rev 2110 : [mq]: is-debugger-present

   1 /*
   2  * Copyright (c) 1997, 2011, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/classLoader.hpp"
  27 #include "classfile/javaClasses.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "classfile/vmSymbols.hpp"
  30 #include "code/scopeDesc.hpp"
  31 #include "compiler/compileBroker.hpp"
  32 #include "interpreter/interpreter.hpp"
  33 #include "interpreter/linkResolver.hpp"
  34 #include "jvmtifiles/jvmtiEnv.hpp"
  35 #include "memory/oopFactory.hpp"
  36 #include "memory/universe.inline.hpp"
  37 #include "oops/instanceKlass.hpp"
  38 #include "oops/objArrayOop.hpp"
  39 #include "oops/oop.inline.hpp"
  40 #include "oops/symbol.hpp"
  41 #include "prims/jvm_misc.hpp"
  42 #include "prims/jvmtiExport.hpp"
  43 #include "prims/jvmtiThreadState.hpp"
  44 #include "prims/privilegedStack.hpp"
  45 #include "runtime/aprofiler.hpp"
  46 #include "runtime/arguments.hpp"
  47 #include "runtime/biasedLocking.hpp"
  48 #include "runtime/deoptimization.hpp"
  49 #include "runtime/fprofiler.hpp"
  50 #include "runtime/frame.inline.hpp"
  51 #include "runtime/init.hpp"
  52 #include "runtime/interfaceSupport.hpp"
  53 #include "runtime/java.hpp"
  54 #include "runtime/javaCalls.hpp"
  55 #include "runtime/jniPeriodicChecker.hpp"
  56 #include "runtime/memprofiler.hpp"
  57 #include "runtime/mutexLocker.hpp"
  58 #include "runtime/objectMonitor.hpp"
  59 #include "runtime/osThread.hpp"
  60 #include "runtime/safepoint.hpp"
  61 #include "runtime/sharedRuntime.hpp"
  62 #include "runtime/statSampler.hpp"
  63 #include "runtime/stubRoutines.hpp"
  64 #include "runtime/task.hpp"
  65 #include "runtime/threadCritical.hpp"
  66 #include "runtime/threadLocalStorage.hpp"
  67 #include "runtime/vframe.hpp"
  68 #include "runtime/vframeArray.hpp"
  69 #include "runtime/vframe_hp.hpp"
  70 #include "runtime/vmThread.hpp"
  71 #include "runtime/vm_operations.hpp"
  72 #include "services/attachListener.hpp"
  73 #include "services/management.hpp"
  74 #include "services/threadService.hpp"
  75 #include "utilities/defaultStream.hpp"
  76 #include "utilities/dtrace.hpp"
  77 #include "utilities/events.hpp"
  78 #include "utilities/preserveException.hpp"
  79 #ifdef TARGET_OS_FAMILY_linux
  80 # include "os_linux.inline.hpp"
  81 # include "thread_linux.inline.hpp"
  82 #endif
  83 #ifdef TARGET_OS_FAMILY_solaris
  84 # include "os_solaris.inline.hpp"
  85 # include "thread_solaris.inline.hpp"
  86 #endif
  87 #ifdef TARGET_OS_FAMILY_windows
  88 # include "os_windows.inline.hpp"
  89 # include "thread_windows.inline.hpp"
  90 #endif
  91 #ifndef SERIALGC
  92 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
  93 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  94 #include "gc_implementation/parallelScavenge/pcTasks.hpp"
  95 #endif
  96 #ifdef COMPILER1
  97 #include "c1/c1_Compiler.hpp"
  98 #endif
  99 #ifdef COMPILER2
 100 #include "opto/c2compiler.hpp"
 101 #include "opto/idealGraphPrinter.hpp"
 102 #endif
 103 
 104 #ifdef DTRACE_ENABLED
 105 
 106 // Only bother with this argument setup if dtrace is available
 107 
 108 HS_DTRACE_PROBE_DECL(hotspot, vm__init__begin);
 109 HS_DTRACE_PROBE_DECL(hotspot, vm__init__end);
 110 HS_DTRACE_PROBE_DECL5(hotspot, thread__start, char*, intptr_t,
 111   intptr_t, intptr_t, bool);
 112 HS_DTRACE_PROBE_DECL5(hotspot, thread__stop, char*, intptr_t,
 113   intptr_t, intptr_t, bool);
 114 
 115 #define DTRACE_THREAD_PROBE(probe, javathread)                             \
 116   {                                                                        \
 117     ResourceMark rm(this);                                                 \
 118     int len = 0;                                                           \
 119     const char* name = (javathread)->get_thread_name();                    \
 120     len = strlen(name);                                                    \
 121     HS_DTRACE_PROBE5(hotspot, thread__##probe,                             \
 122       name, len,                                                           \
 123       java_lang_Thread::thread_id((javathread)->threadObj()),              \
 124       (javathread)->osthread()->thread_id(),                               \
 125       java_lang_Thread::is_daemon((javathread)->threadObj()));             \
 126   }
 127 
 128 #else //  ndef DTRACE_ENABLED
 129 
 130 #define DTRACE_THREAD_PROBE(probe, javathread)
 131 
 132 #endif // ndef DTRACE_ENABLED
 133 
 134 // Class hierarchy
 135 // - Thread
 136 //   - VMThread
 137 //   - WatcherThread
 138 //   - ConcurrentMarkSweepThread
 139 //   - JavaThread
 140 //     - CompilerThread
 141 
 142 // ======= Thread ========
 143 
 144 // Support for forcing alignment of thread objects for biased locking
 145 void* Thread::operator new(size_t size) {
 146   if (UseBiasedLocking) {
 147     const int alignment = markOopDesc::biased_lock_alignment;
 148     size_t aligned_size = size + (alignment - sizeof(intptr_t));
 149     void* real_malloc_addr = CHeapObj::operator new(aligned_size);
 150     void* aligned_addr     = (void*) align_size_up((intptr_t) real_malloc_addr, alignment);
 151     assert(((uintptr_t) aligned_addr + (uintptr_t) size) <=
 152            ((uintptr_t) real_malloc_addr + (uintptr_t) aligned_size),
 153            "JavaThread alignment code overflowed allocated storage");
 154     if (TraceBiasedLocking) {
 155       if (aligned_addr != real_malloc_addr)
 156         tty->print_cr("Aligned thread " INTPTR_FORMAT " to " INTPTR_FORMAT,
 157                       real_malloc_addr, aligned_addr);
 158     }
 159     ((Thread*) aligned_addr)->_real_malloc_address = real_malloc_addr;
 160     return aligned_addr;
 161   } else {
 162     return CHeapObj::operator new(size);
 163   }
 164 }
 165 
 166 void Thread::operator delete(void* p) {
 167   if (UseBiasedLocking) {
 168     void* real_malloc_addr = ((Thread*) p)->_real_malloc_address;
 169     CHeapObj::operator delete(real_malloc_addr);
 170   } else {
 171     CHeapObj::operator delete(p);
 172   }
 173 }
 174 
 175 
 176 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
 177 // JavaThread
 178 
 179 
 180 Thread::Thread() {
 181   // stack and get_thread
 182   set_stack_base(NULL);
 183   set_stack_size(0);
 184   set_self_raw_id(0);
 185   set_lgrp_id(-1);
 186 
 187   // allocated data structures
 188   set_osthread(NULL);
 189   set_resource_area(new ResourceArea());
 190   set_handle_area(new HandleArea(NULL));
 191   set_active_handles(NULL);
 192   set_free_handle_block(NULL);
 193   set_last_handle_mark(NULL);
 194 
 195   // This initial value ==> never claimed.
 196   _oops_do_parity = 0;
 197 
 198   // the handle mark links itself to last_handle_mark
 199   new HandleMark(this);
 200 
 201   // plain initialization
 202   debug_only(_owned_locks = NULL;)
 203   debug_only(_allow_allocation_count = 0;)
 204   NOT_PRODUCT(_allow_safepoint_count = 0;)
 205   NOT_PRODUCT(_skip_gcalot = false;)
 206   CHECK_UNHANDLED_OOPS_ONLY(_gc_locked_out_count = 0;)
 207   _jvmti_env_iteration_count = 0;
 208   set_allocated_bytes(0);
 209   _vm_operation_started_count = 0;
 210   _vm_operation_completed_count = 0;
 211   _current_pending_monitor = NULL;
 212   _current_pending_monitor_is_from_java = true;
 213   _current_waiting_monitor = NULL;
 214   _num_nested_signal = 0;
 215   omFreeList = NULL ;
 216   omFreeCount = 0 ;
 217   omFreeProvision = 32 ;
 218   omInUseList = NULL ;
 219   omInUseCount = 0 ;
 220 
 221   _SR_lock = new Monitor(Mutex::suspend_resume, "SR_lock", true);
 222   _suspend_flags = 0;
 223 
 224   // thread-specific hashCode stream generator state - Marsaglia shift-xor form
 225   _hashStateX = os::random() ;
 226   _hashStateY = 842502087 ;
 227   _hashStateZ = 0x8767 ;    // (int)(3579807591LL & 0xffff) ;
 228   _hashStateW = 273326509 ;
 229 
 230   _OnTrap   = 0 ;
 231   _schedctl = NULL ;
 232   _Stalled  = 0 ;
 233   _TypeTag  = 0x2BAD ;
 234 
 235   // Many of the following fields are effectively final - immutable
 236   // Note that nascent threads can't use the Native Monitor-Mutex
 237   // construct until the _MutexEvent is initialized ...
 238   // CONSIDER: instead of using a fixed set of purpose-dedicated ParkEvents
 239   // we might instead use a stack of ParkEvents that we could provision on-demand.
 240   // The stack would act as a cache to avoid calls to ParkEvent::Allocate()
 241   // and ::Release()
 242   _ParkEvent   = ParkEvent::Allocate (this) ;
 243   _SleepEvent  = ParkEvent::Allocate (this) ;
 244   _MutexEvent  = ParkEvent::Allocate (this) ;
 245   _MuxEvent    = ParkEvent::Allocate (this) ;
 246 
 247 #ifdef CHECK_UNHANDLED_OOPS
 248   if (CheckUnhandledOops) {
 249     _unhandled_oops = new UnhandledOops(this);
 250   }
 251 #endif // CHECK_UNHANDLED_OOPS
 252 #ifdef ASSERT
 253   if (UseBiasedLocking) {
 254     assert((((uintptr_t) this) & (markOopDesc::biased_lock_alignment - 1)) == 0, "forced alignment of thread object failed");
 255     assert(this == _real_malloc_address ||
 256            this == (void*) align_size_up((intptr_t) _real_malloc_address, markOopDesc::biased_lock_alignment),
 257            "bug in forced alignment of thread objects");
 258   }
 259 #endif /* ASSERT */
 260 }
 261 
 262 void Thread::initialize_thread_local_storage() {
 263   // Note: Make sure this method only calls
 264   // non-blocking operations. Otherwise, it might not work
 265   // with the thread-startup/safepoint interaction.
 266 
 267   // During Java thread startup, safepoint code should allow this
 268   // method to complete because it may need to allocate memory to
 269   // store information for the new thread.
 270 
 271   // initialize structure dependent on thread local storage
 272   ThreadLocalStorage::set_thread(this);
 273 
 274   // set up any platform-specific state.
 275   os::initialize_thread();
 276 
 277 }
 278 
 279 void Thread::record_stack_base_and_size() {
 280   set_stack_base(os::current_stack_base());
 281   set_stack_size(os::current_stack_size());
 282 }
 283 
 284 
 285 Thread::~Thread() {
 286   // Reclaim the objectmonitors from the omFreeList of the moribund thread.
