1 /*
   2  * Copyright (c) 1997, 2016, 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/codeCache.hpp"
  31 #include "code/codeCacheExtensions.hpp"
  32 #include "code/scopeDesc.hpp"
  33 #include "compiler/compileBroker.hpp"
  34 #include "compiler/compileTask.hpp"
  35 #include "gc/shared/gcId.hpp"
  36 #include "gc/shared/gcLocker.inline.hpp"
  37 #include "gc/shared/workgroup.hpp"
  38 #include "interpreter/interpreter.hpp"
  39 #include "interpreter/linkResolver.hpp"
  40 #include "interpreter/oopMapCache.hpp"
  41 #include "jvmtifiles/jvmtiEnv.hpp"
  42 #include "logging/log.hpp"
  43 #include "logging/logConfiguration.hpp"
  44 #include "memory/metaspaceShared.hpp"
  45 #include "memory/oopFactory.hpp"
  46 #include "memory/universe.inline.hpp"
  47 #include "oops/instanceKlass.hpp"
  48 #include "oops/objArrayOop.hpp"
  49 #include "oops/oop.inline.hpp"
  50 #include "oops/symbol.hpp"
  51 #include "oops/verifyOopClosure.hpp"
  52 #include "prims/jvm_misc.hpp"
  53 #include "prims/jvmtiExport.hpp"
  54 #include "prims/jvmtiThreadState.hpp"
  55 #include "prims/privilegedStack.hpp"
  56 #include "runtime/arguments.hpp"
  57 #include "runtime/atomic.inline.hpp"
  58 #include "runtime/biasedLocking.hpp"
  59 #include "runtime/commandLineFlagConstraintList.hpp"
  60 #include "runtime/commandLineFlagRangeList.hpp"
  61 #include "runtime/deoptimization.hpp"
  62 #include "runtime/fprofiler.hpp"
  63 #include "runtime/frame.inline.hpp"
  64 #include "runtime/globals.hpp"
  65 #include "runtime/init.hpp"
  66 #include "runtime/interfaceSupport.hpp"
  67 #include "runtime/java.hpp"
  68 #include "runtime/javaCalls.hpp"
  69 #include "runtime/jniPeriodicChecker.hpp"
  70 #include "runtime/logTimer.hpp"
  71 #include "runtime/memprofiler.hpp"
  72 #include "runtime/mutexLocker.hpp"
  73 #include "runtime/objectMonitor.hpp"
  74 #include "runtime/orderAccess.inline.hpp"
  75 #include "runtime/osThread.hpp"
  76 #include "runtime/safepoint.hpp"
  77 #include "runtime/sharedRuntime.hpp"
  78 #include "runtime/statSampler.hpp"
  79 #include "runtime/stubRoutines.hpp"
  80 #include "runtime/sweeper.hpp"
  81 #include "runtime/task.hpp"
  82 #include "runtime/thread.inline.hpp"
  83 #include "runtime/threadCritical.hpp"
  84 #include "runtime/vframe.hpp"
  85 #include "runtime/vframeArray.hpp"
  86 #include "runtime/vframe_hp.hpp"
  87 #include "runtime/vmThread.hpp"
  88 #include "runtime/vm_operations.hpp"
  89 #include "runtime/vm_version.hpp"
  90 #include "services/attachListener.hpp"
  91 #include "services/management.hpp"
  92 #include "services/memTracker.hpp"
  93 #include "services/threadService.hpp"
  94 #include "trace/traceMacros.hpp"
  95 #include "trace/tracing.hpp"
  96 #include "utilities/defaultStream.hpp"
  97 #include "utilities/dtrace.hpp"
  98 #include "utilities/events.hpp"
  99 #include "utilities/macros.hpp"
 100 #include "utilities/preserveException.hpp"
 101 #if INCLUDE_ALL_GCS
 102 #include "gc/cms/concurrentMarkSweepThread.hpp"
 103 #include "gc/g1/concurrentMarkThread.inline.hpp"
 104 #include "gc/parallel/pcTasks.hpp"
 105 #endif // INCLUDE_ALL_GCS
 106 #if INCLUDE_JVMCI
 107 #include "jvmci/jvmciCompiler.hpp"
 108 #include "jvmci/jvmciRuntime.hpp"
 109 #endif
 110 #ifdef COMPILER1
 111 #include "c1/c1_Compiler.hpp"
 112 #endif
 113 #ifdef COMPILER2
 114 #include "opto/c2compiler.hpp"
 115 #include "opto/idealGraphPrinter.hpp"
 116 #endif
 117 #if INCLUDE_RTM_OPT
 118 #include "runtime/rtmLocking.hpp"
 119 #endif
 120 
 121 #ifdef DTRACE_ENABLED
 122 
 123 // Only bother with this argument setup if dtrace is available
 124 
 125   #define HOTSPOT_THREAD_PROBE_start HOTSPOT_THREAD_START
 126   #define HOTSPOT_THREAD_PROBE_stop HOTSPOT_THREAD_STOP
 127 
 128   #define DTRACE_THREAD_PROBE(probe, javathread)                           \
 129     {                                                                      \
 130       ResourceMark rm(this);                                               \
 131       int len = 0;                                                         \
 132       const char* name = (javathread)->get_thread_name();                  \
 133       len = strlen(name);                                                  \
 134       HOTSPOT_THREAD_PROBE_##probe(/* probe = start, stop */               \
 135         (char *) name, len,                                                \
 136         java_lang_Thread::thread_id((javathread)->threadObj()),            \
 137         (uintptr_t) (javathread)->osthread()->thread_id(),                 \
 138         java_lang_Thread::is_daemon((javathread)->threadObj()));           \
 139     }
 140 
 141 #else //  ndef DTRACE_ENABLED
 142 
 143   #define DTRACE_THREAD_PROBE(probe, javathread)
 144 
 145 #endif // ndef DTRACE_ENABLED
 146 
 147 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 148 // Current thread is maintained as a thread-local variable
 149 THREAD_LOCAL_DECL Thread* Thread::_thr_current = NULL;
 150 #endif
 151 
 152 // Class hierarchy
 153 // - Thread
 154 //   - VMThread
 155 //   - WatcherThread
 156 //   - ConcurrentMarkSweepThread
 157 //   - JavaThread
 158 //     - CompilerThread
 159 
 160 // ======= Thread ========
 161 // Support for forcing alignment of thread objects for biased locking
 162 void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
 163   if (UseBiasedLocking) {
 164     const int alignment = markOopDesc::biased_lock_alignment;
 165     size_t aligned_size = size + (alignment - sizeof(intptr_t));
 166     void* real_malloc_addr = throw_excpt? AllocateHeap(aligned_size, flags, CURRENT_PC)
 167                                           : AllocateHeap(aligned_size, flags, CURRENT_PC,
 168                                                          AllocFailStrategy::RETURN_NULL);
 169     void* aligned_addr     = (void*) align_size_up((intptr_t) real_malloc_addr, alignment);
 170     assert(((uintptr_t) aligned_addr + (uintptr_t) size) <=
 171            ((uintptr_t) real_malloc_addr + (uintptr_t) aligned_size),
 172            "JavaThread alignment code overflowed allocated storage");
 173     if (aligned_addr != real_malloc_addr) {
 174       log_info(biasedlocking)("Aligned thread " INTPTR_FORMAT " to " INTPTR_FORMAT,
 175                               p2i(real_malloc_addr),
 176                               p2i(aligned_addr));
 177     }
 178     ((Thread*) aligned_addr)->_real_malloc_address = real_malloc_addr;
 179     return aligned_addr;
 180   } else {
 181     return throw_excpt? AllocateHeap(size, flags, CURRENT_PC)
 182                        : AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
 183   }
 184 }
 185 
 186 void Thread::operator delete(void* p) {
 187   if (UseBiasedLocking) {
 188     void* real_malloc_addr = ((Thread*) p)->_real_malloc_address;
 189     FreeHeap(real_malloc_addr);
 190   } else {
 191     FreeHeap(p);
 192   }
 193 }
 194 
 195 
 196 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
 197 // JavaThread
 198 
 199 
 200 Thread::Thread() {
 201   // stack and get_thread
 202   set_stack_base(NULL);
 203   set_stack_size(0);
 204   set_self_raw_id(0);
 205   set_lgrp_id(-1);
 206   DEBUG_ONLY(clear_suspendible_thread();)
 207 
 208   // allocated data structures
 209   set_osthread(NULL);
 210   set_resource_area(new (mtThread)ResourceArea());
 211   DEBUG_ONLY(_current_resource_mark = NULL;)
 212   set_handle_area(new (mtThread) HandleArea(NULL));
 213   set_metadata_handles(new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(30, true));
 214   set_active_handles(NULL);
 215   set_free_handle_block(NULL);
 216   set_last_handle_mark(NULL);
 217 
 218   // This initial value ==> never claimed.
 219   _oops_do_parity = 0;
 220 
 221   // the handle mark links itself to last_handle_mark
 222   new HandleMark(this);
 223 
 224   // plain initialization
 225   debug_only(_owned_locks = NULL;)
 226   debug_only(_allow_allocation_count = 0;)
 227   NOT_PRODUCT(_allow_safepoint_count = 0;)
 228   NOT_PRODUCT(_skip_gcalot = false;)
 229   _jvmti_env_iteration_count = 0;
 230   set_allocated_bytes(0);
 231   _vm_operation_started_count = 0;
 232   _vm_operation_completed_count = 0;
 233   _current_pending_monitor = NULL;
 234   _current_pending_monitor_is_from_java = true;
 235   _current_waiting_monitor = NULL;
 236   _num_nested_signal = 0;
 237   omFreeList = NULL;
 238   omFreeCount = 0;
 239   omFreeProvision = 32;
 240   omInUseList = NULL;
 241   omInUseCount = 0;
 242 
 243 #ifdef ASSERT
 244   _visited_for_critical_count = false;
 245 #endif
 246 
 247   _SR_lock = new Monitor(Mutex::suspend_resume, "SR_lock", true,
 248                          Monitor::_safepoint_check_sometimes);
 249   _suspend_flags = 0;
 250 
 251   // thread-specific hashCode stream generator state - Marsaglia shift-xor form
 252   _hashStateX = os::random();
 253   _hashStateY = 842502087;
 254   _hashStateZ = 0x8767;    // (int)(3579807591LL & 0xffff) ;
 255   _hashStateW = 273326509;
 256 
 257   _OnTrap   = 0;
 258   _schedctl = NULL;
 259   _Stalled  = 0;
 260   _TypeTag  = 0x2BAD;
 261 
 262   // Many of the following fields are effectively final - immutable
 263   // Note that nascent threads can't use the Native Monitor-Mutex
 264   // construct until the _MutexEvent is initialized ...
 265   // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
 266   // we might instead use a stack of ParkEvents that we could provision on-demand.
 267   // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
 268   // and ::Release()
 269   _ParkEvent   = ParkEvent::Allocate(this);
 270   _SleepEvent  = ParkEvent::Allocate(this);
 271   _MutexEvent  = ParkEvent::Allocate(this);
 272   _MuxEvent    = ParkEvent::Allocate(this);
 273 
 274 #ifdef CHECK_UNHANDLED_OOPS
 275   if (CheckUnhandledOops) {
 276     _unhandled_oops = new UnhandledOops(this);
 277   }
 278 #endif // CHECK_UNHANDLED_OOPS
 279 #ifdef ASSERT
 280   if (UseBiasedLocking) {
 281     assert((((uintptr_t) this) & (markOopDesc::biased_lock_alignment - 1)) == 0, "forced alignment of thread object failed");
 282     assert(this == _real_malloc_address ||
 283            this == (void*) align_size_up((intptr_t) _real_malloc_address, markOopDesc::biased_lock_alignment),
 284            "bug in forced alignment of thread objects");
 285   }
 286 #endif // ASSERT
 287 }
 288 
 289 void Thread::initialize_thread_current() {
 290 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 291   assert(_thr_current == NULL, "Thread::current already initialized");
 292   _thr_current = this;
 293 #endif
 294   assert(ThreadLocalStorage::thread() == NULL, "ThreadLocalStorage::thread already initialized");
 295   ThreadLocalStorage::set_thread(this);
 296   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 297 }
 298 
 299 void Thread::clear_thread_current() {
 300   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 301 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 302   _thr_current = NULL;
 303 #endif
 304   ThreadLocalStorage::set_thread(NULL);
 305 }
 306 
 307 void Thread::record_stack_base_and_size() {
 308   set_stack_base(os::current_stack_base());
 309   set_stack_size(os::current_stack_size());
 310   // CR 7190089: on Solaris, primordial thread's stack is adjusted
 311   // in initialize_thread(). Without the adjustment, stack size is
 312   // incorrect if stack is set to unlimited (ulimit -s unlimited).
 313   // So far, only Solaris has real implementation of initialize_thread().
 314   //
 315   // set up any platform-specific state.
 316   os::initialize_thread(this);
 317 
 318   // Set stack limits after thread is initialized.
 319   if (is_Java_thread()) {
 320     ((JavaThread*) this)->set_stack_overflow_limit();
 321     ((JavaThread*) this)->set_reserved_stack_activation(stack_base());
 322   }
 323 #if INCLUDE_NMT
 324   // record thread's native stack, stack grows downward
 325   MemTracker::record_thread_stack(stack_end(), stack_size());
 326 #endif // INCLUDE_NMT
 327   log_debug(os, thread)("Thread " UINTX_FORMAT " stack dimensions: "
 328     PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT "k).",
 329     os::current_thread_id(), p2i(stack_base() - stack_size()),
 330     p2i(stack_base()), stack_size()/1024);
 331 }
 332 
 333 
 334 Thread::~Thread() {
 335   // Reclaim the objectmonitors from the omFreeList of the moribund thread.
 336   ObjectSynchronizer::omFlush(this);
 337 
 338   EVENT_THREAD_DESTRUCT(this);
 339 
 340   // stack_base can be NULL if the thread is never started or exited before
 341   // record_stack_base_and_size called. Although, we would like to ensure
 342   // that all started threads do call record_stack_base_and_size(), there is
 343   // not proper way to enforce that.
 344 #if INCLUDE_NMT
 345   if (_stack_base != NULL) {
 346     MemTracker::release_thread_stack(stack_end(), stack_size());
 347 #ifdef ASSERT
 348     set_stack_base(NULL);
 349 #endif
 350   }
 351 #endif // INCLUDE_NMT
 352 
 353   // deallocate data structures
 354   delete resource_area();
 355   // since the handle marks are using the handle area, we have to deallocated the root
 356   // handle mark before deallocating the thread's handle area,
 357   assert(last_handle_mark() != NULL, "check we have an element");
 358   delete last_handle_mark();
 359   assert(last_handle_mark() == NULL, "check we have reached the end");
 360 
 361   // It's possible we can encounter a null _ParkEvent, etc., in stillborn threads.
 362   // We NULL out the fields for good hygiene.
 363   ParkEvent::Release(_ParkEvent); _ParkEvent   = NULL;
 364   ParkEvent::Release(_SleepEvent); _SleepEvent  = NULL;
 365   ParkEvent::Release(_MutexEvent); _MutexEvent  = NULL;
 366   ParkEvent::Release(_MuxEvent); _MuxEvent    = NULL;
 367 
 368   delete handle_area();
 369   delete metadata_handles();
 370 
 371   // osthread() can be NULL, if creation of thread failed.
 372   if (osthread() != NULL) os::free_thread(osthread());
 373 
 374   delete _SR_lock;
 375 
 376   // clear Thread::current if thread is deleting itself.
 377   // Needed to ensure JNI correctly detects non-attached threads.
 378   if (this == Thread::current()) {
 379     clear_thread_current();
 380   }
 381 
 382   CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
 383 }
 384 
 385 // NOTE: dummy function for assertion purpose.
 386 void Thread::run() {
 387   ShouldNotReachHere();
 388 }
 389 
 390 #ifdef ASSERT
 391 // Private method to check for dangling thread pointer
 392 void check_for_dangling_thread_pointer(Thread *thread) {
 393   assert(!thread->is_Java_thread() || Thread::current() == thread || Threads_lock->owned_by_self(),
 394          "possibility of dangling Thread pointer");
 395 }
 396 #endif
 397 
 398 ThreadPriority Thread::get_priority(const Thread* const thread) {
 399   ThreadPriority priority;
 400   // Can return an error!
 401   (void)os::get_priority(thread, priority);
 402   assert(MinPriority <= priority && priority <= MaxPriority, "non-Java priority found");
 403   return priority;
 404 }
 405 
 406 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
 407   debug_only(check_for_dangling_thread_pointer(thread);)
 408   // Can return an error!
 409   (void)os::set_priority(thread, priority);
 410 }
 411 
 412 
 413 void Thread::start(Thread* thread) {
 414   // Start is different from resume in that its safety is guaranteed by context or
 415   // being called from a Java method synchronized on the Thread object.
 416   if (!DisableStartThread) {
 417     if (thread->is_Java_thread()) {
 418       // Initialize the thread state to RUNNABLE before starting this thread.
 419       // Can not set it after the thread started because we do not know the
 420       // exact thread state at that time. It could be in MONITOR_WAIT or
 421       // in SLEEPING or some other state.
 422       java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
 423                                           java_lang_Thread::RUNNABLE);
 424     }
 425     os::start_thread(thread);
 426   }
 427 }
 428 
 429 // Enqueue a VM_Operation to do the job for us - sometime later
 430 void Thread::send_async_exception(oop java_thread, oop java_throwable) {
 431   VM_ThreadStop* vm_stop = new VM_ThreadStop(java_thread, java_throwable);
 432   VMThread::execute(vm_stop);
 433 }
 434 
 435 
 436 // Check if an external suspend request has completed (or has been
 437 // cancelled). Returns true if the thread is externally suspended and
 438 // false otherwise.
 439 //
 440 // The bits parameter returns information about the code path through
 441 // the routine. Useful for debugging:
 442 //
 443 // set in is_ext_suspend_completed():
 444 // 0x00000001 - routine was entered
 445 // 0x00000010 - routine return false at end
 446 // 0x00000100 - thread exited (return false)
 447 // 0x00000200 - suspend request cancelled (return false)
 448 // 0x00000400 - thread suspended (return true)
 449 // 0x00001000 - thread is in a suspend equivalent state (return true)
 450 // 0x00002000 - thread is native and walkable (return true)
 451 // 0x00004000 - thread is native_trans and walkable (needed retry)
 452 //
 453 // set in wait_for_ext_suspend_completion():
 454 // 0x00010000 - routine was entered
 455 // 0x00020000 - suspend request cancelled before loop (return false)
 456 // 0x00040000 - thread suspended before loop (return true)
 457 // 0x00080000 - suspend request cancelled in loop (return false)
 458 // 0x00100000 - thread suspended in loop (return true)
 459 // 0x00200000 - suspend not completed during retry loop (return false)
 460 
 461 // Helper class for tracing suspend wait debug bits.
 462 //
 463 // 0x00000100 indicates that the target thread exited before it could
 464 // self-suspend which is not a wait failure. 0x00000200, 0x00020000 and
 465 // 0x00080000 each indicate a cancelled suspend request so they don't
 466 // count as wait failures either.
 467 #define DEBUG_FALSE_BITS (0x00000010 | 0x00200000)
 468 
 469 class TraceSuspendDebugBits : public StackObj {
 470  private:
 471   JavaThread * jt;
 472   bool         is_wait;
 473   bool         called_by_wait;  // meaningful when !is_wait
 474   uint32_t *   bits;
 475 
 476  public:
 477   TraceSuspendDebugBits(JavaThread *_jt, bool _is_wait, bool _called_by_wait,
 478                         uint32_t *_bits) {
 479     jt             = _jt;
 480     is_wait        = _is_wait;
 481     called_by_wait = _called_by_wait;
 482     bits           = _bits;
 483   }
 484 
 485   ~TraceSuspendDebugBits() {
 486     if (!is_wait) {
 487 #if 1
 488       // By default, don't trace bits for is_ext_suspend_completed() calls.
 489       // That trace is very chatty.
 490       return;
 491 #else
 492       if (!called_by_wait) {
 493         // If tracing for is_ext_suspend_completed() is enabled, then only
 494         // trace calls to it from wait_for_ext_suspend_completion()
 495         return;
 496       }
 497 #endif
 498     }
 499 
 500     if (AssertOnSuspendWaitFailure || TraceSuspendWaitFailures) {
 501       if (bits != NULL && (*bits & DEBUG_FALSE_BITS) != 0) {
 502         MutexLocker ml(Threads_lock);  // needed for get_thread_name()
 503         ResourceMark rm;
 504 
 505         tty->print_cr(
 506                       "Failed wait_for_ext_suspend_completion(thread=%s, debug_bits=%x)",
 507                       jt->get_thread_name(), *bits);
 508 
 509         guarantee(!AssertOnSuspendWaitFailure, "external suspend wait failed");
 510       }
 511     }
 512   }
 513 };
 514 #undef DEBUG_FALSE_BITS
 515 
 516 
 517 bool JavaThread::is_ext_suspend_completed(bool called_by_wait, int delay,
 518                                           uint32_t *bits) {
 519   TraceSuspendDebugBits tsdb(this, false /* !is_wait */, called_by_wait, bits);
 520 
 521   bool did_trans_retry = false;  // only do thread_in_native_trans retry once
 522   bool do_trans_retry;           // flag to force the retry
 523 
 524   *bits |= 0x00000001;
 525 
 526   do {
 527     do_trans_retry = false;
 528 
 529     if (is_exiting()) {
 530       // Thread is in the process of exiting. This is always checked
 531       // first to reduce the risk of dereferencing a freed JavaThread.
 532       *bits |= 0x00000100;
 533       return false;
 534     }
 535 
 536     if (!is_external_suspend()) {
 537       // Suspend request is cancelled. This is always checked before
 538       // is_ext_suspended() to reduce the risk of a rogue resume
 539       // confusing the thread that made the suspend request.
 540       *bits |= 0x00000200;
 541       return false;
 542     }
 543 
 544     if (is_ext_suspended()) {
 545       // thread is suspended
 546       *bits |= 0x00000400;
 547       return true;
 548     }
 549 
 550     // Now that we no longer do hard suspends of threads running
 551     // native code, the target thread can be changing thread state
 552     // while we are in this routine:
 553     //
 554     //   _thread_in_native -> _thread_in_native_trans -> _thread_blocked
 555     //
 556     // We save a copy of the thread state as observed at this moment
 557     // and make our decision about suspend completeness based on the
 558     // copy. This closes the race where the thread state is seen as
 559     // _thread_in_native_trans in the if-thread_blocked check, but is
 560     // seen as _thread_blocked in if-thread_in_native_trans check.
 561     JavaThreadState save_state = thread_state();
 562 
 563     if (save_state == _thread_blocked && is_suspend_equivalent()) {
 564       // If the thread's state is _thread_blocked and this blocking
 565       // condition is known to be equivalent to a suspend, then we can
 566       // consider the thread to be externally suspended. This means that
 567       // the code that sets _thread_blocked has been modified to do
 568       // self-suspension if the blocking condition releases. We also
 569       // used to check for CONDVAR_WAIT here, but that is now covered by
 570       // the _thread_blocked with self-suspension check.
