1 /*
   2  * Copyright (c) 1997, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "jvm.h"
  27 #include "classfile/classLoader.hpp"
  28 #include "classfile/javaClasses.hpp"
  29 #include "classfile/moduleEntry.hpp"
  30 #include "classfile/systemDictionary.hpp"
  31 #include "classfile/vmSymbols.hpp"
  32 #include "code/codeCache.hpp"
  33 #include "code/scopeDesc.hpp"
  34 #include "compiler/compileBroker.hpp"
  35 #include "compiler/compileTask.hpp"
  36 #include "gc/shared/barrierSet.hpp"
  37 #include "gc/shared/gcId.hpp"
  38 #include "gc/shared/gcLocker.inline.hpp"
  39 #include "gc/shared/workgroup.hpp"
  40 #include "interpreter/interpreter.hpp"
  41 #include "interpreter/linkResolver.hpp"
  42 #include "interpreter/oopMapCache.hpp"
  43 #include "jfr/jfrEvents.hpp"
  44 #include "jfr/support/jfrThreadId.hpp"
  45 #include "jvmtifiles/jvmtiEnv.hpp"
  46 #include "logging/log.hpp"
  47 #include "logging/logConfiguration.hpp"
  48 #include "logging/logStream.hpp"
  49 #include "memory/allocation.inline.hpp"
  50 #include "memory/metaspaceShared.hpp"
  51 #include "memory/oopFactory.hpp"
  52 #include "memory/resourceArea.hpp"
  53 #include "memory/universe.hpp"
  54 #include "oops/access.inline.hpp"
  55 #include "oops/instanceKlass.hpp"
  56 #include "oops/objArrayOop.hpp"
  57 #include "oops/oop.inline.hpp"
  58 #include "oops/symbol.hpp"
  59 #include "oops/typeArrayOop.inline.hpp"
  60 #include "oops/verifyOopClosure.hpp"
  61 #include "prims/jvm_misc.hpp"
  62 #include "prims/jvmtiExport.hpp"
  63 #include "prims/jvmtiThreadState.hpp"
  64 #include "prims/privilegedStack.hpp"
  65 #include "runtime/arguments.hpp"
  66 #include "runtime/atomic.hpp"
  67 #include "runtime/biasedLocking.hpp"
  68 #include "runtime/fieldDescriptor.inline.hpp"
  69 #include "runtime/flags/jvmFlagConstraintList.hpp"
  70 #include "runtime/flags/jvmFlagRangeList.hpp"
  71 #include "runtime/flags/jvmFlagWriteableList.hpp"
  72 #include "runtime/deoptimization.hpp"
  73 #include "runtime/frame.inline.hpp"
  74 #include "runtime/handshake.hpp"
  75 #include "runtime/init.hpp"
  76 #include "runtime/interfaceSupport.inline.hpp"
  77 #include "runtime/java.hpp"
  78 #include "runtime/javaCalls.hpp"
  79 #include "runtime/jniHandles.inline.hpp"
  80 #include "runtime/jniPeriodicChecker.hpp"
  81 #include "runtime/memprofiler.hpp"
  82 #include "runtime/mutexLocker.hpp"
  83 #include "runtime/objectMonitor.hpp"
  84 #include "runtime/orderAccess.hpp"
  85 #include "runtime/osThread.hpp"
  86 #include "runtime/prefetch.inline.hpp"
  87 #include "runtime/safepoint.hpp"
  88 #include "runtime/safepointMechanism.inline.hpp"
  89 #include "runtime/safepointVerifiers.hpp"
  90 #include "runtime/sharedRuntime.hpp"
  91 #include "runtime/statSampler.hpp"
  92 #include "runtime/stubRoutines.hpp"
  93 #include "runtime/sweeper.hpp"
  94 #include "runtime/task.hpp"
  95 #include "runtime/thread.inline.hpp"
  96 #include "runtime/threadCritical.hpp"
  97 #include "runtime/threadSMR.inline.hpp"
  98 #include "runtime/threadStatisticalInfo.hpp"
  99 #include "runtime/timer.hpp"
 100 #include "runtime/timerTrace.hpp"
 101 #include "runtime/vframe.inline.hpp"
 102 #include "runtime/vframeArray.hpp"
 103 #include "runtime/vframe_hp.hpp"
 104 #include "runtime/vmThread.hpp"
 105 #include "runtime/vm_operations.hpp"
 106 #include "runtime/vm_version.hpp"
 107 #include "services/attachListener.hpp"
 108 #include "services/management.hpp"
 109 #include "services/memTracker.hpp"
 110 #include "services/threadService.hpp"
 111 #include "utilities/align.hpp"
 112 #include "utilities/copy.hpp"
 113 #include "utilities/defaultStream.hpp"
 114 #include "utilities/dtrace.hpp"
 115 #include "utilities/events.hpp"
 116 #include "utilities/macros.hpp"
 117 #include "utilities/preserveException.hpp"
 118 #include "utilities/singleWriterSynchronizer.hpp"
 119 #include "utilities/vmError.hpp"
 120 #if INCLUDE_JVMCI
 121 #include "jvmci/jvmciCompiler.hpp"
 122 #include "jvmci/jvmciRuntime.hpp"
 123 #include "logging/logHandle.hpp"
 124 #endif
 125 #ifdef COMPILER1
 126 #include "c1/c1_Compiler.hpp"
 127 #endif
 128 #ifdef COMPILER2
 129 #include "opto/c2compiler.hpp"
 130 #include "opto/idealGraphPrinter.hpp"
 131 #endif
 132 #if INCLUDE_RTM_OPT
 133 #include "runtime/rtmLocking.hpp"
 134 #endif
 135 #if INCLUDE_JFR
 136 #include "jfr/jfr.hpp"
 137 #endif
 138 
 139 // Initialization after module runtime initialization
 140 void universe_post_module_init();  // must happen after call_initPhase2
 141 
 142 #ifdef DTRACE_ENABLED
 143 
 144 // Only bother with this argument setup if dtrace is available
 145 
 146   #define HOTSPOT_THREAD_PROBE_start HOTSPOT_THREAD_START
 147   #define HOTSPOT_THREAD_PROBE_stop HOTSPOT_THREAD_STOP
 148 
 149   #define DTRACE_THREAD_PROBE(probe, javathread)                           \
 150     {                                                                      \
 151       ResourceMark rm(this);                                               \
 152       int len = 0;                                                         \
 153       const char* name = (javathread)->get_thread_name();                  \
 154       len = strlen(name);                                                  \
 155       HOTSPOT_THREAD_PROBE_##probe(/* probe = start, stop */               \
 156         (char *) name, len,                                                \
 157         java_lang_Thread::thread_id((javathread)->threadObj()),            \
 158         (uintptr_t) (javathread)->osthread()->thread_id(),                 \
 159         java_lang_Thread::is_daemon((javathread)->threadObj()));           \
 160     }
 161 
 162 #else //  ndef DTRACE_ENABLED
 163 
 164   #define DTRACE_THREAD_PROBE(probe, javathread)
 165 
 166 #endif // ndef DTRACE_ENABLED
 167 
 168 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 169 // Current thread is maintained as a thread-local variable
 170 THREAD_LOCAL_DECL Thread* Thread::_thr_current = NULL;
 171 #endif
 172 
 173 // ======= Thread ========
 174 // Support for forcing alignment of thread objects for biased locking
 175 void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
 176   if (UseBiasedLocking) {
 177     const int alignment = markOopDesc::biased_lock_alignment;
 178     size_t aligned_size = size + (alignment - sizeof(intptr_t));
 179     void* real_malloc_addr = throw_excpt? AllocateHeap(aligned_size, flags, CURRENT_PC)
 180                                           : AllocateHeap(aligned_size, flags, CURRENT_PC,
 181                                                          AllocFailStrategy::RETURN_NULL);
 182     void* aligned_addr     = align_up(real_malloc_addr, alignment);
 183     assert(((uintptr_t) aligned_addr + (uintptr_t) size) <=
 184            ((uintptr_t) real_malloc_addr + (uintptr_t) aligned_size),
 185            "JavaThread alignment code overflowed allocated storage");
 186     if (aligned_addr != real_malloc_addr) {
 187       log_info(biasedlocking)("Aligned thread " INTPTR_FORMAT " to " INTPTR_FORMAT,
 188                               p2i(real_malloc_addr),
 189                               p2i(aligned_addr));
 190     }
 191     ((Thread*) aligned_addr)->_real_malloc_address = real_malloc_addr;
 192     return aligned_addr;
 193   } else {
 194     return throw_excpt? AllocateHeap(size, flags, CURRENT_PC)
 195                        : AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
 196   }
 197 }
 198 
 199 void Thread::operator delete(void* p) {
 200   if (UseBiasedLocking) {
 201     FreeHeap(((Thread*) p)->_real_malloc_address);
 202   } else {
 203     FreeHeap(p);
 204   }
 205 }
 206 
 207 void JavaThread::smr_delete() {
 208   if (_on_thread_list) {
 209     ThreadsSMRSupport::smr_delete(this);
 210   } else {
 211     delete this;
 212   }
 213 }
 214 
 215 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
 216 // JavaThread
 217 
 218 
 219 Thread::Thread() {
 220   // stack and get_thread
 221   set_stack_base(NULL);
 222   set_stack_size(0);
 223   set_self_raw_id(0);
 224   set_lgrp_id(-1);
 225   DEBUG_ONLY(clear_suspendible_thread();)
 226 
 227   // allocated data structures
 228   set_osthread(NULL);
 229   set_resource_area(new (mtThread)ResourceArea());
 230   DEBUG_ONLY(_current_resource_mark = NULL;)
 231   set_handle_area(new (mtThread) HandleArea(NULL));
 232   set_metadata_handles(new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(30, true));
 233   set_active_handles(NULL);
 234   set_free_handle_block(NULL);
 235   set_last_handle_mark(NULL);
 236 
 237   // This initial value ==> never claimed.
 238   _oops_do_parity = 0;
 239   _threads_hazard_ptr = NULL;
 240   _threads_list_ptr = NULL;
 241   _nested_threads_hazard_ptr_cnt = 0;
 242   _rcu_counter = 0;
 243 
 244   // the handle mark links itself to last_handle_mark
 245   new HandleMark(this);
 246 
 247   // plain initialization
 248   debug_only(_owned_locks = NULL;)
 249   debug_only(_allow_allocation_count = 0;)
 250   NOT_PRODUCT(_allow_safepoint_count = 0;)
 251   NOT_PRODUCT(_skip_gcalot = false;)
 252   _jvmti_env_iteration_count = 0;
 253   set_allocated_bytes(0);
 254   _vm_operation_started_count = 0;
 255   _vm_operation_completed_count = 0;
 256   _current_pending_monitor = NULL;
 257   _current_pending_monitor_is_from_java = true;
 258   _current_waiting_monitor = NULL;
 259   _num_nested_signal = 0;
 260   omFreeList = NULL;
 261   omFreeCount = 0;
 262   omFreeProvision = 32;
 263   omInUseList = NULL;
 264   omInUseCount = 0;
 265 
 266 #ifdef ASSERT
 267   _visited_for_critical_count = false;
 268 #endif
 269 
 270   _SR_lock = new Monitor(Mutex::suspend_resume, "SR_lock", true,
 271                          Monitor::_safepoint_check_sometimes);
 272   _suspend_flags = 0;
 273 
 274   // thread-specific hashCode stream generator state - Marsaglia shift-xor form
 275   _hashStateX = os::random();
 276   _hashStateY = 842502087;
 277   _hashStateZ = 0x8767;    // (int)(3579807591LL & 0xffff) ;
 278   _hashStateW = 273326509;
 279 
 280   _OnTrap   = 0;
 281   _Stalled  = 0;
 282   _TypeTag  = 0x2BAD;
 283 
 284   // Many of the following fields are effectively final - immutable
 285   // Note that nascent threads can't use the Native Monitor-Mutex
 286   // construct until the _MutexEvent is initialized ...
 287   // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
 288   // we might instead use a stack of ParkEvents that we could provision on-demand.
 289   // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
 290   // and ::Release()
 291   _ParkEvent   = ParkEvent::Allocate(this);
 292   _SleepEvent  = ParkEvent::Allocate(this);
 293   _MutexEvent  = ParkEvent::Allocate(this);
 294   _MuxEvent    = ParkEvent::Allocate(this);
 295 
 296 #ifdef CHECK_UNHANDLED_OOPS
 297   if (CheckUnhandledOops) {
 298     _unhandled_oops = new UnhandledOops(this);
 299   }
 300 #endif // CHECK_UNHANDLED_OOPS
 301 #ifdef ASSERT
 302   if (UseBiasedLocking) {
 303     assert((((uintptr_t) this) & (markOopDesc::biased_lock_alignment - 1)) == 0, "forced alignment of thread object failed");
 304     assert(this == _real_malloc_address ||
 305            this == align_up(_real_malloc_address, (int)markOopDesc::biased_lock_alignment),
 306            "bug in forced alignment of thread objects");
 307   }
 308 #endif // ASSERT
 309 
 310   // Notify the barrier set that a thread is being created. Note that some
 311   // threads are created before a barrier set is available. The call to
 312   // BarrierSet::on_thread_create() for these threads is therefore deferred
 313   // to BarrierSet::set_barrier_set().
 314   BarrierSet* const barrier_set = BarrierSet::barrier_set();
 315   if (barrier_set != NULL) {
 316     barrier_set->on_thread_create(this);
 317   } else {
 318     DEBUG_ONLY(Threads::inc_threads_before_barrier_set();)
 319   }
 320 }
 321 
 322 void Thread::initialize_thread_current() {
 323 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 324   assert(_thr_current == NULL, "Thread::current already initialized");
 325   _thr_current = this;
 326 #endif
 327   assert(ThreadLocalStorage::thread() == NULL, "ThreadLocalStorage::thread already initialized");
 328   ThreadLocalStorage::set_thread(this);
 329   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 330 }
 331 
 332 void Thread::clear_thread_current() {
 333   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 334 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 335   _thr_current = NULL;
 336 #endif
 337   ThreadLocalStorage::set_thread(NULL);
 338 }
 339 
 340 void Thread::record_stack_base_and_size() {
 341   set_stack_base(os::current_stack_base());
 342   set_stack_size(os::current_stack_size());
 343   // CR 7190089: on Solaris, primordial thread's stack is adjusted
 344   // in initialize_thread(). Without the adjustment, stack size is
 345   // incorrect if stack is set to unlimited (ulimit -s unlimited).
 346   // So far, only Solaris has real implementation of initialize_thread().
 347   //
 348   // set up any platform-specific state.
 349   os::initialize_thread(this);
 350 
 351   // Set stack limits after thread is initialized.
 352   if (is_Java_thread()) {
 353     ((JavaThread*) this)->set_stack_overflow_limit();
 354     ((JavaThread*) this)->set_reserved_stack_activation(stack_base());
 355   }
 356 #if INCLUDE_NMT
 357   // record thread's native stack, stack grows downward
 358   MemTracker::record_thread_stack(stack_end(), stack_size());
 359 #endif // INCLUDE_NMT
 360   log_debug(os, thread)("Thread " UINTX_FORMAT " stack dimensions: "
 361     PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT "k).",
 362     os::current_thread_id(), p2i(stack_base() - stack_size()),
 363     p2i(stack_base()), stack_size()/1024);
 364 }
 365 
 366 
 367 Thread::~Thread() {
 368   JFR_ONLY(Jfr::on_thread_destruct(this);)
 369 
 370   // Notify the barrier set that a thread is being destroyed. Note that a barrier
 371   // set might not be available if we encountered errors during bootstrapping.
 372   BarrierSet* const barrier_set = BarrierSet::barrier_set();
 373   if (barrier_set != NULL) {
 374     barrier_set->on_thread_destroy(this);
 375   }
 376 
 377 
 378   // stack_base can be NULL if the thread is never started or exited before
 379   // record_stack_base_and_size called. Although, we would like to ensure
 380   // that all started threads do call record_stack_base_and_size(), there is
 381   // not proper way to enforce that.
 382 #if INCLUDE_NMT
 383   if (_stack_base != NULL) {
 384     MemTracker::release_thread_stack(stack_end(), stack_size());
 385 #ifdef ASSERT
 386     set_stack_base(NULL);
 387 #endif
 388   }
 389 #endif // INCLUDE_NMT
 390 
 391   // deallocate data structures
 392   delete resource_area();
 393   // since the handle marks are using the handle area, we have to deallocated the root
 394   // handle mark before deallocating the thread's handle area,
 395   assert(last_handle_mark() != NULL, "check we have an element");
 396   delete last_handle_mark();
 397   assert(last_handle_mark() == NULL, "check we have reached the end");
 398 
 399   // It's possible we can encounter a null _ParkEvent, etc., in stillborn threads.
 400   // We NULL out the fields for good hygiene.
 401   ParkEvent::Release(_ParkEvent); _ParkEvent   = NULL;
 402   ParkEvent::Release(_SleepEvent); _SleepEvent  = NULL;
 403   ParkEvent::Release(_MutexEvent); _MutexEvent  = NULL;
 404   ParkEvent::Release(_MuxEvent); _MuxEvent    = NULL;
 405 
 406   delete handle_area();
 407   delete metadata_handles();
 408 
 409   // SR_handler uses this as a termination indicator -
 410   // needs to happen before os::free_thread()
 411   delete _SR_lock;
 412   _SR_lock = NULL;
 413 
 414   // osthread() can be NULL, if creation of thread failed.
 415   if (osthread() != NULL) os::free_thread(osthread());
 416 
 417   // clear Thread::current if thread is deleting itself.
 418   // Needed to ensure JNI correctly detects non-attached threads.
 419   if (this == Thread::current()) {
 420     clear_thread_current();
 421   }
 422 
 423   CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
 424 }
 425 
 426 // NOTE: dummy function for assertion purpose.
 427 void Thread::run() {
 428   ShouldNotReachHere();
 429 }
 430 
 431 #ifdef ASSERT
 432 // A JavaThread is considered "dangling" if it is not the current
 433 // thread, has been added the Threads list, the system is not at a
 434 // safepoint and the Thread is not "protected".
 435 //
 436 void Thread::check_for_dangling_thread_pointer(Thread *thread) {
 437   assert(!thread->is_Java_thread() || Thread::current() == thread ||
 438          !((JavaThread *) thread)->on_thread_list() ||
 439          SafepointSynchronize::is_at_safepoint() ||
 440          ThreadsSMRSupport::is_a_protected_JavaThread_with_lock((JavaThread *) thread),
 441          "possibility of dangling Thread pointer");
 442 }
 443 #endif
 444 
 445 ThreadPriority Thread::get_priority(const Thread* const thread) {
 446   ThreadPriority priority;
 447   // Can return an error!
 448   (void)os::get_priority(thread, priority);
 449   assert(MinPriority <= priority && priority <= MaxPriority, "non-Java priority found");
 450   return priority;
 451 }
 452 
 453 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
 454   debug_only(check_for_dangling_thread_pointer(thread);)
 455   // Can return an error!
 456   (void)os::set_priority(thread, priority);
 457 }
 458 
 459 
 460 void Thread::start(Thread* thread) {
 461   // Start is different from resume in that its safety is guaranteed by context or
 462   // being called from a Java method synchronized on the Thread object.
 463   if (!DisableStartThread) {
 464     if (thread->is_Java_thread()) {
 465       // Initialize the thread state to RUNNABLE before starting this thread.
 466       // Can not set it after the thread started because we do not know the
 467       // exact thread state at that time. It could be in MONITOR_WAIT or
 468       // in SLEEPING or some other state.
 469       java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
 470                                           java_lang_Thread::RUNNABLE);
 471     }
 472     os::start_thread(thread);
 473   }
 474 }
 475 
 476 // Enqueue a VM_Operation to do the job for us - sometime later
 477 void Thread::send_async_exception(oop java_thread, oop java_throwable) {
 478   VM_ThreadStop* vm_stop = new VM_ThreadStop(java_thread, java_throwable);
 479   VMThread::execute(vm_stop);
 480 }
 481 
 482 
 483 // Check if an external suspend request has completed (or has been
 484 // cancelled). Returns true if the thread is externally suspended and
 485 // false otherwise.
 486 //
 487 // The bits parameter returns information about the code path through
 488 // the routine. Useful for debugging:
 489 //
 490 // set in is_ext_suspend_completed():
 491 // 0x00000001 - routine was entered
 492 // 0x00000010 - routine return false at end
 493 // 0x00000100 - thread exited (return false)
 494 // 0x00000200 - suspend request cancelled (return false)
 495 // 0x00000400 - thread suspended (return true)
 496 // 0x00001000 - thread is in a suspend equivalent state (return true)
 497 // 0x00002000 - thread is native and walkable (return true)
 498 // 0x00004000 - thread is native_trans and walkable (needed retry)
 499 //
 500 // set in wait_for_ext_suspend_completion():
 501 // 0x00010000 - routine was entered
 502 // 0x00020000 - suspend request cancelled before loop (return false)
 503 // 0x00040000 - thread suspended before loop (return true)
 504 // 0x00080000 - suspend request cancelled in loop (return false)
 505 // 0x00100000 - thread suspended in loop (return true)
 506 // 0x00200000 - suspend not completed during retry loop (return false)
 507 
 508 // Helper class for tracing suspend wait debug bits.
 509 //
 510 // 0x00000100 indicates that the target thread exited before it could
 511 // self-suspend which is not a wait failure. 0x00000200, 0x00020000 and
 512 // 0x00080000 each indicate a cancelled suspend request so they don't
 513 // count as wait failures either.
 514 #define DEBUG_FALSE_BITS (0x00000010 | 0x00200000)
 515 
 516 class TraceSuspendDebugBits : public StackObj {
 517  private:
 518   JavaThread * jt;
 519   bool         is_wait;
 520   bool         called_by_wait;  // meaningful when !is_wait
 521   uint32_t *   bits;
 522 
 523  public:
 524   TraceSuspendDebugBits(JavaThread *_jt, bool _is_wait, bool _called_by_wait,
 525                         uint32_t *_bits) {
 526     jt             = _jt;
 527     is_wait        = _is_wait;
 528     called_by_wait = _called_by_wait;
 529     bits           = _bits;
 530   }
 531 
 532   ~TraceSuspendDebugBits() {
 533     if (!is_wait) {
 534 #if 1
 535       // By default, don't trace bits for is_ext_suspend_completed() calls.
 536       // That trace is very chatty.
 537       return;
 538 #else
 539       if (!called_by_wait) {
 540         // If tracing for is_ext_suspend_completed() is enabled, then only
 541         // trace calls to it from wait_for_ext_suspend_completion()
 542         return;
 543       }
 544 #endif
 545     }
 546 
 547     if (AssertOnSuspendWaitFailure || TraceSuspendWaitFailures) {
 548       if (bits != NULL && (*bits & DEBUG_FALSE_BITS) != 0) {
 549         MutexLocker ml(Threads_lock);  // needed for get_thread_name()
 550         ResourceMark rm;
 551 
 552         tty->print_cr(
 553                       "Failed wait_for_ext_suspend_completion(thread=%s, debug_bits=%x)",
 554                       jt->get_thread_name(), *bits);
 555 
 556         guarantee(!AssertOnSuspendWaitFailure, "external suspend wait failed");
 557       }
 558     }
 559   }
 560 };
 561 #undef DEBUG_FALSE_BITS
 562 
 563 
 564 bool JavaThread::is_ext_suspend_completed(bool called_by_wait, int delay,
 565                                           uint32_t *bits) {
 566   TraceSuspendDebugBits tsdb(this, false /* !is_wait */, called_by_wait, bits);
 567 
 568   bool did_trans_retry = false;  // only do thread_in_native_trans retry once
 569   bool do_trans_retry;           // flag to force the retry
 570 
 571   *bits |= 0x00000001;
 572 
 573   do {
 574     do_trans_retry = false;
 575 
 576     if (is_exiting()) {
 577       // Thread is in the process of exiting. This is always checked
 578       // first to reduce the risk of dereferencing a freed JavaThread.
 579       *bits |= 0x00000100;
 580       return false;
 581     }
 582 
 583     if (!is_external_suspend()) {
 584       // Suspend request is cancelled. This is always checked before
 585       // is_ext_suspended() to reduce the risk of a rogue resume
 586       // confusing the thread that made the suspend request.
