1 /*
   2  * Copyright (c) 1997, 2018, 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 "classfile/classLoader.hpp"
  27 #include "classfile/javaClasses.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "code/scopeDesc.hpp"
  31 #include "compiler/compileBroker.hpp"
  32 #include "interpreter/interpreter.hpp"
  33 #include "interpreter/linkResolver.hpp"
  34 #include "interpreter/oopMapCache.hpp"
  35 #include "jvmtifiles/jvmtiEnv.hpp"
  36 #include "memory/gcLocker.inline.hpp"
  37 #include "memory/metaspaceShared.hpp"
  38 #include "memory/oopFactory.hpp"
  39 #include "memory/universe.inline.hpp"
  40 #include "oops/instanceKlass.hpp"
  41 #include "oops/objArrayOop.hpp"
  42 #include "oops/oop.inline.hpp"
  43 #include "oops/symbol.hpp"
  44 #include "prims/jvm_misc.hpp"
  45 #include "prims/jvmtiExport.hpp"
  46 #include "prims/jvmtiThreadState.hpp"
  47 #include "prims/privilegedStack.hpp"
  48 #include "runtime/arguments.hpp"
  49 #include "runtime/biasedLocking.hpp"
  50 #include "runtime/deoptimization.hpp"
  51 #include "runtime/fprofiler.hpp"
  52 #include "runtime/frame.inline.hpp"
  53 #include "runtime/init.hpp"
  54 #include "runtime/interfaceSupport.hpp"
  55 #include "runtime/java.hpp"
  56 #include "runtime/javaCalls.hpp"
  57 #include "runtime/jniPeriodicChecker.hpp"
  58 #include "runtime/memprofiler.hpp"
  59 #include "runtime/mutexLocker.hpp"
  60 #include "runtime/objectMonitor.hpp"
  61 #include "runtime/orderAccess.inline.hpp"
  62 #include "runtime/osThread.hpp"
  63 #include "runtime/safepoint.hpp"
  64 #include "runtime/sharedRuntime.hpp"
  65 #include "runtime/statSampler.hpp"
  66 #include "runtime/stubRoutines.hpp"
  67 #include "runtime/task.hpp"
  68 #include "runtime/thread.inline.hpp"
  69 #include "runtime/threadCritical.hpp"
  70 #include "runtime/threadLocalStorage.hpp"
  71 #include "runtime/vframe.hpp"
  72 #include "runtime/vframeArray.hpp"
  73 #include "runtime/vframe_hp.hpp"
  74 #include "runtime/vmThread.hpp"
  75 #include "runtime/vm_operations.hpp"
  76 #include "services/attachListener.hpp"
  77 #include "services/management.hpp"
  78 #include "services/memTracker.hpp"
  79 #include "services/threadService.hpp"
  80 #include "trace/tracing.hpp"
  81 #include "trace/traceMacros.hpp"
  82 #include "utilities/defaultStream.hpp"
  83 #include "utilities/dtrace.hpp"
  84 #include "utilities/events.hpp"
  85 #include "utilities/preserveException.hpp"
  86 #include "utilities/macros.hpp"
  87 #ifdef TARGET_OS_FAMILY_linux
  88 # include "os_linux.inline.hpp"
  89 #endif
  90 #ifdef TARGET_OS_FAMILY_solaris
  91 # include "os_solaris.inline.hpp"
  92 #endif
  93 #ifdef TARGET_OS_FAMILY_windows
  94 # include "os_windows.inline.hpp"
  95 #endif
  96 #ifdef TARGET_OS_FAMILY_bsd
  97 # include "os_bsd.inline.hpp"
  98 #endif
  99 #if INCLUDE_ALL_GCS
 100 #include "gc_implementation/shenandoah/shenandoahControlThread.hpp"
 101 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
 102 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
 103 #include "gc_implementation/parallelScavenge/pcTasks.hpp"
 104 #endif // INCLUDE_ALL_GCS
 105 #ifdef COMPILER1
 106 #include "c1/c1_Compiler.hpp"
 107 #endif
 108 #ifdef COMPILER2
 109 #include "opto/c2compiler.hpp"
 110 #include "opto/idealGraphPrinter.hpp"
 111 #endif
 112 #if INCLUDE_RTM_OPT
 113 #include "runtime/rtmLocking.hpp"
 114 #endif
 115 
 116 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
 117 
 118 #ifdef DTRACE_ENABLED
 119 
 120 // Only bother with this argument setup if dtrace is available
 121 
 122 #ifndef USDT2
 123 HS_DTRACE_PROBE_DECL(hotspot, vm__init__begin);
 124 HS_DTRACE_PROBE_DECL(hotspot, vm__init__end);
 125 HS_DTRACE_PROBE_DECL5(hotspot, thread__start, char*, intptr_t,
 126   intptr_t, intptr_t, bool);
 127 HS_DTRACE_PROBE_DECL5(hotspot, thread__stop, char*, intptr_t,
 128   intptr_t, intptr_t, bool);
 129 
 130 #define DTRACE_THREAD_PROBE(probe, javathread)                             \
 131   {                                                                        \
 132     ResourceMark rm(this);                                                 \
 133     int len = 0;                                                           \
 134     const char* name = (javathread)->get_thread_name();                    \
 135     len = strlen(name);                                                    \
 136     HS_DTRACE_PROBE5(hotspot, thread__##probe,                             \
 137       name, len,                                                           \
 138       java_lang_Thread::thread_id((javathread)->threadObj()),              \
 139       (javathread)->osthread()->thread_id(),                               \
 140       java_lang_Thread::is_daemon((javathread)->threadObj()));             \
 141   }
 142 
 143 #else /* USDT2 */
 144 
 145 #define HOTSPOT_THREAD_PROBE_start HOTSPOT_THREAD_START
 146 #define HOTSPOT_THREAD_PROBE_stop HOTSPOT_THREAD_STOP
 147 
 148 #define DTRACE_THREAD_PROBE(probe, javathread)                             \
 149   {                                                                        \
 150     ResourceMark rm(this);                                                 \
 151     int len = 0;                                                           \
 152     const char* name = (javathread)->get_thread_name();                    \
 153     len = strlen(name);                                                    \
 154     HOTSPOT_THREAD_PROBE_##probe(  /* probe = start, stop */               \
 155       (char *) name, len,                                                           \
 156       java_lang_Thread::thread_id((javathread)->threadObj()),              \
 157       (uintptr_t) (javathread)->osthread()->thread_id(),                               \
 158       java_lang_Thread::is_daemon((javathread)->threadObj()));             \
 159   }
 160 
 161 #endif /* USDT2 */
 162 
 163 #else //  ndef DTRACE_ENABLED
 164 
 165 #define DTRACE_THREAD_PROBE(probe, javathread)
 166 
 167 #endif // ndef DTRACE_ENABLED
 168 
 169 
 170 // Class hierarchy
 171 // - Thread
 172 //   - VMThread
 173 //   - WatcherThread
 174 //   - ConcurrentMarkSweepThread
 175 //   - JavaThread
 176 //     - CompilerThread
 177 
 178 // ======= Thread ========
 179 // Support for forcing alignment of thread objects for biased locking
 180 void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
 181   if (UseBiasedLocking) {
 182     const int alignment = markOopDesc::biased_lock_alignment;
 183     size_t aligned_size = size + (alignment - sizeof(intptr_t));
 184     void* real_malloc_addr = throw_excpt? AllocateHeap(aligned_size, flags, CURRENT_PC)
 185                                           : AllocateHeap(aligned_size, flags, CURRENT_PC,
 186                                               AllocFailStrategy::RETURN_NULL);
 187     void* aligned_addr     = (void*) align_size_up((intptr_t) real_malloc_addr, alignment);
 188     assert(((uintptr_t) aligned_addr + (uintptr_t) size) <=
 189            ((uintptr_t) real_malloc_addr + (uintptr_t) aligned_size),
 190            "JavaThread alignment code overflowed allocated storage");
 191     if (TraceBiasedLocking) {
 192       if (aligned_addr != real_malloc_addr)
 193         tty->print_cr("Aligned thread " INTPTR_FORMAT " to " INTPTR_FORMAT,
 194                       real_malloc_addr, aligned_addr);
 195     }
 196     ((Thread*) aligned_addr)->_real_malloc_address = real_malloc_addr;
 197     return aligned_addr;
 198   } else {
 199     return throw_excpt? AllocateHeap(size, flags, CURRENT_PC)
 200                        : AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
 201   }
 202 }
 203 
 204 void Thread::operator delete(void* p) {
 205   if (UseBiasedLocking) {
 206     void* real_malloc_addr = ((Thread*) p)->_real_malloc_address;
 207     FreeHeap(real_malloc_addr, mtThread);
 208   } else {
 209     FreeHeap(p, mtThread);
 210   }
 211 }
 212 
 213 
 214 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
 215 // JavaThread
 216 
 217 
 218 Thread::Thread() {
 219   // stack and get_thread
 220   set_stack_base(NULL);
 221   set_stack_size(0);
 222   set_self_raw_id(0);
 223   set_lgrp_id(-1);
 224 
 225   // allocated data structures
 226   set_osthread(NULL);
 227   set_resource_area(new (mtThread)ResourceArea());
 228   DEBUG_ONLY(_current_resource_mark = NULL;)
 229   set_handle_area(new (mtThread) HandleArea(NULL));
 230   set_metadata_handles(new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(30, true));
 231   set_active_handles(NULL);
 232   set_free_handle_block(NULL);
 233   set_last_handle_mark(NULL);
 234 
 235   // This initial value ==> never claimed.
 236   _oops_do_parity = 0;
 237 
 238   _metadata_on_stack_buffer = NULL;
 239 
 240   // the handle mark links itself to last_handle_mark
 241   new HandleMark(this);
 242 
 243   // plain initialization
 244   debug_only(_owned_locks = NULL;)
 245   debug_only(_allow_allocation_count = 0;)
 246   NOT_PRODUCT(_allow_safepoint_count = 0;)
 247   NOT_PRODUCT(_skip_gcalot = false;)
 248   _jvmti_env_iteration_count = 0;
 249   set_allocated_bytes(0);
 250   _vm_operation_started_count = 0;
 251   _vm_operation_completed_count = 0;
 252   _current_pending_monitor = NULL;
 253   _current_pending_monitor_is_from_java = true;
 254   _current_waiting_monitor = NULL;
 255   _num_nested_signal = 0;
 256   omFreeList = NULL ;
 257   omFreeCount = 0 ;
 258   omFreeProvision = 32 ;
 259   omInUseList = NULL ;
 260   omInUseCount = 0 ;
 261 
 262 #ifdef ASSERT
 263   _visited_for_critical_count = false;
 264 #endif
 265 
 266   _SR_lock = new Monitor(Mutex::suspend_resume, "SR_lock", true);
 267   _suspend_flags = 0;
 268 
 269   // thread-specific hashCode stream generator state - Marsaglia shift-xor form
 270   _hashStateX = os::random() ;
 271   _hashStateY = 842502087 ;
 272   _hashStateZ = 0x8767 ;    // (int)(3579807591LL & 0xffff) ;
 273   _hashStateW = 273326509 ;
 274 
 275   _OnTrap   = 0 ;
 276   _schedctl = NULL ;
 277   _Stalled  = 0 ;
 278   _TypeTag  = 0x2BAD ;
 279 
 280   // Many of the following fields are effectively final - immutable
 281   // Note that nascent threads can't use the Native Monitor-Mutex
 282   // construct until the _MutexEvent is initialized ...
 283   // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
 284   // we might instead use a stack of ParkEvents that we could provision on-demand.
 285   // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
 286   // and ::Release()
 287   _ParkEvent   = ParkEvent::Allocate (this) ;
 288   _SleepEvent  = ParkEvent::Allocate (this) ;
 289   _MutexEvent  = ParkEvent::Allocate (this) ;
 290   _MuxEvent    = ParkEvent::Allocate (this) ;
 291 
 292 #ifdef CHECK_UNHANDLED_OOPS
 293   if (CheckUnhandledOops) {
 294     _unhandled_oops = new UnhandledOops(this);
 295   }
 296 #endif // CHECK_UNHANDLED_OOPS
 297 #ifdef ASSERT
 298   if (UseBiasedLocking) {
 299     assert((((uintptr_t) this) & (markOopDesc::biased_lock_alignment - 1)) == 0, "forced alignment of thread object failed");
 300     assert(this == _real_malloc_address ||
 301            this == (void*) align_size_up((intptr_t) _real_malloc_address, markOopDesc::biased_lock_alignment),
 302            "bug in forced alignment of thread objects");
 303   }
 304 #endif /* ASSERT */
 305 
 306   _oom_during_evac = 0;
 307 #if INCLUDE_ALL_GCS
 308   _gc_state = _gc_state_global;
 309   _worker_id = (uint)(-1); // Actually, ShenandoahWorkerSession::INVALID_WORKER_ID, but avoid dependencies.
 310   _force_satb_flush = false;
 311 #endif
 312 }
 313 
 314 void Thread::set_oom_during_evac(bool oom) {
 315   if (oom) {
 316     _oom_during_evac |= 1;
 317   } else {
 318     _oom_during_evac &= ~1;
 319   }
 320 }
 321 
 322 bool Thread::is_oom_during_evac() const {
 323   return (_oom_during_evac & 1) == 1;
 324 }
 325 
 326 #ifdef ASSERT
 327 void Thread::set_evac_allowed(bool evac_allowed) {
 328   if (evac_allowed) {
 329     _oom_during_evac |= 2;
 330   } else {
 331     _oom_during_evac &= ~2;
 332   }
 333 }
 334 
 335 bool Thread::is_evac_allowed() const {
 336   return (_oom_during_evac & 2) == 2;
 337 }
 338 #endif
 339 
 340 void Thread::initialize_thread_local_storage() {
 341   // Note: Make sure this method only calls
 342   // non-blocking operations. Otherwise, it might not work
 343   // with the thread-startup/safepoint interaction.
 344 
 345   // During Java thread startup, safepoint code should allow this
 346   // method to complete because it may need to allocate memory to
 347   // store information for the new thread.
 348 
 349   // initialize structure dependent on thread local storage
 350   ThreadLocalStorage::set_thread(this);
 351 }
 352 
 353 void Thread::record_stack_base_and_size() {
 354   set_stack_base(os::current_stack_base());
 355   set_stack_size(os::current_stack_size());
 356   if (is_Java_thread()) {
 357     ((JavaThread*) this)->set_stack_overflow_limit();
 358   }
 359   // CR 7190089: on Solaris, primordial thread's stack is adjusted
 360   // in initialize_thread(). Without the adjustment, stack size is
 361   // incorrect if stack is set to unlimited (ulimit -s unlimited).
 362   // So far, only Solaris has real implementation of initialize_thread().
 363   //
 364   // set up any platform-specific state.
 365   os::initialize_thread(this);
 366 
 367 #if INCLUDE_NMT
 368   // record thread's native stack, stack grows downward
 369   address stack_low_addr = stack_base() - stack_size();
 370   MemTracker::record_thread_stack(stack_low_addr, stack_size());
 371 #endif // INCLUDE_NMT
 372 }
 373 
 374 
 375 Thread::~Thread() {
 376   // Reclaim the objectmonitors from the omFreeList of the moribund thread.
 377   ObjectSynchronizer::omFlush (this) ;
 378 
 379   EVENT_THREAD_DESTRUCT(this);
 380 
 381   // stack_base can be NULL if the thread is never started or exited before
 382   // record_stack_base_and_size called. Although, we would like to ensure
 383   // that all started threads do call record_stack_base_and_size(), there is
 384   // not proper way to enforce that.
 385 #if INCLUDE_NMT
 386   if (_stack_base != NULL) {
 387     address low_stack_addr = stack_base() - stack_size();
 388     MemTracker::release_thread_stack(low_stack_addr, stack_size());
 389 #ifdef ASSERT
 390     set_stack_base(NULL);
 391 #endif
 392   }
 393 #endif // INCLUDE_NMT
 394 
 395   // deallocate data structures
 396   delete resource_area();
 397   // since the handle marks are using the handle area, we have to deallocated the root
 398   // handle mark before deallocating the thread's handle area,
 399   assert(last_handle_mark() != NULL, "check we have an element");
 400   delete last_handle_mark();
 401   assert(last_handle_mark() == NULL, "check we have reached the end");
 402 
 403   // It's possible we can encounter a null _ParkEvent, etc., in stillborn threads.
 404   // We NULL out the fields for good hygiene.
 405   ParkEvent::Release (_ParkEvent)   ; _ParkEvent   = NULL ;
 406   ParkEvent::Release (_SleepEvent)  ; _SleepEvent  = NULL ;
 407   ParkEvent::Release (_MutexEvent)  ; _MutexEvent  = NULL ;
 408   ParkEvent::Release (_MuxEvent)    ; _MuxEvent    = NULL ;
 409 
 410   delete handle_area();
 411   delete metadata_handles();
 412 
 413   // osthread() can be NULL, if creation of thread failed.
 414   if (osthread() != NULL) os::free_thread(osthread());
 415 
 416   delete _SR_lock;
 417 
 418   // clear thread local storage if the Thread is deleting itself
 419   if (this == Thread::current()) {
 420     ThreadLocalStorage::set_thread(NULL);
 421   } else {
 422     // In the case where we're not the current thread, invalidate all the
 423     // caches in case some code tries to get the current thread or the
 424     // thread that was destroyed, and gets stale information.
 425     ThreadLocalStorage::invalidate_all();
 426   }
 427   CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
 428 }
 429 
 430 // NOTE: dummy function for assertion purpose.
 431 void Thread::run() {
 432   ShouldNotReachHere();
 433 }
 434 
 435 #ifdef ASSERT
 436 // Private method to check for dangling thread pointer
 437 void check_for_dangling_thread_pointer(Thread *thread) {
 438  assert(!thread->is_Java_thread() || Thread::current() == thread || Threads_lock->owned_by_self(),
 439          "possibility of dangling Thread pointer");
 440 }
 441 #endif
 442 
 443 
 444 #ifndef PRODUCT
 445 // Tracing method for basic thread operations
 446 void Thread::trace(const char* msg, const Thread* const thread) {
 447   if (!TraceThreadEvents) return;
 448   ResourceMark rm;
 449   ThreadCritical tc;
 450   const char *name = "non-Java thread";
 451   int prio = -1;
 452   if (thread->is_Java_thread()
 453       && !thread->is_Compiler_thread()) {
 454     // The Threads_lock must be held to get information about
 455     // this thread but may not be in some situations when
 456     // tracing  thread events.
 457     bool release_Threads_lock = false;
 458     if (!Threads_lock->owned_by_self()) {
 459       Threads_lock->lock();
 460       release_Threads_lock = true;
 461     }
 462     JavaThread* jt = (JavaThread *)thread;
 463     name = (char *)jt->get_thread_name();
 464     oop thread_oop = jt->threadObj();
 465     if (thread_oop != NULL) {
 466       prio = java_lang_Thread::priority(thread_oop);
 467     }
 468     if (release_Threads_lock) {
 469       Threads_lock->unlock();
 470     }
 471   }
 472   tty->print_cr("Thread::%s " INTPTR_FORMAT " [%lx] %s (prio: %d)", msg, thread, thread->osthread()->thread_id(), name, prio);
 473 }
 474 #endif
 475 
 476 
 477 ThreadPriority Thread::get_priority(const Thread* const thread) {
 478   trace("get priority", thread);
 479   ThreadPriority priority;
 480   // Can return an error!
 481   (void)os::get_priority(thread, priority);
 482   assert(MinPriority <= priority && priority <= MaxPriority, "non-Java priority found");
 483   return priority;
 484 }
 485 
 486 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
 487   trace("set priority", thread);
 488   debug_only(check_for_dangling_thread_pointer(thread);)
 489   // Can return an error!
 490   (void)os::set_priority(thread, priority);
 491 }
 492 
 493 
 494 void Thread::start(Thread* thread) {
 495   trace("start", thread);
 496   // Start is different from resume in that its safety is guaranteed by context or
 497   // being called from a Java method synchronized on the Thread object.
 498   if (!DisableStartThread) {
 499     if (thread->is_Java_thread()) {
 500       // Initialize the thread state to RUNNABLE before starting this thread.
 501       // Can not set it after the thread started because we do not know the
 502       // exact thread state at that time. It could be in MONITOR_WAIT or
 503       // in SLEEPING or some other state.
 504       java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
 505                                           java_lang_Thread::RUNNABLE);
 506     }
 507     os::start_thread(thread);
 508   }
 509 }
 510 
 511 // Enqueue a VM_Operation to do the job for us - sometime later
 512 void Thread::send_async_exception(oop java_thread, oop java_throwable) {
 513   VM_ThreadStop* vm_stop = new VM_ThreadStop(java_thread, java_throwable);
 514   VMThread::execute(vm_stop);
 515 }
 516 
 517 
 518 //
 519 // Check if an external suspend request has completed (or has been
 520 // cancelled). Returns true if the thread is externally suspended and
 521 // false otherwise.
 522 //
 523 // The bits parameter returns information about the code path through
 524 // the routine. Useful for debugging:
 525 //
 526 // set in is_ext_suspend_completed():
 527 // 0x00000001 - routine was entered
 528 // 0x00000010 - routine return false at end
 529 // 0x00000100 - thread exited (return false)
 530 // 0x00000200 - suspend request cancelled (return false)
 531 // 0x00000400 - thread suspended (return true)
 532 // 0x00001000 - thread is in a suspend equivalent state (return true)
 533 // 0x00002000 - thread is native and walkable (return true)
 534 // 0x00004000 - thread is native_trans and walkable (needed retry)
 535 //
 536 // set in wait_for_ext_suspend_completion():
 537 // 0x00010000 - routine was entered
 538 // 0x00020000 - suspend request cancelled before loop (return false)
 539 // 0x00040000 - thread suspended before loop (return true)
 540 // 0x00080000 - suspend request cancelled in loop (return false)
 541 // 0x00100000 - thread suspended in loop (return true)
 542 // 0x00200000 - suspend not completed during retry loop (return false)
 543 //
 544 
 545 // Helper class for tracing suspend wait debug bits.
 546 //
 547 // 0x00000100 indicates that the target thread exited before it could
 548 // self-suspend which is not a wait failure. 0x00000200, 0x00020000 and
 549 // 0x00080000 each indicate a cancelled suspend request so they don't
 550 // count as wait failures either.
 551 #define DEBUG_FALSE_BITS (0x00000010 | 0x00200000)
 552 
 553 class TraceSuspendDebugBits : public StackObj {
 554  private:
 555   JavaThread * jt;
 556   bool         is_wait;
 557   bool         called_by_wait;  // meaningful when !is_wait
 558   uint32_t *   bits;
 559 
 560  public:
 561   TraceSuspendDebugBits(JavaThread *_jt, bool _is_wait, bool _called_by_wait,
 562                         uint32_t *_bits) {
 563     jt             = _jt;
 564     is_wait        = _is_wait;
 565     called_by_wait = _called_by_wait;
 566     bits           = _bits;
 567   }
 568 
 569   ~TraceSuspendDebugBits() {
 570     if (!is_wait) {
 571 #if 1
 572       // By default, don't trace bits for is_ext_suspend_completed() calls.