 287   ObjectSynchronizer::omFlush (this) ;
 288 
 289   // deallocate data structures
 290   delete resource_area();
 291   // since the handle marks are using the handle area, we have to deallocated the root
 292   // handle mark before deallocating the thread's handle area,
 293   assert(last_handle_mark() != NULL, "check we have an element");
 294   delete last_handle_mark();
 295   assert(last_handle_mark() == NULL, "check we have reached the end");
 296 
 297   // It's possible we can encounter a null _ParkEvent, etc., in stillborn threads.
 298   // We NULL out the fields for good hygiene.
 299   ParkEvent::Release (_ParkEvent)   ; _ParkEvent   = NULL ;
 300   ParkEvent::Release (_SleepEvent)  ; _SleepEvent  = NULL ;
 301   ParkEvent::Release (_MutexEvent)  ; _MutexEvent  = NULL ;
 302   ParkEvent::Release (_MuxEvent)    ; _MuxEvent    = NULL ;
 303 
 304   delete handle_area();
 305 
 306   // osthread() can be NULL, if creation of thread failed.
 307   if (osthread() != NULL) os::free_thread(osthread());
 308 
 309   delete _SR_lock;
 310 
 311   // clear thread local storage if the Thread is deleting itself
 312   if (this == Thread::current()) {
 313     ThreadLocalStorage::set_thread(NULL);
 314   } else {
 315     // In the case where we're not the current thread, invalidate all the
 316     // caches in case some code tries to get the current thread or the
 317     // thread that was destroyed, and gets stale information.
 318     ThreadLocalStorage::invalidate_all();
 319   }
 320   CHECK_UNHANDLED_OOPS_ONLY(if (CheckUnhandledOops) delete unhandled_oops();)
 321 }
 322 
 323 // NOTE: dummy function for assertion purpose.
 324 void Thread::run() {
 325   ShouldNotReachHere();
 326 }
 327 
 328 #ifdef ASSERT
 329 // Private method to check for dangling thread pointer
 330 void check_for_dangling_thread_pointer(Thread *thread) {
 331  assert(!thread->is_Java_thread() || Thread::current() == thread || Threads_lock->owned_by_self(),
 332          "possibility of dangling Thread pointer");
 333 }
 334 #endif
 335 
 336 
 337 #ifndef PRODUCT
 338 // Tracing method for basic thread operations
 339 void Thread::trace(const char* msg, const Thread* const thread) {
 340   if (!TraceThreadEvents) return;
 341   ResourceMark rm;
 342   ThreadCritical tc;
 343   const char *name = "non-Java thread";
 344   int prio = -1;
 345   if (thread->is_Java_thread()
 346       && !thread->is_Compiler_thread()) {
 347     // The Threads_lock must be held to get information about
 348     // this thread but may not be in some situations when
 349     // tracing  thread events.
 350     bool release_Threads_lock = false;
 351     if (!Threads_lock->owned_by_self()) {
 352       Threads_lock->lock();
 353       release_Threads_lock = true;
 354     }
 355     JavaThread* jt = (JavaThread *)thread;
 356     name = (char *)jt->get_thread_name();
 357     oop thread_oop = jt->threadObj();
 358     if (thread_oop != NULL) {
 359       prio = java_lang_Thread::priority(thread_oop);
 360     }
 361     if (release_Threads_lock) {
 362       Threads_lock->unlock();
 363     }
 364   }
 365   tty->print_cr("Thread::%s " INTPTR_FORMAT " [%lx] %s (prio: %d)", msg, thread, thread->osthread()->thread_id(), name, prio);
 366 }
 367 #endif
 368 
 369 
 370 ThreadPriority Thread::get_priority(const Thread* const thread) {
 371   trace("get priority", thread);
 372   ThreadPriority priority;
 373   // Can return an error!
 374   (void)os::get_priority(thread, priority);
 375   assert(MinPriority <= priority && priority <= MaxPriority, "non-Java priority found");
 376   return priority;
 377 }
 378 
 379 void Thread::set_priority(Thread* thread, ThreadPriority priority) {
 380   trace("set priority", thread);
 381   debug_only(check_for_dangling_thread_pointer(thread);)
 382   // Can return an error!
 383   (void)os::set_priority(thread, priority);
 384 }
 385 
 386 
 387 void Thread::start(Thread* thread) {
 388   trace("start", thread);
 389   // Start is different from resume in that its safety is guaranteed by context or
 390   // being called from a Java method synchronized on the Thread object.
 391   if (!DisableStartThread) {
 392     if (thread->is_Java_thread()) {
 393       // Initialize the thread state to RUNNABLE before starting this thread.
 394       // Can not set it after the thread started because we do not know the
 395       // exact thread state at that time. It could be in MONITOR_WAIT or
 396       // in SLEEPING or some other state.
 397       java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
 398                                           java_lang_Thread::RUNNABLE);
 399     }
 400     os::start_thread(thread);
 401   }
 402 }
 403 
 404 // Enqueue a VM_Operation to do the job for us - sometime later
 405 void Thread::send_async_exception(oop java_thread, oop java_throwable) {
 406   VM_ThreadStop* vm_stop = new VM_ThreadStop(java_thread, java_throwable);
 407   VMThread::execute(vm_stop);
 408 }
 409 
 410 
 411 //
 412 // Check if an external suspend request has completed (or has been
 413 // cancelled). Returns true if the thread is externally suspended and
 414 // false otherwise.
 415 //
 416 // The bits parameter returns information about the code path through
 417 // the routine. Useful for debugging:
 418 //
 419 // set in is_ext_suspend_completed():
 420 // 0x00000001 - routine was entered
 421 // 0x00000010 - routine return false at end
 422 // 0x00000100 - thread exited (return false)
 423 // 0x00000200 - suspend request cancelled (return false)
 424 // 0x00000400 - thread suspended (return true)
 425 // 0x00001000 - thread is in a suspend equivalent state (return true)
 426 // 0x00002000 - thread is native and walkable (return true)
 427 // 0x00004000 - thread is native_trans and walkable (needed retry)
 428 //
 429 // set in wait_for_ext_suspend_completion():
 430 // 0x00010000 - routine was entered
 431 // 0x00020000 - suspend request cancelled before loop (return false)
 432 // 0x00040000 - thread suspended before loop (return true)
 433 // 0x00080000 - suspend request cancelled in loop (return false)
 434 // 0x00100000 - thread suspended in loop (return true)
 435 // 0x00200000 - suspend not completed during retry loop (return false)
 436 //
 437 
 438 // Helper class for tracing suspend wait debug bits.
 439 //
 440 // 0x00000100 indicates that the target thread exited before it could
 441 // self-suspend which is not a wait failure. 0x00000200, 0x00020000 and
 442 // 0x00080000 each indicate a cancelled suspend request so they don't
 443 // count as wait failures either.
 444 #define DEBUG_FALSE_BITS (0x00000010 | 0x00200000)
 445 
 446 class TraceSuspendDebugBits : public StackObj {
 447  private:
 448   JavaThread * jt;
 449   bool         is_wait;
 450   bool         called_by_wait;  // meaningful when !is_wait
 451   uint32_t *   bits;
 452 
 453  public:
 454   TraceSuspendDebugBits(JavaThread *_jt, bool _is_wait, bool _called_by_wait,
 455                         uint32_t *_bits) {
 456     jt             = _jt;
 457     is_wait        = _is_wait;
 458     called_by_wait = _called_by_wait;
 459     bits           = _bits;
 460   }
 461 
 462   ~TraceSuspendDebugBits() {
 463     if (!is_wait) {
 464 #if 1
 465       // By default, don't trace bits for is_ext_suspend_completed() calls.
 466       // That trace is very chatty.
 467       return;
 468 #else
 469       if (!called_by_wait) {
 470         // If tracing for is_ext_suspend_completed() is enabled, then only
 471         // trace calls to it from wait_for_ext_suspend_completion()
 472         return;
 473       }
 474 #endif
 475     }
 476 
 477     if (AssertOnSuspendWaitFailure || TraceSuspendWaitFailures) {
 478       if (bits != NULL && (*bits & DEBUG_FALSE_BITS) != 0) {
 479         MutexLocker ml(Threads_lock);  // needed for get_thread_name()
 480         ResourceMark rm;
 481 
 482         tty->print_cr(
 483             "Failed wait_for_ext_suspend_completion(thread=%s, debug_bits=%x)",
 484             jt->get_thread_name(), *bits);
 485 
 486         guarantee(!AssertOnSuspendWaitFailure, "external suspend wait failed");
 487       }
 488     }
 489   }
 490 };
 491 #undef DEBUG_FALSE_BITS
 492 
 493 
 494 bool JavaThread::is_ext_suspend_completed(bool called_by_wait, int delay, uint32_t *bits) {
 495   TraceSuspendDebugBits tsdb(this, false /* !is_wait */, called_by_wait, bits);
 496 
 497   bool did_trans_retry = false;  // only do thread_in_native_trans retry once
 498   bool do_trans_retry;           // flag to force the retry
 499 
 500   *bits |= 0x00000001;
 501 
 502   do {
 503     do_trans_retry = false;
 504 
 505     if (is_exiting()) {
 506       // Thread is in the process of exiting. This is always checked
 507       // first to reduce the risk of dereferencing a freed JavaThread.
 508       *bits |= 0x00000100;
 509       return false;
 510     }
 511 
 512     if (!is_external_suspend()) {
 513       // Suspend request is cancelled. This is always checked before
 514       // is_ext_suspended() to reduce the risk of a rogue resume
 515       // confusing the thread that made the suspend request.
 516       *bits |= 0x00000200;
 517       return false;
 518     }
 519 
 520     if (is_ext_suspended()) {
 521       // thread is suspended
 522       *bits |= 0x00000400;
 523       return true;
 524     }
 525 
 526     // Now that we no longer do hard suspends of threads running
 527     // native code, the target thread can be changing thread state
 528     // while we are in this routine:
 529     //
 530     //   _thread_in_native -> _thread_in_native_trans -> _thread_blocked
 531     //
 532     // We save a copy of the thread state as observed at this moment
 533     // and make our decision about suspend completeness based on the
 534     // copy. This closes the race where the thread state is seen as
 535     // _thread_in_native_trans in the if-thread_blocked check, but is
 536     // seen as _thread_blocked in if-thread_in_native_trans check.
 537     JavaThreadState save_state = thread_state();
 538 
 539     if (save_state == _thread_blocked && is_suspend_equivalent()) {
 540       // If the thread's state is _thread_blocked and this blocking
 541       // condition is known to be equivalent to a suspend, then we can
 542       // consider the thread to be externally suspended. This means that
 543       // the code that sets _thread_blocked has been modified to do
 544       // self-suspension if the blocking condition releases. We also
 545       // used to check for CONDVAR_WAIT here, but that is now covered by
 546       // the _thread_blocked with self-suspension check.
 547       //
 548       // Return true since we wouldn't be here unless there was still an
 549       // external suspend request.
 550       *bits |= 0x00001000;
 551       return true;
 552     } else if (save_state == _thread_in_native && frame_anchor()->walkable()) {
 553       // Threads running native code will self-suspend on native==>VM/Java
 554       // transitions. If its stack is walkable (should always be the case
 555       // unless this function is called before the actual java_suspend()
 556       // call), then the wait is done.
