hpp"
  96 #include "runtime/vm_operations.hpp"
  97 #include "runtime/vm_version.hpp"
  98 #include "services/attachListener.hpp"
  99 #include "services/management.hpp"
 100 #include "services/memTracker.hpp"
 101 #include "services/threadService.hpp"
 102 #include "trace/traceMacros.hpp"
 103 #include "trace/tracing.hpp"
 104 #include "utilities/align.hpp"
 105 #include "utilities/defaultStream.hpp"
 106 #include "utilities/dtrace.hpp"
 107 #include "utilities/events.hpp"
 108 #include "utilities/macros.hpp"
 109 #include "utilities/preserveException.hpp"
 110 #include "utilities/resourceHash.hpp"
 111 #include "utilities/vmError.hpp"
 112 #if INCLUDE_ALL_GCS
 113 #include "gc/cms/concurrentMarkSweepThread.hpp"
 114 #include "gc/g1/concurrentMarkThread.inline.hpp"
 115 #include "gc/parallel/pcTasks.hpp"
 116 #endif // INCLUDE_ALL_GCS
 117 #if INCLUDE_JVMCI
 118 #include "jvmci/jvmciCompiler.hpp"
 119 #include "jvmci/jvmciRuntime.hpp"
 120 #include "logging/logHandle.hpp"
 121 #endif
 122 #ifdef COMPILER1
 123 #include "c1/c1_Compiler.hpp"
 124 #endif
 125 #ifdef COMPILER2
 126 #include "opto/c2compiler.hpp"
 127 #include "opto/idealGraphPrinter.hpp"
 128 #endif
 129 #if INCLUDE_RTM_OPT
 130 #include "runtime/rtmLocking.hpp"
 131 #endif
 132 
 133 // Initialization after module runtime initialization
 134 void universe_post_module_init();  // must happen after call_initPhase2
 135 
 136 #ifdef DTRACE_ENABLED
 137 
 138 // Only bother with this argument setup if dtrace is available
 139 
 140   #define HOTSPOT_THREAD_PROBE_start HOTSPOT_THREAD_START
 141   #define HOTSPOT_THREAD_PROBE_stop HOTSPOT_THREAD_STOP
 142 
 143   #define DTRACE_THREAD_PROBE(probe, javathread)                           \
 144     {                                                                      \
 145       ResourceMark rm(this);                                               \
 146       int len = 0;                                                         \
 147       const char* name = (javathread)->get_thread_name();                  \
 148       len = strlen(name);                                                  \
 149       HOTSPOT_THREAD_PROBE_##probe(/* probe = start, stop */               \
 150         (char *) name, len,                                                \
 151         java_lang_Thread::thread_id((javathread)->threadObj()),            \
 152         (uintptr_t) (javathread)->osthread()->thread_id(),                 \
 153         java_lang_Thread::is_daemon((javathread)->threadObj()));           \
 154     }
 155 
 156 #else //  ndef DTRACE_ENABLED
 157 
 158   #define DTRACE_THREAD_PROBE(probe, javathread)
 159 
 160 #endif // ndef DTRACE_ENABLED
 161 
 162 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 163 // Current thread is maintained as a thread-local variable
 164 THREAD_LOCAL_DECL Thread* Thread::_thr_current = NULL;
 165 #endif
 166 // Class hierarchy
 167 // - Thread
 168 //   - VMThread
 169 //   - WatcherThread
 170 //   - ConcurrentMarkSweepThread
 171 //   - JavaThread
 172 //     - CompilerThread
 173 
 174 // ======= Thread ========
 175 // Support for forcing alignment of thread objects for biased locking
 176 void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
 177   if (UseBiasedLocking) {
 178     const int alignment = markOopDesc::biased_lock_alignment;
 179     size_t aligned_size = size + (alignment - sizeof(intptr_t));
 180     void* real_malloc_addr = throw_excpt? AllocateHeap(aligned_size, flags, CURRENT_PC)
 181                                           : AllocateHeap(aligned_size, flags, CURRENT_PC,
 182                                                          AllocFailStrategy::RETURN_NULL);
 183     void* aligned_addr     = align_up(real_malloc_addr, alignment);
 184     assert(((uintptr_t) aligned_addr + (uintptr_t) size) <=
 185            ((uintptr_t) real_malloc_addr + (uintptr_t) aligned_size),
 186            "JavaThread alignment code overflowed allocated storage");
 187     if (aligned_addr != real_malloc_addr) {
 188       log_info(biasedlocking)("Aligned thread " INTPTR_FORMAT " to " INTPTR_FORMAT,
 189                               p2i(real_malloc_addr),
 190                               p2i(aligned_addr));
 191     }
 192     ((Thread*) aligned_addr)->_real_malloc_address = real_malloc_addr;
 193     return aligned_addr;
 194   } else {
 195     return throw_excpt? AllocateHeap(size, flags, CURRENT_PC)
 196                        : AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
 197   }
 198 }
 199 
 200 void Thread::operator delete(void* p) {
 201   if (UseBiasedLocking) {
 202     FreeHeap(((Thread*) p)->_real_malloc_address);
 203   } else {
 204     FreeHeap(p);
 205   }
 206 }
 207 
 208 void JavaThread::smr_delete() {
 209   if (_on_thread_list) {
 210     Threads::smr_delete(this);
 211   } else {
 212     delete this;
 213   }
 214 }
 215 
 216 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
 217 // JavaThread
 218 
 219 
 220 Thread::Thread() {
 221   // stack and get_thread
 222   set_stack_base(NULL);
 223   set_stack_size(0);
 224   set_self_raw_id(0);
 225   set_lgrp_id(-1);
 226   DEBUG_ONLY(clear_suspendible_thread();)
 227 
 228   // allocated data structures
 229   set_osthread(NULL);
 230   set_resource_area(new (mtThread)ResourceArea());
 231   DEBUG_ONLY(_current_resource_mark = NULL;)
 232   set_handle_area(new (mtThread) HandleArea(NULL));
 233   set_metadata_handles(new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(30, true));
 234   set_active_handles(NULL);
 235   set_free_handle_block(NULL);
 236   set_last_handle_mark(NULL);
 237 
 238   // This initial value ==> never claimed.
 239   _oops_do_parity = 0;
 240   _threads_hazard_ptr = NULL;
 241   _nested_threads_hazard_ptr = NULL;
 242   _nested_threads_hazard_ptr_cnt = 0;
 243 
 244   // the handle mark links itself to last_handle_mark
 245   new HandleMark(this);
 246 
 247   // plain initialization
 248   debug_only(_owned_locks = NULL;)
 249   debug_only(_allow_allocation_count = 0;)
 250   NOT_PRODUCT(_allow_safepoint_count = 0;)
 251   NOT_PRODUCT(_skip_gcalot = false;)
 252   _jvmti_env_iteration_count = 0;
 253   set_allocated_bytes(0);
 254   _vm_operation_started_count = 0;
 255   _vm_operation_completed_count = 0;
 256   _current_pending_monitor = NULL;
 257   _current_pending_monitor_is_from_java = true;
 258   _current_waiting_monitor = NULL;
 259   _num_nested_signal = 0;
 260   omFreeList = NULL;
 261   omFreeCount = 0;
 262   omFreeProvision = 32;
 263   omInUseList = NULL;
 264   omInUseCount = 0;
 265 
 266 #ifdef ASSERT
 267   _visited_for_critical_count = false;
 268 #endif
 269 
 270   _SR_lock = new Monitor(Mutex::suspend_resume, "SR_lock", true,
 271                          Monitor::_safepoint_check_sometimes);
 272   _suspend_flags = 0;
 273 
 274   // thread-specific hashCode stream generator state - Marsaglia shift-xor form
 275   _hashStateX = os::random();
 276   _hashStateY = 842502087;
 277   _hashStateZ = 0x8767;    // (int)(3579807591LL & 0xffff) ;
 278   _hashStateW = 273326509;
 279 
 280   _OnTrap   = 0;
 281   _schedctl = NULL;
 282   _Stalled  = 0;
 283   _TypeTag  = 0x2BAD;
 284 
 285   // Many of the following fields are effectively final - immutable
 286   // Note that nascent threads can't use the Native Monitor-Mutex
 287   // construct until the _MutexEvent is initialized ...
 288   // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
 289   // we might instead use a stack of ParkEvents that we could provision on-demand.
 290   // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
 291   // and ::Release()
 292   _ParkEvent   = ParkEvent::Allocate(this);
 293   _SleepEvent  = ParkEvent::Allocate(this);
 294   _MutexEvent  = ParkEvent::Allocate(this);
 295   _MuxEvent    = ParkEvent::Allocate(this);
 296 
 297 #ifdef CHECK_UNHANDLED_OOPS
 298   if (CheckUnhandledOops) {
 299     _unhandled_oops = new UnhandledOops(this);
 300   }
 301 #endif // CHECK_UNHANDLED_OOPS
 302 #ifdef ASSERT
 303   if (UseBiasedLocking) {
 304     assert((((uintptr_t) this) & (markOopDesc::biased_lock_alignment - 1)) == 0, "forced alignment of thread object failed");
 305     assert(this == _real_malloc_address ||
 306            this == align_up(_real_malloc_address, (int)markOopDesc::biased_lock_alignment),
 307            "bug in forced alignment of thread objects");
 308   }
 309 #endif // ASSERT
 310 }
 311 
 312 void Thread::initialize_thread_current() {
 313 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 314   assert(_thr_current == NULL, "Thread::current already initialized");
 315   _thr_current = this;
 316 #endif
 317   assert(ThreadLocalStorage::thread() == NULL, "ThreadLocalStorage::thread already initialized");
 318   ThreadLocalStorage::set_thread(this);
 319   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 320 }
 321 
 322 void Thread::clear_thread_current() {
 323   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 324 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 325   _thr_current = NULL;
 326 #endif
 327   ThreadLocalStorage::set_thread(NULL);
 328 }
 329 
 330 void Thread::record_stack_base_and_size() {
 331   set_stack_base(os::current_stack_base());
 332   set_stack_size(os::current_stack_size());
 333   // CR 7190089: on Solaris, primordial thread's stack is adjusted
 334   // in initialize_thread(). Without the adjustment, stack size is
 335   // incorrect if stack is set to unlimited (ulimit -s unlimited).
 336   // So far, only Solaris has real implementation of initialize_thread().
 337   //
 338   // set up any platform-specific state.
 339   os::initialize_thread(this);
 340 
 341   // Set stack limits after thread is initialized.
 342   if (is_Java_thread()) {
 343     ((JavaThread*) this)->set_stack_overflow_limit();
 344     ((JavaThread*) this)->set_reserved_stack_activation(stack_base());
 345   }
 346 #if INCLUDE_NMT
 347   // record thread's native stack, stack grows downward
 348   MemTracker::record_thread_stack(stack_end(), stack_size());
 349 #endif // INCLUDE_NMT
 350   log_debug(os, thread)("Thread " UINTX_FORMAT " stack dimensions: "
 351     PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT "k).",
 352     os::current_thread_id(), p2i(stack_base() - stack_size()),
 353     p2i(stack_base()), stack_size()/1024);
 354 }
 355 
 356 
 357 Thread::~Thread() {
 358   EVENT_THREAD_DESTRUCT(this);
 359 
 360   // stack_base can be NULL if the thread is never started or exited before
 361   // record_stack_base_and_size called. Although, we would like to ensure
 362   // that all started threads do call record_stack_base_and_size(), there is
 363   // not proper way to enforce that.
 364 #if INCLUDE_NMT
 365   if (_stack_base != NULL) {
 366     MemTracker::release_thread_stack(stack_end(), stack_size());
 367 #ifdef ASSERT
 368     set_stack_base(NULL);
 369 #endif
 370   }
 371 #endif // INCLUDE_NMT
 372 
 373   // deallocate data structures
 374   delete resource_area();
 375   // since the handle marks are using the handle area, we have to deallocated the root
 376   // handle mark before deallocating the thread's handle area,
 377   assert(last_handle_mark() != NULL, "check we have an element");
 378   delete last_handle_mark();
 379   assert(last_handle_mark() == NULL, "check we have reached the end");
 380 
 381   // It's possible we can encounter a null _ParkEvent, etc., in stillborn threads.
 382   // We NULL out the fields for good hygiene.
 383   ParkEvent::Release(_ParkEvent); _ParkEvent   = NULL;
 384   ParkEvent::Release(_SleepEvent); _SleepEvent  = NULL;
 385   ParkEvent::Release(_MutexEvent); _MutexEvent  = NULL;
 386   ParkEvent::Release(_MuxEvent); _MuxEvent    = NULL;
 387 
 388   delete handle_area();
 389   delete metadata_handles();
 390 
 391   // SR_handler uses this as a termination indicator -
 392   // needs to happen before os::free_thread()
 393   delete _SR_lock;
 394   _SR_lock = NULL;
 395 
 396   // osthread() can be NULL, if creation of thread failed.
 397   if (osthread() != NULL) os::free_thread(osthread());
 398 
 399   // clear Thread::current if thread is deleting itself.
 400   // Needed to ensure JNI correctly detects non-attached threads.
 401   if (this == Thread::current()) {
 402     clear_thread_current();
 403   }
 404 
 405   CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
 406 }
 407 
 408 // NOTE: dummy function for assertion purpose.
 409 void Thread::run() {
 410   ShouldNotReachHere();
 411 }
 412 
 413 #ifdef ASSERT
 414 // A JavaThread is considered "dangling" if it is not the current
 415 // thread, has been added the Threads list, the system is not at a
 416 // safepoint and the Thread is not "protected".
 417 //
 418 void Thread::check_for_dangling_thread_pointer(Thread *thread) {
 419   assert(!thread->is_Java_thread() || Thread::current() == thread ||
 420          !((JavaThread *) thread)->on_thread_list() ||
 421          SafepointSynchronize::is_at_safepoint() ||
 422          Threads::is_a_protected_JavaThread_with_lock((JavaThread *) thread),
 423          "possibility of dangling Thread pointer");
 424 }
 425 #endif
 426 
 427 ThreadPriority Thread::get_priority(const Thread* const thread) {
 428   ThreadPriority priority;
 429   // Can return an error!
 430   (void)os::get_priority(thread, priority);
 431   assert(MinPriority <= priority && priority <= MaxPriority, "non-Java priority found");
 432   return priority;
 433 }
 434 
 435 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
 436   debug_only(check_for_dangling_thread_pointer(thread);)
 437   // Can return an error!
 438   (void)os::set_priority(thread, priority);
 439 }
 440 
 441 
 442 void Thread::start(Thread* thread) {
 443   // Start is different from resume in that its safety is guaranteed by context or
 444   // being called from a Java method synchronized on the Thread object.
 445   if (!DisableStartThread) {
 446     if (thread->is_Java_thread()) {
 447       // Initialize the thread state to RUNNABLE before starting this thread.
 448       // Can not set it after the thread started because we do not know the
 449       // exact thread state at that time. It could be in MONITOR_WAIT or
 450       // in SLEEPING or some other state.
 451       java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
 452                                           java_lang_Thread::RUNNABLE);
 453     }
 454     os::start_thread(thread);
 455   }
 456 }
 457 
 458 // Enqueue a VM_Operation to do the job for us - sometime later
 459 void Thread::send_async_exception(oop java_thread, oop java_throwable) {
 460   VM_ThreadStop* vm_stop = new VM_ThreadStop(java_thread, java_throwable);
 461   VMThread::execute(vm_stop);
 462 }
 463 
 464 
 465 // Check if an external suspend request has completed (or has been
 466 // cancelled). Returns true if the thread is externally suspended and
 467 // false otherwise.
 468 //
 469 // The bits parameter returns information about the code path through
 470 // the routine. Useful for debugging:
 471 //
 472 // set in is_ext_suspend_completed():
 473 // 0x00000001 - routine was entered
 474 // 0x00000010 - routine return false at end
 475 // 0x00000100 - thread exited (return false)
 476 // 0x00000200 - suspend request cancelled (return false)
 477 // 0x00000400 - thread suspended (return true)
 478 // 0x00001000 - thread is in a suspend equivalent state (return true)
 479 // 0x00002000 - thread is native and walkable (return true)
 480 // 0x00004000 - thread is native_trans and walkable (needed retry)
 481 //
 482 // set in wait_for_ext_suspend_completion():
 483 // 0x00010000 - routine was entered
 484 // 0x00020000 - suspend request cancelled before loop (return false)
 485 // 0x00040000 - thread suspended before loop (return true)
 486 // 0x00080000 - suspend request cancelled in loop (return false)
 487 // 0x00100000 - thread suspended in loop (return true)
 488 // 0x00200000 - suspend not completed during retry loop (return false)
 489 
 490 // Helper class for tracing suspend wait debug bits.
 491 //
 492 // 0x00000100 indicates that the target thread exited before it could
 493 // self-suspend which is not a wait failure. 0x00000200, 0x00020000 and
 494 // 0x00080000 each indicate a cancelled suspend request so they don't
 495 // count as wait failures either.
 496 #define DEBUG_FALSE_BITS (0x00000010 | 0x00200000)
 497 
 498 class TraceSuspendDebugBits : public StackObj {
 499  private:
 500   JavaThread * jt;
 501   bool         is_wait;
 502   bool         called_by_wait;  // meaningful when !is_wait
 503   uint32_t *   bits;
 504 
 505  public:
 506   TraceSuspendDebugBits(JavaThread *_jt, bool _is_wait, bool _called_by_wait,
 507                         uint32_t *_bits) {
 508     jt             = _jt;
 509     is_wait        = _is_wait;
 510     called_by_wait = _called_by_wait;
 511     bits           = _bits;
 512   }
 513 
 514   ~TraceSuspendDebugBits() {
 515     if (!is_wait) {
 516 #if 1
 517       // By default, don't trace bits for is_ext_suspend_completed() calls.
 518       // That trace is very chatty.
 519       return;
 520 #else
 521       if (!called_by_wait) {
 522         // If tracing for is_ext_suspend_completed() is enabled, then only
 523         // trace calls to it from wait_for_ext_suspend_completion()
 524         return;
 525       }
 526 #endif
 527     }
 528 
 529     if (AssertOnSuspendWaitFailure || TraceSuspendWaitFailures) {
 530       if (bits != NULL && (*bits & DEBUG_FALSE_BITS) != 0) {
 531         MutexLocker ml(Threads_lock);  // needed for get_thread_name()
 532         ResourceMark rm;
 533 
 534         tty->print_cr(
 535                       "Failed wait_for_ext_suspend_completion(thread=%s, debug_bits=%x)",
 536                       jt->get_thread_name(), *bits);
 537 
 538         guarantee(!AssertOnSuspendWaitFailure, "external suspend wait failed");
 539       }
 540     }
 541   }
 542 };
 543 #undef DEBUG_FALSE_BITS
 544 
 545 
 546 bool JavaThread::is_ext_suspend_completed(bool called_by_wait, int delay,
 547                                           uint32_t *bits) {
 548   TraceSuspendDebugBits tsdb(this, false /* !is_wait */, called_by_wait, bits);
 549 
 550   bool did_trans_retry = false;  // only do thread_in_native_trans retry once
 551   bool do_trans_retry;           // flag to force the retry
 552 
 553   *bits |= 0x00000001;
 554 
 555   do {
 556     do_trans_retry = false;
 557 
 558     if (is_exiting()) {
 559       // Thread is in the process of exiting. This is always checked
 560       // first to reduce the risk of dereferencing a freed JavaThread.
 561       *bits |= 0x00000100;
 562       return false;
 563     }
 564 
 565     if (!is_external_suspend()) {
 566       // Suspend request is cancelled. This is always checked before
 567       // is_ext_suspended() to reduce the risk of a rogue resume
 568       // confusing the thread that made the suspend request.
 569       *bits |= 0x00000200;
 570       return false;
 571     }
 572 
 573     if (is_ext_suspended()) {
 574       // thread is suspended
 575       *bits |= 0x00000400;
 576       return true;
 577     }
 578 
 579     // Now that we no longer do hard suspends of threads running
 580     // native code, the target thread can be changing thread state
 581     // while we are in this routine:
 582     //
 583     //   _thread_in_native -> _thread_in_native_trans -> _thread_blocked
 584     //
 585     // We save a copy of the thread state as observed at this moment
 586     // and make our decision about suspend completeness based on the
 587     // copy. This closes the race where the thread state is seen as
 588     // _thread_in_native_trans in the if-thread_blocked check, but is
 589     // seen as _thread_blocked in if-thread_in_native_trans check.
 590     JavaThreadState save_state = thread_state();
 591 
 592     if (save_state == _thread_blocked && is_suspend_equivalent()) {
 593       // If the thread's state is _thread_blocked and this blocking
 594       // condition is known to be equivalent to a suspend, then we can
 595       // consider the thread to be externally suspended. This means that
 596       // the code that sets _thread_blocked has been modified to do
 597       // self-suspension if the blocking condition releases. We also
 598       // used to check for CONDVAR_WAIT here, but that is now covered by
 599       // the _thread_blocked with self-suspension check.
 600       //
 601       // Return true since we wouldn't be here unless there was still an
 602       // external suspend request.
 603       *bits |= 0x00001000;
 604       return true;
 605     } else if (save_state == _thread_in_native && frame_anchor()->walkable()) {
 606       // Threads running native code will self-suspend on native==>VM/Java
 607       // transitions. If its stack is walkable (should always be the case
 608       // unless this function is called before the actual java_suspend()
 609       // call), then the wait is done.
 610       *bits |= 0x00002000;
 611       return true;
 612     } else if (!called_by_wait && !did_trans_retry &&
 613                save_state == _thread_in_native_trans &&
 614                frame_anchor()->walkable()) {
 615       // The thread is transitioning from thread_in_native to another
 616       // thread state. check_safepoint_and_suspend_for_native_trans()
 617       // will force the thread to self-suspend. If it hasn't gotten
 618       // there yet we may have caught the thread in-between the native
 619       // code check above and the self-suspend. Lucky us. If we were
 620       // called by wait_for_ext_suspend_completion(), then it
 621       // will be doing the retries so we don't have to.
 622       //
 623       // Since we use the saved thread state in the if-statement above,
 624       // there is a chance that the thread has already transitioned to
 625       // _thread_blocked by the time we get here. In that case, we will
 626       // make a single unnecessary pass through the logic below. This
 627       // doesn't hurt anything since we still do the trans retry.
 628 
 629       *bits |= 0x00004000;
 630 
 631       // Once the thread leaves thread_in_native_trans for another
 632       // thread state, we break out of this retry loop. We shouldn't
 633       // need this flag to prevent us from getting back here, but
 634       // sometimes paranoia is good.
 635       did_trans_retry = true;
 636 
 637       // We wait for the thread to transition to a more usable state.
 638       for (int i = 1; i <= SuspendRetryCount; i++) {
 639         // We used to do an "os::yield_all(i)" call here with the intention
 640         // that yielding would increase on each retry. However, the parameter
 641         // is ignored on Linux which means the yield didn't scale up. Waiting
 642         // on the SR_lock below provides a much more predictable scale up for
 643         // the delay. It also provides a simple/direct point to check for any
 644         // safepoint requests from the VMThread
 645 
 646         // temporarily drops SR_lock while doing wait with safepoint check
 647         // (if we're a JavaThread - the WatcherThread can also call this)
 648         // and increase delay with each retry
 649         SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 650 
 651         // check the actual thread state instead of what we saved above
 652         if (thread_state() != _thread_in_native_trans) {
 653           // the thread has transitioned to another thread state so
 654           // try all the checks (except this one) one more time.
 655           do_trans_retry = true;
 656           break;
 657         }
 658       } // end retry loop
 659 
 660 
 661     }
 662   } while (do_trans_retry);
 663 
 664   *bits |= 0x00000010;
 665   return false;
 666 }
 667 
 668 // Wait for an external suspend request to complete (or be cancelled).
 669 // Returns true if the thread is externally suspended and false otherwise.
 670 //
 671 bool JavaThread::wait_for_ext_suspend_completion(int retries, int delay,
 672                                                  uint32_t *bits) {
 673   TraceSuspendDebugBits tsdb(this, true /* is_wait */,
 674                              false /* !called_by_wait */, bits);
 675 
 676   // local flag copies to minimize SR_lock hold time
 677   bool is_suspended;
 678   bool pending;
 679   uint32_t reset_bits;
 680 
 681   // set a marker so is_ext_suspend_completed() knows we are the caller
 682   *bits |= 0x00010000;
 683 
 684   // We use reset_bits to reinitialize the bits value at the top of
 685   // each retry loop. This allows the caller to make use of any
 686   // unused bits for their own marking purposes.
 687   reset_bits = *bits;
 688 
 689   {
 690     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 691     is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 692                                             delay, bits);
 693     pending = is_external_suspend();
 694   }
 695   // must release SR_lock to allow suspension to complete
 696 
 697   if (!pending) {
 698     // A cancelled suspend request is the only false return from
 699     // is_ext_suspend_completed() that keeps us from entering the
 700     // retry loop.
 701     *bits |= 0x00020000;
 702     return false;
 703   }
 704 
 705   if (is_suspended) {
 706     *bits |= 0x00040000;
 707     return true;
 708   }
 709 
 710   for (int i = 1; i <= retries; i++) {
 711     *bits = reset_bits;  // reinit to only track last retry
 712 
 713     // We used to do an "os::yield_all(i)" call here with the intention
 714     // that yielding would increase on each retry. However, the parameter
 715     // is ignored on Linux which means the yield didn't scale up. Waiting
 716     // on the SR_lock below provides a much more predictable scale up for
 717     // the delay. It also provides a simple/direct point to check for any
 718     // safepoint requests from the VMThread
 719 
 720     {
 721       MutexLocker ml(SR_lock());
 722       // wait with safepoint check (if we're a JavaThread - the WatcherThread
 723       // can also call this)  and increase delay with each retry
 724       SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 725 
 726       is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 727                                               delay, bits);
 728 
 729       // It is possible for the external suspend request to be cancelled
 730       // (by a resume) before the actual suspend operation is completed.
 731       // Refresh our local copy to see if we still need to wait.
 732       pending = is_external_suspend();
 733     }
 734 
 735     if (!pending) {
 736       // A cancelled suspend request is the only false return from
 737       // is_ext_suspend_completed() that keeps us from staying in the
 738       // retry loop.
 739       *bits |= 0x00080000;
 740       return false;
 741     }
 742 
 743     if (is_suspended) {
 744       *bits |= 0x00100000;
 745       return true;
 746     }
 747   } // end retry loop
 748 
 749   // thread did not suspend after all our retries
 750   *bits |= 0x00200000;
 751   return false;
 752 }
 753 
 754 // Called from API entry points which perform stack walking. If the
 755 // associated JavaThread is the current thread, then wait_for_suspend
 756 // is not used. Otherwise, it determines if we should wait for the
 757 // "other" thread to complete external suspension. (NOTE: in future
 758 // releases the suspension mechanism should be reimplemented so this
 759 // is not necessary.)
 760 //
 761 bool
 762 JavaThread::is_thread_fully_suspended(bool wait_for_suspend, uint32_t *bits) {
 763   if (this != JavaThread::current()) {
 764     // "other" threads require special handling.
 765     if (wait_for_suspend) {
 766       // We are allowed to wait for the external suspend to complete
 767       // so give the other thread a chance to get suspended.
 768       if (!wait_for_ext_suspend_completion(SuspendRetryCount,
 769                                            SuspendRetryDelay, bits)) {
 770         // Didn't make it so let the caller know.
 771         return false;
 772       }
 773     }
 774     // We aren't allowed to wait for the external suspend to complete
 775     // so if the other thread isn't externally suspended we need to
 776     // let the caller know.
 777     else if (!is_ext_suspend_completed_with_lock(bits)) {
 778       return false;
 779     }
 780   }
 781 
 782   return true;
 783 }
 784 
 785 #ifndef PRODUCT
 786 void JavaThread::record_jump(address target, address instr, const char* file,
 787                              int line) {
 788 
 789   // This should not need to be atomic as the only way for simultaneous
 790   // updates is via interrupts. Even then this should be rare or non-existent
 791   // and we don't care that much anyway.