 571       //
 572       // Return true since we wouldn't be here unless there was still an
 573       // external suspend request.
 574       *bits |= 0x00001000;
 575       return true;
 576     } else if (save_state == _thread_in_native && frame_anchor()->walkable()) {
 577       // Threads running native code will self-suspend on native==>VM/Java
 578       // transitions. If its stack is walkable (should always be the case
 579       // unless this function is called before the actual java_suspend()
 580       // call), then the wait is done.
 581       *bits |= 0x00002000;
 582       return true;
 583     } else if (!called_by_wait && !did_trans_retry &&
 584                save_state == _thread_in_native_trans &&
 585                frame_anchor()->walkable()) {
 586       // The thread is transitioning from thread_in_native to another
 587       // thread state. check_safepoint_and_suspend_for_native_trans()
 588       // will force the thread to self-suspend. If it hasn't gotten
 589       // there yet we may have caught the thread in-between the native
 590       // code check above and the self-suspend. Lucky us. If we were
 591       // called by wait_for_ext_suspend_completion(), then it
 592       // will be doing the retries so we don't have to.
 593       //
 594       // Since we use the saved thread state in the if-statement above,
 595       // there is a chance that the thread has already transitioned to
 596       // _thread_blocked by the time we get here. In that case, we will
 597       // make a single unnecessary pass through the logic below. This
 598       // doesn't hurt anything since we still do the trans retry.
 599 
 600       *bits |= 0x00004000;
 601 
 602       // Once the thread leaves thread_in_native_trans for another
 603       // thread state, we break out of this retry loop. We shouldn't
 604       // need this flag to prevent us from getting back here, but
 605       // sometimes paranoia is good.
 606       did_trans_retry = true;
 607 
 608       // We wait for the thread to transition to a more usable state.
 609       for (int i = 1; i <= SuspendRetryCount; i++) {
 610         // We used to do an "os::yield_all(i)" call here with the intention
 611         // that yielding would increase on each retry. However, the parameter
 612         // is ignored on Linux which means the yield didn't scale up. Waiting
 613         // on the SR_lock below provides a much more predictable scale up for
 614         // the delay. It also provides a simple/direct point to check for any
 615         // safepoint requests from the VMThread
 616 
 617         // temporarily drops SR_lock while doing wait with safepoint check
 618         // (if we're a JavaThread - the WatcherThread can also call this)
 619         // and increase delay with each retry
 620         SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 621 
 622         // check the actual thread state instead of what we saved above
 623         if (thread_state() != _thread_in_native_trans) {
 624           // the thread has transitioned to another thread state so
 625           // try all the checks (except this one) one more time.
 626           do_trans_retry = true;
 627           break;
 628         }
 629       } // end retry loop
 630 
 631 
 632     }
 633   } while (do_trans_retry);
 634 
 635   *bits |= 0x00000010;
 636   return false;
 637 }
 638 
 639 // Wait for an external suspend request to complete (or be cancelled).
 640 // Returns true if the thread is externally suspended and false otherwise.
 641 //
 642 bool JavaThread::wait_for_ext_suspend_completion(int retries, int delay,
 643                                                  uint32_t *bits) {
 644   TraceSuspendDebugBits tsdb(this, true /* is_wait */,
 645                              false /* !called_by_wait */, bits);
 646 
 647   // local flag copies to minimize SR_lock hold time
 648   bool is_suspended;
 649   bool pending;
 650   uint32_t reset_bits;
 651 
 652   // set a marker so is_ext_suspend_completed() knows we are the caller
 653   *bits |= 0x00010000;
 654 
 655   // We use reset_bits to reinitialize the bits value at the top of
 656   // each retry loop. This allows the caller to make use of any
 657   // unused bits for their own marking purposes.
 658   reset_bits = *bits;
 659 
 660   {
 661     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 662     is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 663                                             delay, bits);
 664     pending = is_external_suspend();
 665   }
 666   // must release SR_lock to allow suspension to complete
 667 
 668   if (!pending) {
 669     // A cancelled suspend request is the only false return from
 670     // is_ext_suspend_completed() that keeps us from entering the
 671     // retry loop.
 672     *bits |= 0x00020000;
 673     return false;
 674   }
 675 
 676   if (is_suspended) {
 677     *bits |= 0x00040000;
 678     return true;
 679   }
 680 
 681   for (int i = 1; i <= retries; i++) {
 682     *bits = reset_bits;  // reinit to only track last retry
 683 
 684     // We used to do an "os::yield_all(i)" call here with the intention
 685     // that yielding would increase on each retry. However, the parameter
 686     // is ignored on Linux which means the yield didn't scale up. Waiting
 687     // on the SR_lock below provides a much more predictable scale up for
 688     // the delay. It also provides a simple/direct point to check for any
 689     // safepoint requests from the VMThread
 690 
 691     {
 692       MutexLocker ml(SR_lock());
 693       // wait with safepoint check (if we're a JavaThread - the WatcherThread
 694       // can also call this)  and increase delay with each retry
 695       SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 696 
 697       is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 698                                               delay, bits);
 699 
 700       // It is possible for the external suspend request to be cancelled
 701       // (by a resume) before the actual suspend operation is completed.
 702       // Refresh our local copy to see if we still need to wait.
 703       pending = is_external_suspend();
 704     }
 705 
 706     if (!pending) {
 707       // A cancelled suspend request is the only false return from
 708       // is_ext_suspend_completed() that keeps us from staying in the
 709       // retry loop.
 710       *bits |= 0x00080000;
 711       return false;
 712     }
 713 
 714     if (is_suspended) {
 715       *bits |= 0x00100000;
 716       return true;
 717     }
 718   } // end retry loop
 719 
 720   // thread did not suspend after all our retries
 721   *bits |= 0x00200000;
 722   return false;
 723 }
 724 
 725 #ifndef PRODUCT
 726 void JavaThread::record_jump(address target, address instr, const char* file,
 727                              int line) {
 728 
 729   // This should not need to be atomic as the only way for simultaneous
 730   // updates is via interrupts. Even then this should be rare or non-existent
 731   // and we don't care that much anyway.
 732 
 733   int index = _jmp_ring_index;
 734   _jmp_ring_index = (index + 1) & (jump_ring_buffer_size - 1);
 735   _jmp_ring[index]._target = (intptr_t) target;
 736   _jmp_ring[index]._instruction = (intptr_t) instr;
 737   _jmp_ring[index]._file = file;
 738   _jmp_ring[index]._line = line;
 739 }
 740 #endif // PRODUCT
 741 
 742 // Called by flat profiler
 743 // Callers have already called wait_for_ext_suspend_completion
 744 // The assertion for that is currently too complex to put here:
 745 bool JavaThread::profile_last_Java_frame(frame* _fr) {
 746   bool gotframe = false;
 747   // self suspension saves needed state.
 748   if (has_last_Java_frame() && _anchor.walkable()) {
 749     *_fr = pd_last_frame();
 750     gotframe = true;
 751   }
 752   return gotframe;
 753 }
 754 
 755 void Thread::interrupt(Thread* thread) {
 756   debug_only(check_for_dangling_thread_pointer(thread);)
 757   os::interrupt(thread);
 758 }
 759 
 760 bool Thread::is_interrupted(Thread* thread, bool clear_interrupted) {
 761   debug_only(check_for_dangling_thread_pointer(thread);)
 762   // Note:  If clear_interrupted==false, this simply fetches and
 763   // returns the value of the field osthread()->interrupted().
 764   return os::is_interrupted(thread, clear_interrupted);
 765 }
 766 
 767 
 768 // GC Support
 769 bool Thread::claim_oops_do_par_case(int strong_roots_parity) {
 770   jint thread_parity = _oops_do_parity;
 771   if (thread_parity != strong_roots_parity) {
 772     jint res = Atomic::cmpxchg(strong_roots_parity, &_oops_do_parity, thread_parity);
 773     if (res == thread_parity) {
 774       return true;
 775     } else {
 776       guarantee(res == strong_roots_parity, "Or else what?");
 777       return false;
 778     }
 779   }
 780   return false;
 781 }
 782 
 783 void Thread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
 784   active_handles()->oops_do(f);
 785   // Do oop for ThreadShadow
 786   f->do_oop((oop*)&_pending_exception);
 787   handle_area()->oops_do(f);
 788 }
 789 
 790 void Thread::nmethods_do(CodeBlobClosure* cf) {
 791   // no nmethods in a generic thread...
 792 }
 793 
 794 void Thread::metadata_handles_do(void f(Metadata*)) {
 795   // Only walk the Handles in Thread.
 796   if (metadata_handles() != NULL) {
 797     for (int i = 0; i< metadata_handles()->length(); i++) {
 798       f(metadata_handles()->at(i));
 799     }
 800   }
 801 }
 802 
 803 void Thread::print_on(outputStream* st) const {
 804   // get_priority assumes osthread initialized
 805   if (osthread() != NULL) {
 806     int os_prio;
 807     if (os::get_native_priority(this, &os_prio) == OS_OK) {
 808       st->print("os_prio=%d ", os_prio);
 809     }
 810     st->print("tid=" INTPTR_FORMAT " ", p2i(this));
 811     ext().print_on(st);
 812     osthread()->print_on(st);
 813   }
 814   debug_only(if (WizardMode) print_owned_locks_on(st);)
 815 }
 816 
 817 // Thread::print_on_error() is called by fatal error handler. Don't use
 818 // any lock or allocate memory.
 819 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
 820   if (is_VM_thread())                 st->print("VMThread");
 821   else if (is_Compiler_thread())      st->print("CompilerThread");
 822   else if (is_Java_thread())          st->print("JavaThread");
 823   else if (is_GC_task_thread())       st->print("GCTaskThread");
 824   else if (is_Watcher_thread())       st->print("WatcherThread");
 825   else if (is_ConcurrentGC_thread())  st->print("ConcurrentGCThread");
 826   else                                st->print("Thread");
 827 
 828   st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
 829             p2i(stack_end()), p2i(stack_base()));
 830 
 831   if (osthread()) {
 832     st->print(" [id=%d]", osthread()->thread_id());
 833   }
 834 }
 835 
 836 #ifdef ASSERT
 837 void Thread::print_owned_locks_on(outputStream* st) const {
 838   Monitor *cur = _owned_locks;
 839   if (cur == NULL) {
 840     st->print(" (no locks) ");
 841   } else {
 842     st->print_cr(" Locks owned:");
 843     while (cur) {
 844       cur->print_on(st);
 845       cur = cur->next();
 846     }
 847   }
 848 }
 849 
 850 static int ref_use_count  = 0;
 851 
 852 bool Thread::owns_locks_but_compiled_lock() const {
 853   for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 854     if (cur != Compile_lock) return true;
 855   }
 856   return false;
 857 }
 858 
 859 
 860 #endif
 861 
 862 #ifndef PRODUCT
 863 
 864 // The flag: potential_vm_operation notifies if this particular safepoint state could potential
 865 // invoke the vm-thread (i.e., and oop allocation). In that case, we also have to make sure that
 866 // no threads which allow_vm_block's are held
 867 void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) {
 868   // Check if current thread is allowed to block at a safepoint
 869   if (!(_allow_safepoint_count == 0)) {
 870     fatal("Possible safepoint reached by thread that does not allow it");
 871   }
 872   if (is_Java_thread() && ((JavaThread*)this)->thread_state() != _thread_in_vm) {
 873     fatal("LEAF method calling lock?");
 874   }
 875 
 876 #ifdef ASSERT
 877   if (potential_vm_operation && is_Java_thread()
 878       && !Universe::is_bootstrapping()) {
 879     // Make sure we do not hold any locks that the VM thread also uses.
 880     // This could potentially lead to deadlocks
 881     for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 882       // Threads_lock is special, since the safepoint synchronization will not start before this is
 883       // acquired. Hence, a JavaThread cannot be holding it at a safepoint. So is VMOperationRequest_lock,
 884       // since it is used to transfer control between JavaThreads and the VMThread
 885       // Do not *exclude* any locks unless you are absolutely sure it is correct. Ask someone else first!
 886       if ((cur->allow_vm_block() &&
 887            cur != Threads_lock &&
 888            cur != Compile_lock &&               // Temporary: should not be necessary when we get separate compilation
 889            cur != VMOperationRequest_lock &&
 890            cur != VMOperationQueue_lock) ||
 891            cur->rank() == Mutex::special) {
 892         fatal("Thread holding lock at safepoint that vm can block on: %s", cur->name());
 893       }
 894     }
 895   }
 896 
 897   if (GCALotAtAllSafepoints) {
 898     // We could enter a safepoint here and thus have a gc
 899     InterfaceSupport::check_gc_alot();
 900   }
 901 #endif
 902 }
 903 #endif
 904 
 905 bool Thread::is_in_stack(address adr) const {
 906   assert(Thread::current() == this, "is_in_stack can only be called from current thread");
 907   address end = os::current_stack_pointer();
 908   // Allow non Java threads to call this without stack_base
 909   if (_stack_base == NULL) return true;
 910   if (stack_base() >= adr && adr >= end) return true;
 911 
 912   return false;
 913 }
 914 
 915 bool Thread::is_in_usable_stack(address adr) const {
 916   size_t stack_guard_size = os::uses_stack_guard_pages() ? JavaThread::stack_guard_zone_size() : 0;
 917   size_t usable_stack_size = _stack_size - stack_guard_size;
 918 
 919   return ((adr < stack_base()) && (adr >= stack_base() - usable_stack_size));
 920 }
 921 
 922 
 923 // We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
 924 // However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
 925 // used for compilation in the future. If that change is made, the need for these methods
 926 // should be revisited, and they should be removed if possible.
 927 
 928 bool Thread::is_lock_owned(address adr) const {
 929   return on_local_stack(adr);
 930 }
 931 
 932 bool Thread::set_as_starting_thread() {
 933   // NOTE: this must be called inside the main thread.
 934   return os::create_main_thread((JavaThread*)this);
 935 }
 936 
 937 static void initialize_class(Symbol* class_name, TRAPS) {
 938   Klass* klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
 939   InstanceKlass::cast(klass)->initialize(CHECK);
 940 }
 941 
 942 
 943 // Creates the initial ThreadGroup
 944 static Handle create_initial_thread_group(TRAPS) {
 945   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_ThreadGroup(), true, CHECK_NH);
 946   instanceKlassHandle klass (THREAD, k);
 947 
 948   Handle system_instance = klass->allocate_instance_handle(CHECK_NH);
 949   {
 950     JavaValue result(T_VOID);
 951     JavaCalls::call_special(&result,
 952                             system_instance,
 953                             klass,
 954                             vmSymbols::object_initializer_name(),
 955                             vmSymbols::void_method_signature(),
 956                             CHECK_NH);
 957   }
 958   Universe::set_system_thread_group(system_instance());
 959 
 960   Handle main_instance = klass->allocate_instance_handle(CHECK_NH);
 961   {
 962     JavaValue result(T_VOID);
 963     Handle string = java_lang_String::create_from_str("main", CHECK_NH);
 964     JavaCalls::call_special(&result,
 965                             main_instance,
 966                             klass,
 967                             vmSymbols::object_initializer_name(),
 968                             vmSymbols::threadgroup_string_void_signature(),
 969                             system_instance,
 970                             string,
 971                             CHECK_NH);
 972   }
 973   return main_instance;
 974 }
 975 
 976 // Creates the initial Thread
 977 static oop create_initial_thread(Handle thread_group, JavaThread* thread,
 978                                  TRAPS) {
 979   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK_NULL);
 980   instanceKlassHandle klass (THREAD, k);
 981   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK_NULL);
 982 
 983   java_lang_Thread::set_thread(thread_oop(), thread);
 984   java_lang_Thread::set_priority(thread_oop(), NormPriority);
 985   thread->set_threadObj(thread_oop());
 986 
 987   Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
 988 
 989   JavaValue result(T_VOID);
 990   JavaCalls::call_special(&result, thread_oop,
 991                           klass,
 992                           vmSymbols::object_initializer_name(),
 993                           vmSymbols::threadgroup_string_void_signature(),
 994                           thread_group,
 995                           string,
 996                           CHECK_NULL);
 997   return thread_oop();
 998 }
 999 
1000 static void call_initializeSystemClass(TRAPS) {
1001   Klass* k =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
1002   instanceKlassHandle klass (THREAD, k);
1003 
1004   JavaValue result(T_VOID);
1005   JavaCalls::call_static(&result, klass, vmSymbols::initializeSystemClass_name(),
1006                          vmSymbols::void_method_signature(), CHECK);
1007 }
1008 
1009 char java_runtime_name[128] = "";
1010 char java_runtime_version[128] = "";
1011 
1012 // extract the JRE name from java.lang.VersionProps.java_runtime_name
1013 static const char* get_java_runtime_name(TRAPS) {
1014   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1015                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1016   fieldDescriptor fd;
1017   bool found = k != NULL &&
1018                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_name_name(),
1019                                                         vmSymbols::string_signature(), &fd);
1020   if (found) {
1021     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1022     if (name_oop == NULL) {
1023       return NULL;
1024     }
1025     const char* name = java_lang_String::as_utf8_string(name_oop,
1026                                                         java_runtime_name,
1027                                                         sizeof(java_runtime_name));
1028     return name;
1029   } else {
1030     return NULL;
1031   }
1032 }
1033 
1034 // extract the JRE version from java.lang.VersionProps.java_runtime_version
1035 static const char* get_java_runtime_version(TRAPS) {
1036   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1037                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1038   fieldDescriptor fd;
1039   bool found = k != NULL &&
1040                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_version_name(),
1041                                                         vmSymbols::string_signature(), &fd);
1042   if (found) {
1043     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1044     if (name_oop == NULL) {
1045       return NULL;
1046     }
1047     const char* name = java_lang_String::as_utf8_string(name_oop,
1048                                                         java_runtime_version,
1049                                                         sizeof(java_runtime_version));
1050     return name;
1051   } else {
1052     return NULL;
1053   }
1054 }
1055 
1056 // General purpose hook into Java code, run once when the VM is initialized.
1057 // The Java library method itself may be changed independently from the VM.
1058 static void call_postVMInitHook(TRAPS) {
1059   Klass* k = SystemDictionary::resolve_or_null(vmSymbols::sun_misc_PostVMInitHook(), THREAD);
1060   instanceKlassHandle klass (THREAD, k);
1061   if (klass.not_null()) {
1062     JavaValue result(T_VOID);
1063     JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
1064                            vmSymbols::void_method_signature(),
1065                            CHECK);
1066   }
1067 }
1068 
1069 static void reset_vm_info_property(TRAPS) {
1070   // the vm info string
1071   ResourceMark rm(THREAD);
1072   const char *vm_info = VM_Version::vm_info_string();
1073 
1074   // java.lang.System class
1075   Klass* k =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
1076   instanceKlassHandle klass (THREAD, k);
1077 
1078   // setProperty arguments
1079   Handle key_str    = java_lang_String::create_from_str("java.vm.info", CHECK);
1080   Handle value_str  = java_lang_String::create_from_str(vm_info, CHECK);
1081 
1082   // return value
1083   JavaValue r(T_OBJECT);
1084 
1085   // public static String setProperty(String key, String value);
1086   JavaCalls::call_static(&r,
1087                          klass,
1088                          vmSymbols::setProperty_name(),
1089                          vmSymbols::string_string_string_signature(),
1090                          key_str,
1091                          value_str,
1092                          CHECK);
1093 }
1094 
1095 
1096 void JavaThread::allocate_threadObj(Handle thread_group, const char* thread_name,
1097                                     bool daemon, TRAPS) {
1098   assert(thread_group.not_null(), "thread group should be specified");
1099   assert(threadObj() == NULL, "should only create Java thread object once");
1100 
1101   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK);
1102   instanceKlassHandle klass (THREAD, k);
1103   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);
1104 
1105   java_lang_Thread::set_thread(thread_oop(), this);
1106   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1107   set_threadObj(thread_oop());
1108 
1109   JavaValue result(T_VOID);
1110   if (thread_name != NULL) {
1111     Handle name = java_lang_String::create_from_str(thread_name, CHECK);
1112     // Thread gets assigned specified name and null target
1113     JavaCalls::call_special(&result,
1114                             thread_oop,
1115                             klass,
1116                             vmSymbols::object_initializer_name(),
1117                             vmSymbols::threadgroup_string_void_signature(),
1118                             thread_group, // Argument 1
1119                             name,         // Argument 2
1120                             THREAD);
1121   } else {
1122     // Thread gets assigned name "Thread-nnn" and null target
1123     // (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
1124     JavaCalls::call_special(&result,
1125                             thread_oop,
1126                             klass,
1127                             vmSymbols::object_initializer_name(),
1128                             vmSymbols::threadgroup_runnable_void_signature(),
1129                             thread_group, // Argument 1
1130                             Handle(),     // Argument 2
1131                             THREAD);
1132   }
1133 
1134 
1135   if (daemon) {
1136     java_lang_Thread::set_daemon(thread_oop());
1137   }
1138 
1139   if (HAS_PENDING_EXCEPTION) {
1140     return;
1141   }
1142 
1143   KlassHandle group(THREAD, SystemDictionary::ThreadGroup_klass());
1144   Handle threadObj(THREAD, this->threadObj());
1145 
1146   JavaCalls::call_special(&result,
1147                           thread_group,
1148                           group,
1149                           vmSymbols::add_method_name(),
1150                           vmSymbols::thread_void_signature(),
1151                           threadObj,          // Arg 1
1152                           THREAD);
1153 }
1154 
1155 // NamedThread --  non-JavaThread subclasses with multiple
1156 // uniquely named instances should derive from this.
1157 NamedThread::NamedThread() : Thread() {
1158   _name = NULL;
1159   _processed_thread = NULL;
1160   _gc_id = GCId::undefined();
1161 }
1162 
1163 NamedThread::~NamedThread() {
1164   if (_name != NULL) {
1165     FREE_C_HEAP_ARRAY(char, _name);
1166     _name = NULL;
1167   }
1168 }
1169 
1170 void NamedThread::set_name(const char* format, ...) {
1171   guarantee(_name == NULL, "Only get to set name once.");
1172   _name = NEW_C_HEAP_ARRAY(char, max_name_len, mtThread);
1173   guarantee(_name != NULL, "alloc failure");
1174   va_list ap;
1175   va_start(ap, format);
1176   jio_vsnprintf(_name, max_name_len, format, ap);
1177   va_end(ap);
1178 }
1179 
1180 void NamedThread::initialize_named_thread() {
1181   set_native_thread_name(name());
1182 }
1183 
1184 void NamedThread::print_on(outputStream* st) const {
1185   st->print("\"%s\" ", name());
1186   Thread::print_on(st);
1187   st->cr();
1188 }
1189 
1190 
1191 // ======= WatcherThread ========
1192 
1193 // The watcher thread exists to simulate timer interrupts.  It should
1194 // be replaced by an abstraction over whatever native support for
1195 // timer interrupts exists on the platform.