 557       *bits |= 0x00002000;
 558       return true;
 559     } else if (!called_by_wait && !did_trans_retry &&
 560                save_state == _thread_in_native_trans &&
 561                frame_anchor()->walkable()) {
 562       // The thread is transitioning from thread_in_native to another
 563       // thread state. check_safepoint_and_suspend_for_native_trans()
 564       // will force the thread to self-suspend. If it hasn't gotten
 565       // there yet we may have caught the thread in-between the native
 566       // code check above and the self-suspend. Lucky us. If we were
 567       // called by wait_for_ext_suspend_completion(), then it
 568       // will be doing the retries so we don't have to.
 569       //
 570       // Since we use the saved thread state in the if-statement above,
 571       // there is a chance that the thread has already transitioned to
 572       // _thread_blocked by the time we get here. In that case, we will
 573       // make a single unnecessary pass through the logic below. This
 574       // doesn't hurt anything since we still do the trans retry.
 575 
 576       *bits |= 0x00004000;
 577 
 578       // Once the thread leaves thread_in_native_trans for another
 579       // thread state, we break out of this retry loop. We shouldn't
 580       // need this flag to prevent us from getting back here, but
 581       // sometimes paranoia is good.
 582       did_trans_retry = true;
 583 
 584       // We wait for the thread to transition to a more usable state.
 585       for (int i = 1; i <= SuspendRetryCount; i++) {
 586         // We used to do an "os::yield_all(i)" call here with the intention
 587         // that yielding would increase on each retry. However, the parameter
 588         // is ignored on Linux which means the yield didn't scale up. Waiting
 589         // on the SR_lock below provides a much more predictable scale up for
 590         // the delay. It also provides a simple/direct point to check for any
 591         // safepoint requests from the VMThread
 592 
 593         // temporarily drops SR_lock while doing wait with safepoint check
 594         // (if we're a JavaThread - the WatcherThread can also call this)
 595         // and increase delay with each retry
 596         SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 597 
 598         // check the actual thread state instead of what we saved above
 599         if (thread_state() != _thread_in_native_trans) {
 600           // the thread has transitioned to another thread state so
 601           // try all the checks (except this one) one more time.
 602           do_trans_retry = true;
 603           break;
 604         }
 605       } // end retry loop
 606 
 607 
 608     }
 609   } while (do_trans_retry);
 610 
 611   *bits |= 0x00000010;
 612   return false;
 613 }
 614 
 615 //
 616 // Wait for an external suspend request to complete (or be cancelled).
 617 // Returns true if the thread is externally suspended and false otherwise.
 618 //
 619 bool JavaThread::wait_for_ext_suspend_completion(int retries, int delay,
 620        uint32_t *bits) {
 621   TraceSuspendDebugBits tsdb(this, true /* is_wait */,
 622                              false /* !called_by_wait */, bits);
 623 
 624   // local flag copies to minimize SR_lock hold time
 625   bool is_suspended;
 626   bool pending;
 627   uint32_t reset_bits;
 628 
 629   // set a marker so is_ext_suspend_completed() knows we are the caller
 630   *bits |= 0x00010000;
 631 
 632   // We use reset_bits to reinitialize the bits value at the top of
 633   // each retry loop. This allows the caller to make use of any
 634   // unused bits for their own marking purposes.
 635   reset_bits = *bits;
 636 
 637   {
 638     MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 639     is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 640                                             delay, bits);
 641     pending = is_external_suspend();
 642   }
 643   // must release SR_lock to allow suspension to complete
 644 
 645   if (!pending) {
 646     // A cancelled suspend request is the only false return from
 647     // is_ext_suspend_completed() that keeps us from entering the
 648     // retry loop.
 649     *bits |= 0x00020000;
 650     return false;
 651   }
 652 
 653   if (is_suspended) {
 654     *bits |= 0x00040000;
 655     return true;
 656   }
 657 
 658   for (int i = 1; i <= retries; i++) {
 659     *bits = reset_bits;  // reinit to only track last retry
 660 
 661     // We used to do an "os::yield_all(i)" call here with the intention
 662     // that yielding would increase on each retry. However, the parameter
 663     // is ignored on Linux which means the yield didn't scale up. Waiting
 664     // on the SR_lock below provides a much more predictable scale up for
 665     // the delay. It also provides a simple/direct point to check for any
 666     // safepoint requests from the VMThread
 667 
 668     {
 669       MutexLocker ml(SR_lock());
 670       // wait with safepoint check (if we're a JavaThread - the WatcherThread
 671       // can also call this)  and increase delay with each retry
 672       SR_lock()->wait(!Thread::current()->is_Java_thread(), i * delay);
 673 
 674       is_suspended = is_ext_suspend_completed(true /* called_by_wait */,
 675                                               delay, bits);
 676 
 677       // It is possible for the external suspend request to be cancelled
 678       // (by a resume) before the actual suspend operation is completed.
 679       // Refresh our local copy to see if we still need to wait.
 680       pending = is_external_suspend();
 681     }
 682 
 683     if (!pending) {
 684       // A cancelled suspend request is the only false return from
 685       // is_ext_suspend_completed() that keeps us from staying in the
 686       // retry loop.
 687       *bits |= 0x00080000;
 688       return false;
 689     }
 690 
 691     if (is_suspended) {
 692       *bits |= 0x00100000;
 693       return true;
 694     }
 695   } // end retry loop
 696 
 697   // thread did not suspend after all our retries
 698   *bits |= 0x00200000;
 699   return false;
 700 }
 701 
 702 #ifndef PRODUCT
 703 void JavaThread::record_jump(address target, address instr, const char* file, int line) {
 704 
 705   // This should not need to be atomic as the only way for simultaneous
 706   // updates is via interrupts. Even then this should be rare or non-existant
 707   // and we don't care that much anyway.
 708 
 709   int index = _jmp_ring_index;
 710   _jmp_ring_index = (index + 1 ) & (jump_ring_buffer_size - 1);
 711   _jmp_ring[index]._target = (intptr_t) target;
 712   _jmp_ring[index]._instruction = (intptr_t) instr;
 713   _jmp_ring[index]._file = file;
 714   _jmp_ring[index]._line = line;
 715 }
 716 #endif /* PRODUCT */
 717 
 718 // Called by flat profiler
 719 // Callers have already called wait_for_ext_suspend_completion
 720 // The assertion for that is currently too complex to put here:
 721 bool JavaThread::profile_last_Java_frame(frame* _fr) {
 722   bool gotframe = false;
 723   // self suspension saves needed state.
 724   if (has_last_Java_frame() && _anchor.walkable()) {
 725      *_fr = pd_last_frame();
 726      gotframe = true;
 727   }
 728   return gotframe;
 729 }
 730 
 731 void Thread::interrupt(Thread* thread) {
 732   trace("interrupt", thread);
 733   debug_only(check_for_dangling_thread_pointer(thread);)
 734   os::interrupt(thread);
 735 }
 736 
 737 bool Thread::is_interrupted(Thread* thread, bool clear_interrupted) {
 738   trace("is_interrupted", thread);
 739   debug_only(check_for_dangling_thread_pointer(thread);)
 740   // Note:  If clear_interrupted==false, this simply fetches and
 741   // returns the value of the field osthread()->interrupted().
 742   return os::is_interrupted(thread, clear_interrupted);
 743 }
 744 
 745 
 746 // GC Support
 747 bool Thread::claim_oops_do_par_case(int strong_roots_parity) {
 748   jint thread_parity = _oops_do_parity;
 749   if (thread_parity != strong_roots_parity) {
 750     jint res = Atomic::cmpxchg(strong_roots_parity, &_oops_do_parity, thread_parity);
 751     if (res == thread_parity) return true;
 752     else {
 753       guarantee(res == strong_roots_parity, "Or else what?");
 754       assert(SharedHeap::heap()->n_par_threads() > 0,
 755              "Should only fail when parallel.");
 756       return false;
 757     }
 758   }
 759   assert(SharedHeap::heap()->n_par_threads() > 0,
 760          "Should only fail when parallel.");
 761   return false;
 762 }
 763 
 764 void Thread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
 765   active_handles()->oops_do(f);
 766   // Do oop for ThreadShadow
 767   f->do_oop((oop*)&_pending_exception);
 768   handle_area()->oops_do(f);
 769 }
 770 
 771 void Thread::nmethods_do(CodeBlobClosure* cf) {
 772   // no nmethods in a generic thread...
 773 }
 774 
 775 void Thread::print_on(outputStream* st) const {
 776   // get_priority assumes osthread initialized
 777   if (osthread() != NULL) {
 778     st->print("prio=%d tid=" INTPTR_FORMAT " ", get_priority(this), this);
 779     osthread()->print_on(st);
 780   }
 781   debug_only(if (WizardMode) print_owned_locks_on(st);)
 782 }
 783 
 784 // Thread::print_on_error() is called by fatal error handler. Don't use
 785 // any lock or allocate memory.
 786 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
 787   if      (is_VM_thread())                  st->print("VMThread");
 788   else if (is_Compiler_thread())            st->print("CompilerThread");
 789   else if (is_Java_thread())                st->print("JavaThread");
 790   else if (is_GC_task_thread())             st->print("GCTaskThread");
 791   else if (is_Watcher_thread())             st->print("WatcherThread");
 792   else if (is_ConcurrentGC_thread())        st->print("ConcurrentGCThread");
 793   else st->print("Thread");
 794 
 795   st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
 796             _stack_base - _stack_size, _stack_base);
 797 
 798   if (osthread()) {
 799     st->print(" [id=%d]", osthread()->thread_id());
 800   }
 801 }
 802 
 803 #ifdef ASSERT
 804 void Thread::print_owned_locks_on(outputStream* st) const {
 805   Monitor *cur = _owned_locks;
 806   if (cur == NULL) {
 807     st->print(" (no locks) ");
 808   } else {
 809     st->print_cr(" Locks owned:");
 810     while(cur) {
 811       cur->print_on(st);
 812       cur = cur->next();
 813     }
 814   }
 815 }
 816 
 817 static int ref_use_count  = 0;
 818 
 819 bool Thread::owns_locks_but_compiled_lock() const {
 820   for(Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 821     if (cur != Compile_lock) return true;
 822   }
 823   return false;
 824 }
 825 
 826 
 827 #endif
 828 
 829 #ifndef PRODUCT
 830 
 831 // The flag: potential_vm_operation notifies if this particular safepoint state could potential
 832 // invoke the vm-thread (i.e., and oop allocation). In that case, we also have to make sure that
 833 // no threads which allow_vm_block's are held
 834 void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) {
 835     // Check if current thread is allowed to block at a safepoint
 836     if (!(_allow_safepoint_count == 0))
 837       fatal("Possible safepoint reached by thread that does not allow it");
 838     if (is_Java_thread() && ((JavaThread*)this)->thread_state() != _thread_in_vm) {
 839       fatal("LEAF method calling lock?");
 840     }
 841 
 842 #ifdef ASSERT
 843     if (potential_vm_operation && is_Java_thread()
 844         && !Universe::is_bootstrapping()) {
 845       // Make sure we do not hold any locks that the VM thread also uses.
 846       // This could potentially lead to deadlocks
 847       for(Monitor *cur = _owned_locks; cur; cur = cur->next()) {
 848         // Threads_lock is special, since the safepoint synchronization will not start before this is
 849         // acquired. Hence, a JavaThread cannot be holding it at a safepoint. So is VMOperationRequest_lock,
 850         // since it is used to transfer control between JavaThreads and the VMThread
 851         // Do not *exclude* any locks unless you are absolutly sure it is correct. Ask someone else first!
