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 "jvmtifiles/jvmtiEnv.hpp"
  45 #include "logging/log.hpp"
  46 #include "logging/logConfiguration.hpp"
  47 #include "logging/logStream.hpp"
  48 #include "memory/allocation.inline.hpp"
  49 #include "memory/metaspaceShared.hpp"
  50 #include "memory/oopFactory.hpp"
  51 #include "memory/resourceArea.hpp"
  52 #include "memory/universe.hpp"
  53 #include "oops/access.inline.hpp"
  54 #include "oops/instanceKlass.hpp"
  55 #include "oops/objArrayOop.hpp"
  56 #include "oops/oop.inline.hpp"
  57 #include "oops/symbol.hpp"
  58 #include "oops/typeArrayOop.inline.hpp"
  59 #include "oops/verifyOopClosure.hpp"
  60 #include "prims/jvm_misc.hpp"
  61 #include "prims/jvmtiExport.hpp"
  62 #include "prims/jvmtiThreadState.hpp"
  63 #include "runtime/arguments.hpp"
  64 #include "runtime/atomic.hpp"
  65 #include "runtime/biasedLocking.hpp"
  66 #include "runtime/fieldDescriptor.inline.hpp"
  67 #include "runtime/flags/jvmFlagConstraintList.hpp"
  68 #include "runtime/flags/jvmFlagRangeList.hpp"
  69 #include "runtime/flags/jvmFlagWriteableList.hpp"
  70 #include "runtime/deoptimization.hpp"
  71 #include "runtime/frame.inline.hpp"
  72 #include "runtime/handshake.hpp"
  73 #include "runtime/init.hpp"
  74 #include "runtime/interfaceSupport.inline.hpp"
  75 #include "runtime/java.hpp"
  76 #include "runtime/javaCalls.hpp"
  77 #include "runtime/jniHandles.inline.hpp"
  78 #include "runtime/jniPeriodicChecker.hpp"
  79 #include "runtime/memprofiler.hpp"
  80 #include "runtime/mutexLocker.hpp"
  81 #include "runtime/objectMonitor.hpp"
  82 #include "runtime/orderAccess.hpp"
  83 #include "runtime/osThread.hpp"
  84 #include "runtime/prefetch.inline.hpp"
  85 #include "runtime/safepoint.hpp"
  86 #include "runtime/safepointMechanism.inline.hpp"
  87 #include "runtime/safepointVerifiers.hpp"
  88 #include "runtime/sharedRuntime.hpp"
  89 #include "runtime/statSampler.hpp"
  90 #include "runtime/stubRoutines.hpp"
  91 #include "runtime/sweeper.hpp"
  92 #include "runtime/task.hpp"
  93 #include "runtime/thread.inline.hpp"
  94 #include "runtime/threadCritical.hpp"
  95 #include "runtime/threadSMR.inline.hpp"
  96 #include "runtime/threadStatisticalInfo.hpp"
  97 #include "runtime/timer.hpp"
  98 #include "runtime/timerTrace.hpp"
  99 #include "runtime/vframe.inline.hpp"
 100 #include "runtime/vframeArray.hpp"
 101 #include "runtime/vframe_hp.hpp"
 102 #include "runtime/vmThread.hpp"
 103 #include "runtime/vm_operations.hpp"
 104 #include "runtime/vm_version.hpp"
 105 #include "services/attachListener.hpp"
 106 #include "services/management.hpp"
 107 #include "services/memTracker.hpp"
 108 #include "services/threadService.hpp"
 109 #include "utilities/align.hpp"
 110 #include "utilities/copy.hpp"
 111 #include "utilities/defaultStream.hpp"
 112 #include "utilities/dtrace.hpp"
 113 #include "utilities/events.hpp"
 114 #include "utilities/macros.hpp"
 115 #include "utilities/preserveException.hpp"
 116 #include "utilities/singleWriterSynchronizer.hpp"
 117 #include "utilities/vmError.hpp"
 118 #if INCLUDE_JVMCI
 119 #include "jvmci/jvmciCompiler.hpp"
 120 #include "jvmci/jvmciRuntime.hpp"
 121 #include "logging/logHandle.hpp"
 122 #endif
 123 #ifdef COMPILER1
 124 #include "c1/c1_Compiler.hpp"
 125 #endif
 126 #ifdef COMPILER2
 127 #include "opto/c2compiler.hpp"
 128 #include "opto/idealGraphPrinter.hpp"
 129 #endif
 130 #if INCLUDE_RTM_OPT
 131 #include "runtime/rtmLocking.hpp"
 132 #endif
 133 #if INCLUDE_JFR
 134 #include "jfr/jfr.hpp"
 135 #endif
 136 
 137 // Initialization after module runtime initialization
 138 void universe_post_module_init();  // must happen after call_initPhase2
 139 
 140 #ifdef DTRACE_ENABLED
 141 
 142 // Only bother with this argument setup if dtrace is available
 143 
 144   #define HOTSPOT_THREAD_PROBE_start HOTSPOT_THREAD_START
 145   #define HOTSPOT_THREAD_PROBE_stop HOTSPOT_THREAD_STOP
 146 
 147   #define DTRACE_THREAD_PROBE(probe, javathread)                           \
 148     {                                                                      \
 149       ResourceMark rm(this);                                               \
 150       int len = 0;                                                         \
 151       const char* name = (javathread)->get_thread_name();                  \
 152       len = strlen(name);                                                  \
 153       HOTSPOT_THREAD_PROBE_##probe(/* probe = start, stop */               \
 154         (char *) name, len,                                                \
 155         java_lang_Thread::thread_id((javathread)->threadObj()),            \
 156         (uintptr_t) (javathread)->osthread()->thread_id(),                 \
 157         java_lang_Thread::is_daemon((javathread)->threadObj()));           \
 158     }
 159 
 160 #else //  ndef DTRACE_ENABLED
 161 
 162   #define DTRACE_THREAD_PROBE(probe, javathread)
 163 
 164 #endif // ndef DTRACE_ENABLED
 165 
 166 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 167 // Current thread is maintained as a thread-local variable
 168 THREAD_LOCAL_DECL Thread* Thread::_thr_current = NULL;
 169 #endif
 170 
 171 // ======= Thread ========
 172 // Support for forcing alignment of thread objects for biased locking
 173 void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
 174   if (UseBiasedLocking) {
 175     const int alignment = markOopDesc::biased_lock_alignment;
 176     size_t aligned_size = size + (alignment - sizeof(intptr_t));
 177     void* real_malloc_addr = throw_excpt? AllocateHeap(aligned_size, flags, CURRENT_PC)
 178                                           : AllocateHeap(aligned_size, flags, CURRENT_PC,
 179                                                          AllocFailStrategy::RETURN_NULL);
 180     void* aligned_addr     = align_up(real_malloc_addr, alignment);
 181     assert(((uintptr_t) aligned_addr + (uintptr_t) size) <=
 182            ((uintptr_t) real_malloc_addr + (uintptr_t) aligned_size),
 183            "JavaThread alignment code overflowed allocated storage");
 184     if (aligned_addr != real_malloc_addr) {
 185       log_info(biasedlocking)("Aligned thread " INTPTR_FORMAT " to " INTPTR_FORMAT,
 186                               p2i(real_malloc_addr),
 187                               p2i(aligned_addr));
 188     }
 189     ((Thread*) aligned_addr)->_real_malloc_address = real_malloc_addr;
 190     return aligned_addr;
 191   } else {
 192     return throw_excpt? AllocateHeap(size, flags, CURRENT_PC)
 193                        : AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
 194   }
 195 }
 196 
 197 void Thread::operator delete(void* p) {
 198   if (UseBiasedLocking) {
 199     FreeHeap(((Thread*) p)->_real_malloc_address);
 200   } else {
 201     FreeHeap(p);
 202   }
 203 }
 204 
 205 void JavaThread::smr_delete() {
 206   if (_on_thread_list) {
 207     ThreadsSMRSupport::smr_delete(this);
 208   } else {
 209     delete this;
 210   }
 211 }
 212 
 213 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
 214 // JavaThread
 215 
 216 
 217 Thread::Thread() {
 218   // stack and get_thread
 219   set_stack_base(NULL);
 220   set_stack_size(0);
 221   set_self_raw_id(0);
 222   set_lgrp_id(-1);
 223   DEBUG_ONLY(clear_suspendible_thread();)
 224 
 225   // allocated data structures
 226   set_osthread(NULL);
 227   set_resource_area(new (mtThread)ResourceArea());
 228   DEBUG_ONLY(_current_resource_mark = NULL;)
 229   set_handle_area(new (mtThread) HandleArea(NULL));
 230   set_metadata_handles(new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(30, true));
 231   set_active_handles(NULL);
 232   set_free_handle_block(NULL);
 233   set_last_handle_mark(NULL);
 234 
 235   // This initial value ==> never claimed.
 236   _oops_do_parity = 0;
 237   _threads_hazard_ptr = NULL;
 238   _threads_list_ptr = NULL;
 239   _nested_threads_hazard_ptr_cnt = 0;
 240   _rcu_counter = 0;
 241 
 242   // the handle mark links itself to last_handle_mark
 243   new HandleMark(this);
 244 
 245   // plain initialization
 246   debug_only(_owned_locks = NULL;)
 247   debug_only(_allow_allocation_count = 0;)
 248   NOT_PRODUCT(_allow_safepoint_count = 0;)
 249   NOT_PRODUCT(_skip_gcalot = false;)
 250   _jvmti_env_iteration_count = 0;
 251   set_allocated_bytes(0);
 252   _vm_operation_started_count = 0;
 253   _vm_operation_completed_count = 0;
 254   _current_pending_monitor = NULL;
 255   _current_pending_monitor_is_from_java = true;
 256   _current_waiting_monitor = NULL;
 257   _num_nested_signal = 0;
 258   omFreeList = NULL;
 259   omFreeCount = 0;
 260   omFreeProvision = 32;
 261   omInUseList = NULL;
 262   omInUseCount = 0;
 263 
 264 #ifdef ASSERT
 265   _visited_for_critical_count = false;
 266 #endif
 267 
 268   _SR_lock = new Monitor(Mutex::suspend_resume, "SR_lock", true,
 269                          Monitor::_safepoint_check_sometimes);
 270   _suspend_flags = 0;
 271 
 272   // thread-specific hashCode stream generator state - Marsaglia shift-xor form
 273   _hashStateX = os::random();
 274   _hashStateY = 842502087;
 275   _hashStateZ = 0x8767;    // (int)(3579807591LL & 0xffff) ;
 276   _hashStateW = 273326509;
 277 
 278   _OnTrap   = 0;
 279   _Stalled  = 0;
 280   _TypeTag  = 0x2BAD;
 281 
 282   // Many of the following fields are effectively final - immutable
 283   // Note that nascent threads can't use the Native Monitor-Mutex
 284   // construct until the _MutexEvent is initialized ...
 285   // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
 286   // we might instead use a stack of ParkEvents that we could provision on-demand.
 287   // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
 288   // and ::Release()
 289   _ParkEvent   = ParkEvent::Allocate(this);
 290   _SleepEvent  = ParkEvent::Allocate(this);
 291   _MutexEvent  = ParkEvent::Allocate(this);
 292   _MuxEvent    = ParkEvent::Allocate(this);
 293 
 294 #ifdef CHECK_UNHANDLED_OOPS
 295   if (CheckUnhandledOops) {
 296     _unhandled_oops = new UnhandledOops(this);
 297   }
 298 #endif // CHECK_UNHANDLED_OOPS
 299 #ifdef ASSERT
 300   if (UseBiasedLocking) {
 301     assert((((uintptr_t) this) & (markOopDesc::biased_lock_alignment - 1)) == 0, "forced alignment of thread object failed");
 302     assert(this == _real_malloc_address ||
 303            this == align_up(_real_malloc_address, (int)markOopDesc::biased_lock_alignment),
 304            "bug in forced alignment of thread objects");
 305   }
 306 #endif // ASSERT
 307 
 308   // Notify the barrier set that a thread is being created. Note that some
 309   // threads are created before a barrier set is available. The call to
 310   // BarrierSet::on_thread_create() for these threads is therefore deferred
 311   // to BarrierSet::set_barrier_set().
 312   BarrierSet* const barrier_set = BarrierSet::barrier_set();
 313   if (barrier_set != NULL) {
 314     barrier_set->on_thread_create(this);
 315   } else {
 316     DEBUG_ONLY(Threads::inc_threads_before_barrier_set();)
 317   }
 318 }
 319 
 320 void Thread::initialize_thread_current() {
 321 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 322   assert(_thr_current == NULL, "Thread::current already initialized");
 323   _thr_current = this;
 324 #endif
 325   assert(ThreadLocalStorage::thread() == NULL, "ThreadLocalStorage::thread already initialized");
 326   ThreadLocalStorage::set_thread(this);
 327   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 328 }
 329 
 330 void Thread::clear_thread_current() {
 331   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 332 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 333   _thr_current = NULL;
 334 #endif
 335   ThreadLocalStorage::set_thread(NULL);
 336 }
 337 
 338 void Thread::record_stack_base_and_size() {
 339   // Note: at this point, Thread object is not yet initialized. Do not rely on
 340   // any members being initialized. Do not rely on Thread::current() being set.
 341   // If possible, refrain from doing anything which may crash or assert since
 342   // quite probably those crash dumps will be useless.
 343   set_stack_base(os::current_stack_base());
 344   set_stack_size(os::current_stack_size());
 345 
 346 #ifdef SOLARIS
 347   if (os::is_primordial_thread()) {
 348     os::Solaris::correct_stack_boundaries_for_primordial_thread(this);
 349   }
 350 #endif
 351 
 352   // Set stack limits after thread is initialized.
 353   if (is_Java_thread()) {
 354     ((JavaThread*) this)->set_stack_overflow_limit();
 355     ((JavaThread*) this)->set_reserved_stack_activation(stack_base());
 356   }
 357 }
 358 
 359 #if INCLUDE_NMT
 360 void Thread::register_thread_stack_with_NMT() {
 361   MemTracker::record_thread_stack(stack_end(), stack_size());
 362 }
 363 #endif // INCLUDE_NMT
 364 
 365 void Thread::call_run() {
 366   // At this point, Thread object should be fully initialized and
 367   // Thread::current() should be set.
 368 
 369   register_thread_stack_with_NMT();
 370 
 371   JFR_ONLY(Jfr::on_thread_start(this);)
 372 
 373   log_debug(os, thread)("Thread " UINTX_FORMAT " stack dimensions: "
 374     PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT "k).",
 375     os::current_thread_id(), p2i(stack_base() - stack_size()),
 376     p2i(stack_base()), stack_size()/1024);
 377 
 378   // Invoke <ChildClass>::run()
 379   this->run();
 380   // Returned from <ChildClass>::run(). Thread finished.
 381 
 382   // Note: at this point the thread object may already have deleted itself.
 383   // So from here on do not dereference *this*.
 384 
 385   // If a thread has not deleted itself ("delete this") as part of its
 386   // termination sequence, we have to ensure thread-local-storage is
 387   // cleared before we actually terminate. No threads should ever be
 388   // deleted asynchronously with respect to their termination.
 389   if (Thread::current_or_null_safe() != NULL) {
 390     assert(Thread::current_or_null_safe() == this, "current thread is wrong");
 391     Thread::clear_thread_current();
 392   }
 393 
 394 }
 395 
 396 Thread::~Thread() {
 397   // Notify the barrier set that a thread is being destroyed. Note that a barrier
 398   // set might not be available if we encountered errors during bootstrapping.
 399   BarrierSet* const barrier_set = BarrierSet::barrier_set();
 400   if (barrier_set != NULL) {
 401     barrier_set->on_thread_destroy(this);
 402   }
 403 
 404   // stack_base can be NULL if the thread is never started or exited before
 405   // record_stack_base_and_size called. Although, we would like to ensure
 406   // that all started threads do call record_stack_base_and_size(), there is
 407   // not proper way to enforce that.
 408 #if INCLUDE_NMT
 409   if (_stack_base != NULL) {
 410     MemTracker::release_thread_stack(stack_end(), stack_size());
 411 #ifdef ASSERT
 412     set_stack_base(NULL);
 413 #endif
 414   }
 415 #endif // INCLUDE_NMT
 416 
 417   // deallocate data structures
 418   delete resource_area();
 419   // since the handle marks are using the handle area, we have to deallocated the root
 420   // handle mark before deallocating the thread's handle area,
 421   assert(last_handle_mark() != NULL, "check we have an element");
 422   delete last_handle_mark();
 423   assert(last_handle_mark() == NULL, "check we have reached the end");
 424 
 425   // It's possible we can encounter a null _ParkEvent, etc., in stillborn threads.
 426   // We NULL out the fields for good hygiene.
 427   ParkEvent::Release(_ParkEvent); _ParkEvent   = NULL;
 428   ParkEvent::Release(_SleepEvent); _SleepEvent  = NULL;
 429   ParkEvent::Release(_MutexEvent); _MutexEvent  = NULL;
 430   ParkEvent::Release(_MuxEvent); _MuxEvent    = NULL;
 431 
 432   delete handle_area();
 433   delete metadata_handles();
 434 
 435   // SR_handler uses this as a termination indicator -
 436   // needs to happen before os::free_thread()
 437   delete _SR_lock;
 438   _SR_lock = NULL;
 439 
 440   // osthread() can be NULL, if creation of thread failed.
 441   if (osthread() != NULL) os::free_thread(osthread());
 442 
 443   // clear Thread::current if thread is deleting itself.
 444   // Needed to ensure JNI correctly detects non-attached threads.
 445   if (this == Thread::current()) {
 446     Thread::clear_thread_current();
 447   }
 448 
 449   CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
 450 }
 451 
 452 #ifdef ASSERT
 453 // A JavaThread is considered "dangling" if it is not the current
 454 // thread, has been added the Threads list, the system is not at a
 455 // safepoint and the Thread is not "protected".
 456 //
 457 void Thread::check_for_dangling_thread_pointer(Thread *thread) {
 458   assert(!thread->is_Java_thread() || Thread::current() == thread ||
 459          !((JavaThread *) thread)->on_thread_list() ||
 460          SafepointSynchronize::is_at_safepoint() ||
 461          ThreadsSMRSupport::is_a_protected_JavaThread_with_lock((JavaThread *) thread),
 462          "possibility of dangling Thread pointer");
 463 }
 464 #endif
 465 
 466 ThreadPriority Thread::get_priority(const Thread* const thread) {
 467   ThreadPriority priority;
 468   // Can return an error!
 469   (void)os::get_priority(thread, priority);
 470   assert(MinPriority <= priority && priority <= MaxPriority, "non-Java priority found");
 471   return priority;
 472 }
 473 
 474 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
 475   debug_only(check_for_dangling_thread_pointer(thread);)
 476   // Can return an error!
 477   (void)os::set_priority(thread, priority);
 478 }
 479 
 480 
 481 void Thread::start(Thread* thread) {
 482   // Start is different from resume in that its safety is guaranteed by context or
 483   // being called from a Java method synchronized on the Thread object.
 484   if (!DisableStartThread) {
 485     if (thread->is_Java_thread()) {
 486       // Initialize the thread state to RUNNABLE before starting this thread.
 487       // Can not set it after the thread started because we do not know the
 488       // exact thread state at that time. It could be in MONITOR_WAIT or
 489       // in SLEEPING or some other state.
 490       java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
 491                                           java_lang_Thread::RUNNABLE);
 492     }
 493     os::start_thread(thread);
 494   }
 495 }
 496 
 497 // Enqueue a VM_Operation to do the job for us - sometime later
 498 void Thread::send_async_exception(oop java_thread, oop java_throwable) {
 499   VM_ThreadStop* vm_stop = new VM_ThreadStop(java_thread, java_throwable);
 500   VMThread::execute(vm_stop);
 501 }
 502 
 503 
 504 // Check if an external suspend request has completed (or has been
 505 // cancelled). Returns true if the thread is externally suspended and
 506 // false otherwise.
 507 //
 508 // The bits parameter returns information about the code path through
 509 // the routine. Useful for debugging:
 510 //
 511 // set in is_ext_suspend_completed():
 512 // 0x00000001 - routine was entered
 513 // 0x00000010 - routine return false at end
 514 // 0x00000100 - thread exited (return false)
 515 // 0x00000200 - suspend request cancelled (return false)
 516 // 0x00000400 - thread suspended (return true)
 517 // 0x00001000 - thread is in a suspend equivalent state (return true)
 518 // 0x00002000 - thread is native and walkable (return true)
 519 // 0x00004000 - thread is native_trans and walkable (needed retry)
 520 //
 521 // set in wait_for_ext_suspend_completion():
 522 // 0x00010000 - routine was entered
 523 // 0x00020000 - suspend request cancelled before loop (return false)
 524 // 0x00040000 - thread suspended before loop (return true)
 525 // 0x00080000 - suspend request cancelled in loop (return false)
 526 // 0x00100000 - thread suspended in loop (return true)
 527 // 0x00200000 - suspend not completed during retry loop (return false)
 528 
 529 // Helper class for tracing suspend wait debug bits.
 530 //
 531 // 0x00000100 indicates that the target thread exited before it could
 532 // self-suspend which is not a wait failure. 0x00000200, 0x00020000 and
 533 // 0x00080000 each indicate a cancelled suspend request so they don't
 534 // count as wait failures either.
 535 #define DEBUG_FALSE_BITS (0x00000010 | 0x00200000)
 536 
 537 class TraceSuspendDebugBits : public StackObj {
 538  private:
 539   JavaThread * jt;
 540   bool         is_wait;
 541   bool         called_by_wait;  // meaningful when !is_wait
 542   uint32_t *   bits;
 543 
 544  public:
 545   TraceSuspendDebugBits(JavaThread *_jt, bool _is_wait, bool _called_by_wait,
 546                         uint32_t *_bits) {
 547     jt             = _jt;
 548     is_wait        = _is_wait;
 549     called_by_wait = _called_by_wait;
 550     bits           = _bits;
 551   }
 552 
 553   ~TraceSuspendDebugBits() {
 554     if (!is_wait) {
 555 #if 1
 556       // By default, don't trace bits for is_ext_suspend_completed() calls.
 557       // That trace is very chatty.
 558       return;
 559 #else
 560       if (!called_by_wait) {
 561         // If tracing for is_ext_suspend_completed() is enabled, then only
 562         // trace calls to it from wait_for_ext_suspend_completion()
 563         return;
 564       }
 565 #endif
 566     }
 567 
 568     if (AssertOnSuspendWaitFailure || TraceSuspendWaitFailures) {
 569       if (bits != NULL && (*bits & DEBUG_FALSE_BITS) != 0) {
 570         MutexLocker ml(Threads_lock);  // needed for get_thread_name()
 571         ResourceMark rm;
 572 
 573         tty->print_cr(
 574                       "Failed wait_for_ext_suspend_completion(thread=%s, debug_bits=%x)",
 575                       jt->get_thread_name(), *bits);
 576 
 577         guarantee(!AssertOnSuspendWaitFailure, "external suspend wait failed");
 578       }
 579     }
 580   }
 581 };
 582 #undef DEBUG_FALSE_BITS
 583 
 584 
 585 bool JavaThread::is_ext_suspend_completed(bool called_by_wait, int delay,
 586                                           uint32_t *bits) {
 587   TraceSuspendDebugBits tsdb(this, false /* !is_wait */, called_by_wait, bits);
 588 
 589   bool did_trans_retry = false;  // only do thread_in_native_trans retry once
 590   bool do_trans_retry;           // flag to force the retry
 591 
 592   *bits |= 0x00000001;
 593 
 594   do {
 595     do_trans_retry = false;
 596 
 597     if (is_exiting()) {
 598       // Thread is in the process of exiting. This is always checked
 599       // first to reduce the risk of dereferencing a freed JavaThread.
 600       *bits |= 0x00000100;
 601       return false;
 602     }
 603 
 604     if (!is_external_suspend()) {
 605       // Suspend request is cancelled. This is always checked before
 606       // is_ext_suspended() to reduce the risk of a rogue resume
 607       // confusing the thread that made the suspend request.
