1 /*
   2  * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "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/gcId.hpp"
  37 #include "gc/shared/gcLocker.inline.hpp"
  38 #include "gc/shared/workgroup.hpp"
  39 #include "interpreter/interpreter.hpp"
  40 #include "interpreter/linkResolver.hpp"
  41 #include "interpreter/oopMapCache.hpp"
  42 #include "jvmtifiles/jvmtiEnv.hpp"
  43 #include "logging/log.hpp"
  44 #include "logging/logConfiguration.hpp"
  45 #include "logging/logStream.hpp"
  46 #include "memory/metaspaceShared.hpp"
  47 #include "memory/oopFactory.hpp"
  48 #include "memory/resourceArea.hpp"
  49 #include "memory/universe.inline.hpp"
  50 #include "oops/instanceKlass.hpp"
  51 #include "oops/objArrayOop.hpp"
  52 #include "oops/oop.inline.hpp"
  53 #include "oops/symbol.hpp"
  54 #include "oops/verifyOopClosure.hpp"
  55 #include "prims/jvm_misc.hpp"
  56 #include "prims/jvmtiExport.hpp"
  57 #include "prims/jvmtiThreadState.hpp"
  58 #include "prims/privilegedStack.hpp"
  59 #include "runtime/arguments.hpp"
  60 #include "runtime/atomic.hpp"
  61 #include "runtime/biasedLocking.hpp"
  62 #include "runtime/commandLineFlagConstraintList.hpp"
  63 #include "runtime/commandLineFlagWriteableList.hpp"
  64 #include "runtime/commandLineFlagRangeList.hpp"
  65 #include "runtime/deoptimization.hpp"
  66 #include "runtime/frame.inline.hpp"
  67 #include "runtime/globals.hpp"
  68 #include "runtime/init.hpp"
  69 #include "runtime/interfaceSupport.hpp"
  70 #include "runtime/java.hpp"
  71 #include "runtime/javaCalls.hpp"
  72 #include "runtime/jniPeriodicChecker.hpp"
  73 #include "runtime/memprofiler.hpp"
  74 #include "runtime/mutexLocker.hpp"
  75 #include "runtime/objectMonitor.hpp"
  76 #include "runtime/orderAccess.inline.hpp"
  77 #include "runtime/osThread.hpp"
  78 #include "runtime/prefetch.inline.hpp"
  79 #include "runtime/safepoint.hpp"
  80 #include "runtime/sharedRuntime.hpp"
  81 #include "runtime/statSampler.hpp"
  82 #include "runtime/stubRoutines.hpp"
  83 #include "runtime/sweeper.hpp"
  84 #include "runtime/task.hpp"
  85 #include "runtime/thread.inline.hpp"
  86 #include "runtime/threadCritical.hpp"
  87 #include "runtime/threadSMR.inline.hpp"
  88 #include "runtime/timer.hpp"
  89 #include "runtime/timerTrace.hpp"
  90 #include "runtime/vframe.hpp"
  91 #include "runtime/vframeArray.hpp"
  92 #include "runtime/vframe_hp.hpp"
  93 #include "runtime/vmThread.hpp"
  94 #include "runtime/vm_operations.hpp"
  95 #include "runtime/vm_version.hpp"
  96 #include "services/attachListener.hpp"
  97 #include "services/management.hpp"
  98 #include "services/memTracker.hpp"
  99 #include "services/threadService.hpp"
 100 #include "trace/traceMacros.hpp"
 101 #include "trace/tracing.hpp"
 102 #include "utilities/align.hpp"
 103 #include "utilities/defaultStream.hpp"
 104 #include "utilities/dtrace.hpp"
 105 #include "utilities/events.hpp"
 106 #include "utilities/macros.hpp"
 107 #include "utilities/preserveException.hpp"
 108 #include "utilities/resourceHash.hpp"
 109 #include "utilities/vmError.hpp"
 110 #if INCLUDE_ALL_GCS
 111 #include "gc/cms/concurrentMarkSweepThread.hpp"
 112 #include "gc/g1/concurrentMarkThread.inline.hpp"
 113 #include "gc/parallel/pcTasks.hpp"
 114 #endif // INCLUDE_ALL_GCS
 115 #if INCLUDE_JVMCI
 116 #include "jvmci/jvmciCompiler.hpp"
 117 #include "jvmci/jvmciRuntime.hpp"
 118 #include "logging/logHandle.hpp"
 119 #endif
 120 #ifdef COMPILER1
 121 #include "c1/c1_Compiler.hpp"
 122 #endif
 123 #ifdef COMPILER2
 124 #include "opto/c2compiler.hpp"
 125 #include "opto/idealGraphPrinter.hpp"
 126 #endif
 127 #if INCLUDE_RTM_OPT
 128 #include "runtime/rtmLocking.hpp"
 129 #endif
 130 
 131 // Initialization after module runtime initialization
 132 void universe_post_module_init();  // must happen after call_initPhase2
 133 
 134 #ifdef DTRACE_ENABLED
 135 
 136 // Only bother with this argument setup if dtrace is available
 137 
 138   #define HOTSPOT_THREAD_PROBE_start HOTSPOT_THREAD_START
 139   #define HOTSPOT_THREAD_PROBE_stop HOTSPOT_THREAD_STOP
 140 
 141   #define DTRACE_THREAD_PROBE(probe, javathread)                           \
 142     {                                                                      \
 143       ResourceMark rm(this);                                               \
 144       int len = 0;                                                         \
 145       const char* name = (javathread)->get_thread_name();                  \
 146       len = strlen(name);                                                  \
 147       HOTSPOT_THREAD_PROBE_##probe(/* probe = start, stop */               \
 148         (char *) name, len,                                                \
 149         java_lang_Thread::thread_id((javathread)->threadObj()),            \
 150         (uintptr_t) (javathread)->osthread()->thread_id(),                 \
 151         java_lang_Thread::is_daemon((javathread)->threadObj()));           \
 152     }
 153 
 154 #else //  ndef DTRACE_ENABLED
 155 
 156   #define DTRACE_THREAD_PROBE(probe, javathread)
 157 
 158 #endif // ndef DTRACE_ENABLED
 159 
 160 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 161 // Current thread is maintained as a thread-local variable
 162 THREAD_LOCAL_DECL Thread* Thread::_thr_current = NULL;
 163 #endif
 164 // Class hierarchy
 165 // - Thread
 166 //   - VMThread
 167 //   - WatcherThread
 168 //   - ConcurrentMarkSweepThread
 169 //   - JavaThread
 170 //     - CompilerThread
 171 
 172 // ======= Thread ========
 173 // Support for forcing alignment of thread objects for biased locking
 174 void* Thread::allocate(size_t size, bool throw_excpt, MEMFLAGS flags) {
 175   if (UseBiasedLocking) {
 176     const int alignment = markOopDesc::biased_lock_alignment;
 177     size_t aligned_size = size + (alignment - sizeof(intptr_t));
 178     void* real_malloc_addr = throw_excpt? AllocateHeap(aligned_size, flags, CURRENT_PC)
 179                                           : AllocateHeap(aligned_size, flags, CURRENT_PC,
 180                                                          AllocFailStrategy::RETURN_NULL);
 181     void* aligned_addr     = align_up(real_malloc_addr, alignment);
 182     assert(((uintptr_t) aligned_addr + (uintptr_t) size) <=
 183            ((uintptr_t) real_malloc_addr + (uintptr_t) aligned_size),
 184            "JavaThread alignment code overflowed allocated storage");
 185     if (aligned_addr != real_malloc_addr) {
 186       log_info(biasedlocking)("Aligned thread " INTPTR_FORMAT " to " INTPTR_FORMAT,
 187                               p2i(real_malloc_addr),
 188                               p2i(aligned_addr));
 189     }
 190     ((Thread*) aligned_addr)->_real_malloc_address = real_malloc_addr;
 191     return aligned_addr;
 192   } else {
 193     return throw_excpt? AllocateHeap(size, flags, CURRENT_PC)
 194                        : AllocateHeap(size, flags, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
 195   }
 196 }
 197 
 198 void Thread::operator delete(void* p) {
 199   if (UseBiasedLocking) {
 200     FreeHeap(((Thread*) p)->_real_malloc_address);
 201   } else {
 202     FreeHeap(p);
 203   }
 204 }
 205 
 206 void JavaThread::smr_delete() {
 207   if (_on_thread_list) {
 208     Threads::smr_delete(this);
 209   } else {
 210     delete this;
 211   }
 212 }
 213 
 214 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
 215 // JavaThread
 216 
 217 
 218 Thread::Thread() {
 219   // stack and get_thread
 220   set_stack_base(NULL);
 221   set_stack_size(0);
 222   set_self_raw_id(0);
 223   set_lgrp_id(-1);
 224   DEBUG_ONLY(clear_suspendible_thread();)
 225 
 226   // allocated data structures
 227   set_osthread(NULL);
 228   set_resource_area(new (mtThread)ResourceArea());
 229   DEBUG_ONLY(_current_resource_mark = NULL;)
 230   set_handle_area(new (mtThread) HandleArea(NULL));
 231   set_metadata_handles(new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(30, true));
 232   set_active_handles(NULL);
 233   set_free_handle_block(NULL);
 234   set_last_handle_mark(NULL);
 235 
 236   // This initial value ==> never claimed.
 237   _oops_do_parity = 0;
 238   _threads_hazard_ptr = NULL;
 239   _nested_threads_hazard_ptr = NULL;
 240   _nested_threads_hazard_ptr_cnt = 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   _schedctl = NULL;
 280   _Stalled  = 0;
 281   _TypeTag  = 0x2BAD;
 282 
 283   // Many of the following fields are effectively final - immutable
 284   // Note that nascent threads can't use the Native Monitor-Mutex
 285   // construct until the _MutexEvent is initialized ...
 286   // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
 287   // we might instead use a stack of ParkEvents that we could provision on-demand.
 288   // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
 289   // and ::Release()
 290   _ParkEvent   = ParkEvent::Allocate(this);
 291   _SleepEvent  = ParkEvent::Allocate(this);
 292   _MutexEvent  = ParkEvent::Allocate(this);
 293   _MuxEvent    = ParkEvent::Allocate(this);
 294 
 295 #ifdef CHECK_UNHANDLED_OOPS
 296   if (CheckUnhandledOops) {
 297     _unhandled_oops = new UnhandledOops(this);
 298   }
 299 #endif // CHECK_UNHANDLED_OOPS
 300 #ifdef ASSERT
 301   if (UseBiasedLocking) {
 302     assert((((uintptr_t) this) & (markOopDesc::biased_lock_alignment - 1)) == 0, "forced alignment of thread object failed");
 303     assert(this == _real_malloc_address ||
 304            this == align_up(_real_malloc_address, (int)markOopDesc::biased_lock_alignment),
 305            "bug in forced alignment of thread objects");
 306   }
 307 #endif // ASSERT
 308 }
 309 
 310 void Thread::initialize_thread_current() {
 311 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 312   assert(_thr_current == NULL, "Thread::current already initialized");
 313   _thr_current = this;
 314 #endif
 315   assert(ThreadLocalStorage::thread() == NULL, "ThreadLocalStorage::thread already initialized");
 316   ThreadLocalStorage::set_thread(this);
 317   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 318 }
 319 
 320 void Thread::clear_thread_current() {
 321   assert(Thread::current() == ThreadLocalStorage::thread(), "TLS mismatch!");
 322 #ifndef USE_LIBRARY_BASED_TLS_ONLY
 323   _thr_current = NULL;
 324 #endif
 325   ThreadLocalStorage::set_thread(NULL);
 326 }
 327 
 328 void Thread::record_stack_base_and_size() {
 329   set_stack_base(os::current_stack_base());
 330   set_stack_size(os::current_stack_size());
 331   // CR 7190089: on Solaris, primordial thread's stack is adjusted
 332   // in initialize_thread(). Without the adjustment, stack size is
 333   // incorrect if stack is set to unlimited (ulimit -s unlimited).
 334   // So far, only Solaris has real implementation of initialize_thread().
 335   //
 336   // set up any platform-specific state.
 337   os::initialize_thread(this);
 338 
 339   // Set stack limits after thread is initialized.
 340   if (is_Java_thread()) {
 341     ((JavaThread*) this)->set_stack_overflow_limit();
 342     ((JavaThread*) this)->set_reserved_stack_activation(stack_base());
 343   }
 344 #if INCLUDE_NMT
 345   // record thread's native stack, stack grows downward
 346   MemTracker::record_thread_stack(stack_end(), stack_size());
 347 #endif // INCLUDE_NMT
 348   log_debug(os, thread)("Thread " UINTX_FORMAT " stack dimensions: "
 349     PTR_FORMAT "-" PTR_FORMAT " (" SIZE_FORMAT "k).",
 350     os::current_thread_id(), p2i(stack_base() - stack_size()),
 351     p2i(stack_base()), stack_size()/1024);
 352 }
 353 
 354 
 355 Thread::~Thread() {
 356   EVENT_THREAD_DESTRUCT(this);
 357 
 358   // stack_base can be NULL if the thread is never started or exited before
 359   // record_stack_base_and_size called. Although, we would like to ensure
 360   // that all started threads do call record_stack_base_and_size(), there is
 361   // not proper way to enforce that.
 362 #if INCLUDE_NMT
 363   if (_stack_base != NULL) {
 364     MemTracker::release_thread_stack(stack_end(), stack_size());
 365 #ifdef ASSERT
 366     set_stack_base(NULL);
 367 #endif
 368   }
 369 #endif // INCLUDE_NMT
 370 
 371   // deallocate data structures
 372   delete resource_area();
 373   // since the handle marks are using the handle area, we have to deallocated the root
 374   // handle mark before deallocating the thread's handle area,
 375   assert(last_handle_mark() != NULL, "check we have an element");
 376   delete last_handle_mark();
 377   assert(last_handle_mark() == NULL, "check we have reached the end");
 378 
 379   // It's possible we can encounter a null _ParkEvent, etc., in stillborn threads.
 380   // We NULL out the fields for good hygiene.
 381   ParkEvent::Release(_ParkEvent); _ParkEvent   = NULL;
 382   ParkEvent::Release(_SleepEvent); _SleepEvent  = NULL;
 383   ParkEvent::Release(_MutexEvent); _MutexEvent  = NULL;
 384   ParkEvent::Release(_MuxEvent); _MuxEvent    = NULL;
 385 
 386   delete handle_area();
 387   delete metadata_handles();
 388 
 389   // SR_handler uses this as a termination indicator -
 390   // needs to happen before os::free_thread()
 391   delete _SR_lock;
 392   _SR_lock = NULL;
 393 
 394   // osthread() can be NULL, if creation of thread failed.
 395   if (osthread() != NULL) os::free_thread(osthread());
 396 
 397   // clear Thread::current if thread is deleting itself.
 398   // Needed to ensure JNI correctly detects non-attached threads.
 399   if (this == Thread::current()) {
 400     clear_thread_current();
 401   }
 402 
 403   CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
 404 }
 405 
 406 // NOTE: dummy function for assertion purpose.
 407 void Thread::run() {
 408   ShouldNotReachHere();
 409 }
 410 
 411 #ifdef ASSERT
 412 // A JavaThread is considered "dangling" if it is not the current
 413 // thread, has been added the Threads list, the system is not at a
 414 // safepoint and the Thread is not "protected".
 415 //
 416 void Thread::check_for_dangling_thread_pointer(Thread *thread) {
 417   assert(!thread->is_Java_thread() || Thread::current() == thread ||
 418          !((JavaThread *) thread)->on_thread_list() ||
 419          SafepointSynchronize::is_at_safepoint() ||
 420          Threads::is_a_protected_JavaThread_with_lock((JavaThread *) thread),
 421          "possibility of dangling Thread pointer");
 422 }
 423 #endif
 424 
 425 ThreadPriority Thread::get_priority(const Thread* const thread) {
 426   ThreadPriority priority;
 427   // Can return an error!
 428   (void)os::get_priority(thread, priority);
 429   assert(MinPriority <= priority && priority <= MaxPriority, "non-Java priority found");
 430   return priority;
 431 }
 432 
 433 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
 434   debug_only(check_for_dangling_thread_pointer(thread);)
 435   // Can return an error!
 436   (void)os::set_priority(thread, priority);
 437 }
 438 
 439 
 440 void Thread::start(Thread* thread) {
 441   // Start is different from resume in that its safety is guaranteed by context or
 442   // being called from a Java method synchronized on the Thread object.
 443   if (!DisableStartThread) {
 444     if (thread->is_Java_thread()) {
 445       // Initialize the thread state to RUNNABLE before starting this thread.
 446       // Can not set it after the thread started because we do not know the
 447       // exact thread state at that time. It could be in MONITOR_WAIT or
 448       // in SLEEPING or some other state.
 449       java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
 450                                           java_lang_Thread::RUNNABLE);
 451     }
 452     os::start_thread(thread);
 453   }
 454 }
 455 
 456 // Enqueue a VM_Operation to do the job for us - sometime later
 457 void Thread::send_async_exception(oop java_thread, oop java_throwable) {
 458   VM_ThreadStop* vm_stop = new VM_ThreadStop(java_thread, java_throwable);
 459   VMThread::execute(vm_stop);
 460 }
 461 
 462 
 463 // Check if an external suspend request has completed (or has been
 464 // cancelled). Returns true if the thread is externally suspended and
 465 // false otherwise.
 466 //
 467 // The bits parameter returns information about the code path through
 468 // the routine. Useful for debugging:
 469 //
 470 // set in is_ext_suspend_completed():
 471 // 0x00000001 - routine was entered
 472 // 0x00000010 - routine return false at end
 473 // 0x00000100 - thread exited (return false)
 474 // 0x00000200 - suspend request cancelled (return false)
 475 // 0x00000400 - thread suspended (return true)
 476 // 0x00001000 - thread is in a suspend equivalent state (return true)
 477 // 0x00002000 - thread is native and walkable (return true)
 478 // 0x00004000 - thread is native_trans and walkable (needed retry)
 479 //
 480 // set in wait_for_ext_suspend_completion():
 481 // 0x00010000 - routine was entered
 482 // 0x00020000 - suspend request cancelled before loop (return false)
 483 // 0x00040000 - thread suspended before loop (return true)
 484 // 0x00080000 - suspend request cancelled in loop (return false)
 485 // 0x00100000 - thread suspended in loop (return true)
 486 // 0x00200000 - suspend not completed during retry loop (return false)
 487 
 488 // Helper class for tracing suspend wait debug bits.
 489 //
 490 // 0x00000100 indicates that the target thread exited before it could
 491 // self-suspend which is not a wait failure. 0x00000200, 0x00020000 and
 492 // 0x00080000 each indicate a cancelled suspend request so they don't
 493 // count as wait failures either.
 494 #define DEBUG_FALSE_BITS (0x00000010 | 0x00200000)
 495 
 496 class TraceSuspendDebugBits : public StackObj {
 497  private:
 498   JavaThread * jt;
 499   bool         is_wait;
 500   bool         called_by_wait;  // meaningful when !is_wait
 501   uint32_t *   bits;
 502 
 503  public:
 504   TraceSuspendDebugBits(JavaThread *_jt, bool _is_wait, bool _called_by_wait,
 505                         uint32_t *_bits) {
 506     jt             = _jt;
 507     is_wait        = _is_wait;
 508     called_by_wait = _called_by_wait;
 509     bits           = _bits;
 510   }
 511 
 512   ~TraceSuspendDebugBits() {
 513     if (!is_wait) {
 514 #if 1
 515       // By default, don't trace bits for is_ext_suspend_completed() calls.
 516       // That trace is very chatty.
 517       return;
 518 #else
 519       if (!called_by_wait) {
 520         // If tracing for is_ext_suspend_completed() is enabled, then only
 521         // trace calls to it from wait_for_ext_suspend_completion()
 522         return;
 523       }
 524 #endif
 525     }
 526 
 527     if (AssertOnSuspendWaitFailure || TraceSuspendWaitFailures) {
 528       if (bits != NULL && (*bits & DEBUG_FALSE_BITS) != 0) {
 529         MutexLocker ml(Threads_lock);  // needed for get_thread_name()
 530         ResourceMark rm;
 531 
 532         tty->print_cr(
 533                       "Failed wait_for_ext_suspend_completion(thread=%s, debug_bits=%x)",
 534                       jt->get_thread_name(), *bits);
 535 
 536         guarantee(!AssertOnSuspendWaitFailure, "external suspend wait failed");
 537       }
 538     }
 539   }
 540 };
 541 #undef DEBUG_FALSE_BITS
 542 
 543 
 544 bool JavaThread::is_ext_suspend_completed(bool called_by_wait, int delay,
 545                                           uint32_t *bits) {
 546   TraceSuspendDebugBits tsdb(this, false /* !is_wait */, called_by_wait, bits);
 547 
 548   bool did_trans_retry = false;  // only do thread_in_native_trans retry once
 549   bool do_trans_retry;           // flag to force the retry
 550 
 551   *bits |= 0x00000001;
 552 
 553   do {
 554     do_trans_retry = false;
 555 
 556     if (is_exiting()) {
 557       // Thread is in the process of exiting. This is always checked
 558       // first to reduce the risk of dereferencing a freed JavaThread.
 559       *bits |= 0x00000100;
 560       return false;
 561     }
 562 
 563     if (!is_external_suspend()) {
 564       // Suspend request is cancelled. This is always checked before
 565       // is_ext_suspended() to reduce the risk of a rogue resume
 566       // confusing the thread that made the suspend request.
 567       *bits |= 0x00000200;
 568       return false;
 569     }
 570 
 571     if (is_ext_suspended()) {
 572       // thread is suspended
 573       *bits |= 0x00000400;
 574       return true;
 575     }
 576 
 577     // Now that we no longer do hard suspends of threads running
 578     // native code, the target thread can be changing thread state
 579     // while we are in this routine:
 580     //
 581     //   _thread_in_native -> _thread_in_native_trans -> _thread_blocked
 582     //
 583     // We save a copy of the thread state as observed at this moment
 584     // and make our decision about suspend completeness based on the
 585     // copy. This closes the race where the thread state is seen as
 586     // _thread_in_native_trans in the if-thread_blocked check, but is
 587     // seen as _thread_blocked in if-thread_in_native_trans check.
 588     JavaThreadState save_state = thread_state();
 589 
 590     if (save_state == _thread_blocked && is_suspend_equivalent()) {
 591       // If the thread's state is _thread_blocked and this blocking
 592       // condition is known to be equivalent to a suspend, then we can
 593       // consider the thread to be externally suspended. This means that
 594       // the code that sets _thread_blocked has been modified to do
 595       // self-suspension if the blocking condition releases. We also
 596       // used to check for CONDVAR_WAIT here, but that is now covered by
 597       // the _thread_blocked with self-suspension check.
 598       //
 599       // Return true since we wouldn't be here unless there was still an
 600       // external suspend request.
 601       *bits |= 0x00001000;
 602       return true;
 603     } else if (save_state == _thread_in_native && frame_anchor()->walkable()) {
 604       // Threads running native code will self-suspend on native==>VM/Java
 605       // transitions. If its stack is walkable (should always be the case
 606       // unless this function is called before the actual java_suspend()
 607       // call), then the wait is done.
 608       *bits |= 0x00002000;
 609       return true;
 610     } else if (!called_by_wait && !did_trans_retry &&
 611                save_state == _thread_in_native_trans &&
 612                frame_anchor()->walkable()) {
 613       // The thread is transitioning from thread_in_native to another
 614       // thread state. check_safepoint_and_suspend_for_native_trans()
 615       // will force the thread to self-suspend. If it hasn't gotten
 616       // there yet we may have caught the thread in-between the native
 617       // code check above and the self-suspend. Lucky us. If we were
 618       // called by wait_for_ext_suspend_completion(), then it
 619       // will be doing the retries so we don't have to.
 620       //
 621       // Since we use the saved thread state in the if-statement above,
 622       // there is a chance that the thread has already transitioned to
 623       // _thread_blocked by the time we get here. In that case, we will
 624       // make a single unnecessary pass through the logic below. This
 625       // doesn't hurt anything since we still do the trans retry.
 626 
 627       *bits |= 0x00004000;
 628 
 629       // Once the thread leaves thread_in_native_trans for another
 630       // thread state, we break out of this retry loop. We shouldn't
 631       // need this flag to prevent us from getting back here, but
 632       // sometimes paranoia is good.
 633       did_trans_retry = true;
 634 
 635       // We wait for the thread to transition to a more usable state.
 636       for (int i = 1; i <= SuspendRetryCount; i++) {
 637         // We used to do an "os::yield_all(i)" call here with the intention
 638         // that yielding would increase on each retry. However, the parameter
 639         // is ignored on Linux which means the yield didn't scale up. Waiting
 640         // on the SR_lock below provides a much more predictable scale up for
 641         // the delay. It also provides a simple/direct point to check for any
 642         // safepoint requests from the VMThread
 643 
 644         // temporarily drops SR_lock while doing wait with safepoint check
 645         // (if we're a JavaThread - the WatcherThread can also call this)
 646         // and increase delay with each retry
 647         SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 648 
 649         // check the actual thread state instead of what we saved above
 650         if (thread_state() != _thread_in_native_trans) {
 651           // the thread has transitioned to another thread state so
 652           // try all the checks (except this one) one more time.
 653           do_trans_retry = true;
 654           break;
 655         }
 656       } // end retry loop
 657 
 658 
 659     }
 660   } while (do_trans_retry);
 661 
 662   *bits |= 0x00000010;
 663   return false;
 664 }
 665 
 666 // Wait for an external suspend request to complete (or be cancelled).
 667 // Returns true if the thread is externally suspended and false otherwise.
 668 //
 669 bool JavaThread::wait_for_ext_suspend_completion(int retries, int delay,
 670                                                  uint32_t *bits) {
 671   TraceSuspendDebugBits tsdb(this, true /* is_wait */,
 672                              false /* !called_by_wait */, bits);
 673 
 674   // local flag copies to minimize SR_lock hold time
 675   bool is_suspended;
 676   bool pending;
 677   uint32_t reset_bits;
 678 
 679   // set a marker so is_ext_suspend_completed() knows we are the caller
 680   *bits |= 0x00010000;
 681 
 682   // We use reset_bits to reinitialize the bits value at the top of
 683   // each retry loop. This allows the caller to make use of any
 684   // unused bits for their own marking purposes.
 685   reset_bits = *bits;
 686 
 687   {
 688     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 689     is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 690                                             delay, bits);
 691     pending = is_external_suspend();
 692   }
 693   // must release SR_lock to allow suspension to complete
 694 
 695   if (!pending) {
 696     // A cancelled suspend request is the only false return from
 697     // is_ext_suspend_completed() that keeps us from entering the
 698     // retry loop.
 699     *bits |= 0x00020000;
 700     return false;
 701   }
 702 
 703   if (is_suspended) {
 704     *bits |= 0x00040000;
 705     return true;
 706   }
 707 
 708   for (int i = 1; i <= retries; i++) {
 709     *bits = reset_bits;  // reinit to only track last retry
 710 
 711     // We used to do an "os::yield_all(i)" call here with the intention
 712     // that yielding would increase on each retry. However, the parameter
 713     // is ignored on Linux which means the yield didn't scale up. Waiting
 714     // on the SR_lock below provides a much more predictable scale up for
 715     // the delay. It also provides a simple/direct point to check for any
 716     // safepoint requests from the VMThread
 717 
 718     {
 719       MutexLocker ml(SR_lock());
 720       // wait with safepoint check (if we're a JavaThread - the WatcherThread
 721       // can also call this)  and increase delay with each retry
 722       SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 723 
 724       is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 725                                               delay, bits);
 726 
 727       // It is possible for the external suspend request to be cancelled
 728       // (by a resume) before the actual suspend operation is completed.
 729       // Refresh our local copy to see if we still need to wait.
 730       pending = is_external_suspend();
 731     }
 732 
 733     if (!pending) {
 734       // A cancelled suspend request is the only false return from
 735       // is_ext_suspend_completed() that keeps us from staying in the
 736       // retry loop.
 737       *bits |= 0x00080000;
 738       return false;
 739     }
 740 
 741     if (is_suspended) {
 742       *bits |= 0x00100000;
 743       return true;
 744     }
 745   } // end retry loop
 746 
 747   // thread did not suspend after all our retries
 748   *bits |= 0x00200000;
 749   return false;
 750 }
 751 
 752 // Called from API entry points which perform stack walking. If the
 753 // associated JavaThread is the current thread, then wait_for_suspend
 754 // is not used. Otherwise, it determines if we should wait for the
 755 // "other" thread to complete external suspension. (NOTE: in future
 756 // releases the suspension mechanism should be reimplemented so this
 757 // is not necessary.)
 758 //
 759 bool
 760 JavaThread::is_thread_fully_suspended(bool wait_for_suspend, uint32_t *bits) {
 761   if (this != JavaThread::current()) {
 762     // "other" threads require special handling.
