1 /*
   2  * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/classLoader.hpp"
  27 #include "classfile/javaClasses.hpp"
  28 #include "classfile/moduleEntry.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "classfile/vmSymbols.hpp"
  31 #include "code/codeCache.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/resourceArea.hpp"
  47 #include "memory/universe.inline.hpp"
  48 #include "oops/instanceKlass.hpp"
  49 #include "oops/objArrayOop.hpp"
  50 #include "oops/oop.inline.hpp"
  51 #include "oops/symbol.hpp"
  52 #include "oops/verifyOopClosure.hpp"
  53 #include "prims/jvm_misc.hpp"
  54 #include "prims/jvmtiExport.hpp"
  55 #include "prims/jvmtiThreadState.hpp"
  56 #include "prims/privilegedStack.hpp"
  57 #include "runtime/arguments.hpp"
  58 #include "runtime/atomic.hpp"
  59 #include "runtime/biasedLocking.hpp"
  60 #include "runtime/commandLineFlagConstraintList.hpp"
  61 #include "runtime/commandLineFlagWriteableList.hpp"
  62 #include "runtime/commandLineFlagRangeList.hpp"
  63 #include "runtime/deoptimization.hpp"
  64 #include "runtime/fprofiler.hpp"
  65 #include "runtime/frame.inline.hpp"
  66 #include "runtime/globals.hpp"
  67 #include "runtime/init.hpp"
  68 #include "runtime/interfaceSupport.hpp"
  69 #include "runtime/java.hpp"
  70 #include "runtime/javaCalls.hpp"
  71 #include "runtime/jniPeriodicChecker.hpp"
  72 #include "runtime/timerTrace.hpp"
  73 #include "runtime/memprofiler.hpp"
  74 #include "runtime/mutexLocker.hpp"
  75 #include "runtime/objectMonitor.hpp"
  76 #include "runtime/orderAccess.inline.hpp"
  77 #include "runtime/osThread.hpp"
  78 #include "runtime/safepoint.hpp"
  79 #include "runtime/sharedRuntime.hpp"
  80 #include "runtime/statSampler.hpp"
  81 #include "runtime/stubRoutines.hpp"
  82 #include "runtime/sweeper.hpp"
  83 #include "runtime/task.hpp"
  84 #include "runtime/thread.inline.hpp"
  85 #include "runtime/threadCritical.hpp"
  86 #include "runtime/vframe.hpp"
  87 #include "runtime/vframeArray.hpp"
  88 #include "runtime/vframe_hp.hpp"
  89 #include "runtime/vmThread.hpp"
  90 #include "runtime/vm_operations.hpp"
  91 #include "runtime/vm_version.hpp"
  92 #include "services/attachListener.hpp"
  93 #include "services/management.hpp"
  94 #include "services/memTracker.hpp"
  95 #include "services/threadService.hpp"
  96 #include "trace/traceMacros.hpp"
  97 #include "trace/tracing.hpp"
  98 #include "utilities/defaultStream.hpp"
  99 #include "utilities/dtrace.hpp"
 100 #include "utilities/events.hpp"
 101 #include "utilities/macros.hpp"
 102 #include "utilities/preserveException.hpp"
 103 #if INCLUDE_ALL_GCS
 104 #include "gc/cms/concurrentMarkSweepThread.hpp"
 105 #include "gc/g1/concurrentMarkThread.inline.hpp"
 106 #include "gc/parallel/pcTasks.hpp"
 107 #endif // INCLUDE_ALL_GCS
 108 #if INCLUDE_JVMCI
 109 #include "jvmci/jvmciCompiler.hpp"
 110 #include "jvmci/jvmciRuntime.hpp"
 111 #endif
 112 #ifdef COMPILER1
 113 #include "c1/c1_Compiler.hpp"
 114 #endif
 115 #ifdef COMPILER2
 116 #include "opto/c2compiler.hpp"
 117 #include "opto/idealGraphPrinter.hpp"
 118 #endif
 119 #if INCLUDE_RTM_OPT
 120 #include "runtime/rtmLocking.hpp"
 121 #endif
 122 
 123 // Initialization after module runtime initialization
 124 void universe_post_module_init();  // must happen after call_initPhase2
 125 
 126 #ifdef DTRACE_ENABLED
 127 
 128 // Only bother with this argument setup if dtrace is available
 129 
 130   #define HOTSPOT_THREAD_PROBE_start HOTSPOT_THREAD_START
 131   #define HOTSPOT_THREAD_PROBE_stop HOTSPOT_THREAD_STOP
 132 
 133   #define DTRACE_THREAD_PROBE(probe, javathread)                           \
 134     {                                                                      \
 135       ResourceMark rm(this);                                               \
 136       int len = 0;                                                         \
 137       const char* name = (javathread)->get_thread_name();                  \
 138       len = strlen(name);                                                  \
 139       HOTSPOT_THREAD_PROBE_##probe(/* probe = start, stop */               \
 140         (char *) name, len,                                                \
 141         java_lang_Thread::thread_id((javathread)->threadObj()),            \
 142         (uintptr_t) (javathread)->osthread()->thread_id(),                 \
 143         java_lang_Thread::is_daemon((javathread)->threadObj()));           \
 144     }
 145 
 146 #else //  ndef DTRACE_ENABLED
 147 
 148   #define DTRACE_THREAD_PROBE(probe, javathread)
 149 
 150 #endif // ndef DTRACE_ENABLED
 151 
 152 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 153 // Current thread is maintained as a thread-local variable
 154 THREAD_LOCAL_DECL Thread* Thread::_thr_current = NULL;
 155 #endif
 156 // Class hierarchy
 157 // - Thread
 158 //   - VMThread
 159 //   - WatcherThread
 160 //   - ConcurrentMarkSweepThread
 161 //   - JavaThread
 162 //     - CompilerThread
 163 
 164 // ======= Thread ========
 165 // Support for forcing alignment of thread objects for biased locking
 166 void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
 167   if (UseBiasedLocking) {
 168     const int alignment = markOopDesc::biased_lock_alignment;
 169     size_t aligned_size = size + (alignment - sizeof(intptr_t));
 170     void* real_malloc_addr = throw_excpt? AllocateHeap(aligned_size, flags, CURRENT_PC)
 171                                           : AllocateHeap(aligned_size, flags, CURRENT_PC,
 172                                                          AllocFailStrategy::RETURN_NULL);
 173     void* aligned_addr     = (void*) align_size_up((intptr_t) real_malloc_addr, alignment);
 174     assert(((uintptr_t) aligned_addr + (uintptr_t) size) <=
 175            ((uintptr_t) real_malloc_addr + (uintptr_t) aligned_size),
 176            "JavaThread alignment code overflowed allocated storage");
 177     if (aligned_addr != real_malloc_addr) {
 178       log_info(biasedlocking)("Aligned thread " INTPTR_FORMAT " to " INTPTR_FORMAT,
 179                               p2i(real_malloc_addr),
 180                               p2i(aligned_addr));
 181     }
 182     ((Thread*) aligned_addr)->_real_malloc_address = real_malloc_addr;
 183     return aligned_addr;
 184   } else {
 185     return throw_excpt? AllocateHeap(size, flags, CURRENT_PC)
 186                        : AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
 187   }
 188 }
 189 
 190 void Thread::operator delete(void* p) {
 191   if (UseBiasedLocking) {
 192     void* real_malloc_addr = ((Thread*) p)->_real_malloc_address;
 193     FreeHeap(real_malloc_addr);
 194   } else {
 195     FreeHeap(p);
 196   }
 197 }
 198 
 199 
 200 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
 201 // JavaThread
 202 
 203 
 204 Thread::Thread() {
 205   // stack and get_thread
 206   set_stack_base(NULL);
 207   set_stack_size(0);
 208   set_self_raw_id(0);
 209   set_lgrp_id(-1);
 210   DEBUG_ONLY(clear_suspendible_thread();)
 211 
 212   // allocated data structures
 213   set_osthread(NULL);
 214   set_resource_area(new (mtThread)ResourceArea());
 215   DEBUG_ONLY(_current_resource_mark = NULL;)
 216   set_handle_area(new (mtThread) HandleArea(NULL));
 217   set_metadata_handles(new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(30, true));
 218   set_active_handles(NULL);
 219   set_free_handle_block(NULL);
 220   set_last_handle_mark(NULL);
 221 
 222   // This initial value ==> never claimed.
 223   _oops_do_parity = 0;
 224 
 225   // the handle mark links itself to last_handle_mark
 226   new HandleMark(this);
 227 
 228   // plain initialization
 229   debug_only(_owned_locks = NULL;)
 230   debug_only(_allow_allocation_count = 0;)
 231   NOT_PRODUCT(_allow_safepoint_count = 0;)
 232   NOT_PRODUCT(_skip_gcalot = false;)
 233   _jvmti_env_iteration_count = 0;
 234   set_allocated_bytes(0);
 235   _vm_operation_started_count = 0;
 236   _vm_operation_completed_count = 0;
 237   _current_pending_monitor = NULL;
 238   _current_pending_monitor_is_from_java = true;
 239   _current_waiting_monitor = NULL;
 240   _num_nested_signal = 0;
 241   omFreeList = NULL;
 242   omFreeCount = 0;
 243   omFreeProvision = 32;
 244   omInUseList = NULL;
 245   omInUseCount = 0;
 246 
 247 #ifdef ASSERT
 248   _visited_for_critical_count = false;
 249 #endif
 250 
 251   _SR_lock = new Monitor(Mutex::suspend_resume, "SR_lock", true,
 252                          Monitor::_safepoint_check_sometimes);
 253   _suspend_flags = 0;
 254 
 255   // thread-specific hashCode stream generator state - Marsaglia shift-xor form
 256   _hashStateX = os::random();
 257   _hashStateY = 842502087;
 258   _hashStateZ = 0x8767;    // (int)(3579807591LL & 0xffff) ;
 259   _hashStateW = 273326509;
 260 
 261   _OnTrap   = 0;
 262   _schedctl = NULL;
 263   _Stalled  = 0;
 264   _TypeTag  = 0x2BAD;
 265 
 266   // Many of the following fields are effectively final - immutable
 267   // Note that nascent threads can't use the Native Monitor-Mutex
 268   // construct until the _MutexEvent is initialized ...
 269   // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
 270   // we might instead use a stack of ParkEvents that we could provision on-demand.
 271   // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
 272   // and ::Release()
 273   _ParkEvent   = ParkEvent::Allocate(this);
 274   _SleepEvent  = ParkEvent::Allocate(this);
 275   _MutexEvent  = ParkEvent::Allocate(this);
 276   _MuxEvent    = ParkEvent::Allocate(this);
 277 
 278 #ifdef CHECK_UNHANDLED_OOPS
 279   if (CheckUnhandledOops) {
 280     _unhandled_oops = new UnhandledOops(this);
 281   }
 282 #endif // CHECK_UNHANDLED_OOPS
 283 #ifdef ASSERT
 284   if (UseBiasedLocking) {
 285     assert((((uintptr_t) this) & (markOopDesc::biased_lock_alignment - 1)) == 0, "forced alignment of thread object failed");
 286     assert(this == _real_malloc_address ||
 287            this == (void*) align_size_up((intptr_t) _real_malloc_address, markOopDesc::biased_lock_alignment),
 288            "bug in forced alignment of thread objects");
 289   }
 290 #endif // ASSERT
 291 }
 292 
 293 void Thread::initialize_thread_current() {
 294 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 295   assert(_thr_current == NULL, "Thread::current already initialized");
 296   _thr_current = this;
 297 #endif
 298   assert(ThreadLocalStorage::thread() == NULL, "ThreadLocalStorage::thread already initialized");
 299   ThreadLocalStorage::set_thread(this);
 300   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 301 }
 302 
 303 void Thread::clear_thread_current() {
 304   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 305 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 306   _thr_current = NULL;
 307 #endif
 308   ThreadLocalStorage::set_thread(NULL);
 309 }
 310 
 311 void Thread::record_stack_base_and_size() {
 312   set_stack_base(os::current_stack_base());
 313   set_stack_size(os::current_stack_size());
 314   // CR 7190089: on Solaris, primordial thread's stack is adjusted
 315   // in initialize_thread(). Without the adjustment, stack size is
 316   // incorrect if stack is set to unlimited (ulimit -s unlimited).
 317   // So far, only Solaris has real implementation of initialize_thread().
 318   //
 319   // set up any platform-specific state.
 320   os::initialize_thread(this);
 321 
 322   // Set stack limits after thread is initialized.
 323   if (is_Java_thread()) {
 324     ((JavaThread*) this)->set_stack_overflow_limit();
 325     ((JavaThread*) this)->set_reserved_stack_activation(stack_base());
 326   }
 327 #if INCLUDE_NMT
 328   // record thread's native stack, stack grows downward
 329   MemTracker::record_thread_stack(stack_end(), stack_size());
 330 #endif // INCLUDE_NMT
 331   log_debug(os, thread)("Thread " UINTX_FORMAT " stack dimensions: "
 332     PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT "k).",
 333     os::current_thread_id(), p2i(stack_base() - stack_size()),
 334     p2i(stack_base()), stack_size()/1024);
 335 }
 336 
 337 
 338 Thread::~Thread() {
 339   EVENT_THREAD_DESTRUCT(this);
 340 
 341   // stack_base can be NULL if the thread is never started or exited before
 342   // record_stack_base_and_size called. Although, we would like to ensure
 343   // that all started threads do call record_stack_base_and_size(), there is
 344   // not proper way to enforce that.
 345 #if INCLUDE_NMT
 346   if (_stack_base != NULL) {
 347     MemTracker::release_thread_stack(stack_end(), stack_size());
 348 #ifdef ASSERT
 349     set_stack_base(NULL);
 350 #endif
 351   }
 352 #endif // INCLUDE_NMT
 353 
 354   // deallocate data structures
 355   delete resource_area();
 356   // since the handle marks are using the handle area, we have to deallocated the root
 357   // handle mark before deallocating the thread's handle area,
 358   assert(last_handle_mark() != NULL, "check we have an element");
 359   delete last_handle_mark();
 360   assert(last_handle_mark() == NULL, "check we have reached the end");
 361 
 362   // It's possible we can encounter a null _ParkEvent, etc., in stillborn threads.
 363   // We NULL out the fields for good hygiene.
 364   ParkEvent::Release(_ParkEvent); _ParkEvent   = NULL;
 365   ParkEvent::Release(_SleepEvent); _SleepEvent  = NULL;
 366   ParkEvent::Release(_MutexEvent); _MutexEvent  = NULL;
 367   ParkEvent::Release(_MuxEvent); _MuxEvent    = NULL;
 368 
 369   delete handle_area();
 370   delete metadata_handles();
 371 
 372   // SR_handler uses this as a termination indicator -
 373   // needs to happen before os::free_thread()
 374   delete _SR_lock;
 375   _SR_lock = NULL;
 376 
 377   // osthread() can be NULL, if creation of thread failed.
 378   if (osthread() != NULL) os::free_thread(osthread());
 379 
 380   // clear Thread::current if thread is deleting itself.
 381   // Needed to ensure JNI correctly detects non-attached threads.
 382   if (this == Thread::current()) {
 383     clear_thread_current();
 384   }
 385 
 386   CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
 387 }
 388 
 389 // NOTE: dummy function for assertion purpose.
 390 void Thread::run() {
 391   ShouldNotReachHere();
 392 }
 393 
 394 #ifdef ASSERT
 395 // Private method to check for dangling thread pointer
 396 void check_for_dangling_thread_pointer(Thread *thread) {
 397   assert(!thread->is_Java_thread() || Thread::current() == thread || Threads_lock->owned_by_self(),
 398          "possibility of dangling Thread pointer");
 399 }
 400 #endif
 401 
 402 ThreadPriority Thread::get_priority(const Thread* const thread) {
 403   ThreadPriority priority;
 404   // Can return an error!
 405   (void)os::get_priority(thread, priority);
 406   assert(MinPriority <= priority && priority <= MaxPriority, "non-Java priority found");
 407   return priority;
 408 }
 409 
 410 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
 411   debug_only(check_for_dangling_thread_pointer(thread);)
 412   // Can return an error!
 413   (void)os::set_priority(thread, priority);
 414 }
 415 
 416 
 417 void Thread::start(Thread* thread) {
 418   // Start is different from resume in that its safety is guaranteed by context or
 419   // being called from a Java method synchronized on the Thread object.
 420   if (!DisableStartThread) {
 421     if (thread->is_Java_thread()) {
 422       // Initialize the thread state to RUNNABLE before starting this thread.
 423       // Can not set it after the thread started because we do not know the
 424       // exact thread state at that time. It could be in MONITOR_WAIT or
 425       // in SLEEPING or some other state.
 426       java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
 427                                           java_lang_Thread::RUNNABLE);
 428     }
 429     os::start_thread(thread);
 430   }
 431 }
 432 
 433 // Enqueue a VM_Operation to do the job for us - sometime later
 434 void Thread::send_async_exception(oop java_thread, oop java_throwable) {
 435   VM_ThreadStop* vm_stop = new VM_ThreadStop(java_thread, java_throwable);
 436   VMThread::execute(vm_stop);
 437 }
 438 
 439 
 440 // Check if an external suspend request has completed (or has been
 441 // cancelled). Returns true if the thread is externally suspended and
 442 // false otherwise.
 443 //
 444 // The bits parameter returns information about the code path through
 445 // the routine. Useful for debugging:
 446 //
 447 // set in is_ext_suspend_completed():
 448 // 0x00000001 - routine was entered
 449 // 0x00000010 - routine return false at end
 450 // 0x00000100 - thread exited (return false)
 451 // 0x00000200 - suspend request cancelled (return false)
 452 // 0x00000400 - thread suspended (return true)
 453 // 0x00001000 - thread is in a suspend equivalent state (return true)
 454 // 0x00002000 - thread is native and walkable (return true)
 455 // 0x00004000 - thread is native_trans and walkable (needed retry)
 456 //
 457 // set in wait_for_ext_suspend_completion():
 458 // 0x00010000 - routine was entered
 459 // 0x00020000 - suspend request cancelled before loop (return false)
 460 // 0x00040000 - thread suspended before loop (return true)
 461 // 0x00080000 - suspend request cancelled in loop (return false)
 462 // 0x00100000 - thread suspended in loop (return true)
 463 // 0x00200000 - suspend not completed during retry loop (return false)
 464 
 465 // Helper class for tracing suspend wait debug bits.
 466 //
 467 // 0x00000100 indicates that the target thread exited before it could
 468 // self-suspend which is not a wait failure. 0x00000200, 0x00020000 and
 469 // 0x00080000 each indicate a cancelled suspend request so they don't
 470 // count as wait failures either.
 471 #define DEBUG_FALSE_BITS (0x00000010 | 0x00200000)
 472 
 473 class TraceSuspendDebugBits : public StackObj {
 474  private:
 475   JavaThread * jt;
 476   bool         is_wait;
 477   bool         called_by_wait;  // meaningful when !is_wait
 478   uint32_t *   bits;
 479 
 480  public:
 481   TraceSuspendDebugBits(JavaThread *_jt, bool _is_wait, bool _called_by_wait,
 482                         uint32_t *_bits) {
 483     jt             = _jt;
 484     is_wait        = _is_wait;
 485     called_by_wait = _called_by_wait;
 486     bits           = _bits;
 487   }
 488 
 489   ~TraceSuspendDebugBits() {
 490     if (!is_wait) {
 491 #if 1
 492       // By default, don't trace bits for is_ext_suspend_completed() calls.
 493       // That trace is very chatty.
 494       return;
 495 #else
 496       if (!called_by_wait) {
 497         // If tracing for is_ext_suspend_completed() is enabled, then only
 498         // trace calls to it from wait_for_ext_suspend_completion()
 499         return;
 500       }
 501 #endif
 502     }
 503 
 504     if (AssertOnSuspendWaitFailure || TraceSuspendWaitFailures) {
 505       if (bits != NULL && (*bits & DEBUG_FALSE_BITS) != 0) {
 506         MutexLocker ml(Threads_lock);  // needed for get_thread_name()
 507         ResourceMark rm;
 508 
 509         tty->print_cr(
 510                       "Failed wait_for_ext_suspend_completion(thread=%s, debug_bits=%x)",
 511                       jt->get_thread_name(), *bits);
 512 
 513         guarantee(!AssertOnSuspendWaitFailure, "external suspend wait failed");
 514       }
 515     }
 516   }
 517 };
 518 #undef DEBUG_FALSE_BITS
 519 
 520 
 521 bool JavaThread::is_ext_suspend_completed(bool called_by_wait, int delay,
 522                                           uint32_t *bits) {
 523   TraceSuspendDebugBits tsdb(this, false /* !is_wait */, called_by_wait, bits);
 524 
 525   bool did_trans_retry = false;  // only do thread_in_native_trans retry once
 526   bool do_trans_retry;           // flag to force the retry
 527 
 528   *bits |= 0x00000001;
 529 
 530   do {
 531     do_trans_retry = false;
 532 
 533     if (is_exiting()) {
 534       // Thread is in the process of exiting. This is always checked
 535       // first to reduce the risk of dereferencing a freed JavaThread.
 536       *bits |= 0x00000100;
 537       return false;
 538     }
 539 
 540     if (!is_external_suspend()) {
 541       // Suspend request is cancelled. This is always checked before
 542       // is_ext_suspended() to reduce the risk of a rogue resume
 543       // confusing the thread that made the suspend request.
 544       *bits |= 0x00000200;
 545       return false;
 546     }
 547 
 548     if (is_ext_suspended()) {
 549       // thread is suspended
 550       *bits |= 0x00000400;
 551       return true;
 552     }
 553 
 554     // Now that we no longer do hard suspends of threads running
 555     // native code, the target thread can be changing thread state
 556     // while we are in this routine:
 557     //
 558     //   _thread_in_native -> _thread_in_native_trans -> _thread_blocked
 559     //
 560     // We save a copy of the thread state as observed at this moment
 561     // and make our decision about suspend completeness based on the
 562     // copy. This closes the race where the thread state is seen as
 563     // _thread_in_native_trans in the if-thread_blocked check, but is
 564     // seen as _thread_blocked in if-thread_in_native_trans check.
 565     JavaThreadState save_state = thread_state();
 566 
 567     if (save_state == _thread_blocked && is_suspend_equivalent()) {
 568       // If the thread's state is _thread_blocked and this blocking
 569       // condition is known to be equivalent to a suspend, then we can
 570       // consider the thread to be externally suspended. This means that
 571       // the code that sets _thread_blocked has been modified to do
 572       // self-suspension if the blocking condition releases. We also
 573       // used to check for CONDVAR_WAIT here, but that is now covered by
 574       // the _thread_blocked with self-suspension check.
 575       //
 576       // Return true since we wouldn't be here unless there was still an
 577       // external suspend request.
 578       *bits |= 0x00001000;
 579       return true;
 580     } else if (save_state == _thread_in_native && frame_anchor()->walkable()) {
 581       // Threads running native code will self-suspend on native==>VM/Java
 582       // transitions. If its stack is walkable (should always be the case
 583       // unless this function is called before the actual java_suspend()
 584       // call), then the wait is done.