1196 
1197 WatcherThread* WatcherThread::_watcher_thread   = NULL;
1198 bool WatcherThread::_startable = false;
1199 volatile bool  WatcherThread::_should_terminate = false;
1200 
1201 WatcherThread::WatcherThread() : Thread(), _crash_protection(NULL) {
1202   assert(watcher_thread() == NULL, "we can only allocate one WatcherThread");
1203   if (os::create_thread(this, os::watcher_thread)) {
1204     _watcher_thread = this;
1205 
1206     // Set the watcher thread to the highest OS priority which should not be
1207     // used, unless a Java thread with priority java.lang.Thread.MAX_PRIORITY
1208     // is created. The only normal thread using this priority is the reference
1209     // handler thread, which runs for very short intervals only.
1210     // If the VMThread's priority is not lower than the WatcherThread profiling
1211     // will be inaccurate.
1212     os::set_priority(this, MaxPriority);
1213     if (!DisableStartThread) {
1214       os::start_thread(this);
1215     }
1216   }
1217 }
1218 
1219 int WatcherThread::sleep() const {
1220   // The WatcherThread does not participate in the safepoint protocol
1221   // for the PeriodicTask_lock because it is not a JavaThread.
1222   MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
1223 
1224   if (_should_terminate) {
1225     // check for termination before we do any housekeeping or wait
1226     return 0;  // we did not sleep.
1227   }
1228 
1229   // remaining will be zero if there are no tasks,
1230   // causing the WatcherThread to sleep until a task is
1231   // enrolled
1232   int remaining = PeriodicTask::time_to_wait();
1233   int time_slept = 0;
1234 
1235   // we expect this to timeout - we only ever get unparked when
1236   // we should terminate or when a new task has been enrolled
1237   OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
1238 
1239   jlong time_before_loop = os::javaTimeNanos();
1240 
1241   while (true) {
1242     bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag,
1243                                             remaining);
1244     jlong now = os::javaTimeNanos();
1245 
1246     if (remaining == 0) {
1247       // if we didn't have any tasks we could have waited for a long time
1248       // consider the time_slept zero and reset time_before_loop
1249       time_slept = 0;
1250       time_before_loop = now;
1251     } else {
1252       // need to recalculate since we might have new tasks in _tasks
1253       time_slept = (int) ((now - time_before_loop) / 1000000);
1254     }
1255 
1256     // Change to task list or spurious wakeup of some kind
1257     if (timedout || _should_terminate) {
1258       break;
1259     }
1260 
1261     remaining = PeriodicTask::time_to_wait();
1262     if (remaining == 0) {
1263       // Last task was just disenrolled so loop around and wait until
1264       // another task gets enrolled
1265       continue;
1266     }
1267 
1268     remaining -= time_slept;
1269     if (remaining <= 0) {
1270       break;
1271     }
1272   }
1273 
1274   return time_slept;
1275 }
1276 
1277 void WatcherThread::run() {
1278   assert(this == watcher_thread(), "just checking");
1279 
1280   this->record_stack_base_and_size();
1281   this->set_native_thread_name(this->name());
1282   this->set_active_handles(JNIHandleBlock::allocate_block());
1283   while (true) {
1284     assert(watcher_thread() == Thread::current(), "thread consistency check");
1285     assert(watcher_thread() == this, "thread consistency check");
1286 
1287     // Calculate how long it'll be until the next PeriodicTask work
1288     // should be done, and sleep that amount of time.
1289     int time_waited = sleep();
1290 
1291     if (is_error_reported()) {
1292       // A fatal error has happened, the error handler(VMError::report_and_die)
1293       // should abort JVM after creating an error log file. However in some
1294       // rare cases, the error handler itself might deadlock. Here we try to
1295       // kill JVM if the fatal error handler fails to abort in 2 minutes.
1296       //
1297       // This code is in WatcherThread because WatcherThread wakes up
1298       // periodically so the fatal error handler doesn't need to do anything;
1299       // also because the WatcherThread is less likely to crash than other
1300       // threads.
1301 
1302       for (;;) {
1303         if (!ShowMessageBoxOnError
1304             && (OnError == NULL || OnError[0] == '\0')
1305             && Arguments::abort_hook() == NULL) {
1306           os::sleep(this, (jlong)ErrorLogTimeout * 1000, false); // in seconds
1307           fdStream err(defaultStream::output_fd());
1308           err.print_raw_cr("# [ timer expired, abort... ]");
1309           // skip atexit/vm_exit/vm_abort hooks
1310           os::die();
1311         }
1312 
1313         // Wake up 5 seconds later, the fatal handler may reset OnError or
1314         // ShowMessageBoxOnError when it is ready to abort.
1315         os::sleep(this, 5 * 1000, false);
1316       }
1317     }
1318 
1319     if (_should_terminate) {
1320       // check for termination before posting the next tick
1321       break;
1322     }
1323 
1324     PeriodicTask::real_time_tick(time_waited);
1325   }
1326 
1327   // Signal that it is terminated
1328   {
1329     MutexLockerEx mu(Terminator_lock, Mutex::_no_safepoint_check_flag);
1330     _watcher_thread = NULL;
1331     Terminator_lock->notify();
1332   }
1333 }
1334 
1335 void WatcherThread::start() {
1336   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1337 
1338   if (watcher_thread() == NULL && _startable) {
1339     _should_terminate = false;
1340     // Create the single instance of WatcherThread
1341     new WatcherThread();
1342   }
1343 }
1344 
1345 void WatcherThread::make_startable() {
1346   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1347   _startable = true;
1348 }
1349 
1350 void WatcherThread::stop() {
1351   {
1352     // Follow normal safepoint aware lock enter protocol since the
1353     // WatcherThread is stopped by another JavaThread.
1354     MutexLocker ml(PeriodicTask_lock);
1355     _should_terminate = true;
1356 
1357     WatcherThread* watcher = watcher_thread();
1358     if (watcher != NULL) {
1359       // unpark the WatcherThread so it can see that it should terminate
1360       watcher->unpark();
1361     }
1362   }
1363 
1364   MutexLocker mu(Terminator_lock);
1365 
1366   while (watcher_thread() != NULL) {
1367     // This wait should make safepoint checks, wait without a timeout,
1368     // and wait as a suspend-equivalent condition.
1369     //
1370     // Note: If the FlatProfiler is running, then this thread is waiting
1371     // for the WatcherThread to terminate and the WatcherThread, via the
1372     // FlatProfiler task, is waiting for the external suspend request on
1373     // this thread to complete. wait_for_ext_suspend_completion() will
1374     // eventually timeout, but that takes time. Making this wait a
1375     // suspend-equivalent condition solves that timeout problem.
1376     //
1377     Terminator_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
1378                           Mutex::_as_suspend_equivalent_flag);
1379   }
1380 }
1381 
1382 void WatcherThread::unpark() {
1383   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1384   PeriodicTask_lock->notify();
1385 }
1386 
1387 void WatcherThread::print_on(outputStream* st) const {
1388   st->print("\"%s\" ", name());
1389   Thread::print_on(st);
1390   st->cr();
1391 }
1392 
1393 // ======= JavaThread ========
1394 
1395 #if INCLUDE_JVMCI
1396 
1397 jlong* JavaThread::_jvmci_old_thread_counters;
1398 
1399 bool jvmci_counters_include(JavaThread* thread) {
1400   oop threadObj = thread->threadObj();
1401   return !JVMCICountersExcludeCompiler || !thread->is_Compiler_thread();
1402 }
1403 
1404 void JavaThread::collect_counters(typeArrayOop array) {
1405   if (JVMCICounterSize > 0) {
1406     MutexLocker tl(Threads_lock);
1407     for (int i = 0; i < array->length(); i++) {
1408       array->long_at_put(i, _jvmci_old_thread_counters[i]);
1409     }
1410     for (JavaThread* tp = Threads::first(); tp != NULL; tp = tp->next()) {
1411       if (jvmci_counters_include(tp)) {
1412         for (int i = 0; i < array->length(); i++) {
1413           array->long_at_put(i, array->long_at(i) + tp->_jvmci_counters[i]);
1414         }
1415       }
1416     }
1417   }
1418 }
1419 
1420 #endif // INCLUDE_JVMCI
1421 
1422 // A JavaThread is a normal Java thread
1423 
1424 void JavaThread::initialize() {
1425   // Initialize fields
1426 
1427   set_saved_exception_pc(NULL);
1428   set_threadObj(NULL);
1429   _anchor.clear();
1430   set_entry_point(NULL);
1431   set_jni_functions(jni_functions());
1432   set_callee_target(NULL);
1433   set_vm_result(NULL);
1434   set_vm_result_2(NULL);
1435   set_vframe_array_head(NULL);
1436   set_vframe_array_last(NULL);
1437   set_deferred_locals(NULL);
1438   set_deopt_mark(NULL);
1439   set_deopt_nmethod(NULL);
1440   clear_must_deopt_id();
1441   set_monitor_chunks(NULL);
1442   set_next(NULL);
1443   set_thread_state(_thread_new);
1444   _terminated = _not_terminated;
1445   _privileged_stack_top = NULL;
1446   _array_for_gc = NULL;
1447   _suspend_equivalent = false;
1448   _in_deopt_handler = 0;
1449   _doing_unsafe_access = false;
1450   _stack_guard_state = stack_guard_unused;
1451 #if INCLUDE_JVMCI
1452   _pending_monitorenter = false;
1453   _pending_deoptimization = -1;
1454   _pending_failed_speculation = NULL;
1455   _pending_transfer_to_interpreter = false;
1456   _jvmci._alternate_call_target = NULL;
1457   assert(_jvmci._implicit_exception_pc == NULL, "must be");
1458   if (JVMCICounterSize > 0) {
1459     _jvmci_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
1460     memset(_jvmci_counters, 0, sizeof(jlong) * JVMCICounterSize);
1461   } else {
1462     _jvmci_counters = NULL;
1463   }
1464 #endif // INCLUDE_JVMCI
1465   _reserved_stack_activation = NULL;  // stack base not known yet
1466   (void)const_cast<oop&>(_exception_oop = oop(NULL));
1467   _exception_pc  = 0;
1468   _exception_handler_pc = 0;
1469   _is_method_handle_return = 0;
1470   _jvmti_thread_state= NULL;
1471   _should_post_on_exceptions_flag = JNI_FALSE;
1472   _jvmti_get_loaded_classes_closure = NULL;
1473   _interp_only_mode    = 0;
1474   _special_runtime_exit_condition = _no_async_condition;
1475   _pending_async_exception = NULL;
1476   _thread_stat = NULL;
1477   _thread_stat = new ThreadStatistics();
1478   _blocked_on_compilation = false;
1479   _jni_active_critical = 0;
1480   _pending_jni_exception_check_fn = NULL;
1481   _do_not_unlock_if_synchronized = false;
1482   _cached_monitor_info = NULL;
1483   _parker = Parker::Allocate(this);
1484 
1485 #ifndef PRODUCT
1486   _jmp_ring_index = 0;
1487   for (int ji = 0; ji < jump_ring_buffer_size; ji++) {
1488     record_jump(NULL, NULL, NULL, 0);
1489   }
1490 #endif // PRODUCT
1491 
1492   set_thread_profiler(NULL);
1493   if (FlatProfiler::is_active()) {
1494     // This is where we would decide to either give each thread it's own profiler
1495     // or use one global one from FlatProfiler,
1496     // or up to some count of the number of profiled threads, etc.
1497     ThreadProfiler* pp = new ThreadProfiler();
1498     pp->engage();
1499     set_thread_profiler(pp);
1500   }
1501 
1502   // Setup safepoint state info for this thread
1503   ThreadSafepointState::create(this);
1504 
1505   debug_only(_java_call_counter = 0);
1506 
1507   // JVMTI PopFrame support
1508   _popframe_condition = popframe_inactive;
1509   _popframe_preserved_args = NULL;
1510   _popframe_preserved_args_size = 0;
1511   _frames_to_pop_failed_realloc = 0;
1512 
1513   pd_initialize();
1514 }
1515 
1516 #if INCLUDE_ALL_GCS
1517 SATBMarkQueueSet JavaThread::_satb_mark_queue_set;
1518 DirtyCardQueueSet JavaThread::_dirty_card_queue_set;
1519 #endif // INCLUDE_ALL_GCS
1520 
1521 JavaThread::JavaThread(bool is_attaching_via_jni) :
1522                        Thread()
1523 #if INCLUDE_ALL_GCS
1524                        , _satb_mark_queue(&_satb_mark_queue_set),
1525                        _dirty_card_queue(&_dirty_card_queue_set)
1526 #endif // INCLUDE_ALL_GCS
1527 {
1528   initialize();
1529   if (is_attaching_via_jni) {
1530     _jni_attach_state = _attaching_via_jni;
1531   } else {
1532     _jni_attach_state = _not_attaching_via_jni;
1533   }
1534   assert(deferred_card_mark().is_empty(), "Default MemRegion ctor");
1535 }
1536 
1537 bool JavaThread::reguard_stack(address cur_sp) {
1538   if (_stack_guard_state != stack_guard_yellow_reserved_disabled
1539       && _stack_guard_state != stack_guard_reserved_disabled) {
1540     return true; // Stack already guarded or guard pages not needed.
1541   }
1542 
1543   if (register_stack_overflow()) {
1544     // For those architectures which have separate register and
1545     // memory stacks, we must check the register stack to see if
1546     // it has overflowed.
1547     return false;
1548   }
1549 
1550   // Java code never executes within the yellow zone: the latter is only
1551   // there to provoke an exception during stack banging.  If java code
1552   // is executing there, either StackShadowPages should be larger, or
1553   // some exception code in c1, c2 or the interpreter isn't unwinding
1554   // when it should.
1555   guarantee(cur_sp > stack_reserved_zone_base(),
1556             "not enough space to reguard - increase StackShadowPages");
1557   if (_stack_guard_state == stack_guard_yellow_reserved_disabled) {
1558     enable_stack_yellow_reserved_zone();
1559     if (reserved_stack_activation() != stack_base()) {
1560       set_reserved_stack_activation(stack_base());
1561     }
1562   } else if (_stack_guard_state == stack_guard_reserved_disabled) {
1563     set_reserved_stack_activation(stack_base());
1564     enable_stack_reserved_zone();
1565   }
1566   return true;
1567 }
1568 
1569 bool JavaThread::reguard_stack(void) {
1570   return reguard_stack(os::current_stack_pointer());
1571 }
1572 
1573 
1574 void JavaThread::block_if_vm_exited() {
1575   if (_terminated == _vm_exited) {
1576     // _vm_exited is set at safepoint, and Threads_lock is never released
1577     // we will block here forever
1578     Threads_lock->lock_without_safepoint_check();
1579     ShouldNotReachHere();
1580   }
1581 }
1582 
1583 
1584 // Remove this ifdef when C1 is ported to the compiler interface.
1585 static void compiler_thread_entry(JavaThread* thread, TRAPS);
1586 static void sweeper_thread_entry(JavaThread* thread, TRAPS);
1587 
1588 JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
1589                        Thread()
1590 #if INCLUDE_ALL_GCS
1591                        , _satb_mark_queue(&_satb_mark_queue_set),
1592                        _dirty_card_queue(&_dirty_card_queue_set)
1593 #endif // INCLUDE_ALL_GCS
1594 {
1595   initialize();
1596   _jni_attach_state = _not_attaching_via_jni;
1597   set_entry_point(entry_point);
1598   // Create the native thread itself.
1599   // %note runtime_23
1600   os::ThreadType thr_type = os::java_thread;
1601   thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
1602                                                      os::java_thread;
1603   os::create_thread(this, thr_type, stack_sz);
1604   // The _osthread may be NULL here because we ran out of memory (too many threads active).
1605   // We need to throw and OutOfMemoryError - however we cannot do this here because the caller
1606   // may hold a lock and all locks must be unlocked before throwing the exception (throwing
1607   // the exception consists of creating the exception object & initializing it, initialization
1608   // will leave the VM via a JavaCall and then all locks must be unlocked).
1609   //
1610   // The thread is still suspended when we reach here. Thread must be explicit started
1611   // by creator! Furthermore, the thread must also explicitly be added to the Threads list
1612   // by calling Threads:add. The reason why this is not done here, is because the thread
1613   // object must be fully initialized (take a look at JVM_Start)
1614 }
1615 
1616 JavaThread::~JavaThread() {
1617 
1618   // JSR166 -- return the parker to the free list
1619   Parker::Release(_parker);
1620   _parker = NULL;
1621 
1622   // Free any remaining  previous UnrollBlock
1623   vframeArray* old_array = vframe_array_last();
1624 
1625   if (old_array != NULL) {
1626     Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
1627     old_array->set_unroll_block(NULL);
1628     delete old_info;
1629     delete old_array;
1630   }
1631 
1632   GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred = deferred_locals();
1633   if (deferred != NULL) {
1634     // This can only happen if thread is destroyed before deoptimization occurs.
1635     assert(deferred->length() != 0, "empty array!");
1636     do {
1637       jvmtiDeferredLocalVariableSet* dlv = deferred->at(0);
1638       deferred->remove_at(0);
1639       // individual jvmtiDeferredLocalVariableSet are CHeapObj's
1640       delete dlv;
1641     } while (deferred->length() != 0);
1642     delete deferred;
1643   }
1644 
1645   // All Java related clean up happens in exit
1646   ThreadSafepointState::destroy(this);
1647   if (_thread_profiler != NULL) delete _thread_profiler;
1648   if (_thread_stat != NULL) delete _thread_stat;
1649 
1650 #if INCLUDE_JVMCI
1651   if (JVMCICounterSize > 0) {
1652     if (jvmci_counters_include(this)) {
1653       for (int i = 0; i < JVMCICounterSize; i++) {
1654         _jvmci_old_thread_counters[i] += _jvmci_counters[i];
1655       }
1656     }
1657     FREE_C_HEAP_ARRAY(jlong, _jvmci_counters);
1658   }
1659 #endif // INCLUDE_JVMCI
1660 }
1661 
1662 
1663 // The first routine called by a new Java thread
1664 void JavaThread::run() {
1665   // initialize thread-local alloc buffer related fields
1666   this->initialize_tlab();
1667 
1668   // used to test validity of stack trace backs
1669   this->record_base_of_stack_pointer();
1670 
1671   // Record real stack base and size.
1672   this->record_stack_base_and_size();
1673 
1674   this->create_stack_guard_pages();
1675 
1676   this->cache_global_variables();
1677 
1678   // Thread is now sufficient initialized to be handled by the safepoint code as being
1679   // in the VM. Change thread state from _thread_new to _thread_in_vm
1680   ThreadStateTransition::transition_and_fence(this, _thread_new, _thread_in_vm);
1681 
1682   assert(JavaThread::current() == this, "sanity check");
1683   assert(!Thread::current()->owns_locks(), "sanity check");
1684 
1685   DTRACE_THREAD_PROBE(start, this);
1686 
1687   // This operation might block. We call that after all safepoint checks for a new thread has
1688   // been completed.
1689   this->set_active_handles(JNIHandleBlock::allocate_block());
1690 
1691   if (JvmtiExport::should_post_thread_life()) {
1692     JvmtiExport::post_thread_start(this);
1693   }
1694 
1695   EventThreadStart event;
1696   if (event.should_commit()) {
1697     event.set_thread(THREAD_TRACE_ID(this));
1698     event.commit();
1699   }
1700 
1701   // We call another function to do the rest so we are sure that the stack addresses used
1702   // from there will be lower than the stack base just computed
1703   thread_main_inner();
1704 
1705   // Note, thread is no longer valid at this point!
1706 }
1707 
1708 
1709 void JavaThread::thread_main_inner() {
1710   assert(JavaThread::current() == this, "sanity check");
1711   assert(this->threadObj() != NULL, "just checking");
1712 
1713   // Execute thread entry point unless this thread has a pending exception
1714   // or has been stopped before starting.
1715   // Note: Due to JVM_StopThread we can have pending exceptions already!
1716   if (!this->has_pending_exception() &&
1717       !java_lang_Thread::is_stillborn(this->threadObj())) {
1718     {
1719       ResourceMark rm(this);
1720       this->set_native_thread_name(this->get_thread_name());
1721     }
1722     HandleMark hm(this);
1723     this->entry_point()(this, this);
1724   }
1725 
1726   DTRACE_THREAD_PROBE(stop, this);
1727 
1728   this->exit(false);
1729   delete this;
1730 }
1731 
1732 
1733 static void ensure_join(JavaThread* thread) {
1734   // We do not need to grap the Threads_lock, since we are operating on ourself.
1735   Handle threadObj(thread, thread->threadObj());
1736   assert(threadObj.not_null(), "java thread object must exist");
1737   ObjectLocker lock(threadObj, thread);
1738   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1739   thread->clear_pending_exception();
1740   // Thread is exiting. So set thread_status field in  java.lang.Thread class to TERMINATED.
1741   java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
1742   // Clear the native thread instance - this makes isAlive return false and allows the join()
1743   // to complete once we've done the notify_all below
1744   java_lang_Thread::set_thread(threadObj(), NULL);
1745   lock.notify_all(thread);
1746   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1747   thread->clear_pending_exception();
1748 }
1749 
1750 
1751 // For any new cleanup additions, please check to see if they need to be applied to
1752 // cleanup_failed_attach_current_thread as well.
1753 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
1754   assert(this == JavaThread::current(), "thread consistency check");
1755 
1756   HandleMark hm(this);
1757   Handle uncaught_exception(this, this->pending_exception());
1758   this->clear_pending_exception();
1759   Handle threadObj(this, this->threadObj());
1760   assert(threadObj.not_null(), "Java thread object should be created");
1761 
1762   if (get_thread_profiler() != NULL) {
1763     get_thread_profiler()->disengage();
1764     ResourceMark rm;
1765     get_thread_profiler()->print(get_thread_name());
1766   }
1767 
1768 
1769   // FIXIT: This code should be moved into else part, when reliable 1.2/1.3 check is in place
1770   {
1771     EXCEPTION_MARK;
1772 
1773     CLEAR_PENDING_EXCEPTION;
1774   }
1775   if (!destroy_vm) {
1776     if (uncaught_exception.not_null()) {
1777       EXCEPTION_MARK;
1778       // Call method Thread.dispatchUncaughtException().
1779       KlassHandle thread_klass(THREAD, SystemDictionary::Thread_klass());
1780       JavaValue result(T_VOID);
1781       JavaCalls::call_virtual(&result,
1782                               threadObj, thread_klass,
1783                               vmSymbols::dispatchUncaughtException_name(),
1784                               vmSymbols::throwable_void_signature(),
1785                               uncaught_exception,
1786                               THREAD);
1787       if (HAS_PENDING_EXCEPTION) {
1788         ResourceMark rm(this);
1789         jio_fprintf(defaultStream::error_stream(),
1790                     "\nException: %s thrown from the UncaughtExceptionHandler"
1791                     " in thread \"%s\"\n",
1792                     pending_exception()->klass()->external_name(),
1793                     get_thread_name());
1794         CLEAR_PENDING_EXCEPTION;
1795       }
1796     }
1797 
1798     // Called before the java thread exit since we want to read info
1799     // from java_lang_Thread object
1800     EventThreadEnd event;
1801     if (event.should_commit()) {
1802       event.set_thread(THREAD_TRACE_ID(this));
1803       event.commit();
1804     }
1805 
1806     // Call after last event on thread
1807     EVENT_THREAD_EXIT(this);
1808 
1809     // Call Thread.exit(). We try 3 times in case we got another Thread.stop during
1810     // the execution of the method. If that is not enough, then we don't really care. Thread.stop
1811     // is deprecated anyhow.