 763     if (wait_for_suspend) {
 764       // We are allowed to wait for the external suspend to complete
 765       // so give the other thread a chance to get suspended.
 766       if (!wait_for_ext_suspend_completion(SuspendRetryCount,
 767                                            SuspendRetryDelay, bits)) {
 768         // Didn't make it so let the caller know.
 769         return false;
 770       }
 771     }
 772     // We aren't allowed to wait for the external suspend to complete
 773     // so if the other thread isn't externally suspended we need to
 774     // let the caller know.
 775     else if (!is_ext_suspend_completed_with_lock(bits)) {
 776       return false;
 777     }
 778   }
 779 
 780   return true;
 781 }
 782 
 783 #ifndef PRODUCT
 784 void JavaThread::record_jump(address target, address instr, const char* file,
 785                              int line) {
 786 
 787   // This should not need to be atomic as the only way for simultaneous
 788   // updates is via interrupts. Even then this should be rare or non-existent
 789   // and we don't care that much anyway.
 790 
 791   int index = _jmp_ring_index;
 792   _jmp_ring_index = (index + 1) & (jump_ring_buffer_size - 1);
 793   _jmp_ring[index]._target = (intptr_t) target;
 794   _jmp_ring[index]._instruction = (intptr_t) instr;
 795   _jmp_ring[index]._file = file;
 796   _jmp_ring[index]._line = line;
 797 }
 798 #endif // PRODUCT
 799 
 800 void Thread::interrupt(Thread* thread) {
 801   debug_only(check_for_dangling_thread_pointer(thread);)
 802   os::interrupt(thread);
 803 }
 804 
 805 bool Thread::is_interrupted(Thread* thread, bool clear_interrupted) {
 806   debug_only(check_for_dangling_thread_pointer(thread);)
 807   // Note:  If clear_interrupted==false, this simply fetches and
 808   // returns the value of the field osthread()->interrupted().
 809   return os::is_interrupted(thread, clear_interrupted);
 810 }
 811 
 812 
 813 // GC Support
 814 bool Thread::claim_oops_do_par_case(int strong_roots_parity) {
 815   int thread_parity = _oops_do_parity;
 816   if (thread_parity != strong_roots_parity) {
 817     jint res = Atomic::cmpxchg(strong_roots_parity, &_oops_do_parity, thread_parity);
 818     if (res == thread_parity) {
 819       return true;
 820     } else {
 821       guarantee(res == strong_roots_parity, "Or else what?");
 822       return false;
 823     }
 824   }
 825   return false;
 826 }
 827 
 828 void Thread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
 829   active_handles()->oops_do(f);
 830   // Do oop for ThreadShadow
 831   f->do_oop((oop*)&_pending_exception);
 832   handle_area()->oops_do(f);
 833 
 834   if (MonitorInUseLists) {
 835     // When using thread local monitor lists, we scan them here,
 836     // and the remaining global monitors in ObjectSynchronizer::oops_do().
 837     ObjectSynchronizer::thread_local_used_oops_do(this, f);
 838   }
 839 }
 840 
 841 void Thread::metadata_handles_do(void f(Metadata*)) {
 842   // Only walk the Handles in Thread.
 843   if (metadata_handles() != NULL) {
 844     for (int i = 0; i< metadata_handles()->length(); i++) {
 845       f(metadata_handles()->at(i));
 846     }
 847   }
 848 }
 849 
 850 void Thread::print_on(outputStream* st) const {
 851   // get_priority assumes osthread initialized
 852   if (osthread() != NULL) {
 853     int os_prio;
 854     if (os::get_native_priority(this, &os_prio) == OS_OK) {
 855       st->print("os_prio=%d ", os_prio);
 856     }
 857     st->print("tid=" INTPTR_FORMAT " ", p2i(this));
 858     ext().print_on(st);
 859     osthread()->print_on(st);
 860   }
 861   if (_threads_hazard_ptr != NULL) {
 862     st->print("_threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr));
 863   }
 864   if (_nested_threads_hazard_ptr != NULL) {
 865     print_nested_threads_hazard_ptrs_on(st);
 866   }
 867   st->print(" ");
 868   debug_only(if (WizardMode) print_owned_locks_on(st);)
 869 }
 870 
 871 void Thread::print_nested_threads_hazard_ptrs_on(outputStream* st) const {
 872   assert(_nested_threads_hazard_ptr != NULL, "must be set to print");
 873 
 874   if (EnableThreadSMRStatistics) {
 875     st->print(", _nested_threads_hazard_ptr_cnt=%u", _nested_threads_hazard_ptr_cnt);
 876   }
 877   st->print(", _nested_threads_hazard_ptrs=");
 878   for (NestedThreadsList* node = _nested_threads_hazard_ptr; node != NULL;
 879        node = node->next()) {
 880     if (node != _nested_threads_hazard_ptr) {
 881       // First node does not need a comma-space separator.
 882       st->print(", ");
 883     }
 884     st->print(INTPTR_FORMAT, p2i(node->t_list()));
 885   }
 886 }
 887 
 888 // Thread::print_on_error() is called by fatal error handler. Don't use
 889 // any lock or allocate memory.
 890 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
 891   assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
 892 
 893   if (is_VM_thread())                 { st->print("VMThread"); }
 894   else if (is_GC_task_thread())       { st->print("GCTaskThread"); }
 895   else if (is_Watcher_thread())       { st->print("WatcherThread"); }
 896   else if (is_ConcurrentGC_thread())  { st->print("ConcurrentGCThread"); }
 897   else                                { st->print("Thread"); }
 898 
 899   if (is_Named_thread()) {
 900     st->print(" \"%s\"", name());
 901   }
 902 
 903   st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
 904             p2i(stack_end()), p2i(stack_base()));
 905 
 906   if (osthread()) {
 907     st->print(" [id=%d]", osthread()->thread_id());
 908   }
 909 
 910   if (_threads_hazard_ptr != NULL) {
 911     st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr));
 912   }
 913   if (_nested_threads_hazard_ptr != NULL) {
 914     print_nested_threads_hazard_ptrs_on(st);
 915   }
 916 }
 917 
 918 void Thread::print_value_on(outputStream* st) const {
 919   if (is_Named_thread()) {
 920     st->print(" \"%s\" ", name());
 921   }
 922   st->print(INTPTR_FORMAT, p2i(this));   // print address
 923 }
 924 
 925 #ifdef ASSERT
 926 void Thread::print_owned_locks_on(outputStream* st) const {
 927   Monitor *cur = _owned_locks;
 928   if (cur == NULL) {
 929     st->print(" (no locks) ");
 930   } else {
 931     st->print_cr(" Locks owned:");
 932     while (cur) {
 933       cur->print_on(st);
 934       cur = cur->next();
 935     }
 936   }
 937 }
 938 
 939 static int ref_use_count  = 0;
 940 
 941 bool Thread::owns_locks_but_compiled_lock() const {
 942   for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 943     if (cur != Compile_lock) return true;
 944   }
 945   return false;
 946 }
 947 
 948 
 949 #endif
 950 
 951 #ifndef PRODUCT
 952 
 953 // The flag: potential_vm_operation notifies if this particular safepoint state could potentially
 954 // invoke the vm-thread (e.g., an oop allocation). In that case, we also have to make sure that
 955 // no threads which allow_vm_block's are held
 956 void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) {
 957   // Check if current thread is allowed to block at a safepoint
 958   if (!(_allow_safepoint_count == 0)) {
 959     fatal("Possible safepoint reached by thread that does not allow it");
 960   }
 961   if (is_Java_thread() && ((JavaThread*)this)->thread_state() != _thread_in_vm) {
 962     fatal("LEAF method calling lock?");
 963   }
 964 
 965 #ifdef ASSERT
 966   if (potential_vm_operation && is_Java_thread()
 967       && !Universe::is_bootstrapping()) {
 968     // Make sure we do not hold any locks that the VM thread also uses.
 969     // This could potentially lead to deadlocks
 970     for (Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 971       // Threads_lock is special, since the safepoint synchronization will not start before this is
 972       // acquired. Hence, a JavaThread cannot be holding it at a safepoint. So is VMOperationRequest_lock,
 973       // since it is used to transfer control between JavaThreads and the VMThread
 974       // Do not *exclude* any locks unless you are absolutely sure it is correct. Ask someone else first!
 975       if ((cur->allow_vm_block() &&
 976            cur != Threads_lock &&
 977            cur != Compile_lock &&               // Temporary: should not be necessary when we get separate compilation
 978            cur != VMOperationRequest_lock &&
 979            cur != VMOperationQueue_lock) ||
 980            cur->rank() == Mutex::special) {
 981         fatal("Thread holding lock at safepoint that vm can block on: %s", cur->name());
 982       }
 983     }
 984   }
 985 
 986   if (GCALotAtAllSafepoints) {
 987     // We could enter a safepoint here and thus have a gc
 988     InterfaceSupport::check_gc_alot();
 989   }
 990 #endif
 991 }
 992 #endif
 993 
 994 bool Thread::is_in_stack(address adr) const {
 995   assert(Thread::current() == this, "is_in_stack can only be called from current thread");
 996   address end = os::current_stack_pointer();
 997   // Allow non Java threads to call this without stack_base
 998   if (_stack_base == NULL) return true;
 999   if (stack_base() >= adr && adr >= end) return true;
1000 
1001   return false;
1002 }
1003 
1004 bool Thread::is_in_usable_stack(address adr) const {
1005   size_t stack_guard_size = os::uses_stack_guard_pages() ? JavaThread::stack_guard_zone_size() : 0;
1006   size_t usable_stack_size = _stack_size - stack_guard_size;
1007 
1008   return ((adr < stack_base()) && (adr >= stack_base() - usable_stack_size));
1009 }
1010 
1011 
1012 // We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
1013 // However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
1014 // used for compilation in the future. If that change is made, the need for these methods
1015 // should be revisited, and they should be removed if possible.
1016 
1017 bool Thread::is_lock_owned(address adr) const {
1018   return on_local_stack(adr);
1019 }
1020 
1021 bool Thread::set_as_starting_thread() {
1022   // NOTE: this must be called inside the main thread.
1023   return os::create_main_thread((JavaThread*)this);
1024 }
1025 
1026 static void initialize_class(Symbol* class_name, TRAPS) {
1027   Klass* klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
1028   InstanceKlass::cast(klass)->initialize(CHECK);
1029 }
1030 
1031 
1032 // Creates the initial ThreadGroup
1033 static Handle create_initial_thread_group(TRAPS) {
1034   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_ThreadGroup(), true, CHECK_NH);
1035   InstanceKlass* ik = InstanceKlass::cast(k);
1036 
1037   Handle system_instance = ik->allocate_instance_handle(CHECK_NH);
1038   {
1039     JavaValue result(T_VOID);
1040     JavaCalls::call_special(&result,
1041                             system_instance,
1042                             ik,
1043                             vmSymbols::object_initializer_name(),
1044                             vmSymbols::void_method_signature(),
1045                             CHECK_NH);
1046   }
1047   Universe::set_system_thread_group(system_instance());
1048 
1049   Handle main_instance = ik->allocate_instance_handle(CHECK_NH);
1050   {
1051     JavaValue result(T_VOID);
1052     Handle string = java_lang_String::create_from_str("main", CHECK_NH);
1053     JavaCalls::call_special(&result,
1054                             main_instance,
1055                             ik,
1056                             vmSymbols::object_initializer_name(),
1057                             vmSymbols::threadgroup_string_void_signature(),
1058                             system_instance,
1059                             string,
1060                             CHECK_NH);
1061   }
1062   return main_instance;
1063 }
1064 
1065 // Creates the initial Thread
1066 static oop create_initial_thread(Handle thread_group, JavaThread* thread,
1067                                  TRAPS) {
1068   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK_NULL);
1069   InstanceKlass* ik = InstanceKlass::cast(k);
1070   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK_NULL);
1071 
1072   java_lang_Thread::set_thread(thread_oop(), thread);
1073   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1074   thread->set_threadObj(thread_oop());
1075 
1076   Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
1077 
1078   JavaValue result(T_VOID);
1079   JavaCalls::call_special(&result, thread_oop,
1080                           ik,
1081                           vmSymbols::object_initializer_name(),
1082                           vmSymbols::threadgroup_string_void_signature(),
1083                           thread_group,
1084                           string,
1085                           CHECK_NULL);
1086   return thread_oop();
1087 }
1088 
1089 char java_runtime_name[128] = "";
1090 char java_runtime_version[128] = "";
1091 
1092 // extract the JRE name from java.lang.VersionProps.java_runtime_name
1093 static const char* get_java_runtime_name(TRAPS) {
1094   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1095                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1096   fieldDescriptor fd;
1097   bool found = k != NULL &&
1098                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_name_name(),
1099                                                         vmSymbols::string_signature(), &fd);
1100   if (found) {
1101     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1102     if (name_oop == NULL) {
1103       return NULL;
1104     }
1105     const char* name = java_lang_String::as_utf8_string(name_oop,
1106                                                         java_runtime_name,
1107                                                         sizeof(java_runtime_name));
1108     return name;
1109   } else {
1110     return NULL;
1111   }
1112 }
1113 
1114 // extract the JRE version from java.lang.VersionProps.java_runtime_version
1115 static const char* get_java_runtime_version(TRAPS) {
1116   Klass* k = SystemDictionary::find(vmSymbols::java_lang_VersionProps(),
1117                                     Handle(), Handle(), CHECK_AND_CLEAR_NULL);
1118   fieldDescriptor fd;
1119   bool found = k != NULL &&
1120                InstanceKlass::cast(k)->find_local_field(vmSymbols::java_runtime_version_name(),
1121                                                         vmSymbols::string_signature(), &fd);
1122   if (found) {
1123     oop name_oop = k->java_mirror()->obj_field(fd.offset());
1124     if (name_oop == NULL) {
1125       return NULL;
1126     }
1127     const char* name = java_lang_String::as_utf8_string(name_oop,
1128                                                         java_runtime_version,
1129                                                         sizeof(java_runtime_version));
1130     return name;
1131   } else {
1132     return NULL;
1133   }
1134 }
1135 
1136 // General purpose hook into Java code, run once when the VM is initialized.
1137 // The Java library method itself may be changed independently from the VM.
1138 static void call_postVMInitHook(TRAPS) {
1139   Klass* klass = SystemDictionary::resolve_or_null(vmSymbols::jdk_internal_vm_PostVMInitHook(), THREAD);
1140   if (klass != NULL) {
1141     JavaValue result(T_VOID);
1142     JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
1143                            vmSymbols::void_method_signature(),
1144                            CHECK);
1145   }
1146 }
1147 
1148 static void reset_vm_info_property(TRAPS) {
1149   // the vm info string
1150   ResourceMark rm(THREAD);
1151   const char *vm_info = VM_Version::vm_info_string();
1152 
1153   // java.lang.System class
1154   Klass* klass =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
1155 
1156   // setProperty arguments
1157   Handle key_str    = java_lang_String::create_from_str("java.vm.info", CHECK);
1158   Handle value_str  = java_lang_String::create_from_str(vm_info, CHECK);
1159 
1160   // return value
1161   JavaValue r(T_OBJECT);
1162 
1163   // public static String setProperty(String key, String value);
1164   JavaCalls::call_static(&r,
1165                          klass,
1166                          vmSymbols::setProperty_name(),
1167                          vmSymbols::string_string_string_signature(),
1168                          key_str,
1169                          value_str,
1170                          CHECK);
1171 }
1172 
1173 
1174 void JavaThread::allocate_threadObj(Handle thread_group, const char* thread_name,
1175                                     bool daemon, TRAPS) {
1176   assert(thread_group.not_null(), "thread group should be specified");
1177   assert(threadObj() == NULL, "should only create Java thread object once");
1178 
1179   Klass* k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK);
1180   InstanceKlass* ik = InstanceKlass::cast(k);
1181   instanceHandle thread_oop = ik->allocate_instance_handle(CHECK);
1182 
1183   java_lang_Thread::set_thread(thread_oop(), this);
1184   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1185   set_threadObj(thread_oop());
1186 
1187   JavaValue result(T_VOID);
1188   if (thread_name != NULL) {
1189     Handle name = java_lang_String::create_from_str(thread_name, CHECK);
1190     // Thread gets assigned specified name and null target
1191     JavaCalls::call_special(&result,
1192                             thread_oop,
1193                             ik,
1194                             vmSymbols::object_initializer_name(),
1195                             vmSymbols::threadgroup_string_void_signature(),
1196                             thread_group, // Argument 1
1197                             name,         // Argument 2
1198                             THREAD);
1199   } else {
1200     // Thread gets assigned name "Thread-nnn" and null target
1201     // (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
1202     JavaCalls::call_special(&result,
1203                             thread_oop,
1204                             ik,
1205                             vmSymbols::object_initializer_name(),
1206                             vmSymbols::threadgroup_runnable_void_signature(),
1207                             thread_group, // Argument 1
1208                             Handle(),     // Argument 2
1209                             THREAD);
1210   }
1211 
1212 
1213   if (daemon) {
1214     java_lang_Thread::set_daemon(thread_oop());
1215   }
1216 
1217   if (HAS_PENDING_EXCEPTION) {
1218     return;
1219   }
1220 
1221   Klass* group =  SystemDictionary::ThreadGroup_klass();
1222   Handle threadObj(THREAD, this->threadObj());
1223 
1224   JavaCalls::call_special(&result,
1225                           thread_group,
1226                           group,
1227                           vmSymbols::add_method_name(),
1228                           vmSymbols::thread_void_signature(),
1229                           threadObj,          // Arg 1
1230                           THREAD);
1231 }
1232 
1233 // NamedThread --  non-JavaThread subclasses with multiple
1234 // uniquely named instances should derive from this.
1235 NamedThread::NamedThread() : Thread() {
1236   _name = NULL;
1237   _processed_thread = NULL;
1238   _gc_id = GCId::undefined();
1239 }
1240 
1241 NamedThread::~NamedThread() {
1242   if (_name != NULL) {
1243     FREE_C_HEAP_ARRAY(char, _name);
1244     _name = NULL;
1245   }
1246 }
1247 
1248 void NamedThread::set_name(const char* format, ...) {
1249   guarantee(_name == NULL, "Only get to set name once.");
1250   _name = NEW_C_HEAP_ARRAY(char, max_name_len, mtThread);
1251   guarantee(_name != NULL, "alloc failure");
1252   va_list ap;
1253   va_start(ap, format);
1254   jio_vsnprintf(_name, max_name_len, format, ap);
1255   va_end(ap);
1256 }
1257 
1258 void NamedThread::initialize_named_thread() {
1259   set_native_thread_name(name());
1260 }
1261 
1262 void NamedThread::print_on(outputStream* st) const {
1263   st->print("\"%s\" ", name());
1264   Thread::print_on(st);
1265   st->cr();
1266 }
1267 
1268 
1269 // ======= WatcherThread ========
1270 
1271 // The watcher thread exists to simulate timer interrupts.  It should
1272 // be replaced by an abstraction over whatever native support for
1273 // timer interrupts exists on the platform.
1274 
1275 WatcherThread* WatcherThread::_watcher_thread   = NULL;
1276 bool WatcherThread::_startable = false;
1277 volatile bool  WatcherThread::_should_terminate = false;
1278 
1279 WatcherThread::WatcherThread() : Thread() {
1280   assert(watcher_thread() == NULL, "we can only allocate one WatcherThread");
1281   if (os::create_thread(this, os::watcher_thread)) {
1282     _watcher_thread = this;
1283 
1284     // Set the watcher thread to the highest OS priority which should not be
1285     // used, unless a Java thread with priority java.lang.Thread.MAX_PRIORITY
1286     // is created. The only normal thread using this priority is the reference
1287     // handler thread, which runs for very short intervals only.
1288     // If the VMThread's priority is not lower than the WatcherThread profiling
1289     // will be inaccurate.
1290     os::set_priority(this, MaxPriority);
1291     if (!DisableStartThread) {
1292       os::start_thread(this);
1293     }
1294   }
1295 }
1296 
1297 int WatcherThread::sleep() const {
1298   // The WatcherThread does not participate in the safepoint protocol
1299   // for the PeriodicTask_lock because it is not a JavaThread.
1300   MutexLockerEx ml(PeriodicTask_lock, Mutex::_no_safepoint_check_flag);
1301 
1302   if (_should_terminate) {
1303     // check for termination before we do any housekeeping or wait
1304     return 0;  // we did not sleep.
1305   }
1306 
1307   // remaining will be zero if there are no tasks,
1308   // causing the WatcherThread to sleep until a task is
1309   // enrolled
1310   int remaining = PeriodicTask::time_to_wait();
1311   int time_slept = 0;
1312 
1313   // we expect this to timeout - we only ever get unparked when
1314   // we should terminate or when a new task has been enrolled
1315   OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
1316 
1317   jlong time_before_loop = os::javaTimeNanos();
1318 
1319   while (true) {
1320     bool timedout = PeriodicTask_lock->wait(Mutex::_no_safepoint_check_flag,
1321                                             remaining);
1322     jlong now = os::javaTimeNanos();
1323 
1324     if (remaining == 0) {
1325       // if we didn't have any tasks we could have waited for a long time
1326       // consider the time_slept zero and reset time_before_loop
1327       time_slept = 0;
1328       time_before_loop = now;
1329     } else {
1330       // need to recalculate since we might have new tasks in _tasks
1331       time_slept = (int) ((now - time_before_loop) / 1000000);
1332     }
1333 
1334     // Change to task list or spurious wakeup of some kind
1335     if (timedout || _should_terminate) {
1336       break;
1337     }
1338 
1339     remaining = PeriodicTask::time_to_wait();
1340     if (remaining == 0) {
1341       // Last task was just disenrolled so loop around and wait until
1342       // another task gets enrolled
1343       continue;
1344     }
1345 
1346     remaining -= time_slept;
1347     if (remaining <= 0) {
1348       break;
1349     }
1350   }
1351 
1352   return time_slept;
1353 }
1354 
1355 void WatcherThread::run() {
1356   assert(this == watcher_thread(), "just checking");
1357 
1358   this->record_stack_base_and_size();
1359   this->set_native_thread_name(this->name());
1360   this->set_active_handles(JNIHandleBlock::allocate_block());
1361   while (true) {
1362     assert(watcher_thread() == Thread::current(), "thread consistency check");
1363     assert(watcher_thread() == this, "thread consistency check");
1364 
1365     // Calculate how long it'll be until the next PeriodicTask work
1366     // should be done, and sleep that amount of time.
1367     int time_waited = sleep();
1368 
1369     if (VMError::is_error_reported()) {
1370       // A fatal error has happened, the error handler(VMError::report_and_die)
1371       // should abort JVM after creating an error log file. However in some
1372       // rare cases, the error handler itself might deadlock. Here periodically
1373       // check for error reporting timeouts, and if it happens, just proceed to
1374       // abort the VM.
1375 
1376       // This code is in WatcherThread because WatcherThread wakes up
1377       // periodically so the fatal error handler doesn't need to do anything;
1378       // also because the WatcherThread is less likely to crash than other
1379       // threads.
1380 
1381       for (;;) {
1382         // Note: we use naked sleep in this loop because we want to avoid using
1383         // any kind of VM infrastructure which may be broken at this point.
1384         if (VMError::check_timeout()) {
1385           // We hit error reporting timeout. Error reporting was interrupted and
1386           // will be wrapping things up now (closing files etc). Give it some more
1387           // time, then quit the VM.
1388           os::naked_short_sleep(200);
1389           // Print a message to stderr.
1390           fdStream err(defaultStream::output_fd());
1391           err.print_raw_cr("# [ timer expired, abort... ]");
1392           // skip atexit/vm_exit/vm_abort hooks
1393           os::die();
1394         }
1395 
1396         // Wait a second, then recheck for timeout.
1397         os::naked_short_sleep(999);
1398       }
1399     }
1400 
1401     if (_should_terminate) {
1402       // check for termination before posting the next tick
1403       break;
1404     }
1405 
1406     PeriodicTask::real_time_tick(time_waited);
1407   }
1408 
1409   // Signal that it is terminated
1410   {
1411     MutexLockerEx mu(Terminator_lock, Mutex::_no_safepoint_check_flag);
1412     _watcher_thread = NULL;
1413     Terminator_lock->notify();
1414   }
1415 }
1416 
1417 void WatcherThread::start() {
1418   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1419 
1420   if (watcher_thread() == NULL && _startable) {
1421     _should_terminate = false;
1422     // Create the single instance of WatcherThread
1423     new WatcherThread();
1424   }
1425 }
1426 
1427 void WatcherThread::make_startable() {
1428   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1429   _startable = true;
1430 }
1431 
1432 void WatcherThread::stop() {
1433   {
1434     // Follow normal safepoint aware lock enter protocol since the
1435     // WatcherThread is stopped by another JavaThread.
1436     MutexLocker ml(PeriodicTask_lock);
1437     _should_terminate = true;
1438 
1439     WatcherThread* watcher = watcher_thread();
1440     if (watcher != NULL) {
1441       // unpark the WatcherThread so it can see that it should terminate
1442       watcher->unpark();
1443     }
1444   }
1445 
1446   MutexLocker mu(Terminator_lock);
1447 
1448   while (watcher_thread() != NULL) {
1449     // This wait should make safepoint checks, wait without a timeout,
1450     // and wait as a suspend-equivalent condition.
1451     Terminator_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
1452                           Mutex::_as_suspend_equivalent_flag);
1453   }
1454 }
1455 
1456 void WatcherThread::unpark() {
1457   assert(PeriodicTask_lock->owned_by_self(), "PeriodicTask_lock required");
1458   PeriodicTask_lock->notify();
1459 }
1460 
1461 void WatcherThread::print_on(outputStream* st) const {
1462   st->print("\"%s\" ", name());
1463   Thread::print_on(st);
1464   st->cr();
1465 }
1466 
1467 // ======= JavaThread ========
1468 
1469 #if INCLUDE_JVMCI
1470 
1471 jlong* JavaThread::_jvmci_old_thread_counters;
1472 
1473 bool jvmci_counters_include(JavaThread* thread) {
1474   oop threadObj = thread->threadObj();
1475   return !JVMCICountersExcludeCompiler || !thread->is_Compiler_thread();
1476 }
1477 
1478 void JavaThread::collect_counters(typeArrayOop array) {
1479   if (JVMCICounterSize > 0) {
1480     // dcubed - Looks like the Threads_lock is for stable access
1481     // to _jvmci_old_thread_counters and _jvmci_counters.