 852         if ( (cur->allow_vm_block() &&
 853               cur != Threads_lock &&
 854               cur != Compile_lock &&               // Temporary: should not be necessary when we get spearate compilation
 855               cur != VMOperationRequest_lock &&
 856               cur != VMOperationQueue_lock) ||
 857               cur->rank() == Mutex::special) {
 858           warning("Thread holding lock at safepoint that vm can block on: %s", cur->name());
 859         }
 860       }
 861     }
 862 
 863     if (GCALotAtAllSafepoints) {
 864       // We could enter a safepoint here and thus have a gc
 865       InterfaceSupport::check_gc_alot();
 866     }
 867 #endif
 868 }
 869 #endif
 870 
 871 bool Thread::is_in_stack(address adr) const {
 872   assert(Thread::current() == this, "is_in_stack can only be called from current thread");
 873   address end = os::current_stack_pointer();
 874   if (stack_base() >= adr && adr >= end) return true;
 875 
 876   return false;
 877 }
 878 
 879 
 880 // We had to move these methods here, because vm threads get into ObjectSynchronizer::enter
 881 // However, there is a note in JavaThread::is_lock_owned() about the VM threads not being
 882 // used for compilation in the future. If that change is made, the need for these methods
 883 // should be revisited, and they should be removed if possible.
 884 
 885 bool Thread::is_lock_owned(address adr) const {
 886   return on_local_stack(adr);
 887 }
 888 
 889 bool Thread::set_as_starting_thread() {
 890  // NOTE: this must be called inside the main thread.
 891   return os::create_main_thread((JavaThread*)this);
 892 }
 893 
 894 static void initialize_class(Symbol* class_name, TRAPS) {
 895   klassOop klass = SystemDictionary::resolve_or_fail(class_name, true, CHECK);
 896   instanceKlass::cast(klass)->initialize(CHECK);
 897 }
 898 
 899 
 900 // Creates the initial ThreadGroup
 901 static Handle create_initial_thread_group(TRAPS) {
 902   klassOop k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_ThreadGroup(), true, CHECK_NH);
 903   instanceKlassHandle klass (THREAD, k);
 904 
 905   Handle system_instance = klass->allocate_instance_handle(CHECK_NH);
 906   {
 907     JavaValue result(T_VOID);
 908     JavaCalls::call_special(&result,
 909                             system_instance,
 910                             klass,
 911                             vmSymbols::object_initializer_name(),
 912                             vmSymbols::void_method_signature(),
 913                             CHECK_NH);
 914   }
 915   Universe::set_system_thread_group(system_instance());
 916 
 917   Handle main_instance = klass->allocate_instance_handle(CHECK_NH);
 918   {
 919     JavaValue result(T_VOID);
 920     Handle string = java_lang_String::create_from_str("main", CHECK_NH);
 921     JavaCalls::call_special(&result,
 922                             main_instance,
 923                             klass,
 924                             vmSymbols::object_initializer_name(),
 925                             vmSymbols::threadgroup_string_void_signature(),
 926                             system_instance,
 927                             string,
 928                             CHECK_NH);
 929   }
 930   return main_instance;
 931 }
 932 
 933 // Creates the initial Thread
 934 static oop create_initial_thread(Handle thread_group, JavaThread* thread, TRAPS) {
 935   klassOop k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK_NULL);
 936   instanceKlassHandle klass (THREAD, k);
 937   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK_NULL);
 938 
 939   java_lang_Thread::set_thread(thread_oop(), thread);
 940   java_lang_Thread::set_priority(thread_oop(), NormPriority);
 941   thread->set_threadObj(thread_oop());
 942 
 943   Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
 944 
 945   JavaValue result(T_VOID);
 946   JavaCalls::call_special(&result, thread_oop,
 947                                    klass,
 948                                    vmSymbols::object_initializer_name(),
 949                                    vmSymbols::threadgroup_string_void_signature(),
 950                                    thread_group,
 951                                    string,
 952                                    CHECK_NULL);
 953   return thread_oop();
 954 }
 955 
 956 static void call_initializeSystemClass(TRAPS) {
 957   klassOop k =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
 958   instanceKlassHandle klass (THREAD, k);
 959 
 960   JavaValue result(T_VOID);
 961   JavaCalls::call_static(&result, klass, vmSymbols::initializeSystemClass_name(),
 962                                          vmSymbols::void_method_signature(), CHECK);
 963 }
 964 
 965 // General purpose hook into Java code, run once when the VM is initialized.
 966 // The Java library method itself may be changed independently from the VM.
 967 static void call_postVMInitHook(TRAPS) {
 968   klassOop k = SystemDictionary::sun_misc_PostVMInitHook_klass();
 969   instanceKlassHandle klass (THREAD, k);
 970   if (klass.not_null()) {
 971     JavaValue result(T_VOID);
 972     JavaCalls::call_static(&result, klass, vmSymbols::run_method_name(),
 973                                            vmSymbols::void_method_signature(),
 974                                            CHECK);
 975   }
 976 }
 977 
 978 static void reset_vm_info_property(TRAPS) {
 979   // the vm info string
 980   ResourceMark rm(THREAD);
 981   const char *vm_info = VM_Version::vm_info_string();
 982 
 983   // java.lang.System class
 984   klassOop k =  SystemDictionary::resolve_or_fail(vmSymbols::java_lang_System(), true, CHECK);
 985   instanceKlassHandle klass (THREAD, k);
 986 
 987   // setProperty arguments
 988   Handle key_str    = java_lang_String::create_from_str("java.vm.info", CHECK);
 989   Handle value_str  = java_lang_String::create_from_str(vm_info, CHECK);
 990 
 991   // return value
 992   JavaValue r(T_OBJECT);
 993 
 994   // public static String setProperty(String key, String value);
 995   JavaCalls::call_static(&r,
 996                          klass,
 997                          vmSymbols::setProperty_name(),
 998                          vmSymbols::string_string_string_signature(),
 999                          key_str,
1000                          value_str,
1001                          CHECK);
1002 }
1003 
1004 
1005 void JavaThread::allocate_threadObj(Handle thread_group, char* thread_name, bool daemon, TRAPS) {
1006   assert(thread_group.not_null(), "thread group should be specified");
1007   assert(threadObj() == NULL, "should only create Java thread object once");
1008 
1009   klassOop k = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK);
1010   instanceKlassHandle klass (THREAD, k);
1011   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);
1012 
1013   java_lang_Thread::set_thread(thread_oop(), this);
1014   java_lang_Thread::set_priority(thread_oop(), NormPriority);
1015   set_threadObj(thread_oop());
1016 
1017   JavaValue result(T_VOID);
1018   if (thread_name != NULL) {
1019     Handle name = java_lang_String::create_from_str(thread_name, CHECK);
1020     // Thread gets assigned specified name and null target
1021     JavaCalls::call_special(&result,
1022                             thread_oop,
1023                             klass,
1024                             vmSymbols::object_initializer_name(),
1025                             vmSymbols::threadgroup_string_void_signature(),
1026                             thread_group, // Argument 1
1027                             name,         // Argument 2
1028                             THREAD);
1029   } else {
1030     // Thread gets assigned name "Thread-nnn" and null target
1031     // (java.lang.Thread doesn't have a constructor taking only a ThreadGroup argument)
1032     JavaCalls::call_special(&result,
1033                             thread_oop,
1034                             klass,
1035                             vmSymbols::object_initializer_name(),
1036                             vmSymbols::threadgroup_runnable_void_signature(),
1037                             thread_group, // Argument 1
1038                             Handle(),     // Argument 2
1039                             THREAD);
1040   }
1041 
1042 
1043   if (daemon) {
1044       java_lang_Thread::set_daemon(thread_oop());
1045   }
1046 
1047   if (HAS_PENDING_EXCEPTION) {
1048     return;
1049   }
1050 
1051   KlassHandle group(this, SystemDictionary::ThreadGroup_klass());
1052   Handle threadObj(this, this->threadObj());
1053 
1054   JavaCalls::call_special(&result,
1055                          thread_group,
1056                          group,
1057                          vmSymbols::add_method_name(),
1058                          vmSymbols::thread_void_signature(),
1059                          threadObj,          // Arg 1
1060                          THREAD);
1061 
1062 
1063 }
1064 
1065 // NamedThread --  non-JavaThread subclasses with multiple
1066 // uniquely named instances should derive from this.
1067 NamedThread::NamedThread() : Thread() {
1068   _name = NULL;
1069   _processed_thread = NULL;
1070 }
1071 
1072 NamedThread::~NamedThread() {
1073   if (_name != NULL) {
1074     FREE_C_HEAP_ARRAY(char, _name);
1075     _name = NULL;
1076   }
1077 }
1078 
1079 void NamedThread::set_name(const char* format, ...) {
1080   guarantee(_name == NULL, "Only get to set name once.");
1081   _name = NEW_C_HEAP_ARRAY(char, max_name_len);
1082   guarantee(_name != NULL, "alloc failure");
1083   va_list ap;
1084   va_start(ap, format);
1085   jio_vsnprintf(_name, max_name_len, format, ap);
1086   va_end(ap);
1087 }
1088 
1089 // ======= WatcherThread ========
1090 
1091 // The watcher thread exists to simulate timer interrupts.  It should
1092 // be replaced by an abstraction over whatever native support for
1093 // timer interrupts exists on the platform.
1094 
1095 WatcherThread* WatcherThread::_watcher_thread   = NULL;
1096 volatile bool  WatcherThread::_should_terminate = false;
1097 
1098 WatcherThread::WatcherThread() : Thread() {
1099   assert(watcher_thread() == NULL, "we can only allocate one WatcherThread");
1100   if (os::create_thread(this, os::watcher_thread)) {
1101     _watcher_thread = this;
1102 
1103     // Set the watcher thread to the highest OS priority which should not be
1104     // used, unless a Java thread with priority java.lang.Thread.MAX_PRIORITY
1105     // is created. The only normal thread using this priority is the reference
1106     // handler thread, which runs for very short intervals only.
1107     // If the VMThread's priority is not lower than the WatcherThread profiling
1108     // will be inaccurate.
1109     os::set_priority(this, MaxPriority);
1110     if (!DisableStartThread) {
1111       os::start_thread(this);
1112     }
1113   }
1114 }
1115 
1116 void WatcherThread::run() {
1117   assert(this == watcher_thread(), "just checking");
1118 
1119   this->record_stack_base_and_size();
1120   this->initialize_thread_local_storage();
1121   this->set_active_handles(JNIHandleBlock::allocate_block());
1122   while(!_should_terminate) {
1123     assert(watcher_thread() == Thread::current(),  "thread consistency check");
1124     assert(watcher_thread() == this,  "thread consistency check");
1125 
1126     // Calculate how long it'll be until the next PeriodicTask work
1127     // should be done, and sleep that amount of time.
1128     size_t time_to_wait = PeriodicTask::time_to_wait();
1129 
1130     // we expect this to timeout - we only ever get unparked when
1131     // we should terminate
1132     {
1133       OSThreadWaitState osts(this->osthread(), false /* not Object.wait() */);
1134 
1135       jlong prev_time = os::javaTimeNanos();
1136       for (;;) {
1137         int res= _SleepEvent->park(time_to_wait);
1138         if (res == OS_TIMEOUT || _should_terminate)
1139           break;
1140         // spurious wakeup of some kind
1141         jlong now = os::javaTimeNanos();
1142         time_to_wait -= (now - prev_time) / 1000000;
1143         if (time_to_wait <= 0)
1144           break;
1145         prev_time = now;
1146       }
1147     }
1148 
1149     if (is_error_reported()) {
1150       // A fatal error has happened, the error handler(VMError::report_and_die)
1151       // should abort JVM after creating an error log file. However in some
1152       // rare cases, the error handler itself might deadlock. Here we try to
1153       // kill JVM if the fatal error handler fails to abort in 2 minutes.