 587       *bits |= 0x00000200;
 588       return false;
 589     }
 590 
 591     if (is_ext_suspended()) {
 592       // thread is suspended
 593       *bits |= 0x00000400;
 594       return true;
 595     }
 596 
 597     // Now that we no longer do hard suspends of threads running
 598     // native code, the target thread can be changing thread state
 599     // while we are in this routine:
 600     //
 601     //   _thread_in_native -> _thread_in_native_trans -> _thread_blocked
 602     //
 603     // We save a copy of the thread state as observed at this moment
 604     // and make our decision about suspend completeness based on the
 605     // copy. This closes the race where the thread state is seen as
 606     // _thread_in_native_trans in the if-thread_blocked check, but is
 607     // seen as _thread_blocked in if-thread_in_native_trans check.
 608     JavaThreadState save_state = thread_state();
 609 
 610     if (save_state == _thread_blocked && is_suspend_equivalent()) {
 611       // If the thread's state is _thread_blocked and this blocking
 612       // condition is known to be equivalent to a suspend, then we can
 613       // consider the thread to be externally suspended. This means that
 614       // the code that sets _thread_blocked has been modified to do
 615       // self-suspension if the blocking condition releases. We also
 616       // used to check for CONDVAR_WAIT here, but that is now covered by
 617       // the _thread_blocked with self-suspension check.
 618       //
 619       // Return true since we wouldn't be here unless there was still an
 620       // external suspend request.
 621       *bits |= 0x00001000;
 622       return true;
 623     } else if (save_state == _thread_in_native && frame_anchor()->walkable()) {
 624       // Threads running native code will self-suspend on native==>VM/Java
 625       // transitions. If its stack is walkable (should always be the case
 626       // unless this function is called before the actual java_suspend()
 627       // call), then the wait is done.
 628       *bits |= 0x00002000;
 629       return true;
 630     } else if (!called_by_wait && !did_trans_retry &&
 631                save_state == _thread_in_native_trans &&
 632                frame_anchor()->walkable()) {
 633       // The thread is transitioning from thread_in_native to another
 634       // thread state. check_safepoint_and_suspend_for_native_trans()
 635       // will force the thread to self-suspend. If it hasn't gotten
 636       // there yet we may have caught the thread in-between the native
 637       // code check above and the self-suspend. Lucky us. If we were
 638       // called by wait_for_ext_suspend_completion(), then it
 639       // will be doing the retries so we don't have to.
 640       //
 641       // Since we use the saved thread state in the if-statement above,
 642       // there is a chance that the thread has already transitioned to
 643       // _thread_blocked by the time we get here. In that case, we will
 644       // make a single unnecessary pass through the logic below. This
 645       // doesn't hurt anything since we still do the trans retry.
 646 
 647       *bits |= 0x00004000;
 648 
 649       // Once the thread leaves thread_in_native_trans for another
 650       // thread state, we break out of this retry loop. We shouldn't
 651       // need this flag to prevent us from getting back here, but
 652       // sometimes paranoia is good.
 653       did_trans_retry = true;
 654 
 655       // We wait for the thread to transition to a more usable state.
 656       for (int i = 1; i <= SuspendRetryCount; i++) {
 657         // We used to do an "os::yield_all(i)" call here with the intention
 658         // that yielding would increase on each retry. However, the parameter
 659         // is ignored on Linux which means the yield didn't scale up. Waiting
 660         // on the SR_lock below provides a much more predictable scale up for
 661         // the delay. It also provides a simple/direct point to check for any
 662         // safepoint requests from the VMThread
 663 
 664         // temporarily drops SR_lock while doing wait with safepoint check
 665         // (if we're a JavaThread - the WatcherThread can also call this)
 666         // and increase delay with each retry
 667         SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 668 
 669         // check the actual thread state instead of what we saved above
 670         if (thread_state() != _thread_in_native_trans) {
 671           // the thread has transitioned to another thread state so
 672           // try all the checks (except this one) one more time.
 673           do_trans_retry = true;
 674           break;
 675         }
 676       } // end retry loop
 677 
 678 
 679     }
 680   } while (do_trans_retry);
 681 
 682   *bits |= 0x00000010;
 683   return false;
 684 }
 685 
 686 // Wait for an external suspend request to complete (or be cancelled).
 687 // Returns true if the thread is externally suspended and false otherwise.
 688 //
 689 bool JavaThread::wait_for_ext_suspend_completion(int retries, int delay,
 690                                                  uint32_t *bits) {
 691   TraceSuspendDebugBits tsdb(this, true /* is_wait */,
 692                              false /* !called_by_wait */, bits);
 693 
 694   // local flag copies to minimize SR_lock hold time
 695   bool is_suspended;
 696   bool pending;
 697   uint32_t reset_bits;
 698 
 699   // set a marker so is_ext_suspend_completed() knows we are the caller
 700   *bits |= 0x00010000;
 701 
 702   // We use reset_bits to reinitialize the bits value at the top of
 703   // each retry loop. This allows the caller to make use of any
 704   // unused bits for their own marking purposes.
 705   reset_bits = *bits;
 706 
 707   {
 708     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 709     is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 710                                             delay, bits);
 711     pending = is_external_suspend();
 712   }
 713   // must release SR_lock to allow suspension to complete
 714 
 715   if (!pending) {
 716     // A cancelled suspend request is the only false return from
 717     // is_ext_suspend_completed() that keeps us from entering the
 718     // retry loop.
 719     *bits |= 0x00020000;
 720     return false;
 721   }
 722 
 723   if (is_suspended) {
 724     *bits |= 0x00040000;
 725     return true;
 726   }
 727 
 728   for (int i = 1; i <= retries; i++) {
 729     *bits = reset_bits;  // reinit to only track last retry
 730 
 731     // We used to do an "os::yield_all(i)" call here with the intention
 732     // that yielding would increase on each retry. However, the parameter
 733     // is ignored on Linux which means the yield didn't scale up. Waiting
 734     // on the SR_lock below provides a much more predictable scale up for
 735     // the delay. It also provides a simple/direct point to check for any
 736     // safepoint requests from the VMThread
 737 
 738     {
 739       MutexLocker ml(SR_lock());
 740       // wait with safepoint check (if we're a JavaThread - the WatcherThread
 741       // can also call this)  and increase delay with each retry
 742       SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 743 
 744       is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 745                                               delay, bits);
 746 
 747       // It is possible for the external suspend request to be cancelled
 748       // (by a resume) before the actual suspend operation is completed.
 749       // Refresh our local copy to see if we still need to wait.
 750       pending = is_external_suspend();
 751     }
 752 
 753     if (!pending) {
 754       // A cancelled suspend request is the only false return from
 755       // is_ext_suspend_completed() that keeps us from staying in the
 756       // retry loop.
 757       *bits |= 0x00080000;
 758       return false;
 759     }
 760 
 761     if (is_suspended) {
 762       *bits |= 0x00100000;
 763       return true;
 764     }
 765   } // end retry loop
 766 
 767   // thread did not suspend after all our retries
 768   *bits |= 0x00200000;
 769   return false;
 770 }
 771 
 772 // Called from API entry points which perform stack walking. If the
 773 // associated JavaThread is the current thread, then wait_for_suspend
 774 // is not used. Otherwise, it determines if we should wait for the
 775 // "other" thread to complete external suspension. (NOTE: in future
 776 // releases the suspension mechanism should be reimplemented so this
 777 // is not necessary.)
 778 //
 779 bool
 780 JavaThread::is_thread_fully_suspended(bool wait_for_suspend, uint32_t *bits) {
 781   if (this != JavaThread::current()) {
 782     // "other" threads require special handling.
 783     if (wait_for_suspend) {
 784       // We are allowed to wait for the external suspend to complete
 785       // so give the other thread a chance to get suspended.
 786       if (!wait_for_ext_suspend_completion(SuspendRetryCount,
 787                                            SuspendRetryDelay, bits)) {
 788         // Didn't make it so let the caller know.
 789         return false;
 790       }
 791     }
 792     // We aren't allowed to wait for the external suspend to complete
 793     // so if the other thread isn't externally suspended we need to
 794     // let the caller know.
 795     else if (!is_ext_suspend_completed_with_lock(bits)) {
 796       return false;
 797     }
 798   }
 799 
 800   return true;
 801 }
 802 
 803 #ifndef PRODUCT
 804 void JavaThread::record_jump(address target, address instr, const char* file,
 805                              int line) {
 806 
 807   // This should not need to be atomic as the only way for simultaneous
 808   // updates is via interrupts. Even then this should be rare or non-existent
 809   // and we don't care that much anyway.
 810 
 811   int index = _jmp_ring_index;
 812   _jmp_ring_index = (index + 1) & (jump_ring_buffer_size - 1);
 813   _jmp_ring[index]._target = (intptr_t) target;
 814   _jmp_ring[index]._instruction = (intptr_t) instr;
 815   _jmp_ring[index]._file = file;
 816   _jmp_ring[index]._line = line;
 817 }
 818 #endif // PRODUCT
 819 
 820 void Thread::interrupt(Thread* thread) {
 821   debug_only(check_for_dangling_thread_pointer(thread);)
 822   os::interrupt(thread);
 823 }
 824 
 825 bool Thread::is_interrupted(Thread* thread, bool clear_interrupted) {
 826   debug_only(check_for_dangling_thread_pointer(thread);)
 827   // Note:  If clear_interrupted==false, this simply fetches and
 828   // returns the value of the field osthread()->interrupted().
 829   return os::is_interrupted(thread, clear_interrupted);
 830 }
 831 
 832 
 833 // GC Support
 834 bool Thread::claim_oops_do_par_case(int strong_roots_parity) {
 835   int thread_parity = _oops_do_parity;
 836   if (thread_parity != strong_roots_parity) {
 837     jint res = Atomic::cmpxchg(strong_roots_parity, &_oops_do_parity, thread_parity);
 838     if (res == thread_parity) {
 839       return true;
 840     } else {
 841       guarantee(res == strong_roots_parity, "Or else what?");
 842       return false;
 843     }
 844   }
 845   return false;
 846 }
 847 
 848 void Thread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
 849   active_handles()->oops_do(f);
 850   // Do oop for ThreadShadow
 851   f->do_oop((oop*)&_pending_exception);
 852   handle_area()->oops_do(f);
 853 
 854   if (MonitorInUseLists) {
 855     // When using thread local monitor lists, we scan them here,
 856     // and the remaining global monitors in ObjectSynchronizer::oops_do().
 857     ObjectSynchronizer::thread_local_used_oops_do(this, f);
 858   }
 859 }
 860 
 861 void Thread::metadata_handles_do(void f(Metadata*)) {
 862   // Only walk the Handles in Thread.
 863   if (metadata_handles() != NULL) {
 864     for (int i = 0; i< metadata_handles()->length(); i++) {
 865       f(metadata_handles()->at(i));
 866     }
 867   }
 868 }
 869 
 870 void Thread::print_on(outputStream* st, bool print_extended_info) const {
 871   // get_priority assumes osthread initialized
 872   if (osthread() != NULL) {
 873     int os_prio;
 874     if (os::get_native_priority(this, &os_prio) == OS_OK) {
 875       st->print("os_prio=%d ", os_prio);
 876     }
 877 
 878     st->print("cpu=%.2fms ",
 879               os::thread_cpu_time(const_cast<Thread*>(this), true) / 1000000.0
 880               );
 881     st->print("elapsed=%.2fs ",
 882               _statistical_info.getElapsedTime() / 1000.0
 883               );
 884     if (is_Java_thread() && (PrintExtendedThreadInfo || print_extended_info)) {
 885       size_t allocated_bytes = (size_t) const_cast<Thread*>(this)->cooked_allocated_bytes();
 886       st->print("allocated=" SIZE_FORMAT "%s ",
 887                 byte_size_in_proper_unit(allocated_bytes),
 888                 proper_unit_for_byte_size(allocated_bytes)
 889                 );
 890       st->print("defined_classes=" INT64_FORMAT " ", _statistical_info.getDefineClassCount());
 891     }
 892 
 893     st->print("tid=" INTPTR_FORMAT " ", p2i(this));
 894     osthread()->print_on(st);
 895   }
 896   ThreadsSMRSupport::print_info_on(this, st);
 897   st->print(" ");
 898   debug_only(if (WizardMode) print_owned_locks_on(st);)
 899 }
 900 
 901 // Thread::print_on_error() is called by fatal error handler. Don't use
 902 // any lock or allocate memory.
 903 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
 904   assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
 905 
 906   if (is_VM_thread())                 { st->print("VMThread"); }
 907   else if (is_GC_task_thread())       { st->print("GCTaskThread"); }
 908   else if (is_Watcher_thread())       { st->print("WatcherThread"); }
 909   else if (is_ConcurrentGC_thread())  { st->print("ConcurrentGCThread"); }
 910   else                                { st->print("Thread"); }
 911 
 912   if (is_Named_thread()) {
 913     st->print(" \"%s\"", name());
 914   }
 915 
 916   st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
 917             p2i(stack_end()), p2i(stack_base()));
 918 
 919   if (osthread()) {
 920     st->print(" [id=%d]", osthread()->thread_id());
 921   }
 922 
 923   ThreadsSMRSupport::print_info_on(this, st);
 924 }
 925 
 926 void Thread::print_value_on(outputStream* st) const {
 927   if (is_Named_thread()) {
 928     st->print(" \"%s\" ", name());
 929   }
 930   st->print(INTPTR_FORMAT, p2i(this));   // print address
 931 }
 932 
 933 #ifdef ASSERT
 934 void Thread::print_owned_locks_on(outputStream* st) const {
 935   Monitor *cur = _owned_locks;
 936   if (cur == NULL) {
 937     st->print(" (no locks) ");
 938   } else {
 939     st->print_cr(" Locks owned:");
 940     while (cur) {
 941       cur->print_on(st);
 942       cur = cur->next();
 943     }
 944   }
 945 }
 946 
 947 static int ref_use_count  = 0;
 948 
 949 bool Thread::owns_locks_but_compiled_lock() const {
 950   for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 951     if (cur != Compile_lock) return true;
 952   }
 953   return false;
 954 }
 955 
 956 
 957 #endif
 958 
 959 #ifndef PRODUCT
 960 
 961 // The flag: potential_vm_operation notifies if this particular safepoint state could potentially
 962 // invoke the vm-thread (e.g., an oop allocation). In that case, we also have to make sure that
 963 // no locks which allow_vm_block's are held
 964 void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) {
 965   // Check if current thread is allowed to block at a safepoint
 966   if (!(_allow_safepoint_count == 0)) {
 967     fatal("Possible safepoint reached by thread that does not allow it");
 968   }
 969   if (is_Java_thread() && ((JavaThread*)this)->thread_state() != _thread_in_vm) {
 970     fatal("LEAF method calling lock?");
 971   }
 972 
 973 #ifdef ASSERT
 974   if (potential_vm_operation && is_Java_thread()
 975       && !Universe::is_bootstrapping()) {
 976     // Make sure we do not hold any locks that the VM thread also uses.
 977     // This could potentially lead to deadlocks
 978     for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 979       // Threads_lock is special, since the safepoint synchronization will not start before this is
 980       // acquired. Hence, a JavaThread cannot be holding it at a safepoint. So is VMOperationRequest_lock,
 981       // since it is used to transfer control between JavaThreads and the VMThread
 982       // Do not *exclude* any locks unless you are absolutely sure it is correct. Ask someone else first!
 983       if ((cur->allow_vm_block() &&
 984            cur != Threads_lock &&
 985            cur != Compile_lock &&               // Temporary: should not be necessary when we get separate compilation
 986            cur != VMOperationRequest_lock &&
 987            cur != VMOperationQueue_lock) ||
 988            cur->rank() == Mutex::special) {
 989         fatal("Thread holding lock at safepoint that vm can block on: %s", cur->name());
 990       }
 991     }
 992   }
 993 
 994   if (GCALotAtAllSafepoints) {
 995     // We could enter a safepoint here and thus have a gc
 996     InterfaceSupport::check_gc_alot();
 997   }
 998 #endif
 999 }
1000 #endif
1001 
1002 bool Thread::is_in_stack(address adr) const {
1003   assert(Thread::current() == this, "is_in_stack can only be called from current thread");
1004   address end = os::current_stack_pointer();
1005   // Allow non Java threads to call this without stack_base
1006   if (_stack_base == NULL) return true;
1007   if (stack_base() >= adr && adr >= end) return true;
1008 
1009   return false;
1010 }
1011 
1012 bool Thread::is_in_usable_stack(address adr) const {
1013   size_t stack_guard_size = os::uses_stack_guard_pages() ? JavaThread::stack_guard_zone_size() : 0;
1014   size_t usable_stack_size = _stack_size - stack_guard_size;
1015 
1016   return ((adr < stack_base()) && (adr >= stack_base() - usable_stack_size));
1017 }
1018 
1019 
1020 // We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
1021 // However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
1022 // used for compilation in the future. If that change is made, the need for these methods
1023 // should be revisited, and they should be removed if possible.
1024 
1025 bool Thread::is_lock_owned(address adr) const {
1026   return on_local_stack(adr);
1027 }
1028 
1029 bool Thread::set_as_starting_thread() {
1030   // NOTE: this must be called inside the main thread.
1031   return os::create_main_thread((JavaThread*)this);
1032 }
1033 
1034 static void initialize_class(Symbol* class_name, TRAPS) {
1035   Klass* klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
1036   InstanceKlass::cast(klass)->initialize(CHECK);
1037 }
1038 
1039 
1040 // Creates the initial ThreadGroup
1041 static Handle create_initial_thread_group(TRAPS) {
1042   Handle system_instance = JavaCalls::construct_new_instance(
1043                             SystemDictionary::ThreadGroup_klass(),
1044                             vmSymbols::void_method_signature(),
1045                             CHECK_NH);
1046   Universe::set_system_thread_group(system_instance());
1047 
1048   Handle string = java_lang_String::create_from_str("main", CHECK_NH);
1049   Handle main_instance = JavaCalls::construct_new_instance(
1050                             SystemDictionary::ThreadGroup_klass(),
1051                             vmSymbols::threadgroup_string_void_signature(),
1052                             system_instance,
1053                             string,
1054                             CHECK_NH);
1055   return main_instance;
1056 }
1057 
1058 // Creates the initial Thread
1059 static oop create_initial_thread(Handle thread_group, JavaThread* thread,
1060                                  TRAPS) {
1061   InstanceKlass* ik = SystemDictionary::Thread_klass();
1062   assert(ik->is_initialized(), "must be");
1063   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK_NULL);
1064 
1065   // Cannot use JavaCalls::construct_new_instance because the java.lang.Thread
1066   // constructor calls Thread.current(), which must be set here for the
1067   // initial thread.
1068   java_lang_Thread::set_thread(thread_oop(), thread);
1069   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1070   thread->set_threadObj(thread_oop());
1071 
1072   Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
1073 
1074   JavaValue result(T_VOID);
1075   JavaCalls::call_special(&result, thread_oop,
1076                           ik,
1077                           vmSymbols::object_initializer_name(),
1078                           vmSymbols::threadgroup_string_void_signature(),
1079                           thread_group,
1080                           string,
1081                           CHECK_NULL);
1082   return thread_oop();
1083 }
1084 
1085 char java_runtime_name[128] = "";
1086 char java_runtime_version[128] = "";
1087 
1088 // extract the JRE name from java.lang.VersionProps.java_runtime_name
1089 static const char* get_java_runtime_name(TRAPS) {
1090   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1091                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1092   fieldDescriptor fd;
1093   bool found = k != NULL &&
1094                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_name_name(),
1095                                                         vmSymbols::string_signature(), &fd);
1096   if (found) {
1097     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1098     if (name_oop == NULL) {
1099       return NULL;
1100     }
1101     const char* name = java_lang_String::as_utf8_string(name_oop,
1102                                                         java_runtime_name,
1103                                                         sizeof(java_runtime_name));
1104     return name;
1105   } else {
1106     return NULL;
1107   }
1108 }
1109 
1110 // extract the JRE version from java.lang.VersionProps.java_runtime_version
1111 static const char* get_java_runtime_version(TRAPS) {
1112   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1113                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1114   fieldDescriptor fd;
1115   bool found = k != NULL &&
1116                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_version_name(),
1117                                                         vmSymbols::string_signature(), &fd);
1118   if (found) {
1119     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1120     if (name_oop == NULL) {
1121       return NULL;
1122     }
1123     const char* name = java_lang_String::as_utf8_string(name_oop,
1124                                                         java_runtime_version,
1125                                                         sizeof(java_runtime_version));
1126     return name;
1127   } else {
1128     return NULL;
1129   }
1130 }
1131 
1132 // General purpose hook into Java code, run once when the VM is initialized.
1133 // The Java library method itself may be changed independently from the VM.
1134 static void call_postVMInitHook(TRAPS) {
1135   Klass* klass = SystemDictionary::resolve_or_null(vmSymbols::jdk_internal_vm_PostVMInitHook(), THREAD);
1136   if (klass != NULL) {
1137     JavaValue result(T_VOID);
1138     JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
1139                            vmSymbols::void_method_signature(),
1140                            CHECK);
1141   }
1142 }
1143 
1144 void JavaThread::allocate_threadObj(Handle thread_group, const char* thread_name,
1145                                     bool daemon, TRAPS) {
1146   assert(thread_group.not_null(), "thread group should be specified");
1147   assert(threadObj() == NULL, "should only create Java thread object once");
1148 
1149   InstanceKlass* ik = SystemDictionary::Thread_klass();
1150   assert(ik->is_initialized(), "must be");
1151   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK);
1152 
1153   // We are called from jni_AttachCurrentThread/jni_AttachCurrentThreadAsDaemon.
1154   // We cannot use JavaCalls::construct_new_instance because the java.lang.Thread
1155   // constructor calls Thread.current(), which must be set here.
1156   java_lang_Thread::set_thread(thread_oop(), this);
1157   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1158   set_threadObj(thread_oop());
1159 
1160   JavaValue result(T_VOID);
1161   if (thread_name != NULL) {
1162     Handle name = java_lang_String::create_from_str(thread_name, CHECK);
1163     // Thread gets assigned specified name and null target
1164     JavaCalls::call_special(&result,
1165                             thread_oop,
1166                             ik,
1167                             vmSymbols::object_initializer_name(),
1168                             vmSymbols::threadgroup_string_void_signature(),
1169                             thread_group,
1170                             name,
1171                             THREAD);
1172   } else {
1173     // Thread gets assigned name "Thread-nnn" and null target
1174     // (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
1175     JavaCalls::call_special(&result,
1176                             thread_oop,
1177                             ik,
1178                             vmSymbols::object_initializer_name(),
1179                             vmSymbols::threadgroup_runnable_void_signature(),
1180                             thread_group,
1181                             Handle(),
1182                             THREAD);
1183   }
1184 
1185 
1186   if (daemon) {
1187     java_lang_Thread::set_daemon(thread_oop());
1188   }
1189 
1190   if (HAS_PENDING_EXCEPTION) {
1191     return;
1192   }
1193 
1194   Klass* group =  SystemDictionary::ThreadGroup_klass();
1195   Handle threadObj(THREAD, this->threadObj());
1196 
1197   JavaCalls::call_special(&result,
1198                           thread_group,
1199                           group,
1200                           vmSymbols::add_method_name(),
1201                           vmSymbols::thread_void_signature(),
1202                           threadObj,          // Arg 1
1203                           THREAD);
1204 }
1205 
1206 // List of all NonJavaThreads and safe iteration over that list.
1207 
1208 class NonJavaThread::List {
1209 public:
1210   NonJavaThread* volatile _head;
1211   SingleWriterSynchronizer _protect;
1212 
1213   List() : _head(NULL), _protect() {}
1214 };
1215 
1216 NonJavaThread::List NonJavaThread::_the_list;
1217 
1218 NonJavaThread::Iterator::Iterator() :
1219   _protect_enter(_the_list._protect.enter()),
1220   _current(OrderAccess::load_acquire(&_the_list._head))
1221 {}
1222 
1223 NonJavaThread::Iterator::~Iterator() {
1224   _the_list._protect.exit(_protect_enter);
1225 }
1226 
1227 void NonJavaThread::Iterator::step() {
1228   assert(!end(), "precondition");
1229   _current = OrderAccess::load_acquire(&_current->_next);
1230 }
1231 
1232 NonJavaThread::NonJavaThread() : Thread(), _next(NULL) {
1233   // Add this thread to _the_list.