 792 
 793   int index = _jmp_ring_index;
 794   _jmp_ring_index = (index + 1) & (jump_ring_buffer_size - 1);
 795   _jmp_ring[index]._target = (intptr_t) target;
 796   _jmp_ring[index]._instruction = (intptr_t) instr;
 797   _jmp_ring[index]._file = file;
 798   _jmp_ring[index]._line = line;
 799 }
 800 #endif // PRODUCT
 801 
 802 void Thread::interrupt(Thread* thread) {
 803   debug_only(check_for_dangling_thread_pointer(thread);)
 804   os::interrupt(thread);
 805 }
 806 
 807 bool Thread::is_interrupted(Thread* thread, bool clear_interrupted) {
 808   debug_only(check_for_dangling_thread_pointer(thread);)
 809   // Note:  If clear_interrupted==false, this simply fetches and
 810   // returns the value of the field osthread()->interrupted().
 811   return os::is_interrupted(thread, clear_interrupted);
 812 }
 813 
 814 
 815 // GC Support
 816 bool Thread::claim_oops_do_par_case(int strong_roots_parity) {
 817   int thread_parity = _oops_do_parity;
 818   if (thread_parity != strong_roots_parity) {
 819     jint res = Atomic::cmpxchg(strong_roots_parity, &_oops_do_parity, thread_parity);
 820     if (res == thread_parity) {
 821       return true;
 822     } else {
 823       guarantee(res == strong_roots_parity, "Or else what?");
 824       return false;
 825     }
 826   }
 827   return false;
 828 }
 829 
 830 void Thread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
 831   active_handles()->oops_do(f);
 832   // Do oop for ThreadShadow
 833   f->do_oop((oop*)&_pending_exception);
 834   handle_area()->oops_do(f);
 835 
 836   if (MonitorInUseLists) {
 837     // When using thread local monitor lists, we scan them here,
 838     // and the remaining global monitors in ObjectSynchronizer::oops_do().
 839     ObjectSynchronizer::thread_local_used_oops_do(this, f);
 840   }
 841 }
 842 
 843 void Thread::metadata_handles_do(void f(Metadata*)) {
 844   // Only walk the Handles in Thread.
 845   if (metadata_handles() != NULL) {
 846     for (int i = 0; i< metadata_handles()->length(); i++) {
 847       f(metadata_handles()->at(i));
 848     }
 849   }
 850 }
 851 
 852 void Thread::print_on(outputStream* st) const {
 853   // get_priority assumes osthread initialized
 854   if (osthread() != NULL) {
 855     int os_prio;
 856     if (os::get_native_priority(this, &os_prio) == OS_OK) {
 857       st->print("os_prio=%d ", os_prio);
 858     }
 859     st->print("tid=" INTPTR_FORMAT " ", p2i(this));
 860     ext().print_on(st);
 861     osthread()->print_on(st);
 862   }
 863   if (_threads_hazard_ptr != NULL) {
 864     st->print("_threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr));
 865   }
 866   if (_nested_threads_hazard_ptr != NULL) {
 867     print_nested_threads_hazard_ptrs_on(st);
 868   }
 869   st->print(" ");
 870   debug_only(if (WizardMode) print_owned_locks_on(st);)
 871 }
 872 
 873 void Thread::print_nested_threads_hazard_ptrs_on(outputStream* st) const {
 874   assert(_nested_threads_hazard_ptr != NULL, "must be set to print");
 875 
 876   if (EnableThreadSMRStatistics) {
 877     st->print(", _nested_threads_hazard_ptr_cnt=%u", _nested_threads_hazard_ptr_cnt);
 878   }
 879   st->print(", _nested_threads_hazard_ptrs=");
 880   for (NestedThreadsList* node = _nested_threads_hazard_ptr; node != NULL;
 881        node = node->next()) {
 882     if (node != _nested_threads_hazard_ptr) {
 883       // First node does not need a comma-space separator.
 884       st->print(", ");
 885     }
 886     st->print(INTPTR_FORMAT, p2i(node->t_list()));
 887   }
 888 }
 889 
 890 // Thread::print_on_error() is called by fatal error handler. Don't use
 891 // any lock or allocate memory.
 892 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
 893   assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
 894 
 895   if (is_VM_thread())                 { st->print("VMThread"); }
 896   else if (is_GC_task_thread())       { st->print("GCTaskThread"); }
 897   else if (is_Watcher_thread())       { st->print("WatcherThread"); }
 898   else if (is_ConcurrentGC_thread())  { st->print("ConcurrentGCThread"); }
 899   else                                { st->print("Thread"); }
 900 
 901   if (is_Named_thread()) {
 902     st->print(" \"%s\"", name());
 903   }
 904 
 905   st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
 906             p2i(stack_end()), p2i(stack_base()));
 907 
 908   if (osthread()) {
 909     st->print(" [id=%d]", osthread()->thread_id());
 910   }
 911 
 912   if (_threads_hazard_ptr != NULL) {
 913     st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr));
 914   }
 915   if (_nested_threads_hazard_ptr != NULL) {
 916     print_nested_threads_hazard_ptrs_on(st);
 917   }
 918 }
 919 
 920 void Thread::print_value_on(outputStream* st) const {
 921   if (is_Named_thread()) {
 922     st->print(" \"%s\" ", name());
 923   }
 924   st->print(INTPTR_FORMAT, p2i(this));   // print address
 925 }
 926 
 927 #ifdef ASSERT
 928 void Thread::print_owned_locks_on(outputStream* st) const {
 929   Monitor *cur = _owned_locks;
 930   if (cur == NULL) {
 931     st->print(" (no locks) ");
 932   } else {
 933     st->print_cr(" Locks owned:");
 934     while (cur) {
 935       cur->print_on(st);
 936       cur = cur->next();
 937     }
 938   }
 939 }
 940 
 941 static int ref_use_count  = 0;
 942 
 943 bool Thread::owns_locks_but_compiled_lock() const {
 944   for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 945     if (cur != Compile_lock) return true;
 946   }
 947   return false;
 948 }
 949 
 950 
 951 #endif
 952 
 953 #ifndef PRODUCT
 954 
 955 // The flag: potential_vm_operation notifies if this particular safepoint state could potentially
 956 // invoke the vm-thread (e.g., an oop allocation). In that case, we also have to make sure that
 957 // no threads which allow_vm_block's are held
 958 void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) {
 959   // Check if current thread is allowed to block at a safepoint
 960   if (!(_allow_safepoint_count == 0)) {
 961     fatal("Possible safepoint reached by thread that does not allow it");
 962   }
 963   if (is_Java_thread() && ((JavaThread*)this)->thread_state() != _thread_in_vm) {
 964     fatal("LEAF method calling lock?");
 965   }
 966 
 967 #ifdef ASSERT
 968   if (potential_vm_operation && is_Java_thread()
 969       && !Universe::is_bootstrapping()) {
 970     // Make sure we do not hold any locks that the VM thread also uses.
 971     // This could potentially lead to deadlocks
 972     for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 973       // Threads_lock is special, since the safepoint synchronization will not start before this is
 974       // acquired. Hence, a JavaThread cannot be holding it at a safepoint. So is VMOperationRequest_lock,
 975       // since it is used to transfer control between JavaThreads and the VMThread
 976       // Do not *exclude* any locks unless you are absolutely sure it is correct. Ask someone else first!
 977       if ((cur->allow_vm_block() &&
 978            cur != Threads_lock &&
 979            cur != Compile_lock &&               // Temporary: should not be necessary when we get separate compilation
 980            cur != VMOperationRequest_lock &&
 981            cur != VMOperationQueue_lock) ||
 982            cur->rank() == Mutex::special) {
 983         fatal("Thread holding lock at safepoint that vm can block on: %s", cur->name());
 984       }
 985     }
 986   }
 987 
 988   if (GCALotAtAllSafepoints) {
 989     // We could enter a safepoint here and thus have a gc
 990     InterfaceSupport::check_gc_alot();
 991   }
 992 #endif
 993 }
 994 #endif
 995 
 996 bool Thread::is_in_stack(address adr) const {
 997   assert(Thread::current() == this, "is_in_stack can only be called from current thread");
 998   address end = os::current_stack_pointer();
 999   // Allow non Java threads to call this without stack_base
1000   if (_stack_base == NULL) return true;
1001   if (stack_base() >= adr && adr >= end) return true;
1002 
1003   return false;
1004 }
1005 
1006 bool Thread::is_in_usable_stack(address adr) const {
1007   size_t stack_guard_size = os::uses_stack_guard_pages() ? JavaThread::stack_guard_zone_size() : 0;
1008   size_t usable_stack_size = _stack_size - stack_guard_size;
1009 
1010   return ((adr < stack_base()) && (adr >= stack_base() - usable_stack_size));
1011 }
1012 
1013 
1014 // We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
1015 // However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
1016 // used for compilation in the future. If that change is made, the need for these methods
1017 // should be revisited, and they should be removed if possible.
1018 
1019 bool Thread::is_lock_owned(address adr) const {
1020   return on_local_stack(adr);
1021 }
1022 
1023 bool Thread::set_as_starting_thread() {
1024   // NOTE: this must be called inside the main thread.
1025   return os::create_main_thread((JavaThread*)this);
1026 }
1027 
1028 static void initialize_class(Symbol* class_name, TRAPS) {
1029   Klass* klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
1030   InstanceKlass::cast(klass)->initialize(CHECK);
1031 }
1032 
1033 
1034 // Creates the initial ThreadGroup
1035 static Handle create_initial_thread_group(TRAPS) {
1036   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_ThreadGroup(), true, CHECK_NH);
1037   InstanceKlass* ik = InstanceKlass::cast(k);
1038 
1039   Handle system_instance = ik->allocate_instance_handle(CHECK_NH);
1040   {
1041     JavaValue result(T_VOID);
1042     JavaCalls::call_special(&result,
1043                             system_instance,
1044                             ik,
1045                             vmSymbols::object_initializer_name(),
1046                             vmSymbols::void_method_signature(),
1047                             CHECK_NH);
1048   }
1049   Universe::set_system_thread_group(system_instance());
1050 
1051   Handle main_instance = ik->allocate_instance_handle(CHECK_NH);
1052   {
1053     JavaValue result(T_VOID);
1054     Handle string = java_lang_String::create_from_str("main", CHECK_NH);
1055     JavaCalls::call_special(&result,
1056                             main_instance,
1057                             ik,
1058                             vmSymbols::object_initializer_name(),
1059                             vmSymbols::threadgroup_string_void_signature(),
1060                             system_instance,
1061                             string,
1062                             CHECK_NH);
1063   }
1064   return main_instance;
1065 }
1066 
1067 // Creates the initial Thread
1068 static oop create_initial_thread(Handle thread_group, JavaThread* thread,
1069                                  TRAPS) {
1070   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK_NULL);
1071   InstanceKlass* ik = InstanceKlass::cast(k);
1072   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK_NULL);
1073 
1074   java_lang_Thread::set_thread(thread_oop(), thread);
1075   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1076   thread->set_threadObj(thread_oop());
1077 
1078   Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
1079 
1080   JavaValue result(T_VOID);
1081   JavaCalls::call_special(&result, thread_oop,
1082                           ik,
1083                           vmSymbols::object_initializer_name(),
1084                           vmSymbols::threadgroup_string_void_signature(),
1085                           thread_group,
1086                           string,
1087                           CHECK_NULL);
1088   return thread_oop();
1089 }
1090 
1091 char java_runtime_name[128] = "";
1092 char java_runtime_version[128] = "";
1093 
1094 // extract the JRE name from java.lang.VersionProps.java_runtime_name
1095 static const char* get_java_runtime_name(TRAPS) {
1096   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1097                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1098   fieldDescriptor fd;
1099   bool found = k != NULL &&
1100                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_name_name(),
1101                                                         vmSymbols::string_signature(), &fd);
1102   if (found) {
1103     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1104     if (name_oop == NULL) {
1105       return NULL;
1106     }
1107     const char* name = java_lang_String::as_utf8_string(name_oop,
1108                                                         java_runtime_name,
1109                                                         sizeof(java_runtime_name));
1110     return name;
1111   } else {
1112     return NULL;
1113   }
1114 }
1115 
1116 // extract the JRE version from java.lang.VersionProps.java_runtime_version
1117 static const char* get_java_runtime_version(TRAPS) {
1118   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1119                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1120   fieldDescriptor fd;
1121   bool found = k != NULL &&
1122                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_version_name(),
1123                                                         vmSymbols::string_signature(), &fd);
1124   if (found) {
1125     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1126     if (name_oop == NULL) {
1127       return NULL;
1128     }
1129     const char* name = java_lang_String::as_utf8_string(name_oop,
1130                                                         java_runtime_version,
1131                                                         sizeof(java_runtime_version));
1132     return name;
1133   } else {
1134     return NULL;
1135   }
1136 }
1137 
1138 // General purpose hook into Java code, run once when the VM is initialized.
1139 // The Java library method itself may be changed independently from the VM.
1140 static void call_postVMInitHook(TRAPS) {
1141   Klass* klass = SystemDictionary::resolve_or_null(vmSymbols::jdk_internal_vm_PostVMInitHook(), THREAD);
1142   if (klass != NULL) {
1143     JavaValue result(T_VOID);
1144     JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
1145                            vmSymbols::void_method_signature(),
1146                            CHECK);
1147   }
1148 }
1149 
1150 static void reset_vm_info_property(TRAPS) {
1151   // the vm info string
1152   ResourceMark rm(THREAD);
1153   const char *vm_info = VM_Version::vm_info_string();
1154 
1155   // java.lang.System class
1156   Klass* klass =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
1157 
1158   // setProperty arguments
1159   Handle key_str    = java_lang_String::create_from_str("java.vm.info", CHECK);
1160   Handle value_str  = java_lang_String::create_from_str(vm_info, CHECK);
1161 
1162   // return value
1163   JavaValue r(T_OBJECT);
1164 
1165   // public static String setProperty(String key, String value);
1166   JavaCalls::call_static(&r,
1167                          klass,
1168                          vmSymbols::setProperty_name(),
1169                          vmSymbols::string_string_string_signature(),
1170                          key_str,
1171                          value_str,
1172                          CHECK);
1173 }
1174 
1175 
1176 void JavaThread::allocate_threadObj(Handle thread_group, const char* thread_name,
1177                                     bool daemon, TRAPS) {
1178   assert(thread_group.not_null(), "thread group should be specified");
1179   assert(threadObj() == NULL, "should only create Java thread object once");
1180 
1181   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK);
1182   InstanceKlass* ik = InstanceKlass::cast(k);
1183   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK);
1184 
1185   java_lang_Thread::set_thread(thread_oop(), this);
1186   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1187   set_threadObj(thread_oop());
1188 
1189   JavaValue result(T_VOID);
1190   if (thread_name != NULL) {
1191     Handle name = java_lang_String::create_from_str(thread_name, CHECK);
1192     // Thread gets assigned specified name and null target
1193     JavaCalls::call_special(&result,
1194                             thread_oop,
1195                             ik,
1196                             vmSymbols::object_initializer_name(),
1197                             vmSymbols::threadgroup_string_void_signature(),
1198                             thread_group, // Argument 1
1199                             name,         // Argument 2
1200                             THREAD);
1201   } else {
1202     // Thread gets assigned name "Thread-nnn" and null target
1203     // (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
1204     JavaCalls::call_special(&result,
1205                             thread_oop,
1206                             ik,
1207                             vmSymbols::object_initializer_name(),
1208                             vmSymbols::threadgroup_runnable_void_signature(),
1209                             thread_group, // Argument 1
1210                             Handle(),     // Argument 2
1211                             THREAD);
1212   }
1213 
1214 
1215   if (daemon) {
1216     java_lang_Thread::set_daemon(thread_oop());
1217   }
1218 
1219   if (HAS_PENDING_EXCEPTION) {
1220     return;
1221   }
1222 
1223   Klass* group =  SystemDictionary::ThreadGroup_klass();
1224   Handle threadObj(THREAD, this->threadObj());
1225 
1226   JavaCalls::call_special(&result,
1227                           thread_group,
1228                           group,
1229                           vmSymbols::add_method_name(),
1230                           vmSymbols::thread_void_signature(),
1231                           threadObj,          // Arg 1
1232                           THREAD);
1233 }
1234 
1235 // NamedThread --  non-JavaThread subclasses with multiple
1236 // uniquely named instances should derive from this.
1237 NamedThread::NamedThread() : Thread() {
1238   _name = NULL;
1239   _processed_thread = NULL;
1240   _gc_id = GCId::undefined();
1241 }
1242 
1243 NamedThread::~NamedThread() {
1244   if (_name != NULL) {
1245     FREE_C_HEAP_ARRAY(char, _name);
1246     _name = NULL;
1247   }
1248 }
1249 
1250 void NamedThread::set_name(const char* format, ...) {
1251   guarantee(_name == NULL, "Only get to set name once.");
1252   _name = NEW_C_HEAP_ARRAY(char, max_name_len, mtThread);
1253   guarantee(_name != NULL, "alloc failure");
1254   va_list ap;
1255   va_start(ap, format);
1256   jio_vsnprintf(_name, max_name_len, format, ap);
1257   va_end(ap);
1258 }
1259 
1260 void NamedThread::initialize_named_thread() {
1261   set_native_thread_name(name());
1262 }
1263 
1264 void NamedThread::print_on(outputStream* st) const {
1265   st->print("\"%s\" ", name());
1266   Thread::print_on(st);
1267   st->cr();
1268 }
1269 
1270 
1271 // ======= WatcherThread ========
1272 
1273 // The watcher thread exists to simulate timer interrupts.  It should
1274 // be replaced by an abstraction over whatever native support for
1275 // timer interrupts exists on the platform.
1276 
1277 WatcherThread* WatcherThread::_watcher_thread   = NULL;
1278 bool WatcherThread::_startable = false;
1279 volatile bool  WatcherThread::_should_terminate = false;
1280 
1281 WatcherThread::WatcherThread() : Thread() {
1282   assert(watcher_thread() == NULL, "we can only allocate one WatcherThread");
1283   if (os::create_thread(this, os::watcher_thread)) {
1284     _watcher_thread = this;
1285 
1286     // Set the watcher thread to the highest OS priority which should not be
1287     // used, unless a Java thread with priority java.lang.Thread.MAX_PRIORITY
1288     // is created. The only normal thread using this priority is the reference
1289     // handler thread, which runs for very short intervals only.
1290     // If the VMThread's priority is not lower than the WatcherThread profiling
1291     // will be inaccurate.
1292     os::set_priority(this, MaxPriority);
1293     if (!DisableStartThread) {
1294       os::start_thread(this);
1295     }
1296   }
1297 }
1298 
1299 int WatcherThread::sleep() const {
1300   // The WatcherThread does not participate in the safepoint protocol
1301   // for the PeriodicTask_lock because it is not a JavaThread.
1302   MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
1303 
1304   if (_should_terminate) {
1305     // check for termination before we do any housekeeping or wait
1306     return 0;  // we did not sleep.
1307   }
1308 
1309   // remaining will be zero if there are no tasks,
1310   // causing the WatcherThread to sleep until a task is
1311   // enrolled
1312   int remaining = PeriodicTask::time_to_wait();
1313   int time_slept = 0;
1314 
1315   // we expect this to timeout - we only ever get unparked when
1316   // we should terminate or when a new task has been enrolled
1317   OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
1318 
1319   jlong time_before_loop = os::javaTimeNanos();
1320 
1321   while (true) {
1322     bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag,
1323                                             remaining);
1324     jlong now = os::javaTimeNanos();
1325 
1326     if (remaining == 0) {
1327       // if we didn't have any tasks we could have waited for a long time
1328       // consider the time_slept zero and reset time_before_loop
1329       time_slept = 0;
1330       time_before_loop = now;
1331     } else {
1332       // need to recalculate since we might have new tasks in _tasks
1333       time_slept = (int) ((now - time_before_loop) / 1000000);
1334     }
1335 
1336     // Change to task list or spurious wakeup of some kind
1337     if (timedout || _should_terminate) {
1338       break;
1339     }
1340 
1341     remaining = PeriodicTask::time_to_wait();
1342     if (remaining == 0) {
1343       // Last task was just disenrolled so loop around and wait until
1344       // another task gets enrolled
1345       continue;
1346     }
1347 
1348     remaining -= time_slept;
1349     if (remaining <= 0) {
1350       break;
1351     }
1352   }
1353 
1354   return time_slept;
1355 }
1356 
1357 void WatcherThread::run() {
1358   assert(this == watcher_thread(), "just checking");
1359 
1360   this->record_stack_base_and_size();
1361   this->set_native_thread_name(this->name());
1362   this->set_active_handles(JNIHandleBlock::allocate_block());
1363   while (true) {
1364     assert(watcher_thread() == Thread::current(), "thread consistency check");
1365     assert(watcher_thread() == this, "thread consistency check");
1366 
1367     // Calculate how long it'll be until the next PeriodicTask work
1368     // should be done, and sleep that amount of time.
1369     int time_waited = sleep();
1370 
1371     if (VMError::is_error_reported()) {
1372       // A fatal error has happened, the error handler(VMError::report_and_die)
1373       // should abort JVM after creating an error log file. However in some
1374       // rare cases, the error handler itself might deadlock. Here periodically
1375       // check for error reporting timeouts, and if it happens, just proceed to
1376       // abort the VM.
1377 
1378       // This code is in WatcherThread because WatcherThread wakes up
1379       // periodically so the fatal error handler doesn't need to do anything;
1380       // also because the WatcherThread is less likely to crash than other
1381       // threads.
1382 
1383       for (;;) {
1384         // Note: we use naked sleep in this loop because we want to avoid using
1385         // any kind of VM infrastructure which may be broken at this point.
1386         if (VMError::check_timeout()) {
1387           // We hit error reporting timeout. Error reporting was interrupted and
1388           // will be wrapping things up now (closing files etc). Give it some more
1389           // time, then quit the VM.
1390           os::naked_short_sleep(200);
1391           // Print a message to stderr.
1392           fdStream err(defaultStream::output_fd());
1393           err.print_raw_cr("# [ timer expired, abort... ]");
1394           // skip atexit/vm_exit/vm_abort hooks
1395           os::die();
1396         }
1397 
1398         // Wait a second, then recheck for timeout.
1399         os::naked_short_sleep(999);
1400       }
1401     }
1402 
1403     if (_should_terminate) {
1404       // check for termination before posting the next tick
1405       break;
1406     }
1407 
1408     PeriodicTask::real_time_tick(time_waited);
1409   }
1410 
1411   // Signal that it is terminated
1412   {
1413     MutexLockerEx mu(Terminator_lock, Mutex::_no_safepoint_check_flag);
1414     _watcher_thread = NULL;
1415     Terminator_lock->notify();
1416   }
1417 }
1418 
1419 void WatcherThread::start() {
1420   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1421 
1422   if (watcher_thread() == NULL && _startable) {
1423     _should_terminate = false;
1424     // Create the single instance of WatcherThread
1425     new WatcherThread();
1426   }
1427 }
1428 
1429 void WatcherThread::make_startable() {
1430   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1431   _startable = true;
1432 }
1433 
1434 void WatcherThread::stop() {
1435   {
1436     // Follow normal safepoint aware lock enter protocol since the
1437     // WatcherThread is stopped by another JavaThread.
1438     MutexLocker ml(PeriodicTask_lock);
1439     _should_terminate = true;
1440 
1441     WatcherThread* watcher = watcher_thread();
1442     if (watcher != NULL) {
1443       // unpark the WatcherThread so it can see that it should terminate
1444       watcher->unpark();
1445     }
1446   }
1447 
1448   MutexLocker mu(Terminator_lock);
1449 
1450   while (watcher_thread() != NULL) {
1451     // This wait should make safepoint checks, wait without a timeout,
1452     // and wait as a suspend-equivalent condition.
1453     Terminator_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
1454                           Mutex::_as_suspend_equivalent_flag);
1455   }
1456 }
1457 
1458 void WatcherThread::unpark() {
1459   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1460   PeriodicTask_lock->notify();
1461 }
1462 
1463 void WatcherThread::print_on(outputStream* st) const {
1464   st->print("\"%s\" ", name());
1465   Thread::print_on(st);
1466   st->cr();
1467 }
1468 
1469 // ======= JavaThread ========
1470 
1471 #if INCLUDE_JVMCI
1472 
1473 jlong* JavaThread::_jvmci_old_thread_counters;
1474 
1475 bool jvmci_counters_include(JavaThread* thread) {
1476   oop threadObj = thread->threadObj();
1477   return !JVMCICountersExcludeCompiler || !thread->is_Compiler_thread();
1478 }
1479 
1480 void JavaThread::collect_counters(typeArrayOop array) {
1481   if (JVMCICounterSize > 0) {
1482     // dcubed - Looks like the Threads_lock is for stable access
1483     // to _jvmci_old_thread_counters and _jvmci_counters.
1484     MutexLocker tl(Threads_lock);
1485     JavaThreadIteratorWithHandle jtiwh;
1486     for (int i = 0; i < array->length(); i++) {
1487       array->long_at_put(i, _jvmci_old_thread_counters[i]);
1488     }
1489     for (; JavaThread *tp = jtiwh.next(); ) {
1490       if (jvmci_counters_include(tp)) {
1491         for (int i = 0; i < array->length(); i++) {
1492           array->long_at_put(i, array->long_at(i) + tp->_jvmci_counters[i]);
1493         }
1494       }
1495     }
1496   }
1497 }
1498 
1499 #endif // INCLUDE_JVMCI
1500 
1501 // A JavaThread is a normal Java thread
1502 
1503 void JavaThread::initialize() {
1504   // Initialize fields
1505 
1506   set_saved_exception_pc(NULL);
1507   set_threadObj(NULL);
1508   _anchor.clear();
1509   set_entry_point(NULL);
1510   set_jni_functions(jni_functions());
1511   set_callee_target(NULL);
1512   set_vm_result(NULL);
1513   set_vm_result_2(NULL);
1514   set_vframe_array_head(NULL);
1515   set_vframe_array_last(NULL);
1516   set_deferred_locals(NULL);
1517   set_deopt_mark(NULL);
1518   set_deopt_compiled_method(NULL);
1519   clear_must_deopt_id();
1520   set_monitor_chunks(NULL);
1521   set_next(NULL);
1522   _on_thread_list = false;
1523   set_thread_state(_thread_new);
1524   _terminated = _not_terminated;
1525   _privileged_stack_top = NULL;
1526   _array_for_gc = NULL;
1527   _suspend_equivalent = false;
1528   _in_deopt_handler = 0;
1529   _doing_unsafe_access = false;
1530   _stack_guard_state = stack_guard_unused;
1531 #if INCLUDE_JVMCI
1532   _pending_monitorenter = false;
1533   _pending_deoptimization = -1;
1534   _pending_failed_speculation = NULL;
1535   _pending_transfer_to_interpreter = false;
1536   _adjusting_comp_level = false;
1537   _jvmci._alternate_call_target = NULL;
1538   assert(_jvmci._implicit_exception_pc == NULL, "must be");
1539   if (JVMCICounterSize > 0) {
1540     _jvmci_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
1541     memset(_jvmci_counters, 0, sizeof(jlong) * JVMCICounterSize);
1542   } else {
1543     _jvmci_counters = NULL;
1544   }
1545 #endif // INCLUDE_JVMCI
1546   _reserved_stack_activation = NULL;  // stack base not known yet
1547   (void)const_cast<oop&>(_exception_oop = oop(NULL));
1548   _exception_pc  = 0;
1549   _exception_handler_pc = 0;
1550   _is_method_handle_return = 0;
1551   _jvmti_thread_state= NULL;
1552   _should_post_on_exceptions_flag = JNI_FALSE;
1553   _jvmti_get_loaded_classes_closure = NULL;
1554   _interp_only_mode    = 0;
1555   _special_runtime_exit_condition = _no_async_condition;
1556   _pending_async_exception = NULL;
1557   _thread_stat = NULL;
1558   _thread_stat = new ThreadStatistics();
1559   _blocked_on_compilation = false;
1560   _jni_active_critical = 0;
1561   _pending_jni_exception_check_fn = NULL;
1562   _do_not_unlock_if_synchronized = false;
1563   _cached_monitor_info = NULL;
1564   _parker = Parker::Allocate(this);
1565 
1566 #ifndef PRODUCT
1567   _jmp_ring_index = 0;
1568   for (int ji = 0; ji < jump_ring_buffer_size; ji++) {
1569     record_jump(NULL, NULL, NULL, 0);
1570   }
1571 #endif // PRODUCT
1572 
1573   // Setup safepoint state info for this thread
1574   ThreadSafepointState::create(this);
1575 
1576   debug_only(_java_call_counter = 0);
1577 
1578   // JVMTI PopFrame support
1579   _popframe_condition = popframe_inactive;
1580   _popframe_preserved_args = NULL;
1581   _popframe_preserved_args_size = 0;
1582   _frames_to_pop_failed_realloc = 0;
1583 
1584   if (SafepointMechanism::uses_thread_local_poll()) {
1585     SafepointMechanism::initialize_header(this);
1586   }
1587 
1588   pd_initialize();
1589 }
1590 
1591 #if INCLUDE_ALL_GCS
1592 SATBMarkQueueSet JavaThread::_satb_mark_queue_set;
1593 DirtyCardQueueSet JavaThread::_dirty_card_queue_set;
1594 #endif // INCLUDE_ALL_GCS
1595 
1596 JavaThread::JavaThread(bool is_attaching_via_jni) :
1597                        Thread()
1598 #if INCLUDE_ALL_GCS
1599                        , _satb_mark_queue(&_satb_mark_queue_set),
1600                        _dirty_card_queue(&_dirty_card_queue_set)
1601 #endif // INCLUDE_ALL_GCS
1602 {
1603   initialize();
1604   if (is_attaching_via_jni) {
1605     _jni_attach_state = _attaching_via_jni;
1606   } else {
1607     _jni_attach_state = _not_attaching_via_jni;
1608   }
1609   assert(deferred_card_mark().is_empty(), "Default MemRegion ctor");
1610 }
1611 
1612 bool JavaThread::reguard_stack(address cur_sp) {
1613   if (_stack_guard_state != stack_guard_yellow_reserved_disabled
1614       && _stack_guard_state != stack_guard_reserved_disabled) {
1615     return true; // Stack already guarded or guard pages not needed.