 573       // That trace is very chatty.
 574       return;
 575 #else
 576       if (!called_by_wait) {
 577         // If tracing for is_ext_suspend_completed() is enabled, then only
 578         // trace calls to it from wait_for_ext_suspend_completion()
 579         return;
 580       }
 581 #endif
 582     }
 583 
 584     if (AssertOnSuspendWaitFailure || TraceSuspendWaitFailures) {
 585       if (bits != NULL && (*bits & DEBUG_FALSE_BITS) != 0) {
 586         MutexLocker ml(Threads_lock);  // needed for get_thread_name()
 587         ResourceMark rm;
 588 
 589         tty->print_cr(
 590             "Failed wait_for_ext_suspend_completion(thread=%s, debug_bits=%x)",
 591             jt->get_thread_name(), *bits);
 592 
 593         guarantee(!AssertOnSuspendWaitFailure, "external suspend wait failed");
 594       }
 595     }
 596   }
 597 };
 598 #undef DEBUG_FALSE_BITS
 599 
 600 
 601 bool JavaThread::is_ext_suspend_completed(bool called_by_wait, int delay, uint32_t *bits) {
 602   TraceSuspendDebugBits tsdb(this, false /* !is_wait */, called_by_wait, bits);
 603 
 604   bool did_trans_retry = false;  // only do thread_in_native_trans retry once
 605   bool do_trans_retry;           // flag to force the retry
 606 
 607   *bits |= 0x00000001;
 608 
 609   do {
 610     do_trans_retry = false;
 611 
 612     if (is_exiting()) {
 613       // Thread is in the process of exiting. This is always checked
 614       // first to reduce the risk of dereferencing a freed JavaThread.
 615       *bits |= 0x00000100;
 616       return false;
 617     }
 618 
 619     if (!is_external_suspend()) {
 620       // Suspend request is cancelled. This is always checked before
 621       // is_ext_suspended() to reduce the risk of a rogue resume
 622       // confusing the thread that made the suspend request.
 623       *bits |= 0x00000200;
 624       return false;
 625     }
 626 
 627     if (is_ext_suspended()) {
 628       // thread is suspended
 629       *bits |= 0x00000400;
 630       return true;
 631     }
 632 
 633     // Now that we no longer do hard suspends of threads running
 634     // native code, the target thread can be changing thread state
 635     // while we are in this routine:
 636     //
 637     //   _thread_in_native -> _thread_in_native_trans -> _thread_blocked
 638     //
 639     // We save a copy of the thread state as observed at this moment
 640     // and make our decision about suspend completeness based on the
 641     // copy. This closes the race where the thread state is seen as
 642     // _thread_in_native_trans in the if-thread_blocked check, but is
 643     // seen as _thread_blocked in if-thread_in_native_trans check.
 644     JavaThreadState save_state = thread_state();
 645 
 646     if (save_state == _thread_blocked && is_suspend_equivalent()) {
 647       // If the thread's state is _thread_blocked and this blocking
 648       // condition is known to be equivalent to a suspend, then we can
 649       // consider the thread to be externally suspended. This means that
 650       // the code that sets _thread_blocked has been modified to do
 651       // self-suspension if the blocking condition releases. We also
 652       // used to check for CONDVAR_WAIT here, but that is now covered by
 653       // the _thread_blocked with self-suspension check.
 654       //
 655       // Return true since we wouldn't be here unless there was still an
 656       // external suspend request.
 657       *bits |= 0x00001000;
 658       return true;
 659     } else if (save_state == _thread_in_native && frame_anchor()->walkable()) {
 660       // Threads running native code will self-suspend on native==>VM/Java
 661       // transitions. If its stack is walkable (should always be the case
 662       // unless this function is called before the actual java_suspend()
 663       // call), then the wait is done.
 664       *bits |= 0x00002000;
 665       return true;
 666     } else if (!called_by_wait && !did_trans_retry &&
 667                save_state == _thread_in_native_trans &&
 668                frame_anchor()->walkable()) {
 669       // The thread is transitioning from thread_in_native to another
 670       // thread state. check_safepoint_and_suspend_for_native_trans()
 671       // will force the thread to self-suspend. If it hasn't gotten
 672       // there yet we may have caught the thread in-between the native
 673       // code check above and the self-suspend. Lucky us. If we were
 674       // called by wait_for_ext_suspend_completion(), then it
 675       // will be doing the retries so we don't have to.
 676       //
 677       // Since we use the saved thread state in the if-statement above,
 678       // there is a chance that the thread has already transitioned to
 679       // _thread_blocked by the time we get here. In that case, we will
 680       // make a single unnecessary pass through the logic below. This
 681       // doesn't hurt anything since we still do the trans retry.
 682 
 683       *bits |= 0x00004000;
 684 
 685       // Once the thread leaves thread_in_native_trans for another
 686       // thread state, we break out of this retry loop. We shouldn't
 687       // need this flag to prevent us from getting back here, but
 688       // sometimes paranoia is good.
 689       did_trans_retry = true;
 690 
 691       // We wait for the thread to transition to a more usable state.
 692       for (int i = 1; i <= SuspendRetryCount; i++) {
 693         // We used to do an "os::yield_all(i)" call here with the intention
 694         // that yielding would increase on each retry. However, the parameter
 695         // is ignored on Linux which means the yield didn't scale up. Waiting
 696         // on the SR_lock below provides a much more predictable scale up for
 697         // the delay. It also provides a simple/direct point to check for any
 698         // safepoint requests from the VMThread
 699 
 700         // temporarily drops SR_lock while doing wait with safepoint check
 701         // (if we're a JavaThread - the WatcherThread can also call this)
 702         // and increase delay with each retry
 703         SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 704 
 705         // check the actual thread state instead of what we saved above
 706         if (thread_state() != _thread_in_native_trans) {
 707           // the thread has transitioned to another thread state so
 708           // try all the checks (except this one) one more time.
 709           do_trans_retry = true;
 710           break;
 711         }
 712       } // end retry loop
 713 
 714 
 715     }
 716   } while (do_trans_retry);
 717 
 718   *bits |= 0x00000010;
 719   return false;
 720 }
 721 
 722 //
 723 // Wait for an external suspend request to complete (or be cancelled).
 724 // Returns true if the thread is externally suspended and false otherwise.
 725 //
 726 bool JavaThread::wait_for_ext_suspend_completion(int retries, int delay,
 727        uint32_t *bits) {
 728   TraceSuspendDebugBits tsdb(this, true /* is_wait */,
 729                              false /* !called_by_wait */, bits);
 730 
 731   // local flag copies to minimize SR_lock hold time
 732   bool is_suspended;
 733   bool pending;
 734   uint32_t reset_bits;
 735 
 736   // set a marker so is_ext_suspend_completed() knows we are the caller
 737   *bits |= 0x00010000;
 738 
 739   // We use reset_bits to reinitialize the bits value at the top of
 740   // each retry loop. This allows the caller to make use of any
 741   // unused bits for their own marking purposes.
 742   reset_bits = *bits;
 743 
 744   {
 745     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 746     is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 747                                             delay, bits);
 748     pending = is_external_suspend();
 749   }
 750   // must release SR_lock to allow suspension to complete
 751 
 752   if (!pending) {
 753     // A cancelled suspend request is the only false return from
 754     // is_ext_suspend_completed() that keeps us from entering the
 755     // retry loop.
 756     *bits |= 0x00020000;
 757     return false;
 758   }
 759 
 760   if (is_suspended) {
 761     *bits |= 0x00040000;
 762     return true;
 763   }
 764 
 765   for (int i = 1; i <= retries; i++) {
 766     *bits = reset_bits;  // reinit to only track last retry
 767 
 768     // We used to do an "os::yield_all(i)" call here with the intention
 769     // that yielding would increase on each retry. However, the parameter
 770     // is ignored on Linux which means the yield didn't scale up. Waiting
 771     // on the SR_lock below provides a much more predictable scale up for
 772     // the delay. It also provides a simple/direct point to check for any
 773     // safepoint requests from the VMThread
 774 
 775     {
 776       MutexLocker ml(SR_lock());
 777       // wait with safepoint check (if we're a JavaThread - the WatcherThread
 778       // can also call this)  and increase delay with each retry
 779       SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 780 
 781       is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 782                                               delay, bits);
 783 
 784       // It is possible for the external suspend request to be cancelled
 785       // (by a resume) before the actual suspend operation is completed.
 786       // Refresh our local copy to see if we still need to wait.
 787       pending = is_external_suspend();
 788     }
 789 
 790     if (!pending) {
 791       // A cancelled suspend request is the only false return from
 792       // is_ext_suspend_completed() that keeps us from staying in the
 793       // retry loop.
 794       *bits |= 0x00080000;
 795       return false;
 796     }
 797 
 798     if (is_suspended) {
 799       *bits |= 0x00100000;
 800       return true;
 801     }
 802   } // end retry loop
 803 
 804   // thread did not suspend after all our retries
 805   *bits |= 0x00200000;
 806   return false;
 807 }
 808 
 809 #ifndef PRODUCT
 810 void JavaThread::record_jump(address target, address instr, const char* file, int line) {
 811 
 812   // This should not need to be atomic as the only way for simultaneous
 813   // updates is via interrupts. Even then this should be rare or non-existant
 814   // and we don't care that much anyway.
 815 
 816   int index = _jmp_ring_index;
 817   _jmp_ring_index = (index + 1 ) & (jump_ring_buffer_size - 1);
 818   _jmp_ring[index]._target = (intptr_t) target;
 819   _jmp_ring[index]._instruction = (intptr_t) instr;
 820   _jmp_ring[index]._file = file;
 821   _jmp_ring[index]._line = line;
 822 }
 823 #endif /* PRODUCT */
 824 
 825 // Called by flat profiler
 826 // Callers have already called wait_for_ext_suspend_completion
 827 // The assertion for that is currently too complex to put here:
 828 bool JavaThread::profile_last_Java_frame(frame* _fr) {
 829   bool gotframe = false;
 830   // self suspension saves needed state.
 831   if (has_last_Java_frame() && _anchor.walkable()) {
 832      *_fr = pd_last_frame();
 833      gotframe = true;
 834   }
 835   return gotframe;
 836 }
 837 
 838 void Thread::interrupt(Thread* thread) {
 839   trace("interrupt", thread);
 840   debug_only(check_for_dangling_thread_pointer(thread);)
 841   os::interrupt(thread);
 842 }
 843 
 844 bool Thread::is_interrupted(Thread* thread, bool clear_interrupted) {
 845   trace("is_interrupted", thread);
 846   debug_only(check_for_dangling_thread_pointer(thread);)
 847   // Note:  If clear_interrupted==false, this simply fetches and
 848   // returns the value of the field osthread()->interrupted().
 849   return os::is_interrupted(thread, clear_interrupted);
 850 }
 851 
 852 
 853 // GC Support
 854 bool Thread::claim_oops_do_par_case(int strong_roots_parity) {
 855   jint thread_parity = _oops_do_parity;
 856   if (thread_parity != strong_roots_parity) {
 857     jint res = Atomic::cmpxchg(strong_roots_parity, &_oops_do_parity, thread_parity);
 858     if (res == thread_parity) {
 859       return true;
 860     } else {
 861       guarantee(res == strong_roots_parity, "Or else what?");
 862       assert(SharedHeap::heap()->workers()->active_workers() > 0,
 863          "Should only fail when parallel.");
 864       return false;
 865     }
 866   }
 867   assert(SharedHeap::heap()->workers()->active_workers() > 0,
 868          "Should only fail when parallel.");
 869   return false;
 870 }
 871 
 872 void Thread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
 873   active_handles()->oops_do(f);
 874   // Do oop for ThreadShadow
 875   f->do_oop((oop*)&_pending_exception);
 876   handle_area()->oops_do(f);
 877 }
 878 
 879 void Thread::nmethods_do(CodeBlobClosure* cf) {
 880   // no nmethods in a generic thread...
 881 }
 882 
 883 void Thread::metadata_do(void f(Metadata*)) {
 884   if (metadata_handles() != NULL) {
 885     for (int i = 0; i< metadata_handles()->length(); i++) {
 886       f(metadata_handles()->at(i));
 887     }
 888   }
 889 }
 890 
 891 void Thread::print_on(outputStream* st) const {
 892   // get_priority assumes osthread initialized
 893   if (osthread() != NULL) {
 894     int os_prio;
 895     if (os::get_native_priority(this, &os_prio) == OS_OK) {
 896       st->print("os_prio=%d ", os_prio);
 897     }
 898     st->print("tid=" INTPTR_FORMAT " ", this);
 899     ext().print_on(st);
 900     osthread()->print_on(st);
 901   }
 902   debug_only(if (WizardMode) print_owned_locks_on(st);)
 903 }
 904 
 905 // Thread::print_on_error() is called by fatal error handler. Don't use
 906 // any lock or allocate memory.
 907 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
 908   if      (is_VM_thread())                  st->print("VMThread");
 909   else if (is_Compiler_thread())            st->print("CompilerThread");
 910   else if (is_Java_thread())                st->print("JavaThread");
 911   else if (is_GC_task_thread())             st->print("GCTaskThread");
 912   else if (is_Watcher_thread())             st->print("WatcherThread");
 913   else if (is_ConcurrentGC_thread())        st->print("ConcurrentGCThread");
 914   else st->print("Thread");
 915 
 916   st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
 917             _stack_base - _stack_size, _stack_base);
 918 
 919   if (osthread()) {
 920     st->print(" [id=%d]", osthread()->thread_id());
 921   }
 922 }
 923 
 924 #ifdef ASSERT
 925 void Thread::print_owned_locks_on(outputStream* st) const {
 926   Monitor *cur = _owned_locks;
 927   if (cur == NULL) {
 928     st->print(" (no locks) ");
 929   } else {
 930     st->print_cr(" Locks owned:");
 931     while(cur) {
 932       cur->print_on(st);
 933       cur = cur->next();
 934     }
 935   }
 936 }
 937 
 938 static int ref_use_count  = 0;
 939 
 940 bool Thread::owns_locks_but_compiled_lock() const {
 941   for(Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 942     if (cur != Compile_lock) return true;
 943   }
 944   return false;
 945 }
 946 
 947 
 948 #endif
 949 
 950 #ifndef PRODUCT
 951 
 952 // The flag: potential_vm_operation notifies if this particular safepoint state could potential
 953 // invoke the vm-thread (i.e., and oop allocation). In that case, we also have to make sure that
 954 // no threads which allow_vm_block's are held
 955 void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) {
 956     // Check if current thread is allowed to block at a safepoint
 957     if (!(_allow_safepoint_count == 0))
 958       fatal("Possible safepoint reached by thread that does not allow it");
 959     if (is_Java_thread() && ((JavaThread*)this)->thread_state() != _thread_in_vm) {
 960       fatal("LEAF method calling lock?");
 961     }
 962 
 963 #ifdef ASSERT
 964     if (potential_vm_operation && is_Java_thread()
 965         && !Universe::is_bootstrapping()) {
 966       // Make sure we do not hold any locks that the VM thread also uses.
 967       // This could potentially lead to deadlocks
 968       for(Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 969         // Threads_lock is special, since the safepoint synchronization will not start before this is
 970         // acquired. Hence, a JavaThread cannot be holding it at a safepoint. So is VMOperationRequest_lock,
 971         // since it is used to transfer control between JavaThreads and the VMThread
 972         // Do not *exclude* any locks unless you are absolutly sure it is correct. Ask someone else first!
 973         if ( (cur->allow_vm_block() &&
 974               cur != Threads_lock &&
 975               cur != Compile_lock &&               // Temporary: should not be necessary when we get spearate compilation
 976               cur != VMOperationRequest_lock &&
 977               cur != VMOperationQueue_lock) ||
 978               cur->rank() == Mutex::special) {
 979           fatal(err_msg("Thread holding lock at safepoint that vm can block on: %s", cur->name()));
 980         }
 981       }
 982     }
 983 
 984     if (GCALotAtAllSafepoints) {
 985       // We could enter a safepoint here and thus have a gc
 986       InterfaceSupport::check_gc_alot();
 987     }
 988 #endif
 989 }
 990 #endif
 991 
 992 bool Thread::is_in_stack(address adr) const {
 993   assert(Thread::current() == this, "is_in_stack can only be called from current thread");
 994   address end = os::current_stack_pointer();
 995   // Allow non Java threads to call this without stack_base
 996   if (_stack_base == NULL) return true;
 997   if (stack_base() >= adr && adr >= end) return true;
 998 
 999   return false;
1000 }
1001 
1002 
1003 bool Thread::is_in_usable_stack(address adr) const {
1004   size_t stack_guard_size = os::uses_stack_guard_pages() ? (StackYellowPages + StackRedPages) * os::vm_page_size() : 0;
1005   size_t usable_stack_size = _stack_size - stack_guard_size;
1006 
1007   return ((adr < stack_base()) && (adr >= stack_base() - usable_stack_size));
1008 }
1009 
1010 
1011 // We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
1012 // However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
1013 // used for compilation in the future. If that change is made, the need for these methods
1014 // should be revisited, and they should be removed if possible.
1015 
1016 bool Thread::is_lock_owned(address adr) const {
1017   return on_local_stack(adr);
1018 }
1019 
1020 bool Thread::set_as_starting_thread() {
1021  // NOTE: this must be called inside the main thread.
1022   return os::create_main_thread((JavaThread*)this);
1023 }
1024 
1025 static void initialize_class(Symbol* class_name, TRAPS) {
1026   Klass* klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
1027   InstanceKlass::cast(klass)->initialize(CHECK);
1028 }
1029 
1030 
1031 // Creates the initial ThreadGroup
1032 static Handle create_initial_thread_group(TRAPS) {
1033   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_ThreadGroup(), true, CHECK_NH);
1034   instanceKlassHandle klass (THREAD, k);
1035 
1036   Handle system_instance = klass->allocate_instance_handle(CHECK_NH);
1037   {
1038     JavaValue result(T_VOID);
1039     JavaCalls::call_special(&result,
1040                             system_instance,
1041                             klass,
1042                             vmSymbols::object_initializer_name(),
1043                             vmSymbols::void_method_signature(),
1044                             CHECK_NH);
1045   }
1046   Universe::set_system_thread_group(system_instance());
1047 
1048   Handle main_instance = klass->allocate_instance_handle(CHECK_NH);
1049   {
1050     JavaValue result(T_VOID);
1051     Handle string = java_lang_String::create_from_str("main", CHECK_NH);
1052     JavaCalls::call_special(&result,
1053                             main_instance,
1054                             klass,
1055                             vmSymbols::object_initializer_name(),
1056                             vmSymbols::threadgroup_string_void_signature(),
1057                             system_instance,
1058                             string,
1059                             CHECK_NH);
1060   }
1061   return main_instance;
1062 }
1063 
1064 // Creates the initial Thread
1065 static oop create_initial_thread(Handle thread_group, JavaThread* thread, TRAPS) {
1066   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK_NULL);
1067   instanceKlassHandle klass (THREAD, k);
1068   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK_NULL);
1069 
1070   java_lang_Thread::set_thread(thread_oop(), thread);
1071   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1072   thread->set_threadObj(thread_oop());
1073 
1074   Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
1075 
1076   JavaValue result(T_VOID);
1077   JavaCalls::call_special(&result, thread_oop,
1078                                    klass,
1079                                    vmSymbols::object_initializer_name(),
1080                                    vmSymbols::threadgroup_string_void_signature(),
1081                                    thread_group,
1082                                    string,
1083                                    CHECK_NULL);
1084   return thread_oop();
1085 }
1086 
1087 static void call_initializeSystemClass(TRAPS) {
1088   Klass* k =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
1089   instanceKlassHandle klass (THREAD, k);
1090 
1091   JavaValue result(T_VOID);
1092   JavaCalls::call_static(&result, klass, vmSymbols::initializeSystemClass_name(),
1093                                          vmSymbols::void_method_signature(), CHECK);
1094 }
1095 
1096 char java_runtime_name[128] = "";
1097 char java_runtime_version[128] = "";
1098 
1099 // extract the JRE name from sun.misc.Version.java_runtime_name
1100 static const char* get_java_runtime_name(TRAPS) {
1101   Klass* k = SystemDictionary::find(vmSymbols::sun_misc_Version(),
1102                                       Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1103   fieldDescriptor fd;
1104   bool found = k != NULL &&
1105                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_name_name(),
1106                                                         vmSymbols::string_signature(), &fd);
1107   if (found) {
1108     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1109     if (name_oop == NULL)
1110       return NULL;
1111     const char* name = java_lang_String::as_utf8_string(name_oop,
1112                                                         java_runtime_name,
1113                                                         sizeof(java_runtime_name));
1114     return name;
1115   } else {
1116     return NULL;
1117   }
1118 }
1119 
1120 // extract the JRE version from sun.misc.Version.java_runtime_version
1121 static const char* get_java_runtime_version(TRAPS) {
1122   Klass* k = SystemDictionary::find(vmSymbols::sun_misc_Version(),
1123                                       Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1124   fieldDescriptor fd;
1125   bool found = k != NULL &&
1126                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_version_name(),
1127                                                         vmSymbols::string_signature(), &fd);
1128   if (found) {
1129     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1130     if (name_oop == NULL)
1131       return NULL;
1132     const char* name = java_lang_String::as_utf8_string(name_oop,
1133                                                         java_runtime_version,
1134                                                         sizeof(java_runtime_version));
1135     return name;
1136   } else {
1137     return NULL;
1138   }
1139 }
1140 
1141 // General purpose hook into Java code, run once when the VM is initialized.
1142 // The Java library method itself may be changed independently from the VM.