1812     if (!is_Compiler_thread()) {
1813       int count = 3;
1814       while (java_lang_Thread::threadGroup(threadObj()) != NULL && (count-- > 0)) {
1815         EXCEPTION_MARK;
1816         JavaValue result(T_VOID);
1817         KlassHandle thread_klass(THREAD, SystemDictionary::Thread_klass());
1818         JavaCalls::call_virtual(&result,
1819                                 threadObj, thread_klass,
1820                                 vmSymbols::exit_method_name(),
1821                                 vmSymbols::void_method_signature(),
1822                                 THREAD);
1823         CLEAR_PENDING_EXCEPTION;
1824       }
1825     }
1826     // notify JVMTI
1827     if (JvmtiExport::should_post_thread_life()) {
1828       JvmtiExport::post_thread_end(this);
1829     }
1830 
1831     // We have notified the agents that we are exiting, before we go on,
1832     // we must check for a pending external suspend request and honor it
1833     // in order to not surprise the thread that made the suspend request.
1834     while (true) {
1835       {
1836         MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
1837         if (!is_external_suspend()) {
1838           set_terminated(_thread_exiting);
1839           ThreadService::current_thread_exiting(this);
1840           break;
1841         }
1842         // Implied else:
1843         // Things get a little tricky here. We have a pending external
1844         // suspend request, but we are holding the SR_lock so we
1845         // can't just self-suspend. So we temporarily drop the lock
1846         // and then self-suspend.
1847       }
1848 
1849       ThreadBlockInVM tbivm(this);
1850       java_suspend_self();
1851 
1852       // We're done with this suspend request, but we have to loop around
1853       // and check again. Eventually we will get SR_lock without a pending
1854       // external suspend request and will be able to mark ourselves as
1855       // exiting.
1856     }
1857     // no more external suspends are allowed at this point
1858   } else {
1859     // before_exit() has already posted JVMTI THREAD_END events
1860   }
1861 
1862   // Notify waiters on thread object. This has to be done after exit() is called
1863   // on the thread (if the thread is the last thread in a daemon ThreadGroup the
1864   // group should have the destroyed bit set before waiters are notified).
1865   ensure_join(this);
1866   assert(!this->has_pending_exception(), "ensure_join should have cleared");
1867 
1868   // 6282335 JNI DetachCurrentThread spec states that all Java monitors
1869   // held by this thread must be released. The spec does not distinguish
1870   // between JNI-acquired and regular Java monitors. We can only see
1871   // regular Java monitors here if monitor enter-exit matching is broken.
1872   //
1873   // Optionally release any monitors for regular JavaThread exits. This
1874   // is provided as a work around for any bugs in monitor enter-exit
1875   // matching. This can be expensive so it is not enabled by default.
1876   //
1877   // ensure_join() ignores IllegalThreadStateExceptions, and so does
1878   // ObjectSynchronizer::release_monitors_owned_by_thread().
1879   if (exit_type == jni_detach || ObjectMonitor::Knob_ExitRelease) {
1880     // Sanity check even though JNI DetachCurrentThread() would have
1881     // returned JNI_ERR if there was a Java frame. JavaThread exit
1882     // should be done executing Java code by the time we get here.
1883     assert(!this->has_last_Java_frame(),
1884            "should not have a Java frame when detaching or exiting");
1885     ObjectSynchronizer::release_monitors_owned_by_thread(this);
1886     assert(!this->has_pending_exception(), "release_monitors should have cleared");
1887   }
1888 
1889   // These things needs to be done while we are still a Java Thread. Make sure that thread
1890   // is in a consistent state, in case GC happens
1891   assert(_privileged_stack_top == NULL, "must be NULL when we get here");
1892 
1893   if (active_handles() != NULL) {
1894     JNIHandleBlock* block = active_handles();
1895     set_active_handles(NULL);
1896     JNIHandleBlock::release_block(block);
1897   }
1898 
1899   if (free_handle_block() != NULL) {
1900     JNIHandleBlock* block = free_handle_block();
1901     set_free_handle_block(NULL);
1902     JNIHandleBlock::release_block(block);
1903   }
1904 
1905   // These have to be removed while this is still a valid thread.
1906   remove_stack_guard_pages();
1907 
1908   if (UseTLAB) {
1909     tlab().make_parsable(true);  // retire TLAB
1910   }
1911 
1912   if (JvmtiEnv::environments_might_exist()) {
1913     JvmtiExport::cleanup_thread(this);
1914   }
1915 
1916   // We must flush any deferred card marks before removing a thread from
1917   // the list of active threads.
1918   Universe::heap()->flush_deferred_store_barrier(this);
1919   assert(deferred_card_mark().is_empty(), "Should have been flushed");
1920 
1921 #if INCLUDE_ALL_GCS
1922   // We must flush the G1-related buffers before removing a thread
1923   // from the list of active threads. We must do this after any deferred
1924   // card marks have been flushed (above) so that any entries that are
1925   // added to the thread's dirty card queue as a result are not lost.
1926   if (UseG1GC) {
1927     flush_barrier_queues();
1928   }
1929 #endif // INCLUDE_ALL_GCS
1930 
1931   log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").",
1932     exit_type == JavaThread::normal_exit ? "exiting" : "detaching",
1933     os::current_thread_id());
1934 
1935   // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
1936   Threads::remove(this);
1937 }
1938 
1939 #if INCLUDE_ALL_GCS
1940 // Flush G1-related queues.
1941 void JavaThread::flush_barrier_queues() {
1942   satb_mark_queue().flush();
1943   dirty_card_queue().flush();
1944 }
1945 
1946 void JavaThread::initialize_queues() {
1947   assert(!SafepointSynchronize::is_at_safepoint(),
1948          "we should not be at a safepoint");
1949 
1950   SATBMarkQueue& satb_queue = satb_mark_queue();
1951   SATBMarkQueueSet& satb_queue_set = satb_mark_queue_set();
1952   // The SATB queue should have been constructed with its active
1953   // field set to false.
1954   assert(!satb_queue.is_active(), "SATB queue should not be active");
1955   assert(satb_queue.is_empty(), "SATB queue should be empty");
1956   // If we are creating the thread during a marking cycle, we should
1957   // set the active field of the SATB queue to true.
1958   if (satb_queue_set.is_active()) {
1959     satb_queue.set_active(true);
1960   }
1961 
1962   DirtyCardQueue& dirty_queue = dirty_card_queue();
1963   // The dirty card queue should have been constructed with its
1964   // active field set to true.
1965   assert(dirty_queue.is_active(), "dirty card queue should be active");
1966 }
1967 #endif // INCLUDE_ALL_GCS
1968 
1969 void JavaThread::cleanup_failed_attach_current_thread() {
1970   if (get_thread_profiler() != NULL) {
1971     get_thread_profiler()->disengage();
1972     ResourceMark rm;
1973     get_thread_profiler()->print(get_thread_name());
1974   }
1975 
1976   if (active_handles() != NULL) {
1977     JNIHandleBlock* block = active_handles();
1978     set_active_handles(NULL);
1979     JNIHandleBlock::release_block(block);
1980   }
1981 
1982   if (free_handle_block() != NULL) {
1983     JNIHandleBlock* block = free_handle_block();
1984     set_free_handle_block(NULL);
1985     JNIHandleBlock::release_block(block);
1986   }
1987 
1988   // These have to be removed while this is still a valid thread.
1989   remove_stack_guard_pages();
1990 
1991   if (UseTLAB) {
1992     tlab().make_parsable(true);  // retire TLAB, if any
1993   }
1994 
1995 #if INCLUDE_ALL_GCS
1996   if (UseG1GC) {
1997     flush_barrier_queues();
1998   }
1999 #endif // INCLUDE_ALL_GCS
2000 
2001   Threads::remove(this);
2002   delete this;
2003 }
2004 
2005 
2006 
2007 
2008 JavaThread* JavaThread::active() {
2009   Thread* thread = Thread::current();
2010   if (thread->is_Java_thread()) {
2011     return (JavaThread*) thread;
2012   } else {
2013     assert(thread->is_VM_thread(), "this must be a vm thread");
2014     VM_Operation* op = ((VMThread*) thread)->vm_operation();
2015     JavaThread *ret=op == NULL ? NULL : (JavaThread *)op->calling_thread();
2016     assert(ret->is_Java_thread(), "must be a Java thread");
2017     return ret;
2018   }
2019 }
2020 
2021 bool JavaThread::is_lock_owned(address adr) const {
2022   if (Thread::is_lock_owned(adr)) return true;
2023 
2024   for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2025     if (chunk->contains(adr)) return true;
2026   }
2027 
2028   return false;
2029 }
2030 
2031 
2032 void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
2033   chunk->set_next(monitor_chunks());
2034   set_monitor_chunks(chunk);
2035 }
2036 
2037 void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
2038   guarantee(monitor_chunks() != NULL, "must be non empty");
2039   if (monitor_chunks() == chunk) {
2040     set_monitor_chunks(chunk->next());
2041   } else {
2042     MonitorChunk* prev = monitor_chunks();
2043     while (prev->next() != chunk) prev = prev->next();
2044     prev->set_next(chunk->next());
2045   }
2046 }
2047 
2048 // JVM support.
2049 
2050 // Note: this function shouldn't block if it's called in
2051 // _thread_in_native_trans state (such as from
2052 // check_special_condition_for_native_trans()).
2053 void JavaThread::check_and_handle_async_exceptions(bool check_unsafe_error) {
2054 
2055   if (has_last_Java_frame() && has_async_condition()) {
2056     // If we are at a polling page safepoint (not a poll return)
2057     // then we must defer async exception because live registers
2058     // will be clobbered by the exception path. Poll return is
2059     // ok because the call we a returning from already collides
2060     // with exception handling registers and so there is no issue.
2061     // (The exception handling path kills call result registers but
2062     //  this is ok since the exception kills the result anyway).
2063 
2064     if (is_at_poll_safepoint()) {
2065       // if the code we are returning to has deoptimized we must defer
2066       // the exception otherwise live registers get clobbered on the
2067       // exception path before deoptimization is able to retrieve them.
2068       //
2069       RegisterMap map(this, false);
2070       frame caller_fr = last_frame().sender(&map);
2071       assert(caller_fr.is_compiled_frame(), "what?");
2072       if (caller_fr.is_deoptimized_frame()) {
2073         log_info(exceptions)("deferred async exception at compiled safepoint");
2074         return;
2075       }
2076     }
2077   }
2078 
2079   JavaThread::AsyncRequests condition = clear_special_runtime_exit_condition();
2080   if (condition == _no_async_condition) {
2081     // Conditions have changed since has_special_runtime_exit_condition()
2082     // was called:
2083     // - if we were here only because of an external suspend request,
2084     //   then that was taken care of above (or cancelled) so we are done
2085     // - if we were here because of another async request, then it has
2086     //   been cleared between the has_special_runtime_exit_condition()
2087     //   and now so again we are done
2088     return;
2089   }
2090 
2091   // Check for pending async. exception
2092   if (_pending_async_exception != NULL) {
2093     // Only overwrite an already pending exception, if it is not a threadDeath.
2094     if (!has_pending_exception() || !pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())) {
2095 
2096       // We cannot call Exceptions::_throw(...) here because we cannot block
2097       set_pending_exception(_pending_async_exception, __FILE__, __LINE__);
2098 
2099       if (log_is_enabled(Info, exceptions)) {
2100         ResourceMark rm;
2101         outputStream* logstream = LogHandle(exceptions)::info_stream();
2102         logstream->print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", p2i(this));
2103           if (has_last_Java_frame()) {
2104             frame f = last_frame();
2105            logstream->print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", p2i(f.pc()), p2i(f.sp()));
2106           }
2107         logstream->print_cr(" of type: %s", _pending_async_exception->klass()->external_name());
2108       }
2109       _pending_async_exception = NULL;
2110       clear_has_async_exception();
2111     }
2112   }
2113 
2114   if (check_unsafe_error &&
2115       condition == _async_unsafe_access_error && !has_pending_exception()) {
2116     condition = _no_async_condition;  // done
2117     switch (thread_state()) {
2118     case _thread_in_vm: {
2119       JavaThread* THREAD = this;
2120       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2121     }
2122     case _thread_in_native: {
2123       ThreadInVMfromNative tiv(this);
2124       JavaThread* THREAD = this;
2125       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2126     }
2127     case _thread_in_Java: {
2128       ThreadInVMfromJava tiv(this);
2129       JavaThread* THREAD = this;
2130       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in a recent unsafe memory access operation in compiled Java code");
2131     }
2132     default:
2133       ShouldNotReachHere();
2134     }
2135   }
2136 
2137   assert(condition == _no_async_condition || has_pending_exception() ||
2138          (!check_unsafe_error && condition == _async_unsafe_access_error),
2139          "must have handled the async condition, if no exception");
2140 }
2141 
2142 void JavaThread::handle_special_runtime_exit_condition(bool check_asyncs) {
2143   //
2144   // Check for pending external suspend. Internal suspend requests do
2145   // not use handle_special_runtime_exit_condition().
2146   // If JNIEnv proxies are allowed, don't self-suspend if the target
2147   // thread is not the current thread. In older versions of jdbx, jdbx
2148   // threads could call into the VM with another thread's JNIEnv so we
2149   // can be here operating on behalf of a suspended thread (4432884).
2150   bool do_self_suspend = is_external_suspend_with_lock();
2151   if (do_self_suspend && (!AllowJNIEnvProxy || this == JavaThread::current())) {
2152     //
2153     // Because thread is external suspended the safepoint code will count
2154     // thread as at a safepoint. This can be odd because we can be here
2155     // as _thread_in_Java which would normally transition to _thread_blocked
2156     // at a safepoint. We would like to mark the thread as _thread_blocked
2157     // before calling java_suspend_self like all other callers of it but
2158     // we must then observe proper safepoint protocol. (We can't leave
2159     // _thread_blocked with a safepoint in progress). However we can be
2160     // here as _thread_in_native_trans so we can't use a normal transition
2161     // constructor/destructor pair because they assert on that type of
2162     // transition. We could do something like:
2163     //
2164     // JavaThreadState state = thread_state();
2165     // set_thread_state(_thread_in_vm);
2166     // {
2167     //   ThreadBlockInVM tbivm(this);
2168     //   java_suspend_self()
2169     // }
2170     // set_thread_state(_thread_in_vm_trans);
2171     // if (safepoint) block;
2172     // set_thread_state(state);
2173     //
2174     // but that is pretty messy. Instead we just go with the way the
2175     // code has worked before and note that this is the only path to
2176     // java_suspend_self that doesn't put the thread in _thread_blocked
2177     // mode.
2178 
2179     frame_anchor()->make_walkable(this);
2180     java_suspend_self();
2181 
2182     // We might be here for reasons in addition to the self-suspend request
2183     // so check for other async requests.
2184   }
2185 
2186   if (check_asyncs) {
2187     check_and_handle_async_exceptions();
2188   }
2189 }
2190 
2191 void JavaThread::send_thread_stop(oop java_throwable)  {
2192   assert(Thread::current()->is_VM_thread(), "should be in the vm thread");
2193   assert(Threads_lock->is_locked(), "Threads_lock should be locked by safepoint code");
2194   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
2195 
2196   // Do not throw asynchronous exceptions against the compiler thread
2197   // (the compiler thread should not be a Java thread -- fix in 1.4.2)
2198   if (!can_call_java()) return;
2199 
2200   {
2201     // Actually throw the Throwable against the target Thread - however
2202     // only if there is no thread death exception installed already.
2203     if (_pending_async_exception == NULL || !_pending_async_exception->is_a(SystemDictionary::ThreadDeath_klass())) {
2204       // If the topmost frame is a runtime stub, then we are calling into
2205       // OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
2206       // must deoptimize the caller before continuing, as the compiled  exception handler table
2207       // may not be valid
2208       if (has_last_Java_frame()) {
2209         frame f = last_frame();
2210         if (f.is_runtime_frame() || f.is_safepoint_blob_frame()) {
2211           // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2212           RegisterMap reg_map(this, UseBiasedLocking);
2213           frame compiled_frame = f.sender(&reg_map);
2214           if (!StressCompiledExceptionHandlers && compiled_frame.can_be_deoptimized()) {
2215             Deoptimization::deoptimize(this, compiled_frame, &reg_map);
2216           }
2217         }
2218       }
2219 
2220       // Set async. pending exception in thread.
2221       set_pending_async_exception(java_throwable);
2222 
2223       if (log_is_enabled(Info, exceptions)) {
2224          ResourceMark rm;
2225         log_info(exceptions)("Pending Async. exception installed of type: %s",
2226                              InstanceKlass::cast(_pending_async_exception->klass())->external_name());
2227       }
2228       // for AbortVMOnException flag
2229       Exceptions::debug_check_abort(_pending_async_exception->klass()->external_name());
2230     }
2231   }
2232 
2233 
2234   // Interrupt thread so it will wake up from a potential wait()
2235   Thread::interrupt(this);
2236 }
2237 
2238 // External suspension mechanism.
2239 //
2240 // Tell the VM to suspend a thread when ever it knows that it does not hold on
2241 // to any VM_locks and it is at a transition
2242 // Self-suspension will happen on the transition out of the vm.
2243 // Catch "this" coming in from JNIEnv pointers when the thread has been freed
2244 //
2245 // Guarantees on return:
2246 //   + Target thread will not execute any new bytecode (that's why we need to
2247 //     force a safepoint)
2248 //   + Target thread will not enter any new monitors
2249 //
2250 void JavaThread::java_suspend() {
2251   { MutexLocker mu(Threads_lock);
2252     if (!Threads::includes(this) || is_exiting() || this->threadObj() == NULL) {
2253       return;
2254     }
2255   }
2256 
2257   { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2258     if (!is_external_suspend()) {
2259       // a racing resume has cancelled us; bail out now
2260       return;
2261     }
2262 
2263     // suspend is done
2264     uint32_t debug_bits = 0;
2265     // Warning: is_ext_suspend_completed() may temporarily drop the
2266     // SR_lock to allow the thread to reach a stable thread state if
2267     // it is currently in a transient thread state.
2268     if (is_ext_suspend_completed(false /* !called_by_wait */,
2269                                  SuspendRetryDelay, &debug_bits)) {
2270       return;
2271     }
2272   }
2273 
2274   VM_ForceSafepoint vm_suspend;
2275   VMThread::execute(&vm_suspend);
2276 }
2277 
2278 // Part II of external suspension.
2279 // A JavaThread self suspends when it detects a pending external suspend
2280 // request. This is usually on transitions. It is also done in places
2281 // where continuing to the next transition would surprise the caller,
2282 // e.g., monitor entry.
2283 //
2284 // Returns the number of times that the thread self-suspended.
2285 //
2286 // Note: DO NOT call java_suspend_self() when you just want to block current
2287 //       thread. java_suspend_self() is the second stage of cooperative
2288 //       suspension for external suspend requests and should only be used
2289 //       to complete an external suspend request.
2290 //
2291 int JavaThread::java_suspend_self() {
2292   int ret = 0;
2293 
2294   // we are in the process of exiting so don't suspend
2295   if (is_exiting()) {
2296     clear_external_suspend();
2297     return ret;
2298   }
2299 
2300   assert(_anchor.walkable() ||
2301          (is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
2302          "must have walkable stack");
2303 
2304   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2305 
2306   assert(!this->is_ext_suspended(),
2307          "a thread trying to self-suspend should not already be suspended");
2308 
2309   if (this->is_suspend_equivalent()) {
2310     // If we are self-suspending as a result of the lifting of a
2311     // suspend equivalent condition, then the suspend_equivalent
2312     // flag is not cleared until we set the ext_suspended flag so
2313     // that wait_for_ext_suspend_completion() returns consistent
2314     // results.
2315     this->clear_suspend_equivalent();
2316   }
2317 
2318   // A racing resume may have cancelled us before we grabbed SR_lock
2319   // above. Or another external suspend request could be waiting for us
2320   // by the time we return from SR_lock()->wait(). The thread
2321   // that requested the suspension may already be trying to walk our
2322   // stack and if we return now, we can change the stack out from under
2323   // it. This would be a "bad thing (TM)" and cause the stack walker
2324   // to crash. We stay self-suspended until there are no more pending
2325   // external suspend requests.
2326   while (is_external_suspend()) {
2327     ret++;
2328     this->set_ext_suspended();
2329 
2330     // _ext_suspended flag is cleared by java_resume()
2331     while (is_ext_suspended()) {
2332       this->SR_lock()->wait(Mutex::_no_safepoint_check_flag);
2333     }
2334   }
2335 
2336   return ret;
2337 }
2338 
2339 #ifdef ASSERT
2340 // verify the JavaThread has not yet been published in the Threads::list, and
2341 // hence doesn't need protection from concurrent access at this stage
2342 void JavaThread::verify_not_published() {
2343   if (!Threads_lock->owned_by_self()) {
2344     MutexLockerEx ml(Threads_lock,  Mutex::_no_safepoint_check_flag);
2345     assert(!Threads::includes(this),
2346            "java thread shouldn't have been published yet!");
2347   } else {
2348     assert(!Threads::includes(this),
2349            "java thread shouldn't have been published yet!");
2350   }
2351 }
2352 #endif
2353 
2354 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2355 // progress or when _suspend_flags is non-zero.
2356 // Current thread needs to self-suspend if there is a suspend request and/or
2357 // block if a safepoint is in progress.
2358 // Async exception ISN'T checked.
2359 // Note only the ThreadInVMfromNative transition can call this function
2360 // directly and when thread state is _thread_in_native_trans
2361 void JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread *thread) {
2362   assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
2363 
2364   JavaThread *curJT = JavaThread::current();
2365   bool do_self_suspend = thread->is_external_suspend();
2366 
2367   assert(!curJT->has_last_Java_frame() || curJT->frame_anchor()->walkable(), "Unwalkable stack in native->vm transition");
2368 
2369   // If JNIEnv proxies are allowed, don't self-suspend if the target
2370   // thread is not the current thread. In older versions of jdbx, jdbx
2371   // threads could call into the VM with another thread's JNIEnv so we
2372   // can be here operating on behalf of a suspended thread (4432884).
2373   if (do_self_suspend && (!AllowJNIEnvProxy || curJT == thread)) {
2374     JavaThreadState state = thread->thread_state();
2375 
2376     // We mark this thread_blocked state as a suspend-equivalent so
2377     // that a caller to is_ext_suspend_completed() won't be confused.