 608       *bits |= 0x00000200;
 609       return false;
 610     }
 611 
 612     if (is_ext_suspended()) {
 613       // thread is suspended
 614       *bits |= 0x00000400;
 615       return true;
 616     }
 617 
 618     // Now that we no longer do hard suspends of threads running
 619     // native code, the target thread can be changing thread state
 620     // while we are in this routine:
 621     //
 622     //   _thread_in_native -> _thread_in_native_trans -> _thread_blocked
 623     //
 624     // We save a copy of the thread state as observed at this moment
 625     // and make our decision about suspend completeness based on the
 626     // copy. This closes the race where the thread state is seen as
 627     // _thread_in_native_trans in the if-thread_blocked check, but is
 628     // seen as _thread_blocked in if-thread_in_native_trans check.
 629     JavaThreadState save_state = thread_state();
 630 
 631     if (save_state == _thread_blocked && is_suspend_equivalent()) {
 632       // If the thread's state is _thread_blocked and this blocking
 633       // condition is known to be equivalent to a suspend, then we can
 634       // consider the thread to be externally suspended. This means that
 635       // the code that sets _thread_blocked has been modified to do
 636       // self-suspension if the blocking condition releases. We also
 637       // used to check for CONDVAR_WAIT here, but that is now covered by
 638       // the _thread_blocked with self-suspension check.
 639       //
 640       // Return true since we wouldn't be here unless there was still an
 641       // external suspend request.
 642       *bits |= 0x00001000;
 643       return true;
 644     } else if (save_state == _thread_in_native && frame_anchor()->walkable()) {
 645       // Threads running native code will self-suspend on native==>VM/Java
 646       // transitions. If its stack is walkable (should always be the case
 647       // unless this function is called before the actual java_suspend()
 648       // call), then the wait is done.
 649       *bits |= 0x00002000;
 650       return true;
 651     } else if (!called_by_wait && !did_trans_retry &&
 652                save_state == _thread_in_native_trans &&
 653                frame_anchor()->walkable()) {
 654       // The thread is transitioning from thread_in_native to another
 655       // thread state. check_safepoint_and_suspend_for_native_trans()
 656       // will force the thread to self-suspend. If it hasn't gotten
 657       // there yet we may have caught the thread in-between the native
 658       // code check above and the self-suspend. Lucky us. If we were
 659       // called by wait_for_ext_suspend_completion(), then it
 660       // will be doing the retries so we don't have to.
 661       //
 662       // Since we use the saved thread state in the if-statement above,
 663       // there is a chance that the thread has already transitioned to
 664       // _thread_blocked by the time we get here. In that case, we will
 665       // make a single unnecessary pass through the logic below. This
 666       // doesn't hurt anything since we still do the trans retry.
 667 
 668       *bits |= 0x00004000;
 669 
 670       // Once the thread leaves thread_in_native_trans for another
 671       // thread state, we break out of this retry loop. We shouldn't
 672       // need this flag to prevent us from getting back here, but
 673       // sometimes paranoia is good.
 674       did_trans_retry = true;
 675 
 676       // We wait for the thread to transition to a more usable state.
 677       for (int i = 1; i <= SuspendRetryCount; i++) {
 678         // We used to do an "os::yield_all(i)" call here with the intention
 679         // that yielding would increase on each retry. However, the parameter
 680         // is ignored on Linux which means the yield didn't scale up. Waiting
 681         // on the SR_lock below provides a much more predictable scale up for
 682         // the delay. It also provides a simple/direct point to check for any
 683         // safepoint requests from the VMThread
 684 
 685         // temporarily drops SR_lock while doing wait with safepoint check
 686         // (if we're a JavaThread - the WatcherThread can also call this)
 687         // and increase delay with each retry
 688         SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 689 
 690         // check the actual thread state instead of what we saved above
 691         if (thread_state() != _thread_in_native_trans) {
 692           // the thread has transitioned to another thread state so
 693           // try all the checks (except this one) one more time.
 694           do_trans_retry = true;
 695           break;
 696         }
 697       } // end retry loop
 698 
 699 
 700     }
 701   } while (do_trans_retry);
 702 
 703   *bits |= 0x00000010;
 704   return false;
 705 }
 706 
 707 // Wait for an external suspend request to complete (or be cancelled).
 708 // Returns true if the thread is externally suspended and false otherwise.
 709 //
 710 bool JavaThread::wait_for_ext_suspend_completion(int retries, int delay,
 711                                                  uint32_t *bits) {
 712   TraceSuspendDebugBits tsdb(this, true /* is_wait */,
 713                              false /* !called_by_wait */, bits);
 714 
 715   // local flag copies to minimize SR_lock hold time
 716   bool is_suspended;
 717   bool pending;
 718   uint32_t reset_bits;
 719 
 720   // set a marker so is_ext_suspend_completed() knows we are the caller
 721   *bits |= 0x00010000;
 722 
 723   // We use reset_bits to reinitialize the bits value at the top of
 724   // each retry loop. This allows the caller to make use of any
 725   // unused bits for their own marking purposes.
 726   reset_bits = *bits;
 727 
 728   {
 729     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 730     is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 731                                             delay, bits);
 732     pending = is_external_suspend();
 733   }
 734   // must release SR_lock to allow suspension to complete
 735 
 736   if (!pending) {
 737     // A cancelled suspend request is the only false return from
 738     // is_ext_suspend_completed() that keeps us from entering the
 739     // retry loop.
 740     *bits |= 0x00020000;
 741     return false;
 742   }
 743 
 744   if (is_suspended) {
 745     *bits |= 0x00040000;
 746     return true;
 747   }
 748 
 749   for (int i = 1; i <= retries; i++) {
 750     *bits = reset_bits;  // reinit to only track last retry
 751 
 752     // We used to do an "os::yield_all(i)" call here with the intention
 753     // that yielding would increase on each retry. However, the parameter
 754     // is ignored on Linux which means the yield didn't scale up. Waiting
 755     // on the SR_lock below provides a much more predictable scale up for
 756     // the delay. It also provides a simple/direct point to check for any
 757     // safepoint requests from the VMThread
 758 
 759     {
 760       MutexLocker ml(SR_lock());
 761       // wait with safepoint check (if we're a JavaThread - the WatcherThread
 762       // can also call this)  and increase delay with each retry
 763       SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 764 
 765       is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 766                                               delay, bits);
 767 
 768       // It is possible for the external suspend request to be cancelled
 769       // (by a resume) before the actual suspend operation is completed.
 770       // Refresh our local copy to see if we still need to wait.
 771       pending = is_external_suspend();
 772     }
 773 
 774     if (!pending) {
 775       // A cancelled suspend request is the only false return from
 776       // is_ext_suspend_completed() that keeps us from staying in the
 777       // retry loop.
 778       *bits |= 0x00080000;
 779       return false;
 780     }
 781 
 782     if (is_suspended) {
 783       *bits |= 0x00100000;
 784       return true;
 785     }
 786   } // end retry loop
 787 
 788   // thread did not suspend after all our retries
 789   *bits |= 0x00200000;
 790   return false;
 791 }
 792 
 793 // Called from API entry points which perform stack walking. If the
 794 // associated JavaThread is the current thread, then wait_for_suspend
 795 // is not used. Otherwise, it determines if we should wait for the
 796 // "other" thread to complete external suspension. (NOTE: in future
 797 // releases the suspension mechanism should be reimplemented so this
 798 // is not necessary.)
 799 //
 800 bool
 801 JavaThread::is_thread_fully_suspended(bool wait_for_suspend, uint32_t *bits) {
 802   if (this != JavaThread::current()) {
 803     // "other" threads require special handling.
 804     if (wait_for_suspend) {
 805       // We are allowed to wait for the external suspend to complete
 806       // so give the other thread a chance to get suspended.
 807       if (!wait_for_ext_suspend_completion(SuspendRetryCount,
 808                                            SuspendRetryDelay, bits)) {
 809         // Didn't make it so let the caller know.
 810         return false;
 811       }
 812     }
 813     // We aren't allowed to wait for the external suspend to complete
 814     // so if the other thread isn't externally suspended we need to
 815     // let the caller know.
 816     else if (!is_ext_suspend_completed_with_lock(bits)) {
 817       return false;
 818     }
 819   }
 820 
 821   return true;
 822 }
 823 
 824 #ifndef PRODUCT
 825 void JavaThread::record_jump(address target, address instr, const char* file,
 826                              int line) {
 827 
 828   // This should not need to be atomic as the only way for simultaneous
 829   // updates is via interrupts. Even then this should be rare or non-existent
 830   // and we don't care that much anyway.
 831 
 832   int index = _jmp_ring_index;
 833   _jmp_ring_index = (index + 1) & (jump_ring_buffer_size - 1);
 834   _jmp_ring[index]._target = (intptr_t) target;
 835   _jmp_ring[index]._instruction = (intptr_t) instr;
 836   _jmp_ring[index]._file = file;
 837   _jmp_ring[index]._line = line;
 838 }
 839 #endif // PRODUCT
 840 
 841 void Thread::interrupt(Thread* thread) {
 842   debug_only(check_for_dangling_thread_pointer(thread);)
 843   os::interrupt(thread);
 844 }
 845 
 846 bool Thread::is_interrupted(Thread* thread, bool clear_interrupted) {
 847   debug_only(check_for_dangling_thread_pointer(thread);)
 848   // Note:  If clear_interrupted==false, this simply fetches and
 849   // returns the value of the field osthread()->interrupted().
 850   return os::is_interrupted(thread, clear_interrupted);
 851 }
 852 
 853 
 854 // GC Support
 855 bool Thread::claim_oops_do_par_case(int strong_roots_parity) {
 856   int thread_parity = _oops_do_parity;
 857   if (thread_parity != strong_roots_parity) {
 858     jint res = Atomic::cmpxchg(strong_roots_parity, &_oops_do_parity, thread_parity);
 859     if (res == thread_parity) {
 860       return true;
 861     } else {
 862       guarantee(res == strong_roots_parity, "Or else what?");
 863       return false;
 864     }
 865   }
 866   return false;
 867 }
 868 
 869 void Thread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
 870   active_handles()->oops_do(f);
 871   // Do oop for ThreadShadow
 872   f->do_oop((oop*)&_pending_exception);
 873   handle_area()->oops_do(f);
 874 
 875   // We scan thread local monitor lists here, and the remaining global
 876   // monitors in ObjectSynchronizer::oops_do().
 877   ObjectSynchronizer::thread_local_used_oops_do(this, f);
 878 }
 879 
 880 void Thread::metadata_handles_do(void f(Metadata*)) {
 881   // Only walk the Handles in Thread.
 882   if (metadata_handles() != NULL) {
 883     for (int i = 0; i< metadata_handles()->length(); i++) {
 884       f(metadata_handles()->at(i));
 885     }
 886   }
 887 }
 888 
 889 void Thread::print_on(outputStream* st, bool print_extended_info) const {
 890   // get_priority assumes osthread initialized
 891   if (osthread() != NULL) {
 892     int os_prio;
 893     if (os::get_native_priority(this, &os_prio) == OS_OK) {
 894       st->print("os_prio=%d ", os_prio);
 895     }
 896 
 897     st->print("cpu=%.2fms ",
 898               os::thread_cpu_time(const_cast<Thread*>(this), true) / 1000000.0
 899               );
 900     st->print("elapsed=%.2fs ",
 901               _statistical_info.getElapsedTime() / 1000.0
 902               );
 903     if (is_Java_thread() && (PrintExtendedThreadInfo || print_extended_info)) {
 904       size_t allocated_bytes = (size_t) const_cast<Thread*>(this)->cooked_allocated_bytes();
 905       st->print("allocated=" SIZE_FORMAT "%s ",
 906                 byte_size_in_proper_unit(allocated_bytes),
 907                 proper_unit_for_byte_size(allocated_bytes)
 908                 );
 909       st->print("defined_classes=" INT64_FORMAT " ", _statistical_info.getDefineClassCount());
 910     }
 911 
 912     st->print("tid=" INTPTR_FORMAT " ", p2i(this));
 913     osthread()->print_on(st);
 914   }
 915   ThreadsSMRSupport::print_info_on(this, st);
 916   st->print(" ");
 917   debug_only(if (WizardMode) print_owned_locks_on(st);)
 918 }
 919 
 920 // Thread::print_on_error() is called by fatal error handler. Don't use
 921 // any lock or allocate memory.
 922 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
 923   assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
 924 
 925   if (is_VM_thread())                 { st->print("VMThread"); }
 926   else if (is_GC_task_thread())       { st->print("GCTaskThread"); }
 927   else if (is_Watcher_thread())       { st->print("WatcherThread"); }
 928   else if (is_ConcurrentGC_thread())  { st->print("ConcurrentGCThread"); }
 929   else                                { st->print("Thread"); }
 930 
 931   if (is_Named_thread()) {
 932     st->print(" \"%s\"", name());
 933   }
 934 
 935   st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
 936             p2i(stack_end()), p2i(stack_base()));
 937 
 938   if (osthread()) {
 939     st->print(" [id=%d]", osthread()->thread_id());
 940   }
 941 
 942   ThreadsSMRSupport::print_info_on(this, st);
 943 }
 944 
 945 void Thread::print_value_on(outputStream* st) const {
 946   if (is_Named_thread()) {
 947     st->print(" \"%s\" ", name());
 948   }
 949   st->print(INTPTR_FORMAT, p2i(this));   // print address
 950 }
 951 
 952 #ifdef ASSERT
 953 void Thread::print_owned_locks_on(outputStream* st) const {
 954   Monitor *cur = _owned_locks;
 955   if (cur == NULL) {
 956     st->print(" (no locks) ");
 957   } else {
 958     st->print_cr(" Locks owned:");
 959     while (cur) {
 960       cur->print_on(st);
 961       cur = cur->next();
 962     }
 963   }
 964 }
 965 
 966 static int ref_use_count  = 0;
 967 
 968 bool Thread::owns_locks_but_compiled_lock() const {
 969   for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 970     if (cur != Compile_lock) return true;
 971   }
 972   return false;
 973 }
 974 
 975 
 976 #endif
 977 
 978 #ifndef PRODUCT
 979 
 980 // The flag: potential_vm_operation notifies if this particular safepoint state could potentially
 981 // invoke the vm-thread (e.g., an oop allocation). In that case, we also have to make sure that
 982 // no locks which allow_vm_block's are held
 983 void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) {
 984   // Check if current thread is allowed to block at a safepoint
 985   if (!(_allow_safepoint_count == 0)) {
 986     fatal("Possible safepoint reached by thread that does not allow it");
 987   }
 988   if (is_Java_thread() && ((JavaThread*)this)->thread_state() != _thread_in_vm) {
 989     fatal("LEAF method calling lock?");
 990   }
 991 
 992 #ifdef ASSERT
 993   if (potential_vm_operation && is_Java_thread()
 994       && !Universe::is_bootstrapping()) {
 995     // Make sure we do not hold any locks that the VM thread also uses.
 996     // This could potentially lead to deadlocks
 997     for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 998       // Threads_lock is special, since the safepoint synchronization will not start before this is
 999       // acquired. Hence, a JavaThread cannot be holding it at a safepoint. So is VMOperationRequest_lock,
1000       // since it is used to transfer control between JavaThreads and the VMThread
1001       // Do not *exclude* any locks unless you are absolutely sure it is correct. Ask someone else first!
1002       if ((cur->allow_vm_block() &&
1003            cur != Threads_lock &&
1004            cur != Compile_lock &&               // Temporary: should not be necessary when we get separate compilation
1005            cur != VMOperationRequest_lock &&
1006            cur != VMOperationQueue_lock) ||
1007            cur->rank() == Mutex::special) {
1008         fatal("Thread holding lock at safepoint that vm can block on: %s", cur->name());
1009       }
1010     }
1011   }
1012 
1013   if (GCALotAtAllSafepoints) {
1014     // We could enter a safepoint here and thus have a gc
1015     InterfaceSupport::check_gc_alot();
1016   }
1017 #endif
1018 }
1019 #endif
1020 
1021 bool Thread::is_in_stack(address adr) const {
1022   assert(Thread::current() == this, "is_in_stack can only be called from current thread");
1023   address end = os::current_stack_pointer();
1024   // Allow non Java threads to call this without stack_base
1025   if (_stack_base == NULL) return true;
1026   if (stack_base() >= adr && adr >= end) return true;
1027 
1028   return false;
1029 }
1030 
1031 bool Thread::is_in_usable_stack(address adr) const {
1032   size_t stack_guard_size = os::uses_stack_guard_pages() ? JavaThread::stack_guard_zone_size() : 0;
1033   size_t usable_stack_size = _stack_size - stack_guard_size;
1034 
1035   return ((adr < stack_base()) && (adr >= stack_base() - usable_stack_size));
1036 }
1037 
1038 
1039 // We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
1040 // However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
1041 // used for compilation in the future. If that change is made, the need for these methods
1042 // should be revisited, and they should be removed if possible.
1043 
1044 bool Thread::is_lock_owned(address adr) const {
1045   return on_local_stack(adr);
1046 }
1047 
1048 bool Thread::set_as_starting_thread() {
1049   // NOTE: this must be called inside the main thread.
1050   return os::create_main_thread((JavaThread*)this);
1051 }
1052 
1053 static void initialize_class(Symbol* class_name, TRAPS) {
1054   Klass* klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
1055   InstanceKlass::cast(klass)->initialize(CHECK);
1056 }
1057 
1058 
1059 // Creates the initial ThreadGroup
1060 static Handle create_initial_thread_group(TRAPS) {
1061   Handle system_instance = JavaCalls::construct_new_instance(
1062                             SystemDictionary::ThreadGroup_klass(),
1063                             vmSymbols::void_method_signature(),
1064                             CHECK_NH);
1065   Universe::set_system_thread_group(system_instance());
1066 
1067   Handle string = java_lang_String::create_from_str("main", CHECK_NH);
1068   Handle main_instance = JavaCalls::construct_new_instance(
1069                             SystemDictionary::ThreadGroup_klass(),
1070                             vmSymbols::threadgroup_string_void_signature(),
1071                             system_instance,
1072                             string,
1073                             CHECK_NH);
1074   return main_instance;
1075 }
1076 
1077 // Creates the initial Thread
1078 static oop create_initial_thread(Handle thread_group, JavaThread* thread,
1079                                  TRAPS) {
1080   InstanceKlass* ik = SystemDictionary::Thread_klass();
1081   assert(ik->is_initialized(), "must be");
1082   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK_NULL);
1083 
1084   // Cannot use JavaCalls::construct_new_instance because the java.lang.Thread
1085   // constructor calls Thread.current(), which must be set here for the
1086   // initial thread.
1087   java_lang_Thread::set_thread(thread_oop(), thread);
1088   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1089   thread->set_threadObj(thread_oop());
1090 
1091   Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
1092 
1093   JavaValue result(T_VOID);
1094   JavaCalls::call_special(&result, thread_oop,
1095                           ik,
1096                           vmSymbols::object_initializer_name(),
1097                           vmSymbols::threadgroup_string_void_signature(),
1098                           thread_group,
1099                           string,
1100                           CHECK_NULL);
1101   return thread_oop();
1102 }
1103 
1104 char java_runtime_name[128] = "";
1105 char java_runtime_version[128] = "";
1106 
1107 // extract the JRE name from java.lang.VersionProps.java_runtime_name
1108 static const char* get_java_runtime_name(TRAPS) {
1109   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1110                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1111   fieldDescriptor fd;
1112   bool found = k != NULL &&
1113                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_name_name(),
1114                                                         vmSymbols::string_signature(), &fd);
1115   if (found) {
1116     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1117     if (name_oop == NULL) {
1118       return NULL;
1119     }
1120     const char* name = java_lang_String::as_utf8_string(name_oop,
1121                                                         java_runtime_name,
1122                                                         sizeof(java_runtime_name));
1123     return name;
1124   } else {
1125     return NULL;
1126   }
1127 }
1128 
1129 // extract the JRE version from java.lang.VersionProps.java_runtime_version
1130 static const char* get_java_runtime_version(TRAPS) {
1131   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1132                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1133   fieldDescriptor fd;
1134   bool found = k != NULL &&
1135                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_version_name(),
1136                                                         vmSymbols::string_signature(), &fd);
1137   if (found) {
1138     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1139     if (name_oop == NULL) {
1140       return NULL;
1141     }
1142     const char* name = java_lang_String::as_utf8_string(name_oop,
1143                                                         java_runtime_version,
1144                                                         sizeof(java_runtime_version));
1145     return name;
1146   } else {
1147     return NULL;
1148   }
1149 }
1150 
1151 // General purpose hook into Java code, run once when the VM is initialized.
1152 // The Java library method itself may be changed independently from the VM.
1153 static void call_postVMInitHook(TRAPS) {
1154   Klass* klass = SystemDictionary::resolve_or_null(vmSymbols::jdk_internal_vm_PostVMInitHook(), THREAD);
1155   if (klass != NULL) {
1156     JavaValue result(T_VOID);
1157     JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
1158                            vmSymbols::void_method_signature(),
1159                            CHECK);
1160   }
1161 }
1162 
1163 void JavaThread::allocate_threadObj(Handle thread_group, const char* thread_name,
1164                                     bool daemon, TRAPS) {
1165   assert(thread_group.not_null(), "thread group should be specified");
1166   assert(threadObj() == NULL, "should only create Java thread object once");
1167 
1168   InstanceKlass* ik = SystemDictionary::Thread_klass();
1169   assert(ik->is_initialized(), "must be");
1170   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK);
1171 
1172   // We are called from jni_AttachCurrentThread/jni_AttachCurrentThreadAsDaemon.
1173   // We cannot use JavaCalls::construct_new_instance because the java.lang.Thread
1174   // constructor calls Thread.current(), which must be set here.
1175   java_lang_Thread::set_thread(thread_oop(), this);
1176   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1177   set_threadObj(thread_oop());
1178 
1179   JavaValue result(T_VOID);
1180   if (thread_name != NULL) {
1181     Handle name = java_lang_String::create_from_str(thread_name, CHECK);
1182     // Thread gets assigned specified name and null target
1183     JavaCalls::call_special(&result,
1184                             thread_oop,
1185                             ik,
1186                             vmSymbols::object_initializer_name(),
1187                             vmSymbols::threadgroup_string_void_signature(),
1188                             thread_group,
1189                             name,
1190                             THREAD);
1191   } else {
1192     // Thread gets assigned name "Thread-nnn" and null target
1193     // (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
1194     JavaCalls::call_special(&result,
1195                             thread_oop,
1196                             ik,
1197                             vmSymbols::object_initializer_name(),
1198                             vmSymbols::threadgroup_runnable_void_signature(),
1199                             thread_group,
1200                             Handle(),
1201                             THREAD);
1202   }
1203 
1204 
1205   if (daemon) {
1206     java_lang_Thread::set_daemon(thread_oop());
1207   }
1208 
1209   if (HAS_PENDING_EXCEPTION) {
1210     return;
1211   }
1212 
1213   Klass* group =  SystemDictionary::ThreadGroup_klass();
1214   Handle threadObj(THREAD, this->threadObj());
1215 
1216   JavaCalls::call_special(&result,
1217                           thread_group,
1218                           group,
1219                           vmSymbols::add_method_name(),
1220                           vmSymbols::thread_void_signature(),
1221                           threadObj,          // Arg 1
1222                           THREAD);
1223 }
1224 
1225 // List of all NonJavaThreads and safe iteration over that list.
1226 
1227 class NonJavaThread::List {
1228 public:
1229   NonJavaThread* volatile _head;
1230   SingleWriterSynchronizer _protect;
1231 
1232   List() : _head(NULL), _protect() {}
1233 };
1234 
1235 NonJavaThread::List NonJavaThread::_the_list;
1236 
1237 NonJavaThread::Iterator::Iterator() :
1238   _protect_enter(_the_list._protect.enter()),
1239   _current(OrderAccess::load_acquire(&_the_list._head))
1240 {}
1241 
1242 NonJavaThread::Iterator::~Iterator() {
1243   _the_list._protect.exit(_protect_enter);
1244 }
1245 
1246 void NonJavaThread::Iterator::step() {
1247   assert(!end(), "precondition");
1248   _current = OrderAccess::load_acquire(&_current->_next);
1249 }
1250 
1251 NonJavaThread::NonJavaThread() : Thread(), _next(NULL) {
1252   // Add this thread to _the_list.