1482     MutexLocker tl(Threads_lock);
1483     JavaThreadIteratorWithHandle jtiwh;
1484     for (int i = 0; i < array->length(); i++) {
1485       array->long_at_put(i, _jvmci_old_thread_counters[i]);
1486     }
1487     for (; JavaThread *tp = jtiwh.next(); ) {
1488       if (jvmci_counters_include(tp)) {
1489         for (int i = 0; i < array->length(); i++) {
1490           array->long_at_put(i, array->long_at(i) + tp->_jvmci_counters[i]);
1491         }
1492       }
1493     }
1494   }
1495 }
1496 
1497 #endif // INCLUDE_JVMCI
1498 
1499 // A JavaThread is a normal Java thread
1500 
1501 void JavaThread::initialize() {
1502   // Initialize fields
1503 
1504   set_saved_exception_pc(NULL);
1505   set_threadObj(NULL);
1506   _anchor.clear();
1507   set_entry_point(NULL);
1508   set_jni_functions(jni_functions());
1509   set_callee_target(NULL);
1510   set_vm_result(NULL);
1511   set_vm_result_2(NULL);
1512   set_vframe_array_head(NULL);
1513   set_vframe_array_last(NULL);
1514   set_deferred_locals(NULL);
1515   set_deopt_mark(NULL);
1516   set_deopt_compiled_method(NULL);
1517   clear_must_deopt_id();
1518   set_monitor_chunks(NULL);
1519   set_next(NULL);
1520   _on_thread_list = false;
1521   set_thread_state(_thread_new);
1522   _terminated = _not_terminated;
1523   _privileged_stack_top = NULL;
1524   _array_for_gc = NULL;
1525   _suspend_equivalent = false;
1526   _in_deopt_handler = 0;
1527   _doing_unsafe_access = false;
1528   _stack_guard_state = stack_guard_unused;
1529 #if INCLUDE_JVMCI
1530   _pending_monitorenter = false;
1531   _pending_deoptimization = -1;
1532   _pending_failed_speculation = NULL;
1533   _pending_transfer_to_interpreter = false;
1534   _adjusting_comp_level = false;
1535   _jvmci._alternate_call_target = NULL;
1536   assert(_jvmci._implicit_exception_pc == NULL, "must be");
1537   if (JVMCICounterSize > 0) {
1538     _jvmci_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
1539     memset(_jvmci_counters, 0, sizeof(jlong) * JVMCICounterSize);
1540   } else {
1541     _jvmci_counters = NULL;
1542   }
1543 #endif // INCLUDE_JVMCI
1544   _reserved_stack_activation = NULL;  // stack base not known yet
1545   (void)const_cast<oop&>(_exception_oop = oop(NULL));
1546   _exception_pc  = 0;
1547   _exception_handler_pc = 0;
1548   _is_method_handle_return = 0;
1549   _jvmti_thread_state= NULL;
1550   _should_post_on_exceptions_flag = JNI_FALSE;
1551   _jvmti_get_loaded_classes_closure = NULL;
1552   _interp_only_mode    = 0;
1553   _special_runtime_exit_condition = _no_async_condition;
1554   _pending_async_exception = NULL;
1555   _thread_stat = NULL;
1556   _thread_stat = new ThreadStatistics();
1557   _blocked_on_compilation = false;
1558   _jni_active_critical = 0;
1559   _pending_jni_exception_check_fn = NULL;
1560   _do_not_unlock_if_synchronized = false;
1561   _cached_monitor_info = NULL;
1562   _parker = Parker::Allocate(this);
1563 
1564 #ifndef PRODUCT
1565   _jmp_ring_index = 0;
1566   for (int ji = 0; ji < jump_ring_buffer_size; ji++) {
1567     record_jump(NULL, NULL, NULL, 0);
1568   }
1569 #endif // PRODUCT
1570 
1571   // Setup safepoint state info for this thread
1572   ThreadSafepointState::create(this);
1573 
1574   debug_only(_java_call_counter = 0);
1575 
1576   // JVMTI PopFrame support
1577   _popframe_condition = popframe_inactive;
1578   _popframe_preserved_args = NULL;
1579   _popframe_preserved_args_size = 0;
1580   _frames_to_pop_failed_realloc = 0;
1581 
1582   pd_initialize();
1583 }
1584 
1585 #if INCLUDE_ALL_GCS
1586 SATBMarkQueueSet JavaThread::_satb_mark_queue_set;
1587 DirtyCardQueueSet JavaThread::_dirty_card_queue_set;
1588 #endif // INCLUDE_ALL_GCS
1589 
1590 JavaThread::JavaThread(bool is_attaching_via_jni) :
1591                        Thread()
1592 #if INCLUDE_ALL_GCS
1593                        , _satb_mark_queue(&_satb_mark_queue_set),
1594                        _dirty_card_queue(&_dirty_card_queue_set)
1595 #endif // INCLUDE_ALL_GCS
1596 {
1597   initialize();
1598   if (is_attaching_via_jni) {
1599     _jni_attach_state = _attaching_via_jni;
1600   } else {
1601     _jni_attach_state = _not_attaching_via_jni;
1602   }
1603   assert(deferred_card_mark().is_empty(), "Default MemRegion ctor");
1604 }
1605 
1606 bool JavaThread::reguard_stack(address cur_sp) {
1607   if (_stack_guard_state != stack_guard_yellow_reserved_disabled
1608       && _stack_guard_state != stack_guard_reserved_disabled) {
1609     return true; // Stack already guarded or guard pages not needed.
1610   }
1611 
1612   if (register_stack_overflow()) {
1613     // For those architectures which have separate register and
1614     // memory stacks, we must check the register stack to see if
1615     // it has overflowed.
1616     return false;
1617   }
1618 
1619   // Java code never executes within the yellow zone: the latter is only
1620   // there to provoke an exception during stack banging.  If java code
1621   // is executing there, either StackShadowPages should be larger, or
1622   // some exception code in c1, c2 or the interpreter isn't unwinding
1623   // when it should.
1624   guarantee(cur_sp > stack_reserved_zone_base(),
1625             "not enough space to reguard - increase StackShadowPages");
1626   if (_stack_guard_state == stack_guard_yellow_reserved_disabled) {
1627     enable_stack_yellow_reserved_zone();
1628     if (reserved_stack_activation() != stack_base()) {
1629       set_reserved_stack_activation(stack_base());
1630     }
1631   } else if (_stack_guard_state == stack_guard_reserved_disabled) {
1632     set_reserved_stack_activation(stack_base());
1633     enable_stack_reserved_zone();
1634   }
1635   return true;
1636 }
1637 
1638 bool JavaThread::reguard_stack(void) {
1639   return reguard_stack(os::current_stack_pointer());
1640 }
1641 
1642 
1643 void JavaThread::block_if_vm_exited() {
1644   if (_terminated == _vm_exited) {
1645     // _vm_exited is set at safepoint, and Threads_lock is never released
1646     // we will block here forever
1647     Threads_lock->lock_without_safepoint_check();
1648     ShouldNotReachHere();
1649   }
1650 }
1651 
1652 
1653 // Remove this ifdef when C1 is ported to the compiler interface.
1654 static void compiler_thread_entry(JavaThread* thread, TRAPS);
1655 static void sweeper_thread_entry(JavaThread* thread, TRAPS);
1656 
1657 JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
1658                        Thread()
1659 #if INCLUDE_ALL_GCS
1660                        , _satb_mark_queue(&_satb_mark_queue_set),
1661                        _dirty_card_queue(&_dirty_card_queue_set)
1662 #endif // INCLUDE_ALL_GCS
1663 {
1664   initialize();
1665   _jni_attach_state = _not_attaching_via_jni;
1666   set_entry_point(entry_point);
1667   // Create the native thread itself.
1668   // %note runtime_23
1669   os::ThreadType thr_type = os::java_thread;
1670   thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
1671                                                      os::java_thread;
1672   os::create_thread(this, thr_type, stack_sz);
1673   // The _osthread may be NULL here because we ran out of memory (too many threads active).
1674   // We need to throw and OutOfMemoryError - however we cannot do this here because the caller
1675   // may hold a lock and all locks must be unlocked before throwing the exception (throwing
1676   // the exception consists of creating the exception object & initializing it, initialization
1677   // will leave the VM via a JavaCall and then all locks must be unlocked).
1678   //
1679   // The thread is still suspended when we reach here. Thread must be explicit started
1680   // by creator! Furthermore, the thread must also explicitly be added to the Threads list
1681   // by calling Threads:add. The reason why this is not done here, is because the thread
1682   // object must be fully initialized (take a look at JVM_Start)
1683 }
1684 
1685 JavaThread::~JavaThread() {
1686 
1687   // JSR166 -- return the parker to the free list
1688   Parker::Release(_parker);
1689   _parker = NULL;
1690 
1691   // Free any remaining  previous UnrollBlock
1692   vframeArray* old_array = vframe_array_last();
1693 
1694   if (old_array != NULL) {
1695     Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
1696     old_array->set_unroll_block(NULL);
1697     delete old_info;
1698     delete old_array;
1699   }
1700 
1701   GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred = deferred_locals();
1702   if (deferred != NULL) {
1703     // This can only happen if thread is destroyed before deoptimization occurs.
1704     assert(deferred->length() != 0, "empty array!");
1705     do {
1706       jvmtiDeferredLocalVariableSet* dlv = deferred->at(0);
1707       deferred->remove_at(0);
1708       // individual jvmtiDeferredLocalVariableSet are CHeapObj's
1709       delete dlv;
1710     } while (deferred->length() != 0);
1711     delete deferred;
1712   }
1713 
1714   // All Java related clean up happens in exit
1715   ThreadSafepointState::destroy(this);
1716   if (_thread_stat != NULL) delete _thread_stat;
1717 
1718 #if INCLUDE_JVMCI
1719   if (JVMCICounterSize > 0) {
1720     if (jvmci_counters_include(this)) {
1721       for (int i = 0; i < JVMCICounterSize; i++) {
1722         _jvmci_old_thread_counters[i] += _jvmci_counters[i];
1723       }
1724     }
1725     FREE_C_HEAP_ARRAY(jlong, _jvmci_counters);
1726   }
1727 #endif // INCLUDE_JVMCI
1728 }
1729 
1730 
1731 // The first routine called by a new Java thread
1732 void JavaThread::run() {
1733   // initialize thread-local alloc buffer related fields
1734   this->initialize_tlab();
1735 
1736   // used to test validity of stack trace backs
1737   this->record_base_of_stack_pointer();
1738 
1739   // Record real stack base and size.
1740   this->record_stack_base_and_size();
1741 
1742   this->create_stack_guard_pages();
1743 
1744   this->cache_global_variables();
1745 
1746   // Thread is now sufficient initialized to be handled by the safepoint code as being
1747   // in the VM. Change thread state from _thread_new to _thread_in_vm
1748   ThreadStateTransition::transition_and_fence(this, _thread_new, _thread_in_vm);
1749 
1750   assert(JavaThread::current() == this, "sanity check");
1751   assert(!Thread::current()->owns_locks(), "sanity check");
1752 
1753   DTRACE_THREAD_PROBE(start, this);
1754 
1755   // This operation might block. We call that after all safepoint checks for a new thread has
1756   // been completed.
1757   this->set_active_handles(JNIHandleBlock::allocate_block());
1758 
1759   if (JvmtiExport::should_post_thread_life()) {
1760     JvmtiExport::post_thread_start(this);
1761   }
1762 
1763   EventThreadStart event;
1764   if (event.should_commit()) {
1765     event.set_thread(THREAD_TRACE_ID(this));
1766     event.commit();
1767   }
1768 
1769   // We call another function to do the rest so we are sure that the stack addresses used
1770   // from there will be lower than the stack base just computed
1771   thread_main_inner();
1772 
1773   // Note, thread is no longer valid at this point!
1774 }
1775 
1776 
1777 void JavaThread::thread_main_inner() {
1778   assert(JavaThread::current() == this, "sanity check");
1779   assert(this->threadObj() != NULL, "just checking");
1780 
1781   // Execute thread entry point unless this thread has a pending exception
1782   // or has been stopped before starting.
1783   // Note: Due to JVM_StopThread we can have pending exceptions already!
1784   if (!this->has_pending_exception() &&
1785       !java_lang_Thread::is_stillborn(this->threadObj())) {
1786     {
1787       ResourceMark rm(this);
1788       this->set_native_thread_name(this->get_thread_name());
1789     }
1790     HandleMark hm(this);
1791     this->entry_point()(this, this);
1792   }
1793 
1794   DTRACE_THREAD_PROBE(stop, this);
1795 
1796   this->exit(false);
1797   this->smr_delete();
1798 }
1799 
1800 
1801 static void ensure_join(JavaThread* thread) {
1802   // We do not need to grab the Threads_lock, since we are operating on ourself.
1803   Handle threadObj(thread, thread->threadObj());
1804   assert(threadObj.not_null(), "java thread object must exist");
1805   ObjectLocker lock(threadObj, thread);
1806   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1807   thread->clear_pending_exception();
1808   // Thread is exiting. So set thread_status field in  java.lang.Thread class to TERMINATED.
1809   java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
1810   // Clear the native thread instance - this makes isAlive return false and allows the join()
1811   // to complete once we've done the notify_all below
1812   java_lang_Thread::set_thread(threadObj(), NULL);
1813   lock.notify_all(thread);
1814   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1815   thread->clear_pending_exception();
1816 }
1817 
1818 
1819 // For any new cleanup additions, please check to see if they need to be applied to
1820 // cleanup_failed_attach_current_thread as well.
1821 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
1822   assert(this == JavaThread::current(), "thread consistency check");
1823 
1824   elapsedTimer _timer_exit_phase1;
1825   elapsedTimer _timer_exit_phase2;
1826   elapsedTimer _timer_exit_phase3;
1827   elapsedTimer _timer_exit_phase4;
1828 
1829   if (log_is_enabled(Debug, os, thread, timer)) {
1830     _timer_exit_phase1.start();
1831   }
1832 
1833   HandleMark hm(this);
1834   Handle uncaught_exception(this, this->pending_exception());
1835   this->clear_pending_exception();
1836   Handle threadObj(this, this->threadObj());
1837   assert(threadObj.not_null(), "Java thread object should be created");
1838 
1839   // FIXIT: This code should be moved into else part, when reliable 1.2/1.3 check is in place
1840   {
1841     EXCEPTION_MARK;
1842 
1843     CLEAR_PENDING_EXCEPTION;
1844   }
1845   if (!destroy_vm) {
1846     if (uncaught_exception.not_null()) {
1847       EXCEPTION_MARK;
1848       // Call method Thread.dispatchUncaughtException().
1849       Klass* thread_klass = SystemDictionary::Thread_klass();
1850       JavaValue result(T_VOID);
1851       JavaCalls::call_virtual(&result,
1852                               threadObj, thread_klass,
1853                               vmSymbols::dispatchUncaughtException_name(),
1854                               vmSymbols::throwable_void_signature(),
1855                               uncaught_exception,
1856                               THREAD);
1857       if (HAS_PENDING_EXCEPTION) {
1858         ResourceMark rm(this);
1859         jio_fprintf(defaultStream::error_stream(),
1860                     "\nException: %s thrown from the UncaughtExceptionHandler"
1861                     " in thread \"%s\"\n",
1862                     pending_exception()->klass()->external_name(),
1863                     get_thread_name());
1864         CLEAR_PENDING_EXCEPTION;
1865       }
1866     }
1867 
1868     // Called before the java thread exit since we want to read info
1869     // from java_lang_Thread object
1870     EventThreadEnd event;
1871     if (event.should_commit()) {
1872       event.set_thread(THREAD_TRACE_ID(this));
1873       event.commit();
1874     }
1875 
1876     // Call after last event on thread
1877     EVENT_THREAD_EXIT(this);
1878 
1879     // Call Thread.exit(). We try 3 times in case we got another Thread.stop during
1880     // the execution of the method. If that is not enough, then we don't really care. Thread.stop
1881     // is deprecated anyhow.
1882     if (!is_Compiler_thread()) {
1883       int count = 3;
1884       while (java_lang_Thread::threadGroup(threadObj()) != NULL && (count-- > 0)) {
1885         EXCEPTION_MARK;
1886         JavaValue result(T_VOID);
1887         Klass* thread_klass = SystemDictionary::Thread_klass();
1888         JavaCalls::call_virtual(&result,
1889                                 threadObj, thread_klass,
1890                                 vmSymbols::exit_method_name(),
1891                                 vmSymbols::void_method_signature(),
1892                                 THREAD);
1893         CLEAR_PENDING_EXCEPTION;
1894       }
1895     }
1896     // notify JVMTI
1897     if (JvmtiExport::should_post_thread_life()) {
1898       JvmtiExport::post_thread_end(this);
1899     }
1900 
1901     // We have notified the agents that we are exiting, before we go on,
1902     // we must check for a pending external suspend request and honor it
1903     // in order to not surprise the thread that made the suspend request.
1904     while (true) {
1905       {
1906         MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
1907         if (!is_external_suspend()) {
1908           set_terminated(_thread_exiting);
1909           ThreadService::current_thread_exiting(this);
1910           break;
1911         }
1912         // Implied else:
1913         // Things get a little tricky here. We have a pending external
1914         // suspend request, but we are holding the SR_lock so we
1915         // can't just self-suspend. So we temporarily drop the lock
1916         // and then self-suspend.
1917       }
1918 
1919       ThreadBlockInVM tbivm(this);
1920       java_suspend_self();
1921 
1922       // We're done with this suspend request, but we have to loop around
1923       // and check again. Eventually we will get SR_lock without a pending
1924       // external suspend request and will be able to mark ourselves as
1925       // exiting.
1926     }
1927     // no more external suspends are allowed at this point
1928   } else {
1929     // before_exit() has already posted JVMTI THREAD_END events
1930   }
1931 
1932   if (log_is_enabled(Debug, os, thread, timer)) {
1933     _timer_exit_phase1.stop();
1934     _timer_exit_phase2.start();
1935   }
1936   // Notify waiters on thread object. This has to be done after exit() is called
1937   // on the thread (if the thread is the last thread in a daemon ThreadGroup the
1938   // group should have the destroyed bit set before waiters are notified).
1939   ensure_join(this);
1940   assert(!this->has_pending_exception(), "ensure_join should have cleared");
1941 
1942   if (log_is_enabled(Debug, os, thread, timer)) {
1943     _timer_exit_phase2.stop();
1944     _timer_exit_phase3.start();
1945   }
1946   // 6282335 JNI DetachCurrentThread spec states that all Java monitors
1947   // held by this thread must be released. The spec does not distinguish
1948   // between JNI-acquired and regular Java monitors. We can only see
1949   // regular Java monitors here if monitor enter-exit matching is broken.
1950   //
1951   // Optionally release any monitors for regular JavaThread exits. This
1952   // is provided as a work around for any bugs in monitor enter-exit
1953   // matching. This can be expensive so it is not enabled by default.
1954   //
1955   // ensure_join() ignores IllegalThreadStateExceptions, and so does
1956   // ObjectSynchronizer::release_monitors_owned_by_thread().
1957   if (exit_type == jni_detach || ObjectMonitor::Knob_ExitRelease) {
1958     // Sanity check even though JNI DetachCurrentThread() would have
1959     // returned JNI_ERR if there was a Java frame. JavaThread exit
1960     // should be done executing Java code by the time we get here.
1961     assert(!this->has_last_Java_frame(),
1962            "should not have a Java frame when detaching or exiting");
1963     ObjectSynchronizer::release_monitors_owned_by_thread(this);
1964     assert(!this->has_pending_exception(), "release_monitors should have cleared");
1965   }
1966 
1967   // These things needs to be done while we are still a Java Thread. Make sure that thread
1968   // is in a consistent state, in case GC happens
1969   assert(_privileged_stack_top == NULL, "must be NULL when we get here");
1970 
1971   if (active_handles() != NULL) {
1972     JNIHandleBlock* block = active_handles();
1973     set_active_handles(NULL);
1974     JNIHandleBlock::release_block(block);
1975   }
1976 
1977   if (free_handle_block() != NULL) {
1978     JNIHandleBlock* block = free_handle_block();
1979     set_free_handle_block(NULL);
1980     JNIHandleBlock::release_block(block);
1981   }
1982 
1983   // These have to be removed while this is still a valid thread.
1984   remove_stack_guard_pages();
1985 
1986   if (UseTLAB) {
1987     tlab().make_parsable(true);  // retire TLAB
1988   }
1989 
1990   if (JvmtiEnv::environments_might_exist()) {
1991     JvmtiExport::cleanup_thread(this);
1992   }
1993 
1994   // We must flush any deferred card marks before removing a thread from
1995   // the list of active threads.
1996   Universe::heap()->flush_deferred_store_barrier(this);
1997   assert(deferred_card_mark().is_empty(), "Should have been flushed");
1998 
1999 #if INCLUDE_ALL_GCS
2000   // We must flush the G1-related buffers before removing a thread
2001   // from the list of active threads. We must do this after any deferred
2002   // card marks have been flushed (above) so that any entries that are
2003   // added to the thread's dirty card queue as a result are not lost.
2004   if (UseG1GC) {
2005     flush_barrier_queues();
2006   }
2007 #endif // INCLUDE_ALL_GCS
2008 
2009   log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").",
2010     exit_type == JavaThread::normal_exit ? "exiting" : "detaching",
2011     os::current_thread_id());
2012 
2013   if (log_is_enabled(Debug, os, thread, timer)) {
2014     _timer_exit_phase3.stop();
2015     _timer_exit_phase4.start();
2016   }
2017   // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
2018   Threads::remove(this);
2019 
2020   if (log_is_enabled(Debug, os, thread, timer)) {
2021     _timer_exit_phase4.stop();
2022     ResourceMark rm(this);
2023     log_debug(os, thread, timer)("name='%s'"
2024                                  ", exit-phase1=" JLONG_FORMAT
2025                                  ", exit-phase2=" JLONG_FORMAT
2026                                  ", exit-phase3=" JLONG_FORMAT
2027                                  ", exit-phase4=" JLONG_FORMAT,
2028                                  get_thread_name(),
2029                                  _timer_exit_phase1.milliseconds(),
2030                                  _timer_exit_phase2.milliseconds(),
2031                                  _timer_exit_phase3.milliseconds(),
2032                                  _timer_exit_phase4.milliseconds());
2033   }
2034 }
2035 
2036 #if INCLUDE_ALL_GCS
2037 // Flush G1-related queues.
2038 void JavaThread::flush_barrier_queues() {
2039   satb_mark_queue().flush();
2040   dirty_card_queue().flush();
2041 }
2042 
2043 void JavaThread::initialize_queues() {
2044   assert(!SafepointSynchronize::is_at_safepoint(),
2045          "we should not be at a safepoint");
2046 
2047   SATBMarkQueue& satb_queue = satb_mark_queue();
2048   SATBMarkQueueSet& satb_queue_set = satb_mark_queue_set();
2049   // The SATB queue should have been constructed with its active
2050   // field set to false.
2051   assert(!satb_queue.is_active(), "SATB queue should not be active");
2052   assert(satb_queue.is_empty(), "SATB queue should be empty");
2053   // If we are creating the thread during a marking cycle, we should
2054   // set the active field of the SATB queue to true.
2055   if (satb_queue_set.is_active()) {
2056     satb_queue.set_active(true);
2057   }
2058 
2059   DirtyCardQueue& dirty_queue = dirty_card_queue();
2060   // The dirty card queue should have been constructed with its
2061   // active field set to true.
2062   assert(dirty_queue.is_active(), "dirty card queue should be active");
2063 }
2064 #endif // INCLUDE_ALL_GCS
2065 
2066 void JavaThread::cleanup_failed_attach_current_thread() {
2067   if (active_handles() != NULL) {
2068     JNIHandleBlock* block = active_handles();
2069     set_active_handles(NULL);
2070     JNIHandleBlock::release_block(block);
2071   }
2072 
2073   if (free_handle_block() != NULL) {
2074     JNIHandleBlock* block = free_handle_block();
2075     set_free_handle_block(NULL);
2076     JNIHandleBlock::release_block(block);
2077   }
2078 
2079   // These have to be removed while this is still a valid thread.
2080   remove_stack_guard_pages();
2081 
2082   if (UseTLAB) {
2083     tlab().make_parsable(true);  // retire TLAB, if any
2084   }
2085 
2086 #if INCLUDE_ALL_GCS
2087   if (UseG1GC) {
2088     flush_barrier_queues();
2089   }
2090 #endif // INCLUDE_ALL_GCS
2091 
2092   Threads::remove(this);
2093   this->smr_delete();
2094 }
2095 
2096 
2097 
2098 
2099 JavaThread* JavaThread::active() {
2100   Thread* thread = Thread::current();
2101   if (thread->is_Java_thread()) {
2102     return (JavaThread*) thread;
2103   } else {
2104     assert(thread->is_VM_thread(), "this must be a vm thread");
2105     VM_Operation* op = ((VMThread*) thread)->vm_operation();
2106     JavaThread *ret=op == NULL ? NULL : (JavaThread *)op->calling_thread();
2107     assert(ret->is_Java_thread(), "must be a Java thread");
2108     return ret;
2109   }
2110 }
2111 
2112 bool JavaThread::is_lock_owned(address adr) const {
2113   if (Thread::is_lock_owned(adr)) return true;
2114 
2115   for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2116     if (chunk->contains(adr)) return true;
2117   }
2118 
2119   return false;
2120 }
2121 
2122 
2123 void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
2124   chunk->set_next(monitor_chunks());
2125   set_monitor_chunks(chunk);
2126 }
2127 
2128 void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
2129   guarantee(monitor_chunks() != NULL, "must be non empty");
2130   if (monitor_chunks() == chunk) {
2131     set_monitor_chunks(chunk->next());
2132   } else {
2133     MonitorChunk* prev = monitor_chunks();
2134     while (prev->next() != chunk) prev = prev->next();
2135     prev->set_next(chunk->next());
2136   }
2137 }
2138 
2139 // JVM support.
2140 
2141 // Note: this function shouldn't block if it's called in
2142 // _thread_in_native_trans state (such as from
2143 // check_special_condition_for_native_trans()).
2144 void JavaThread::check_and_handle_async_exceptions(bool check_unsafe_error) {
2145 
2146   if (has_last_Java_frame() && has_async_condition()) {
2147     // If we are at a polling page safepoint (not a poll return)
2148     // then we must defer async exception because live registers
2149     // will be clobbered by the exception path. Poll return is
2150     // ok because the call we a returning from already collides
2151     // with exception handling registers and so there is no issue.
2152     // (The exception handling path kills call result registers but
2153     //  this is ok since the exception kills the result anyway).
2154 
2155     if (is_at_poll_safepoint()) {
2156       // if the code we are returning to has deoptimized we must defer
2157       // the exception otherwise live registers get clobbered on the
2158       // exception path before deoptimization is able to retrieve them.
2159       //
2160       RegisterMap map(this, false);
2161       frame caller_fr = last_frame().sender(&map);
2162       assert(caller_fr.is_compiled_frame(), "what?");
2163       if (caller_fr.is_deoptimized_frame()) {
2164         log_info(exceptions)("deferred async exception at compiled safepoint");
2165         return;
2166       }
2167     }
2168   }
2169 
2170   JavaThread::AsyncRequests condition = clear_special_runtime_exit_condition();
2171   if (condition == _no_async_condition) {
2172     // Conditions have changed since has_special_runtime_exit_condition()
2173     // was called:
2174     // - if we were here only because of an external suspend request,
2175     //   then that was taken care of above (or cancelled) so we are done
2176     // - if we were here because of another async request, then it has
2177     //   been cleared between the has_special_runtime_exit_condition()
2178     //   and now so again we are done
2179     return;
2180   }
2181 
2182   // Check for pending async. exception
2183   if (_pending_async_exception != NULL) {
2184     // Only overwrite an already pending exception, if it is not a threadDeath.
2185     if (!has_pending_exception() || !pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())) {
2186 
2187       // We cannot call Exceptions::_throw(...) here because we cannot block
2188       set_pending_exception(_pending_async_exception, __FILE__, __LINE__);
2189 
2190       LogTarget(Info, exceptions) lt;
2191       if (lt.is_enabled()) {
2192         ResourceMark rm;
2193         LogStream ls(lt);
2194         ls.print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", p2i(this));
2195           if (has_last_Java_frame()) {
2196             frame f = last_frame();
2197            ls.print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", p2i(f.pc()), p2i(f.sp()));
2198           }
2199         ls.print_cr(" of type: %s", _pending_async_exception->klass()->external_name());
2200       }
2201       _pending_async_exception = NULL;
2202       clear_has_async_exception();
2203     }
2204   }
2205 
2206   if (check_unsafe_error &&
2207       condition == _async_unsafe_access_error && !has_pending_exception()) {
2208     condition = _no_async_condition;  // done
2209     switch (thread_state()) {
2210     case _thread_in_vm: {
2211       JavaThread* THREAD = this;
2212       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2213     }
2214     case _thread_in_native: {
2215       ThreadInVMfromNative tiv(this);
2216       JavaThread* THREAD = this;
2217       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
2218     }
2219     case _thread_in_Java: {
2220       ThreadInVMfromJava tiv(this);
2221       JavaThread* THREAD = this;
2222       THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in a recent unsafe memory access operation in compiled Java code");
2223     }
2224     default:
2225       ShouldNotReachHere();
2226     }
2227   }
2228 
2229   assert(condition == _no_async_condition || has_pending_exception() ||
2230          (!check_unsafe_error && condition == _async_unsafe_access_error),
2231          "must have handled the async condition, if no exception");
2232 }
2233 
2234 void JavaThread::handle_special_runtime_exit_condition(bool check_asyncs) {
2235   //
2236   // Check for pending external suspend. Internal suspend requests do
2237   // not use handle_special_runtime_exit_condition().
2238   // If JNIEnv proxies are allowed, don't self-suspend if the target
2239   // thread is not the current thread. In older versions of jdbx, jdbx
2240   // threads could call into the VM with another thread's JNIEnv so we
2241   // can be here operating on behalf of a suspended thread (4432884).
2242   bool do_self_suspend = is_external_suspend_with_lock();
2243   if (do_self_suspend && (!AllowJNIEnvProxy || this == JavaThread::current())) {
2244     //
2245     // Because thread is external suspended the safepoint code will count
2246     // thread as at a safepoint. This can be odd because we can be here
2247     // as _thread_in_Java which would normally transition to _thread_blocked
2248     // at a safepoint. We would like to mark the thread as _thread_blocked
2249     // before calling java_suspend_self like all other callers of it but
2250     // we must then observe proper safepoint protocol. (We can't leave
2251     // _thread_blocked with a safepoint in progress). However we can be
2252     // here as _thread_in_native_trans so we can't use a normal transition
2253     // constructor/destructor pair because they assert on that type of
2254     // transition. We could do something like:
2255     //
2256     // JavaThreadState state = thread_state();
2257     // set_thread_state(_thread_in_vm);
2258     // {
2259     //   ThreadBlockInVM tbivm(this);
2260     //   java_suspend_self()
2261     // }
2262     // set_thread_state(_thread_in_vm_trans);
2263     // if (safepoint) block;
2264     // set_thread_state(state);
2265     //
2266     // but that is pretty messy. Instead we just go with the way the
2267     // code has worked before and note that this is the only path to
2268     // java_suspend_self that doesn't put the thread in _thread_blocked
2269     // mode.