1154       //
1155       // This code is in WatcherThread because WatcherThread wakes up
1156       // periodically so the fatal error handler doesn't need to do anything;
1157       // also because the WatcherThread is less likely to crash than other
1158       // threads.
1159 
1160       for (;;) {
1161         if (!ShowMessageBoxOnError
1162          && (OnError == NULL || OnError[0] == '\0')
1163          && Arguments::abort_hook() == NULL) {
1164              os::sleep(this, 2 * 60 * 1000, false);
1165              fdStream err(defaultStream::output_fd());
1166              err.print_raw_cr("# [ timer expired, abort... ]");
1167              // skip atexit/vm_exit/vm_abort hooks
1168              os::die();
1169         }
1170 
1171         // Wake up 5 seconds later, the fatal handler may reset OnError or
1172         // ShowMessageBoxOnError when it is ready to abort.
1173         os::sleep(this, 5 * 1000, false);
1174       }
1175     }
1176 
1177     PeriodicTask::real_time_tick(time_to_wait);
1178 
1179     // If we have no more tasks left due to dynamic disenrollment,
1180     // shut down the thread since we don't currently support dynamic enrollment
1181     if (PeriodicTask::num_tasks() == 0) {
1182       _should_terminate = true;
1183     }
1184   }
1185 
1186   // Signal that it is terminated
1187   {
1188     MutexLockerEx mu(Terminator_lock, Mutex::_no_safepoint_check_flag);
1189     _watcher_thread = NULL;
1190     Terminator_lock->notify();
1191   }
1192 
1193   // Thread destructor usually does this..
1194   ThreadLocalStorage::set_thread(NULL);
1195 }
1196 
1197 void WatcherThread::start() {
1198   if (watcher_thread() == NULL) {
1199     _should_terminate = false;
1200     // Create the single instance of WatcherThread
1201     new WatcherThread();
1202   }
1203 }
1204 
1205 void WatcherThread::stop() {
1206   // it is ok to take late safepoints here, if needed
1207   MutexLocker mu(Terminator_lock);
1208   _should_terminate = true;
1209   OrderAccess::fence();  // ensure WatcherThread sees update in main loop
1210 
1211   Thread* watcher = watcher_thread();
1212   if (watcher != NULL)
1213     watcher->_SleepEvent->unpark();
1214 
1215   while(watcher_thread() != NULL) {
1216     // This wait should make safepoint checks, wait without a timeout,
1217     // and wait as a suspend-equivalent condition.
1218     //
1219     // Note: If the FlatProfiler is running, then this thread is waiting
1220     // for the WatcherThread to terminate and the WatcherThread, via the
1221     // FlatProfiler task, is waiting for the external suspend request on
1222     // this thread to complete. wait_for_ext_suspend_completion() will
1223     // eventually timeout, but that takes time. Making this wait a
1224     // suspend-equivalent condition solves that timeout problem.
1225     //
1226     Terminator_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
1227                           Mutex::_as_suspend_equivalent_flag);
1228   }
1229 }
1230 
1231 void WatcherThread::print_on(outputStream* st) const {
1232   st->print("\"%s\" ", name());
1233   Thread::print_on(st);
1234   st->cr();
1235 }
1236 
1237 // ======= JavaThread ========
1238 
1239 // A JavaThread is a normal Java thread
1240 
1241 void JavaThread::initialize() {
1242   // Initialize fields
1243 
1244   // Set the claimed par_id to -1 (ie not claiming any par_ids)
1245   set_claimed_par_id(-1);
1246 
1247   set_saved_exception_pc(NULL);
1248   set_threadObj(NULL);
1249   _anchor.clear();
1250   set_entry_point(NULL);
1251   set_jni_functions(jni_functions());
1252   set_callee_target(NULL);
1253   set_vm_result(NULL);
1254   set_vm_result_2(NULL);
1255   set_vframe_array_head(NULL);
1256   set_vframe_array_last(NULL);
1257   set_deferred_locals(NULL);
1258   set_deopt_mark(NULL);
1259   set_deopt_nmethod(NULL);
1260   clear_must_deopt_id();
1261   set_monitor_chunks(NULL);
1262   set_next(NULL);
1263   set_thread_state(_thread_new);
1264   _terminated = _not_terminated;
1265   _privileged_stack_top = NULL;
1266   _array_for_gc = NULL;
1267   _suspend_equivalent = false;
1268   _in_deopt_handler = 0;
1269   _doing_unsafe_access = false;
1270   _stack_guard_state = stack_guard_unused;
1271   _exception_oop = NULL;
1272   _exception_pc  = 0;
1273   _exception_handler_pc = 0;
1274   _exception_stack_size = 0;
1275   _is_method_handle_return = 0;
1276   _jvmti_thread_state= NULL;
1277   _should_post_on_exceptions_flag = JNI_FALSE;
1278   _jvmti_get_loaded_classes_closure = NULL;
1279   _interp_only_mode    = 0;
1280   _special_runtime_exit_condition = _no_async_condition;
1281   _pending_async_exception = NULL;
1282   _is_compiling = false;
1283   _thread_stat = NULL;
1284   _thread_stat = new ThreadStatistics();
1285   _blocked_on_compilation = false;
1286   _jni_active_critical = 0;
1287   _do_not_unlock_if_synchronized = false;
1288   _cached_monitor_info = NULL;
1289   _parker = Parker::Allocate(this) ;
1290 
1291 #ifndef PRODUCT
1292   _jmp_ring_index = 0;
1293   for (int ji = 0 ; ji < jump_ring_buffer_size ; ji++ ) {
1294     record_jump(NULL, NULL, NULL, 0);
1295   }
1296 #endif /* PRODUCT */
1297 
1298   set_thread_profiler(NULL);
1299   if (FlatProfiler::is_active()) {
1300     // This is where we would decide to either give each thread it's own profiler
1301     // or use one global one from FlatProfiler,
1302     // or up to some count of the number of profiled threads, etc.
1303     ThreadProfiler* pp = new ThreadProfiler();
1304     pp->engage();
1305     set_thread_profiler(pp);
1306   }
1307 
1308   // Setup safepoint state info for this thread
1309   ThreadSafepointState::create(this);
1310 
1311   debug_only(_java_call_counter = 0);
1312 
1313   // JVMTI PopFrame support
1314   _popframe_condition = popframe_inactive;
1315   _popframe_preserved_args = NULL;
1316   _popframe_preserved_args_size = 0;
1317 
1318   pd_initialize();
1319 }
1320 
1321 #ifndef SERIALGC
1322 SATBMarkQueueSet JavaThread::_satb_mark_queue_set;
1323 DirtyCardQueueSet JavaThread::_dirty_card_queue_set;
1324 #endif // !SERIALGC
1325 
1326 JavaThread::JavaThread(bool is_attaching) :
1327   Thread()
1328 #ifndef SERIALGC
1329   , _satb_mark_queue(&_satb_mark_queue_set),
1330   _dirty_card_queue(&_dirty_card_queue_set)
1331 #endif // !SERIALGC
1332 {
1333   initialize();
1334   _is_attaching = is_attaching;
1335   assert(_deferred_card_mark.is_empty(), "Default MemRegion ctor");
1336 }
1337 
1338 bool JavaThread::reguard_stack(address cur_sp) {
1339   if (_stack_guard_state != stack_guard_yellow_disabled) {
1340     return true; // Stack already guarded or guard pages not needed.
1341   }
1342 
1343   if (register_stack_overflow()) {
1344     // For those architectures which have separate register and
1345     // memory stacks, we must check the register stack to see if
1346     // it has overflowed.
1347     return false;
1348   }
1349 
1350   // Java code never executes within the yellow zone: the latter is only
1351   // there to provoke an exception during stack banging.  If java code
1352   // is executing there, either StackShadowPages should be larger, or
1353   // some exception code in c1, c2 or the interpreter isn't unwinding
1354   // when it should.
1355   guarantee(cur_sp > stack_yellow_zone_base(), "not enough space to reguard - increase StackShadowPages");
1356 
1357   enable_stack_yellow_zone();
1358   return true;
1359 }
1360 
1361 bool JavaThread::reguard_stack(void) {
1362   return reguard_stack(os::current_stack_pointer());
1363 }
1364 
1365 
1366 void JavaThread::block_if_vm_exited() {
1367   if (_terminated == _vm_exited) {
1368     // _vm_exited is set at safepoint, and Threads_lock is never released
1369     // we will block here forever
1370     Threads_lock->lock_without_safepoint_check();
1371     ShouldNotReachHere();
1372   }
1373 }
1374 
1375 
1376 // Remove this ifdef when C1 is ported to the compiler interface.
1377 static void compiler_thread_entry(JavaThread* thread, TRAPS);
1378 
1379 JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
1380   Thread()
1381 #ifndef SERIALGC
1382   , _satb_mark_queue(&_satb_mark_queue_set),
1383   _dirty_card_queue(&_dirty_card_queue_set)
1384 #endif // !SERIALGC
1385 {
1386   if (TraceThreadEvents) {
1387     tty->print_cr("creating thread %p", this);
1388   }
1389   initialize();
1390   _is_attaching = false;
1391   set_entry_point(entry_point);
1392   // Create the native thread itself.
1393   // %note runtime_23
1394   os::ThreadType thr_type = os::java_thread;
1395   thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
1396                                                      os::java_thread;
1397   os::create_thread(this, thr_type, stack_sz);
1398 
1399   // The _osthread may be NULL here because we ran out of memory (too many threads active).
1400   // We need to throw and OutOfMemoryError - however we cannot do this here because the caller
1401   // may hold a lock and all locks must be unlocked before throwing the exception (throwing
1402   // the exception consists of creating the exception object & initializing it, initialization
1403   // will leave the VM via a JavaCall and then all locks must be unlocked).
1404   //
1405   // The thread is still suspended when we reach here. Thread must be explicit started
1406   // by creator! Furthermore, the thread must also explicitly be added to the Threads list
1407   // by calling Threads:add. The reason why this is not done here, is because the thread
1408   // object must be fully initialized (take a look at JVM_Start)
1409 }
1410 
1411 JavaThread::~JavaThread() {
1412   if (TraceThreadEvents) {
1413       tty->print_cr("terminate thread %p", this);
1414   }
1415 
1416   // JSR166 -- return the parker to the free list
1417   Parker::Release(_parker);
1418   _parker = NULL ;
1419 
1420   // Free any remaining  previous UnrollBlock
1421   vframeArray* old_array = vframe_array_last();
1422 
1423   if (old_array != NULL) {
1424     Deoptimization::UnrollBlock* old_info = old_array->unroll_block();
1425     old_array->set_unroll_block(NULL);
1426     delete old_info;
1427     delete old_array;
1428   }
1429 
1430   GrowableArray<jvmtiDeferredLocalVariableSet*>* deferred = deferred_locals();
1431   if (deferred != NULL) {
1432     // This can only happen if thread is destroyed before deoptimization occurs.