1253   MutexLockerEx lock(NonJavaThreadsList_lock, Mutex::_no_safepoint_check_flag);
1254   _next = _the_list._head;
1255   OrderAccess::release_store(&_the_list._head, this);
1256 }
1257 
1258 NonJavaThread::~NonJavaThread() {
1259   JFR_ONLY(Jfr::on_thread_exit(this);)
1260   // Remove this thread from _the_list.
1261   MutexLockerEx lock(NonJavaThreadsList_lock, Mutex::_no_safepoint_check_flag);
1262   NonJavaThread* volatile* p = &_the_list._head;
1263   for (NonJavaThread* t = *p; t != NULL; p = &t->_next, t = *p) {
1264     if (t == this) {
1265       *p = this->_next;
1266       // Wait for any in-progress iterators.
1267       _the_list._protect.synchronize();
1268       break;
1269     }
1270   }
1271 }
1272 
1273 // NamedThread --  non-JavaThread subclasses with multiple
1274 // uniquely named instances should derive from this.
1275 NamedThread::NamedThread() :
1276   NonJavaThread(),
1277   _name(NULL),
1278   _processed_thread(NULL),
1279   _gc_id(GCId::undefined())
1280 {}
1281 
1282 NamedThread::~NamedThread() {
1283   if (_name != NULL) {
1284     FREE_C_HEAP_ARRAY(char, _name);
1285     _name = NULL;
1286   }
1287 }
1288 
1289 void NamedThread::set_name(const char* format, ...) {
1290   guarantee(_name == NULL, "Only get to set name once.");
1291   _name = NEW_C_HEAP_ARRAY(char, max_name_len, mtThread);
1292   guarantee(_name != NULL, "alloc failure");
1293   va_list ap;
1294   va_start(ap, format);
1295   jio_vsnprintf(_name, max_name_len, format, ap);
1296   va_end(ap);
1297 }
1298 
1299 void NamedThread::initialize_named_thread() {
1300   set_native_thread_name(name());
1301 }
1302 
1303 void NamedThread::print_on(outputStream* st) const {
1304   st->print("\"%s\" ", name());
1305   Thread::print_on(st);
1306   st->cr();
1307 }
1308 
1309 
1310 // ======= WatcherThread ========
1311 
1312 // The watcher thread exists to simulate timer interrupts.  It should
1313 // be replaced by an abstraction over whatever native support for
1314 // timer interrupts exists on the platform.
1315 
1316 WatcherThread* WatcherThread::_watcher_thread   = NULL;
1317 bool WatcherThread::_startable = false;
1318 volatile bool  WatcherThread::_should_terminate = false;
1319 
1320 WatcherThread::WatcherThread() : NonJavaThread() {
1321   assert(watcher_thread() == NULL, "we can only allocate one WatcherThread");
1322   if (os::create_thread(this, os::watcher_thread)) {
1323     _watcher_thread = this;
1324 
1325     // Set the watcher thread to the highest OS priority which should not be
1326     // used, unless a Java thread with priority java.lang.Thread.MAX_PRIORITY
1327     // is created. The only normal thread using this priority is the reference
1328     // handler thread, which runs for very short intervals only.
1329     // If the VMThread's priority is not lower than the WatcherThread profiling
1330     // will be inaccurate.
1331     os::set_priority(this, MaxPriority);
1332     if (!DisableStartThread) {
1333       os::start_thread(this);
1334     }
1335   }
1336 }
1337 
1338 int WatcherThread::sleep() const {
1339   // The WatcherThread does not participate in the safepoint protocol
1340   // for the PeriodicTask_lock because it is not a JavaThread.
1341   MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
1342 
1343   if (_should_terminate) {
1344     // check for termination before we do any housekeeping or wait
1345     return 0;  // we did not sleep.
1346   }
1347 
1348   // remaining will be zero if there are no tasks,
1349   // causing the WatcherThread to sleep until a task is
1350   // enrolled
1351   int remaining = PeriodicTask::time_to_wait();
1352   int time_slept = 0;
1353 
1354   // we expect this to timeout - we only ever get unparked when
1355   // we should terminate or when a new task has been enrolled
1356   OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
1357 
1358   jlong time_before_loop = os::javaTimeNanos();
1359 
1360   while (true) {
1361     bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag,
1362                                             remaining);
1363     jlong now = os::javaTimeNanos();
1364 
1365     if (remaining == 0) {
1366       // if we didn't have any tasks we could have waited for a long time
1367       // consider the time_slept zero and reset time_before_loop
1368       time_slept = 0;
1369       time_before_loop = now;
1370     } else {
1371       // need to recalculate since we might have new tasks in _tasks
1372       time_slept = (int) ((now - time_before_loop) / 1000000);
1373     }
1374 
1375     // Change to task list or spurious wakeup of some kind
1376     if (timedout || _should_terminate) {
1377       break;
1378     }
1379 
1380     remaining = PeriodicTask::time_to_wait();
1381     if (remaining == 0) {
1382       // Last task was just disenrolled so loop around and wait until
1383       // another task gets enrolled
1384       continue;
1385     }
1386 
1387     remaining -= time_slept;
1388     if (remaining <= 0) {
1389       break;
1390     }
1391   }
1392 
1393   return time_slept;
1394 }
1395 
1396 void WatcherThread::run() {
1397   assert(this == watcher_thread(), "just checking");
1398 
1399   this->set_native_thread_name(this->name());
1400   this->set_active_handles(JNIHandleBlock::allocate_block());
1401   while (true) {
1402     assert(watcher_thread() == Thread::current(), "thread consistency check");
1403     assert(watcher_thread() == this, "thread consistency check");
1404 
1405     // Calculate how long it'll be until the next PeriodicTask work
1406     // should be done, and sleep that amount of time.
1407     int time_waited = sleep();
1408 
1409     if (VMError::is_error_reported()) {
1410       // A fatal error has happened, the error handler(VMError::report_and_die)
1411       // should abort JVM after creating an error log file. However in some
1412       // rare cases, the error handler itself might deadlock. Here periodically
1413       // check for error reporting timeouts, and if it happens, just proceed to
1414       // abort the VM.
1415 
1416       // This code is in WatcherThread because WatcherThread wakes up
1417       // periodically so the fatal error handler doesn't need to do anything;
1418       // also because the WatcherThread is less likely to crash than other
1419       // threads.
1420 
1421       for (;;) {
1422         // Note: we use naked sleep in this loop because we want to avoid using
1423         // any kind of VM infrastructure which may be broken at this point.
1424         if (VMError::check_timeout()) {
1425           // We hit error reporting timeout. Error reporting was interrupted and
1426           // will be wrapping things up now (closing files etc). Give it some more
1427           // time, then quit the VM.
1428           os::naked_short_sleep(200);
1429           // Print a message to stderr.
1430           fdStream err(defaultStream::output_fd());
1431           err.print_raw_cr("# [ timer expired, abort... ]");
1432           // skip atexit/vm_exit/vm_abort hooks
1433           os::die();
1434         }
1435 
1436         // Wait a second, then recheck for timeout.
1437         os::naked_short_sleep(999);
1438       }
1439     }
1440 
1441     if (_should_terminate) {
1442       // check for termination before posting the next tick
1443       break;
1444     }
1445 
1446     PeriodicTask::real_time_tick(time_waited);
1447   }
1448 
1449   // Signal that it is terminated
1450   {
1451     MutexLockerEx mu(Terminator_lock, Mutex::_no_safepoint_check_flag);
1452     _watcher_thread = NULL;
1453     Terminator_lock->notify();
1454   }
1455 }
1456 
1457 void WatcherThread::start() {
1458   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1459 
1460   if (watcher_thread() == NULL && _startable) {
1461     _should_terminate = false;
1462     // Create the single instance of WatcherThread
1463     new WatcherThread();
1464   }
1465 }
1466 
1467 void WatcherThread::make_startable() {
1468   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1469   _startable = true;
1470 }
1471 
1472 void WatcherThread::stop() {
1473   {
1474     // Follow normal safepoint aware lock enter protocol since the
1475     // WatcherThread is stopped by another JavaThread.
1476     MutexLocker ml(PeriodicTask_lock);
1477     _should_terminate = true;
1478 
1479     WatcherThread* watcher = watcher_thread();
1480     if (watcher != NULL) {
1481       // unpark the WatcherThread so it can see that it should terminate
1482       watcher->unpark();
1483     }
1484   }
1485 
1486   MutexLocker mu(Terminator_lock);
1487 
1488   while (watcher_thread() != NULL) {
1489     // This wait should make safepoint checks, wait without a timeout,
1490     // and wait as a suspend-equivalent condition.
1491     Terminator_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
1492                           Mutex::_as_suspend_equivalent_flag);
1493   }
1494 }
1495 
1496 void WatcherThread::unpark() {
1497   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1498   PeriodicTask_lock->notify();
1499 }
1500 
1501 void WatcherThread::print_on(outputStream* st) const {
1502   st->print("\"%s\" ", name());
1503   Thread::print_on(st);
1504   st->cr();
1505 }
1506 
1507 // ======= JavaThread ========
1508 
1509 #if INCLUDE_JVMCI
1510 
1511 jlong* JavaThread::_jvmci_old_thread_counters;
1512 
1513 bool jvmci_counters_include(JavaThread* thread) {
1514   return !JVMCICountersExcludeCompiler || !thread->is_Compiler_thread();
1515 }
1516 
1517 void JavaThread::collect_counters(typeArrayOop array) {
1518   if (JVMCICounterSize > 0) {
1519     JavaThreadIteratorWithHandle jtiwh;
1520     for (int i = 0; i < array->length(); i++) {
1521       array->long_at_put(i, _jvmci_old_thread_counters[i]);
1522     }
1523     for (; JavaThread *tp = jtiwh.next(); ) {
1524       if (jvmci_counters_include(tp)) {
1525         for (int i = 0; i < array->length(); i++) {
1526           array->long_at_put(i, array->long_at(i) + tp->_jvmci_counters[i]);
1527         }
1528       }
1529     }
1530   }
1531 }
1532 
1533 #endif // INCLUDE_JVMCI
1534 
1535 // A JavaThread is a normal Java thread
1536 
1537 void JavaThread::initialize() {
1538   // Initialize fields
1539 
1540   set_saved_exception_pc(NULL);
1541   set_threadObj(NULL);
1542   _anchor.clear();
1543   set_entry_point(NULL);
1544   set_jni_functions(jni_functions());
1545   set_callee_target(NULL);
1546   set_vm_result(NULL);
1547   set_vm_result_2(NULL);
1548   set_vframe_array_head(NULL);
1549   set_vframe_array_last(NULL);
1550   set_deferred_locals(NULL);
1551   set_deopt_mark(NULL);
1552   set_deopt_compiled_method(NULL);
1553   clear_must_deopt_id();
1554   set_monitor_chunks(NULL);
1555   set_next(NULL);
1556   _on_thread_list = false;
1557   set_thread_state(_thread_new);
1558   _terminated = _not_terminated;
1559   _array_for_gc = NULL;
1560   _suspend_equivalent = false;
1561   _in_deopt_handler = 0;
1562   _doing_unsafe_access = false;
1563   _stack_guard_state = stack_guard_unused;
1564 #if INCLUDE_JVMCI
1565   _pending_monitorenter = false;
1566   _pending_deoptimization = -1;
1567   _pending_failed_speculation = 0;
1568   _pending_transfer_to_interpreter = false;
1569   _adjusting_comp_level = false;
1570   _in_retryable_allocation = false;
1571   _jvmci._alternate_call_target = NULL;
1572   assert(_jvmci._implicit_exception_pc == NULL, "must be");
1573   if (JVMCICounterSize > 0) {
1574     _jvmci_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
1575     memset(_jvmci_counters, 0, sizeof(jlong) * JVMCICounterSize);
1576   } else {
1577     _jvmci_counters = NULL;
1578   }
1579 #endif // INCLUDE_JVMCI
1580   _reserved_stack_activation = NULL;  // stack base not known yet
1581   (void)const_cast<oop&>(_exception_oop = oop(NULL));
1582   _exception_pc  = 0;
1583   _exception_handler_pc = 0;
1584   _is_method_handle_return = 0;
1585   _jvmti_thread_state= NULL;
1586   _should_post_on_exceptions_flag = JNI_FALSE;
1587   _interp_only_mode    = 0;
1588   _special_runtime_exit_condition = _no_async_condition;
1589   _pending_async_exception = NULL;
1590   _thread_stat = NULL;
1591   _thread_stat = new ThreadStatistics();
1592   _blocked_on_compilation = false;
1593   _jni_active_critical = 0;
1594   _pending_jni_exception_check_fn = NULL;
1595   _do_not_unlock_if_synchronized = false;
1596   _cached_monitor_info = NULL;
1597   _parker = Parker::Allocate(this);
1598 
1599 #ifndef PRODUCT
1600   _jmp_ring_index = 0;
1601   for (int ji = 0; ji < jump_ring_buffer_size; ji++) {
1602     record_jump(NULL, NULL, NULL, 0);
1603   }
1604 #endif // PRODUCT
1605 
1606   // Setup safepoint state info for this thread
1607   ThreadSafepointState::create(this);
1608 
1609   debug_only(_java_call_counter = 0);
1610 
1611   // JVMTI PopFrame support
1612   _popframe_condition = popframe_inactive;
1613   _popframe_preserved_args = NULL;
1614   _popframe_preserved_args_size = 0;
1615   _frames_to_pop_failed_realloc = 0;
1616 
1617   if (SafepointMechanism::uses_thread_local_poll()) {
1618     SafepointMechanism::initialize_header(this);
1619   }
1620 
1621   pd_initialize();
1622 }
1623 
1624 JavaThread::JavaThread(bool is_attaching_via_jni) :
1625                        Thread() {
1626   initialize();
1627   if (is_attaching_via_jni) {
1628     _jni_attach_state = _attaching_via_jni;
1629   } else {
1630     _jni_attach_state = _not_attaching_via_jni;
1631   }
1632   assert(deferred_card_mark().is_empty(), "Default MemRegion ctor");
1633 }
1634 
1635 bool JavaThread::reguard_stack(address cur_sp) {
1636   if (_stack_guard_state != stack_guard_yellow_reserved_disabled
1637       && _stack_guard_state != stack_guard_reserved_disabled) {
1638     return true; // Stack already guarded or guard pages not needed.
1639   }
1640 
1641   if (register_stack_overflow()) {
1642     // For those architectures which have separate register and
1643     // memory stacks, we must check the register stack to see if
1644     // it has overflowed.
1645     return false;
1646   }
1647 
1648   // Java code never executes within the yellow zone: the latter is only
1649   // there to provoke an exception during stack banging.  If java code
1650   // is executing there, either StackShadowPages should be larger, or
1651   // some exception code in c1, c2 or the interpreter isn't unwinding
1652   // when it should.
1653   guarantee(cur_sp > stack_reserved_zone_base(),
1654             "not enough space to reguard - increase StackShadowPages");
1655   if (_stack_guard_state == stack_guard_yellow_reserved_disabled) {
1656     enable_stack_yellow_reserved_zone();
1657     if (reserved_stack_activation() != stack_base()) {
1658       set_reserved_stack_activation(stack_base());
1659     }
1660   } else if (_stack_guard_state == stack_guard_reserved_disabled) {
1661     set_reserved_stack_activation(stack_base());
1662     enable_stack_reserved_zone();
1663   }
1664   return true;
1665 }
1666 
1667 bool JavaThread::reguard_stack(void) {
1668   return reguard_stack(os::current_stack_pointer());
1669 }
1670 
1671 
1672 void JavaThread::block_if_vm_exited() {
1673   if (_terminated == _vm_exited) {
1674     // _vm_exited is set at safepoint, and Threads_lock is never released
1675     // we will block here forever
1676     Threads_lock->lock_without_safepoint_check();
1677     ShouldNotReachHere();
1678   }
1679 }
1680 
1681 
1682 // Remove this ifdef when C1 is ported to the compiler interface.
1683 static void compiler_thread_entry(JavaThread* thread, TRAPS);
1684 static void sweeper_thread_entry(JavaThread* thread, TRAPS);
1685 
1686 JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
1687                        Thread() {
1688   initialize();
1689   _jni_attach_state = _not_attaching_via_jni;
1690   set_entry_point(entry_point);
1691   // Create the native thread itself.
1692   // %note runtime_23
1693   os::ThreadType thr_type = os::java_thread;
1694   thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
1695                                                      os::java_thread;
1696   os::create_thread(this, thr_type, stack_sz);
1697   // The _osthread may be NULL here because we ran out of memory (too many threads active).
1698   // We need to throw and OutOfMemoryError - however we cannot do this here because the caller
1699   // may hold a lock and all locks must be unlocked before throwing the exception (throwing
1700   // the exception consists of creating the exception object & initializing it, initialization
1701   // will leave the VM via a JavaCall and then all locks must be unlocked).
1702   //
1703   // The thread is still suspended when we reach here. Thread must be explicit started
1704   // by creator! Furthermore, the thread must also explicitly be added to the Threads list
1705   // by calling Threads:add. The reason why this is not done here, is because the thread
1706   // object must be fully initialized (take a look at JVM_Start)
1707 }
1708 
1709 JavaThread::~JavaThread() {
1710 
1711   // JSR166 -- return the parker to the free list
1712   Parker::Release(_parker);
1713   _parker = NULL;
1714 
1715   // Free any remaining  previous UnrollBlock
1716   vframeArray* old_array = vframe_array_last();
1717 
1718   if (old_array != NULL) {
1719     Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
1720     old_array->set_unroll_block(NULL);
1721     delete old_info;
1722     delete old_array;
1723   }
1724 
1725   GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred = deferred_locals();
1726   if (deferred != NULL) {
1727     // This can only happen if thread is destroyed before deoptimization occurs.
1728     assert(deferred->length() != 0, "empty array!");
1729     do {
1730       jvmtiDeferredLocalVariableSet* dlv = deferred->at(0);
1731       deferred->remove_at(0);
1732       // individual jvmtiDeferredLocalVariableSet are CHeapObj's
1733       delete dlv;
1734     } while (deferred->length() != 0);
1735     delete deferred;
1736   }
1737 
1738   // All Java related clean up happens in exit
1739   ThreadSafepointState::destroy(this);
1740   if (_thread_stat != NULL) delete _thread_stat;
1741 
1742 #if INCLUDE_JVMCI
1743   if (JVMCICounterSize > 0) {
1744     if (jvmci_counters_include(this)) {
1745       for (int i = 0; i < JVMCICounterSize; i++) {
1746         _jvmci_old_thread_counters[i] += _jvmci_counters[i];
1747       }
1748     }
1749     FREE_C_HEAP_ARRAY(jlong, _jvmci_counters);
1750   }
1751 #endif // INCLUDE_JVMCI
1752 }
1753 
1754 
1755 // The first routine called by a new Java thread
1756 void JavaThread::run() {
1757   // initialize thread-local alloc buffer related fields
1758   this->initialize_tlab();
1759 
1760   // used to test validity of stack trace backs
1761   this->record_base_of_stack_pointer();
1762 
1763   this->create_stack_guard_pages();
1764 
1765   this->cache_global_variables();
1766 
1767   // Thread is now sufficient initialized to be handled by the safepoint code as being
1768   // in the VM. Change thread state from _thread_new to _thread_in_vm
1769   ThreadStateTransition::transition_and_fence(this, _thread_new, _thread_in_vm);
1770 
1771   assert(JavaThread::current() == this, "sanity check");
1772   assert(!Thread::current()->owns_locks(), "sanity check");
1773 
1774   DTRACE_THREAD_PROBE(start, this);
1775 
1776   // This operation might block. We call that after all safepoint checks for a new thread has
1777   // been completed.
1778   this->set_active_handles(JNIHandleBlock::allocate_block());
1779 
1780   if (JvmtiExport::should_post_thread_life()) {
1781     JvmtiExport::post_thread_start(this);
1782 
1783   }
1784 
1785   // We call another function to do the rest so we are sure that the stack addresses used
1786   // from there will be lower than the stack base just computed
1787   thread_main_inner();
1788 
1789   // Note, thread is no longer valid at this point!
1790 }
1791 
1792 
1793 void JavaThread::thread_main_inner() {
1794   assert(JavaThread::current() == this, "sanity check");
1795   assert(this->threadObj() != NULL, "just checking");
1796 
1797   // Execute thread entry point unless this thread has a pending exception
1798   // or has been stopped before starting.
1799   // Note: Due to JVM_StopThread we can have pending exceptions already!
1800   if (!this->has_pending_exception() &&
1801       !java_lang_Thread::is_stillborn(this->threadObj())) {
1802     {
1803       ResourceMark rm(this);
1804       this->set_native_thread_name(this->get_thread_name());
1805     }
1806     HandleMark hm(this);
1807     this->entry_point()(this, this);
1808   }
1809 
1810   DTRACE_THREAD_PROBE(stop, this);
1811 
1812   this->exit(false);
1813   this->smr_delete();
1814 }
1815 
1816 
1817 static void ensure_join(JavaThread* thread) {
1818   // We do not need to grab the Threads_lock, since we are operating on ourself.
1819   Handle threadObj(thread, thread->threadObj());
1820   assert(threadObj.not_null(), "java thread object must exist");
1821   ObjectLocker lock(threadObj, thread);
1822   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1823   thread->clear_pending_exception();
1824   // Thread is exiting. So set thread_status field in  java.lang.Thread class to TERMINATED.
1825   java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
1826   // Clear the native thread instance - this makes isAlive return false and allows the join()
1827   // to complete once we've done the notify_all below
1828   java_lang_Thread::set_thread(threadObj(), NULL);
1829   lock.notify_all(thread);
1830   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1831   thread->clear_pending_exception();
1832 }
1833 
1834 static bool is_daemon(oop threadObj) {
1835   return (threadObj != NULL && java_lang_Thread::is_daemon(threadObj));
1836 }
1837 
1838 // For any new cleanup additions, please check to see if they need to be applied to
1839 // cleanup_failed_attach_current_thread as well.
1840 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
1841   assert(this == JavaThread::current(), "thread consistency check");
1842 
1843   elapsedTimer _timer_exit_phase1;
1844   elapsedTimer _timer_exit_phase2;
1845   elapsedTimer _timer_exit_phase3;
1846   elapsedTimer _timer_exit_phase4;
1847 
1848   if (log_is_enabled(Debug, os, thread, timer)) {
1849     _timer_exit_phase1.start();
1850   }
1851 
1852   HandleMark hm(this);
1853   Handle uncaught_exception(this, this->pending_exception());
1854   this->clear_pending_exception();
1855   Handle threadObj(this, this->threadObj());
1856   assert(threadObj.not_null(), "Java thread object should be created");
1857 
1858   // FIXIT: This code should be moved into else part, when reliable 1.2/1.3 check is in place
1859   {
1860     EXCEPTION_MARK;
1861 
1862     CLEAR_PENDING_EXCEPTION;
1863   }
1864   if (!destroy_vm) {
1865     if (uncaught_exception.not_null()) {
1866       EXCEPTION_MARK;
1867       // Call method Thread.dispatchUncaughtException().
1868       Klass* thread_klass = SystemDictionary::Thread_klass();
1869       JavaValue result(T_VOID);
1870       JavaCalls::call_virtual(&result,
1871                               threadObj, thread_klass,
1872                               vmSymbols::dispatchUncaughtException_name(),
1873                               vmSymbols::throwable_void_signature(),
1874                               uncaught_exception,
1875                               THREAD);
1876       if (HAS_PENDING_EXCEPTION) {
1877         ResourceMark rm(this);
1878         jio_fprintf(defaultStream::error_stream(),
1879                     "\nException: %s thrown from the UncaughtExceptionHandler"
1880                     " in thread \"%s\"\n",
1881                     pending_exception()->klass()->external_name(),
1882                     get_thread_name());
1883         CLEAR_PENDING_EXCEPTION;
1884       }
1885     }
1886     JFR_ONLY(Jfr::on_java_thread_dismantle(this);)
1887 
1888     // Call Thread.exit(). We try 3 times in case we got another Thread.stop during
1889     // the execution of the method. If that is not enough, then we don't really care. Thread.stop
1890     // is deprecated anyhow.