2270 
2271     frame_anchor()->make_walkable(this);
2272     java_suspend_self();
2273 
2274     // We might be here for reasons in addition to the self-suspend request
2275     // so check for other async requests.
2276   }
2277 
2278   if (check_asyncs) {
2279     check_and_handle_async_exceptions();
2280   }
2281 #if INCLUDE_TRACE
2282   if (is_trace_suspend()) {
2283     TRACE_SUSPEND_THREAD(this);
2284   }
2285 #endif
2286 }
2287 
2288 void JavaThread::send_thread_stop(oop java_throwable)  {
2289   assert(Thread::current()->is_VM_thread(), "should be in the vm thread");
2290   assert(Threads_lock->is_locked(), "Threads_lock should be locked by safepoint code");
2291   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
2292 
2293   // Do not throw asynchronous exceptions against the compiler thread
2294   // (the compiler thread should not be a Java thread -- fix in 1.4.2)
2295   if (!can_call_java()) return;
2296 
2297   {
2298     // Actually throw the Throwable against the target Thread - however
2299     // only if there is no thread death exception installed already.
2300     if (_pending_async_exception == NULL || !_pending_async_exception->is_a(SystemDictionary::ThreadDeath_klass())) {
2301       // If the topmost frame is a runtime stub, then we are calling into
2302       // OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
2303       // must deoptimize the caller before continuing, as the compiled  exception handler table
2304       // may not be valid
2305       if (has_last_Java_frame()) {
2306         frame f = last_frame();
2307         if (f.is_runtime_frame() || f.is_safepoint_blob_frame()) {
2308           // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2309           RegisterMap reg_map(this, UseBiasedLocking);
2310           frame compiled_frame = f.sender(&reg_map);
2311           if (!StressCompiledExceptionHandlers && compiled_frame.can_be_deoptimized()) {
2312             Deoptimization::deoptimize(this, compiled_frame, &reg_map);
2313           }
2314         }
2315       }
2316 
2317       // Set async. pending exception in thread.
2318       set_pending_async_exception(java_throwable);
2319 
2320       if (log_is_enabled(Info, exceptions)) {
2321          ResourceMark rm;
2322         log_info(exceptions)("Pending Async. exception installed of type: %s",
2323                              InstanceKlass::cast(_pending_async_exception->klass())->external_name());
2324       }
2325       // for AbortVMOnException flag
2326       Exceptions::debug_check_abort(_pending_async_exception->klass()->external_name());
2327     }
2328   }
2329 
2330 
2331   // Interrupt thread so it will wake up from a potential wait()
2332   Thread::interrupt(this);
2333 }
2334 
2335 // External suspension mechanism.
2336 //
2337 // Tell the VM to suspend a thread when ever it knows that it does not hold on
2338 // to any VM_locks and it is at a transition
2339 // Self-suspension will happen on the transition out of the vm.
2340 // Catch "this" coming in from JNIEnv pointers when the thread has been freed
2341 //
2342 // Guarantees on return:
2343 //   + Target thread will not execute any new bytecode (that's why we need to
2344 //     force a safepoint)
2345 //   + Target thread will not enter any new monitors
2346 //
2347 void JavaThread::java_suspend() {
2348   ThreadsListHandle tlh;
2349   if (!tlh.includes(this) || threadObj() == NULL || is_exiting()) {
2350     return;
2351   }
2352 
2353   { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2354     if (!is_external_suspend()) {
2355       // a racing resume has cancelled us; bail out now
2356       return;
2357     }
2358 
2359     // suspend is done
2360     uint32_t debug_bits = 0;
2361     // Warning: is_ext_suspend_completed() may temporarily drop the
2362     // SR_lock to allow the thread to reach a stable thread state if
2363     // it is currently in a transient thread state.
2364     if (is_ext_suspend_completed(false /* !called_by_wait */,
2365                                  SuspendRetryDelay, &debug_bits)) {
2366       return;
2367     }
2368   }
2369 
2370   VM_ThreadSuspend vm_suspend;
2371   VMThread::execute(&vm_suspend);
2372 }
2373 
2374 // Part II of external suspension.
2375 // A JavaThread self suspends when it detects a pending external suspend
2376 // request. This is usually on transitions. It is also done in places
2377 // where continuing to the next transition would surprise the caller,
2378 // e.g., monitor entry.
2379 //
2380 // Returns the number of times that the thread self-suspended.
2381 //
2382 // Note: DO NOT call java_suspend_self() when you just want to block current
2383 //       thread. java_suspend_self() is the second stage of cooperative
2384 //       suspension for external suspend requests and should only be used
2385 //       to complete an external suspend request.
2386 //
2387 int JavaThread::java_suspend_self() {
2388   int ret = 0;
2389 
2390   // we are in the process of exiting so don't suspend
2391   if (is_exiting()) {
2392     clear_external_suspend();
2393     return ret;
2394   }
2395 
2396   assert(_anchor.walkable() ||
2397          (is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
2398          "must have walkable stack");
2399 
2400   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2401 
2402   assert(!this->is_ext_suspended(),
2403          "a thread trying to self-suspend should not already be suspended");
2404 
2405   if (this->is_suspend_equivalent()) {
2406     // If we are self-suspending as a result of the lifting of a
2407     // suspend equivalent condition, then the suspend_equivalent
2408     // flag is not cleared until we set the ext_suspended flag so
2409     // that wait_for_ext_suspend_completion() returns consistent
2410     // results.
2411     this->clear_suspend_equivalent();
2412   }
2413 
2414   // A racing resume may have cancelled us before we grabbed SR_lock
2415   // above. Or another external suspend request could be waiting for us
2416   // by the time we return from SR_lock()->wait(). The thread
2417   // that requested the suspension may already be trying to walk our
2418   // stack and if we return now, we can change the stack out from under
2419   // it. This would be a "bad thing (TM)" and cause the stack walker
2420   // to crash. We stay self-suspended until there are no more pending
2421   // external suspend requests.
2422   while (is_external_suspend()) {
2423     ret++;
2424     this->set_ext_suspended();
2425 
2426     // _ext_suspended flag is cleared by java_resume()
2427     while (is_ext_suspended()) {
2428       this->SR_lock()->wait(Mutex::_no_safepoint_check_flag);
2429     }
2430   }
2431 
2432   return ret;
2433 }
2434 
2435 #ifdef ASSERT
2436 // verify the JavaThread has not yet been published in the Threads::list, and
2437 // hence doesn't need protection from concurrent access at this stage
2438 void JavaThread::verify_not_published() {
2439   ThreadsListHandle tlh;
2440   assert(!tlh.includes(this), "JavaThread shouldn't have been published yet!");
2441 }
2442 #endif
2443 
2444 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2445 // progress or when _suspend_flags is non-zero.
2446 // Current thread needs to self-suspend if there is a suspend request and/or
2447 // block if a safepoint is in progress.
2448 // Async exception ISN'T checked.
2449 // Note only the ThreadInVMfromNative transition can call this function
2450 // directly and when thread state is _thread_in_native_trans
2451 void JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread *thread) {
2452   assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
2453 
2454   JavaThread *curJT = JavaThread::current();
2455   bool do_self_suspend = thread->is_external_suspend();
2456 
2457   assert(!curJT->has_last_Java_frame() || curJT->frame_anchor()->walkable(), "Unwalkable stack in native->vm transition");
2458 
2459   // If JNIEnv proxies are allowed, don't self-suspend if the target
2460   // thread is not the current thread. In older versions of jdbx, jdbx
2461   // threads could call into the VM with another thread's JNIEnv so we
2462   // can be here operating on behalf of a suspended thread (4432884).
2463   if (do_self_suspend && (!AllowJNIEnvProxy || curJT == thread)) {
2464     JavaThreadState state = thread->thread_state();
2465 
2466     // We mark this thread_blocked state as a suspend-equivalent so
2467     // that a caller to is_ext_suspend_completed() won't be confused.
2468     // The suspend-equivalent state is cleared by java_suspend_self().
2469     thread->set_suspend_equivalent();
2470 
2471     // If the safepoint code sees the _thread_in_native_trans state, it will
2472     // wait until the thread changes to other thread state. There is no
2473     // guarantee on how soon we can obtain the SR_lock and complete the
2474     // self-suspend request. It would be a bad idea to let safepoint wait for
2475     // too long. Temporarily change the state to _thread_blocked to
2476     // let the VM thread know that this thread is ready for GC. The problem
2477     // of changing thread state is that safepoint could happen just after
2478     // java_suspend_self() returns after being resumed, and VM thread will
2479     // see the _thread_blocked state. We must check for safepoint
2480     // after restoring the state and make sure we won't leave while a safepoint
2481     // is in progress.
2482     thread->set_thread_state(_thread_blocked);
2483     thread->java_suspend_self();
2484     thread->set_thread_state(state);
2485 
2486     InterfaceSupport::serialize_thread_state_with_handler(thread);
2487   }
2488 
2489   if (SafepointSynchronize::do_call_back()) {
2490     // If we are safepointing, then block the caller which may not be
2491     // the same as the target thread (see above).
2492     SafepointSynchronize::block(curJT);
2493   }
2494 
2495   if (thread->is_deopt_suspend()) {
2496     thread->clear_deopt_suspend();
2497     RegisterMap map(thread, false);
2498     frame f = thread->last_frame();
2499     while (f.id() != thread->must_deopt_id() && ! f.is_first_frame()) {
2500       f = f.sender(&map);
2501     }
2502     if (f.id() == thread->must_deopt_id()) {
2503       thread->clear_must_deopt_id();
2504       f.deoptimize(thread);
2505     } else {
2506       fatal("missed deoptimization!");
2507     }
2508   }
2509 #if INCLUDE_TRACE
2510   if (thread->is_trace_suspend()) {
2511     TRACE_SUSPEND_THREAD(thread);
2512   }
2513 #endif
2514 }
2515 
2516 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2517 // progress or when _suspend_flags is non-zero.
2518 // Current thread needs to self-suspend if there is a suspend request and/or
2519 // block if a safepoint is in progress.
2520 // Also check for pending async exception (not including unsafe access error).
2521 // Note only the native==>VM/Java barriers can call this function and when
2522 // thread state is _thread_in_native_trans.
2523 void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
2524   check_safepoint_and_suspend_for_native_trans(thread);
2525 
2526   if (thread->has_async_exception()) {
2527     // We are in _thread_in_native_trans state, don't handle unsafe
2528     // access error since that may block.
2529     thread->check_and_handle_async_exceptions(false);
2530   }
2531 }
2532 
2533 // This is a variant of the normal
2534 // check_special_condition_for_native_trans with slightly different
2535 // semantics for use by critical native wrappers.  It does all the
2536 // normal checks but also performs the transition back into
2537 // thread_in_Java state.  This is required so that critical natives
2538 // can potentially block and perform a GC if they are the last thread
2539 // exiting the GCLocker.
2540 void JavaThread::check_special_condition_for_native_trans_and_transition(JavaThread *thread) {
2541   check_special_condition_for_native_trans(thread);
2542 
2543   // Finish the transition
2544   thread->set_thread_state(_thread_in_Java);
2545 
2546   if (thread->do_critical_native_unlock()) {
2547     ThreadInVMfromJavaNoAsyncException tiv(thread);
2548     GCLocker::unlock_critical(thread);
2549     thread->clear_critical_native_unlock();
2550   }
2551 }
2552 
2553 // We need to guarantee the Threads_lock here, since resumes are not
2554 // allowed during safepoint synchronization
2555 // Can only resume from an external suspension
2556 void JavaThread::java_resume() {
2557   assert_locked_or_safepoint(Threads_lock);
2558 
2559   // Sanity check: thread is gone, has started exiting or the thread
2560   // was not externally suspended.
2561   ThreadsListHandle tlh;
2562   if (!tlh.includes(this) || is_exiting() || !is_external_suspend()) {
2563     return;
2564   }
2565 
2566   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2567 
2568   clear_external_suspend();
2569 
2570   if (is_ext_suspended()) {
2571     clear_ext_suspended();
2572     SR_lock()->notify_all();
2573   }
2574 }
2575 
2576 size_t JavaThread::_stack_red_zone_size = 0;
2577 size_t JavaThread::_stack_yellow_zone_size = 0;
2578 size_t JavaThread::_stack_reserved_zone_size = 0;
2579 size_t JavaThread::_stack_shadow_zone_size = 0;
2580 
2581 void JavaThread::create_stack_guard_pages() {
2582   if (!os::uses_stack_guard_pages() || _stack_guard_state != stack_guard_unused) { return; }
2583   address low_addr = stack_end();
2584   size_t len = stack_guard_zone_size();
2585 
2586   assert(is_aligned(low_addr, os::vm_page_size()), "Stack base should be the start of a page");
2587   assert(is_aligned(len, os::vm_page_size()), "Stack size should be a multiple of page size");
2588 
2589   int must_commit = os::must_commit_stack_guard_pages();
2590   // warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);
2591 
2592   if (must_commit && !os::create_stack_guard_pages((char *) low_addr, len)) {
2593     log_warning(os, thread)("Attempt to allocate stack guard pages failed.");
2594     return;
2595   }
2596 
2597   if (os::guard_memory((char *) low_addr, len)) {
2598     _stack_guard_state = stack_guard_enabled;
2599   } else {
2600     log_warning(os, thread)("Attempt to protect stack guard pages failed ("
2601       PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2602     if (os::uncommit_memory((char *) low_addr, len)) {
2603       log_warning(os, thread)("Attempt to deallocate stack guard pages failed.");
2604     }
2605     return;
2606   }
2607 
2608   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages activated: "
2609     PTR_FORMAT "-" PTR_FORMAT ".",
2610     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2611 }
2612 
2613 void JavaThread::remove_stack_guard_pages() {
2614   assert(Thread::current() == this, "from different thread");
2615   if (_stack_guard_state == stack_guard_unused) return;
2616   address low_addr = stack_end();
2617   size_t len = stack_guard_zone_size();
2618 
2619   if (os::must_commit_stack_guard_pages()) {
2620     if (os::remove_stack_guard_pages((char *) low_addr, len)) {
2621       _stack_guard_state = stack_guard_unused;
2622     } else {
2623       log_warning(os, thread)("Attempt to deallocate stack guard pages failed ("
2624         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2625       return;
2626     }
2627   } else {
2628     if (_stack_guard_state == stack_guard_unused) return;
2629     if (os::unguard_memory((char *) low_addr, len)) {
2630       _stack_guard_state = stack_guard_unused;
2631     } else {
2632       log_warning(os, thread)("Attempt to unprotect stack guard pages failed ("
2633         PTR_FORMAT "-" PTR_FORMAT ").", p2i(low_addr), p2i(low_addr + len));
2634       return;
2635     }
2636   }
2637 
2638   log_debug(os, thread)("Thread " UINTX_FORMAT " stack guard pages removed: "
2639     PTR_FORMAT "-" PTR_FORMAT ".",
2640     os::current_thread_id(), p2i(low_addr), p2i(low_addr + len));
2641 }
2642 
2643 void JavaThread::enable_stack_reserved_zone() {
2644   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2645   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2646 
2647   // The base notation is from the stack's point of view, growing downward.
2648   // We need to adjust it to work correctly with guard_memory()
2649   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2650 
2651   guarantee(base < stack_base(),"Error calculating stack reserved zone");
2652   guarantee(base < os::current_stack_pointer(),"Error calculating stack reserved zone");
2653 
2654   if (os::guard_memory((char *) base, stack_reserved_zone_size())) {
2655     _stack_guard_state = stack_guard_enabled;
2656   } else {
2657     warning("Attempt to guard stack reserved zone failed.");
2658   }
2659   enable_register_stack_guard();
2660 }
2661 
2662 void JavaThread::disable_stack_reserved_zone() {
2663   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2664   assert(_stack_guard_state != stack_guard_reserved_disabled, "already disabled");
2665 
2666   // Simply return if called for a thread that does not use guard pages.
2667   if (_stack_guard_state == stack_guard_unused) return;
2668 
2669   // The base notation is from the stack's point of view, growing downward.
2670   // We need to adjust it to work correctly with guard_memory()
2671   address base = stack_reserved_zone_base() - stack_reserved_zone_size();
2672 
2673   if (os::unguard_memory((char *)base, stack_reserved_zone_size())) {
2674     _stack_guard_state = stack_guard_reserved_disabled;
2675   } else {
2676     warning("Attempt to unguard stack reserved zone failed.");
2677   }
2678   disable_register_stack_guard();
2679 }
2680 
2681 void JavaThread::enable_stack_yellow_reserved_zone() {
2682   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2683   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2684 
2685   // The base notation is from the stacks point of view, growing downward.
2686   // We need to adjust it to work correctly with guard_memory()
2687   address base = stack_red_zone_base();
2688 
2689   guarantee(base < stack_base(), "Error calculating stack yellow zone");
2690   guarantee(base < os::current_stack_pointer(), "Error calculating stack yellow zone");
2691 
2692   if (os::guard_memory((char *) base, stack_yellow_reserved_zone_size())) {
2693     _stack_guard_state = stack_guard_enabled;
2694   } else {
2695     warning("Attempt to guard stack yellow zone failed.");
2696   }
2697   enable_register_stack_guard();
2698 }
2699 
2700 void JavaThread::disable_stack_yellow_reserved_zone() {
2701   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2702   assert(_stack_guard_state != stack_guard_yellow_reserved_disabled, "already disabled");
2703 
2704   // Simply return if called for a thread that does not use guard pages.
2705   if (_stack_guard_state == stack_guard_unused) return;
2706 
2707   // The base notation is from the stacks point of view, growing downward.
2708   // We need to adjust it to work correctly with guard_memory()
2709   address base = stack_red_zone_base();
2710 
2711   if (os::unguard_memory((char *)base, stack_yellow_reserved_zone_size())) {
2712     _stack_guard_state = stack_guard_yellow_reserved_disabled;
2713   } else {
2714     warning("Attempt to unguard stack yellow zone failed.");
2715   }
2716   disable_register_stack_guard();
2717 }
2718 
2719 void JavaThread::enable_stack_red_zone() {
2720   // The base notation is from the stacks point of view, growing downward.
2721   // We need to adjust it to work correctly with guard_memory()
2722   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2723   address base = stack_red_zone_base() - stack_red_zone_size();
2724 
2725   guarantee(base < stack_base(), "Error calculating stack red zone");
2726   guarantee(base < os::current_stack_pointer(), "Error calculating stack red zone");
2727 
2728   if (!os::guard_memory((char *) base, stack_red_zone_size())) {
2729     warning("Attempt to guard stack red zone failed.");
2730   }
2731 }
2732 
2733 void JavaThread::disable_stack_red_zone() {
2734   // The base notation is from the stacks point of view, growing downward.
2735   // We need to adjust it to work correctly with guard_memory()
2736   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2737   address base = stack_red_zone_base() - stack_red_zone_size();
2738   if (!os::unguard_memory((char *)base, stack_red_zone_size())) {
2739     warning("Attempt to unguard stack red zone failed.");
2740   }
2741 }
2742 
2743 void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
2744   // ignore is there is no stack
2745   if (!has_last_Java_frame()) return;
2746   // traverse the stack frames. Starts from top frame.
2747   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2748     frame* fr = fst.current();
2749     f(fr, fst.register_map());
2750   }
2751 }
2752 
2753 
2754 #ifndef PRODUCT
2755 // Deoptimization
2756 // Function for testing deoptimization
2757 void JavaThread::deoptimize() {
2758   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2759   StackFrameStream fst(this, UseBiasedLocking);
2760   bool deopt = false;           // Dump stack only if a deopt actually happens.
2761   bool only_at = strlen(DeoptimizeOnlyAt) > 0;
2762   // Iterate over all frames in the thread and deoptimize
2763   for (; !fst.is_done(); fst.next()) {
2764     if (fst.current()->can_be_deoptimized()) {
2765 
2766       if (only_at) {
2767         // Deoptimize only at particular bcis.  DeoptimizeOnlyAt
2768         // consists of comma or carriage return separated numbers so
2769         // search for the current bci in that string.
2770         address pc = fst.current()->pc();
2771         nmethod* nm =  (nmethod*) fst.current()->cb();
2772         ScopeDesc* sd = nm->scope_desc_at(pc);
2773         char buffer[8];
2774         jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
2775         size_t len = strlen(buffer);
2776         const char * found = strstr(DeoptimizeOnlyAt, buffer);
2777         while (found != NULL) {
2778           if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
2779               (found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
2780             // Check that the bci found is bracketed by terminators.
2781             break;
2782           }
2783           found = strstr(found + 1, buffer);
2784         }
2785         if (!found) {
2786           continue;
2787         }
2788       }
2789 
2790       if (DebugDeoptimization && !deopt) {
2791         deopt = true; // One-time only print before deopt
2792         tty->print_cr("[BEFORE Deoptimization]");
2793         trace_frames();
2794         trace_stack();
2795       }
2796       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2797     }
2798   }
2799 
2800   if (DebugDeoptimization && deopt) {
2801     tty->print_cr("[AFTER Deoptimization]");
2802     trace_frames();
2803   }
2804 }
2805 
2806 
2807 // Make zombies
2808 void JavaThread::make_zombies() {
2809   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2810     if (fst.current()->can_be_deoptimized()) {
2811       // it is a Java nmethod
2812       nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
2813       nm->make_not_entrant();
2814     }
2815   }
2816 }
2817 #endif // PRODUCT
2818 
2819 
2820 void JavaThread::deoptimized_wrt_marked_nmethods() {
2821   if (!has_last_Java_frame()) return;
2822   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2823   StackFrameStream fst(this, UseBiasedLocking);
2824   for (; !fst.is_done(); fst.next()) {
2825     if (fst.current()->should_be_deoptimized()) {
2826       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2827     }
2828   }
2829 }
2830 
2831 
2832 // If the caller is a NamedThread, then remember, in the current scope,
2833 // the given JavaThread in its _processed_thread field.
2834 class RememberProcessedThread: public StackObj {
2835   NamedThread* _cur_thr;
2836  public:
2837   RememberProcessedThread(JavaThread* jthr) {
2838     Thread* thread = Thread::current();
2839     if (thread->is_Named_thread()) {
2840       _cur_thr = (NamedThread *)thread;
2841       _cur_thr->set_processed_thread(jthr);
2842     } else {
2843       _cur_thr = NULL;
2844     }
2845   }
2846 
2847   ~RememberProcessedThread() {
2848     if (_cur_thr) {
2849       _cur_thr->set_processed_thread(NULL);
2850     }
2851   }
2852 };
2853 
2854 void JavaThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
2855   // Verify that the deferred card marks have been flushed.
2856   assert(deferred_card_mark().is_empty(), "Should be empty during GC");
2857 
2858   // Traverse the GCHandles
2859   Thread::oops_do(f, cf);
2860 
2861   JVMCI_ONLY(f->do_oop((oop*)&_pending_failed_speculation);)
2862 
2863   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2864          (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2865 
2866   if (has_last_Java_frame()) {
2867     // Record JavaThread to GC thread
2868     RememberProcessedThread rpt(this);
2869 
2870     // Traverse the privileged stack
2871     if (_privileged_stack_top != NULL) {
2872       _privileged_stack_top->oops_do(f);
2873     }
2874 
2875     // traverse the registered growable array
2876     if (_array_for_gc != NULL) {
2877       for (int index = 0; index < _array_for_gc->length(); index++) {
2878         f->do_oop(_array_for_gc->adr_at(index));
2879       }
2880     }
2881 
2882     // Traverse the monitor chunks
2883     for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2884       chunk->oops_do(f);
2885     }
2886 
2887     // Traverse the execution stack
2888     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2889       fst.current()->oops_do(f, cf, fst.register_map());
2890     }
2891   }
2892 
2893   // callee_target is never live across a gc point so NULL it here should
2894   // it still contain a methdOop.
2895 
2896   set_callee_target(NULL);
2897 
2898   assert(vframe_array_head() == NULL, "deopt in progress at a safepoint!");
2899   // If we have deferred set_locals there might be oops waiting to be
2900   // written
2901   GrowableArray<jvmtiDeferredLocalVariableSet*>* list = deferred_locals();
2902   if (list != NULL) {
2903     for (int i = 0; i < list->length(); i++) {
2904       list->at(i)->oops_do(f);
2905     }
2906   }
2907 
2908   // Traverse instance variables at the end since the GC may be moving things
2909   // around using this function
2910   f->do_oop((oop*) &_threadObj);
2911   f->do_oop((oop*) &_vm_result);
2912   f->do_oop((oop*) &_exception_oop);
2913   f->do_oop((oop*) &_pending_async_exception);
2914 
2915   if (jvmti_thread_state() != NULL) {
2916     jvmti_thread_state()->oops_do(f);
2917   }
2918 }
2919 
2920 void JavaThread::nmethods_do(CodeBlobClosure* cf) {
2921   assert((!has_last_Java_frame() && java_call_counter() == 0) ||
2922          (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2923 
2924   if (has_last_Java_frame()) {
2925     // Traverse the execution stack
2926     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2927       fst.current()->nmethods_do(cf);
2928     }
2929   }
2930 }
2931 
2932 void JavaThread::metadata_do(void f(Metadata*)) {
2933   if (has_last_Java_frame()) {
2934     // Traverse the execution stack to call f() on the methods in the stack
2935     for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2936       fst.current()->metadata_do(f);
2937     }
2938   } else if (is_Compiler_thread()) {
2939     // need to walk ciMetadata in current compile tasks to keep alive.
2940     CompilerThread* ct = (CompilerThread*)this;
2941     if (ct->env() != NULL) {
2942       ct->env()->metadata_do(f);
2943     }
2944     if (ct->task() != NULL) {
2945       ct->task()->metadata_do(f);
2946     }
2947   }
2948 }
2949 
2950 // Printing
2951 const char* _get_thread_state_name(JavaThreadState _thread_state) {
2952   switch (_thread_state) {
2953   case _thread_uninitialized:     return "_thread_uninitialized";
2954   case _thread_new:               return "_thread_new";
2955   case _thread_new_trans:         return "_thread_new_trans";
2956   case _thread_in_native:         return "_thread_in_native";
2957   case _thread_in_native_trans:   return "_thread_in_native_trans";
2958   case _thread_in_vm:             return "_thread_in_vm";
2959   case _thread_in_vm_trans:       return "_thread_in_vm_trans";
2960   case _thread_in_Java:           return "_thread_in_Java";
2961   case _thread_in_Java_trans:     return "_thread_in_Java_trans";
2962   case _thread_blocked:           return "_thread_blocked";
2963   case _thread_blocked_trans:     return "_thread_blocked_trans";
2964   default:                        return "unknown thread state";
2965   }
2966 }
2967 
2968 #ifndef PRODUCT
2969 void JavaThread::print_thread_state_on(outputStream *st) const {
2970   st->print_cr("   JavaThread state: %s", _get_thread_state_name(_thread_state));
2971 };
2972 void JavaThread::print_thread_state() const {
2973   print_thread_state_on(tty);
2974 }
2975 #endif // PRODUCT
2976 
2977 // Called by Threads::print() for VM_PrintThreads operation
2978 void JavaThread::print_on(outputStream *st) const {
2979   st->print_raw("\"");
2980   st->print_raw(get_thread_name());
2981   st->print_raw("\" ");
2982   oop thread_oop = threadObj();
2983   if (thread_oop != NULL) {
2984     st->print("#" INT64_FORMAT " ", (int64_t)java_lang_Thread::thread_id(thread_oop));
2985     if (java_lang_Thread::is_daemon(thread_oop))  st->print("daemon ");
2986     st->print("prio=%d ", java_lang_Thread::priority(thread_oop));
2987   }
2988   Thread::print_on(st);
2989   // print guess for valid stack memory region (assume 4K pages); helps lock debugging
2990   st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
2991   if (thread_oop != NULL) {
2992     st->print_cr("   java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
2993   }
2994 #ifndef PRODUCT
2995   print_thread_state_on(st);
2996   _safepoint_state->print_on(st);
2997 #endif // PRODUCT
2998   if (is_Compiler_thread()) {
2999     CompilerThread* ct = (CompilerThread*)this;
3000     if (ct->task() != NULL) {
3001       st->print("   Compiling: ");
3002       ct->task()->print(st, NULL, true, false);
3003     } else {
3004       st->print("   No compile task");
3005     }
3006     st->cr();
3007   }
3008 }
3009 
3010 void JavaThread::print_name_on_error(outputStream* st, char *buf, int buflen) const {
3011   st->print("%s", get_thread_name_string(buf, buflen));
3012 }
3013 
3014 // Called by fatal error handler. The difference between this and
3015 // JavaThread::print() is that we can't grab lock or allocate memory.