2378     // The suspend-equivalent state is cleared by java_suspend_self().
2379     thread->set_suspend_equivalent();
2380 
2381     // If the safepoint code sees the _thread_in_native_trans state, it will
2382     // wait until the thread changes to other thread state. There is no
2383     // guarantee on how soon we can obtain the SR_lock and complete the
2384     // self-suspend request. It would be a bad idea to let safepoint wait for
2385     // too long. Temporarily change the state to _thread_blocked to
2386     // let the VM thread know that this thread is ready for GC. The problem
2387     // of changing thread state is that safepoint could happen just after
2388     // java_suspend_self() returns after being resumed, and VM thread will
2389     // see the _thread_blocked state. We must check for safepoint
2390     // after restoring the state and make sure we won't leave while a safepoint
2391     // is in progress.
2392     thread->set_thread_state(_thread_blocked);
2393     thread->java_suspend_self();
2394     thread->set_thread_state(state);
2395     // Make sure new state is seen by VM thread
2396     if (os::is_MP()) {
2397       if (UseMembar) {
2398         // Force a fence between the write above and read below
2399         OrderAccess::fence();
2400       } else {
2401         // Must use this rather than serialization page in particular on Windows
2402         InterfaceSupport::serialize_memory(thread);
2403       }
2404     }
2405   }
2406 
2407   if (SafepointSynchronize::do_call_back()) {
2408     // If we are safepointing, then block the caller which may not be
2409     // the same as the target thread (see above).
2410     SafepointSynchronize::block(curJT);
2411   }
2412 
2413   if (thread->is_deopt_suspend()) {
2414     thread->clear_deopt_suspend();
2415     RegisterMap map(thread, false);
2416     frame f = thread->last_frame();
2417     while (f.id() != thread->must_deopt_id() && ! f.is_first_frame()) {
2418       f = f.sender(&map);
2419     }
2420     if (f.id() == thread->must_deopt_id()) {
2421       thread->clear_must_deopt_id();
2422       f.deoptimize(thread);
2423     } else {
2424       fatal("missed deoptimization!");
2425     }
2426   }
2427 }
2428 
2429 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2430 // progress or when _suspend_flags is non-zero.
2431 // Current thread needs to self-suspend if there is a suspend request and/or
2432 // block if a safepoint is in progress.
2433 // Also check for pending async exception (not including unsafe access error).
2434 // Note only the native==>VM/Java barriers can call this function and when
2435 // thread state is _thread_in_native_trans.
2436 void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
2437   check_safepoint_and_suspend_for_native_trans(thread);
2438 
2439   if (thread->has_async_exception()) {
2440     // We are in _thread_in_native_trans state, don't handle unsafe
2441     // access error since that may block.
2442     thread->check_and_handle_async_exceptions(false);
2443   }
2444 }
2445 
2446 // This is a variant of the normal
2447 // check_special_condition_for_native_trans with slightly different
2448 // semantics for use by critical native wrappers.  It does all the
2449 // normal checks but also performs the transition back into
2450 // thread_in_Java state.  This is required so that critical natives
2451 // can potentially block and perform a GC if they are the last thread
2452 // exiting the GCLocker.
2453 void JavaThread::check_special_condition_for_native_trans_and_transition(JavaThread *thread) {
2454   check_special_condition_for_native_trans(thread);
2455 
2456   // Finish the transition
2457   thread->set_thread_state(_thread_in_Java);
2458 
2459   if (thread->do_critical_native_unlock()) {
2460     ThreadInVMfromJavaNoAsyncException tiv(thread);
2461     GCLocker::unlock_critical(thread);
2462     thread->clear_critical_native_unlock();
2463   }
2464 }
2465 
2466 // We need to guarantee the Threads_lock here, since resumes are not
2467 // allowed during safepoint synchronization
2468 // Can only resume from an external suspension
2469 void JavaThread::java_resume() {
2470   assert_locked_or_safepoint(Threads_lock);
2471 
2472   // Sanity check: thread is gone, has started exiting or the thread
2473   // was not externally suspended.
2474   if (!Threads::includes(this) || is_exiting() || !is_external_suspend()) {
2475     return;
2476   }
2477 
2478   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2479 
2480   clear_external_suspend();
2481 
2482   if (is_ext_suspended()) {
2483     clear_ext_suspended();
2484     SR_lock()->notify_all();
2485   }
2486 }
2487 
2488 size_t JavaThread::_stack_red_zone_size = 0;
2489 size_t JavaThread::_stack_yellow_zone_size = 0;
2490 size_t JavaThread::_stack_reserved_zone_size = 0;
2491 size_t JavaThread::_stack_shadow_zone_size = 0;
2492 
2493 void JavaThread::create_stack_guard_pages() {
2494   if (!os::uses_stack_guard_pages() || _stack_guard_state != stack_guard_unused) { return; }
2495   address low_addr = stack_end();
2496   size_t len = stack_guard_zone_size();
2497 
2498   int allocate = os::allocate_stack_guard_pages();
2499   // warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);
2500 
2501   if (allocate && !os::create_stack_guard_pages((char *) low_addr, len)) {
2502     log_warning(os, thread)("Attempt to allocate stack guard pages failed.");
2503     return;
2504   }
2505 
2506   if (os::guard_memory((char *) low_addr, len)) {
2507     _stack_guard_state = stack_guard_enabled;
2508   } else {
2509     log_warning(os, thread)("Attempt to protect stack guard pages failed ("
2510       PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2511     if (os::uncommit_memory((char *) low_addr, len)) {
2512       log_warning(os, thread)("Attempt to deallocate stack guard pages failed.");
2513     }
2514     return;
2515   }
2516 
2517   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages activated: "
2518     PTR_FORMAT "-" PTR_FORMAT ".",
2519     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2520 
2521 }
2522 
2523 void JavaThread::remove_stack_guard_pages() {
2524   assert(Thread::current() == this, "from different thread");
2525   if (_stack_guard_state == stack_guard_unused) return;
2526   address low_addr = stack_end();
2527   size_t len = stack_guard_zone_size();
2528 
2529   if (os::allocate_stack_guard_pages()) {
2530     if (os::remove_stack_guard_pages((char *) low_addr, len)) {
2531       _stack_guard_state = stack_guard_unused;
2532     } else {
2533       log_warning(os, thread)("Attempt to deallocate stack guard pages failed ("
2534         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2535       return;
2536     }
2537   } else {
2538     if (_stack_guard_state == stack_guard_unused) return;
2539     if (os::unguard_memory((char *) low_addr, len)) {
2540       _stack_guard_state = stack_guard_unused;
2541     } else {
2542       log_warning(os, thread)("Attempt to unprotect stack guard pages failed ("
2543         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2544       return;
2545     }
2546   }
2547 
2548   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages removed: "
2549     PTR_FORMAT "-" PTR_FORMAT ".",
2550     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2551 
2552 }
2553 
2554 void JavaThread::enable_stack_reserved_zone() {
2555   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2556   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2557 
2558   // The base notation is from the stack's point of view, growing downward.
2559   // We need to adjust it to work correctly with guard_memory()
2560   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2561 
2562   guarantee(base < stack_base(),"Error calculating stack reserved zone");
2563   guarantee(base < os::current_stack_pointer(),"Error calculating stack reserved zone");
2564 
2565   if (os::guard_memory((char *) base, stack_reserved_zone_size())) {
2566     _stack_guard_state = stack_guard_enabled;
2567   } else {
2568     warning("Attempt to guard stack reserved zone failed.");
2569   }
2570   enable_register_stack_guard();
2571 }
2572 
2573 void JavaThread::disable_stack_reserved_zone() {
2574   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2575   assert(_stack_guard_state != stack_guard_reserved_disabled, "already disabled");
2576 
2577   // Simply return if called for a thread that does not use guard pages.
2578   if (_stack_guard_state == stack_guard_unused) return;
2579 
2580   // The base notation is from the stack's point of view, growing downward.
2581   // We need to adjust it to work correctly with guard_memory()
2582   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2583 
2584   if (os::unguard_memory((char *)base, stack_reserved_zone_size())) {
2585     _stack_guard_state = stack_guard_reserved_disabled;
2586   } else {
2587     warning("Attempt to unguard stack reserved zone failed.");
2588   }
2589   disable_register_stack_guard();
2590 }
2591 
2592 void JavaThread::enable_stack_yellow_reserved_zone() {
2593   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2594   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2595 
2596   // The base notation is from the stacks point of view, growing downward.
2597   // We need to adjust it to work correctly with guard_memory()
2598   address base = stack_red_zone_base();
2599 
2600   guarantee(base < stack_base(), "Error calculating stack yellow zone");
2601   guarantee(base < os::current_stack_pointer(), "Error calculating stack yellow zone");
2602 
2603   if (os::guard_memory((char *) base, stack_yellow_reserved_zone_size())) {
2604     _stack_guard_state = stack_guard_enabled;
2605   } else {
2606     warning("Attempt to guard stack yellow zone failed.");
2607   }
2608   enable_register_stack_guard();
2609 }
2610 
2611 void JavaThread::disable_stack_yellow_reserved_zone() {
2612   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2613   assert(_stack_guard_state != stack_guard_yellow_reserved_disabled, "already disabled");
2614 
2615   // Simply return if called for a thread that does not use guard pages.
2616   if (_stack_guard_state == stack_guard_unused) return;
2617 
2618   // The base notation is from the stacks point of view, growing downward.
2619   // We need to adjust it to work correctly with guard_memory()
2620   address base = stack_red_zone_base();
2621 
2622   if (os::unguard_memory((char *)base, stack_yellow_reserved_zone_size())) {
2623     _stack_guard_state = stack_guard_yellow_reserved_disabled;
2624   } else {
2625     warning("Attempt to unguard stack yellow zone failed.");
2626   }
2627   disable_register_stack_guard();
2628 }
2629 
2630 void JavaThread::enable_stack_red_zone() {
2631   // The base notation is from the stacks point of view, growing downward.
2632   // We need to adjust it to work correctly with guard_memory()
2633   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2634   address base = stack_red_zone_base() - stack_red_zone_size();
2635 
2636   guarantee(base < stack_base(), "Error calculating stack red zone");
2637   guarantee(base < os::current_stack_pointer(), "Error calculating stack red zone");
2638 
2639   if (!os::guard_memory((char *) base, stack_red_zone_size())) {
2640     warning("Attempt to guard stack red zone failed.");
2641   }
2642 }
2643 
2644 void JavaThread::disable_stack_red_zone() {
2645   // The base notation is from the stacks point of view, growing downward.
2646   // We need to adjust it to work correctly with guard_memory()
2647   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2648   address base = stack_red_zone_base() - stack_red_zone_size();
2649   if (!os::unguard_memory((char *)base, stack_red_zone_size())) {
2650     warning("Attempt to unguard stack red zone failed.");
2651   }
2652 }
2653 
2654 void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
2655   // ignore is there is no stack
2656   if (!has_last_Java_frame()) return;
2657   // traverse the stack frames. Starts from top frame.
2658   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2659     frame* fr = fst.current();
2660     f(fr, fst.register_map());
2661   }
2662 }
2663 
2664 
2665 #ifndef PRODUCT
2666 // Deoptimization
2667 // Function for testing deoptimization
2668 void JavaThread::deoptimize() {
2669   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2670   StackFrameStream fst(this, UseBiasedLocking);
2671   bool deopt = false;           // Dump stack only if a deopt actually happens.
2672   bool only_at = strlen(DeoptimizeOnlyAt) > 0;
2673   // Iterate over all frames in the thread and deoptimize
2674   for (; !fst.is_done(); fst.next()) {
2675     if (fst.current()->can_be_deoptimized()) {
2676 
2677       if (only_at) {
2678         // Deoptimize only at particular bcis.  DeoptimizeOnlyAt
2679         // consists of comma or carriage return separated numbers so
2680         // search for the current bci in that string.
2681         address pc = fst.current()->pc();
2682         nmethod* nm =  (nmethod*) fst.current()->cb();
2683         ScopeDesc* sd = nm->scope_desc_at(pc);
2684         char buffer[8];
2685         jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
2686         size_t len = strlen(buffer);
2687         const char * found = strstr(DeoptimizeOnlyAt, buffer);
2688         while (found != NULL) {
2689           if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
2690               (found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
2691             // Check that the bci found is bracketed by terminators.
2692             break;
2693           }
2694           found = strstr(found + 1, buffer);
2695         }
2696         if (!found) {
2697           continue;
2698         }
2699       }
2700 
2701       if (DebugDeoptimization && !deopt) {
2702         deopt = true; // One-time only print before deopt
2703         tty->print_cr("[BEFORE Deoptimization]");
2704         trace_frames();
2705         trace_stack();
2706       }
2707       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2708     }
2709   }
2710 
2711   if (DebugDeoptimization && deopt) {
2712     tty->print_cr("[AFTER Deoptimization]");
2713     trace_frames();
2714   }
2715 }
2716 
2717 
2718 // Make zombies
2719 void JavaThread::make_zombies() {
2720   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2721     if (fst.current()->can_be_deoptimized()) {
2722       // it is a Java nmethod
2723       nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
2724       nm->make_not_entrant();
2725     }
2726   }
2727 }
2728 #endif // PRODUCT
2729 
2730 
2731 void JavaThread::deoptimized_wrt_marked_nmethods() {
2732   if (!has_last_Java_frame()) return;
2733   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2734   StackFrameStream fst(this, UseBiasedLocking);
2735   for (; !fst.is_done(); fst.next()) {
2736     if (fst.current()->should_be_deoptimized()) {
2737       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2738     }
2739   }
2740 }
2741 
2742 
2743 // If the caller is a NamedThread, then remember, in the current scope,
2744 // the given JavaThread in its _processed_thread field.
2745 class RememberProcessedThread: public StackObj {
2746   NamedThread* _cur_thr;
2747  public:
2748   RememberProcessedThread(JavaThread* jthr) {
2749     Thread* thread = Thread::current();
2750     if (thread->is_Named_thread()) {
2751       _cur_thr = (NamedThread *)thread;
2752       _cur_thr->set_processed_thread(jthr);
2753     } else {
2754       _cur_thr = NULL;
2755     }
2756   }
2757 
2758   ~RememberProcessedThread() {
2759     if (_cur_thr) {
2760       _cur_thr->set_processed_thread(NULL);
2761     }
2762   }
2763 };
2764 
2765 void JavaThread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
2766   // Verify that the deferred card marks have been flushed.
2767   assert(deferred_card_mark().is_empty(), "Should be empty during GC");
2768 
2769   // The ThreadProfiler oops_do is done from FlatProfiler::oops_do
2770   // since there may be more than one thread using each ThreadProfiler.
2771 
2772   // Traverse the GCHandles
2773   Thread::oops_do(f, cld_f, cf);
2774 
2775   JVMCI_ONLY(f->do_oop((oop*)&_pending_failed_speculation);)
2776 
2777   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2778          (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2779 
2780   if (has_last_Java_frame()) {
2781     // Record JavaThread to GC thread
2782     RememberProcessedThread rpt(this);
2783 
2784     // Traverse the privileged stack
2785     if (_privileged_stack_top != NULL) {
2786       _privileged_stack_top->oops_do(f);
2787     }
2788 
2789     // traverse the registered growable array
2790     if (_array_for_gc != NULL) {
2791       for (int index = 0; index < _array_for_gc->length(); index++) {
2792         f->do_oop(_array_for_gc->adr_at(index));
2793       }
2794     }
2795 
2796     // Traverse the monitor chunks
2797     for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2798       chunk->oops_do(f);
2799     }
2800 
2801     // Traverse the execution stack
2802     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2803       fst.current()->oops_do(f, cld_f, cf, fst.register_map());
2804     }
2805   }
2806 
2807   // callee_target is never live across a gc point so NULL it here should
2808   // it still contain a methdOop.
2809 
2810   set_callee_target(NULL);
2811 
2812   assert(vframe_array_head() == NULL, "deopt in progress at a safepoint!");
2813   // If we have deferred set_locals there might be oops waiting to be
2814   // written
2815   GrowableArray<jvmtiDeferredLocalVariableSet*>* list = deferred_locals();
2816   if (list != NULL) {
2817     for (int i = 0; i < list->length(); i++) {
2818       list->at(i)->oops_do(f);
2819     }
2820   }
2821 
2822   // Traverse instance variables at the end since the GC may be moving things
2823   // around using this function
2824   f->do_oop((oop*) &_threadObj);
2825   f->do_oop((oop*) &_vm_result);
2826   f->do_oop((oop*) &_exception_oop);
2827   f->do_oop((oop*) &_pending_async_exception);
2828 
2829   if (jvmti_thread_state() != NULL) {
2830     jvmti_thread_state()->oops_do(f);
2831   }
2832 }
2833 
2834 void JavaThread::nmethods_do(CodeBlobClosure* cf) {
2835   Thread::nmethods_do(cf);  // (super method is a no-op)
2836 
2837   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2838          (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2839 
2840   if (has_last_Java_frame()) {
2841     // Traverse the execution stack
2842     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2843       fst.current()->nmethods_do(cf);
2844     }
2845   }
2846 }
2847 
2848 void JavaThread::metadata_do(void f(Metadata*)) {
2849   if (has_last_Java_frame()) {
2850     // Traverse the execution stack to call f() on the methods in the stack
2851     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2852       fst.current()->metadata_do(f);
2853     }
2854   } else if (is_Compiler_thread()) {
2855     // need to walk ciMetadata in current compile tasks to keep alive.
2856     CompilerThread* ct = (CompilerThread*)this;
2857     if (ct->env() != NULL) {
2858       ct->env()->metadata_do(f);
2859     }
2860     if (ct->task() != NULL) {
2861       ct->task()->metadata_do(f);
2862     }
2863   }
2864 }
2865 
2866 // Printing
2867 const char* _get_thread_state_name(JavaThreadState _thread_state) {
2868   switch (_thread_state) {
2869   case _thread_uninitialized:     return "_thread_uninitialized";
2870   case _thread_new:               return "_thread_new";
2871   case _thread_new_trans:         return "_thread_new_trans";
2872   case _thread_in_native:         return "_thread_in_native";
2873   case _thread_in_native_trans:   return "_thread_in_native_trans";
2874   case _thread_in_vm:             return "_thread_in_vm";
2875   case _thread_in_vm_trans:       return "_thread_in_vm_trans";
2876   case _thread_in_Java:           return "_thread_in_Java";
2877   case _thread_in_Java_trans:     return "_thread_in_Java_trans";
2878   case _thread_blocked:           return "_thread_blocked";
2879   case _thread_blocked_trans:     return "_thread_blocked_trans";
2880   default:                        return "unknown thread state";
2881   }
2882 }
2883 
2884 #ifndef PRODUCT
2885 void JavaThread::print_thread_state_on(outputStream *st) const {
2886   st->print_cr("   JavaThread state: %s", _get_thread_state_name(_thread_state));
2887 };
2888 void JavaThread::print_thread_state() const {
2889   print_thread_state_on(tty);
2890 }
2891 #endif // PRODUCT
2892 
2893 // Called by Threads::print() for VM_PrintThreads operation
2894 void JavaThread::print_on(outputStream *st) const {
2895   st->print("\"%s\" ", get_thread_name());
2896   oop thread_oop = threadObj();
2897   if (thread_oop != NULL) {
2898     st->print("#" INT64_FORMAT " ", java_lang_Thread::thread_id(thread_oop));
2899     if (java_lang_Thread::is_daemon(thread_oop))  st->print("daemon ");
2900     st->print("prio=%d ", java_lang_Thread::priority(thread_oop));
2901   }
2902   Thread::print_on(st);
2903   // print guess for valid stack memory region (assume 4K pages); helps lock debugging
2904   st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
2905   if (thread_oop != NULL) {
2906     st->print_cr("   java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
2907   }
2908 #ifndef PRODUCT
2909   print_thread_state_on(st);
2910   _safepoint_state->print_on(st);
2911 #endif // PRODUCT
2912   if (is_Compiler_thread()) {
2913     CompilerThread* ct = (CompilerThread*)this;
2914     if (ct->task() != NULL) {
2915       st->print("   Compiling: ");
2916       ct->task()->print(st, NULL, true, false);
2917     } else {
2918       st->print("   No compile task");
2919     }
2920     st->cr();
2921   }
2922 }
2923 
2924 void JavaThread::print_name_on_error(outputStream* st, char *buf, int buflen) const {
2925   st->print("%s", get_thread_name_string(buf, buflen));
2926 }
2927 
2928 // Called by fatal error handler. The difference between this and
2929 // JavaThread::print() is that we can't grab lock or allocate memory.
2930 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
2931   st->print("JavaThread \"%s\"", get_thread_name_string(buf, buflen));
2932   oop thread_obj = threadObj();
2933   if (thread_obj != NULL) {
2934     if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
2935   }
2936   st->print(" [");
2937   st->print("%s", _get_thread_state_name(_thread_state));
2938   if (osthread()) {
2939     st->print(", id=%d", osthread()->thread_id());
2940   }
2941   st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
2942             p2i(stack_end()), p2i(stack_base()));
2943   st->print("]");
2944   return;
2945 }
2946 
2947 // Verification
2948 
2949 static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
2950 
2951 void JavaThread::verify() {
2952   // Verify oops in the thread.
2953   oops_do(&VerifyOopClosure::verify_oop, NULL, NULL);
2954 
2955   // Verify the stack frames.
2956   frames_do(frame_verify);
2957 }
2958 
2959 // CR 6300358 (sub-CR 2137150)
2960 // Most callers of this method assume that it can't return NULL but a
2961 // thread may not have a name whilst it is in the process of attaching to
2962 // the VM - see CR 6412693, and there are places where a JavaThread can be
2963 // seen prior to having it's threadObj set (eg JNI attaching threads and
2964 // if vm exit occurs during initialization). These cases can all be accounted
2965 // for such that this method never returns NULL.
2966 const char* JavaThread::get_thread_name() const {
2967 #ifdef ASSERT
2968   // early safepoints can hit while current thread does not yet have TLS
2969   if (!SafepointSynchronize::is_at_safepoint()) {
2970     Thread *cur = Thread::current();
2971     if (!(cur->is_Java_thread() && cur == this)) {
2972       // Current JavaThreads are allowed to get their own name without
2973       // the Threads_lock.