1891     if (!is_Compiler_thread()) {
1892       int count = 3;
1893       while (java_lang_Thread::threadGroup(threadObj()) != NULL && (count-- > 0)) {
1894         EXCEPTION_MARK;
1895         JavaValue result(T_VOID);
1896         Klass* thread_klass = SystemDictionary::Thread_klass();
1897         JavaCalls::call_virtual(&result,
1898                                 threadObj, thread_klass,
1899                                 vmSymbols::exit_method_name(),
1900                                 vmSymbols::void_method_signature(),
1901                                 THREAD);
1902         CLEAR_PENDING_EXCEPTION;
1903       }
1904     }
1905     // notify JVMTI
1906     if (JvmtiExport::should_post_thread_life()) {
1907       JvmtiExport::post_thread_end(this);
1908     }
1909 
1910     // We have notified the agents that we are exiting, before we go on,
1911     // we must check for a pending external suspend request and honor it
1912     // in order to not surprise the thread that made the suspend request.
1913     while (true) {
1914       {
1915         MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
1916         if (!is_external_suspend()) {
1917           set_terminated(_thread_exiting);
1918           ThreadService::current_thread_exiting(this, is_daemon(threadObj()));
1919           break;
1920         }
1921         // Implied else:
1922         // Things get a little tricky here. We have a pending external
1923         // suspend request, but we are holding the SR_lock so we
1924         // can't just self-suspend. So we temporarily drop the lock
1925         // and then self-suspend.
1926       }
1927 
1928       ThreadBlockInVM tbivm(this);
1929       java_suspend_self();
1930 
1931       // We're done with this suspend request, but we have to loop around
1932       // and check again. Eventually we will get SR_lock without a pending
1933       // external suspend request and will be able to mark ourselves as
1934       // exiting.
1935     }
1936     // no more external suspends are allowed at this point
1937   } else {
1938     assert(!is_terminated() && !is_exiting(), "must not be exiting");
1939     // before_exit() has already posted JVMTI THREAD_END events
1940   }
1941 
1942   if (log_is_enabled(Debug, os, thread, timer)) {
1943     _timer_exit_phase1.stop();
1944     _timer_exit_phase2.start();
1945   }
1946   // Notify waiters on thread object. This has to be done after exit() is called
1947   // on the thread (if the thread is the last thread in a daemon ThreadGroup the
1948   // group should have the destroyed bit set before waiters are notified).
1949   ensure_join(this);
1950   assert(!this->has_pending_exception(), "ensure_join should have cleared");
1951 
1952   if (log_is_enabled(Debug, os, thread, timer)) {
1953     _timer_exit_phase2.stop();
1954     _timer_exit_phase3.start();
1955   }
1956   // 6282335 JNI DetachCurrentThread spec states that all Java monitors
1957   // held by this thread must be released. The spec does not distinguish
1958   // between JNI-acquired and regular Java monitors. We can only see
1959   // regular Java monitors here if monitor enter-exit matching is broken.
1960   //
1961   // ensure_join() ignores IllegalThreadStateExceptions, and so does
1962   // ObjectSynchronizer::release_monitors_owned_by_thread().
1963   if (exit_type == jni_detach) {
1964     // Sanity check even though JNI DetachCurrentThread() would have
1965     // returned JNI_ERR if there was a Java frame. JavaThread exit
1966     // should be done executing Java code by the time we get here.
1967     assert(!this->has_last_Java_frame(),
1968            "should not have a Java frame when detaching or exiting");
1969     ObjectSynchronizer::release_monitors_owned_by_thread(this);
1970     assert(!this->has_pending_exception(), "release_monitors should have cleared");
1971   }
1972 
1973   // These things needs to be done while we are still a Java Thread. Make sure that thread
1974   // is in a consistent state, in case GC happens
1975   JFR_ONLY(Jfr::on_thread_exit(this);)
1976 
1977   if (active_handles() != NULL) {
1978     JNIHandleBlock* block = active_handles();
1979     set_active_handles(NULL);
1980     JNIHandleBlock::release_block(block);
1981   }
1982 
1983   if (free_handle_block() != NULL) {
1984     JNIHandleBlock* block = free_handle_block();
1985     set_free_handle_block(NULL);
1986     JNIHandleBlock::release_block(block);
1987   }
1988 
1989   // These have to be removed while this is still a valid thread.
1990   remove_stack_guard_pages();
1991 
1992   if (UseTLAB) {
1993     tlab().retire();
1994   }
1995 
1996   if (JvmtiEnv::environments_might_exist()) {
1997     JvmtiExport::cleanup_thread(this);
1998   }
1999 
2000   // We must flush any deferred card marks and other various GC barrier
2001   // related buffers (e.g. G1 SATB buffer and G1 dirty card queue buffer)
2002   // before removing a thread from the list of active threads.
2003   BarrierSet::barrier_set()->on_thread_detach(this);
2004 
2005   log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").",
2006     exit_type == JavaThread::normal_exit ? "exiting" : "detaching",
2007     os::current_thread_id());
2008 
2009   if (log_is_enabled(Debug, os, thread, timer)) {
2010     _timer_exit_phase3.stop();
2011     _timer_exit_phase4.start();
2012   }
2013   // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
2014   Threads::remove(this);
2015 
2016   if (log_is_enabled(Debug, os, thread, timer)) {
2017     _timer_exit_phase4.stop();
2018     ResourceMark rm(this);
2019     log_debug(os, thread, timer)("name='%s'"
2020                                  ", exit-phase1=" JLONG_FORMAT
2021                                  ", exit-phase2=" JLONG_FORMAT
2022                                  ", exit-phase3=" JLONG_FORMAT
2023                                  ", exit-phase4=" JLONG_FORMAT,
2024                                  get_thread_name(),
2025                                  _timer_exit_phase1.milliseconds(),
2026                                  _timer_exit_phase2.milliseconds(),
2027                                  _timer_exit_phase3.milliseconds(),
2028                                  _timer_exit_phase4.milliseconds());
2029   }
2030 }
2031 
2032 void JavaThread::cleanup_failed_attach_current_thread() {
2033   if (active_handles() != NULL) {
2034     JNIHandleBlock* block = active_handles();
2035     set_active_handles(NULL);
2036     JNIHandleBlock::release_block(block);
2037   }
2038 
2039   if (free_handle_block() != NULL) {
2040     JNIHandleBlock* block = free_handle_block();
2041     set_free_handle_block(NULL);
2042     JNIHandleBlock::release_block(block);
2043   }
2044 
2045   // These have to be removed while this is still a valid thread.
2046   remove_stack_guard_pages();
2047 
2048   if (UseTLAB) {
2049     tlab().retire();
2050   }
2051 
2052   BarrierSet::barrier_set()->on_thread_detach(this);
2053 
2054   Threads::remove(this);
2055   this->smr_delete();
2056 }
2057 
2058 JavaThread* JavaThread::active() {
2059   Thread* thread = Thread::current();
2060   if (thread->is_Java_thread()) {
2061     return (JavaThread*) thread;
2062   } else {
2063     assert(thread->is_VM_thread(), "this must be a vm thread");
2064     VM_Operation* op = ((VMThread*) thread)->vm_operation();
2065     JavaThread *ret=op == NULL ? NULL : (JavaThread *)op->calling_thread();
2066     assert(ret->is_Java_thread(), "must be a Java thread");
2067     return ret;
2068   }
2069 }
2070 
2071 bool JavaThread::is_lock_owned(address adr) const {
2072   if (Thread::is_lock_owned(adr)) return true;
2073 
2074   for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2075     if (chunk->contains(adr)) return true;
2076   }
2077 
2078   return false;
2079 }
2080 
2081 
2082 void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
2083   chunk->set_next(monitor_chunks());
2084   set_monitor_chunks(chunk);
2085 }
2086 
2087 void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
2088   guarantee(monitor_chunks() != NULL, "must be non empty");
2089   if (monitor_chunks() == chunk) {
2090     set_monitor_chunks(chunk->next());
2091   } else {
2092     MonitorChunk* prev = monitor_chunks();
2093     while (prev->next() != chunk) prev = prev->next();
2094     prev->set_next(chunk->next());
2095   }
2096 }
2097 
2098 // JVM support.
2099 
2100 // Note: this function shouldn't block if it's called in
2101 // _thread_in_native_trans state (such as from
2102 // check_special_condition_for_native_trans()).
2103 void JavaThread::check_and_handle_async_exceptions(bool check_unsafe_error) {
2104 
2105   if (has_last_Java_frame() && has_async_condition()) {
2106     // If we are at a polling page safepoint (not a poll return)
2107     // then we must defer async exception because live registers
2108     // will be clobbered by the exception path. Poll return is
2109     // ok because the call we a returning from already collides
2110     // with exception handling registers and so there is no issue.
2111     // (The exception handling path kills call result registers but
2112     //  this is ok since the exception kills the result anyway).
2113 
2114     if (is_at_poll_safepoint()) {
2115       // if the code we are returning to has deoptimized we must defer
2116       // the exception otherwise live registers get clobbered on the
2117       // exception path before deoptimization is able to retrieve them.
2118       //
2119       RegisterMap map(this, false);
2120       frame caller_fr = last_frame().sender(&map);
2121       assert(caller_fr.is_compiled_frame(), "what?");
2122       if (caller_fr.is_deoptimized_frame()) {
2123         log_info(exceptions)("deferred async exception at compiled safepoint");
2124         return;
2125       }
2126     }
2127   }
2128 
2129   JavaThread::AsyncRequests condition = clear_special_runtime_exit_condition();
2130   if (condition == _no_async_condition) {
2131     // Conditions have changed since has_special_runtime_exit_condition()
2132     // was called:
2133     // - if we were here only because of an external suspend request,
2134     //   then that was taken care of above (or cancelled) so we are done
2135     // - if we were here because of another async request, then it has
2136     //   been cleared between the has_special_runtime_exit_condition()
2137     //   and now so again we are done
2138     return;
2139   }
2140 
2141   // Check for pending async. exception
2142   if (_pending_async_exception != NULL) {
2143     // Only overwrite an already pending exception, if it is not a threadDeath.
2144     if (!has_pending_exception() || !pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())) {
2145 
2146       // We cannot call Exceptions::_throw(...) here because we cannot block
2147       set_pending_exception(_pending_async_exception, __FILE__, __LINE__);
2148 
2149       LogTarget(Info, exceptions) lt;
2150       if (lt.is_enabled()) {
2151         ResourceMark rm;
2152         LogStream ls(lt);
2153         ls.print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", p2i(this));
2154           if (has_last_Java_frame()) {
2155             frame f = last_frame();
2156            ls.print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", p2i(f.pc()), p2i(f.sp()));
2157           }
2158         ls.print_cr(" of type: %s", _pending_async_exception->klass()->external_name());
2159       }
2160       _pending_async_exception = NULL;
2161       clear_has_async_exception();
2162     }
2163   }
2164 
2165   if (check_unsafe_error &&
2166       condition == _async_unsafe_access_error && !has_pending_exception()) {
2167     condition = _no_async_condition;  // done
2168     switch (thread_state()) {
2169     case _thread_in_vm: {
2170       JavaThread* THREAD = this;
2171       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2172     }
2173     case _thread_in_native: {
2174       ThreadInVMfromNative tiv(this);
2175       JavaThread* THREAD = this;
2176       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2177     }
2178     case _thread_in_Java: {
2179       ThreadInVMfromJava tiv(this);
2180       JavaThread* THREAD = this;
2181       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in a recent unsafe memory access operation in compiled Java code");
2182     }
2183     default:
2184       ShouldNotReachHere();
2185     }
2186   }
2187 
2188   assert(condition == _no_async_condition || has_pending_exception() ||
2189          (!check_unsafe_error && condition == _async_unsafe_access_error),
2190          "must have handled the async condition, if no exception");
2191 }
2192 
2193 void JavaThread::handle_special_runtime_exit_condition(bool check_asyncs) {
2194   //
2195   // Check for pending external suspend. Internal suspend requests do
2196   // not use handle_special_runtime_exit_condition().
2197   // If JNIEnv proxies are allowed, don't self-suspend if the target
2198   // thread is not the current thread. In older versions of jdbx, jdbx
2199   // threads could call into the VM with another thread's JNIEnv so we
2200   // can be here operating on behalf of a suspended thread (4432884).
2201   bool do_self_suspend = is_external_suspend_with_lock();
2202   if (do_self_suspend && (!AllowJNIEnvProxy || this == JavaThread::current())) {
2203     //
2204     // Because thread is external suspended the safepoint code will count
2205     // thread as at a safepoint. This can be odd because we can be here
2206     // as _thread_in_Java which would normally transition to _thread_blocked
2207     // at a safepoint. We would like to mark the thread as _thread_blocked
2208     // before calling java_suspend_self like all other callers of it but
2209     // we must then observe proper safepoint protocol. (We can't leave
2210     // _thread_blocked with a safepoint in progress). However we can be
2211     // here as _thread_in_native_trans so we can't use a normal transition
2212     // constructor/destructor pair because they assert on that type of
2213     // transition. We could do something like:
2214     //
2215     // JavaThreadState state = thread_state();
2216     // set_thread_state(_thread_in_vm);
2217     // {
2218     //   ThreadBlockInVM tbivm(this);
2219     //   java_suspend_self()
2220     // }
2221     // set_thread_state(_thread_in_vm_trans);
2222     // if (safepoint) block;
2223     // set_thread_state(state);
2224     //
2225     // but that is pretty messy. Instead we just go with the way the
2226     // code has worked before and note that this is the only path to
2227     // java_suspend_self that doesn't put the thread in _thread_blocked
2228     // mode.
2229 
2230     frame_anchor()->make_walkable(this);
2231     java_suspend_self();
2232 
2233     // We might be here for reasons in addition to the self-suspend request
2234     // so check for other async requests.
2235   }
2236 
2237   if (check_asyncs) {
2238     check_and_handle_async_exceptions();
2239   }
2240 
2241   JFR_ONLY(SUSPEND_THREAD_CONDITIONAL(this);)
2242 }
2243 
2244 void JavaThread::send_thread_stop(oop java_throwable)  {
2245   assert(Thread::current()->is_VM_thread(), "should be in the vm thread");
2246   assert(Threads_lock->is_locked(), "Threads_lock should be locked by safepoint code");
2247   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
2248 
2249   // Do not throw asynchronous exceptions against the compiler thread
2250   // (the compiler thread should not be a Java thread -- fix in 1.4.2)
2251   if (!can_call_java()) return;
2252 
2253   {
2254     // Actually throw the Throwable against the target Thread - however
2255     // only if there is no thread death exception installed already.
2256     if (_pending_async_exception == NULL || !_pending_async_exception->is_a(SystemDictionary::ThreadDeath_klass())) {
2257       // If the topmost frame is a runtime stub, then we are calling into
2258       // OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
2259       // must deoptimize the caller before continuing, as the compiled  exception handler table
2260       // may not be valid
2261       if (has_last_Java_frame()) {
2262         frame f = last_frame();
2263         if (f.is_runtime_frame() || f.is_safepoint_blob_frame()) {
2264           // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2265           RegisterMap reg_map(this, UseBiasedLocking);
2266           frame compiled_frame = f.sender(&reg_map);
2267           if (!StressCompiledExceptionHandlers && compiled_frame.can_be_deoptimized()) {
2268             Deoptimization::deoptimize(this, compiled_frame, &reg_map);
2269           }
2270         }
2271       }
2272 
2273       // Set async. pending exception in thread.
2274       set_pending_async_exception(java_throwable);
2275 
2276       if (log_is_enabled(Info, exceptions)) {
2277          ResourceMark rm;
2278         log_info(exceptions)("Pending Async. exception installed of type: %s",
2279                              InstanceKlass::cast(_pending_async_exception->klass())->external_name());
2280       }
2281       // for AbortVMOnException flag
2282       Exceptions::debug_check_abort(_pending_async_exception->klass()->external_name());
2283     }
2284   }
2285 
2286 
2287   // Interrupt thread so it will wake up from a potential wait()
2288   Thread::interrupt(this);
2289 }
2290 
2291 // External suspension mechanism.
2292 //
2293 // Tell the VM to suspend a thread when ever it knows that it does not hold on
2294 // to any VM_locks and it is at a transition
2295 // Self-suspension will happen on the transition out of the vm.
2296 // Catch "this" coming in from JNIEnv pointers when the thread has been freed
2297 //
2298 // Guarantees on return:
2299 //   + Target thread will not execute any new bytecode (that's why we need to
2300 //     force a safepoint)
2301 //   + Target thread will not enter any new monitors
2302 //
2303 void JavaThread::java_suspend() {
2304   ThreadsListHandle tlh;
2305   if (!tlh.includes(this) || threadObj() == NULL || is_exiting()) {
2306     return;
2307   }
2308 
2309   { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2310     if (!is_external_suspend()) {
2311       // a racing resume has cancelled us; bail out now
2312       return;
2313     }
2314 
2315     // suspend is done
2316     uint32_t debug_bits = 0;
2317     // Warning: is_ext_suspend_completed() may temporarily drop the
2318     // SR_lock to allow the thread to reach a stable thread state if
2319     // it is currently in a transient thread state.
2320     if (is_ext_suspend_completed(false /* !called_by_wait */,
2321                                  SuspendRetryDelay, &debug_bits)) {
2322       return;
2323     }
2324   }
2325 
2326   VM_ThreadSuspend vm_suspend;
2327   VMThread::execute(&vm_suspend);
2328 }
2329 
2330 // Part II of external suspension.
2331 // A JavaThread self suspends when it detects a pending external suspend
2332 // request. This is usually on transitions. It is also done in places
2333 // where continuing to the next transition would surprise the caller,
2334 // e.g., monitor entry.
2335 //
2336 // Returns the number of times that the thread self-suspended.
2337 //
2338 // Note: DO NOT call java_suspend_self() when you just want to block current
2339 //       thread. java_suspend_self() is the second stage of cooperative
2340 //       suspension for external suspend requests and should only be used
2341 //       to complete an external suspend request.
2342 //
2343 int JavaThread::java_suspend_self() {
2344   int ret = 0;
2345 
2346   // we are in the process of exiting so don't suspend
2347   if (is_exiting()) {
2348     clear_external_suspend();
2349     return ret;
2350   }
2351 
2352   assert(_anchor.walkable() ||
2353          (is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
2354          "must have walkable stack");
2355 
2356   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2357 
2358   assert(!this->is_ext_suspended(),
2359          "a thread trying to self-suspend should not already be suspended");
2360 
2361   if (this->is_suspend_equivalent()) {
2362     // If we are self-suspending as a result of the lifting of a
2363     // suspend equivalent condition, then the suspend_equivalent
2364     // flag is not cleared until we set the ext_suspended flag so
2365     // that wait_for_ext_suspend_completion() returns consistent
2366     // results.
2367     this->clear_suspend_equivalent();
2368   }
2369 
2370   // A racing resume may have cancelled us before we grabbed SR_lock
2371   // above. Or another external suspend request could be waiting for us
2372   // by the time we return from SR_lock()->wait(). The thread
2373   // that requested the suspension may already be trying to walk our
2374   // stack and if we return now, we can change the stack out from under
2375   // it. This would be a "bad thing (TM)" and cause the stack walker
2376   // to crash. We stay self-suspended until there are no more pending
2377   // external suspend requests.
2378   while (is_external_suspend()) {
2379     ret++;
2380     this->set_ext_suspended();
2381 
2382     // _ext_suspended flag is cleared by java_resume()
2383     while (is_ext_suspended()) {
2384       this->SR_lock()->wait(Mutex::_no_safepoint_check_flag);
2385     }
2386   }
2387 
2388   return ret;
2389 }
2390 
2391 #ifdef ASSERT
2392 // Verify the JavaThread has not yet been published in the Threads::list, and
2393 // hence doesn't need protection from concurrent access at this stage.
2394 void JavaThread::verify_not_published() {
2395   // Cannot create a ThreadsListHandle here and check !tlh.includes(this)
2396   // since an unpublished JavaThread doesn't participate in the
2397   // Thread-SMR protocol for keeping a ThreadsList alive.
2398   assert(!on_thread_list(), "JavaThread shouldn't have been published yet!");
2399 }
2400 #endif
2401 
2402 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2403 // progress or when _suspend_flags is non-zero.
2404 // Current thread needs to self-suspend if there is a suspend request and/or
2405 // block if a safepoint is in progress.
2406 // Async exception ISN'T checked.
2407 // Note only the ThreadInVMfromNative transition can call this function
2408 // directly and when thread state is _thread_in_native_trans
2409 void JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread *thread) {
2410   assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
2411 
2412   JavaThread *curJT = JavaThread::current();
2413   bool do_self_suspend = thread->is_external_suspend();
2414 
2415   assert(!curJT->has_last_Java_frame() || curJT->frame_anchor()->walkable(), "Unwalkable stack in native->vm transition");
2416 
2417   // If JNIEnv proxies are allowed, don't self-suspend if the target
2418   // thread is not the current thread. In older versions of jdbx, jdbx
2419   // threads could call into the VM with another thread's JNIEnv so we
2420   // can be here operating on behalf of a suspended thread (4432884).
2421   if (do_self_suspend && (!AllowJNIEnvProxy || curJT == thread)) {
2422     JavaThreadState state = thread->thread_state();
2423 
2424     // We mark this thread_blocked state as a suspend-equivalent so
2425     // that a caller to is_ext_suspend_completed() won't be confused.
2426     // The suspend-equivalent state is cleared by java_suspend_self().
2427     thread->set_suspend_equivalent();
2428 
2429     // If the safepoint code sees the _thread_in_native_trans state, it will
2430     // wait until the thread changes to other thread state. There is no
2431     // guarantee on how soon we can obtain the SR_lock and complete the
2432     // self-suspend request. It would be a bad idea to let safepoint wait for
2433     // too long. Temporarily change the state to _thread_blocked to
2434     // let the VM thread know that this thread is ready for GC. The problem
2435     // of changing thread state is that safepoint could happen just after
2436     // java_suspend_self() returns after being resumed, and VM thread will
2437     // see the _thread_blocked state. We must check for safepoint
2438     // after restoring the state and make sure we won't leave while a safepoint
2439     // is in progress.
2440     thread->set_thread_state(_thread_blocked);
2441     thread->java_suspend_self();
2442     thread->set_thread_state(state);
2443 
2444     InterfaceSupport::serialize_thread_state_with_handler(thread);
2445   }
2446 
2447   SafepointMechanism::block_if_requested(curJT);
2448 
2449   if (thread->is_deopt_suspend()) {
2450     thread->clear_deopt_suspend();
2451     RegisterMap map(thread, false);
2452     frame f = thread->last_frame();
2453     while (f.id() != thread->must_deopt_id() && ! f.is_first_frame()) {
2454       f = f.sender(&map);
2455     }
2456     if (f.id() == thread->must_deopt_id()) {
2457       thread->clear_must_deopt_id();
2458       f.deoptimize(thread);
2459     } else {
2460       fatal("missed deoptimization!");
2461     }
2462   }
2463 
2464   JFR_ONLY(SUSPEND_THREAD_CONDITIONAL(thread);)
2465 }
2466 
2467 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2468 // progress or when _suspend_flags is non-zero.
2469 // Current thread needs to self-suspend if there is a suspend request and/or
2470 // block if a safepoint is in progress.
2471 // Also check for pending async exception (not including unsafe access error).
2472 // Note only the native==>VM/Java barriers can call this function and when
2473 // thread state is _thread_in_native_trans.
2474 void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
2475   check_safepoint_and_suspend_for_native_trans(thread);
2476 
2477   if (thread->has_async_exception()) {
2478     // We are in _thread_in_native_trans state, don't handle unsafe
2479     // access error since that may block.
2480     thread->check_and_handle_async_exceptions(false);
2481   }
2482 }
2483 
2484 // This is a variant of the normal
2485 // check_special_condition_for_native_trans with slightly different
2486 // semantics for use by critical native wrappers.  It does all the
2487 // normal checks but also performs the transition back into
2488 // thread_in_Java state.  This is required so that critical natives
2489 // can potentially block and perform a GC if they are the last thread
2490 // exiting the GCLocker.
2491 void JavaThread::check_special_condition_for_native_trans_and_transition(JavaThread *thread) {
2492   check_special_condition_for_native_trans(thread);
2493 
2494   // Finish the transition
2495   thread->set_thread_state(_thread_in_Java);
2496 
2497   if (thread->do_critical_native_unlock()) {
2498     ThreadInVMfromJavaNoAsyncException tiv(thread);
2499     GCLocker::unlock_critical(thread);
2500     thread->clear_critical_native_unlock();
2501   }
2502 }
2503 
2504 // We need to guarantee the Threads_lock here, since resumes are not
2505 // allowed during safepoint synchronization
2506 // Can only resume from an external suspension
2507 void JavaThread::java_resume() {
2508   assert_locked_or_safepoint(Threads_lock);
2509 
2510   // Sanity check: thread is gone, has started exiting or the thread
2511   // was not externally suspended.