1616   }
1617 
1618   if (register_stack_overflow()) {
1619     // For those architectures which have separate register and
1620     // memory stacks, we must check the register stack to see if
1621     // it has overflowed.
1622     return false;
1623   }
1624 
1625   // Java code never executes within the yellow zone: the latter is only
1626   // there to provoke an exception during stack banging.  If java code
1627   // is executing there, either StackShadowPages should be larger, or
1628   // some exception code in c1, c2 or the interpreter isn't unwinding
1629   // when it should.
1630   guarantee(cur_sp > stack_reserved_zone_base(),
1631             "not enough space to reguard - increase StackShadowPages");
1632   if (_stack_guard_state == stack_guard_yellow_reserved_disabled) {
1633     enable_stack_yellow_reserved_zone();
1634     if (reserved_stack_activation() != stack_base()) {
1635       set_reserved_stack_activation(stack_base());
1636     }
1637   } else if (_stack_guard_state == stack_guard_reserved_disabled) {
1638     set_reserved_stack_activation(stack_base());
1639     enable_stack_reserved_zone();
1640   }
1641   return true;
1642 }
1643 
1644 bool JavaThread::reguard_stack(void) {
1645   return reguard_stack(os::current_stack_pointer());
1646 }
1647 
1648 
1649 void JavaThread::block_if_vm_exited() {
1650   if (_terminated == _vm_exited) {
1651     // _vm_exited is set at safepoint, and Threads_lock is never released
1652     // we will block here forever
1653     Threads_lock->lock_without_safepoint_check();
1654     ShouldNotReachHere();
1655   }
1656 }
1657 
1658 
1659 // Remove this ifdef when C1 is ported to the compiler interface.
1660 static void compiler_thread_entry(JavaThread* thread, TRAPS);
1661 static void sweeper_thread_entry(JavaThread* thread, TRAPS);
1662 
1663 JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
1664                        Thread()
1665 #if INCLUDE_ALL_GCS
1666                        , _satb_mark_queue(&_satb_mark_queue_set),
1667                        _dirty_card_queue(&_dirty_card_queue_set)
1668 #endif // INCLUDE_ALL_GCS
1669 {
1670   initialize();
1671   _jni_attach_state = _not_attaching_via_jni;
1672   set_entry_point(entry_point);
1673   // Create the native thread itself.
1674   // %note runtime_23
1675   os::ThreadType thr_type = os::java_thread;
1676   thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
1677                                                      os::java_thread;
1678   os::create_thread(this, thr_type, stack_sz);
1679   // The _osthread may be NULL here because we ran out of memory (too many threads active).
1680   // We need to throw and OutOfMemoryError - however we cannot do this here because the caller
1681   // may hold a lock and all locks must be unlocked before throwing the exception (throwing
1682   // the exception consists of creating the exception object & initializing it, initialization
1683   // will leave the VM via a JavaCall and then all locks must be unlocked).
1684   //
1685   // The thread is still suspended when we reach here. Thread must be explicit started
1686   // by creator! Furthermore, the thread must also explicitly be added to the Threads list
1687   // by calling Threads:add. The reason why this is not done here, is because the thread
1688   // object must be fully initialized (take a look at JVM_Start)
1689 }
1690 
1691 JavaThread::~JavaThread() {
1692 
1693   // JSR166 -- return the parker to the free list
1694   Parker::Release(_parker);
1695   _parker = NULL;
1696 
1697   // Free any remaining  previous UnrollBlock
1698   vframeArray* old_array = vframe_array_last();
1699 
1700   if (old_array != NULL) {
1701     Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
1702     old_array->set_unroll_block(NULL);
1703     delete old_info;
1704     delete old_array;
1705   }
1706 
1707   GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred = deferred_locals();
1708   if (deferred != NULL) {
1709     // This can only happen if thread is destroyed before deoptimization occurs.
1710     assert(deferred->length() != 0, "empty array!");
1711     do {
1712       jvmtiDeferredLocalVariableSet* dlv = deferred->at(0);
1713       deferred->remove_at(0);
1714       // individual jvmtiDeferredLocalVariableSet are CHeapObj's
1715       delete dlv;
1716     } while (deferred->length() != 0);
1717     delete deferred;
1718   }
1719 
1720   // All Java related clean up happens in exit
1721   ThreadSafepointState::destroy(this);
1722   if (_thread_stat != NULL) delete _thread_stat;
1723 
1724 #if INCLUDE_JVMCI
1725   if (JVMCICounterSize > 0) {
1726     if (jvmci_counters_include(this)) {
1727       for (int i = 0; i < JVMCICounterSize; i++) {
1728         _jvmci_old_thread_counters[i] += _jvmci_counters[i];
1729       }
1730     }
1731     FREE_C_HEAP_ARRAY(jlong, _jvmci_counters);
1732   }
1733 #endif // INCLUDE_JVMCI
1734 }
1735 
1736 
1737 // The first routine called by a new Java thread
1738 void JavaThread::run() {
1739   // initialize thread-local alloc buffer related fields
1740   this->initialize_tlab();
1741 
1742   // used to test validity of stack trace backs
1743   this->record_base_of_stack_pointer();
1744 
1745   // Record real stack base and size.
1746   this->record_stack_base_and_size();
1747 
1748   this->create_stack_guard_pages();
1749 
1750   this->cache_global_variables();
1751 
1752   // Thread is now sufficient initialized to be handled by the safepoint code as being
1753   // in the VM. Change thread state from _thread_new to _thread_in_vm
1754   ThreadStateTransition::transition_and_fence(this, _thread_new, _thread_in_vm);
1755 
1756   assert(JavaThread::current() == this, "sanity check");
1757   assert(!Thread::current()->owns_locks(), "sanity check");
1758 
1759   DTRACE_THREAD_PROBE(start, this);
1760 
1761   // This operation might block. We call that after all safepoint checks for a new thread has
1762   // been completed.
1763   this->set_active_handles(JNIHandleBlock::allocate_block());
1764 
1765   if (JvmtiExport::should_post_thread_life()) {
1766     JvmtiExport::post_thread_start(this);
1767   }
1768 
1769   EventThreadStart event;
1770   if (event.should_commit()) {
1771     event.set_thread(THREAD_TRACE_ID(this));
1772     event.commit();
1773   }
1774 
1775   // We call another function to do the rest so we are sure that the stack addresses used
1776   // from there will be lower than the stack base just computed
1777   thread_main_inner();
1778 
1779   // Note, thread is no longer valid at this point!
1780 }
1781 
1782 
1783 void JavaThread::thread_main_inner() {
1784   assert(JavaThread::current() == this, "sanity check");
1785   assert(this->threadObj() != NULL, "just checking");
1786 
1787   // Execute thread entry point unless this thread has a pending exception
1788   // or has been stopped before starting.
1789   // Note: Due to JVM_StopThread we can have pending exceptions already!
1790   if (!this->has_pending_exception() &&
1791       !java_lang_Thread::is_stillborn(this->threadObj())) {
1792     {
1793       ResourceMark rm(this);
1794       this->set_native_thread_name(this->get_thread_name());
1795     }
1796     HandleMark hm(this);
1797     this->entry_point()(this, this);
1798   }
1799 
1800   DTRACE_THREAD_PROBE(stop, this);
1801 
1802   this->exit(false);
1803   this->smr_delete();
1804 }
1805 
1806 
1807 static void ensure_join(JavaThread* thread) {
1808   // We do not need to grab the Threads_lock, since we are operating on ourself.
1809   Handle threadObj(thread, thread->threadObj());
1810   assert(threadObj.not_null(), "java thread object must exist");
1811   ObjectLocker lock(threadObj, thread);
1812   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1813   thread->clear_pending_exception();
1814   // Thread is exiting. So set thread_status field in  java.lang.Thread class to TERMINATED.
1815   java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
1816   // Clear the native thread instance - this makes isAlive return false and allows the join()
1817   // to complete once we've done the notify_all below
1818   java_lang_Thread::set_thread(threadObj(), NULL);
1819   lock.notify_all(thread);
1820   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1821   thread->clear_pending_exception();
1822 }
1823 
1824 
1825 // For any new cleanup additions, please check to see if they need to be applied to
1826 // cleanup_failed_attach_current_thread as well.
1827 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
1828   assert(this == JavaThread::current(), "thread consistency check");
1829 
1830   elapsedTimer _timer_exit_phase1;
1831   elapsedTimer _timer_exit_phase2;
1832   elapsedTimer _timer_exit_phase3;
1833   elapsedTimer _timer_exit_phase4;
1834 
1835   if (log_is_enabled(Debug, os, thread, timer)) {
1836     _timer_exit_phase1.start();
1837   }
1838 
1839   HandleMark hm(this);
1840   Handle uncaught_exception(this, this->pending_exception());
1841   this->clear_pending_exception();
1842   Handle threadObj(this, this->threadObj());
1843   assert(threadObj.not_null(), "Java thread object should be created");
1844 
1845   // FIXIT: This code should be moved into else part, when reliable 1.2/1.3 check is in place
1846   {
1847     EXCEPTION_MARK;
1848 
1849     CLEAR_PENDING_EXCEPTION;
1850   }
1851   if (!destroy_vm) {
1852     if (uncaught_exception.not_null()) {
1853       EXCEPTION_MARK;
1854       // Call method Thread.dispatchUncaughtException().
1855       Klass* thread_klass = SystemDictionary::Thread_klass();
1856       JavaValue result(T_VOID);
1857       JavaCalls::call_virtual(&result,
1858                               threadObj, thread_klass,
1859                               vmSymbols::dispatchUncaughtException_name(),
1860                               vmSymbols::throwable_void_signature(),
1861                               uncaught_exception,
1862                               THREAD);
1863       if (HAS_PENDING_EXCEPTION) {
1864         ResourceMark rm(this);
1865         jio_fprintf(defaultStream::error_stream(),
1866                     "\nException: %s thrown from the UncaughtExceptionHandler"
1867                     " in thread \"%s\"\n",
1868                     pending_exception()->klass()->external_name(),
1869                     get_thread_name());
1870         CLEAR_PENDING_EXCEPTION;
1871       }
1872     }
1873 
1874     // Called before the java thread exit since we want to read info
1875     // from java_lang_Thread object
1876     EventThreadEnd event;
1877     if (event.should_commit()) {
1878       event.set_thread(THREAD_TRACE_ID(this));
1879       event.commit();
1880     }
1881 
1882     // Call after last event on thread
1883     EVENT_THREAD_EXIT(this);
1884 
1885     // Call Thread.exit(). We try 3 times in case we got another Thread.stop during
1886     // the execution of the method. If that is not enough, then we don't really care. Thread.stop
1887     // is deprecated anyhow.
1888     if (!is_Compiler_thread()) {
1889       int count = 3;
1890       while (java_lang_Thread::threadGroup(threadObj()) != NULL && (count-- > 0)) {
1891         EXCEPTION_MARK;
1892         JavaValue result(T_VOID);
1893         Klass* thread_klass = SystemDictionary::Thread_klass();
1894         JavaCalls::call_virtual(&result,
1895                                 threadObj, thread_klass,
1896                                 vmSymbols::exit_method_name(),
1897                                 vmSymbols::void_method_signature(),
1898                                 THREAD);
1899         CLEAR_PENDING_EXCEPTION;
1900       }
1901     }
1902     // notify JVMTI
1903     if (JvmtiExport::should_post_thread_life()) {
1904       JvmtiExport::post_thread_end(this);
1905     }
1906 
1907     // We have notified the agents that we are exiting, before we go on,
1908     // we must check for a pending external suspend request and honor it
1909     // in order to not surprise the thread that made the suspend request.
1910     while (true) {
1911       {
1912         MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
1913         if (!is_external_suspend()) {
1914           set_terminated(_thread_exiting);
1915           ThreadService::current_thread_exiting(this);
1916           break;
1917         }
1918         // Implied else:
1919         // Things get a little tricky here. We have a pending external
1920         // suspend request, but we are holding the SR_lock so we
1921         // can't just self-suspend. So we temporarily drop the lock
1922         // and then self-suspend.
1923       }
1924 
1925       ThreadBlockInVM tbivm(this);
1926       java_suspend_self();
1927 
1928       // We're done with this suspend request, but we have to loop around
1929       // and check again. Eventually we will get SR_lock without a pending
1930       // external suspend request and will be able to mark ourselves as
1931       // exiting.
1932     }
1933     // no more external suspends are allowed at this point
1934   } else {
1935     // before_exit() has already posted JVMTI THREAD_END events
1936   }
1937 
1938   if (log_is_enabled(Debug, os, thread, timer)) {
1939     _timer_exit_phase1.stop();
1940     _timer_exit_phase2.start();
1941   }
1942   // Notify waiters on thread object. This has to be done after exit() is called
1943   // on the thread (if the thread is the last thread in a daemon ThreadGroup the
1944   // group should have the destroyed bit set before waiters are notified).
1945   ensure_join(this);
1946   assert(!this->has_pending_exception(), "ensure_join should have cleared");
1947 
1948   if (log_is_enabled(Debug, os, thread, timer)) {
1949     _timer_exit_phase2.stop();
1950     _timer_exit_phase3.start();
1951   }
1952   // 6282335 JNI DetachCurrentThread spec states that all Java monitors
1953   // held by this thread must be released. The spec does not distinguish
1954   // between JNI-acquired and regular Java monitors. We can only see
1955   // regular Java monitors here if monitor enter-exit matching is broken.
1956   //
1957   // Optionally release any monitors for regular JavaThread exits. This
1958   // is provided as a work around for any bugs in monitor enter-exit
1959   // matching. This can be expensive so it is not enabled by default.
1960   //
1961   // ensure_join() ignores IllegalThreadStateExceptions, and so does
1962   // ObjectSynchronizer::release_monitors_owned_by_thread().
1963   if (exit_type == jni_detach || ObjectMonitor::Knob_ExitRelease) {
1964     // Sanity check even though JNI DetachCurrentThread() would have
1965     // returned JNI_ERR if there was a Java frame. JavaThread exit
1966     // should be done executing Java code by the time we get here.
1967     assert(!this->has_last_Java_frame(),
1968            "should not have a Java frame when detaching or exiting");
1969     ObjectSynchronizer::release_monitors_owned_by_thread(this);
1970     assert(!this->has_pending_exception(), "release_monitors should have cleared");
1971   }
1972 
1973   // These things needs to be done while we are still a Java Thread. Make sure that thread
1974   // is in a consistent state, in case GC happens
1975   assert(_privileged_stack_top == NULL, "must be NULL when we get here");
1976 
1977   if (active_handles() != NULL) {
1978     JNIHandleBlock* block = active_handles();
1979     set_active_handles(NULL);
1980     JNIHandleBlock::release_block(block);
1981   }
1982 
1983   if (free_handle_block() != NULL) {
1984     JNIHandleBlock* block = free_handle_block();
1985     set_free_handle_block(NULL);
1986     JNIHandleBlock::release_block(block);
1987   }
1988 
1989   // These have to be removed while this is still a valid thread.
1990   remove_stack_guard_pages();
1991 
1992   if (UseTLAB) {
1993     tlab().make_parsable(true);  // retire TLAB
1994   }
1995 
1996   if (JvmtiEnv::environments_might_exist()) {
1997     JvmtiExport::cleanup_thread(this);
1998   }
1999 
2000   // We must flush any deferred card marks before removing a thread from
2001   // the list of active threads.
2002   Universe::heap()->flush_deferred_store_barrier(this);
2003   assert(deferred_card_mark().is_empty(), "Should have been flushed");
2004 
2005 #if INCLUDE_ALL_GCS
2006   // We must flush the G1-related buffers before removing a thread
2007   // from the list of active threads. We must do this after any deferred
2008   // card marks have been flushed (above) so that any entries that are
2009   // added to the thread's dirty card queue as a result are not lost.
2010   if (UseG1GC) {
2011     flush_barrier_queues();
2012   }
2013 #endif // INCLUDE_ALL_GCS
2014 
2015   log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").",
2016     exit_type == JavaThread::normal_exit ? "exiting" : "detaching",
2017     os::current_thread_id());
2018 
2019   // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
2020   Threads::remove(this);
2021 
2022   // If someone set a handshake on us just as we entered exit path, we simple cancel it.
2023   if (ThreadLocalHandshakes) {
2024     cancel_handshake();
2025   }
2026 }
2027 
2028 #if INCLUDE_ALL_GCS
2029 // Flush G1-related queues.
2030 void JavaThread::flush_barrier_queues() {
2031   satb_mark_queue().flush();
2032   dirty_card_queue().flush();
2033 }
2034 
2035 void JavaThread::initialize_queues() {
2036   assert(!SafepointSynchronize::is_at_safepoint(),
2037          "we should not be at a safepoint");
2038 
2039   SATBMarkQueue& satb_queue = satb_mark_queue();
2040   SATBMarkQueueSet& satb_queue_set = satb_mark_queue_set();
2041   // The SATB queue should have been constructed with its active
2042   // field set to false.
2043   assert(!satb_queue.is_active(), "SATB queue should not be active");
2044   assert(satb_queue.is_empty(), "SATB queue should be empty");
2045   // If we are creating the thread during a marking cycle, we should
2046   // set the active field of the SATB queue to true.
2047   if (satb_queue_set.is_active()) {
2048     satb_queue.set_active(true);
2049   }
2050 
2051   DirtyCardQueue& dirty_queue = dirty_card_queue();
2052   // The dirty card queue should have been constructed with its
2053   // active field set to true.
2054   assert(dirty_queue.is_active(), "dirty card queue should be active");
2055 }
2056 #endif // INCLUDE_ALL_GCS
2057 
2058 void JavaThread::cleanup_failed_attach_current_thread() {
2059   if (active_handles() != NULL) {
2060     JNIHandleBlock* block = active_handles();
2061     set_active_handles(NULL);
2062     JNIHandleBlock::release_block(block);
2063   }
2064 
2065   if (free_handle_block() != NULL) {
2066     JNIHandleBlock* block = free_handle_block();
2067     set_free_handle_block(NULL);
2068     JNIHandleBlock::release_block(block);
2069   }
2070 
2071   // These have to be removed while this is still a valid thread.
2072   remove_stack_guard_pages();
2073 
2074   if (UseTLAB) {
2075     tlab().make_parsable(true);  // retire TLAB, if any
2076   }
2077 
2078 #if INCLUDE_ALL_GCS
2079   if (UseG1GC) {
2080     flush_barrier_queues();
2081   }
2082 #endif // INCLUDE_ALL_GCS
2083 
2084   Threads::remove(this);
2085   this->smr_delete();
2086 }
2087 
2088 
2089 
2090 
2091 JavaThread* JavaThread::active() {
2092   Thread* thread = Thread::current();
2093   if (thread->is_Java_thread()) {
2094     return (JavaThread*) thread;
2095   } else {
2096     assert(thread->is_VM_thread(), "this must be a vm thread");
2097     VM_Operation* op = ((VMThread*) thread)->vm_operation();
2098     JavaThread *ret=op == NULL ? NULL : (JavaThread *)op->calling_thread();
2099     assert(ret->is_Java_thread(), "must be a Java thread");
2100     return ret;
2101   }
2102 }
2103 
2104 bool JavaThread::is_lock_owned(address adr) const {
2105   if (Thread::is_lock_owned(adr)) return true;
2106 
2107   for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2108     if (chunk->contains(adr)) return true;
2109   }
2110 
2111   return false;
2112 }
2113 
2114 
2115 void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
2116   chunk->set_next(monitor_chunks());
2117   set_monitor_chunks(chunk);
2118 }
2119 
2120 void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
2121   guarantee(monitor_chunks() != NULL, "must be non empty");
2122   if (monitor_chunks() == chunk) {
2123     set_monitor_chunks(chunk->next());
2124   } else {
2125     MonitorChunk* prev = monitor_chunks();
2126     while (prev->next() != chunk) prev = prev->next();
2127     prev->set_next(chunk->next());
2128   }
2129 }
2130 
2131 // JVM support.
2132 
2133 // Note: this function shouldn't block if it's called in
2134 // _thread_in_native_trans state (such as from
2135 // check_special_condition_for_native_trans()).
2136 void JavaThread::check_and_handle_async_exceptions(bool check_unsafe_error) {
2137 
2138   if (has_last_Java_frame() && has_async_condition()) {
2139     // If we are at a polling page safepoint (not a poll return)
2140     // then we must defer async exception because live registers
2141     // will be clobbered by the exception path. Poll return is
2142     // ok because the call we a returning from already collides
2143     // with exception handling registers and so there is no issue.
2144     // (The exception handling path kills call result registers but
2145     //  this is ok since the exception kills the result anyway).
2146 
2147     if (is_at_poll_safepoint()) {
2148       // if the code we are returning to has deoptimized we must defer
2149       // the exception otherwise live registers get clobbered on the
2150       // exception path before deoptimization is able to retrieve them.
2151       //
2152       RegisterMap map(this, false);
2153       frame caller_fr = last_frame().sender(&map);
2154       assert(caller_fr.is_compiled_frame(), "what?");
2155       if (caller_fr.is_deoptimized_frame()) {
2156         log_info(exceptions)("deferred async exception at compiled safepoint");
2157         return;
2158       }
2159     }
2160   }
2161 
2162   JavaThread::AsyncRequests condition = clear_special_runtime_exit_condition();
2163   if (condition == _no_async_condition) {
2164     // Conditions have changed since has_special_runtime_exit_condition()
2165     // was called:
2166     // - if we were here only because of an external suspend request,
2167     //   then that was taken care of above (or cancelled) so we are done
2168     // - if we were here because of another async request, then it has
2169     //   been cleared between the has_special_runtime_exit_condition()
2170     //   and now so again we are done
2171     return;
2172   }
2173 
2174   // Check for pending async. exception
2175   if (_pending_async_exception != NULL) {
2176     // Only overwrite an already pending exception, if it is not a threadDeath.
2177     if (!has_pending_exception() || !pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())) {
2178 
2179       // We cannot call Exceptions::_throw(...) here because we cannot block
2180       set_pending_exception(_pending_async_exception, __FILE__, __LINE__);
2181 
2182       LogTarget(Info, exceptions) lt;
2183       if (lt.is_enabled()) {
2184         ResourceMark rm;
2185         LogStream ls(lt);
2186         ls.print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", p2i(this));
2187           if (has_last_Java_frame()) {
2188             frame f = last_frame();
2189            ls.print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", p2i(f.pc()), p2i(f.sp()));
2190           }
2191         ls.print_cr(" of type: %s", _pending_async_exception->klass()->external_name());
2192       }
2193       _pending_async_exception = NULL;
2194       clear_has_async_exception();
2195     }
2196   }
2197 
2198   if (check_unsafe_error &&
2199       condition == _async_unsafe_access_error && !has_pending_exception()) {
2200     condition = _no_async_condition;  // done
2201     switch (thread_state()) {
2202     case _thread_in_vm: {
2203       JavaThread* THREAD = this;
2204       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2205     }
2206     case _thread_in_native: {
2207       ThreadInVMfromNative tiv(this);
2208       JavaThread* THREAD = this;
2209       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2210     }
2211     case _thread_in_Java: {
2212       ThreadInVMfromJava tiv(this);
2213       JavaThread* THREAD = this;
2214       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in a recent unsafe memory access operation in compiled Java code");
2215     }
2216     default:
2217       ShouldNotReachHere();
2218     }
2219   }
2220 
2221   assert(condition == _no_async_condition || has_pending_exception() ||
2222          (!check_unsafe_error && condition == _async_unsafe_access_error),
2223          "must have handled the async condition, if no exception");
2224 }
2225 
2226 void JavaThread::handle_special_runtime_exit_condition(bool check_asyncs) {
2227   //
2228   // Check for pending external suspend. Internal suspend requests do
2229   // not use handle_special_runtime_exit_condition().
2230   // If JNIEnv proxies are allowed, don't self-suspend if the target
2231   // thread is not the current thread. In older versions of jdbx, jdbx
2232   // threads could call into the VM with another thread's JNIEnv so we
2233   // can be here operating on behalf of a suspended thread (4432884).
2234   bool do_self_suspend = is_external_suspend_with_lock();
2235   if (do_self_suspend && (!AllowJNIEnvProxy || this == JavaThread::current())) {
2236     //
2237     // Because thread is external suspended the safepoint code will count
2238     // thread as at a safepoint. This can be odd because we can be here
2239     // as _thread_in_Java which would normally transition to _thread_blocked
2240     // at a safepoint. We would like to mark the thread as _thread_blocked
2241     // before calling java_suspend_self like all other callers of it but
2242     // we must then observe proper safepoint protocol. (We can't leave
2243     // _thread_blocked with a safepoint in progress). However we can be
2244     // here as _thread_in_native_trans so we can't use a normal transition
2245     // constructor/destructor pair because they assert on that type of
2246     // transition. We could do something like:
2247     //
2248     // JavaThreadState state = thread_state();
2249     // set_thread_state(_thread_in_vm);
2250     // {
2251     //   ThreadBlockInVM tbivm(this);
2252     //   java_suspend_self()
2253     // }
2254     // set_thread_state(_thread_in_vm_trans);
2255     // if (safepoint) block;
2256     // set_thread_state(state);
2257     //
2258     // but that is pretty messy. Instead we just go with the way the
2259     // code has worked before and note that this is the only path to
2260     // java_suspend_self that doesn't put the thread in _thread_blocked
2261     // mode.
2262 
2263     frame_anchor()->make_walkable(this);
2264     java_suspend_self();
2265 
2266     // We might be here for reasons in addition to the self-suspend request
2267     // so check for other async requests.
2268   }
2269 
2270   if (check_asyncs) {
2271     check_and_handle_async_exceptions();
2272   }
2273 #if INCLUDE_TRACE
2274   if (is_trace_suspend()) {
2275     TRACE_SUSPEND_THREAD(this);
2276   }
2277 #endif
2278 }
2279 
2280 void JavaThread::send_thread_stop(oop java_throwable)  {
2281   assert(Thread::current()->is_VM_thread(), "should be in the vm thread");
2282   assert(Threads_lock->is_locked(), "Threads_lock should be locked by safepoint code");
2283   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
2284 
2285   // Do not throw asynchronous exceptions against the compiler thread
2286   // (the compiler thread should not be a Java thread -- fix in 1.4.2)
2287   if (!can_call_java()) return;
2288 
2289   {
2290     // Actually throw the Throwable against the target Thread - however
2291     // only if there is no thread death exception installed already.