 585       *bits |= 0x00002000;
 586       return true;
 587     } else if (!called_by_wait && !did_trans_retry &&
 588                save_state == _thread_in_native_trans &&
 589                frame_anchor()->walkable()) {
 590       // The thread is transitioning from thread_in_native to another
 591       // thread state. check_safepoint_and_suspend_for_native_trans()
 592       // will force the thread to self-suspend. If it hasn't gotten
 593       // there yet we may have caught the thread in-between the native
 594       // code check above and the self-suspend. Lucky us. If we were
 595       // called by wait_for_ext_suspend_completion(), then it
 596       // will be doing the retries so we don't have to.
 597       //
 598       // Since we use the saved thread state in the if-statement above,
 599       // there is a chance that the thread has already transitioned to
 600       // _thread_blocked by the time we get here. In that case, we will
 601       // make a single unnecessary pass through the logic below. This
 602       // doesn't hurt anything since we still do the trans retry.
 603 
 604       *bits |= 0x00004000;
 605 
 606       // Once the thread leaves thread_in_native_trans for another
 607       // thread state, we break out of this retry loop. We shouldn't
 608       // need this flag to prevent us from getting back here, but
 609       // sometimes paranoia is good.
 610       did_trans_retry = true;
 611 
 612       // We wait for the thread to transition to a more usable state.
 613       for (int i = 1; i <= SuspendRetryCount; i++) {
 614         // We used to do an "os::yield_all(i)" call here with the intention
 615         // that yielding would increase on each retry. However, the parameter
 616         // is ignored on Linux which means the yield didn't scale up. Waiting
 617         // on the SR_lock below provides a much more predictable scale up for
 618         // the delay. It also provides a simple/direct point to check for any
 619         // safepoint requests from the VMThread
 620 
 621         // temporarily drops SR_lock while doing wait with safepoint check
 622         // (if we're a JavaThread - the WatcherThread can also call this)
 623         // and increase delay with each retry
 624         SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 625 
 626         // check the actual thread state instead of what we saved above
 627         if (thread_state() != _thread_in_native_trans) {
 628           // the thread has transitioned to another thread state so
 629           // try all the checks (except this one) one more time.
 630           do_trans_retry = true;
 631           break;
 632         }
 633       } // end retry loop
 634 
 635 
 636     }
 637   } while (do_trans_retry);
 638 
 639   *bits |= 0x00000010;
 640   return false;
 641 }
 642 
 643 // Wait for an external suspend request to complete (or be cancelled).
 644 // Returns true if the thread is externally suspended and false otherwise.
 645 //
 646 bool JavaThread::wait_for_ext_suspend_completion(int retries, int delay,
 647                                                  uint32_t *bits) {
 648   TraceSuspendDebugBits tsdb(this, true /* is_wait */,
 649                              false /* !called_by_wait */, bits);
 650 
 651   // local flag copies to minimize SR_lock hold time
 652   bool is_suspended;
 653   bool pending;
 654   uint32_t reset_bits;
 655 
 656   // set a marker so is_ext_suspend_completed() knows we are the caller
 657   *bits |= 0x00010000;
 658 
 659   // We use reset_bits to reinitialize the bits value at the top of
 660   // each retry loop. This allows the caller to make use of any
 661   // unused bits for their own marking purposes.
 662   reset_bits = *bits;
 663 
 664   {
 665     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 666     is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 667                                             delay, bits);
 668     pending = is_external_suspend();
 669   }
 670   // must release SR_lock to allow suspension to complete
 671 
 672   if (!pending) {
 673     // A cancelled suspend request is the only false return from
 674     // is_ext_suspend_completed() that keeps us from entering the
 675     // retry loop.
 676     *bits |= 0x00020000;
 677     return false;
 678   }
 679 
 680   if (is_suspended) {
 681     *bits |= 0x00040000;
 682     return true;
 683   }
 684 
 685   for (int i = 1; i <= retries; i++) {
 686     *bits = reset_bits;  // reinit to only track last retry
 687 
 688     // We used to do an "os::yield_all(i)" call here with the intention
 689     // that yielding would increase on each retry. However, the parameter
 690     // is ignored on Linux which means the yield didn't scale up. Waiting
 691     // on the SR_lock below provides a much more predictable scale up for
 692     // the delay. It also provides a simple/direct point to check for any
 693     // safepoint requests from the VMThread
 694 
 695     {
 696       MutexLocker ml(SR_lock());
 697       // wait with safepoint check (if we're a JavaThread - the WatcherThread
 698       // can also call this)  and increase delay with each retry
 699       SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 700 
 701       is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 702                                               delay, bits);
 703 
 704       // It is possible for the external suspend request to be cancelled
 705       // (by a resume) before the actual suspend operation is completed.
 706       // Refresh our local copy to see if we still need to wait.
 707       pending = is_external_suspend();
 708     }
 709 
 710     if (!pending) {
 711       // A cancelled suspend request is the only false return from
 712       // is_ext_suspend_completed() that keeps us from staying in the
 713       // retry loop.
 714       *bits |= 0x00080000;
 715       return false;
 716     }
 717 
 718     if (is_suspended) {
 719       *bits |= 0x00100000;
 720       return true;
 721     }
 722   } // end retry loop
 723 
 724   // thread did not suspend after all our retries
 725   *bits |= 0x00200000;
 726   return false;
 727 }
 728 
 729 #ifndef PRODUCT
 730 void JavaThread::record_jump(address target, address instr, const char* file,
 731                              int line) {
 732 
 733   // This should not need to be atomic as the only way for simultaneous
 734   // updates is via interrupts. Even then this should be rare or non-existent
 735   // and we don't care that much anyway.
 736 
 737   int index = _jmp_ring_index;
 738   _jmp_ring_index = (index + 1) & (jump_ring_buffer_size - 1);
 739   _jmp_ring[index]._target = (intptr_t) target;
 740   _jmp_ring[index]._instruction = (intptr_t) instr;
 741   _jmp_ring[index]._file = file;
 742   _jmp_ring[index]._line = line;
 743 }
 744 #endif // PRODUCT
 745 
 746 // Called by flat profiler
 747 // Callers have already called wait_for_ext_suspend_completion
 748 // The assertion for that is currently too complex to put here:
 749 bool JavaThread::profile_last_Java_frame(frame* _fr) {
 750   bool gotframe = false;
 751   // self suspension saves needed state.
 752   if (has_last_Java_frame() && _anchor.walkable()) {
 753     *_fr = pd_last_frame();
 754     gotframe = true;
 755   }
 756   return gotframe;
 757 }
 758 
 759 void Thread::interrupt(Thread* thread) {
 760   debug_only(check_for_dangling_thread_pointer(thread);)
 761   os::interrupt(thread);
 762 }
 763 
 764 bool Thread::is_interrupted(Thread* thread, bool clear_interrupted) {
 765   debug_only(check_for_dangling_thread_pointer(thread);)
 766   // Note:  If clear_interrupted==false, this simply fetches and
 767   // returns the value of the field osthread()->interrupted().
 768   return os::is_interrupted(thread, clear_interrupted);
 769 }
 770 
 771 
 772 // GC Support
 773 bool Thread::claim_oops_do_par_case(int strong_roots_parity) {
 774   jint thread_parity = _oops_do_parity;
 775   if (thread_parity != strong_roots_parity) {
 776     jint res = Atomic::cmpxchg(strong_roots_parity, &_oops_do_parity, thread_parity);
 777     if (res == thread_parity) {
 778       return true;
 779     } else {
 780       guarantee(res == strong_roots_parity, "Or else what?");
 781       return false;
 782     }
 783   }
 784   return false;
 785 }
 786 
 787 void Thread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
 788   active_handles()->oops_do(f);
 789   // Do oop for ThreadShadow
 790   f->do_oop((oop*)&_pending_exception);
 791   handle_area()->oops_do(f);
 792 
 793   if (MonitorInUseLists) {
 794     // When using thread local monitor lists, we scan them here,
 795     // and the remaining global monitors in ObjectSynchronizer::oops_do().
 796     ObjectSynchronizer::thread_local_used_oops_do(this, f);
 797   }
 798 }
 799 
 800 void Thread::metadata_handles_do(void f(Metadata*)) {
 801   // Only walk the Handles in Thread.
 802   if (metadata_handles() != NULL) {
 803     for (int i = 0; i< metadata_handles()->length(); i++) {
 804       f(metadata_handles()->at(i));
 805     }
 806   }
 807 }
 808 
 809 void Thread::print_on(outputStream* st) const {
 810   // get_priority assumes osthread initialized
 811   if (osthread() != NULL) {
 812     int os_prio;
 813     if (os::get_native_priority(this, &os_prio) == OS_OK) {
 814       st->print("os_prio=%d ", os_prio);
 815     }
 816     st->print("tid=" INTPTR_FORMAT " ", p2i(this));
 817     ext().print_on(st);
 818     osthread()->print_on(st);
 819   }
 820   debug_only(if (WizardMode) print_owned_locks_on(st);)
 821 }
 822 
 823 // Thread::print_on_error() is called by fatal error handler. Don't use
 824 // any lock or allocate memory.
 825 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
 826   assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
 827 
 828   if (is_VM_thread())                 { st->print("VMThread"); }
 829   else if (is_GC_task_thread())       { st->print("GCTaskThread"); }
 830   else if (is_Watcher_thread())       { st->print("WatcherThread"); }
 831   else if (is_ConcurrentGC_thread())  { st->print("ConcurrentGCThread"); }
 832   else                                { st->print("Thread"); }
 833 
 834   if (is_Named_thread()) {
 835     st->print(" \"%s\"", name());
 836   }
 837 
 838   st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
 839             p2i(stack_end()), p2i(stack_base()));
 840 
 841   if (osthread()) {
 842     st->print(" [id=%d]", osthread()->thread_id());
 843   }
 844 }
 845 
 846 #ifdef ASSERT
 847 void Thread::print_owned_locks_on(outputStream* st) const {
 848   Monitor *cur = _owned_locks;
 849   if (cur == NULL) {
 850     st->print(" (no locks) ");
 851   } else {
 852     st->print_cr(" Locks owned:");
 853     while (cur) {
 854       cur->print_on(st);
 855       cur = cur->next();
 856     }
 857   }
 858 }
 859 
 860 static int ref_use_count  = 0;
 861 
 862 bool Thread::owns_locks_but_compiled_lock() const {
 863   for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 864     if (cur != Compile_lock) return true;
 865   }
 866   return false;
 867 }
 868 
 869 
 870 #endif
 871 
 872 #ifndef PRODUCT
 873 
 874 // The flag: potential_vm_operation notifies if this particular safepoint state could potential
 875 // invoke the vm-thread (i.e., and oop allocation). In that case, we also have to make sure that
 876 // no threads which allow_vm_block's are held
 877 void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) {
 878   // Check if current thread is allowed to block at a safepoint
 879   if (!(_allow_safepoint_count == 0)) {
 880     fatal("Possible safepoint reached by thread that does not allow it");
 881   }
 882   if (is_Java_thread() && ((JavaThread*)this)->thread_state() != _thread_in_vm) {
 883     fatal("LEAF method calling lock?");
 884   }
 885 
 886 #ifdef ASSERT
 887   if (potential_vm_operation && is_Java_thread()
 888       && !Universe::is_bootstrapping()) {
 889     // Make sure we do not hold any locks that the VM thread also uses.
 890     // This could potentially lead to deadlocks
 891     for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 892       // Threads_lock is special, since the safepoint synchronization will not start before this is
 893       // acquired. Hence, a JavaThread cannot be holding it at a safepoint. So is VMOperationRequest_lock,
 894       // since it is used to transfer control between JavaThreads and the VMThread
 895       // Do not *exclude* any locks unless you are absolutely sure it is correct. Ask someone else first!
 896       if ((cur->allow_vm_block() &&
 897            cur != Threads_lock &&
 898            cur != Compile_lock &&               // Temporary: should not be necessary when we get separate compilation
 899            cur != VMOperationRequest_lock &&
 900            cur != VMOperationQueue_lock) ||
 901            cur->rank() == Mutex::special) {
 902         fatal("Thread holding lock at safepoint that vm can block on: %s", cur->name());
 903       }
 904     }
 905   }
 906 
 907   if (GCALotAtAllSafepoints) {
 908     // We could enter a safepoint here and thus have a gc
 909     InterfaceSupport::check_gc_alot();
 910   }
 911 #endif
 912 }
 913 #endif
 914 
 915 bool Thread::is_in_stack(address adr) const {
 916   assert(Thread::current() == this, "is_in_stack can only be called from current thread");
 917   address end = os::current_stack_pointer();
 918   // Allow non Java threads to call this without stack_base
 919   if (_stack_base == NULL) return true;
 920   if (stack_base() >= adr && adr >= end) return true;
 921 
 922   return false;
 923 }
 924 
 925 bool Thread::is_in_usable_stack(address adr) const {
 926   size_t stack_guard_size = os::uses_stack_guard_pages() ? JavaThread::stack_guard_zone_size() : 0;
 927   size_t usable_stack_size = _stack_size - stack_guard_size;
 928 
 929   return ((adr < stack_base()) && (adr >= stack_base() - usable_stack_size));
 930 }
 931 
 932 
 933 // We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
 934 // However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
 935 // used for compilation in the future. If that change is made, the need for these methods
 936 // should be revisited, and they should be removed if possible.
 937 
 938 bool Thread::is_lock_owned(address adr) const {
 939   return on_local_stack(adr);
 940 }
 941 
 942 bool Thread::set_as_starting_thread() {
 943   // NOTE: this must be called inside the main thread.
 944   return os::create_main_thread((JavaThread*)this);
 945 }
 946 
 947 static void initialize_class(Symbol* class_name, TRAPS) {
 948   Klass* klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
 949   InstanceKlass::cast(klass)->initialize(CHECK);
 950 }
 951 
 952 
 953 // Creates the initial ThreadGroup
 954 static Handle create_initial_thread_group(TRAPS) {
 955   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_ThreadGroup(), true, CHECK_NH);
 956   InstanceKlass* ik = InstanceKlass::cast(k);
 957 
 958   Handle system_instance = ik->allocate_instance_handle(CHECK_NH);
 959   {
 960     JavaValue result(T_VOID);
 961     JavaCalls::call_special(&result,
 962                             system_instance,
 963                             ik,
 964                             vmSymbols::object_initializer_name(),
 965                             vmSymbols::void_method_signature(),
 966                             CHECK_NH);
 967   }
 968   Universe::set_system_thread_group(system_instance());
 969 
 970   Handle main_instance = ik->allocate_instance_handle(CHECK_NH);
 971   {
 972     JavaValue result(T_VOID);
 973     Handle string = java_lang_String::create_from_str("main", CHECK_NH);
 974     JavaCalls::call_special(&result,
 975                             main_instance,
 976                             ik,
 977                             vmSymbols::object_initializer_name(),
 978                             vmSymbols::threadgroup_string_void_signature(),
 979                             system_instance,
 980                             string,
 981                             CHECK_NH);
 982   }
 983   return main_instance;
 984 }
 985 
 986 // Creates the initial Thread
 987 static oop create_initial_thread(Handle thread_group, JavaThread* thread,
 988                                  TRAPS) {
 989   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK_NULL);
 990   InstanceKlass* ik = InstanceKlass::cast(k);
 991   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK_NULL);
 992 
 993   java_lang_Thread::set_thread(thread_oop(), thread);
 994   java_lang_Thread::set_priority(thread_oop(), NormPriority);
 995   thread->set_threadObj(thread_oop());
 996 
 997   Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
 998 
 999   JavaValue result(T_VOID);
1000   JavaCalls::call_special(&result, thread_oop,
1001                           ik,
1002                           vmSymbols::object_initializer_name(),
1003                           vmSymbols::threadgroup_string_void_signature(),
1004                           thread_group,
1005                           string,
1006                           CHECK_NULL);
1007   return thread_oop();
1008 }
1009 
1010 char java_runtime_name[128] = "";
1011 char java_runtime_version[128] = "";
1012 
1013 // extract the JRE name from java.lang.VersionProps.java_runtime_name
1014 static const char* get_java_runtime_name(TRAPS) {
1015   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1016                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1017   fieldDescriptor fd;
1018   bool found = k != NULL &&
1019                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_name_name(),
1020                                                         vmSymbols::string_signature(), &fd);
1021   if (found) {
1022     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1023     if (name_oop == NULL) {
1024       return NULL;
1025     }
1026     const char* name = java_lang_String::as_utf8_string(name_oop,
1027                                                         java_runtime_name,
1028                                                         sizeof(java_runtime_name));
1029     return name;
1030   } else {
1031     return NULL;
1032   }
1033 }
1034 
1035 // extract the JRE version from java.lang.VersionProps.java_runtime_version
1036 static const char* get_java_runtime_version(TRAPS) {
1037   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1038                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1039   fieldDescriptor fd;
1040   bool found = k != NULL &&
1041                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_version_name(),
1042                                                         vmSymbols::string_signature(), &fd);
1043   if (found) {
1044     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1045     if (name_oop == NULL) {
1046       return NULL;
1047     }
1048     const char* name = java_lang_String::as_utf8_string(name_oop,
1049                                                         java_runtime_version,
1050                                                         sizeof(java_runtime_version));
1051     return name;
1052   } else {
1053     return NULL;
1054   }
1055 }
1056 
1057 // General purpose hook into Java code, run once when the VM is initialized.
1058 // The Java library method itself may be changed independently from the VM.
1059 static void call_postVMInitHook(TRAPS) {
1060   Klass* klass = SystemDictionary::resolve_or_null(vmSymbols::jdk_internal_vm_PostVMInitHook(), THREAD);
1061   if (klass != 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* klass =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
1076 
1077   // setProperty arguments
1078   Handle key_str    = java_lang_String::create_from_str("java.vm.info", CHECK);
1079   Handle value_str  = java_lang_String::create_from_str(vm_info, CHECK);
1080 
1081   // return value
1082   JavaValue r(T_OBJECT);
1083 
1084   // public static String setProperty(String key, String value);
1085   JavaCalls::call_static(&r,
1086                          klass,
1087                          vmSymbols::setProperty_name(),
1088                          vmSymbols::string_string_string_signature(),
1089                          key_str,
1090                          value_str,
1091                          CHECK);
1092 }
1093 
1094 
1095 void JavaThread::allocate_threadObj(Handle thread_group, const char* thread_name,
1096                                     bool daemon, TRAPS) {
1097   assert(thread_group.not_null(), "thread group should be specified");
1098   assert(threadObj() == NULL, "should only create Java thread object once");
1099 
1100   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK);
1101   InstanceKlass* ik = InstanceKlass::cast(k);
1102   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK);
1103 
1104   java_lang_Thread::set_thread(thread_oop(), this);
1105   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1106   set_threadObj(thread_oop());
1107 
1108   JavaValue result(T_VOID);
1109   if (thread_name != NULL) {
1110     Handle name = java_lang_String::create_from_str(thread_name, CHECK);
1111     // Thread gets assigned specified name and null target
1112     JavaCalls::call_special(&result,
1113                             thread_oop,
1114                             ik,
1115                             vmSymbols::object_initializer_name(),
1116                             vmSymbols::threadgroup_string_void_signature(),
1117                             thread_group, // Argument 1
1118                             name,         // Argument 2
1119                             THREAD);
1120   } else {
1121     // Thread gets assigned name "Thread-nnn" and null target
1122     // (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
1123     JavaCalls::call_special(&result,
1124                             thread_oop,
1125                             ik,
1126                             vmSymbols::object_initializer_name(),
1127                             vmSymbols::threadgroup_runnable_void_signature(),
1128                             thread_group, // Argument 1
1129                             Handle(),     // Argument 2
1130                             THREAD);
1131   }
1132 
1133 
1134   if (daemon) {
1135     java_lang_Thread::set_daemon(thread_oop());
1136   }
1137 
1138   if (HAS_PENDING_EXCEPTION) {
1139     return;
1140   }
1141 
1142   Klass* group =  SystemDictionary::ThreadGroup_klass();
1143   Handle threadObj(THREAD, this->threadObj());
1144 
1145   JavaCalls::call_special(&result,
1146                           thread_group,
1147                           group,
1148                           vmSymbols::add_method_name(),
1149                           vmSymbols::thread_void_signature(),
1150                           threadObj,          // Arg 1
1151                           THREAD);
1152 }
1153 
1154 // NamedThread --  non-JavaThread subclasses with multiple
1155 // uniquely named instances should derive from this.
1156 NamedThread::NamedThread() : Thread() {
1157   _name = NULL;
1158   _processed_thread = NULL;
1159   _gc_id = GCId::undefined();
1160 }
1161 
1162 NamedThread::~NamedThread() {
1163   if (_name != NULL) {
1164     FREE_C_HEAP_ARRAY(char, _name);
1165     _name = NULL;
1166   }
1167 }
1168 
1169 void NamedThread::set_name(const char* format, ...) {
1170   guarantee(_name == NULL, "Only get to set name once.");
1171   _name = NEW_C_HEAP_ARRAY(char, max_name_len, mtThread);
1172   guarantee(_name != NULL, "alloc failure");
1173   va_list ap;
1174   va_start(ap, format);
1175   jio_vsnprintf(_name, max_name_len, format, ap);
1176   va_end(ap);
1177 }
1178 
1179 void NamedThread::initialize_named_thread() {
1180   set_native_thread_name(name());
1181 }
1182 
1183 void NamedThread::print_on(outputStream* st) const {
1184   st->print("\"%s\" ", name());
1185   Thread::print_on(st);
1186   st->cr();
1187 }
1188 
1189 
1190 // ======= WatcherThread ========
1191 
1192 // The watcher thread exists to simulate timer interrupts.  It should
1193 // be replaced by an abstraction over whatever native support for
1194 // timer interrupts exists on the platform.
1195 
1196 WatcherThread* WatcherThread::_watcher_thread   = NULL;
1197 bool WatcherThread::_startable = false;
1198 volatile bool  WatcherThread::_should_terminate = false;
1199 
1200 WatcherThread::WatcherThread() : Thread(), _crash_protection(NULL) {
1201   assert(watcher_thread() == NULL, "we can only allocate one WatcherThread");
1202   if (os::create_thread(this, os::watcher_thread)) {
1203     _watcher_thread = this;
1204 
1205     // Set the watcher thread to the highest OS priority which should not be
1206     // used, unless a Java thread with priority java.lang.Thread.MAX_PRIORITY
1207     // is created. The only normal thread using this priority is the reference
1208     // handler thread, which runs for very short intervals only.
1209     // If the VMThread's priority is not lower than the WatcherThread profiling
1210     // will be inaccurate.
1211     os::set_priority(this, MaxPriority);
1212     if (!DisableStartThread) {
1213       os::start_thread(this);
1214     }
1215   }
1216 }
1217 
1218 int WatcherThread::sleep() const {
1219   // The WatcherThread does not participate in the safepoint protocol
1220   // for the PeriodicTask_lock because it is not a JavaThread.
1221   MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
1222 
1223   if (_should_terminate) {
1224     // check for termination before we do any housekeeping or wait
1225     return 0;  // we did not sleep.