1143 static void call_postVMInitHook(TRAPS) {
1144   Klass* k = SystemDictionary::resolve_or_null(vmSymbols::sun_misc_PostVMInitHook(), THREAD);
1145   instanceKlassHandle klass (THREAD, k);
1146   if (klass.not_null()) {
1147     JavaValue result(T_VOID);
1148     JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
1149                                            vmSymbols::void_method_signature(),
1150                                            CHECK);
1151   }
1152 }
1153 
1154 static void reset_vm_info_property(TRAPS) {
1155   // the vm info string
1156   ResourceMark rm(THREAD);
1157   const char *vm_info = VM_Version::vm_info_string();
1158 
1159   // java.lang.System class
1160   Klass* k =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
1161   instanceKlassHandle klass (THREAD, k);
1162 
1163   // setProperty arguments
1164   Handle key_str    = java_lang_String::create_from_str("java.vm.info", CHECK);
1165   Handle value_str  = java_lang_String::create_from_str(vm_info, CHECK);
1166 
1167   // return value
1168   JavaValue r(T_OBJECT);
1169 
1170   // public static String setProperty(String key, String value);
1171   JavaCalls::call_static(&r,
1172                          klass,
1173                          vmSymbols::setProperty_name(),
1174                          vmSymbols::string_string_string_signature(),
1175                          key_str,
1176                          value_str,
1177                          CHECK);
1178 }
1179 
1180 
1181 void JavaThread::allocate_threadObj(Handle thread_group, char* thread_name, bool daemon, TRAPS) {
1182   assert(thread_group.not_null(), "thread group should be specified");
1183   assert(threadObj() == NULL, "should only create Java thread object once");
1184 
1185   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK);
1186   instanceKlassHandle klass (THREAD, k);
1187   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);
1188 
1189   java_lang_Thread::set_thread(thread_oop(), this);
1190   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1191   set_threadObj(thread_oop());
1192 
1193   JavaValue result(T_VOID);
1194   if (thread_name != NULL) {
1195     Handle name = java_lang_String::create_from_str(thread_name, CHECK);
1196     // Thread gets assigned specified name and null target
1197     JavaCalls::call_special(&result,
1198                             thread_oop,
1199                             klass,
1200                             vmSymbols::object_initializer_name(),
1201                             vmSymbols::threadgroup_string_void_signature(),
1202                             thread_group, // Argument 1
1203                             name,         // Argument 2
1204                             THREAD);
1205   } else {
1206     // Thread gets assigned name "Thread-nnn" and null target
1207     // (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
1208     JavaCalls::call_special(&result,
1209                             thread_oop,
1210                             klass,
1211                             vmSymbols::object_initializer_name(),
1212                             vmSymbols::threadgroup_runnable_void_signature(),
1213                             thread_group, // Argument 1
1214                             Handle(),     // Argument 2
1215                             THREAD);
1216   }
1217 
1218 
1219   if (daemon) {
1220       java_lang_Thread::set_daemon(thread_oop());
1221   }
1222 
1223   if (HAS_PENDING_EXCEPTION) {
1224     return;
1225   }
1226 
1227   KlassHandle group(this, SystemDictionary::ThreadGroup_klass());
1228   Handle threadObj(this, this->threadObj());
1229 
1230   JavaCalls::call_special(&result,
1231                          thread_group,
1232                          group,
1233                          vmSymbols::add_method_name(),
1234                          vmSymbols::thread_void_signature(),
1235                          threadObj,          // Arg 1
1236                          THREAD);
1237 
1238 
1239 }
1240 
1241 // NamedThread --  non-JavaThread subclasses with multiple
1242 // uniquely named instances should derive from this.
1243 NamedThread::NamedThread() : Thread() {
1244   _name = NULL;
1245   _processed_thread = NULL;
1246 }
1247 
1248 NamedThread::~NamedThread() {
1249   if (_name != NULL) {
1250     FREE_C_HEAP_ARRAY(char, _name, mtThread);
1251     _name = NULL;
1252   }
1253 }
1254 
1255 void NamedThread::set_name(const char* format, ...) {
1256   guarantee(_name == NULL, "Only get to set name once.");
1257   _name = NEW_C_HEAP_ARRAY(char, max_name_len, mtThread);
1258   guarantee(_name != NULL, "alloc failure");
1259   va_list ap;
1260   va_start(ap, format);
1261   jio_vsnprintf(_name, max_name_len, format, ap);
1262   va_end(ap);
1263 }
1264 
1265 // ======= WatcherThread ========
1266 
1267 // The watcher thread exists to simulate timer interrupts.  It should
1268 // be replaced by an abstraction over whatever native support for
1269 // timer interrupts exists on the platform.
1270 
1271 WatcherThread* WatcherThread::_watcher_thread   = NULL;
1272 bool WatcherThread::_startable = false;
1273 volatile bool  WatcherThread::_should_terminate = false;
1274 
1275 WatcherThread::WatcherThread() : Thread(), _crash_protection(NULL) {
1276   assert(watcher_thread() == NULL, "we can only allocate one WatcherThread");
1277   if (os::create_thread(this, os::watcher_thread)) {
1278     _watcher_thread = this;
1279 
1280     // Set the watcher thread to the highest OS priority which should not be
1281     // used, unless a Java thread with priority java.lang.Thread.MAX_PRIORITY
1282     // is created. The only normal thread using this priority is the reference
1283     // handler thread, which runs for very short intervals only.
1284     // If the VMThread's priority is not lower than the WatcherThread profiling
1285     // will be inaccurate.
1286     os::set_priority(this, MaxPriority);
1287     if (!DisableStartThread) {
1288       os::start_thread(this);
1289     }
1290   }
1291 }
1292 
1293 int WatcherThread::sleep() const {
1294   MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
1295 
1296   // remaining will be zero if there are no tasks,
1297   // causing the WatcherThread to sleep until a task is
1298   // enrolled
1299   int remaining = PeriodicTask::time_to_wait();
1300   int time_slept = 0;
1301 
1302   // we expect this to timeout - we only ever get unparked when
1303   // we should terminate or when a new task has been enrolled
1304   OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
1305 
1306   jlong time_before_loop = os::javaTimeNanos();
1307 
1308   for (;;) {
1309     bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag, remaining);
1310     jlong now = os::javaTimeNanos();
1311 
1312     if (remaining == 0) {
1313         // if we didn't have any tasks we could have waited for a long time
1314         // consider the time_slept zero and reset time_before_loop
1315         time_slept = 0;
1316         time_before_loop = now;
1317     } else {
1318         // need to recalulate since we might have new tasks in _tasks
1319         time_slept = (int) ((now - time_before_loop) / 1000000);
1320     }
1321 
1322     // Change to task list or spurious wakeup of some kind
1323     if (timedout || _should_terminate) {
1324         break;
1325     }
1326 
1327     remaining = PeriodicTask::time_to_wait();
1328     if (remaining == 0) {
1329         // Last task was just disenrolled so loop around and wait until
1330         // another task gets enrolled
1331         continue;
1332     }
1333 
1334     remaining -= time_slept;
1335     if (remaining <= 0)
1336       break;
1337   }
1338 
1339   return time_slept;
1340 }
1341 
1342 void WatcherThread::run() {
1343   assert(this == watcher_thread(), "just checking");
1344 
1345   this->record_stack_base_and_size();
1346   this->initialize_thread_local_storage();
1347   this->set_native_thread_name(this->name());
1348   this->set_active_handles(JNIHandleBlock::allocate_block());
1349   while(!_should_terminate) {
1350     assert(watcher_thread() == Thread::current(),  "thread consistency check");
1351     assert(watcher_thread() == this,  "thread consistency check");
1352 
1353     // Calculate how long it'll be until the next PeriodicTask work
1354     // should be done, and sleep that amount of time.
1355     int time_waited = sleep();
1356 
1357     if (is_error_reported()) {
1358       // A fatal error has happened, the error handler(VMError::report_and_die)
1359       // should abort JVM after creating an error log file. However in some
1360       // rare cases, the error handler itself might deadlock. Here we try to
1361       // kill JVM if the fatal error handler fails to abort in 2 minutes.
1362       //
1363       // This code is in WatcherThread because WatcherThread wakes up
1364       // periodically so the fatal error handler doesn't need to do anything;
1365       // also because the WatcherThread is less likely to crash than other
1366       // threads.
1367 
1368       for (;;) {
1369         if (!ShowMessageBoxOnError
1370          && (OnError == NULL || OnError[0] == '\0')
1371          && Arguments::abort_hook() == NULL) {
1372              os::sleep(this, 2 * 60 * 1000, false);
1373              fdStream err(defaultStream::output_fd());
1374              err.print_raw_cr("# [ timer expired, abort... ]");
1375              // skip atexit/vm_exit/vm_abort hooks
1376              os::die();
1377         }
1378 
1379         // Wake up 5 seconds later, the fatal handler may reset OnError or
1380         // ShowMessageBoxOnError when it is ready to abort.
1381         os::sleep(this, 5 * 1000, false);
1382       }
1383     }
1384 
1385     PeriodicTask::real_time_tick(time_waited);
1386   }
1387 
1388   // Signal that it is terminated
1389   {
1390     MutexLockerEx mu(Terminator_lock, Mutex::_no_safepoint_check_flag);
1391     _watcher_thread = NULL;
1392     Terminator_lock->notify();
1393   }
1394 
1395   // Thread destructor usually does this..
1396   ThreadLocalStorage::set_thread(NULL);
1397 }
1398 
1399 void WatcherThread::start() {
1400   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1401 
1402   if (watcher_thread() == NULL && _startable) {
1403     _should_terminate = false;
1404     // Create the single instance of WatcherThread
1405     new WatcherThread();
1406   }
1407 }
1408 
1409 void WatcherThread::make_startable() {
1410   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1411   _startable = true;
1412 }
1413 
1414 void WatcherThread::stop() {
1415   {
1416     MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
1417     _should_terminate = true;
1418     OrderAccess::fence();  // ensure WatcherThread sees update in main loop
1419 
1420     WatcherThread* watcher = watcher_thread();
1421     if (watcher != NULL)
1422       watcher->unpark();
1423   }
1424 
1425   // it is ok to take late safepoints here, if needed
1426   MutexLocker mu(Terminator_lock);
1427 
1428   while(watcher_thread() != NULL) {
1429     // This wait should make safepoint checks, wait without a timeout,
1430     // and wait as a suspend-equivalent condition.
1431     //
1432     // Note: If the FlatProfiler is running, then this thread is waiting
1433     // for the WatcherThread to terminate and the WatcherThread, via the
1434     // FlatProfiler task, is waiting for the external suspend request on
1435     // this thread to complete. wait_for_ext_suspend_completion() will
1436     // eventually timeout, but that takes time. Making this wait a
1437     // suspend-equivalent condition solves that timeout problem.
1438     //
1439     Terminator_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
1440                           Mutex::_as_suspend_equivalent_flag);
1441   }
1442 }
1443 
1444 void WatcherThread::unpark() {
1445   MutexLockerEx ml(PeriodicTask_lock->owned_by_self() ? NULL : PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
1446   PeriodicTask_lock->notify();
1447 }
1448 
1449 void WatcherThread::print_on(outputStream* st) const {
1450   st->print("\"%s\" ", name());
1451   Thread::print_on(st);
1452   st->cr();
1453 }
1454 
1455 // ======= JavaThread ========
1456 
1457 // A JavaThread is a normal Java thread
1458 
1459 void JavaThread::initialize() {
1460   // Initialize fields
1461 
1462   // Set the claimed par_id to UINT_MAX (ie not claiming any par_ids)
1463   set_claimed_par_id(UINT_MAX);
1464 
1465   set_saved_exception_pc(NULL);
1466   set_threadObj(NULL);
1467   _anchor.clear();
1468   set_entry_point(NULL);
1469   set_jni_functions(jni_functions());
1470   set_callee_target(NULL);
1471   set_vm_result(NULL);
1472   set_vm_result_2(NULL);
1473   set_vframe_array_head(NULL);
1474   set_vframe_array_last(NULL);
1475   set_deferred_locals(NULL);
1476   set_deopt_mark(NULL);
1477   set_deopt_nmethod(NULL);
1478   clear_must_deopt_id();
1479   set_monitor_chunks(NULL);
1480   set_next(NULL);
1481   set_thread_state(_thread_new);
1482   _terminated = _not_terminated;
1483   _privileged_stack_top = NULL;
1484   _array_for_gc = NULL;
1485   _suspend_equivalent = false;
1486   _in_deopt_handler = 0;
1487   _doing_unsafe_access = false;
1488   _stack_guard_state = stack_guard_unused;
1489   (void)const_cast<oop&>(_exception_oop = oop(NULL));
1490   _exception_pc  = 0;
1491   _exception_handler_pc = 0;
1492   _is_method_handle_return = 0;
1493   _jvmti_thread_state= NULL;
1494   _should_post_on_exceptions_flag = JNI_FALSE;
1495   _jvmti_get_loaded_classes_closure = NULL;
1496   _interp_only_mode    = 0;
1497   _special_runtime_exit_condition = _no_async_condition;
1498   _pending_async_exception = NULL;
1499   _thread_stat = NULL;
1500   _thread_stat = new ThreadStatistics();
1501   _blocked_on_compilation = false;
1502   _jni_active_critical = 0;
1503   _pending_jni_exception_check_fn = NULL;
1504   _do_not_unlock_if_synchronized = false;
1505   _cached_monitor_info = NULL;
1506   _parker = Parker::Allocate(this) ;
1507 
1508 #ifndef PRODUCT
1509   _jmp_ring_index = 0;
1510   for (int ji = 0 ; ji < jump_ring_buffer_size ; ji++ ) {
1511     record_jump(NULL, NULL, NULL, 0);
1512   }
1513 #endif /* PRODUCT */
1514 
1515   set_thread_profiler(NULL);
1516   if (FlatProfiler::is_active()) {
1517     // This is where we would decide to either give each thread it's own profiler
1518     // or use one global one from FlatProfiler,
1519     // or up to some count of the number of profiled threads, etc.
1520     ThreadProfiler* pp = new ThreadProfiler();
1521     pp->engage();
1522     set_thread_profiler(pp);
1523   }
1524 
1525   // Setup safepoint state info for this thread
1526   ThreadSafepointState::create(this);
1527 
1528   debug_only(_java_call_counter = 0);
1529 
1530   // JVMTI PopFrame support
1531   _popframe_condition = popframe_inactive;
1532   _popframe_preserved_args = NULL;
1533   _popframe_preserved_args_size = 0;
1534   _frames_to_pop_failed_realloc = 0;
1535 
1536   pd_initialize();
1537 }
1538 
1539 #if INCLUDE_ALL_GCS
1540 SATBMarkQueueSet JavaThread::_satb_mark_queue_set;
1541 DirtyCardQueueSet JavaThread::_dirty_card_queue_set;
1542 char Thread::_gc_state_global = 0;
1543 #endif // INCLUDE_ALL_GCS
1544 
1545 JavaThread::JavaThread(bool is_attaching_via_jni) :
1546   Thread()
1547 #if INCLUDE_ALL_GCS
1548   , _satb_mark_queue(&_satb_mark_queue_set),
1549     _dirty_card_queue(&_dirty_card_queue_set)
1550 #endif // INCLUDE_ALL_GCS
1551 {
1552   initialize();
1553   if (is_attaching_via_jni) {
1554     _jni_attach_state = _attaching_via_jni;
1555   } else {
1556     _jni_attach_state = _not_attaching_via_jni;
1557   }
1558   assert(deferred_card_mark().is_empty(), "Default MemRegion ctor");
1559 }
1560 
1561 bool JavaThread::reguard_stack(address cur_sp) {
1562   if (_stack_guard_state != stack_guard_yellow_disabled) {
1563     return true; // Stack already guarded or guard pages not needed.
1564   }
1565 
1566   if (register_stack_overflow()) {
1567     // For those architectures which have separate register and
1568     // memory stacks, we must check the register stack to see if
1569     // it has overflowed.
1570     return false;
1571   }
1572 
1573   // Java code never executes within the yellow zone: the latter is only
1574   // there to provoke an exception during stack banging.  If java code
1575   // is executing there, either StackShadowPages should be larger, or
1576   // some exception code in c1, c2 or the interpreter isn't unwinding
1577   // when it should.
1578   guarantee(cur_sp > stack_yellow_zone_base(), "not enough space to reguard - increase StackShadowPages");
1579 
1580   enable_stack_yellow_zone();
1581   return true;
1582 }
1583 
1584 bool JavaThread::reguard_stack(void) {
1585   return reguard_stack(os::current_stack_pointer());
1586 }
1587 
1588 
1589 void JavaThread::block_if_vm_exited() {
1590   if (_terminated == _vm_exited) {
1591     // _vm_exited is set at safepoint, and Threads_lock is never released
1592     // we will block here forever
1593     Threads_lock->lock_without_safepoint_check();
1594     ShouldNotReachHere();
1595   }
1596 }
1597 
1598 
1599 // Remove this ifdef when C1 is ported to the compiler interface.
1600 static void compiler_thread_entry(JavaThread* thread, TRAPS);
1601 
1602 JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
1603   Thread()
1604 #if INCLUDE_ALL_GCS
1605   , _satb_mark_queue(&_satb_mark_queue_set),
1606     _dirty_card_queue(&_dirty_card_queue_set)
1607 #endif // INCLUDE_ALL_GCS
1608 {
1609   if (TraceThreadEvents) {
1610     tty->print_cr("creating thread %p", this);
1611   }
1612   initialize();
1613   _jni_attach_state = _not_attaching_via_jni;
1614   set_entry_point(entry_point);
1615   // Create the native thread itself.
1616   // %note runtime_23
1617   os::ThreadType thr_type = os::java_thread;
1618   thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
1619                                                      os::java_thread;
1620   os::create_thread(this, thr_type, stack_sz);
1621   // The _osthread may be NULL here because we ran out of memory (too many threads active).
1622   // We need to throw and OutOfMemoryError - however we cannot do this here because the caller
1623   // may hold a lock and all locks must be unlocked before throwing the exception (throwing
1624   // the exception consists of creating the exception object & initializing it, initialization
1625   // will leave the VM via a JavaCall and then all locks must be unlocked).
1626   //
1627   // The thread is still suspended when we reach here. Thread must be explicit started
1628   // by creator! Furthermore, the thread must also explicitly be added to the Threads list
1629   // by calling Threads:add. The reason why this is not done here, is because the thread
1630   // object must be fully initialized (take a look at JVM_Start)
1631 }
1632 
1633 JavaThread::~JavaThread() {
1634   if (TraceThreadEvents) {
1635       tty->print_cr("terminate thread %p", this);
1636   }
1637 
1638   // JSR166 -- return the parker to the free list
1639   Parker::Release(_parker);
1640   _parker = NULL ;
1641 
1642   // Free any remaining  previous UnrollBlock
1643   vframeArray* old_array = vframe_array_last();
1644 
1645   if (old_array != NULL) {
1646     Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
1647     old_array->set_unroll_block(NULL);
1648     delete old_info;
1649     delete old_array;
1650   }
1651 
1652   GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred = deferred_locals();
1653   if (deferred != NULL) {
1654     // This can only happen if thread is destroyed before deoptimization occurs.
1655     assert(deferred->length() != 0, "empty array!");
1656     do {
1657       jvmtiDeferredLocalVariableSet* dlv = deferred->at(0);
1658       deferred->remove_at(0);
1659       // individual jvmtiDeferredLocalVariableSet are CHeapObj's
1660       delete dlv;
1661     } while (deferred->length() != 0);
1662     delete deferred;
1663   }
1664 
1665   // All Java related clean up happens in exit
1666   ThreadSafepointState::destroy(this);
1667   if (_thread_profiler != NULL) delete _thread_profiler;
1668   if (_thread_stat != NULL) delete _thread_stat;
1669 }
1670 
1671 
1672 // The first routine called by a new Java thread
1673 void JavaThread::run() {
1674   // initialize thread-local alloc buffer related fields
1675   this->initialize_tlab();
1676 
1677   // used to test validitity of stack trace backs
1678   this->record_base_of_stack_pointer();
1679 
1680   // Record real stack base and size.
1681   this->record_stack_base_and_size();
1682 
1683   // Initialize thread local storage; set before calling MutexLocker
1684   this->initialize_thread_local_storage();
1685 
1686   this->create_stack_guard_pages();
1687 
1688   this->cache_global_variables();
1689 
1690   // Thread is now sufficient initialized to be handled by the safepoint code as being
1691   // in the VM. Change thread state from _thread_new to _thread_in_vm
1692   ThreadStateTransition::transition_and_fence(this, _thread_new, _thread_in_vm);
1693 
1694   assert(JavaThread::current() == this, "sanity check");
1695   assert(!Thread::current()->owns_locks(), "sanity check");
1696 
1697   DTRACE_THREAD_PROBE(start, this);
1698 
1699   // This operation might block. We call that after all safepoint checks for a new thread has
1700   // been completed.
1701   this->set_active_handles(JNIHandleBlock::allocate_block());
1702 
1703   if (JvmtiExport::should_post_thread_life()) {
1704     JvmtiExport::post_thread_start(this);
1705   }
1706 
1707   EventThreadStart event;
1708   if (event.should_commit()) {
1709      event.set_javalangthread(java_lang_Thread::thread_id(this->threadObj()));
1710      event.commit();
1711   }
1712 
1713   // We call another function to do the rest so we are sure that the stack addresses used
1714   // from there will be lower than the stack base just computed
1715   thread_main_inner();
1716 
1717   // Note, thread is no longer valid at this point!
1718 }
1719 
1720 
1721 void JavaThread::thread_main_inner() {
1722   assert(JavaThread::current() == this, "sanity check");
1723   assert(this->threadObj() != NULL, "just checking");
1724 
1725   // Execute thread entry point unless this thread has a pending exception
1726   // or has been stopped before starting.
1727   // Note: Due to JVM_StopThread we can have pending exceptions already!
1728   if (!this->has_pending_exception() &&
1729       !java_lang_Thread::is_stillborn(this->threadObj())) {
1730     {
1731       ResourceMark rm(this);
1732       this->set_native_thread_name(this->get_thread_name());
1733     }
1734     HandleMark hm(this);
1735     this->entry_point()(this, this);
1736   }
1737 
1738   DTRACE_THREAD_PROBE(stop, this);
1739 
1740   this->exit(false);
1741   delete this;
1742 }
1743 
1744 
1745 static void ensure_join(JavaThread* thread) {
1746   // We do not need to grap the Threads_lock, since we are operating on ourself.
1747   Handle threadObj(thread, thread->threadObj());
1748   assert(threadObj.not_null(), "java thread object must exist");
1749   ObjectLocker lock(threadObj, thread);
1750   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1751   thread->clear_pending_exception();
1752   // Thread is exiting. So set thread_status field in  java.lang.Thread class to TERMINATED.
1753   java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
1754   // Clear the native thread instance - this makes isAlive return false and allows the join()
1755   // to complete once we've done the notify_all below
1756   java_lang_Thread::set_thread(threadObj(), NULL);
1757   lock.notify_all(thread);
1758   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1759   thread->clear_pending_exception();
1760 }
1761 
1762 
1763 // For any new cleanup additions, please check to see if they need to be applied to
1764 // cleanup_failed_attach_current_thread as well.