2512   ThreadsListHandle tlh;
2513   if (!tlh.includes(this) || is_exiting() || !is_external_suspend()) {
2514     return;
2515   }
2516 
2517   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2518 
2519   clear_external_suspend();
2520 
2521   if (is_ext_suspended()) {
2522     clear_ext_suspended();
2523     SR_lock()->notify_all();
2524   }
2525 }
2526 
2527 size_t JavaThread::_stack_red_zone_size = 0;
2528 size_t JavaThread::_stack_yellow_zone_size = 0;
2529 size_t JavaThread::_stack_reserved_zone_size = 0;
2530 size_t JavaThread::_stack_shadow_zone_size = 0;
2531 
2532 void JavaThread::create_stack_guard_pages() {
2533   if (!os::uses_stack_guard_pages() ||
2534       _stack_guard_state != stack_guard_unused ||
2535       (DisablePrimordialThreadGuardPages && os::is_primordial_thread())) {
2536       log_info(os, thread)("Stack guard page creation for thread "
2537                            UINTX_FORMAT " disabled", os::current_thread_id());
2538     return;
2539   }
2540   address low_addr = stack_end();
2541   size_t len = stack_guard_zone_size();
2542 
2543   assert(is_aligned(low_addr, os::vm_page_size()), "Stack base should be the start of a page");
2544   assert(is_aligned(len, os::vm_page_size()), "Stack size should be a multiple of page size");
2545 
2546   int must_commit = os::must_commit_stack_guard_pages();
2547   // warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);
2548 
2549   if (must_commit && !os::create_stack_guard_pages((char *) low_addr, len)) {
2550     log_warning(os, thread)("Attempt to allocate stack guard pages failed.");
2551     return;
2552   }
2553 
2554   if (os::guard_memory((char *) low_addr, len)) {
2555     _stack_guard_state = stack_guard_enabled;
2556   } else {
2557     log_warning(os, thread)("Attempt to protect stack guard pages failed ("
2558       PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2559     if (os::uncommit_memory((char *) low_addr, len)) {
2560       log_warning(os, thread)("Attempt to deallocate stack guard pages failed.");
2561     }
2562     return;
2563   }
2564 
2565   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages activated: "
2566     PTR_FORMAT "-" PTR_FORMAT ".",
2567     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2568 }
2569 
2570 void JavaThread::remove_stack_guard_pages() {
2571   assert(Thread::current() == this, "from different thread");
2572   if (_stack_guard_state == stack_guard_unused) return;
2573   address low_addr = stack_end();
2574   size_t len = stack_guard_zone_size();
2575 
2576   if (os::must_commit_stack_guard_pages()) {
2577     if (os::remove_stack_guard_pages((char *) low_addr, len)) {
2578       _stack_guard_state = stack_guard_unused;
2579     } else {
2580       log_warning(os, thread)("Attempt to deallocate stack guard pages failed ("
2581         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2582       return;
2583     }
2584   } else {
2585     if (_stack_guard_state == stack_guard_unused) return;
2586     if (os::unguard_memory((char *) low_addr, len)) {
2587       _stack_guard_state = stack_guard_unused;
2588     } else {
2589       log_warning(os, thread)("Attempt to unprotect stack guard pages failed ("
2590         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2591       return;
2592     }
2593   }
2594 
2595   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages removed: "
2596     PTR_FORMAT "-" PTR_FORMAT ".",
2597     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2598 }
2599 
2600 void JavaThread::enable_stack_reserved_zone() {
2601   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2602   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2603 
2604   // The base notation is from the stack's point of view, growing downward.
2605   // We need to adjust it to work correctly with guard_memory()
2606   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2607 
2608   guarantee(base < stack_base(),"Error calculating stack reserved zone");
2609   guarantee(base < os::current_stack_pointer(),"Error calculating stack reserved zone");
2610 
2611   if (os::guard_memory((char *) base, stack_reserved_zone_size())) {
2612     _stack_guard_state = stack_guard_enabled;
2613   } else {
2614     warning("Attempt to guard stack reserved zone failed.");
2615   }
2616   enable_register_stack_guard();
2617 }
2618 
2619 void JavaThread::disable_stack_reserved_zone() {
2620   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2621   assert(_stack_guard_state != stack_guard_reserved_disabled, "already disabled");
2622 
2623   // Simply return if called for a thread that does not use guard pages.
2624   if (_stack_guard_state == stack_guard_unused) return;
2625 
2626   // The base notation is from the stack's point of view, growing downward.
2627   // We need to adjust it to work correctly with guard_memory()
2628   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2629 
2630   if (os::unguard_memory((char *)base, stack_reserved_zone_size())) {
2631     _stack_guard_state = stack_guard_reserved_disabled;
2632   } else {
2633     warning("Attempt to unguard stack reserved zone failed.");
2634   }
2635   disable_register_stack_guard();
2636 }
2637 
2638 void JavaThread::enable_stack_yellow_reserved_zone() {
2639   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2640   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2641 
2642   // The base notation is from the stacks point of view, growing downward.
2643   // We need to adjust it to work correctly with guard_memory()
2644   address base = stack_red_zone_base();
2645 
2646   guarantee(base < stack_base(), "Error calculating stack yellow zone");
2647   guarantee(base < os::current_stack_pointer(), "Error calculating stack yellow zone");
2648 
2649   if (os::guard_memory((char *) base, stack_yellow_reserved_zone_size())) {
2650     _stack_guard_state = stack_guard_enabled;
2651   } else {
2652     warning("Attempt to guard stack yellow zone failed.");
2653   }
2654   enable_register_stack_guard();
2655 }
2656 
2657 void JavaThread::disable_stack_yellow_reserved_zone() {
2658   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2659   assert(_stack_guard_state != stack_guard_yellow_reserved_disabled, "already disabled");
2660 
2661   // Simply return if called for a thread that does not use guard pages.
2662   if (_stack_guard_state == stack_guard_unused) return;
2663 
2664   // The base notation is from the stacks point of view, growing downward.
2665   // We need to adjust it to work correctly with guard_memory()
2666   address base = stack_red_zone_base();
2667 
2668   if (os::unguard_memory((char *)base, stack_yellow_reserved_zone_size())) {
2669     _stack_guard_state = stack_guard_yellow_reserved_disabled;
2670   } else {
2671     warning("Attempt to unguard stack yellow zone failed.");
2672   }
2673   disable_register_stack_guard();
2674 }
2675 
2676 void JavaThread::enable_stack_red_zone() {
2677   // The base notation is from the stacks point of view, growing downward.
2678   // We need to adjust it to work correctly with guard_memory()
2679   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2680   address base = stack_red_zone_base() - stack_red_zone_size();
2681 
2682   guarantee(base < stack_base(), "Error calculating stack red zone");
2683   guarantee(base < os::current_stack_pointer(), "Error calculating stack red zone");
2684 
2685   if (!os::guard_memory((char *) base, stack_red_zone_size())) {
2686     warning("Attempt to guard stack red zone failed.");
2687   }
2688 }
2689 
2690 void JavaThread::disable_stack_red_zone() {
2691   // The base notation is from the stacks point of view, growing downward.
2692   // We need to adjust it to work correctly with guard_memory()
2693   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2694   address base = stack_red_zone_base() - stack_red_zone_size();
2695   if (!os::unguard_memory((char *)base, stack_red_zone_size())) {
2696     warning("Attempt to unguard stack red zone failed.");
2697   }
2698 }
2699 
2700 void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
2701   // ignore is there is no stack
2702   if (!has_last_Java_frame()) return;
2703   // traverse the stack frames. Starts from top frame.
2704   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2705     frame* fr = fst.current();
2706     f(fr, fst.register_map());
2707   }
2708 }
2709 
2710 
2711 #ifndef PRODUCT
2712 // Deoptimization
2713 // Function for testing deoptimization
2714 void JavaThread::deoptimize() {
2715   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2716   StackFrameStream fst(this, UseBiasedLocking);
2717   bool deopt = false;           // Dump stack only if a deopt actually happens.
2718   bool only_at = strlen(DeoptimizeOnlyAt) > 0;
2719   // Iterate over all frames in the thread and deoptimize
2720   for (; !fst.is_done(); fst.next()) {
2721     if (fst.current()->can_be_deoptimized()) {
2722 
2723       if (only_at) {
2724         // Deoptimize only at particular bcis.  DeoptimizeOnlyAt
2725         // consists of comma or carriage return separated numbers so
2726         // search for the current bci in that string.
2727         address pc = fst.current()->pc();
2728         nmethod* nm =  (nmethod*) fst.current()->cb();
2729         ScopeDesc* sd = nm->scope_desc_at(pc);
2730         char buffer[8];
2731         jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
2732         size_t len = strlen(buffer);
2733         const char * found = strstr(DeoptimizeOnlyAt, buffer);
2734         while (found != NULL) {
2735           if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
2736               (found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
2737             // Check that the bci found is bracketed by terminators.
2738             break;
2739           }
2740           found = strstr(found + 1, buffer);
2741         }
2742         if (!found) {
2743           continue;
2744         }
2745       }
2746 
2747       if (DebugDeoptimization && !deopt) {
2748         deopt = true; // One-time only print before deopt
2749         tty->print_cr("[BEFORE Deoptimization]");
2750         trace_frames();
2751         trace_stack();
2752       }
2753       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2754     }
2755   }
2756 
2757   if (DebugDeoptimization && deopt) {
2758     tty->print_cr("[AFTER Deoptimization]");
2759     trace_frames();
2760   }
2761 }
2762 
2763 
2764 // Make zombies
2765 void JavaThread::make_zombies() {
2766   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2767     if (fst.current()->can_be_deoptimized()) {
2768       // it is a Java nmethod
2769       nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
2770       nm->make_not_entrant();
2771     }
2772   }
2773 }
2774 #endif // PRODUCT
2775 
2776 
2777 void JavaThread::deoptimized_wrt_marked_nmethods() {
2778   if (!has_last_Java_frame()) return;
2779   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2780   StackFrameStream fst(this, UseBiasedLocking);
2781   for (; !fst.is_done(); fst.next()) {
2782     if (fst.current()->should_be_deoptimized()) {
2783       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2784     }
2785   }
2786 }
2787 
2788 
2789 // If the caller is a NamedThread, then remember, in the current scope,
2790 // the given JavaThread in its _processed_thread field.
2791 class RememberProcessedThread: public StackObj {
2792   NamedThread* _cur_thr;
2793  public:
2794   RememberProcessedThread(JavaThread* jthr) {
2795     Thread* thread = Thread::current();
2796     if (thread->is_Named_thread()) {
2797       _cur_thr = (NamedThread *)thread;
2798       _cur_thr->set_processed_thread(jthr);
2799     } else {
2800       _cur_thr = NULL;
2801     }
2802   }
2803 
2804   ~RememberProcessedThread() {
2805     if (_cur_thr) {
2806       _cur_thr->set_processed_thread(NULL);
2807     }
2808   }
2809 };
2810 
2811 void JavaThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
2812   // Verify that the deferred card marks have been flushed.
2813   assert(deferred_card_mark().is_empty(), "Should be empty during GC");
2814 
2815   // Traverse the GCHandles
2816   Thread::oops_do(f, cf);
2817 
2818   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2819          (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2820 
2821   if (has_last_Java_frame()) {
2822     // Record JavaThread to GC thread
2823     RememberProcessedThread rpt(this);
2824 
2825     // traverse the registered growable array
2826     if (_array_for_gc != NULL) {
2827       for (int index = 0; index < _array_for_gc->length(); index++) {
2828         f->do_oop(_array_for_gc->adr_at(index));
2829       }
2830     }
2831 
2832     // Traverse the monitor chunks
2833     for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2834       chunk->oops_do(f);
2835     }
2836 
2837     // Traverse the execution stack
2838     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2839       fst.current()->oops_do(f, cf, fst.register_map());
2840     }
2841   }
2842 
2843   // callee_target is never live across a gc point so NULL it here should
2844   // it still contain a methdOop.
2845 
2846   set_callee_target(NULL);
2847 
2848   assert(vframe_array_head() == NULL, "deopt in progress at a safepoint!");
2849   // If we have deferred set_locals there might be oops waiting to be
2850   // written
2851   GrowableArray<jvmtiDeferredLocalVariableSet*>* list = deferred_locals();
2852   if (list != NULL) {
2853     for (int i = 0; i < list->length(); i++) {
2854       list->at(i)->oops_do(f);
2855     }
2856   }
2857 
2858   // Traverse instance variables at the end since the GC may be moving things
2859   // around using this function
2860   f->do_oop((oop*) &_threadObj);
2861   f->do_oop((oop*) &_vm_result);
2862   f->do_oop((oop*) &_exception_oop);
2863   f->do_oop((oop*) &_pending_async_exception);
2864 
2865   if (jvmti_thread_state() != NULL) {
2866     jvmti_thread_state()->oops_do(f);
2867   }
2868 }
2869 
2870 void JavaThread::nmethods_do(CodeBlobClosure* cf) {
2871   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2872          (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2873 
2874   if (has_last_Java_frame()) {
2875     // Traverse the execution stack
2876     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2877       fst.current()->nmethods_do(cf);
2878     }
2879   }
2880 }
2881 
2882 void JavaThread::metadata_do(void f(Metadata*)) {
2883   if (has_last_Java_frame()) {
2884     // Traverse the execution stack to call f() on the methods in the stack
2885     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2886       fst.current()->metadata_do(f);
2887     }
2888   } else if (is_Compiler_thread()) {
2889     // need to walk ciMetadata in current compile tasks to keep alive.
2890     CompilerThread* ct = (CompilerThread*)this;
2891     if (ct->env() != NULL) {
2892       ct->env()->metadata_do(f);
2893     }
2894     CompileTask* task = ct->task();
2895     if (task != NULL) {
2896       task->metadata_do(f);
2897     }
2898   }
2899 }
2900 
2901 // Printing
2902 const char* _get_thread_state_name(JavaThreadState _thread_state) {
2903   switch (_thread_state) {
2904   case _thread_uninitialized:     return "_thread_uninitialized";
2905   case _thread_new:               return "_thread_new";
2906   case _thread_new_trans:         return "_thread_new_trans";
2907   case _thread_in_native:         return "_thread_in_native";
2908   case _thread_in_native_trans:   return "_thread_in_native_trans";
2909   case _thread_in_vm:             return "_thread_in_vm";
2910   case _thread_in_vm_trans:       return "_thread_in_vm_trans";
2911   case _thread_in_Java:           return "_thread_in_Java";
2912   case _thread_in_Java_trans:     return "_thread_in_Java_trans";
2913   case _thread_blocked:           return "_thread_blocked";
2914   case _thread_blocked_trans:     return "_thread_blocked_trans";
2915   default:                        return "unknown thread state";
2916   }
2917 }
2918 
2919 #ifndef PRODUCT
2920 void JavaThread::print_thread_state_on(outputStream *st) const {
2921   st->print_cr("   JavaThread state: %s", _get_thread_state_name(_thread_state));
2922 };
2923 void JavaThread::print_thread_state() const {
2924   print_thread_state_on(tty);
2925 }
2926 #endif // PRODUCT
2927 
2928 // Called by Threads::print() for VM_PrintThreads operation
2929 void JavaThread::print_on(outputStream *st, bool print_extended_info) const {
2930   st->print_raw("\"");
2931   st->print_raw(get_thread_name());
2932   st->print_raw("\" ");
2933   oop thread_oop = threadObj();
2934   if (thread_oop != NULL) {
2935     st->print("#" INT64_FORMAT " ", (int64_t)java_lang_Thread::thread_id(thread_oop));
2936     if (java_lang_Thread::is_daemon(thread_oop))  st->print("daemon ");
2937     st->print("prio=%d ", java_lang_Thread::priority(thread_oop));
2938   }
2939   Thread::print_on(st, print_extended_info);
2940   // print guess for valid stack memory region (assume 4K pages); helps lock debugging
2941   st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
2942   if (thread_oop != NULL) {
2943     st->print_cr("   java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
2944   }
2945 #ifndef PRODUCT
2946   _safepoint_state->print_on(st);
2947 #endif // PRODUCT
2948   if (is_Compiler_thread()) {
2949     CompileTask *task = ((CompilerThread*)this)->task();
2950     if (task != NULL) {
2951       st->print("   Compiling: ");
2952       task->print(st, NULL, true, false);
2953     } else {
2954       st->print("   No compile task");
2955     }
2956     st->cr();
2957   }
2958 }
2959 
2960 void JavaThread::print_name_on_error(outputStream* st, char *buf, int buflen) const {
2961   st->print("%s", get_thread_name_string(buf, buflen));
2962 }
2963 
2964 // Called by fatal error handler. The difference between this and
2965 // JavaThread::print() is that we can't grab lock or allocate memory.
2966 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
2967   st->print("JavaThread \"%s\"", get_thread_name_string(buf, buflen));
2968   oop thread_obj = threadObj();
2969   if (thread_obj != NULL) {
2970     if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
2971   }
2972   st->print(" [");
2973   st->print("%s", _get_thread_state_name(_thread_state));
2974   if (osthread()) {
2975     st->print(", id=%d", osthread()->thread_id());
2976   }
2977   st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
2978             p2i(stack_end()), p2i(stack_base()));
2979   st->print("]");
2980 
2981   ThreadsSMRSupport::print_info_on(this, st);
2982   return;
2983 }
2984 
2985 // Verification
2986 
2987 static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
2988 
2989 void JavaThread::verify() {
2990   // Verify oops in the thread.
2991   oops_do(&VerifyOopClosure::verify_oop, NULL);
2992 
2993   // Verify the stack frames.
2994   frames_do(frame_verify);
2995 }
2996 
2997 // CR 6300358 (sub-CR 2137150)
2998 // Most callers of this method assume that it can't return NULL but a
2999 // thread may not have a name whilst it is in the process of attaching to
3000 // the VM - see CR 6412693, and there are places where a JavaThread can be
3001 // seen prior to having it's threadObj set (eg JNI attaching threads and
3002 // if vm exit occurs during initialization). These cases can all be accounted
3003 // for such that this method never returns NULL.
3004 const char* JavaThread::get_thread_name() const {
3005 #ifdef ASSERT
3006   // early safepoints can hit while current thread does not yet have TLS
3007   if (!SafepointSynchronize::is_at_safepoint()) {
3008     Thread *cur = Thread::current();
3009     if (!(cur->is_Java_thread() && cur == this)) {
3010       // Current JavaThreads are allowed to get their own name without
3011       // the Threads_lock.
3012       assert_locked_or_safepoint(Threads_lock);
3013     }
3014   }
3015 #endif // ASSERT
3016   return get_thread_name_string();
3017 }
3018 
3019 // Returns a non-NULL representation of this thread's name, or a suitable
3020 // descriptive string if there is no set name
3021 const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
3022   const char* name_str;
3023   oop thread_obj = threadObj();
3024   if (thread_obj != NULL) {
3025     oop name = java_lang_Thread::name(thread_obj);
3026     if (name != NULL) {
3027       if (buf == NULL) {
3028         name_str = java_lang_String::as_utf8_string(name);
3029       } else {
3030         name_str = java_lang_String::as_utf8_string(name, buf, buflen);
3031       }
3032     } else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
3033       name_str = "<no-name - thread is attaching>";
3034     } else {
3035       name_str = Thread::name();
3036     }
3037   } else {
3038     name_str = Thread::name();
3039   }
3040   assert(name_str != NULL, "unexpected NULL thread name");
3041   return name_str;
3042 }
3043 
3044 
3045 const char* JavaThread::get_threadgroup_name() const {
3046   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3047   oop thread_obj = threadObj();
3048   if (thread_obj != NULL) {
3049     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3050     if (thread_group != NULL) {
3051       // ThreadGroup.name can be null
3052       return java_lang_ThreadGroup::name(thread_group);
3053     }
3054   }
3055   return NULL;
3056 }
3057 
3058 const char* JavaThread::get_parent_name() const {
3059   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3060   oop thread_obj = threadObj();
3061   if (thread_obj != NULL) {
3062     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3063     if (thread_group != NULL) {
3064       oop parent = java_lang_ThreadGroup::parent(thread_group);
3065       if (parent != NULL) {
3066         // ThreadGroup.name can be null
3067         return java_lang_ThreadGroup::name(parent);
3068       }
3069     }
3070   }
3071   return NULL;
3072 }
3073 
3074 ThreadPriority JavaThread::java_priority() const {
3075   oop thr_oop = threadObj();
3076   if (thr_oop == NULL) return NormPriority; // Bootstrapping
3077   ThreadPriority priority = java_lang_Thread::priority(thr_oop);
3078   assert(MinPriority <= priority && priority <= MaxPriority, "sanity check");
3079   return priority;
3080 }
3081 
3082 void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
3083 
3084   assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
3085   // Link Java Thread object <-> C++ Thread
3086 
3087   // Get the C++ thread object (an oop) from the JNI handle (a jthread)
3088   // and put it into a new Handle.  The Handle "thread_oop" can then
3089   // be used to pass the C++ thread object to other methods.
3090 
3091   // Set the Java level thread object (jthread) field of the
3092   // new thread (a JavaThread *) to C++ thread object using the
3093   // "thread_oop" handle.
3094 
3095   // Set the thread field (a JavaThread *) of the
3096   // oop representing the java_lang_Thread to the new thread (a JavaThread *).
3097 
3098   Handle thread_oop(Thread::current(),
3099                     JNIHandles::resolve_non_null(jni_thread));
3100   assert(InstanceKlass::cast(thread_oop->klass())->is_linked(),
3101          "must be initialized");
3102   set_threadObj(thread_oop());
3103   java_lang_Thread::set_thread(thread_oop(), this);
3104 
3105   if (prio == NoPriority) {
3106     prio = java_lang_Thread::priority(thread_oop());
3107     assert(prio != NoPriority, "A valid priority should be present");
3108   }
3109 
3110   // Push the Java priority down to the native thread; needs Threads_lock
3111   Thread::set_priority(this, prio);
3112 
3113   // Add the new thread to the Threads list and set it in motion.
3114   // We must have threads lock in order to call Threads::add.
3115   // It is crucial that we do not block before the thread is
3116   // added to the Threads list for if a GC happens, then the java_thread oop
3117   // will not be visited by GC.