1226   }
1227 
1228   // remaining will be zero if there are no tasks,
1229   // causing the WatcherThread to sleep until a task is
1230   // enrolled
1231   int remaining = PeriodicTask::time_to_wait();
1232   int time_slept = 0;
1233 
1234   // we expect this to timeout - we only ever get unparked when
1235   // we should terminate or when a new task has been enrolled
1236   OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
1237 
1238   jlong time_before_loop = os::javaTimeNanos();
1239 
1240   while (true) {
1241     bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag,
1242                                             remaining);
1243     jlong now = os::javaTimeNanos();
1244 
1245     if (remaining == 0) {
1246       // if we didn't have any tasks we could have waited for a long time
1247       // consider the time_slept zero and reset time_before_loop
1248       time_slept = 0;
1249       time_before_loop = now;
1250     } else {
1251       // need to recalculate since we might have new tasks in _tasks
1252       time_slept = (int) ((now - time_before_loop) / 1000000);
1253     }
1254 
1255     // Change to task list or spurious wakeup of some kind
1256     if (timedout || _should_terminate) {
1257       break;
1258     }
1259 
1260     remaining = PeriodicTask::time_to_wait();
1261     if (remaining == 0) {
1262       // Last task was just disenrolled so loop around and wait until
1263       // another task gets enrolled
1264       continue;
1265     }
1266 
1267     remaining -= time_slept;
1268     if (remaining <= 0) {
1269       break;
1270     }
1271   }
1272 
1273   return time_slept;
1274 }
1275 
1276 void WatcherThread::run() {
1277   assert(this == watcher_thread(), "just checking");
1278 
1279   this->record_stack_base_and_size();
1280   this->set_native_thread_name(this->name());
1281   this->set_active_handles(JNIHandleBlock::allocate_block());
1282   while (true) {
1283     assert(watcher_thread() == Thread::current(), "thread consistency check");
1284     assert(watcher_thread() == this, "thread consistency check");
1285 
1286     // Calculate how long it'll be until the next PeriodicTask work
1287     // should be done, and sleep that amount of time.
1288     int time_waited = sleep();
1289 
1290     if (is_error_reported()) {
1291       // A fatal error has happened, the error handler(VMError::report_and_die)
1292       // should abort JVM after creating an error log file. However in some
1293       // rare cases, the error handler itself might deadlock. Here periodically
1294       // check for error reporting timeouts, and if it happens, just proceed to
1295       // abort the VM.
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         // Note: we use naked sleep in this loop because we want to avoid using
1304         // any kind of VM infrastructure which may be broken at this point.
1305         if (VMError::check_timeout()) {
1306           // We hit error reporting timeout. Error reporting was interrupted and
1307           // will be wrapping things up now (closing files etc). Give it some more
1308           // time, then quit the VM.
1309           os::naked_short_sleep(200);
1310           // Print a message to stderr.
1311           fdStream err(defaultStream::output_fd());
1312           err.print_raw_cr("# [ timer expired, abort... ]");
1313           // skip atexit/vm_exit/vm_abort hooks
1314           os::die();
1315         }
1316 
1317         // Wait a second, then recheck for timeout.
1318         os::naked_short_sleep(999);
1319       }
1320     }
1321 
1322     if (_should_terminate) {
1323       // check for termination before posting the next tick
1324       break;
1325     }
1326 
1327     PeriodicTask::real_time_tick(time_waited);
1328   }
1329 
1330   // Signal that it is terminated
1331   {
1332     MutexLockerEx mu(Terminator_lock, Mutex::_no_safepoint_check_flag);
1333     _watcher_thread = NULL;
1334     Terminator_lock->notify();
1335   }
1336 }
1337 
1338 void WatcherThread::start() {
1339   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1340 
1341   if (watcher_thread() == NULL && _startable) {
1342     _should_terminate = false;
1343     // Create the single instance of WatcherThread
1344     new WatcherThread();
1345   }
1346 }
1347 
1348 void WatcherThread::make_startable() {
1349   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1350   _startable = true;
1351 }
1352 
1353 void WatcherThread::stop() {
1354   {
1355     // Follow normal safepoint aware lock enter protocol since the
1356     // WatcherThread is stopped by another JavaThread.
1357     MutexLocker ml(PeriodicTask_lock);
1358     _should_terminate = true;
1359 
1360     WatcherThread* watcher = watcher_thread();
1361     if (watcher != NULL) {
1362       // unpark the WatcherThread so it can see that it should terminate
1363       watcher->unpark();
1364     }
1365   }
1366 
1367   MutexLocker mu(Terminator_lock);
1368 
1369   while (watcher_thread() != NULL) {
1370     // This wait should make safepoint checks, wait without a timeout,
1371     // and wait as a suspend-equivalent condition.
1372     //
1373     // Note: If the FlatProfiler is running, then this thread is waiting
1374     // for the WatcherThread to terminate and the WatcherThread, via the
1375     // FlatProfiler task, is waiting for the external suspend request on
1376     // this thread to complete. wait_for_ext_suspend_completion() will
1377     // eventually timeout, but that takes time. Making this wait a
1378     // suspend-equivalent condition solves that timeout problem.
1379     //
1380     Terminator_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
1381                           Mutex::_as_suspend_equivalent_flag);
1382   }
1383 }
1384 
1385 void WatcherThread::unpark() {
1386   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1387   PeriodicTask_lock->notify();
1388 }
1389 
1390 void WatcherThread::print_on(outputStream* st) const {
1391   st->print("\"%s\" ", name());
1392   Thread::print_on(st);
1393   st->cr();
1394 }
1395 
1396 // ======= JavaThread ========
1397 
1398 #if INCLUDE_JVMCI
1399 
1400 jlong* JavaThread::_jvmci_old_thread_counters;
1401 
1402 bool jvmci_counters_include(JavaThread* thread) {
1403   oop threadObj = thread->threadObj();
1404   return !JVMCICountersExcludeCompiler || !thread->is_Compiler_thread();
1405 }
1406 
1407 void JavaThread::collect_counters(typeArrayOop array) {
1408   if (JVMCICounterSize > 0) {
1409     MutexLocker tl(Threads_lock);
1410     for (int i = 0; i < array->length(); i++) {
1411       array->long_at_put(i, _jvmci_old_thread_counters[i]);
1412     }
1413     for (JavaThread* tp = Threads::first(); tp != NULL; tp = tp->next()) {
1414       if (jvmci_counters_include(tp)) {
1415         for (int i = 0; i < array->length(); i++) {
1416           array->long_at_put(i, array->long_at(i) + tp->_jvmci_counters[i]);
1417         }
1418       }
1419     }
1420   }
1421 }
1422 
1423 #endif // INCLUDE_JVMCI
1424 
1425 // A JavaThread is a normal Java thread
1426 
1427 void JavaThread::initialize() {
1428   // Initialize fields
1429 
1430   set_saved_exception_pc(NULL);
1431   set_threadObj(NULL);
1432   _anchor.clear();
1433   set_entry_point(NULL);
1434   set_jni_functions(jni_functions());
1435   set_callee_target(NULL);
1436   set_vm_result(NULL);
1437   set_vm_result_2(NULL);
1438   set_vframe_array_head(NULL);
1439   set_vframe_array_last(NULL);
1440   set_deferred_locals(NULL);
1441   set_deopt_mark(NULL);
1442   set_deopt_compiled_method(NULL);
1443   clear_must_deopt_id();
1444   set_monitor_chunks(NULL);
1445   set_next(NULL);
1446   set_thread_state(_thread_new);
1447   _terminated = _not_terminated;
1448   _privileged_stack_top = NULL;
1449   _array_for_gc = NULL;
1450   _suspend_equivalent = false;
1451   _in_deopt_handler = 0;
1452   _doing_unsafe_access = false;
1453   _stack_guard_state = stack_guard_unused;
1454 #if INCLUDE_JVMCI
1455   _pending_monitorenter = false;
1456   _pending_deoptimization = -1;
1457   _pending_failed_speculation = NULL;
1458   _pending_transfer_to_interpreter = false;
1459   _adjusting_comp_level = false;
1460   _jvmci._alternate_call_target = NULL;
1461   assert(_jvmci._implicit_exception_pc == NULL, "must be");
1462   if (JVMCICounterSize > 0) {
1463     _jvmci_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
1464     memset(_jvmci_counters, 0, sizeof(jlong) * JVMCICounterSize);
1465   } else {
1466     _jvmci_counters = NULL;
1467   }
1468 #endif // INCLUDE_JVMCI
1469   _reserved_stack_activation = NULL;  // stack base not known yet
1470   (void)const_cast<oop&>(_exception_oop = oop(NULL));
1471   _exception_pc  = 0;
1472   _exception_handler_pc = 0;
1473   _is_method_handle_return = 0;
1474   _jvmti_thread_state= NULL;
1475   _should_post_on_exceptions_flag = JNI_FALSE;
1476   _jvmti_get_loaded_classes_closure = NULL;
1477   _interp_only_mode    = 0;
1478   _special_runtime_exit_condition = _no_async_condition;
1479   _pending_async_exception = NULL;
1480   _thread_stat = NULL;
1481   _thread_stat = new ThreadStatistics();
1482   _blocked_on_compilation = false;
1483   _jni_active_critical = 0;
1484   _pending_jni_exception_check_fn = NULL;
1485   _do_not_unlock_if_synchronized = false;
1486   _cached_monitor_info = NULL;
1487   _parker = Parker::Allocate(this);
1488 
1489 #ifndef PRODUCT
1490   _jmp_ring_index = 0;
1491   for (int ji = 0; ji < jump_ring_buffer_size; ji++) {
1492     record_jump(NULL, NULL, NULL, 0);
1493   }
1494 #endif // PRODUCT
1495 
1496   set_thread_profiler(NULL);
1497   if (FlatProfiler::is_active()) {
1498     // This is where we would decide to either give each thread it's own profiler
1499     // or use one global one from FlatProfiler,
1500     // or up to some count of the number of profiled threads, etc.
1501     ThreadProfiler* pp = new ThreadProfiler();
1502     pp->engage();
1503     set_thread_profiler(pp);
1504   }
1505 
1506   // Setup safepoint state info for this thread
1507   ThreadSafepointState::create(this);
1508 
1509   debug_only(_java_call_counter = 0);
1510 
1511   // JVMTI PopFrame support
1512   _popframe_condition = popframe_inactive;
1513   _popframe_preserved_args = NULL;
1514   _popframe_preserved_args_size = 0;
1515   _frames_to_pop_failed_realloc = 0;
1516 
1517   pd_initialize();
1518 }
1519 
1520 #if INCLUDE_ALL_GCS
1521 SATBMarkQueueSet JavaThread::_satb_mark_queue_set;
1522 DirtyCardQueueSet JavaThread::_dirty_card_queue_set;
1523 #endif // INCLUDE_ALL_GCS
1524 
1525 JavaThread::JavaThread(bool is_attaching_via_jni) :
1526                        Thread()
1527 #if INCLUDE_ALL_GCS
1528                        , _satb_mark_queue(&_satb_mark_queue_set),
1529                        _dirty_card_queue(&_dirty_card_queue_set)
1530 #endif // INCLUDE_ALL_GCS
1531 {
1532   initialize();
1533   if (is_attaching_via_jni) {
1534     _jni_attach_state = _attaching_via_jni;
1535   } else {
1536     _jni_attach_state = _not_attaching_via_jni;
1537   }
1538   assert(deferred_card_mark().is_empty(), "Default MemRegion ctor");
1539 }
1540 
1541 bool JavaThread::reguard_stack(address cur_sp) {
1542   if (_stack_guard_state != stack_guard_yellow_reserved_disabled
1543       && _stack_guard_state != stack_guard_reserved_disabled) {
1544     return true; // Stack already guarded or guard pages not needed.
1545   }
1546 
1547   if (register_stack_overflow()) {
1548     // For those architectures which have separate register and
1549     // memory stacks, we must check the register stack to see if
1550     // it has overflowed.
1551     return false;
1552   }
1553 
1554   // Java code never executes within the yellow zone: the latter is only
1555   // there to provoke an exception during stack banging.  If java code
1556   // is executing there, either StackShadowPages should be larger, or
1557   // some exception code in c1, c2 or the interpreter isn't unwinding
1558   // when it should.
1559   guarantee(cur_sp > stack_reserved_zone_base(),
1560             "not enough space to reguard - increase StackShadowPages");
1561   if (_stack_guard_state == stack_guard_yellow_reserved_disabled) {
1562     enable_stack_yellow_reserved_zone();
1563     if (reserved_stack_activation() != stack_base()) {
1564       set_reserved_stack_activation(stack_base());
1565     }
1566   } else if (_stack_guard_state == stack_guard_reserved_disabled) {
1567     set_reserved_stack_activation(stack_base());
1568     enable_stack_reserved_zone();
1569   }
1570   return true;
1571 }
1572 
1573 bool JavaThread::reguard_stack(void) {
1574   return reguard_stack(os::current_stack_pointer());
1575 }
1576 
1577 
1578 void JavaThread::block_if_vm_exited() {
1579   if (_terminated == _vm_exited) {
1580     // _vm_exited is set at safepoint, and Threads_lock is never released
1581     // we will block here forever
1582     Threads_lock->lock_without_safepoint_check();
1583     ShouldNotReachHere();
1584   }
1585 }
1586 
1587 
1588 // Remove this ifdef when C1 is ported to the compiler interface.
1589 static void compiler_thread_entry(JavaThread* thread, TRAPS);
1590 static void sweeper_thread_entry(JavaThread* thread, TRAPS);
1591 
1592 JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
1593                        Thread()
1594 #if INCLUDE_ALL_GCS
1595                        , _satb_mark_queue(&_satb_mark_queue_set),
1596                        _dirty_card_queue(&_dirty_card_queue_set)
1597 #endif // INCLUDE_ALL_GCS
1598 {
1599   initialize();
1600   _jni_attach_state = _not_attaching_via_jni;
1601   set_entry_point(entry_point);
1602   // Create the native thread itself.
1603   // %note runtime_23
1604   os::ThreadType thr_type = os::java_thread;
1605   thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
1606                                                      os::java_thread;
1607   os::create_thread(this, thr_type, stack_sz);
1608   // The _osthread may be NULL here because we ran out of memory (too many threads active).
1609   // We need to throw and OutOfMemoryError - however we cannot do this here because the caller
1610   // may hold a lock and all locks must be unlocked before throwing the exception (throwing
1611   // the exception consists of creating the exception object & initializing it, initialization
1612   // will leave the VM via a JavaCall and then all locks must be unlocked).
1613   //
1614   // The thread is still suspended when we reach here. Thread must be explicit started
1615   // by creator! Furthermore, the thread must also explicitly be added to the Threads list
1616   // by calling Threads:add. The reason why this is not done here, is because the thread
1617   // object must be fully initialized (take a look at JVM_Start)
1618 }
1619 
1620 JavaThread::~JavaThread() {
1621 
1622   // JSR166 -- return the parker to the free list
1623   Parker::Release(_parker);
1624   _parker = NULL;
1625 
1626   // Free any remaining  previous UnrollBlock
1627   vframeArray* old_array = vframe_array_last();
1628 
1629   if (old_array != NULL) {
1630     Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
1631     old_array->set_unroll_block(NULL);
1632     delete old_info;
1633     delete old_array;
1634   }
1635 
1636   GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred = deferred_locals();
1637   if (deferred != NULL) {
1638     // This can only happen if thread is destroyed before deoptimization occurs.
1639     assert(deferred->length() != 0, "empty array!");
1640     do {
1641       jvmtiDeferredLocalVariableSet* dlv = deferred->at(0);
1642       deferred->remove_at(0);
1643       // individual jvmtiDeferredLocalVariableSet are CHeapObj's
1644       delete dlv;
1645     } while (deferred->length() != 0);
1646     delete deferred;
1647   }
1648 
1649   // All Java related clean up happens in exit
1650   ThreadSafepointState::destroy(this);
1651   if (_thread_profiler != NULL) delete _thread_profiler;
1652   if (_thread_stat != NULL) delete _thread_stat;
1653 
1654 #if INCLUDE_JVMCI
1655   if (JVMCICounterSize > 0) {
1656     if (jvmci_counters_include(this)) {
1657       for (int i = 0; i < JVMCICounterSize; i++) {
1658         _jvmci_old_thread_counters[i] += _jvmci_counters[i];
1659       }
1660     }
1661     FREE_C_HEAP_ARRAY(jlong, _jvmci_counters);
1662   }
1663 #endif // INCLUDE_JVMCI
1664 }
1665 
1666 
1667 // The first routine called by a new Java thread
1668 void JavaThread::run() {
1669   // initialize thread-local alloc buffer related fields
1670   this->initialize_tlab();
1671 
1672   // used to test validity of stack trace backs
1673   this->record_base_of_stack_pointer();
1674 
1675   // Record real stack base and size.
1676   this->record_stack_base_and_size();
1677 
1678   this->create_stack_guard_pages();
1679 
1680   this->cache_global_variables();
1681 
1682   // Thread is now sufficient initialized to be handled by the safepoint code as being
1683   // in the VM. Change thread state from _thread_new to _thread_in_vm
1684   ThreadStateTransition::transition_and_fence(this, _thread_new, _thread_in_vm);
1685 
1686   assert(JavaThread::current() == this, "sanity check");
1687   assert(!Thread::current()->owns_locks(), "sanity check");
1688 
1689   DTRACE_THREAD_PROBE(start, this);
1690 
1691   // This operation might block. We call that after all safepoint checks for a new thread has
1692   // been completed.
1693   this->set_active_handles(JNIHandleBlock::allocate_block());
1694 
1695   if (JvmtiExport::should_post_thread_life()) {
1696     JvmtiExport::post_thread_start(this);
1697   }
1698 
1699   EventThreadStart event;
1700   if (event.should_commit()) {
1701     event.set_thread(THREAD_TRACE_ID(this));
1702     event.commit();
1703   }
1704 
1705   // We call another function to do the rest so we are sure that the stack addresses used
1706   // from there will be lower than the stack base just computed
1707   thread_main_inner();
1708 
1709   // Note, thread is no longer valid at this point!
1710 }
1711 
1712 
1713 void JavaThread::thread_main_inner() {
1714   assert(JavaThread::current() == this, "sanity check");
1715   assert(this->threadObj() != NULL, "just checking");
1716 
1717   // Execute thread entry point unless this thread has a pending exception
1718   // or has been stopped before starting.
1719   // Note: Due to JVM_StopThread we can have pending exceptions already!
1720   if (!this->has_pending_exception() &&
1721       !java_lang_Thread::is_stillborn(this->threadObj())) {
1722     {
1723       ResourceMark rm(this);
1724       this->set_native_thread_name(this->get_thread_name());
1725     }
1726     HandleMark hm(this);
1727     this->entry_point()(this, this);
1728   }
1729 
1730   DTRACE_THREAD_PROBE(stop, this);
1731 
1732   this->exit(false);
1733   delete this;
1734 }
1735 
1736 
1737 static void ensure_join(JavaThread* thread) {
1738   // We do not need to grap the Threads_lock, since we are operating on ourself.
1739   Handle threadObj(thread, thread->threadObj());
1740   assert(threadObj.not_null(), "java thread object must exist");
1741   ObjectLocker lock(threadObj, thread);
1742   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1743   thread->clear_pending_exception();
1744   // Thread is exiting. So set thread_status field in  java.lang.Thread class to TERMINATED.
1745   java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
1746   // Clear the native thread instance - this makes isAlive return false and allows the join()
1747   // to complete once we've done the notify_all below
1748   java_lang_Thread::set_thread(threadObj(), NULL);
1749   lock.notify_all(thread);
1750   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1751   thread->clear_pending_exception();
1752 }
1753 
1754 
1755 // For any new cleanup additions, please check to see if they need to be applied to
1756 // cleanup_failed_attach_current_thread as well.
1757 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
1758   assert(this == JavaThread::current(), "thread consistency check");
1759 
1760   HandleMark hm(this);
1761   Handle uncaught_exception(this, this->pending_exception());
1762   this->clear_pending_exception();
1763   Handle threadObj(this, this->threadObj());
1764   assert(threadObj.not_null(), "Java thread object should be created");
1765 
1766   if (get_thread_profiler() != NULL) {
1767     get_thread_profiler()->disengage();
1768     ResourceMark rm;
1769     get_thread_profiler()->print(get_thread_name());
1770   }
1771 
1772 
1773   // FIXIT: This code should be moved into else part, when reliable 1.2/1.3 check is in place
1774   {
1775     EXCEPTION_MARK;
1776 
1777     CLEAR_PENDING_EXCEPTION;
1778   }
1779   if (!destroy_vm) {
1780     if (uncaught_exception.not_null()) {
1781       EXCEPTION_MARK;
1782       // Call method Thread.dispatchUncaughtException().
1783       Klass* thread_klass = SystemDictionary::Thread_klass();
1784       JavaValue result(T_VOID);
1785       JavaCalls::call_virtual(&result,
1786                               threadObj, thread_klass,
1787                               vmSymbols::dispatchUncaughtException_name(),
1788                               vmSymbols::throwable_void_signature(),
1789                               uncaught_exception,
1790                               THREAD);
1791       if (HAS_PENDING_EXCEPTION) {
1792         ResourceMark rm(this);
1793         jio_fprintf(defaultStream::error_stream(),
1794                     "\nException: %s thrown from the UncaughtExceptionHandler"
1795                     " in thread \"%s\"\n",
1796                     pending_exception()->klass()->external_name(),
1797                     get_thread_name());
1798         CLEAR_PENDING_EXCEPTION;
1799       }
1800     }
1801 
1802     // Called before the java thread exit since we want to read info
1803     // from java_lang_Thread object
1804     EventThreadEnd event;
1805     if (event.should_commit()) {
1806       event.set_thread(THREAD_TRACE_ID(this));
1807       event.commit();
1808     }
1809 
1810     // Call after last event on thread
1811     EVENT_THREAD_EXIT(this);
1812 
1813     // Call Thread.exit(). We try 3 times in case we got another Thread.stop during
1814     // the execution of the method. If that is not enough, then we don't really care. Thread.stop
1815     // is deprecated anyhow.
1816     if (!is_Compiler_thread()) {
1817       int count = 3;
1818       while (java_lang_Thread::threadGroup(threadObj()) != NULL && (count-- > 0)) {
1819         EXCEPTION_MARK;
1820         JavaValue result(T_VOID);
1821         Klass* thread_klass = SystemDictionary::Thread_klass();
1822         JavaCalls::call_virtual(&result,
1823                                 threadObj, thread_klass,
1824                                 vmSymbols::exit_method_name(),
1825                                 vmSymbols::void_method_signature(),
1826                                 THREAD);
1827         CLEAR_PENDING_EXCEPTION;
1828       }
1829     }
1830     // notify JVMTI
1831     if (JvmtiExport::should_post_thread_life()) {
1832       JvmtiExport::post_thread_end(this);
1833     }
1834 
1835     // We have notified the agents that we are exiting, before we go on,
1836     // we must check for a pending external suspend request and honor it
1837     // in order to not surprise the thread that made the suspend request.
1838     while (true) {
1839       {
1840         MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
1841         if (!is_external_suspend()) {
1842           set_terminated(_thread_exiting);
1843           ThreadService::current_thread_exiting(this);
1844           break;
1845         }
1846         // Implied else:
1847         // Things get a little tricky here. We have a pending external
1848         // suspend request, but we are holding the SR_lock so we
1849         // can't just self-suspend. So we temporarily drop the lock
1850         // and then self-suspend.