3016 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
3017   st->print("JavaThread \"%s\"", get_thread_name_string(buf, buflen));
3018   oop thread_obj = threadObj();
3019   if (thread_obj != NULL) {
3020     if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
3021   }
3022   st->print(" [");
3023   st->print("%s", _get_thread_state_name(_thread_state));
3024   if (osthread()) {
3025     st->print(", id=%d", osthread()->thread_id());
3026   }
3027   st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
3028             p2i(stack_end()), p2i(stack_base()));
3029   st->print("]");
3030 
3031   if (_threads_hazard_ptr != NULL) {
3032     st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr));
3033   }
3034   if (_nested_threads_hazard_ptr != NULL) {
3035     print_nested_threads_hazard_ptrs_on(st);
3036   }
3037   return;
3038 }
3039 
3040 // Verification
3041 
3042 static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
3043 
3044 void JavaThread::verify() {
3045   // Verify oops in the thread.
3046   oops_do(&VerifyOopClosure::verify_oop, NULL);
3047 
3048   // Verify the stack frames.
3049   frames_do(frame_verify);
3050 }
3051 
3052 // CR 6300358 (sub-CR 2137150)
3053 // Most callers of this method assume that it can't return NULL but a
3054 // thread may not have a name whilst it is in the process of attaching to
3055 // the VM - see CR 6412693, and there are places where a JavaThread can be
3056 // seen prior to having it's threadObj set (eg JNI attaching threads and
3057 // if vm exit occurs during initialization). These cases can all be accounted
3058 // for such that this method never returns NULL.
3059 const char* JavaThread::get_thread_name() const {
3060 #ifdef ASSERT
3061   // early safepoints can hit while current thread does not yet have TLS
3062   if (!SafepointSynchronize::is_at_safepoint()) {
3063     Thread *cur = Thread::current();
3064     if (!(cur->is_Java_thread() && cur == this)) {
3065       // Current JavaThreads are allowed to get their own name without
3066       // the Threads_lock.
3067       assert_locked_or_safepoint(Threads_lock);
3068     }
3069   }
3070 #endif // ASSERT
3071   return get_thread_name_string();
3072 }
3073 
3074 // Returns a non-NULL representation of this thread's name, or a suitable
3075 // descriptive string if there is no set name
3076 const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
3077   const char* name_str;
3078   oop thread_obj = threadObj();
3079   if (thread_obj != NULL) {
3080     oop name = java_lang_Thread::name(thread_obj);
3081     if (name != NULL) {
3082       if (buf == NULL) {
3083         name_str = java_lang_String::as_utf8_string(name);
3084       } else {
3085         name_str = java_lang_String::as_utf8_string(name, buf, buflen);
3086       }
3087     } else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
3088       name_str = "<no-name - thread is attaching>";
3089     } else {
3090       name_str = Thread::name();
3091     }
3092   } else {
3093     name_str = Thread::name();
3094   }
3095   assert(name_str != NULL, "unexpected NULL thread name");
3096   return name_str;
3097 }
3098 
3099 
3100 const char* JavaThread::get_threadgroup_name() const {
3101   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3102   oop thread_obj = threadObj();
3103   if (thread_obj != NULL) {
3104     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3105     if (thread_group != NULL) {
3106       // ThreadGroup.name can be null
3107       return java_lang_ThreadGroup::name(thread_group);
3108     }
3109   }
3110   return NULL;
3111 }
3112 
3113 const char* JavaThread::get_parent_name() const {
3114   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
3115   oop thread_obj = threadObj();
3116   if (thread_obj != NULL) {
3117     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
3118     if (thread_group != NULL) {
3119       oop parent = java_lang_ThreadGroup::parent(thread_group);
3120       if (parent != NULL) {
3121         // ThreadGroup.name can be null
3122         return java_lang_ThreadGroup::name(parent);
3123       }
3124     }
3125   }
3126   return NULL;
3127 }
3128 
3129 ThreadPriority JavaThread::java_priority() const {
3130   oop thr_oop = threadObj();
3131   if (thr_oop == NULL) return NormPriority; // Bootstrapping
3132   ThreadPriority priority = java_lang_Thread::priority(thr_oop);
3133   assert(MinPriority <= priority && priority <= MaxPriority, "sanity check");
3134   return priority;
3135 }
3136 
3137 void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
3138 
3139   assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
3140   // Link Java Thread object <-> C++ Thread
3141 
3142   // Get the C++ thread object (an oop) from the JNI handle (a jthread)
3143   // and put it into a new Handle.  The Handle "thread_oop" can then
3144   // be used to pass the C++ thread object to other methods.
3145 
3146   // Set the Java level thread object (jthread) field of the
3147   // new thread (a JavaThread *) to C++ thread object using the
3148   // "thread_oop" handle.
3149 
3150   // Set the thread field (a JavaThread *) of the
3151   // oop representing the java_lang_Thread to the new thread (a JavaThread *).
3152 
3153   Handle thread_oop(Thread::current(),
3154                     JNIHandles::resolve_non_null(jni_thread));
3155   assert(InstanceKlass::cast(thread_oop->klass())->is_linked(),
3156          "must be initialized");
3157   set_threadObj(thread_oop());
3158   java_lang_Thread::set_thread(thread_oop(), this);
3159 
3160   if (prio == NoPriority) {
3161     prio = java_lang_Thread::priority(thread_oop());
3162     assert(prio != NoPriority, "A valid priority should be present");
3163   }
3164 
3165   // Push the Java priority down to the native thread; needs Threads_lock
3166   Thread::set_priority(this, prio);
3167 
3168   prepare_ext();
3169 
3170   // Add the new thread to the Threads list and set it in motion.
3171   // We must have threads lock in order to call Threads::add.
3172   // It is crucial that we do not block before the thread is
3173   // added to the Threads list for if a GC happens, then the java_thread oop
3174   // will not be visited by GC.
3175   Threads::add(this);
3176 }
3177 
3178 oop JavaThread::current_park_blocker() {
3179   // Support for JSR-166 locks
3180   oop thread_oop = threadObj();
3181   if (thread_oop != NULL &&
3182       JDK_Version::current().supports_thread_park_blocker()) {
3183     return java_lang_Thread::park_blocker(thread_oop);
3184   }
3185   return NULL;
3186 }
3187 
3188 
3189 void JavaThread::print_stack_on(outputStream* st) {
3190   if (!has_last_Java_frame()) return;
3191   ResourceMark rm;
3192   HandleMark   hm;
3193 
3194   RegisterMap reg_map(this);
3195   vframe* start_vf = last_java_vframe(&reg_map);
3196   int count = 0;
3197   for (vframe* f = start_vf; f; f = f->sender()) {
3198     if (f->is_java_frame()) {
3199       javaVFrame* jvf = javaVFrame::cast(f);
3200       java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
3201 
3202       // Print out lock information
3203       if (JavaMonitorsInStackTrace) {
3204         jvf->print_lock_info_on(st, count);
3205       }
3206     } else {
3207       // Ignore non-Java frames
3208     }
3209 
3210     // Bail-out case for too deep stacks
3211     count++;
3212     if (MaxJavaStackTraceDepth == count) return;
3213   }
3214 }
3215 
3216 
3217 // JVMTI PopFrame support
3218 void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
3219   assert(_popframe_preserved_args == NULL, "should not wipe out old PopFrame preserved arguments");
3220   if (in_bytes(size_in_bytes) != 0) {
3221     _popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes), mtThread);
3222     _popframe_preserved_args_size = in_bytes(size_in_bytes);
3223     Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
3224   }
3225 }
3226 
3227 void* JavaThread::popframe_preserved_args() {
3228   return _popframe_preserved_args;
3229 }
3230 
3231 ByteSize JavaThread::popframe_preserved_args_size() {
3232   return in_ByteSize(_popframe_preserved_args_size);
3233 }
3234 
3235 WordSize JavaThread::popframe_preserved_args_size_in_words() {
3236   int sz = in_bytes(popframe_preserved_args_size());
3237   assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
3238   return in_WordSize(sz / wordSize);
3239 }
3240 
3241 void JavaThread::popframe_free_preserved_args() {
3242   assert(_popframe_preserved_args != NULL, "should not free PopFrame preserved arguments twice");
3243   FREE_C_HEAP_ARRAY(char, (char*) _popframe_preserved_args);
3244   _popframe_preserved_args = NULL;
3245   _popframe_preserved_args_size = 0;
3246 }
3247 
3248 #ifndef PRODUCT
3249 
3250 void JavaThread::trace_frames() {
3251   tty->print_cr("[Describe stack]");
3252   int frame_no = 1;
3253   for (StackFrameStream fst(this); !fst.is_done(); fst.next()) {
3254     tty->print("  %d. ", frame_no++);
3255     fst.current()->print_value_on(tty, this);
3256     tty->cr();
3257   }
3258 }
3259 
3260 class PrintAndVerifyOopClosure: public OopClosure {
3261  protected:
3262   template <class T> inline void do_oop_work(T* p) {
3263     oop obj = oopDesc::load_decode_heap_oop(p);
3264     if (obj == NULL) return;
3265     tty->print(INTPTR_FORMAT ": ", p2i(p));
3266     if (oopDesc::is_oop_or_null(obj)) {
3267       if (obj->is_objArray()) {
3268         tty->print_cr("valid objArray: " INTPTR_FORMAT, p2i(obj));
3269       } else {
3270         obj->print();
3271       }
3272     } else {
3273       tty->print_cr("invalid oop: " INTPTR_FORMAT, p2i(obj));
3274     }
3275     tty->cr();
3276   }
3277  public:
3278   virtual void do_oop(oop* p) { do_oop_work(p); }
3279   virtual void do_oop(narrowOop* p)  { do_oop_work(p); }
3280 };
3281 
3282 
3283 static void oops_print(frame* f, const RegisterMap *map) {
3284   PrintAndVerifyOopClosure print;
3285   f->print_value();
3286   f->oops_do(&print, NULL, (RegisterMap*)map);
3287 }
3288 
3289 // Print our all the locations that contain oops and whether they are
3290 // valid or not.  This useful when trying to find the oldest frame
3291 // where an oop has gone bad since the frame walk is from youngest to
3292 // oldest.
3293 void JavaThread::trace_oops() {
3294   tty->print_cr("[Trace oops]");
3295   frames_do(oops_print);
3296 }
3297 
3298 
3299 #ifdef ASSERT
3300 // Print or validate the layout of stack frames
3301 void JavaThread::print_frame_layout(int depth, bool validate_only) {
3302   ResourceMark rm;
3303   PRESERVE_EXCEPTION_MARK;
3304   FrameValues values;
3305   int frame_no = 0;
3306   for (StackFrameStream fst(this, false); !fst.is_done(); fst.next()) {
3307     fst.current()->describe(values, ++frame_no);
3308     if (depth == frame_no) break;
3309   }
3310   if (validate_only) {
3311     values.validate();
3312   } else {
3313     tty->print_cr("[Describe stack layout]");
3314     values.print(this);
3315   }
3316 }
3317 #endif
3318 
3319 void JavaThread::trace_stack_from(vframe* start_vf) {
3320   ResourceMark rm;
3321   int vframe_no = 1;
3322   for (vframe* f = start_vf; f; f = f->sender()) {
3323     if (f->is_java_frame()) {
3324       javaVFrame::cast(f)->print_activation(vframe_no++);
3325     } else {
3326       f->print();
3327     }
3328     if (vframe_no > StackPrintLimit) {
3329       tty->print_cr("...<more frames>...");
3330       return;
3331     }
3332   }
3333 }
3334 
3335 
3336 void JavaThread::trace_stack() {
3337   if (!has_last_Java_frame()) return;
3338   ResourceMark rm;
3339   HandleMark   hm;
3340   RegisterMap reg_map(this);
3341   trace_stack_from(last_java_vframe(&reg_map));
3342 }
3343 
3344 
3345 #endif // PRODUCT
3346 
3347 
3348 javaVFrame* JavaThread::last_java_vframe(RegisterMap *reg_map) {
3349   assert(reg_map != NULL, "a map must be given");
3350   frame f = last_frame();
3351   for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender()) {
3352     if (vf->is_java_frame()) return javaVFrame::cast(vf);
3353   }
3354   return NULL;
3355 }
3356 
3357 
3358 Klass* JavaThread::security_get_caller_class(int depth) {
3359   vframeStream vfst(this);
3360   vfst.security_get_caller_frame(depth);
3361   if (!vfst.at_end()) {
3362     return vfst.method()->method_holder();
3363   }
3364   return NULL;
3365 }
3366 
3367 static void compiler_thread_entry(JavaThread* thread, TRAPS) {
3368   assert(thread->is_Compiler_thread(), "must be compiler thread");
3369   CompileBroker::compiler_thread_loop();
3370 }
3371 
3372 static void sweeper_thread_entry(JavaThread* thread, TRAPS) {
3373   NMethodSweeper::sweeper_loop();
3374 }
3375 
3376 // Create a CompilerThread
3377 CompilerThread::CompilerThread(CompileQueue* queue,
3378                                CompilerCounters* counters)
3379                                : JavaThread(&compiler_thread_entry) {
3380   _env   = NULL;
3381   _log   = NULL;
3382   _task  = NULL;
3383   _queue = queue;
3384   _counters = counters;
3385   _buffer_blob = NULL;
3386   _compiler = NULL;
3387 
3388   // Compiler uses resource area for compilation, let's bias it to mtCompiler
3389   resource_area()->bias_to(mtCompiler);
3390 
3391 #ifndef PRODUCT
3392   _ideal_graph_printer = NULL;
3393 #endif
3394 }
3395 
3396 bool CompilerThread::can_call_java() const {
3397   return _compiler != NULL && _compiler->is_jvmci();
3398 }
3399 
3400 // Create sweeper thread
3401 CodeCacheSweeperThread::CodeCacheSweeperThread()
3402 : JavaThread(&sweeper_thread_entry) {
3403   _scanned_compiled_method = NULL;
3404 }
3405 
3406 void CodeCacheSweeperThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
3407   JavaThread::oops_do(f, cf);
3408   if (_scanned_compiled_method != NULL && cf != NULL) {
3409     // Safepoints can occur when the sweeper is scanning an nmethod so
3410     // process it here to make sure it isn't unloaded in the middle of
3411     // a scan.
3412     cf->do_code_blob(_scanned_compiled_method);
3413   }
3414 }
3415 
3416 void CodeCacheSweeperThread::nmethods_do(CodeBlobClosure* cf) {
3417   JavaThread::nmethods_do(cf);
3418   if (_scanned_compiled_method != NULL && cf != NULL) {
3419     // Safepoints can occur when the sweeper is scanning an nmethod so
3420     // process it here to make sure it isn't unloaded in the middle of
3421     // a scan.
3422     cf->do_code_blob(_scanned_compiled_method);
3423   }
3424 }
3425 
3426 
3427 // ======= Threads ========
3428 
3429 // The Threads class links together all active threads, and provides
3430 // operations over all threads.  It is protected by its own Mutex
3431 // lock, which is also used in other contexts to protect thread
3432 // operations from having the thread being operated on from exiting
3433 // and going away unexpectedly (e.g., safepoint synchronization)
3434 
3435 JavaThread*           Threads::_thread_list = NULL;
3436 int                   Threads::_number_of_threads = 0;
3437 int                   Threads::_number_of_non_daemon_threads = 0;
3438 int                   Threads::_return_code = 0;
3439 int                   Threads::_thread_claim_parity = 0;
3440 size_t                JavaThread::_stack_size_at_create = 0;
3441 Monitor*              Threads::_smr_delete_lock =
3442                           new Monitor(Monitor::special, "smr_delete_lock",
3443                                       false /* allow_vm_block */,
3444                                       Monitor::_safepoint_check_never);
3445 // The '_cnt', '_max' and '_times" fields are enabled via
3446 // -XX:+EnableThreadSMRStatistics:
3447 uint                  Threads::_smr_delete_lock_wait_cnt = 0;
3448 uint                  Threads::_smr_delete_lock_wait_max = 0;
3449 volatile jint         Threads::_smr_delete_notify = 0;
3450 volatile jint         Threads::_smr_deleted_thread_cnt = 0;
3451 volatile jint         Threads::_smr_deleted_thread_time_max = 0;
3452 volatile jint         Threads::_smr_deleted_thread_times = 0;
3453 ThreadsList* volatile Threads::_smr_java_thread_list = new ThreadsList(0);
3454 long                  Threads::_smr_java_thread_list_alloc_cnt = 1;
3455 long                  Threads::_smr_java_thread_list_free_cnt = 0;
3456 uint                  Threads::_smr_java_thread_list_max = 0;
3457 uint                  Threads::_smr_nested_thread_list_max = 0;
3458 volatile jint         Threads::_smr_tlh_cnt = 0;
3459 volatile jint         Threads::_smr_tlh_time_max = 0;
3460 volatile jint         Threads::_smr_tlh_times = 0;
3461 ThreadsList*          Threads::_smr_to_delete_list = NULL;
3462 uint                  Threads::_smr_to_delete_list_cnt = 0;
3463 uint                  Threads::_smr_to_delete_list_max = 0;
3464 
3465 #ifdef ASSERT
3466 bool                  Threads::_vm_complete = false;
3467 #endif
3468 
3469 static inline void *prefetch_and_load_ptr(void **addr, intx prefetch_interval) {
3470   Prefetch::read((void*)addr, prefetch_interval);
3471   return *addr;
3472 }
3473 
3474 // Possibly the ugliest for loop the world has seen. C++ does not allow
3475 // multiple types in the declaration section of the for loop. In this case
3476 // we are only dealing with pointers and hence can cast them. It looks ugly
3477 // but macros are ugly and therefore it's fine to make things absurdly ugly.
3478 #define DO_JAVA_THREADS(LIST, X)                                                                                          \
3479     for (JavaThread *MACRO_scan_interval = (JavaThread*)(uintptr_t)PrefetchScanIntervalInBytes,                           \
3480              *MACRO_list = (JavaThread*)(LIST),                                                                           \
3481              **MACRO_end = ((JavaThread**)((ThreadsList*)MACRO_list)->threads()) + ((ThreadsList*)MACRO_list)->length(),  \
3482              **MACRO_current_p = (JavaThread**)((ThreadsList*)MACRO_list)->threads(),                                     \
3483              *X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval);                 \
3484          MACRO_current_p != MACRO_end;                                                                                    \
3485          MACRO_current_p++,                                                                                               \
3486              X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval))
3487 
3488 // All JavaThreads
3489 #define ALL_JAVA_THREADS(X) DO_JAVA_THREADS(get_smr_java_thread_list(), X)
3490 
3491 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system)
3492 void Threads::threads_do(ThreadClosure* tc) {
3493   assert_locked_or_safepoint(Threads_lock);
3494   // ALL_JAVA_THREADS iterates through all JavaThreads
3495   ALL_JAVA_THREADS(p) {
3496     tc->do_thread(p);
3497   }
3498   // Someday we could have a table or list of all non-JavaThreads.
3499   // For now, just manually iterate through them.
3500   tc->do_thread(VMThread::vm_thread());
3501   Universe::heap()->gc_threads_do(tc);
3502   WatcherThread *wt = WatcherThread::watcher_thread();
3503   // Strictly speaking, the following NULL check isn't sufficient to make sure
3504   // the data for WatcherThread is still valid upon being examined. However,
3505   // considering that WatchThread terminates when the VM is on the way to
3506   // exit at safepoint, the chance of the above is extremely small. The right
3507   // way to prevent termination of WatcherThread would be to acquire
3508   // Terminator_lock, but we can't do that without violating the lock rank
3509   // checking in some cases.
3510   if (wt != NULL) {
3511     tc->do_thread(wt);
3512   }
3513 
3514   // If CompilerThreads ever become non-JavaThreads, add them here
3515 }
3516 
3517 void Threads::possibly_parallel_threads_do(bool is_par, ThreadClosure* tc) {
3518   int cp = Threads::thread_claim_parity();
3519   ALL_JAVA_THREADS(p) {
3520     if (p->claim_oops_do(is_par, cp)) {
3521       tc->do_thread(p);
3522     }
3523   }
3524   VMThread* vmt = VMThread::vm_thread();
3525   if (vmt->claim_oops_do(is_par, cp)) {
3526     tc->do_thread(vmt);
3527   }
3528 }
3529 
3530 // The system initialization in the library has three phases.
3531 //
3532 // Phase 1: java.lang.System class initialization
3533 //     java.lang.System is a primordial class loaded and initialized
3534 //     by the VM early during startup.  java.lang.System.<clinit>
3535 //     only does registerNatives and keeps the rest of the class
3536 //     initialization work later until thread initialization completes.
3537 //
3538 //     System.initPhase1 initializes the system properties, the static
3539 //     fields in, out, and err. Set up java signal handlers, OS-specific
3540 //     system settings, and thread group of the main thread.
3541 static void call_initPhase1(TRAPS) {
3542   Klass* klass =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3543   JavaValue result(T_VOID);
3544   JavaCalls::call_static(&result, klass, vmSymbols::initPhase1_name(),
3545                                          vmSymbols::void_method_signature(), CHECK);
3546 }
3547 
3548 // Phase 2. Module system initialization
3549 //     This will initialize the module system.  Only java.base classes
3550 //     can be loaded until phase 2 completes.
3551 //
3552 //     Call System.initPhase2 after the compiler initialization and jsr292
3553 //     classes get initialized because module initialization runs a lot of java
3554 //     code, that for performance reasons, should be compiled.  Also, this will
3555 //     enable the startup code to use lambda and other language features in this
3556 //     phase and onward.
3557 //
3558 //     After phase 2, The VM will begin search classes from -Xbootclasspath/a.
3559 static void call_initPhase2(TRAPS) {
3560   TraceTime timer("Initialize module system", TRACETIME_LOG(Info, startuptime));
3561 
3562   Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3563 
3564   JavaValue result(T_INT);
3565   JavaCallArguments args;
3566   args.push_int(DisplayVMOutputToStderr);
3567   args.push_int(log_is_enabled(Debug, init)); // print stack trace if exception thrown
3568   JavaCalls::call_static(&result, klass, vmSymbols::initPhase2_name(),
3569                                          vmSymbols::boolean_boolean_int_signature(), &args, CHECK);
3570   if (result.get_jint() != JNI_OK) {
3571     vm_exit_during_initialization(); // no message or exception
3572   }
3573 
3574   universe_post_module_init();
3575 }
3576 
3577 // Phase 3. final setup - set security manager, system class loader and TCCL
3578 //
3579 //     This will instantiate and set the security manager, set the system class
3580 //     loader as well as the thread context class loader.  The security manager
3581 //     and system class loader may be a custom class loaded from -Xbootclasspath/a,
3582 //     other modules or the application's classpath.
3583 static void call_initPhase3(TRAPS) {
3584   Klass* klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
3585   JavaValue result(T_VOID);
3586   JavaCalls::call_static(&result, klass, vmSymbols::initPhase3_name(),
3587                                          vmSymbols::void_method_signature(), CHECK);
3588 }
3589 
3590 // Safe Memory Reclamation (SMR) support:
3591 //
3592 
3593 // Acquire a stable ThreadsList.
3594 //
3595 ThreadsList *Threads::acquire_stable_list(Thread *self, bool is_ThreadsListSetter) {
3596   assert(self != NULL, "sanity check");
3597   // acquire_stable_list_nested_path() will grab the Threads_lock
3598   // so let's make sure the ThreadsListHandle is in a safe place.
3599   // ThreadsListSetter cannot make this check on this code path.
3600   debug_only(if (!is_ThreadsListSetter && StrictSafepointChecks) self->check_for_valid_safepoint_state(/* potential_vm_operation */ false);)
3601 
3602   if (self->get_threads_hazard_ptr() == NULL) {
3603     // The typical case is first.
3604     return acquire_stable_list_fast_path(self);
3605   }
3606 
3607   // The nested case is rare.
3608   return acquire_stable_list_nested_path(self);
3609 }
3610 
3611 // Fast path (and lock free) way to acquire a stable ThreadsList.
3612 //
3613 ThreadsList *Threads::acquire_stable_list_fast_path(Thread *self) {
3614   assert(self != NULL, "sanity check");
3615   assert(self->get_threads_hazard_ptr() == NULL, "sanity check");
3616   assert(self->get_nested_threads_hazard_ptr() == NULL,
3617          "cannot have a nested hazard ptr with a NULL regular hazard ptr");
3618 
3619   ThreadsList* threads;
3620 
3621   // Stable recording of a hazard ptr for SMR. This code does not use
3622   // locks so its use of the _smr_java_thread_list & _threads_hazard_ptr
3623   // fields is racy relative to code that uses those fields with locks.
3624   // OrderAccess and Atomic functions are used to deal with those races.
3625   //
3626   while (true) {
3627     threads = get_smr_java_thread_list();
3628 
3629     // Publish a tagged hazard ptr to denote that the hazard ptr is not
3630     // yet verified as being stable. Due to the fence after the hazard
3631     // ptr write, it will be sequentially consistent w.r.t. the
3632     // sequentially consistent writes of the ThreadsList, even on
3633     // non-multiple copy atomic machines where stores can be observed
3634     // in different order from different observer threads.
3635     ThreadsList* unverified_threads = Thread::tag_hazard_ptr(threads);
3636     self->set_threads_hazard_ptr(unverified_threads);
3637 
3638     // If _smr_java_thread_list has changed, we have lost a race with
3639     // Threads::add() or Threads::remove() and have to try again.
3640     if (get_smr_java_thread_list() != threads) {
3641       continue;
3642     }
3643 
3644     // We try to remove the tag which will verify the hazard ptr as
3645     // being stable. This exchange can race with a scanning thread
3646     // which might invalidate the tagged hazard ptr to keep it from
3647     // being followed to access JavaThread ptrs. If we lose the race,
3648     // we simply retry. If we win the race, then the stable hazard
3649     // ptr is officially published.
3650     if (self->cmpxchg_threads_hazard_ptr(threads, unverified_threads) == unverified_threads) {
3651       break;
3652     }
3653   }
3654 
3655   // A stable hazard ptr has been published letting other threads know
3656   // that the ThreadsList and the JavaThreads reachable from this list
3657   // are protected and hence they should not be deleted until everyone
3658   // agrees it is safe to do so.
3659 
3660   return threads;
3661 }
3662 
3663 // Acquire a nested stable ThreadsList; this is rare so it uses
3664 // Threads_lock.
3665 //
3666 ThreadsList *Threads::acquire_stable_list_nested_path(Thread *self) {
3667   assert(self != NULL, "sanity check");
3668   assert(self->get_threads_hazard_ptr() != NULL,
3669          "cannot have a NULL regular hazard ptr when acquiring a nested hazard ptr");
3670 
3671   // The thread already has a hazard ptr (ThreadsList ref) so we need
3672   // to create a nested ThreadsListHandle with the current ThreadsList
3673   // since it might be different than our current hazard ptr. The need
3674   // for a nested ThreadsListHandle is rare so we do this while holding
3675   // the Threads_lock so we don't race with the scanning code; the code
3676   // is so much simpler this way.
3677 
3678   NestedThreadsList* node;
3679   {
3680     // Only grab the Threads_lock if we don't already own it.
3681     MutexLockerEx ml(Threads_lock->owned_by_self() ? NULL : Threads_lock);
3682     node = new NestedThreadsList(get_smr_java_thread_list());
3683     // We insert at the front of the list to match up with the delete
3684     // in release_stable_list().
3685     node->set_next(self->get_nested_threads_hazard_ptr());
3686     self->set_nested_threads_hazard_ptr(node);
3687     if (EnableThreadSMRStatistics) {
3688       self->inc_nested_threads_hazard_ptr_cnt();
3689       if (self->nested_threads_hazard_ptr_cnt() > _smr_nested_thread_list_max) {
3690         _smr_nested_thread_list_max = self->nested_threads_hazard_ptr_cnt();
3691       }
3692     }
3693   }
3694   log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::acquire_stable_list: add NestedThreadsList node containing ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(node->t_list()));
3695 
3696   return node->t_list();
3697 }
3698 
3699 // Release a stable ThreadsList.
3700 //
3701 void Threads::release_stable_list(Thread *self) {
3702   assert(self != NULL, "sanity check");
3703   // release_stable_list_nested_path() will grab the Threads_lock
3704   // so let's make sure the ThreadsListHandle is in a safe place.
3705   debug_only(if (StrictSafepointChecks) self->check_for_valid_safepoint_state(/* potential_vm_operation */ false);)
3706 
3707   if (self->get_nested_threads_hazard_ptr() == NULL) {
3708     // The typical case is first.
3709     release_stable_list_fast_path(self);
3710     return;
3711   }
3712 
3713   // The nested case is rare.