1234   MutexLockerEx lock(NonJavaThreadsList_lock, Mutex::_no_safepoint_check_flag);
1235   _next = _the_list._head;
1236   OrderAccess::release_store(&_the_list._head, this);
1237 }
1238 
1239 NonJavaThread::~NonJavaThread() {
1240   // Remove this thread from _the_list.
1241   MutexLockerEx lock(NonJavaThreadsList_lock, Mutex::_no_safepoint_check_flag);
1242   NonJavaThread* volatile* p = &_the_list._head;
1243   for (NonJavaThread* t = *p; t != NULL; p = &t->_next, t = *p) {
1244     if (t == this) {
1245       *p = this->_next;
1246       // Wait for any in-progress iterators.
1247       _the_list._protect.synchronize();
1248       break;
1249     }
1250   }
1251 }
1252 
1253 // NamedThread --  non-JavaThread subclasses with multiple
1254 // uniquely named instances should derive from this.
1255 NamedThread::NamedThread() :
1256   NonJavaThread(),
1257   _name(NULL),
1258   _processed_thread(NULL),
1259   _gc_id(GCId::undefined())
1260 {}
1261 
1262 NamedThread::~NamedThread() {
1263   if (_name != NULL) {
1264     FREE_C_HEAP_ARRAY(char, _name);
1265     _name = NULL;
1266   }
1267 }
1268 
1269 void NamedThread::set_name(const char* format, ...) {
1270   guarantee(_name == NULL, "Only get to set name once.");
1271   _name = NEW_C_HEAP_ARRAY(char, max_name_len, mtThread);
1272   guarantee(_name != NULL, "alloc failure");
1273   va_list ap;
1274   va_start(ap, format);
1275   jio_vsnprintf(_name, max_name_len, format, ap);
1276   va_end(ap);
1277 }
1278 
1279 void NamedThread::initialize_named_thread() {
1280   set_native_thread_name(name());
1281 }
1282 
1283 void NamedThread::print_on(outputStream* st) const {
1284   st->print("\"%s\" ", name());
1285   Thread::print_on(st);
1286   st->cr();
1287 }
1288 
1289 
1290 // ======= WatcherThread ========
1291 
1292 // The watcher thread exists to simulate timer interrupts.  It should
1293 // be replaced by an abstraction over whatever native support for
1294 // timer interrupts exists on the platform.
1295 
1296 WatcherThread* WatcherThread::_watcher_thread   = NULL;
1297 bool WatcherThread::_startable = false;
1298 volatile bool  WatcherThread::_should_terminate = false;
1299 
1300 WatcherThread::WatcherThread() : NonJavaThread() {
1301   assert(watcher_thread() == NULL, "we can only allocate one WatcherThread");
1302   if (os::create_thread(this, os::watcher_thread)) {
1303     _watcher_thread = this;
1304 
1305     // Set the watcher thread to the highest OS priority which should not be
1306     // used, unless a Java thread with priority java.lang.Thread.MAX_PRIORITY
1307     // is created. The only normal thread using this priority is the reference
1308     // handler thread, which runs for very short intervals only.
1309     // If the VMThread's priority is not lower than the WatcherThread profiling
1310     // will be inaccurate.
1311     os::set_priority(this, MaxPriority);
1312     if (!DisableStartThread) {
1313       os::start_thread(this);
1314     }
1315   }
1316 }
1317 
1318 int WatcherThread::sleep() const {
1319   // The WatcherThread does not participate in the safepoint protocol
1320   // for the PeriodicTask_lock because it is not a JavaThread.
1321   MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
1322 
1323   if (_should_terminate) {
1324     // check for termination before we do any housekeeping or wait
1325     return 0;  // we did not sleep.
1326   }
1327 
1328   // remaining will be zero if there are no tasks,
1329   // causing the WatcherThread to sleep until a task is
1330   // enrolled
1331   int remaining = PeriodicTask::time_to_wait();
1332   int time_slept = 0;
1333 
1334   // we expect this to timeout - we only ever get unparked when
1335   // we should terminate or when a new task has been enrolled
1336   OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
1337 
1338   jlong time_before_loop = os::javaTimeNanos();
1339 
1340   while (true) {
1341     bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag,
1342                                             remaining);
1343     jlong now = os::javaTimeNanos();
1344 
1345     if (remaining == 0) {
1346       // if we didn't have any tasks we could have waited for a long time
1347       // consider the time_slept zero and reset time_before_loop
1348       time_slept = 0;
1349       time_before_loop = now;
1350     } else {
1351       // need to recalculate since we might have new tasks in _tasks
1352       time_slept = (int) ((now - time_before_loop) / 1000000);
1353     }
1354 
1355     // Change to task list or spurious wakeup of some kind
1356     if (timedout || _should_terminate) {
1357       break;
1358     }
1359 
1360     remaining = PeriodicTask::time_to_wait();
1361     if (remaining == 0) {
1362       // Last task was just disenrolled so loop around and wait until
1363       // another task gets enrolled
1364       continue;
1365     }
1366 
1367     remaining -= time_slept;
1368     if (remaining <= 0) {
1369       break;
1370     }
1371   }
1372 
1373   return time_slept;
1374 }
1375 
1376 void WatcherThread::run() {
1377   assert(this == watcher_thread(), "just checking");
1378 
1379   this->record_stack_base_and_size();
1380   this->set_native_thread_name(this->name());
1381   this->set_active_handles(JNIHandleBlock::allocate_block());
1382   while (true) {
1383     assert(watcher_thread() == Thread::current(), "thread consistency check");
1384     assert(watcher_thread() == this, "thread consistency check");
1385 
1386     // Calculate how long it'll be until the next PeriodicTask work
1387     // should be done, and sleep that amount of time.
1388     int time_waited = sleep();
1389 
1390     if (VMError::is_error_reported()) {
1391       // A fatal error has happened, the error handler(VMError::report_and_die)
1392       // should abort JVM after creating an error log file. However in some
1393       // rare cases, the error handler itself might deadlock. Here periodically
1394       // check for error reporting timeouts, and if it happens, just proceed to
1395       // abort the VM.
1396 
1397       // This code is in WatcherThread because WatcherThread wakes up
1398       // periodically so the fatal error handler doesn't need to do anything;
1399       // also because the WatcherThread is less likely to crash than other
1400       // threads.
1401 
1402       for (;;) {
1403         // Note: we use naked sleep in this loop because we want to avoid using
1404         // any kind of VM infrastructure which may be broken at this point.
1405         if (VMError::check_timeout()) {
1406           // We hit error reporting timeout. Error reporting was interrupted and
1407           // will be wrapping things up now (closing files etc). Give it some more
1408           // time, then quit the VM.
1409           os::naked_short_sleep(200);
1410           // Print a message to stderr.
1411           fdStream err(defaultStream::output_fd());
1412           err.print_raw_cr("# [ timer expired, abort... ]");
1413           // skip atexit/vm_exit/vm_abort hooks
1414           os::die();
1415         }
1416 
1417         // Wait a second, then recheck for timeout.
1418         os::naked_short_sleep(999);
1419       }
1420     }
1421 
1422     if (_should_terminate) {
1423       // check for termination before posting the next tick
1424       break;
1425     }
1426 
1427     PeriodicTask::real_time_tick(time_waited);
1428   }
1429 
1430   // Signal that it is terminated
1431   {
1432     MutexLockerEx mu(Terminator_lock, Mutex::_no_safepoint_check_flag);
1433     _watcher_thread = NULL;
1434     Terminator_lock->notify();
1435   }
1436 }
1437 
1438 void WatcherThread::start() {
1439   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1440 
1441   if (watcher_thread() == NULL && _startable) {
1442     _should_terminate = false;
1443     // Create the single instance of WatcherThread
1444     new WatcherThread();
1445   }
1446 }
1447 
1448 void WatcherThread::make_startable() {
1449   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1450   _startable = true;
1451 }
1452 
1453 void WatcherThread::stop() {
1454   {
1455     // Follow normal safepoint aware lock enter protocol since the
1456     // WatcherThread is stopped by another JavaThread.
1457     MutexLocker ml(PeriodicTask_lock);
1458     _should_terminate = true;
1459 
1460     WatcherThread* watcher = watcher_thread();
1461     if (watcher != NULL) {
1462       // unpark the WatcherThread so it can see that it should terminate
1463       watcher->unpark();
1464     }
1465   }
1466 
1467   MutexLocker mu(Terminator_lock);
1468 
1469   while (watcher_thread() != NULL) {
1470     // This wait should make safepoint checks, wait without a timeout,
1471     // and wait as a suspend-equivalent condition.
1472     Terminator_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
1473                           Mutex::_as_suspend_equivalent_flag);
1474   }
1475 }
1476 
1477 void WatcherThread::unpark() {
1478   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1479   PeriodicTask_lock->notify();
1480 }
1481 
1482 void WatcherThread::print_on(outputStream* st) const {
1483   st->print("\"%s\" ", name());
1484   Thread::print_on(st);
1485   st->cr();
1486 }
1487 
1488 // ======= JavaThread ========
1489 
1490 #if INCLUDE_JVMCI
1491 
1492 jlong* JavaThread::_jvmci_old_thread_counters;
1493 
1494 bool jvmci_counters_include(JavaThread* thread) {
1495   return !JVMCICountersExcludeCompiler || !thread->is_Compiler_thread();
1496 }
1497 
1498 void JavaThread::collect_counters(typeArrayOop array) {
1499   if (JVMCICounterSize > 0) {
1500     JavaThreadIteratorWithHandle jtiwh;
1501     for (int i = 0; i < array->length(); i++) {
1502       array->long_at_put(i, _jvmci_old_thread_counters[i]);
1503     }
1504     for (; JavaThread *tp = jtiwh.next(); ) {
1505       if (jvmci_counters_include(tp)) {
1506         for (int i = 0; i < array->length(); i++) {
1507           array->long_at_put(i, array->long_at(i) + tp->_jvmci_counters[i]);
1508         }
1509       }
1510     }
1511   }
1512 }
1513 
1514 #endif // INCLUDE_JVMCI
1515 
1516 // A JavaThread is a normal Java thread
1517 
1518 void JavaThread::initialize() {
1519   // Initialize fields
1520 
1521   set_saved_exception_pc(NULL);
1522   set_threadObj(NULL);
1523   _anchor.clear();
1524   set_entry_point(NULL);
1525   set_jni_functions(jni_functions());
1526   set_callee_target(NULL);
1527   set_vm_result(NULL);
1528   set_vm_result_2(NULL);
1529   set_vframe_array_head(NULL);
1530   set_vframe_array_last(NULL);
1531   set_deferred_locals(NULL);
1532   set_deopt_mark(NULL);
1533   set_deopt_compiled_method(NULL);
1534   clear_must_deopt_id();
1535   set_monitor_chunks(NULL);
1536   set_next(NULL);
1537   _on_thread_list = false;
1538   set_thread_state(_thread_new);
1539   _terminated = _not_terminated;
1540   _privileged_stack_top = NULL;
1541   _array_for_gc = NULL;
1542   _suspend_equivalent = false;
1543   _in_deopt_handler = 0;
1544   _doing_unsafe_access = false;
1545   _stack_guard_state = stack_guard_unused;
1546 #if INCLUDE_JVMCI
1547   _pending_monitorenter = false;
1548   _pending_deoptimization = -1;
1549   _pending_failed_speculation = 0;
1550   _pending_transfer_to_interpreter = false;
1551   _adjusting_comp_level = false;
1552   _jvmci._alternate_call_target = NULL;
1553   assert(_jvmci._implicit_exception_pc == NULL, "must be");
1554   if (JVMCICounterSize > 0) {
1555     _jvmci_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
1556     memset(_jvmci_counters, 0, sizeof(jlong) * JVMCICounterSize);
1557   } else {
1558     _jvmci_counters = NULL;
1559   }
1560 #endif // INCLUDE_JVMCI
1561   _reserved_stack_activation = NULL;  // stack base not known yet
1562   (void)const_cast<oop&>(_exception_oop = oop(NULL));
1563   _exception_pc  = 0;
1564   _exception_handler_pc = 0;
1565   _is_method_handle_return = 0;
1566   _jvmti_thread_state= NULL;
1567   _should_post_on_exceptions_flag = JNI_FALSE;
1568   _interp_only_mode    = 0;
1569   _special_runtime_exit_condition = _no_async_condition;
1570   _pending_async_exception = NULL;
1571   _thread_stat = NULL;
1572   _thread_stat = new ThreadStatistics();
1573   _blocked_on_compilation = false;
1574   _jni_active_critical = 0;
1575   _pending_jni_exception_check_fn = NULL;
1576   _do_not_unlock_if_synchronized = false;
1577   _cached_monitor_info = NULL;
1578   _parker = Parker::Allocate(this);
1579 
1580 #ifndef PRODUCT
1581   _jmp_ring_index = 0;
1582   for (int ji = 0; ji < jump_ring_buffer_size; ji++) {
1583     record_jump(NULL, NULL, NULL, 0);
1584   }
1585 #endif // PRODUCT
1586 
1587   // Setup safepoint state info for this thread
1588   ThreadSafepointState::create(this);
1589 
1590   debug_only(_java_call_counter = 0);
1591 
1592   // JVMTI PopFrame support
1593   _popframe_condition = popframe_inactive;
1594   _popframe_preserved_args = NULL;
1595   _popframe_preserved_args_size = 0;
1596   _frames_to_pop_failed_realloc = 0;
1597 
1598   if (SafepointMechanism::uses_thread_local_poll()) {
1599     SafepointMechanism::initialize_header(this);
1600   }
1601 
1602   pd_initialize();
1603 }
1604 
1605 JavaThread::JavaThread(bool is_attaching_via_jni) :
1606                        Thread() {
1607   initialize();
1608   if (is_attaching_via_jni) {
1609     _jni_attach_state = _attaching_via_jni;
1610   } else {
1611     _jni_attach_state = _not_attaching_via_jni;
1612   }
1613   assert(deferred_card_mark().is_empty(), "Default MemRegion ctor");
1614 }
1615 
1616 bool JavaThread::reguard_stack(address cur_sp) {
1617   if (_stack_guard_state != stack_guard_yellow_reserved_disabled
1618       && _stack_guard_state != stack_guard_reserved_disabled) {
1619     return true; // Stack already guarded or guard pages not needed.
1620   }
1621 
1622   if (register_stack_overflow()) {
1623     // For those architectures which have separate register and
1624     // memory stacks, we must check the register stack to see if
1625     // it has overflowed.
1626     return false;
1627   }
1628 
1629   // Java code never executes within the yellow zone: the latter is only
1630   // there to provoke an exception during stack banging.  If java code
1631   // is executing there, either StackShadowPages should be larger, or
1632   // some exception code in c1, c2 or the interpreter isn't unwinding
1633   // when it should.
1634   guarantee(cur_sp > stack_reserved_zone_base(),
1635             "not enough space to reguard - increase StackShadowPages");
1636   if (_stack_guard_state == stack_guard_yellow_reserved_disabled) {
1637     enable_stack_yellow_reserved_zone();
1638     if (reserved_stack_activation() != stack_base()) {
1639       set_reserved_stack_activation(stack_base());
1640     }
1641   } else if (_stack_guard_state == stack_guard_reserved_disabled) {
1642     set_reserved_stack_activation(stack_base());
1643     enable_stack_reserved_zone();
1644   }
1645   return true;
1646 }
1647 
1648 bool JavaThread::reguard_stack(void) {
1649   return reguard_stack(os::current_stack_pointer());
1650 }
1651 
1652 
1653 void JavaThread::block_if_vm_exited() {
1654   if (_terminated == _vm_exited) {
1655     // _vm_exited is set at safepoint, and Threads_lock is never released
1656     // we will block here forever
1657     Threads_lock->lock_without_safepoint_check();
1658     ShouldNotReachHere();
1659   }
1660 }
1661 
1662 
1663 // Remove this ifdef when C1 is ported to the compiler interface.
1664 static void compiler_thread_entry(JavaThread* thread, TRAPS);
1665 static void sweeper_thread_entry(JavaThread* thread, TRAPS);
1666 
1667 JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
1668                        Thread() {
1669   initialize();
1670   _jni_attach_state = _not_attaching_via_jni;
1671   set_entry_point(entry_point);
1672   // Create the native thread itself.
1673   // %note runtime_23
1674   os::ThreadType thr_type = os::java_thread;
1675   thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
1676                                                      os::java_thread;
1677   os::create_thread(this, thr_type, stack_sz);
1678   // The _osthread may be NULL here because we ran out of memory (too many threads active).
1679   // We need to throw and OutOfMemoryError - however we cannot do this here because the caller
1680   // may hold a lock and all locks must be unlocked before throwing the exception (throwing
1681   // the exception consists of creating the exception object & initializing it, initialization
1682   // will leave the VM via a JavaCall and then all locks must be unlocked).
1683   //
1684   // The thread is still suspended when we reach here. Thread must be explicit started
1685   // by creator! Furthermore, the thread must also explicitly be added to the Threads list
1686   // by calling Threads:add. The reason why this is not done here, is because the thread
1687   // object must be fully initialized (take a look at JVM_Start)
1688 }
1689 
1690 JavaThread::~JavaThread() {
1691 
1692   // JSR166 -- return the parker to the free list
1693   Parker::Release(_parker);
1694   _parker = NULL;
1695 
1696   // Free any remaining  previous UnrollBlock
1697   vframeArray* old_array = vframe_array_last();
1698 
1699   if (old_array != NULL) {
1700     Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
1701     old_array->set_unroll_block(NULL);
1702     delete old_info;
1703     delete old_array;
1704   }
1705 
1706   GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred = deferred_locals();
1707   if (deferred != NULL) {
1708     // This can only happen if thread is destroyed before deoptimization occurs.
1709     assert(deferred->length() != 0, "empty array!");
1710     do {
1711       jvmtiDeferredLocalVariableSet* dlv = deferred->at(0);
1712       deferred->remove_at(0);
1713       // individual jvmtiDeferredLocalVariableSet are CHeapObj's
1714       delete dlv;
1715     } while (deferred->length() != 0);
1716     delete deferred;
1717   }
1718 
1719   // All Java related clean up happens in exit
1720   ThreadSafepointState::destroy(this);
1721   if (_thread_stat != NULL) delete _thread_stat;
1722 
1723 #if INCLUDE_JVMCI
1724   if (JVMCICounterSize > 0) {
1725     if (jvmci_counters_include(this)) {
1726       for (int i = 0; i < JVMCICounterSize; i++) {
1727         _jvmci_old_thread_counters[i] += _jvmci_counters[i];
1728       }
1729     }
1730     FREE_C_HEAP_ARRAY(jlong, _jvmci_counters);
1731   }
1732 #endif // INCLUDE_JVMCI
1733 }
1734 
1735 
1736 // The first routine called by a new Java thread
1737 void JavaThread::run() {
1738   // initialize thread-local alloc buffer related fields
1739   this->initialize_tlab();
1740 
1741   // used to test validity of stack trace backs
1742   this->record_base_of_stack_pointer();
1743 
1744   // Record real stack base and size.
1745   this->record_stack_base_and_size();
1746 
1747   this->create_stack_guard_pages();
1748 
1749   this->cache_global_variables();
1750 
1751   // Thread is now sufficient initialized to be handled by the safepoint code as being
1752   // in the VM. Change thread state from _thread_new to _thread_in_vm
1753   ThreadStateTransition::transition_and_fence(this, _thread_new, _thread_in_vm);
1754 
1755   assert(JavaThread::current() == this, "sanity check");
1756   assert(!Thread::current()->owns_locks(), "sanity check");
1757 
1758   DTRACE_THREAD_PROBE(start, this);
1759 
1760   // This operation might block. We call that after all safepoint checks for a new thread has
1761   // been completed.
1762   this->set_active_handles(JNIHandleBlock::allocate_block());
1763 
1764   if (JvmtiExport::should_post_thread_life()) {
1765     JvmtiExport::post_thread_start(this);
1766   }
1767 
1768   EventThreadStart event;
1769   if (event.should_commit()) {
1770     event.set_thread(JFR_THREAD_ID(this));
1771     event.commit();
1772   }
1773 
1774   // We call another function to do the rest so we are sure that the stack addresses used
1775   // from there will be lower than the stack base just computed
1776   thread_main_inner();
1777 
1778   // Note, thread is no longer valid at this point!
1779 }
1780 
1781 
1782 void JavaThread::thread_main_inner() {
1783   assert(JavaThread::current() == this, "sanity check");
1784   assert(this->threadObj() != NULL, "just checking");
1785 
1786   // Execute thread entry point unless this thread has a pending exception
1787   // or has been stopped before starting.
1788   // Note: Due to JVM_StopThread we can have pending exceptions already!
1789   if (!this->has_pending_exception() &&
1790       !java_lang_Thread::is_stillborn(this->threadObj())) {
1791     {
1792       ResourceMark rm(this);
1793       this->set_native_thread_name(this->get_thread_name());
1794     }
1795     HandleMark hm(this);
1796     this->entry_point()(this, this);
1797   }
1798 
1799   DTRACE_THREAD_PROBE(stop, this);
1800 
1801   this->exit(false);
1802   this->smr_delete();
1803 }
1804 
1805 
1806 static void ensure_join(JavaThread* thread) {
1807   // We do not need to grab the Threads_lock, since we are operating on ourself.
1808   Handle threadObj(thread, thread->threadObj());
1809   assert(threadObj.not_null(), "java thread object must exist");
1810   ObjectLocker lock(threadObj, thread);
1811   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1812   thread->clear_pending_exception();
1813   // Thread is exiting. So set thread_status field in  java.lang.Thread class to TERMINATED.
1814   java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
1815   // Clear the native thread instance - this makes isAlive return false and allows the join()
1816   // to complete once we've done the notify_all below
1817   java_lang_Thread::set_thread(threadObj(), NULL);
1818   lock.notify_all(thread);
1819   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1820   thread->clear_pending_exception();
1821 }
1822 
1823 
1824 // For any new cleanup additions, please check to see if they need to be applied to
1825 // cleanup_failed_attach_current_thread as well.
1826 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
1827   assert(this == JavaThread::current(), "thread consistency check");
1828 
1829   elapsedTimer _timer_exit_phase1;
1830   elapsedTimer _timer_exit_phase2;
1831   elapsedTimer _timer_exit_phase3;
1832   elapsedTimer _timer_exit_phase4;
1833 
1834   if (log_is_enabled(Debug, os, thread, timer)) {
1835     _timer_exit_phase1.start();
1836   }
1837 
1838   HandleMark hm(this);
1839   Handle uncaught_exception(this, this->pending_exception());
1840   this->clear_pending_exception();
1841   Handle threadObj(this, this->threadObj());
1842   assert(threadObj.not_null(), "Java thread object should be created");
1843 
1844   // FIXIT: This code should be moved into else part, when reliable 1.2/1.3 check is in place
1845   {
1846     EXCEPTION_MARK;
1847 
1848     CLEAR_PENDING_EXCEPTION;
1849   }
1850   if (!destroy_vm) {
1851     if (uncaught_exception.not_null()) {
1852       EXCEPTION_MARK;
1853       // Call method Thread.dispatchUncaughtException().
1854       Klass* thread_klass = SystemDictionary::Thread_klass();
1855       JavaValue result(T_VOID);
1856       JavaCalls::call_virtual(&result,
1857                               threadObj, thread_klass,
1858                               vmSymbols::dispatchUncaughtException_name(),
1859                               vmSymbols::throwable_void_signature(),
1860                               uncaught_exception,
1861                               THREAD);
1862       if (HAS_PENDING_EXCEPTION) {
1863         ResourceMark rm(this);
1864         jio_fprintf(defaultStream::error_stream(),
1865                     "\nException: %s thrown from the UncaughtExceptionHandler"
1866                     " in thread \"%s\"\n",
1867                     pending_exception()->klass()->external_name(),
1868                     get_thread_name());
1869         CLEAR_PENDING_EXCEPTION;
1870       }
1871     }
1872 
1873     // Called before the java thread exit since we want to read info
1874     // from java_lang_Thread object
1875     EventThreadEnd event;
1876     if (event.should_commit()) {
1877       event.set_thread(JFR_THREAD_ID(this));
1878       event.commit();
1879     }
1880 
1881     // Call after last event on thread
1882     JFR_ONLY(Jfr::on_thread_exit(this);)
1883 
1884     // Call Thread.exit(). We try 3 times in case we got another Thread.stop during
1885     // the execution of the method. If that is not enough, then we don't really care. Thread.stop
1886     // is deprecated anyhow.