1765 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
1766   assert(this == JavaThread::current(),  "thread consistency check");
1767 
1768   HandleMark hm(this);
1769   Handle uncaught_exception(this, this->pending_exception());
1770   this->clear_pending_exception();
1771   Handle threadObj(this, this->threadObj());
1772   assert(threadObj.not_null(), "Java thread object should be created");
1773 
1774   if (get_thread_profiler() != NULL) {
1775     get_thread_profiler()->disengage();
1776     ResourceMark rm;
1777     get_thread_profiler()->print(get_thread_name());
1778   }
1779 
1780 
1781   // FIXIT: This code should be moved into else part, when reliable 1.2/1.3 check is in place
1782   {
1783     EXCEPTION_MARK;
1784 
1785     CLEAR_PENDING_EXCEPTION;
1786   }
1787   // FIXIT: The is_null check is only so it works better on JDK1.2 VM's. This
1788   // has to be fixed by a runtime query method
1789   if (!destroy_vm || JDK_Version::is_jdk12x_version()) {
1790     // JSR-166: change call from from ThreadGroup.uncaughtException to
1791     // java.lang.Thread.dispatchUncaughtException
1792     if (uncaught_exception.not_null()) {
1793       Handle group(this, java_lang_Thread::threadGroup(threadObj()));
1794       {
1795         EXCEPTION_MARK;
1796         // Check if the method Thread.dispatchUncaughtException() exists. If so
1797         // call it.  Otherwise we have an older library without the JSR-166 changes,
1798         // so call ThreadGroup.uncaughtException()
1799         KlassHandle recvrKlass(THREAD, threadObj->klass());
1800         CallInfo callinfo;
1801         KlassHandle thread_klass(THREAD, SystemDictionary::Thread_klass());
1802         LinkResolver::resolve_virtual_call(callinfo, threadObj, recvrKlass, thread_klass,
1803                                            vmSymbols::dispatchUncaughtException_name(),
1804                                            vmSymbols::throwable_void_signature(),
1805                                            KlassHandle(), false, false, THREAD);
1806         CLEAR_PENDING_EXCEPTION;
1807         methodHandle method = callinfo.selected_method();
1808         if (method.not_null()) {
1809           JavaValue result(T_VOID);
1810           JavaCalls::call_virtual(&result,
1811                                   threadObj, thread_klass,
1812                                   vmSymbols::dispatchUncaughtException_name(),
1813                                   vmSymbols::throwable_void_signature(),
1814                                   uncaught_exception,
1815                                   THREAD);
1816         } else {
1817           KlassHandle thread_group(THREAD, SystemDictionary::ThreadGroup_klass());
1818           JavaValue result(T_VOID);
1819           JavaCalls::call_virtual(&result,
1820                                   group, thread_group,
1821                                   vmSymbols::uncaughtException_name(),
1822                                   vmSymbols::thread_throwable_void_signature(),
1823                                   threadObj,           // Arg 1
1824                                   uncaught_exception,  // Arg 2
1825                                   THREAD);
1826         }
1827         if (HAS_PENDING_EXCEPTION) {
1828           ResourceMark rm(this);
1829           jio_fprintf(defaultStream::error_stream(),
1830                 "\nException: %s thrown from the UncaughtExceptionHandler"
1831                 " in thread \"%s\"\n",
1832                 pending_exception()->klass()->external_name(),
1833                 get_thread_name());
1834           CLEAR_PENDING_EXCEPTION;
1835         }
1836       }
1837     }
1838 
1839     // Called before the java thread exit since we want to read info
1840     // from java_lang_Thread object
1841     EventThreadEnd event;
1842     if (event.should_commit()) {
1843         event.set_javalangthread(java_lang_Thread::thread_id(this->threadObj()));
1844         event.commit();
1845     }
1846 
1847     // Call after last event on thread
1848     EVENT_THREAD_EXIT(this);
1849 
1850     // Call Thread.exit(). We try 3 times in case we got another Thread.stop during
1851     // the execution of the method. If that is not enough, then we don't really care. Thread.stop
1852     // is deprecated anyhow.
1853     if (!is_Compiler_thread()) {
1854       int count = 3;
1855       while (java_lang_Thread::threadGroup(threadObj()) != NULL && (count-- > 0)) {
1856         EXCEPTION_MARK;
1857         JavaValue result(T_VOID);
1858         KlassHandle thread_klass(THREAD, SystemDictionary::Thread_klass());
1859         JavaCalls::call_virtual(&result,
1860                               threadObj, thread_klass,
1861                               vmSymbols::exit_method_name(),
1862                               vmSymbols::void_method_signature(),
1863                               THREAD);
1864         CLEAR_PENDING_EXCEPTION;
1865       }
1866     }
1867     // notify JVMTI
1868     if (JvmtiExport::should_post_thread_life()) {
1869       JvmtiExport::post_thread_end(this);
1870     }
1871 
1872     // We have notified the agents that we are exiting, before we go on,
1873     // we must check for a pending external suspend request and honor it
1874     // in order to not surprise the thread that made the suspend request.
1875     while (true) {
1876       {
1877         MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
1878         if (!is_external_suspend()) {
1879           set_terminated(_thread_exiting);
1880           ThreadService::current_thread_exiting(this);
1881           break;
1882         }
1883         // Implied else:
1884         // Things get a little tricky here. We have a pending external
1885         // suspend request, but we are holding the SR_lock so we
1886         // can't just self-suspend. So we temporarily drop the lock
1887         // and then self-suspend.
1888       }
1889 
1890       ThreadBlockInVM tbivm(this);
1891       java_suspend_self();
1892 
1893       // We're done with this suspend request, but we have to loop around
1894       // and check again. Eventually we will get SR_lock without a pending
1895       // external suspend request and will be able to mark ourselves as
1896       // exiting.
1897     }
1898     // no more external suspends are allowed at this point
1899   } else {
1900     // before_exit() has already posted JVMTI THREAD_END events
1901   }
1902 
1903   // Notify waiters on thread object. This has to be done after exit() is called
1904   // on the thread (if the thread is the last thread in a daemon ThreadGroup the
1905   // group should have the destroyed bit set before waiters are notified).
1906   ensure_join(this);
1907   assert(!this->has_pending_exception(), "ensure_join should have cleared");
1908 
1909   // 6282335 JNI DetachCurrentThread spec states that all Java monitors
1910   // held by this thread must be released.  A detach operation must only
1911   // get here if there are no Java frames on the stack.  Therefore, any
1912   // owned monitors at this point MUST be JNI-acquired monitors which are
1913   // pre-inflated and in the monitor cache.
1914   //
1915   // ensure_join() ignores IllegalThreadStateExceptions, and so does this.
1916   if (exit_type == jni_detach && JNIDetachReleasesMonitors) {
1917     assert(!this->has_last_Java_frame(), "detaching with Java frames?");
1918     ObjectSynchronizer::release_monitors_owned_by_thread(this);
1919     assert(!this->has_pending_exception(), "release_monitors should have cleared");
1920   }
1921 
1922   // These things needs to be done while we are still a Java Thread. Make sure that thread
1923   // is in a consistent state, in case GC happens
1924   assert(_privileged_stack_top == NULL, "must be NULL when we get here");
1925 
1926   if (active_handles() != NULL) {
1927     JNIHandleBlock* block = active_handles();
1928     set_active_handles(NULL);
1929     JNIHandleBlock::release_block(block);
1930   }
1931 
1932   if (free_handle_block() != NULL) {
1933     JNIHandleBlock* block = free_handle_block();
1934     set_free_handle_block(NULL);
1935     JNIHandleBlock::release_block(block);
1936   }
1937 
1938   // These have to be removed while this is still a valid thread.
1939   remove_stack_guard_pages();
1940 
1941   if (UseTLAB) {
1942     tlab().make_parsable(true);  // retire TLAB
1943   }
1944 
1945   if (JvmtiEnv::environments_might_exist()) {
1946     JvmtiExport::cleanup_thread(this);
1947   }
1948 
1949   // We must flush any deferred card marks before removing a thread from
1950   // the list of active threads.
1951   Universe::heap()->flush_deferred_store_barrier(this);
1952   assert(deferred_card_mark().is_empty(), "Should have been flushed");
1953 
1954 #if INCLUDE_ALL_GCS
1955   // We must flush the G1-related buffers before removing a thread
1956   // from the list of active threads. We must do this after any deferred
1957   // card marks have been flushed (above) so that any entries that are
1958   // added to the thread's dirty card queue as a result are not lost.
1959   if (UseG1GC || (UseShenandoahGC)) {
1960     flush_barrier_queues();
1961   }
1962   if (UseShenandoahGC && UseTLAB && gclab().is_initialized()) {
1963     gclab().make_parsable(true);
1964   }
1965 #endif // INCLUDE_ALL_GCS
1966 
1967   // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
1968   Threads::remove(this);
1969 }
1970 
1971 #if INCLUDE_ALL_GCS
1972 // Flush G1-related queues.
1973 void JavaThread::flush_barrier_queues() {
1974   satb_mark_queue().flush();
1975   dirty_card_queue().flush();
1976 }
1977 
1978 void JavaThread::initialize_queues() {
1979   assert(!SafepointSynchronize::is_at_safepoint(),
1980          "we should not be at a safepoint");
1981 
1982   ObjPtrQueue& satb_queue = satb_mark_queue();
1983   SATBMarkQueueSet& satb_queue_set = satb_mark_queue_set();
1984   // The SATB queue should have been constructed with its active
1985   // field set to false.
1986   assert(!satb_queue.is_active(), "SATB queue should not be active");
1987   assert(satb_queue.is_empty(), "SATB queue should be empty");
1988   // If we are creating the thread during a marking cycle, we should
1989   // set the active field of the SATB queue to true.
1990   if (satb_queue_set.is_active()) {
1991     satb_queue.set_active(true);
1992   }
1993 
1994   DirtyCardQueue& dirty_queue = dirty_card_queue();
1995   // The dirty card queue should have been constructed with its
1996   // active field set to true.
1997   assert(dirty_queue.is_active(), "dirty card queue should be active");
1998 
1999   _gc_state = _gc_state_global;
2000 }
2001 
2002 void JavaThread::set_gc_state(char in_prog) {
2003   _gc_state = in_prog;
2004 }
2005 
2006 void JavaThread::set_gc_state_all_threads(char in_prog) {
2007   assert_locked_or_safepoint(Threads_lock);
2008   _gc_state_global = in_prog;
2009   for (JavaThread* t = Threads::first(); t != NULL; t = t->next()) {
2010     t->set_gc_state(in_prog);
2011   }
2012 }
2013 
2014 void JavaThread::set_force_satb_flush_all_threads(bool value) {
2015   assert_locked_or_safepoint(Threads_lock);
2016   for (JavaThread* t = Threads::first(); t != NULL; t = t->next()) {
2017     t->set_force_satb_flush(value);
2018   }
2019 }
2020 #endif // INCLUDE_ALL_GCS
2021 
2022 void JavaThread::cleanup_failed_attach_current_thread() {
2023   if (get_thread_profiler() != NULL) {
2024     get_thread_profiler()->disengage();
2025     ResourceMark rm;
2026     get_thread_profiler()->print(get_thread_name());
2027   }
2028 
2029   if (active_handles() != NULL) {
2030     JNIHandleBlock* block = active_handles();
2031     set_active_handles(NULL);
2032     JNIHandleBlock::release_block(block);
2033   }
2034 
2035   if (free_handle_block() != NULL) {
2036     JNIHandleBlock* block = free_handle_block();
2037     set_free_handle_block(NULL);
2038     JNIHandleBlock::release_block(block);
2039   }
2040 
2041   // These have to be removed while this is still a valid thread.
2042   remove_stack_guard_pages();
2043 
2044   if (UseTLAB) {
2045     tlab().make_parsable(true);  // retire TLAB, if any
2046   }
2047 
2048 #if INCLUDE_ALL_GCS
2049   if (UseG1GC || (UseShenandoahGC)) {
2050     flush_barrier_queues();
2051   }
2052   if (UseShenandoahGC && UseTLAB && gclab().is_initialized()) {
2053     gclab().make_parsable(true);
2054   }
2055 #endif // INCLUDE_ALL_GCS
2056 
2057   Threads::remove(this);
2058   delete this;
2059 }
2060 
2061 
2062 
2063 
2064 JavaThread* JavaThread::active() {
2065   Thread* thread = ThreadLocalStorage::thread();
2066   assert(thread != NULL, "just checking");
2067   if (thread->is_Java_thread()) {
2068     return (JavaThread*) thread;
2069   } else {
2070     assert(thread->is_VM_thread(), "this must be a vm thread");
2071     VM_Operation* op = ((VMThread*) thread)->vm_operation();
2072     JavaThread *ret=op == NULL ? NULL : (JavaThread *)op->calling_thread();
2073     assert(ret->is_Java_thread(), "must be a Java thread");
2074     return ret;
2075   }
2076 }
2077 
2078 bool JavaThread::is_lock_owned(address adr) const {
2079   if (Thread::is_lock_owned(adr)) return true;
2080 
2081   for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2082     if (chunk->contains(adr)) return true;
2083   }
2084 
2085   return false;
2086 }
2087 
2088 
2089 void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
2090   chunk->set_next(monitor_chunks());
2091   set_monitor_chunks(chunk);
2092 }
2093 
2094 void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
2095   guarantee(monitor_chunks() != NULL, "must be non empty");
2096   if (monitor_chunks() == chunk) {
2097     set_monitor_chunks(chunk->next());
2098   } else {
2099     MonitorChunk* prev = monitor_chunks();
2100     while (prev->next() != chunk) prev = prev->next();
2101     prev->set_next(chunk->next());
2102   }
2103 }
2104 
2105 // JVM support.
2106 
2107 // Note: this function shouldn't block if it's called in
2108 // _thread_in_native_trans state (such as from
2109 // check_special_condition_for_native_trans()).
2110 void JavaThread::check_and_handle_async_exceptions(bool check_unsafe_error) {
2111 
2112   if (has_last_Java_frame() && has_async_condition()) {
2113     // If we are at a polling page safepoint (not a poll return)
2114     // then we must defer async exception because live registers
2115     // will be clobbered by the exception path. Poll return is
2116     // ok because the call we a returning from already collides
2117     // with exception handling registers and so there is no issue.
2118     // (The exception handling path kills call result registers but
2119     //  this is ok since the exception kills the result anyway).
2120 
2121     if (is_at_poll_safepoint()) {
2122       // if the code we are returning to has deoptimized we must defer
2123       // the exception otherwise live registers get clobbered on the
2124       // exception path before deoptimization is able to retrieve them.
2125       //
2126       RegisterMap map(this, false);
2127       frame caller_fr = last_frame().sender(&map);
2128       assert(caller_fr.is_compiled_frame(), "what?");
2129       if (caller_fr.is_deoptimized_frame()) {
2130         if (TraceExceptions) {
2131           ResourceMark rm;
2132           tty->print_cr("deferred async exception at compiled safepoint");
2133         }
2134         return;
2135       }
2136     }
2137   }
2138 
2139   JavaThread::AsyncRequests condition = clear_special_runtime_exit_condition();
2140   if (condition == _no_async_condition) {
2141     // Conditions have changed since has_special_runtime_exit_condition()
2142     // was called:
2143     // - if we were here only because of an external suspend request,
2144     //   then that was taken care of above (or cancelled) so we are done
2145     // - if we were here because of another async request, then it has
2146     //   been cleared between the has_special_runtime_exit_condition()
2147     //   and now so again we are done
2148     return;
2149   }
2150 
2151   // Check for pending async. exception
2152   if (_pending_async_exception != NULL) {
2153     // Only overwrite an already pending exception, if it is not a threadDeath.
2154     if (!has_pending_exception() || !pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())) {
2155 
2156       // We cannot call Exceptions::_throw(...) here because we cannot block
2157       set_pending_exception(_pending_async_exception, __FILE__, __LINE__);
2158 
2159       if (TraceExceptions) {
2160         ResourceMark rm;
2161         tty->print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", this);
2162         if (has_last_Java_frame() ) {
2163           frame f = last_frame();
2164           tty->print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", f.pc(), f.sp());
2165         }
2166         tty->print_cr(" of type: %s", InstanceKlass::cast(_pending_async_exception->klass())->external_name());
2167       }
2168       _pending_async_exception = NULL;
2169       clear_has_async_exception();
2170     }
2171   }
2172 
2173   if (check_unsafe_error &&
2174       condition == _async_unsafe_access_error && !has_pending_exception()) {
2175     condition = _no_async_condition;  // done
2176     switch (thread_state()) {
2177     case _thread_in_vm:
2178       {
2179         JavaThread* THREAD = this;
2180         THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2181       }
2182     case _thread_in_native:
2183       {
2184         ThreadInVMfromNative tiv(this);
2185         JavaThread* THREAD = this;
2186         THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2187       }
2188     case _thread_in_Java:
2189       {
2190         ThreadInVMfromJava tiv(this);
2191         JavaThread* THREAD = this;
2192         THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in a recent unsafe memory access operation in compiled Java code");
2193       }
2194     default:
2195       ShouldNotReachHere();
2196     }
2197   }
2198 
2199   assert(condition == _no_async_condition || has_pending_exception() ||
2200          (!check_unsafe_error && condition == _async_unsafe_access_error),
2201          "must have handled the async condition, if no exception");
2202 }
2203 
2204 void JavaThread::handle_special_runtime_exit_condition(bool check_asyncs) {
2205   //
2206   // Check for pending external suspend. Internal suspend requests do
2207   // not use handle_special_runtime_exit_condition().
2208   // If JNIEnv proxies are allowed, don't self-suspend if the target
2209   // thread is not the current thread. In older versions of jdbx, jdbx
2210   // threads could call into the VM with another thread's JNIEnv so we
2211   // can be here operating on behalf of a suspended thread (4432884).
2212   bool do_self_suspend = is_external_suspend_with_lock();
2213   if (do_self_suspend && (!AllowJNIEnvProxy || this == JavaThread::current())) {
2214     //
2215     // Because thread is external suspended the safepoint code will count
2216     // thread as at a safepoint. This can be odd because we can be here
2217     // as _thread_in_Java which would normally transition to _thread_blocked
2218     // at a safepoint. We would like to mark the thread as _thread_blocked
2219     // before calling java_suspend_self like all other callers of it but
2220     // we must then observe proper safepoint protocol. (We can't leave
2221     // _thread_blocked with a safepoint in progress). However we can be
2222     // here as _thread_in_native_trans so we can't use a normal transition
2223     // constructor/destructor pair because they assert on that type of
2224     // transition. We could do something like:
2225     //
2226     // JavaThreadState state = thread_state();
2227     // set_thread_state(_thread_in_vm);
2228     // {
2229     //   ThreadBlockInVM tbivm(this);
2230     //   java_suspend_self()
2231     // }
2232     // set_thread_state(_thread_in_vm_trans);
2233     // if (safepoint) block;
2234     // set_thread_state(state);
2235     //
2236     // but that is pretty messy. Instead we just go with the way the
2237     // code has worked before and note that this is the only path to
2238     // java_suspend_self that doesn't put the thread in _thread_blocked
2239     // mode.
2240 
2241     frame_anchor()->make_walkable(this);
2242     java_suspend_self();
2243 
2244     // We might be here for reasons in addition to the self-suspend request
2245     // so check for other async requests.
2246   }
2247 
2248   if (check_asyncs) {
2249     check_and_handle_async_exceptions();
2250   }
2251 }
2252 
2253 void JavaThread::send_thread_stop(oop java_throwable)  {
2254   assert(Thread::current()->is_VM_thread(), "should be in the vm thread");
2255   assert(Threads_lock->is_locked(), "Threads_lock should be locked by safepoint code");
2256   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
2257 
2258   // Do not throw asynchronous exceptions against the compiler thread
2259   // (the compiler thread should not be a Java thread -- fix in 1.4.2)
2260   if (is_Compiler_thread()) return;
2261 
2262   {
2263     // Actually throw the Throwable against the target Thread - however
2264     // only if there is no thread death exception installed already.
2265     if (_pending_async_exception == NULL || !_pending_async_exception->is_a(SystemDictionary::ThreadDeath_klass())) {
2266       // If the topmost frame is a runtime stub, then we are calling into
2267       // OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
2268       // must deoptimize the caller before continuing, as the compiled  exception handler table
2269       // may not be valid
2270       if (has_last_Java_frame()) {
2271         frame f = last_frame();
2272         if (f.is_runtime_frame() || f.is_safepoint_blob_frame()) {
2273           // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2274           RegisterMap reg_map(this, UseBiasedLocking);
2275           frame compiled_frame = f.sender(&reg_map);
2276           if (!StressCompiledExceptionHandlers && compiled_frame.can_be_deoptimized()) {
2277             Deoptimization::deoptimize(this, compiled_frame, &reg_map);
2278           }
2279         }
2280       }
2281 
2282       // Set async. pending exception in thread.
2283       set_pending_async_exception(java_throwable);
2284 
2285       if (TraceExceptions) {
2286        ResourceMark rm;
2287        tty->print_cr("Pending Async. exception installed of type: %s", InstanceKlass::cast(_pending_async_exception->klass())->external_name());
2288       }
2289       // for AbortVMOnException flag
2290       NOT_PRODUCT(Exceptions::debug_check_abort(InstanceKlass::cast(_pending_async_exception->klass())->external_name()));
2291     }
2292   }
2293 
2294 
2295   // Interrupt thread so it will wake up from a potential wait()
2296   Thread::interrupt(this);
2297 }
2298 
2299 // External suspension mechanism.
2300 //
2301 // Tell the VM to suspend a thread when ever it knows that it does not hold on
2302 // to any VM_locks and it is at a transition
2303 // Self-suspension will happen on the transition out of the vm.
2304 // Catch "this" coming in from JNIEnv pointers when the thread has been freed
2305 //
2306 // Guarantees on return:
2307 //   + Target thread will not execute any new bytecode (that's why we need to
2308 //     force a safepoint)
2309 //   + Target thread will not enter any new monitors
2310 //
2311 void JavaThread::java_suspend() {
2312   { MutexLocker mu(Threads_lock);
2313     if (!Threads::includes(this) || is_exiting() || this->threadObj() == NULL) {
2314        return;
2315     }
2316   }
2317 
2318   { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2319     if (!is_external_suspend()) {
2320       // a racing resume has cancelled us; bail out now
2321       return;
2322     }
2323 
2324     // suspend is done
2325     uint32_t debug_bits = 0;
2326     // Warning: is_ext_suspend_completed() may temporarily drop the
2327     // SR_lock to allow the thread to reach a stable thread state if
2328     // it is currently in a transient thread state.
2329     if (is_ext_suspend_completed(false /* !called_by_wait */,
2330                                  SuspendRetryDelay, &debug_bits) ) {
2331       return;
2332     }
2333   }
2334 
2335   VM_ForceSafepoint vm_suspend;
2336   VMThread::execute(&vm_suspend);
2337 }
2338 
2339 // Part II of external suspension.
2340 // A JavaThread self suspends when it detects a pending external suspend
2341 // request. This is usually on transitions. It is also done in places
2342 // where continuing to the next transition would surprise the caller,
2343 // e.g., monitor entry.
2344 //
2345 // Returns the number of times that the thread self-suspended.
2346 //
2347 // Note: DO NOT call java_suspend_self() when you just want to block current
2348 //       thread. java_suspend_self() is the second stage of cooperative
2349 //       suspension for external suspend requests and should only be used
2350 //       to complete an external suspend request.
2351 //
2352 int JavaThread::java_suspend_self() {
2353   int ret = 0;
2354 
2355   // we are in the process of exiting so don't suspend
2356   if (is_exiting()) {
2357      clear_external_suspend();
2358      return ret;
2359   }
2360 
2361   assert(_anchor.walkable() ||
2362     (is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
2363     "must have walkable stack");
2364 
2365   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2366 
2367   assert(!this->is_ext_suspended(),
2368     "a thread trying to self-suspend should not already be suspended");
2369 
2370   if (this->is_suspend_equivalent()) {
2371     // If we are self-suspending as a result of the lifting of a
2372     // suspend equivalent condition, then the suspend_equivalent
2373     // flag is not cleared until we set the ext_suspended flag so
2374     // that wait_for_ext_suspend_completion() returns consistent
2375     // results.
2376     this->clear_suspend_equivalent();
2377   }
2378 
2379   // A racing resume may have cancelled us before we grabbed SR_lock
2380   // above. Or another external suspend request could be waiting for us
2381   // by the time we return from SR_lock()->wait(). The thread
2382   // that requested the suspension may already be trying to walk our
2383   // stack and if we return now, we can change the stack out from under
2384   // it. This would be a "bad thing (TM)" and cause the stack walker
2385   // to crash. We stay self-suspended until there are no more pending
2386   // external suspend requests.