1851       }
1852 
1853       ThreadBlockInVM tbivm(this);
1854       java_suspend_self();
1855 
1856       // We're done with this suspend request, but we have to loop around
1857       // and check again. Eventually we will get SR_lock without a pending
1858       // external suspend request and will be able to mark ourselves as
1859       // exiting.
1860     }
1861     // no more external suspends are allowed at this point
1862   } else {
1863     // before_exit() has already posted JVMTI THREAD_END events
1864   }
1865 
1866   // Notify waiters on thread object. This has to be done after exit() is called
1867   // on the thread (if the thread is the last thread in a daemon ThreadGroup the
1868   // group should have the destroyed bit set before waiters are notified).
1869   ensure_join(this);
1870   assert(!this->has_pending_exception(), "ensure_join should have cleared");
1871 
1872   // 6282335 JNI DetachCurrentThread spec states that all Java monitors
1873   // held by this thread must be released. The spec does not distinguish
1874   // between JNI-acquired and regular Java monitors. We can only see
1875   // regular Java monitors here if monitor enter-exit matching is broken.
1876   //
1877   // Optionally release any monitors for regular JavaThread exits. This
1878   // is provided as a work around for any bugs in monitor enter-exit
1879   // matching. This can be expensive so it is not enabled by default.
1880   //
1881   // ensure_join() ignores IllegalThreadStateExceptions, and so does
1882   // ObjectSynchronizer::release_monitors_owned_by_thread().
1883   if (exit_type == jni_detach || ObjectMonitor::Knob_ExitRelease) {
1884     // Sanity check even though JNI DetachCurrentThread() would have
1885     // returned JNI_ERR if there was a Java frame. JavaThread exit
1886     // should be done executing Java code by the time we get here.
1887     assert(!this->has_last_Java_frame(),
1888            "should not have a Java frame when detaching or exiting");
1889     ObjectSynchronizer::release_monitors_owned_by_thread(this);
1890     assert(!this->has_pending_exception(), "release_monitors should have cleared");
1891   }
1892 
1893   // These things needs to be done while we are still a Java Thread. Make sure that thread
1894   // is in a consistent state, in case GC happens
1895   assert(_privileged_stack_top == NULL, "must be NULL when we get here");
1896 
1897   if (active_handles() != NULL) {
1898     JNIHandleBlock* block = active_handles();
1899     set_active_handles(NULL);
1900     JNIHandleBlock::release_block(block);
1901   }
1902 
1903   if (free_handle_block() != NULL) {
1904     JNIHandleBlock* block = free_handle_block();
1905     set_free_handle_block(NULL);
1906     JNIHandleBlock::release_block(block);
1907   }
1908 
1909   // These have to be removed while this is still a valid thread.
1910   remove_stack_guard_pages();
1911 
1912   if (UseTLAB) {
1913     tlab().make_parsable(true);  // retire TLAB
1914   }
1915 
1916   if (JvmtiEnv::environments_might_exist()) {
1917     JvmtiExport::cleanup_thread(this);
1918   }
1919 
1920   // We must flush any deferred card marks before removing a thread from
1921   // the list of active threads.
1922   Universe::heap()->flush_deferred_store_barrier(this);
1923   assert(deferred_card_mark().is_empty(), "Should have been flushed");
1924 
1925 #if INCLUDE_ALL_GCS
1926   // We must flush the G1-related buffers before removing a thread
1927   // from the list of active threads. We must do this after any deferred
1928   // card marks have been flushed (above) so that any entries that are
1929   // added to the thread's dirty card queue as a result are not lost.
1930   if (UseG1GC) {
1931     flush_barrier_queues();
1932   }
1933 #endif // INCLUDE_ALL_GCS
1934 
1935   log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").",
1936     exit_type == JavaThread::normal_exit ? "exiting" : "detaching",
1937     os::current_thread_id());
1938 
1939   // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
1940   Threads::remove(this);
1941 }
1942 
1943 #if INCLUDE_ALL_GCS
1944 // Flush G1-related queues.
1945 void JavaThread::flush_barrier_queues() {
1946   satb_mark_queue().flush();
1947   dirty_card_queue().flush();
1948 }
1949 
1950 void JavaThread::initialize_queues() {
1951   assert(!SafepointSynchronize::is_at_safepoint(),
1952          "we should not be at a safepoint");
1953 
1954   SATBMarkQueue& satb_queue = satb_mark_queue();
1955   SATBMarkQueueSet& satb_queue_set = satb_mark_queue_set();
1956   // The SATB queue should have been constructed with its active
1957   // field set to false.
1958   assert(!satb_queue.is_active(), "SATB queue should not be active");
1959   assert(satb_queue.is_empty(), "SATB queue should be empty");
1960   // If we are creating the thread during a marking cycle, we should
1961   // set the active field of the SATB queue to true.
1962   if (satb_queue_set.is_active()) {
1963     satb_queue.set_active(true);
1964   }
1965 
1966   DirtyCardQueue& dirty_queue = dirty_card_queue();
1967   // The dirty card queue should have been constructed with its
1968   // active field set to true.
1969   assert(dirty_queue.is_active(), "dirty card queue should be active");
1970 }
1971 #endif // INCLUDE_ALL_GCS
1972 
1973 void JavaThread::cleanup_failed_attach_current_thread() {
1974   if (get_thread_profiler() != NULL) {
1975     get_thread_profiler()->disengage();
1976     ResourceMark rm;
1977     get_thread_profiler()->print(get_thread_name());
1978   }
1979 
1980   if (active_handles() != NULL) {
1981     JNIHandleBlock* block = active_handles();
1982     set_active_handles(NULL);
1983     JNIHandleBlock::release_block(block);
1984   }
1985 
1986   if (free_handle_block() != NULL) {
1987     JNIHandleBlock* block = free_handle_block();
1988     set_free_handle_block(NULL);
1989     JNIHandleBlock::release_block(block);
1990   }
1991 
1992   // These have to be removed while this is still a valid thread.
1993   remove_stack_guard_pages();
1994 
1995   if (UseTLAB) {
1996     tlab().make_parsable(true);  // retire TLAB, if any
1997   }
1998 
1999 #if INCLUDE_ALL_GCS
2000   if (UseG1GC) {
2001     flush_barrier_queues();
2002   }
2003 #endif // INCLUDE_ALL_GCS
2004 
2005   Threads::remove(this);
2006   delete this;
2007 }
2008 
2009 
2010 
2011 
2012 JavaThread* JavaThread::active() {
2013   Thread* thread = Thread::current();
2014   if (thread->is_Java_thread()) {
2015     return (JavaThread*) thread;
2016   } else {
2017     assert(thread->is_VM_thread(), "this must be a vm thread");
2018     VM_Operation* op = ((VMThread*) thread)->vm_operation();
2019     JavaThread *ret=op == NULL ? NULL : (JavaThread *)op->calling_thread();
2020     assert(ret->is_Java_thread(), "must be a Java thread");
2021     return ret;
2022   }
2023 }
2024 
2025 bool JavaThread::is_lock_owned(address adr) const {
2026   if (Thread::is_lock_owned(adr)) return true;
2027 
2028   for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2029     if (chunk->contains(adr)) return true;
2030   }
2031 
2032   return false;
2033 }
2034 
2035 
2036 void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
2037   chunk->set_next(monitor_chunks());
2038   set_monitor_chunks(chunk);
2039 }
2040 
2041 void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
2042   guarantee(monitor_chunks() != NULL, "must be non empty");
2043   if (monitor_chunks() == chunk) {
2044     set_monitor_chunks(chunk->next());
2045   } else {
2046     MonitorChunk* prev = monitor_chunks();
2047     while (prev->next() != chunk) prev = prev->next();
2048     prev->set_next(chunk->next());
2049   }
2050 }
2051 
2052 // JVM support.
2053 
2054 // Note: this function shouldn't block if it's called in
2055 // _thread_in_native_trans state (such as from
2056 // check_special_condition_for_native_trans()).
2057 void JavaThread::check_and_handle_async_exceptions(bool check_unsafe_error) {
2058 
2059   if (has_last_Java_frame() && has_async_condition()) {
2060     // If we are at a polling page safepoint (not a poll return)
2061     // then we must defer async exception because live registers
2062     // will be clobbered by the exception path. Poll return is
2063     // ok because the call we a returning from already collides
2064     // with exception handling registers and so there is no issue.
2065     // (The exception handling path kills call result registers but
2066     //  this is ok since the exception kills the result anyway).
2067 
2068     if (is_at_poll_safepoint()) {
2069       // if the code we are returning to has deoptimized we must defer
2070       // the exception otherwise live registers get clobbered on the
2071       // exception path before deoptimization is able to retrieve them.
2072       //
2073       RegisterMap map(this, false);
2074       frame caller_fr = last_frame().sender(&map);
2075       assert(caller_fr.is_compiled_frame(), "what?");
2076       if (caller_fr.is_deoptimized_frame()) {
2077         log_info(exceptions)("deferred async exception at compiled safepoint");
2078         return;
2079       }
2080     }
2081   }
2082 
2083   JavaThread::AsyncRequests condition = clear_special_runtime_exit_condition();
2084   if (condition == _no_async_condition) {
2085     // Conditions have changed since has_special_runtime_exit_condition()
2086     // was called:
2087     // - if we were here only because of an external suspend request,
2088     //   then that was taken care of above (or cancelled) so we are done
2089     // - if we were here because of another async request, then it has
2090     //   been cleared between the has_special_runtime_exit_condition()
2091     //   and now so again we are done
2092     return;
2093   }
2094 
2095   // Check for pending async. exception
2096   if (_pending_async_exception != NULL) {
2097     // Only overwrite an already pending exception, if it is not a threadDeath.
2098     if (!has_pending_exception() || !pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())) {
2099 
2100       // We cannot call Exceptions::_throw(...) here because we cannot block
2101       set_pending_exception(_pending_async_exception, __FILE__, __LINE__);
2102 
2103       if (log_is_enabled(Info, exceptions)) {
2104         ResourceMark rm;
2105         outputStream* logstream = Log(exceptions)::info_stream();
2106         logstream->print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", p2i(this));
2107           if (has_last_Java_frame()) {
2108             frame f = last_frame();
2109            logstream->print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", p2i(f.pc()), p2i(f.sp()));
2110           }
2111         logstream->print_cr(" of type: %s", _pending_async_exception->klass()->external_name());
2112       }
2113       _pending_async_exception = NULL;
2114       clear_has_async_exception();
2115     }
2116   }
2117 
2118   if (check_unsafe_error &&
2119       condition == _async_unsafe_access_error && !has_pending_exception()) {
2120     condition = _no_async_condition;  // done
2121     switch (thread_state()) {
2122     case _thread_in_vm: {
2123       JavaThread* THREAD = this;
2124       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2125     }
2126     case _thread_in_native: {
2127       ThreadInVMfromNative tiv(this);
2128       JavaThread* THREAD = this;
2129       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2130     }
2131     case _thread_in_Java: {
2132       ThreadInVMfromJava tiv(this);
2133       JavaThread* THREAD = this;
2134       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in a recent unsafe memory access operation in compiled Java code");
2135     }
2136     default:
2137       ShouldNotReachHere();
2138     }
2139   }
2140 
2141   assert(condition == _no_async_condition || has_pending_exception() ||
2142          (!check_unsafe_error && condition == _async_unsafe_access_error),
2143          "must have handled the async condition, if no exception");
2144 }
2145 
2146 void JavaThread::handle_special_runtime_exit_condition(bool check_asyncs) {
2147   //
2148   // Check for pending external suspend. Internal suspend requests do
2149   // not use handle_special_runtime_exit_condition().
2150   // If JNIEnv proxies are allowed, don't self-suspend if the target
2151   // thread is not the current thread. In older versions of jdbx, jdbx
2152   // threads could call into the VM with another thread's JNIEnv so we
2153   // can be here operating on behalf of a suspended thread (4432884).
2154   bool do_self_suspend = is_external_suspend_with_lock();
2155   if (do_self_suspend && (!AllowJNIEnvProxy || this == JavaThread::current())) {
2156     //
2157     // Because thread is external suspended the safepoint code will count
2158     // thread as at a safepoint. This can be odd because we can be here
2159     // as _thread_in_Java which would normally transition to _thread_blocked
2160     // at a safepoint. We would like to mark the thread as _thread_blocked
2161     // before calling java_suspend_self like all other callers of it but
2162     // we must then observe proper safepoint protocol. (We can't leave
2163     // _thread_blocked with a safepoint in progress). However we can be
2164     // here as _thread_in_native_trans so we can't use a normal transition
2165     // constructor/destructor pair because they assert on that type of
2166     // transition. We could do something like:
2167     //
2168     // JavaThreadState state = thread_state();
2169     // set_thread_state(_thread_in_vm);
2170     // {
2171     //   ThreadBlockInVM tbivm(this);
2172     //   java_suspend_self()
2173     // }
2174     // set_thread_state(_thread_in_vm_trans);
2175     // if (safepoint) block;
2176     // set_thread_state(state);
2177     //
2178     // but that is pretty messy. Instead we just go with the way the
2179     // code has worked before and note that this is the only path to
2180     // java_suspend_self that doesn't put the thread in _thread_blocked
2181     // mode.
2182 
2183     frame_anchor()->make_walkable(this);
2184     java_suspend_self();
2185 
2186     // We might be here for reasons in addition to the self-suspend request
2187     // so check for other async requests.
2188   }
2189 
2190   if (check_asyncs) {
2191     check_and_handle_async_exceptions();
2192   }
2193 }
2194 
2195 void JavaThread::send_thread_stop(oop java_throwable)  {
2196   assert(Thread::current()->is_VM_thread(), "should be in the vm thread");
2197   assert(Threads_lock->is_locked(), "Threads_lock should be locked by safepoint code");
2198   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
2199 
2200   // Do not throw asynchronous exceptions against the compiler thread
2201   // (the compiler thread should not be a Java thread -- fix in 1.4.2)
2202   if (!can_call_java()) return;
2203 
2204   {
2205     // Actually throw the Throwable against the target Thread - however
2206     // only if there is no thread death exception installed already.
2207     if (_pending_async_exception == NULL || !_pending_async_exception->is_a(SystemDictionary::ThreadDeath_klass())) {
2208       // If the topmost frame is a runtime stub, then we are calling into
2209       // OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
2210       // must deoptimize the caller before continuing, as the compiled  exception handler table
2211       // may not be valid
2212       if (has_last_Java_frame()) {
2213         frame f = last_frame();
2214         if (f.is_runtime_frame() || f.is_safepoint_blob_frame()) {
2215           // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2216           RegisterMap reg_map(this, UseBiasedLocking);
2217           frame compiled_frame = f.sender(&reg_map);
2218           if (!StressCompiledExceptionHandlers && compiled_frame.can_be_deoptimized()) {
2219             Deoptimization::deoptimize(this, compiled_frame, &reg_map);
2220           }
2221         }
2222       }
2223 
2224       // Set async. pending exception in thread.
2225       set_pending_async_exception(java_throwable);
2226 
2227       if (log_is_enabled(Info, exceptions)) {
2228          ResourceMark rm;
2229         log_info(exceptions)("Pending Async. exception installed of type: %s",
2230                              InstanceKlass::cast(_pending_async_exception->klass())->external_name());
2231       }
2232       // for AbortVMOnException flag
2233       Exceptions::debug_check_abort(_pending_async_exception->klass()->external_name());
2234     }
2235   }
2236 
2237 
2238   // Interrupt thread so it will wake up from a potential wait()
2239   Thread::interrupt(this);
2240 }
2241 
2242 // External suspension mechanism.
2243 //
2244 // Tell the VM to suspend a thread when ever it knows that it does not hold on
2245 // to any VM_locks and it is at a transition
2246 // Self-suspension will happen on the transition out of the vm.
2247 // Catch "this" coming in from JNIEnv pointers when the thread has been freed
2248 //
2249 // Guarantees on return:
2250 //   + Target thread will not execute any new bytecode (that's why we need to
2251 //     force a safepoint)
2252 //   + Target thread will not enter any new monitors
2253 //
2254 void JavaThread::java_suspend() {
2255   { MutexLocker mu(Threads_lock);
2256     if (!Threads::includes(this) || is_exiting() || this->threadObj() == NULL) {
2257       return;
2258     }
2259   }
2260 
2261   { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2262     if (!is_external_suspend()) {
2263       // a racing resume has cancelled us; bail out now
2264       return;
2265     }
2266 
2267     // suspend is done
2268     uint32_t debug_bits = 0;
2269     // Warning: is_ext_suspend_completed() may temporarily drop the
2270     // SR_lock to allow the thread to reach a stable thread state if
2271     // it is currently in a transient thread state.
2272     if (is_ext_suspend_completed(false /* !called_by_wait */,
2273                                  SuspendRetryDelay, &debug_bits)) {
2274       return;
2275     }
2276   }
2277 
2278   VM_ThreadSuspend vm_suspend;
2279   VMThread::execute(&vm_suspend);
2280 }
2281 
2282 // Part II of external suspension.
2283 // A JavaThread self suspends when it detects a pending external suspend
2284 // request. This is usually on transitions. It is also done in places
2285 // where continuing to the next transition would surprise the caller,
2286 // e.g., monitor entry.
2287 //
2288 // Returns the number of times that the thread self-suspended.
2289 //
2290 // Note: DO NOT call java_suspend_self() when you just want to block current
2291 //       thread. java_suspend_self() is the second stage of cooperative
2292 //       suspension for external suspend requests and should only be used
2293 //       to complete an external suspend request.
2294 //
2295 int JavaThread::java_suspend_self() {
2296   int ret = 0;
2297 
2298   // we are in the process of exiting so don't suspend
2299   if (is_exiting()) {
2300     clear_external_suspend();
2301     return ret;
2302   }
2303 
2304   assert(_anchor.walkable() ||
2305          (is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
2306          "must have walkable stack");
2307 
2308   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2309 
2310   assert(!this->is_ext_suspended(),
2311          "a thread trying to self-suspend should not already be suspended");
2312 
2313   if (this->is_suspend_equivalent()) {
2314     // If we are self-suspending as a result of the lifting of a
2315     // suspend equivalent condition, then the suspend_equivalent
2316     // flag is not cleared until we set the ext_suspended flag so
2317     // that wait_for_ext_suspend_completion() returns consistent
2318     // results.
2319     this->clear_suspend_equivalent();
2320   }
2321 
2322   // A racing resume may have cancelled us before we grabbed SR_lock
2323   // above. Or another external suspend request could be waiting for us
2324   // by the time we return from SR_lock()->wait(). The thread
2325   // that requested the suspension may already be trying to walk our
2326   // stack and if we return now, we can change the stack out from under
2327   // it. This would be a "bad thing (TM)" and cause the stack walker
2328   // to crash. We stay self-suspended until there are no more pending
2329   // external suspend requests.
2330   while (is_external_suspend()) {
2331     ret++;
2332     this->set_ext_suspended();
2333 
2334     // _ext_suspended flag is cleared by java_resume()
2335     while (is_ext_suspended()) {
2336       this->SR_lock()->wait(Mutex::_no_safepoint_check_flag);
2337     }
2338   }
2339 
2340   return ret;
2341 }
2342 
2343 #ifdef ASSERT
2344 // verify the JavaThread has not yet been published in the Threads::list, and
2345 // hence doesn't need protection from concurrent access at this stage
2346 void JavaThread::verify_not_published() {
2347   if (!Threads_lock->owned_by_self()) {
2348     MutexLockerEx ml(Threads_lock,  Mutex::_no_safepoint_check_flag);
2349     assert(!Threads::includes(this),
2350            "java thread shouldn't have been published yet!");
2351   } else {
2352     assert(!Threads::includes(this),
2353            "java thread shouldn't have been published yet!");
2354   }
2355 }
2356 #endif
2357 
2358 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2359 // progress or when _suspend_flags is non-zero.
2360 // Current thread needs to self-suspend if there is a suspend request and/or
2361 // block if a safepoint is in progress.
2362 // Async exception ISN'T checked.
2363 // Note only the ThreadInVMfromNative transition can call this function
2364 // directly and when thread state is _thread_in_native_trans
2365 void JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread *thread) {
2366   assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
2367 
2368   JavaThread *curJT = JavaThread::current();
2369   bool do_self_suspend = thread->is_external_suspend();
2370 
2371   assert(!curJT->has_last_Java_frame() || curJT->frame_anchor()->walkable(), "Unwalkable stack in native->vm transition");
2372 
2373   // If JNIEnv proxies are allowed, don't self-suspend if the target
2374   // thread is not the current thread. In older versions of jdbx, jdbx
2375   // threads could call into the VM with another thread's JNIEnv so we
2376   // can be here operating on behalf of a suspended thread (4432884).
2377   if (do_self_suspend && (!AllowJNIEnvProxy || curJT == thread)) {
2378     JavaThreadState state = thread->thread_state();
2379 
2380     // We mark this thread_blocked state as a suspend-equivalent so
2381     // that a caller to is_ext_suspend_completed() won't be confused.
2382     // The suspend-equivalent state is cleared by java_suspend_self().
2383     thread->set_suspend_equivalent();
2384 
2385     // If the safepoint code sees the _thread_in_native_trans state, it will
2386     // wait until the thread changes to other thread state. There is no
2387     // guarantee on how soon we can obtain the SR_lock and complete the
2388     // self-suspend request. It would be a bad idea to let safepoint wait for
2389     // too long. Temporarily change the state to _thread_blocked to
2390     // let the VM thread know that this thread is ready for GC. The problem
2391     // of changing thread state is that safepoint could happen just after
2392     // java_suspend_self() returns after being resumed, and VM thread will
2393     // see the _thread_blocked state. We must check for safepoint
2394     // after restoring the state and make sure we won't leave while a safepoint
2395     // is in progress.
2396     thread->set_thread_state(_thread_blocked);
2397     thread->java_suspend_self();
2398     thread->set_thread_state(state);
2399     // Make sure new state is seen by VM thread
2400     if (os::is_MP()) {
2401       if (UseMembar) {
2402         // Force a fence between the write above and read below
2403         OrderAccess::fence();
2404       } else {
2405         // Must use this rather than serialization page in particular on Windows
2406         InterfaceSupport::serialize_memory(thread);
2407       }
2408     }
2409   }
2410 
2411   if (SafepointSynchronize::do_call_back()) {
2412     // If we are safepointing, then block the caller which may not be
2413     // the same as the target thread (see above).
2414     SafepointSynchronize::block(curJT);
2415   }
2416 
2417   if (thread->is_deopt_suspend()) {
2418     thread->clear_deopt_suspend();
2419     RegisterMap map(thread, false);
2420     frame f = thread->last_frame();
2421     while (f.id() != thread->must_deopt_id() && ! f.is_first_frame()) {
2422       f = f.sender(&map);
2423     }
2424     if (f.id() == thread->must_deopt_id()) {
2425       thread->clear_must_deopt_id();
2426       f.deoptimize(thread);
2427     } else {
2428       fatal("missed deoptimization!");
2429     }
2430   }
2431 }
2432 
2433 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2434 // progress or when _suspend_flags is non-zero.