3714   release_stable_list_nested_path(self);
3715 }
3716 
3717 // Fast path way to release a stable ThreadsList. The release portion
3718 // is lock-free, but the wake up portion is not.
3719 //
3720 void Threads::release_stable_list_fast_path(Thread *self) {
3721   assert(self != NULL, "sanity check");
3722   assert(self->get_threads_hazard_ptr() != NULL, "sanity check");
3723   assert(self->get_nested_threads_hazard_ptr() == NULL,
3724          "cannot have a nested hazard ptr when releasing a regular hazard ptr");
3725 
3726   // After releasing the hazard ptr, other threads may go ahead and
3727   // free up some memory temporarily used by a ThreadsList snapshot.
3728   self->set_threads_hazard_ptr(NULL);
3729 
3730   // We use double-check locking to reduce traffic on the system
3731   // wide smr_delete_lock.
3732   if (Threads::smr_delete_notify()) {
3733     // An exiting thread might be waiting in smr_delete(); we need to
3734     // check with smr_delete_lock to be sure.
3735     release_stable_list_wake_up((char *) "regular hazard ptr");
3736   }
3737 }
3738 
3739 // Release a nested stable ThreadsList; this is rare so it uses
3740 // Threads_lock.
3741 //
3742 void Threads::release_stable_list_nested_path(Thread *self) {
3743   assert(self != NULL, "sanity check");
3744   assert(self->get_nested_threads_hazard_ptr() != NULL, "sanity check");
3745   assert(self->get_threads_hazard_ptr() != NULL,
3746          "must have a regular hazard ptr to have nested hazard ptrs");
3747 
3748   // We have a nested ThreadsListHandle so we have to release it first.
3749   // The need for a nested ThreadsListHandle is rare so we do this while
3750   // holding the Threads_lock so we don't race with the scanning code;
3751   // the code is so much simpler this way.
3752 
3753   NestedThreadsList *node;
3754   {
3755     // Only grab the Threads_lock if we don't already own it.
3756     MutexLockerEx ml(Threads_lock->owned_by_self() ? NULL : Threads_lock);
3757     // We remove from the front of the list to match up with the insert
3758     // in acquire_stable_list().
3759     node = self->get_nested_threads_hazard_ptr();
3760     self->set_nested_threads_hazard_ptr(node->next());
3761     if (EnableThreadSMRStatistics) {
3762       self->dec_nested_threads_hazard_ptr_cnt();
3763     }
3764   }
3765 
3766   // An exiting thread might be waiting in smr_delete(); we need to
3767   // check with smr_delete_lock to be sure.
3768   release_stable_list_wake_up((char *) "nested hazard ptr");
3769 
3770   log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::release_stable_list: delete NestedThreadsList node containing ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(node->t_list()));
3771 
3772   delete node;
3773 }
3774 
3775 // Wake up portion of the release stable ThreadsList protocol;
3776 // uses the smr_delete_lock().
3777 //
3778 void Threads::release_stable_list_wake_up(char *log_str) {
3779   assert(log_str != NULL, "sanity check");
3780 
3781   // Note: smr_delete_lock is held in smr_delete() for the entire
3782   // hazard ptr search so that we do not lose this notify() if
3783   // the exiting thread has to wait. That code path also holds
3784   // Threads_lock (which was grabbed before smr_delete_lock) so that
3785   // threads_do() can be called. This means the system can't start a
3786   // safepoint which means this thread can't take too long to get to
3787   // a safepoint because of being blocked on smr_delete_lock.
3788   //
3789   MonitorLockerEx ml(Threads::smr_delete_lock(), Monitor::_no_safepoint_check_flag);
3790   if (Threads::smr_delete_notify()) {
3791     // Notify any exiting JavaThreads that are waiting in smr_delete()
3792     // that we've released a ThreadsList.
3793     ml.notify_all();
3794     log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::release_stable_list notified %s", os::current_thread_id(), log_str);
3795   }
3796 }
3797 
3798 void Threads::initialize_java_lang_classes(JavaThread* main_thread, TRAPS) {
3799   TraceTime timer("Initialize java.lang classes", TRACETIME_LOG(Info, startuptime));
3800 
3801   if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
3802     create_vm_init_libraries();
3803   }
3804 
3805   initialize_class(vmSymbols::java_lang_String(), CHECK);
3806 
3807   // Inject CompactStrings value after the static initializers for String ran.
3808   java_lang_String::set_compact_strings(CompactStrings);
3809 
3810   // Initialize java_lang.System (needed before creating the thread)
3811   initialize_class(vmSymbols::java_lang_System(), CHECK);
3812   // The VM creates & returns objects of this class. Make sure it's initialized.
3813   initialize_class(vmSymbols::java_lang_Class(), CHECK);
3814   initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK);
3815   Handle thread_group = create_initial_thread_group(CHECK);
3816   Universe::set_main_thread_group(thread_group());
3817   initialize_class(vmSymbols::java_lang_Thread(), CHECK);
3818   oop thread_object = create_initial_thread(thread_group, main_thread, CHECK);
3819   main_thread->set_threadObj(thread_object);
3820   // Set thread status to running since main thread has
3821   // been started and running.
3822   java_lang_Thread::set_thread_status(thread_object,
3823                                       java_lang_Thread::RUNNABLE);
3824 
3825   // The VM creates objects of this class.
3826   initialize_class(vmSymbols::java_lang_Module(), CHECK);
3827 
3828   // The VM preresolves methods to these classes. Make sure that they get initialized
3829   initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK);
3830   initialize_class(vmSymbols::java_lang_ref_Finalizer(), CHECK);
3831 
3832   // Phase 1 of the system initialization in the library, java.lang.System class initialization
3833   call_initPhase1(CHECK);
3834 
3835   // get the Java runtime name after java.lang.System is initialized
3836   JDK_Version::set_runtime_name(get_java_runtime_name(THREAD));
3837   JDK_Version::set_runtime_version(get_java_runtime_version(THREAD));
3838 
3839   // an instance of OutOfMemory exception has been allocated earlier
3840   initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK);
3841   initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK);
3842   initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK);
3843   initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK);
3844   initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK);
3845   initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK);
3846   initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK);
3847   initialize_class(vmSymbols::java_lang_IllegalArgumentException(), CHECK);
3848 }
3849 
3850 void Threads::initialize_jsr292_core_classes(TRAPS) {
3851   TraceTime timer("Initialize java.lang.invoke classes", TRACETIME_LOG(Info, startuptime));
3852 
3853   initialize_class(vmSymbols::java_lang_invoke_MethodHandle(), CHECK);
3854   initialize_class(vmSymbols::java_lang_invoke_ResolvedMethodName(), CHECK);
3855   initialize_class(vmSymbols::java_lang_invoke_MemberName(), CHECK);
3856   initialize_class(vmSymbols::java_lang_invoke_MethodHandleNatives(), CHECK);
3857 }
3858 
3859 jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
3860   extern void JDK_Version_init();
3861 
3862   // Preinitialize version info.
3863   VM_Version::early_initialize();
3864 
3865   // Check version
3866   if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
3867 
3868   // Initialize library-based TLS
3869   ThreadLocalStorage::init();
3870 
3871   // Initialize the output stream module
3872   ostream_init();
3873 
3874   // Process java launcher properties.
3875   Arguments::process_sun_java_launcher_properties(args);
3876 
3877   // Initialize the os module
3878   os::init();
3879 
3880   // Record VM creation timing statistics
3881   TraceVmCreationTime create_vm_timer;
3882   create_vm_timer.start();
3883 
3884   // Initialize system properties.
3885   Arguments::init_system_properties();
3886 
3887   // So that JDK version can be used as a discriminator when parsing arguments
3888   JDK_Version_init();
3889 
3890   // Update/Initialize System properties after JDK version number is known
3891   Arguments::init_version_specific_system_properties();
3892 
3893   // Make sure to initialize log configuration *before* parsing arguments
3894   LogConfiguration::initialize(create_vm_timer.begin_time());
3895 
3896   // Parse arguments
3897   jint parse_result = Arguments::parse(args);
3898   if (parse_result != JNI_OK) return parse_result;
3899 
3900   os::init_before_ergo();
3901 
3902   jint ergo_result = Arguments::apply_ergo();
3903   if (ergo_result != JNI_OK) return ergo_result;
3904 
3905   // Final check of all ranges after ergonomics which may change values.
3906   if (!CommandLineFlagRangeList::check_ranges()) {
3907     return JNI_EINVAL;
3908   }
3909 
3910   // Final check of all 'AfterErgo' constraints after ergonomics which may change values.
3911   bool constraint_result = CommandLineFlagConstraintList::check_constraints(CommandLineFlagConstraint::AfterErgo);
3912   if (!constraint_result) {
3913     return JNI_EINVAL;
3914   }
3915 
3916   CommandLineFlagWriteableList::mark_startup();
3917 
3918   if (PauseAtStartup) {
3919     os::pause();
3920   }
3921 
3922   HOTSPOT_VM_INIT_BEGIN();
3923 
3924   // Timing (must come after argument parsing)
3925   TraceTime timer("Create VM", TRACETIME_LOG(Info, startuptime));
3926 
3927   // Initialize the os module after parsing the args
3928   jint os_init_2_result = os::init_2();
3929   if (os_init_2_result != JNI_OK) return os_init_2_result;
3930 
3931   jint adjust_after_os_result = Arguments::adjust_after_os();
3932   if (adjust_after_os_result != JNI_OK) return adjust_after_os_result;
3933 
3934   // Initialize output stream logging
3935   ostream_init_log();
3936 
3937   // Convert -Xrun to -agentlib: if there is no JVM_OnLoad
3938   // Must be before create_vm_init_agents()
3939   if (Arguments::init_libraries_at_startup()) {
3940     convert_vm_init_libraries_to_agents();
3941   }
3942 
3943   // Launch -agentlib/-agentpath and converted -Xrun agents
3944   if (Arguments::init_agents_at_startup()) {
3945     create_vm_init_agents();
3946   }
3947 
3948   // Initialize Threads state
3949   _thread_list = NULL;
3950   _number_of_threads = 0;
3951   _number_of_non_daemon_threads = 0;
3952 
3953   // Initialize global data structures and create system classes in heap
3954   vm_init_globals();
3955 
3956 #if INCLUDE_JVMCI
3957   if (JVMCICounterSize > 0) {
3958     JavaThread::_jvmci_old_thread_counters = NEW_C_HEAP_ARRAY(jlong, JVMCICounterSize, mtInternal);
3959     memset(JavaThread::_jvmci_old_thread_counters, 0, sizeof(jlong) * JVMCICounterSize);
3960   } else {
3961     JavaThread::_jvmci_old_thread_counters = NULL;
3962   }
3963 #endif // INCLUDE_JVMCI
3964 
3965   // Attach the main thread to this os thread
3966   JavaThread* main_thread = new JavaThread();
3967   main_thread->set_thread_state(_thread_in_vm);
3968   main_thread->initialize_thread_current();
3969   // must do this before set_active_handles
3970   main_thread->record_stack_base_and_size();
3971   main_thread->set_active_handles(JNIHandleBlock::allocate_block());
3972 
3973   if (!main_thread->set_as_starting_thread()) {
3974     vm_shutdown_during_initialization(
3975                                       "Failed necessary internal allocation. Out of swap space");
3976     main_thread->smr_delete();
3977     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3978     return JNI_ENOMEM;
3979   }
3980 
3981   // Enable guard page *after* os::create_main_thread(), otherwise it would
3982   // crash Linux VM, see notes in os_linux.cpp.
3983   main_thread->create_stack_guard_pages();
3984 
3985   // Initialize Java-Level synchronization subsystem
3986   ObjectMonitor::Initialize();
3987 
3988   // Initialize global modules
3989   jint status = init_globals();
3990   if (status != JNI_OK) {
3991     main_thread->smr_delete();
3992     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3993     return status;
3994   }
3995 
3996   if (TRACE_INITIALIZE() != JNI_OK) {
3997     vm_exit_during_initialization("Failed to initialize tracing backend");
3998   }
3999 
4000   // Should be done after the heap is fully created
4001   main_thread->cache_global_variables();
4002 
4003   HandleMark hm;
4004 
4005   { MutexLocker mu(Threads_lock);
4006     Threads::add(main_thread);
4007   }
4008 
4009   // Any JVMTI raw monitors entered in onload will transition into
4010   // real raw monitor. VM is setup enough here for raw monitor enter.
4011   JvmtiExport::transition_pending_onload_raw_monitors();
4012 
4013   // Create the VMThread
4014   { TraceTime timer("Start VMThread", TRACETIME_LOG(Info, startuptime));
4015 
4016   VMThread::create();
4017     Thread* vmthread = VMThread::vm_thread();
4018 
4019     if (!os::create_thread(vmthread, os::vm_thread)) {
4020       vm_exit_during_initialization("Cannot create VM thread. "
4021                                     "Out of system resources.");
4022     }
4023 
4024     // Wait for the VM thread to become ready, and VMThread::run to initialize
4025     // Monitors can have spurious returns, must always check another state flag
4026     {
4027       MutexLocker ml(Notify_lock);
4028       os::start_thread(vmthread);
4029       while (vmthread->active_handles() == NULL) {
4030         Notify_lock->wait();
4031       }
4032     }
4033   }
4034 
4035   assert(Universe::is_fully_initialized(), "not initialized");
4036   if (VerifyDuringStartup) {
4037     // Make sure we're starting with a clean slate.
4038     VM_Verify verify_op;
4039     VMThread::execute(&verify_op);
4040   }
4041 
4042   Thread* THREAD = Thread::current();
4043 
4044   // Always call even when there are not JVMTI environments yet, since environments
4045   // may be attached late and JVMTI must track phases of VM execution
4046   JvmtiExport::enter_early_start_phase();
4047 
4048   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
4049   JvmtiExport::post_early_vm_start();
4050 
4051   initialize_java_lang_classes(main_thread, CHECK_JNI_ERR);
4052 
4053   // We need this for ClassDataSharing - the initial vm.info property is set
4054   // with the default value of CDS "sharing" which may be reset through
4055   // command line options.
4056   reset_vm_info_property(CHECK_JNI_ERR);
4057 
4058   quicken_jni_functions();
4059 
4060   // No more stub generation allowed after that point.
4061   StubCodeDesc::freeze();
4062 
4063   // Set flag that basic initialization has completed. Used by exceptions and various
4064   // debug stuff, that does not work until all basic classes have been initialized.
4065   set_init_completed();
4066 
4067   LogConfiguration::post_initialize();
4068   Metaspace::post_initialize();
4069 
4070   HOTSPOT_VM_INIT_END();
4071 
4072   // record VM initialization completion time
4073 #if INCLUDE_MANAGEMENT
4074   Management::record_vm_init_completed();
4075 #endif // INCLUDE_MANAGEMENT
4076 
4077   // Signal Dispatcher needs to be started before VMInit event is posted
4078   os::signal_init(CHECK_JNI_ERR);
4079 
4080   // Start Attach Listener if +StartAttachListener or it can't be started lazily
4081   if (!DisableAttachMechanism) {
4082     AttachListener::vm_start();
4083     if (StartAttachListener || AttachListener::init_at_startup()) {
4084       AttachListener::init();
4085     }
4086   }
4087 
4088   // Launch -Xrun agents
4089   // Must be done in the JVMTI live phase so that for backward compatibility the JDWP
4090   // back-end can launch with -Xdebug -Xrunjdwp.
4091   if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
4092     create_vm_init_libraries();
4093   }
4094 
4095   if (CleanChunkPoolAsync) {
4096     Chunk::start_chunk_pool_cleaner_task();
4097   }
4098 
4099   // initialize compiler(s)
4100 #if defined(COMPILER1) || COMPILER2_OR_JVMCI
4101   CompileBroker::compilation_init(CHECK_JNI_ERR);
4102 #endif
4103 
4104   // Pre-initialize some JSR292 core classes to avoid deadlock during class loading.
4105   // It is done after compilers are initialized, because otherwise compilations of
4106   // signature polymorphic MH intrinsics can be missed
4107   // (see SystemDictionary::find_method_handle_intrinsic).
4108   initialize_jsr292_core_classes(CHECK_JNI_ERR);
4109 
4110   // This will initialize the module system.  Only java.base classes can be
4111   // loaded until phase 2 completes
4112   call_initPhase2(CHECK_JNI_ERR);
4113 
4114   // Always call even when there are not JVMTI environments yet, since environments
4115   // may be attached late and JVMTI must track phases of VM execution
4116   JvmtiExport::enter_start_phase();
4117 
4118   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
4119   JvmtiExport::post_vm_start();
4120 
4121   // Final system initialization including security manager and system class loader
4122   call_initPhase3(CHECK_JNI_ERR);
4123 
4124   // cache the system and platform class loaders
4125   SystemDictionary::compute_java_loaders(CHECK_JNI_ERR);
4126 
4127 #if INCLUDE_JVMCI
4128   if (EnableJVMCI) {
4129     // Initialize JVMCI eagerly if JVMCIPrintProperties is enabled.
4130     // The JVMCI Java initialization code will read this flag and
4131     // do the printing if it's set.
4132     bool init = JVMCIPrintProperties;
4133 
4134     if (!init) {
4135       // 8145270: Force initialization of JVMCI runtime otherwise requests for blocking
4136       // compilations via JVMCI will not actually block until JVMCI is initialized.
4137       init = UseJVMCICompiler && (!UseInterpreter || !BackgroundCompilation);
4138     }
4139 
4140     if (init) {
4141       JVMCIRuntime::force_initialization(CHECK_JNI_ERR);
4142     }
4143   }
4144 #endif
4145 
4146   // Always call even when there are not JVMTI environments yet, since environments
4147   // may be attached late and JVMTI must track phases of VM execution
4148   JvmtiExport::enter_live_phase();
4149 
4150   // Notify JVMTI agents that VM initialization is complete - nop if no agents.
4151   JvmtiExport::post_vm_initialized();
4152 
4153   if (TRACE_START() != JNI_OK) {
4154     vm_exit_during_initialization("Failed to start tracing backend.");
4155   }
4156 
4157 #if INCLUDE_MANAGEMENT
4158   Management::initialize(THREAD);
4159 
4160   if (HAS_PENDING_EXCEPTION) {
4161     // management agent fails to start possibly due to
4162     // configuration problem and is responsible for printing
4163     // stack trace if appropriate. Simply exit VM.
4164     vm_exit(1);
4165   }
4166 #endif // INCLUDE_MANAGEMENT
4167 
4168   if (MemProfiling)                   MemProfiler::engage();
4169   StatSampler::engage();
4170   if (CheckJNICalls)                  JniPeriodicChecker::engage();
4171 
4172   BiasedLocking::init();
4173 
4174 #if INCLUDE_RTM_OPT
4175   RTMLockingCounters::init();
4176 #endif
4177 
4178   if (JDK_Version::current().post_vm_init_hook_enabled()) {
4179     call_postVMInitHook(THREAD);
4180     // The Java side of PostVMInitHook.run must deal with all
4181     // exceptions and provide means of diagnosis.
4182     if (HAS_PENDING_EXCEPTION) {
4183       CLEAR_PENDING_EXCEPTION;
4184     }
4185   }
4186 
4187   {
4188     MutexLocker ml(PeriodicTask_lock);
4189     // Make sure the WatcherThread can be started by WatcherThread::start()
4190     // or by dynamic enrollment.
4191     WatcherThread::make_startable();
4192     // Start up the WatcherThread if there are any periodic tasks
4193     // NOTE:  All PeriodicTasks should be registered by now. If they
4194     //   aren't, late joiners might appear to start slowly (we might
4195     //   take a while to process their first tick).
4196     if (PeriodicTask::num_tasks() > 0) {
4197       WatcherThread::start();
4198     }
4199   }
4200 
4201   create_vm_timer.end();
4202 #ifdef ASSERT
4203   _vm_complete = true;
4204 #endif
4205 
4206   if (DumpSharedSpaces) {
4207     MetaspaceShared::preload_and_dump(CHECK_JNI_ERR);
4208     ShouldNotReachHere();
4209   }
4210 
4211   return JNI_OK;
4212 }
4213 
4214 // type for the Agent_OnLoad and JVM_OnLoad entry points
4215 extern "C" {
4216   typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
4217 }
4218 // Find a command line agent library and return its entry point for
4219 //         -agentlib:  -agentpath:   -Xrun
4220 // num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array.
4221 static OnLoadEntry_t lookup_on_load(AgentLibrary* agent,
4222                                     const char *on_load_symbols[],
4223                                     size_t num_symbol_entries) {
4224   OnLoadEntry_t on_load_entry = NULL;
4225   void *library = NULL;
4226 
4227   if (!agent->valid()) {
4228     char buffer[JVM_MAXPATHLEN];
4229     char ebuf[1024] = "";
4230     const char *name = agent->name();
4231     const char *msg = "Could not find agent library ";
4232 
4233     // First check to see if agent is statically linked into executable
4234     if (os::find_builtin_agent(agent, on_load_symbols, num_symbol_entries)) {
4235       library = agent->os_lib();
4236     } else if (agent->is_absolute_path()) {
4237       library = os::dll_load(name, ebuf, sizeof ebuf);
4238       if (library == NULL) {
4239         const char *sub_msg = " in absolute path, with error: ";
4240         size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
4241         char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
4242         jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
4243         // If we can't find the agent, exit.
4244         vm_exit_during_initialization(buf, NULL);
4245         FREE_C_HEAP_ARRAY(char, buf);
4246       }
4247     } else {
4248       // Try to load the agent from the standard dll directory
4249       if (os::dll_locate_lib(buffer, sizeof(buffer), Arguments::get_dll_dir(),
4250                              name)) {
4251         library = os::dll_load(buffer, ebuf, sizeof ebuf);
4252       }
4253       if (library == NULL) { // Try the library path directory.
4254         if (os::dll_build_name(buffer, sizeof(buffer), name)) {
4255           library = os::dll_load(buffer, ebuf, sizeof ebuf);
4256         }
4257         if (library == NULL) {
4258           const char *sub_msg = " on the library path, with error: ";
4259           size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
4260           char *buf = NEW_C_HEAP_ARRAY(char, len, mtThread);
4261           jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
4262           // If we can't find the agent, exit.
4263           vm_exit_during_initialization(buf, NULL);
4264           FREE_C_HEAP_ARRAY(char, buf);
4265         }
4266       }
4267     }
4268     agent->set_os_lib(library);
4269     agent->set_valid();
4270   }
4271 
4272   // Find the OnLoad function.
4273   on_load_entry =
4274     CAST_TO_FN_PTR(OnLoadEntry_t, os::find_agent_function(agent,
4275                                                           false,
4276                                                           on_load_symbols,
4277                                                           num_symbol_entries));
4278   return on_load_entry;
4279 }
4280 
4281 // Find the JVM_OnLoad entry point
4282 static OnLoadEntry_t lookup_jvm_on_load(AgentLibrary* agent) {
4283   const char *on_load_symbols[] = JVM_ONLOAD_SYMBOLS;
4284   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
4285 }
4286 
4287 // Find the Agent_OnLoad entry point
4288 static OnLoadEntry_t lookup_agent_on_load(AgentLibrary* agent) {
4289   const char *on_load_symbols[] = AGENT_ONLOAD_SYMBOLS;
4290   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
4291 }
4292 
4293 // For backwards compatibility with -Xrun
4294 // Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be
4295 // treated like -agentpath:
4296 // Must be called before agent libraries are created
4297 void Threads::convert_vm_init_libraries_to_agents() {
4298   AgentLibrary* agent;
4299   AgentLibrary* next;
4300 
4301   for (agent = Arguments::libraries(); agent != NULL; agent = next) {
4302     next = agent->next();  // cache the next agent now as this agent may get moved off this list
4303     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
4304 
4305     // If there is an JVM_OnLoad function it will get called later,
4306     // otherwise see if there is an Agent_OnLoad
4307     if (on_load_entry == NULL) {
4308       on_load_entry = lookup_agent_on_load(agent);
4309       if (on_load_entry != NULL) {
4310         // switch it to the agent list -- so that Agent_OnLoad will be called,
4311         // JVM_OnLoad won't be attempted and Agent_OnUnload will
4312         Arguments::convert_library_to_agent(agent);
4313       } else {
4314         vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
4315       }
4316     }
4317   }
4318 }
4319 
4320 // Create agents for -agentlib:  -agentpath:  and converted -Xrun
4321 // Invokes Agent_OnLoad
4322 // Called very early -- before JavaThreads exist
4323 void Threads::create_vm_init_agents() {
4324   extern struct JavaVM_ main_vm;
4325   AgentLibrary* agent;
4326 
4327   JvmtiExport::enter_onload_phase();
4328 
4329   for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
4330     OnLoadEntry_t  on_load_entry = lookup_agent_on_load(agent);
4331 
4332     if (on_load_entry != NULL) {
4333       // Invoke the Agent_OnLoad function
4334       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
4335       if (err != JNI_OK) {
4336         vm_exit_during_initialization("agent library failed to init", agent->name());
4337       }
4338     } else {
4339       vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
4340     }
4341   }
4342   JvmtiExport::enter_primordial_phase();
4343 }
4344 
4345 extern "C" {
4346   typedef void (JNICALL *Agent_OnUnload_t)(JavaVM *);
4347 }
4348 
4349 void Threads::shutdown_vm_agents() {
4350   // Send any Agent_OnUnload notifications
4351   const char *on_unload_symbols[] = AGENT_ONUNLOAD_SYMBOLS;
4352   size_t num_symbol_entries = ARRAY_SIZE(on_unload_symbols);
4353   extern struct JavaVM_ main_vm;
4354   for (AgentLibrary* agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
4355 
4356     // Find the Agent_OnUnload function.
4357     Agent_OnUnload_t unload_entry = CAST_TO_FN_PTR(Agent_OnUnload_t,
4358                                                    os::find_agent_function(agent,
4359                                                    false,
4360                                                    on_unload_symbols,
4361                                                    num_symbol_entries));
4362 
4363     // Invoke the Agent_OnUnload function
4364     if (unload_entry != NULL) {
4365       JavaThread* thread = JavaThread::current();
4366       ThreadToNativeFromVM ttn(thread);
4367       HandleMark hm(thread);
4368       (*unload_entry)(&main_vm);
4369     }
4370   }
4371 }
4372 
4373 // Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries
4374 // Invokes JVM_OnLoad
4375 void Threads::create_vm_init_libraries() {
4376   extern struct JavaVM_ main_vm;
4377   AgentLibrary* agent;
4378 
4379   for (agent = Arguments::libraries(); agent != NULL; agent = agent->next()) {
4380     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
4381 
4382     if (on_load_entry != NULL) {
4383       // Invoke the JVM_OnLoad function
4384       JavaThread* thread = JavaThread::current();
4385       ThreadToNativeFromVM ttn(thread);
4386       HandleMark hm(thread);
4387       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
4388       if (err != JNI_OK) {
4389         vm_exit_during_initialization("-Xrun library failed to init", agent->name());
4390       }
4391     } else {
4392       vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
4393     }
4394   }
4395 }
4396 
4397 
4398 // Last thread running calls java.lang.Shutdown.shutdown()
4399 void JavaThread::invoke_shutdown_hooks() {
4400   HandleMark hm(this);
4401 
4402   // We could get here with a pending exception, if so clear it now.
4403   if (this->has_pending_exception()) {
4404     this->clear_pending_exception();
4405   }
4406 
4407   EXCEPTION_MARK;
4408   Klass* shutdown_klass =
4409     SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
4410                                       THREAD);
4411   if (shutdown_klass != NULL) {
4412     // SystemDictionary::resolve_or_null will return null if there was
4413     // an exception.  If we cannot load the Shutdown class, just don't
4414     // call Shutdown.shutdown() at all.  This will mean the shutdown hooks
4415     // and finalizers (if runFinalizersOnExit is set) won't be run.
4416     // Note that if a shutdown hook was registered or runFinalizersOnExit
4417     // was called, the Shutdown class would have already been loaded
4418     // (Runtime.addShutdownHook and runFinalizersOnExit will load it).
4419     JavaValue result(T_VOID);
4420     JavaCalls::call_static(&result,
4421                            shutdown_klass,
4422                            vmSymbols::shutdown_method_name(),
4423                            vmSymbols::void_method_signature(),
4424                            THREAD);
4425   }
4426   CLEAR_PENDING_EXCEPTION;
4427 }
4428 
4429 // Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
4430 // the program falls off the end of main(). Another VM exit path is through
4431 // vm_exit() when the program calls System.exit() to return a value or when
4432 // there is a serious error in VM. The two shutdown paths are not exactly
4433 // the same, but they share Shutdown.shutdown() at Java level and before_exit()
4434 // and VM_Exit op at VM level.