2387   while (is_external_suspend()) {
2388     ret++;
2389     this->set_ext_suspended();
2390 
2391     // _ext_suspended flag is cleared by java_resume()
2392     while (is_ext_suspended()) {
2393       this->SR_lock()->wait(Mutex::_no_safepoint_check_flag);
2394     }
2395   }
2396 
2397   return ret;
2398 }
2399 
2400 #ifdef ASSERT
2401 // verify the JavaThread has not yet been published in the Threads::list, and
2402 // hence doesn't need protection from concurrent access at this stage
2403 void JavaThread::verify_not_published() {
2404   if (!Threads_lock->owned_by_self()) {
2405    MutexLockerEx ml(Threads_lock,  Mutex::_no_safepoint_check_flag);
2406    assert( !Threads::includes(this),
2407            "java thread shouldn't have been published yet!");
2408   }
2409   else {
2410    assert( !Threads::includes(this),
2411            "java thread shouldn't have been published yet!");
2412   }
2413 }
2414 #endif
2415 
2416 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2417 // progress or when _suspend_flags is non-zero.
2418 // Current thread needs to self-suspend if there is a suspend request and/or
2419 // block if a safepoint is in progress.
2420 // Async exception ISN'T checked.
2421 // Note only the ThreadInVMfromNative transition can call this function
2422 // directly and when thread state is _thread_in_native_trans
2423 void JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread *thread) {
2424   assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
2425 
2426   JavaThread *curJT = JavaThread::current();
2427   bool do_self_suspend = thread->is_external_suspend();
2428 
2429   assert(!curJT->has_last_Java_frame() || curJT->frame_anchor()->walkable(), "Unwalkable stack in native->vm transition");
2430 
2431   // If JNIEnv proxies are allowed, don't self-suspend if the target
2432   // thread is not the current thread. In older versions of jdbx, jdbx
2433   // threads could call into the VM with another thread's JNIEnv so we
2434   // can be here operating on behalf of a suspended thread (4432884).
2435   if (do_self_suspend && (!AllowJNIEnvProxy || curJT == thread)) {
2436     JavaThreadState state = thread->thread_state();
2437 
2438     // We mark this thread_blocked state as a suspend-equivalent so
2439     // that a caller to is_ext_suspend_completed() won't be confused.
2440     // The suspend-equivalent state is cleared by java_suspend_self().
2441     thread->set_suspend_equivalent();
2442 
2443     // If the safepoint code sees the _thread_in_native_trans state, it will
2444     // wait until the thread changes to other thread state. There is no
2445     // guarantee on how soon we can obtain the SR_lock and complete the
2446     // self-suspend request. It would be a bad idea to let safepoint wait for
2447     // too long. Temporarily change the state to _thread_blocked to
2448     // let the VM thread know that this thread is ready for GC. The problem
2449     // of changing thread state is that safepoint could happen just after
2450     // java_suspend_self() returns after being resumed, and VM thread will
2451     // see the _thread_blocked state. We must check for safepoint
2452     // after restoring the state and make sure we won't leave while a safepoint
2453     // is in progress.
2454     thread->set_thread_state(_thread_blocked);
2455     thread->java_suspend_self();
2456     thread->set_thread_state(state);
2457     // Make sure new state is seen by VM thread
2458     if (os::is_MP()) {
2459       if (UseMembar) {
2460         // Force a fence between the write above and read below
2461         OrderAccess::fence();
2462       } else {
2463         // Must use this rather than serialization page in particular on Windows
2464         InterfaceSupport::serialize_memory(thread);
2465       }
2466     }
2467   }
2468 
2469   if (SafepointSynchronize::do_call_back()) {
2470     // If we are safepointing, then block the caller which may not be
2471     // the same as the target thread (see above).
2472     SafepointSynchronize::block(curJT);
2473   }
2474 
2475   if (thread->is_deopt_suspend()) {
2476     thread->clear_deopt_suspend();
2477     RegisterMap map(thread, false);
2478     frame f = thread->last_frame();
2479     while ( f.id() != thread->must_deopt_id() && ! f.is_first_frame()) {
2480       f = f.sender(&map);
2481     }
2482     if (f.id() == thread->must_deopt_id()) {
2483       thread->clear_must_deopt_id();
2484       f.deoptimize(thread);
2485     } else {
2486       fatal("missed deoptimization!");
2487     }
2488   }
2489 }
2490 
2491 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2492 // progress or when _suspend_flags is non-zero.
2493 // Current thread needs to self-suspend if there is a suspend request and/or
2494 // block if a safepoint is in progress.
2495 // Also check for pending async exception (not including unsafe access error).
2496 // Note only the native==>VM/Java barriers can call this function and when
2497 // thread state is _thread_in_native_trans.
2498 void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
2499   check_safepoint_and_suspend_for_native_trans(thread);
2500 
2501   if (thread->has_async_exception()) {
2502     // We are in _thread_in_native_trans state, don't handle unsafe
2503     // access error since that may block.
2504     thread->check_and_handle_async_exceptions(false);
2505   }
2506 }
2507 
2508 // This is a variant of the normal
2509 // check_special_condition_for_native_trans with slightly different
2510 // semantics for use by critical native wrappers.  It does all the
2511 // normal checks but also performs the transition back into
2512 // thread_in_Java state.  This is required so that critical natives
2513 // can potentially block and perform a GC if they are the last thread
2514 // exiting the GC_locker.
2515 void JavaThread::check_special_condition_for_native_trans_and_transition(JavaThread *thread) {
2516   check_special_condition_for_native_trans(thread);
2517 
2518   // Finish the transition
2519   thread->set_thread_state(_thread_in_Java);
2520 
2521   if (thread->do_critical_native_unlock()) {
2522     ThreadInVMfromJavaNoAsyncException tiv(thread);
2523     GC_locker::unlock_critical(thread);
2524     thread->clear_critical_native_unlock();
2525   }
2526 }
2527 
2528 // We need to guarantee the Threads_lock here, since resumes are not
2529 // allowed during safepoint synchronization
2530 // Can only resume from an external suspension
2531 void JavaThread::java_resume() {
2532   assert_locked_or_safepoint(Threads_lock);
2533 
2534   // Sanity check: thread is gone, has started exiting or the thread
2535   // was not externally suspended.
2536   if (!Threads::includes(this) || is_exiting() || !is_external_suspend()) {
2537     return;
2538   }
2539 
2540   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2541 
2542   clear_external_suspend();
2543 
2544   if (is_ext_suspended()) {
2545     clear_ext_suspended();
2546     SR_lock()->notify_all();
2547   }
2548 }
2549 
2550 void JavaThread::create_stack_guard_pages() {
2551   if (!os::uses_stack_guard_pages() ||
2552       _stack_guard_state != stack_guard_unused ||
2553       (DisablePrimordialThreadGuardPages && os::is_primordial_thread())) {
2554       if (TraceThreadEvents) {
2555         tty->print_cr("Stack guard page creation for thread "
2556                       UINTX_FORMAT " disabled", os::current_thread_id());
2557       }
2558     return;
2559   }
2560   address low_addr = stack_base() - stack_size();
2561   size_t len = (StackYellowPages + StackRedPages) * os::vm_page_size();
2562 
2563   int allocate = os::allocate_stack_guard_pages();
2564   // warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);
2565 
2566   if (allocate && !os::create_stack_guard_pages((char *) low_addr, len)) {
2567     warning("Attempt to allocate stack guard pages failed.");
2568     return;
2569   }
2570 
2571   if (os::guard_memory((char *) low_addr, len)) {
2572     _stack_guard_state = stack_guard_enabled;
2573   } else {
2574     warning("Attempt to protect stack guard pages failed.");
2575     if (os::uncommit_memory((char *) low_addr, len)) {
2576       warning("Attempt to deallocate stack guard pages failed.");
2577     }
2578   }
2579 }
2580 
2581 void JavaThread::remove_stack_guard_pages() {
2582   assert(Thread::current() == this, "from different thread");
2583   if (_stack_guard_state == stack_guard_unused) return;
2584   address low_addr = stack_base() - stack_size();
2585   size_t len = (StackYellowPages + StackRedPages) * os::vm_page_size();
2586 
2587   if (os::allocate_stack_guard_pages()) {
2588     if (os::remove_stack_guard_pages((char *) low_addr, len)) {
2589       _stack_guard_state = stack_guard_unused;
2590     } else {
2591       warning("Attempt to deallocate stack guard pages failed.");
2592     }
2593   } else {
2594     if (_stack_guard_state == stack_guard_unused) return;
2595     if (os::unguard_memory((char *) low_addr, len)) {
2596       _stack_guard_state = stack_guard_unused;
2597     } else {
2598         warning("Attempt to unprotect stack guard pages failed.");
2599     }
2600   }
2601 }
2602 
2603 void JavaThread::enable_stack_yellow_zone() {
2604   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2605   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2606 
2607   // The base notation is from the stacks point of view, growing downward.
2608   // We need to adjust it to work correctly with guard_memory()
2609   address base = stack_yellow_zone_base() - stack_yellow_zone_size();
2610 
2611   guarantee(base < stack_base(),"Error calculating stack yellow zone");
2612   guarantee(base < os::current_stack_pointer(),"Error calculating stack yellow zone");
2613 
2614   if (os::guard_memory((char *) base, stack_yellow_zone_size())) {
2615     _stack_guard_state = stack_guard_enabled;
2616   } else {
2617     warning("Attempt to guard stack yellow zone failed.");
2618   }
2619   enable_register_stack_guard();
2620 }
2621 
2622 void JavaThread::disable_stack_yellow_zone() {
2623   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2624   assert(_stack_guard_state != stack_guard_yellow_disabled, "already disabled");
2625 
2626   // Simply return if called for a thread that does not use guard pages.
2627   if (_stack_guard_state == stack_guard_unused) return;
2628 
2629   // The base notation is from the stacks point of view, growing downward.
2630   // We need to adjust it to work correctly with guard_memory()
2631   address base = stack_yellow_zone_base() - stack_yellow_zone_size();
2632 
2633   if (os::unguard_memory((char *)base, stack_yellow_zone_size())) {
2634     _stack_guard_state = stack_guard_yellow_disabled;
2635   } else {
2636     warning("Attempt to unguard stack yellow zone failed.");
2637   }
2638   disable_register_stack_guard();
2639 }
2640 
2641 void JavaThread::enable_stack_red_zone() {
2642   // The base notation is from the stacks point of view, growing downward.
2643   // We need to adjust it to work correctly with guard_memory()
2644   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2645   address base = stack_red_zone_base() - stack_red_zone_size();
2646 
2647   guarantee(base < stack_base(),"Error calculating stack red zone");
2648   guarantee(base < os::current_stack_pointer(),"Error calculating stack red zone");
2649 
2650   if(!os::guard_memory((char *) base, stack_red_zone_size())) {
2651     warning("Attempt to guard stack red zone failed.");
2652   }
2653 }
2654 
2655 void JavaThread::disable_stack_red_zone() {
2656   // The base notation is from the stacks point of view, growing downward.
2657   // We need to adjust it to work correctly with guard_memory()
2658   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2659   address base = stack_red_zone_base() - stack_red_zone_size();
2660   if (!os::unguard_memory((char *)base, stack_red_zone_size())) {
2661     warning("Attempt to unguard stack red zone failed.");
2662   }
2663 }
2664 
2665 void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
2666   // ignore is there is no stack
2667   if (!has_last_Java_frame()) return;
2668   // traverse the stack frames. Starts from top frame.
2669   for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2670     frame* fr = fst.current();
2671     f(fr, fst.register_map());
2672   }
2673 }
2674 
2675 
2676 #ifndef PRODUCT
2677 // Deoptimization
2678 // Function for testing deoptimization
2679 void JavaThread::deoptimize() {
2680   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2681   StackFrameStream fst(this, UseBiasedLocking);
2682   bool deopt = false;           // Dump stack only if a deopt actually happens.
2683   bool only_at = strlen(DeoptimizeOnlyAt) > 0;
2684   // Iterate over all frames in the thread and deoptimize
2685   for(; !fst.is_done(); fst.next()) {
2686     if(fst.current()->can_be_deoptimized()) {
2687 
2688       if (only_at) {
2689         // Deoptimize only at particular bcis.  DeoptimizeOnlyAt
2690         // consists of comma or carriage return separated numbers so
2691         // search for the current bci in that string.
2692         address pc = fst.current()->pc();
2693         nmethod* nm =  (nmethod*) fst.current()->cb();
2694         ScopeDesc* sd = nm->scope_desc_at( pc);
2695         char buffer[8];
2696         jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
2697         size_t len = strlen(buffer);
2698         const char * found = strstr(DeoptimizeOnlyAt, buffer);
2699         while (found != NULL) {
2700           if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
2701               (found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
2702             // Check that the bci found is bracketed by terminators.
2703             break;
2704           }
2705           found = strstr(found + 1, buffer);
2706         }
2707         if (!found) {
2708           continue;
2709         }
2710       }
2711 
2712       if (DebugDeoptimization && !deopt) {
2713         deopt = true; // One-time only print before deopt
2714         tty->print_cr("[BEFORE Deoptimization]");
2715         trace_frames();
2716         trace_stack();
2717       }
2718       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2719     }
2720   }
2721 
2722   if (DebugDeoptimization && deopt) {
2723     tty->print_cr("[AFTER Deoptimization]");
2724     trace_frames();
2725   }
2726 }
2727 
2728 
2729 // Make zombies
2730 void JavaThread::make_zombies() {
2731   for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2732     if (fst.current()->can_be_deoptimized()) {
2733       // it is a Java nmethod
2734       nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
2735       nm->make_not_entrant();
2736     }
2737   }
2738 }
2739 #endif // PRODUCT
2740 
2741 
2742 void JavaThread::deoptimized_wrt_marked_nmethods() {
2743   if (!has_last_Java_frame()) return;
2744   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2745   StackFrameStream fst(this, UseBiasedLocking);
2746   for(; !fst.is_done(); fst.next()) {
2747     if (fst.current()->should_be_deoptimized()) {
2748       if (LogCompilation && xtty != NULL) {
2749         nmethod* nm = fst.current()->cb()->as_nmethod_or_null();
2750         xtty->elem("deoptimized thread='" UINTX_FORMAT "' compile_id='%d'",
2751                    this->name(), nm != NULL ? nm->compile_id() : -1);
2752       }
2753 
2754       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2755     }
2756   }
2757 }
2758 
2759 
2760 // GC support
2761 static void frame_gc_epilogue(frame* f, const RegisterMap* map) { f->gc_epilogue(); }
2762 
2763 void JavaThread::gc_epilogue() {
2764   frames_do(frame_gc_epilogue);
2765 }
2766 
2767 
2768 static void frame_gc_prologue(frame* f, const RegisterMap* map) { f->gc_prologue(); }
2769 
2770 void JavaThread::gc_prologue() {
2771   frames_do(frame_gc_prologue);
2772 }
2773 
2774 // If the caller is a NamedThread, then remember, in the current scope,
2775 // the given JavaThread in its _processed_thread field.
2776 class RememberProcessedThread: public StackObj {
2777   NamedThread* _cur_thr;
2778 public:
2779   RememberProcessedThread(JavaThread* jthr) {
2780     Thread* thread = Thread::current();
2781     if (thread->is_Named_thread()) {
2782       _cur_thr = (NamedThread *)thread;
2783       _cur_thr->set_processed_thread(jthr);
2784     } else {
2785       _cur_thr = NULL;
2786     }
2787   }
2788 
2789   ~RememberProcessedThread() {
2790     if (_cur_thr) {
2791       _cur_thr->set_processed_thread(NULL);
2792     }
2793   }
2794 };
2795 
2796 void JavaThread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
2797   // Verify that the deferred card marks have been flushed.
2798   assert(deferred_card_mark().is_empty(), "Should be empty during GC");
2799 
2800   // The ThreadProfiler oops_do is done from FlatProfiler::oops_do
2801   // since there may be more than one thread using each ThreadProfiler.
2802 
2803   // Traverse the GCHandles
2804   Thread::oops_do(f, cld_f, cf);
2805 
2806   assert( (!has_last_Java_frame() && java_call_counter() == 0) ||
2807           (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2808 
2809   if (has_last_Java_frame()) {
2810     // Record JavaThread to GC thread
2811     RememberProcessedThread rpt(this);
2812 
2813     // Traverse the privileged stack
2814     if (_privileged_stack_top != NULL) {
2815       _privileged_stack_top->oops_do(f);
2816     }
2817 
2818     // traverse the registered growable array
2819     if (_array_for_gc != NULL) {
2820       for (int index = 0; index < _array_for_gc->length(); index++) {
2821         f->do_oop(_array_for_gc->adr_at(index));
2822       }
2823     }
2824 
2825     // Traverse the monitor chunks
2826     for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2827       chunk->oops_do(f);
2828     }
2829 
2830     // Traverse the execution stack
2831     for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2832       fst.current()->oops_do(f, cld_f, cf, fst.register_map());
2833     }
2834   }
2835 
2836   // callee_target is never live across a gc point so NULL it here should
2837   // it still contain a methdOop.
2838 
2839   set_callee_target(NULL);
2840 
2841   assert(vframe_array_head() == NULL, "deopt in progress at a safepoint!");
2842   // If we have deferred set_locals there might be oops waiting to be
2843   // written
2844   GrowableArray<jvmtiDeferredLocalVariableSet*>* list = deferred_locals();
2845   if (list != NULL) {
2846     for (int i = 0; i < list->length(); i++) {
2847       list->at(i)->oops_do(f);
2848     }
2849   }
2850 
2851   // Traverse instance variables at the end since the GC may be moving things
2852   // around using this function
2853   f->do_oop((oop*) &_threadObj);
2854   f->do_oop((oop*) &_vm_result);
2855   f->do_oop((oop*) &_exception_oop);
2856   f->do_oop((oop*) &_pending_async_exception);
2857 
2858   if (jvmti_thread_state() != NULL) {
2859     jvmti_thread_state()->oops_do(f);
2860   }
2861 }
2862 
2863 void JavaThread::nmethods_do(CodeBlobClosure* cf) {
2864   Thread::nmethods_do(cf);  // (super method is a no-op)
2865 
2866   assert( (!has_last_Java_frame() && java_call_counter() == 0) ||
2867           (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2868 
2869   if (has_last_Java_frame()) {
2870     // Traverse the execution stack
2871     for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2872       fst.current()->nmethods_do(cf);
2873     }
2874   }
2875 }
2876 
2877 void JavaThread::metadata_do(void f(Metadata*)) {
2878   Thread::metadata_do(f);
2879   if (has_last_Java_frame()) {
2880     // Traverse the execution stack to call f() on the methods in the stack
2881     for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2882       fst.current()->metadata_do(f);
2883     }
2884   } else if (is_Compiler_thread()) {
2885     // need to walk ciMetadata in current compile tasks to keep alive.
2886     CompilerThread* ct = (CompilerThread*)this;
2887     if (ct->env() != NULL) {
2888       ct->env()->metadata_do(f);
2889     }
2890   }
2891 }
2892 
2893 // Printing
2894 const char* _get_thread_state_name(JavaThreadState _thread_state) {
2895   switch (_thread_state) {
2896   case _thread_uninitialized:     return "_thread_uninitialized";
2897   case _thread_new:               return "_thread_new";
2898   case _thread_new_trans:         return "_thread_new_trans";
2899   case _thread_in_native:         return "_thread_in_native";
2900   case _thread_in_native_trans:   return "_thread_in_native_trans";
2901   case _thread_in_vm:             return "_thread_in_vm";
2902   case _thread_in_vm_trans:       return "_thread_in_vm_trans";
2903   case _thread_in_Java:           return "_thread_in_Java";
2904   case _thread_in_Java_trans:     return "_thread_in_Java_trans";
2905   case _thread_blocked:           return "_thread_blocked";
2906   case _thread_blocked_trans:     return "_thread_blocked_trans";
2907   default:                        return "unknown thread state";
2908   }
2909 }
2910 
2911 #ifndef PRODUCT
2912 void JavaThread::print_thread_state_on(outputStream *st) const {
2913   st->print_cr("   JavaThread state: %s", _get_thread_state_name(_thread_state));
2914 };
2915 void JavaThread::print_thread_state() const {
2916   print_thread_state_on(tty);
2917 };
2918 #endif // PRODUCT
2919 
2920 // Called by Threads::print() for VM_PrintThreads operation
2921 void JavaThread::print_on(outputStream *st) const {
2922   st->print("\"%s\" ", get_thread_name());
2923   oop thread_oop = threadObj();
2924   if (thread_oop != NULL) {
2925     st->print("#" INT64_FORMAT " ", java_lang_Thread::thread_id(thread_oop));
2926     if (java_lang_Thread::is_daemon(thread_oop))  st->print("daemon ");
2927     st->print("prio=%d ", java_lang_Thread::priority(thread_oop));
2928   }
2929   Thread::print_on(st);
2930   // print guess for valid stack memory region (assume 4K pages); helps lock debugging
2931   st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
2932   if (thread_oop != NULL && JDK_Version::is_gte_jdk15x_version()) {
2933     st->print_cr("   java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
2934   }
2935 #ifndef PRODUCT
2936   print_thread_state_on(st);
2937   _safepoint_state->print_on(st);
2938 #endif // PRODUCT
2939 }
2940 
2941 // Called by fatal error handler. The difference between this and
2942 // JavaThread::print() is that we can't grab lock or allocate memory.
2943 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
2944   st->print("JavaThread \"%s\"",  get_thread_name_string(buf, buflen));
2945   oop thread_obj = threadObj();
2946   if (thread_obj != NULL) {
2947      if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
2948   }
2949   st->print(" [");
2950   st->print("%s", _get_thread_state_name(_thread_state));
2951   if (osthread()) {
2952     st->print(", id=%d", osthread()->thread_id());
2953   }
2954   st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
2955             _stack_base - _stack_size, _stack_base);
2956   st->print("]");
2957   return;
2958 }
2959 
2960 // Verification
2961 
2962 static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
2963 
2964 void JavaThread::verify() {
2965   // Verify oops in the thread.
2966   oops_do(&VerifyOopClosure::verify_oop, NULL, NULL);
2967 
2968   // Verify the stack frames.
2969   frames_do(frame_verify);
2970 }
2971 
2972 // CR 6300358 (sub-CR 2137150)
2973 // Most callers of this method assume that it can't return NULL but a
2974 // thread may not have a name whilst it is in the process of attaching to
2975 // the VM - see CR 6412693, and there are places where a JavaThread can be
2976 // seen prior to having it's threadObj set (eg JNI attaching threads and
2977 // if vm exit occurs during initialization). These cases can all be accounted
2978 // for such that this method never returns NULL.
2979 const char* JavaThread::get_thread_name() const {
2980 #ifdef ASSERT
2981   // early safepoints can hit while current thread does not yet have TLS
2982   if (!SafepointSynchronize::is_at_safepoint()) {
2983     Thread *cur = Thread::current();
2984     if (!(cur->is_Java_thread() && cur == this)) {
2985       // Current JavaThreads are allowed to get their own name without
2986       // the Threads_lock.