2292     if (_pending_async_exception == NULL || !_pending_async_exception->is_a(SystemDictionary::ThreadDeath_klass())) {
2293       // If the topmost frame is a runtime stub, then we are calling into
2294       // OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
2295       // must deoptimize the caller before continuing, as the compiled  exception handler table
2296       // may not be valid
2297       if (has_last_Java_frame()) {
2298         frame f = last_frame();
2299         if (f.is_runtime_frame() || f.is_safepoint_blob_frame()) {
2300           // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2301           RegisterMap reg_map(this, UseBiasedLocking);
2302           frame compiled_frame = f.sender(&reg_map);
2303           if (!StressCompiledExceptionHandlers && compiled_frame.can_be_deoptimized()) {
2304             Deoptimization::deoptimize(this, compiled_frame, &reg_map);
2305           }
2306         }
2307       }
2308 
2309       // Set async. pending exception in thread.
2310       set_pending_async_exception(java_throwable);
2311 
2312       if (log_is_enabled(Info, exceptions)) {
2313          ResourceMark rm;
2314         log_info(exceptions)("Pending Async. exception installed of type: %s",
2315                              InstanceKlass::cast(_pending_async_exception->klass())->external_name());
2316       }
2317       // for AbortVMOnException flag
2318       Exceptions::debug_check_abort(_pending_async_exception->klass()->external_name());
2319     }
2320   }
2321 
2322 
2323   // Interrupt thread so it will wake up from a potential wait()
2324   Thread::interrupt(this);
2325 }
2326 
2327 // External suspension mechanism.
2328 //
2329 // Tell the VM to suspend a thread when ever it knows that it does not hold on
2330 // to any VM_locks and it is at a transition
2331 // Self-suspension will happen on the transition out of the vm.
2332 // Catch "this" coming in from JNIEnv pointers when the thread has been freed
2333 //
2334 // Guarantees on return:
2335 //   + Target thread will not execute any new bytecode (that's why we need to
2336 //     force a safepoint)
2337 //   + Target thread will not enter any new monitors
2338 //
2339 void JavaThread::java_suspend() {
2340   ThreadsListHandle tlh;
2341   if (!tlh.includes(this) || threadObj() == NULL || is_exiting()) {
2342     return;
2343   }
2344 
2345   { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2346     if (!is_external_suspend()) {
2347       // a racing resume has cancelled us; bail out now
2348       return;
2349     }
2350 
2351     // suspend is done
2352     uint32_t debug_bits = 0;
2353     // Warning: is_ext_suspend_completed() may temporarily drop the
2354     // SR_lock to allow the thread to reach a stable thread state if
2355     // it is currently in a transient thread state.
2356     if (is_ext_suspend_completed(false /* !called_by_wait */,
2357                                  SuspendRetryDelay, &debug_bits)) {
2358       return;
2359     }
2360   }
2361 
2362   VM_ThreadSuspend vm_suspend;
2363   VMThread::execute(&vm_suspend);
2364 }
2365 
2366 // Part II of external suspension.
2367 // A JavaThread self suspends when it detects a pending external suspend
2368 // request. This is usually on transitions. It is also done in places
2369 // where continuing to the next transition would surprise the caller,
2370 // e.g., monitor entry.
2371 //
2372 // Returns the number of times that the thread self-suspended.
2373 //
2374 // Note: DO NOT call java_suspend_self() when you just want to block current
2375 //       thread. java_suspend_self() is the second stage of cooperative
2376 //       suspension for external suspend requests and should only be used
2377 //       to complete an external suspend request.
2378 //
2379 int JavaThread::java_suspend_self() {
2380   int ret = 0;
2381 
2382   // we are in the process of exiting so don't suspend
2383   if (is_exiting()) {
2384     clear_external_suspend();
2385     return ret;
2386   }
2387 
2388   assert(_anchor.walkable() ||
2389          (is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
2390          "must have walkable stack");
2391 
2392   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2393 
2394   assert(!this->is_ext_suspended(),
2395          "a thread trying to self-suspend should not already be suspended");
2396 
2397   if (this->is_suspend_equivalent()) {
2398     // If we are self-suspending as a result of the lifting of a
2399     // suspend equivalent condition, then the suspend_equivalent
2400     // flag is not cleared until we set the ext_suspended flag so
2401     // that wait_for_ext_suspend_completion() returns consistent
2402     // results.
2403     this->clear_suspend_equivalent();
2404   }
2405 
2406   // A racing resume may have cancelled us before we grabbed SR_lock
2407   // above. Or another external suspend request could be waiting for us
2408   // by the time we return from SR_lock()->wait(). The thread
2409   // that requested the suspension may already be trying to walk our
2410   // stack and if we return now, we can change the stack out from under
2411   // it. This would be a "bad thing (TM)" and cause the stack walker
2412   // to crash. We stay self-suspended until there are no more pending
2413   // external suspend requests.
2414   while (is_external_suspend()) {
2415     ret++;
2416     this->set_ext_suspended();
2417 
2418     // _ext_suspended flag is cleared by java_resume()
2419     while (is_ext_suspended()) {
2420       this->SR_lock()->wait(Mutex::_no_safepoint_check_flag);
2421     }
2422   }
2423 
2424   return ret;
2425 }
2426 
2427 #ifdef ASSERT
2428 // verify the JavaThread has not yet been published in the Threads::list, and
2429 // hence doesn't need protection from concurrent access at this stage
2430 void JavaThread::verify_not_published() {
2431   ThreadsListHandle tlh;
2432   assert(!tlh.includes(this), "JavaThread shouldn't have been published yet!");
2433 }
2434 #endif
2435 
2436 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2437 // progress or when _suspend_flags is non-zero.
2438 // Current thread needs to self-suspend if there is a suspend request and/or
2439 // block if a safepoint is in progress.
2440 // Async exception ISN'T checked.
2441 // Note only the ThreadInVMfromNative transition can call this function
2442 // directly and when thread state is _thread_in_native_trans
2443 void JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread *thread) {
2444   assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
2445 
2446   JavaThread *curJT = JavaThread::current();
2447   bool do_self_suspend = thread->is_external_suspend();
2448 
2449   assert(!curJT->has_last_Java_frame() || curJT->frame_anchor()->walkable(), "Unwalkable stack in native->vm transition");
2450 
2451   // If JNIEnv proxies are allowed, don't self-suspend if the target
2452   // thread is not the current thread. In older versions of jdbx, jdbx
2453   // threads could call into the VM with another thread's JNIEnv so we
2454   // can be here operating on behalf of a suspended thread (4432884).
2455   if (do_self_suspend && (!AllowJNIEnvProxy || curJT == thread)) {
2456     JavaThreadState state = thread->thread_state();
2457 
2458     // We mark this thread_blocked state as a suspend-equivalent so
2459     // that a caller to is_ext_suspend_completed() won't be confused.
2460     // The suspend-equivalent state is cleared by java_suspend_self().
2461     thread->set_suspend_equivalent();
2462 
2463     // If the safepoint code sees the _thread_in_native_trans state, it will
2464     // wait until the thread changes to other thread state. There is no
2465     // guarantee on how soon we can obtain the SR_lock and complete the
2466     // self-suspend request. It would be a bad idea to let safepoint wait for
2467     // too long. Temporarily change the state to _thread_blocked to
2468     // let the VM thread know that this thread is ready for GC. The problem
2469     // of changing thread state is that safepoint could happen just after
2470     // java_suspend_self() returns after being resumed, and VM thread will
2471     // see the _thread_blocked state. We must check for safepoint
2472     // after restoring the state and make sure we won't leave while a safepoint
2473     // is in progress.
2474     thread->set_thread_state(_thread_blocked);
2475     thread->java_suspend_self();
2476     thread->set_thread_state(state);
2477 
2478     InterfaceSupport::serialize_thread_state_with_handler(thread);
2479   }
2480 
2481   SafepointMechanism::block_if_requested(curJT);
2482 
2483   if (thread->is_deopt_suspend()) {
2484     thread->clear_deopt_suspend();
2485     RegisterMap map(thread, false);
2486     frame f = thread->last_frame();
2487     while (f.id() != thread->must_deopt_id() && ! f.is_first_frame()) {
2488       f = f.sender(&map);
2489     }
2490     if (f.id() == thread->must_deopt_id()) {
2491       thread->clear_must_deopt_id();
2492       f.deoptimize(thread);
2493     } else {
2494       fatal("missed deoptimization!");
2495     }
2496   }
2497 #if INCLUDE_TRACE
2498   if (thread->is_trace_suspend()) {
2499     TRACE_SUSPEND_THREAD(thread);
2500   }
2501 #endif
2502 }
2503 
2504 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2505 // progress or when _suspend_flags is non-zero.
2506 // Current thread needs to self-suspend if there is a suspend request and/or
2507 // block if a safepoint is in progress.
2508 // Also check for pending async exception (not including unsafe access error).
2509 // Note only the native==>VM/Java barriers can call this function and when
2510 // thread state is _thread_in_native_trans.
2511 void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
2512   check_safepoint_and_suspend_for_native_trans(thread);
2513 
2514   if (thread->has_async_exception()) {
2515     // We are in _thread_in_native_trans state, don't handle unsafe
2516     // access error since that may block.
2517     thread->check_and_handle_async_exceptions(false);
2518   }
2519 }
2520 
2521 // This is a variant of the normal
2522 // check_special_condition_for_native_trans with slightly different
2523 // semantics for use by critical native wrappers.  It does all the
2524 // normal checks but also performs the transition back into
2525 // thread_in_Java state.  This is required so that critical natives
2526 // can potentially block and perform a GC if they are the last thread
2527 // exiting the GCLocker.
2528 void JavaThread::check_special_condition_for_native_trans_and_transition(JavaThread *thread) {
2529   check_special_condition_for_native_trans(thread);
2530 
2531   // Finish the transition
2532   thread->set_thread_state(_thread_in_Java);
2533 
2534   if (thread->do_critical_native_unlock()) {
2535     ThreadInVMfromJavaNoAsyncException tiv(thread);
2536     GCLocker::unlock_critical(thread);
2537     thread->clear_critical_native_unlock();
2538   }
2539 }
2540 
2541 // We need to guarantee the Threads_lock here, since resumes are not
2542 // allowed during safepoint synchronization
2543 // Can only resume from an external suspension
2544 void JavaThread::java_resume() {
2545   assert_locked_or_safepoint(Threads_lock);
2546 
2547   // Sanity check: thread is gone, has started exiting or the thread
2548   // was not externally suspended.
2549   ThreadsListHandle tlh;
2550   if (!tlh.includes(this) || is_exiting() || !is_external_suspend()) {
2551     return;
2552   }
2553 
2554   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2555 
2556   clear_external_suspend();
2557 
2558   if (is_ext_suspended()) {
2559     clear_ext_suspended();
2560     SR_lock()->notify_all();
2561   }
2562 }
2563 
2564 size_t JavaThread::_stack_red_zone_size = 0;
2565 size_t JavaThread::_stack_yellow_zone_size = 0;
2566 size_t JavaThread::_stack_reserved_zone_size = 0;
2567 size_t JavaThread::_stack_shadow_zone_size = 0;
2568 
2569 void JavaThread::create_stack_guard_pages() {
2570   if (!os::uses_stack_guard_pages() || _stack_guard_state != stack_guard_unused) { return; }
2571   address low_addr = stack_end();
2572   size_t len = stack_guard_zone_size();
2573 
2574   assert(is_aligned(low_addr, os::vm_page_size()), "Stack base should be the start of a page");
2575   assert(is_aligned(len, os::vm_page_size()), "Stack size should be a multiple of page size");
2576 
2577   int must_commit = os::must_commit_stack_guard_pages();
2578   // warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);
2579 
2580   if (must_commit && !os::create_stack_guard_pages((char *) low_addr, len)) {
2581     log_warning(os, thread)("Attempt to allocate stack guard pages failed.");
2582     return;
2583   }
2584 
2585   if (os::guard_memory((char *) low_addr, len)) {
2586     _stack_guard_state = stack_guard_enabled;
2587   } else {
2588     log_warning(os, thread)("Attempt to protect stack guard pages failed ("
2589       PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2590     if (os::uncommit_memory((char *) low_addr, len)) {
2591       log_warning(os, thread)("Attempt to deallocate stack guard pages failed.");
2592     }
2593     return;
2594   }
2595 
2596   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages activated: "
2597     PTR_FORMAT "-" PTR_FORMAT ".",
2598     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2599 }
2600 
2601 void JavaThread::remove_stack_guard_pages() {
2602   assert(Thread::current() == this, "from different thread");
2603   if (_stack_guard_state == stack_guard_unused) return;
2604   address low_addr = stack_end();
2605   size_t len = stack_guard_zone_size();
2606 
2607   if (os::must_commit_stack_guard_pages()) {
2608     if (os::remove_stack_guard_pages((char *) low_addr, len)) {
2609       _stack_guard_state = stack_guard_unused;
2610     } else {
2611       log_warning(os, thread)("Attempt to deallocate stack guard pages failed ("
2612         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2613       return;
2614     }
2615   } else {
2616     if (_stack_guard_state == stack_guard_unused) return;
2617     if (os::unguard_memory((char *) low_addr, len)) {
2618       _stack_guard_state = stack_guard_unused;
2619     } else {
2620       log_warning(os, thread)("Attempt to unprotect stack guard pages failed ("
2621         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2622       return;
2623     }
2624   }
2625 
2626   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages removed: "
2627     PTR_FORMAT "-" PTR_FORMAT ".",
2628     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2629 }
2630 
2631 void JavaThread::enable_stack_reserved_zone() {
2632   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2633   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2634 
2635   // The base notation is from the stack's point of view, growing downward.
2636   // We need to adjust it to work correctly with guard_memory()
2637   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2638 
2639   guarantee(base < stack_base(),"Error calculating stack reserved zone");
2640   guarantee(base < os::current_stack_pointer(),"Error calculating stack reserved zone");
2641 
2642   if (os::guard_memory((char *) base, stack_reserved_zone_size())) {
2643     _stack_guard_state = stack_guard_enabled;
2644   } else {
2645     warning("Attempt to guard stack reserved zone failed.");
2646   }
2647   enable_register_stack_guard();
2648 }
2649 
2650 void JavaThread::disable_stack_reserved_zone() {
2651   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2652   assert(_stack_guard_state != stack_guard_reserved_disabled, "already disabled");
2653 
2654   // Simply return if called for a thread that does not use guard pages.
2655   if (_stack_guard_state == stack_guard_unused) return;
2656 
2657   // The base notation is from the stack's point of view, growing downward.
2658   // We need to adjust it to work correctly with guard_memory()
2659   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2660 
2661   if (os::unguard_memory((char *)base, stack_reserved_zone_size())) {
2662     _stack_guard_state = stack_guard_reserved_disabled;
2663   } else {
2664     warning("Attempt to unguard stack reserved zone failed.");
2665   }
2666   disable_register_stack_guard();
2667 }
2668 
2669 void JavaThread::enable_stack_yellow_reserved_zone() {
2670   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2671   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2672 
2673   // The base notation is from the stacks point of view, growing downward.
2674   // We need to adjust it to work correctly with guard_memory()
2675   address base = stack_red_zone_base();
2676 
2677   guarantee(base < stack_base(), "Error calculating stack yellow zone");
2678   guarantee(base < os::current_stack_pointer(), "Error calculating stack yellow zone");
2679 
2680   if (os::guard_memory((char *) base, stack_yellow_reserved_zone_size())) {
2681     _stack_guard_state = stack_guard_enabled;
2682   } else {
2683     warning("Attempt to guard stack yellow zone failed.");
2684   }
2685   enable_register_stack_guard();
2686 }
2687 
2688 void JavaThread::disable_stack_yellow_reserved_zone() {
2689   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2690   assert(_stack_guard_state != stack_guard_yellow_reserved_disabled, "already disabled");
2691 
2692   // Simply return if called for a thread that does not use guard pages.
2693   if (_stack_guard_state == stack_guard_unused) return;
2694 
2695   // The base notation is from the stacks point of view, growing downward.
2696   // We need to adjust it to work correctly with guard_memory()
2697   address base = stack_red_zone_base();
2698 
2699   if (os::unguard_memory((char *)base, stack_yellow_reserved_zone_size())) {
2700     _stack_guard_state = stack_guard_yellow_reserved_disabled;
2701   } else {
2702     warning("Attempt to unguard stack yellow zone failed.");
2703   }
2704   disable_register_stack_guard();
2705 }
2706 
2707 void JavaThread::enable_stack_red_zone() {
2708   // The base notation is from the stacks point of view, growing downward.
2709   // We need to adjust it to work correctly with guard_memory()
2710   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2711   address base = stack_red_zone_base() - stack_red_zone_size();
2712 
2713   guarantee(base < stack_base(), "Error calculating stack red zone");
2714   guarantee(base < os::current_stack_pointer(), "Error calculating stack red zone");
2715 
2716   if (!os::guard_memory((char *) base, stack_red_zone_size())) {
2717     warning("Attempt to guard stack red zone failed.");
2718   }
2719 }
2720 
2721 void JavaThread::disable_stack_red_zone() {
2722   // The base notation is from the stacks point of view, growing downward.
2723   // We need to adjust it to work correctly with guard_memory()
2724   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2725   address base = stack_red_zone_base() - stack_red_zone_size();
2726   if (!os::unguard_memory((char *)base, stack_red_zone_size())) {
2727     warning("Attempt to unguard stack red zone failed.");
2728   }
2729 }
2730 
2731 void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
2732   // ignore is there is no stack
2733   if (!has_last_Java_frame()) return;
2734   // traverse the stack frames. Starts from top frame.
2735   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2736     frame* fr = fst.current();
2737     f(fr, fst.register_map());
2738   }
2739 }
2740 
2741 
2742 #ifndef PRODUCT
2743 // Deoptimization
2744 // Function for testing deoptimization
2745 void JavaThread::deoptimize() {
2746   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2747   StackFrameStream fst(this, UseBiasedLocking);
2748   bool deopt = false;           // Dump stack only if a deopt actually happens.
2749   bool only_at = strlen(DeoptimizeOnlyAt) > 0;
2750   // Iterate over all frames in the thread and deoptimize
2751   for (; !fst.is_done(); fst.next()) {
2752     if (fst.current()->can_be_deoptimized()) {
2753 
2754       if (only_at) {
2755         // Deoptimize only at particular bcis.  DeoptimizeOnlyAt
2756         // consists of comma or carriage return separated numbers so
2757         // search for the current bci in that string.
2758         address pc = fst.current()->pc();
2759         nmethod* nm =  (nmethod*) fst.current()->cb();
2760         ScopeDesc* sd = nm->scope_desc_at(pc);
2761         char buffer[8];
2762         jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
2763         size_t len = strlen(buffer);
2764         const char * found = strstr(DeoptimizeOnlyAt, buffer);
2765         while (found != NULL) {
2766           if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
2767               (found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
2768             // Check that the bci found is bracketed by terminators.
2769             break;
2770           }
2771           found = strstr(found + 1, buffer);
2772         }
2773         if (!found) {
2774           continue;
2775         }
2776       }
2777 
2778       if (DebugDeoptimization && !deopt) {
2779         deopt = true; // One-time only print before deopt
2780         tty->print_cr("[BEFORE Deoptimization]");
2781         trace_frames();
2782         trace_stack();
2783       }
2784       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2785     }
2786   }
2787 
2788   if (DebugDeoptimization && deopt) {
2789     tty->print_cr("[AFTER Deoptimization]");
2790     trace_frames();
2791   }
2792 }
2793 
2794 
2795 // Make zombies
2796 void JavaThread::make_zombies() {
2797   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2798     if (fst.current()->can_be_deoptimized()) {
2799       // it is a Java nmethod
2800       nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
2801       nm->make_not_entrant();
2802     }
2803   }
2804 }
2805 #endif // PRODUCT
2806 
2807 
2808 void JavaThread::deoptimized_wrt_marked_nmethods() {
2809   if (!has_last_Java_frame()) return;
2810   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2811   StackFrameStream fst(this, UseBiasedLocking);
2812   for (; !fst.is_done(); fst.next()) {
2813     if (fst.current()->should_be_deoptimized()) {
2814       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2815     }
2816   }
2817 }
2818 
2819 
2820 // If the caller is a NamedThread, then remember, in the current scope,
2821 // the given JavaThread in its _processed_thread field.
2822 class RememberProcessedThread: public StackObj {
2823   NamedThread* _cur_thr;
2824  public:
2825   RememberProcessedThread(JavaThread* jthr) {
2826     Thread* thread = Thread::current();
2827     if (thread->is_Named_thread()) {
2828       _cur_thr = (NamedThread *)thread;
2829       _cur_thr->set_processed_thread(jthr);
2830     } else {
2831       _cur_thr = NULL;
2832     }
2833   }
2834 
2835   ~RememberProcessedThread() {
2836     if (_cur_thr) {
2837       _cur_thr->set_processed_thread(NULL);
2838     }
2839   }
2840 };
2841 
2842 void JavaThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
2843   // Verify that the deferred card marks have been flushed.
2844   assert(deferred_card_mark().is_empty(), "Should be empty during GC");
2845 
2846   // Traverse the GCHandles
2847   Thread::oops_do(f, cf);
2848 
2849   JVMCI_ONLY(f->do_oop((oop*)&_pending_failed_speculation);)
2850 
2851   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2852          (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2853 
2854   if (has_last_Java_frame()) {
2855     // Record JavaThread to GC thread
2856     RememberProcessedThread rpt(this);
2857 
2858     // Traverse the privileged stack
2859     if (_privileged_stack_top != NULL) {
2860       _privileged_stack_top->oops_do(f);
2861     }
2862 
2863     // traverse the registered growable array
2864     if (_array_for_gc != NULL) {
2865       for (int index = 0; index < _array_for_gc->length(); index++) {
2866         f->do_oop(_array_for_gc->adr_at(index));
2867       }
2868     }
2869 
2870     // Traverse the monitor chunks
2871     for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2872       chunk->oops_do(f);
2873     }
2874 
2875     // Traverse the execution stack
2876     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2877       fst.current()->oops_do(f, cf, fst.register_map());
2878     }
2879   }
2880 
2881   // callee_target is never live across a gc point so NULL it here should
2882   // it still contain a methdOop.
2883 
2884   set_callee_target(NULL);
2885 
2886   assert(vframe_array_head() == NULL, "deopt in progress at a safepoint!");
2887   // If we have deferred set_locals there might be oops waiting to be
2888   // written
2889   GrowableArray<jvmtiDeferredLocalVariableSet*>* list = deferred_locals();
2890   if (list != NULL) {
2891     for (int i = 0; i < list->length(); i++) {
2892       list->at(i)->oops_do(f);
2893     }
2894   }
2895 
2896   // Traverse instance variables at the end since the GC may be moving things
2897   // around using this function
2898   f->do_oop((oop*) &_threadObj);
2899   f->do_oop((oop*) &_vm_result);
2900   f->do_oop((oop*) &_exception_oop);
2901   f->do_oop((oop*) &_pending_async_exception);
2902 
2903   if (jvmti_thread_state() != NULL) {
2904     jvmti_thread_state()->oops_do(f);
2905   }
2906 }
2907 
2908 void JavaThread::nmethods_do(CodeBlobClosure* cf) {
2909   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2910          (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2911 
2912   if (has_last_Java_frame()) {
2913     // Traverse the execution stack
2914     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2915       fst.current()->nmethods_do(cf);
2916     }
2917   }
2918 }
2919 
2920 void JavaThread::metadata_do(void f(Metadata*)) {
2921   if (has_last_Java_frame()) {
2922     // Traverse the execution stack to call f() on the methods in the stack
2923     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2924       fst.current()->metadata_do(f);
2925     }
2926   } else if (is_Compiler_thread()) {
2927     // need to walk ciMetadata in current compile tasks to keep alive.
2928     CompilerThread* ct = (CompilerThread*)this;
2929     if (ct->env() != NULL) {
2930       ct->env()->metadata_do(f);
2931     }
2932     if (ct->task() != NULL) {
2933       ct->task()->metadata_do(f);
2934     }
2935   }
2936 }
2937 
2938 // Printing
2939 const char* _get_thread_state_name(JavaThreadState _thread_state) {
2940   switch (_thread_state) {
2941   case _thread_uninitialized:     return "_thread_uninitialized";
2942   case _thread_new:               return "_thread_new";
2943   case _thread_new_trans:         return "_thread_new_trans";
2944   case _thread_in_native:         return "_thread_in_native";
2945   case _thread_in_native_trans:   return "_thread_in_native_trans";
2946   case _thread_in_vm:             return "_thread_in_vm";
2947   case _thread_in_vm_trans:       return "_thread_in_vm_trans";
2948   case _thread_in_Java:           return "_thread_in_Java";
2949   case _thread_in_Java_trans:     return "_thread_in_Java_trans";
2950   case _thread_blocked:           return "_thread_blocked";
2951   case _thread_blocked_trans:     return "_thread_blocked_trans";
2952   default:                        return "unknown thread state";
2953   }
2954 }
2955 
2956 #ifndef PRODUCT
2957 void JavaThread::print_thread_state_on(outputStream *st) const {
2958   st->print_cr("   JavaThread state: %s", _get_thread_state_name(_thread_state));
2959 };
2960 void JavaThread::print_thread_state() const {
2961   print_thread_state_on(tty);
2962 }
2963 #endif // PRODUCT
2964 
2965 // Called by Threads::print() for VM_PrintThreads operation
2966 void JavaThread::print_on(outputStream *st) const {
2967   st->print_raw("\"");
2968   st->print_raw(get_thread_name());
2969   st->print_raw("\" ");
2970   oop thread_oop = threadObj();
2971   if (thread_oop != NULL) {
2972     st->print("#" INT64_FORMAT " ", (int64_t)java_lang_Thread::thread_id(thread_oop));
2973     if (java_lang_Thread::is_daemon(thread_oop))  st->print("daemon ");
2974     st->print("prio=%d ", java_lang_Thread::priority(thread_oop));
2975   }
2976   Thread::print_on(st);
2977   // print guess for valid stack memory region (assume 4K pages); helps lock debugging
2978   st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
2979   if (thread_oop != NULL) {
2980     st->print_cr("   java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
2981   }
2982 #ifndef PRODUCT
2983   print_thread_state_on(st);
2984   _safepoint_state->print_on(st);
2985 #endif // PRODUCT
2986   if (is_Compiler_thread()) {
2987     CompilerThread* ct = (CompilerThread*)this;
2988     if (ct->task() != NULL) {
2989       st->print("   Compiling: ");
2990       ct->task()->print(st, NULL, true, false);
2991     } else {
2992       st->print("   No compile task");
2993     }
2994     st->cr();
2995   }
2996 }
2997 
2998 void JavaThread::print_name_on_error(outputStream* st, char *buf, int buflen) const {
2999   st->print("%s", get_thread_name_string(buf, buflen));
3000 }
3001 
3002 // Called by fatal error handler. The difference between this and
3003 // JavaThread::print() is that we can't grab lock or allocate memory.
3004 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
3005   st->print("JavaThread \"%s\"", get_thread_name_string(buf, buflen));
3006   oop thread_obj = threadObj();
3007   if (thread_obj != NULL) {
3008     if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
3009   }
3010   st->print(" [");
3011   st->print("%s", _get_thread_state_name(_thread_state));
3012   if (osthread()) {
3013     st->print(", id=%d", osthread()->thread_id());
3014   }
3015   st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
3016             p2i(stack_end()), p2i(stack_base()));
3017   st->print("]");
3018 
3019   if (_threads_hazard_ptr != NULL) {
3020     st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr));
3021   }
3022   if (_nested_threads_hazard_ptr != NULL) {
3023     print_nested_threads_hazard_ptrs_on(st);
3024   }
3025   return;
3026 }
3027 
3028 // Verification
3029 
3030 static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
3031 
3032 void JavaThread::verify() {
3033   // Verify oops in the thread.
3034   oops_do(&VerifyOopClosure::verify_oop, NULL);
3035 
3036   // Verify the stack frames.
3037   frames_do(frame_verify);
3038 }
3039 
3040 // CR 6300358 (sub-CR 2137150)
3041 // Most callers of this method assume that it can't return NULL but a
3042 // thread may not have a name whilst it is in the process of attaching to
3043 // the VM - see CR 6412693, and there are places where a JavaThread can be
3044 // seen prior to having it's threadObj set (eg JNI attaching threads and
3045 // if vm exit occurs during initialization). These cases can all be accounted
3046 // for such that this method never returns NULL.