1433     assert(deferred->length() != 0, "empty array!");
1434     do {
1435       jvmtiDeferredLocalVariableSet* dlv = deferred->at(0);
1436       deferred->remove_at(0);
1437       // individual jvmtiDeferredLocalVariableSet are CHeapObj's
1438       delete dlv;
1439     } while (deferred->length() != 0);
1440     delete deferred;
1441   }
1442 
1443   // All Java related clean up happens in exit
1444   ThreadSafepointState::destroy(this);
1445   if (_thread_profiler != NULL) delete _thread_profiler;
1446   if (_thread_stat != NULL) delete _thread_stat;
1447 }
1448 
1449 
1450 // The first routine called by a new Java thread
1451 void JavaThread::run() {
1452   // initialize thread-local alloc buffer related fields
1453   this->initialize_tlab();
1454 
1455   // used to test validitity of stack trace backs
1456   this->record_base_of_stack_pointer();
1457 
1458   // Record real stack base and size.
1459   this->record_stack_base_and_size();
1460 
1461   // Initialize thread local storage; set before calling MutexLocker
1462   this->initialize_thread_local_storage();
1463 
1464   this->create_stack_guard_pages();
1465 
1466   this->cache_global_variables();
1467 
1468   // Thread is now sufficient initialized to be handled by the safepoint code as being
1469   // in the VM. Change thread state from _thread_new to _thread_in_vm
1470   ThreadStateTransition::transition_and_fence(this, _thread_new, _thread_in_vm);
1471 
1472   assert(JavaThread::current() == this, "sanity check");
1473   assert(!Thread::current()->owns_locks(), "sanity check");
1474 
1475   DTRACE_THREAD_PROBE(start, this);
1476 
1477   // This operation might block. We call that after all safepoint checks for a new thread has
1478   // been completed.
1479   this->set_active_handles(JNIHandleBlock::allocate_block());
1480 
1481   if (JvmtiExport::should_post_thread_life()) {
1482     JvmtiExport::post_thread_start(this);
1483   }
1484 
1485   // We call another function to do the rest so we are sure that the stack addresses used
1486   // from there will be lower than the stack base just computed
1487   thread_main_inner();
1488 
1489   // Note, thread is no longer valid at this point!
1490 }
1491 
1492 
1493 void JavaThread::thread_main_inner() {
1494   assert(JavaThread::current() == this, "sanity check");
1495   assert(this->threadObj() != NULL, "just checking");
1496 
1497   // Execute thread entry point unless this thread has a pending exception
1498   // or has been stopped before starting.
1499   // Note: Due to JVM_StopThread we can have pending exceptions already!
1500   if (!this->has_pending_exception() &&
1501       !java_lang_Thread::is_stillborn(this->threadObj())) {
1502     HandleMark hm(this);
1503     this->entry_point()(this, this);
1504   }
1505 
1506   DTRACE_THREAD_PROBE(stop, this);
1507 
1508   this->exit(false);
1509   delete this;
1510 }
1511 
1512 
1513 static void ensure_join(JavaThread* thread) {
1514   // We do not need to grap the Threads_lock, since we are operating on ourself.
1515   Handle threadObj(thread, thread->threadObj());
1516   assert(threadObj.not_null(), "java thread object must exist");
1517   ObjectLocker lock(threadObj, thread);
1518   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1519   thread->clear_pending_exception();
1520   // Thread is exiting. So set thread_status field in  java.lang.Thread class to TERMINATED.
1521   java_lang_Thread::set_thread_status(threadObj(), java_lang_Thread::TERMINATED);
1522   // Clear the native thread instance - this makes isAlive return false and allows the join()
1523   // to complete once we've done the notify_all below
1524   java_lang_Thread::set_thread(threadObj(), NULL);
1525   lock.notify_all(thread);
1526   // Ignore pending exception (ThreadDeath), since we are exiting anyway
1527   thread->clear_pending_exception();
1528 }
1529 
1530 
1531 // For any new cleanup additions, please check to see if they need to be applied to
1532 // cleanup_failed_attach_current_thread as well.
1533 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
1534   assert(this == JavaThread::current(),  "thread consistency check");
1535   if (!InitializeJavaLangSystem) return;
1536 
1537   HandleMark hm(this);
1538   Handle uncaught_exception(this, this->pending_exception());
1539   this->clear_pending_exception();
1540   Handle threadObj(this, this->threadObj());
1541   assert(threadObj.not_null(), "Java thread object should be created");
1542 
1543   if (get_thread_profiler() != NULL) {
1544     get_thread_profiler()->disengage();
1545     ResourceMark rm;
1546     get_thread_profiler()->print(get_thread_name());
1547   }
1548 
1549 
1550   // FIXIT: This code should be moved into else part, when reliable 1.2/1.3 check is in place
1551   {
1552     EXCEPTION_MARK;
1553 
1554     CLEAR_PENDING_EXCEPTION;
1555   }
1556   // FIXIT: The is_null check is only so it works better on JDK1.2 VM's. This
1557   // has to be fixed by a runtime query method
1558   if (!destroy_vm || JDK_Version::is_jdk12x_version()) {
1559     // JSR-166: change call from from ThreadGroup.uncaughtException to
1560     // java.lang.Thread.dispatchUncaughtException
1561     if (uncaught_exception.not_null()) {
1562       Handle group(this, java_lang_Thread::threadGroup(threadObj()));
1563       Events::log("uncaught exception INTPTR_FORMAT " " INTPTR_FORMAT " " INTPTR_FORMAT",
1564         (address)uncaught_exception(), (address)threadObj(), (address)group());
1565       {
1566         EXCEPTION_MARK;
1567         // Check if the method Thread.dispatchUncaughtException() exists. If so
1568         // call it.  Otherwise we have an older library without the JSR-166 changes,
1569         // so call ThreadGroup.uncaughtException()
1570         KlassHandle recvrKlass(THREAD, threadObj->klass());
1571         CallInfo callinfo;
1572         KlassHandle thread_klass(THREAD, SystemDictionary::Thread_klass());
1573         LinkResolver::resolve_virtual_call(callinfo, threadObj, recvrKlass, thread_klass,
1574                                            vmSymbols::dispatchUncaughtException_name(),
1575                                            vmSymbols::throwable_void_signature(),
1576                                            KlassHandle(), false, false, THREAD);
1577         CLEAR_PENDING_EXCEPTION;
1578         methodHandle method = callinfo.selected_method();
1579         if (method.not_null()) {
1580           JavaValue result(T_VOID);
1581           JavaCalls::call_virtual(&result,
1582                                   threadObj, thread_klass,
1583                                   vmSymbols::dispatchUncaughtException_name(),
1584                                   vmSymbols::throwable_void_signature(),
1585                                   uncaught_exception,
1586                                   THREAD);
1587         } else {
1588           KlassHandle thread_group(THREAD, SystemDictionary::ThreadGroup_klass());
1589           JavaValue result(T_VOID);
1590           JavaCalls::call_virtual(&result,
1591                                   group, thread_group,
1592                                   vmSymbols::uncaughtException_name(),
1593                                   vmSymbols::thread_throwable_void_signature(),
1594                                   threadObj,           // Arg 1
1595                                   uncaught_exception,  // Arg 2
1596                                   THREAD);
1597         }
1598         if (HAS_PENDING_EXCEPTION) {
1599           ResourceMark rm(this);
1600           jio_fprintf(defaultStream::error_stream(),
1601                 "\nException: %s thrown from the UncaughtExceptionHandler"
1602                 " in thread \"%s\"\n",
1603                 Klass::cast(pending_exception()->klass())->external_name(),
1604                 get_thread_name());
1605           CLEAR_PENDING_EXCEPTION;
1606         }
1607       }
1608     }
1609 
1610     // Call Thread.exit(). We try 3 times in case we got another Thread.stop during
1611     // the execution of the method. If that is not enough, then we don't really care. Thread.stop
1612     // is deprecated anyhow.
1613     { int count = 3;
1614       while (java_lang_Thread::threadGroup(threadObj()) != NULL && (count-- > 0)) {
1615         EXCEPTION_MARK;
1616         JavaValue result(T_VOID);
1617         KlassHandle thread_klass(THREAD, SystemDictionary::Thread_klass());
1618         JavaCalls::call_virtual(&result,
1619                               threadObj, thread_klass,
1620                               vmSymbols::exit_method_name(),
1621                               vmSymbols::void_method_signature(),
1622                               THREAD);
1623         CLEAR_PENDING_EXCEPTION;
1624       }
1625     }
1626 
1627     // notify JVMTI
1628     if (JvmtiExport::should_post_thread_life()) {
1629       JvmtiExport::post_thread_end(this);
1630     }
1631 
1632     // We have notified the agents that we are exiting, before we go on,
1633     // we must check for a pending external suspend request and honor it
1634     // in order to not surprise the thread that made the suspend request.
1635     while (true) {
1636       {
1637         MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
1638         if (!is_external_suspend()) {
1639           set_terminated(_thread_exiting);
1640           ThreadService::current_thread_exiting(this);
1641           break;
1642         }
1643         // Implied else:
1644         // Things get a little tricky here. We have a pending external
1645         // suspend request, but we are holding the SR_lock so we
1646         // can't just self-suspend. So we temporarily drop the lock
1647         // and then self-suspend.
1648       }
1649 
1650       ThreadBlockInVM tbivm(this);
1651       java_suspend_self();
1652 
1653       // We're done with this suspend request, but we have to loop around
1654       // and check again. Eventually we will get SR_lock without a pending
1655       // external suspend request and will be able to mark ourselves as
1656       // exiting.
1657     }
1658     // no more external suspends are allowed at this point
1659   } else {
1660     // before_exit() has already posted JVMTI THREAD_END events
1661   }
1662 
1663   // Notify waiters on thread object. This has to be done after exit() is called
1664   // on the thread (if the thread is the last thread in a daemon ThreadGroup the
1665   // group should have the destroyed bit set before waiters are notified).
1666   ensure_join(this);
1667   assert(!this->has_pending_exception(), "ensure_join should have cleared");
1668 
1669   // 6282335 JNI DetachCurrentThread spec states that all Java monitors
1670   // held by this thread must be released.  A detach operation must only
1671   // get here if there are no Java frames on the stack.  Therefore, any
1672   // owned monitors at this point MUST be JNI-acquired monitors which are
1673   // pre-inflated and in the monitor cache.
1674   //
1675   // ensure_join() ignores IllegalThreadStateExceptions, and so does this.
1676   if (exit_type == jni_detach && JNIDetachReleasesMonitors) {
1677     assert(!this->has_last_Java_frame(), "detaching with Java frames?");
1678     ObjectSynchronizer::release_monitors_owned_by_thread(this);
1679     assert(!this->has_pending_exception(), "release_monitors should have cleared");
1680   }
1681 
1682   // These things needs to be done while we are still a Java Thread. Make sure that thread
1683   // is in a consistent state, in case GC happens
1684   assert(_privileged_stack_top == NULL, "must be NULL when we get here");
1685 
1686   if (active_handles() != NULL) {
1687     JNIHandleBlock* block = active_handles();
1688     set_active_handles(NULL);
1689     JNIHandleBlock::release_block(block);
1690   }
1691 
1692   if (free_handle_block() != NULL) {
1693     JNIHandleBlock* block = free_handle_block();
1694     set_free_handle_block(NULL);
1695     JNIHandleBlock::release_block(block);
1696   }
1697 
1698   // These have to be removed while this is still a valid thread.
1699   remove_stack_guard_pages();
1700 
1701   if (UseTLAB) {
1702     tlab().make_parsable(true);  // retire TLAB
1703   }
1704 
1705   if (JvmtiEnv::environments_might_exist()) {
1706     JvmtiExport::cleanup_thread(this);
1707   }
1708 
1709 #ifndef SERIALGC
1710   // We must flush G1-related buffers before removing a thread from
1711   // the list of active threads.