2974       assert_locked_or_safepoint(Threads_lock);
2975     }
2976   }
2977 #endif // ASSERT
2978   return get_thread_name_string();
2979 }
2980 
2981 // Returns a non-NULL representation of this thread's name, or a suitable
2982 // descriptive string if there is no set name
2983 const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
2984   const char* name_str;
2985   oop thread_obj = threadObj();
2986   if (thread_obj != NULL) {
2987     oop name = java_lang_Thread::name(thread_obj);
2988     if (name != NULL) {
2989       if (buf == NULL) {
2990         name_str = java_lang_String::as_utf8_string(name);
2991       } else {
2992         name_str = java_lang_String::as_utf8_string(name, buf, buflen);
2993       }
2994     } else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
2995       name_str = "<no-name - thread is attaching>";
2996     } else {
2997       name_str = Thread::name();
2998     }
2999   } else {
3000     name_str = Thread::name();
3001   }
3002   assert(name_str != NULL, "unexpected NULL thread name");
3003   return name_str;
3004 }
3005 
3006 
3007 const char* JavaThread::get_threadgroup_name() const {
3008   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3009   oop thread_obj = threadObj();
3010   if (thread_obj != NULL) {
3011     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3012     if (thread_group != NULL) {
3013       // ThreadGroup.name can be null
3014       return java_lang_ThreadGroup::name(thread_group);
3015     }
3016   }
3017   return NULL;
3018 }
3019 
3020 const char* JavaThread::get_parent_name() const {
3021   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3022   oop thread_obj = threadObj();
3023   if (thread_obj != NULL) {
3024     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3025     if (thread_group != NULL) {
3026       oop parent = java_lang_ThreadGroup::parent(thread_group);
3027       if (parent != NULL) {
3028         // ThreadGroup.name can be null
3029         return java_lang_ThreadGroup::name(parent);
3030       }
3031     }
3032   }
3033   return NULL;
3034 }
3035 
3036 ThreadPriority JavaThread::java_priority() const {
3037   oop thr_oop = threadObj();
3038   if (thr_oop == NULL) return NormPriority; // Bootstrapping
3039   ThreadPriority priority = java_lang_Thread::priority(thr_oop);
3040   assert(MinPriority <= priority && priority <= MaxPriority, "sanity check");
3041   return priority;
3042 }
3043 
3044 void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
3045 
3046   assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
3047   // Link Java Thread object <-> C++ Thread
3048 
3049   // Get the C++ thread object (an oop) from the JNI handle (a jthread)
3050   // and put it into a new Handle.  The Handle "thread_oop" can then
3051   // be used to pass the C++ thread object to other methods.
3052 
3053   // Set the Java level thread object (jthread) field of the
3054   // new thread (a JavaThread *) to C++ thread object using the
3055   // "thread_oop" handle.
3056 
3057   // Set the thread field (a JavaThread *) of the
3058   // oop representing the java_lang_Thread to the new thread (a JavaThread *).
3059 
3060   Handle thread_oop(Thread::current(),
3061                     JNIHandles::resolve_non_null(jni_thread));
3062   assert(InstanceKlass::cast(thread_oop->klass())->is_linked(),
3063          "must be initialized");
3064   set_threadObj(thread_oop());
3065   java_lang_Thread::set_thread(thread_oop(), this);
3066 
3067   if (prio == NoPriority) {
3068     prio = java_lang_Thread::priority(thread_oop());
3069     assert(prio != NoPriority, "A valid priority should be present");
3070   }
3071 
3072   // Push the Java priority down to the native thread; needs Threads_lock
3073   Thread::set_priority(this, prio);
3074 
3075   prepare_ext();
3076 
3077   // Add the new thread to the Threads list and set it in motion.
3078   // We must have threads lock in order to call Threads::add.
3079   // It is crucial that we do not block before the thread is
3080   // added to the Threads list for if a GC happens, then the java_thread oop
3081   // will not be visited by GC.
3082   Threads::add(this);
3083 }
3084 
3085 oop JavaThread::current_park_blocker() {
3086   // Support for JSR-166 locks
3087   oop thread_oop = threadObj();
3088   if (thread_oop != NULL &&
3089       JDK_Version::current().supports_thread_park_blocker()) {
3090     return java_lang_Thread::park_blocker(thread_oop);
3091   }
3092   return NULL;
3093 }
3094 
3095 
3096 void JavaThread::print_stack_on(outputStream* st) {
3097   if (!has_last_Java_frame()) return;
3098   ResourceMark rm;
3099   HandleMark   hm;
3100 
3101   RegisterMap reg_map(this);
3102   vframe* start_vf = last_java_vframe(&reg_map);
3103   int count = 0;
3104   for (vframe* f = start_vf; f; f = f->sender()) {
3105     if (f->is_java_frame()) {
3106       javaVFrame* jvf = javaVFrame::cast(f);
3107       java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
3108 
3109       // Print out lock information
3110       if (JavaMonitorsInStackTrace) {
3111         jvf->print_lock_info_on(st, count);
3112       }
3113     } else {
3114       // Ignore non-Java frames
3115     }
3116 
3117     // Bail-out case for too deep stacks
3118     count++;
3119     if (MaxJavaStackTraceDepth == count) return;
3120   }
3121 }
3122 
3123 
3124 // JVMTI PopFrame support
3125 void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
3126   assert(_popframe_preserved_args == NULL, "should not wipe out old PopFrame preserved arguments");
3127   if (in_bytes(size_in_bytes) != 0) {
3128     _popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes), mtThread);
3129     _popframe_preserved_args_size = in_bytes(size_in_bytes);
3130     Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
3131   }
3132 }
3133 
3134 void* JavaThread::popframe_preserved_args() {
3135   return _popframe_preserved_args;
3136 }
3137 
3138 ByteSize JavaThread::popframe_preserved_args_size() {
3139   return in_ByteSize(_popframe_preserved_args_size);
3140 }
3141 
3142 WordSize JavaThread::popframe_preserved_args_size_in_words() {
3143   int sz = in_bytes(popframe_preserved_args_size());
3144   assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
3145   return in_WordSize(sz / wordSize);
3146 }
3147 
3148 void JavaThread::popframe_free_preserved_args() {
3149   assert(_popframe_preserved_args != NULL, "should not free PopFrame preserved arguments twice");
3150   FREE_C_HEAP_ARRAY(char, (char*) _popframe_preserved_args);
3151   _popframe_preserved_args = NULL;
3152   _popframe_preserved_args_size = 0;
3153 }
3154 
3155 #ifndef PRODUCT
3156 
3157 void JavaThread::trace_frames() {
3158   tty->print_cr("[Describe stack]");
3159   int frame_no = 1;
3160   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
3161     tty->print("  %d. ", frame_no++);
3162     fst.current()->print_value_on(tty, this);
3163     tty->cr();
3164   }
3165 }
3166 
3167 class PrintAndVerifyOopClosure: public OopClosure {
3168  protected:
3169   template <class T> inline void do_oop_work(T* p) {
3170     oop obj = oopDesc::load_decode_heap_oop(p);
3171     if (obj == NULL) return;
3172     tty->print(INTPTR_FORMAT ": ", p2i(p));
3173     if (obj->is_oop_or_null()) {
3174       if (obj->is_objArray()) {
3175         tty->print_cr("valid objArray: " INTPTR_FORMAT, p2i(obj));
3176       } else {
3177         obj->print();
3178       }
3179     } else {
3180       tty->print_cr("invalid oop: " INTPTR_FORMAT, p2i(obj));
3181     }
3182     tty->cr();
3183   }
3184  public:
3185   virtual void do_oop(oop* p) { do_oop_work(p); }
3186   virtual void do_oop(narrowOop* p)  { do_oop_work(p); }
3187 };
3188 
3189 
3190 static void oops_print(frame* f, const RegisterMap *map) {
3191   PrintAndVerifyOopClosure print;
3192   f->print_value();
3193   f->oops_do(&print, NULL, NULL, (RegisterMap*)map);
3194 }
3195 
3196 // Print our all the locations that contain oops and whether they are
3197 // valid or not.  This useful when trying to find the oldest frame
3198 // where an oop has gone bad since the frame walk is from youngest to
3199 // oldest.
3200 void JavaThread::trace_oops() {
3201   tty->print_cr("[Trace oops]");
3202   frames_do(oops_print);
3203 }
3204 
3205 
3206 #ifdef ASSERT
3207 // Print or validate the layout of stack frames
3208 void JavaThread::print_frame_layout(int depth, bool validate_only) {
3209   ResourceMark rm;
3210   PRESERVE_EXCEPTION_MARK;
3211   FrameValues values;
3212   int frame_no = 0;
3213   for (StackFrameStream fst(this, false); !fst.is_done(); fst.next()) {
3214     fst.current()->describe(values, ++frame_no);
3215     if (depth == frame_no) break;
3216   }
3217   if (validate_only) {
3218     values.validate();
3219   } else {
3220     tty->print_cr("[Describe stack layout]");
3221     values.print(this);
3222   }
3223 }
3224 #endif
3225 
3226 void JavaThread::trace_stack_from(vframe* start_vf) {
3227   ResourceMark rm;
3228   int vframe_no = 1;
3229   for (vframe* f = start_vf; f; f = f->sender()) {
3230     if (f->is_java_frame()) {
3231       javaVFrame::cast(f)->print_activation(vframe_no++);
3232     } else {
3233       f->print();
3234     }
3235     if (vframe_no > StackPrintLimit) {
3236       tty->print_cr("...<more frames>...");
3237       return;
3238     }
3239   }
3240 }
3241 
3242 
3243 void JavaThread::trace_stack() {
3244   if (!has_last_Java_frame()) return;
3245   ResourceMark rm;
3246   HandleMark   hm;
3247   RegisterMap reg_map(this);
3248   trace_stack_from(last_java_vframe(&reg_map));
3249 }
3250 
3251 
3252 #endif // PRODUCT
3253 
3254 
3255 javaVFrame* JavaThread::last_java_vframe(RegisterMap *reg_map) {
3256   assert(reg_map != NULL, "a map must be given");
3257   frame f = last_frame();
3258   for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender()) {
3259     if (vf->is_java_frame()) return javaVFrame::cast(vf);
3260   }
3261   return NULL;
3262 }
3263 
3264 
3265 Klass* JavaThread::security_get_caller_class(int depth) {
3266   vframeStream vfst(this);
3267   vfst.security_get_caller_frame(depth);
3268   if (!vfst.at_end()) {
3269     return vfst.method()->method_holder();
3270   }
3271   return NULL;
3272 }
3273 
3274 static void compiler_thread_entry(JavaThread* thread, TRAPS) {
3275   assert(thread->is_Compiler_thread(), "must be compiler thread");
3276   CompileBroker::compiler_thread_loop();
3277 }
3278 
3279 static void sweeper_thread_entry(JavaThread* thread, TRAPS) {
3280   NMethodSweeper::sweeper_loop();
3281 }
3282 
3283 // Create a CompilerThread
3284 CompilerThread::CompilerThread(CompileQueue* queue,
3285                                CompilerCounters* counters)
3286                                : JavaThread(&compiler_thread_entry) {
3287   _env   = NULL;
3288   _log   = NULL;
3289   _task  = NULL;
3290   _queue = queue;
3291   _counters = counters;
3292   _buffer_blob = NULL;
3293   _compiler = NULL;
3294 
3295 #ifndef PRODUCT
3296   _ideal_graph_printer = NULL;
3297 #endif
3298 }
3299 
3300 bool CompilerThread::can_call_java() const {
3301   return _compiler != NULL && _compiler->is_jvmci();
3302 }
3303 
3304 // Create sweeper thread
3305 CodeCacheSweeperThread::CodeCacheSweeperThread()
3306 : JavaThread(&sweeper_thread_entry) {
3307   _scanned_nmethod = NULL;
3308 }
3309 void CodeCacheSweeperThread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
3310   JavaThread::oops_do(f, cld_f, cf);
3311   if (_scanned_nmethod != NULL && cf != NULL) {
3312     // Safepoints can occur when the sweeper is scanning an nmethod so
3313     // process it here to make sure it isn't unloaded in the middle of
3314     // a scan.
3315     cf->do_code_blob(_scanned_nmethod);
3316   }
3317 }
3318 
3319 
3320 // ======= Threads ========
3321 
3322 // The Threads class links together all active threads, and provides
3323 // operations over all threads.  It is protected by its own Mutex
3324 // lock, which is also used in other contexts to protect thread
3325 // operations from having the thread being operated on from exiting
3326 // and going away unexpectedly (e.g., safepoint synchronization)
3327 
3328 JavaThread* Threads::_thread_list = NULL;
3329 int         Threads::_number_of_threads = 0;
3330 int         Threads::_number_of_non_daemon_threads = 0;
3331 int         Threads::_return_code = 0;
3332 int         Threads::_thread_claim_parity = 0;
3333 size_t      JavaThread::_stack_size_at_create = 0;
3334 #ifdef ASSERT
3335 bool        Threads::_vm_complete = false;
3336 #endif
3337 
3338 // All JavaThreads
3339 #define ALL_JAVA_THREADS(X) for (JavaThread* X = _thread_list; X; X = X->next())
3340 
3341 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system)
3342 void Threads::threads_do(ThreadClosure* tc) {
3343   assert_locked_or_safepoint(Threads_lock);
3344   // ALL_JAVA_THREADS iterates through all JavaThreads
3345   ALL_JAVA_THREADS(p) {
3346     tc->do_thread(p);
3347   }
3348   // Someday we could have a table or list of all non-JavaThreads.
3349   // For now, just manually iterate through them.
3350   tc->do_thread(VMThread::vm_thread());
3351   Universe::heap()->gc_threads_do(tc);
3352   WatcherThread *wt = WatcherThread::watcher_thread();
3353   // Strictly speaking, the following NULL check isn't sufficient to make sure
3354   // the data for WatcherThread is still valid upon being examined. However,
3355   // considering that WatchThread terminates when the VM is on the way to
3356   // exit at safepoint, the chance of the above is extremely small. The right
3357   // way to prevent termination of WatcherThread would be to acquire
3358   // Terminator_lock, but we can't do that without violating the lock rank
3359   // checking in some cases.
3360   if (wt != NULL) {
3361     tc->do_thread(wt);
3362   }
3363 
3364   // If CompilerThreads ever become non-JavaThreads, add them here
3365 }
3366 
3367 void Threads::initialize_java_lang_classes(JavaThread* main_thread, TRAPS) {
3368   TraceStartupTime timer("Initialize java.lang classes");
3369 
3370   if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
3371     create_vm_init_libraries();
3372   }
3373 
3374   initialize_class(vmSymbols::java_lang_String(), CHECK);
3375 
3376   // Inject CompactStrings value after the static initializers for String ran.
3377   java_lang_String::set_compact_strings(CompactStrings);
3378 
3379   // Initialize java_lang.System (needed before creating the thread)
3380   initialize_class(vmSymbols::java_lang_System(), CHECK);
3381   // The VM creates & returns objects of this class. Make sure it's initialized.
3382   initialize_class(vmSymbols::java_lang_Class(), CHECK);
3383   initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK);
3384   Handle thread_group = create_initial_thread_group(CHECK);
3385   Universe::set_main_thread_group(thread_group());
3386   initialize_class(vmSymbols::java_lang_Thread(), CHECK);
3387   oop thread_object = create_initial_thread(thread_group, main_thread, CHECK);
3388   main_thread->set_threadObj(thread_object);
3389   // Set thread status to running since main thread has
3390   // been started and running.
3391   java_lang_Thread::set_thread_status(thread_object,
3392                                       java_lang_Thread::RUNNABLE);
3393 
3394   // The VM preresolves methods to these classes. Make sure that they get initialized
3395   initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK);
3396   initialize_class(vmSymbols::java_lang_ref_Finalizer(), CHECK);
3397   call_initializeSystemClass(CHECK);
3398 
3399   // get the Java runtime name after java.lang.System is initialized
3400   JDK_Version::set_runtime_name(get_java_runtime_name(THREAD));
3401   JDK_Version::set_runtime_version(get_java_runtime_version(THREAD));
3402 
3403   // an instance of OutOfMemory exception has been allocated earlier
3404   initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK);
3405   initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK);
3406   initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK);
3407   initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK);
3408   initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK);
3409   initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK);
3410   initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK);
3411   initialize_class(vmSymbols::java_lang_IllegalArgumentException(), CHECK);
3412 }
3413 
3414 void Threads::initialize_jsr292_core_classes(TRAPS) {
3415   TraceStartupTime timer("Initialize java.lang.invoke classes");
3416 
3417   initialize_class(vmSymbols::java_lang_invoke_MethodHandle(), CHECK);
3418   initialize_class(vmSymbols::java_lang_invoke_MemberName(), CHECK);
3419   initialize_class(vmSymbols::java_lang_invoke_MethodHandleNatives(), CHECK);
3420 }
3421 
3422 jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
3423   extern void JDK_Version_init();
3424 
3425   // Preinitialize version info.
3426   VM_Version::early_initialize();
3427 
3428   // Check version
3429   if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
3430 
3431   // Initialize library-based TLS
3432   ThreadLocalStorage::init();
3433 
3434   // Initialize the output stream module
3435   ostream_init();
3436 
3437   // Process java launcher properties.
3438   Arguments::process_sun_java_launcher_properties(args);
3439 
3440   // Initialize the os module
3441   os::init();
3442 
3443   // Record VM creation timing statistics
3444   TraceVmCreationTime create_vm_timer;
3445   create_vm_timer.start();
3446 
3447   // Initialize system properties.
3448   Arguments::init_system_properties();
3449 
3450   // So that JDK version can be used as a discriminator when parsing arguments
3451   JDK_Version_init();
3452 
3453   // Update/Initialize System properties after JDK version number is known
3454   Arguments::init_version_specific_system_properties();
3455 
3456   // Make sure to initialize log configuration *before* parsing arguments
3457   LogConfiguration::initialize(create_vm_timer.begin_time());
3458 
3459   // Parse arguments
3460   jint parse_result = Arguments::parse(args);
3461   if (parse_result != JNI_OK) return parse_result;
3462 
3463   os::init_before_ergo();
3464 
3465   jint ergo_result = Arguments::apply_ergo();
3466   if (ergo_result != JNI_OK) return ergo_result;
3467 
3468   // Final check of all ranges after ergonomics which may change values.
3469   if (!CommandLineFlagRangeList::check_ranges()) {
3470     return JNI_EINVAL;
3471   }
3472 
3473   // Final check of all 'AfterErgo' constraints after ergonomics which may change values.
3474   bool constraint_result = CommandLineFlagConstraintList::check_constraints(CommandLineFlagConstraint::AfterErgo);
3475   if (!constraint_result) {
3476     return JNI_EINVAL;
3477   }
3478 
3479   if (PauseAtStartup) {
3480     os::pause();
3481   }
3482 
3483   HOTSPOT_VM_INIT_BEGIN();
3484 
3485   // Timing (must come after argument parsing)
3486   TraceStartupTime timer("Create VM");
3487 
3488   // Initialize the os module after parsing the args
3489   jint os_init_2_result = os::init_2();
3490   if (os_init_2_result != JNI_OK) return os_init_2_result;
3491 
3492   jint adjust_after_os_result = Arguments::adjust_after_os();
3493   if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;
3494 
3495   // Initialize output stream logging
3496   ostream_init_log();
3497 
3498   // Convert -Xrun to -agentlib: if there is no JVM_OnLoad
3499   // Must be before create_vm_init_agents()
3500   if (Arguments::init_libraries_at_startup()) {
3501     convert_vm_init_libraries_to_agents();
3502   }
3503 
3504   // Launch -agentlib/-agentpath and converted -Xrun agents
3505   if (Arguments::init_agents_at_startup()) {
3506     create_vm_init_agents();
3507   }
3508 
3509   // Initialize Threads state
3510   _thread_list = NULL;
3511   _number_of_threads = 0;
3512   _number_of_non_daemon_threads = 0;
3513 
3514   // Initialize global data structures and create system classes in heap
3515   vm_init_globals();
3516 
3517 #if INCLUDE_JVMCI
3518   if (JVMCICounterSize > 0) {
3519     JavaThread::_jvmci_old_thread_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
3520     memset(JavaThread::_jvmci_old_thread_counters, 0, sizeof(jlong) * JVMCICounterSize);
3521   } else {
3522     JavaThread::_jvmci_old_thread_counters = NULL;
3523   }
3524 #endif // INCLUDE_JVMCI
3525 
3526   // Attach the main thread to this os thread
3527   JavaThread* main_thread = new JavaThread();
3528   main_thread->set_thread_state(_thread_in_vm);
3529   main_thread->initialize_thread_current();
3530   // must do this before set_active_handles
3531   main_thread->record_stack_base_and_size();
3532   main_thread->set_active_handles(JNIHandleBlock::allocate_block());
3533 
3534   if (!main_thread->set_as_starting_thread()) {
3535     vm_shutdown_during_initialization(
3536                                       "Failed necessary internal allocation. Out of swap space");
3537     delete main_thread;
3538     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3539     return JNI_ENOMEM;
3540   }
3541 
3542   // Enable guard page *after* os::create_main_thread(), otherwise it would
3543   // crash Linux VM, see notes in os_linux.cpp.
3544   main_thread->create_stack_guard_pages();
3545 
3546   // Initialize Java-Level synchronization subsystem
3547   ObjectMonitor::Initialize();
3548 
3549   // Initialize global modules
3550   jint status = init_globals();
3551   if (status != JNI_OK) {
3552     delete main_thread;
3553     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3554     return status;
3555   }
3556 
3557   if (TRACE_INITIALIZE() != JNI_OK) {
3558     vm_exit_during_initialization("Failed to initialize tracing backend");
3559   }
3560 
3561   // Should be done after the heap is fully created
3562   main_thread->cache_global_variables();
3563 
3564   HandleMark hm;
3565 
3566   { MutexLocker mu(Threads_lock);
3567     Threads::add(main_thread);
3568   }
3569 
3570   // Any JVMTI raw monitors entered in onload will transition into
3571   // real raw monitor. VM is setup enough here for raw monitor enter.
3572   JvmtiExport::transition_pending_onload_raw_monitors();
3573 
3574   // Create the VMThread
3575   { TraceStartupTime timer("Start VMThread");
3576 
3577   VMThread::create();
3578     Thread* vmthread = VMThread::vm_thread();
3579 
3580     if (!os::create_thread(vmthread, os::vm_thread)) {
3581       vm_exit_during_initialization("Cannot create VM thread. "
3582                                     "Out of system resources.");
3583     }
3584 
3585     // Wait for the VM thread to become ready, and VMThread::run to initialize
3586     // Monitors can have spurious returns, must always check another state flag
3587     {
3588       MutexLocker ml(Notify_lock);
3589       os::start_thread(vmthread);
3590       while (vmthread->active_handles() == NULL) {
3591         Notify_lock->wait();
3592       }
3593     }
3594   }
3595 
3596   assert(Universe::is_fully_initialized(), "not initialized");
3597   if (VerifyDuringStartup) {
3598     // Make sure we're starting with a clean slate.
3599     VM_Verify verify_op;
3600     VMThread::execute(&verify_op);
3601   }
3602 
3603   Thread* THREAD = Thread::current();
3604 
3605   // At this point, the Universe is initialized, but we have not executed
3606   // any byte code.  Now is a good time (the only time) to dump out the
3607   // internal state of the JVM for sharing.
3608   if (DumpSharedSpaces) {
3609     MetaspaceShared::preload_and_dump(CHECK_JNI_ERR);
3610     ShouldNotReachHere();
3611   }
3612 
3613   // Always call even when there are not JVMTI environments yet, since environments
3614   // may be attached late and JVMTI must track phases of VM execution
3615   JvmtiExport::enter_start_phase();
3616 
3617   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
3618   JvmtiExport::post_vm_start();
3619 
3620   initialize_java_lang_classes(main_thread, CHECK_JNI_ERR);
3621 
3622   // We need this for ClassDataSharing - the initial vm.info property is set
3623   // with the default value of CDS "sharing" which may be reset through
3624   // command line options.