3047 const char* JavaThread::get_thread_name() const {
3048 #ifdef ASSERT
3049   // early safepoints can hit while current thread does not yet have TLS
3050   if (!SafepointSynchronize::is_at_safepoint()) {
3051     Thread *cur = Thread::current();
3052     if (!(cur->is_Java_thread() && cur == this)) {
3053       // Current JavaThreads are allowed to get their own name without
3054       // the Threads_lock.
3055       assert_locked_or_safepoint(Threads_lock);
3056     }
3057   }
3058 #endif // ASSERT
3059   return get_thread_name_string();
3060 }
3061 
3062 // Returns a non-NULL representation of this thread's name, or a suitable
3063 // descriptive string if there is no set name
3064 const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
3065   const char* name_str;
3066   oop thread_obj = threadObj();
3067   if (thread_obj != NULL) {
3068     oop name = java_lang_Thread::name(thread_obj);
3069     if (name != NULL) {
3070       if (buf == NULL) {
3071         name_str = java_lang_String::as_utf8_string(name);
3072       } else {
3073         name_str = java_lang_String::as_utf8_string(name, buf, buflen);
3074       }
3075     } else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
3076       name_str = "<no-name - thread is attaching>";
3077     } else {
3078       name_str = Thread::name();
3079     }
3080   } else {
3081     name_str = Thread::name();
3082   }
3083   assert(name_str != NULL, "unexpected NULL thread name");
3084   return name_str;
3085 }
3086 
3087 
3088 const char* JavaThread::get_threadgroup_name() const {
3089   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3090   oop thread_obj = threadObj();
3091   if (thread_obj != NULL) {
3092     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3093     if (thread_group != NULL) {
3094       // ThreadGroup.name can be null
3095       return java_lang_ThreadGroup::name(thread_group);
3096     }
3097   }
3098   return NULL;
3099 }
3100 
3101 const char* JavaThread::get_parent_name() const {
3102   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3103   oop thread_obj = threadObj();
3104   if (thread_obj != NULL) {
3105     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3106     if (thread_group != NULL) {
3107       oop parent = java_lang_ThreadGroup::parent(thread_group);
3108       if (parent != NULL) {
3109         // ThreadGroup.name can be null
3110         return java_lang_ThreadGroup::name(parent);
3111       }
3112     }
3113   }
3114   return NULL;
3115 }
3116 
3117 ThreadPriority JavaThread::java_priority() const {
3118   oop thr_oop = threadObj();
3119   if (thr_oop == NULL) return NormPriority; // Bootstrapping
3120   ThreadPriority priority = java_lang_Thread::priority(thr_oop);
3121   assert(MinPriority <= priority && priority <= MaxPriority, "sanity check");
3122   return priority;
3123 }
3124 
3125 void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
3126 
3127   assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
3128   // Link Java Thread object <-> C++ Thread
3129 
3130   // Get the C++ thread object (an oop) from the JNI handle (a jthread)
3131   // and put it into a new Handle.  The Handle "thread_oop" can then
3132   // be used to pass the C++ thread object to other methods.
3133 
3134   // Set the Java level thread object (jthread) field of the
3135   // new thread (a JavaThread *) to C++ thread object using the
3136   // "thread_oop" handle.
3137 
3138   // Set the thread field (a JavaThread *) of the
3139   // oop representing the java_lang_Thread to the new thread (a JavaThread *).
3140 
3141   Handle thread_oop(Thread::current(),
3142                     JNIHandles::resolve_non_null(jni_thread));
3143   assert(InstanceKlass::cast(thread_oop->klass())->is_linked(),
3144          "must be initialized");
3145   set_threadObj(thread_oop());
3146   java_lang_Thread::set_thread(thread_oop(), this);
3147 
3148   if (prio == NoPriority) {
3149     prio = java_lang_Thread::priority(thread_oop());
3150     assert(prio != NoPriority, "A valid priority should be present");
3151   }
3152 
3153   // Push the Java priority down to the native thread; needs Threads_lock
3154   Thread::set_priority(this, prio);
3155 
3156   prepare_ext();
3157 
3158   // Add the new thread to the Threads list and set it in motion.
3159   // We must have threads lock in order to call Threads::add.
3160   // It is crucial that we do not block before the thread is
3161   // added to the Threads list for if a GC happens, then the java_thread oop
3162   // will not be visited by GC.
3163   Threads::add(this);
3164 }
3165 
3166 oop JavaThread::current_park_blocker() {
3167   // Support for JSR-166 locks
3168   oop thread_oop = threadObj();
3169   if (thread_oop != NULL &&
3170       JDK_Version::current().supports_thread_park_blocker()) {
3171     return java_lang_Thread::park_blocker(thread_oop);
3172   }
3173   return NULL;
3174 }
3175 
3176 
3177 void JavaThread::print_stack_on(outputStream* st) {
3178   if (!has_last_Java_frame()) return;
3179   ResourceMark rm;
3180   HandleMark   hm;
3181 
3182   RegisterMap reg_map(this);
3183   vframe* start_vf = last_java_vframe(&reg_map);
3184   int count = 0;
3185   for (vframe* f = start_vf; f; f = f->sender()) {
3186     if (f->is_java_frame()) {
3187       javaVFrame* jvf = javaVFrame::cast(f);
3188       java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
3189 
3190       // Print out lock information
3191       if (JavaMonitorsInStackTrace) {
3192         jvf->print_lock_info_on(st, count);
3193       }
3194     } else {
3195       // Ignore non-Java frames
3196     }
3197 
3198     // Bail-out case for too deep stacks
3199     count++;
3200     if (MaxJavaStackTraceDepth == count) return;
3201   }
3202 }
3203 
3204 
3205 // JVMTI PopFrame support
3206 void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
3207   assert(_popframe_preserved_args == NULL, "should not wipe out old PopFrame preserved arguments");
3208   if (in_bytes(size_in_bytes) != 0) {
3209     _popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes), mtThread);
3210     _popframe_preserved_args_size = in_bytes(size_in_bytes);
3211     Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
3212   }
3213 }
3214 
3215 void* JavaThread::popframe_preserved_args() {
3216   return _popframe_preserved_args;
3217 }
3218 
3219 ByteSize JavaThread::popframe_preserved_args_size() {
3220   return in_ByteSize(_popframe_preserved_args_size);
3221 }
3222 
3223 WordSize JavaThread::popframe_preserved_args_size_in_words() {
3224   int sz = in_bytes(popframe_preserved_args_size());
3225   assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
3226   return in_WordSize(sz / wordSize);
3227 }
3228 
3229 void JavaThread::popframe_free_preserved_args() {
3230   assert(_popframe_preserved_args != NULL, "should not free PopFrame preserved arguments twice");
3231   FREE_C_HEAP_ARRAY(char, (char*) _popframe_preserved_args);
3232   _popframe_preserved_args = NULL;
3233   _popframe_preserved_args_size = 0;
3234 }
3235 
3236 #ifndef PRODUCT
3237 
3238 void JavaThread::trace_frames() {
3239   tty->print_cr("[Describe stack]");
3240   int frame_no = 1;
3241   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
3242     tty->print("  %d. ", frame_no++);
3243     fst.current()->print_value_on(tty, this);
3244     tty->cr();
3245   }
3246 }
3247 
3248 class PrintAndVerifyOopClosure: public OopClosure {
3249  protected:
3250   template <class T> inline void do_oop_work(T* p) {
3251     oop obj = oopDesc::load_decode_heap_oop(p);
3252     if (obj == NULL) return;
3253     tty->print(INTPTR_FORMAT ": ", p2i(p));
3254     if (oopDesc::is_oop_or_null(obj)) {
3255       if (obj->is_objArray()) {
3256         tty->print_cr("valid objArray: " INTPTR_FORMAT, p2i(obj));
3257       } else {
3258         obj->print();
3259       }
3260     } else {
3261       tty->print_cr("invalid oop: " INTPTR_FORMAT, p2i(obj));
3262     }
3263     tty->cr();
3264   }
3265  public:
3266   virtual void do_oop(oop* p) { do_oop_work(p); }
3267   virtual void do_oop(narrowOop* p)  { do_oop_work(p); }
3268 };
3269 
3270 
3271 static void oops_print(frame* f, const RegisterMap *map) {
3272   PrintAndVerifyOopClosure print;
3273   f->print_value();
3274   f->oops_do(&print, NULL, (RegisterMap*)map);
3275 }
3276 
3277 // Print our all the locations that contain oops and whether they are
3278 // valid or not.  This useful when trying to find the oldest frame
3279 // where an oop has gone bad since the frame walk is from youngest to
3280 // oldest.
3281 void JavaThread::trace_oops() {
3282   tty->print_cr("[Trace oops]");
3283   frames_do(oops_print);
3284 }
3285 
3286 
3287 #ifdef ASSERT
3288 // Print or validate the layout of stack frames
3289 void JavaThread::print_frame_layout(int depth, bool validate_only) {
3290   ResourceMark rm;
3291   PRESERVE_EXCEPTION_MARK;
3292   FrameValues values;
3293   int frame_no = 0;
3294   for (StackFrameStream fst(this, false); !fst.is_done(); fst.next()) {
3295     fst.current()->describe(values, ++frame_no);
3296     if (depth == frame_no) break;
3297   }
3298   if (validate_only) {
3299     values.validate();
3300   } else {
3301     tty->print_cr("[Describe stack layout]");
3302     values.print(this);
3303   }
3304 }
3305 #endif
3306 
3307 void JavaThread::trace_stack_from(vframe* start_vf) {
3308   ResourceMark rm;
3309   int vframe_no = 1;
3310   for (vframe* f = start_vf; f; f = f->sender()) {
3311     if (f->is_java_frame()) {
3312       javaVFrame::cast(f)->print_activation(vframe_no++);
3313     } else {
3314       f->print();
3315     }
3316     if (vframe_no > StackPrintLimit) {
3317       tty->print_cr("...<more frames>...");
3318       return;
3319     }
3320   }
3321 }
3322 
3323 
3324 void JavaThread::trace_stack() {
3325   if (!has_last_Java_frame()) return;
3326   ResourceMark rm;
3327   HandleMark   hm;
3328   RegisterMap reg_map(this);
3329   trace_stack_from(last_java_vframe(&reg_map));
3330 }
3331 
3332 
3333 #endif // PRODUCT
3334 
3335 
3336 javaVFrame* JavaThread::last_java_vframe(RegisterMap *reg_map) {
3337   assert(reg_map != NULL, "a map must be given");
3338   frame f = last_frame();
3339   for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender()) {
3340     if (vf->is_java_frame()) return javaVFrame::cast(vf);
3341   }
3342   return NULL;
3343 }
3344 
3345 
3346 Klass* JavaThread::security_get_caller_class(int depth) {
3347   vframeStream vfst(this);
3348   vfst.security_get_caller_frame(depth);
3349   if (!vfst.at_end()) {
3350     return vfst.method()->method_holder();
3351   }
3352   return NULL;
3353 }
3354 
3355 static void compiler_thread_entry(JavaThread* thread, TRAPS) {
3356   assert(thread->is_Compiler_thread(), "must be compiler thread");
3357   CompileBroker::compiler_thread_loop();
3358 }
3359 
3360 static void sweeper_thread_entry(JavaThread* thread, TRAPS) {
3361   NMethodSweeper::sweeper_loop();
3362 }
3363 
3364 // Create a CompilerThread
3365 CompilerThread::CompilerThread(CompileQueue* queue,
3366                                CompilerCounters* counters)
3367                                : JavaThread(&compiler_thread_entry) {
3368   _env   = NULL;
3369   _log   = NULL;
3370   _task  = NULL;
3371   _queue = queue;
3372   _counters = counters;
3373   _buffer_blob = NULL;
3374   _compiler = NULL;
3375 
3376   // Compiler uses resource area for compilation, let's bias it to mtCompiler
3377   resource_area()->bias_to(mtCompiler);
3378 
3379 #ifndef PRODUCT
3380   _ideal_graph_printer = NULL;
3381 #endif
3382 }
3383 
3384 bool CompilerThread::can_call_java() const {
3385   return _compiler != NULL && _compiler->is_jvmci();
3386 }
3387 
3388 // Create sweeper thread
3389 CodeCacheSweeperThread::CodeCacheSweeperThread()
3390 : JavaThread(&sweeper_thread_entry) {
3391   _scanned_compiled_method = NULL;
3392 }
3393 
3394 void CodeCacheSweeperThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
3395   JavaThread::oops_do(f, cf);
3396   if (_scanned_compiled_method != NULL && cf != NULL) {
3397     // Safepoints can occur when the sweeper is scanning an nmethod so
3398     // process it here to make sure it isn't unloaded in the middle of
3399     // a scan.
3400     cf->do_code_blob(_scanned_compiled_method);
3401   }
3402 }
3403 
3404 void CodeCacheSweeperThread::nmethods_do(CodeBlobClosure* cf) {
3405   JavaThread::nmethods_do(cf);
3406   if (_scanned_compiled_method != NULL && cf != NULL) {
3407     // Safepoints can occur when the sweeper is scanning an nmethod so
3408     // process it here to make sure it isn't unloaded in the middle of
3409     // a scan.
3410     cf->do_code_blob(_scanned_compiled_method);
3411   }
3412 }
3413 
3414 
3415 // ======= Threads ========
3416 
3417 // The Threads class links together all active threads, and provides
3418 // operations over all threads.  It is protected by its own Mutex
3419 // lock, which is also used in other contexts to protect thread
3420 // operations from having the thread being operated on from exiting
3421 // and going away unexpectedly (e.g., safepoint synchronization)
3422 
3423 JavaThread*           Threads::_thread_list = NULL;
3424 int                   Threads::_number_of_threads = 0;
3425 int                   Threads::_number_of_non_daemon_threads = 0;
3426 int                   Threads::_return_code = 0;
3427 int                   Threads::_thread_claim_parity = 0;
3428 size_t                JavaThread::_stack_size_at_create = 0;
3429 Monitor*              Threads::_smr_delete_lock =
3430                           new Monitor(Monitor::special, "smr_delete_lock",
3431                                       false /* allow_vm_block */,
3432                                       Monitor::_safepoint_check_never);
3433 // The '_cnt', '_max' and '_times" fields are enabled via
3434 // -XX:+EnableThreadSMRStatistics:
3435 uint                  Threads::_smr_delete_lock_wait_cnt = 0;
3436 uint                  Threads::_smr_delete_lock_wait_max = 0;
3437 volatile jint         Threads::_smr_delete_notify = 0;
3438 volatile jint         Threads::_smr_deleted_thread_cnt = 0;
3439 volatile jint         Threads::_smr_deleted_thread_time_max = 0;
3440 volatile jint         Threads::_smr_deleted_thread_times = 0;
3441 ThreadsList* volatile Threads::_smr_java_thread_list = new ThreadsList(0);
3442 long                  Threads::_smr_java_thread_list_alloc_cnt = 1;
3443 long                  Threads::_smr_java_thread_list_free_cnt = 0;
3444 uint                  Threads::_smr_java_thread_list_max = 0;
3445 uint                  Threads::_smr_nested_thread_list_max = 0;
3446 volatile jint         Threads::_smr_tlh_cnt = 0;
3447 volatile jint         Threads::_smr_tlh_time_max = 0;
3448 volatile jint         Threads::_smr_tlh_times = 0;
3449 ThreadsList*          Threads::_smr_to_delete_list = NULL;
3450 uint                  Threads::_smr_to_delete_list_cnt = 0;
3451 uint                  Threads::_smr_to_delete_list_max = 0;
3452 
3453 #ifdef ASSERT
3454 bool                  Threads::_vm_complete = false;
3455 #endif
3456 
3457 static inline void *prefetch_and_load_ptr(void **addr, intx prefetch_interval) {
3458   Prefetch::read((void*)addr, prefetch_interval);
3459   return *addr;
3460 }
3461 
3462 // Possibly the ugliest for loop the world has seen. C++ does not allow
3463 // multiple types in the declaration section of the for loop. In this case
3464 // we are only dealing with pointers and hence can cast them. It looks ugly
3465 // but macros are ugly and therefore it's fine to make things absurdly ugly.
3466 #define DO_JAVA_THREADS(LIST, X)                                                                                          \
3467     for (JavaThread *MACRO_scan_interval = (JavaThread*)(uintptr_t)PrefetchScanIntervalInBytes,                           \
3468              *MACRO_list = (JavaThread*)(LIST),                                                                           \
3469              **MACRO_end = ((JavaThread**)((ThreadsList*)MACRO_list)->threads()) + ((ThreadsList*)MACRO_list)->length(),  \
3470              **MACRO_current_p = (JavaThread**)((ThreadsList*)MACRO_list)->threads(),                                     \
3471              *X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval);                 \
3472          MACRO_current_p != MACRO_end;                                                                                    \
3473          MACRO_current_p++,                                                                                               \
3474              X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval))
3475 
3476 // All JavaThreads
3477 #define ALL_JAVA_THREADS(X) DO_JAVA_THREADS(get_smr_java_thread_list(), X)
3478 
3479 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system)
3480 void Threads::threads_do(ThreadClosure* tc) {
3481   assert_locked_or_safepoint(Threads_lock);
3482   // ALL_JAVA_THREADS iterates through all JavaThreads
3483   ALL_JAVA_THREADS(p) {
3484     tc->do_thread(p);
3485   }
3486   // Someday we could have a table or list of all non-JavaThreads.
3487   // For now, just manually iterate through them.
3488   tc->do_thread(VMThread::vm_thread());
3489   Universe::heap()->gc_threads_do(tc);
3490   WatcherThread *wt = WatcherThread::watcher_thread();
3491   // Strictly speaking, the following NULL check isn't sufficient to make sure
3492   // the data for WatcherThread is still valid upon being examined. However,
3493   // considering that WatchThread terminates when the VM is on the way to
3494   // exit at safepoint, the chance of the above is extremely small. The right
3495   // way to prevent termination of WatcherThread would be to acquire
3496   // Terminator_lock, but we can't do that without violating the lock rank
3497   // checking in some cases.
3498   if (wt != NULL) {
3499     tc->do_thread(wt);
3500   }
3501 
3502   // If CompilerThreads ever become non-JavaThreads, add them here
3503 }
3504 
3505 void Threads::possibly_parallel_threads_do(bool is_par, ThreadClosure* tc) {
3506   int cp = Threads::thread_claim_parity();
3507   ALL_JAVA_THREADS(p) {
3508     if (p->claim_oops_do(is_par, cp)) {
3509       tc->do_thread(p);
3510     }
3511   }
3512   VMThread* vmt = VMThread::vm_thread();
3513   if (vmt->claim_oops_do(is_par, cp)) {
3514     tc->do_thread(vmt);
3515   }
3516 }
3517 
3518 // The system initialization in the library has three phases.
3519 //
3520 // Phase 1: java.lang.System class initialization
3521 //     java.lang.System is a primordial class loaded and initialized
3522 //     by the VM early during startup.  java.lang.System.<clinit>
3523 //     only does registerNatives and keeps the rest of the class
3524 //     initialization work later until thread initialization completes.
3525 //
3526 //     System.initPhase1 initializes the system properties, the static
3527 //     fields in, out, and err. Set up java signal handlers, OS-specific
3528 //     system settings, and thread group of the main thread.
3529 static void call_initPhase1(TRAPS) {
3530   Klass* klass =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3531   JavaValue result(T_VOID);
3532   JavaCalls::call_static(&result, klass, vmSymbols::initPhase1_name(),
3533                                          vmSymbols::void_method_signature(), CHECK);
3534 }
3535 
3536 // Phase 2. Module system initialization
3537 //     This will initialize the module system.  Only java.base classes
3538 //     can be loaded until phase 2 completes.
3539 //
3540 //     Call System.initPhase2 after the compiler initialization and jsr292
3541 //     classes get initialized because module initialization runs a lot of java
3542 //     code, that for performance reasons, should be compiled.  Also, this will
3543 //     enable the startup code to use lambda and other language features in this
3544 //     phase and onward.
3545 //
3546 //     After phase 2, The VM will begin search classes from -Xbootclasspath/a.
3547 static void call_initPhase2(TRAPS) {
3548   TraceTime timer("Initialize module system", TRACETIME_LOG(Info, startuptime));
3549 
3550   Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3551 
3552   JavaValue result(T_INT);
3553   JavaCallArguments args;
3554   args.push_int(DisplayVMOutputToStderr);
3555   args.push_int(log_is_enabled(Debug, init)); // print stack trace if exception thrown
3556   JavaCalls::call_static(&result, klass, vmSymbols::initPhase2_name(),
3557                                          vmSymbols::boolean_boolean_int_signature(), &args, CHECK);
3558   if (result.get_jint() != JNI_OK) {
3559     vm_exit_during_initialization(); // no message or exception
3560   }
3561 
3562   universe_post_module_init();
3563 }
3564 
3565 // Phase 3. final setup - set security manager, system class loader and TCCL
3566 //
3567 //     This will instantiate and set the security manager, set the system class
3568 //     loader as well as the thread context class loader.  The security manager
3569 //     and system class loader may be a custom class loaded from -Xbootclasspath/a,
3570 //     other modules or the application's classpath.
3571 static void call_initPhase3(TRAPS) {
3572   Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3573   JavaValue result(T_VOID);
3574   JavaCalls::call_static(&result, klass, vmSymbols::initPhase3_name(),
3575                                          vmSymbols::void_method_signature(), CHECK);
3576 }
3577 
3578 // Safe Memory Reclamation (SMR) support:
3579 //
3580 
3581 // Acquire a stable ThreadsList.
3582 //
3583 ThreadsList *Threads::acquire_stable_list(Thread *self, bool is_ThreadsListSetter) {
3584   assert(self != NULL, "sanity check");
3585   // acquire_stable_list_nested_path() will grab the Threads_lock
3586   // so let's make sure the ThreadsListHandle is in a safe place.
3587   // ThreadsListSetter cannot make this check on this code path.
3588   debug_only(if (!is_ThreadsListSetter && StrictSafepointChecks) self->check_for_valid_safepoint_state(/* potential_vm_operation */ false);)
3589 
3590   if (self->get_threads_hazard_ptr() == NULL) {
3591     // The typical case is first.
3592     return acquire_stable_list_fast_path(self);
3593   }
3594 
3595   // The nested case is rare.
3596   return acquire_stable_list_nested_path(self);
3597 }
3598 
3599 // Fast path (and lock free) way to acquire a stable ThreadsList.
3600 //
3601 ThreadsList *Threads::acquire_stable_list_fast_path(Thread *self) {
3602   assert(self != NULL, "sanity check");
3603   assert(self->get_threads_hazard_ptr() == NULL, "sanity check");
3604   assert(self->get_nested_threads_hazard_ptr() == NULL,
3605          "cannot have a nested hazard ptr with a NULL regular hazard ptr");
3606 
3607   ThreadsList* threads;
3608 
3609   // Stable recording of a hazard ptr for SMR. This code does not use
3610   // locks so its use of the _smr_java_thread_list & _threads_hazard_ptr
3611   // fields is racy relative to code that uses those fields with locks.
3612   // OrderAccess and Atomic functions are used to deal with those races.
3613   //
3614   while (true) {
3615     threads = get_smr_java_thread_list();
3616 
3617     // Publish a tagged hazard ptr to denote that the hazard ptr is not
3618     // yet verified as being stable. Due to the fence after the hazard
3619     // ptr write, it will be sequentially consistent w.r.t. the
3620     // sequentially consistent writes of the ThreadsList, even on
3621     // non-multiple copy atomic machines where stores can be observed
3622     // in different order from different observer threads.
3623     ThreadsList* unverified_threads = Thread::tag_hazard_ptr(threads);
3624     self->set_threads_hazard_ptr(unverified_threads);
3625 
3626     // If _smr_java_thread_list has changed, we have lost a race with
3627     // Threads::add() or Threads::remove() and have to try again.
3628     if (get_smr_java_thread_list() != threads) {
3629       continue;
3630     }
3631 
3632     // We try to remove the tag which will verify the hazard ptr as
3633     // being stable. This exchange can race with a scanning thread
3634     // which might invalidate the tagged hazard ptr to keep it from
3635     // being followed to access JavaThread ptrs. If we lose the race,
3636     // we simply retry. If we win the race, then the stable hazard
3637     // ptr is officially published.
3638     if (self->cmpxchg_threads_hazard_ptr(threads, unverified_threads) == unverified_threads) {
3639       break;
3640     }
3641   }
3642 
3643   // A stable hazard ptr has been published letting other threads know
3644   // that the ThreadsList and the JavaThreads reachable from this list
3645   // are protected and hence they should not be deleted until everyone
3646   // agrees it is safe to do so.
3647 
3648   return threads;
3649 }
3650 
3651 // Acquire a nested stable ThreadsList; this is rare so it uses
3652 // Threads_lock.
3653 //
3654 ThreadsList *Threads::acquire_stable_list_nested_path(Thread *self) {
3655   assert(self != NULL, "sanity check");
3656   assert(self->get_threads_hazard_ptr() != NULL,
3657          "cannot have a NULL regular hazard ptr when acquiring a nested hazard ptr");
3658 
3659   // The thread already has a hazard ptr (ThreadsList ref) so we need
3660   // to create a nested ThreadsListHandle with the current ThreadsList
3661   // since it might be different than our current hazard ptr. The need
3662   // for a nested ThreadsListHandle is rare so we do this while holding
3663   // the Threads_lock so we don't race with the scanning code; the code
3664   // is so much simpler this way.
3665 
3666   NestedThreadsList* node;
3667   {
3668     // Only grab the Threads_lock if we don't already own it.
3669     MutexLockerEx ml(Threads_lock->owned_by_self() ? NULL : Threads_lock);
3670     node = new NestedThreadsList(get_smr_java_thread_list());
3671     // We insert at the front of the list to match up with the delete
3672     // in release_stable_list().
3673     node->set_next(self->get_nested_threads_hazard_ptr());
3674     self->set_nested_threads_hazard_ptr(node);
3675     if (EnableThreadSMRStatistics) {
3676       self->inc_nested_threads_hazard_ptr_cnt();
3677       if (self->nested_threads_hazard_ptr_cnt() > _smr_nested_thread_list_max) {
3678         _smr_nested_thread_list_max = self->nested_threads_hazard_ptr_cnt();
3679       }
3680     }
3681   }
3682   log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::acquire_stable_list: add NestedThreadsList node containing ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(node->t_list()));
3683 
3684   return node->t_list();
3685 }
3686 
3687 // Release a stable ThreadsList.
3688 //
3689 void Threads::release_stable_list(Thread *self) {
3690   assert(self != NULL, "sanity check");
3691   // release_stable_list_nested_path() will grab the Threads_lock
3692   // so let's make sure the ThreadsListHandle is in a safe place.
3693   debug_only(if (StrictSafepointChecks) self->check_for_valid_safepoint_state(/* potential_vm_operation */ false);)
3694 
3695   if (self->get_nested_threads_hazard_ptr() == NULL) {
3696     // The typical case is first.
3697     release_stable_list_fast_path(self);
3698     return;
3699   }
3700 
3701   // The nested case is rare.
3702   release_stable_list_nested_path(self);
3703 }
3704 
3705 // Fast path way to release a stable ThreadsList. The release portion
3706 // is lock-free, but the wake up portion is not.
3707 //
3708 void Threads::release_stable_list_fast_path(Thread *self) {
3709   assert(self != NULL, "sanity check");
3710   assert(self->get_threads_hazard_ptr() != NULL, "sanity check");
3711   assert(self->get_nested_threads_hazard_ptr() == NULL,
3712          "cannot have a nested hazard ptr when releasing a regular hazard ptr");
3713 
3714   // After releasing the hazard ptr, other threads may go ahead and
3715   // free up some memory temporarily used by a ThreadsList snapshot.
3716   self->set_threads_hazard_ptr(NULL);
3717 
3718   // We use double-check locking to reduce traffic on the system
3719   // wide smr_delete_lock.
3720   if (Threads::smr_delete_notify()) {
3721     // An exiting thread might be waiting in smr_delete(); we need to
3722     // check with smr_delete_lock to be sure.
3723     release_stable_list_wake_up((char *) "regular hazard ptr");
3724   }
3725 }
3726 
3727 // Release a nested stable ThreadsList; this is rare so it uses
3728 // Threads_lock.