1712   if (UseG1GC) {
1713     flush_barrier_queues();
1714   }
1715 #endif
1716 
1717   // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
1718   Threads::remove(this);
1719 }
1720 
1721 #ifndef SERIALGC
1722 // Flush G1-related queues.
1723 void JavaThread::flush_barrier_queues() {
1724   satb_mark_queue().flush();
1725   dirty_card_queue().flush();
1726 }
1727 
1728 void JavaThread::initialize_queues() {
1729   assert(!SafepointSynchronize::is_at_safepoint(),
1730          "we should not be at a safepoint");
1731 
1732   ObjPtrQueue& satb_queue = satb_mark_queue();
1733   SATBMarkQueueSet& satb_queue_set = satb_mark_queue_set();
1734   // The SATB queue should have been constructed with its active
1735   // field set to false.
1736   assert(!satb_queue.is_active(), "SATB queue should not be active");
1737   assert(satb_queue.is_empty(), "SATB queue should be empty");
1738   // If we are creating the thread during a marking cycle, we should
1739   // set the active field of the SATB queue to true.
1740   if (satb_queue_set.is_active()) {
1741     satb_queue.set_active(true);
1742   }
1743 
1744   DirtyCardQueue& dirty_queue = dirty_card_queue();
1745   // The dirty card queue should have been constructed with its
1746   // active field set to true.
1747   assert(dirty_queue.is_active(), "dirty card queue should be active");
1748 }
1749 #endif // !SERIALGC
1750 
1751 void JavaThread::cleanup_failed_attach_current_thread() {
1752   if (get_thread_profiler() != NULL) {
1753     get_thread_profiler()->disengage();
1754     ResourceMark rm;
1755     get_thread_profiler()->print(get_thread_name());
1756   }
1757 
1758   if (active_handles() != NULL) {
1759     JNIHandleBlock* block = active_handles();
1760     set_active_handles(NULL);
1761     JNIHandleBlock::release_block(block);
1762   }
1763 
1764   if (free_handle_block() != NULL) {
1765     JNIHandleBlock* block = free_handle_block();
1766     set_free_handle_block(NULL);
1767     JNIHandleBlock::release_block(block);
1768   }
1769 
1770   // These have to be removed while this is still a valid thread.
1771   remove_stack_guard_pages();
1772 
1773   if (UseTLAB) {
1774     tlab().make_parsable(true);  // retire TLAB, if any
1775   }
1776 
1777 #ifndef SERIALGC
1778   if (UseG1GC) {
1779     flush_barrier_queues();
1780   }
1781 #endif
1782 
1783   Threads::remove(this);
1784   delete this;
1785 }
1786 
1787 
1788 
1789 
1790 JavaThread* JavaThread::active() {
1791   Thread* thread = ThreadLocalStorage::thread();
1792   assert(thread != NULL, "just checking");
1793   if (thread->is_Java_thread()) {
1794     return (JavaThread*) thread;
1795   } else {
1796     assert(thread->is_VM_thread(), "this must be a vm thread");
1797     VM_Operation* op = ((VMThread*) thread)->vm_operation();
1798     JavaThread *ret=op == NULL ? NULL : (JavaThread *)op->calling_thread();
1799     assert(ret->is_Java_thread(), "must be a Java thread");
1800     return ret;
1801   }
1802 }
1803 
1804 bool JavaThread::is_lock_owned(address adr) const {
1805   if (Thread::is_lock_owned(adr)) return true;
1806 
1807   for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
1808     if (chunk->contains(adr)) return true;
1809   }
1810 
1811   return false;
1812 }
1813 
1814 
1815 void JavaThread::add_monitor_chunk(MonitorChunk* chunk) {
1816   chunk->set_next(monitor_chunks());
1817   set_monitor_chunks(chunk);
1818 }
1819 
1820 void JavaThread::remove_monitor_chunk(MonitorChunk* chunk) {
1821   guarantee(monitor_chunks() != NULL, "must be non empty");
1822   if (monitor_chunks() == chunk) {
1823     set_monitor_chunks(chunk->next());
1824   } else {
1825     MonitorChunk* prev = monitor_chunks();
1826     while (prev->next() != chunk) prev = prev->next();
1827     prev->set_next(chunk->next());
1828   }
1829 }
1830 
1831 // JVM support.
1832 
1833 // Note: this function shouldn't block if it's called in
1834 // _thread_in_native_trans state (such as from
1835 // check_special_condition_for_native_trans()).
1836 void JavaThread::check_and_handle_async_exceptions(bool check_unsafe_error) {
1837 
1838   if (has_last_Java_frame() && has_async_condition()) {
1839     // If we are at a polling page safepoint (not a poll return)
1840     // then we must defer async exception because live registers
1841     // will be clobbered by the exception path. Poll return is
1842     // ok because the call we a returning from already collides
1843     // with exception handling registers and so there is no issue.
1844     // (The exception handling path kills call result registers but
1845     //  this is ok since the exception kills the result anyway).
1846 
1847     if (is_at_poll_safepoint()) {
1848       // if the code we are returning to has deoptimized we must defer
1849       // the exception otherwise live registers get clobbered on the
1850       // exception path before deoptimization is able to retrieve them.
1851       //
1852       RegisterMap map(this, false);
1853       frame caller_fr = last_frame().sender(&map);
1854       assert(caller_fr.is_compiled_frame(), "what?");
1855       if (caller_fr.is_deoptimized_frame()) {
1856         if (TraceExceptions) {
1857           ResourceMark rm;
1858           tty->print_cr("deferred async exception at compiled safepoint");
1859         }
1860         return;
1861       }
1862     }
1863   }
1864 
1865   JavaThread::AsyncRequests condition = clear_special_runtime_exit_condition();
1866   if (condition == _no_async_condition) {
1867     // Conditions have changed since has_special_runtime_exit_condition()
1868     // was called:
1869     // - if we were here only because of an external suspend request,
1870     //   then that was taken care of above (or cancelled) so we are done
1871     // - if we were here because of another async request, then it has
1872     //   been cleared between the has_special_runtime_exit_condition()
1873     //   and now so again we are done
1874     return;
1875   }
1876 
1877   // Check for pending async. exception
1878   if (_pending_async_exception != NULL) {
1879     // Only overwrite an already pending exception, if it is not a threadDeath.
1880     if (!has_pending_exception() || !pending_exception()->is_a(SystemDictionary::ThreadDeath_klass())) {
1881 
1882       // We cannot call Exceptions::_throw(...) here because we cannot block
1883       set_pending_exception(_pending_async_exception, __FILE__, __LINE__);
1884 
1885       if (TraceExceptions) {
1886         ResourceMark rm;
1887         tty->print("Async. exception installed at runtime exit (" INTPTR_FORMAT ")", this);
1888         if (has_last_Java_frame() ) {
1889           frame f = last_frame();
1890           tty->print(" (pc: " INTPTR_FORMAT " sp: " INTPTR_FORMAT " )", f.pc(), f.sp());
1891         }
1892         tty->print_cr(" of type: %s", instanceKlass::cast(_pending_async_exception->klass())->external_name());
1893       }
1894       _pending_async_exception = NULL;
1895       clear_has_async_exception();
1896     }
1897   }
1898 
1899   if (check_unsafe_error &&
1900       condition == _async_unsafe_access_error && !has_pending_exception()) {
1901     condition = _no_async_condition;  // done
1902     switch (thread_state()) {
1903     case _thread_in_vm:
1904       {
1905         JavaThread* THREAD = this;
1906         THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
1907       }
1908     case _thread_in_native:
1909       {
1910         ThreadInVMfromNative tiv(this);
1911         JavaThread* THREAD = this;
1912         THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in an unsafe memory access operation");
1913       }
1914     case _thread_in_Java:
1915       {
1916         ThreadInVMfromJava tiv(this);
1917         JavaThread* THREAD = this;
1918         THROW_MSG(vmSymbols::java_lang_InternalError(), "a fault occurred in a recent unsafe memory access operation in compiled Java code");
1919       }
1920     default:
1921       ShouldNotReachHere();
1922     }
1923   }
1924 
1925   assert(condition == _no_async_condition || has_pending_exception() ||
1926          (!check_unsafe_error && condition == _async_unsafe_access_error),
1927          "must have handled the async condition, if no exception");
1928 }
1929 
1930 void JavaThread::handle_special_runtime_exit_condition(bool check_asyncs) {
1931   //
1932   // Check for pending external suspend. Internal suspend requests do
1933   // not use handle_special_runtime_exit_condition().
1934   // If JNIEnv proxies are allowed, don't self-suspend if the target
1935   // thread is not the current thread. In older versions of jdbx, jdbx
1936   // threads could call into the VM with another thread's JNIEnv so we
1937   // can be here operating on behalf of a suspended thread (4432884).
1938   bool do_self_suspend = is_external_suspend_with_lock();
1939   if (do_self_suspend && (!AllowJNIEnvProxy || this == JavaThread::current())) {
1940     //
1941     // Because thread is external suspended the safepoint code will count
1942     // thread as at a safepoint. This can be odd because we can be here
1943     // as _thread_in_Java which would normally transition to _thread_blocked
1944     // at a safepoint. We would like to mark the thread as _thread_blocked
1945     // before calling java_suspend_self like all other callers of it but
1946     // we must then observe proper safepoint protocol. (We can't leave
1947     // _thread_blocked with a safepoint in progress). However we can be
1948     // here as _thread_in_native_trans so we can't use a normal transition
1949     // constructor/destructor pair because they assert on that type of
1950     // transition. We could do something like:
1951     //
1952     // JavaThreadState state = thread_state();
1953     // set_thread_state(_thread_in_vm);
1954     // {
1955     //   ThreadBlockInVM tbivm(this);
1956     //   java_suspend_self()
1957     // }
1958     // set_thread_state(_thread_in_vm_trans);
1959     // if (safepoint) block;
1960     // set_thread_state(state);
1961     //
1962     // but that is pretty messy. Instead we just go with the way the
1963     // code has worked before and note that this is the only path to
1964     // java_suspend_self that doesn't put the thread in _thread_blocked
1965     // mode.
1966 
1967     frame_anchor()->make_walkable(this);
1968     java_suspend_self();
1969 
1970     // We might be here for reasons in addition to the self-suspend request
1971     // so check for other async requests.
1972   }
1973 
1974   if (check_asyncs) {
1975     check_and_handle_async_exceptions();
1976   }
1977 }
1978 
1979 void JavaThread::send_thread_stop(oop java_throwable)  {
1980   assert(Thread::current()->is_VM_thread(), "should be in the vm thread");
1981   assert(Threads_lock->is_locked(), "Threads_lock should be locked by safepoint code");
1982   assert(SafepointSynchronize::is_at_safepoint(), "all threads are stopped");
1983 
1984   // Do not throw asynchronous exceptions against the compiler thread
1985   // (the compiler thread should not be a Java thread -- fix in 1.4.2)
1986   if (is_Compiler_thread()) return;
1987 
1988   {
1989     // Actually throw the Throwable against the target Thread - however
1990     // only if there is no thread death exception installed already.
1991     if (_pending_async_exception == NULL || !_pending_async_exception->is_a(SystemDictionary::ThreadDeath_klass())) {
1992       // If the topmost frame is a runtime stub, then we are calling into
1993       // OptoRuntime from compiled code. Some runtime stubs (new, monitor_exit..)