2435 // Current thread needs to self-suspend if there is a suspend request and/or
2436 // block if a safepoint is in progress.
2437 // Also check for pending async exception (not including unsafe access error).
2438 // Note only the native==>VM/Java barriers can call this function and when
2439 // thread state is _thread_in_native_trans.
2440 void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
2441   check_safepoint_and_suspend_for_native_trans(thread);
2442 
2443   if (thread->has_async_exception()) {
2444     // We are in _thread_in_native_trans state, don't handle unsafe
2445     // access error since that may block.
2446     thread->check_and_handle_async_exceptions(false);
2447   }
2448 }
2449 
2450 // This is a variant of the normal
2451 // check_special_condition_for_native_trans with slightly different
2452 // semantics for use by critical native wrappers.  It does all the
2453 // normal checks but also performs the transition back into
2454 // thread_in_Java state.  This is required so that critical natives
2455 // can potentially block and perform a GC if they are the last thread
2456 // exiting the GCLocker.
2457 void JavaThread::check_special_condition_for_native_trans_and_transition(JavaThread *thread) {
2458   check_special_condition_for_native_trans(thread);
2459 
2460   // Finish the transition
2461   thread->set_thread_state(_thread_in_Java);
2462 
2463   if (thread->do_critical_native_unlock()) {
2464     ThreadInVMfromJavaNoAsyncException tiv(thread);
2465     GCLocker::unlock_critical(thread);
2466     thread->clear_critical_native_unlock();
2467   }
2468 }
2469 
2470 // We need to guarantee the Threads_lock here, since resumes are not
2471 // allowed during safepoint synchronization
2472 // Can only resume from an external suspension
2473 void JavaThread::java_resume() {
2474   assert_locked_or_safepoint(Threads_lock);
2475 
2476   // Sanity check: thread is gone, has started exiting or the thread
2477   // was not externally suspended.
2478   if (!Threads::includes(this) || is_exiting() || !is_external_suspend()) {
2479     return;
2480   }
2481 
2482   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2483 
2484   clear_external_suspend();
2485 
2486   if (is_ext_suspended()) {
2487     clear_ext_suspended();
2488     SR_lock()->notify_all();
2489   }
2490 }
2491 
2492 size_t JavaThread::_stack_red_zone_size = 0;
2493 size_t JavaThread::_stack_yellow_zone_size = 0;
2494 size_t JavaThread::_stack_reserved_zone_size = 0;
2495 size_t JavaThread::_stack_shadow_zone_size = 0;
2496 
2497 void JavaThread::create_stack_guard_pages() {
2498   if (!os::uses_stack_guard_pages() || _stack_guard_state != stack_guard_unused) { return; }
2499   address low_addr = stack_end();
2500   size_t len = stack_guard_zone_size();
2501 
2502   int must_commit = os::must_commit_stack_guard_pages();
2503   // warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);
2504 
2505   if (must_commit && !os::create_stack_guard_pages((char *) low_addr, len)) {
2506     log_warning(os, thread)("Attempt to allocate stack guard pages failed.");
2507     return;
2508   }
2509 
2510   if (os::guard_memory((char *) low_addr, len)) {
2511     _stack_guard_state = stack_guard_enabled;
2512   } else {
2513     log_warning(os, thread)("Attempt to protect stack guard pages failed ("
2514       PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2515     if (os::uncommit_memory((char *) low_addr, len)) {
2516       log_warning(os, thread)("Attempt to deallocate stack guard pages failed.");
2517     }
2518     return;
2519   }
2520 
2521   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages activated: "
2522     PTR_FORMAT "-" PTR_FORMAT ".",
2523     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2524 }
2525 
2526 void JavaThread::remove_stack_guard_pages() {
2527   assert(Thread::current() == this, "from different thread");
2528   if (_stack_guard_state == stack_guard_unused) return;
2529   address low_addr = stack_end();
2530   size_t len = stack_guard_zone_size();
2531 
2532   if (os::must_commit_stack_guard_pages()) {
2533     if (os::remove_stack_guard_pages((char *) low_addr, len)) {
2534       _stack_guard_state = stack_guard_unused;
2535     } else {
2536       log_warning(os, thread)("Attempt to deallocate stack guard pages failed ("
2537         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2538       return;
2539     }
2540   } else {
2541     if (_stack_guard_state == stack_guard_unused) return;
2542     if (os::unguard_memory((char *) low_addr, len)) {
2543       _stack_guard_state = stack_guard_unused;
2544     } else {
2545       log_warning(os, thread)("Attempt to unprotect stack guard pages failed ("
2546         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2547       return;
2548     }
2549   }
2550 
2551   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages removed: "
2552     PTR_FORMAT "-" PTR_FORMAT ".",
2553     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2554 }
2555 
2556 void JavaThread::enable_stack_reserved_zone() {
2557   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2558   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2559 
2560   // The base notation is from the stack's point of view, growing downward.
2561   // We need to adjust it to work correctly with guard_memory()
2562   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2563 
2564   guarantee(base < stack_base(),"Error calculating stack reserved zone");
2565   guarantee(base < os::current_stack_pointer(),"Error calculating stack reserved zone");
2566 
2567   if (os::guard_memory((char *) base, stack_reserved_zone_size())) {
2568     _stack_guard_state = stack_guard_enabled;
2569   } else {
2570     warning("Attempt to guard stack reserved zone failed.");
2571   }
2572   enable_register_stack_guard();
2573 }
2574 
2575 void JavaThread::disable_stack_reserved_zone() {
2576   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2577   assert(_stack_guard_state != stack_guard_reserved_disabled, "already disabled");
2578 
2579   // Simply return if called for a thread that does not use guard pages.
2580   if (_stack_guard_state == stack_guard_unused) return;
2581 
2582   // The base notation is from the stack's point of view, growing downward.
2583   // We need to adjust it to work correctly with guard_memory()
2584   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2585 
2586   if (os::unguard_memory((char *)base, stack_reserved_zone_size())) {
2587     _stack_guard_state = stack_guard_reserved_disabled;
2588   } else {
2589     warning("Attempt to unguard stack reserved zone failed.");
2590   }
2591   disable_register_stack_guard();
2592 }
2593 
2594 void JavaThread::enable_stack_yellow_reserved_zone() {
2595   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2596   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2597 
2598   // The base notation is from the stacks point of view, growing downward.
2599   // We need to adjust it to work correctly with guard_memory()
2600   address base = stack_red_zone_base();
2601 
2602   guarantee(base < stack_base(), "Error calculating stack yellow zone");
2603   guarantee(base < os::current_stack_pointer(), "Error calculating stack yellow zone");
2604 
2605   if (os::guard_memory((char *) base, stack_yellow_reserved_zone_size())) {
2606     _stack_guard_state = stack_guard_enabled;
2607   } else {
2608     warning("Attempt to guard stack yellow zone failed.");
2609   }
2610   enable_register_stack_guard();
2611 }
2612 
2613 void JavaThread::disable_stack_yellow_reserved_zone() {
2614   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2615   assert(_stack_guard_state != stack_guard_yellow_reserved_disabled, "already disabled");
2616 
2617   // Simply return if called for a thread that does not use guard pages.
2618   if (_stack_guard_state == stack_guard_unused) return;
2619 
2620   // The base notation is from the stacks point of view, growing downward.
2621   // We need to adjust it to work correctly with guard_memory()
2622   address base = stack_red_zone_base();
2623 
2624   if (os::unguard_memory((char *)base, stack_yellow_reserved_zone_size())) {
2625     _stack_guard_state = stack_guard_yellow_reserved_disabled;
2626   } else {
2627     warning("Attempt to unguard stack yellow zone failed.");
2628   }
2629   disable_register_stack_guard();
2630 }
2631 
2632 void JavaThread::enable_stack_red_zone() {
2633   // The base notation is from the stacks point of view, growing downward.
2634   // We need to adjust it to work correctly with guard_memory()
2635   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2636   address base = stack_red_zone_base() - stack_red_zone_size();
2637 
2638   guarantee(base < stack_base(), "Error calculating stack red zone");
2639   guarantee(base < os::current_stack_pointer(), "Error calculating stack red zone");
2640 
2641   if (!os::guard_memory((char *) base, stack_red_zone_size())) {
2642     warning("Attempt to guard stack red zone failed.");
2643   }
2644 }
2645 
2646 void JavaThread::disable_stack_red_zone() {
2647   // The base notation is from the stacks point of view, growing downward.
2648   // We need to adjust it to work correctly with guard_memory()
2649   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2650   address base = stack_red_zone_base() - stack_red_zone_size();
2651   if (!os::unguard_memory((char *)base, stack_red_zone_size())) {
2652     warning("Attempt to unguard stack red zone failed.");
2653   }
2654 }
2655 
2656 void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
2657   // ignore is there is no stack
2658   if (!has_last_Java_frame()) return;
2659   // traverse the stack frames. Starts from top frame.
2660   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2661     frame* fr = fst.current();
2662     f(fr, fst.register_map());
2663   }
2664 }
2665 
2666 
2667 #ifndef PRODUCT
2668 // Deoptimization
2669 // Function for testing deoptimization
2670 void JavaThread::deoptimize() {
2671   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2672   StackFrameStream fst(this, UseBiasedLocking);
2673   bool deopt = false;           // Dump stack only if a deopt actually happens.
2674   bool only_at = strlen(DeoptimizeOnlyAt) > 0;
2675   // Iterate over all frames in the thread and deoptimize
2676   for (; !fst.is_done(); fst.next()) {
2677     if (fst.current()->can_be_deoptimized()) {
2678 
2679       if (only_at) {
2680         // Deoptimize only at particular bcis.  DeoptimizeOnlyAt
2681         // consists of comma or carriage return separated numbers so
2682         // search for the current bci in that string.
2683         address pc = fst.current()->pc();
2684         nmethod* nm =  (nmethod*) fst.current()->cb();
2685         ScopeDesc* sd = nm->scope_desc_at(pc);
2686         char buffer[8];
2687         jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
2688         size_t len = strlen(buffer);
2689         const char * found = strstr(DeoptimizeOnlyAt, buffer);
2690         while (found != NULL) {
2691           if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
2692               (found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
2693             // Check that the bci found is bracketed by terminators.
2694             break;
2695           }
2696           found = strstr(found + 1, buffer);
2697         }
2698         if (!found) {
2699           continue;
2700         }
2701       }
2702 
2703       if (DebugDeoptimization && !deopt) {
2704         deopt = true; // One-time only print before deopt
2705         tty->print_cr("[BEFORE Deoptimization]");
2706         trace_frames();
2707         trace_stack();
2708       }
2709       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2710     }
2711   }
2712 
2713   if (DebugDeoptimization && deopt) {
2714     tty->print_cr("[AFTER Deoptimization]");
2715     trace_frames();
2716   }
2717 }
2718 
2719 
2720 // Make zombies
2721 void JavaThread::make_zombies() {
2722   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2723     if (fst.current()->can_be_deoptimized()) {
2724       // it is a Java nmethod
2725       nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
2726       nm->make_not_entrant();
2727     }
2728   }
2729 }
2730 #endif // PRODUCT
2731 
2732 
2733 void JavaThread::deoptimized_wrt_marked_nmethods() {
2734   if (!has_last_Java_frame()) return;
2735   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2736   StackFrameStream fst(this, UseBiasedLocking);
2737   for (; !fst.is_done(); fst.next()) {
2738     if (fst.current()->should_be_deoptimized()) {
2739       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2740     }
2741   }
2742 }
2743 
2744 
2745 // If the caller is a NamedThread, then remember, in the current scope,
2746 // the given JavaThread in its _processed_thread field.
2747 class RememberProcessedThread: public StackObj {
2748   NamedThread* _cur_thr;
2749  public:
2750   RememberProcessedThread(JavaThread* jthr) {
2751     Thread* thread = Thread::current();
2752     if (thread->is_Named_thread()) {
2753       _cur_thr = (NamedThread *)thread;
2754       _cur_thr->set_processed_thread(jthr);
2755     } else {
2756       _cur_thr = NULL;
2757     }
2758   }
2759 
2760   ~RememberProcessedThread() {
2761     if (_cur_thr) {
2762       _cur_thr->set_processed_thread(NULL);
2763     }
2764   }
2765 };
2766 
2767 void JavaThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
2768   // Verify that the deferred card marks have been flushed.
2769   assert(deferred_card_mark().is_empty(), "Should be empty during GC");
2770 
2771   // The ThreadProfiler oops_do is done from FlatProfiler::oops_do
2772   // since there may be more than one thread using each ThreadProfiler.
2773 
2774   // Traverse the GCHandles
2775   Thread::oops_do(f, cf);
2776 
2777   JVMCI_ONLY(f->do_oop((oop*)&_pending_failed_speculation);)
2778 
2779   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2780          (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2781 
2782   if (has_last_Java_frame()) {
2783     // Record JavaThread to GC thread
2784     RememberProcessedThread rpt(this);
2785 
2786     // Traverse the privileged stack
2787     if (_privileged_stack_top != NULL) {
2788       _privileged_stack_top->oops_do(f);
2789     }
2790 
2791     // traverse the registered growable array
2792     if (_array_for_gc != NULL) {
2793       for (int index = 0; index < _array_for_gc->length(); index++) {
2794         f->do_oop(_array_for_gc->adr_at(index));
2795       }
2796     }
2797 
2798     // Traverse the monitor chunks
2799     for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2800       chunk->oops_do(f);
2801     }
2802 
2803     // Traverse the execution stack
2804     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2805       fst.current()->oops_do(f, cf, fst.register_map());
2806     }
2807   }
2808 
2809   // callee_target is never live across a gc point so NULL it here should
2810   // it still contain a methdOop.
2811 
2812   set_callee_target(NULL);
2813 
2814   assert(vframe_array_head() == NULL, "deopt in progress at a safepoint!");
2815   // If we have deferred set_locals there might be oops waiting to be
2816   // written
2817   GrowableArray<jvmtiDeferredLocalVariableSet*>* list = deferred_locals();
2818   if (list != NULL) {
2819     for (int i = 0; i < list->length(); i++) {
2820       list->at(i)->oops_do(f);
2821     }
2822   }
2823 
2824   // Traverse instance variables at the end since the GC may be moving things
2825   // around using this function
2826   f->do_oop((oop*) &_threadObj);
2827   f->do_oop((oop*) &_vm_result);
2828   f->do_oop((oop*) &_exception_oop);
2829   f->do_oop((oop*) &_pending_async_exception);
2830 
2831   if (jvmti_thread_state() != NULL) {
2832     jvmti_thread_state()->oops_do(f);
2833   }
2834 }
2835 
2836 void JavaThread::nmethods_do(CodeBlobClosure* cf) {
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_raw("\"");
2896   st->print_raw(get_thread_name());
2897   st->print_raw("\" ");
2898   oop thread_oop = threadObj();
2899   if (thread_oop != NULL) {
2900     st->print("#" INT64_FORMAT " ", java_lang_Thread::thread_id(thread_oop));
2901     if (java_lang_Thread::is_daemon(thread_oop))  st->print("daemon ");
2902     st->print("prio=%d ", java_lang_Thread::priority(thread_oop));
2903   }
2904   Thread::print_on(st);
2905   // print guess for valid stack memory region (assume 4K pages); helps lock debugging
2906   st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
2907   if (thread_oop != NULL) {
2908     st->print_cr("   java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
2909   }
2910 #ifndef PRODUCT
2911   print_thread_state_on(st);
2912   _safepoint_state->print_on(st);
2913 #endif // PRODUCT
2914   if (is_Compiler_thread()) {
2915     CompilerThread* ct = (CompilerThread*)this;
2916     if (ct->task() != NULL) {
2917       st->print("   Compiling: ");
2918       ct->task()->print(st, NULL, true, false);
2919     } else {
2920       st->print("   No compile task");
2921     }
2922     st->cr();
2923   }
2924 }
2925 
2926 void JavaThread::print_name_on_error(outputStream* st, char *buf, int buflen) const {
2927   st->print("%s", get_thread_name_string(buf, buflen));
2928 }
2929 
2930 // Called by fatal error handler. The difference between this and
2931 // JavaThread::print() is that we can't grab lock or allocate memory.
2932 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
2933   st->print("JavaThread \"%s\"", get_thread_name_string(buf, buflen));
2934   oop thread_obj = threadObj();
2935   if (thread_obj != NULL) {
2936     if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
2937   }
2938   st->print(" [");
2939   st->print("%s", _get_thread_state_name(_thread_state));
2940   if (osthread()) {
2941     st->print(", id=%d", osthread()->thread_id());
2942   }
2943   st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
2944             p2i(stack_end()), p2i(stack_base()));
2945   st->print("]");
2946   return;
2947 }
2948 
2949 // Verification
2950 
2951 static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
2952 
2953 void JavaThread::verify() {
2954   // Verify oops in the thread.
2955   oops_do(&VerifyOopClosure::verify_oop, NULL);
2956 
2957   // Verify the stack frames.
2958   frames_do(frame_verify);
2959 }
2960 
2961 // CR 6300358 (sub-CR 2137150)
2962 // Most callers of this method assume that it can't return NULL but a
2963 // thread may not have a name whilst it is in the process of attaching to
2964 // the VM - see CR 6412693, and there are places where a JavaThread can be
2965 // seen prior to having it's threadObj set (eg JNI attaching threads and
2966 // if vm exit occurs during initialization). These cases can all be accounted
2967 // for such that this method never returns NULL.
2968 const char* JavaThread::get_thread_name() const {
2969 #ifdef ASSERT
2970   // early safepoints can hit while current thread does not yet have TLS
2971   if (!SafepointSynchronize::is_at_safepoint()) {
2972     Thread *cur = Thread::current();
2973     if (!(cur->is_Java_thread() && cur == this)) {
2974       // Current JavaThreads are allowed to get their own name without
2975       // the Threads_lock.
2976       assert_locked_or_safepoint(Threads_lock);
2977     }
2978   }
2979 #endif // ASSERT
2980   return get_thread_name_string();
2981 }
2982 
2983 // Returns a non-NULL representation of this thread's name, or a suitable
2984 // descriptive string if there is no set name
2985 const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
2986   const char* name_str;
2987   oop thread_obj = threadObj();
2988   if (thread_obj != NULL) {
2989     oop name = java_lang_Thread::name(thread_obj);
2990     if (name != NULL) {
2991       if (buf == NULL) {
2992         name_str = java_lang_String::as_utf8_string(name);
2993       } else {
2994         name_str = java_lang_String::as_utf8_string(name, buf, buflen);
2995       }
2996     } else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
2997       name_str = "<no-name - thread is attaching>";
2998     } else {
2999       name_str = Thread::name();
3000     }
3001   } else {
3002     name_str = Thread::name();
3003   }
3004   assert(name_str != NULL, "unexpected NULL thread name");
3005   return name_str;
3006 }
3007 
3008 
3009 const char* JavaThread::get_threadgroup_name() const {
3010   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3011   oop thread_obj = threadObj();
3012   if (thread_obj != NULL) {
3013     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3014     if (thread_group != NULL) {
3015       // ThreadGroup.name can be null
3016       return java_lang_ThreadGroup::name(thread_group);
3017     }
3018   }
3019   return NULL;
3020 }
3021 
3022 const char* JavaThread::get_parent_name() const {
3023   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3024   oop thread_obj = threadObj();
3025   if (thread_obj != NULL) {
3026     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3027     if (thread_group != NULL) {
3028       oop parent = java_lang_ThreadGroup::parent(thread_group);
3029       if (parent != NULL) {
3030         // ThreadGroup.name can be null
3031         return java_lang_ThreadGroup::name(parent);
3032       }
3033     }
3034   }
3035   return NULL;
3036 }
3037 
3038 ThreadPriority JavaThread::java_priority() const {
3039   oop thr_oop = threadObj();
3040   if (thr_oop == NULL) return NormPriority; // Bootstrapping
3041   ThreadPriority priority = java_lang_Thread::priority(thr_oop);
3042   assert(MinPriority <= priority && priority <= MaxPriority, "sanity check");
3043   return priority;
3044 }
3045 
3046 void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
3047 
3048   assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
3049   // Link Java Thread object <-> C++ Thread
3050 
3051   // Get the C++ thread object (an oop) from the JNI handle (a jthread)
3052   // and put it into a new Handle.  The Handle "thread_oop" can then
3053   // be used to pass the C++ thread object to other methods.
3054 
3055   // Set the Java level thread object (jthread) field of the
3056   // new thread (a JavaThread *) to C++ thread object using the
3057   // "thread_oop" handle.
3058 
3059   // Set the thread field (a JavaThread *) of the
3060   // oop representing the java_lang_Thread to the new thread (a JavaThread *).
3061 
3062   Handle thread_oop(Thread::current(),
3063                     JNIHandles::resolve_non_null(jni_thread));
3064   assert(InstanceKlass::cast(thread_oop->klass())->is_linked(),
3065          "must be initialized");
3066   set_threadObj(thread_oop());
3067   java_lang_Thread::set_thread(thread_oop(), this);
3068 
3069   if (prio == NoPriority) {
3070     prio = java_lang_Thread::priority(thread_oop());
3071     assert(prio != NoPriority, "A valid priority should be present");
3072   }
3073 
3074   // Push the Java priority down to the native thread; needs Threads_lock
3075   Thread::set_priority(this, prio);
3076 
3077   prepare_ext();
3078 
3079   // Add the new thread to the Threads list and set it in motion.
3080   // We must have threads lock in order to call Threads::add.
3081   // It is crucial that we do not block before the thread is
3082   // added to the Threads list for if a GC happens, then the java_thread oop
3083   // will not be visited by GC.