3729 //
3730 void Threads::release_stable_list_nested_path(Thread *self) {
3731   assert(self != NULL, "sanity check");
3732   assert(self->get_nested_threads_hazard_ptr() != NULL, "sanity check");
3733   assert(self->get_threads_hazard_ptr() != NULL,
3734          "must have a regular hazard ptr to have nested hazard ptrs");
3735 
3736   // We have a nested ThreadsListHandle so we have to release it first.
3737   // The need for a nested ThreadsListHandle is rare so we do this while
3738   // holding the Threads_lock so we don't race with the scanning code;
3739   // the code is so much simpler this way.
3740 
3741   NestedThreadsList *node;
3742   {
3743     // Only grab the Threads_lock if we don't already own it.
3744     MutexLockerEx ml(Threads_lock->owned_by_self() ? NULL : Threads_lock);
3745     // We remove from the front of the list to match up with the insert
3746     // in acquire_stable_list().
3747     node = self->get_nested_threads_hazard_ptr();
3748     self->set_nested_threads_hazard_ptr(node->next());
3749     if (EnableThreadSMRStatistics) {
3750       self->dec_nested_threads_hazard_ptr_cnt();
3751     }
3752   }
3753 
3754   // An exiting thread might be waiting in smr_delete(); we need to
3755   // check with smr_delete_lock to be sure.
3756   release_stable_list_wake_up((char *) "nested hazard ptr");
3757 
3758   log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::release_stable_list: delete NestedThreadsList node containing ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(node->t_list()));
3759 
3760   delete node;
3761 }
3762 
3763 // Wake up portion of the release stable ThreadsList protocol;
3764 // uses the smr_delete_lock().
3765 //
3766 void Threads::release_stable_list_wake_up(char *log_str) {
3767   assert(log_str != NULL, "sanity check");
3768 
3769   // Note: smr_delete_lock is held in smr_delete() for the entire
3770   // hazard ptr search so that we do not lose this notify() if
3771   // the exiting thread has to wait. That code path also holds
3772   // Threads_lock (which was grabbed before smr_delete_lock) so that
3773   // threads_do() can be called. This means the system can't start a
3774   // safepoint which means this thread can't take too long to get to
3775   // a safepoint because of being blocked on smr_delete_lock.
3776   //
3777   MonitorLockerEx ml(Threads::smr_delete_lock(), Monitor::_no_safepoint_check_flag);
3778   if (Threads::smr_delete_notify()) {
3779     // Notify any exiting JavaThreads that are waiting in smr_delete()
3780     // that we've released a ThreadsList.
3781     ml.notify_all();
3782     log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::release_stable_list notified %s", os::current_thread_id(), log_str);
3783   }
3784 }
3785 
3786 void Threads::initialize_java_lang_classes(JavaThread* main_thread, TRAPS) {
3787   TraceTime timer("Initialize java.lang classes", TRACETIME_LOG(Info, startuptime));
3788 
3789   if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
3790     create_vm_init_libraries();
3791   }
3792 
3793   initialize_class(vmSymbols::java_lang_String(), CHECK);
3794 
3795   // Inject CompactStrings value after the static initializers for String ran.
3796   java_lang_String::set_compact_strings(CompactStrings);
3797 
3798   // Initialize java_lang.System (needed before creating the thread)
3799   initialize_class(vmSymbols::java_lang_System(), CHECK);
3800   // The VM creates & returns objects of this class. Make sure it's initialized.
3801   initialize_class(vmSymbols::java_lang_Class(), CHECK);
3802   initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK);
3803   Handle thread_group = create_initial_thread_group(CHECK);
3804   Universe::set_main_thread_group(thread_group());
3805   initialize_class(vmSymbols::java_lang_Thread(), CHECK);
3806   oop thread_object = create_initial_thread(thread_group, main_thread, CHECK);
3807   main_thread->set_threadObj(thread_object);
3808   // Set thread status to running since main thread has
3809   // been started and running.
3810   java_lang_Thread::set_thread_status(thread_object,
3811                                       java_lang_Thread::RUNNABLE);
3812 
3813   // The VM creates objects of this class.
3814   initialize_class(vmSymbols::java_lang_Module(), CHECK);
3815 
3816   // The VM preresolves methods to these classes. Make sure that they get initialized
3817   initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK);
3818   initialize_class(vmSymbols::java_lang_ref_Finalizer(), CHECK);
3819 
3820   // Phase 1 of the system initialization in the library, java.lang.System class initialization
3821   call_initPhase1(CHECK);
3822 
3823   // get the Java runtime name after java.lang.System is initialized
3824   JDK_Version::set_runtime_name(get_java_runtime_name(THREAD));
3825   JDK_Version::set_runtime_version(get_java_runtime_version(THREAD));
3826 
3827   // an instance of OutOfMemory exception has been allocated earlier
3828   initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK);
3829   initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK);
3830   initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK);
3831   initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK);
3832   initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK);
3833   initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK);
3834   initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK);
3835   initialize_class(vmSymbols::java_lang_IllegalArgumentException(), CHECK);
3836 }
3837 
3838 void Threads::initialize_jsr292_core_classes(TRAPS) {
3839   TraceTime timer("Initialize java.lang.invoke classes", TRACETIME_LOG(Info, startuptime));
3840 
3841   initialize_class(vmSymbols::java_lang_invoke_MethodHandle(), CHECK);
3842   initialize_class(vmSymbols::java_lang_invoke_ResolvedMethodName(), CHECK);
3843   initialize_class(vmSymbols::java_lang_invoke_MemberName(), CHECK);
3844   initialize_class(vmSymbols::java_lang_invoke_MethodHandleNatives(), CHECK);
3845 }
3846 
3847 jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
3848   extern void JDK_Version_init();
3849 
3850   // Preinitialize version info.
3851   VM_Version::early_initialize();
3852 
3853   // Check version
3854   if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
3855 
3856   // Initialize library-based TLS
3857   ThreadLocalStorage::init();
3858 
3859   // Initialize the output stream module
3860   ostream_init();
3861 
3862   // Process java launcher properties.
3863   Arguments::process_sun_java_launcher_properties(args);
3864 
3865   // Initialize the os module
3866   os::init();
3867 
3868   // Record VM creation timing statistics
3869   TraceVmCreationTime create_vm_timer;
3870   create_vm_timer.start();
3871 
3872   // Initialize system properties.
3873   Arguments::init_system_properties();
3874 
3875   // So that JDK version can be used as a discriminator when parsing arguments
3876   JDK_Version_init();
3877 
3878   // Update/Initialize System properties after JDK version number is known
3879   Arguments::init_version_specific_system_properties();
3880 
3881   // Make sure to initialize log configuration *before* parsing arguments
3882   LogConfiguration::initialize(create_vm_timer.begin_time());
3883 
3884   // Parse arguments
3885   jint parse_result = Arguments::parse(args);
3886   if (parse_result != JNI_OK) return parse_result;
3887 
3888   os::init_before_ergo();
3889 
3890   jint ergo_result = Arguments::apply_ergo();
3891   if (ergo_result != JNI_OK) return ergo_result;
3892 
3893   // Final check of all ranges after ergonomics which may change values.
3894   if (!CommandLineFlagRangeList::check_ranges()) {
3895     return JNI_EINVAL;
3896   }
3897 
3898   // Final check of all 'AfterErgo' constraints after ergonomics which may change values.
3899   bool constraint_result = CommandLineFlagConstraintList::check_constraints(CommandLineFlagConstraint::AfterErgo);
3900   if (!constraint_result) {
3901     return JNI_EINVAL;
3902   }
3903 
3904   CommandLineFlagWriteableList::mark_startup();
3905 
3906   if (PauseAtStartup) {
3907     os::pause();
3908   }
3909 
3910   HOTSPOT_VM_INIT_BEGIN();
3911 
3912   // Timing (must come after argument parsing)
3913   TraceTime timer("Create VM", TRACETIME_LOG(Info, startuptime));
3914 
3915   SafepointMechanism::initialize();
3916 
3917   // Initialize the os module after parsing the args
3918   jint os_init_2_result = os::init_2();
3919   if (os_init_2_result != JNI_OK) return os_init_2_result;
3920 
3921   jint adjust_after_os_result = Arguments::adjust_after_os();
3922   if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;
3923 
3924   // Initialize output stream logging
3925   ostream_init_log();
3926 
3927   // Convert -Xrun to -agentlib: if there is no JVM_OnLoad
3928   // Must be before create_vm_init_agents()
3929   if (Arguments::init_libraries_at_startup()) {
3930     convert_vm_init_libraries_to_agents();
3931   }
3932 
3933   // Launch -agentlib/-agentpath and converted -Xrun agents
3934   if (Arguments::init_agents_at_startup()) {
3935     create_vm_init_agents();
3936   }
3937 
3938   // Initialize Threads state
3939   _thread_list = NULL;
3940   _number_of_threads = 0;
3941   _number_of_non_daemon_threads = 0;
3942 
3943   // Initialize global data structures and create system classes in heap
3944   vm_init_globals();
3945 
3946 #if INCLUDE_JVMCI
3947   if (JVMCICounterSize > 0) {
3948     JavaThread::_jvmci_old_thread_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
3949     memset(JavaThread::_jvmci_old_thread_counters, 0, sizeof(jlong) * JVMCICounterSize);
3950   } else {
3951     JavaThread::_jvmci_old_thread_counters = NULL;
3952   }
3953 #endif // INCLUDE_JVMCI
3954 
3955   // Attach the main thread to this os thread
3956   JavaThread* main_thread = new JavaThread();
3957   main_thread->set_thread_state(_thread_in_vm);
3958   main_thread->initialize_thread_current();
3959   // must do this before set_active_handles
3960   main_thread->record_stack_base_and_size();
3961   main_thread->set_active_handles(JNIHandleBlock::allocate_block());
3962 
3963   if (!main_thread->set_as_starting_thread()) {
3964     vm_shutdown_during_initialization(
3965                                       "Failed necessary internal allocation. Out of swap space");
3966     main_thread->smr_delete();
3967     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3968     return JNI_ENOMEM;
3969   }
3970 
3971   // Enable guard page *after* os::create_main_thread(), otherwise it would
3972   // crash Linux VM, see notes in os_linux.cpp.
3973   main_thread->create_stack_guard_pages();
3974 
3975   // Initialize Java-Level synchronization subsystem
3976   ObjectMonitor::Initialize();
3977 
3978   // Initialize global modules
3979   jint status = init_globals();
3980   if (status != JNI_OK) {
3981     main_thread->smr_delete();
3982     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3983     return status;
3984   }
3985 
3986   if (TRACE_INITIALIZE() != JNI_OK) {
3987     vm_exit_during_initialization("Failed to initialize tracing backend");
3988   }
3989 
3990   // Should be done after the heap is fully created
3991   main_thread->cache_global_variables();
3992 
3993   HandleMark hm;
3994 
3995   { MutexLocker mu(Threads_lock);
3996     Threads::add(main_thread);
3997   }
3998 
3999   // Any JVMTI raw monitors entered in onload will transition into
4000   // real raw monitor. VM is setup enough here for raw monitor enter.
4001   JvmtiExport::transition_pending_onload_raw_monitors();
4002 
4003   // Create the VMThread
4004   { TraceTime timer("Start VMThread", TRACETIME_LOG(Info, startuptime));
4005 
4006   VMThread::create();
4007     Thread* vmthread = VMThread::vm_thread();
4008 
4009     if (!os::create_thread(vmthread, os::vm_thread)) {
4010       vm_exit_during_initialization("Cannot create VM thread. "
4011                                     "Out of system resources.");
4012     }
4013 
4014     // Wait for the VM thread to become ready, and VMThread::run to initialize
4015     // Monitors can have spurious returns, must always check another state flag
4016     {
4017       MutexLocker ml(Notify_lock);
4018       os::start_thread(vmthread);
4019       while (vmthread->active_handles() == NULL) {
4020         Notify_lock->wait();
4021       }
4022     }
4023   }
4024 
4025   assert(Universe::is_fully_initialized(), "not initialized");
4026   if (VerifyDuringStartup) {
4027     // Make sure we're starting with a clean slate.
4028     VM_Verify verify_op;
4029     VMThread::execute(&verify_op);
4030   }
4031 
4032   Thread* THREAD = Thread::current();
4033 
4034   // Always call even when there are not JVMTI environments yet, since environments
4035   // may be attached late and JVMTI must track phases of VM execution
4036   JvmtiExport::enter_early_start_phase();
4037 
4038   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
4039   JvmtiExport::post_early_vm_start();
4040 
4041   initialize_java_lang_classes(main_thread, CHECK_JNI_ERR);
4042 
4043   // We need this for ClassDataSharing - the initial vm.info property is set
4044   // with the default value of CDS "sharing" which may be reset through
4045   // command line options.
4046   reset_vm_info_property(CHECK_JNI_ERR);
4047 
4048   quicken_jni_functions();
4049 
4050   // No more stub generation allowed after that point.
4051   StubCodeDesc::freeze();
4052 
4053   // Set flag that basic initialization has completed. Used by exceptions and various
4054   // debug stuff, that does not work until all basic classes have been initialized.
4055   set_init_completed();
4056 
4057   LogConfiguration::post_initialize();
4058   Metaspace::post_initialize();
4059 
4060   HOTSPOT_VM_INIT_END();
4061 
4062   // record VM initialization completion time
4063 #if INCLUDE_MANAGEMENT
4064   Management::record_vm_init_completed();
4065 #endif // INCLUDE_MANAGEMENT
4066 
4067   // Signal Dispatcher needs to be started before VMInit event is posted
4068   os::signal_init(CHECK_JNI_ERR);
4069 
4070   // Start Attach Listener if +StartAttachListener or it can't be started lazily
4071   if (!DisableAttachMechanism) {
4072     AttachListener::vm_start();
4073     if (StartAttachListener || AttachListener::init_at_startup()) {
4074       AttachListener::init();
4075     }
4076   }
4077 
4078   // Launch -Xrun agents
4079   // Must be done in the JVMTI live phase so that for backward compatibility the JDWP
4080   // back-end can launch with -Xdebug -Xrunjdwp.
4081   if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
4082     create_vm_init_libraries();
4083   }
4084 
4085   if (CleanChunkPoolAsync) {
4086     Chunk::start_chunk_pool_cleaner_task();
4087   }
4088 
4089   // initialize compiler(s)
4090 #if defined(COMPILER1) || COMPILER2_OR_JVMCI
4091   CompileBroker::compilation_init(CHECK_JNI_ERR);
4092 #endif
4093 
4094   // Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
4095   // It is done after compilers are initialized, because otherwise compilations of
4096   // signature polymorphic MH intrinsics can be missed
4097   // (see SystemDictionary::find_method_handle_intrinsic).
4098   initialize_jsr292_core_classes(CHECK_JNI_ERR);
4099 
4100   // This will initialize the module system.  Only java.base classes can be
4101   // loaded until phase 2 completes
4102   call_initPhase2(CHECK_JNI_ERR);
4103 
4104   // Always call even when there are not JVMTI environments yet, since environments
4105   // may be attached late and JVMTI must track phases of VM execution
4106   JvmtiExport::enter_start_phase();
4107 
4108   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
4109   JvmtiExport::post_vm_start();
4110 
4111   // Final system initialization including security manager and system class loader
4112   call_initPhase3(CHECK_JNI_ERR);
4113 
4114   // cache the system and platform class loaders
4115   SystemDictionary::compute_java_loaders(CHECK_JNI_ERR);
4116 
4117 #if INCLUDE_JVMCI
4118   if (EnableJVMCI) {
4119     // Initialize JVMCI eagerly if JVMCIPrintProperties is enabled.
4120     // The JVMCI Java initialization code will read this flag and
4121     // do the printing if it's set.
4122     bool init = JVMCIPrintProperties;
4123 
4124     if (!init) {
4125       // 8145270: Force initialization of JVMCI runtime otherwise requests for blocking
4126       // compilations via JVMCI will not actually block until JVMCI is initialized.
4127       init = UseJVMCICompiler && (!UseInterpreter || !BackgroundCompilation);
4128     }
4129 
4130     if (init) {
4131       JVMCIRuntime::force_initialization(CHECK_JNI_ERR);
4132     }
4133   }
4134 #endif
4135 
4136   // Always call even when there are not JVMTI environments yet, since environments
4137   // may be attached late and JVMTI must track phases of VM execution
4138   JvmtiExport::enter_live_phase();
4139 
4140   // Notify JVMTI agents that VM initialization is complete - nop if no agents.
4141   JvmtiExport::post_vm_initialized();
4142 
4143   if (TRACE_START() != JNI_OK) {
4144     vm_exit_during_initialization("Failed to start tracing backend.");
4145   }
4146 
4147 #if INCLUDE_MANAGEMENT
4148   Management::initialize(THREAD);
4149 
4150   if (HAS_PENDING_EXCEPTION) {
4151     // management agent fails to start possibly due to
4152     // configuration problem and is responsible for printing
4153     // stack trace if appropriate. Simply exit VM.
4154     vm_exit(1);
4155   }
4156 #endif // INCLUDE_MANAGEMENT
4157 
4158   if (MemProfiling)                   MemProfiler::engage();
4159   StatSampler::engage();
4160   if (CheckJNICalls)                  JniPeriodicChecker::engage();
4161 
4162   BiasedLocking::init();
4163 
4164 #if INCLUDE_RTM_OPT
4165   RTMLockingCounters::init();
4166 #endif
4167 
4168   if (JDK_Version::current().post_vm_init_hook_enabled()) {
4169     call_postVMInitHook(THREAD);
4170     // The Java side of PostVMInitHook.run must deal with all
4171     // exceptions and provide means of diagnosis.
4172     if (HAS_PENDING_EXCEPTION) {
4173       CLEAR_PENDING_EXCEPTION;
4174     }
4175   }
4176 
4177   {
4178     MutexLocker ml(PeriodicTask_lock);
4179     // Make sure the WatcherThread can be started by WatcherThread::start()
4180     // or by dynamic enrollment.
4181     WatcherThread::make_startable();
4182     // Start up the WatcherThread if there are any periodic tasks
4183     // NOTE:  All PeriodicTasks should be registered by now. If they
4184     //   aren't, late joiners might appear to start slowly (we might
4185     //   take a while to process their first tick).
4186     if (PeriodicTask::num_tasks() > 0) {
4187       WatcherThread::start();
4188     }
4189   }
4190 
4191   create_vm_timer.end();
4192 #ifdef ASSERT
4193   _vm_complete = true;
4194 #endif
4195 
4196   if (DumpSharedSpaces) {
4197     MetaspaceShared::preload_and_dump(CHECK_JNI_ERR);
4198     ShouldNotReachHere();
4199   }
4200 
4201   return JNI_OK;
4202 }
4203 
4204 // type for the Agent_OnLoad and JVM_OnLoad entry points
4205 extern "C" {
4206   typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
4207 }
4208 // Find a command line agent library and return its entry point for
4209 //         -agentlib:  -agentpath:   -Xrun
4210 // num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array.
4211 static OnLoadEntry_t lookup_on_load(AgentLibrary* agent,
4212                                     const char *on_load_symbols[],
4213                                     size_t num_symbol_entries) {
4214   OnLoadEntry_t on_load_entry = NULL;
4215   void *library = NULL;
4216 
4217   if (!agent->valid()) {
4218     char buffer[JVM_MAXPATHLEN];
4219     char ebuf[1024] = "";
4220     const char *name = agent->name();
4221     const char *msg = "Could not find agent library ";
4222 
4223     // First check to see if agent is statically linked into executable
4224     if (os::find_builtin_agent(agent, on_load_symbols, num_symbol_entries)) {
4225       library = agent->os_lib();
4226     } else if (agent->is_absolute_path()) {
4227       library = os::dll_load(name, ebuf, sizeof ebuf);
4228       if (library == NULL) {
4229         const char *sub_msg = " in absolute path, with error: ";
4230         size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
4231         char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
4232         jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
4233         // If we can't find the agent, exit.
4234         vm_exit_during_initialization(buf, NULL);
4235         FREE_C_HEAP_ARRAY(char, buf);
4236       }
4237     } else {
4238       // Try to load the agent from the standard dll directory
4239       if (os::dll_locate_lib(buffer, sizeof(buffer), Arguments::get_dll_dir(),
4240                              name)) {
4241         library = os::dll_load(buffer, ebuf, sizeof ebuf);
4242       }
4243       if (library == NULL) { // Try the library path directory.
4244         if (os::dll_build_name(buffer, sizeof(buffer), name)) {
4245           library = os::dll_load(buffer, ebuf, sizeof ebuf);
4246         }
4247         if (library == NULL) {
4248           const char *sub_msg = " on the library path, with error: ";
4249           size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
4250           char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
4251           jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
4252           // If we can't find the agent, exit.
4253           vm_exit_during_initialization(buf, NULL);
4254           FREE_C_HEAP_ARRAY(char, buf);
4255         }
4256       }
4257     }
4258     agent->set_os_lib(library);
4259     agent->set_valid();
4260   }
4261 
4262   // Find the OnLoad function.
4263   on_load_entry =
4264     CAST_TO_FN_PTR(OnLoadEntry_t, os::find_agent_function(agent,
4265                                                           false,
4266                                                           on_load_symbols,
4267                                                           num_symbol_entries));
4268   return on_load_entry;
4269 }
4270 
4271 // Find the JVM_OnLoad entry point
4272 static OnLoadEntry_t lookup_jvm_on_load(AgentLibrary* agent) {
4273   const char *on_load_symbols[] = JVM_ONLOAD_SYMBOLS;
4274   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
4275 }
4276 
4277 // Find the Agent_OnLoad entry point
4278 static OnLoadEntry_t lookup_agent_on_load(AgentLibrary* agent) {
4279   const char *on_load_symbols[] = AGENT_ONLOAD_SYMBOLS;
4280   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
4281 }
4282 
4283 // For backwards compatibility with -Xrun
4284 // Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be
4285 // treated like -agentpath:
4286 // Must be called before agent libraries are created
4287 void Threads::convert_vm_init_libraries_to_agents() {
4288   AgentLibrary* agent;
4289   AgentLibrary* next;
4290 
4291   for (agent = Arguments::libraries(); agent != NULL; agent = next) {
4292     next = agent->next();  // cache the next agent now as this agent may get moved off this list
4293     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
4294 
4295     // If there is an JVM_OnLoad function it will get called later,
4296     // otherwise see if there is an Agent_OnLoad
4297     if (on_load_entry == NULL) {
4298       on_load_entry = lookup_agent_on_load(agent);
4299       if (on_load_entry != NULL) {
4300         // switch it to the agent list -- so that Agent_OnLoad will be called,
4301         // JVM_OnLoad won't be attempted and Agent_OnUnload will
4302         Arguments::convert_library_to_agent(agent);
4303       } else {
4304         vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
4305       }
4306     }
4307   }
4308 }
4309 
4310 // Create agents for -agentlib:  -agentpath:  and converted -Xrun
4311 // Invokes Agent_OnLoad
4312 // Called very early -- before JavaThreads exist
4313 void Threads::create_vm_init_agents() {
4314   extern struct JavaVM_ main_vm;
4315   AgentLibrary* agent;
4316 
4317   JvmtiExport::enter_onload_phase();
4318 
4319   for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
4320     OnLoadEntry_t  on_load_entry = lookup_agent_on_load(agent);
4321 
4322     if (on_load_entry != NULL) {
4323       // Invoke the Agent_OnLoad function
4324       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
4325       if (err != JNI_OK) {
4326         vm_exit_during_initialization("agent library failed to init", agent->name());
4327       }
4328     } else {
4329       vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
4330     }
4331   }
4332   JvmtiExport::enter_primordial_phase();
4333 }
4334 
4335 extern "C" {
4336   typedef void (JNICALL *Agent_OnUnload_t)(JavaVM *);
4337 }
4338 
4339 void Threads::shutdown_vm_agents() {
4340   // Send any Agent_OnUnload notifications
4341   const char *on_unload_symbols[] = AGENT_ONUNLOAD_SYMBOLS;
4342   size_t num_symbol_entries = ARRAY_SIZE(on_unload_symbols);
4343   extern struct JavaVM_ main_vm;
4344   for (AgentLibrary* agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
4345 
4346     // Find the Agent_OnUnload function.
4347     Agent_OnUnload_t unload_entry = CAST_TO_FN_PTR(Agent_OnUnload_t,
4348                                                    os::find_agent_function(agent,
4349                                                    false,
4350                                                    on_unload_symbols,
4351                                                    num_symbol_entries));
4352 
4353     // Invoke the Agent_OnUnload function
4354     if (unload_entry != NULL) {
4355       JavaThread* thread = JavaThread::current();
4356       ThreadToNativeFromVM ttn(thread);
4357       HandleMark hm(thread);
4358       (*unload_entry)(&main_vm);
4359     }
4360   }
4361 }
4362 
4363 // Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries
4364 // Invokes JVM_OnLoad
4365 void Threads::create_vm_init_libraries() {
4366   extern struct JavaVM_ main_vm;
4367   AgentLibrary* agent;
4368 
4369   for (agent = Arguments::libraries(); agent != NULL; agent = agent->next()) {
4370     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
4371 
4372     if (on_load_entry != NULL) {
4373       // Invoke the JVM_OnLoad function
4374       JavaThread* thread = JavaThread::current();
4375       ThreadToNativeFromVM ttn(thread);
4376       HandleMark hm(thread);
4377       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
4378       if (err != JNI_OK) {
4379         vm_exit_during_initialization("-Xrun library failed to init", agent->name());
4380       }
4381     } else {
4382       vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
4383     }
4384   }
4385 }
4386 
4387 
4388 // Last thread running calls java.lang.Shutdown.shutdown()
4389 void JavaThread::invoke_shutdown_hooks() {
4390   HandleMark hm(this);
4391 
4392   // We could get here with a pending exception, if so clear it now.
4393   if (this->has_pending_exception()) {
4394     this->clear_pending_exception();
4395   }
4396 
4397   EXCEPTION_MARK;
4398   Klass* shutdown_klass =
4399     SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
4400                                       THREAD);
4401   if (shutdown_klass != NULL) {
4402     // SystemDictionary::resolve_or_null will return null if there was
4403     // an exception.  If we cannot load the Shutdown class, just don't
4404     // call Shutdown.shutdown() at all.  This will mean the shutdown hooks
4405     // and finalizers (if runFinalizersOnExit is set) won't be run.
4406     // Note that if a shutdown hook was registered or runFinalizersOnExit
4407     // was called, the Shutdown class would have already been loaded
4408     // (Runtime.addShutdownHook and runFinalizersOnExit will load it).
4409     JavaValue result(T_VOID);
4410     JavaCalls::call_static(&result,
4411                            shutdown_klass,
4412                            vmSymbols::shutdown_method_name(),
4413                            vmSymbols::void_method_signature(),
4414                            THREAD);
4415   }
4416   CLEAR_PENDING_EXCEPTION;
4417 }
4418 
4419 // Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
4420 // the program falls off the end of main(). Another VM exit path is through
4421 // vm_exit() when the program calls System.exit() to return a value or when
4422 // there is a serious error in VM. The two shutdown paths are not exactly
4423 // the same, but they share Shutdown.shutdown() at Java level and before_exit()
4424 // and VM_Exit op at VM level.
4425 //
4426 // Shutdown sequence:
4427 //   + Shutdown native memory tracking if it is on
4428 //   + Wait until we are the last non-daemon thread to execute
4429 //     <-- every thing is still working at this moment -->
4430 //   + Call java.lang.Shutdown.shutdown(), which will invoke Java level
4431 //        shutdown hooks, run finalizers if finalization-on-exit
4432 //   + Call before_exit(), prepare for VM exit
4433 //      > run VM level shutdown hooks (they are registered through JVM_OnExit(),
4434 //        currently the only user of this mechanism is File.deleteOnExit())
4435 //      > stop StatSampler, watcher thread, CMS threads,
4436 //        post thread end and vm death events to JVMTI,
4437 //        stop signal thread
4438 //   + Call JavaThread::exit(), it will:
4439 //      > release JNI handle blocks, remove stack guard pages
4440 //      > remove this thread from Threads list
4441 //     <-- no more Java code from this thread after this point -->
4442 //   + Stop VM thread, it will bring the remaining VM to a safepoint and stop
4443 //     the compiler threads at safepoint
4444 //     <-- do not use anything that could get blocked by Safepoint -->
4445 //   + Disable tracing at JNI/JVM barriers
4446 //   + Set _vm_exited flag for threads that are still running native code
4447 //   + Delete this thread
4448 //   + Call exit_globals()
4449 //      > deletes tty
4450 //      > deletes PerfMemory resources
4451 //   + Return to caller
4452 
4453 bool Threads::destroy_vm() {
4454   JavaThread* thread = JavaThread::current();
4455 
4456 #ifdef ASSERT
4457   _vm_complete = false;
4458 #endif
4459   // Wait until we are the last non-daemon thread to execute
4460   { MutexLocker nu(Threads_lock);
4461     while (Threads::number_of_non_daemon_threads() > 1)
4462       // This wait should make safepoint checks, wait without a timeout,
4463       // and wait as a suspend-equivalent condition.