1887     if (!is_Compiler_thread()) {
1888       int count = 3;
1889       while (java_lang_Thread::threadGroup(threadObj()) != NULL && (count-- > 0)) {
1890         EXCEPTION_MARK;
1891         JavaValue result(T_VOID);
1892         Klass* thread_klass = SystemDictionary::Thread_klass();
1893         JavaCalls::call_virtual(&result,
1894                                 threadObj, thread_klass,
1895                                 vmSymbols::exit_method_name(),
1896                                 vmSymbols::void_method_signature(),
1897                                 THREAD);
1898         CLEAR_PENDING_EXCEPTION;
1899       }
1900     }
1901     // notify JVMTI
1902     if (JvmtiExport::should_post_thread_life()) {
1903       JvmtiExport::post_thread_end(this);
1904     }
1905 
1906     // We have notified the agents that we are exiting, before we go on,
1907     // we must check for a pending external suspend request and honor it
1908     // in order to not surprise the thread that made the suspend request.
1909     while (true) {
1910       {
1911         MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
1912         if (!is_external_suspend()) {
1913           set_terminated(_thread_exiting);
1914           ThreadService::current_thread_exiting(this);
1915           break;
1916         }
1917         // Implied else:
1918         // Things get a little tricky here. We have a pending external
1919         // suspend request, but we are holding the SR_lock so we
1920         // can't just self-suspend. So we temporarily drop the lock
1921         // and then self-suspend.
1922       }
1923 
1924       ThreadBlockInVM tbivm(this);
1925       java_suspend_self();
1926 
1927       // We're done with this suspend request, but we have to loop around
1928       // and check again. Eventually we will get SR_lock without a pending
1929       // external suspend request and will be able to mark ourselves as
1930       // exiting.
1931     }
1932     // no more external suspends are allowed at this point
1933   } else {
1934     // before_exit() has already posted JVMTI THREAD_END events
1935   }
1936 
1937   if (log_is_enabled(Debug, os, thread, timer)) {
1938     _timer_exit_phase1.stop();
1939     _timer_exit_phase2.start();
1940   }
1941   // Notify waiters on thread object. This has to be done after exit() is called
1942   // on the thread (if the thread is the last thread in a daemon ThreadGroup the
1943   // group should have the destroyed bit set before waiters are notified).
1944   ensure_join(this);
1945   assert(!this->has_pending_exception(), "ensure_join should have cleared");
1946 
1947   if (log_is_enabled(Debug, os, thread, timer)) {
1948     _timer_exit_phase2.stop();
1949     _timer_exit_phase3.start();
1950   }
1951   // 6282335 JNI DetachCurrentThread spec states that all Java monitors
1952   // held by this thread must be released. The spec does not distinguish
1953   // between JNI-acquired and regular Java monitors. We can only see
1954   // regular Java monitors here if monitor enter-exit matching is broken.
1955   //
1956   // Optionally release any monitors for regular JavaThread exits. This
1957   // is provided as a work around for any bugs in monitor enter-exit
1958   // matching. This can be expensive so it is not enabled by default.
1959   //
1960   // ensure_join() ignores IllegalThreadStateExceptions, and so does
1961   // ObjectSynchronizer::release_monitors_owned_by_thread().
1962   if (exit_type == jni_detach) {
1963     // Sanity check even though JNI DetachCurrentThread() would have
1964     // returned JNI_ERR if there was a Java frame. JavaThread exit
1965     // should be done executing Java code by the time we get here.
1966     assert(!this->has_last_Java_frame(),
1967            "should not have a Java frame when detaching or exiting");
1968     ObjectSynchronizer::release_monitors_owned_by_thread(this);
1969     assert(!this->has_pending_exception(), "release_monitors should have cleared");
1970   }
1971 
1972   // These things needs to be done while we are still a Java Thread. Make sure that thread
1973   // is in a consistent state, in case GC happens
1974   assert(_privileged_stack_top == NULL, "must be NULL when we get here");
1975 
1976   if (active_handles() != NULL) {
1977     JNIHandleBlock* block = active_handles();
1978     set_active_handles(NULL);
1979     JNIHandleBlock::release_block(block);
1980   }
1981 
1982   if (free_handle_block() != NULL) {
1983     JNIHandleBlock* block = free_handle_block();
1984     set_free_handle_block(NULL);
1985     JNIHandleBlock::release_block(block);
1986   }
1987 
1988   // These have to be removed while this is still a valid thread.
1989   remove_stack_guard_pages();
1990 
1991   if (UseTLAB) {
1992     tlab().make_parsable(true);  // retire TLAB
1993   }
1994 
1995   if (JvmtiEnv::environments_might_exist()) {
1996     JvmtiExport::cleanup_thread(this);
1997   }
1998 
1999   // We must flush any deferred card marks and other various GC barrier
2000   // related buffers (e.g. G1 SATB buffer and G1 dirty card queue buffer)
2001   // before removing a thread from the list of active threads.
2002   BarrierSet::barrier_set()->on_thread_detach(this);
2003 
2004   log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").",
2005     exit_type == JavaThread::normal_exit ? "exiting" : "detaching",
2006     os::current_thread_id());
2007 
2008   if (log_is_enabled(Debug, os, thread, timer)) {
2009     _timer_exit_phase3.stop();
2010     _timer_exit_phase4.start();
2011   }
2012   // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
2013   Threads::remove(this);
2014 
2015   if (log_is_enabled(Debug, os, thread, timer)) {
2016     _timer_exit_phase4.stop();
2017     ResourceMark rm(this);
2018     log_debug(os, thread, timer)("name='%s'"
2019                                  ", exit-phase1=" JLONG_FORMAT
2020                                  ", exit-phase2=" JLONG_FORMAT
2021                                  ", exit-phase3=" JLONG_FORMAT
2022                                  ", exit-phase4=" JLONG_FORMAT,
2023                                  get_thread_name(),
2024                                  _timer_exit_phase1.milliseconds(),
2025                                  _timer_exit_phase2.milliseconds(),
2026                                  _timer_exit_phase3.milliseconds(),
2027                                  _timer_exit_phase4.milliseconds());
2028   }
2029 }
2030 
2031 void JavaThread::cleanup_failed_attach_current_thread() {
2032   if (active_handles() != NULL) {
2033     JNIHandleBlock* block = active_handles();
2034     set_active_handles(NULL);
2035     JNIHandleBlock::release_block(block);
2036   }
2037 
2038   if (free_handle_block() != NULL) {
2039     JNIHandleBlock* block = free_handle_block();
2040     set_free_handle_block(NULL);
2041     JNIHandleBlock::release_block(block);
2042   }
2043 
2044   // These have to be removed while this is still a valid thread.
2045   remove_stack_guard_pages();
2046 
2047   if (UseTLAB) {
2048     tlab().make_parsable(true);  // retire TLAB, if any
2049   }
2050 
2051   BarrierSet::barrier_set()->on_thread_detach(this);
2052 
2053   Threads::remove(this);
2054   this->smr_delete();
2055 }
2056 
2057 JavaThread* JavaThread::active() {
2058   Thread* thread = Thread::current();
2059   if (thread->is_Java_thread()) {
2060     return (JavaThread*) thread;
2061   } else {
2062     assert(thread->is_VM_thread(), "this must be a vm thread");
2063     VM_Operation* op = ((VMThread*) thread)->vm_operation();
2064     JavaThread *ret=op == NULL ? NULL : (JavaThread *)op->calling_thread();
2065     assert(ret->is_Java_thread(), "must be a Java thread");
2066     return ret;
2067   }
2068 }
2069 
2070 bool JavaThread::is_lock_owned(address adr) const {
2071   if (Thread::is_lock_owned(adr)) return true;
2072 
2073   for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2074     if (chunk->contains(adr)) return true;
2075   }
2076 
2077   return false;
2078 }
2079 
2080 
2081 void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
2082   chunk->set_next(monitor_chunks());
2083   set_monitor_chunks(chunk);
2084 }
2085 
2086 void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
2087   guarantee(monitor_chunks() != NULL, "must be non empty");
2088   if (monitor_chunks() == chunk) {
2089     set_monitor_chunks(chunk->next());
2090   } else {
2091     MonitorChunk* prev = monitor_chunks();
2092     while (prev->next() != chunk) prev = prev->next();
2093     prev->set_next(chunk->next());
2094   }
2095 }
2096 
2097 // JVM support.
2098 
2099 // Note: this function shouldn't block if it's called in
2100 // _thread_in_native_trans state (such as from
2101 // check_special_condition_for_native_trans()).
2102 void JavaThread::check_and_handle_async_exceptions(bool check_unsafe_error) {
2103 
2104   if (has_last_Java_frame() && has_async_condition()) {
2105     // If we are at a polling page safepoint (not a poll return)
2106     // then we must defer async exception because live registers
2107     // will be clobbered by the exception path. Poll return is
2108     // ok because the call we a returning from already collides
2109     // with exception handling registers and so there is no issue.
2110     // (The exception handling path kills call result registers but
2111     //  this is ok since the exception kills the result anyway).
2112 
2113     if (is_at_poll_safepoint()) {
2114       // if the code we are returning to has deoptimized we must defer
2115       // the exception otherwise live registers get clobbered on the
2116       // exception path before deoptimization is able to retrieve them.
2117       //
2118       RegisterMap map(this, false);
2119       frame caller_fr = last_frame().sender(&map);
2120       assert(caller_fr.is_compiled_frame(), "what?");
2121       if (caller_fr.is_deoptimized_frame()) {
2122         log_info(exceptions)("deferred async exception at compiled safepoint");
2123         return;
2124       }
2125     }
2126   }
2127 
2128   JavaThread::AsyncRequests condition = clear_special_runtime_exit_condition();
2129   if (condition == _no_async_condition) {
2130     // Conditions have changed since has_special_runtime_exit_condition()
2131     // was called:
2132     // - if we were here only because of an external suspend request,
2133     //   then that was taken care of above (or cancelled) so we are done
2134     // - if we were here because of another async request, then it has
2135     //   been cleared between the has_special_runtime_exit_condition()
2136     //   and now so again we are done
2137     return;
2138   }
2139 
2140   // Check for pending async. exception
2141   if (_pending_async_exception != NULL) {
2142     // Only overwrite an already pending exception, if it is not a threadDeath.
2143     if (!has_pending_exception() || !pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())) {
2144 
2145       // We cannot call Exceptions::_throw(...) here because we cannot block
2146       set_pending_exception(_pending_async_exception, __FILE__, __LINE__);
2147 
2148       LogTarget(Info, exceptions) lt;
2149       if (lt.is_enabled()) {
2150         ResourceMark rm;
2151         LogStream ls(lt);
2152         ls.print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", p2i(this));
2153           if (has_last_Java_frame()) {
2154             frame f = last_frame();
2155            ls.print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", p2i(f.pc()), p2i(f.sp()));
2156           }
2157         ls.print_cr(" of type: %s", _pending_async_exception->klass()->external_name());
2158       }
2159       _pending_async_exception = NULL;
2160       clear_has_async_exception();
2161     }
2162   }
2163 
2164   if (check_unsafe_error &&
2165       condition == _async_unsafe_access_error && !has_pending_exception()) {
2166     condition = _no_async_condition;  // done
2167     switch (thread_state()) {
2168     case _thread_in_vm: {
2169       JavaThread* THREAD = this;
2170       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2171     }
2172     case _thread_in_native: {
2173       ThreadInVMfromNative tiv(this);
2174       JavaThread* THREAD = this;
2175       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2176     }
2177     case _thread_in_Java: {
2178       ThreadInVMfromJava tiv(this);
2179       JavaThread* THREAD = this;
2180       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in a recent unsafe memory access operation in compiled Java code");
2181     }
2182     default:
2183       ShouldNotReachHere();
2184     }
2185   }
2186 
2187   assert(condition == _no_async_condition || has_pending_exception() ||
2188          (!check_unsafe_error && condition == _async_unsafe_access_error),
2189          "must have handled the async condition, if no exception");
2190 }
2191 
2192 void JavaThread::handle_special_runtime_exit_condition(bool check_asyncs) {
2193   //
2194   // Check for pending external suspend. Internal suspend requests do
2195   // not use handle_special_runtime_exit_condition().
2196   // If JNIEnv proxies are allowed, don't self-suspend if the target
2197   // thread is not the current thread. In older versions of jdbx, jdbx
2198   // threads could call into the VM with another thread's JNIEnv so we
2199   // can be here operating on behalf of a suspended thread (4432884).
2200   bool do_self_suspend = is_external_suspend_with_lock();
2201   if (do_self_suspend && (!AllowJNIEnvProxy || this == JavaThread::current())) {
2202     //
2203     // Because thread is external suspended the safepoint code will count
2204     // thread as at a safepoint. This can be odd because we can be here
2205     // as _thread_in_Java which would normally transition to _thread_blocked
2206     // at a safepoint. We would like to mark the thread as _thread_blocked
2207     // before calling java_suspend_self like all other callers of it but
2208     // we must then observe proper safepoint protocol. (We can't leave
2209     // _thread_blocked with a safepoint in progress). However we can be
2210     // here as _thread_in_native_trans so we can't use a normal transition
2211     // constructor/destructor pair because they assert on that type of
2212     // transition. We could do something like:
2213     //
2214     // JavaThreadState state = thread_state();
2215     // set_thread_state(_thread_in_vm);
2216     // {
2217     //   ThreadBlockInVM tbivm(this);
2218     //   java_suspend_self()
2219     // }
2220     // set_thread_state(_thread_in_vm_trans);
2221     // if (safepoint) block;
2222     // set_thread_state(state);
2223     //
2224     // but that is pretty messy. Instead we just go with the way the
2225     // code has worked before and note that this is the only path to
2226     // java_suspend_self that doesn't put the thread in _thread_blocked
2227     // mode.
2228 
2229     frame_anchor()->make_walkable(this);
2230     java_suspend_self();
2231 
2232     // We might be here for reasons in addition to the self-suspend request
2233     // so check for other async requests.
2234   }
2235 
2236   if (check_asyncs) {
2237     check_and_handle_async_exceptions();
2238   }
2239 
2240   JFR_ONLY(SUSPEND_THREAD_CONDITIONAL(this);)
2241 }
2242 
2243 void JavaThread::send_thread_stop(oop java_throwable)  {
2244   assert(Thread::current()->is_VM_thread(), "should be in the vm thread");
2245   assert(Threads_lock->is_locked(), "Threads_lock should be locked by safepoint code");
2246   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
2247 
2248   // Do not throw asynchronous exceptions against the compiler thread
2249   // (the compiler thread should not be a Java thread -- fix in 1.4.2)
2250   if (!can_call_java()) return;
2251 
2252   {
2253     // Actually throw the Throwable against the target Thread - however
2254     // only if there is no thread death exception installed already.
2255     if (_pending_async_exception == NULL || !_pending_async_exception->is_a(SystemDictionary::ThreadDeath_klass())) {
2256       // If the topmost frame is a runtime stub, then we are calling into
2257       // OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
2258       // must deoptimize the caller before continuing, as the compiled  exception handler table
2259       // may not be valid
2260       if (has_last_Java_frame()) {
2261         frame f = last_frame();
2262         if (f.is_runtime_frame() || f.is_safepoint_blob_frame()) {
2263           // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2264           RegisterMap reg_map(this, UseBiasedLocking);
2265           frame compiled_frame = f.sender(&reg_map);
2266           if (!StressCompiledExceptionHandlers && compiled_frame.can_be_deoptimized()) {
2267             Deoptimization::deoptimize(this, compiled_frame, &reg_map);
2268           }
2269         }
2270       }
2271 
2272       // Set async. pending exception in thread.
2273       set_pending_async_exception(java_throwable);
2274 
2275       if (log_is_enabled(Info, exceptions)) {
2276          ResourceMark rm;
2277         log_info(exceptions)("Pending Async. exception installed of type: %s",
2278                              InstanceKlass::cast(_pending_async_exception->klass())->external_name());
2279       }
2280       // for AbortVMOnException flag
2281       Exceptions::debug_check_abort(_pending_async_exception->klass()->external_name());
2282     }
2283   }
2284 
2285 
2286   // Interrupt thread so it will wake up from a potential wait()
2287   Thread::interrupt(this);
2288 }
2289 
2290 // External suspension mechanism.
2291 //
2292 // Tell the VM to suspend a thread when ever it knows that it does not hold on
2293 // to any VM_locks and it is at a transition
2294 // Self-suspension will happen on the transition out of the vm.
2295 // Catch "this" coming in from JNIEnv pointers when the thread has been freed
2296 //
2297 // Guarantees on return:
2298 //   + Target thread will not execute any new bytecode (that's why we need to
2299 //     force a safepoint)
2300 //   + Target thread will not enter any new monitors
2301 //
2302 void JavaThread::java_suspend() {
2303   ThreadsListHandle tlh;
2304   if (!tlh.includes(this) || threadObj() == NULL || is_exiting()) {
2305     return;
2306   }
2307 
2308   { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2309     if (!is_external_suspend()) {
2310       // a racing resume has cancelled us; bail out now
2311       return;
2312     }
2313 
2314     // suspend is done
2315     uint32_t debug_bits = 0;
2316     // Warning: is_ext_suspend_completed() may temporarily drop the
2317     // SR_lock to allow the thread to reach a stable thread state if
2318     // it is currently in a transient thread state.
2319     if (is_ext_suspend_completed(false /* !called_by_wait */,
2320                                  SuspendRetryDelay, &debug_bits)) {
2321       return;
2322     }
2323   }
2324 
2325   VM_ThreadSuspend vm_suspend;
2326   VMThread::execute(&vm_suspend);
2327 }
2328 
2329 // Part II of external suspension.
2330 // A JavaThread self suspends when it detects a pending external suspend
2331 // request. This is usually on transitions. It is also done in places
2332 // where continuing to the next transition would surprise the caller,
2333 // e.g., monitor entry.
2334 //
2335 // Returns the number of times that the thread self-suspended.
2336 //
2337 // Note: DO NOT call java_suspend_self() when you just want to block current
2338 //       thread. java_suspend_self() is the second stage of cooperative
2339 //       suspension for external suspend requests and should only be used
2340 //       to complete an external suspend request.
2341 //
2342 int JavaThread::java_suspend_self() {
2343   int ret = 0;
2344 
2345   // we are in the process of exiting so don't suspend
2346   if (is_exiting()) {
2347     clear_external_suspend();
2348     return ret;
2349   }
2350 
2351   assert(_anchor.walkable() ||
2352          (is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
2353          "must have walkable stack");
2354 
2355   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2356 
2357   assert(!this->is_ext_suspended(),
2358          "a thread trying to self-suspend should not already be suspended");
2359 
2360   if (this->is_suspend_equivalent()) {
2361     // If we are self-suspending as a result of the lifting of a
2362     // suspend equivalent condition, then the suspend_equivalent
2363     // flag is not cleared until we set the ext_suspended flag so
2364     // that wait_for_ext_suspend_completion() returns consistent
2365     // results.
2366     this->clear_suspend_equivalent();
2367   }
2368 
2369   // A racing resume may have cancelled us before we grabbed SR_lock
2370   // above. Or another external suspend request could be waiting for us
2371   // by the time we return from SR_lock()->wait(). The thread
2372   // that requested the suspension may already be trying to walk our
2373   // stack and if we return now, we can change the stack out from under
2374   // it. This would be a "bad thing (TM)" and cause the stack walker
2375   // to crash. We stay self-suspended until there are no more pending
2376   // external suspend requests.
2377   while (is_external_suspend()) {
2378     ret++;
2379     this->set_ext_suspended();
2380 
2381     // _ext_suspended flag is cleared by java_resume()
2382     while (is_ext_suspended()) {
2383       this->SR_lock()->wait(Mutex::_no_safepoint_check_flag);
2384     }
2385   }
2386 
2387   return ret;
2388 }
2389 
2390 #ifdef ASSERT
2391 // Verify the JavaThread has not yet been published in the Threads::list, and
2392 // hence doesn't need protection from concurrent access at this stage.
2393 void JavaThread::verify_not_published() {
2394   // Cannot create a ThreadsListHandle here and check !tlh.includes(this)
2395   // since an unpublished JavaThread doesn't participate in the
2396   // Thread-SMR protocol for keeping a ThreadsList alive.
2397   assert(!on_thread_list(), "JavaThread shouldn't have been published yet!");
2398 }
2399 #endif
2400 
2401 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2402 // progress or when _suspend_flags is non-zero.
2403 // Current thread needs to self-suspend if there is a suspend request and/or
2404 // block if a safepoint is in progress.
2405 // Async exception ISN'T checked.
2406 // Note only the ThreadInVMfromNative transition can call this function
2407 // directly and when thread state is _thread_in_native_trans
2408 void JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread *thread) {
2409   assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
2410 
2411   JavaThread *curJT = JavaThread::current();
2412   bool do_self_suspend = thread->is_external_suspend();
2413 
2414   assert(!curJT->has_last_Java_frame() || curJT->frame_anchor()->walkable(), "Unwalkable stack in native->vm transition");
2415 
2416   // If JNIEnv proxies are allowed, don't self-suspend if the target
2417   // thread is not the current thread. In older versions of jdbx, jdbx
2418   // threads could call into the VM with another thread's JNIEnv so we
2419   // can be here operating on behalf of a suspended thread (4432884).
2420   if (do_self_suspend && (!AllowJNIEnvProxy || curJT == thread)) {
2421     JavaThreadState state = thread->thread_state();
2422 
2423     // We mark this thread_blocked state as a suspend-equivalent so
2424     // that a caller to is_ext_suspend_completed() won't be confused.
2425     // The suspend-equivalent state is cleared by java_suspend_self().
2426     thread->set_suspend_equivalent();
2427 
2428     // If the safepoint code sees the _thread_in_native_trans state, it will
2429     // wait until the thread changes to other thread state. There is no
2430     // guarantee on how soon we can obtain the SR_lock and complete the
2431     // self-suspend request. It would be a bad idea to let safepoint wait for
2432     // too long. Temporarily change the state to _thread_blocked to
2433     // let the VM thread know that this thread is ready for GC. The problem
2434     // of changing thread state is that safepoint could happen just after
2435     // java_suspend_self() returns after being resumed, and VM thread will
2436     // see the _thread_blocked state. We must check for safepoint
2437     // after restoring the state and make sure we won't leave while a safepoint
2438     // is in progress.
2439     thread->set_thread_state(_thread_blocked);
2440     thread->java_suspend_self();
2441     thread->set_thread_state(state);
2442 
2443     InterfaceSupport::serialize_thread_state_with_handler(thread);
2444   }
2445 
2446   SafepointMechanism::block_if_requested(curJT);
2447 
2448   if (thread->is_deopt_suspend()) {
2449     thread->clear_deopt_suspend();
2450     RegisterMap map(thread, false);
2451     frame f = thread->last_frame();
2452     while (f.id() != thread->must_deopt_id() && ! f.is_first_frame()) {
2453       f = f.sender(&map);
2454     }
2455     if (f.id() == thread->must_deopt_id()) {
2456       thread->clear_must_deopt_id();
2457       f.deoptimize(thread);
2458     } else {
2459       fatal("missed deoptimization!");
2460     }
2461   }
2462 
2463   JFR_ONLY(SUSPEND_THREAD_CONDITIONAL(thread);)
2464 }
2465 
2466 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2467 // progress or when _suspend_flags is non-zero.
2468 // Current thread needs to self-suspend if there is a suspend request and/or
2469 // block if a safepoint is in progress.
2470 // Also check for pending async exception (not including unsafe access error).
2471 // Note only the native==>VM/Java barriers can call this function and when
2472 // thread state is _thread_in_native_trans.
2473 void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
2474   check_safepoint_and_suspend_for_native_trans(thread);
2475 
2476   if (thread->has_async_exception()) {
2477     // We are in _thread_in_native_trans state, don't handle unsafe
2478     // access error since that may block.
2479     thread->check_and_handle_async_exceptions(false);
2480   }
2481 }
2482 
2483 // This is a variant of the normal
2484 // check_special_condition_for_native_trans with slightly different
2485 // semantics for use by critical native wrappers.  It does all the
2486 // normal checks but also performs the transition back into
2487 // thread_in_Java state.  This is required so that critical natives
2488 // can potentially block and perform a GC if they are the last thread
2489 // exiting the GCLocker.