3084   Threads::add(this);
3085 }
3086 
3087 oop JavaThread::current_park_blocker() {
3088   // Support for JSR-166 locks
3089   oop thread_oop = threadObj();
3090   if (thread_oop != NULL &&
3091       JDK_Version::current().supports_thread_park_blocker()) {
3092     return java_lang_Thread::park_blocker(thread_oop);
3093   }
3094   return NULL;
3095 }
3096 
3097 
3098 void JavaThread::print_stack_on(outputStream* st) {
3099   if (!has_last_Java_frame()) return;
3100   ResourceMark rm;
3101   HandleMark   hm;
3102 
3103   RegisterMap reg_map(this);
3104   vframe* start_vf = last_java_vframe(&reg_map);
3105   int count = 0;
3106   for (vframe* f = start_vf; f; f = f->sender()) {
3107     if (f->is_java_frame()) {
3108       javaVFrame* jvf = javaVFrame::cast(f);
3109       java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
3110 
3111       // Print out lock information
3112       if (JavaMonitorsInStackTrace) {
3113         jvf->print_lock_info_on(st, count);
3114       }
3115     } else {
3116       // Ignore non-Java frames
3117     }
3118 
3119     // Bail-out case for too deep stacks
3120     count++;
3121     if (MaxJavaStackTraceDepth == count) return;
3122   }
3123 }
3124 
3125 
3126 // JVMTI PopFrame support
3127 void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
3128   assert(_popframe_preserved_args == NULL, "should not wipe out old PopFrame preserved arguments");
3129   if (in_bytes(size_in_bytes) != 0) {
3130     _popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes), mtThread);
3131     _popframe_preserved_args_size = in_bytes(size_in_bytes);
3132     Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
3133   }
3134 }
3135 
3136 void* JavaThread::popframe_preserved_args() {
3137   return _popframe_preserved_args;
3138 }
3139 
3140 ByteSize JavaThread::popframe_preserved_args_size() {
3141   return in_ByteSize(_popframe_preserved_args_size);
3142 }
3143 
3144 WordSize JavaThread::popframe_preserved_args_size_in_words() {
3145   int sz = in_bytes(popframe_preserved_args_size());
3146   assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
3147   return in_WordSize(sz / wordSize);
3148 }
3149 
3150 void JavaThread::popframe_free_preserved_args() {
3151   assert(_popframe_preserved_args != NULL, "should not free PopFrame preserved arguments twice");
3152   FREE_C_HEAP_ARRAY(char, (char*) _popframe_preserved_args);
3153   _popframe_preserved_args = NULL;
3154   _popframe_preserved_args_size = 0;
3155 }
3156 
3157 #ifndef PRODUCT
3158 
3159 void JavaThread::trace_frames() {
3160   tty->print_cr("[Describe stack]");
3161   int frame_no = 1;
3162   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
3163     tty->print("  %d. ", frame_no++);
3164     fst.current()->print_value_on(tty, this);
3165     tty->cr();
3166   }
3167 }
3168 
3169 class PrintAndVerifyOopClosure: public OopClosure {
3170  protected:
3171   template <class T> inline void do_oop_work(T* p) {
3172     oop obj = oopDesc::load_decode_heap_oop(p);
3173     if (obj == NULL) return;
3174     tty->print(INTPTR_FORMAT ": ", p2i(p));
3175     if (obj->is_oop_or_null()) {
3176       if (obj->is_objArray()) {
3177         tty->print_cr("valid objArray: " INTPTR_FORMAT, p2i(obj));
3178       } else {
3179         obj->print();
3180       }
3181     } else {
3182       tty->print_cr("invalid oop: " INTPTR_FORMAT, p2i(obj));
3183     }
3184     tty->cr();
3185   }
3186  public:
3187   virtual void do_oop(oop* p) { do_oop_work(p); }
3188   virtual void do_oop(narrowOop* p)  { do_oop_work(p); }
3189 };
3190 
3191 
3192 static void oops_print(frame* f, const RegisterMap *map) {
3193   PrintAndVerifyOopClosure print;
3194   f->print_value();
3195   f->oops_do(&print, NULL, (RegisterMap*)map);
3196 }
3197 
3198 // Print our all the locations that contain oops and whether they are
3199 // valid or not.  This useful when trying to find the oldest frame
3200 // where an oop has gone bad since the frame walk is from youngest to
3201 // oldest.
3202 void JavaThread::trace_oops() {
3203   tty->print_cr("[Trace oops]");
3204   frames_do(oops_print);
3205 }
3206 
3207 
3208 #ifdef ASSERT
3209 // Print or validate the layout of stack frames
3210 void JavaThread::print_frame_layout(int depth, bool validate_only) {
3211   ResourceMark rm;
3212   PRESERVE_EXCEPTION_MARK;
3213   FrameValues values;
3214   int frame_no = 0;
3215   for (StackFrameStream fst(this, false); !fst.is_done(); fst.next()) {
3216     fst.current()->describe(values, ++frame_no);
3217     if (depth == frame_no) break;
3218   }
3219   if (validate_only) {
3220     values.validate();
3221   } else {
3222     tty->print_cr("[Describe stack layout]");
3223     values.print(this);
3224   }
3225 }
3226 #endif
3227 
3228 void JavaThread::trace_stack_from(vframe* start_vf) {
3229   ResourceMark rm;
3230   int vframe_no = 1;
3231   for (vframe* f = start_vf; f; f = f->sender()) {
3232     if (f->is_java_frame()) {
3233       javaVFrame::cast(f)->print_activation(vframe_no++);
3234     } else {
3235       f->print();
3236     }
3237     if (vframe_no > StackPrintLimit) {
3238       tty->print_cr("...<more frames>...");
3239       return;
3240     }
3241   }
3242 }
3243 
3244 
3245 void JavaThread::trace_stack() {
3246   if (!has_last_Java_frame()) return;
3247   ResourceMark rm;
3248   HandleMark   hm;
3249   RegisterMap reg_map(this);
3250   trace_stack_from(last_java_vframe(&reg_map));
3251 }
3252 
3253 
3254 #endif // PRODUCT
3255 
3256 
3257 javaVFrame* JavaThread::last_java_vframe(RegisterMap *reg_map) {
3258   assert(reg_map != NULL, "a map must be given");
3259   frame f = last_frame();
3260   for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender()) {
3261     if (vf->is_java_frame()) return javaVFrame::cast(vf);
3262   }
3263   return NULL;
3264 }
3265 
3266 
3267 Klass* JavaThread::security_get_caller_class(int depth) {
3268   vframeStream vfst(this);
3269   vfst.security_get_caller_frame(depth);
3270   if (!vfst.at_end()) {
3271     return vfst.method()->method_holder();
3272   }
3273   return NULL;
3274 }
3275 
3276 static void compiler_thread_entry(JavaThread* thread, TRAPS) {
3277   assert(thread->is_Compiler_thread(), "must be compiler thread");
3278   CompileBroker::compiler_thread_loop();
3279 }
3280 
3281 static void sweeper_thread_entry(JavaThread* thread, TRAPS) {
3282   NMethodSweeper::sweeper_loop();
3283 }
3284 
3285 // Create a CompilerThread
3286 CompilerThread::CompilerThread(CompileQueue* queue,
3287                                CompilerCounters* counters)
3288                                : JavaThread(&compiler_thread_entry) {
3289   _env   = NULL;
3290   _log   = NULL;
3291   _task  = NULL;
3292   _queue = queue;
3293   _counters = counters;
3294   _buffer_blob = NULL;
3295   _compiler = NULL;
3296 
3297 #ifndef PRODUCT
3298   _ideal_graph_printer = NULL;
3299 #endif
3300 }
3301 
3302 bool CompilerThread::can_call_java() const {
3303   return _compiler != NULL && _compiler->is_jvmci();
3304 }
3305 
3306 // Create sweeper thread
3307 CodeCacheSweeperThread::CodeCacheSweeperThread()
3308 : JavaThread(&sweeper_thread_entry) {
3309   _scanned_compiled_method = NULL;
3310 }
3311 
3312 void CodeCacheSweeperThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
3313   JavaThread::oops_do(f, cf);
3314   if (_scanned_compiled_method != NULL && cf != NULL) {
3315     // Safepoints can occur when the sweeper is scanning an nmethod so
3316     // process it here to make sure it isn't unloaded in the middle of
3317     // a scan.
3318     cf->do_code_blob(_scanned_compiled_method);
3319   }
3320 }
3321 
3322 void CodeCacheSweeperThread::nmethods_do(CodeBlobClosure* cf) {
3323   JavaThread::nmethods_do(cf);
3324   if (_scanned_compiled_method != NULL && cf != NULL) {
3325     // Safepoints can occur when the sweeper is scanning an nmethod so
3326     // process it here to make sure it isn't unloaded in the middle of
3327     // a scan.
3328     cf->do_code_blob(_scanned_compiled_method);
3329   }
3330 }
3331 
3332 
3333 // ======= Threads ========
3334 
3335 // The Threads class links together all active threads, and provides
3336 // operations over all threads.  It is protected by its own Mutex
3337 // lock, which is also used in other contexts to protect thread
3338 // operations from having the thread being operated on from exiting
3339 // and going away unexpectedly (e.g., safepoint synchronization)
3340 
3341 JavaThread* Threads::_thread_list = NULL;
3342 int         Threads::_number_of_threads = 0;
3343 int         Threads::_number_of_non_daemon_threads = 0;
3344 int         Threads::_return_code = 0;
3345 int         Threads::_thread_claim_parity = 0;
3346 size_t      JavaThread::_stack_size_at_create = 0;
3347 #ifdef ASSERT
3348 bool        Threads::_vm_complete = false;
3349 #endif
3350 
3351 // All JavaThreads
3352 #define ALL_JAVA_THREADS(X) for (JavaThread* X = _thread_list; X; X = X->next())
3353 
3354 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system)
3355 void Threads::threads_do(ThreadClosure* tc) {
3356   assert_locked_or_safepoint(Threads_lock);
3357   // ALL_JAVA_THREADS iterates through all JavaThreads
3358   ALL_JAVA_THREADS(p) {
3359     tc->do_thread(p);
3360   }
3361   // Someday we could have a table or list of all non-JavaThreads.
3362   // For now, just manually iterate through them.
3363   tc->do_thread(VMThread::vm_thread());
3364   Universe::heap()->gc_threads_do(tc);
3365   WatcherThread *wt = WatcherThread::watcher_thread();
3366   // Strictly speaking, the following NULL check isn't sufficient to make sure
3367   // the data for WatcherThread is still valid upon being examined. However,
3368   // considering that WatchThread terminates when the VM is on the way to
3369   // exit at safepoint, the chance of the above is extremely small. The right
3370   // way to prevent termination of WatcherThread would be to acquire
3371   // Terminator_lock, but we can't do that without violating the lock rank
3372   // checking in some cases.
3373   if (wt != NULL) {
3374     tc->do_thread(wt);
3375   }
3376 
3377   // If CompilerThreads ever become non-JavaThreads, add them here
3378 }
3379 
3380 void Threads::parallel_java_threads_do(ThreadClosure* tc) {
3381   int cp = Threads::thread_claim_parity();
3382   ALL_JAVA_THREADS(p) {
3383     if (p->claim_oops_do(true, cp)) {
3384       tc->do_thread(p);
3385     }
3386   }
3387 }
3388 
3389 // The system initialization in the library has three phases.
3390 //
3391 // Phase 1: java.lang.System class initialization
3392 //     java.lang.System is a primordial class loaded and initialized
3393 //     by the VM early during startup.  java.lang.System.<clinit>
3394 //     only does registerNatives and keeps the rest of the class
3395 //     initialization work later until thread initialization completes.
3396 //
3397 //     System.initPhase1 initializes the system properties, the static
3398 //     fields in, out, and err. Set up java signal handlers, OS-specific
3399 //     system settings, and thread group of the main thread.
3400 static void call_initPhase1(TRAPS) {
3401   Klass* klass =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3402   JavaValue result(T_VOID);
3403   JavaCalls::call_static(&result, klass, vmSymbols::initPhase1_name(),
3404                                          vmSymbols::void_method_signature(), CHECK);
3405 }
3406 
3407 // Phase 2. Module system initialization
3408 //     This will initialize the module system.  Only java.base classes
3409 //     can be loaded until phase 2 completes.
3410 //
3411 //     Call System.initPhase2 after the compiler initialization and jsr292
3412 //     classes get initialized because module initialization runs a lot of java
3413 //     code, that for performance reasons, should be compiled.  Also, this will
3414 //     enable the startup code to use lambda and other language features in this
3415 //     phase and onward.
3416 //
3417 //     After phase 2, The VM will begin search classes from -Xbootclasspath/a.
3418 static void call_initPhase2(TRAPS) {
3419   TraceTime timer("Phase2 initialization", TRACETIME_LOG(Info, module, startuptime));
3420 
3421   Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3422 
3423   JavaValue result(T_INT);
3424   JavaCallArguments args;
3425   args.push_int(DisplayVMOutputToStderr);
3426   args.push_int(log_is_enabled(Debug, init)); // print stack trace if exception thrown
3427   JavaCalls::call_static(&result, klass, vmSymbols::initPhase2_name(),
3428                                          vmSymbols::boolean_boolean_int_signature(), &args, CHECK);
3429   if (result.get_jint() != JNI_OK) {
3430     vm_exit_during_initialization(); // no message or exception
3431   }
3432 
3433   universe_post_module_init();
3434 }
3435 
3436 // Phase 3. final setup - set security manager, system class loader and TCCL
3437 //
3438 //     This will instantiate and set the security manager, set the system class
3439 //     loader as well as the thread context class loader.  The security manager
3440 //     and system class loader may be a custom class loaded from -Xbootclasspath/a,
3441 //     other modules or the application's classpath.
3442 static void call_initPhase3(TRAPS) {
3443   Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3444   JavaValue result(T_VOID);
3445   JavaCalls::call_static(&result, klass, vmSymbols::initPhase3_name(),
3446                                          vmSymbols::void_method_signature(), CHECK);
3447 }
3448 
3449 void Threads::initialize_java_lang_classes(JavaThread* main_thread, TRAPS) {
3450   TraceTime timer("Initialize java.lang classes", TRACETIME_LOG(Info, startuptime));
3451 
3452   if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
3453     create_vm_init_libraries();
3454   }
3455 
3456   initialize_class(vmSymbols::java_lang_String(), CHECK);
3457 
3458   // Inject CompactStrings value after the static initializers for String ran.
3459   java_lang_String::set_compact_strings(CompactStrings);
3460 
3461   // Initialize java_lang.System (needed before creating the thread)
3462   initialize_class(vmSymbols::java_lang_System(), CHECK);
3463   // The VM creates & returns objects of this class. Make sure it's initialized.
3464   initialize_class(vmSymbols::java_lang_Class(), CHECK);
3465   initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK);
3466   Handle thread_group = create_initial_thread_group(CHECK);
3467   Universe::set_main_thread_group(thread_group());
3468   initialize_class(vmSymbols::java_lang_Thread(), CHECK);
3469   oop thread_object = create_initial_thread(thread_group, main_thread, CHECK);
3470   main_thread->set_threadObj(thread_object);
3471   // Set thread status to running since main thread has
3472   // been started and running.
3473   java_lang_Thread::set_thread_status(thread_object,
3474                                       java_lang_Thread::RUNNABLE);
3475 
3476   // The VM creates objects of this class.
3477   initialize_class(vmSymbols::java_lang_Module(), CHECK);
3478 
3479   // The VM preresolves methods to these classes. Make sure that they get initialized
3480   initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK);
3481   initialize_class(vmSymbols::java_lang_ref_Finalizer(), CHECK);
3482 
3483   // Phase 1 of the system initialization in the library, java.lang.System class initialization
3484   call_initPhase1(CHECK);
3485 
3486   // get the Java runtime name after java.lang.System is initialized
3487   JDK_Version::set_runtime_name(get_java_runtime_name(THREAD));
3488   JDK_Version::set_runtime_version(get_java_runtime_version(THREAD));
3489 
3490   // an instance of OutOfMemory exception has been allocated earlier
3491   initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK);
3492   initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK);
3493   initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK);
3494   initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK);
3495   initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK);
3496   initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK);
3497   initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK);
3498   initialize_class(vmSymbols::java_lang_IllegalArgumentException(), CHECK);
3499 }
3500 
3501 void Threads::initialize_jsr292_core_classes(TRAPS) {
3502   TraceTime timer("Initialize java.lang.invoke classes", TRACETIME_LOG(Info, startuptime));
3503 
3504   initialize_class(vmSymbols::java_lang_invoke_MethodHandle(), CHECK);
3505   initialize_class(vmSymbols::java_lang_invoke_ResolvedMethodName(), CHECK);
3506   initialize_class(vmSymbols::java_lang_invoke_MemberName(), CHECK);
3507   initialize_class(vmSymbols::java_lang_invoke_MethodHandleNatives(), CHECK);
3508 }
3509 
3510 jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
3511   extern void JDK_Version_init();
3512 
3513   // Preinitialize version info.
3514   VM_Version::early_initialize();
3515 
3516   // Check version
3517   if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
3518 
3519   // Initialize library-based TLS
3520   ThreadLocalStorage::init();
3521 
3522   // Initialize the output stream module
3523   ostream_init();
3524 
3525   // Process java launcher properties.
3526   Arguments::process_sun_java_launcher_properties(args);
3527 
3528   // Initialize the os module
3529   os::init();
3530 
3531   // Record VM creation timing statistics
3532   TraceVmCreationTime create_vm_timer;
3533   create_vm_timer.start();
3534 
3535   // Initialize system properties.
3536   Arguments::init_system_properties();
3537 
3538   // So that JDK version can be used as a discriminator when parsing arguments
3539   JDK_Version_init();
3540 
3541   // Update/Initialize System properties after JDK version number is known
3542   Arguments::init_version_specific_system_properties();
3543 
3544   // Make sure to initialize log configuration *before* parsing arguments
3545   LogConfiguration::initialize(create_vm_timer.begin_time());
3546 
3547   // Parse arguments
3548   jint parse_result = Arguments::parse(args);
3549   if (parse_result != JNI_OK) return parse_result;
3550 
3551   os::init_before_ergo();
3552 
3553   jint ergo_result = Arguments::apply_ergo();
3554   if (ergo_result != JNI_OK) return ergo_result;
3555 
3556   // Final check of all ranges after ergonomics which may change values.
3557   if (!CommandLineFlagRangeList::check_ranges()) {
3558     return JNI_EINVAL;
3559   }
3560 
3561   // Final check of all 'AfterErgo' constraints after ergonomics which may change values.
3562   bool constraint_result = CommandLineFlagConstraintList::check_constraints(CommandLineFlagConstraint::AfterErgo);
3563   if (!constraint_result) {
3564     return JNI_EINVAL;
3565   }
3566 
3567   CommandLineFlagWriteableList::mark_startup();
3568 
3569   if (PauseAtStartup) {
3570     os::pause();
3571   }
3572 
3573   HOTSPOT_VM_INIT_BEGIN();
3574 
3575   // Timing (must come after argument parsing)
3576   TraceTime timer("Create VM", TRACETIME_LOG(Info, startuptime));
3577 
3578   // Initialize the os module after parsing the args
3579   jint os_init_2_result = os::init_2();
3580   if (os_init_2_result != JNI_OK) return os_init_2_result;
3581 
3582   jint adjust_after_os_result = Arguments::adjust_after_os();
3583   if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;
3584 
3585   // Initialize output stream logging
3586   ostream_init_log();
3587 
3588   // Convert -Xrun to -agentlib: if there is no JVM_OnLoad
3589   // Must be before create_vm_init_agents()
3590   if (Arguments::init_libraries_at_startup()) {
3591     convert_vm_init_libraries_to_agents();
3592   }
3593 
3594   // Launch -agentlib/-agentpath and converted -Xrun agents
3595   if (Arguments::init_agents_at_startup()) {
3596     create_vm_init_agents();
3597   }
3598 
3599   // Initialize Threads state
3600   _thread_list = NULL;
3601   _number_of_threads = 0;
3602   _number_of_non_daemon_threads = 0;
3603 
3604   // Initialize global data structures and create system classes in heap
3605   vm_init_globals();
3606 
3607 #if INCLUDE_JVMCI
3608   if (JVMCICounterSize > 0) {
3609     JavaThread::_jvmci_old_thread_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
3610     memset(JavaThread::_jvmci_old_thread_counters, 0, sizeof(jlong) * JVMCICounterSize);
3611   } else {
3612     JavaThread::_jvmci_old_thread_counters = NULL;
3613   }
3614 #endif // INCLUDE_JVMCI
3615 
3616   // Attach the main thread to this os thread
3617   JavaThread* main_thread = new JavaThread();
3618   main_thread->set_thread_state(_thread_in_vm);
3619   main_thread->initialize_thread_current();
3620   // must do this before set_active_handles
3621   main_thread->record_stack_base_and_size();
3622   main_thread->set_active_handles(JNIHandleBlock::allocate_block());
3623 
3624   if (!main_thread->set_as_starting_thread()) {
3625     vm_shutdown_during_initialization(
3626                                       "Failed necessary internal allocation. Out of swap space");
3627     delete main_thread;
3628     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3629     return JNI_ENOMEM;
3630   }
3631 
3632   // Enable guard page *after* os::create_main_thread(), otherwise it would
3633   // crash Linux VM, see notes in os_linux.cpp.
3634   main_thread->create_stack_guard_pages();
3635 
3636   // Initialize Java-Level synchronization subsystem
3637   ObjectMonitor::Initialize();
3638 
3639   // Initialize global modules
3640   jint status = init_globals();
3641   if (status != JNI_OK) {
3642     delete main_thread;
3643     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3644     return status;
3645   }
3646 
3647   if (TRACE_INITIALIZE() != JNI_OK) {
3648     vm_exit_during_initialization("Failed to initialize tracing backend");
3649   }
3650 
3651   // Should be done after the heap is fully created
3652   main_thread->cache_global_variables();
3653 
3654   HandleMark hm;
3655 
3656   { MutexLocker mu(Threads_lock);
3657     Threads::add(main_thread);
3658   }
3659 
3660   // Any JVMTI raw monitors entered in onload will transition into
3661   // real raw monitor. VM is setup enough here for raw monitor enter.
3662   JvmtiExport::transition_pending_onload_raw_monitors();
3663 
3664   // Create the VMThread
3665   { TraceTime timer("Start VMThread", TRACETIME_LOG(Info, startuptime));
3666 
3667   VMThread::create();
3668     Thread* vmthread = VMThread::vm_thread();
3669 
3670     if (!os::create_thread(vmthread, os::vm_thread)) {
3671       vm_exit_during_initialization("Cannot create VM thread. "
3672                                     "Out of system resources.");
3673     }
3674 
3675     // Wait for the VM thread to become ready, and VMThread::run to initialize
3676     // Monitors can have spurious returns, must always check another state flag
3677     {
3678       MutexLocker ml(Notify_lock);
3679       os::start_thread(vmthread);
3680       while (vmthread->active_handles() == NULL) {
3681         Notify_lock->wait();
3682       }
3683     }
3684   }
3685 
3686   assert(Universe::is_fully_initialized(), "not initialized");
3687   if (VerifyDuringStartup) {
3688     // Make sure we're starting with a clean slate.
3689     VM_Verify verify_op;
3690     VMThread::execute(&verify_op);
3691   }
3692 
3693   Thread* THREAD = Thread::current();
3694 
3695   // At this point, the Universe is initialized, but we have not executed
3696   // any byte code.  Now is a good time (the only time) to dump out the
3697   // internal state of the JVM for sharing.
3698   if (DumpSharedSpaces) {
3699     MetaspaceShared::preload_and_dump(CHECK_JNI_ERR);
3700     ShouldNotReachHere();
3701   }
3702 
3703   // Always call even when there are not JVMTI environments yet, since environments
3704   // may be attached late and JVMTI must track phases of VM execution
3705   JvmtiExport::enter_early_start_phase();
3706 
3707   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
3708   JvmtiExport::post_early_vm_start();
3709 
3710   initialize_java_lang_classes(main_thread, CHECK_JNI_ERR);
3711 
3712   // We need this for ClassDataSharing - the initial vm.info property is set
3713   // with the default value of CDS "sharing" which may be reset through
3714   // command line options.
3715   reset_vm_info_property(CHECK_JNI_ERR);
3716 
3717   quicken_jni_functions();
3718 
3719   // No more stub generation allowed after that point.
3720   StubCodeDesc::freeze();
3721 
3722   // Set flag that basic initialization has completed. Used by exceptions and various
3723   // debug stuff, that does not work until all basic classes have been initialized.