4464       Threads_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
4465                          Mutex::_as_suspend_equivalent_flag);
4466   }
4467 
4468   // Hang forever on exit if we are reporting an error.
4469   if (ShowMessageBoxOnError && VMError::is_error_reported()) {
4470     os::infinite_sleep();
4471   }
4472   os::wait_for_keypress_at_exit();
4473 
4474   // run Java level shutdown hooks
4475   thread->invoke_shutdown_hooks();
4476 
4477   before_exit(thread);
4478 
4479   thread->exit(true);
4480 
4481   // Stop VM thread.
4482   {
4483     // 4945125 The vm thread comes to a safepoint during exit.
4484     // GC vm_operations can get caught at the safepoint, and the
4485     // heap is unparseable if they are caught. Grab the Heap_lock
4486     // to prevent this. The GC vm_operations will not be able to
4487     // queue until after the vm thread is dead. After this point,
4488     // we'll never emerge out of the safepoint before the VM exits.
4489 
4490     MutexLocker ml(Heap_lock);
4491 
4492     VMThread::wait_for_vm_thread_exit();
4493     assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
4494     VMThread::destroy();
4495   }
4496 
4497   // clean up ideal graph printers
4498 #if defined(COMPILER2) && !defined(PRODUCT)
4499   IdealGraphPrinter::clean_up();
4500 #endif
4501 
4502   // Now, all Java threads are gone except daemon threads. Daemon threads
4503   // running Java code or in VM are stopped by the Safepoint. However,
4504   // daemon threads executing native code are still running.  But they
4505   // will be stopped at native=>Java/VM barriers. Note that we can't
4506   // simply kill or suspend them, as it is inherently deadlock-prone.
4507 
4508   VM_Exit::set_vm_exited();
4509 
4510   notify_vm_shutdown();
4511 
4512   // We are after VM_Exit::set_vm_exited() so we can't call
4513   // thread->smr_delete() or we will block on the Threads_lock.
4514   // Deleting the shutdown thread here is safe because another
4515   // JavaThread cannot have an active ThreadsListHandle for
4516   // this JavaThread.
4517   delete thread;
4518 
4519 #if INCLUDE_JVMCI
4520   if (JVMCICounterSize > 0) {
4521     FREE_C_HEAP_ARRAY(jlong, JavaThread::_jvmci_old_thread_counters);
4522   }
4523 #endif
4524 
4525   // exit_globals() will delete tty
4526   exit_globals();
4527 
4528   LogConfiguration::finalize();
4529 
4530   return true;
4531 }
4532 
4533 
4534 jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
4535   if (version == JNI_VERSION_1_1) return JNI_TRUE;
4536   return is_supported_jni_version(version);
4537 }
4538 
4539 
4540 jboolean Threads::is_supported_jni_version(jint version) {
4541   if (version == JNI_VERSION_1_2) return JNI_TRUE;
4542   if (version == JNI_VERSION_1_4) return JNI_TRUE;
4543   if (version == JNI_VERSION_1_6) return JNI_TRUE;
4544   if (version == JNI_VERSION_1_8) return JNI_TRUE;
4545   if (version == JNI_VERSION_9) return JNI_TRUE;
4546   if (version == JNI_VERSION_10) return JNI_TRUE;
4547   return JNI_FALSE;
4548 }
4549 
4550 // Hash table of pointers found by a scan. Used for collecting hazard
4551 // pointers (ThreadsList references). Also used for collecting JavaThreads
4552 // that are indirectly referenced by hazard ptrs. An instance of this
4553 // class only contains one type of pointer.
4554 //
4555 class ThreadScanHashtable : public CHeapObj<mtThread> {
4556  private:
4557   static bool ptr_equals(void * const& s1, void * const& s2) {
4558     return s1 == s2;
4559   }
4560 
4561   static unsigned int ptr_hash(void * const& s1) {
4562     return (unsigned int)(((uint32_t)(uintptr_t)s1) * 2654435761u);
4563   }
4564 
4565   int _table_size;
4566   // ResourceHashtable SIZE is specified at compile time so our
4567   // dynamic _table_size is unused for now; 1031 is the first prime
4568   // after 1024.
4569   typedef ResourceHashtable<void *, int, &ThreadScanHashtable::ptr_hash,
4570                             &ThreadScanHashtable::ptr_equals, 1031,
4571                             ResourceObj::C_HEAP, mtThread> PtrTable;
4572   PtrTable * _ptrs;
4573 
4574  public:
4575   // ResourceHashtable is passed to various functions and populated in
4576   // different places so we allocate it using C_HEAP to make it immune
4577   // from any ResourceMarks that happen to be in the code paths.
4578   ThreadScanHashtable(int table_size) : _table_size(table_size), _ptrs(new (ResourceObj::C_HEAP, mtThread) PtrTable()) {}
4579 
4580   ~ThreadScanHashtable() { delete _ptrs; }
4581 
4582   bool has_entry(void *pointer) {
4583     int *val_ptr = _ptrs->get(pointer);
4584     return val_ptr != NULL && *val_ptr == 1;
4585   }
4586 
4587   void add_entry(void *pointer) {
4588     _ptrs->put(pointer, 1);
4589   }
4590 };
4591 
4592 // Closure to gather JavaThreads indirectly referenced by hazard ptrs
4593 // (ThreadsList references) into a hash table. This closure handles part 2
4594 // of the dance - adding all the JavaThreads referenced by the hazard
4595 // pointer (ThreadsList reference) to the hash table.
4596 //
4597 class AddThreadHazardPointerThreadClosure : public ThreadClosure {
4598  private:
4599   ThreadScanHashtable *_table;
4600 
4601  public:
4602   AddThreadHazardPointerThreadClosure(ThreadScanHashtable *table) : _table(table) {}
4603 
4604   virtual void do_thread(Thread *thread) {
4605     if (!_table->has_entry((void*)thread)) {
4606       // The same JavaThread might be on more than one ThreadsList or
4607       // more than one thread might be using the same ThreadsList. In
4608       // either case, we only need a single entry for a JavaThread.
4609       _table->add_entry((void*)thread);
4610     }
4611   }
4612 };
4613 
4614 // Closure to gather JavaThreads indirectly referenced by hazard ptrs
4615 // (ThreadsList references) into a hash table. This closure handles part 1
4616 // of the dance - hazard ptr chain walking and dispatch to another
4617 // closure.
4618 //
4619 class ScanHazardPtrGatherProtectedThreadsClosure : public ThreadClosure {
4620  private:
4621   ThreadScanHashtable *_table;
4622  public:
4623   ScanHazardPtrGatherProtectedThreadsClosure(ThreadScanHashtable *table) : _table(table) {}
4624 
4625   virtual void do_thread(Thread *thread) {
4626     assert_locked_or_safepoint(Threads_lock);
4627 
4628     if (thread == NULL) return;
4629 
4630     // This code races with Threads::acquire_stable_list() which is
4631     // lock-free so we have to handle some special situations.
4632     //
4633     ThreadsList *current_list = NULL;
4634     while (true) {
4635       current_list = thread->get_threads_hazard_ptr();
4636       // No hazard ptr so nothing more to do.
4637       if (current_list == NULL) {
4638         assert(thread->get_nested_threads_hazard_ptr() == NULL,
4639                "cannot have a nested hazard ptr with a NULL regular hazard ptr");
4640         return;
4641       }
4642 
4643       // If the hazard ptr is verified as stable (since it is not tagged),
4644       // then it is safe to use.
4645       if (!Thread::is_hazard_ptr_tagged(current_list)) break;
4646 
4647       // The hazard ptr is tagged as not yet verified as being stable
4648       // so we are racing with acquire_stable_list(). This exchange
4649       // attempts to invalidate the hazard ptr. If we win the race,
4650       // then we can ignore this unstable hazard ptr and the other
4651       // thread will retry the attempt to publish a stable hazard ptr.
4652       // If we lose the race, then we retry our attempt to look at the
4653       // hazard ptr.
4654       if (thread->cmpxchg_threads_hazard_ptr(NULL, current_list) == current_list) return;
4655     }
4656 
4657     // The current JavaThread has a hazard ptr (ThreadsList reference)
4658     // which might be _smr_java_thread_list or it might be an older
4659     // ThreadsList that has been removed but not freed. In either case,
4660     // the hazard ptr is protecting all the JavaThreads on that
4661     // ThreadsList.
4662     AddThreadHazardPointerThreadClosure add_cl(_table);
4663     current_list->threads_do(&add_cl);
4664 
4665     // Any NestedThreadsLists are also protecting JavaThreads so
4666     // gather those also; the ThreadsLists may be different.
4667     for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr();
4668          node != NULL; node = node->next()) {
4669       node->t_list()->threads_do(&add_cl);
4670     }
4671   }
4672 };
4673 
4674 // Closure to print JavaThreads that have a hazard ptr (ThreadsList
4675 // reference) that contains an indirect reference to a specific JavaThread.
4676 //
4677 class ScanHazardPtrPrintMatchingThreadsClosure : public ThreadClosure {
4678  private:
4679   JavaThread *_thread;
4680  public:
4681   ScanHazardPtrPrintMatchingThreadsClosure(JavaThread *thread) : _thread(thread) {}
4682 
4683   virtual void do_thread(Thread *thread) {
4684     assert_locked_or_safepoint(Threads_lock);
4685 
4686     if (thread == NULL) return;
4687     ThreadsList *current_list = thread->get_threads_hazard_ptr();
4688     if (current_list == NULL) {
4689       assert(thread->get_nested_threads_hazard_ptr() == NULL,
4690              "cannot have a nested hazard ptr with a NULL regular hazard ptr");
4691       return;
4692     }
4693     // If the hazard ptr is unverified, then ignore it.
4694     if (Thread::is_hazard_ptr_tagged(current_list)) return;
4695 
4696     // The current JavaThread has a hazard ptr (ThreadsList reference)
4697     // which might be _smr_java_thread_list or it might be an older
4698     // ThreadsList that has been removed but not freed. In either case,
4699     // the hazard ptr is protecting all the JavaThreads on that
4700     // ThreadsList, but we only care about matching a specific JavaThread.
4701     DO_JAVA_THREADS(current_list, p) {
4702       if (p == _thread) {
4703         log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread1=" INTPTR_FORMAT " has a hazard pointer for thread2=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread), p2i(_thread));
4704         break;
4705       }
4706     }
4707 
4708     // Any NestedThreadsLists are also protecting JavaThreads so
4709     // check those also; the ThreadsLists may be different.
4710     for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr();
4711          node != NULL; node = node->next()) {
4712       DO_JAVA_THREADS(node->t_list(), p) {
4713         if (p == _thread) {
4714           log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread1=" INTPTR_FORMAT " has a nested hazard pointer for thread2=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread), p2i(_thread));
4715           return;
4716         }
4717       }
4718     }
4719   }
4720 };
4721 
4722 // Return true if the specified JavaThread is protected by a hazard
4723 // pointer (ThreadsList reference). Otherwise, returns false.
4724 //
4725 bool Threads::is_a_protected_JavaThread(JavaThread *thread) {
4726   assert_locked_or_safepoint(Threads_lock);
4727 
4728   // Hash table size should be first power of two higher than twice
4729   // the length of the Threads list.
4730   int hash_table_size = MIN2(_number_of_threads, 32) << 1;
4731   hash_table_size--;
4732   hash_table_size |= hash_table_size >> 1;
4733   hash_table_size |= hash_table_size >> 2;
4734   hash_table_size |= hash_table_size >> 4;
4735   hash_table_size |= hash_table_size >> 8;
4736   hash_table_size |= hash_table_size >> 16;
4737   hash_table_size++;
4738 
4739   // Gather a hash table of the JavaThreads indirectly referenced by
4740   // hazard ptrs.
4741   ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size);
4742   ScanHazardPtrGatherProtectedThreadsClosure scan_cl(scan_table);
4743   Threads::threads_do(&scan_cl);
4744 
4745   bool thread_is_protected = false;
4746   if (scan_table->has_entry((void*)thread)) {
4747     thread_is_protected = true;
4748   }
4749   delete scan_table;
4750   return thread_is_protected;
4751 }
4752 
4753 // Safely delete a JavaThread when it is no longer in use by a
4754 // ThreadsListHandle.
4755 //
4756 void Threads::smr_delete(JavaThread *thread) {
4757   assert(!Threads_lock->owned_by_self(), "sanity");
4758 
4759   bool has_logged_once = false;
4760   elapsedTimer timer;
4761   if (EnableThreadSMRStatistics) {
4762     timer.start();
4763   }
4764 
4765   while (true) {
4766     {
4767       // No safepoint check because this JavaThread is not on the
4768       // Threads list.
4769       MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
4770       // Cannot use a MonitorLockerEx helper here because we have
4771       // to drop the Threads_lock first if we wait.
4772       Threads::smr_delete_lock()->lock_without_safepoint_check();
4773       // Set the smr_delete_notify flag after we grab smr_delete_lock
4774       // and before we scan hazard ptrs because we're doing
4775       // double-check locking in release_stable_list().
4776       Threads::set_smr_delete_notify();
4777 
4778       if (!is_a_protected_JavaThread(thread)) {
4779         // This is the common case.
4780         Threads::clear_smr_delete_notify();
4781         Threads::smr_delete_lock()->unlock();
4782         break;
4783       }
4784       if (!has_logged_once) {
4785         has_logged_once = true;
4786         log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread=" INTPTR_FORMAT " is not deleted.", os::current_thread_id(), p2i(thread));
4787         if (log_is_enabled(Debug, os, thread)) {
4788           ScanHazardPtrPrintMatchingThreadsClosure scan_cl(thread);
4789           Threads::threads_do(&scan_cl);
4790         }
4791       }
4792     } // We have to drop the Threads_lock to wait or delete the thread
4793 
4794     if (EnableThreadSMRStatistics) {
4795       _smr_delete_lock_wait_cnt++;
4796       if (_smr_delete_lock_wait_cnt > _smr_delete_lock_wait_max) {
4797         _smr_delete_lock_wait_max = _smr_delete_lock_wait_cnt;
4798       }
4799     }
4800     // Wait for a release_stable_list() call before we check again. No
4801     // safepoint check, no timeout, and not as suspend equivalent flag
4802     // because this JavaThread is not on the Threads list.
4803     Threads::smr_delete_lock()->wait(Mutex::_no_safepoint_check_flag, 0,
4804                                      !Mutex::_as_suspend_equivalent_flag);
4805     if (EnableThreadSMRStatistics) {
4806       _smr_delete_lock_wait_cnt--;
4807     }
4808 
4809     Threads::clear_smr_delete_notify();
4810     Threads::smr_delete_lock()->unlock();
4811     // Retry the whole scenario.
4812   }
4813 
4814   delete thread;
4815   if (EnableThreadSMRStatistics) {
4816     timer.stop();
4817     jint millis = (jint)timer.milliseconds();
4818     Threads::inc_smr_deleted_thread_cnt();
4819     Threads::add_smr_deleted_thread_times(millis);
4820     Threads::update_smr_deleted_thread_time_max(millis);
4821   }
4822 
4823   log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread=" INTPTR_FORMAT " is deleted.", os::current_thread_id(), p2i(thread));
4824 }
4825 
4826 bool Threads::smr_delete_notify() {
4827   // Use load_acquire() in order to see any updates to _smr_delete_notify
4828   // earlier than when smr_delete_lock is grabbed.
4829   return (OrderAccess::load_acquire(&_smr_delete_notify) != 0);
4830 }
4831 
4832 // set_smr_delete_notify() and clear_smr_delete_notify() are called
4833 // under the protection of the smr_delete_lock, but we also use an
4834 // Atomic operation to ensure the memory update is seen earlier than
4835 // when the smr_delete_lock is dropped.
4836 //
4837 void Threads::set_smr_delete_notify() {
4838   Atomic::inc(&_smr_delete_notify);
4839 }
4840 
4841 void Threads::clear_smr_delete_notify() {
4842   Atomic::dec(&_smr_delete_notify);
4843 }
4844 
4845 // Closure to gather hazard ptrs (ThreadsList references) into a hash table.
4846 //
4847 class ScanHazardPtrGatherThreadsListClosure : public ThreadClosure {
4848  private:
4849   ThreadScanHashtable *_table;
4850  public:
4851   ScanHazardPtrGatherThreadsListClosure(ThreadScanHashtable *table) : _table(table) {}
4852 
4853   virtual void do_thread(Thread* thread) {
4854     assert_locked_or_safepoint(Threads_lock);
4855 
4856     if (thread == NULL) return;
4857     ThreadsList *threads = thread->get_threads_hazard_ptr();
4858     if (threads == NULL) {
4859       assert(thread->get_nested_threads_hazard_ptr() == NULL,
4860              "cannot have a nested hazard ptr with a NULL regular hazard ptr");
4861       return;
4862     }
4863     // In this closure we always ignore the tag that might mark this
4864     // hazard ptr as not yet verified. If we happen to catch an
4865     // unverified hazard ptr that is subsequently discarded (not
4866     // published), then the only side effect is that we might keep a
4867     // to-be-deleted ThreadsList alive a little longer.
4868     threads = Thread::untag_hazard_ptr(threads);
4869     if (!_table->has_entry((void*)threads)) {
4870       _table->add_entry((void*)threads);
4871     }
4872 
4873     // Any NestedThreadsLists are also protecting JavaThreads so
4874     // gather those also; the ThreadsLists may be different.
4875     for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr();
4876          node != NULL; node = node->next()) {
4877       threads = node->t_list();
4878       if (!_table->has_entry((void*)threads)) {
4879         _table->add_entry((void*)threads);
4880       }
4881     }
4882   }
4883 };
4884 
4885 // Safely free a ThreadsList after a Threads::add() or Threads::remove().
4886 // The specified ThreadsList may not get deleted during this call if it
4887 // is still in-use (referenced by a hazard ptr). Other ThreadsLists
4888 // in the chain may get deleted by this call if they are no longer in-use.
4889 void Threads::smr_free_list(ThreadsList* threads) {
4890   assert_locked_or_safepoint(Threads_lock);
4891 
4892   threads->set_next_list(_smr_to_delete_list);
4893   _smr_to_delete_list = threads;
4894   if (EnableThreadSMRStatistics) {
4895     _smr_to_delete_list_cnt++;
4896     if (_smr_to_delete_list_cnt > _smr_to_delete_list_max) {
4897       _smr_to_delete_list_max = _smr_to_delete_list_cnt;
4898     }
4899   }
4900 
4901   // Hash table size should be first power of two higher than twice the length of the ThreadsList
4902   int hash_table_size = MIN2(_number_of_threads, 32) << 1;
4903   hash_table_size--;
4904   hash_table_size |= hash_table_size >> 1;
4905   hash_table_size |= hash_table_size >> 2;
4906   hash_table_size |= hash_table_size >> 4;
4907   hash_table_size |= hash_table_size >> 8;
4908   hash_table_size |= hash_table_size >> 16;
4909   hash_table_size++;
4910 
4911   // Gather a hash table of the current hazard ptrs:
4912   ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size);
4913   ScanHazardPtrGatherThreadsListClosure scan_cl(scan_table);
4914   Threads::threads_do(&scan_cl);
4915 
4916   // Walk through the linked list of pending freeable ThreadsLists
4917   // and free the ones that are not referenced from hazard ptrs.
4918   ThreadsList* current = _smr_to_delete_list;
4919   ThreadsList* prev = NULL;
4920   ThreadsList* next = NULL;
4921   bool threads_is_freed = false;
4922   while (current != NULL) {
4923     next = current->next_list();
4924     if (!scan_table->has_entry((void*)current)) {
4925       // This ThreadsList is not referenced by a hazard ptr.
4926       if (prev != NULL) {
4927         prev->set_next_list(next);
4928       }
4929       if (_smr_to_delete_list == current) {
4930         _smr_to_delete_list = next;
4931       }
4932 
4933       log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_free_list: threads=" INTPTR_FORMAT " is freed.", os::current_thread_id(), p2i(current));
4934       if (current == threads) threads_is_freed = true;
4935       delete current;
4936       if (EnableThreadSMRStatistics) {
4937         _smr_java_thread_list_free_cnt++;
4938         _smr_to_delete_list_cnt--;
4939       }
4940     } else {
4941       prev = current;
4942     }
4943     current = next;
4944   }
4945 
4946   if (!threads_is_freed) {
4947     // Only report "is not freed" on the original call to
4948     // smr_free_list() for this ThreadsList.
4949     log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_free_list: threads=" INTPTR_FORMAT " is not freed.", os::current_thread_id(), p2i(threads));
4950   }
4951 
4952   delete scan_table;
4953 }
4954 
4955 // Remove a JavaThread from a ThreadsList. The returned ThreadsList is a
4956 // new copy of the specified ThreadsList with the specified JavaThread
4957 // removed.
4958 ThreadsList *ThreadsList::remove_thread(ThreadsList* list, JavaThread* java_thread) {
4959   assert(list->_length > 0, "sanity");
4960 
4961   uint i = 0;
4962   DO_JAVA_THREADS(list, current) {
4963     if (current == java_thread) {
4964       break;
4965     }
4966     i++;
4967   }
4968   assert(i < list->_length, "did not find JavaThread on the list");
4969   const uint index = i;
4970   const uint new_length = list->_length - 1;
4971   const uint head_length = index;
4972   const uint tail_length = (new_length >= index) ? (new_length - index) : 0;
4973   ThreadsList *const new_list = new ThreadsList(new_length);
4974 
4975   if (head_length > 0) {
4976     Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length);
4977   }
4978   if (tail_length > 0) {
4979     Copy::disjoint_words((HeapWord*)list->_threads + index + 1, (HeapWord*)new_list->_threads + index, tail_length);
4980   }
4981 
4982   return new_list;
4983 }
4984 
4985 // Add a JavaThread to a ThreadsList. The returned ThreadsList is a
4986 // new copy of the specified ThreadsList with the specified JavaThread
4987 // appended to the end.
4988 ThreadsList *ThreadsList::add_thread(ThreadsList *list, JavaThread *java_thread) {
4989   const uint index = list->_length;
4990   const uint new_length = index + 1;
4991   const uint head_length = index;
4992   ThreadsList *const new_list = new ThreadsList(new_length);
4993 
4994   if (head_length > 0) {
4995     Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length);
4996   }
4997   *(JavaThread**)(new_list->_threads + index) = java_thread;
4998 
4999   return new_list;
5000 }
5001 
5002 int ThreadsList::find_index_of_JavaThread(JavaThread *target) {
5003   if (target == NULL) {
5004     return -1;
5005   }
5006   for (uint i = 0; i < length(); i++) {
5007     if (target == thread_at(i)) {
5008       return (int)i;
5009     }
5010   }
5011   return -1;
5012 }
5013 
5014 JavaThread* ThreadsList::find_JavaThread_from_java_tid(jlong java_tid) const {
5015   DO_JAVA_THREADS(this, thread) {
5016     oop tobj = thread->threadObj();
5017     // Ignore the thread if it hasn't run yet, has exited
5018     // or is starting to exit.
5019     if (tobj != NULL && !thread->is_exiting() &&
5020         java_tid == java_lang_Thread::thread_id(tobj)) {
5021       // found a match
5022       return thread;
5023     }
5024   }
5025   return NULL;
5026 }
5027 
5028 bool ThreadsList::includes(const JavaThread * const p) const {
5029   if (p == NULL) {
5030     return false;
5031   }
5032   DO_JAVA_THREADS(this, q) {
5033     if (q == p) {
5034       return true;
5035     }
5036   }
5037   return false;
5038 }
5039 
5040 void Threads::add(JavaThread* p, bool force_daemon) {
5041   // The threads lock must be owned at this point
5042   assert_locked_or_safepoint(Threads_lock);
5043 
5044   // See the comment for this method in thread.hpp for its purpose and
5045   // why it is called here.
5046   p->initialize_queues();
5047   p->set_next(_thread_list);
5048   _thread_list = p;
5049 
5050   // Once a JavaThread is added to the Threads list, smr_delete() has
5051   // to be used to delete it. Otherwise we can just delete it directly.
5052   p->set_on_thread_list();
5053 
5054   _number_of_threads++;
5055   oop threadObj = p->threadObj();
5056   bool daemon = true;
5057   // Bootstrapping problem: threadObj can be null for initial
5058   // JavaThread (or for threads attached via JNI)
5059   if ((!force_daemon) && (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj))) {
5060     _number_of_non_daemon_threads++;
5061     daemon = false;
5062   }
5063 
5064   ThreadService::add_thread(p, daemon);
5065 
5066   // Maintain fast thread list
5067   ThreadsList *new_list = ThreadsList::add_thread(get_smr_java_thread_list(), p);
5068   if (EnableThreadSMRStatistics) {
5069     _smr_java_thread_list_alloc_cnt++;
5070     if (new_list->length() > _smr_java_thread_list_max) {
5071       _smr_java_thread_list_max = new_list->length();
5072     }
5073   }
5074   // Initial _smr_java_thread_list will not generate a "Threads::add" mesg.
5075   log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::add: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list));
5076 
5077   ThreadsList *old_list = xchg_smr_java_thread_list(new_list);
5078   smr_free_list(old_list);
5079 
5080   // Possible GC point.
5081   Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p));
5082 }
5083 
5084 void Threads::remove(JavaThread* p) {
5085 
5086   // Reclaim the objectmonitors from the omInUseList and omFreeList of the moribund thread.
5087   ObjectSynchronizer::omFlush(p);
5088 
5089   // Extra scope needed for Thread_lock, so we can check
5090   // that we do not remove thread without safepoint code notice
5091   { MutexLocker ml(Threads_lock);
5092 
5093     assert(get_smr_java_thread_list()->includes(p), "p must be present");
5094 
5095     // Maintain fast thread list
5096     ThreadsList *new_list = ThreadsList::remove_thread(get_smr_java_thread_list(), p);
5097     if (EnableThreadSMRStatistics) {
5098       _smr_java_thread_list_alloc_cnt++;
5099       // This list is smaller so no need to check for a "longest" update.
5100     }
5101 
5102     // Final _smr_java_thread_list will not generate a "Threads::remove" mesg.
5103     log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::remove: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list));
5104 
5105     ThreadsList *old_list = xchg_smr_java_thread_list(new_list);
5106     smr_free_list(old_list);
5107 
5108     JavaThread* current = _thread_list;
5109     JavaThread* prev    = NULL;
5110 
5111     while (current != p) {
5112       prev    = current;
5113       current = current->next();
5114     }
5115 
5116     if (prev) {
5117       prev->set_next(current->next());
5118     } else {
5119       _thread_list = p->next();
5120     }
5121 
5122     _number_of_threads--;
5123     oop threadObj = p->threadObj();
5124     bool daemon = true;
5125     if (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj)) {
5126       _number_of_non_daemon_threads--;
5127       daemon = false;
5128 
5129       // Only one thread left, do a notify on the Threads_lock so a thread waiting
5130       // on destroy_vm will wake up.
5131       if (number_of_non_daemon_threads() == 1) {
5132         Threads_lock->notify_all();
5133       }
5134     }
5135     ThreadService::remove_thread(p, daemon);
5136 
5137     // Make sure that safepoint code disregard this thread. This is needed since
5138     // the thread might mess around with locks after this point. This can cause it
5139     // to do callbacks into the safepoint code. However, the safepoint code is not aware
5140     // of this thread since it is removed from the queue.