2490 void JavaThread::check_special_condition_for_native_trans_and_transition(JavaThread *thread) {
2491   check_special_condition_for_native_trans(thread);
2492 
2493   // Finish the transition
2494   thread->set_thread_state(_thread_in_Java);
2495 
2496   if (thread->do_critical_native_unlock()) {
2497     ThreadInVMfromJavaNoAsyncException tiv(thread);
2498     GCLocker::unlock_critical(thread);
2499     thread->clear_critical_native_unlock();
2500   }
2501 }
2502 
2503 // We need to guarantee the Threads_lock here, since resumes are not
2504 // allowed during safepoint synchronization
2505 // Can only resume from an external suspension
2506 void JavaThread::java_resume() {
2507   assert_locked_or_safepoint(Threads_lock);
2508 
2509   // Sanity check: thread is gone, has started exiting or the thread
2510   // was not externally suspended.
2511   ThreadsListHandle tlh;
2512   if (!tlh.includes(this) || is_exiting() || !is_external_suspend()) {
2513     return;
2514   }
2515 
2516   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2517 
2518   clear_external_suspend();
2519 
2520   if (is_ext_suspended()) {
2521     clear_ext_suspended();
2522     SR_lock()->notify_all();
2523   }
2524 }
2525 
2526 size_t JavaThread::_stack_red_zone_size = 0;
2527 size_t JavaThread::_stack_yellow_zone_size = 0;
2528 size_t JavaThread::_stack_reserved_zone_size = 0;
2529 size_t JavaThread::_stack_shadow_zone_size = 0;
2530 
2531 void JavaThread::create_stack_guard_pages() {
2532   if (!os::uses_stack_guard_pages() ||
2533       _stack_guard_state != stack_guard_unused ||
2534       (DisablePrimordialThreadGuardPages && os::is_primordial_thread())) {
2535       log_info(os, thread)("Stack guard page creation for thread "
2536                            UINTX_FORMAT " disabled", os::current_thread_id());
2537     return;
2538   }
2539   address low_addr = stack_end();
2540   size_t len = stack_guard_zone_size();
2541 
2542   assert(is_aligned(low_addr, os::vm_page_size()), "Stack base should be the start of a page");
2543   assert(is_aligned(len, os::vm_page_size()), "Stack size should be a multiple of page size");
2544 
2545   int must_commit = os::must_commit_stack_guard_pages();
2546   // warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);
2547 
2548   if (must_commit && !os::create_stack_guard_pages((char *) low_addr, len)) {
2549     log_warning(os, thread)("Attempt to allocate stack guard pages failed.");
2550     return;
2551   }
2552 
2553   if (os::guard_memory((char *) low_addr, len)) {
2554     _stack_guard_state = stack_guard_enabled;
2555   } else {
2556     log_warning(os, thread)("Attempt to protect stack guard pages failed ("
2557       PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2558     if (os::uncommit_memory((char *) low_addr, len)) {
2559       log_warning(os, thread)("Attempt to deallocate stack guard pages failed.");
2560     }
2561     return;
2562   }
2563 
2564   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages activated: "
2565     PTR_FORMAT "-" PTR_FORMAT ".",
2566     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2567 }
2568 
2569 void JavaThread::remove_stack_guard_pages() {
2570   assert(Thread::current() == this, "from different thread");
2571   if (_stack_guard_state == stack_guard_unused) return;
2572   address low_addr = stack_end();
2573   size_t len = stack_guard_zone_size();
2574 
2575   if (os::must_commit_stack_guard_pages()) {
2576     if (os::remove_stack_guard_pages((char *) low_addr, len)) {
2577       _stack_guard_state = stack_guard_unused;
2578     } else {
2579       log_warning(os, thread)("Attempt to deallocate stack guard pages failed ("
2580         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2581       return;
2582     }
2583   } else {
2584     if (_stack_guard_state == stack_guard_unused) return;
2585     if (os::unguard_memory((char *) low_addr, len)) {
2586       _stack_guard_state = stack_guard_unused;
2587     } else {
2588       log_warning(os, thread)("Attempt to unprotect stack guard pages failed ("
2589         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2590       return;
2591     }
2592   }
2593 
2594   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages removed: "
2595     PTR_FORMAT "-" PTR_FORMAT ".",
2596     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2597 }
2598 
2599 void JavaThread::enable_stack_reserved_zone() {
2600   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2601   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2602 
2603   // The base notation is from the stack's point of view, growing downward.
2604   // We need to adjust it to work correctly with guard_memory()
2605   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2606 
2607   guarantee(base < stack_base(),"Error calculating stack reserved zone");
2608   guarantee(base < os::current_stack_pointer(),"Error calculating stack reserved zone");
2609 
2610   if (os::guard_memory((char *) base, stack_reserved_zone_size())) {
2611     _stack_guard_state = stack_guard_enabled;
2612   } else {
2613     warning("Attempt to guard stack reserved zone failed.");
2614   }
2615   enable_register_stack_guard();
2616 }
2617 
2618 void JavaThread::disable_stack_reserved_zone() {
2619   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2620   assert(_stack_guard_state != stack_guard_reserved_disabled, "already disabled");
2621 
2622   // Simply return if called for a thread that does not use guard pages.
2623   if (_stack_guard_state == stack_guard_unused) return;
2624 
2625   // The base notation is from the stack's point of view, growing downward.
2626   // We need to adjust it to work correctly with guard_memory()
2627   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2628 
2629   if (os::unguard_memory((char *)base, stack_reserved_zone_size())) {
2630     _stack_guard_state = stack_guard_reserved_disabled;
2631   } else {
2632     warning("Attempt to unguard stack reserved zone failed.");
2633   }
2634   disable_register_stack_guard();
2635 }
2636 
2637 void JavaThread::enable_stack_yellow_reserved_zone() {
2638   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2639   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2640 
2641   // The base notation is from the stacks point of view, growing downward.
2642   // We need to adjust it to work correctly with guard_memory()
2643   address base = stack_red_zone_base();
2644 
2645   guarantee(base < stack_base(), "Error calculating stack yellow zone");
2646   guarantee(base < os::current_stack_pointer(), "Error calculating stack yellow zone");
2647 
2648   if (os::guard_memory((char *) base, stack_yellow_reserved_zone_size())) {
2649     _stack_guard_state = stack_guard_enabled;
2650   } else {
2651     warning("Attempt to guard stack yellow zone failed.");
2652   }
2653   enable_register_stack_guard();
2654 }
2655 
2656 void JavaThread::disable_stack_yellow_reserved_zone() {
2657   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2658   assert(_stack_guard_state != stack_guard_yellow_reserved_disabled, "already disabled");
2659 
2660   // Simply return if called for a thread that does not use guard pages.
2661   if (_stack_guard_state == stack_guard_unused) return;
2662 
2663   // The base notation is from the stacks point of view, growing downward.
2664   // We need to adjust it to work correctly with guard_memory()
2665   address base = stack_red_zone_base();
2666 
2667   if (os::unguard_memory((char *)base, stack_yellow_reserved_zone_size())) {
2668     _stack_guard_state = stack_guard_yellow_reserved_disabled;
2669   } else {
2670     warning("Attempt to unguard stack yellow zone failed.");
2671   }
2672   disable_register_stack_guard();
2673 }
2674 
2675 void JavaThread::enable_stack_red_zone() {
2676   // The base notation is from the stacks point of view, growing downward.
2677   // We need to adjust it to work correctly with guard_memory()
2678   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2679   address base = stack_red_zone_base() - stack_red_zone_size();
2680 
2681   guarantee(base < stack_base(), "Error calculating stack red zone");
2682   guarantee(base < os::current_stack_pointer(), "Error calculating stack red zone");
2683 
2684   if (!os::guard_memory((char *) base, stack_red_zone_size())) {
2685     warning("Attempt to guard stack red zone failed.");
2686   }
2687 }
2688 
2689 void JavaThread::disable_stack_red_zone() {
2690   // The base notation is from the stacks point of view, growing downward.
2691   // We need to adjust it to work correctly with guard_memory()
2692   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2693   address base = stack_red_zone_base() - stack_red_zone_size();
2694   if (!os::unguard_memory((char *)base, stack_red_zone_size())) {
2695     warning("Attempt to unguard stack red zone failed.");
2696   }
2697 }
2698 
2699 void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
2700   // ignore is there is no stack
2701   if (!has_last_Java_frame()) return;
2702   // traverse the stack frames. Starts from top frame.
2703   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2704     frame* fr = fst.current();
2705     f(fr, fst.register_map());
2706   }
2707 }
2708 
2709 
2710 #ifndef PRODUCT
2711 // Deoptimization
2712 // Function for testing deoptimization
2713 void JavaThread::deoptimize() {
2714   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2715   StackFrameStream fst(this, UseBiasedLocking);
2716   bool deopt = false;           // Dump stack only if a deopt actually happens.
2717   bool only_at = strlen(DeoptimizeOnlyAt) > 0;
2718   // Iterate over all frames in the thread and deoptimize
2719   for (; !fst.is_done(); fst.next()) {
2720     if (fst.current()->can_be_deoptimized()) {
2721 
2722       if (only_at) {
2723         // Deoptimize only at particular bcis.  DeoptimizeOnlyAt
2724         // consists of comma or carriage return separated numbers so
2725         // search for the current bci in that string.
2726         address pc = fst.current()->pc();
2727         nmethod* nm =  (nmethod*) fst.current()->cb();
2728         ScopeDesc* sd = nm->scope_desc_at(pc);
2729         char buffer[8];
2730         jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
2731         size_t len = strlen(buffer);
2732         const char * found = strstr(DeoptimizeOnlyAt, buffer);
2733         while (found != NULL) {
2734           if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
2735               (found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
2736             // Check that the bci found is bracketed by terminators.
2737             break;
2738           }
2739           found = strstr(found + 1, buffer);
2740         }
2741         if (!found) {
2742           continue;
2743         }
2744       }
2745 
2746       if (DebugDeoptimization && !deopt) {
2747         deopt = true; // One-time only print before deopt
2748         tty->print_cr("[BEFORE Deoptimization]");
2749         trace_frames();
2750         trace_stack();
2751       }
2752       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2753     }
2754   }
2755 
2756   if (DebugDeoptimization && deopt) {
2757     tty->print_cr("[AFTER Deoptimization]");
2758     trace_frames();
2759   }
2760 }
2761 
2762 
2763 // Make zombies
2764 void JavaThread::make_zombies() {
2765   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2766     if (fst.current()->can_be_deoptimized()) {
2767       // it is a Java nmethod
2768       nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
2769       nm->make_not_entrant();
2770     }
2771   }
2772 }
2773 #endif // PRODUCT
2774 
2775 
2776 void JavaThread::deoptimized_wrt_marked_nmethods() {
2777   if (!has_last_Java_frame()) return;
2778   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2779   StackFrameStream fst(this, UseBiasedLocking);
2780   for (; !fst.is_done(); fst.next()) {
2781     if (fst.current()->should_be_deoptimized()) {
2782       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2783     }
2784   }
2785 }
2786 
2787 
2788 // If the caller is a NamedThread, then remember, in the current scope,
2789 // the given JavaThread in its _processed_thread field.
2790 class RememberProcessedThread: public StackObj {
2791   NamedThread* _cur_thr;
2792  public:
2793   RememberProcessedThread(JavaThread* jthr) {
2794     Thread* thread = Thread::current();
2795     if (thread->is_Named_thread()) {
2796       _cur_thr = (NamedThread *)thread;
2797       _cur_thr->set_processed_thread(jthr);
2798     } else {
2799       _cur_thr = NULL;
2800     }
2801   }
2802 
2803   ~RememberProcessedThread() {
2804     if (_cur_thr) {
2805       _cur_thr->set_processed_thread(NULL);
2806     }
2807   }
2808 };
2809 
2810 void JavaThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
2811   // Verify that the deferred card marks have been flushed.
2812   assert(deferred_card_mark().is_empty(), "Should be empty during GC");
2813 
2814   // Traverse the GCHandles
2815   Thread::oops_do(f, cf);
2816 
2817   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2818          (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2819 
2820   if (has_last_Java_frame()) {
2821     // Record JavaThread to GC thread
2822     RememberProcessedThread rpt(this);
2823 
2824     // Traverse the privileged stack
2825     if (_privileged_stack_top != NULL) {
2826       _privileged_stack_top->oops_do(f);
2827     }
2828 
2829     // traverse the registered growable array
2830     if (_array_for_gc != NULL) {
2831       for (int index = 0; index < _array_for_gc->length(); index++) {
2832         f->do_oop(_array_for_gc->adr_at(index));
2833       }
2834     }
2835 
2836     // Traverse the monitor chunks
2837     for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2838       chunk->oops_do(f);
2839     }
2840 
2841     // Traverse the execution stack
2842     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2843       fst.current()->oops_do(f, cf, fst.register_map());
2844     }
2845   }
2846 
2847   // callee_target is never live across a gc point so NULL it here should
2848   // it still contain a methdOop.
2849 
2850   set_callee_target(NULL);
2851 
2852   assert(vframe_array_head() == NULL, "deopt in progress at a safepoint!");
2853   // If we have deferred set_locals there might be oops waiting to be
2854   // written
2855   GrowableArray<jvmtiDeferredLocalVariableSet*>* list = deferred_locals();
2856   if (list != NULL) {
2857     for (int i = 0; i < list->length(); i++) {
2858       list->at(i)->oops_do(f);
2859     }
2860   }
2861 
2862   // Traverse instance variables at the end since the GC may be moving things
2863   // around using this function
2864   f->do_oop((oop*) &_threadObj);
2865   f->do_oop((oop*) &_vm_result);
2866   f->do_oop((oop*) &_exception_oop);
2867   f->do_oop((oop*) &_pending_async_exception);
2868 
2869   if (jvmti_thread_state() != NULL) {
2870     jvmti_thread_state()->oops_do(f);
2871   }
2872 }
2873 
2874 void JavaThread::nmethods_do(CodeBlobClosure* cf) {
2875   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2876          (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2877 
2878   if (has_last_Java_frame()) {
2879     // Traverse the execution stack
2880     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2881       fst.current()->nmethods_do(cf);
2882     }
2883   }
2884 }
2885 
2886 void JavaThread::metadata_do(void f(Metadata*)) {
2887   if (has_last_Java_frame()) {
2888     // Traverse the execution stack to call f() on the methods in the stack
2889     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2890       fst.current()->metadata_do(f);
2891     }
2892   } else if (is_Compiler_thread()) {
2893     // need to walk ciMetadata in current compile tasks to keep alive.
2894     CompilerThread* ct = (CompilerThread*)this;
2895     if (ct->env() != NULL) {
2896       ct->env()->metadata_do(f);
2897     }
2898     CompileTask* task = ct->task();
2899     if (task != NULL) {
2900       task->metadata_do(f);
2901     }
2902   }
2903 }
2904 
2905 // Printing
2906 const char* _get_thread_state_name(JavaThreadState _thread_state) {
2907   switch (_thread_state) {
2908   case _thread_uninitialized:     return "_thread_uninitialized";
2909   case _thread_new:               return "_thread_new";
2910   case _thread_new_trans:         return "_thread_new_trans";
2911   case _thread_in_native:         return "_thread_in_native";
2912   case _thread_in_native_trans:   return "_thread_in_native_trans";
2913   case _thread_in_vm:             return "_thread_in_vm";
2914   case _thread_in_vm_trans:       return "_thread_in_vm_trans";
2915   case _thread_in_Java:           return "_thread_in_Java";
2916   case _thread_in_Java_trans:     return "_thread_in_Java_trans";
2917   case _thread_blocked:           return "_thread_blocked";
2918   case _thread_blocked_trans:     return "_thread_blocked_trans";
2919   default:                        return "unknown thread state";
2920   }
2921 }
2922 
2923 #ifndef PRODUCT
2924 void JavaThread::print_thread_state_on(outputStream *st) const {
2925   st->print_cr("   JavaThread state: %s", _get_thread_state_name(_thread_state));
2926 };
2927 void JavaThread::print_thread_state() const {
2928   print_thread_state_on(tty);
2929 }
2930 #endif // PRODUCT
2931 
2932 // Called by Threads::print() for VM_PrintThreads operation
2933 void JavaThread::print_on(outputStream *st, bool print_extended_info) const {
2934   st->print_raw("\"");
2935   st->print_raw(get_thread_name());
2936   st->print_raw("\" ");
2937   oop thread_oop = threadObj();
2938   if (thread_oop != NULL) {
2939     st->print("#" INT64_FORMAT " ", (int64_t)java_lang_Thread::thread_id(thread_oop));
2940     if (java_lang_Thread::is_daemon(thread_oop))  st->print("daemon ");
2941     st->print("prio=%d ", java_lang_Thread::priority(thread_oop));
2942   }
2943   Thread::print_on(st, print_extended_info);
2944   // print guess for valid stack memory region (assume 4K pages); helps lock debugging
2945   st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
2946   if (thread_oop != NULL) {
2947     st->print_cr("   java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
2948   }
2949 #ifndef PRODUCT
2950   print_thread_state_on(st);
2951   _safepoint_state->print_on(st);
2952 #endif // PRODUCT
2953   if (is_Compiler_thread()) {
2954     CompileTask *task = ((CompilerThread*)this)->task();
2955     if (task != NULL) {
2956       st->print("   Compiling: ");
2957       task->print(st, NULL, true, false);
2958     } else {
2959       st->print("   No compile task");
2960     }
2961     st->cr();
2962   }
2963 }
2964 
2965 void JavaThread::print_name_on_error(outputStream* st, char *buf, int buflen) const {
2966   st->print("%s", get_thread_name_string(buf, buflen));
2967 }
2968 
2969 // Called by fatal error handler. The difference between this and
2970 // JavaThread::print() is that we can't grab lock or allocate memory.
2971 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
2972   st->print("JavaThread \"%s\"", get_thread_name_string(buf, buflen));
2973   oop thread_obj = threadObj();
2974   if (thread_obj != NULL) {
2975     if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
2976   }
2977   st->print(" [");
2978   st->print("%s", _get_thread_state_name(_thread_state));
2979   if (osthread()) {
2980     st->print(", id=%d", osthread()->thread_id());
2981   }
2982   st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
2983             p2i(stack_end()), p2i(stack_base()));
2984   st->print("]");
2985 
2986   ThreadsSMRSupport::print_info_on(this, st);
2987   return;
2988 }
2989 
2990 // Verification
2991 
2992 static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
2993 
2994 void JavaThread::verify() {
2995   // Verify oops in the thread.
2996   oops_do(&VerifyOopClosure::verify_oop, NULL);
2997 
2998   // Verify the stack frames.
2999   frames_do(frame_verify);
3000 }
3001 
3002 // CR 6300358 (sub-CR 2137150)
3003 // Most callers of this method assume that it can't return NULL but a
3004 // thread may not have a name whilst it is in the process of attaching to
3005 // the VM - see CR 6412693, and there are places where a JavaThread can be
3006 // seen prior to having it's threadObj set (eg JNI attaching threads and
3007 // if vm exit occurs during initialization). These cases can all be accounted
3008 // for such that this method never returns NULL.
3009 const char* JavaThread::get_thread_name() const {
3010 #ifdef ASSERT
3011   // early safepoints can hit while current thread does not yet have TLS
3012   if (!SafepointSynchronize::is_at_safepoint()) {
3013     Thread *cur = Thread::current();
3014     if (!(cur->is_Java_thread() && cur == this)) {
3015       // Current JavaThreads are allowed to get their own name without
3016       // the Threads_lock.
3017       assert_locked_or_safepoint(Threads_lock);
3018     }
3019   }
3020 #endif // ASSERT
3021   return get_thread_name_string();
3022 }
3023 
3024 // Returns a non-NULL representation of this thread's name, or a suitable
3025 // descriptive string if there is no set name
3026 const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
3027   const char* name_str;
3028   oop thread_obj = threadObj();
3029   if (thread_obj != NULL) {
3030     oop name = java_lang_Thread::name(thread_obj);
3031     if (name != NULL) {
3032       if (buf == NULL) {
3033         name_str = java_lang_String::as_utf8_string(name);
3034       } else {
3035         name_str = java_lang_String::as_utf8_string(name, buf, buflen);
3036       }
3037     } else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
3038       name_str = "<no-name - thread is attaching>";
3039     } else {
3040       name_str = Thread::name();
3041     }
3042   } else {
3043     name_str = Thread::name();
3044   }
3045   assert(name_str != NULL, "unexpected NULL thread name");
3046   return name_str;
3047 }
3048 
3049 
3050 const char* JavaThread::get_threadgroup_name() const {
3051   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3052   oop thread_obj = threadObj();
3053   if (thread_obj != NULL) {
3054     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3055     if (thread_group != NULL) {
3056       // ThreadGroup.name can be null
3057       return java_lang_ThreadGroup::name(thread_group);
3058     }
3059   }
3060   return NULL;
3061 }
3062 
3063 const char* JavaThread::get_parent_name() const {
3064   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3065   oop thread_obj = threadObj();
3066   if (thread_obj != NULL) {
3067     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3068     if (thread_group != NULL) {
3069       oop parent = java_lang_ThreadGroup::parent(thread_group);
3070       if (parent != NULL) {
3071         // ThreadGroup.name can be null
3072         return java_lang_ThreadGroup::name(parent);
3073       }
3074     }
3075   }
3076   return NULL;
3077 }
3078 
3079 ThreadPriority JavaThread::java_priority() const {
3080   oop thr_oop = threadObj();
3081   if (thr_oop == NULL) return NormPriority; // Bootstrapping
3082   ThreadPriority priority = java_lang_Thread::priority(thr_oop);
3083   assert(MinPriority <= priority && priority <= MaxPriority, "sanity check");
3084   return priority;
3085 }
3086 
3087 void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
3088 
3089   assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
3090   // Link Java Thread object <-> C++ Thread
3091 
3092   // Get the C++ thread object (an oop) from the JNI handle (a jthread)
3093   // and put it into a new Handle.  The Handle "thread_oop" can then
3094   // be used to pass the C++ thread object to other methods.
3095 
3096   // Set the Java level thread object (jthread) field of the
3097   // new thread (a JavaThread *) to C++ thread object using the
3098   // "thread_oop" handle.
3099 
3100   // Set the thread field (a JavaThread *) of the
3101   // oop representing the java_lang_Thread to the new thread (a JavaThread *).
3102 
3103   Handle thread_oop(Thread::current(),
3104                     JNIHandles::resolve_non_null(jni_thread));
3105   assert(InstanceKlass::cast(thread_oop->klass())->is_linked(),
3106          "must be initialized");
3107   set_threadObj(thread_oop());
3108   java_lang_Thread::set_thread(thread_oop(), this);
3109 
3110   if (prio == NoPriority) {
3111     prio = java_lang_Thread::priority(thread_oop());
3112     assert(prio != NoPriority, "A valid priority should be present");
3113   }
3114 
3115   // Push the Java priority down to the native thread; needs Threads_lock
3116   Thread::set_priority(this, prio);
3117 
3118   // Add the new thread to the Threads list and set it in motion.
3119   // We must have threads lock in order to call Threads::add.
3120   // It is crucial that we do not block before the thread is
3121   // added to the Threads list for if a GC happens, then the java_thread oop
3122   // will not be visited by GC.