4435 //
4436 // Shutdown sequence:
4437 //   + Shutdown native memory tracking if it is on
4438 //   + Wait until we are the last non-daemon thread to execute
4439 //     <-- every thing is still working at this moment -->
4440 //   + Call java.lang.Shutdown.shutdown(), which will invoke Java level
4441 //        shutdown hooks, run finalizers if finalization-on-exit
4442 //   + Call before_exit(), prepare for VM exit
4443 //      > run VM level shutdown hooks (they are registered through JVM_OnExit(),
4444 //        currently the only user of this mechanism is File.deleteOnExit())
4445 //      > stop StatSampler, watcher thread, CMS threads,
4446 //        post thread end and vm death events to JVMTI,
4447 //        stop signal thread
4448 //   + Call JavaThread::exit(), it will:
4449 //      > release JNI handle blocks, remove stack guard pages
4450 //      > remove this thread from Threads list
4451 //     <-- no more Java code from this thread after this point -->
4452 //   + Stop VM thread, it will bring the remaining VM to a safepoint and stop
4453 //     the compiler threads at safepoint
4454 //     <-- do not use anything that could get blocked by Safepoint -->
4455 //   + Disable tracing at JNI/JVM barriers
4456 //   + Set _vm_exited flag for threads that are still running native code
4457 //   + Delete this thread
4458 //   + Call exit_globals()
4459 //      > deletes tty
4460 //      > deletes PerfMemory resources
4461 //   + Return to caller
4462 
4463 bool Threads::destroy_vm() {
4464   JavaThread* thread = JavaThread::current();
4465 
4466 #ifdef ASSERT
4467   _vm_complete = false;
4468 #endif
4469   // Wait until we are the last non-daemon thread to execute
4470   { MutexLocker nu(Threads_lock);
4471     while (Threads::number_of_non_daemon_threads() > 1)
4472       // This wait should make safepoint checks, wait without a timeout,
4473       // and wait as a suspend-equivalent condition.
4474       Threads_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
4475                          Mutex::_as_suspend_equivalent_flag);
4476   }
4477 
4478   // Hang forever on exit if we are reporting an error.
4479   if (ShowMessageBoxOnError && VMError::is_error_reported()) {
4480     os::infinite_sleep();
4481   }
4482   os::wait_for_keypress_at_exit();
4483 
4484   // run Java level shutdown hooks
4485   thread->invoke_shutdown_hooks();
4486 
4487   before_exit(thread);
4488 
4489   thread->exit(true);
4490 
4491   // Stop VM thread.
4492   {
4493     // 4945125 The vm thread comes to a safepoint during exit.
4494     // GC vm_operations can get caught at the safepoint, and the
4495     // heap is unparseable if they are caught. Grab the Heap_lock
4496     // to prevent this. The GC vm_operations will not be able to
4497     // queue until after the vm thread is dead. After this point,
4498     // we'll never emerge out of the safepoint before the VM exits.
4499 
4500     MutexLocker ml(Heap_lock);
4501 
4502     VMThread::wait_for_vm_thread_exit();
4503     assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
4504     VMThread::destroy();
4505   }
4506 
4507   // clean up ideal graph printers
4508 #if defined(COMPILER2) && !defined(PRODUCT)
4509   IdealGraphPrinter::clean_up();
4510 #endif
4511 
4512   // Now, all Java threads are gone except daemon threads. Daemon threads
4513   // running Java code or in VM are stopped by the Safepoint. However,
4514   // daemon threads executing native code are still running.  But they
4515   // will be stopped at native=>Java/VM barriers. Note that we can't
4516   // simply kill or suspend them, as it is inherently deadlock-prone.
4517 
4518   VM_Exit::set_vm_exited();
4519 
4520   notify_vm_shutdown();
4521 
4522   // We are after VM_Exit::set_vm_exited() so we can't call
4523   // thread->smr_delete() or we will block on the Threads_lock.
4524   // Deleting the shutdown thread here is safe because another
4525   // JavaThread cannot have an active ThreadsListHandle for
4526   // this JavaThread.
4527   delete thread;
4528 
4529 #if INCLUDE_JVMCI
4530   if (JVMCICounterSize > 0) {
4531     FREE_C_HEAP_ARRAY(jlong, JavaThread::_jvmci_old_thread_counters);
4532   }
4533 #endif
4534 
4535   // exit_globals() will delete tty
4536   exit_globals();
4537 
4538   LogConfiguration::finalize();
4539 
4540   return true;
4541 }
4542 
4543 
4544 jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
4545   if (version == JNI_VERSION_1_1) return JNI_TRUE;
4546   return is_supported_jni_version(version);
4547 }
4548 
4549 
4550 jboolean Threads::is_supported_jni_version(jint version) {
4551   if (version == JNI_VERSION_1_2) return JNI_TRUE;
4552   if (version == JNI_VERSION_1_4) return JNI_TRUE;
4553   if (version == JNI_VERSION_1_6) return JNI_TRUE;
4554   if (version == JNI_VERSION_1_8) return JNI_TRUE;
4555   if (version == JNI_VERSION_9) return JNI_TRUE;
4556   if (version == JNI_VERSION_10) return JNI_TRUE;
4557   return JNI_FALSE;
4558 }
4559 
4560 // Hash table of pointers found by a scan. Used for collecting hazard
4561 // pointers (ThreadsList references). Also used for collecting JavaThreads
4562 // that are indirectly referenced by hazard ptrs. An instance of this
4563 // class only contains one type of pointer.
4564 //
4565 class ThreadScanHashtable : public CHeapObj<mtThread> {
4566  private:
4567   static bool ptr_equals(void * const& s1, void * const& s2) {
4568     return s1 == s2;
4569   }
4570 
4571   static unsigned int ptr_hash(void * const& s1) {
4572     return (unsigned int)(((uint32_t)(uintptr_t)s1) * 2654435761u);
4573   }
4574 
4575   int _table_size;
4576   // ResourceHashtable SIZE is specified at compile time so our
4577   // dynamic _table_size is unused for now; 1031 is the first prime
4578   // after 1024.
4579   typedef ResourceHashtable<void *, int, &ThreadScanHashtable::ptr_hash,
4580                             &ThreadScanHashtable::ptr_equals, 1031,
4581                             ResourceObj::C_HEAP, mtThread> PtrTable;
4582   PtrTable * _ptrs;
4583 
4584  public:
4585   // ResourceHashtable is passed to various functions and populated in
4586   // different places so we allocate it using C_HEAP to make it immune
4587   // from any ResourceMarks that happen to be in the code paths.
4588   ThreadScanHashtable(int table_size) : _table_size(table_size), _ptrs(new (ResourceObj::C_HEAP, mtThread) PtrTable()) {}
4589 
4590   ~ThreadScanHashtable() { delete _ptrs; }
4591 
4592   bool has_entry(void *pointer) {
4593     int *val_ptr = _ptrs->get(pointer);
4594     return val_ptr != NULL && *val_ptr == 1;
4595   }
4596 
4597   void add_entry(void *pointer) {
4598     _ptrs->put(pointer, 1);
4599   }
4600 };
4601 
4602 // Closure to gather JavaThreads indirectly referenced by hazard ptrs
4603 // (ThreadsList references) into a hash table. This closure handles part 2
4604 // of the dance - adding all the JavaThreads referenced by the hazard
4605 // pointer (ThreadsList reference) to the hash table.
4606 //
4607 class AddThreadHazardPointerThreadClosure : public ThreadClosure {
4608  private:
4609   ThreadScanHashtable *_table;
4610 
4611  public:
4612   AddThreadHazardPointerThreadClosure(ThreadScanHashtable *table) : _table(table) {}
4613 
4614   virtual void do_thread(Thread *thread) {
4615     if (!_table->has_entry((void*)thread)) {
4616       // The same JavaThread might be on more than one ThreadsList or
4617       // more than one thread might be using the same ThreadsList. In
4618       // either case, we only need a single entry for a JavaThread.
4619       _table->add_entry((void*)thread);
4620     }
4621   }
4622 };
4623 
4624 // Closure to gather JavaThreads indirectly referenced by hazard ptrs
4625 // (ThreadsList references) into a hash table. This closure handles part 1
4626 // of the dance - hazard ptr chain walking and dispatch to another
4627 // closure.
4628 //
4629 class ScanHazardPtrGatherProtectedThreadsClosure : public ThreadClosure {
4630  private:
4631   ThreadScanHashtable *_table;
4632  public:
4633   ScanHazardPtrGatherProtectedThreadsClosure(ThreadScanHashtable *table) : _table(table) {}
4634 
4635   virtual void do_thread(Thread *thread) {
4636     assert_locked_or_safepoint(Threads_lock);
4637 
4638     if (thread == NULL) return;
4639 
4640     // This code races with Threads::acquire_stable_list() which is
4641     // lock-free so we have to handle some special situations.
4642     //
4643     ThreadsList *current_list = NULL;
4644     while (true) {
4645       current_list = thread->get_threads_hazard_ptr();
4646       // No hazard ptr so nothing more to do.
4647       if (current_list == NULL) {
4648         assert(thread->get_nested_threads_hazard_ptr() == NULL,
4649                "cannot have a nested hazard ptr with a NULL regular hazard ptr");
4650         return;
4651       }
4652 
4653       // If the hazard ptr is verified as stable (since it is not tagged),
4654       // then it is safe to use.
4655       if (!Thread::is_hazard_ptr_tagged(current_list)) break;
4656 
4657       // The hazard ptr is tagged as not yet verified as being stable
4658       // so we are racing with acquire_stable_list(). This exchange
4659       // attempts to invalidate the hazard ptr. If we win the race,
4660       // then we can ignore this unstable hazard ptr and the other
4661       // thread will retry the attempt to publish a stable hazard ptr.
4662       // If we lose the race, then we retry our attempt to look at the
4663       // hazard ptr.
4664       if (thread->cmpxchg_threads_hazard_ptr(NULL, current_list) == current_list) return;
4665     }
4666 
4667     // The current JavaThread has a hazard ptr (ThreadsList reference)
4668     // which might be _smr_java_thread_list or it might be an older
4669     // ThreadsList that has been removed but not freed. In either case,
4670     // the hazard ptr is protecting all the JavaThreads on that
4671     // ThreadsList.
4672     AddThreadHazardPointerThreadClosure add_cl(_table);
4673     current_list->threads_do(&add_cl);
4674 
4675     // Any NestedThreadsLists are also protecting JavaThreads so
4676     // gather those also; the ThreadsLists may be different.
4677     for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr();
4678          node != NULL; node = node->next()) {
4679       node->t_list()->threads_do(&add_cl);
4680     }
4681   }
4682 };
4683 
4684 // Closure to print JavaThreads that have a hazard ptr (ThreadsList
4685 // reference) that contains an indirect reference to a specific JavaThread.
4686 //
4687 class ScanHazardPtrPrintMatchingThreadsClosure : public ThreadClosure {
4688  private:
4689   JavaThread *_thread;
4690  public:
4691   ScanHazardPtrPrintMatchingThreadsClosure(JavaThread *thread) : _thread(thread) {}
4692 
4693   virtual void do_thread(Thread *thread) {
4694     assert_locked_or_safepoint(Threads_lock);
4695 
4696     if (thread == NULL) return;
4697     ThreadsList *current_list = thread->get_threads_hazard_ptr();
4698     if (current_list == NULL) {
4699       assert(thread->get_nested_threads_hazard_ptr() == NULL,
4700              "cannot have a nested hazard ptr with a NULL regular hazard ptr");
4701       return;
4702     }
4703     // If the hazard ptr is unverified, then ignore it.
4704     if (Thread::is_hazard_ptr_tagged(current_list)) return;
4705 
4706     // The current JavaThread has a hazard ptr (ThreadsList reference)
4707     // which might be _smr_java_thread_list or it might be an older
4708     // ThreadsList that has been removed but not freed. In either case,
4709     // the hazard ptr is protecting all the JavaThreads on that
4710     // ThreadsList, but we only care about matching a specific JavaThread.
4711     DO_JAVA_THREADS(current_list, p) {
4712       if (p == _thread) {
4713         log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread1=" INTPTR_FORMAT " has a hazard pointer for thread2=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread), p2i(_thread));
4714         break;
4715       }
4716     }
4717 
4718     // Any NestedThreadsLists are also protecting JavaThreads so
4719     // check those also; the ThreadsLists may be different.
4720     for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr();
4721          node != NULL; node = node->next()) {
4722       DO_JAVA_THREADS(node->t_list(), p) {
4723         if (p == _thread) {
4724           log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread1=" INTPTR_FORMAT " has a nested hazard pointer for thread2=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread), p2i(_thread));
4725           return;
4726         }
4727       }
4728     }
4729   }
4730 };
4731 
4732 // Return true if the specified JavaThread is protected by a hazard
4733 // pointer (ThreadsList reference). Otherwise, returns false.
4734 //
4735 bool Threads::is_a_protected_JavaThread(JavaThread *thread) {
4736   assert_locked_or_safepoint(Threads_lock);
4737 
4738   // Hash table size should be first power of two higher than twice
4739   // the length of the Threads list.
4740   int hash_table_size = MIN2(_number_of_threads, 32) << 1;
4741   hash_table_size--;
4742   hash_table_size |= hash_table_size >> 1;
4743   hash_table_size |= hash_table_size >> 2;
4744   hash_table_size |= hash_table_size >> 4;
4745   hash_table_size |= hash_table_size >> 8;
4746   hash_table_size |= hash_table_size >> 16;
4747   hash_table_size++;
4748 
4749   // Gather a hash table of the JavaThreads indirectly referenced by
4750   // hazard ptrs.
4751   ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size);
4752   ScanHazardPtrGatherProtectedThreadsClosure scan_cl(scan_table);
4753   Threads::threads_do(&scan_cl);
4754 
4755   bool thread_is_protected = false;
4756   if (scan_table->has_entry((void*)thread)) {
4757     thread_is_protected = true;
4758   }
4759   delete scan_table;
4760   return thread_is_protected;
4761 }
4762 
4763 // Safely delete a JavaThread when it is no longer in use by a
4764 // ThreadsListHandle.
4765 //
4766 void Threads::smr_delete(JavaThread *thread) {
4767   assert(!Threads_lock->owned_by_self(), "sanity");
4768 
4769   bool has_logged_once = false;
4770   elapsedTimer timer;
4771   if (EnableThreadSMRStatistics) {
4772     timer.start();
4773   }
4774 
4775   while (true) {
4776     {
4777       // No safepoint check because this JavaThread is not on the
4778       // Threads list.
4779       MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
4780       // Cannot use a MonitorLockerEx helper here because we have
4781       // to drop the Threads_lock first if we wait.
4782       Threads::smr_delete_lock()->lock_without_safepoint_check();
4783       // Set the smr_delete_notify flag after we grab smr_delete_lock
4784       // and before we scan hazard ptrs because we're doing
4785       // double-check locking in release_stable_list().
4786       Threads::set_smr_delete_notify();
4787 
4788       if (!is_a_protected_JavaThread(thread)) {
4789         // This is the common case.
4790         Threads::clear_smr_delete_notify();
4791         Threads::smr_delete_lock()->unlock();
4792         break;
4793       }
4794       if (!has_logged_once) {
4795         has_logged_once = true;
4796         log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread=" INTPTR_FORMAT " is not deleted.", os::current_thread_id(), p2i(thread));
4797         if (log_is_enabled(Debug, os, thread)) {
4798           ScanHazardPtrPrintMatchingThreadsClosure scan_cl(thread);
4799           Threads::threads_do(&scan_cl);
4800         }
4801       }
4802     } // We have to drop the Threads_lock to wait or delete the thread
4803 
4804     if (EnableThreadSMRStatistics) {
4805       _smr_delete_lock_wait_cnt++;
4806       if (_smr_delete_lock_wait_cnt > _smr_delete_lock_wait_max) {
4807         _smr_delete_lock_wait_max = _smr_delete_lock_wait_cnt;
4808       }
4809     }
4810     // Wait for a release_stable_list() call before we check again. No
4811     // safepoint check, no timeout, and not as suspend equivalent flag
4812     // because this JavaThread is not on the Threads list.
4813     Threads::smr_delete_lock()->wait(Mutex::_no_safepoint_check_flag, 0,
4814                                      !Mutex::_as_suspend_equivalent_flag);
4815     if (EnableThreadSMRStatistics) {
4816       _smr_delete_lock_wait_cnt--;
4817     }
4818 
4819     Threads::clear_smr_delete_notify();
4820     Threads::smr_delete_lock()->unlock();
4821     // Retry the whole scenario.
4822   }
4823 
4824   delete thread;
4825   if (EnableThreadSMRStatistics) {
4826     timer.stop();
4827     jint millis = (jint)timer.milliseconds();
4828     Threads::inc_smr_deleted_thread_cnt();
4829     Threads::add_smr_deleted_thread_times(millis);
4830     Threads::update_smr_deleted_thread_time_max(millis);
4831   }
4832 
4833   log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread=" INTPTR_FORMAT " is deleted.", os::current_thread_id(), p2i(thread));
4834 }
4835 
4836 bool Threads::smr_delete_notify() {
4837   // Use load_acquire() in order to see any updates to _smr_delete_notify
4838   // earlier than when smr_delete_lock is grabbed.
4839   return (OrderAccess::load_acquire(&_smr_delete_notify) != 0);
4840 }
4841 
4842 // set_smr_delete_notify() and clear_smr_delete_notify() are called
4843 // under the protection of the smr_delete_lock, but we also use an
4844 // Atomic operation to ensure the memory update is seen earlier than
4845 // when the smr_delete_lock is dropped.
4846 //
4847 void Threads::set_smr_delete_notify() {
4848   Atomic::inc(&_smr_delete_notify);
4849 }
4850 
4851 void Threads::clear_smr_delete_notify() {
4852   Atomic::dec(&_smr_delete_notify);
4853 }
4854 
4855 // Closure to gather hazard ptrs (ThreadsList references) into a hash table.
4856 //
4857 class ScanHazardPtrGatherThreadsListClosure : public ThreadClosure {
4858  private:
4859   ThreadScanHashtable *_table;
4860  public:
4861   ScanHazardPtrGatherThreadsListClosure(ThreadScanHashtable *table) : _table(table) {}
4862 
4863   virtual void do_thread(Thread* thread) {
4864     assert_locked_or_safepoint(Threads_lock);
4865 
4866     if (thread == NULL) return;
4867     ThreadsList *threads = thread->get_threads_hazard_ptr();
4868     if (threads == NULL) {
4869       assert(thread->get_nested_threads_hazard_ptr() == NULL,
4870              "cannot have a nested hazard ptr with a NULL regular hazard ptr");
4871       return;
4872     }
4873     // In this closure we always ignore the tag that might mark this
4874     // hazard ptr as not yet verified. If we happen to catch an
4875     // unverified hazard ptr that is subsequently discarded (not
4876     // published), then the only side effect is that we might keep a
4877     // to-be-deleted ThreadsList alive a little longer.
4878     threads = Thread::untag_hazard_ptr(threads);
4879     if (!_table->has_entry((void*)threads)) {
4880       _table->add_entry((void*)threads);
4881     }
4882 
4883     // Any NestedThreadsLists are also protecting JavaThreads so
4884     // gather those also; the ThreadsLists may be different.
4885     for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr();
4886          node != NULL; node = node->next()) {
4887       threads = node->t_list();
4888       if (!_table->has_entry((void*)threads)) {
4889         _table->add_entry((void*)threads);
4890       }
4891     }
4892   }
4893 };
4894 
4895 // Safely free a ThreadsList after a Threads::add() or Threads::remove().
4896 // The specified ThreadsList may not get deleted during this call if it
4897 // is still in-use (referenced by a hazard ptr). Other ThreadsLists
4898 // in the chain may get deleted by this call if they are no longer in-use.
4899 void Threads::smr_free_list(ThreadsList* threads) {
4900   assert_locked_or_safepoint(Threads_lock);
4901 
4902   threads->set_next_list(_smr_to_delete_list);
4903   _smr_to_delete_list = threads;
4904   if (EnableThreadSMRStatistics) {
4905     _smr_to_delete_list_cnt++;
4906     if (_smr_to_delete_list_cnt > _smr_to_delete_list_max) {
4907       _smr_to_delete_list_max = _smr_to_delete_list_cnt;
4908     }
4909   }
4910 
4911   // Hash table size should be first power of two higher than twice the length of the ThreadsList
4912   int hash_table_size = MIN2(_number_of_threads, 32) << 1;
4913   hash_table_size--;
4914   hash_table_size |= hash_table_size >> 1;
4915   hash_table_size |= hash_table_size >> 2;
4916   hash_table_size |= hash_table_size >> 4;
4917   hash_table_size |= hash_table_size >> 8;
4918   hash_table_size |= hash_table_size >> 16;
4919   hash_table_size++;
4920 
4921   // Gather a hash table of the current hazard ptrs:
4922   ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size);
4923   ScanHazardPtrGatherThreadsListClosure scan_cl(scan_table);
4924   Threads::threads_do(&scan_cl);
4925 
4926   // Walk through the linked list of pending freeable ThreadsLists
4927   // and free the ones that are not referenced from hazard ptrs.
4928   ThreadsList* current = _smr_to_delete_list;
4929   ThreadsList* prev = NULL;
4930   ThreadsList* next = NULL;
4931   bool threads_is_freed = false;
4932   while (current != NULL) {
4933     next = current->next_list();
4934     if (!scan_table->has_entry((void*)current)) {
4935       // This ThreadsList is not referenced by a hazard ptr.
4936       if (prev != NULL) {
4937         prev->set_next_list(next);
4938       }
4939       if (_smr_to_delete_list == current) {
4940         _smr_to_delete_list = next;
4941       }
4942 
4943       log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_free_list: threads=" INTPTR_FORMAT " is freed.", os::current_thread_id(), p2i(current));
4944       if (current == threads) threads_is_freed = true;
4945       delete current;
4946       if (EnableThreadSMRStatistics) {
4947         _smr_java_thread_list_free_cnt++;
4948         _smr_to_delete_list_cnt--;
4949       }
4950     } else {
4951       prev = current;
4952     }
4953     current = next;
4954   }
4955 
4956   if (!threads_is_freed) {
4957     // Only report "is not freed" on the original call to
4958     // smr_free_list() for this ThreadsList.
4959     log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_free_list: threads=" INTPTR_FORMAT " is not freed.", os::current_thread_id(), p2i(threads));
4960   }
4961 
4962   delete scan_table;
4963 }
4964 
4965 // Remove a JavaThread from a ThreadsList. The returned ThreadsList is a
4966 // new copy of the specified ThreadsList with the specified JavaThread
4967 // removed.
4968 ThreadsList *ThreadsList::remove_thread(ThreadsList* list, JavaThread* java_thread) {
4969   assert(list->_length > 0, "sanity");
4970 
4971   uint i = 0;
4972   DO_JAVA_THREADS(list, current) {
4973     if (current == java_thread) {
4974       break;
4975     }
4976     i++;
4977   }
4978   assert(i < list->_length, "did not find JavaThread on the list");
4979   const uint index = i;
4980   const uint new_length = list->_length - 1;
4981   const uint head_length = index;
4982   const uint tail_length = (new_length >= index) ? (new_length - index) : 0;
4983   ThreadsList *const new_list = new ThreadsList(new_length);
4984 
4985   if (head_length > 0) {
4986     Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length);
4987   }
4988   if (tail_length > 0) {
4989     Copy::disjoint_words((HeapWord*)list->_threads + index + 1, (HeapWord*)new_list->_threads + index, tail_length);
4990   }
4991 
4992   return new_list;
4993 }
4994 
4995 // Add a JavaThread to a ThreadsList. The returned ThreadsList is a
4996 // new copy of the specified ThreadsList with the specified JavaThread
4997 // appended to the end.
4998 ThreadsList *ThreadsList::add_thread(ThreadsList *list, JavaThread *java_thread) {
4999   const uint index = list->_length;
5000   const uint new_length = index + 1;
5001   const uint head_length = index;
5002   ThreadsList *const new_list = new ThreadsList(new_length);
5003 
5004   if (head_length > 0) {
5005     Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length);
5006   }
5007   *(JavaThread**)(new_list->_threads + index) = java_thread;
5008 
5009   return new_list;
5010 }
5011 
5012 int ThreadsList::find_index_of_JavaThread(JavaThread *target) {
5013   if (target == NULL) {
5014     return -1;
5015   }
5016   for (uint i = 0; i < length(); i++) {
5017     if (target == thread_at(i)) {
5018       return (int)i;
5019     }
5020   }
5021   return -1;
5022 }
5023 
5024 JavaThread* ThreadsList::find_JavaThread_from_java_tid(jlong java_tid) const {
5025   DO_JAVA_THREADS(this, thread) {
5026     oop tobj = thread->threadObj();
5027     // Ignore the thread if it hasn't run yet, has exited
5028     // or is starting to exit.
5029     if (tobj != NULL && !thread->is_exiting() &&
5030         java_tid == java_lang_Thread::thread_id(tobj)) {
5031       // found a match
5032       return thread;
5033     }
5034   }
5035   return NULL;
5036 }
5037 
5038 bool ThreadsList::includes(const JavaThread * const p) const {
5039   if (p == NULL) {
5040     return false;
5041   }
5042   DO_JAVA_THREADS(this, q) {
5043     if (q == p) {
5044       return true;
5045     }
5046   }
5047   return false;
5048 }
5049 
5050 void Threads::add(JavaThread* p, bool force_daemon) {
5051   // The threads lock must be owned at this point
5052   assert_locked_or_safepoint(Threads_lock);
5053 
5054   // See the comment for this method in thread.hpp for its purpose and
5055   // why it is called here.
5056   p->initialize_queues();
5057   p->set_next(_thread_list);
5058   _thread_list = p;
5059 
5060   // Once a JavaThread is added to the Threads list, smr_delete() has
5061   // to be used to delete it. Otherwise we can just delete it directly.
5062   p->set_on_thread_list();
5063 
5064   _number_of_threads++;
5065   oop threadObj = p->threadObj();
5066   bool daemon = true;
5067   // Bootstrapping problem: threadObj can be null for initial
5068   // JavaThread (or for threads attached via JNI)
5069   if ((!force_daemon) && (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj))) {
5070     _number_of_non_daemon_threads++;
5071     daemon = false;
5072   }
5073 
5074   ThreadService::add_thread(p, daemon);
5075 
5076   // Maintain fast thread list
5077   ThreadsList *new_list = ThreadsList::add_thread(get_smr_java_thread_list(), p);
5078   if (EnableThreadSMRStatistics) {
5079     _smr_java_thread_list_alloc_cnt++;
5080     if (new_list->length() > _smr_java_thread_list_max) {
5081       _smr_java_thread_list_max = new_list->length();
5082     }
5083   }
5084   // Initial _smr_java_thread_list will not generate a "Threads::add" mesg.
5085   log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::add: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list));
5086 
5087   ThreadsList *old_list = xchg_smr_java_thread_list(new_list);
5088   smr_free_list(old_list);
5089 
5090   // Possible GC point.
5091   Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p));
5092 }
5093 
5094 void Threads::remove(JavaThread* p) {
5095 
5096   // Reclaim the objectmonitors from the omInUseList and omFreeList of the moribund thread.
5097   ObjectSynchronizer::omFlush(p);
5098 
5099   // Extra scope needed for Thread_lock, so we can check
5100   // that we do not remove thread without safepoint code notice
5101   { MutexLocker ml(Threads_lock);
5102 
5103     assert(get_smr_java_thread_list()->includes(p), "p must be present");
5104 
5105     // Maintain fast thread list
5106     ThreadsList *new_list = ThreadsList::remove_thread(get_smr_java_thread_list(), p);
5107     if (EnableThreadSMRStatistics) {
5108       _smr_java_thread_list_alloc_cnt++;
5109       // This list is smaller so no need to check for a "longest" update.
5110     }
5111 
5112     // Final _smr_java_thread_list will not generate a "Threads::remove" mesg.
5113     log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::remove: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list));
5114 
5115     ThreadsList *old_list = xchg_smr_java_thread_list(new_list);
5116     smr_free_list(old_list);
5117 
5118     JavaThread* current = _thread_list;
5119     JavaThread* prev    = NULL;
5120 
5121     while (current != p) {
5122       prev    = current;
5123       current = current->next();
5124     }
5125 
5126     if (prev) {
5127       prev->set_next(current->next());
5128     } else {
5129       _thread_list = p->next();
5130     }
5131 
5132     _number_of_threads--;
5133     oop threadObj = p->threadObj();
5134     bool daemon = true;
5135     if (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj)) {
5136       _number_of_non_daemon_threads--;
5137       daemon = false;
5138 
5139       // Only one thread left, do a notify on the Threads_lock so a thread waiting
5140       // on destroy_vm will wake up.