2987       assert_locked_or_safepoint(Threads_lock);
2988     }
2989   }
2990 #endif // ASSERT
2991     return get_thread_name_string();
2992 }
2993 
2994 // Returns a non-NULL representation of this thread's name, or a suitable
2995 // descriptive string if there is no set name
2996 const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
2997   const char* name_str;
2998   oop thread_obj = threadObj();
2999   if (thread_obj != NULL) {
3000     oop name = java_lang_Thread::name(thread_obj);
3001     if (name != NULL) {
3002       if (buf == NULL) {
3003         name_str = java_lang_String::as_utf8_string(name);
3004       }
3005       else {
3006         name_str = java_lang_String::as_utf8_string(name, buf, buflen);
3007       }
3008     }
3009     else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
3010       name_str = "<no-name - thread is attaching>";
3011     }
3012     else {
3013       name_str = Thread::name();
3014     }
3015   }
3016   else {
3017     name_str = Thread::name();
3018   }
3019   assert(name_str != NULL, "unexpected NULL thread name");
3020   return name_str;
3021 }
3022 
3023 
3024 const char* JavaThread::get_threadgroup_name() const {
3025   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3026   oop thread_obj = threadObj();
3027   if (thread_obj != NULL) {
3028     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3029     if (thread_group != NULL) {
3030       typeArrayOop name = java_lang_ThreadGroup::name(thread_group);
3031       // ThreadGroup.name can be null
3032       if (name != NULL) {
3033         const char* str = UNICODE::as_utf8((jchar*) name->base(T_CHAR), name->length());
3034         return str;
3035       }
3036     }
3037   }
3038   return NULL;
3039 }
3040 
3041 const char* JavaThread::get_parent_name() const {
3042   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3043   oop thread_obj = threadObj();
3044   if (thread_obj != NULL) {
3045     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3046     if (thread_group != NULL) {
3047       oop parent = java_lang_ThreadGroup::parent(thread_group);
3048       if (parent != NULL) {
3049         typeArrayOop name = java_lang_ThreadGroup::name(parent);
3050         // ThreadGroup.name can be null
3051         if (name != NULL) {
3052           const char* str = UNICODE::as_utf8((jchar*) name->base(T_CHAR), name->length());
3053           return str;
3054         }
3055       }
3056     }
3057   }
3058   return NULL;
3059 }
3060 
3061 ThreadPriority JavaThread::java_priority() const {
3062   oop thr_oop = threadObj();
3063   if (thr_oop == NULL) return NormPriority; // Bootstrapping
3064   ThreadPriority priority = java_lang_Thread::priority(thr_oop);
3065   assert(MinPriority <= priority && priority <= MaxPriority, "sanity check");
3066   return priority;
3067 }
3068 
3069 void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
3070 
3071   assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
3072   // Link Java Thread object <-> C++ Thread
3073 
3074   // Get the C++ thread object (an oop) from the JNI handle (a jthread)
3075   // and put it into a new Handle.  The Handle "thread_oop" can then
3076   // be used to pass the C++ thread object to other methods.
3077 
3078   // Set the Java level thread object (jthread) field of the
3079   // new thread (a JavaThread *) to C++ thread object using the
3080   // "thread_oop" handle.
3081 
3082   // Set the thread field (a JavaThread *) of the
3083   // oop representing the java_lang_Thread to the new thread (a JavaThread *).
3084 
3085   Handle thread_oop(Thread::current(),
3086                     JNIHandles::resolve_non_null(jni_thread));
3087   assert(InstanceKlass::cast(thread_oop->klass())->is_linked(),
3088     "must be initialized");
3089   set_threadObj(thread_oop());
3090   java_lang_Thread::set_thread(thread_oop(), this);
3091 
3092   if (prio == NoPriority) {
3093     prio = java_lang_Thread::priority(thread_oop());
3094     assert(prio != NoPriority, "A valid priority should be present");
3095   }
3096 
3097   // Push the Java priority down to the native thread; needs Threads_lock
3098   Thread::set_priority(this, prio);
3099 
3100   prepare_ext();
3101 
3102   // Add the new thread to the Threads list and set it in motion.
3103   // We must have threads lock in order to call Threads::add.
3104   // It is crucial that we do not block before the thread is
3105   // added to the Threads list for if a GC happens, then the java_thread oop
3106   // will not be visited by GC.
3107   Threads::add(this);
3108 }
3109 
3110 oop JavaThread::current_park_blocker() {
3111   // Support for JSR-166 locks
3112   oop thread_oop = threadObj();
3113   if (thread_oop != NULL &&
3114       JDK_Version::current().supports_thread_park_blocker()) {
3115     return java_lang_Thread::park_blocker(thread_oop);
3116   }
3117   return NULL;
3118 }
3119 
3120 
3121 void JavaThread::print_stack_on(outputStream* st) {
3122   if (!has_last_Java_frame()) return;
3123   ResourceMark rm;
3124   HandleMark   hm;
3125 
3126   RegisterMap reg_map(this);
3127   vframe* start_vf = last_java_vframe(&reg_map);
3128   int count = 0;
3129   for (vframe* f = start_vf; f; f = f->sender() ) {
3130     if (f->is_java_frame()) {
3131       javaVFrame* jvf = javaVFrame::cast(f);
3132       java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
3133 
3134       // Print out lock information
3135       if (JavaMonitorsInStackTrace) {
3136         jvf->print_lock_info_on(st, count);
3137       }
3138     } else {
3139       // Ignore non-Java frames
3140     }
3141 
3142     // Bail-out case for too deep stacks
3143     count++;
3144     if (MaxJavaStackTraceDepth == count) return;
3145   }
3146 }
3147 
3148 
3149 // JVMTI PopFrame support
3150 void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
3151   assert(_popframe_preserved_args == NULL, "should not wipe out old PopFrame preserved arguments");
3152   if (in_bytes(size_in_bytes) != 0) {
3153     _popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes), mtThread);
3154     _popframe_preserved_args_size = in_bytes(size_in_bytes);
3155     Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
3156   }
3157 }
3158 
3159 void* JavaThread::popframe_preserved_args() {
3160   return _popframe_preserved_args;
3161 }
3162 
3163 ByteSize JavaThread::popframe_preserved_args_size() {
3164   return in_ByteSize(_popframe_preserved_args_size);
3165 }
3166 
3167 WordSize JavaThread::popframe_preserved_args_size_in_words() {
3168   int sz = in_bytes(popframe_preserved_args_size());
3169   assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
3170   return in_WordSize(sz / wordSize);
3171 }
3172 
3173 void JavaThread::popframe_free_preserved_args() {
3174   assert(_popframe_preserved_args != NULL, "should not free PopFrame preserved arguments twice");
3175   FREE_C_HEAP_ARRAY(char, (char*) _popframe_preserved_args, mtThread);
3176   _popframe_preserved_args = NULL;
3177   _popframe_preserved_args_size = 0;
3178 }
3179 
3180 #ifndef PRODUCT
3181 
3182 void JavaThread::trace_frames() {
3183   tty->print_cr("[Describe stack]");
3184   int frame_no = 1;
3185   for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
3186     tty->print("  %d. ", frame_no++);
3187     fst.current()->print_value_on(tty,this);
3188     tty->cr();
3189   }
3190 }
3191 
3192 class PrintAndVerifyOopClosure: public OopClosure {
3193  protected:
3194   template <class T> inline void do_oop_work(T* p) {
3195     oop obj = oopDesc::load_decode_heap_oop(p);
3196     if (obj == NULL) return;
3197     tty->print(INTPTR_FORMAT ": ", p);
3198     if (obj->is_oop_or_null()) {
3199       if (obj->is_objArray()) {
3200         tty->print_cr("valid objArray: " INTPTR_FORMAT, (oopDesc*) obj);
3201       } else {
3202         obj->print();
3203       }
3204     } else {
3205       tty->print_cr("invalid oop: " INTPTR_FORMAT, (oopDesc*) obj);
3206     }
3207     tty->cr();
3208   }
3209  public:
3210   virtual void do_oop(oop* p) { do_oop_work(p); }
3211   virtual void do_oop(narrowOop* p)  { do_oop_work(p); }
3212 };
3213 
3214 
3215 static void oops_print(frame* f, const RegisterMap *map) {
3216   PrintAndVerifyOopClosure print;
3217   f->print_value();
3218   f->oops_do(&print, NULL, NULL, (RegisterMap*)map);
3219 }
3220 
3221 // Print our all the locations that contain oops and whether they are
3222 // valid or not.  This useful when trying to find the oldest frame
3223 // where an oop has gone bad since the frame walk is from youngest to
3224 // oldest.
3225 void JavaThread::trace_oops() {
3226   tty->print_cr("[Trace oops]");
3227   frames_do(oops_print);
3228 }
3229 
3230 
3231 #ifdef ASSERT
3232 // Print or validate the layout of stack frames
3233 void JavaThread::print_frame_layout(int depth, bool validate_only) {
3234   ResourceMark rm;
3235   PRESERVE_EXCEPTION_MARK;
3236   FrameValues values;
3237   int frame_no = 0;
3238   for(StackFrameStream fst(this, false); !fst.is_done(); fst.next()) {
3239     fst.current()->describe(values, ++frame_no);
3240     if (depth == frame_no) break;
3241   }
3242   if (validate_only) {
3243     values.validate();
3244   } else {
3245     tty->print_cr("[Describe stack layout]");
3246     values.print(this);
3247   }
3248 }
3249 #endif
3250 
3251 void JavaThread::trace_stack_from(vframe* start_vf) {
3252   ResourceMark rm;
3253   int vframe_no = 1;
3254   for (vframe* f = start_vf; f; f = f->sender() ) {
3255     if (f->is_java_frame()) {
3256       javaVFrame::cast(f)->print_activation(vframe_no++);
3257     } else {
3258       f->print();
3259     }
3260     if (vframe_no > StackPrintLimit) {
3261       tty->print_cr("...<more frames>...");
3262       return;
3263     }
3264   }
3265 }
3266 
3267 
3268 void JavaThread::trace_stack() {
3269   if (!has_last_Java_frame()) return;
3270   ResourceMark rm;
3271   HandleMark   hm;
3272   RegisterMap reg_map(this);
3273   trace_stack_from(last_java_vframe(&reg_map));
3274 }
3275 
3276 
3277 #endif // PRODUCT
3278 
3279 
3280 javaVFrame* JavaThread::last_java_vframe(RegisterMap *reg_map) {
3281   assert(reg_map != NULL, "a map must be given");
3282   frame f = last_frame();
3283   for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender() ) {
3284     if (vf->is_java_frame()) return javaVFrame::cast(vf);
3285   }
3286   return NULL;
3287 }
3288 
3289 
3290 Klass* JavaThread::security_get_caller_class(int depth) {
3291   vframeStream vfst(this);
3292   vfst.security_get_caller_frame(depth);
3293   if (!vfst.at_end()) {
3294     return vfst.method()->method_holder();
3295   }
3296   return NULL;
3297 }
3298 
3299 static void compiler_thread_entry(JavaThread* thread, TRAPS) {
3300   assert(thread->is_Compiler_thread(), "must be compiler thread");
3301   CompileBroker::compiler_thread_loop();
3302 }
3303 
3304 // Create a CompilerThread
3305 CompilerThread::CompilerThread(CompileQueue* queue, CompilerCounters* counters)
3306 : JavaThread(&compiler_thread_entry) {
3307   _env   = NULL;
3308   _log   = NULL;
3309   _task  = NULL;
3310   _queue = queue;
3311   _counters = counters;
3312   _buffer_blob = NULL;
3313   _scanned_nmethod = NULL;
3314   _compiler = NULL;
3315 
3316   // Compiler uses resource area for compilation, let's bias it to mtCompiler
3317   resource_area()->bias_to(mtCompiler);
3318 
3319 #ifndef PRODUCT
3320   _ideal_graph_printer = NULL;
3321 #endif
3322 }
3323 
3324 void CompilerThread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
3325   JavaThread::oops_do(f, cld_f, cf);
3326   if (_scanned_nmethod != NULL && cf != NULL) {
3327     // Safepoints can occur when the sweeper is scanning an nmethod so
3328     // process it here to make sure it isn't unloaded in the middle of
3329     // a scan.
3330     cf->do_code_blob(_scanned_nmethod);
3331   }
3332 }
3333 
3334 
3335 // ======= Threads ========
3336 
3337 // The Threads class links together all active threads, and provides
3338 // operations over all threads.  It is protected by its own Mutex
3339 // lock, which is also used in other contexts to protect thread
3340 // operations from having the thread being operated on from exiting
3341 // and going away unexpectedly (e.g., safepoint synchronization)
3342 
3343 JavaThread* Threads::_thread_list = NULL;
3344 int         Threads::_number_of_threads = 0;
3345 int         Threads::_number_of_non_daemon_threads = 0;
3346 int         Threads::_return_code = 0;
3347 size_t      JavaThread::_stack_size_at_create = 0;
3348 #ifdef ASSERT
3349 bool        Threads::_vm_complete = false;
3350 #endif
3351 
3352 // All JavaThreads
3353 #define ALL_JAVA_THREADS(X) for (JavaThread* X = _thread_list; X; X = X->next())
3354 
3355 void Threads::java_threads_do(ThreadClosure* tc) {
3356   assert_locked_or_safepoint(Threads_lock);
3357   ALL_JAVA_THREADS(p) {
3358     tc->do_thread(p);
3359   }
3360 }
3361 
3362 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system)
3363 void Threads::threads_do(ThreadClosure* tc) {
3364   assert_locked_or_safepoint(Threads_lock);
3365   // ALL_JAVA_THREADS iterates through all JavaThreads
3366   ALL_JAVA_THREADS(p) {
3367     tc->do_thread(p);
3368   }
3369   // Someday we could have a table or list of all non-JavaThreads.
3370   // For now, just manually iterate through them.
3371   tc->do_thread(VMThread::vm_thread());
3372   Universe::heap()->gc_threads_do(tc);
3373   WatcherThread *wt = WatcherThread::watcher_thread();
3374   // Strictly speaking, the following NULL check isn't sufficient to make sure
3375   // the data for WatcherThread is still valid upon being examined. However,
3376   // considering that WatchThread terminates when the VM is on the way to
3377   // exit at safepoint, the chance of the above is extremely small. The right
3378   // way to prevent termination of WatcherThread would be to acquire
3379   // Terminator_lock, but we can't do that without violating the lock rank
3380   // checking in some cases.
3381   if (wt != NULL)
3382     tc->do_thread(wt);
3383 
3384   // If CompilerThreads ever become non-JavaThreads, add them here
3385 }
3386 
3387 jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
3388 
3389   extern void JDK_Version_init();
3390 
3391   // Preinitialize version info.
3392   VM_Version::early_initialize();
3393 
3394   // Check version
3395   if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
3396 
3397   // Initialize the output stream module
3398   ostream_init();
3399 
3400   // Process java launcher properties.
3401   Arguments::process_sun_java_launcher_properties(args);
3402 
3403   // Initialize the os module before using TLS
3404   os::init();
3405 
3406   // Initialize system properties.
3407   Arguments::init_system_properties();
3408 
3409   // So that JDK version can be used as a discrimintor when parsing arguments
3410   JDK_Version_init();
3411 
3412   // Update/Initialize System properties after JDK version number is known
3413   Arguments::init_version_specific_system_properties();
3414 
3415   // Parse arguments
3416   // Note: this internally calls os::init_container_support()
3417   jint parse_result = Arguments::parse(args);
3418   if (parse_result != JNI_OK) return parse_result;
3419 
3420   os::init_before_ergo();
3421 
3422   jint ergo_result = Arguments::apply_ergo();
3423   if (ergo_result != JNI_OK) return ergo_result;
3424 
3425   if (PauseAtStartup) {
3426     os::pause();
3427   }
3428 
3429 #ifndef USDT2
3430   HS_DTRACE_PROBE(hotspot, vm__init__begin);
3431 #else /* USDT2 */
3432   HOTSPOT_VM_INIT_BEGIN();
3433 #endif /* USDT2 */
3434 
3435   // Record VM creation timing statistics
3436   TraceVmCreationTime create_vm_timer;
3437   create_vm_timer.start();
3438 
3439   // Timing (must come after argument parsing)
3440   TraceTime timer("Create VM", TraceStartupTime);
3441 
3442   // Initialize the os module after parsing the args
3443   jint os_init_2_result = os::init_2();
3444   if (os_init_2_result != JNI_OK) return os_init_2_result;
3445 
3446   jint adjust_after_os_result = Arguments::adjust_after_os();
3447   if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;
3448 
3449   // intialize TLS
3450   ThreadLocalStorage::init();
3451 
3452   // Initialize output stream logging
3453   ostream_init_log();
3454 
3455   // Convert -Xrun to -agentlib: if there is no JVM_OnLoad
3456   // Must be before create_vm_init_agents()
3457   if (Arguments::init_libraries_at_startup()) {
3458     convert_vm_init_libraries_to_agents();
3459   }
3460 
3461   // Launch -agentlib/-agentpath and converted -Xrun agents
3462   if (Arguments::init_agents_at_startup()) {
3463     create_vm_init_agents();
3464   }
3465 
3466   // Initialize Threads state
3467   _thread_list = NULL;
3468   _number_of_threads = 0;
3469   _number_of_non_daemon_threads = 0;
3470 
3471   // Initialize global data structures and create system classes in heap
3472   vm_init_globals();
3473 
3474   // Attach the main thread to this os thread
3475   JavaThread* main_thread = new JavaThread();
3476   main_thread->set_thread_state(_thread_in_vm);
3477   // must do this before set_active_handles and initialize_thread_local_storage
3478   // Note: on solaris initialize_thread_local_storage() will (indirectly)
3479   // change the stack size recorded here to one based on the java thread
3480   // stacksize. This adjusted size is what is used to figure the placement
3481   // of the guard pages.
3482   main_thread->record_stack_base_and_size();
3483   main_thread->initialize_thread_local_storage();
3484 
3485   main_thread->set_active_handles(JNIHandleBlock::allocate_block());
3486 
3487   if (!main_thread->set_as_starting_thread()) {
3488     vm_shutdown_during_initialization(
3489       "Failed necessary internal allocation. Out of swap space");
3490     delete main_thread;
3491     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3492     return JNI_ENOMEM;
3493   }
3494 
3495   // Enable guard page *after* os::create_main_thread(), otherwise it would
3496   // crash Linux VM, see notes in os_linux.cpp.
3497   main_thread->create_stack_guard_pages();
3498 
3499   // Initialize Java-Level synchronization subsystem
3500   ObjectMonitor::Initialize() ;
3501 
3502   // Initialize global modules
3503   jint status = init_globals();
3504   if (status != JNI_OK) {
3505     delete main_thread;
3506     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3507     return status;
3508   }
3509 
3510   // Should be done after the heap is fully created
3511   main_thread->cache_global_variables();
3512 
3513   HandleMark hm;
3514 
3515   { MutexLocker mu(Threads_lock);
3516     Threads::add(main_thread);
3517   }
3518 
3519   // Any JVMTI raw monitors entered in onload will transition into
3520   // real raw monitor. VM is setup enough here for raw monitor enter.
3521   JvmtiExport::transition_pending_onload_raw_monitors();
3522 
3523   // Create the VMThread
3524   { TraceTime timer("Start VMThread", TraceStartupTime);
3525     VMThread::create();
3526     Thread* vmthread = VMThread::vm_thread();
3527 
3528     if (!os::create_thread(vmthread, os::vm_thread))
3529       vm_exit_during_initialization("Cannot create VM thread. Out of system resources.");
3530 
3531     // Wait for the VM thread to become ready, and VMThread::run to initialize
3532     // Monitors can have spurious returns, must always check another state flag
3533     {
3534       MutexLocker ml(Notify_lock);
3535       os::start_thread(vmthread);
3536       while (vmthread->active_handles() == NULL) {
3537         Notify_lock->wait();
3538       }
3539     }
3540   }
3541 
3542   assert (Universe::is_fully_initialized(), "not initialized");
3543   if (VerifyDuringStartup) {
3544     // Make sure we're starting with a clean slate.
3545     VM_Verify verify_op;
3546     VMThread::execute(&verify_op);
3547   }
3548 
3549   EXCEPTION_MARK;
3550 
3551   // At this point, the Universe is initialized, but we have not executed
3552   // any byte code.  Now is a good time (the only time) to dump out the
3553   // internal state of the JVM for sharing.
3554   if (DumpSharedSpaces) {
3555     MetaspaceShared::preload_and_dump(CHECK_0);
3556     ShouldNotReachHere();
3557   }
3558 
3559   // Always call even when there are not JVMTI environments yet, since environments
3560   // may be attached late and JVMTI must track phases of VM execution
3561   JvmtiExport::enter_start_phase();
3562 
3563   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
3564   JvmtiExport::post_vm_start();
3565 
3566   {
3567     TraceTime timer("Initialize java.lang classes", TraceStartupTime);
3568 
3569     if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
3570       create_vm_init_libraries();
3571     }
3572 
3573     initialize_class(vmSymbols::java_lang_String(), CHECK_0);
3574 
3575     // Initialize java_lang.System (needed before creating the thread)
3576     initialize_class(vmSymbols::java_lang_System(), CHECK_0);
3577     initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK_0);
3578     Handle thread_group = create_initial_thread_group(CHECK_0);
3579     Universe::set_main_thread_group(thread_group());
3580     initialize_class(vmSymbols::java_lang_Thread(), CHECK_0);
3581     oop thread_object = create_initial_thread(thread_group, main_thread, CHECK_0);
3582     main_thread->set_threadObj(thread_object);
3583     // Set thread status to running since main thread has
3584     // been started and running.
3585     java_lang_Thread::set_thread_status(thread_object,
3586                                         java_lang_Thread::RUNNABLE);
3587 
3588     // The VM creates & returns objects of this class. Make sure it's initialized.
3589     initialize_class(vmSymbols::java_lang_Class(), CHECK_0);
3590 
3591     // The VM preresolves methods to these classes. Make sure that they get initialized
3592     initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK_0);
3593     initialize_class(vmSymbols::java_lang_ref_Finalizer(),  CHECK_0);
3594     call_initializeSystemClass(CHECK_0);
3595 
3596     // get the Java runtime name after java.lang.System is initialized
3597     JDK_Version::set_runtime_name(get_java_runtime_name(THREAD));
3598     JDK_Version::set_runtime_version(get_java_runtime_version(THREAD));
3599 
3600     // an instance of OutOfMemory exception has been allocated earlier
3601     initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK_0);
3602     initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK_0);
3603     initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK_0);
3604     initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK_0);
3605     initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK_0);
3606     initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK_0);
3607     initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK_0);
3608     initialize_class(vmSymbols::java_lang_IllegalArgumentException(), CHECK_0);
3609   }
3610 
3611   // See        : bugid 4211085.
3612   // Background : the static initializer of java.lang.Compiler tries to read
3613   //              property"java.compiler" and read & write property "java.vm.info".