3123   Threads::add(this);
3124 }
3125 
3126 oop JavaThread::current_park_blocker() {
3127   // Support for JSR-166 locks
3128   oop thread_oop = threadObj();
3129   if (thread_oop != NULL &&
3130       JDK_Version::current().supports_thread_park_blocker()) {
3131     return java_lang_Thread::park_blocker(thread_oop);
3132   }
3133   return NULL;
3134 }
3135 
3136 
3137 void JavaThread::print_stack_on(outputStream* st) {
3138   if (!has_last_Java_frame()) return;
3139   ResourceMark rm;
3140   HandleMark   hm;
3141 
3142   RegisterMap reg_map(this);
3143   vframe* start_vf = last_java_vframe(&reg_map);
3144   int count = 0;
3145   for (vframe* f = start_vf; f != NULL; f = f->sender()) {
3146     if (f->is_java_frame()) {
3147       javaVFrame* jvf = javaVFrame::cast(f);
3148       java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
3149 
3150       // Print out lock information
3151       if (JavaMonitorsInStackTrace) {
3152         jvf->print_lock_info_on(st, count);
3153       }
3154     } else {
3155       // Ignore non-Java frames
3156     }
3157 
3158     // Bail-out case for too deep stacks if MaxJavaStackTraceDepth > 0
3159     count++;
3160     if (MaxJavaStackTraceDepth > 0 && MaxJavaStackTraceDepth == count) return;
3161   }
3162 }
3163 
3164 
3165 // JVMTI PopFrame support
3166 void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
3167   assert(_popframe_preserved_args == NULL, "should not wipe out old PopFrame preserved arguments");
3168   if (in_bytes(size_in_bytes) != 0) {
3169     _popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes), mtThread);
3170     _popframe_preserved_args_size = in_bytes(size_in_bytes);
3171     Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
3172   }
3173 }
3174 
3175 void* JavaThread::popframe_preserved_args() {
3176   return _popframe_preserved_args;
3177 }
3178 
3179 ByteSize JavaThread::popframe_preserved_args_size() {
3180   return in_ByteSize(_popframe_preserved_args_size);
3181 }
3182 
3183 WordSize JavaThread::popframe_preserved_args_size_in_words() {
3184   int sz = in_bytes(popframe_preserved_args_size());
3185   assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
3186   return in_WordSize(sz / wordSize);
3187 }
3188 
3189 void JavaThread::popframe_free_preserved_args() {
3190   assert(_popframe_preserved_args != NULL, "should not free PopFrame preserved arguments twice");
3191   FREE_C_HEAP_ARRAY(char, (char*) _popframe_preserved_args);
3192   _popframe_preserved_args = NULL;
3193   _popframe_preserved_args_size = 0;
3194 }
3195 
3196 #ifndef PRODUCT
3197 
3198 void JavaThread::trace_frames() {
3199   tty->print_cr("[Describe stack]");
3200   int frame_no = 1;
3201   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
3202     tty->print("  %d. ", frame_no++);
3203     fst.current()->print_value_on(tty, this);
3204     tty->cr();
3205   }
3206 }
3207 
3208 class PrintAndVerifyOopClosure: public OopClosure {
3209  protected:
3210   template <class T> inline void do_oop_work(T* p) {
3211     oop obj = RawAccess<>::oop_load(p);
3212     if (obj == NULL) return;
3213     tty->print(INTPTR_FORMAT ": ", p2i(p));
3214     if (oopDesc::is_oop_or_null(obj)) {
3215       if (obj->is_objArray()) {
3216         tty->print_cr("valid objArray: " INTPTR_FORMAT, p2i(obj));
3217       } else {
3218         obj->print();
3219       }
3220     } else {
3221       tty->print_cr("invalid oop: " INTPTR_FORMAT, p2i(obj));
3222     }
3223     tty->cr();
3224   }
3225  public:
3226   virtual void do_oop(oop* p) { do_oop_work(p); }
3227   virtual void do_oop(narrowOop* p)  { do_oop_work(p); }
3228 };
3229 
3230 
3231 static void oops_print(frame* f, const RegisterMap *map) {
3232   PrintAndVerifyOopClosure print;
3233   f->print_value();
3234   f->oops_do(&print, NULL, (RegisterMap*)map);
3235 }
3236 
3237 // Print our all the locations that contain oops and whether they are
3238 // valid or not.  This useful when trying to find the oldest frame
3239 // where an oop has gone bad since the frame walk is from youngest to
3240 // oldest.
3241 void JavaThread::trace_oops() {
3242   tty->print_cr("[Trace oops]");
3243   frames_do(oops_print);
3244 }
3245 
3246 
3247 #ifdef ASSERT
3248 // Print or validate the layout of stack frames
3249 void JavaThread::print_frame_layout(int depth, bool validate_only) {
3250   ResourceMark rm;
3251   PRESERVE_EXCEPTION_MARK;
3252   FrameValues values;
3253   int frame_no = 0;
3254   for (StackFrameStream fst(this, false); !fst.is_done(); fst.next()) {
3255     fst.current()->describe(values, ++frame_no);
3256     if (depth == frame_no) break;
3257   }
3258   if (validate_only) {
3259     values.validate();
3260   } else {
3261     tty->print_cr("[Describe stack layout]");
3262     values.print(this);
3263   }
3264 }
3265 #endif
3266 
3267 void JavaThread::trace_stack_from(vframe* start_vf) {
3268   ResourceMark rm;
3269   int vframe_no = 1;
3270   for (vframe* f = start_vf; f; f = f->sender()) {
3271     if (f->is_java_frame()) {
3272       javaVFrame::cast(f)->print_activation(vframe_no++);
3273     } else {
3274       f->print();
3275     }
3276     if (vframe_no > StackPrintLimit) {
3277       tty->print_cr("...<more frames>...");
3278       return;
3279     }
3280   }
3281 }
3282 
3283 
3284 void JavaThread::trace_stack() {
3285   if (!has_last_Java_frame()) return;
3286   ResourceMark rm;
3287   HandleMark   hm;
3288   RegisterMap reg_map(this);
3289   trace_stack_from(last_java_vframe(&reg_map));
3290 }
3291 
3292 
3293 #endif // PRODUCT
3294 
3295 
3296 javaVFrame* JavaThread::last_java_vframe(RegisterMap *reg_map) {
3297   assert(reg_map != NULL, "a map must be given");
3298   frame f = last_frame();
3299   for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender()) {
3300     if (vf->is_java_frame()) return javaVFrame::cast(vf);
3301   }
3302   return NULL;
3303 }
3304 
3305 
3306 Klass* JavaThread::security_get_caller_class(int depth) {
3307   vframeStream vfst(this);
3308   vfst.security_get_caller_frame(depth);
3309   if (!vfst.at_end()) {
3310     return vfst.method()->method_holder();
3311   }
3312   return NULL;
3313 }
3314 
3315 static void compiler_thread_entry(JavaThread* thread, TRAPS) {
3316   assert(thread->is_Compiler_thread(), "must be compiler thread");
3317   CompileBroker::compiler_thread_loop();
3318 }
3319 
3320 static void sweeper_thread_entry(JavaThread* thread, TRAPS) {
3321   NMethodSweeper::sweeper_loop();
3322 }
3323 
3324 // Create a CompilerThread
3325 CompilerThread::CompilerThread(CompileQueue* queue,
3326                                CompilerCounters* counters)
3327                                : JavaThread(&compiler_thread_entry) {
3328   _env   = NULL;
3329   _log   = NULL;
3330   _task  = NULL;
3331   _queue = queue;
3332   _counters = counters;
3333   _buffer_blob = NULL;
3334   _compiler = NULL;
3335 
3336   // Compiler uses resource area for compilation, let's bias it to mtCompiler
3337   resource_area()->bias_to(mtCompiler);
3338 
3339 #ifndef PRODUCT
3340   _ideal_graph_printer = NULL;
3341 #endif
3342 }
3343 
3344 CompilerThread::~CompilerThread() {
3345   // Delete objects which were allocated on heap.
3346   delete _counters;
3347 }
3348 
3349 bool CompilerThread::can_call_java() const {
3350   return _compiler != NULL && _compiler->is_jvmci();
3351 }
3352 
3353 // Create sweeper thread
3354 CodeCacheSweeperThread::CodeCacheSweeperThread()
3355 : JavaThread(&sweeper_thread_entry) {
3356   _scanned_compiled_method = NULL;
3357 }
3358 
3359 void CodeCacheSweeperThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
3360   JavaThread::oops_do(f, cf);
3361   if (_scanned_compiled_method != NULL && cf != NULL) {
3362     // Safepoints can occur when the sweeper is scanning an nmethod so
3363     // process it here to make sure it isn't unloaded in the middle of
3364     // a scan.
3365     cf->do_code_blob(_scanned_compiled_method);
3366   }
3367 }
3368 
3369 void CodeCacheSweeperThread::nmethods_do(CodeBlobClosure* cf) {
3370   JavaThread::nmethods_do(cf);
3371   if (_scanned_compiled_method != NULL && cf != NULL) {
3372     // Safepoints can occur when the sweeper is scanning an nmethod so
3373     // process it here to make sure it isn't unloaded in the middle of
3374     // a scan.
3375     cf->do_code_blob(_scanned_compiled_method);
3376   }
3377 }
3378 
3379 
3380 // ======= Threads ========
3381 
3382 // The Threads class links together all active threads, and provides
3383 // operations over all threads. It is protected by the Threads_lock,
3384 // which is also used in other global contexts like safepointing.
3385 // ThreadsListHandles are used to safely perform operations on one
3386 // or more threads without the risk of the thread exiting during the
3387 // operation.
3388 //
3389 // Note: The Threads_lock is currently more widely used than we
3390 // would like. We are actively migrating Threads_lock uses to other
3391 // mechanisms in order to reduce Threads_lock contention.
3392 
3393 JavaThread* Threads::_thread_list = NULL;
3394 int         Threads::_number_of_threads = 0;
3395 int         Threads::_number_of_non_daemon_threads = 0;
3396 int         Threads::_return_code = 0;
3397 int         Threads::_thread_claim_parity = 0;
3398 size_t      JavaThread::_stack_size_at_create = 0;
3399 
3400 #ifdef ASSERT
3401 bool        Threads::_vm_complete = false;
3402 size_t      Threads::_threads_before_barrier_set = 0;
3403 #endif
3404 
3405 static inline void *prefetch_and_load_ptr(void **addr, intx prefetch_interval) {
3406   Prefetch::read((void*)addr, prefetch_interval);
3407   return *addr;
3408 }
3409 
3410 // Possibly the ugliest for loop the world has seen. C++ does not allow
3411 // multiple types in the declaration section of the for loop. In this case
3412 // we are only dealing with pointers and hence can cast them. It looks ugly
3413 // but macros are ugly and therefore it's fine to make things absurdly ugly.
3414 #define DO_JAVA_THREADS(LIST, X)                                                                                          \
3415     for (JavaThread *MACRO_scan_interval = (JavaThread*)(uintptr_t)PrefetchScanIntervalInBytes,                           \
3416              *MACRO_list = (JavaThread*)(LIST),                                                                           \
3417              **MACRO_end = ((JavaThread**)((ThreadsList*)MACRO_list)->threads()) + ((ThreadsList*)MACRO_list)->length(),  \
3418              **MACRO_current_p = (JavaThread**)((ThreadsList*)MACRO_list)->threads(),                                     \
3419              *X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval);                 \
3420          MACRO_current_p != MACRO_end;                                                                                    \
3421          MACRO_current_p++,                                                                                               \
3422              X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval))
3423 
3424 // All JavaThreads
3425 #define ALL_JAVA_THREADS(X) DO_JAVA_THREADS(ThreadsSMRSupport::get_java_thread_list(), X)
3426 
3427 // All NonJavaThreads (i.e., every non-JavaThread in the system).
3428 void Threads::non_java_threads_do(ThreadClosure* tc) {
3429   NoSafepointVerifier nsv(!SafepointSynchronize::is_at_safepoint(), false);
3430   for (NonJavaThread::Iterator njti; !njti.end(); njti.step()) {
3431     tc->do_thread(njti.current());
3432   }
3433 }
3434 
3435 // All JavaThreads
3436 void Threads::java_threads_do(ThreadClosure* tc) {
3437   assert_locked_or_safepoint(Threads_lock);
3438   // ALL_JAVA_THREADS iterates through all JavaThreads.
3439   ALL_JAVA_THREADS(p) {
3440     tc->do_thread(p);
3441   }
3442 }
3443 
3444 void Threads::java_threads_and_vm_thread_do(ThreadClosure* tc) {
3445   assert_locked_or_safepoint(Threads_lock);
3446   java_threads_do(tc);
3447   tc->do_thread(VMThread::vm_thread());
3448 }
3449 
3450 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system).
3451 void Threads::threads_do(ThreadClosure* tc) {
3452   assert_locked_or_safepoint(Threads_lock);
3453   java_threads_do(tc);
3454   non_java_threads_do(tc);
3455 }
3456 
3457 void Threads::possibly_parallel_threads_do(bool is_par, ThreadClosure* tc) {
3458   int cp = Threads::thread_claim_parity();
3459   ALL_JAVA_THREADS(p) {
3460     if (p->claim_oops_do(is_par, cp)) {
3461       tc->do_thread(p);
3462     }
3463   }
3464   VMThread* vmt = VMThread::vm_thread();
3465   if (vmt->claim_oops_do(is_par, cp)) {
3466     tc->do_thread(vmt);
3467   }
3468 }
3469 
3470 // The system initialization in the library has three phases.
3471 //
3472 // Phase 1: java.lang.System class initialization
3473 //     java.lang.System is a primordial class loaded and initialized
3474 //     by the VM early during startup.  java.lang.System.<clinit>
3475 //     only does registerNatives and keeps the rest of the class
3476 //     initialization work later until thread initialization completes.
3477 //
3478 //     System.initPhase1 initializes the system properties, the static
3479 //     fields in, out, and err. Set up java signal handlers, OS-specific
3480 //     system settings, and thread group of the main thread.
3481 static void call_initPhase1(TRAPS) {
3482   Klass* klass =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3483   JavaValue result(T_VOID);
3484   JavaCalls::call_static(&result, klass, vmSymbols::initPhase1_name(),
3485                                          vmSymbols::void_method_signature(), CHECK);
3486 }
3487 
3488 // Phase 2. Module system initialization
3489 //     This will initialize the module system.  Only java.base classes
3490 //     can be loaded until phase 2 completes.
3491 //
3492 //     Call System.initPhase2 after the compiler initialization and jsr292
3493 //     classes get initialized because module initialization runs a lot of java
3494 //     code, that for performance reasons, should be compiled.  Also, this will
3495 //     enable the startup code to use lambda and other language features in this
3496 //     phase and onward.
3497 //
3498 //     After phase 2, The VM will begin search classes from -Xbootclasspath/a.
3499 static void call_initPhase2(TRAPS) {
3500   TraceTime timer("Initialize module system", TRACETIME_LOG(Info, startuptime));
3501 
3502   Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3503 
3504   JavaValue result(T_INT);
3505   JavaCallArguments args;
3506   args.push_int(DisplayVMOutputToStderr);
3507   args.push_int(log_is_enabled(Debug, init)); // print stack trace if exception thrown
3508   JavaCalls::call_static(&result, klass, vmSymbols::initPhase2_name(),
3509                                          vmSymbols::boolean_boolean_int_signature(), &args, CHECK);
3510   if (result.get_jint() != JNI_OK) {
3511     vm_exit_during_initialization(); // no message or exception
3512   }
3513 
3514   universe_post_module_init();
3515 }
3516 
3517 // Phase 3. final setup - set security manager, system class loader and TCCL
3518 //
3519 //     This will instantiate and set the security manager, set the system class
3520 //     loader as well as the thread context class loader.  The security manager
3521 //     and system class loader may be a custom class loaded from -Xbootclasspath/a,
3522 //     other modules or the application's classpath.
3523 static void call_initPhase3(TRAPS) {
3524   Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3525   JavaValue result(T_VOID);
3526   JavaCalls::call_static(&result, klass, vmSymbols::initPhase3_name(),
3527                                          vmSymbols::void_method_signature(), CHECK);
3528 }
3529 
3530 void Threads::initialize_java_lang_classes(JavaThread* main_thread, TRAPS) {
3531   TraceTime timer("Initialize java.lang classes", TRACETIME_LOG(Info, startuptime));
3532 
3533   if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
3534     create_vm_init_libraries();
3535   }
3536 
3537   initialize_class(vmSymbols::java_lang_String(), CHECK);
3538 
3539   // Inject CompactStrings value after the static initializers for String ran.
3540   java_lang_String::set_compact_strings(CompactStrings);
3541 
3542   // Initialize java_lang.System (needed before creating the thread)
3543   initialize_class(vmSymbols::java_lang_System(), CHECK);
3544   // The VM creates & returns objects of this class. Make sure it's initialized.
3545   initialize_class(vmSymbols::java_lang_Class(), CHECK);
3546   initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK);
3547   Handle thread_group = create_initial_thread_group(CHECK);
3548   Universe::set_main_thread_group(thread_group());
3549   initialize_class(vmSymbols::java_lang_Thread(), CHECK);
3550   oop thread_object = create_initial_thread(thread_group, main_thread, CHECK);
3551   main_thread->set_threadObj(thread_object);
3552   // Set thread status to running since main thread has
3553   // been started and running.
3554   java_lang_Thread::set_thread_status(thread_object,
3555                                       java_lang_Thread::RUNNABLE);
3556 
3557   // The VM creates objects of this class.
3558   initialize_class(vmSymbols::java_lang_Module(), CHECK);
3559 
3560   // The VM preresolves methods to these classes. Make sure that they get initialized
3561   initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK);
3562   initialize_class(vmSymbols::java_lang_ref_Finalizer(), CHECK);
3563 
3564   // Phase 1 of the system initialization in the library, java.lang.System class initialization
3565   call_initPhase1(CHECK);
3566 
3567   // get the Java runtime name after java.lang.System is initialized
3568   JDK_Version::set_runtime_name(get_java_runtime_name(THREAD));
3569   JDK_Version::set_runtime_version(get_java_runtime_version(THREAD));
3570 
3571   // an instance of OutOfMemory exception has been allocated earlier
3572   initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK);
3573   initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK);
3574   initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK);
3575   initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK);
3576   initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK);
3577   initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK);
3578   initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK);
3579   initialize_class(vmSymbols::java_lang_IllegalArgumentException(), CHECK);
3580 }
3581 
3582 void Threads::initialize_jsr292_core_classes(TRAPS) {
3583   TraceTime timer("Initialize java.lang.invoke classes", TRACETIME_LOG(Info, startuptime));
3584 
3585   initialize_class(vmSymbols::java_lang_invoke_MethodHandle(), CHECK);
3586   initialize_class(vmSymbols::java_lang_invoke_ResolvedMethodName(), CHECK);
3587   initialize_class(vmSymbols::java_lang_invoke_MemberName(), CHECK);
3588   initialize_class(vmSymbols::java_lang_invoke_MethodHandleNatives(), CHECK);
3589 }
3590 
3591 jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
3592   extern void JDK_Version_init();
3593 
3594   // Preinitialize version info.
3595   VM_Version::early_initialize();
3596 
3597   // Check version
3598   if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
3599 
3600   // Initialize library-based TLS
3601   ThreadLocalStorage::init();
3602 
3603   // Initialize the output stream module
3604   ostream_init();
3605 
3606   // Process java launcher properties.
3607   Arguments::process_sun_java_launcher_properties(args);
3608 
3609   // Initialize the os module
3610   os::init();
3611 
3612   // Record VM creation timing statistics
3613   TraceVmCreationTime create_vm_timer;
3614   create_vm_timer.start();
3615 
3616   // Initialize system properties.
3617   Arguments::init_system_properties();
3618 
3619   // So that JDK version can be used as a discriminator when parsing arguments
3620   JDK_Version_init();
3621 
3622   // Update/Initialize System properties after JDK version number is known
3623   Arguments::init_version_specific_system_properties();
3624 
3625   // Make sure to initialize log configuration *before* parsing arguments
3626   LogConfiguration::initialize(create_vm_timer.begin_time());
3627 
3628   // Parse arguments
3629   // Note: this internally calls os::init_container_support()
3630   jint parse_result = Arguments::parse(args);
3631   if (parse_result != JNI_OK) return parse_result;
3632 
3633   os::init_before_ergo();
3634 
3635   jint ergo_result = Arguments::apply_ergo();
3636   if (ergo_result != JNI_OK) return ergo_result;
3637 
3638   // Final check of all ranges after ergonomics which may change values.
3639   if (!JVMFlagRangeList::check_ranges()) {
3640     return JNI_EINVAL;
3641   }
3642 
3643   // Final check of all 'AfterErgo' constraints after ergonomics which may change values.
3644   bool constraint_result = JVMFlagConstraintList::check_constraints(JVMFlagConstraint::AfterErgo);
3645   if (!constraint_result) {
3646     return JNI_EINVAL;
3647   }
3648 
3649   JVMFlagWriteableList::mark_startup();
3650 
3651   if (PauseAtStartup) {
3652     os::pause();
3653   }
3654 
3655   HOTSPOT_VM_INIT_BEGIN();
3656 
3657   // Timing (must come after argument parsing)
3658   TraceTime timer("Create VM", TRACETIME_LOG(Info, startuptime));
3659 
3660 #ifdef CAN_SHOW_REGISTERS_ON_ASSERT
3661   // Initialize assert poison page mechanism.
3662   if (ShowRegistersOnAssert) {
3663     initialize_assert_poison();
3664   }
3665 #endif // CAN_SHOW_REGISTERS_ON_ASSERT
3666 
3667   // Initialize the os module after parsing the args
3668   jint os_init_2_result = os::init_2();
3669   if (os_init_2_result != JNI_OK) return os_init_2_result;
3670 
3671   SafepointMechanism::initialize();
3672 
3673   jint adjust_after_os_result = Arguments::adjust_after_os();
3674   if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;
3675 
3676   // Initialize output stream logging
3677   ostream_init_log();
3678 
3679   // Convert -Xrun to -agentlib: if there is no JVM_OnLoad
3680   // Must be before create_vm_init_agents()
3681   if (Arguments::init_libraries_at_startup()) {
3682     convert_vm_init_libraries_to_agents();
3683   }
3684 
3685   // Launch -agentlib/-agentpath and converted -Xrun agents
3686   if (Arguments::init_agents_at_startup()) {
3687     create_vm_init_agents();
3688   }
3689 
3690   // Initialize Threads state
3691   _thread_list = NULL;
3692   _number_of_threads = 0;
3693   _number_of_non_daemon_threads = 0;
3694 
3695   // Initialize global data structures and create system classes in heap
3696   vm_init_globals();
3697 
3698 #if INCLUDE_JVMCI
3699   if (JVMCICounterSize > 0) {
3700     JavaThread::_jvmci_old_thread_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
3701     memset(JavaThread::_jvmci_old_thread_counters, 0, sizeof(jlong) * JVMCICounterSize);
3702   } else {
3703     JavaThread::_jvmci_old_thread_counters = NULL;
3704   }
3705 #endif // INCLUDE_JVMCI
3706 
3707   // Attach the main thread to this os thread
3708   JavaThread* main_thread = new JavaThread();
3709   main_thread->set_thread_state(_thread_in_vm);
3710   main_thread->initialize_thread_current();
3711   // must do this before set_active_handles
3712   main_thread->record_stack_base_and_size();
3713   main_thread->set_active_handles(JNIHandleBlock::allocate_block());
3714 
3715   if (!main_thread->set_as_starting_thread()) {
3716     vm_shutdown_during_initialization(
3717                                       "Failed necessary internal allocation. Out of swap space");
3718     main_thread->smr_delete();
3719     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3720     return JNI_ENOMEM;
3721   }
3722 
3723   // Enable guard page *after* os::create_main_thread(), otherwise it would
3724   // crash Linux VM, see notes in os_linux.cpp.
3725   main_thread->create_stack_guard_pages();
3726 
3727   // Initialize Java-Level synchronization subsystem
3728   ObjectMonitor::Initialize();
3729 
3730   // Initialize global modules
3731   jint status = init_globals();
3732   if (status != JNI_OK) {
3733     main_thread->smr_delete();
3734     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3735     return status;
3736   }
3737 
3738   JFR_ONLY(Jfr::on_vm_init();)
3739 
3740   // Should be done after the heap is fully created
3741   main_thread->cache_global_variables();
3742 
3743   HandleMark hm;
3744 
3745   { MutexLocker mu(Threads_lock);
3746     Threads::add(main_thread);
3747   }
3748 
3749   // Any JVMTI raw monitors entered in onload will transition into
3750   // real raw monitor. VM is setup enough here for raw monitor enter.