3118   Threads::add(this);
3119 }
3120 
3121 oop JavaThread::current_park_blocker() {
3122   // Support for JSR-166 locks
3123   oop thread_oop = threadObj();
3124   if (thread_oop != NULL &&
3125       JDK_Version::current().supports_thread_park_blocker()) {
3126     return java_lang_Thread::park_blocker(thread_oop);
3127   }
3128   return NULL;
3129 }
3130 
3131 
3132 void JavaThread::print_stack_on(outputStream* st) {
3133   if (!has_last_Java_frame()) return;
3134   ResourceMark rm;
3135   HandleMark   hm;
3136 
3137   RegisterMap reg_map(this);
3138   vframe* start_vf = last_java_vframe(&reg_map);
3139   int count = 0;
3140   for (vframe* f = start_vf; f != NULL; f = f->sender()) {
3141     if (f->is_java_frame()) {
3142       javaVFrame* jvf = javaVFrame::cast(f);
3143       java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
3144 
3145       // Print out lock information
3146       if (JavaMonitorsInStackTrace) {
3147         jvf->print_lock_info_on(st, count);
3148       }
3149     } else {
3150       // Ignore non-Java frames
3151     }
3152 
3153     // Bail-out case for too deep stacks if MaxJavaStackTraceDepth > 0
3154     count++;
3155     if (MaxJavaStackTraceDepth > 0 && MaxJavaStackTraceDepth == count) return;
3156   }
3157 }
3158 
3159 
3160 // JVMTI PopFrame support
3161 void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
3162   assert(_popframe_preserved_args == NULL, "should not wipe out old PopFrame preserved arguments");
3163   if (in_bytes(size_in_bytes) != 0) {
3164     _popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes), mtThread);
3165     _popframe_preserved_args_size = in_bytes(size_in_bytes);
3166     Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
3167   }
3168 }
3169 
3170 void* JavaThread::popframe_preserved_args() {
3171   return _popframe_preserved_args;
3172 }
3173 
3174 ByteSize JavaThread::popframe_preserved_args_size() {
3175   return in_ByteSize(_popframe_preserved_args_size);
3176 }
3177 
3178 WordSize JavaThread::popframe_preserved_args_size_in_words() {
3179   int sz = in_bytes(popframe_preserved_args_size());
3180   assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
3181   return in_WordSize(sz / wordSize);
3182 }
3183 
3184 void JavaThread::popframe_free_preserved_args() {
3185   assert(_popframe_preserved_args != NULL, "should not free PopFrame preserved arguments twice");
3186   FREE_C_HEAP_ARRAY(char, (char*) _popframe_preserved_args);
3187   _popframe_preserved_args = NULL;
3188   _popframe_preserved_args_size = 0;
3189 }
3190 
3191 #ifndef PRODUCT
3192 
3193 void JavaThread::trace_frames() {
3194   tty->print_cr("[Describe stack]");
3195   int frame_no = 1;
3196   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
3197     tty->print("  %d. ", frame_no++);
3198     fst.current()->print_value_on(tty, this);
3199     tty->cr();
3200   }
3201 }
3202 
3203 class PrintAndVerifyOopClosure: public OopClosure {
3204  protected:
3205   template <class T> inline void do_oop_work(T* p) {
3206     oop obj = RawAccess<>::oop_load(p);
3207     if (obj == NULL) return;
3208     tty->print(INTPTR_FORMAT ": ", p2i(p));
3209     if (oopDesc::is_oop_or_null(obj)) {
3210       if (obj->is_objArray()) {
3211         tty->print_cr("valid objArray: " INTPTR_FORMAT, p2i(obj));
3212       } else {
3213         obj->print();
3214       }
3215     } else {
3216       tty->print_cr("invalid oop: " INTPTR_FORMAT, p2i(obj));
3217     }
3218     tty->cr();
3219   }
3220  public:
3221   virtual void do_oop(oop* p) { do_oop_work(p); }
3222   virtual void do_oop(narrowOop* p)  { do_oop_work(p); }
3223 };
3224 
3225 
3226 static void oops_print(frame* f, const RegisterMap *map) {
3227   PrintAndVerifyOopClosure print;
3228   f->print_value();
3229   f->oops_do(&print, NULL, (RegisterMap*)map);
3230 }
3231 
3232 // Print our all the locations that contain oops and whether they are
3233 // valid or not.  This useful when trying to find the oldest frame
3234 // where an oop has gone bad since the frame walk is from youngest to
3235 // oldest.
3236 void JavaThread::trace_oops() {
3237   tty->print_cr("[Trace oops]");
3238   frames_do(oops_print);
3239 }
3240 
3241 
3242 #ifdef ASSERT
3243 // Print or validate the layout of stack frames
3244 void JavaThread::print_frame_layout(int depth, bool validate_only) {
3245   ResourceMark rm;
3246   PRESERVE_EXCEPTION_MARK;
3247   FrameValues values;
3248   int frame_no = 0;
3249   for (StackFrameStream fst(this, false); !fst.is_done(); fst.next()) {
3250     fst.current()->describe(values, ++frame_no);
3251     if (depth == frame_no) break;
3252   }
3253   if (validate_only) {
3254     values.validate();
3255   } else {
3256     tty->print_cr("[Describe stack layout]");
3257     values.print(this);
3258   }
3259 }
3260 #endif
3261 
3262 void JavaThread::trace_stack_from(vframe* start_vf) {
3263   ResourceMark rm;
3264   int vframe_no = 1;
3265   for (vframe* f = start_vf; f; f = f->sender()) {
3266     if (f->is_java_frame()) {
3267       javaVFrame::cast(f)->print_activation(vframe_no++);
3268     } else {
3269       f->print();
3270     }
3271     if (vframe_no > StackPrintLimit) {
3272       tty->print_cr("...<more frames>...");
3273       return;
3274     }
3275   }
3276 }
3277 
3278 
3279 void JavaThread::trace_stack() {
3280   if (!has_last_Java_frame()) return;
3281   ResourceMark rm;
3282   HandleMark   hm;
3283   RegisterMap reg_map(this);
3284   trace_stack_from(last_java_vframe(&reg_map));
3285 }
3286 
3287 
3288 #endif // PRODUCT
3289 
3290 
3291 javaVFrame* JavaThread::last_java_vframe(RegisterMap *reg_map) {
3292   assert(reg_map != NULL, "a map must be given");
3293   frame f = last_frame();
3294   for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender()) {
3295     if (vf->is_java_frame()) return javaVFrame::cast(vf);
3296   }
3297   return NULL;
3298 }
3299 
3300 
3301 Klass* JavaThread::security_get_caller_class(int depth) {
3302   vframeStream vfst(this);
3303   vfst.security_get_caller_frame(depth);
3304   if (!vfst.at_end()) {
3305     return vfst.method()->method_holder();
3306   }
3307   return NULL;
3308 }
3309 
3310 static void compiler_thread_entry(JavaThread* thread, TRAPS) {
3311   assert(thread->is_Compiler_thread(), "must be compiler thread");
3312   CompileBroker::compiler_thread_loop();
3313 }
3314 
3315 static void sweeper_thread_entry(JavaThread* thread, TRAPS) {
3316   NMethodSweeper::sweeper_loop();
3317 }
3318 
3319 // Create a CompilerThread
3320 CompilerThread::CompilerThread(CompileQueue* queue,
3321                                CompilerCounters* counters)
3322                                : JavaThread(&compiler_thread_entry) {
3323   _env   = NULL;
3324   _log   = NULL;
3325   _task  = NULL;
3326   _queue = queue;
3327   _counters = counters;
3328   _buffer_blob = NULL;
3329   _compiler = NULL;
3330 
3331   // Compiler uses resource area for compilation, let's bias it to mtCompiler
3332   resource_area()->bias_to(mtCompiler);
3333 
3334 #ifndef PRODUCT
3335   _ideal_graph_printer = NULL;
3336 #endif
3337 }
3338 
3339 CompilerThread::~CompilerThread() {
3340   // Delete objects which were allocated on heap.
3341   delete _counters;
3342 }
3343 
3344 bool CompilerThread::can_call_java() const {
3345   return _compiler != NULL && _compiler->is_jvmci();
3346 }
3347 
3348 // Create sweeper thread
3349 CodeCacheSweeperThread::CodeCacheSweeperThread()
3350 : JavaThread(&sweeper_thread_entry) {
3351   _scanned_compiled_method = NULL;
3352 }
3353 
3354 void CodeCacheSweeperThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
3355   JavaThread::oops_do(f, cf);
3356   if (_scanned_compiled_method != NULL && cf != NULL) {
3357     // Safepoints can occur when the sweeper is scanning an nmethod so
3358     // process it here to make sure it isn't unloaded in the middle of
3359     // a scan.
3360     cf->do_code_blob(_scanned_compiled_method);
3361   }
3362 }
3363 
3364 void CodeCacheSweeperThread::nmethods_do(CodeBlobClosure* cf) {
3365   JavaThread::nmethods_do(cf);
3366   if (_scanned_compiled_method != NULL && cf != NULL) {
3367     // Safepoints can occur when the sweeper is scanning an nmethod so
3368     // process it here to make sure it isn't unloaded in the middle of
3369     // a scan.
3370     cf->do_code_blob(_scanned_compiled_method);
3371   }
3372 }
3373 
3374 
3375 // ======= Threads ========
3376 
3377 // The Threads class links together all active threads, and provides
3378 // operations over all threads. It is protected by the Threads_lock,
3379 // which is also used in other global contexts like safepointing.
3380 // ThreadsListHandles are used to safely perform operations on one
3381 // or more threads without the risk of the thread exiting during the
3382 // operation.
3383 //
3384 // Note: The Threads_lock is currently more widely used than we
3385 // would like. We are actively migrating Threads_lock uses to other
3386 // mechanisms in order to reduce Threads_lock contention.
3387 
3388 JavaThread* Threads::_thread_list = NULL;
3389 int         Threads::_number_of_threads = 0;
3390 int         Threads::_number_of_non_daemon_threads = 0;
3391 int         Threads::_return_code = 0;
3392 int         Threads::_thread_claim_parity = 0;
3393 size_t      JavaThread::_stack_size_at_create = 0;
3394 
3395 #ifdef ASSERT
3396 bool        Threads::_vm_complete = false;
3397 size_t      Threads::_threads_before_barrier_set = 0;
3398 #endif
3399 
3400 static inline void *prefetch_and_load_ptr(void **addr, intx prefetch_interval) {
3401   Prefetch::read((void*)addr, prefetch_interval);
3402   return *addr;
3403 }
3404 
3405 // Possibly the ugliest for loop the world has seen. C++ does not allow
3406 // multiple types in the declaration section of the for loop. In this case
3407 // we are only dealing with pointers and hence can cast them. It looks ugly
3408 // but macros are ugly and therefore it's fine to make things absurdly ugly.
3409 #define DO_JAVA_THREADS(LIST, X)                                                                                          \
3410     for (JavaThread *MACRO_scan_interval = (JavaThread*)(uintptr_t)PrefetchScanIntervalInBytes,                           \
3411              *MACRO_list = (JavaThread*)(LIST),                                                                           \
3412              **MACRO_end = ((JavaThread**)((ThreadsList*)MACRO_list)->threads()) + ((ThreadsList*)MACRO_list)->length(),  \
3413              **MACRO_current_p = (JavaThread**)((ThreadsList*)MACRO_list)->threads(),                                     \
3414              *X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval);                 \
3415          MACRO_current_p != MACRO_end;                                                                                    \
3416          MACRO_current_p++,                                                                                               \
3417              X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval))
3418 
3419 // All JavaThreads
3420 #define ALL_JAVA_THREADS(X) DO_JAVA_THREADS(ThreadsSMRSupport::get_java_thread_list(), X)
3421 
3422 // All NonJavaThreads (i.e., every non-JavaThread in the system).
3423 void Threads::non_java_threads_do(ThreadClosure* tc) {
3424   NoSafepointVerifier nsv(!SafepointSynchronize::is_at_safepoint(), false);
3425   for (NonJavaThread::Iterator njti; !njti.end(); njti.step()) {
3426     tc->do_thread(njti.current());
3427   }
3428 }
3429 
3430 // All JavaThreads
3431 void Threads::java_threads_do(ThreadClosure* tc) {
3432   assert_locked_or_safepoint(Threads_lock);
3433   // ALL_JAVA_THREADS iterates through all JavaThreads.
3434   ALL_JAVA_THREADS(p) {
3435     tc->do_thread(p);
3436   }
3437 }
3438 
3439 void Threads::java_threads_and_vm_thread_do(ThreadClosure* tc) {
3440   assert_locked_or_safepoint(Threads_lock);
3441   java_threads_do(tc);
3442   tc->do_thread(VMThread::vm_thread());
3443 }
3444 
3445 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system).
3446 void Threads::threads_do(ThreadClosure* tc) {
3447   assert_locked_or_safepoint(Threads_lock);
3448   java_threads_do(tc);
3449   non_java_threads_do(tc);
3450 }
3451 
3452 void Threads::possibly_parallel_threads_do(bool is_par, ThreadClosure* tc) {
3453   int cp = Threads::thread_claim_parity();
3454   ALL_JAVA_THREADS(p) {
3455     if (p->claim_oops_do(is_par, cp)) {
3456       tc->do_thread(p);
3457     }
3458   }
3459   VMThread* vmt = VMThread::vm_thread();
3460   if (vmt->claim_oops_do(is_par, cp)) {
3461     tc->do_thread(vmt);
3462   }
3463 }
3464 
3465 // The system initialization in the library has three phases.
3466 //
3467 // Phase 1: java.lang.System class initialization
3468 //     java.lang.System is a primordial class loaded and initialized
3469 //     by the VM early during startup.  java.lang.System.<clinit>
3470 //     only does registerNatives and keeps the rest of the class
3471 //     initialization work later until thread initialization completes.
3472 //
3473 //     System.initPhase1 initializes the system properties, the static
3474 //     fields in, out, and err. Set up java signal handlers, OS-specific
3475 //     system settings, and thread group of the main thread.
3476 static void call_initPhase1(TRAPS) {
3477   Klass* klass =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3478   JavaValue result(T_VOID);
3479   JavaCalls::call_static(&result, klass, vmSymbols::initPhase1_name(),
3480                                          vmSymbols::void_method_signature(), CHECK);
3481 }
3482 
3483 // Phase 2. Module system initialization
3484 //     This will initialize the module system.  Only java.base classes
3485 //     can be loaded until phase 2 completes.
3486 //
3487 //     Call System.initPhase2 after the compiler initialization and jsr292
3488 //     classes get initialized because module initialization runs a lot of java
3489 //     code, that for performance reasons, should be compiled.  Also, this will
3490 //     enable the startup code to use lambda and other language features in this
3491 //     phase and onward.
3492 //
3493 //     After phase 2, The VM will begin search classes from -Xbootclasspath/a.
3494 static void call_initPhase2(TRAPS) {
3495   TraceTime timer("Initialize module system", TRACETIME_LOG(Info, startuptime));
3496 
3497   Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3498 
3499   JavaValue result(T_INT);
3500   JavaCallArguments args;
3501   args.push_int(DisplayVMOutputToStderr);
3502   args.push_int(log_is_enabled(Debug, init)); // print stack trace if exception thrown
3503   JavaCalls::call_static(&result, klass, vmSymbols::initPhase2_name(),
3504                                          vmSymbols::boolean_boolean_int_signature(), &args, CHECK);
3505   if (result.get_jint() != JNI_OK) {
3506     vm_exit_during_initialization(); // no message or exception
3507   }
3508 
3509   universe_post_module_init();
3510 }
3511 
3512 // Phase 3. final setup - set security manager, system class loader and TCCL
3513 //
3514 //     This will instantiate and set the security manager, set the system class
3515 //     loader as well as the thread context class loader.  The security manager
3516 //     and system class loader may be a custom class loaded from -Xbootclasspath/a,
3517 //     other modules or the application's classpath.
3518 static void call_initPhase3(TRAPS) {
3519   Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3520   JavaValue result(T_VOID);
3521   JavaCalls::call_static(&result, klass, vmSymbols::initPhase3_name(),
3522                                          vmSymbols::void_method_signature(), CHECK);
3523 }
3524 
3525 void Threads::initialize_java_lang_classes(JavaThread* main_thread, TRAPS) {
3526   TraceTime timer("Initialize java.lang classes", TRACETIME_LOG(Info, startuptime));
3527 
3528   if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
3529     create_vm_init_libraries();
3530   }
3531 
3532   initialize_class(vmSymbols::java_lang_String(), CHECK);
3533 
3534   // Inject CompactStrings value after the static initializers for String ran.
3535   java_lang_String::set_compact_strings(CompactStrings);
3536 
3537   // Initialize java_lang.System (needed before creating the thread)
3538   initialize_class(vmSymbols::java_lang_System(), CHECK);
3539   // The VM creates & returns objects of this class. Make sure it's initialized.
3540   initialize_class(vmSymbols::java_lang_Class(), CHECK);
3541   initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK);
3542   Handle thread_group = create_initial_thread_group(CHECK);
3543   Universe::set_main_thread_group(thread_group());
3544   initialize_class(vmSymbols::java_lang_Thread(), CHECK);
3545   oop thread_object = create_initial_thread(thread_group, main_thread, CHECK);
3546   main_thread->set_threadObj(thread_object);
3547   // Set thread status to running since main thread has
3548   // been started and running.
3549   java_lang_Thread::set_thread_status(thread_object,
3550                                       java_lang_Thread::RUNNABLE);
3551 
3552   // The VM creates objects of this class.
3553   initialize_class(vmSymbols::java_lang_Module(), CHECK);
3554 
3555   // The VM preresolves methods to these classes. Make sure that they get initialized
3556   initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK);
3557   initialize_class(vmSymbols::java_lang_ref_Finalizer(), CHECK);
3558 
3559   // Phase 1 of the system initialization in the library, java.lang.System class initialization
3560   call_initPhase1(CHECK);
3561 
3562   // get the Java runtime name after java.lang.System is initialized
3563   JDK_Version::set_runtime_name(get_java_runtime_name(THREAD));
3564   JDK_Version::set_runtime_version(get_java_runtime_version(THREAD));
3565 
3566   // an instance of OutOfMemory exception has been allocated earlier
3567   initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK);
3568   initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK);
3569   initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK);
3570   initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK);
3571   initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK);
3572   initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK);
3573   initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK);
3574   initialize_class(vmSymbols::java_lang_IllegalArgumentException(), CHECK);
3575 }
3576 
3577 void Threads::initialize_jsr292_core_classes(TRAPS) {
3578   TraceTime timer("Initialize java.lang.invoke classes", TRACETIME_LOG(Info, startuptime));
3579 
3580   initialize_class(vmSymbols::java_lang_invoke_MethodHandle(), CHECK);
3581   initialize_class(vmSymbols::java_lang_invoke_ResolvedMethodName(), CHECK);
3582   initialize_class(vmSymbols::java_lang_invoke_MemberName(), CHECK);
3583   initialize_class(vmSymbols::java_lang_invoke_MethodHandleNatives(), CHECK);
3584 }
3585 
3586 jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
3587   extern void JDK_Version_init();
3588 
3589   // Preinitialize version info.
3590   VM_Version::early_initialize();
3591 
3592   // Check version
3593   if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
3594 
3595   // Initialize library-based TLS
3596   ThreadLocalStorage::init();
3597 
3598   // Initialize the output stream module
3599   ostream_init();
3600 
3601   // Process java launcher properties.
3602   Arguments::process_sun_java_launcher_properties(args);
3603 
3604   // Initialize the os module
3605   os::init();
3606 
3607   // Record VM creation timing statistics
3608   TraceVmCreationTime create_vm_timer;
3609   create_vm_timer.start();
3610 
3611   // Initialize system properties.
3612   Arguments::init_system_properties();
3613 
3614   // So that JDK version can be used as a discriminator when parsing arguments
3615   JDK_Version_init();
3616 
3617   // Update/Initialize System properties after JDK version number is known
3618   Arguments::init_version_specific_system_properties();
3619 
3620   // Make sure to initialize log configuration *before* parsing arguments
3621   LogConfiguration::initialize(create_vm_timer.begin_time());
3622 
3623   // Parse arguments
3624   // Note: this internally calls os::init_container_support()
3625   jint parse_result = Arguments::parse(args);
3626   if (parse_result != JNI_OK) return parse_result;
3627 
3628   os::init_before_ergo();
3629 
3630   jint ergo_result = Arguments::apply_ergo();
3631   if (ergo_result != JNI_OK) return ergo_result;
3632 
3633   // Final check of all ranges after ergonomics which may change values.
3634   if (!JVMFlagRangeList::check_ranges()) {
3635     return JNI_EINVAL;
3636   }
3637 
3638   // Final check of all 'AfterErgo' constraints after ergonomics which may change values.
3639   bool constraint_result = JVMFlagConstraintList::check_constraints(JVMFlagConstraint::AfterErgo);
3640   if (!constraint_result) {
3641     return JNI_EINVAL;
3642   }
3643 
3644   JVMFlagWriteableList::mark_startup();
3645 
3646   if (PauseAtStartup) {
3647     os::pause();
3648   }
3649 
3650   HOTSPOT_VM_INIT_BEGIN();
3651 
3652   // Timing (must come after argument parsing)
3653   TraceTime timer("Create VM", TRACETIME_LOG(Info, startuptime));
3654 
3655 #ifdef CAN_SHOW_REGISTERS_ON_ASSERT
3656   // Initialize assert poison page mechanism.
3657   if (ShowRegistersOnAssert) {
3658     initialize_assert_poison();
3659   }
3660 #endif // CAN_SHOW_REGISTERS_ON_ASSERT
3661 
3662   // Initialize the os module after parsing the args
3663   jint os_init_2_result = os::init_2();
3664   if (os_init_2_result != JNI_OK) return os_init_2_result;
3665 
3666   SafepointMechanism::initialize();
3667 
3668   jint adjust_after_os_result = Arguments::adjust_after_os();
3669   if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;
3670 
3671   // Initialize output stream logging
3672   ostream_init_log();
3673 
3674   // Convert -Xrun to -agentlib: if there is no JVM_OnLoad
3675   // Must be before create_vm_init_agents()
3676   if (Arguments::init_libraries_at_startup()) {
3677     convert_vm_init_libraries_to_agents();
3678   }
3679 
3680   // Launch -agentlib/-agentpath and converted -Xrun agents
3681   if (Arguments::init_agents_at_startup()) {
3682     create_vm_init_agents();
3683   }
3684 
3685   // Initialize Threads state
3686   _thread_list = NULL;
3687   _number_of_threads = 0;
3688   _number_of_non_daemon_threads = 0;
3689 
3690   // Initialize global data structures and create system classes in heap
3691   vm_init_globals();
3692 
3693 #if INCLUDE_JVMCI
3694   if (JVMCICounterSize > 0) {
3695     JavaThread::_jvmci_old_thread_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
3696     memset(JavaThread::_jvmci_old_thread_counters, 0, sizeof(jlong) * JVMCICounterSize);
3697   } else {
3698     JavaThread::_jvmci_old_thread_counters = NULL;
3699   }
3700 #endif // INCLUDE_JVMCI
3701 
3702   // Attach the main thread to this os thread
3703   JavaThread* main_thread = new JavaThread();
3704   main_thread->set_thread_state(_thread_in_vm);
3705   main_thread->initialize_thread_current();
3706   // must do this before set_active_handles
3707   main_thread->record_stack_base_and_size();
3708   main_thread->register_thread_stack_with_NMT();
3709   main_thread->set_active_handles(JNIHandleBlock::allocate_block());
3710 
3711   if (!main_thread->set_as_starting_thread()) {
3712     vm_shutdown_during_initialization(
3713                                       "Failed necessary internal allocation. Out of swap space");
3714     main_thread->smr_delete();
3715     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3716     return JNI_ENOMEM;
3717   }
3718 
3719   // Enable guard page *after* os::create_main_thread(), otherwise it would
3720   // crash Linux VM, see notes in os_linux.cpp.
3721   main_thread->create_stack_guard_pages();
3722 
3723   // Initialize Java-Level synchronization subsystem
3724   ObjectMonitor::Initialize();
3725 
3726   // Initialize global modules
3727   jint status = init_globals();
3728   if (status != JNI_OK) {
3729     main_thread->smr_delete();
3730     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3731     return status;
3732   }
3733 
3734   JFR_ONLY(Jfr::on_vm_init();)
3735 
3736   // Should be done after the heap is fully created
3737   main_thread->cache_global_variables();
3738 
3739   HandleMark hm;
3740 
3741   { MutexLocker mu(Threads_lock);
3742     Threads::add(main_thread);
3743   }
3744 
3745   // Any JVMTI raw monitors entered in onload will transition into
3746   // real raw monitor. VM is setup enough here for raw monitor enter.
3747   JvmtiExport::transition_pending_onload_raw_monitors();
3748 
3749   // Create the VMThread
3750   { TraceTime timer("Start VMThread", TRACETIME_LOG(Info, startuptime));
3751 
3752   VMThread::create();
3753     Thread* vmthread = VMThread::vm_thread();
3754 
3755     if (!os::create_thread(vmthread, os::vm_thread)) {
3756       vm_exit_during_initialization("Cannot create VM thread. "
3757                                     "Out of system resources.");
3758     }
3759 
3760     // Wait for the VM thread to become ready, and VMThread::run to initialize
3761     // Monitors can have spurious returns, must always check another state flag
3762     {
3763       MutexLocker ml(Notify_lock);
3764       os::start_thread(vmthread);
3765       while (vmthread->active_handles() == NULL) {
3766         Notify_lock->wait();
3767       }
3768     }
3769   }
3770 
3771   assert(Universe::is_fully_initialized(), "not initialized");
3772   if (VerifyDuringStartup) {
3773     // Make sure we're starting with a clean slate.