3625   reset_vm_info_property(CHECK_JNI_ERR);
3626 
3627   quicken_jni_functions();
3628 
3629   // No more stub generation allowed after that point.
3630   StubCodeDesc::freeze();
3631 
3632   // Set flag that basic initialization has completed. Used by exceptions and various
3633   // debug stuff, that does not work until all basic classes have been initialized.
3634   set_init_completed();
3635 
3636   LogConfiguration::post_initialize();
3637   Metaspace::post_initialize();
3638 
3639   HOTSPOT_VM_INIT_END();
3640 
3641   // record VM initialization completion time
3642 #if INCLUDE_MANAGEMENT
3643   Management::record_vm_init_completed();
3644 #endif // INCLUDE_MANAGEMENT
3645 
3646   // Compute system loader. Note that this has to occur after set_init_completed, since
3647   // valid exceptions may be thrown in the process.
3648   // Note that we do not use CHECK_0 here since we are inside an EXCEPTION_MARK and
3649   // set_init_completed has just been called, causing exceptions not to be shortcut
3650   // anymore. We call vm_exit_during_initialization directly instead.
3651   SystemDictionary::compute_java_system_loader(CHECK_(JNI_ERR));
3652 
3653 #if INCLUDE_ALL_GCS
3654   // Support for ConcurrentMarkSweep. This should be cleaned up
3655   // and better encapsulated. The ugly nested if test would go away
3656   // once things are properly refactored. XXX YSR
3657   if (UseConcMarkSweepGC || UseG1GC) {
3658     if (UseConcMarkSweepGC) {
3659       ConcurrentMarkSweepThread::makeSurrogateLockerThread(CHECK_JNI_ERR);
3660     } else {
3661       ConcurrentMarkThread::makeSurrogateLockerThread(CHECK_JNI_ERR);
3662     }
3663   }
3664 #endif // INCLUDE_ALL_GCS
3665 
3666   // Always call even when there are not JVMTI environments yet, since environments
3667   // may be attached late and JVMTI must track phases of VM execution
3668   JvmtiExport::enter_live_phase();
3669 
3670   // Signal Dispatcher needs to be started before VMInit event is posted
3671   os::signal_init();
3672 
3673   // Start Attach Listener if +StartAttachListener or it can't be started lazily
3674   if (!DisableAttachMechanism) {
3675     AttachListener::vm_start();
3676     if (StartAttachListener || AttachListener::init_at_startup()) {
3677       AttachListener::init();
3678     }
3679   }
3680 
3681   // Launch -Xrun agents
3682   // Must be done in the JVMTI live phase so that for backward compatibility the JDWP
3683   // back-end can launch with -Xdebug -Xrunjdwp.
3684   if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
3685     create_vm_init_libraries();
3686   }
3687 
3688   // Notify JVMTI agents that VM initialization is complete - nop if no agents.
3689   JvmtiExport::post_vm_initialized();
3690 
3691   if (TRACE_START() != JNI_OK) {
3692     vm_exit_during_initialization("Failed to start tracing backend.");
3693   }
3694 
3695   if (CleanChunkPoolAsync) {
3696     Chunk::start_chunk_pool_cleaner_task();
3697   }
3698 
3699   // initialize compiler(s)
3700 #if defined(COMPILER1) || defined(COMPILER2) || defined(SHARK) || INCLUDE_JVMCI
3701   CompileBroker::compilation_init(CHECK_JNI_ERR);
3702 #endif
3703 
3704   // Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
3705   // It is done after compilers are initialized, because otherwise compilations of
3706   // signature polymorphic MH intrinsics can be missed
3707   // (see SystemDictionary::find_method_handle_intrinsic).
3708   initialize_jsr292_core_classes(CHECK_JNI_ERR);
3709 
3710 #if INCLUDE_MANAGEMENT
3711   Management::initialize(THREAD);
3712 
3713   if (HAS_PENDING_EXCEPTION) {
3714     // management agent fails to start possibly due to
3715     // configuration problem and is responsible for printing
3716     // stack trace if appropriate. Simply exit VM.
3717     vm_exit(1);
3718   }
3719 #endif // INCLUDE_MANAGEMENT
3720 
3721   if (Arguments::has_profile())       FlatProfiler::engage(main_thread, true);
3722   if (MemProfiling)                   MemProfiler::engage();
3723   StatSampler::engage();
3724   if (CheckJNICalls)                  JniPeriodicChecker::engage();
3725 
3726   BiasedLocking::init();
3727 
3728 #if INCLUDE_RTM_OPT
3729   RTMLockingCounters::init();
3730 #endif
3731 
3732   if (JDK_Version::current().post_vm_init_hook_enabled()) {
3733     call_postVMInitHook(THREAD);
3734     // The Java side of PostVMInitHook.run must deal with all
3735     // exceptions and provide means of diagnosis.
3736     if (HAS_PENDING_EXCEPTION) {
3737       CLEAR_PENDING_EXCEPTION;
3738     }
3739   }
3740 
3741   {
3742     MutexLocker ml(PeriodicTask_lock);
3743     // Make sure the WatcherThread can be started by WatcherThread::start()
3744     // or by dynamic enrollment.
3745     WatcherThread::make_startable();
3746     // Start up the WatcherThread if there are any periodic tasks
3747     // NOTE:  All PeriodicTasks should be registered by now. If they
3748     //   aren't, late joiners might appear to start slowly (we might
3749     //   take a while to process their first tick).
3750     if (PeriodicTask::num_tasks() > 0) {
3751       WatcherThread::start();
3752     }
3753   }
3754 
3755   CodeCacheExtensions::complete_step(CodeCacheExtensionsSteps::CreateVM);
3756 
3757   create_vm_timer.end();
3758 #ifdef ASSERT
3759   _vm_complete = true;
3760 #endif
3761   return JNI_OK;
3762 }
3763 
3764 // type for the Agent_OnLoad and JVM_OnLoad entry points
3765 extern "C" {
3766   typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
3767 }
3768 // Find a command line agent library and return its entry point for
3769 //         -agentlib:  -agentpath:   -Xrun
3770 // num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array.
3771 static OnLoadEntry_t lookup_on_load(AgentLibrary* agent,
3772                                     const char *on_load_symbols[],
3773                                     size_t num_symbol_entries) {
3774   OnLoadEntry_t on_load_entry = NULL;
3775   void *library = NULL;
3776 
3777   if (!agent->valid()) {
3778     char buffer[JVM_MAXPATHLEN];
3779     char ebuf[1024] = "";
3780     const char *name = agent->name();
3781     const char *msg = "Could not find agent library ";
3782 
3783     // First check to see if agent is statically linked into executable
3784     if (os::find_builtin_agent(agent, on_load_symbols, num_symbol_entries)) {
3785       library = agent->os_lib();
3786     } else if (agent->is_absolute_path()) {
3787       library = os::dll_load(name, ebuf, sizeof ebuf);
3788       if (library == NULL) {
3789         const char *sub_msg = " in absolute path, with error: ";
3790         size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3791         char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
3792         jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
3793         // If we can't find the agent, exit.
3794         vm_exit_during_initialization(buf, NULL);
3795         FREE_C_HEAP_ARRAY(char, buf);
3796       }
3797     } else {
3798       // Try to load the agent from the standard dll directory
3799       if (os::dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(),
3800                              name)) {
3801         library = os::dll_load(buffer, ebuf, sizeof ebuf);
3802       }
3803       if (library == NULL) { // Try the local directory
3804         char ns[1] = {0};
3805         if (os::dll_build_name(buffer, sizeof(buffer), ns, name)) {
3806           library = os::dll_load(buffer, ebuf, sizeof ebuf);
3807         }
3808         if (library == NULL) {
3809           const char *sub_msg = " on the library path, with error: ";
3810           size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3811           char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
3812           jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
3813           // If we can't find the agent, exit.
3814           vm_exit_during_initialization(buf, NULL);
3815           FREE_C_HEAP_ARRAY(char, buf);
3816         }
3817       }
3818     }
3819     agent->set_os_lib(library);
3820     agent->set_valid();
3821   }
3822 
3823   // Find the OnLoad function.
3824   on_load_entry =
3825     CAST_TO_FN_PTR(OnLoadEntry_t, os::find_agent_function(agent,
3826                                                           false,
3827                                                           on_load_symbols,
3828                                                           num_symbol_entries));
3829   return on_load_entry;
3830 }
3831 
3832 // Find the JVM_OnLoad entry point
3833 static OnLoadEntry_t lookup_jvm_on_load(AgentLibrary* agent) {
3834   const char *on_load_symbols[] = JVM_ONLOAD_SYMBOLS;
3835   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
3836 }
3837 
3838 // Find the Agent_OnLoad entry point
3839 static OnLoadEntry_t lookup_agent_on_load(AgentLibrary* agent) {
3840   const char *on_load_symbols[] = AGENT_ONLOAD_SYMBOLS;
3841   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
3842 }
3843 
3844 // For backwards compatibility with -Xrun
3845 // Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be
3846 // treated like -agentpath:
3847 // Must be called before agent libraries are created
3848 void Threads::convert_vm_init_libraries_to_agents() {
3849   AgentLibrary* agent;
3850   AgentLibrary* next;
3851 
3852   for (agent = Arguments::libraries(); agent != NULL; agent = next) {
3853     next = agent->next();  // cache the next agent now as this agent may get moved off this list
3854     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
3855 
3856     // If there is an JVM_OnLoad function it will get called later,
3857     // otherwise see if there is an Agent_OnLoad
3858     if (on_load_entry == NULL) {
3859       on_load_entry = lookup_agent_on_load(agent);
3860       if (on_load_entry != NULL) {
3861         // switch it to the agent list -- so that Agent_OnLoad will be called,
3862         // JVM_OnLoad won't be attempted and Agent_OnUnload will
3863         Arguments::convert_library_to_agent(agent);
3864       } else {
3865         vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
3866       }
3867     }
3868   }
3869 }
3870 
3871 // Create agents for -agentlib:  -agentpath:  and converted -Xrun
3872 // Invokes Agent_OnLoad
3873 // Called very early -- before JavaThreads exist
3874 void Threads::create_vm_init_agents() {
3875   extern struct JavaVM_ main_vm;
3876   AgentLibrary* agent;
3877 
3878   JvmtiExport::enter_onload_phase();
3879 
3880   for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
3881     OnLoadEntry_t  on_load_entry = lookup_agent_on_load(agent);
3882 
3883     if (on_load_entry != NULL) {
3884       // Invoke the Agent_OnLoad function
3885       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
3886       if (err != JNI_OK) {
3887         vm_exit_during_initialization("agent library failed to init", agent->name());
3888       }
3889     } else {
3890       vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
3891     }
3892   }
3893   JvmtiExport::enter_primordial_phase();
3894 }
3895 
3896 extern "C" {
3897   typedef void (JNICALL *Agent_OnUnload_t)(JavaVM *);
3898 }
3899 
3900 void Threads::shutdown_vm_agents() {
3901   // Send any Agent_OnUnload notifications
3902   const char *on_unload_symbols[] = AGENT_ONUNLOAD_SYMBOLS;
3903   size_t num_symbol_entries = ARRAY_SIZE(on_unload_symbols);
3904   extern struct JavaVM_ main_vm;
3905   for (AgentLibrary* agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
3906 
3907     // Find the Agent_OnUnload function.
3908     Agent_OnUnload_t unload_entry = CAST_TO_FN_PTR(Agent_OnUnload_t,
3909                                                    os::find_agent_function(agent,
3910                                                    false,
3911                                                    on_unload_symbols,
3912                                                    num_symbol_entries));
3913 
3914     // Invoke the Agent_OnUnload function
3915     if (unload_entry != NULL) {
3916       JavaThread* thread = JavaThread::current();
3917       ThreadToNativeFromVM ttn(thread);
3918       HandleMark hm(thread);
3919       (*unload_entry)(&main_vm);
3920     }
3921   }
3922 }
3923 
3924 // Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries
3925 // Invokes JVM_OnLoad
3926 void Threads::create_vm_init_libraries() {
3927   extern struct JavaVM_ main_vm;
3928   AgentLibrary* agent;
3929 
3930   for (agent = Arguments::libraries(); agent != NULL; agent = agent->next()) {
3931     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
3932 
3933     if (on_load_entry != NULL) {
3934       // Invoke the JVM_OnLoad function
3935       JavaThread* thread = JavaThread::current();
3936       ThreadToNativeFromVM ttn(thread);
3937       HandleMark hm(thread);
3938       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
3939       if (err != JNI_OK) {
3940         vm_exit_during_initialization("-Xrun library failed to init", agent->name());
3941       }
3942     } else {
3943       vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
3944     }
3945   }
3946 }
3947 
3948 JavaThread* Threads::find_java_thread_from_java_tid(jlong java_tid) {
3949   assert(Threads_lock->owned_by_self(), "Must hold Threads_lock");
3950 
3951   JavaThread* java_thread = NULL;
3952   // Sequential search for now.  Need to do better optimization later.
3953   for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) {
3954     oop tobj = thread->threadObj();
3955     if (!thread->is_exiting() &&
3956         tobj != NULL &&
3957         java_tid == java_lang_Thread::thread_id(tobj)) {
3958       java_thread = thread;
3959       break;
3960     }
3961   }
3962   return java_thread;
3963 }
3964 
3965 
3966 // Last thread running calls java.lang.Shutdown.shutdown()
3967 void JavaThread::invoke_shutdown_hooks() {
3968   HandleMark hm(this);
3969 
3970   // We could get here with a pending exception, if so clear it now.
3971   if (this->has_pending_exception()) {
3972     this->clear_pending_exception();
3973   }
3974 
3975   EXCEPTION_MARK;
3976   Klass* k =
3977     SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
3978                                       THREAD);
3979   if (k != NULL) {
3980     // SystemDictionary::resolve_or_null will return null if there was
3981     // an exception.  If we cannot load the Shutdown class, just don't
3982     // call Shutdown.shutdown() at all.  This will mean the shutdown hooks
3983     // and finalizers (if runFinalizersOnExit is set) won't be run.
3984     // Note that if a shutdown hook was registered or runFinalizersOnExit
3985     // was called, the Shutdown class would have already been loaded
3986     // (Runtime.addShutdownHook and runFinalizersOnExit will load it).
3987     instanceKlassHandle shutdown_klass (THREAD, k);
3988     JavaValue result(T_VOID);
3989     JavaCalls::call_static(&result,
3990                            shutdown_klass,
3991                            vmSymbols::shutdown_method_name(),
3992                            vmSymbols::void_method_signature(),
3993                            THREAD);
3994   }
3995   CLEAR_PENDING_EXCEPTION;
3996 }
3997 
3998 // Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
3999 // the program falls off the end of main(). Another VM exit path is through
4000 // vm_exit() when the program calls System.exit() to return a value or when
4001 // there is a serious error in VM. The two shutdown paths are not exactly
4002 // the same, but they share Shutdown.shutdown() at Java level and before_exit()
4003 // and VM_Exit op at VM level.
4004 //
4005 // Shutdown sequence:
4006 //   + Shutdown native memory tracking if it is on
4007 //   + Wait until we are the last non-daemon thread to execute
4008 //     <-- every thing is still working at this moment -->
4009 //   + Call java.lang.Shutdown.shutdown(), which will invoke Java level
4010 //        shutdown hooks, run finalizers if finalization-on-exit
4011 //   + Call before_exit(), prepare for VM exit
4012 //      > run VM level shutdown hooks (they are registered through JVM_OnExit(),
4013 //        currently the only user of this mechanism is File.deleteOnExit())
4014 //      > stop flat profiler, StatSampler, watcher thread, CMS threads,
4015 //        post thread end and vm death events to JVMTI,
4016 //        stop signal thread
4017 //   + Call JavaThread::exit(), it will:
4018 //      > release JNI handle blocks, remove stack guard pages
4019 //      > remove this thread from Threads list
4020 //     <-- no more Java code from this thread after this point -->
4021 //   + Stop VM thread, it will bring the remaining VM to a safepoint and stop
4022 //     the compiler threads at safepoint
4023 //     <-- do not use anything that could get blocked by Safepoint -->
4024 //   + Disable tracing at JNI/JVM barriers
4025 //   + Set _vm_exited flag for threads that are still running native code
4026 //   + Delete this thread
4027 //   + Call exit_globals()
4028 //      > deletes tty
4029 //      > deletes PerfMemory resources
4030 //   + Return to caller
4031 
4032 bool Threads::destroy_vm() {
4033   JavaThread* thread = JavaThread::current();
4034 
4035 #ifdef ASSERT
4036   _vm_complete = false;
4037 #endif
4038   // Wait until we are the last non-daemon thread to execute
4039   { MutexLocker nu(Threads_lock);
4040     while (Threads::number_of_non_daemon_threads() > 1)
4041       // This wait should make safepoint checks, wait without a timeout,
4042       // and wait as a suspend-equivalent condition.
4043       //
4044       // Note: If the FlatProfiler is running and this thread is waiting
4045       // for another non-daemon thread to finish, then the FlatProfiler
4046       // is waiting for the external suspend request on this thread to
4047       // complete. wait_for_ext_suspend_completion() will eventually
4048       // timeout, but that takes time. Making this wait a suspend-
4049       // equivalent condition solves that timeout problem.
4050       //
4051       Threads_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
4052                          Mutex::_as_suspend_equivalent_flag);
4053   }
4054 
4055   // Hang forever on exit if we are reporting an error.
4056   if (ShowMessageBoxOnError && is_error_reported()) {
4057     os::infinite_sleep();
4058   }
4059   os::wait_for_keypress_at_exit();
4060 
4061   // run Java level shutdown hooks
4062   thread->invoke_shutdown_hooks();
4063 
4064   before_exit(thread);
4065 
4066   thread->exit(true);
4067 
4068   // Stop VM thread.
4069   {
4070     // 4945125 The vm thread comes to a safepoint during exit.
4071     // GC vm_operations can get caught at the safepoint, and the
4072     // heap is unparseable if they are caught. Grab the Heap_lock
4073     // to prevent this. The GC vm_operations will not be able to
4074     // queue until after the vm thread is dead. After this point,
4075     // we'll never emerge out of the safepoint before the VM exits.
4076 
4077     MutexLocker ml(Heap_lock);
4078 
4079     VMThread::wait_for_vm_thread_exit();
4080     assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
4081     VMThread::destroy();
4082   }
4083 
4084   // clean up ideal graph printers
4085 #if defined(COMPILER2) && !defined(PRODUCT)
4086   IdealGraphPrinter::clean_up();
4087 #endif
4088 
4089   // Now, all Java threads are gone except daemon threads. Daemon threads
4090   // running Java code or in VM are stopped by the Safepoint. However,
4091   // daemon threads executing native code are still running.  But they
4092   // will be stopped at native=>Java/VM barriers. Note that we can't
4093   // simply kill or suspend them, as it is inherently deadlock-prone.
4094 
4095   VM_Exit::set_vm_exited();
4096 
4097   notify_vm_shutdown();
4098 
4099   delete thread;
4100 
4101 #if INCLUDE_JVMCI
4102   if (JVMCICounterSize > 0) {
4103     FREE_C_HEAP_ARRAY(jlong, JavaThread::_jvmci_old_thread_counters);
4104   }
4105 #endif
4106 
4107   // exit_globals() will delete tty
4108   exit_globals();
4109 
4110   LogConfiguration::finalize();
4111 
4112   return true;
4113 }
4114 
4115 
4116 jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
4117   if (version == JNI_VERSION_1_1) return JNI_TRUE;
4118   return is_supported_jni_version(version);
4119 }
4120 
4121 
4122 jboolean Threads::is_supported_jni_version(jint version) {
4123   if (version == JNI_VERSION_1_2) return JNI_TRUE;
4124   if (version == JNI_VERSION_1_4) return JNI_TRUE;
4125   if (version == JNI_VERSION_1_6) return JNI_TRUE;
4126   if (version == JNI_VERSION_1_8) return JNI_TRUE;
4127   if (version == JNI_VERSION_9) return JNI_TRUE;
4128   return JNI_FALSE;
4129 }
4130 
4131 
4132 void Threads::add(JavaThread* p, bool force_daemon) {
4133   // The threads lock must be owned at this point
4134   assert_locked_or_safepoint(Threads_lock);
4135 
4136   // See the comment for this method in thread.hpp for its purpose and
4137   // why it is called here.
4138   p->initialize_queues();
4139   p->set_next(_thread_list);
4140   _thread_list = p;
4141   _number_of_threads++;
4142   oop threadObj = p->threadObj();
4143   bool daemon = true;
4144   // Bootstrapping problem: threadObj can be null for initial
4145   // JavaThread (or for threads attached via JNI)
4146   if ((!force_daemon) && (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj))) {
4147     _number_of_non_daemon_threads++;
4148     daemon = false;
4149   }
4150 
4151   ThreadService::add_thread(p, daemon);
4152 
4153   // Possible GC point.
4154   Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p));
4155 }
4156 
4157 void Threads::remove(JavaThread* p) {
4158   // Extra scope needed for Thread_lock, so we can check
4159   // that we do not remove thread without safepoint code notice
4160   { MutexLocker ml(Threads_lock);
4161 
4162     assert(includes(p), "p must be present");
4163 
4164     JavaThread* current = _thread_list;
4165     JavaThread* prev    = NULL;
4166 
4167     while (current != p) {
4168       prev    = current;
4169       current = current->next();
4170     }
4171 
4172     if (prev) {
4173       prev->set_next(current->next());
4174     } else {
4175       _thread_list = p->next();
4176     }
4177     _number_of_threads--;
4178     oop threadObj = p->threadObj();
4179     bool daemon = true;
4180     if (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj)) {
4181       _number_of_non_daemon_threads--;
4182       daemon = false;
4183 
4184       // Only one thread left, do a notify on the Threads_lock so a thread waiting
4185       // on destroy_vm will wake up.
4186       if (number_of_non_daemon_threads() == 1) {
4187         Threads_lock->notify_all();
4188       }
4189     }
4190     ThreadService::remove_thread(p, daemon);
4191 
4192     // Make sure that safepoint code disregard this thread. This is needed since
4193     // the thread might mess around with locks after this point. This can cause it
4194     // to do callbacks into the safepoint code. However, the safepoint code is not aware
4195     // of this thread since it is removed from the queue.
4196     p->set_terminated_value();
4197   } // unlock Threads_lock
4198 
4199   // Since Events::log uses a lock, we grab it outside the Threads_lock
4200   Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p));
4201 }
4202 
4203 // Threads_lock must be held when this is called (or must be called during a safepoint)
4204 bool Threads::includes(JavaThread* p) {
4205   assert(Threads_lock->is_locked(), "sanity check");
4206   ALL_JAVA_THREADS(q) {
4207     if (q == p) {
4208       return true;
4209     }
4210   }
4211   return false;
4212 }
4213 
4214 // Operations on the Threads list for GC.  These are not explicitly locked,
4215 // but the garbage collector must provide a safe context for them to run.