3751   JvmtiExport::transition_pending_onload_raw_monitors();
3752 
3753   // Create the VMThread
3754   { TraceTime timer("Start VMThread", TRACETIME_LOG(Info, startuptime));
3755 
3756   VMThread::create();
3757     Thread* vmthread = VMThread::vm_thread();
3758 
3759     if (!os::create_thread(vmthread, os::vm_thread)) {
3760       vm_exit_during_initialization("Cannot create VM thread. "
3761                                     "Out of system resources.");
3762     }
3763 
3764     // Wait for the VM thread to become ready, and VMThread::run to initialize
3765     // Monitors can have spurious returns, must always check another state flag
3766     {
3767       MutexLocker ml(Notify_lock);
3768       os::start_thread(vmthread);
3769       while (vmthread->active_handles() == NULL) {
3770         Notify_lock->wait();
3771       }
3772     }
3773   }
3774 
3775   assert(Universe::is_fully_initialized(), "not initialized");
3776   if (VerifyDuringStartup) {
3777     // Make sure we're starting with a clean slate.
3778     VM_Verify verify_op;
3779     VMThread::execute(&verify_op);
3780   }
3781 
3782   // We need this to update the java.vm.info property in case any flags used
3783   // to initially define it have been changed. This is needed for both CDS and
3784   // AOT, since UseSharedSpaces and UseAOT may be changed after java.vm.info
3785   // is initially computed. See Abstract_VM_Version::vm_info_string().
3786   // This update must happen before we initialize the java classes, but
3787   // after any initialization logic that might modify the flags.
3788   Arguments::update_vm_info_property(VM_Version::vm_info_string());
3789 
3790   Thread* THREAD = Thread::current();
3791 
3792   // Always call even when there are not JVMTI environments yet, since environments
3793   // may be attached late and JVMTI must track phases of VM execution
3794   JvmtiExport::enter_early_start_phase();
3795 
3796   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
3797   JvmtiExport::post_early_vm_start();
3798 
3799   initialize_java_lang_classes(main_thread, CHECK_JNI_ERR);
3800 
3801   quicken_jni_functions();
3802 
3803   // No more stub generation allowed after that point.
3804   StubCodeDesc::freeze();
3805 
3806   // Set flag that basic initialization has completed. Used by exceptions and various
3807   // debug stuff, that does not work until all basic classes have been initialized.
3808   set_init_completed();
3809 
3810   LogConfiguration::post_initialize();
3811   Metaspace::post_initialize();
3812 
3813   HOTSPOT_VM_INIT_END();
3814 
3815   // record VM initialization completion time
3816 #if INCLUDE_MANAGEMENT
3817   Management::record_vm_init_completed();
3818 #endif // INCLUDE_MANAGEMENT
3819 
3820   // Signal Dispatcher needs to be started before VMInit event is posted
3821   os::initialize_jdk_signal_support(CHECK_JNI_ERR);
3822 
3823   // Start Attach Listener if +StartAttachListener or it can't be started lazily
3824   if (!DisableAttachMechanism) {
3825     AttachListener::vm_start();
3826     if (StartAttachListener || AttachListener::init_at_startup()) {
3827       AttachListener::init();
3828     }
3829   }
3830 
3831   // Launch -Xrun agents
3832   // Must be done in the JVMTI live phase so that for backward compatibility the JDWP
3833   // back-end can launch with -Xdebug -Xrunjdwp.
3834   if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
3835     create_vm_init_libraries();
3836   }
3837 
3838   if (CleanChunkPoolAsync) {
3839     Chunk::start_chunk_pool_cleaner_task();
3840   }
3841 
3842   // initialize compiler(s)
3843 #if defined(COMPILER1) || COMPILER2_OR_JVMCI
3844 #if INCLUDE_JVMCI
3845   bool force_JVMCI_intialization = false;
3846   if (EnableJVMCI) {
3847     // Initialize JVMCI eagerly when it is explicitly requested.
3848     // Or when JVMCIPrintProperties is enabled.
3849     // The JVMCI Java initialization code will read this flag and
3850     // do the printing if it's set.
3851     force_JVMCI_intialization = EagerJVMCI || JVMCIPrintProperties;
3852 
3853     if (!force_JVMCI_intialization) {
3854       // 8145270: Force initialization of JVMCI runtime otherwise requests for blocking
3855       // compilations via JVMCI will not actually block until JVMCI is initialized.
3856       force_JVMCI_intialization = UseJVMCICompiler && (!UseInterpreter || !BackgroundCompilation);
3857     }
3858   }
3859 #endif
3860   CompileBroker::compilation_init_phase1(CHECK_JNI_ERR);
3861   // Postpone completion of compiler initialization to after JVMCI
3862   // is initialized to avoid timeouts of blocking compilations.
3863   if (JVMCI_ONLY(!force_JVMCI_intialization) NOT_JVMCI(true)) {
3864     CompileBroker::compilation_init_phase2();
3865   }
3866 #endif
3867 
3868   // Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
3869   // It is done after compilers are initialized, because otherwise compilations of
3870   // signature polymorphic MH intrinsics can be missed
3871   // (see SystemDictionary::find_method_handle_intrinsic).
3872   initialize_jsr292_core_classes(CHECK_JNI_ERR);
3873 
3874   // This will initialize the module system.  Only java.base classes can be
3875   // loaded until phase 2 completes
3876   call_initPhase2(CHECK_JNI_ERR);
3877 
3878   // Always call even when there are not JVMTI environments yet, since environments
3879   // may be attached late and JVMTI must track phases of VM execution
3880   JvmtiExport::enter_start_phase();
3881 
3882   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
3883   JvmtiExport::post_vm_start();
3884 
3885   // Final system initialization including security manager and system class loader
3886   call_initPhase3(CHECK_JNI_ERR);
3887 
3888   // cache the system and platform class loaders
3889   SystemDictionary::compute_java_loaders(CHECK_JNI_ERR);
3890 
3891 #if INCLUDE_CDS
3892   if (DumpSharedSpaces) {
3893     // capture the module path info from the ModuleEntryTable
3894     ClassLoader::initialize_module_path(THREAD);
3895   }
3896 #endif
3897 
3898 #if INCLUDE_JVMCI
3899   if (force_JVMCI_intialization) {
3900     JVMCIRuntime::force_initialization(CHECK_JNI_ERR);
3901     CompileBroker::compilation_init_phase2();
3902   }
3903 #endif
3904 
3905   // Always call even when there are not JVMTI environments yet, since environments
3906   // may be attached late and JVMTI must track phases of VM execution
3907   JvmtiExport::enter_live_phase();
3908 
3909   // Notify JVMTI agents that VM initialization is complete - nop if no agents.
3910   JvmtiExport::post_vm_initialized();
3911 
3912   JFR_ONLY(Jfr::on_vm_start();)
3913 
3914 #if INCLUDE_MANAGEMENT
3915   Management::initialize(THREAD);
3916 
3917   if (HAS_PENDING_EXCEPTION) {
3918     // management agent fails to start possibly due to
3919     // configuration problem and is responsible for printing
3920     // stack trace if appropriate. Simply exit VM.
3921     vm_exit(1);
3922   }
3923 #endif // INCLUDE_MANAGEMENT
3924 
3925   if (MemProfiling)                   MemProfiler::engage();
3926   StatSampler::engage();
3927   if (CheckJNICalls)                  JniPeriodicChecker::engage();
3928 
3929   BiasedLocking::init();
3930 
3931 #if INCLUDE_RTM_OPT
3932   RTMLockingCounters::init();
3933 #endif
3934 
3935   if (JDK_Version::current().post_vm_init_hook_enabled()) {
3936     call_postVMInitHook(THREAD);
3937     // The Java side of PostVMInitHook.run must deal with all
3938     // exceptions and provide means of diagnosis.
3939     if (HAS_PENDING_EXCEPTION) {
3940       CLEAR_PENDING_EXCEPTION;
3941     }
3942   }
3943 
3944   {
3945     MutexLocker ml(PeriodicTask_lock);
3946     // Make sure the WatcherThread can be started by WatcherThread::start()
3947     // or by dynamic enrollment.
3948     WatcherThread::make_startable();
3949     // Start up the WatcherThread if there are any periodic tasks
3950     // NOTE:  All PeriodicTasks should be registered by now. If they
3951     //   aren't, late joiners might appear to start slowly (we might
3952     //   take a while to process their first tick).
3953     if (PeriodicTask::num_tasks() > 0) {
3954       WatcherThread::start();
3955     }
3956   }
3957 
3958   create_vm_timer.end();
3959 #ifdef ASSERT
3960   _vm_complete = true;
3961 #endif
3962 
3963   if (DumpSharedSpaces) {
3964     MetaspaceShared::preload_and_dump(CHECK_JNI_ERR);
3965     ShouldNotReachHere();
3966   }
3967 
3968   return JNI_OK;
3969 }
3970 
3971 // type for the Agent_OnLoad and JVM_OnLoad entry points
3972 extern "C" {
3973   typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
3974 }
3975 // Find a command line agent library and return its entry point for
3976 //         -agentlib:  -agentpath:   -Xrun
3977 // num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array.
3978 static OnLoadEntry_t lookup_on_load(AgentLibrary* agent,
3979                                     const char *on_load_symbols[],
3980                                     size_t num_symbol_entries) {
3981   OnLoadEntry_t on_load_entry = NULL;
3982   void *library = NULL;
3983 
3984   if (!agent->valid()) {
3985     char buffer[JVM_MAXPATHLEN];
3986     char ebuf[1024] = "";
3987     const char *name = agent->name();
3988     const char *msg = "Could not find agent library ";
3989 
3990     // First check to see if agent is statically linked into executable
3991     if (os::find_builtin_agent(agent, on_load_symbols, num_symbol_entries)) {
3992       library = agent->os_lib();
3993     } else if (agent->is_absolute_path()) {
3994       library = os::dll_load(name, ebuf, sizeof ebuf);
3995       if (library == NULL) {
3996         const char *sub_msg = " in absolute path, with error: ";
3997         size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3998         char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
3999         jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
4000         // If we can't find the agent, exit.
4001         vm_exit_during_initialization(buf, NULL);
4002         FREE_C_HEAP_ARRAY(char, buf);
4003       }
4004     } else {
4005       // Try to load the agent from the standard dll directory
4006       if (os::dll_locate_lib(buffer, sizeof(buffer), Arguments::get_dll_dir(),
4007                              name)) {
4008         library = os::dll_load(buffer, ebuf, sizeof ebuf);
4009       }
4010       if (library == NULL) { // Try the library path directory.
4011         if (os::dll_build_name(buffer, sizeof(buffer), name)) {
4012           library = os::dll_load(buffer, ebuf, sizeof ebuf);
4013         }
4014         if (library == NULL) {
4015           const char *sub_msg = " on the library path, with error: ";
4016           const char *sub_msg2 = "\nModule java.instrument may be missing from runtime image.";
4017 
4018           size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) +
4019                        strlen(ebuf) + strlen(sub_msg2) + 1;
4020           char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
4021           if (!agent->is_instrument_lib()) {
4022             jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
4023           } else {
4024             jio_snprintf(buf, len, "%s%s%s%s%s", msg, name, sub_msg, ebuf, sub_msg2);
4025           }
4026           // If we can't find the agent, exit.
4027           vm_exit_during_initialization(buf, NULL);
4028           FREE_C_HEAP_ARRAY(char, buf);
4029         }
4030       }
4031     }
4032     agent->set_os_lib(library);
4033     agent->set_valid();
4034   }
4035 
4036   // Find the OnLoad function.
4037   on_load_entry =
4038     CAST_TO_FN_PTR(OnLoadEntry_t, os::find_agent_function(agent,
4039                                                           false,
4040                                                           on_load_symbols,
4041                                                           num_symbol_entries));
4042   return on_load_entry;
4043 }
4044 
4045 // Find the JVM_OnLoad entry point
4046 static OnLoadEntry_t lookup_jvm_on_load(AgentLibrary* agent) {
4047   const char *on_load_symbols[] = JVM_ONLOAD_SYMBOLS;
4048   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
4049 }
4050 
4051 // Find the Agent_OnLoad entry point
4052 static OnLoadEntry_t lookup_agent_on_load(AgentLibrary* agent) {
4053   const char *on_load_symbols[] = AGENT_ONLOAD_SYMBOLS;
4054   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
4055 }
4056 
4057 // For backwards compatibility with -Xrun
4058 // Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be
4059 // treated like -agentpath:
4060 // Must be called before agent libraries are created
4061 void Threads::convert_vm_init_libraries_to_agents() {
4062   AgentLibrary* agent;
4063   AgentLibrary* next;
4064 
4065   for (agent = Arguments::libraries(); agent != NULL; agent = next) {
4066     next = agent->next();  // cache the next agent now as this agent may get moved off this list
4067     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
4068 
4069     // If there is an JVM_OnLoad function it will get called later,
4070     // otherwise see if there is an Agent_OnLoad
4071     if (on_load_entry == NULL) {
4072       on_load_entry = lookup_agent_on_load(agent);
4073       if (on_load_entry != NULL) {
4074         // switch it to the agent list -- so that Agent_OnLoad will be called,
4075         // JVM_OnLoad won't be attempted and Agent_OnUnload will
4076         Arguments::convert_library_to_agent(agent);
4077       } else {
4078         vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
4079       }
4080     }
4081   }
4082 }
4083 
4084 // Create agents for -agentlib:  -agentpath:  and converted -Xrun
4085 // Invokes Agent_OnLoad
4086 // Called very early -- before JavaThreads exist
4087 void Threads::create_vm_init_agents() {
4088   extern struct JavaVM_ main_vm;
4089   AgentLibrary* agent;
4090 
4091   JvmtiExport::enter_onload_phase();
4092 
4093   for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
4094     OnLoadEntry_t  on_load_entry = lookup_agent_on_load(agent);
4095 
4096     if (on_load_entry != NULL) {
4097       // Invoke the Agent_OnLoad function
4098       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
4099       if (err != JNI_OK) {
4100         vm_exit_during_initialization("agent library failed to init", agent->name());
4101       }
4102     } else {
4103       vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
4104     }
4105   }
4106   JvmtiExport::enter_primordial_phase();
4107 }
4108 
4109 extern "C" {
4110   typedef void (JNICALL *Agent_OnUnload_t)(JavaVM *);
4111 }
4112 
4113 void Threads::shutdown_vm_agents() {
4114   // Send any Agent_OnUnload notifications
4115   const char *on_unload_symbols[] = AGENT_ONUNLOAD_SYMBOLS;
4116   size_t num_symbol_entries = ARRAY_SIZE(on_unload_symbols);
4117   extern struct JavaVM_ main_vm;
4118   for (AgentLibrary* agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
4119 
4120     // Find the Agent_OnUnload function.
4121     Agent_OnUnload_t unload_entry = CAST_TO_FN_PTR(Agent_OnUnload_t,
4122                                                    os::find_agent_function(agent,
4123                                                    false,
4124                                                    on_unload_symbols,
4125                                                    num_symbol_entries));
4126 
4127     // Invoke the Agent_OnUnload function
4128     if (unload_entry != NULL) {
4129       JavaThread* thread = JavaThread::current();
4130       ThreadToNativeFromVM ttn(thread);
4131       HandleMark hm(thread);
4132       (*unload_entry)(&main_vm);
4133     }
4134   }
4135 }
4136 
4137 // Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries
4138 // Invokes JVM_OnLoad
4139 void Threads::create_vm_init_libraries() {
4140   extern struct JavaVM_ main_vm;
4141   AgentLibrary* agent;
4142 
4143   for (agent = Arguments::libraries(); agent != NULL; agent = agent->next()) {
4144     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
4145 
4146     if (on_load_entry != NULL) {
4147       // Invoke the JVM_OnLoad function
4148       JavaThread* thread = JavaThread::current();
4149       ThreadToNativeFromVM ttn(thread);
4150       HandleMark hm(thread);
4151       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
4152       if (err != JNI_OK) {
4153         vm_exit_during_initialization("-Xrun library failed to init", agent->name());
4154       }
4155     } else {
4156       vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
4157     }
4158   }
4159 }
4160 
4161 
4162 // Last thread running calls java.lang.Shutdown.shutdown()
4163 void JavaThread::invoke_shutdown_hooks() {
4164   HandleMark hm(this);
4165 
4166   // We could get here with a pending exception, if so clear it now.
4167   if (this->has_pending_exception()) {
4168     this->clear_pending_exception();
4169   }
4170 
4171   EXCEPTION_MARK;
4172   Klass* shutdown_klass =
4173     SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
4174                                       THREAD);
4175   if (shutdown_klass != NULL) {
4176     // SystemDictionary::resolve_or_null will return null if there was
4177     // an exception.  If we cannot load the Shutdown class, just don't
4178     // call Shutdown.shutdown() at all.  This will mean the shutdown hooks
4179     // won't be run.  Note that if a shutdown hook was registered,
4180     // the Shutdown class would have already been loaded
4181     // (Runtime.addShutdownHook will load it).
4182     JavaValue result(T_VOID);
4183     JavaCalls::call_static(&result,
4184                            shutdown_klass,
4185                            vmSymbols::shutdown_method_name(),
4186                            vmSymbols::void_method_signature(),
4187                            THREAD);
4188   }
4189   CLEAR_PENDING_EXCEPTION;
4190 }
4191 
4192 // Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
4193 // the program falls off the end of main(). Another VM exit path is through
4194 // vm_exit() when the program calls System.exit() to return a value or when
4195 // there is a serious error in VM. The two shutdown paths are not exactly
4196 // the same, but they share Shutdown.shutdown() at Java level and before_exit()
4197 // and VM_Exit op at VM level.
4198 //
4199 // Shutdown sequence:
4200 //   + Shutdown native memory tracking if it is on
4201 //   + Wait until we are the last non-daemon thread to execute
4202 //     <-- every thing is still working at this moment -->
4203 //   + Call java.lang.Shutdown.shutdown(), which will invoke Java level
4204 //        shutdown hooks
4205 //   + Call before_exit(), prepare for VM exit
4206 //      > run VM level shutdown hooks (they are registered through JVM_OnExit(),
4207 //        currently the only user of this mechanism is File.deleteOnExit())
4208 //      > stop StatSampler, watcher thread, CMS threads,
4209 //        post thread end and vm death events to JVMTI,
4210 //        stop signal thread
4211 //   + Call JavaThread::exit(), it will:
4212 //      > release JNI handle blocks, remove stack guard pages
4213 //      > remove this thread from Threads list
4214 //     <-- no more Java code from this thread after this point -->
4215 //   + Stop VM thread, it will bring the remaining VM to a safepoint and stop
4216 //     the compiler threads at safepoint
4217 //     <-- do not use anything that could get blocked by Safepoint -->
4218 //   + Disable tracing at JNI/JVM barriers
4219 //   + Set _vm_exited flag for threads that are still running native code
4220 //   + Delete this thread
4221 //   + Call exit_globals()
4222 //      > deletes tty
4223 //      > deletes PerfMemory resources
4224 //   + Return to caller
4225 
4226 bool Threads::destroy_vm() {
4227   JavaThread* thread = JavaThread::current();
4228 
4229 #ifdef ASSERT
4230   _vm_complete = false;
4231 #endif
4232   // Wait until we are the last non-daemon thread to execute
4233   { MutexLocker nu(Threads_lock);
4234     while (Threads::number_of_non_daemon_threads() > 1)
4235       // This wait should make safepoint checks, wait without a timeout,
4236       // and wait as a suspend-equivalent condition.
4237       Threads_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
4238                          Mutex::_as_suspend_equivalent_flag);
4239   }
4240 
4241   EventShutdown e;
4242   if (e.should_commit()) {
4243     e.set_reason("No remaining non-daemon Java threads");
4244     e.commit();
4245   }
4246 
4247   // Hang forever on exit if we are reporting an error.
4248   if (ShowMessageBoxOnError && VMError::is_error_reported()) {
4249     os::infinite_sleep();
4250   }
4251   os::wait_for_keypress_at_exit();
4252 
4253   // run Java level shutdown hooks
4254   thread->invoke_shutdown_hooks();
4255 
4256   before_exit(thread);
4257 
4258   thread->exit(true);
4259   // thread will never call smr_delete, instead of implicit cancel
4260   // in wait_for_vm_thread_exit we do it explicit.
4261   thread->cancel_handshake();
4262 
4263   // Stop VM thread.
4264   {
4265     // 4945125 The vm thread comes to a safepoint during exit.
4266     // GC vm_operations can get caught at the safepoint, and the
4267     // heap is unparseable if they are caught. Grab the Heap_lock
4268     // to prevent this. The GC vm_operations will not be able to
4269     // queue until after the vm thread is dead. After this point,
4270     // we'll never emerge out of the safepoint before the VM exits.
4271 
4272     MutexLocker ml(Heap_lock);
4273 
4274     VMThread::wait_for_vm_thread_exit();
4275     assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
4276     VMThread::destroy();
4277   }
4278 
4279   // Now, all Java threads are gone except daemon threads. Daemon threads
4280   // running Java code or in VM are stopped by the Safepoint. However,
4281   // daemon threads executing native code are still running.  But they
4282   // will be stopped at native=>Java/VM barriers. Note that we can't
4283   // simply kill or suspend them, as it is inherently deadlock-prone.
4284 
4285   VM_Exit::set_vm_exited();
4286 
4287   // Clean up ideal graph printers after the VMThread has started
4288   // the final safepoint which will block all the Compiler threads.
4289   // Note that this Thread has already logically exited so the
4290   // clean_up() function's use of a JavaThreadIteratorWithHandle
4291   // would be a problem except set_vm_exited() has remembered the
4292   // shutdown thread which is granted a policy exception.
4293 #if defined(COMPILER2) && !defined(PRODUCT)
4294   IdealGraphPrinter::clean_up();
4295 #endif
4296 
4297   notify_vm_shutdown();
4298 
4299   // We are after VM_Exit::set_vm_exited() so we can't call
4300   // thread->smr_delete() or we will block on the Threads_lock.
4301   // Deleting the shutdown thread here is safe because another
4302   // JavaThread cannot have an active ThreadsListHandle for
4303   // this JavaThread.
4304   delete thread;
4305 
4306 #if INCLUDE_JVMCI
4307   if (JVMCICounterSize > 0) {
4308     FREE_C_HEAP_ARRAY(jlong, JavaThread::_jvmci_old_thread_counters);
4309   }
4310 #endif
4311 
4312   // exit_globals() will delete tty
4313   exit_globals();
4314 
4315   LogConfiguration::finalize();
4316 
4317   return true;
4318 }
4319 
4320 
4321 jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
4322   if (version == JNI_VERSION_1_1) return JNI_TRUE;
4323   return is_supported_jni_version(version);
4324 }
4325 
4326 
4327 jboolean Threads::is_supported_jni_version(jint version) {
4328   if (version == JNI_VERSION_1_2) return JNI_TRUE;
4329   if (version == JNI_VERSION_1_4) return JNI_TRUE;
4330   if (version == JNI_VERSION_1_6) return JNI_TRUE;
4331   if (version == JNI_VERSION_1_8) return JNI_TRUE;
4332   if (version == JNI_VERSION_9) return JNI_TRUE;
4333   if (version == JNI_VERSION_10) return JNI_TRUE;
4334   return JNI_FALSE;
4335 }
4336 
4337 
4338 void Threads::add(JavaThread* p, bool force_daemon) {
4339   // The threads lock must be owned at this point
4340   assert_locked_or_safepoint(Threads_lock);
4341 
4342   BarrierSet::barrier_set()->on_thread_attach(p);
4343 
4344   p->set_next(_thread_list);
4345   _thread_list = p;
4346 
4347   // Once a JavaThread is added to the Threads list, smr_delete() has
4348   // to be used to delete it. Otherwise we can just delete it directly.
4349   p->set_on_thread_list();
4350 
4351   _number_of_threads++;
4352   oop threadObj = p->threadObj();
4353   bool daemon = true;
4354   // Bootstrapping problem: threadObj can be null for initial
4355   // JavaThread (or for threads attached via JNI)
4356   if ((!force_daemon) && (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj))) {
4357     _number_of_non_daemon_threads++;
4358     daemon = false;
4359   }
4360 
4361   ThreadService::add_thread(p, daemon);
4362 
4363   // Maintain fast thread list
4364   ThreadsSMRSupport::add_thread(p);
4365 
4366   // Possible GC point.
4367   Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p));
4368 }
4369 
4370 void Threads::remove(JavaThread* p) {
4371 
4372   // Reclaim the objectmonitors from the omInUseList and omFreeList of the moribund thread.