5141     p->set_terminated_value();
5142   } // unlock Threads_lock
5143 
5144   // Since Events::log uses a lock, we grab it outside the Threads_lock
5145   Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p));
5146 }
5147 
5148 // Operations on the Threads list for GC.  These are not explicitly locked,
5149 // but the garbage collector must provide a safe context for them to run.
5150 // In particular, these things should never be called when the Threads_lock
5151 // is held by some other thread. (Note: the Safepoint abstraction also
5152 // uses the Threads_lock to guarantee this property. It also makes sure that
5153 // all threads gets blocked when exiting or starting).
5154 
5155 void Threads::oops_do(OopClosure* f, CodeBlobClosure* cf) {
5156   ALL_JAVA_THREADS(p) {
5157     p->oops_do(f, cf);
5158   }
5159   VMThread::vm_thread()->oops_do(f, cf);
5160 }
5161 
5162 void Threads::change_thread_claim_parity() {
5163   // Set the new claim parity.
5164   assert(_thread_claim_parity >= 0 && _thread_claim_parity <= 2,
5165          "Not in range.");
5166   _thread_claim_parity++;
5167   if (_thread_claim_parity == 3) _thread_claim_parity = 1;
5168   assert(_thread_claim_parity >= 1 && _thread_claim_parity <= 2,
5169          "Not in range.");
5170 }
5171 
5172 #ifdef ASSERT
5173 void Threads::assert_all_threads_claimed() {
5174   ALL_JAVA_THREADS(p) {
5175     const int thread_parity = p->oops_do_parity();
5176     assert((thread_parity == _thread_claim_parity),
5177            "Thread " PTR_FORMAT " has incorrect parity %d != %d", p2i(p), thread_parity, _thread_claim_parity);
5178   }
5179   VMThread* vmt = VMThread::vm_thread();
5180   const int thread_parity = vmt->oops_do_parity();
5181   assert((thread_parity == _thread_claim_parity),
5182          "VMThread " PTR_FORMAT " has incorrect parity %d != %d", p2i(vmt), thread_parity, _thread_claim_parity);
5183 }
5184 #endif // ASSERT
5185 
5186 class ParallelOopsDoThreadClosure : public ThreadClosure {
5187 private:
5188   OopClosure* _f;
5189   CodeBlobClosure* _cf;
5190 public:
5191   ParallelOopsDoThreadClosure(OopClosure* f, CodeBlobClosure* cf) : _f(f), _cf(cf) {}
5192   void do_thread(Thread* t) {
5193     t->oops_do(_f, _cf);
5194   }
5195 };
5196 
5197 void Threads::possibly_parallel_oops_do(bool is_par, OopClosure* f, CodeBlobClosure* cf) {
5198   ParallelOopsDoThreadClosure tc(f, cf);
5199   possibly_parallel_threads_do(is_par, &tc);
5200 }
5201 
5202 #if INCLUDE_ALL_GCS
5203 // Used by ParallelScavenge
5204 void Threads::create_thread_roots_tasks(GCTaskQueue* q) {
5205   ALL_JAVA_THREADS(p) {
5206     q->enqueue(new ThreadRootsTask(p));
5207   }
5208   q->enqueue(new ThreadRootsTask(VMThread::vm_thread()));
5209 }
5210 
5211 // Used by Parallel Old
5212 void Threads::create_thread_roots_marking_tasks(GCTaskQueue* q) {
5213   ALL_JAVA_THREADS(p) {
5214     q->enqueue(new ThreadRootsMarkingTask(p));
5215   }
5216   q->enqueue(new ThreadRootsMarkingTask(VMThread::vm_thread()));
5217 }
5218 #endif // INCLUDE_ALL_GCS
5219 
5220 void Threads::nmethods_do(CodeBlobClosure* cf) {
5221   ALL_JAVA_THREADS(p) {
5222     // This is used by the code cache sweeper to mark nmethods that are active
5223     // on the stack of a Java thread. Ignore the sweeper thread itself to avoid
5224     // marking CodeCacheSweeperThread::_scanned_compiled_method as active.
5225     if(!p->is_Code_cache_sweeper_thread()) {
5226       p->nmethods_do(cf);
5227     }
5228   }
5229 }
5230 
5231 void Threads::metadata_do(void f(Metadata*)) {
5232   ALL_JAVA_THREADS(p) {
5233     p->metadata_do(f);
5234   }
5235 }
5236 
5237 class ThreadHandlesClosure : public ThreadClosure {
5238   void (*_f)(Metadata*);
5239  public:
5240   ThreadHandlesClosure(void f(Metadata*)) : _f(f) {}
5241   virtual void do_thread(Thread* thread) {
5242     thread->metadata_handles_do(_f);
5243   }
5244 };
5245 
5246 void Threads::metadata_handles_do(void f(Metadata*)) {
5247   // Only walk the Handles in Thread.
5248   ThreadHandlesClosure handles_closure(f);
5249   threads_do(&handles_closure);
5250 }
5251 
5252 void Threads::deoptimized_wrt_marked_nmethods() {
5253   ALL_JAVA_THREADS(p) {
5254     p->deoptimized_wrt_marked_nmethods();
5255   }
5256 }
5257 
5258 
5259 // Get count Java threads that are waiting to enter the specified monitor.
5260 GrowableArray<JavaThread*>* Threads::get_pending_threads(ThreadsList * t_list,
5261                                                          int count,
5262                                                          address monitor) {
5263   GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
5264 
5265   int i = 0;
5266   DO_JAVA_THREADS(t_list, p) {
5267     if (!p->can_call_java()) continue;
5268 
5269     address pending = (address)p->current_pending_monitor();
5270     if (pending == monitor) {             // found a match
5271       if (i < count) result->append(p);   // save the first count matches
5272       i++;
5273     }
5274   }
5275 
5276   return result;
5277 }
5278 
5279 
5280 JavaThread *Threads::owning_thread_from_monitor_owner(ThreadsList * t_list,
5281                                                       address owner) {
5282   // NULL owner means not locked so we can skip the search
5283   if (owner == NULL) return NULL;
5284 
5285   DO_JAVA_THREADS(t_list, p) {
5286     // first, see if owner is the address of a Java thread
5287     if (owner == (address)p) return p;
5288   }
5289 
5290   // Cannot assert on lack of success here since this function may be
5291   // used by code that is trying to report useful problem information
5292   // like deadlock detection.
5293   if (UseHeavyMonitors) return NULL;
5294 
5295   // If we didn't find a matching Java thread and we didn't force use of
5296   // heavyweight monitors, then the owner is the stack address of the
5297   // Lock Word in the owning Java thread's stack.
5298   //
5299   JavaThread* the_owner = NULL;
5300   DO_JAVA_THREADS(t_list, q) {
5301     if (q->is_lock_owned(owner)) {
5302       the_owner = q;
5303       break;
5304     }
5305   }
5306 
5307   // cannot assert on lack of success here; see above comment
5308   return the_owner;
5309 }
5310 
5311 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
5312 void Threads::print_on(outputStream* st, bool print_stacks,
5313                        bool internal_format, bool print_concurrent_locks) {
5314   char buf[32];
5315   st->print_raw_cr(os::local_time_string(buf, sizeof(buf)));
5316 
5317   st->print_cr("Full thread dump %s (%s %s):",
5318                Abstract_VM_Version::vm_name(),
5319                Abstract_VM_Version::vm_release(),
5320                Abstract_VM_Version::vm_info_string());
5321   st->cr();
5322 
5323 #if INCLUDE_SERVICES
5324   // Dump concurrent locks
5325   ConcurrentLocksDump concurrent_locks;
5326   if (print_concurrent_locks) {
5327     concurrent_locks.dump_at_safepoint();
5328   }
5329 #endif // INCLUDE_SERVICES
5330 
5331   print_smr_info_on(st);
5332   st->cr();
5333 
5334   ALL_JAVA_THREADS(p) {
5335     ResourceMark rm;
5336     p->print_on(st);
5337     if (print_stacks) {
5338       if (internal_format) {
5339         p->trace_stack();
5340       } else {
5341         p->print_stack_on(st);
5342       }
5343     }
5344     st->cr();
5345 #if INCLUDE_SERVICES
5346     if (print_concurrent_locks) {
5347       concurrent_locks.print_locks_on(p, st);
5348     }
5349 #endif // INCLUDE_SERVICES
5350   }
5351 
5352   VMThread::vm_thread()->print_on(st);
5353   st->cr();
5354   Universe::heap()->print_gc_threads_on(st);
5355   WatcherThread* wt = WatcherThread::watcher_thread();
5356   if (wt != NULL) {
5357     wt->print_on(st);
5358     st->cr();
5359   }
5360 
5361   st->flush();
5362 }
5363 
5364 // Log Threads class SMR info.
5365 void Threads::log_smr_statistics() {
5366   LogTarget(Info, thread, smr) log;
5367   if (log.is_enabled()) {
5368     LogStream out(log);
5369     print_smr_info_on(&out);
5370   }
5371 }
5372 
5373 // Print Threads class SMR info.
5374 void Threads::print_smr_info_on(outputStream* st) {
5375   // Only grab the Threads_lock if we don't already own it
5376   // and if we are not reporting an error.
5377   MutexLockerEx ml((Threads_lock->owned_by_self() || VMError::is_error_reported()) ? NULL : Threads_lock);
5378 
5379   st->print_cr("Threads class SMR info:");
5380   st->print_cr("_smr_java_thread_list=" INTPTR_FORMAT ", length=%u, "
5381                "elements={", p2i(_smr_java_thread_list),
5382                _smr_java_thread_list->length());
5383   print_smr_info_elements_on(st, _smr_java_thread_list);
5384   st->print_cr("}");
5385   if (_smr_to_delete_list != NULL) {
5386     st->print_cr("_smr_to_delete_list=" INTPTR_FORMAT ", length=%u, "
5387                  "elements={", p2i(_smr_to_delete_list),
5388                  _smr_to_delete_list->length());
5389     print_smr_info_elements_on(st, _smr_to_delete_list);
5390     st->print_cr("}");
5391     for (ThreadsList *t_list = _smr_to_delete_list->next_list();
5392          t_list != NULL; t_list = t_list->next_list()) {
5393       st->print("next-> " INTPTR_FORMAT ", length=%u, "
5394                 "elements={", p2i(t_list), t_list->length());
5395       print_smr_info_elements_on(st, t_list);
5396       st->print_cr("}");
5397     }
5398   }
5399   if (!EnableThreadSMRStatistics) {
5400     return;
5401   }
5402   st->print_cr("_smr_java_thread_list_alloc_cnt=%ld, "
5403                "_smr_java_thread_list_free_cnt=%ld, "
5404                "_smr_java_thread_list_max=%u, "
5405                "_smr_nested_thread_list_max=%u",
5406                _smr_java_thread_list_alloc_cnt,
5407                _smr_java_thread_list_free_cnt,
5408                _smr_java_thread_list_max,
5409                _smr_nested_thread_list_max);
5410   if (_smr_tlh_cnt > 0) {
5411     st->print_cr("_smr_tlh_cnt=" INT32_FORMAT
5412                  ", _smr_tlh_times=" INT32_FORMAT
5413                  ", avg_smr_tlh_time=%0.2f"
5414                  ", _smr_tlh_time_max=" INT32_FORMAT,
5415                  _smr_tlh_cnt, _smr_tlh_times,
5416                  ((double) _smr_tlh_times / _smr_tlh_cnt),
5417                  _smr_tlh_time_max);
5418   }
5419   if (_smr_deleted_thread_cnt > 0) {
5420     st->print_cr("_smr_deleted_thread_cnt=" INT32_FORMAT
5421                  ", _smr_deleted_thread_times=" INT32_FORMAT
5422                  ", avg_smr_deleted_thread_time=%0.2f"
5423                  ", _smr_deleted_thread_time_max=" INT32_FORMAT,
5424                  _smr_deleted_thread_cnt, _smr_deleted_thread_times,
5425                  ((double) _smr_deleted_thread_times / _smr_deleted_thread_cnt),
5426                  _smr_deleted_thread_time_max);
5427   }
5428   st->print_cr("_smr_delete_lock_wait_cnt=%u, _smr_delete_lock_wait_max=%u",
5429                _smr_delete_lock_wait_cnt, _smr_delete_lock_wait_max);
5430   st->print_cr("_smr_to_delete_list_cnt=%u, _smr_to_delete_list_max=%u",
5431                _smr_to_delete_list_cnt, _smr_to_delete_list_max);
5432 }
5433 
5434 // Print ThreadsList elements (4 per line).
5435 void Threads::print_smr_info_elements_on(outputStream* st,
5436                                          ThreadsList* t_list) {
5437   uint cnt = 0;
5438   JavaThreadIterator jti(t_list);
5439   for (JavaThread *jt = jti.first(); jt != NULL; jt = jti.next()) {
5440     st->print(INTPTR_FORMAT, p2i(jt));
5441     if (cnt < t_list->length() - 1) {
5442       // Separate with comma or comma-space except for the last one.
5443       if (((cnt + 1) % 4) == 0) {
5444         // Four INTPTR_FORMAT fit on an 80 column line so end the
5445         // current line with just a comma.
5446         st->print_cr(",");
5447       } else {
5448         // Not the last one on the current line so use comma-space:
5449         st->print(", ");
5450       }
5451     } else {
5452       // Last one so just end the current line.
5453       st->cr();
5454     }
5455     cnt++;
5456   }
5457 }
5458 
5459 void Threads::print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf,
5460                              int buflen, bool* found_current) {
5461   if (this_thread != NULL) {
5462     bool is_current = (current == this_thread);
5463     *found_current = *found_current || is_current;
5464     st->print("%s", is_current ? "=>" : "  ");
5465 
5466     st->print(PTR_FORMAT, p2i(this_thread));
5467     st->print(" ");
5468     this_thread->print_on_error(st, buf, buflen);
5469     st->cr();
5470   }
5471 }
5472 
5473 class PrintOnErrorClosure : public ThreadClosure {
5474   outputStream* _st;
5475   Thread* _current;
5476   char* _buf;
5477   int _buflen;
5478   bool* _found_current;
5479  public:
5480   PrintOnErrorClosure(outputStream* st, Thread* current, char* buf,
5481                       int buflen, bool* found_current) :
5482    _st(st), _current(current), _buf(buf), _buflen(buflen), _found_current(found_current) {}
5483 
5484   virtual void do_thread(Thread* thread) {
5485     Threads::print_on_error(thread, _st, _current, _buf, _buflen, _found_current);
5486   }
5487 };
5488 
5489 // Threads::print_on_error() is called by fatal error handler. It's possible
5490 // that VM is not at safepoint and/or current thread is inside signal handler.
5491 // Don't print stack trace, as the stack may not be walkable. Don't allocate
5492 // memory (even in resource area), it might deadlock the error handler.
5493 void Threads::print_on_error(outputStream* st, Thread* current, char* buf,
5494                              int buflen) {
5495   print_smr_info_on(st);
5496   st->cr();
5497 
5498   bool found_current = false;
5499   st->print_cr("Java Threads: ( => current thread )");
5500   ALL_JAVA_THREADS(thread) {
5501     print_on_error(thread, st, current, buf, buflen, &found_current);
5502   }
5503   st->cr();
5504 
5505   st->print_cr("Other Threads:");
5506   print_on_error(VMThread::vm_thread(), st, current, buf, buflen, &found_current);
5507   print_on_error(WatcherThread::watcher_thread(), st, current, buf, buflen, &found_current);
5508 
5509   PrintOnErrorClosure print_closure(st, current, buf, buflen, &found_current);
5510   Universe::heap()->gc_threads_do(&print_closure);
5511 
5512   if (!found_current) {
5513     st->cr();
5514     st->print("=>" PTR_FORMAT " (exited) ", p2i(current));
5515     current->print_on_error(st, buf, buflen);
5516     st->cr();
5517   }
5518   st->cr();
5519 
5520   st->print_cr("Threads with active compile tasks:");
5521   print_threads_compiling(st, buf, buflen);
5522 }
5523 
5524 void Threads::print_threads_compiling(outputStream* st, char* buf, int buflen) {
5525   ALL_JAVA_THREADS(thread) {
5526     if (thread->is_Compiler_thread()) {
5527       CompilerThread* ct = (CompilerThread*) thread;
5528       if (ct->task() != NULL) {
5529         thread->print_name_on_error(st, buf, buflen);
5530         ct->task()->print(st, NULL, true, true);
5531       }
5532     }
5533   }
5534 }
5535 
5536 
5537 // Internal SpinLock and Mutex
5538 // Based on ParkEvent
5539 
5540 // Ad-hoc mutual exclusion primitives: SpinLock and Mux
5541 //
5542 // We employ SpinLocks _only for low-contention, fixed-length
5543 // short-duration critical sections where we're concerned
5544 // about native mutex_t or HotSpot Mutex:: latency.
5545 // The mux construct provides a spin-then-block mutual exclusion
5546 // mechanism.
5547 //
5548 // Testing has shown that contention on the ListLock guarding gFreeList
5549 // is common.  If we implement ListLock as a simple SpinLock it's common
5550 // for the JVM to devolve to yielding with little progress.  This is true
5551 // despite the fact that the critical sections protected by ListLock are
5552 // extremely short.
5553 //
5554 // TODO-FIXME: ListLock should be of type SpinLock.
5555 // We should make this a 1st-class type, integrated into the lock
5556 // hierarchy as leaf-locks.  Critically, the SpinLock structure
5557 // should have sufficient padding to avoid false-sharing and excessive
5558 // cache-coherency traffic.
5559 
5560 
5561 typedef volatile int SpinLockT;
5562 
5563 void Thread::SpinAcquire(volatile int * adr, const char * LockName) {
5564   if (Atomic::cmpxchg (1, adr, 0) == 0) {
5565     return;   // normal fast-path return
5566   }
5567 
5568   // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
5569   TEVENT(SpinAcquire - ctx);
5570   int ctr = 0;
5571   int Yields = 0;
5572   for (;;) {
5573     while (*adr != 0) {
5574       ++ctr;
5575       if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
5576         if (Yields > 5) {
5577           os::naked_short_sleep(1);
5578         } else {
5579           os::naked_yield();
5580           ++Yields;
5581         }
5582       } else {
5583         SpinPause();
5584       }
5585     }
5586     if (Atomic::cmpxchg(1, adr, 0) == 0) return;
5587   }
5588 }
5589 
5590 void Thread::SpinRelease(volatile int * adr) {
5591   assert(*adr != 0, "invariant");
5592   OrderAccess::fence();      // guarantee at least release consistency.
5593   // Roach-motel semantics.
5594   // It's safe if subsequent LDs and STs float "up" into the critical section,
5595   // but prior LDs and STs within the critical section can't be allowed
5596   // to reorder or float past the ST that releases the lock.
5597   // Loads and stores in the critical section - which appear in program
5598   // order before the store that releases the lock - must also appear
5599   // before the store that releases the lock in memory visibility order.
5600   // Conceptually we need a #loadstore|#storestore "release" MEMBAR before
5601   // the ST of 0 into the lock-word which releases the lock, so fence
5602   // more than covers this on all platforms.
5603   *adr = 0;
5604 }
5605 
5606 // muxAcquire and muxRelease:
5607 //
5608 // *  muxAcquire and muxRelease support a single-word lock-word construct.
5609 //    The LSB of the word is set IFF the lock is held.
5610 //    The remainder of the word points to the head of a singly-linked list
5611 //    of threads blocked on the lock.
5612 //
5613 // *  The current implementation of muxAcquire-muxRelease uses its own
5614 //    dedicated Thread._MuxEvent instance.  If we're interested in
5615 //    minimizing the peak number of extant ParkEvent instances then
5616 //    we could eliminate _MuxEvent and "borrow" _ParkEvent as long
5617 //    as certain invariants were satisfied.  Specifically, care would need
5618 //    to be taken with regards to consuming unpark() "permits".
5619 //    A safe rule of thumb is that a thread would never call muxAcquire()
5620 //    if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
5621 //    park().  Otherwise the _ParkEvent park() operation in muxAcquire() could
5622 //    consume an unpark() permit intended for monitorenter, for instance.
5623 //    One way around this would be to widen the restricted-range semaphore
5624 //    implemented in park().  Another alternative would be to provide
5625 //    multiple instances of the PlatformEvent() for each thread.  One
5626 //    instance would be dedicated to muxAcquire-muxRelease, for instance.
5627 //
5628 // *  Usage:
5629 //    -- Only as leaf locks
5630 //    -- for short-term locking only as muxAcquire does not perform
5631 //       thread state transitions.
5632 //
5633 // Alternatives:
5634 // *  We could implement muxAcquire and muxRelease with MCS or CLH locks
5635 //    but with parking or spin-then-park instead of pure spinning.
5636 // *  Use Taura-Oyama-Yonenzawa locks.
5637 // *  It's possible to construct a 1-0 lock if we encode the lockword as
5638 //    (List,LockByte).  Acquire will CAS the full lockword while Release
5639 //    will STB 0 into the LockByte.  The 1-0 scheme admits stranding, so
5640 //    acquiring threads use timers (ParkTimed) to detect and recover from
5641 //    the stranding window.  Thread/Node structures must be aligned on 256-byte
5642 //    boundaries by using placement-new.
5643 // *  Augment MCS with advisory back-link fields maintained with CAS().
5644 //    Pictorially:  LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
5645 //    The validity of the backlinks must be ratified before we trust the value.
5646 //    If the backlinks are invalid the exiting thread must back-track through the
5647 //    the forward links, which are always trustworthy.
5648 // *  Add a successor indication.  The LockWord is currently encoded as
5649 //    (List, LOCKBIT:1).  We could also add a SUCCBIT or an explicit _succ variable
5650 //    to provide the usual futile-wakeup optimization.
5651 //    See RTStt for details.
5652 // *  Consider schedctl.sc_nopreempt to cover the critical section.
5653 //
5654 
5655 
5656 const intptr_t LOCKBIT = 1;
5657 
5658 void Thread::muxAcquire(volatile intptr_t * Lock, const char * LockName) {
5659   intptr_t w = Atomic::cmpxchg(LOCKBIT, Lock, (intptr_t)0);
5660   if (w == 0) return;
5661   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5662     return;
5663   }
5664 
5665   TEVENT(muxAcquire - Contention);
5666   ParkEvent * const Self = Thread::current()->_MuxEvent;
5667   assert((intptr_t(Self) & LOCKBIT) == 0, "invariant");
5668   for (;;) {
5669     int its = (os::is_MP() ? 100 : 0) + 1;
5670 
5671     // Optional spin phase: spin-then-park strategy
5672     while (--its >= 0) {
5673       w = *Lock;
5674       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5675         return;
5676       }
5677     }
5678 
5679     Self->reset();
5680     Self->OnList = intptr_t(Lock);
5681     // The following fence() isn't _strictly necessary as the subsequent
5682     // CAS() both serializes execution and ratifies the fetched *Lock value.
5683     OrderAccess::fence();
5684     for (;;) {
5685       w = *Lock;
5686       if ((w & LOCKBIT) == 0) {
5687         if (Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5688           Self->OnList = 0;   // hygiene - allows stronger asserts
5689           return;
5690         }
5691         continue;      // Interference -- *Lock changed -- Just retry
5692       }
5693       assert(w & LOCKBIT, "invariant");
5694       Self->ListNext = (ParkEvent *) (w & ~LOCKBIT);
5695       if (Atomic::cmpxchg(intptr_t(Self)|LOCKBIT, Lock, w) == w) break;
5696     }
5697 
5698     while (Self->OnList != 0) {
5699       Self->park();
5700     }
5701   }
5702 }
5703 
5704 void Thread::muxAcquireW(volatile intptr_t * Lock, ParkEvent * ev) {
5705   intptr_t w = Atomic::cmpxchg(LOCKBIT, Lock, (intptr_t)0);
5706   if (w == 0) return;
5707   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5708     return;
5709   }
5710 
5711   TEVENT(muxAcquire - Contention);
5712   ParkEvent * ReleaseAfter = NULL;
5713   if (ev == NULL) {
5714     ev = ReleaseAfter = ParkEvent::Allocate(NULL);
5715   }
5716   assert((intptr_t(ev) & LOCKBIT) == 0, "invariant");
5717   for (;;) {
5718     guarantee(ev->OnList == 0, "invariant");
5719     int its = (os::is_MP() ? 100 : 0) + 1;
5720 
5721     // Optional spin phase: spin-then-park strategy
5722     while (--its >= 0) {
5723       w = *Lock;
5724       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5725         if (ReleaseAfter != NULL) {
5726           ParkEvent::Release(ReleaseAfter);
5727         }
5728         return;
5729       }
5730     }
5731 
5732     ev->reset();
5733     ev->OnList = intptr_t(Lock);
5734     // The following fence() isn't _strictly necessary as the subsequent
5735     // CAS() both serializes execution and ratifies the fetched *Lock value.
5736     OrderAccess::fence();
5737     for (;;) {
5738       w = *Lock;
5739       if ((w & LOCKBIT) == 0) {
5740         if (Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5741           ev->OnList = 0;
5742           // We call ::Release while holding the outer lock, thus
5743           // artificially lengthening the critical section.
5744           // Consider deferring the ::Release() until the subsequent unlock(),
5745           // after we've dropped the outer lock.
5746           if (ReleaseAfter != NULL) {
5747             ParkEvent::Release(ReleaseAfter);
5748           }
5749           return;
5750         }
5751         continue;      // Interference -- *Lock changed -- Just retry
5752       }
5753       assert(w & LOCKBIT, "invariant");
5754       ev->ListNext = (ParkEvent *) (w & ~LOCKBIT);
5755       if (Atomic::cmpxchg(intptr_t(ev)|LOCKBIT, Lock, w) == w) break;
5756     }
5757 
5758     while (ev->OnList != 0) {
5759       ev->park();
5760     }
5761   }
5762 }
5763 
5764 // Release() must extract a successor from the list and then wake that thread.
5765 // It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
5766 // similar to that used by ParkEvent::Allocate() and ::Release().  DMR-based
5767 // Release() would :
5768 // (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
5769 // (B) Extract a successor from the private list "in-hand"
5770 // (C) attempt to CAS() the residual back into *Lock over null.
5771 //     If there were any newly arrived threads and the CAS() would fail.
5772 //     In that case Release() would detach the RATs, re-merge the list in-hand
5773 //     with the RATs and repeat as needed.  Alternately, Release() might
5774 //     detach and extract a successor, but then pass the residual list to the wakee.
5775 //     The wakee would be responsible for reattaching and remerging before it
5776 //     competed for the lock.
5777 //
5778 // Both "pop" and DMR are immune from ABA corruption -- there can be
5779 // multiple concurrent pushers, but only one popper or detacher.
5780 // This implementation pops from the head of the list.  This is unfair,
5781 // but tends to provide excellent throughput as hot threads remain hot.
5782 // (We wake recently run threads first).
5783 //
5784 // All paths through muxRelease() will execute a CAS.
5785 // Release consistency -- We depend on the CAS in muxRelease() to provide full
5786 // bidirectional fence/MEMBAR semantics, ensuring that all prior memory operations
5787 // executed within the critical section are complete and globally visible before the
5788 // store (CAS) to the lock-word that releases the lock becomes globally visible.
5789 void Thread::muxRelease(volatile intptr_t * Lock)  {
5790   for (;;) {
5791     const intptr_t w = Atomic::cmpxchg((intptr_t)0, Lock, LOCKBIT);
5792     assert(w & LOCKBIT, "invariant");
5793     if (w == LOCKBIT) return;
5794     ParkEvent * const List = (ParkEvent *) (w & ~LOCKBIT);
5795     assert(List != NULL, "invariant");
5796     assert(List->OnList == intptr_t(Lock), "invariant");
5797     ParkEvent * const nxt = List->ListNext;
5798     guarantee((intptr_t(nxt) & LOCKBIT) == 0, "invariant");
5799 
5800     // The following CAS() releases the lock and pops the head element.
5801     // The CAS() also ratifies the previously fetched lock-word value.
5802     if (Atomic::cmpxchg(intptr_t(nxt), Lock, w) != w) {
5803       continue;
5804     }
5805     List->OnList = 0;
5806     OrderAccess::fence();
5807     List->unpark();
5808     return;
5809   }
5810 }
5811 
5812 
5813 void Threads::verify() {
5814   ALL_JAVA_THREADS(p) {
5815     p->verify();
5816   }
5817   VMThread* thread = VMThread::vm_thread();
5818   if (thread != NULL) thread->verify();
5819 }