4216 // In particular, these things should never be called when the Threads_lock
4217 // is held by some other thread. (Note: the Safepoint abstraction also
4218 // uses the Threads_lock to guarantee this property. It also makes sure that
4219 // all threads gets blocked when exiting or starting).
4220 
4221 void Threads::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
4222   ALL_JAVA_THREADS(p) {
4223     p->oops_do(f, cld_f, cf);
4224   }
4225   VMThread::vm_thread()->oops_do(f, cld_f, cf);
4226 }
4227 
4228 void Threads::change_thread_claim_parity() {
4229   // Set the new claim parity.
4230   assert(_thread_claim_parity >= 0 && _thread_claim_parity <= 2,
4231          "Not in range.");
4232   _thread_claim_parity++;
4233   if (_thread_claim_parity == 3) _thread_claim_parity = 1;
4234   assert(_thread_claim_parity >= 1 && _thread_claim_parity <= 2,
4235          "Not in range.");
4236 }
4237 
4238 #ifdef ASSERT
4239 void Threads::assert_all_threads_claimed() {
4240   ALL_JAVA_THREADS(p) {
4241     const int thread_parity = p->oops_do_parity();
4242     assert((thread_parity == _thread_claim_parity),
4243            "Thread " PTR_FORMAT " has incorrect parity %d != %d", p2i(p), thread_parity, _thread_claim_parity);
4244   }
4245 }
4246 #endif // ASSERT
4247 
4248 void Threads::possibly_parallel_oops_do(bool is_par, OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
4249   int cp = Threads::thread_claim_parity();
4250   ALL_JAVA_THREADS(p) {
4251     if (p->claim_oops_do(is_par, cp)) {
4252       p->oops_do(f, cld_f, cf);
4253     }
4254   }
4255   VMThread* vmt = VMThread::vm_thread();
4256   if (vmt->claim_oops_do(is_par, cp)) {
4257     vmt->oops_do(f, cld_f, cf);
4258   }
4259 }
4260 
4261 #if INCLUDE_ALL_GCS
4262 // Used by ParallelScavenge
4263 void Threads::create_thread_roots_tasks(GCTaskQueue* q) {
4264   ALL_JAVA_THREADS(p) {
4265     q->enqueue(new ThreadRootsTask(p));
4266   }
4267   q->enqueue(new ThreadRootsTask(VMThread::vm_thread()));
4268 }
4269 
4270 // Used by Parallel Old
4271 void Threads::create_thread_roots_marking_tasks(GCTaskQueue* q) {
4272   ALL_JAVA_THREADS(p) {
4273     q->enqueue(new ThreadRootsMarkingTask(p));
4274   }
4275   q->enqueue(new ThreadRootsMarkingTask(VMThread::vm_thread()));
4276 }
4277 #endif // INCLUDE_ALL_GCS
4278 
4279 void Threads::nmethods_do(CodeBlobClosure* cf) {
4280   ALL_JAVA_THREADS(p) {
4281     p->nmethods_do(cf);
4282   }
4283   VMThread::vm_thread()->nmethods_do(cf);
4284 }
4285 
4286 void Threads::metadata_do(void f(Metadata*)) {
4287   ALL_JAVA_THREADS(p) {
4288     p->metadata_do(f);
4289   }
4290 }
4291 
4292 class ThreadHandlesClosure : public ThreadClosure {
4293   void (*_f)(Metadata*);
4294  public:
4295   ThreadHandlesClosure(void f(Metadata*)) : _f(f) {}
4296   virtual void do_thread(Thread* thread) {
4297     thread->metadata_handles_do(_f);
4298   }
4299 };
4300 
4301 void Threads::metadata_handles_do(void f(Metadata*)) {
4302   // Only walk the Handles in Thread.
4303   ThreadHandlesClosure handles_closure(f);
4304   threads_do(&handles_closure);
4305 }
4306 
4307 void Threads::deoptimized_wrt_marked_nmethods() {
4308   ALL_JAVA_THREADS(p) {
4309     p->deoptimized_wrt_marked_nmethods();
4310   }
4311 }
4312 
4313 
4314 // Get count Java threads that are waiting to enter the specified monitor.
4315 GrowableArray<JavaThread*>* Threads::get_pending_threads(int count,
4316                                                          address monitor,
4317                                                          bool doLock) {
4318   assert(doLock || SafepointSynchronize::is_at_safepoint(),
4319          "must grab Threads_lock or be at safepoint");
4320   GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
4321 
4322   int i = 0;
4323   {
4324     MutexLockerEx ml(doLock ? Threads_lock : NULL);
4325     ALL_JAVA_THREADS(p) {
4326       if (!p->can_call_java()) continue;
4327 
4328       address pending = (address)p->current_pending_monitor();
4329       if (pending == monitor) {             // found a match
4330         if (i < count) result->append(p);   // save the first count matches
4331         i++;
4332       }
4333     }
4334   }
4335   return result;
4336 }
4337 
4338 
4339 JavaThread *Threads::owning_thread_from_monitor_owner(address owner,
4340                                                       bool doLock) {
4341   assert(doLock ||
4342          Threads_lock->owned_by_self() ||
4343          SafepointSynchronize::is_at_safepoint(),
4344          "must grab Threads_lock or be at safepoint");
4345 
4346   // NULL owner means not locked so we can skip the search
4347   if (owner == NULL) return NULL;
4348 
4349   {
4350     MutexLockerEx ml(doLock ? Threads_lock : NULL);
4351     ALL_JAVA_THREADS(p) {
4352       // first, see if owner is the address of a Java thread
4353       if (owner == (address)p) return p;
4354     }
4355   }
4356   // Cannot assert on lack of success here since this function may be
4357   // used by code that is trying to report useful problem information
4358   // like deadlock detection.
4359   if (UseHeavyMonitors) return NULL;
4360 
4361   // If we didn't find a matching Java thread and we didn't force use of
4362   // heavyweight monitors, then the owner is the stack address of the
4363   // Lock Word in the owning Java thread's stack.
4364   //
4365   JavaThread* the_owner = NULL;
4366   {
4367     MutexLockerEx ml(doLock ? Threads_lock : NULL);
4368     ALL_JAVA_THREADS(q) {
4369       if (q->is_lock_owned(owner)) {
4370         the_owner = q;
4371         break;
4372       }
4373     }
4374   }
4375   // cannot assert on lack of success here; see above comment
4376   return the_owner;
4377 }
4378 
4379 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
4380 void Threads::print_on(outputStream* st, bool print_stacks,
4381                        bool internal_format, bool print_concurrent_locks) {
4382   char buf[32];
4383   st->print_raw_cr(os::local_time_string(buf, sizeof(buf)));
4384 
4385   st->print_cr("Full thread dump %s (%s %s):",
4386                Abstract_VM_Version::vm_name(),
4387                Abstract_VM_Version::vm_release(),
4388                Abstract_VM_Version::vm_info_string());
4389   st->cr();
4390 
4391 #if INCLUDE_SERVICES
4392   // Dump concurrent locks
4393   ConcurrentLocksDump concurrent_locks;
4394   if (print_concurrent_locks) {
4395     concurrent_locks.dump_at_safepoint();
4396   }
4397 #endif // INCLUDE_SERVICES
4398 
4399   ALL_JAVA_THREADS(p) {
4400     ResourceMark rm;
4401     p->print_on(st);
4402     if (print_stacks) {
4403       if (internal_format) {
4404         p->trace_stack();
4405       } else {
4406         p->print_stack_on(st);
4407       }
4408     }
4409     st->cr();
4410 #if INCLUDE_SERVICES
4411     if (print_concurrent_locks) {
4412       concurrent_locks.print_locks_on(p, st);
4413     }
4414 #endif // INCLUDE_SERVICES
4415   }
4416 
4417   VMThread::vm_thread()->print_on(st);
4418   st->cr();
4419   Universe::heap()->print_gc_threads_on(st);
4420   WatcherThread* wt = WatcherThread::watcher_thread();
4421   if (wt != NULL) {
4422     wt->print_on(st);
4423     st->cr();
4424   }
4425   st->flush();
4426 }
4427 
4428 // Threads::print_on_error() is called by fatal error handler. It's possible
4429 // that VM is not at safepoint and/or current thread is inside signal handler.
4430 // Don't print stack trace, as the stack may not be walkable. Don't allocate
4431 // memory (even in resource area), it might deadlock the error handler.
4432 void Threads::print_on_error(outputStream* st, Thread* current, char* buf,
4433                              int buflen) {
4434   bool found_current = false;
4435   st->print_cr("Java Threads: ( => current thread )");
4436   ALL_JAVA_THREADS(thread) {
4437     bool is_current = (current == thread);
4438     found_current = found_current || is_current;
4439 
4440     st->print("%s", is_current ? "=>" : "  ");
4441 
4442     st->print(PTR_FORMAT, p2i(thread));
4443     st->print(" ");
4444     thread->print_on_error(st, buf, buflen);
4445     st->cr();
4446   }
4447   st->cr();
4448 
4449   st->print_cr("Other Threads:");
4450   if (VMThread::vm_thread()) {
4451     bool is_current = (current == VMThread::vm_thread());
4452     found_current = found_current || is_current;
4453     st->print("%s", current == VMThread::vm_thread() ? "=>" : "  ");
4454 
4455     st->print(PTR_FORMAT, p2i(VMThread::vm_thread()));
4456     st->print(" ");
4457     VMThread::vm_thread()->print_on_error(st, buf, buflen);
4458     st->cr();
4459   }
4460   WatcherThread* wt = WatcherThread::watcher_thread();
4461   if (wt != NULL) {
4462     bool is_current = (current == wt);
4463     found_current = found_current || is_current;
4464     st->print("%s", is_current ? "=>" : "  ");
4465 
4466     st->print(PTR_FORMAT, p2i(wt));
4467     st->print(" ");
4468     wt->print_on_error(st, buf, buflen);
4469     st->cr();
4470   }
4471   if (!found_current) {
4472     st->cr();
4473     st->print("=>" PTR_FORMAT " (exited) ", p2i(current));
4474     current->print_on_error(st, buf, buflen);
4475     st->cr();
4476   }
4477   st->cr();
4478   st->print_cr("Threads with active compile tasks:");
4479   print_threads_compiling(st, buf, buflen);
4480 }
4481 
4482 void Threads::print_threads_compiling(outputStream* st, char* buf, int buflen) {
4483   ALL_JAVA_THREADS(thread) {
4484     if (thread->is_Compiler_thread()) {
4485       CompilerThread* ct = (CompilerThread*) thread;
4486       if (ct->task() != NULL) {
4487         thread->print_name_on_error(st, buf, buflen);
4488         ct->task()->print(st, NULL, true, true);
4489       }
4490     }
4491   }
4492 }
4493 
4494 
4495 // Internal SpinLock and Mutex
4496 // Based on ParkEvent
4497 
4498 // Ad-hoc mutual exclusion primitives: SpinLock and Mux
4499 //
4500 // We employ SpinLocks _only for low-contention, fixed-length
4501 // short-duration critical sections where we're concerned
4502 // about native mutex_t or HotSpot Mutex:: latency.
4503 // The mux construct provides a spin-then-block mutual exclusion
4504 // mechanism.
4505 //
4506 // Testing has shown that contention on the ListLock guarding gFreeList
4507 // is common.  If we implement ListLock as a simple SpinLock it's common
4508 // for the JVM to devolve to yielding with little progress.  This is true
4509 // despite the fact that the critical sections protected by ListLock are
4510 // extremely short.
4511 //
4512 // TODO-FIXME: ListLock should be of type SpinLock.
4513 // We should make this a 1st-class type, integrated into the lock
4514 // hierarchy as leaf-locks.  Critically, the SpinLock structure
4515 // should have sufficient padding to avoid false-sharing and excessive
4516 // cache-coherency traffic.
4517 
4518 
4519 typedef volatile int SpinLockT;
4520 
4521 void Thread::SpinAcquire(volatile int * adr, const char * LockName) {
4522   if (Atomic::cmpxchg (1, adr, 0) == 0) {
4523     return;   // normal fast-path return
4524   }
4525 
4526   // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
4527   TEVENT(SpinAcquire - ctx);
4528   int ctr = 0;
4529   int Yields = 0;
4530   for (;;) {
4531     while (*adr != 0) {
4532       ++ctr;
4533       if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
4534         if (Yields > 5) {
4535           os::naked_short_sleep(1);
4536         } else {
4537           os::naked_yield();
4538           ++Yields;
4539         }
4540       } else {
4541         SpinPause();
4542       }
4543     }
4544     if (Atomic::cmpxchg(1, adr, 0) == 0) return;
4545   }
4546 }
4547 
4548 void Thread::SpinRelease(volatile int * adr) {
4549   assert(*adr != 0, "invariant");
4550   OrderAccess::fence();      // guarantee at least release consistency.
4551   // Roach-motel semantics.
4552   // It's safe if subsequent LDs and STs float "up" into the critical section,
4553   // but prior LDs and STs within the critical section can't be allowed
4554   // to reorder or float past the ST that releases the lock.
4555   // Loads and stores in the critical section - which appear in program
4556   // order before the store that releases the lock - must also appear
4557   // before the store that releases the lock in memory visibility order.
4558   // Conceptually we need a #loadstore|#storestore "release" MEMBAR before
4559   // the ST of 0 into the lock-word which releases the lock, so fence
4560   // more than covers this on all platforms.
4561   *adr = 0;
4562 }
4563 
4564 // muxAcquire and muxRelease:
4565 //
4566 // *  muxAcquire and muxRelease support a single-word lock-word construct.
4567 //    The LSB of the word is set IFF the lock is held.
4568 //    The remainder of the word points to the head of a singly-linked list
4569 //    of threads blocked on the lock.
4570 //
4571 // *  The current implementation of muxAcquire-muxRelease uses its own
4572 //    dedicated Thread._MuxEvent instance.  If we're interested in
4573 //    minimizing the peak number of extant ParkEvent instances then
4574 //    we could eliminate _MuxEvent and "borrow" _ParkEvent as long
4575 //    as certain invariants were satisfied.  Specifically, care would need
4576 //    to be taken with regards to consuming unpark() "permits".
4577 //    A safe rule of thumb is that a thread would never call muxAcquire()
4578 //    if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
4579 //    park().  Otherwise the _ParkEvent park() operation in muxAcquire() could
4580 //    consume an unpark() permit intended for monitorenter, for instance.
4581 //    One way around this would be to widen the restricted-range semaphore
4582 //    implemented in park().  Another alternative would be to provide
4583 //    multiple instances of the PlatformEvent() for each thread.  One
4584 //    instance would be dedicated to muxAcquire-muxRelease, for instance.
4585 //
4586 // *  Usage:
4587 //    -- Only as leaf locks
4588 //    -- for short-term locking only as muxAcquire does not perform
4589 //       thread state transitions.
4590 //
4591 // Alternatives:
4592 // *  We could implement muxAcquire and muxRelease with MCS or CLH locks
4593 //    but with parking or spin-then-park instead of pure spinning.
4594 // *  Use Taura-Oyama-Yonenzawa locks.
4595 // *  It's possible to construct a 1-0 lock if we encode the lockword as
4596 //    (List,LockByte).  Acquire will CAS the full lockword while Release
4597 //    will STB 0 into the LockByte.  The 1-0 scheme admits stranding, so
4598 //    acquiring threads use timers (ParkTimed) to detect and recover from
4599 //    the stranding window.  Thread/Node structures must be aligned on 256-byte
4600 //    boundaries by using placement-new.
4601 // *  Augment MCS with advisory back-link fields maintained with CAS().
4602 //    Pictorially:  LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
4603 //    The validity of the backlinks must be ratified before we trust the value.
4604 //    If the backlinks are invalid the exiting thread must back-track through the
4605 //    the forward links, which are always trustworthy.
4606 // *  Add a successor indication.  The LockWord is currently encoded as
4607 //    (List, LOCKBIT:1).  We could also add a SUCCBIT or an explicit _succ variable
4608 //    to provide the usual futile-wakeup optimization.
4609 //    See RTStt for details.
4610 // *  Consider schedctl.sc_nopreempt to cover the critical section.
4611 //
4612 
4613 
4614 typedef volatile intptr_t MutexT;      // Mux Lock-word
4615 enum MuxBits { LOCKBIT = 1 };
4616 
4617 void Thread::muxAcquire(volatile intptr_t * Lock, const char * LockName) {
4618   intptr_t w = Atomic::cmpxchg_ptr(LOCKBIT, Lock, 0);
4619   if (w == 0) return;
4620   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4621     return;
4622   }
4623 
4624   TEVENT(muxAcquire - Contention);
4625   ParkEvent * const Self = Thread::current()->_MuxEvent;
4626   assert((intptr_t(Self) & LOCKBIT) == 0, "invariant");
4627   for (;;) {
4628     int its = (os::is_MP() ? 100 : 0) + 1;
4629 
4630     // Optional spin phase: spin-then-park strategy
4631     while (--its >= 0) {
4632       w = *Lock;
4633       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4634         return;
4635       }
4636     }
4637 
4638     Self->reset();
4639     Self->OnList = intptr_t(Lock);
4640     // The following fence() isn't _strictly necessary as the subsequent
4641     // CAS() both serializes execution and ratifies the fetched *Lock value.
4642     OrderAccess::fence();
4643     for (;;) {
4644       w = *Lock;
4645       if ((w & LOCKBIT) == 0) {
4646         if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4647           Self->OnList = 0;   // hygiene - allows stronger asserts
4648           return;
4649         }
4650         continue;      // Interference -- *Lock changed -- Just retry
4651       }
4652       assert(w & LOCKBIT, "invariant");
4653       Self->ListNext = (ParkEvent *) (w & ~LOCKBIT);
4654       if (Atomic::cmpxchg_ptr(intptr_t(Self)|LOCKBIT, Lock, w) == w) break;
4655     }
4656 
4657     while (Self->OnList != 0) {
4658       Self->park();
4659     }
4660   }
4661 }
4662 
4663 void Thread::muxAcquireW(volatile intptr_t * Lock, ParkEvent * ev) {
4664   intptr_t w = Atomic::cmpxchg_ptr(LOCKBIT, Lock, 0);
4665   if (w == 0) return;
4666   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4667     return;
4668   }
4669 
4670   TEVENT(muxAcquire - Contention);
4671   ParkEvent * ReleaseAfter = NULL;
4672   if (ev == NULL) {
4673     ev = ReleaseAfter = ParkEvent::Allocate(NULL);
4674   }
4675   assert((intptr_t(ev) & LOCKBIT) == 0, "invariant");
4676   for (;;) {
4677     guarantee(ev->OnList == 0, "invariant");
4678     int its = (os::is_MP() ? 100 : 0) + 1;
4679 
4680     // Optional spin phase: spin-then-park strategy
4681     while (--its >= 0) {
4682       w = *Lock;
4683       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4684         if (ReleaseAfter != NULL) {
4685           ParkEvent::Release(ReleaseAfter);
4686         }
4687         return;
4688       }
4689     }
4690 
4691     ev->reset();
4692     ev->OnList = intptr_t(Lock);
4693     // The following fence() isn't _strictly necessary as the subsequent
4694     // CAS() both serializes execution and ratifies the fetched *Lock value.
4695     OrderAccess::fence();
4696     for (;;) {
4697       w = *Lock;
4698       if ((w & LOCKBIT) == 0) {
4699         if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4700           ev->OnList = 0;
4701           // We call ::Release while holding the outer lock, thus
4702           // artificially lengthening the critical section.
4703           // Consider deferring the ::Release() until the subsequent unlock(),
4704           // after we've dropped the outer lock.
4705           if (ReleaseAfter != NULL) {
4706             ParkEvent::Release(ReleaseAfter);
4707           }
4708           return;
4709         }
4710         continue;      // Interference -- *Lock changed -- Just retry
4711       }
4712       assert(w & LOCKBIT, "invariant");
4713       ev->ListNext = (ParkEvent *) (w & ~LOCKBIT);
4714       if (Atomic::cmpxchg_ptr(intptr_t(ev)|LOCKBIT, Lock, w) == w) break;
4715     }
4716 
4717     while (ev->OnList != 0) {
4718       ev->park();
4719     }
4720   }
4721 }
4722 
4723 // Release() must extract a successor from the list and then wake that thread.
4724 // It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
4725 // similar to that used by ParkEvent::Allocate() and ::Release().  DMR-based
4726 // Release() would :
4727 // (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
4728 // (B) Extract a successor from the private list "in-hand"
4729 // (C) attempt to CAS() the residual back into *Lock over null.
4730 //     If there were any newly arrived threads and the CAS() would fail.
4731 //     In that case Release() would detach the RATs, re-merge the list in-hand
4732 //     with the RATs and repeat as needed.  Alternately, Release() might
4733 //     detach and extract a successor, but then pass the residual list to the wakee.
4734 //     The wakee would be responsible for reattaching and remerging before it
4735 //     competed for the lock.
4736 //
4737 // Both "pop" and DMR are immune from ABA corruption -- there can be
4738 // multiple concurrent pushers, but only one popper or detacher.
4739 // This implementation pops from the head of the list.  This is unfair,
4740 // but tends to provide excellent throughput as hot threads remain hot.
4741 // (We wake recently run threads first).
4742 //
4743 // All paths through muxRelease() will execute a CAS.
4744 // Release consistency -- We depend on the CAS in muxRelease() to provide full
4745 // bidirectional fence/MEMBAR semantics, ensuring that all prior memory operations
4746 // executed within the critical section are complete and globally visible before the
4747 // store (CAS) to the lock-word that releases the lock becomes globally visible.
4748 void Thread::muxRelease(volatile intptr_t * Lock)  {
4749   for (;;) {
4750     const intptr_t w = Atomic::cmpxchg_ptr(0, Lock, LOCKBIT);
4751     assert(w & LOCKBIT, "invariant");
4752     if (w == LOCKBIT) return;
4753     ParkEvent * const List = (ParkEvent *) (w & ~LOCKBIT);
4754     assert(List != NULL, "invariant");
4755     assert(List->OnList == intptr_t(Lock), "invariant");
4756     ParkEvent * const nxt = List->ListNext;
4757     guarantee((intptr_t(nxt) & LOCKBIT) == 0, "invariant");
4758 
4759     // The following CAS() releases the lock and pops the head element.
4760     // The CAS() also ratifies the previously fetched lock-word value.
4761     if (Atomic::cmpxchg_ptr (intptr_t(nxt), Lock, w) != w) {
4762       continue;
4763     }
4764     List->OnList = 0;
4765     OrderAccess::fence();
4766     List->unpark();
4767     return;
4768   }
4769 }
4770 
4771 
4772 void Threads::verify() {
4773   ALL_JAVA_THREADS(p) {
4774     p->verify();
4775   }
4776   VMThread* thread = VMThread::vm_thread();
4777   if (thread != NULL) thread->verify();
4778 }