3774     VM_Verify verify_op;
3775     VMThread::execute(&verify_op);
3776   }
3777 
3778   // We need this to update the java.vm.info property in case any flags used
3779   // to initially define it have been changed. This is needed for both CDS and
3780   // AOT, since UseSharedSpaces and UseAOT may be changed after java.vm.info
3781   // is initially computed. See Abstract_VM_Version::vm_info_string().
3782   // This update must happen before we initialize the java classes, but
3783   // after any initialization logic that might modify the flags.
3784   Arguments::update_vm_info_property(VM_Version::vm_info_string());
3785 
3786   Thread* THREAD = Thread::current();
3787 
3788   // Always call even when there are not JVMTI environments yet, since environments
3789   // may be attached late and JVMTI must track phases of VM execution
3790   JvmtiExport::enter_early_start_phase();
3791 
3792   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
3793   JvmtiExport::post_early_vm_start();
3794 
3795   initialize_java_lang_classes(main_thread, CHECK_JNI_ERR);
3796 
3797   quicken_jni_functions();
3798 
3799   // No more stub generation allowed after that point.
3800   StubCodeDesc::freeze();
3801 
3802   // Set flag that basic initialization has completed. Used by exceptions and various
3803   // debug stuff, that does not work until all basic classes have been initialized.
3804   set_init_completed();
3805 
3806   LogConfiguration::post_initialize();
3807   Metaspace::post_initialize();
3808 
3809   HOTSPOT_VM_INIT_END();
3810 
3811   // record VM initialization completion time
3812 #if INCLUDE_MANAGEMENT
3813   Management::record_vm_init_completed();
3814 #endif // INCLUDE_MANAGEMENT
3815 
3816   // Signal Dispatcher needs to be started before VMInit event is posted
3817   os::initialize_jdk_signal_support(CHECK_JNI_ERR);
3818 
3819   // Start Attach Listener if +StartAttachListener or it can't be started lazily
3820   if (!DisableAttachMechanism) {
3821     AttachListener::vm_start();
3822     if (StartAttachListener || AttachListener::init_at_startup()) {
3823       AttachListener::init();
3824     }
3825   }
3826 
3827   // Launch -Xrun agents
3828   // Must be done in the JVMTI live phase so that for backward compatibility the JDWP
3829   // back-end can launch with -Xdebug -Xrunjdwp.
3830   if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
3831     create_vm_init_libraries();
3832   }
3833 
3834   if (CleanChunkPoolAsync) {
3835     Chunk::start_chunk_pool_cleaner_task();
3836   }
3837 
3838   // initialize compiler(s)
3839 #if defined(COMPILER1) || COMPILER2_OR_JVMCI
3840 #if INCLUDE_JVMCI
3841   bool force_JVMCI_intialization = false;
3842   if (EnableJVMCI) {
3843     // Initialize JVMCI eagerly when it is explicitly requested.
3844     // Or when JVMCIPrintProperties is enabled.
3845     // The JVMCI Java initialization code will read this flag and
3846     // do the printing if it's set.
3847     force_JVMCI_intialization = EagerJVMCI || JVMCIPrintProperties;
3848 
3849     if (!force_JVMCI_intialization) {
3850       // 8145270: Force initialization of JVMCI runtime otherwise requests for blocking
3851       // compilations via JVMCI will not actually block until JVMCI is initialized.
3852       force_JVMCI_intialization = UseJVMCICompiler && (!UseInterpreter || !BackgroundCompilation);
3853     }
3854   }
3855 #endif
3856   CompileBroker::compilation_init_phase1(CHECK_JNI_ERR);
3857   // Postpone completion of compiler initialization to after JVMCI
3858   // is initialized to avoid timeouts of blocking compilations.
3859   if (JVMCI_ONLY(!force_JVMCI_intialization) NOT_JVMCI(true)) {
3860     CompileBroker::compilation_init_phase2();
3861   }
3862 #endif
3863 
3864   // Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
3865   // It is done after compilers are initialized, because otherwise compilations of
3866   // signature polymorphic MH intrinsics can be missed
3867   // (see SystemDictionary::find_method_handle_intrinsic).
3868   initialize_jsr292_core_classes(CHECK_JNI_ERR);
3869 
3870   // This will initialize the module system.  Only java.base classes can be
3871   // loaded until phase 2 completes
3872   call_initPhase2(CHECK_JNI_ERR);
3873 
3874   // Always call even when there are not JVMTI environments yet, since environments
3875   // may be attached late and JVMTI must track phases of VM execution
3876   JvmtiExport::enter_start_phase();
3877 
3878   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
3879   JvmtiExport::post_vm_start();
3880 
3881   // Final system initialization including security manager and system class loader
3882   call_initPhase3(CHECK_JNI_ERR);
3883 
3884   // cache the system and platform class loaders
3885   SystemDictionary::compute_java_loaders(CHECK_JNI_ERR);
3886 
3887 #if INCLUDE_CDS
3888   if (DumpSharedSpaces) {
3889     // capture the module path info from the ModuleEntryTable
3890     ClassLoader::initialize_module_path(THREAD);
3891   }
3892 #endif
3893 
3894 #if INCLUDE_JVMCI
3895   if (force_JVMCI_intialization) {
3896     JVMCIRuntime::force_initialization(CHECK_JNI_ERR);
3897     CompileBroker::compilation_init_phase2();
3898   }
3899 #endif
3900 
3901   // Always call even when there are not JVMTI environments yet, since environments
3902   // may be attached late and JVMTI must track phases of VM execution
3903   JvmtiExport::enter_live_phase();
3904 
3905   // Make perfmemory accessible
3906   PerfMemory::set_accessible(true);
3907 
3908   // Notify JVMTI agents that VM initialization is complete - nop if no agents.
3909   JvmtiExport::post_vm_initialized();
3910 
3911   JFR_ONLY(Jfr::on_vm_start();)
3912 
3913 #if INCLUDE_MANAGEMENT
3914   Management::initialize(THREAD);
3915 
3916   if (HAS_PENDING_EXCEPTION) {
3917     // management agent fails to start possibly due to
3918     // configuration problem and is responsible for printing
3919     // stack trace if appropriate. Simply exit VM.
3920     vm_exit(1);
3921   }
3922 #endif // INCLUDE_MANAGEMENT
3923 
3924   if (MemProfiling)                   MemProfiler::engage();
3925   StatSampler::engage();
3926   if (CheckJNICalls)                  JniPeriodicChecker::engage();
3927 
3928   BiasedLocking::init();
3929 
3930 #if INCLUDE_RTM_OPT
3931   RTMLockingCounters::init();
3932 #endif
3933 
3934   if (JDK_Version::current().post_vm_init_hook_enabled()) {
3935     call_postVMInitHook(THREAD);
3936     // The Java side of PostVMInitHook.run must deal with all
3937     // exceptions and provide means of diagnosis.
3938     if (HAS_PENDING_EXCEPTION) {
3939       CLEAR_PENDING_EXCEPTION;
3940     }
3941   }
3942 
3943   {
3944     MutexLocker ml(PeriodicTask_lock);
3945     // Make sure the WatcherThread can be started by WatcherThread::start()
3946     // or by dynamic enrollment.
3947     WatcherThread::make_startable();
3948     // Start up the WatcherThread if there are any periodic tasks
3949     // NOTE:  All PeriodicTasks should be registered by now. If they
3950     //   aren't, late joiners might appear to start slowly (we might
3951     //   take a while to process their first tick).
3952     if (PeriodicTask::num_tasks() > 0) {
3953       WatcherThread::start();
3954     }
3955   }
3956 
3957   create_vm_timer.end();
3958 #ifdef ASSERT
3959   _vm_complete = true;
3960 #endif
3961 
3962   if (DumpSharedSpaces) {
3963     MetaspaceShared::preload_and_dump(CHECK_JNI_ERR);
3964     ShouldNotReachHere();
3965   }
3966 
3967   return JNI_OK;
3968 }
3969 
3970 // type for the Agent_OnLoad and JVM_OnLoad entry points
3971 extern "C" {
3972   typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
3973 }
3974 // Find a command line agent library and return its entry point for
3975 //         -agentlib:  -agentpath:   -Xrun
3976 // num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array.
3977 static OnLoadEntry_t lookup_on_load(AgentLibrary* agent,
3978                                     const char *on_load_symbols[],
3979                                     size_t num_symbol_entries) {
3980   OnLoadEntry_t on_load_entry = NULL;
3981   void *library = NULL;
3982 
3983   if (!agent->valid()) {
3984     char buffer[JVM_MAXPATHLEN];
3985     char ebuf[1024] = "";
3986     const char *name = agent->name();
3987     const char *msg = "Could not find agent library ";
3988 
3989     // First check to see if agent is statically linked into executable
3990     if (os::find_builtin_agent(agent, on_load_symbols, num_symbol_entries)) {
3991       library = agent->os_lib();
3992     } else if (agent->is_absolute_path()) {
3993       library = os::dll_load(name, ebuf, sizeof ebuf);
3994       if (library == NULL) {
3995         const char *sub_msg = " in absolute path, with error: ";
3996         size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3997         char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
3998         jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
3999         // If we can't find the agent, exit.
4000         vm_exit_during_initialization(buf, NULL);
4001         FREE_C_HEAP_ARRAY(char, buf);
4002       }
4003     } else {
4004       // Try to load the agent from the standard dll directory
4005       if (os::dll_locate_lib(buffer, sizeof(buffer), Arguments::get_dll_dir(),
4006                              name)) {
4007         library = os::dll_load(buffer, ebuf, sizeof ebuf);
4008       }
4009       if (library == NULL) { // Try the library path directory.
4010         if (os::dll_build_name(buffer, sizeof(buffer), name)) {
4011           library = os::dll_load(buffer, ebuf, sizeof ebuf);
4012         }
4013         if (library == NULL) {
4014           const char *sub_msg = " on the library path, with error: ";
4015           const char *sub_msg2 = "\nModule java.instrument may be missing from runtime image.";
4016 
4017           size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) +
4018                        strlen(ebuf) + strlen(sub_msg2) + 1;
4019           char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
4020           if (!agent->is_instrument_lib()) {
4021             jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
4022           } else {
4023             jio_snprintf(buf, len, "%s%s%s%s%s", msg, name, sub_msg, ebuf, sub_msg2);
4024           }
4025           // If we can't find the agent, exit.
4026           vm_exit_during_initialization(buf, NULL);
4027           FREE_C_HEAP_ARRAY(char, buf);
4028         }
4029       }
4030     }
4031     agent->set_os_lib(library);
4032     agent->set_valid();
4033   }
4034 
4035   // Find the OnLoad function.
4036   on_load_entry =
4037     CAST_TO_FN_PTR(OnLoadEntry_t, os::find_agent_function(agent,
4038                                                           false,
4039                                                           on_load_symbols,
4040                                                           num_symbol_entries));
4041   return on_load_entry;
4042 }
4043 
4044 // Find the JVM_OnLoad entry point
4045 static OnLoadEntry_t lookup_jvm_on_load(AgentLibrary* agent) {
4046   const char *on_load_symbols[] = JVM_ONLOAD_SYMBOLS;
4047   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
4048 }
4049 
4050 // Find the Agent_OnLoad entry point
4051 static OnLoadEntry_t lookup_agent_on_load(AgentLibrary* agent) {
4052   const char *on_load_symbols[] = AGENT_ONLOAD_SYMBOLS;
4053   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
4054 }
4055 
4056 // For backwards compatibility with -Xrun
4057 // Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be
4058 // treated like -agentpath:
4059 // Must be called before agent libraries are created
4060 void Threads::convert_vm_init_libraries_to_agents() {
4061   AgentLibrary* agent;
4062   AgentLibrary* next;
4063 
4064   for (agent = Arguments::libraries(); agent != NULL; agent = next) {
4065     next = agent->next();  // cache the next agent now as this agent may get moved off this list
4066     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
4067 
4068     // If there is an JVM_OnLoad function it will get called later,
4069     // otherwise see if there is an Agent_OnLoad
4070     if (on_load_entry == NULL) {
4071       on_load_entry = lookup_agent_on_load(agent);
4072       if (on_load_entry != NULL) {
4073         // switch it to the agent list -- so that Agent_OnLoad will be called,
4074         // JVM_OnLoad won't be attempted and Agent_OnUnload will
4075         Arguments::convert_library_to_agent(agent);
4076       } else {
4077         vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
4078       }
4079     }
4080   }
4081 }
4082 
4083 // Create agents for -agentlib:  -agentpath:  and converted -Xrun
4084 // Invokes Agent_OnLoad
4085 // Called very early -- before JavaThreads exist
4086 void Threads::create_vm_init_agents() {
4087   extern struct JavaVM_ main_vm;
4088   AgentLibrary* agent;
4089 
4090   JvmtiExport::enter_onload_phase();
4091 
4092   for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
4093     // CDS dumping does not support native JVMTI agent.
4094     // CDS dumping supports Java agent if the AllowArchivingWithJavaAgent diagnostic option is specified.
4095     if (DumpSharedSpaces) {
4096       if(!agent->is_instrument_lib()) {
4097         vm_exit_during_cds_dumping("CDS dumping does not support native JVMTI agent, name", agent->name());
4098       } else if (!AllowArchivingWithJavaAgent) {
4099         vm_exit_during_cds_dumping(
4100           "Must enable AllowArchivingWithJavaAgent in order to run Java agent during CDS dumping");
4101       }
4102     }
4103 
4104     OnLoadEntry_t  on_load_entry = lookup_agent_on_load(agent);
4105 
4106     if (on_load_entry != NULL) {
4107       // Invoke the Agent_OnLoad function
4108       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
4109       if (err != JNI_OK) {
4110         vm_exit_during_initialization("agent library failed to init", agent->name());
4111       }
4112     } else {
4113       vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
4114     }
4115   }
4116 
4117   JvmtiExport::enter_primordial_phase();
4118 }
4119 
4120 extern "C" {
4121   typedef void (JNICALL *Agent_OnUnload_t)(JavaVM *);
4122 }
4123 
4124 void Threads::shutdown_vm_agents() {
4125   // Send any Agent_OnUnload notifications
4126   const char *on_unload_symbols[] = AGENT_ONUNLOAD_SYMBOLS;
4127   size_t num_symbol_entries = ARRAY_SIZE(on_unload_symbols);
4128   extern struct JavaVM_ main_vm;
4129   for (AgentLibrary* agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
4130 
4131     // Find the Agent_OnUnload function.
4132     Agent_OnUnload_t unload_entry = CAST_TO_FN_PTR(Agent_OnUnload_t,
4133                                                    os::find_agent_function(agent,
4134                                                    false,
4135                                                    on_unload_symbols,
4136                                                    num_symbol_entries));
4137 
4138     // Invoke the Agent_OnUnload function
4139     if (unload_entry != NULL) {
4140       JavaThread* thread = JavaThread::current();
4141       ThreadToNativeFromVM ttn(thread);
4142       HandleMark hm(thread);
4143       (*unload_entry)(&main_vm);
4144     }
4145   }
4146 }
4147 
4148 // Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries
4149 // Invokes JVM_OnLoad
4150 void Threads::create_vm_init_libraries() {
4151   extern struct JavaVM_ main_vm;
4152   AgentLibrary* agent;
4153 
4154   for (agent = Arguments::libraries(); agent != NULL; agent = agent->next()) {
4155     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
4156 
4157     if (on_load_entry != NULL) {
4158       // Invoke the JVM_OnLoad function
4159       JavaThread* thread = JavaThread::current();
4160       ThreadToNativeFromVM ttn(thread);
4161       HandleMark hm(thread);
4162       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
4163       if (err != JNI_OK) {
4164         vm_exit_during_initialization("-Xrun library failed to init", agent->name());
4165       }
4166     } else {
4167       vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
4168     }
4169   }
4170 }
4171 
4172 
4173 // Last thread running calls java.lang.Shutdown.shutdown()
4174 void JavaThread::invoke_shutdown_hooks() {
4175   HandleMark hm(this);
4176 
4177   // We could get here with a pending exception, if so clear it now.
4178   if (this->has_pending_exception()) {
4179     this->clear_pending_exception();
4180   }
4181 
4182   EXCEPTION_MARK;
4183   Klass* shutdown_klass =
4184     SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
4185                                       THREAD);
4186   if (shutdown_klass != NULL) {
4187     // SystemDictionary::resolve_or_null will return null if there was
4188     // an exception.  If we cannot load the Shutdown class, just don't
4189     // call Shutdown.shutdown() at all.  This will mean the shutdown hooks
4190     // won't be run.  Note that if a shutdown hook was registered,
4191     // the Shutdown class would have already been loaded
4192     // (Runtime.addShutdownHook will load it).
4193     JavaValue result(T_VOID);
4194     JavaCalls::call_static(&result,
4195                            shutdown_klass,
4196                            vmSymbols::shutdown_method_name(),
4197                            vmSymbols::void_method_signature(),
4198                            THREAD);
4199   }
4200   CLEAR_PENDING_EXCEPTION;
4201 }
4202 
4203 // Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
4204 // the program falls off the end of main(). Another VM exit path is through
4205 // vm_exit() when the program calls System.exit() to return a value or when
4206 // there is a serious error in VM. The two shutdown paths are not exactly
4207 // the same, but they share Shutdown.shutdown() at Java level and before_exit()
4208 // and VM_Exit op at VM level.
4209 //
4210 // Shutdown sequence:
4211 //   + Shutdown native memory tracking if it is on
4212 //   + Wait until we are the last non-daemon thread to execute
4213 //     <-- every thing is still working at this moment -->
4214 //   + Call java.lang.Shutdown.shutdown(), which will invoke Java level
4215 //        shutdown hooks
4216 //   + Call before_exit(), prepare for VM exit
4217 //      > run VM level shutdown hooks (they are registered through JVM_OnExit(),
4218 //        currently the only user of this mechanism is File.deleteOnExit())
4219 //      > stop StatSampler, watcher thread, CMS threads,
4220 //        post thread end and vm death events to JVMTI,
4221 //        stop signal thread
4222 //   + Call JavaThread::exit(), it will:
4223 //      > release JNI handle blocks, remove stack guard pages
4224 //      > remove this thread from Threads list
4225 //     <-- no more Java code from this thread after this point -->
4226 //   + Stop VM thread, it will bring the remaining VM to a safepoint and stop
4227 //     the compiler threads at safepoint
4228 //     <-- do not use anything that could get blocked by Safepoint -->
4229 //   + Disable tracing at JNI/JVM barriers
4230 //   + Set _vm_exited flag for threads that are still running native code
4231 //   + Call exit_globals()
4232 //      > deletes tty
4233 //      > deletes PerfMemory resources
4234 //   + Delete this thread
4235 //   + Return to caller
4236 
4237 bool Threads::destroy_vm() {
4238   JavaThread* thread = JavaThread::current();
4239 
4240 #ifdef ASSERT
4241   _vm_complete = false;
4242 #endif
4243   // Wait until we are the last non-daemon thread to execute
4244   { MutexLocker nu(Threads_lock);
4245     while (Threads::number_of_non_daemon_threads() > 1)
4246       // This wait should make safepoint checks, wait without a timeout,
4247       // and wait as a suspend-equivalent condition.
4248       Threads_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
4249                          Mutex::_as_suspend_equivalent_flag);
4250   }
4251 
4252   EventShutdown e;
4253   if (e.should_commit()) {
4254     e.set_reason("No remaining non-daemon Java threads");
4255     e.commit();
4256   }
4257 
4258   // Hang forever on exit if we are reporting an error.
4259   if (ShowMessageBoxOnError && VMError::is_error_reported()) {
4260     os::infinite_sleep();
4261   }
4262   os::wait_for_keypress_at_exit();
4263 
4264   // run Java level shutdown hooks
4265   thread->invoke_shutdown_hooks();
4266 
4267   before_exit(thread);
4268 
4269   thread->exit(true);
4270 
4271   // Stop VM thread.
4272   {
4273     // 4945125 The vm thread comes to a safepoint during exit.
4274     // GC vm_operations can get caught at the safepoint, and the
4275     // heap is unparseable if they are caught. Grab the Heap_lock
4276     // to prevent this. The GC vm_operations will not be able to
4277     // queue until after the vm thread is dead. After this point,
4278     // we'll never emerge out of the safepoint before the VM exits.
4279 
4280     MutexLockerEx ml(Heap_lock, Mutex::_no_safepoint_check_flag);
4281 
4282     VMThread::wait_for_vm_thread_exit();
4283     assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
4284     VMThread::destroy();
4285   }
4286 
4287   // Now, all Java threads are gone except daemon threads. Daemon threads
4288   // running Java code or in VM are stopped by the Safepoint. However,
4289   // daemon threads executing native code are still running.  But they
4290   // will be stopped at native=>Java/VM barriers. Note that we can't
4291   // simply kill or suspend them, as it is inherently deadlock-prone.
4292 
4293   VM_Exit::set_vm_exited();
4294 
4295   // Clean up ideal graph printers after the VMThread has started
4296   // the final safepoint which will block all the Compiler threads.
4297   // Note that this Thread has already logically exited so the
4298   // clean_up() function's use of a JavaThreadIteratorWithHandle
4299   // would be a problem except set_vm_exited() has remembered the
4300   // shutdown thread which is granted a policy exception.
4301 #if defined(COMPILER2) && !defined(PRODUCT)
4302   IdealGraphPrinter::clean_up();
4303 #endif
4304 
4305   notify_vm_shutdown();
4306 
4307   // exit_globals() will delete tty
4308   exit_globals();
4309 
4310   // We are after VM_Exit::set_vm_exited() so we can't call
4311   // thread->smr_delete() or we will block on the Threads_lock.
4312   // Deleting the shutdown thread here is safe because another
4313   // JavaThread cannot have an active ThreadsListHandle for
4314   // this JavaThread.
4315   delete thread;
4316 
4317 #if INCLUDE_JVMCI
4318   if (JVMCICounterSize > 0) {
4319     FREE_C_HEAP_ARRAY(jlong, JavaThread::_jvmci_old_thread_counters);
4320   }
4321 #endif
4322 
4323   LogConfiguration::finalize();
4324 
4325   return true;
4326 }
4327 
4328 
4329 jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
4330   if (version == JNI_VERSION_1_1) return JNI_TRUE;
4331   return is_supported_jni_version(version);
4332 }
4333 
4334 
4335 jboolean Threads::is_supported_jni_version(jint version) {
4336   if (version == JNI_VERSION_1_2) return JNI_TRUE;
4337   if (version == JNI_VERSION_1_4) return JNI_TRUE;
4338   if (version == JNI_VERSION_1_6) return JNI_TRUE;
4339   if (version == JNI_VERSION_1_8) return JNI_TRUE;
4340   if (version == JNI_VERSION_9) return JNI_TRUE;
4341   if (version == JNI_VERSION_10) return JNI_TRUE;
4342   return JNI_FALSE;
4343 }
4344 
4345 
4346 void Threads::add(JavaThread* p, bool force_daemon) {
4347   // The threads lock must be owned at this point
4348   assert(Threads_lock->owned_by_self(), "must have threads lock");
4349 
4350   BarrierSet::barrier_set()->on_thread_attach(p);
4351 
4352   p->set_next(_thread_list);
4353   _thread_list = p;
4354 
4355   // Once a JavaThread is added to the Threads list, smr_delete() has
4356   // to be used to delete it. Otherwise we can just delete it directly.
4357   p->set_on_thread_list();
4358 
4359   _number_of_threads++;
4360   oop threadObj = p->threadObj();
4361   bool daemon = true;
4362   // Bootstrapping problem: threadObj can be null for initial
4363   // JavaThread (or for threads attached via JNI)
4364   if ((!force_daemon) && !is_daemon((threadObj))) {
4365     _number_of_non_daemon_threads++;
4366     daemon = false;
4367   }
4368 
4369   ThreadService::add_thread(p, daemon);
4370 
4371   // Maintain fast thread list
4372   ThreadsSMRSupport::add_thread(p);
4373 
4374   // Possible GC point.
4375   Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p));
4376 }
4377 
4378 void Threads::remove(JavaThread* p) {
4379 
4380   // Reclaim the objectmonitors from the omInUseList and omFreeList of the moribund thread.