3614   //              When a security manager is installed through the command line
3615   //              option "-Djava.security.manager", the above properties are not
3616   //              readable and the static initializer for java.lang.Compiler fails
3617   //              resulting in a NoClassDefFoundError.  This can happen in any
3618   //              user code which calls methods in java.lang.Compiler.
3619   // Hack :       the hack is to pre-load and initialize this class, so that only
3620   //              system domains are on the stack when the properties are read.
3621   //              Currently even the AWT code has calls to methods in java.lang.Compiler.
3622   //              On the classic VM, java.lang.Compiler is loaded very early to load the JIT.
3623   // Future Fix : the best fix is to grant everyone permissions to read "java.compiler" and
3624   //              read and write"java.vm.info" in the default policy file. See bugid 4211383
3625   //              Once that is done, we should remove this hack.
3626   initialize_class(vmSymbols::java_lang_Compiler(), CHECK_0);
3627 
3628   // More hackery - the static initializer of java.lang.Compiler adds the string "nojit" to
3629   // the java.vm.info property if no jit gets loaded through java.lang.Compiler (the hotspot
3630   // compiler does not get loaded through java.lang.Compiler).  "java -version" with the
3631   // hotspot vm says "nojit" all the time which is confusing.  So, we reset it here.
3632   // This should also be taken out as soon as 4211383 gets fixed.
3633   reset_vm_info_property(CHECK_0);
3634 
3635   quicken_jni_functions();
3636 
3637   // Must be run after init_ft which initializes ft_enabled
3638   if (TRACE_INITIALIZE() != JNI_OK) {
3639     vm_exit_during_initialization("Failed to initialize tracing backend");
3640   }
3641 
3642   // Set flag that basic initialization has completed. Used by exceptions and various
3643   // debug stuff, that does not work until all basic classes have been initialized.
3644   set_init_completed();
3645 
3646   Metaspace::post_initialize();
3647 
3648 #ifndef USDT2
3649   HS_DTRACE_PROBE(hotspot, vm__init__end);
3650 #else /* USDT2 */
3651   HOTSPOT_VM_INIT_END();
3652 #endif /* USDT2 */
3653 
3654   // record VM initialization completion time
3655 #if INCLUDE_MANAGEMENT
3656   Management::record_vm_init_completed();
3657 #endif // INCLUDE_MANAGEMENT
3658 
3659   // Compute system loader. Note that this has to occur after set_init_completed, since
3660   // valid exceptions may be thrown in the process.
3661   // Note that we do not use CHECK_0 here since we are inside an EXCEPTION_MARK and
3662   // set_init_completed has just been called, causing exceptions not to be shortcut
3663   // anymore. We call vm_exit_during_initialization directly instead.
3664   SystemDictionary::compute_java_system_loader(THREAD);
3665   if (HAS_PENDING_EXCEPTION) {
3666     vm_exit_during_initialization(Handle(THREAD, PENDING_EXCEPTION));
3667   }
3668 
3669 #if INCLUDE_ALL_GCS
3670   // Support for ConcurrentMarkSweep. This should be cleaned up
3671   // and better encapsulated. The ugly nested if test would go away
3672   // once things are properly refactored. XXX YSR
3673   if (UseConcMarkSweepGC || UseG1GC || UseShenandoahGC) {
3674     if (UseConcMarkSweepGC) {
3675       ConcurrentMarkSweepThread::makeSurrogateLockerThread(THREAD);
3676     } else if (UseShenandoahGC) {
3677       ShenandoahControlThread::makeSurrogateLockerThread(THREAD);
3678     } else {
3679       ConcurrentMarkThread::makeSurrogateLockerThread(THREAD);
3680     }
3681     if (HAS_PENDING_EXCEPTION) {
3682       vm_exit_during_initialization(Handle(THREAD, PENDING_EXCEPTION));
3683     }
3684   }
3685 #endif // INCLUDE_ALL_GCS
3686 
3687   // Always call even when there are not JVMTI environments yet, since environments
3688   // may be attached late and JVMTI must track phases of VM execution
3689   JvmtiExport::enter_live_phase();
3690 
3691   // Signal Dispatcher needs to be started before VMInit event is posted
3692   os::signal_init();
3693 
3694   // Start Attach Listener if +StartAttachListener or it can't be started lazily
3695   if (!DisableAttachMechanism) {
3696     AttachListener::vm_start();
3697     if (StartAttachListener || AttachListener::init_at_startup()) {
3698       AttachListener::init();
3699     }
3700   }
3701 
3702   // Launch -Xrun agents
3703   // Must be done in the JVMTI live phase so that for backward compatibility the JDWP
3704   // back-end can launch with -Xdebug -Xrunjdwp.
3705   if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
3706     create_vm_init_libraries();
3707   }
3708 
3709   // Notify JVMTI agents that VM initialization is complete - nop if no agents.
3710   JvmtiExport::post_vm_initialized();
3711 
3712   if (TRACE_START() != JNI_OK) {
3713     vm_exit_during_initialization("Failed to start tracing backend.");
3714   }
3715 
3716   if (CleanChunkPoolAsync) {
3717     Chunk::start_chunk_pool_cleaner_task();
3718   }
3719 
3720   // initialize compiler(s)
3721 #if defined(COMPILER1) || defined(COMPILER2) || defined(SHARK)
3722   CompileBroker::compilation_init();
3723 #endif
3724 
3725   if (EnableInvokeDynamic) {
3726     // Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
3727     // It is done after compilers are initialized, because otherwise compilations of
3728     // signature polymorphic MH intrinsics can be missed
3729     // (see SystemDictionary::find_method_handle_intrinsic).
3730     initialize_class(vmSymbols::java_lang_invoke_MethodHandle(), CHECK_0);
3731     initialize_class(vmSymbols::java_lang_invoke_MemberName(), CHECK_0);
3732     initialize_class(vmSymbols::java_lang_invoke_MethodHandleNatives(), CHECK_0);
3733   }
3734 
3735 #if INCLUDE_MANAGEMENT
3736   Management::initialize(THREAD);
3737 #endif // INCLUDE_MANAGEMENT
3738 
3739   if (HAS_PENDING_EXCEPTION) {
3740     // management agent fails to start possibly due to
3741     // configuration problem and is responsible for printing
3742     // stack trace if appropriate. Simply exit VM.
3743     vm_exit(1);
3744   }
3745 
3746   if (Arguments::has_profile())       FlatProfiler::engage(main_thread, true);
3747   if (MemProfiling)                   MemProfiler::engage();
3748   StatSampler::engage();
3749   if (CheckJNICalls)                  JniPeriodicChecker::engage();
3750 
3751   BiasedLocking::init();
3752 
3753 #if INCLUDE_RTM_OPT
3754   RTMLockingCounters::init();
3755 #endif
3756 
3757   if (JDK_Version::current().post_vm_init_hook_enabled()) {
3758     call_postVMInitHook(THREAD);
3759     // The Java side of PostVMInitHook.run must deal with all
3760     // exceptions and provide means of diagnosis.
3761     if (HAS_PENDING_EXCEPTION) {
3762       CLEAR_PENDING_EXCEPTION;
3763     }
3764   }
3765 
3766   {
3767       MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
3768       // Make sure the watcher thread can be started by WatcherThread::start()
3769       // or by dynamic enrollment.
3770       WatcherThread::make_startable();
3771       // Start up the WatcherThread if there are any periodic tasks
3772       // NOTE:  All PeriodicTasks should be registered by now. If they
3773       //   aren't, late joiners might appear to start slowly (we might
3774       //   take a while to process their first tick).
3775       if (PeriodicTask::num_tasks() > 0) {
3776           WatcherThread::start();
3777       }
3778   }
3779 
3780   create_vm_timer.end();
3781 #ifdef ASSERT
3782   _vm_complete = true;
3783 #endif
3784   return JNI_OK;
3785 }
3786 
3787 // type for the Agent_OnLoad and JVM_OnLoad entry points
3788 extern "C" {
3789   typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
3790 }
3791 // Find a command line agent library and return its entry point for
3792 //         -agentlib:  -agentpath:   -Xrun
3793 // num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array.
3794 static OnLoadEntry_t lookup_on_load(AgentLibrary* agent, const char *on_load_symbols[], size_t num_symbol_entries) {
3795   OnLoadEntry_t on_load_entry = NULL;
3796   void *library = NULL;
3797 
3798   if (!agent->valid()) {
3799     char buffer[JVM_MAXPATHLEN];
3800     char ebuf[1024];
3801     const char *name = agent->name();
3802     const char *msg = "Could not find agent library ";
3803 
3804     // First check to see if agent is statically linked into executable
3805     if (os::find_builtin_agent(agent, on_load_symbols, num_symbol_entries)) {
3806       library = agent->os_lib();
3807     } else if (agent->is_absolute_path()) {
3808       library = os::dll_load(name, ebuf, sizeof ebuf);
3809       if (library == NULL) {
3810         const char *sub_msg = " in absolute path, with error: ";
3811         size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3812         char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
3813         jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
3814         // If we can't find the agent, exit.
3815         vm_exit_during_initialization(buf, NULL);
3816         FREE_C_HEAP_ARRAY(char, buf, mtThread);
3817       }
3818     } else {
3819       // Try to load the agent from the standard dll directory
3820       if (os::dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(),
3821                              name)) {
3822         library = os::dll_load(buffer, ebuf, sizeof ebuf);
3823       }
3824       if (library == NULL) { // Try the local directory
3825         char ns[1] = {0};
3826         if (os::dll_build_name(buffer, sizeof(buffer), ns, name)) {
3827           library = os::dll_load(buffer, ebuf, sizeof ebuf);
3828         }
3829         if (library == NULL) {
3830           const char *sub_msg = " on the library path, with error: ";
3831           size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3832           char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
3833           jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
3834           // If we can't find the agent, exit.
3835           vm_exit_during_initialization(buf, NULL);
3836           FREE_C_HEAP_ARRAY(char, buf, mtThread);
3837         }
3838       }
3839     }
3840     agent->set_os_lib(library);
3841     agent->set_valid();
3842   }
3843 
3844   // Find the OnLoad function.
3845   on_load_entry =
3846     CAST_TO_FN_PTR(OnLoadEntry_t, os::find_agent_function(agent,
3847                                                           false,
3848                                                           on_load_symbols,
3849                                                           num_symbol_entries));
3850   return on_load_entry;
3851 }
3852 
3853 // Find the JVM_OnLoad entry point
3854 static OnLoadEntry_t lookup_jvm_on_load(AgentLibrary* agent) {
3855   const char *on_load_symbols[] = JVM_ONLOAD_SYMBOLS;
3856   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
3857 }
3858 
3859 // Find the Agent_OnLoad entry point
3860 static OnLoadEntry_t lookup_agent_on_load(AgentLibrary* agent) {
3861   const char *on_load_symbols[] = AGENT_ONLOAD_SYMBOLS;
3862   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
3863 }
3864 
3865 // For backwards compatibility with -Xrun
3866 // Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be
3867 // treated like -agentpath:
3868 // Must be called before agent libraries are created
3869 void Threads::convert_vm_init_libraries_to_agents() {
3870   AgentLibrary* agent;
3871   AgentLibrary* next;
3872 
3873   for (agent = Arguments::libraries(); agent != NULL; agent = next) {
3874     next = agent->next();  // cache the next agent now as this agent may get moved off this list
3875     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
3876 
3877     // If there is an JVM_OnLoad function it will get called later,
3878     // otherwise see if there is an Agent_OnLoad
3879     if (on_load_entry == NULL) {
3880       on_load_entry = lookup_agent_on_load(agent);
3881       if (on_load_entry != NULL) {
3882         // switch it to the agent list -- so that Agent_OnLoad will be called,
3883         // JVM_OnLoad won't be attempted and Agent_OnUnload will
3884         Arguments::convert_library_to_agent(agent);
3885       } else {
3886         vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
3887       }
3888     }
3889   }
3890 }
3891 
3892 // Create agents for -agentlib:  -agentpath:  and converted -Xrun
3893 // Invokes Agent_OnLoad
3894 // Called very early -- before JavaThreads exist
3895 void Threads::create_vm_init_agents() {
3896   extern struct JavaVM_ main_vm;
3897   AgentLibrary* agent;
3898 
3899   JvmtiExport::enter_onload_phase();
3900 
3901   for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
3902     OnLoadEntry_t  on_load_entry = lookup_agent_on_load(agent);
3903 
3904     if (on_load_entry != NULL) {
3905       // Invoke the Agent_OnLoad function
3906       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
3907       if (err != JNI_OK) {
3908         vm_exit_during_initialization("agent library failed to init", agent->name());
3909       }
3910     } else {
3911       vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
3912     }
3913   }
3914   JvmtiExport::enter_primordial_phase();
3915 }
3916 
3917 extern "C" {
3918   typedef void (JNICALL *Agent_OnUnload_t)(JavaVM *);
3919 }
3920 
3921 void Threads::shutdown_vm_agents() {
3922   // Send any Agent_OnUnload notifications
3923   const char *on_unload_symbols[] = AGENT_ONUNLOAD_SYMBOLS;
3924   size_t num_symbol_entries = ARRAY_SIZE(on_unload_symbols);
3925   extern struct JavaVM_ main_vm;
3926   for (AgentLibrary* agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
3927 
3928     // Find the Agent_OnUnload function.
3929     Agent_OnUnload_t unload_entry = CAST_TO_FN_PTR(Agent_OnUnload_t,
3930       os::find_agent_function(agent,
3931       false,
3932       on_unload_symbols,
3933       num_symbol_entries));
3934 
3935     // Invoke the Agent_OnUnload function
3936     if (unload_entry != NULL) {
3937       JavaThread* thread = JavaThread::current();
3938       ThreadToNativeFromVM ttn(thread);
3939       HandleMark hm(thread);
3940       (*unload_entry)(&main_vm);
3941     }
3942   }
3943 }
3944 
3945 // Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries
3946 // Invokes JVM_OnLoad
3947 void Threads::create_vm_init_libraries() {
3948   extern struct JavaVM_ main_vm;
3949   AgentLibrary* agent;
3950 
3951   for (agent = Arguments::libraries(); agent != NULL; agent = agent->next()) {
3952     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
3953 
3954     if (on_load_entry != NULL) {
3955       // Invoke the JVM_OnLoad function
3956       JavaThread* thread = JavaThread::current();
3957       ThreadToNativeFromVM ttn(thread);
3958       HandleMark hm(thread);
3959       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
3960       if (err != JNI_OK) {
3961         vm_exit_during_initialization("-Xrun library failed to init", agent->name());
3962       }
3963     } else {
3964       vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
3965     }
3966   }
3967 }
3968 
3969 JavaThread* Threads::find_java_thread_from_java_tid(jlong java_tid) {
3970   assert(Threads_lock->owned_by_self(), "Must hold Threads_lock");
3971 
3972   JavaThread* java_thread = NULL;
3973   // Sequential search for now.  Need to do better optimization later.
3974   for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) {
3975     oop tobj = thread->threadObj();
3976     if (!thread->is_exiting() &&
3977         tobj != NULL &&
3978         java_tid == java_lang_Thread::thread_id(tobj)) {
3979       java_thread = thread;
3980       break;
3981     }
3982   }
3983   return java_thread;
3984 }
3985 
3986 
3987 // Last thread running calls java.lang.Shutdown.shutdown()
3988 void JavaThread::invoke_shutdown_hooks() {
3989   HandleMark hm(this);
3990 
3991   // We could get here with a pending exception, if so clear it now.
3992   if (this->has_pending_exception()) {
3993     this->clear_pending_exception();
3994   }
3995 
3996   EXCEPTION_MARK;
3997   Klass* k =
3998     SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
3999                                       THREAD);
4000   if (k != NULL) {
4001     // SystemDictionary::resolve_or_null will return null if there was
4002     // an exception.  If we cannot load the Shutdown class, just don't
4003     // call Shutdown.shutdown() at all.  This will mean the shutdown hooks
4004     // and finalizers (if runFinalizersOnExit is set) won't be run.
4005     // Note that if a shutdown hook was registered or runFinalizersOnExit
4006     // was called, the Shutdown class would have already been loaded
4007     // (Runtime.addShutdownHook and runFinalizersOnExit will load it).
4008     instanceKlassHandle shutdown_klass (THREAD, k);
4009     JavaValue result(T_VOID);
4010     JavaCalls::call_static(&result,
4011                            shutdown_klass,
4012                            vmSymbols::shutdown_method_name(),
4013                            vmSymbols::void_method_signature(),
4014                            THREAD);
4015   }
4016   CLEAR_PENDING_EXCEPTION;
4017 }
4018 
4019 // Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
4020 // the program falls off the end of main(). Another VM exit path is through
4021 // vm_exit() when the program calls System.exit() to return a value or when
4022 // there is a serious error in VM. The two shutdown paths are not exactly
4023 // the same, but they share Shutdown.shutdown() at Java level and before_exit()
4024 // and VM_Exit op at VM level.
4025 //
4026 // Shutdown sequence:
4027 //   + Shutdown native memory tracking if it is on
4028 //   + Wait until we are the last non-daemon thread to execute
4029 //     <-- every thing is still working at this moment -->
4030 //   + Call java.lang.Shutdown.shutdown(), which will invoke Java level
4031 //        shutdown hooks, run finalizers if finalization-on-exit
4032 //   + Call before_exit(), prepare for VM exit
4033 //      > run VM level shutdown hooks (they are registered through JVM_OnExit(),
4034 //        currently the only user of this mechanism is File.deleteOnExit())
4035 //      > stop flat profiler, StatSampler, watcher thread, CMS threads,
4036 //        post thread end and vm death events to JVMTI,
4037 //        stop signal thread
4038 //   + Call JavaThread::exit(), it will:
4039 //      > release JNI handle blocks, remove stack guard pages
4040 //      > remove this thread from Threads list
4041 //     <-- no more Java code from this thread after this point -->
4042 //   + Stop VM thread, it will bring the remaining VM to a safepoint and stop
4043 //     the compiler threads at safepoint
4044 //     <-- do not use anything that could get blocked by Safepoint -->
4045 //   + Disable tracing at JNI/JVM barriers
4046 //   + Set _vm_exited flag for threads that are still running native code
4047 //   + Delete this thread
4048 //   + Call exit_globals()
4049 //      > deletes tty
4050 //      > deletes PerfMemory resources
4051 //   + Return to caller
4052 
4053 bool Threads::destroy_vm() {
4054   JavaThread* thread = JavaThread::current();
4055 
4056 #ifdef ASSERT
4057   _vm_complete = false;
4058 #endif
4059   // Wait until we are the last non-daemon thread to execute
4060   { MutexLocker nu(Threads_lock);
4061     while (Threads::number_of_non_daemon_threads() > 1 )
4062       // This wait should make safepoint checks, wait without a timeout,
4063       // and wait as a suspend-equivalent condition.
4064       //
4065       // Note: If the FlatProfiler is running and this thread is waiting
4066       // for another non-daemon thread to finish, then the FlatProfiler
4067       // is waiting for the external suspend request on this thread to
4068       // complete. wait_for_ext_suspend_completion() will eventually
4069       // timeout, but that takes time. Making this wait a suspend-
4070       // equivalent condition solves that timeout problem.
4071       //
4072       Threads_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
4073                          Mutex::_as_suspend_equivalent_flag);
4074   }
4075 
4076   // Hang forever on exit if we are reporting an error.
4077   if (ShowMessageBoxOnError && is_error_reported()) {
4078     os::infinite_sleep();
4079   }
4080   os::wait_for_keypress_at_exit();
4081 
4082   if (JDK_Version::is_jdk12x_version()) {
4083     // We are the last thread running, so check if finalizers should be run.
4084     // For 1.3 or later this is done in thread->invoke_shutdown_hooks()
4085     HandleMark rm(thread);
4086     Universe::run_finalizers_on_exit();
4087   } else {
4088     // run Java level shutdown hooks
4089     thread->invoke_shutdown_hooks();
4090   }
4091 
4092   before_exit(thread);
4093 
4094   thread->exit(true);
4095 
4096   // Stop VM thread.
4097   {
4098     // 4945125 The vm thread comes to a safepoint during exit.
4099     // GC vm_operations can get caught at the safepoint, and the
4100     // heap is unparseable if they are caught. Grab the Heap_lock
4101     // to prevent this. The GC vm_operations will not be able to
4102     // queue until after the vm thread is dead. After this point,
4103     // we'll never emerge out of the safepoint before the VM exits.
4104 
4105     MutexLocker ml(Heap_lock);
4106 
4107     VMThread::wait_for_vm_thread_exit();
4108     assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
4109     VMThread::destroy();
4110   }
4111 
4112   // clean up ideal graph printers
4113 #if defined(COMPILER2) && !defined(PRODUCT)
4114   IdealGraphPrinter::clean_up();
4115 #endif
4116 
4117   // Now, all Java threads are gone except daemon threads. Daemon threads
4118   // running Java code or in VM are stopped by the Safepoint. However,
4119   // daemon threads executing native code are still running.  But they
4120   // will be stopped at native=>Java/VM barriers. Note that we can't
4121   // simply kill or suspend them, as it is inherently deadlock-prone.
4122 
4123 #ifndef PRODUCT
4124   // disable function tracing at JNI/JVM barriers
4125   TraceJNICalls = false;
4126   TraceJVMCalls = false;
4127   TraceRuntimeCalls = false;
4128 #endif
4129 
4130   VM_Exit::set_vm_exited();
4131 
4132   notify_vm_shutdown();
4133 
4134   delete thread;
4135 
4136   // exit_globals() will delete tty
4137   exit_globals();
4138 
4139   return true;
4140 }
4141 
4142 
4143 jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
4144   if (version == JNI_VERSION_1_1) return JNI_TRUE;
4145   return is_supported_jni_version(version);
4146 }
4147 
4148 
4149 jboolean Threads::is_supported_jni_version(jint version) {
4150   if (version == JNI_VERSION_1_2) return JNI_TRUE;
4151   if (version == JNI_VERSION_1_4) return JNI_TRUE;
4152   if (version == JNI_VERSION_1_6) return JNI_TRUE;
4153   if (version == JNI_VERSION_1_8) return JNI_TRUE;
4154   return JNI_FALSE;
4155 }
4156 
4157 
4158 void Threads::add(JavaThread* p, bool force_daemon) {
4159   // The threads lock must be owned at this point
4160   assert_locked_or_safepoint(Threads_lock);
4161 
4162   // See the comment for this method in thread.hpp for its purpose and
4163   // why it is called here.
4164   p->initialize_queues();
4165   p->set_next(_thread_list);
4166   _thread_list = p;
4167   _number_of_threads++;
4168   oop threadObj = p->threadObj();
4169   bool daemon = true;
4170   // Bootstrapping problem: threadObj can be null for initial
4171   // JavaThread (or for threads attached via JNI)
4172   if ((!force_daemon) && (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj))) {
4173     _number_of_non_daemon_threads++;
4174     daemon = false;
4175   }
4176 
4177   ThreadService::add_thread(p, daemon);
4178 
4179   // Possible GC point.