3724   set_init_completed();
3725 
3726   LogConfiguration::post_initialize();
3727   Metaspace::post_initialize();
3728 
3729   HOTSPOT_VM_INIT_END();
3730 
3731   // record VM initialization completion time
3732 #if INCLUDE_MANAGEMENT
3733   Management::record_vm_init_completed();
3734 #endif // INCLUDE_MANAGEMENT
3735 
3736   // Signal Dispatcher needs to be started before VMInit event is posted
3737   os::signal_init(CHECK_JNI_ERR);
3738 
3739   // Start Attach Listener if +StartAttachListener or it can't be started lazily
3740   if (!DisableAttachMechanism) {
3741     AttachListener::vm_start();
3742     if (StartAttachListener || AttachListener::init_at_startup()) {
3743       AttachListener::init();
3744     }
3745   }
3746 
3747   // Launch -Xrun agents
3748   // Must be done in the JVMTI live phase so that for backward compatibility the JDWP
3749   // back-end can launch with -Xdebug -Xrunjdwp.
3750   if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
3751     create_vm_init_libraries();
3752   }
3753 
3754   if (CleanChunkPoolAsync) {
3755     Chunk::start_chunk_pool_cleaner_task();
3756   }
3757 
3758   // initialize compiler(s)
3759 #if defined(COMPILER1) || defined(COMPILER2) || defined(SHARK) || INCLUDE_JVMCI
3760   CompileBroker::compilation_init(CHECK_JNI_ERR);
3761 #endif
3762 
3763   // Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
3764   // It is done after compilers are initialized, because otherwise compilations of
3765   // signature polymorphic MH intrinsics can be missed
3766   // (see SystemDictionary::find_method_handle_intrinsic).
3767   initialize_jsr292_core_classes(CHECK_JNI_ERR);
3768 
3769   // This will initialize the module system.  Only java.base classes can be
3770   // loaded until phase 2 completes
3771   call_initPhase2(CHECK_JNI_ERR);
3772 
3773   // Always call even when there are not JVMTI environments yet, since environments
3774   // may be attached late and JVMTI must track phases of VM execution
3775   JvmtiExport::enter_start_phase();
3776 
3777   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
3778   JvmtiExport::post_vm_start();
3779 
3780   // Final system initialization including security manager and system class loader
3781   call_initPhase3(CHECK_JNI_ERR);
3782 
3783   // cache the system class loader
3784   SystemDictionary::compute_java_system_loader(CHECK_(JNI_ERR));
3785 
3786 #if INCLUDE_JVMCI
3787   if (EnableJVMCI) {
3788     // Initialize JVMCI eagerly if JVMCIPrintProperties is enabled.
3789     // The JVMCI Java initialization code will read this flag and
3790     // do the printing if it's set.
3791     bool init = JVMCIPrintProperties;
3792 
3793     if (!init) {
3794       // 8145270: Force initialization of JVMCI runtime otherwise requests for blocking
3795       // compilations via JVMCI will not actually block until JVMCI is initialized.
3796       init = UseJVMCICompiler && (!UseInterpreter || !BackgroundCompilation);
3797     }
3798 
3799     if (init) {
3800       JVMCIRuntime::force_initialization(CHECK_JNI_ERR);
3801     }
3802   }
3803 #endif
3804 
3805   // Always call even when there are not JVMTI environments yet, since environments
3806   // may be attached late and JVMTI must track phases of VM execution
3807   JvmtiExport::enter_live_phase();
3808 
3809   // Notify JVMTI agents that VM initialization is complete - nop if no agents.
3810   JvmtiExport::post_vm_initialized();
3811 
3812   if (TRACE_START() != JNI_OK) {
3813     vm_exit_during_initialization("Failed to start tracing backend.");
3814   }
3815 
3816 #if INCLUDE_MANAGEMENT
3817   Management::initialize(THREAD);
3818 
3819   if (HAS_PENDING_EXCEPTION) {
3820     // management agent fails to start possibly due to
3821     // configuration problem and is responsible for printing
3822     // stack trace if appropriate. Simply exit VM.
3823     vm_exit(1);
3824   }
3825 #endif // INCLUDE_MANAGEMENT
3826 
3827   if (Arguments::has_profile())       FlatProfiler::engage(main_thread, true);
3828   if (MemProfiling)                   MemProfiler::engage();
3829   StatSampler::engage();
3830   if (CheckJNICalls)                  JniPeriodicChecker::engage();
3831 
3832   BiasedLocking::init();
3833 
3834 #if INCLUDE_RTM_OPT
3835   RTMLockingCounters::init();
3836 #endif
3837 
3838   if (JDK_Version::current().post_vm_init_hook_enabled()) {
3839     call_postVMInitHook(THREAD);
3840     // The Java side of PostVMInitHook.run must deal with all
3841     // exceptions and provide means of diagnosis.
3842     if (HAS_PENDING_EXCEPTION) {
3843       CLEAR_PENDING_EXCEPTION;
3844     }
3845   }
3846 
3847   {
3848     MutexLocker ml(PeriodicTask_lock);
3849     // Make sure the WatcherThread can be started by WatcherThread::start()
3850     // or by dynamic enrollment.
3851     WatcherThread::make_startable();
3852     // Start up the WatcherThread if there are any periodic tasks
3853     // NOTE:  All PeriodicTasks should be registered by now. If they
3854     //   aren't, late joiners might appear to start slowly (we might
3855     //   take a while to process their first tick).
3856     if (PeriodicTask::num_tasks() > 0) {
3857       WatcherThread::start();
3858     }
3859   }
3860 
3861   create_vm_timer.end();
3862 #ifdef ASSERT
3863   _vm_complete = true;
3864 #endif
3865   return JNI_OK;
3866 }
3867 
3868 // type for the Agent_OnLoad and JVM_OnLoad entry points
3869 extern "C" {
3870   typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
3871 }
3872 // Find a command line agent library and return its entry point for
3873 //         -agentlib:  -agentpath:   -Xrun
3874 // num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array.
3875 static OnLoadEntry_t lookup_on_load(AgentLibrary* agent,
3876                                     const char *on_load_symbols[],
3877                                     size_t num_symbol_entries) {
3878   OnLoadEntry_t on_load_entry = NULL;
3879   void *library = NULL;
3880 
3881   if (!agent->valid()) {
3882     char buffer[JVM_MAXPATHLEN];
3883     char ebuf[1024] = "";
3884     const char *name = agent->name();
3885     const char *msg = "Could not find agent library ";
3886 
3887     // First check to see if agent is statically linked into executable
3888     if (os::find_builtin_agent(agent, on_load_symbols, num_symbol_entries)) {
3889       library = agent->os_lib();
3890     } else if (agent->is_absolute_path()) {
3891       library = os::dll_load(name, ebuf, sizeof ebuf);
3892       if (library == NULL) {
3893         const char *sub_msg = " in absolute path, with error: ";
3894         size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3895         char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
3896         jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
3897         // If we can't find the agent, exit.
3898         vm_exit_during_initialization(buf, NULL);
3899         FREE_C_HEAP_ARRAY(char, buf);
3900       }
3901     } else {
3902       // Try to load the agent from the standard dll directory
3903       if (os::dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(),
3904                              name)) {
3905         library = os::dll_load(buffer, ebuf, sizeof ebuf);
3906       }
3907       if (library == NULL) { // Try the local directory
3908         char ns[1] = {0};
3909         if (os::dll_build_name(buffer, sizeof(buffer), ns, name)) {
3910           library = os::dll_load(buffer, ebuf, sizeof ebuf);
3911         }
3912         if (library == NULL) {
3913           const char *sub_msg = " on the library path, with error: ";
3914           size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3915           char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
3916           jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
3917           // If we can't find the agent, exit.
3918           vm_exit_during_initialization(buf, NULL);
3919           FREE_C_HEAP_ARRAY(char, buf);
3920         }
3921       }
3922     }
3923     agent->set_os_lib(library);
3924     agent->set_valid();
3925   }
3926 
3927   // Find the OnLoad function.
3928   on_load_entry =
3929     CAST_TO_FN_PTR(OnLoadEntry_t, os::find_agent_function(agent,
3930                                                           false,
3931                                                           on_load_symbols,
3932                                                           num_symbol_entries));
3933   return on_load_entry;
3934 }
3935 
3936 // Find the JVM_OnLoad entry point
3937 static OnLoadEntry_t lookup_jvm_on_load(AgentLibrary* agent) {
3938   const char *on_load_symbols[] = JVM_ONLOAD_SYMBOLS;
3939   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
3940 }
3941 
3942 // Find the Agent_OnLoad entry point
3943 static OnLoadEntry_t lookup_agent_on_load(AgentLibrary* agent) {
3944   const char *on_load_symbols[] = AGENT_ONLOAD_SYMBOLS;
3945   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
3946 }
3947 
3948 // For backwards compatibility with -Xrun
3949 // Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be
3950 // treated like -agentpath:
3951 // Must be called before agent libraries are created
3952 void Threads::convert_vm_init_libraries_to_agents() {
3953   AgentLibrary* agent;
3954   AgentLibrary* next;
3955 
3956   for (agent = Arguments::libraries(); agent != NULL; agent = next) {
3957     next = agent->next();  // cache the next agent now as this agent may get moved off this list
3958     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
3959 
3960     // If there is an JVM_OnLoad function it will get called later,
3961     // otherwise see if there is an Agent_OnLoad
3962     if (on_load_entry == NULL) {
3963       on_load_entry = lookup_agent_on_load(agent);
3964       if (on_load_entry != NULL) {
3965         // switch it to the agent list -- so that Agent_OnLoad will be called,
3966         // JVM_OnLoad won't be attempted and Agent_OnUnload will
3967         Arguments::convert_library_to_agent(agent);
3968       } else {
3969         vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
3970       }
3971     }
3972   }
3973 }
3974 
3975 // Create agents for -agentlib:  -agentpath:  and converted -Xrun
3976 // Invokes Agent_OnLoad
3977 // Called very early -- before JavaThreads exist
3978 void Threads::create_vm_init_agents() {
3979   extern struct JavaVM_ main_vm;
3980   AgentLibrary* agent;
3981 
3982   JvmtiExport::enter_onload_phase();
3983 
3984   for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
3985     OnLoadEntry_t  on_load_entry = lookup_agent_on_load(agent);
3986 
3987     if (on_load_entry != NULL) {
3988       // Invoke the Agent_OnLoad function
3989       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
3990       if (err != JNI_OK) {
3991         vm_exit_during_initialization("agent library failed to init", agent->name());
3992       }
3993     } else {
3994       vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
3995     }
3996   }
3997   JvmtiExport::enter_primordial_phase();
3998 }
3999 
4000 extern "C" {
4001   typedef void (JNICALL *Agent_OnUnload_t)(JavaVM *);
4002 }
4003 
4004 void Threads::shutdown_vm_agents() {
4005   // Send any Agent_OnUnload notifications
4006   const char *on_unload_symbols[] = AGENT_ONUNLOAD_SYMBOLS;
4007   size_t num_symbol_entries = ARRAY_SIZE(on_unload_symbols);
4008   extern struct JavaVM_ main_vm;
4009   for (AgentLibrary* agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
4010 
4011     // Find the Agent_OnUnload function.
4012     Agent_OnUnload_t unload_entry = CAST_TO_FN_PTR(Agent_OnUnload_t,
4013                                                    os::find_agent_function(agent,
4014                                                    false,
4015                                                    on_unload_symbols,
4016                                                    num_symbol_entries));
4017 
4018     // Invoke the Agent_OnUnload function
4019     if (unload_entry != NULL) {
4020       JavaThread* thread = JavaThread::current();
4021       ThreadToNativeFromVM ttn(thread);
4022       HandleMark hm(thread);
4023       (*unload_entry)(&main_vm);
4024     }
4025   }
4026 }
4027 
4028 // Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries
4029 // Invokes JVM_OnLoad
4030 void Threads::create_vm_init_libraries() {
4031   extern struct JavaVM_ main_vm;
4032   AgentLibrary* agent;
4033 
4034   for (agent = Arguments::libraries(); agent != NULL; agent = agent->next()) {
4035     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
4036 
4037     if (on_load_entry != NULL) {
4038       // Invoke the JVM_OnLoad function
4039       JavaThread* thread = JavaThread::current();
4040       ThreadToNativeFromVM ttn(thread);
4041       HandleMark hm(thread);
4042       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
4043       if (err != JNI_OK) {
4044         vm_exit_during_initialization("-Xrun library failed to init", agent->name());
4045       }
4046     } else {
4047       vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
4048     }
4049   }
4050 }
4051 
4052 JavaThread* Threads::find_java_thread_from_java_tid(jlong java_tid) {
4053   assert(Threads_lock->owned_by_self(), "Must hold Threads_lock");
4054 
4055   JavaThread* java_thread = NULL;
4056   // Sequential search for now.  Need to do better optimization later.
4057   for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) {
4058     oop tobj = thread->threadObj();
4059     if (!thread->is_exiting() &&
4060         tobj != NULL &&
4061         java_tid == java_lang_Thread::thread_id(tobj)) {
4062       java_thread = thread;
4063       break;
4064     }
4065   }
4066   return java_thread;
4067 }
4068 
4069 
4070 // Last thread running calls java.lang.Shutdown.shutdown()
4071 void JavaThread::invoke_shutdown_hooks() {
4072   HandleMark hm(this);
4073 
4074   // We could get here with a pending exception, if so clear it now.
4075   if (this->has_pending_exception()) {
4076     this->clear_pending_exception();
4077   }
4078 
4079   EXCEPTION_MARK;
4080   Klass* shutdown_klass =
4081     SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
4082                                       THREAD);
4083   if (shutdown_klass != NULL) {
4084     // SystemDictionary::resolve_or_null will return null if there was
4085     // an exception.  If we cannot load the Shutdown class, just don't
4086     // call Shutdown.shutdown() at all.  This will mean the shutdown hooks
4087     // and finalizers (if runFinalizersOnExit is set) won't be run.
4088     // Note that if a shutdown hook was registered or runFinalizersOnExit
4089     // was called, the Shutdown class would have already been loaded
4090     // (Runtime.addShutdownHook and runFinalizersOnExit will load it).
4091     JavaValue result(T_VOID);
4092     JavaCalls::call_static(&result,
4093                            shutdown_klass,
4094                            vmSymbols::shutdown_method_name(),
4095                            vmSymbols::void_method_signature(),
4096                            THREAD);
4097   }
4098   CLEAR_PENDING_EXCEPTION;
4099 }
4100 
4101 // Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
4102 // the program falls off the end of main(). Another VM exit path is through
4103 // vm_exit() when the program calls System.exit() to return a value or when
4104 // there is a serious error in VM. The two shutdown paths are not exactly
4105 // the same, but they share Shutdown.shutdown() at Java level and before_exit()
4106 // and VM_Exit op at VM level.
4107 //
4108 // Shutdown sequence:
4109 //   + Shutdown native memory tracking if it is on
4110 //   + Wait until we are the last non-daemon thread to execute
4111 //     <-- every thing is still working at this moment -->
4112 //   + Call java.lang.Shutdown.shutdown(), which will invoke Java level
4113 //        shutdown hooks, run finalizers if finalization-on-exit
4114 //   + Call before_exit(), prepare for VM exit
4115 //      > run VM level shutdown hooks (they are registered through JVM_OnExit(),
4116 //        currently the only user of this mechanism is File.deleteOnExit())
4117 //      > stop flat profiler, StatSampler, watcher thread, CMS threads,
4118 //        post thread end and vm death events to JVMTI,
4119 //        stop signal thread
4120 //   + Call JavaThread::exit(), it will:
4121 //      > release JNI handle blocks, remove stack guard pages
4122 //      > remove this thread from Threads list
4123 //     <-- no more Java code from this thread after this point -->
4124 //   + Stop VM thread, it will bring the remaining VM to a safepoint and stop
4125 //     the compiler threads at safepoint
4126 //     <-- do not use anything that could get blocked by Safepoint -->
4127 //   + Disable tracing at JNI/JVM barriers
4128 //   + Set _vm_exited flag for threads that are still running native code
4129 //   + Delete this thread
4130 //   + Call exit_globals()
4131 //      > deletes tty
4132 //      > deletes PerfMemory resources
4133 //   + Return to caller
4134 
4135 bool Threads::destroy_vm() {
4136   JavaThread* thread = JavaThread::current();
4137 
4138 #ifdef ASSERT
4139   _vm_complete = false;
4140 #endif
4141   // Wait until we are the last non-daemon thread to execute
4142   { MutexLocker nu(Threads_lock);
4143     while (Threads::number_of_non_daemon_threads() > 1)
4144       // This wait should make safepoint checks, wait without a timeout,
4145       // and wait as a suspend-equivalent condition.
4146       //
4147       // Note: If the FlatProfiler is running and this thread is waiting
4148       // for another non-daemon thread to finish, then the FlatProfiler
4149       // is waiting for the external suspend request on this thread to
4150       // complete. wait_for_ext_suspend_completion() will eventually
4151       // timeout, but that takes time. Making this wait a suspend-
4152       // equivalent condition solves that timeout problem.
4153       //
4154       Threads_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
4155                          Mutex::_as_suspend_equivalent_flag);
4156   }
4157 
4158   // Hang forever on exit if we are reporting an error.
4159   if (ShowMessageBoxOnError && is_error_reported()) {
4160     os::infinite_sleep();
4161   }
4162   os::wait_for_keypress_at_exit();
4163 
4164   // run Java level shutdown hooks
4165   thread->invoke_shutdown_hooks();
4166 
4167   before_exit(thread);
4168 
4169   thread->exit(true);
4170 
4171   // Stop VM thread.
4172   {
4173     // 4945125 The vm thread comes to a safepoint during exit.
4174     // GC vm_operations can get caught at the safepoint, and the
4175     // heap is unparseable if they are caught. Grab the Heap_lock
4176     // to prevent this. The GC vm_operations will not be able to
4177     // queue until after the vm thread is dead. After this point,
4178     // we'll never emerge out of the safepoint before the VM exits.
4179 
4180     MutexLocker ml(Heap_lock);
4181 
4182     VMThread::wait_for_vm_thread_exit();
4183     assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
4184     VMThread::destroy();
4185   }
4186 
4187   // clean up ideal graph printers
4188 #if defined(COMPILER2) && !defined(PRODUCT)
4189   IdealGraphPrinter::clean_up();
4190 #endif
4191 
4192   // Now, all Java threads are gone except daemon threads. Daemon threads
4193   // running Java code or in VM are stopped by the Safepoint. However,
4194   // daemon threads executing native code are still running.  But they
4195   // will be stopped at native=>Java/VM barriers. Note that we can't
4196   // simply kill or suspend them, as it is inherently deadlock-prone.
4197 
4198   VM_Exit::set_vm_exited();
4199 
4200   notify_vm_shutdown();
4201 
4202   delete thread;
4203 
4204 #if INCLUDE_JVMCI
4205   if (JVMCICounterSize > 0) {
4206     FREE_C_HEAP_ARRAY(jlong, JavaThread::_jvmci_old_thread_counters);
4207   }
4208 #endif
4209 
4210   // exit_globals() will delete tty
4211   exit_globals();
4212 
4213   LogConfiguration::finalize();
4214 
4215   return true;
4216 }
4217 
4218 
4219 jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
4220   if (version == JNI_VERSION_1_1) return JNI_TRUE;
4221   return is_supported_jni_version(version);
4222 }
4223 
4224 
4225 jboolean Threads::is_supported_jni_version(jint version) {
4226   if (version == JNI_VERSION_1_2) return JNI_TRUE;
4227   if (version == JNI_VERSION_1_4) return JNI_TRUE;
4228   if (version == JNI_VERSION_1_6) return JNI_TRUE;
4229   if (version == JNI_VERSION_1_8) return JNI_TRUE;
4230   if (version == JNI_VERSION_9) return JNI_TRUE;
4231   return JNI_FALSE;
4232 }
4233 
4234 
4235 void Threads::add(JavaThread* p, bool force_daemon) {
4236   // The threads lock must be owned at this point
4237   assert_locked_or_safepoint(Threads_lock);
4238 
4239   // See the comment for this method in thread.hpp for its purpose and
4240   // why it is called here.
4241   p->initialize_queues();
4242   p->set_next(_thread_list);
4243   _thread_list = p;
4244   _number_of_threads++;
4245   oop threadObj = p->threadObj();
4246   bool daemon = true;
4247   // Bootstrapping problem: threadObj can be null for initial
4248   // JavaThread (or for threads attached via JNI)
4249   if ((!force_daemon) && (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj))) {
4250     _number_of_non_daemon_threads++;
4251     daemon = false;
4252   }
4253 
4254   ThreadService::add_thread(p, daemon);
4255 
4256   // Possible GC point.
4257   Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p));
4258 }
4259 
4260 void Threads::remove(JavaThread* p) {
4261 
4262   // Reclaim the objectmonitors from the omInUseList and omFreeList of the moribund thread.
4263   ObjectSynchronizer::omFlush(p);
4264 
4265   // Extra scope needed for Thread_lock, so we can check
4266   // that we do not remove thread without safepoint code notice
4267   { MutexLocker ml(Threads_lock);
4268 
4269     assert(includes(p), "p must be present");
4270 
4271     JavaThread* current = _thread_list;
4272     JavaThread* prev    = NULL;
4273 
4274     while (current != p) {
4275       prev    = current;
4276       current = current->next();
4277     }
4278 
4279     if (prev) {
4280       prev->set_next(current->next());
4281     } else {
4282       _thread_list = p->next();
4283     }
4284     _number_of_threads--;
4285     oop threadObj = p->threadObj();
4286     bool daemon = true;
4287     if (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj)) {
4288       _number_of_non_daemon_threads--;
4289       daemon = false;
4290 
4291       // Only one thread left, do a notify on the Threads_lock so a thread waiting
4292       // on destroy_vm will wake up.
4293       if (number_of_non_daemon_threads() == 1) {
4294         Threads_lock->notify_all();
4295       }
4296     }
4297     ThreadService::remove_thread(p, daemon);
4298 
4299     // Make sure that safepoint code disregard this thread. This is needed since
4300     // the thread might mess around with locks after this point. This can cause it
4301     // to do callbacks into the safepoint code. However, the safepoint code is not aware
4302     // of this thread since it is removed from the queue.
4303     p->set_terminated_value();
4304   } // unlock Threads_lock
4305 
4306   // Since Events::log uses a lock, we grab it outside the Threads_lock
4307   Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p));
4308 }
4309 
4310 // Threads_lock must be held when this is called (or must be called during a safepoint)
4311 bool Threads::includes(JavaThread* p) {
4312   assert(Threads_lock->is_locked(), "sanity check");
4313   ALL_JAVA_THREADS(q) {
4314     if (q == p) {
4315       return true;
4316     }
4317   }
4318   return false;
4319 }
4320 
4321 // Operations on the Threads list for GC.  These are not explicitly locked,
4322 // but the garbage collector must provide a safe context for them to run.
4323 // In particular, these things should never be called when the Threads_lock
4324 // is held by some other thread. (Note: the Safepoint abstraction also
4325 // uses the Threads_lock to guarantee this property. It also makes sure that
4326 // all threads gets blocked when exiting or starting).