4381   ObjectSynchronizer::omFlush(p);
4382 
4383   // Extra scope needed for Thread_lock, so we can check
4384   // that we do not remove thread without safepoint code notice
4385   { MutexLocker ml(Threads_lock);
4386 
4387     assert(ThreadsSMRSupport::get_java_thread_list()->includes(p), "p must be present");
4388 
4389     // Maintain fast thread list
4390     ThreadsSMRSupport::remove_thread(p);
4391 
4392     JavaThread* current = _thread_list;
4393     JavaThread* prev    = NULL;
4394 
4395     while (current != p) {
4396       prev    = current;
4397       current = current->next();
4398     }
4399 
4400     if (prev) {
4401       prev->set_next(current->next());
4402     } else {
4403       _thread_list = p->next();
4404     }
4405 
4406     _number_of_threads--;
4407     oop threadObj = p->threadObj();
4408     bool daemon = true;
4409     if (!is_daemon(threadObj)) {
4410       _number_of_non_daemon_threads--;
4411       daemon = false;
4412 
4413       // Only one thread left, do a notify on the Threads_lock so a thread waiting
4414       // on destroy_vm will wake up.
4415       if (number_of_non_daemon_threads() == 1) {
4416         Threads_lock->notify_all();
4417       }
4418     }
4419     ThreadService::remove_thread(p, daemon);
4420 
4421     // Make sure that safepoint code disregard this thread. This is needed since
4422     // the thread might mess around with locks after this point. This can cause it
4423     // to do callbacks into the safepoint code. However, the safepoint code is not aware
4424     // of this thread since it is removed from the queue.
4425     p->set_terminated_value();
4426   } // unlock Threads_lock
4427 
4428   // Since Events::log uses a lock, we grab it outside the Threads_lock
4429   Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p));
4430 }
4431 
4432 // Operations on the Threads list for GC.  These are not explicitly locked,
4433 // but the garbage collector must provide a safe context for them to run.
4434 // In particular, these things should never be called when the Threads_lock
4435 // is held by some other thread. (Note: the Safepoint abstraction also
4436 // uses the Threads_lock to guarantee this property. It also makes sure that
4437 // all threads gets blocked when exiting or starting).
4438 
4439 void Threads::oops_do(OopClosure* f, CodeBlobClosure* cf) {
4440   ALL_JAVA_THREADS(p) {
4441     p->oops_do(f, cf);
4442   }
4443   VMThread::vm_thread()->oops_do(f, cf);
4444 }
4445 
4446 void Threads::change_thread_claim_parity() {
4447   // Set the new claim parity.
4448   assert(_thread_claim_parity >= 0 && _thread_claim_parity <= 2,
4449          "Not in range.");
4450   _thread_claim_parity++;
4451   if (_thread_claim_parity == 3) _thread_claim_parity = 1;
4452   assert(_thread_claim_parity >= 1 && _thread_claim_parity <= 2,
4453          "Not in range.");
4454 }
4455 
4456 #ifdef ASSERT
4457 void Threads::assert_all_threads_claimed() {
4458   ALL_JAVA_THREADS(p) {
4459     const int thread_parity = p->oops_do_parity();
4460     assert((thread_parity == _thread_claim_parity),
4461            "Thread " PTR_FORMAT " has incorrect parity %d != %d", p2i(p), thread_parity, _thread_claim_parity);
4462   }
4463   VMThread* vmt = VMThread::vm_thread();
4464   const int thread_parity = vmt->oops_do_parity();
4465   assert((thread_parity == _thread_claim_parity),
4466          "VMThread " PTR_FORMAT " has incorrect parity %d != %d", p2i(vmt), thread_parity, _thread_claim_parity);
4467 }
4468 #endif // ASSERT
4469 
4470 class ParallelOopsDoThreadClosure : public ThreadClosure {
4471 private:
4472   OopClosure* _f;
4473   CodeBlobClosure* _cf;
4474 public:
4475   ParallelOopsDoThreadClosure(OopClosure* f, CodeBlobClosure* cf) : _f(f), _cf(cf) {}
4476   void do_thread(Thread* t) {
4477     t->oops_do(_f, _cf);
4478   }
4479 };
4480 
4481 void Threads::possibly_parallel_oops_do(bool is_par, OopClosure* f, CodeBlobClosure* cf) {
4482   ParallelOopsDoThreadClosure tc(f, cf);
4483   possibly_parallel_threads_do(is_par, &tc);
4484 }
4485 
4486 void Threads::nmethods_do(CodeBlobClosure* cf) {
4487   ALL_JAVA_THREADS(p) {
4488     // This is used by the code cache sweeper to mark nmethods that are active
4489     // on the stack of a Java thread. Ignore the sweeper thread itself to avoid
4490     // marking CodeCacheSweeperThread::_scanned_compiled_method as active.
4491     if(!p->is_Code_cache_sweeper_thread()) {
4492       p->nmethods_do(cf);
4493     }
4494   }
4495 }
4496 
4497 void Threads::metadata_do(void f(Metadata*)) {
4498   ALL_JAVA_THREADS(p) {
4499     p->metadata_do(f);
4500   }
4501 }
4502 
4503 class ThreadHandlesClosure : public ThreadClosure {
4504   void (*_f)(Metadata*);
4505  public:
4506   ThreadHandlesClosure(void f(Metadata*)) : _f(f) {}
4507   virtual void do_thread(Thread* thread) {
4508     thread->metadata_handles_do(_f);
4509   }
4510 };
4511 
4512 void Threads::metadata_handles_do(void f(Metadata*)) {
4513   // Only walk the Handles in Thread.
4514   ThreadHandlesClosure handles_closure(f);
4515   threads_do(&handles_closure);
4516 }
4517 
4518 void Threads::deoptimized_wrt_marked_nmethods() {
4519   ALL_JAVA_THREADS(p) {
4520     p->deoptimized_wrt_marked_nmethods();
4521   }
4522 }
4523 
4524 
4525 // Get count Java threads that are waiting to enter the specified monitor.
4526 GrowableArray<JavaThread*>* Threads::get_pending_threads(ThreadsList * t_list,
4527                                                          int count,
4528                                                          address monitor) {
4529   GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
4530 
4531   int i = 0;
4532   DO_JAVA_THREADS(t_list, p) {
4533     if (!p->can_call_java()) continue;
4534 
4535     address pending = (address)p->current_pending_monitor();
4536     if (pending == monitor) {             // found a match
4537       if (i < count) result->append(p);   // save the first count matches
4538       i++;
4539     }
4540   }
4541 
4542   return result;
4543 }
4544 
4545 
4546 JavaThread *Threads::owning_thread_from_monitor_owner(ThreadsList * t_list,
4547                                                       address owner) {
4548   // NULL owner means not locked so we can skip the search
4549   if (owner == NULL) return NULL;
4550 
4551   DO_JAVA_THREADS(t_list, p) {
4552     // first, see if owner is the address of a Java thread
4553     if (owner == (address)p) return p;
4554   }
4555 
4556   // Cannot assert on lack of success here since this function may be
4557   // used by code that is trying to report useful problem information
4558   // like deadlock detection.
4559   if (UseHeavyMonitors) return NULL;
4560 
4561   // If we didn't find a matching Java thread and we didn't force use of
4562   // heavyweight monitors, then the owner is the stack address of the
4563   // Lock Word in the owning Java thread's stack.
4564   //
4565   JavaThread* the_owner = NULL;
4566   DO_JAVA_THREADS(t_list, q) {
4567     if (q->is_lock_owned(owner)) {
4568       the_owner = q;
4569       break;
4570     }
4571   }
4572 
4573   // cannot assert on lack of success here; see above comment
4574   return the_owner;
4575 }
4576 
4577 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
4578 void Threads::print_on(outputStream* st, bool print_stacks,
4579                        bool internal_format, bool print_concurrent_locks,
4580                        bool print_extended_info) {
4581   char buf[32];
4582   st->print_raw_cr(os::local_time_string(buf, sizeof(buf)));
4583 
4584   st->print_cr("Full thread dump %s (%s %s):",
4585                VM_Version::vm_name(),
4586                VM_Version::vm_release(),
4587                VM_Version::vm_info_string());
4588   st->cr();
4589 
4590 #if INCLUDE_SERVICES
4591   // Dump concurrent locks
4592   ConcurrentLocksDump concurrent_locks;
4593   if (print_concurrent_locks) {
4594     concurrent_locks.dump_at_safepoint();
4595   }
4596 #endif // INCLUDE_SERVICES
4597 
4598   ThreadsSMRSupport::print_info_on(st);
4599   st->cr();
4600 
4601   ALL_JAVA_THREADS(p) {
4602     ResourceMark rm;
4603     p->print_on(st, print_extended_info);
4604     if (print_stacks) {
4605       if (internal_format) {
4606         p->trace_stack();
4607       } else {
4608         p->print_stack_on(st);
4609       }
4610     }
4611     st->cr();
4612 #if INCLUDE_SERVICES
4613     if (print_concurrent_locks) {
4614       concurrent_locks.print_locks_on(p, st);
4615     }
4616 #endif // INCLUDE_SERVICES
4617   }
4618 
4619   VMThread::vm_thread()->print_on(st);
4620   st->cr();
4621   Universe::heap()->print_gc_threads_on(st);
4622   WatcherThread* wt = WatcherThread::watcher_thread();
4623   if (wt != NULL) {
4624     wt->print_on(st);
4625     st->cr();
4626   }
4627 
4628   st->flush();
4629 }
4630 
4631 void Threads::print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf,
4632                              int buflen, bool* found_current) {
4633   if (this_thread != NULL) {
4634     bool is_current = (current == this_thread);
4635     *found_current = *found_current || is_current;
4636     st->print("%s", is_current ? "=>" : "  ");
4637 
4638     st->print(PTR_FORMAT, p2i(this_thread));
4639     st->print(" ");
4640     this_thread->print_on_error(st, buf, buflen);
4641     st->cr();
4642   }
4643 }
4644 
4645 class PrintOnErrorClosure : public ThreadClosure {
4646   outputStream* _st;
4647   Thread* _current;
4648   char* _buf;
4649   int _buflen;
4650   bool* _found_current;
4651  public:
4652   PrintOnErrorClosure(outputStream* st, Thread* current, char* buf,
4653                       int buflen, bool* found_current) :
4654    _st(st), _current(current), _buf(buf), _buflen(buflen), _found_current(found_current) {}
4655 
4656   virtual void do_thread(Thread* thread) {
4657     Threads::print_on_error(thread, _st, _current, _buf, _buflen, _found_current);
4658   }
4659 };
4660 
4661 // Threads::print_on_error() is called by fatal error handler. It's possible
4662 // that VM is not at safepoint and/or current thread is inside signal handler.
4663 // Don't print stack trace, as the stack may not be walkable. Don't allocate
4664 // memory (even in resource area), it might deadlock the error handler.
4665 void Threads::print_on_error(outputStream* st, Thread* current, char* buf,
4666                              int buflen) {
4667   ThreadsSMRSupport::print_info_on(st);
4668   st->cr();
4669 
4670   bool found_current = false;
4671   st->print_cr("Java Threads: ( => current thread )");
4672   ALL_JAVA_THREADS(thread) {
4673     print_on_error(thread, st, current, buf, buflen, &found_current);
4674   }
4675   st->cr();
4676 
4677   st->print_cr("Other Threads:");
4678   print_on_error(VMThread::vm_thread(), st, current, buf, buflen, &found_current);
4679   print_on_error(WatcherThread::watcher_thread(), st, current, buf, buflen, &found_current);
4680 
4681   PrintOnErrorClosure print_closure(st, current, buf, buflen, &found_current);
4682   Universe::heap()->gc_threads_do(&print_closure);
4683 
4684   if (!found_current) {
4685     st->cr();
4686     st->print("=>" PTR_FORMAT " (exited) ", p2i(current));
4687     current->print_on_error(st, buf, buflen);
4688     st->cr();
4689   }
4690   st->cr();
4691 
4692   st->print_cr("Threads with active compile tasks:");
4693   print_threads_compiling(st, buf, buflen);
4694 }
4695 
4696 void Threads::print_threads_compiling(outputStream* st, char* buf, int buflen) {
4697   ALL_JAVA_THREADS(thread) {
4698     if (thread->is_Compiler_thread()) {
4699       CompilerThread* ct = (CompilerThread*) thread;
4700 
4701       // Keep task in local variable for NULL check.
4702       // ct->_task might be set to NULL by concurring compiler thread
4703       // because it completed the compilation. The task is never freed,
4704       // though, just returned to a free list.
4705       CompileTask* task = ct->task();
4706       if (task != NULL) {
4707         thread->print_name_on_error(st, buf, buflen);
4708         st->print("  ");
4709         task->print(st, NULL, true, true);
4710       }
4711     }
4712   }
4713 }
4714 
4715 
4716 // Internal SpinLock and Mutex
4717 // Based on ParkEvent
4718 
4719 // Ad-hoc mutual exclusion primitives: SpinLock and Mux
4720 //
4721 // We employ SpinLocks _only for low-contention, fixed-length
4722 // short-duration critical sections where we're concerned
4723 // about native mutex_t or HotSpot Mutex:: latency.
4724 // The mux construct provides a spin-then-block mutual exclusion
4725 // mechanism.
4726 //
4727 // Testing has shown that contention on the ListLock guarding gFreeList
4728 // is common.  If we implement ListLock as a simple SpinLock it's common
4729 // for the JVM to devolve to yielding with little progress.  This is true
4730 // despite the fact that the critical sections protected by ListLock are
4731 // extremely short.
4732 //
4733 // TODO-FIXME: ListLock should be of type SpinLock.
4734 // We should make this a 1st-class type, integrated into the lock
4735 // hierarchy as leaf-locks.  Critically, the SpinLock structure
4736 // should have sufficient padding to avoid false-sharing and excessive
4737 // cache-coherency traffic.
4738 
4739 
4740 typedef volatile int SpinLockT;
4741 
4742 void Thread::SpinAcquire(volatile int * adr, const char * LockName) {
4743   if (Atomic::cmpxchg (1, adr, 0) == 0) {
4744     return;   // normal fast-path return
4745   }
4746 
4747   // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
4748   int ctr = 0;
4749   int Yields = 0;
4750   for (;;) {
4751     while (*adr != 0) {
4752       ++ctr;
4753       if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
4754         if (Yields > 5) {
4755           os::naked_short_sleep(1);
4756         } else {
4757           os::naked_yield();
4758           ++Yields;
4759         }
4760       } else {
4761         SpinPause();
4762       }
4763     }
4764     if (Atomic::cmpxchg(1, adr, 0) == 0) return;
4765   }
4766 }
4767 
4768 void Thread::SpinRelease(volatile int * adr) {
4769   assert(*adr != 0, "invariant");
4770   OrderAccess::fence();      // guarantee at least release consistency.
4771   // Roach-motel semantics.
4772   // It's safe if subsequent LDs and STs float "up" into the critical section,
4773   // but prior LDs and STs within the critical section can't be allowed
4774   // to reorder or float past the ST that releases the lock.
4775   // Loads and stores in the critical section - which appear in program
4776   // order before the store that releases the lock - must also appear
4777   // before the store that releases the lock in memory visibility order.
4778   // Conceptually we need a #loadstore|#storestore "release" MEMBAR before
4779   // the ST of 0 into the lock-word which releases the lock, so fence
4780   // more than covers this on all platforms.
4781   *adr = 0;
4782 }
4783 
4784 // muxAcquire and muxRelease:
4785 //
4786 // *  muxAcquire and muxRelease support a single-word lock-word construct.
4787 //    The LSB of the word is set IFF the lock is held.
4788 //    The remainder of the word points to the head of a singly-linked list
4789 //    of threads blocked on the lock.
4790 //
4791 // *  The current implementation of muxAcquire-muxRelease uses its own
4792 //    dedicated Thread._MuxEvent instance.  If we're interested in
4793 //    minimizing the peak number of extant ParkEvent instances then
4794 //    we could eliminate _MuxEvent and "borrow" _ParkEvent as long
4795 //    as certain invariants were satisfied.  Specifically, care would need
4796 //    to be taken with regards to consuming unpark() "permits".
4797 //    A safe rule of thumb is that a thread would never call muxAcquire()
4798 //    if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
4799 //    park().  Otherwise the _ParkEvent park() operation in muxAcquire() could
4800 //    consume an unpark() permit intended for monitorenter, for instance.
4801 //    One way around this would be to widen the restricted-range semaphore
4802 //    implemented in park().  Another alternative would be to provide
4803 //    multiple instances of the PlatformEvent() for each thread.  One
4804 //    instance would be dedicated to muxAcquire-muxRelease, for instance.
4805 //
4806 // *  Usage:
4807 //    -- Only as leaf locks
4808 //    -- for short-term locking only as muxAcquire does not perform
4809 //       thread state transitions.
4810 //
4811 // Alternatives:
4812 // *  We could implement muxAcquire and muxRelease with MCS or CLH locks
4813 //    but with parking or spin-then-park instead of pure spinning.
4814 // *  Use Taura-Oyama-Yonenzawa locks.
4815 // *  It's possible to construct a 1-0 lock if we encode the lockword as
4816 //    (List,LockByte).  Acquire will CAS the full lockword while Release
4817 //    will STB 0 into the LockByte.  The 1-0 scheme admits stranding, so
4818 //    acquiring threads use timers (ParkTimed) to detect and recover from
4819 //    the stranding window.  Thread/Node structures must be aligned on 256-byte
4820 //    boundaries by using placement-new.
4821 // *  Augment MCS with advisory back-link fields maintained with CAS().
4822 //    Pictorially:  LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
4823 //    The validity of the backlinks must be ratified before we trust the value.
4824 //    If the backlinks are invalid the exiting thread must back-track through the
4825 //    the forward links, which are always trustworthy.
4826 // *  Add a successor indication.  The LockWord is currently encoded as
4827 //    (List, LOCKBIT:1).  We could also add a SUCCBIT or an explicit _succ variable
4828 //    to provide the usual futile-wakeup optimization.
4829 //    See RTStt for details.
4830 //
4831 
4832 
4833 const intptr_t LOCKBIT = 1;
4834 
4835 void Thread::muxAcquire(volatile intptr_t * Lock, const char * LockName) {
4836   intptr_t w = Atomic::cmpxchg(LOCKBIT, Lock, (intptr_t)0);
4837   if (w == 0) return;
4838   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4839     return;
4840   }
4841 
4842   ParkEvent * const Self = Thread::current()->_MuxEvent;
4843   assert((intptr_t(Self) & LOCKBIT) == 0, "invariant");
4844   for (;;) {
4845     int its = (os::is_MP() ? 100 : 0) + 1;
4846 
4847     // Optional spin phase: spin-then-park strategy
4848     while (--its >= 0) {
4849       w = *Lock;
4850       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4851         return;
4852       }
4853     }
4854 
4855     Self->reset();
4856     Self->OnList = intptr_t(Lock);
4857     // The following fence() isn't _strictly necessary as the subsequent
4858     // CAS() both serializes execution and ratifies the fetched *Lock value.
4859     OrderAccess::fence();
4860     for (;;) {
4861       w = *Lock;
4862       if ((w & LOCKBIT) == 0) {
4863         if (Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4864           Self->OnList = 0;   // hygiene - allows stronger asserts
4865           return;
4866         }
4867         continue;      // Interference -- *Lock changed -- Just retry
4868       }
4869       assert(w & LOCKBIT, "invariant");
4870       Self->ListNext = (ParkEvent *) (w & ~LOCKBIT);
4871       if (Atomic::cmpxchg(intptr_t(Self)|LOCKBIT, Lock, w) == w) break;
4872     }
4873 
4874     while (Self->OnList != 0) {
4875       Self->park();
4876     }
4877   }
4878 }
4879 
4880 void Thread::muxAcquireW(volatile intptr_t * Lock, ParkEvent * ev) {
4881   intptr_t w = Atomic::cmpxchg(LOCKBIT, Lock, (intptr_t)0);
4882   if (w == 0) return;
4883   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4884     return;
4885   }
4886 
4887   ParkEvent * ReleaseAfter = NULL;
4888   if (ev == NULL) {
4889     ev = ReleaseAfter = ParkEvent::Allocate(NULL);
4890   }
4891   assert((intptr_t(ev) & LOCKBIT) == 0, "invariant");
4892   for (;;) {
4893     guarantee(ev->OnList == 0, "invariant");
4894     int its = (os::is_MP() ? 100 : 0) + 1;
4895 
4896     // Optional spin phase: spin-then-park strategy
4897     while (--its >= 0) {
4898       w = *Lock;
4899       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4900         if (ReleaseAfter != NULL) {
4901           ParkEvent::Release(ReleaseAfter);
4902         }
4903         return;
4904       }
4905     }
4906 
4907     ev->reset();
4908     ev->OnList = intptr_t(Lock);
4909     // The following fence() isn't _strictly necessary as the subsequent
4910     // CAS() both serializes execution and ratifies the fetched *Lock value.
4911     OrderAccess::fence();
4912     for (;;) {
4913       w = *Lock;
4914       if ((w & LOCKBIT) == 0) {
4915         if (Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
4916           ev->OnList = 0;
4917           // We call ::Release while holding the outer lock, thus
4918           // artificially lengthening the critical section.
4919           // Consider deferring the ::Release() until the subsequent unlock(),
4920           // after we've dropped the outer lock.
4921           if (ReleaseAfter != NULL) {
4922             ParkEvent::Release(ReleaseAfter);
4923           }
4924           return;
4925         }
4926         continue;      // Interference -- *Lock changed -- Just retry
4927       }
4928       assert(w & LOCKBIT, "invariant");
4929       ev->ListNext = (ParkEvent *) (w & ~LOCKBIT);
4930       if (Atomic::cmpxchg(intptr_t(ev)|LOCKBIT, Lock, w) == w) break;
4931     }
4932 
4933     while (ev->OnList != 0) {
4934       ev->park();
4935     }
4936   }
4937 }
4938 
4939 // Release() must extract a successor from the list and then wake that thread.
4940 // It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
4941 // similar to that used by ParkEvent::Allocate() and ::Release().  DMR-based
4942 // Release() would :
4943 // (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
4944 // (B) Extract a successor from the private list "in-hand"
4945 // (C) attempt to CAS() the residual back into *Lock over null.
4946 //     If there were any newly arrived threads and the CAS() would fail.
4947 //     In that case Release() would detach the RATs, re-merge the list in-hand
4948 //     with the RATs and repeat as needed.  Alternately, Release() might
4949 //     detach and extract a successor, but then pass the residual list to the wakee.
4950 //     The wakee would be responsible for reattaching and remerging before it
4951 //     competed for the lock.
4952 //
4953 // Both "pop" and DMR are immune from ABA corruption -- there can be
4954 // multiple concurrent pushers, but only one popper or detacher.
4955 // This implementation pops from the head of the list.  This is unfair,
4956 // but tends to provide excellent throughput as hot threads remain hot.
4957 // (We wake recently run threads first).
4958 //
4959 // All paths through muxRelease() will execute a CAS.
4960 // Release consistency -- We depend on the CAS in muxRelease() to provide full
4961 // bidirectional fence/MEMBAR semantics, ensuring that all prior memory operations
4962 // executed within the critical section are complete and globally visible before the
4963 // store (CAS) to the lock-word that releases the lock becomes globally visible.
4964 void Thread::muxRelease(volatile intptr_t * Lock)  {
4965   for (;;) {
4966     const intptr_t w = Atomic::cmpxchg((intptr_t)0, Lock, LOCKBIT);
4967     assert(w & LOCKBIT, "invariant");
4968     if (w == LOCKBIT) return;
4969     ParkEvent * const List = (ParkEvent *) (w & ~LOCKBIT);
4970     assert(List != NULL, "invariant");
4971     assert(List->OnList == intptr_t(Lock), "invariant");
4972     ParkEvent * const nxt = List->ListNext;
4973     guarantee((intptr_t(nxt) & LOCKBIT) == 0, "invariant");
4974 
4975     // The following CAS() releases the lock and pops the head element.
4976     // The CAS() also ratifies the previously fetched lock-word value.
4977     if (Atomic::cmpxchg(intptr_t(nxt), Lock, w) != w) {
4978       continue;
4979     }
4980     List->OnList = 0;
4981     OrderAccess::fence();
4982     List->unpark();
4983     return;
4984   }
4985 }
4986 
4987 
4988 void Threads::verify() {
4989   ALL_JAVA_THREADS(p) {
4990     p->verify();
4991   }
4992   VMThread* thread = VMThread::vm_thread();
4993   if (thread != NULL) thread->verify();
4994 }