5141       if (number_of_non_daemon_threads() == 1) {
5142         Threads_lock->notify_all();
5143       }
5144     }
5145     ThreadService::remove_thread(p, daemon);
5146 
5147     // Make sure that safepoint code disregard this thread. This is needed since
5148     // the thread might mess around with locks after this point. This can cause it
5149     // to do callbacks into the safepoint code. However, the safepoint code is not aware
5150     // of this thread since it is removed from the queue.
5151     p->set_terminated_value();
5152   } // unlock Threads_lock
5153 
5154   // Since Events::log uses a lock, we grab it outside the Threads_lock
5155   Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p));
5156 }
5157 
5158 // Operations on the Threads list for GC.  These are not explicitly locked,
5159 // but the garbage collector must provide a safe context for them to run.
5160 // In particular, these things should never be called when the Threads_lock
5161 // is held by some other thread. (Note: the Safepoint abstraction also
5162 // uses the Threads_lock to guarantee this property. It also makes sure that
5163 // all threads gets blocked when exiting or starting).
5164 
5165 void Threads::oops_do(OopClosure* f, CodeBlobClosure* cf) {
5166   ALL_JAVA_THREADS(p) {
5167     p->oops_do(f, cf);
5168   }
5169   VMThread::vm_thread()->oops_do(f, cf);
5170 }
5171 
5172 void Threads::change_thread_claim_parity() {
5173   // Set the new claim parity.
5174   assert(_thread_claim_parity >= 0 && _thread_claim_parity <= 2,
5175          "Not in range.");
5176   _thread_claim_parity++;
5177   if (_thread_claim_parity == 3) _thread_claim_parity = 1;
5178   assert(_thread_claim_parity >= 1 && _thread_claim_parity <= 2,
5179          "Not in range.");
5180 }
5181 
5182 #ifdef ASSERT
5183 void Threads::assert_all_threads_claimed() {
5184   ALL_JAVA_THREADS(p) {
5185     const int thread_parity = p->oops_do_parity();
5186     assert((thread_parity == _thread_claim_parity),
5187            "Thread " PTR_FORMAT " has incorrect parity %d != %d", p2i(p), thread_parity, _thread_claim_parity);
5188   }
5189   VMThread* vmt = VMThread::vm_thread();
5190   const int thread_parity = vmt->oops_do_parity();
5191   assert((thread_parity == _thread_claim_parity),
5192          "VMThread " PTR_FORMAT " has incorrect parity %d != %d", p2i(vmt), thread_parity, _thread_claim_parity);
5193 }
5194 #endif // ASSERT
5195 
5196 class ParallelOopsDoThreadClosure : public ThreadClosure {
5197 private:
5198   OopClosure* _f;
5199   CodeBlobClosure* _cf;
5200 public:
5201   ParallelOopsDoThreadClosure(OopClosure* f, CodeBlobClosure* cf) : _f(f), _cf(cf) {}
5202   void do_thread(Thread* t) {
5203     t->oops_do(_f, _cf);
5204   }
5205 };
5206 
5207 void Threads::possibly_parallel_oops_do(bool is_par, OopClosure* f, CodeBlobClosure* cf) {
5208   ParallelOopsDoThreadClosure tc(f, cf);
5209   possibly_parallel_threads_do(is_par, &tc);
5210 }
5211 
5212 #if INCLUDE_ALL_GCS
5213 // Used by ParallelScavenge
5214 void Threads::create_thread_roots_tasks(GCTaskQueue* q) {
5215   ALL_JAVA_THREADS(p) {
5216     q->enqueue(new ThreadRootsTask(p));
5217   }
5218   q->enqueue(new ThreadRootsTask(VMThread::vm_thread()));
5219 }
5220 
5221 // Used by Parallel Old
5222 void Threads::create_thread_roots_marking_tasks(GCTaskQueue* q) {
5223   ALL_JAVA_THREADS(p) {
5224     q->enqueue(new ThreadRootsMarkingTask(p));
5225   }
5226   q->enqueue(new ThreadRootsMarkingTask(VMThread::vm_thread()));
5227 }
5228 #endif // INCLUDE_ALL_GCS
5229 
5230 void Threads::nmethods_do(CodeBlobClosure* cf) {
5231   ALL_JAVA_THREADS(p) {
5232     // This is used by the code cache sweeper to mark nmethods that are active
5233     // on the stack of a Java thread. Ignore the sweeper thread itself to avoid
5234     // marking CodeCacheSweeperThread::_scanned_compiled_method as active.
5235     if(!p->is_Code_cache_sweeper_thread()) {
5236       p->nmethods_do(cf);
5237     }
5238   }
5239 }
5240 
5241 void Threads::metadata_do(void f(Metadata*)) {
5242   ALL_JAVA_THREADS(p) {
5243     p->metadata_do(f);
5244   }
5245 }
5246 
5247 class ThreadHandlesClosure : public ThreadClosure {
5248   void (*_f)(Metadata*);
5249  public:
5250   ThreadHandlesClosure(void f(Metadata*)) : _f(f) {}
5251   virtual void do_thread(Thread* thread) {
5252     thread->metadata_handles_do(_f);
5253   }
5254 };
5255 
5256 void Threads::metadata_handles_do(void f(Metadata*)) {
5257   // Only walk the Handles in Thread.
5258   ThreadHandlesClosure handles_closure(f);
5259   threads_do(&handles_closure);
5260 }
5261 
5262 void Threads::deoptimized_wrt_marked_nmethods() {
5263   ALL_JAVA_THREADS(p) {
5264     p->deoptimized_wrt_marked_nmethods();
5265   }
5266 }
5267 
5268 
5269 // Get count Java threads that are waiting to enter the specified monitor.
5270 GrowableArray<JavaThread*>* Threads::get_pending_threads(ThreadsList * t_list,
5271                                                          int count,
5272                                                          address monitor) {
5273   GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
5274 
5275   int i = 0;
5276   DO_JAVA_THREADS(t_list, p) {
5277     if (!p->can_call_java()) continue;
5278 
5279     address pending = (address)p->current_pending_monitor();
5280     if (pending == monitor) {             // found a match
5281       if (i < count) result->append(p);   // save the first count matches
5282       i++;
5283     }
5284   }
5285 
5286   return result;
5287 }
5288 
5289 
5290 JavaThread *Threads::owning_thread_from_monitor_owner(ThreadsList * t_list,
5291                                                       address owner) {
5292   // NULL owner means not locked so we can skip the search
5293   if (owner == NULL) return NULL;
5294 
5295   DO_JAVA_THREADS(t_list, p) {
5296     // first, see if owner is the address of a Java thread
5297     if (owner == (address)p) return p;
5298   }
5299 
5300   // Cannot assert on lack of success here since this function may be
5301   // used by code that is trying to report useful problem information
5302   // like deadlock detection.
5303   if (UseHeavyMonitors) return NULL;
5304 
5305   // If we didn't find a matching Java thread and we didn't force use of
5306   // heavyweight monitors, then the owner is the stack address of the
5307   // Lock Word in the owning Java thread's stack.
5308   //
5309   JavaThread* the_owner = NULL;
5310   DO_JAVA_THREADS(t_list, q) {
5311     if (q->is_lock_owned(owner)) {
5312       the_owner = q;
5313       break;
5314     }
5315   }
5316 
5317   // cannot assert on lack of success here; see above comment
5318   return the_owner;
5319 }
5320 
5321 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
5322 void Threads::print_on(outputStream* st, bool print_stacks,
5323                        bool internal_format, bool print_concurrent_locks) {
5324   char buf[32];
5325   st->print_raw_cr(os::local_time_string(buf, sizeof(buf)));
5326 
5327   st->print_cr("Full thread dump %s (%s %s):",
5328                Abstract_VM_Version::vm_name(),
5329                Abstract_VM_Version::vm_release(),
5330                Abstract_VM_Version::vm_info_string());
5331   st->cr();
5332 
5333 #if INCLUDE_SERVICES
5334   // Dump concurrent locks
5335   ConcurrentLocksDump concurrent_locks;
5336   if (print_concurrent_locks) {
5337     concurrent_locks.dump_at_safepoint();
5338   }
5339 #endif // INCLUDE_SERVICES
5340 
5341   print_smr_info_on(st);
5342   st->cr();
5343 
5344   ALL_JAVA_THREADS(p) {
5345     ResourceMark rm;
5346     p->print_on(st);
5347     if (print_stacks) {
5348       if (internal_format) {
5349         p->trace_stack();
5350       } else {
5351         p->print_stack_on(st);
5352       }
5353     }
5354     st->cr();
5355 #if INCLUDE_SERVICES
5356     if (print_concurrent_locks) {
5357       concurrent_locks.print_locks_on(p, st);
5358     }
5359 #endif // INCLUDE_SERVICES
5360   }
5361 
5362   VMThread::vm_thread()->print_on(st);
5363   st->cr();
5364   Universe::heap()->print_gc_threads_on(st);
5365   WatcherThread* wt = WatcherThread::watcher_thread();
5366   if (wt != NULL) {
5367     wt->print_on(st);
5368     st->cr();
5369   }
5370 
5371   st->flush();
5372 }
5373 
5374 // Log Threads class SMR info.
5375 void Threads::log_smr_statistics() {
5376   LogTarget(Info, thread, smr) log;
5377   if (log.is_enabled()) {
5378     LogStream out(log);
5379     print_smr_info_on(&out);
5380   }
5381 }
5382 
5383 // Print Threads class SMR info.
5384 void Threads::print_smr_info_on(outputStream* st) {
5385   // Only grab the Threads_lock if we don't already own it
5386   // and if we are not reporting an error.
5387   MutexLockerEx ml((Threads_lock->owned_by_self() || VMError::is_error_reported()) ? NULL : Threads_lock);
5388 
5389   st->print_cr("Threads class SMR info:");
5390   st->print_cr("_smr_java_thread_list=" INTPTR_FORMAT ", length=%u, "
5391                "elements={", p2i(_smr_java_thread_list),
5392                _smr_java_thread_list->length());
5393   print_smr_info_elements_on(st, _smr_java_thread_list);
5394   st->print_cr("}");
5395   if (_smr_to_delete_list != NULL) {
5396     st->print_cr("_smr_to_delete_list=" INTPTR_FORMAT ", length=%u, "
5397                  "elements={", p2i(_smr_to_delete_list),
5398                  _smr_to_delete_list->length());
5399     print_smr_info_elements_on(st, _smr_to_delete_list);
5400     st->print_cr("}");
5401     for (ThreadsList *t_list = _smr_to_delete_list->next_list();
5402          t_list != NULL; t_list = t_list->next_list()) {
5403       st->print("next-> " INTPTR_FORMAT ", length=%u, "
5404                 "elements={", p2i(t_list), t_list->length());
5405       print_smr_info_elements_on(st, t_list);
5406       st->print_cr("}");
5407     }
5408   }
5409   if (!EnableThreadSMRStatistics) {
5410     return;
5411   }
5412   st->print_cr("_smr_java_thread_list_alloc_cnt=%ld, "
5413                "_smr_java_thread_list_free_cnt=%ld, "
5414                "_smr_java_thread_list_max=%u, "
5415                "_smr_nested_thread_list_max=%u",
5416                _smr_java_thread_list_alloc_cnt,
5417                _smr_java_thread_list_free_cnt,
5418                _smr_java_thread_list_max,
5419                _smr_nested_thread_list_max);
5420   if (_smr_tlh_cnt > 0) {
5421     st->print_cr("_smr_tlh_cnt=" INT32_FORMAT
5422                  ", _smr_tlh_times=" INT32_FORMAT
5423                  ", avg_smr_tlh_time=%0.2f"
5424                  ", _smr_tlh_time_max=" INT32_FORMAT,
5425                  _smr_tlh_cnt, _smr_tlh_times,
5426                  ((double) _smr_tlh_times / _smr_tlh_cnt),
5427                  _smr_tlh_time_max);
5428   }
5429   if (_smr_deleted_thread_cnt > 0) {
5430     st->print_cr("_smr_deleted_thread_cnt=" INT32_FORMAT
5431                  ", _smr_deleted_thread_times=" INT32_FORMAT
5432                  ", avg_smr_deleted_thread_time=%0.2f"
5433                  ", _smr_deleted_thread_time_max=" INT32_FORMAT,
5434                  _smr_deleted_thread_cnt, _smr_deleted_thread_times,
5435                  ((double) _smr_deleted_thread_times / _smr_deleted_thread_cnt),
5436                  _smr_deleted_thread_time_max);
5437   }
5438   st->print_cr("_smr_delete_lock_wait_cnt=%u, _smr_delete_lock_wait_max=%u",
5439                _smr_delete_lock_wait_cnt, _smr_delete_lock_wait_max);
5440   st->print_cr("_smr_to_delete_list_cnt=%u, _smr_to_delete_list_max=%u",
5441                _smr_to_delete_list_cnt, _smr_to_delete_list_max);
5442 }
5443 
5444 // Print ThreadsList elements (4 per line).
5445 void Threads::print_smr_info_elements_on(outputStream* st,
5446                                          ThreadsList* t_list) {
5447   uint cnt = 0;
5448   JavaThreadIterator jti(t_list);
5449   for (JavaThread *jt = jti.first(); jt != NULL; jt = jti.next()) {
5450     st->print(INTPTR_FORMAT, p2i(jt));
5451     if (cnt < t_list->length() - 1) {
5452       // Separate with comma or comma-space except for the last one.
5453       if (((cnt + 1) % 4) == 0) {
5454         // Four INTPTR_FORMAT fit on an 80 column line so end the
5455         // current line with just a comma.
5456         st->print_cr(",");
5457       } else {
5458         // Not the last one on the current line so use comma-space:
5459         st->print(", ");
5460       }
5461     } else {
5462       // Last one so just end the current line.
5463       st->cr();
5464     }
5465     cnt++;
5466   }
5467 }
5468 
5469 void Threads::print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf,
5470                              int buflen, bool* found_current) {
5471   if (this_thread != NULL) {
5472     bool is_current = (current == this_thread);
5473     *found_current = *found_current || is_current;
5474     st->print("%s", is_current ? "=>" : "  ");
5475 
5476     st->print(PTR_FORMAT, p2i(this_thread));
5477     st->print(" ");
5478     this_thread->print_on_error(st, buf, buflen);
5479     st->cr();
5480   }
5481 }
5482 
5483 class PrintOnErrorClosure : public ThreadClosure {
5484   outputStream* _st;
5485   Thread* _current;
5486   char* _buf;
5487   int _buflen;
5488   bool* _found_current;
5489  public:
5490   PrintOnErrorClosure(outputStream* st, Thread* current, char* buf,
5491                       int buflen, bool* found_current) :
5492    _st(st), _current(current), _buf(buf), _buflen(buflen), _found_current(found_current) {}
5493 
5494   virtual void do_thread(Thread* thread) {
5495     Threads::print_on_error(thread, _st, _current, _buf, _buflen, _found_current);
5496   }
5497 };
5498 
5499 // Threads::print_on_error() is called by fatal error handler. It's possible
5500 // that VM is not at safepoint and/or current thread is inside signal handler.
5501 // Don't print stack trace, as the stack may not be walkable. Don't allocate
5502 // memory (even in resource area), it might deadlock the error handler.
5503 void Threads::print_on_error(outputStream* st, Thread* current, char* buf,
5504                              int buflen) {
5505   print_smr_info_on(st);
5506   st->cr();
5507 
5508   bool found_current = false;
5509   st->print_cr("Java Threads: ( => current thread )");
5510   ALL_JAVA_THREADS(thread) {
5511     print_on_error(thread, st, current, buf, buflen, &found_current);
5512   }
5513   st->cr();
5514 
5515   st->print_cr("Other Threads:");
5516   print_on_error(VMThread::vm_thread(), st, current, buf, buflen, &found_current);
5517   print_on_error(WatcherThread::watcher_thread(), st, current, buf, buflen, &found_current);
5518 
5519   PrintOnErrorClosure print_closure(st, current, buf, buflen, &found_current);
5520   Universe::heap()->gc_threads_do(&print_closure);
5521 
5522   if (!found_current) {
5523     st->cr();
5524     st->print("=>" PTR_FORMAT " (exited) ", p2i(current));
5525     current->print_on_error(st, buf, buflen);
5526     st->cr();
5527   }
5528   st->cr();
5529 
5530   st->print_cr("Threads with active compile tasks:");
5531   print_threads_compiling(st, buf, buflen);
5532 }
5533 
5534 void Threads::print_threads_compiling(outputStream* st, char* buf, int buflen) {
5535   ALL_JAVA_THREADS(thread) {
5536     if (thread->is_Compiler_thread()) {
5537       CompilerThread* ct = (CompilerThread*) thread;
5538       if (ct->task() != NULL) {
5539         thread->print_name_on_error(st, buf, buflen);
5540         ct->task()->print(st, NULL, true, true);
5541       }
5542     }
5543   }
5544 }
5545 
5546 
5547 // Internal SpinLock and Mutex
5548 // Based on ParkEvent
5549 
5550 // Ad-hoc mutual exclusion primitives: SpinLock and Mux
5551 //
5552 // We employ SpinLocks _only for low-contention, fixed-length
5553 // short-duration critical sections where we're concerned
5554 // about native mutex_t or HotSpot Mutex:: latency.
5555 // The mux construct provides a spin-then-block mutual exclusion
5556 // mechanism.
5557 //
5558 // Testing has shown that contention on the ListLock guarding gFreeList
5559 // is common.  If we implement ListLock as a simple SpinLock it's common
5560 // for the JVM to devolve to yielding with little progress.  This is true
5561 // despite the fact that the critical sections protected by ListLock are
5562 // extremely short.
5563 //
5564 // TODO-FIXME: ListLock should be of type SpinLock.
5565 // We should make this a 1st-class type, integrated into the lock
5566 // hierarchy as leaf-locks.  Critically, the SpinLock structure
5567 // should have sufficient padding to avoid false-sharing and excessive
5568 // cache-coherency traffic.
5569 
5570 
5571 typedef volatile int SpinLockT;
5572 
5573 void Thread::SpinAcquire(volatile int * adr, const char * LockName) {
5574   if (Atomic::cmpxchg (1, adr, 0) == 0) {
5575     return;   // normal fast-path return
5576   }
5577 
5578   // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
5579   TEVENT(SpinAcquire - ctx);
5580   int ctr = 0;
5581   int Yields = 0;
5582   for (;;) {
5583     while (*adr != 0) {
5584       ++ctr;
5585       if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
5586         if (Yields > 5) {
5587           os::naked_short_sleep(1);
5588         } else {
5589           os::naked_yield();
5590           ++Yields;
5591         }
5592       } else {
5593         SpinPause();
5594       }
5595     }
5596     if (Atomic::cmpxchg(1, adr, 0) == 0) return;
5597   }
5598 }
5599 
5600 void Thread::SpinRelease(volatile int * adr) {
5601   assert(*adr != 0, "invariant");
5602   OrderAccess::fence();      // guarantee at least release consistency.
5603   // Roach-motel semantics.
5604   // It's safe if subsequent LDs and STs float "up" into the critical section,
5605   // but prior LDs and STs within the critical section can't be allowed
5606   // to reorder or float past the ST that releases the lock.
5607   // Loads and stores in the critical section - which appear in program
5608   // order before the store that releases the lock - must also appear
5609   // before the store that releases the lock in memory visibility order.
5610   // Conceptually we need a #loadstore|#storestore "release" MEMBAR before
5611   // the ST of 0 into the lock-word which releases the lock, so fence
5612   // more than covers this on all platforms.
5613   *adr = 0;
5614 }
5615 
5616 // muxAcquire and muxRelease:
5617 //
5618 // *  muxAcquire and muxRelease support a single-word lock-word construct.
5619 //    The LSB of the word is set IFF the lock is held.
5620 //    The remainder of the word points to the head of a singly-linked list
5621 //    of threads blocked on the lock.
5622 //
5623 // *  The current implementation of muxAcquire-muxRelease uses its own
5624 //    dedicated Thread._MuxEvent instance.  If we're interested in
5625 //    minimizing the peak number of extant ParkEvent instances then
5626 //    we could eliminate _MuxEvent and "borrow" _ParkEvent as long
5627 //    as certain invariants were satisfied.  Specifically, care would need
5628 //    to be taken with regards to consuming unpark() "permits".
5629 //    A safe rule of thumb is that a thread would never call muxAcquire()
5630 //    if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
5631 //    park().  Otherwise the _ParkEvent park() operation in muxAcquire() could
5632 //    consume an unpark() permit intended for monitorenter, for instance.
5633 //    One way around this would be to widen the restricted-range semaphore
5634 //    implemented in park().  Another alternative would be to provide
5635 //    multiple instances of the PlatformEvent() for each thread.  One
5636 //    instance would be dedicated to muxAcquire-muxRelease, for instance.
5637 //
5638 // *  Usage:
5639 //    -- Only as leaf locks
5640 //    -- for short-term locking only as muxAcquire does not perform
5641 //       thread state transitions.
5642 //
5643 // Alternatives:
5644 // *  We could implement muxAcquire and muxRelease with MCS or CLH locks
5645 //    but with parking or spin-then-park instead of pure spinning.
5646 // *  Use Taura-Oyama-Yonenzawa locks.
5647 // *  It's possible to construct a 1-0 lock if we encode the lockword as
5648 //    (List,LockByte).  Acquire will CAS the full lockword while Release
5649 //    will STB 0 into the LockByte.  The 1-0 scheme admits stranding, so
5650 //    acquiring threads use timers (ParkTimed) to detect and recover from
5651 //    the stranding window.  Thread/Node structures must be aligned on 256-byte
5652 //    boundaries by using placement-new.
5653 // *  Augment MCS with advisory back-link fields maintained with CAS().
5654 //    Pictorially:  LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
5655 //    The validity of the backlinks must be ratified before we trust the value.
5656 //    If the backlinks are invalid the exiting thread must back-track through the
5657 //    the forward links, which are always trustworthy.
5658 // *  Add a successor indication.  The LockWord is currently encoded as
5659 //    (List, LOCKBIT:1).  We could also add a SUCCBIT or an explicit _succ variable
5660 //    to provide the usual futile-wakeup optimization.
5661 //    See RTStt for details.
5662 // *  Consider schedctl.sc_nopreempt to cover the critical section.
5663 //
5664 
5665 
5666 const intptr_t LOCKBIT = 1;
5667 
5668 void Thread::muxAcquire(volatile intptr_t * Lock, const char * LockName) {
5669   intptr_t w = Atomic::cmpxchg(LOCKBIT, Lock, (intptr_t)0);
5670   if (w == 0) return;
5671   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5672     return;
5673   }
5674 
5675   TEVENT(muxAcquire - Contention);
5676   ParkEvent * const Self = Thread::current()->_MuxEvent;
5677   assert((intptr_t(Self) & LOCKBIT) == 0, "invariant");
5678   for (;;) {
5679     int its = (os::is_MP() ? 100 : 0) + 1;
5680 
5681     // Optional spin phase: spin-then-park strategy
5682     while (--its >= 0) {
5683       w = *Lock;
5684       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5685         return;
5686       }
5687     }
5688 
5689     Self->reset();
5690     Self->OnList = intptr_t(Lock);
5691     // The following fence() isn't _strictly necessary as the subsequent
5692     // CAS() both serializes execution and ratifies the fetched *Lock value.
5693     OrderAccess::fence();
5694     for (;;) {
5695       w = *Lock;
5696       if ((w & LOCKBIT) == 0) {
5697         if (Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5698           Self->OnList = 0;   // hygiene - allows stronger asserts
5699           return;
5700         }
5701         continue;      // Interference -- *Lock changed -- Just retry
5702       }
5703       assert(w & LOCKBIT, "invariant");
5704       Self->ListNext = (ParkEvent *) (w & ~LOCKBIT);
5705       if (Atomic::cmpxchg(intptr_t(Self)|LOCKBIT, Lock, w) == w) break;
5706     }
5707 
5708     while (Self->OnList != 0) {
5709       Self->park();
5710     }
5711   }
5712 }
5713 
5714 void Thread::muxAcquireW(volatile intptr_t * Lock, ParkEvent * ev) {
5715   intptr_t w = Atomic::cmpxchg(LOCKBIT, Lock, (intptr_t)0);
5716   if (w == 0) return;
5717   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5718     return;
5719   }
5720 
5721   TEVENT(muxAcquire - Contention);
5722   ParkEvent * ReleaseAfter = NULL;
5723   if (ev == NULL) {
5724     ev = ReleaseAfter = ParkEvent::Allocate(NULL);
5725   }
5726   assert((intptr_t(ev) & LOCKBIT) == 0, "invariant");
5727   for (;;) {
5728     guarantee(ev->OnList == 0, "invariant");
5729     int its = (os::is_MP() ? 100 : 0) + 1;
5730 
5731     // Optional spin phase: spin-then-park strategy
5732     while (--its >= 0) {
5733       w = *Lock;
5734       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5735         if (ReleaseAfter != NULL) {
5736           ParkEvent::Release(ReleaseAfter);
5737         }
5738         return;
5739       }
5740     }
5741 
5742     ev->reset();
5743     ev->OnList = intptr_t(Lock);
5744     // The following fence() isn't _strictly necessary as the subsequent
5745     // CAS() both serializes execution and ratifies the fetched *Lock value.
5746     OrderAccess::fence();
5747     for (;;) {
5748       w = *Lock;
5749       if ((w & LOCKBIT) == 0) {
5750         if (Atomic::cmpxchg(w|LOCKBIT, Lock, w) == w) {
5751           ev->OnList = 0;
5752           // We call ::Release while holding the outer lock, thus
5753           // artificially lengthening the critical section.
5754           // Consider deferring the ::Release() until the subsequent unlock(),
5755           // after we've dropped the outer lock.
5756           if (ReleaseAfter != NULL) {
5757             ParkEvent::Release(ReleaseAfter);
5758           }
5759           return;
5760         }
5761         continue;      // Interference -- *Lock changed -- Just retry
5762       }
5763       assert(w & LOCKBIT, "invariant");
5764       ev->ListNext = (ParkEvent *) (w & ~LOCKBIT);
5765       if (Atomic::cmpxchg(intptr_t(ev)|LOCKBIT, Lock, w) == w) break;
5766     }
5767 
5768     while (ev->OnList != 0) {
5769       ev->park();
5770     }
5771   }
5772 }
5773 
5774 // Release() must extract a successor from the list and then wake that thread.
5775 // It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
5776 // similar to that used by ParkEvent::Allocate() and ::Release().  DMR-based
5777 // Release() would :
5778 // (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
5779 // (B) Extract a successor from the private list "in-hand"
5780 // (C) attempt to CAS() the residual back into *Lock over null.
5781 //     If there were any newly arrived threads and the CAS() would fail.
5782 //     In that case Release() would detach the RATs, re-merge the list in-hand
5783 //     with the RATs and repeat as needed.  Alternately, Release() might
5784 //     detach and extract a successor, but then pass the residual list to the wakee.
5785 //     The wakee would be responsible for reattaching and remerging before it
5786 //     competed for the lock.
5787 //
5788 // Both "pop" and DMR are immune from ABA corruption -- there can be
5789 // multiple concurrent pushers, but only one popper or detacher.
5790 // This implementation pops from the head of the list.  This is unfair,
5791 // but tends to provide excellent throughput as hot threads remain hot.
5792 // (We wake recently run threads first).
5793 //
5794 // All paths through muxRelease() will execute a CAS.
5795 // Release consistency -- We depend on the CAS in muxRelease() to provide full
5796 // bidirectional fence/MEMBAR semantics, ensuring that all prior memory operations
5797 // executed within the critical section are complete and globally visible before the
5798 // store (CAS) to the lock-word that releases the lock becomes globally visible.
5799 void Thread::muxRelease(volatile intptr_t * Lock)  {
5800   for (;;) {
5801     const intptr_t w = Atomic::cmpxchg((intptr_t)0, Lock, LOCKBIT);
5802     assert(w & LOCKBIT, "invariant");
5803     if (w == LOCKBIT) return;
5804     ParkEvent * const List = (ParkEvent *) (w & ~LOCKBIT);
5805     assert(List != NULL, "invariant");
5806     assert(List->OnList == intptr_t(Lock), "invariant");
5807     ParkEvent * const nxt = List->ListNext;
5808     guarantee((intptr_t(nxt) & LOCKBIT) == 0, "invariant");
5809 
5810     // The following CAS() releases the lock and pops the head element.
5811     // The CAS() also ratifies the previously fetched lock-word value.
5812     if (Atomic::cmpxchg(intptr_t(nxt), Lock, w) != w) {
5813       continue;
5814     }
5815     List->OnList = 0;
5816     OrderAccess::fence();
5817     List->unpark();
5818     return;
5819   }
5820 }
5821 
5822 
5823 void Threads::verify() {
5824   ALL_JAVA_THREADS(p) {
5825     p->verify();
5826   }
5827   VMThread* thread = VMThread::vm_thread();
5828   if (thread != NULL) thread->verify();
5829 }