4373   ObjectSynchronizer::omFlush(p);
4374 
4375   // Extra scope needed for Thread_lock, so we can check
4376   // that we do not remove thread without safepoint code notice
4377   { MutexLocker ml(Threads_lock);
4378 
4379     assert(ThreadsSMRSupport::get_java_thread_list()->includes(p), "p must be present");
4380 
4381     // Maintain fast thread list
4382     ThreadsSMRSupport::remove_thread(p);
4383 
4384     JavaThread* current = _thread_list;
4385     JavaThread* prev    = NULL;
4386 
4387     while (current != p) {
4388       prev    = current;
4389       current = current->next();
4390     }
4391 
4392     if (prev) {
4393       prev->set_next(current->next());
4394     } else {
4395       _thread_list = p->next();
4396     }
4397 
4398     _number_of_threads--;
4399     oop threadObj = p->threadObj();
4400     bool daemon = true;
4401     if (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj)) {
4402       _number_of_non_daemon_threads--;
4403       daemon = false;
4404 
4405       // Only one thread left, do a notify on the Threads_lock so a thread waiting
4406       // on destroy_vm will wake up.
4407       if (number_of_non_daemon_threads() == 1) {
4408         Threads_lock->notify_all();
4409       }
4410     }
4411     ThreadService::remove_thread(p, daemon);
4412 
4413     // Make sure that safepoint code disregard this thread. This is needed since
4414     // the thread might mess around with locks after this point. This can cause it
4415     // to do callbacks into the safepoint code. However, the safepoint code is not aware
4416     // of this thread since it is removed from the queue.
4417     p->set_terminated_value();
4418   } // unlock Threads_lock
4419 
4420   // Since Events::log uses a lock, we grab it outside the Threads_lock
4421   Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p));
4422 }
4423 
4424 // Operations on the Threads list for GC.  These are not explicitly locked,
4425 // but the garbage collector must provide a safe context for them to run.
4426 // In particular, these things should never be called when the Threads_lock
4427 // is held by some other thread. (Note: the Safepoint abstraction also
4428 // uses the Threads_lock to guarantee this property. It also makes sure that
4429 // all threads gets blocked when exiting or starting).
4430 
4431 void Threads::oops_do(OopClosure* f, CodeBlobClosure* cf) {
4432   ALL_JAVA_THREADS(p) {
4433     p->oops_do(f, cf);
4434   }
4435   VMThread::vm_thread()->oops_do(f, cf);
4436 }
4437 
4438 void Threads::change_thread_claim_parity() {
4439   // Set the new claim parity.
4440   assert(_thread_claim_parity >= 0 && _thread_claim_parity <= 2,
4441          "Not in range.");
4442   _thread_claim_parity++;
4443   if (_thread_claim_parity == 3) _thread_claim_parity = 1;
4444   assert(_thread_claim_parity >= 1 && _thread_claim_parity <= 2,
4445          "Not in range.");
4446 }
4447 
4448 #ifdef ASSERT
4449 void Threads::assert_all_threads_claimed() {
4450   ALL_JAVA_THREADS(p) {
4451     const int thread_parity = p->oops_do_parity();
4452     assert((thread_parity == _thread_claim_parity),
4453            "Thread " PTR_FORMAT " has incorrect parity %d != %d", p2i(p), thread_parity, _thread_claim_parity);
4454   }
4455   VMThread* vmt = VMThread::vm_thread();
4456   const int thread_parity = vmt->oops_do_parity();
4457   assert((thread_parity == _thread_claim_parity),
4458          "VMThread " PTR_FORMAT " has incorrect parity %d != %d", p2i(vmt), thread_parity, _thread_claim_parity);
4459 }
4460 #endif // ASSERT
4461 
4462 class ParallelOopsDoThreadClosure : public ThreadClosure {
4463 private:
4464   OopClosure* _f;
4465   CodeBlobClosure* _cf;
4466 public:
4467   ParallelOopsDoThreadClosure(OopClosure* f, CodeBlobClosure* cf) : _f(f), _cf(cf) {}
4468   void do_thread(Thread* t) {
4469     t->oops_do(_f, _cf);
4470   }
4471 };
4472 
4473 void Threads::possibly_parallel_oops_do(bool is_par, OopClosure* f, CodeBlobClosure* cf) {
4474   ParallelOopsDoThreadClosure tc(f, cf);
4475   possibly_parallel_threads_do(is_par, &tc);
4476 }
4477 
4478 void Threads::nmethods_do(CodeBlobClosure* cf) {
4479   ALL_JAVA_THREADS(p) {
4480     // This is used by the code cache sweeper to mark nmethods that are active
4481     // on the stack of a Java thread. Ignore the sweeper thread itself to avoid
4482     // marking CodeCacheSweeperThread::_scanned_compiled_method as active.
4483     if(!p->is_Code_cache_sweeper_thread()) {
4484       p->nmethods_do(cf);
4485     }
4486   }
4487 }
4488 
4489 void Threads::metadata_do(void f(Metadata*)) {
4490   ALL_JAVA_THREADS(p) {
4491     p->metadata_do(f);
4492   }
4493 }
4494 
4495 class ThreadHandlesClosure : public ThreadClosure {
4496   void (*_f)(Metadata*);
4497  public:
4498   ThreadHandlesClosure(void f(Metadata*)) : _f(f) {}
4499   virtual void do_thread(Thread* thread) {
4500     thread->metadata_handles_do(_f);
4501   }
4502 };
4503 
4504 void Threads::metadata_handles_do(void f(Metadata*)) {
4505   // Only walk the Handles in Thread.
4506   ThreadHandlesClosure handles_closure(f);
4507   threads_do(&handles_closure);
4508 }
4509 
4510 void Threads::deoptimized_wrt_marked_nmethods() {
4511   ALL_JAVA_THREADS(p) {
4512     p->deoptimized_wrt_marked_nmethods();
4513   }
4514 }
4515 
4516 
4517 // Get count Java threads that are waiting to enter the specified monitor.
4518 GrowableArray<JavaThread*>* Threads::get_pending_threads(ThreadsList * t_list,
4519                                                          int count,
4520                                                          address monitor) {
4521   GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
4522 
4523   int i = 0;
4524   DO_JAVA_THREADS(t_list, p) {
4525     if (!p->can_call_java()) continue;
4526 
4527     address pending = (address)p->current_pending_monitor();
4528     if (pending == monitor) {             // found a match
4529       if (i < count) result->append(p);   // save the first count matches
4530       i++;
4531     }
4532   }
4533 
4534   return result;
4535 }
4536 
4537 
4538 JavaThread *Threads::owning_thread_from_monitor_owner(ThreadsList * t_list,
4539                                                       address owner) {
4540   // NULL owner means not locked so we can skip the search
4541   if (owner == NULL) return NULL;
4542 
4543   DO_JAVA_THREADS(t_list, p) {
4544     // first, see if owner is the address of a Java thread
4545     if (owner == (address)p) return p;
4546   }
4547 
4548   // Cannot assert on lack of success here since this function may be
4549   // used by code that is trying to report useful problem information
4550   // like deadlock detection.
4551   if (UseHeavyMonitors) return NULL;
4552 
4553   // If we didn't find a matching Java thread and we didn't force use of
4554   // heavyweight monitors, then the owner is the stack address of the
4555   // Lock Word in the owning Java thread's stack.
4556   //
4557   JavaThread* the_owner = NULL;
4558   DO_JAVA_THREADS(t_list, q) {
4559     if (q->is_lock_owned(owner)) {
4560       the_owner = q;
4561       break;
4562     }
4563   }
4564 
4565   // cannot assert on lack of success here; see above comment
4566   return the_owner;
4567 }
4568 
4569 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
4570 void Threads::print_on(outputStream* st, bool print_stacks,
4571                        bool internal_format, bool print_concurrent_locks,
4572                        bool print_extended_info) {
4573   char buf[32];
4574   st->print_raw_cr(os::local_time_string(buf, sizeof(buf)));
4575 
4576   st->print_cr("Full thread dump %s (%s %s):",
4577                Abstract_VM_Version::vm_name(),
4578                Abstract_VM_Version::vm_release(),
4579                Abstract_VM_Version::vm_info_string());
4580   st->cr();
4581 
4582 #if INCLUDE_SERVICES
4583   // Dump concurrent locks
4584   ConcurrentLocksDump concurrent_locks;
4585   if (print_concurrent_locks) {
4586     concurrent_locks.dump_at_safepoint();
4587   }
4588 #endif // INCLUDE_SERVICES
4589 
4590   ThreadsSMRSupport::print_info_on(st);
4591   st->cr();
4592 
4593   ALL_JAVA_THREADS(p) {
4594     ResourceMark rm;
4595     p->print_on(st, print_extended_info);
4596     if (print_stacks) {
4597       if (internal_format) {
4598         p->trace_stack();
4599       } else {
4600         p->print_stack_on(st);
4601       }
4602     }
4603     st->cr();
4604 #if INCLUDE_SERVICES
4605     if (print_concurrent_locks) {
4606       concurrent_locks.print_locks_on(p, st);
4607     }
4608 #endif // INCLUDE_SERVICES
4609   }
4610 
4611   VMThread::vm_thread()->print_on(st);
4612   st->cr();
4613   Universe::heap()->print_gc_threads_on(st);
4614   WatcherThread* wt = WatcherThread::watcher_thread();
4615   if (wt != NULL) {
4616     wt->print_on(st);
4617     st->cr();
4618   }
4619 
4620   st->flush();
4621 }
4622 
4623 void Threads::print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf,
4624                              int buflen, bool* found_current) {
4625   if (this_thread != NULL) {
4626     bool is_current = (current == this_thread);
4627     *found_current = *found_current || is_current;
4628     st->print("%s", is_current ? "=>" : "  ");
4629 
4630     st->print(PTR_FORMAT, p2i(this_thread));
4631     st->print(" ");
4632     this_thread->print_on_error(st, buf, buflen);
4633     st->cr();
4634   }
4635 }
4636 
4637 class PrintOnErrorClosure : public ThreadClosure {
4638   outputStream* _st;
4639   Thread* _current;
4640   char* _buf;
4641   int _buflen;
4642   bool* _found_current;
4643  public:
4644   PrintOnErrorClosure(outputStream* st, Thread* current, char* buf,
4645                       int buflen, bool* found_current) :
4646    _st(st), _current(current), _buf(buf), _buflen(buflen), _found_current(found_current) {}
4647 
4648   virtual void do_thread(Thread* thread) {
4649     Threads::print_on_error(thread, _st, _current, _buf, _buflen, _found_current);
4650   }
4651 };
4652 
4653 // Threads::print_on_error() is called by fatal error handler. It's possible
4654 // that VM is not at safepoint and/or current thread is inside signal handler.
4655 // Don't print stack trace, as the stack may not be walkable. Don't allocate
4656 // memory (even in resource area), it might deadlock the error handler.
4657 void Threads::print_on_error(outputStream* st, Thread* current, char* buf,
4658                              int buflen) {
4659   ThreadsSMRSupport::print_info_on(st);
4660   st->cr();
4661 
4662   bool found_current = false;
4663   st->print_cr("Java Threads: ( => current thread )");
4664   ALL_JAVA_THREADS(thread) {
4665     print_on_error(thread, st, current, buf, buflen, &found_current);
4666   }
4667   st->cr();
4668 
4669   st->print_cr("Other Threads:");
4670   print_on_error(VMThread::vm_thread(), st, current, buf, buflen, &found_current);
4671   print_on_error(WatcherThread::watcher_thread(), st, current, buf, buflen, &found_current);
4672 
4673   PrintOnErrorClosure print_closure(st, current, buf, buflen, &found_current);
4674   Universe::heap()->gc_threads_do(&print_closure);
4675 
4676   if (!found_current) {
4677     st->cr();
4678     st->print("=>" PTR_FORMAT " (exited) ", p2i(current));
4679     current->print_on_error(st, buf, buflen);
4680     st->cr();
4681   }
4682   st->cr();
4683 
4684   st->print_cr("Threads with active compile tasks:");
4685   print_threads_compiling(st, buf, buflen);
4686 }
4687 
4688 void Threads::print_threads_compiling(outputStream* st, char* buf, int buflen) {
4689   ALL_JAVA_THREADS(thread) {
4690     if (thread->is_Compiler_thread()) {
4691       CompilerThread* ct = (CompilerThread*) thread;
4692 
4693       // Keep task in local variable for NULL check.
4694       // ct->_task might be set to NULL by concurring compiler thread
4695       // because it completed the compilation. The task is never freed,
4696       // though, just returned to a free list.
4697       CompileTask* task = ct->task();
4698       if (task != NULL) {
4699         thread->print_name_on_error(st, buf, buflen);
4700         task->print(st, NULL, true, true);
4701       }
4702     }
4703   }
4704 }
4705 
4706 
4707 // Internal SpinLock and Mutex
4708 // Based on ParkEvent
4709 
4710 // Ad-hoc mutual exclusion primitives: SpinLock and Mux
4711 //
4712 // We employ SpinLocks _only for low-contention, fixed-length
4713 // short-duration critical sections where we're concerned
4714 // about native mutex_t or HotSpot Mutex:: latency.
4715 // The mux construct provides a spin-then-block mutual exclusion
4716 // mechanism.
4717 //
4718 // Testing has shown that contention on the ListLock guarding gFreeList
4719 // is common.  If we implement ListLock as a simple SpinLock it's common
4720 // for the JVM to devolve to yielding with little progress.  This is true
4721 // despite the fact that the critical sections protected by ListLock are
4722 // extremely short.
4723 //
4724 // TODO-FIXME: ListLock should be of type SpinLock.
4725 // We should make this a 1st-class type, integrated into the lock
4726 // hierarchy as leaf-locks.  Critically, the SpinLock structure
4727 // should have sufficient padding to avoid false-sharing and excessive
4728 // cache-coherency traffic.
4729 
4730 
4731 typedef volatile int SpinLockT;
4732 
4733 void Thread::SpinAcquire(volatile int * adr, const char * LockName) {
4734   if (Atomic::cmpxchg (1, adr, 0) == 0) {
4735     return;   // normal fast-path return
4736   }
4737 
4738   // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
4739   int ctr = 0;
4740   int Yields = 0;
4741   for (;;) {
4742     while (*adr != 0) {
4743       ++ctr;
4744       if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
4745         if (Yields > 5) {
4746           os::naked_short_sleep(1);
4747         } else {
4748           os::naked_yield();
4749           ++Yields;
4750         }
4751       } else {
4752         SpinPause();
4753       }
4754     }
4755     if (Atomic::cmpxchg(1, adr, 0) == 0) return;
4756   }
4757 }
4758 
4759 void Thread::SpinRelease(volatile int * adr) {
4760   assert(*adr != 0, "invariant");
4761   OrderAccess::fence();      // guarantee at least release consistency.
4762   // Roach-motel semantics.
4763   // It's safe if subsequent LDs and STs float "up" into the critical section,
4764   // but prior LDs and STs within the critical section can't be allowed
4765   // to reorder or float past the ST that releases the lock.
4766   // Loads and stores in the critical section - which appear in program
4767   // order before the store that releases the lock - must also appear
4768   // before the store that releases the lock in memory visibility order.
4769   // Conceptually we need a #loadstore|#storestore "release" MEMBAR before
4770   // the ST of 0 into the lock-word which releases the lock, so fence
4771   // more than covers this on all platforms.
4772   *adr = 0;
4773 }
4774 
4775 // muxAcquire and muxRelease:
4776 //
4777 // *  muxAcquire and muxRelease support a single-word lock-word construct.
4778 //    The LSB of the word is set IFF the lock is held.
4779 //    The remainder of the word points to the head of a singly-linked list
4780 //    of threads blocked on the lock.
4781 //
4782 // *  The current implementation of muxAcquire-muxRelease uses its own
4783 //    dedicated Thread._MuxEvent instance.  If we're interested in
4784 //    minimizing the peak number of extant ParkEvent instances then
4785 //    we could eliminate _MuxEvent and "borrow" _ParkEvent as long
4786 //    as certain invariants were satisfied.  Specifically, care would need
4787 //    to be taken with regards to consuming unpark() "permits".
4788 //    A safe rule of thumb is that a thread would never call muxAcquire()
4789 //    if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
4790 //    park().  Otherwise the _ParkEvent park() operation in muxAcquire() could
4791 //    consume an unpark() permit intended for monitorenter, for instance.
4792 //    One way around this would be to widen the restricted-range semaphore
4793 //    implemented in park().  Another alternative would be to provide
4794 //    multiple instances of the PlatformEvent() for each thread.  One
4795 //    instance would be dedicated to muxAcquire-muxRelease, for instance.
4796 //
4797 // *  Usage:
4798 //    -- Only as leaf locks
4799 //    -- for short-term locking only as muxAcquire does not perform
4800 //       thread state transitions.
4801 //
4802 // Alternatives:
4803 // *  We could implement muxAcquire and muxRelease with MCS or CLH locks
4804 //    but with parking or spin-then-park instead of pure spinning.
4805 // *  Use Taura-Oyama-Yonenzawa locks.
4806 // *  It's possible to construct a 1-0 lock if we encode the lockword as
4807 //    (List,LockByte).  Acquire will CAS the full lockword while Release
4808 //    will STB 0 into the LockByte.  The 1-0 scheme admits stranding, so
4809 //    acquiring threads use timers (ParkTimed) to detect and recover from
4810 //    the stranding window.  Thread/Node structures must be aligned on 256-byte
4811 //    boundaries by using placement-new.
4812 // *  Augment MCS with advisory back-link fields maintained with CAS().
4813 //    Pictorially:  LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
4814 //    The validity of the backlinks must be ratified before we trust the value.
4815 //    If the backlinks are invalid the exiting thread must back-track through the
4816 //    the forward links, which are always trustworthy.
4817 // *  Add a successor indication.  The LockWord is currently encoded as
4818 //    (List, LOCKBIT:1).  We could also add a SUCCBIT or an explicit _succ variable
4819 //    to provide the usual futile-wakeup optimization.
4820 //    See RTStt for details.
4821 //
4822 
4823 
4824 const intptr_t LOCKBIT = 1;
4825 
4826 void Thread::muxAcquire(volatile intptr_t * Lock, const char * LockName) {
4827   intptr_t w = Atomic::cmpxchg(LOCKBIT, Lock, (intptr_t)0);
4828   if (w == 0) return;
4829   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4830     return;
4831   }
4832 
4833   ParkEvent * const Self = Thread::current()->_MuxEvent;
4834   assert((intptr_t(Self) & LOCKBIT) == 0, "invariant");
4835   for (;;) {
4836     int its = (os::is_MP() ? 100 : 0) + 1;
4837 
4838     // Optional spin phase: spin-then-park strategy
4839     while (--its >= 0) {
4840       w = *Lock;
4841       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4842         return;
4843       }
4844     }
4845 
4846     Self->reset();
4847     Self->OnList = intptr_t(Lock);
4848     // The following fence() isn't _strictly necessary as the subsequent
4849     // CAS() both serializes execution and ratifies the fetched *Lock value.
4850     OrderAccess::fence();
4851     for (;;) {
4852       w = *Lock;
4853       if ((w & LOCKBIT) == 0) {
4854         if (Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4855           Self->OnList = 0;   // hygiene - allows stronger asserts
4856           return;
4857         }
4858         continue;      // Interference -- *Lock changed -- Just retry
4859       }
4860       assert(w & LOCKBIT, "invariant");
4861       Self->ListNext = (ParkEvent *) (w & ~LOCKBIT);
4862       if (Atomic::cmpxchg(intptr_t(Self)|LOCKBIT, Lock, w) == w) break;
4863     }
4864 
4865     while (Self->OnList != 0) {
4866       Self->park();
4867     }
4868   }
4869 }
4870 
4871 void Thread::muxAcquireW(volatile intptr_t * Lock, ParkEvent * ev) {
4872   intptr_t w = Atomic::cmpxchg(LOCKBIT, Lock, (intptr_t)0);
4873   if (w == 0) return;
4874   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4875     return;
4876   }
4877 
4878   ParkEvent * ReleaseAfter = NULL;
4879   if (ev == NULL) {
4880     ev = ReleaseAfter = ParkEvent::Allocate(NULL);
4881   }
4882   assert((intptr_t(ev) & LOCKBIT) == 0, "invariant");
4883   for (;;) {
4884     guarantee(ev->OnList == 0, "invariant");
4885     int its = (os::is_MP() ? 100 : 0) + 1;
4886 
4887     // Optional spin phase: spin-then-park strategy
4888     while (--its >= 0) {
4889       w = *Lock;
4890       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4891         if (ReleaseAfter != NULL) {
4892           ParkEvent::Release(ReleaseAfter);
4893         }
4894         return;
4895       }
4896     }
4897 
4898     ev->reset();
4899     ev->OnList = intptr_t(Lock);
4900     // The following fence() isn't _strictly necessary as the subsequent
4901     // CAS() both serializes execution and ratifies the fetched *Lock value.
4902     OrderAccess::fence();
4903     for (;;) {
4904       w = *Lock;
4905       if ((w & LOCKBIT) == 0) {
4906         if (Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4907           ev->OnList = 0;
4908           // We call ::Release while holding the outer lock, thus
4909           // artificially lengthening the critical section.
4910           // Consider deferring the ::Release() until the subsequent unlock(),
4911           // after we've dropped the outer lock.
4912           if (ReleaseAfter != NULL) {
4913             ParkEvent::Release(ReleaseAfter);
4914           }
4915           return;
4916         }
4917         continue;      // Interference -- *Lock changed -- Just retry
4918       }
4919       assert(w & LOCKBIT, "invariant");
4920       ev->ListNext = (ParkEvent *) (w & ~LOCKBIT);
4921       if (Atomic::cmpxchg(intptr_t(ev)|LOCKBIT, Lock, w) == w) break;
4922     }
4923 
4924     while (ev->OnList != 0) {
4925       ev->park();
4926     }
4927   }
4928 }
4929 
4930 // Release() must extract a successor from the list and then wake that thread.
4931 // It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
4932 // similar to that used by ParkEvent::Allocate() and ::Release().  DMR-based
4933 // Release() would :
4934 // (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
4935 // (B) Extract a successor from the private list "in-hand"
4936 // (C) attempt to CAS() the residual back into *Lock over null.
4937 //     If there were any newly arrived threads and the CAS() would fail.
4938 //     In that case Release() would detach the RATs, re-merge the list in-hand
4939 //     with the RATs and repeat as needed.  Alternately, Release() might
4940 //     detach and extract a successor, but then pass the residual list to the wakee.
4941 //     The wakee would be responsible for reattaching and remerging before it
4942 //     competed for the lock.
4943 //
4944 // Both "pop" and DMR are immune from ABA corruption -- there can be
4945 // multiple concurrent pushers, but only one popper or detacher.
4946 // This implementation pops from the head of the list.  This is unfair,
4947 // but tends to provide excellent throughput as hot threads remain hot.
4948 // (We wake recently run threads first).
4949 //
4950 // All paths through muxRelease() will execute a CAS.
4951 // Release consistency -- We depend on the CAS in muxRelease() to provide full
4952 // bidirectional fence/MEMBAR semantics, ensuring that all prior memory operations
4953 // executed within the critical section are complete and globally visible before the
4954 // store (CAS) to the lock-word that releases the lock becomes globally visible.
4955 void Thread::muxRelease(volatile intptr_t * Lock)  {
4956   for (;;) {
4957     const intptr_t w = Atomic::cmpxchg((intptr_t)0, Lock, LOCKBIT);
4958     assert(w & LOCKBIT, "invariant");
4959     if (w == LOCKBIT) return;
4960     ParkEvent * const List = (ParkEvent *) (w & ~LOCKBIT);
4961     assert(List != NULL, "invariant");
4962     assert(List->OnList == intptr_t(Lock), "invariant");
4963     ParkEvent * const nxt = List->ListNext;
4964     guarantee((intptr_t(nxt) & LOCKBIT) == 0, "invariant");
4965 
4966     // The following CAS() releases the lock and pops the head element.
4967     // The CAS() also ratifies the previously fetched lock-word value.
4968     if (Atomic::cmpxchg(intptr_t(nxt), Lock, w) != w) {
4969       continue;
4970     }
4971     List->OnList = 0;
4972     OrderAccess::fence();
4973     List->unpark();
4974     return;
4975   }
4976 }
4977 
4978 
4979 void Threads::verify() {
4980   ALL_JAVA_THREADS(p) {
4981     p->verify();
4982   }
4983   VMThread* thread = VMThread::vm_thread();
4984   if (thread != NULL) thread->verify();
4985 }