4327 
4328 void Threads::oops_do(OopClosure* f, CodeBlobClosure* cf) {
4329   ALL_JAVA_THREADS(p) {
4330     p->oops_do(f, cf);
4331   }
4332   VMThread::vm_thread()->oops_do(f, cf);
4333 }
4334 
4335 void Threads::change_thread_claim_parity() {
4336   // Set the new claim parity.
4337   assert(_thread_claim_parity >= 0 && _thread_claim_parity <= 2,
4338          "Not in range.");
4339   _thread_claim_parity++;
4340   if (_thread_claim_parity == 3) _thread_claim_parity = 1;
4341   assert(_thread_claim_parity >= 1 && _thread_claim_parity <= 2,
4342          "Not in range.");
4343 }
4344 
4345 #ifdef ASSERT
4346 void Threads::assert_all_threads_claimed() {
4347   ALL_JAVA_THREADS(p) {
4348     const int thread_parity = p->oops_do_parity();
4349     assert((thread_parity == _thread_claim_parity),
4350            "Thread " PTR_FORMAT " has incorrect parity %d != %d", p2i(p), thread_parity, _thread_claim_parity);
4351   }
4352 }
4353 #endif // ASSERT
4354 
4355 void Threads::possibly_parallel_oops_do(bool is_par, OopClosure* f, CodeBlobClosure* cf) {
4356   int cp = Threads::thread_claim_parity();
4357   ALL_JAVA_THREADS(p) {
4358     if (p->claim_oops_do(is_par, cp)) {
4359       p->oops_do(f, cf);
4360     }
4361   }
4362   VMThread* vmt = VMThread::vm_thread();
4363   if (vmt->claim_oops_do(is_par, cp)) {
4364     vmt->oops_do(f, cf);
4365   }
4366 }
4367 
4368 #if INCLUDE_ALL_GCS
4369 // Used by ParallelScavenge
4370 void Threads::create_thread_roots_tasks(GCTaskQueue* q) {
4371   ALL_JAVA_THREADS(p) {
4372     q->enqueue(new ThreadRootsTask(p));
4373   }
4374   q->enqueue(new ThreadRootsTask(VMThread::vm_thread()));
4375 }
4376 
4377 // Used by Parallel Old
4378 void Threads::create_thread_roots_marking_tasks(GCTaskQueue* q) {
4379   ALL_JAVA_THREADS(p) {
4380     q->enqueue(new ThreadRootsMarkingTask(p));
4381   }
4382   q->enqueue(new ThreadRootsMarkingTask(VMThread::vm_thread()));
4383 }
4384 #endif // INCLUDE_ALL_GCS
4385 
4386 void Threads::nmethods_do(CodeBlobClosure* cf) {
4387   ALL_JAVA_THREADS(p) {
4388     // This is used by the code cache sweeper to mark nmethods that are active
4389     // on the stack of a Java thread. Ignore the sweeper thread itself to avoid
4390     // marking CodeCacheSweeperThread::_scanned_compiled_method as active.
4391     if(!p->is_Code_cache_sweeper_thread()) {
4392       p->nmethods_do(cf);
4393     }
4394   }
4395 }
4396 
4397 void Threads::metadata_do(void f(Metadata*)) {
4398   ALL_JAVA_THREADS(p) {
4399     p->metadata_do(f);
4400   }
4401 }
4402 
4403 class ThreadHandlesClosure : public ThreadClosure {
4404   void (*_f)(Metadata*);
4405  public:
4406   ThreadHandlesClosure(void f(Metadata*)) : _f(f) {}
4407   virtual void do_thread(Thread* thread) {
4408     thread->metadata_handles_do(_f);
4409   }
4410 };
4411 
4412 void Threads::metadata_handles_do(void f(Metadata*)) {
4413   // Only walk the Handles in Thread.
4414   ThreadHandlesClosure handles_closure(f);
4415   threads_do(&handles_closure);
4416 }
4417 
4418 void Threads::deoptimized_wrt_marked_nmethods() {
4419   ALL_JAVA_THREADS(p) {
4420     p->deoptimized_wrt_marked_nmethods();
4421   }
4422 }
4423 
4424 
4425 // Get count Java threads that are waiting to enter the specified monitor.
4426 GrowableArray<JavaThread*>* Threads::get_pending_threads(int count,
4427                                                          address monitor,
4428                                                          bool doLock) {
4429   assert(doLock || SafepointSynchronize::is_at_safepoint(),
4430          "must grab Threads_lock or be at safepoint");
4431   GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
4432 
4433   int i = 0;
4434   {
4435     MutexLockerEx ml(doLock ? Threads_lock : NULL);
4436     ALL_JAVA_THREADS(p) {
4437       if (!p->can_call_java()) continue;
4438 
4439       address pending = (address)p->current_pending_monitor();
4440       if (pending == monitor) {             // found a match
4441         if (i < count) result->append(p);   // save the first count matches
4442         i++;
4443       }
4444     }
4445   }
4446   return result;
4447 }
4448 
4449 
4450 JavaThread *Threads::owning_thread_from_monitor_owner(address owner,
4451                                                       bool doLock) {
4452   assert(doLock ||
4453          Threads_lock->owned_by_self() ||
4454          SafepointSynchronize::is_at_safepoint(),
4455          "must grab Threads_lock or be at safepoint");
4456 
4457   // NULL owner means not locked so we can skip the search
4458   if (owner == NULL) return NULL;
4459 
4460   {
4461     MutexLockerEx ml(doLock ? Threads_lock : NULL);
4462     ALL_JAVA_THREADS(p) {
4463       // first, see if owner is the address of a Java thread
4464       if (owner == (address)p) return p;
4465     }
4466   }
4467   // Cannot assert on lack of success here since this function may be
4468   // used by code that is trying to report useful problem information
4469   // like deadlock detection.
4470   if (UseHeavyMonitors) return NULL;
4471 
4472   // If we didn't find a matching Java thread and we didn't force use of
4473   // heavyweight monitors, then the owner is the stack address of the
4474   // Lock Word in the owning Java thread's stack.
4475   //
4476   JavaThread* the_owner = NULL;
4477   {
4478     MutexLockerEx ml(doLock ? Threads_lock : NULL);
4479     ALL_JAVA_THREADS(q) {
4480       if (q->is_lock_owned(owner)) {
4481         the_owner = q;
4482         break;
4483       }
4484     }
4485   }
4486   // cannot assert on lack of success here; see above comment
4487   return the_owner;
4488 }
4489 
4490 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
4491 void Threads::print_on(outputStream* st, bool print_stacks,
4492                        bool internal_format, bool print_concurrent_locks) {
4493   char buf[32];
4494   st->print_raw_cr(os::local_time_string(buf, sizeof(buf)));
4495 
4496   st->print_cr("Full thread dump %s (%s %s):",
4497                Abstract_VM_Version::vm_name(),
4498                Abstract_VM_Version::vm_release(),
4499                Abstract_VM_Version::vm_info_string());
4500   st->cr();
4501 
4502 #if INCLUDE_SERVICES
4503   // Dump concurrent locks
4504   ConcurrentLocksDump concurrent_locks;
4505   if (print_concurrent_locks) {
4506     concurrent_locks.dump_at_safepoint();
4507   }
4508 #endif // INCLUDE_SERVICES
4509 
4510   ALL_JAVA_THREADS(p) {
4511     ResourceMark rm;
4512     p->print_on(st);
4513     if (print_stacks) {
4514       if (internal_format) {
4515         p->trace_stack();
4516       } else {
4517         p->print_stack_on(st);
4518       }
4519     }
4520     st->cr();
4521 #if INCLUDE_SERVICES
4522     if (print_concurrent_locks) {
4523       concurrent_locks.print_locks_on(p, st);
4524     }
4525 #endif // INCLUDE_SERVICES
4526   }
4527 
4528   VMThread::vm_thread()->print_on(st);
4529   st->cr();
4530   Universe::heap()->print_gc_threads_on(st);
4531   WatcherThread* wt = WatcherThread::watcher_thread();
4532   if (wt != NULL) {
4533     wt->print_on(st);
4534     st->cr();
4535   }
4536   st->flush();
4537 }
4538 
4539 void Threads::print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf,
4540                              int buflen, bool* found_current) {
4541   if (this_thread != NULL) {
4542     bool is_current = (current == this_thread);
4543     *found_current = *found_current || is_current;
4544     st->print("%s", is_current ? "=>" : "  ");
4545 
4546     st->print(PTR_FORMAT, p2i(this_thread));
4547     st->print(" ");
4548     this_thread->print_on_error(st, buf, buflen);
4549     st->cr();
4550   }
4551 }
4552 
4553 class PrintOnErrorClosure : public ThreadClosure {
4554   outputStream* _st;
4555   Thread* _current;
4556   char* _buf;
4557   int _buflen;
4558   bool* _found_current;
4559  public:
4560   PrintOnErrorClosure(outputStream* st, Thread* current, char* buf,
4561                       int buflen, bool* found_current) :
4562    _st(st), _current(current), _buf(buf), _buflen(buflen), _found_current(found_current) {}
4563 
4564   virtual void do_thread(Thread* thread) {
4565     Threads::print_on_error(thread, _st, _current, _buf, _buflen, _found_current);
4566   }
4567 };
4568 
4569 // Threads::print_on_error() is called by fatal error handler. It's possible
4570 // that VM is not at safepoint and/or current thread is inside signal handler.
4571 // Don't print stack trace, as the stack may not be walkable. Don't allocate
4572 // memory (even in resource area), it might deadlock the error handler.
4573 void Threads::print_on_error(outputStream* st, Thread* current, char* buf,
4574                              int buflen) {
4575   bool found_current = false;
4576   st->print_cr("Java Threads: ( => current thread )");
4577   ALL_JAVA_THREADS(thread) {
4578     print_on_error(thread, st, current, buf, buflen, &found_current);
4579   }
4580   st->cr();
4581 
4582   st->print_cr("Other Threads:");
4583   print_on_error(VMThread::vm_thread(), st, current, buf, buflen, &found_current);
4584   print_on_error(WatcherThread::watcher_thread(), st, current, buf, buflen, &found_current);
4585 
4586   PrintOnErrorClosure print_closure(st, current, buf, buflen, &found_current);
4587   Universe::heap()->gc_threads_do(&print_closure);
4588 
4589   if (!found_current) {
4590     st->cr();
4591     st->print("=>" PTR_FORMAT " (exited) ", p2i(current));
4592     current->print_on_error(st, buf, buflen);
4593     st->cr();
4594   }
4595   st->cr();
4596   st->print_cr("Threads with active compile tasks:");
4597   print_threads_compiling(st, buf, buflen);
4598 }
4599 
4600 void Threads::print_threads_compiling(outputStream* st, char* buf, int buflen) {
4601   ALL_JAVA_THREADS(thread) {
4602     if (thread->is_Compiler_thread()) {
4603       CompilerThread* ct = (CompilerThread*) thread;
4604       if (ct->task() != NULL) {
4605         thread->print_name_on_error(st, buf, buflen);
4606         ct->task()->print(st, NULL, true, true);
4607       }
4608     }
4609   }
4610 }
4611 
4612 
4613 // Internal SpinLock and Mutex
4614 // Based on ParkEvent
4615 
4616 // Ad-hoc mutual exclusion primitives: SpinLock and Mux
4617 //
4618 // We employ SpinLocks _only for low-contention, fixed-length
4619 // short-duration critical sections where we're concerned
4620 // about native mutex_t or HotSpot Mutex:: latency.
4621 // The mux construct provides a spin-then-block mutual exclusion
4622 // mechanism.
4623 //
4624 // Testing has shown that contention on the ListLock guarding gFreeList
4625 // is common.  If we implement ListLock as a simple SpinLock it's common
4626 // for the JVM to devolve to yielding with little progress.  This is true
4627 // despite the fact that the critical sections protected by ListLock are
4628 // extremely short.
4629 //
4630 // TODO-FIXME: ListLock should be of type SpinLock.
4631 // We should make this a 1st-class type, integrated into the lock
4632 // hierarchy as leaf-locks.  Critically, the SpinLock structure
4633 // should have sufficient padding to avoid false-sharing and excessive
4634 // cache-coherency traffic.
4635 
4636 
4637 typedef volatile int SpinLockT;
4638 
4639 void Thread::SpinAcquire(volatile int * adr, const char * LockName) {
4640   if (Atomic::cmpxchg (1, adr, 0) == 0) {
4641     return;   // normal fast-path return
4642   }
4643 
4644   // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
4645   TEVENT(SpinAcquire - ctx);
4646   int ctr = 0;
4647   int Yields = 0;
4648   for (;;) {
4649     while (*adr != 0) {
4650       ++ctr;
4651       if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
4652         if (Yields > 5) {
4653           os::naked_short_sleep(1);
4654         } else {
4655           os::naked_yield();
4656           ++Yields;
4657         }
4658       } else {
4659         SpinPause();
4660       }
4661     }
4662     if (Atomic::cmpxchg(1, adr, 0) == 0) return;
4663   }
4664 }
4665 
4666 void Thread::SpinRelease(volatile int * adr) {
4667   assert(*adr != 0, "invariant");
4668   OrderAccess::fence();      // guarantee at least release consistency.
4669   // Roach-motel semantics.
4670   // It's safe if subsequent LDs and STs float "up" into the critical section,
4671   // but prior LDs and STs within the critical section can't be allowed
4672   // to reorder or float past the ST that releases the lock.
4673   // Loads and stores in the critical section - which appear in program
4674   // order before the store that releases the lock - must also appear
4675   // before the store that releases the lock in memory visibility order.
4676   // Conceptually we need a #loadstore|#storestore "release" MEMBAR before
4677   // the ST of 0 into the lock-word which releases the lock, so fence
4678   // more than covers this on all platforms.
4679   *adr = 0;
4680 }
4681 
4682 // muxAcquire and muxRelease:
4683 //
4684 // *  muxAcquire and muxRelease support a single-word lock-word construct.
4685 //    The LSB of the word is set IFF the lock is held.
4686 //    The remainder of the word points to the head of a singly-linked list
4687 //    of threads blocked on the lock.
4688 //
4689 // *  The current implementation of muxAcquire-muxRelease uses its own
4690 //    dedicated Thread._MuxEvent instance.  If we're interested in
4691 //    minimizing the peak number of extant ParkEvent instances then
4692 //    we could eliminate _MuxEvent and "borrow" _ParkEvent as long
4693 //    as certain invariants were satisfied.  Specifically, care would need
4694 //    to be taken with regards to consuming unpark() "permits".
4695 //    A safe rule of thumb is that a thread would never call muxAcquire()
4696 //    if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
4697 //    park().  Otherwise the _ParkEvent park() operation in muxAcquire() could
4698 //    consume an unpark() permit intended for monitorenter, for instance.
4699 //    One way around this would be to widen the restricted-range semaphore
4700 //    implemented in park().  Another alternative would be to provide
4701 //    multiple instances of the PlatformEvent() for each thread.  One
4702 //    instance would be dedicated to muxAcquire-muxRelease, for instance.
4703 //
4704 // *  Usage:
4705 //    -- Only as leaf locks
4706 //    -- for short-term locking only as muxAcquire does not perform
4707 //       thread state transitions.
4708 //
4709 // Alternatives:
4710 // *  We could implement muxAcquire and muxRelease with MCS or CLH locks
4711 //    but with parking or spin-then-park instead of pure spinning.
4712 // *  Use Taura-Oyama-Yonenzawa locks.
4713 // *  It's possible to construct a 1-0 lock if we encode the lockword as
4714 //    (List,LockByte).  Acquire will CAS the full lockword while Release
4715 //    will STB 0 into the LockByte.  The 1-0 scheme admits stranding, so
4716 //    acquiring threads use timers (ParkTimed) to detect and recover from
4717 //    the stranding window.  Thread/Node structures must be aligned on 256-byte
4718 //    boundaries by using placement-new.
4719 // *  Augment MCS with advisory back-link fields maintained with CAS().
4720 //    Pictorially:  LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
4721 //    The validity of the backlinks must be ratified before we trust the value.
4722 //    If the backlinks are invalid the exiting thread must back-track through the
4723 //    the forward links, which are always trustworthy.
4724 // *  Add a successor indication.  The LockWord is currently encoded as
4725 //    (List, LOCKBIT:1).  We could also add a SUCCBIT or an explicit _succ variable
4726 //    to provide the usual futile-wakeup optimization.
4727 //    See RTStt for details.
4728 // *  Consider schedctl.sc_nopreempt to cover the critical section.
4729 //
4730 
4731 
4732 typedef volatile intptr_t MutexT;      // Mux Lock-word
4733 enum MuxBits { LOCKBIT = 1 };
4734 
4735 void Thread::muxAcquire(volatile intptr_t * Lock, const char * LockName) {
4736   intptr_t w = Atomic::cmpxchg_ptr(LOCKBIT, Lock, 0);
4737   if (w == 0) return;
4738   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4739     return;
4740   }
4741 
4742   TEVENT(muxAcquire - Contention);
4743   ParkEvent * const Self = Thread::current()->_MuxEvent;
4744   assert((intptr_t(Self) & LOCKBIT) == 0, "invariant");
4745   for (;;) {
4746     int its = (os::is_MP() ? 100 : 0) + 1;
4747 
4748     // Optional spin phase: spin-then-park strategy
4749     while (--its >= 0) {
4750       w = *Lock;
4751       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4752         return;
4753       }
4754     }
4755 
4756     Self->reset();
4757     Self->OnList = intptr_t(Lock);
4758     // The following fence() isn't _strictly necessary as the subsequent
4759     // CAS() both serializes execution and ratifies the fetched *Lock value.
4760     OrderAccess::fence();
4761     for (;;) {
4762       w = *Lock;
4763       if ((w & LOCKBIT) == 0) {
4764         if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4765           Self->OnList = 0;   // hygiene - allows stronger asserts
4766           return;
4767         }
4768         continue;      // Interference -- *Lock changed -- Just retry
4769       }
4770       assert(w & LOCKBIT, "invariant");
4771       Self->ListNext = (ParkEvent *) (w & ~LOCKBIT);
4772       if (Atomic::cmpxchg_ptr(intptr_t(Self)|LOCKBIT, Lock, w) == w) break;
4773     }
4774 
4775     while (Self->OnList != 0) {
4776       Self->park();
4777     }
4778   }
4779 }
4780 
4781 void Thread::muxAcquireW(volatile intptr_t * Lock, ParkEvent * ev) {
4782   intptr_t w = Atomic::cmpxchg_ptr(LOCKBIT, Lock, 0);
4783   if (w == 0) return;
4784   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4785     return;
4786   }
4787 
4788   TEVENT(muxAcquire - Contention);
4789   ParkEvent * ReleaseAfter = NULL;
4790   if (ev == NULL) {
4791     ev = ReleaseAfter = ParkEvent::Allocate(NULL);
4792   }
4793   assert((intptr_t(ev) & LOCKBIT) == 0, "invariant");
4794   for (;;) {
4795     guarantee(ev->OnList == 0, "invariant");
4796     int its = (os::is_MP() ? 100 : 0) + 1;
4797 
4798     // Optional spin phase: spin-then-park strategy
4799     while (--its >= 0) {
4800       w = *Lock;
4801       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4802         if (ReleaseAfter != NULL) {
4803           ParkEvent::Release(ReleaseAfter);
4804         }
4805         return;
4806       }
4807     }
4808 
4809     ev->reset();
4810     ev->OnList = intptr_t(Lock);
4811     // The following fence() isn't _strictly necessary as the subsequent
4812     // CAS() both serializes execution and ratifies the fetched *Lock value.
4813     OrderAccess::fence();
4814     for (;;) {
4815       w = *Lock;
4816       if ((w & LOCKBIT) == 0) {
4817         if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4818           ev->OnList = 0;
4819           // We call ::Release while holding the outer lock, thus
4820           // artificially lengthening the critical section.
4821           // Consider deferring the ::Release() until the subsequent unlock(),
4822           // after we've dropped the outer lock.
4823           if (ReleaseAfter != NULL) {
4824             ParkEvent::Release(ReleaseAfter);
4825           }
4826           return;
4827         }
4828         continue;      // Interference -- *Lock changed -- Just retry
4829       }
4830       assert(w & LOCKBIT, "invariant");
4831       ev->ListNext = (ParkEvent *) (w & ~LOCKBIT);
4832       if (Atomic::cmpxchg_ptr(intptr_t(ev)|LOCKBIT, Lock, w) == w) break;
4833     }
4834 
4835     while (ev->OnList != 0) {
4836       ev->park();
4837     }
4838   }
4839 }
4840 
4841 // Release() must extract a successor from the list and then wake that thread.
4842 // It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
4843 // similar to that used by ParkEvent::Allocate() and ::Release().  DMR-based
4844 // Release() would :
4845 // (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
4846 // (B) Extract a successor from the private list "in-hand"
4847 // (C) attempt to CAS() the residual back into *Lock over null.
4848 //     If there were any newly arrived threads and the CAS() would fail.
4849 //     In that case Release() would detach the RATs, re-merge the list in-hand
4850 //     with the RATs and repeat as needed.  Alternately, Release() might
4851 //     detach and extract a successor, but then pass the residual list to the wakee.
4852 //     The wakee would be responsible for reattaching and remerging before it
4853 //     competed for the lock.
4854 //
4855 // Both "pop" and DMR are immune from ABA corruption -- there can be
4856 // multiple concurrent pushers, but only one popper or detacher.
4857 // This implementation pops from the head of the list.  This is unfair,
4858 // but tends to provide excellent throughput as hot threads remain hot.
4859 // (We wake recently run threads first).
4860 //
4861 // All paths through muxRelease() will execute a CAS.
4862 // Release consistency -- We depend on the CAS in muxRelease() to provide full
4863 // bidirectional fence/MEMBAR semantics, ensuring that all prior memory operations
4864 // executed within the critical section are complete and globally visible before the
4865 // store (CAS) to the lock-word that releases the lock becomes globally visible.
4866 void Thread::muxRelease(volatile intptr_t * Lock)  {
4867   for (;;) {
4868     const intptr_t w = Atomic::cmpxchg_ptr(0, Lock, LOCKBIT);
4869     assert(w & LOCKBIT, "invariant");
4870     if (w == LOCKBIT) return;
4871     ParkEvent * const List = (ParkEvent *) (w & ~LOCKBIT);
4872     assert(List != NULL, "invariant");
4873     assert(List->OnList == intptr_t(Lock), "invariant");
4874     ParkEvent * const nxt = List->ListNext;
4875     guarantee((intptr_t(nxt) & LOCKBIT) == 0, "invariant");
4876 
4877     // The following CAS() releases the lock and pops the head element.
4878     // The CAS() also ratifies the previously fetched lock-word value.
4879     if (Atomic::cmpxchg_ptr (intptr_t(nxt), Lock, w) != w) {
4880       continue;
4881     }
4882     List->OnList = 0;
4883     OrderAccess::fence();
4884     List->unpark();
4885     return;
4886   }
4887 }
4888 
4889 
4890 void Threads::verify() {
4891   ALL_JAVA_THREADS(p) {
4892     p->verify();
4893   }
4894   VMThread* thread = VMThread::vm_thread();
4895   if (thread != NULL) thread->verify();
4896 }