4180   Events::log(p, "Thread added: " INTPTR_FORMAT, p);
4181 }
4182 
4183 void Threads::remove(JavaThread* p) {
4184   // Extra scope needed for Thread_lock, so we can check
4185   // that we do not remove thread without safepoint code notice
4186   { MutexLocker ml(Threads_lock);
4187 
4188     assert(includes(p), "p must be present");
4189 
4190     JavaThread* current = _thread_list;
4191     JavaThread* prev    = NULL;
4192 
4193     while (current != p) {
4194       prev    = current;
4195       current = current->next();
4196     }
4197 
4198     if (prev) {
4199       prev->set_next(current->next());
4200     } else {
4201       _thread_list = p->next();
4202     }
4203     _number_of_threads--;
4204     oop threadObj = p->threadObj();
4205     bool daemon = true;
4206     if (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj)) {
4207       _number_of_non_daemon_threads--;
4208       daemon = false;
4209 
4210       // Only one thread left, do a notify on the Threads_lock so a thread waiting
4211       // on destroy_vm will wake up.
4212       if (number_of_non_daemon_threads() == 1)
4213         Threads_lock->notify_all();
4214     }
4215     ThreadService::remove_thread(p, daemon);
4216 
4217     // Make sure that safepoint code disregard this thread. This is needed since
4218     // the thread might mess around with locks after this point. This can cause it
4219     // to do callbacks into the safepoint code. However, the safepoint code is not aware
4220     // of this thread since it is removed from the queue.
4221     p->set_terminated_value();
4222   } // unlock Threads_lock
4223 
4224   // Since Events::log uses a lock, we grab it outside the Threads_lock
4225   Events::log(p, "Thread exited: " INTPTR_FORMAT, p);
4226 }
4227 
4228 // Threads_lock must be held when this is called (or must be called during a safepoint)
4229 bool Threads::includes(JavaThread* p) {
4230   assert(Threads_lock->is_locked(), "sanity check");
4231   ALL_JAVA_THREADS(q) {
4232     if (q == p ) {
4233       return true;
4234     }
4235   }
4236   return false;
4237 }
4238 
4239 // Operations on the Threads list for GC.  These are not explicitly locked,
4240 // but the garbage collector must provide a safe context for them to run.
4241 // In particular, these things should never be called when the Threads_lock
4242 // is held by some other thread. (Note: the Safepoint abstraction also
4243 // uses the Threads_lock to gurantee this property. It also makes sure that
4244 // all threads gets blocked when exiting or starting).
4245 
4246 void Threads::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
4247   ALL_JAVA_THREADS(p) {
4248     p->oops_do(f, cld_f, cf);
4249   }
4250   VMThread::vm_thread()->oops_do(f, cld_f, cf);
4251 }
4252 
4253 void Threads::possibly_parallel_oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
4254   // Introduce a mechanism allowing parallel threads to claim threads as
4255   // root groups.  Overhead should be small enough to use all the time,
4256   // even in sequential code.
4257   SharedHeap* sh = SharedHeap::heap();
4258   // Cannot yet substitute active_workers for n_par_threads
4259   // because of G1CollectedHeap::verify() use of
4260   // SharedHeap::process_roots().  n_par_threads == 0 will
4261   // turn off parallelism in process_roots while active_workers
4262   // is being used for parallelism elsewhere.
4263   bool is_par = sh->n_par_threads() > 0;
4264   assert(!is_par ||
4265          (SharedHeap::heap()->n_par_threads() ==
4266           SharedHeap::heap()->workers()->active_workers()
4267           || UseShenandoahGC), "Mismatch");
4268   int cp = SharedHeap::heap()->strong_roots_parity();
4269   ALL_JAVA_THREADS(p) {
4270     if (p->claim_oops_do(is_par, cp)) {
4271       p->oops_do(f, cld_f, cf);
4272     }
4273   }
4274   VMThread* vmt = VMThread::vm_thread();
4275   if (vmt->claim_oops_do(is_par, cp)) {
4276     vmt->oops_do(f, cld_f, cf);
4277   }
4278 }
4279 
4280 #if INCLUDE_ALL_GCS
4281 // Used by ParallelScavenge
4282 void Threads::create_thread_roots_tasks(GCTaskQueue* q) {
4283   ALL_JAVA_THREADS(p) {
4284     q->enqueue(new ThreadRootsTask(p));
4285   }
4286   q->enqueue(new ThreadRootsTask(VMThread::vm_thread()));
4287 }
4288 
4289 // Used by Parallel Old
4290 void Threads::create_thread_roots_marking_tasks(GCTaskQueue* q) {
4291   ALL_JAVA_THREADS(p) {
4292     q->enqueue(new ThreadRootsMarkingTask(p));
4293   }
4294   q->enqueue(new ThreadRootsMarkingTask(VMThread::vm_thread()));
4295 }
4296 #endif // INCLUDE_ALL_GCS
4297 
4298 void Threads::nmethods_do(CodeBlobClosure* cf) {
4299   ALL_JAVA_THREADS(p) {
4300     p->nmethods_do(cf);
4301   }
4302   VMThread::vm_thread()->nmethods_do(cf);
4303 }
4304 
4305 void Threads::metadata_do(void f(Metadata*)) {
4306   ALL_JAVA_THREADS(p) {
4307     p->metadata_do(f);
4308   }
4309 }
4310 
4311 void Threads::gc_epilogue() {
4312   ALL_JAVA_THREADS(p) {
4313     p->gc_epilogue();
4314   }
4315 }
4316 
4317 void Threads::gc_prologue() {
4318   ALL_JAVA_THREADS(p) {
4319     p->gc_prologue();
4320   }
4321 }
4322 
4323 void Threads::deoptimized_wrt_marked_nmethods() {
4324   ALL_JAVA_THREADS(p) {
4325     p->deoptimized_wrt_marked_nmethods();
4326   }
4327 }
4328 
4329 
4330 // Get count Java threads that are waiting to enter the specified monitor.
4331 GrowableArray<JavaThread*>* Threads::get_pending_threads(int count,
4332   address monitor, bool doLock) {
4333   assert(doLock || SafepointSynchronize::is_at_safepoint(),
4334     "must grab Threads_lock or be at safepoint");
4335   GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
4336 
4337   int i = 0;
4338   {
4339     MutexLockerEx ml(doLock ? Threads_lock : NULL);
4340     ALL_JAVA_THREADS(p) {
4341       if (p->is_Compiler_thread()) continue;
4342 
4343       address pending = (address)p->current_pending_monitor();
4344       if (pending == monitor) {             // found a match
4345         if (i < count) result->append(p);   // save the first count matches
4346         i++;
4347       }
4348     }
4349   }
4350   return result;
4351 }
4352 
4353 
4354 JavaThread *Threads::owning_thread_from_monitor_owner(address owner, bool doLock) {
4355   assert(doLock ||
4356          Threads_lock->owned_by_self() ||
4357          SafepointSynchronize::is_at_safepoint(),
4358          "must grab Threads_lock or be at safepoint");
4359 
4360   // NULL owner means not locked so we can skip the search
4361   if (owner == NULL) return NULL;
4362 
4363   {
4364     MutexLockerEx ml(doLock ? Threads_lock : NULL);
4365     ALL_JAVA_THREADS(p) {
4366       // first, see if owner is the address of a Java thread
4367       if (owner == (address)p) return p;
4368     }
4369   }
4370   // Cannot assert on lack of success here since this function may be
4371   // used by code that is trying to report useful problem information
4372   // like deadlock detection.
4373   if (UseHeavyMonitors) return NULL;
4374 
4375   //
4376   // If we didn't find a matching Java thread and we didn't force use of
4377   // heavyweight monitors, then the owner is the stack address of the
4378   // Lock Word in the owning Java thread's stack.
4379   //
4380   JavaThread* the_owner = NULL;
4381   {
4382     MutexLockerEx ml(doLock ? Threads_lock : NULL);
4383     ALL_JAVA_THREADS(q) {
4384       if (q->is_lock_owned(owner)) {
4385         the_owner = q;
4386         break;
4387       }
4388     }
4389   }
4390   // cannot assert on lack of success here; see above comment
4391   return the_owner;
4392 }
4393 
4394 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
4395 void Threads::print_on(outputStream* st, bool print_stacks, bool internal_format, bool print_concurrent_locks) {
4396   char buf[32];
4397   st->print_cr("%s", os::local_time_string(buf, sizeof(buf)));
4398 
4399   st->print_cr("Full thread dump %s (%s %s):",
4400                 Abstract_VM_Version::vm_name(),
4401                 Abstract_VM_Version::vm_release(),
4402                 Abstract_VM_Version::vm_info_string()
4403                );
4404   st->cr();
4405 
4406 #if INCLUDE_ALL_GCS
4407   // Dump concurrent locks
4408   ConcurrentLocksDump concurrent_locks;
4409   if (print_concurrent_locks) {
4410     concurrent_locks.dump_at_safepoint();
4411   }
4412 #endif // INCLUDE_ALL_GCS
4413 
4414   ALL_JAVA_THREADS(p) {
4415     ResourceMark rm;
4416     p->print_on(st);
4417     if (print_stacks) {
4418       if (internal_format) {
4419         p->trace_stack();
4420       } else {
4421         p->print_stack_on(st);
4422       }
4423     }
4424     st->cr();
4425 #if INCLUDE_ALL_GCS
4426     if (print_concurrent_locks) {
4427       concurrent_locks.print_locks_on(p, st);
4428     }
4429 #endif // INCLUDE_ALL_GCS
4430   }
4431 
4432   VMThread::vm_thread()->print_on(st);
4433   st->cr();
4434   Universe::heap()->print_gc_threads_on(st);
4435   WatcherThread* wt = WatcherThread::watcher_thread();
4436   if (wt != NULL) {
4437     wt->print_on(st);
4438     st->cr();
4439   }
4440   CompileBroker::print_compiler_threads_on(st);
4441   st->flush();
4442 }
4443 
4444 // Threads::print_on_error() is called by fatal error handler. It's possible
4445 // that VM is not at safepoint and/or current thread is inside signal handler.
4446 // Don't print stack trace, as the stack may not be walkable. Don't allocate
4447 // memory (even in resource area), it might deadlock the error handler.
4448 void Threads::print_on_error(outputStream* st, Thread* current, char* buf, int buflen) {
4449   bool found_current = false;
4450   st->print_cr("Java Threads: ( => current thread )");
4451   ALL_JAVA_THREADS(thread) {
4452     bool is_current = (current == thread);
4453     found_current = found_current || is_current;
4454 
4455     st->print("%s", is_current ? "=>" : "  ");
4456 
4457     st->print(PTR_FORMAT, thread);
4458     st->print(" ");
4459     thread->print_on_error(st, buf, buflen);
4460     st->cr();
4461   }
4462   st->cr();
4463 
4464   st->print_cr("Other Threads:");
4465   if (VMThread::vm_thread()) {
4466     bool is_current = (current == VMThread::vm_thread());
4467     found_current = found_current || is_current;
4468     st->print("%s", current == VMThread::vm_thread() ? "=>" : "  ");
4469 
4470     st->print(PTR_FORMAT, VMThread::vm_thread());
4471     st->print(" ");
4472     VMThread::vm_thread()->print_on_error(st, buf, buflen);
4473     st->cr();
4474   }
4475   WatcherThread* wt = WatcherThread::watcher_thread();
4476   if (wt != NULL) {
4477     bool is_current = (current == wt);
4478     found_current = found_current || is_current;
4479     st->print("%s", is_current ? "=>" : "  ");
4480 
4481     st->print(PTR_FORMAT, wt);
4482     st->print(" ");
4483     wt->print_on_error(st, buf, buflen);
4484     st->cr();
4485   }
4486   if (!found_current) {
4487     st->cr();
4488     st->print("=>" PTR_FORMAT " (exited) ", current);
4489     current->print_on_error(st, buf, buflen);
4490     st->cr();
4491   }
4492 }
4493 
4494 // Internal SpinLock and Mutex
4495 // Based on ParkEvent
4496 
4497 // Ad-hoc mutual exclusion primitives: SpinLock and Mux
4498 //
4499 // We employ SpinLocks _only for low-contention, fixed-length
4500 // short-duration critical sections where we're concerned
4501 // about native mutex_t or HotSpot Mutex:: latency.
4502 // The mux construct provides a spin-then-block mutual exclusion
4503 // mechanism.
4504 //
4505 // Testing has shown that contention on the ListLock guarding gFreeList
4506 // is common.  If we implement ListLock as a simple SpinLock it's common
4507 // for the JVM to devolve to yielding with little progress.  This is true
4508 // despite the fact that the critical sections protected by ListLock are
4509 // extremely short.
4510 //
4511 // TODO-FIXME: ListLock should be of type SpinLock.
4512 // We should make this a 1st-class type, integrated into the lock
4513 // hierarchy as leaf-locks.  Critically, the SpinLock structure
4514 // should have sufficient padding to avoid false-sharing and excessive
4515 // cache-coherency traffic.
4516 
4517 
4518 typedef volatile int SpinLockT ;
4519 
4520 void Thread::SpinAcquire (volatile int * adr, const char * LockName) {
4521   if (Atomic::cmpxchg (1, adr, 0) == 0) {
4522      return ;   // normal fast-path return
4523   }
4524 
4525   // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
4526   TEVENT (SpinAcquire - ctx) ;
4527   int ctr = 0 ;
4528   int Yields = 0 ;
4529   for (;;) {
4530      while (*adr != 0) {
4531         ++ctr ;
4532         if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
4533            if (Yields > 5) {
4534              os::naked_short_sleep(1);
4535            } else {
4536              os::NakedYield() ;
4537              ++Yields ;
4538            }
4539         } else {
4540            SpinPause() ;
4541         }
4542      }
4543      if (Atomic::cmpxchg (1, adr, 0) == 0) return ;
4544   }
4545 }
4546 
4547 void Thread::SpinRelease (volatile int * adr) {
4548   assert (*adr != 0, "invariant") ;
4549   OrderAccess::fence() ;      // guarantee at least release consistency.
4550   // Roach-motel semantics.
4551   // It's safe if subsequent LDs and STs float "up" into the critical section,
4552   // but prior LDs and STs within the critical section can't be allowed
4553   // to reorder or float past the ST that releases the lock.
4554   *adr = 0 ;
4555 }
4556 
4557 // muxAcquire and muxRelease:
4558 //
4559 // *  muxAcquire and muxRelease support a single-word lock-word construct.
4560 //    The LSB of the word is set IFF the lock is held.
4561 //    The remainder of the word points to the head of a singly-linked list
4562 //    of threads blocked on the lock.
4563 //
4564 // *  The current implementation of muxAcquire-muxRelease uses its own
4565 //    dedicated Thread._MuxEvent instance.  If we're interested in
4566 //    minimizing the peak number of extant ParkEvent instances then
4567 //    we could eliminate _MuxEvent and "borrow" _ParkEvent as long
4568 //    as certain invariants were satisfied.  Specifically, care would need
4569 //    to be taken with regards to consuming unpark() "permits".
4570 //    A safe rule of thumb is that a thread would never call muxAcquire()
4571 //    if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
4572 //    park().  Otherwise the _ParkEvent park() operation in muxAcquire() could
4573 //    consume an unpark() permit intended for monitorenter, for instance.
4574 //    One way around this would be to widen the restricted-range semaphore
4575 //    implemented in park().  Another alternative would be to provide
4576 //    multiple instances of the PlatformEvent() for each thread.  One
4577 //    instance would be dedicated to muxAcquire-muxRelease, for instance.
4578 //
4579 // *  Usage:
4580 //    -- Only as leaf locks
4581 //    -- for short-term locking only as muxAcquire does not perform
4582 //       thread state transitions.
4583 //
4584 // Alternatives:
4585 // *  We could implement muxAcquire and muxRelease with MCS or CLH locks
4586 //    but with parking or spin-then-park instead of pure spinning.
4587 // *  Use Taura-Oyama-Yonenzawa locks.
4588 // *  It's possible to construct a 1-0 lock if we encode the lockword as
4589 //    (List,LockByte).  Acquire will CAS the full lockword while Release
4590 //    will STB 0 into the LockByte.  The 1-0 scheme admits stranding, so
4591 //    acquiring threads use timers (ParkTimed) to detect and recover from
4592 //    the stranding window.  Thread/Node structures must be aligned on 256-byte
4593 //    boundaries by using placement-new.
4594 // *  Augment MCS with advisory back-link fields maintained with CAS().
4595 //    Pictorially:  LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
4596 //    The validity of the backlinks must be ratified before we trust the value.
4597 //    If the backlinks are invalid the exiting thread must back-track through the
4598 //    the forward links, which are always trustworthy.
4599 // *  Add a successor indication.  The LockWord is currently encoded as
4600 //    (List, LOCKBIT:1).  We could also add a SUCCBIT or an explicit _succ variable
4601 //    to provide the usual futile-wakeup optimization.
4602 //    See RTStt for details.
4603 // *  Consider schedctl.sc_nopreempt to cover the critical section.
4604 //
4605 
4606 
4607 typedef volatile intptr_t MutexT ;      // Mux Lock-word
4608 enum MuxBits { LOCKBIT = 1 } ;
4609 
4610 void Thread::muxAcquire (volatile intptr_t * Lock, const char * LockName) {
4611   intptr_t w = Atomic::cmpxchg_ptr (LOCKBIT, Lock, 0) ;
4612   if (w == 0) return ;
4613   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4614      return ;
4615   }
4616 
4617   TEVENT (muxAcquire - Contention) ;
4618   ParkEvent * const Self = Thread::current()->_MuxEvent ;
4619   assert ((intptr_t(Self) & LOCKBIT) == 0, "invariant") ;
4620   for (;;) {
4621      int its = (os::is_MP() ? 100 : 0) + 1 ;
4622 
4623      // Optional spin phase: spin-then-park strategy
4624      while (--its >= 0) {
4625        w = *Lock ;
4626        if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4627           return ;
4628        }
4629      }
4630 
4631      Self->reset() ;
4632      Self->OnList = intptr_t(Lock) ;
4633      // The following fence() isn't _strictly necessary as the subsequent
4634      // CAS() both serializes execution and ratifies the fetched *Lock value.
4635      OrderAccess::fence();
4636      for (;;) {
4637         w = *Lock ;
4638         if ((w & LOCKBIT) == 0) {
4639             if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4640                 Self->OnList = 0 ;   // hygiene - allows stronger asserts
4641                 return ;
4642             }
4643             continue ;      // Interference -- *Lock changed -- Just retry
4644         }
4645         assert (w & LOCKBIT, "invariant") ;
4646         Self->ListNext = (ParkEvent *) (w & ~LOCKBIT );
4647         if (Atomic::cmpxchg_ptr (intptr_t(Self)|LOCKBIT, Lock, w) == w) break ;
4648      }
4649 
4650      while (Self->OnList != 0) {
4651         Self->park() ;
4652      }
4653   }
4654 }
4655 
4656 void Thread::muxAcquireW (volatile intptr_t * Lock, ParkEvent * ev) {
4657   intptr_t w = Atomic::cmpxchg_ptr (LOCKBIT, Lock, 0) ;
4658   if (w == 0) return ;
4659   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4660     return ;
4661   }
4662 
4663   TEVENT (muxAcquire - Contention) ;
4664   ParkEvent * ReleaseAfter = NULL ;
4665   if (ev == NULL) {
4666     ev = ReleaseAfter = ParkEvent::Allocate (NULL) ;
4667   }
4668   assert ((intptr_t(ev) & LOCKBIT) == 0, "invariant") ;
4669   for (;;) {
4670     guarantee (ev->OnList == 0, "invariant") ;
4671     int its = (os::is_MP() ? 100 : 0) + 1 ;
4672 
4673     // Optional spin phase: spin-then-park strategy
4674     while (--its >= 0) {
4675       w = *Lock ;
4676       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4677         if (ReleaseAfter != NULL) {
4678           ParkEvent::Release (ReleaseAfter) ;
4679         }
4680         return ;
4681       }
4682     }
4683 
4684     ev->reset() ;
4685     ev->OnList = intptr_t(Lock) ;
4686     // The following fence() isn't _strictly necessary as the subsequent
4687     // CAS() both serializes execution and ratifies the fetched *Lock value.
4688     OrderAccess::fence();
4689     for (;;) {
4690       w = *Lock ;
4691       if ((w & LOCKBIT) == 0) {
4692         if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4693           ev->OnList = 0 ;
4694           // We call ::Release while holding the outer lock, thus
4695           // artificially lengthening the critical section.
4696           // Consider deferring the ::Release() until the subsequent unlock(),
4697           // after we've dropped the outer lock.
4698           if (ReleaseAfter != NULL) {
4699             ParkEvent::Release (ReleaseAfter) ;
4700           }
4701           return ;
4702         }
4703         continue ;      // Interference -- *Lock changed -- Just retry
4704       }
4705       assert (w & LOCKBIT, "invariant") ;
4706       ev->ListNext = (ParkEvent *) (w & ~LOCKBIT );
4707       if (Atomic::cmpxchg_ptr (intptr_t(ev)|LOCKBIT, Lock, w) == w) break ;
4708     }
4709 
4710     while (ev->OnList != 0) {
4711       ev->park() ;
4712     }
4713   }
4714 }
4715 
4716 // Release() must extract a successor from the list and then wake that thread.
4717 // It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
4718 // similar to that used by ParkEvent::Allocate() and ::Release().  DMR-based
4719 // Release() would :
4720 // (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
4721 // (B) Extract a successor from the private list "in-hand"
4722 // (C) attempt to CAS() the residual back into *Lock over null.
4723 //     If there were any newly arrived threads and the CAS() would fail.
4724 //     In that case Release() would detach the RATs, re-merge the list in-hand
4725 //     with the RATs and repeat as needed.  Alternately, Release() might
4726 //     detach and extract a successor, but then pass the residual list to the wakee.
4727 //     The wakee would be responsible for reattaching and remerging before it
4728 //     competed for the lock.
4729 //
4730 // Both "pop" and DMR are immune from ABA corruption -- there can be
4731 // multiple concurrent pushers, but only one popper or detacher.
4732 // This implementation pops from the head of the list.  This is unfair,
4733 // but tends to provide excellent throughput as hot threads remain hot.
4734 // (We wake recently run threads first).
4735 
4736 void Thread::muxRelease (volatile intptr_t * Lock)  {
4737   for (;;) {
4738     const intptr_t w = Atomic::cmpxchg_ptr (0, Lock, LOCKBIT) ;
4739     assert (w & LOCKBIT, "invariant") ;
4740     if (w == LOCKBIT) return ;
4741     ParkEvent * List = (ParkEvent *) (w & ~LOCKBIT) ;
4742     assert (List != NULL, "invariant") ;
4743     assert (List->OnList == intptr_t(Lock), "invariant") ;
4744     ParkEvent * nxt = List->ListNext ;
4745 
4746     // The following CAS() releases the lock and pops the head element.
4747     if (Atomic::cmpxchg_ptr (intptr_t(nxt), Lock, w) != w) {
4748       continue ;
4749     }
4750     List->OnList = 0 ;
4751     OrderAccess::fence() ;
4752     List->unpark () ;
4753     return ;
4754   }
4755 }
4756 
4757 
4758 void Threads::verify() {
4759   ALL_JAVA_THREADS(p) {
4760     p->verify();
4761   }
4762   VMThread* thread = VMThread::vm_thread();
4763   if (thread != NULL) thread->verify();
4764 }