1994       // must deoptimize the caller before continuing, as the compiled  exception handler table
1995       // may not be valid
1996       if (has_last_Java_frame()) {
1997         frame f = last_frame();
1998         if (f.is_runtime_frame() || f.is_safepoint_blob_frame()) {
1999           // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2000           RegisterMap reg_map(this, UseBiasedLocking);
2001           frame compiled_frame = f.sender(&reg_map);
2002           if (compiled_frame.can_be_deoptimized()) {
2003             Deoptimization::deoptimize(this, compiled_frame, &reg_map);
2004           }
2005         }
2006       }
2007 
2008       // Set async. pending exception in thread.
2009       set_pending_async_exception(java_throwable);
2010 
2011       if (TraceExceptions) {
2012        ResourceMark rm;
2013        tty->print_cr("Pending Async. exception installed of type: %s", instanceKlass::cast(_pending_async_exception->klass())->external_name());
2014       }
2015       // for AbortVMOnException flag
2016       NOT_PRODUCT(Exceptions::debug_check_abort(instanceKlass::cast(_pending_async_exception->klass())->external_name()));
2017     }
2018   }
2019 
2020 
2021   // Interrupt thread so it will wake up from a potential wait()
2022   Thread::interrupt(this);
2023 }
2024 
2025 // External suspension mechanism.
2026 //
2027 // Tell the VM to suspend a thread when ever it knows that it does not hold on
2028 // to any VM_locks and it is at a transition
2029 // Self-suspension will happen on the transition out of the vm.
2030 // Catch "this" coming in from JNIEnv pointers when the thread has been freed
2031 //
2032 // Guarantees on return:
2033 //   + Target thread will not execute any new bytecode (that's why we need to
2034 //     force a safepoint)
2035 //   + Target thread will not enter any new monitors
2036 //
2037 void JavaThread::java_suspend() {
2038   { MutexLocker mu(Threads_lock);
2039     if (!Threads::includes(this) || is_exiting() || this->threadObj() == NULL) {
2040        return;
2041     }
2042   }
2043 
2044   { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2045     if (!is_external_suspend()) {
2046       // a racing resume has cancelled us; bail out now
2047       return;
2048     }
2049 
2050     // suspend is done
2051     uint32_t debug_bits = 0;
2052     // Warning: is_ext_suspend_completed() may temporarily drop the
2053     // SR_lock to allow the thread to reach a stable thread state if
2054     // it is currently in a transient thread state.
2055     if (is_ext_suspend_completed(false /* !called_by_wait */,
2056                                  SuspendRetryDelay, &debug_bits) ) {
2057       return;
2058     }
2059   }
2060 
2061   VM_ForceSafepoint vm_suspend;
2062   VMThread::execute(&vm_suspend);
2063 }
2064 
2065 // Part II of external suspension.
2066 // A JavaThread self suspends when it detects a pending external suspend
2067 // request. This is usually on transitions. It is also done in places
2068 // where continuing to the next transition would surprise the caller,
2069 // e.g., monitor entry.
2070 //
2071 // Returns the number of times that the thread self-suspended.
2072 //
2073 // Note: DO NOT call java_suspend_self() when you just want to block current
2074 //       thread. java_suspend_self() is the second stage of cooperative
2075 //       suspension for external suspend requests and should only be used
2076 //       to complete an external suspend request.
2077 //
2078 int JavaThread::java_suspend_self() {
2079   int ret = 0;
2080 
2081   // we are in the process of exiting so don't suspend
2082   if (is_exiting()) {
2083      clear_external_suspend();
2084      return ret;
2085   }
2086 
2087   assert(_anchor.walkable() ||
2088     (is_Java_thread() && !((JavaThread*)this)->has_last_Java_frame()),
2089     "must have walkable stack");
2090 
2091   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2092 
2093   assert(!this->is_ext_suspended(),
2094     "a thread trying to self-suspend should not already be suspended");
2095 
2096   if (this->is_suspend_equivalent()) {
2097     // If we are self-suspending as a result of the lifting of a
2098     // suspend equivalent condition, then the suspend_equivalent
2099     // flag is not cleared until we set the ext_suspended flag so
2100     // that wait_for_ext_suspend_completion() returns consistent
2101     // results.
2102     this->clear_suspend_equivalent();
2103   }
2104 
2105   // A racing resume may have cancelled us before we grabbed SR_lock
2106   // above. Or another external suspend request could be waiting for us
2107   // by the time we return from SR_lock()->wait(). The thread
2108   // that requested the suspension may already be trying to walk our
2109   // stack and if we return now, we can change the stack out from under
2110   // it. This would be a "bad thing (TM)" and cause the stack walker
2111   // to crash. We stay self-suspended until there are no more pending
2112   // external suspend requests.
2113   while (is_external_suspend()) {
2114     ret++;
2115     this->set_ext_suspended();
2116 
2117     // _ext_suspended flag is cleared by java_resume()
2118     while (is_ext_suspended()) {
2119       this->SR_lock()->wait(Mutex::_no_safepoint_check_flag);
2120     }
2121   }
2122 
2123   return ret;
2124 }
2125 
2126 #ifdef ASSERT
2127 // verify the JavaThread has not yet been published in the Threads::list, and
2128 // hence doesn't need protection from concurrent access at this stage
2129 void JavaThread::verify_not_published() {
2130   if (!Threads_lock->owned_by_self()) {
2131    MutexLockerEx ml(Threads_lock,  Mutex::_no_safepoint_check_flag);
2132    assert( !Threads::includes(this),
2133            "java thread shouldn't have been published yet!");
2134   }
2135   else {
2136    assert( !Threads::includes(this),
2137            "java thread shouldn't have been published yet!");
2138   }
2139 }
2140 #endif
2141 
2142 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2143 // progress or when _suspend_flags is non-zero.
2144 // Current thread needs to self-suspend if there is a suspend request and/or
2145 // block if a safepoint is in progress.
2146 // Async exception ISN'T checked.
2147 // Note only the ThreadInVMfromNative transition can call this function
2148 // directly and when thread state is _thread_in_native_trans
2149 void JavaThread::check_safepoint_and_suspend_for_native_trans(JavaThread *thread) {
2150   assert(thread->thread_state() == _thread_in_native_trans, "wrong state");
2151 
2152   JavaThread *curJT = JavaThread::current();
2153   bool do_self_suspend = thread->is_external_suspend();
2154 
2155   assert(!curJT->has_last_Java_frame() || curJT->frame_anchor()->walkable(), "Unwalkable stack in native->vm transition");
2156 
2157   // If JNIEnv proxies are allowed, don't self-suspend if the target
2158   // thread is not the current thread. In older versions of jdbx, jdbx
2159   // threads could call into the VM with another thread's JNIEnv so we
2160   // can be here operating on behalf of a suspended thread (4432884).
2161   if (do_self_suspend && (!AllowJNIEnvProxy || curJT == thread)) {
2162     JavaThreadState state = thread->thread_state();
2163 
2164     // We mark this thread_blocked state as a suspend-equivalent so
2165     // that a caller to is_ext_suspend_completed() won't be confused.
2166     // The suspend-equivalent state is cleared by java_suspend_self().
2167     thread->set_suspend_equivalent();
2168 
2169     // If the safepoint code sees the _thread_in_native_trans state, it will
2170     // wait until the thread changes to other thread state. There is no
2171     // guarantee on how soon we can obtain the SR_lock and complete the
2172     // self-suspend request. It would be a bad idea to let safepoint wait for
2173     // too long. Temporarily change the state to _thread_blocked to
2174     // let the VM thread know that this thread is ready for GC. The problem
2175     // of changing thread state is that safepoint could happen just after
2176     // java_suspend_self() returns after being resumed, and VM thread will
2177     // see the _thread_blocked state. We must check for safepoint
2178     // after restoring the state and make sure we won't leave while a safepoint
2179     // is in progress.
2180     thread->set_thread_state(_thread_blocked);
2181     thread->java_suspend_self();
2182     thread->set_thread_state(state);
2183     // Make sure new state is seen by VM thread
2184     if (os::is_MP()) {
2185       if (UseMembar) {
2186         // Force a fence between the write above and read below
2187         OrderAccess::fence();
2188       } else {
2189         // Must use this rather than serialization page in particular on Windows
2190         InterfaceSupport::serialize_memory(thread);
2191       }
2192     }
2193   }
2194 
2195   if (SafepointSynchronize::do_call_back()) {
2196     // If we are safepointing, then block the caller which may not be
2197     // the same as the target thread (see above).
2198     SafepointSynchronize::block(curJT);
2199   }
2200 
2201   if (thread->is_deopt_suspend()) {
2202     thread->clear_deopt_suspend();
2203     RegisterMap map(thread, false);
2204     frame f = thread->last_frame();
2205     while ( f.id() != thread->must_deopt_id() && ! f.is_first_frame()) {
2206       f = f.sender(&map);
2207     }
2208     if (f.id() == thread->must_deopt_id()) {
2209       thread->clear_must_deopt_id();
2210       f.deoptimize(thread);
2211     } else {
2212       fatal("missed deoptimization!");
2213     }
2214   }
2215 }
2216 
2217 // Slow path when the native==>VM/Java barriers detect a safepoint is in
2218 // progress or when _suspend_flags is non-zero.
2219 // Current thread needs to self-suspend if there is a suspend request and/or
2220 // block if a safepoint is in progress.
2221 // Also check for pending async exception (not including unsafe access error).
2222 // Note only the native==>VM/Java barriers can call this function and when
2223 // thread state is _thread_in_native_trans.
2224 void JavaThread::check_special_condition_for_native_trans(JavaThread *thread) {
2225   check_safepoint_and_suspend_for_native_trans(thread);
2226 
2227   if (thread->has_async_exception()) {
2228     // We are in _thread_in_native_trans state, don't handle unsafe
2229     // access error since that may block.
2230     thread->check_and_handle_async_exceptions(false);
2231   }
2232 }
2233 
2234 // We need to guarantee the Threads_lock here, since resumes are not
2235 // allowed during safepoint synchronization
2236 // Can only resume from an external suspension
2237 void JavaThread::java_resume() {
2238   assert_locked_or_safepoint(Threads_lock);
2239 
2240   // Sanity check: thread is gone, has started exiting or the thread
2241   // was not externally suspended.
2242   if (!Threads::includes(this) || is_exiting() || !is_external_suspend()) {
2243     return;
2244   }
2245 
2246   MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
2247 
2248   clear_external_suspend();
2249 
2250   if (is_ext_suspended()) {
2251     clear_ext_suspended();
2252     SR_lock()->notify_all();
2253   }
2254 }
2255 
2256 void JavaThread::create_stack_guard_pages() {
2257   if (! os::uses_stack_guard_pages() || _stack_guard_state != stack_guard_unused) return;
2258   address low_addr = stack_base() - stack_size();
2259   size_t len = (StackYellowPages + StackRedPages) * os::vm_page_size();
2260 
2261   int allocate = os::allocate_stack_guard_pages();
2262   // warning("Guarding at " PTR_FORMAT " for len " SIZE_FORMAT "\n", low_addr, len);
2263 
2264   if (allocate && !os::create_stack_guard_pages((char *) low_addr, len)) {
2265     warning("Attempt to allocate stack guard pages failed.");
2266     return;
2267   }
2268 
2269   if (os::guard_memory((char *) low_addr, len)) {
2270     _stack_guard_state = stack_guard_enabled;
2271   } else {
2272     warning("Attempt to protect stack guard pages failed.");
2273     if (os::uncommit_memory((char *) low_addr, len)) {
2274       warning("Attempt to deallocate stack guard pages failed.");
2275     }
2276   }
2277 }
2278 
2279 void JavaThread::remove_stack_guard_pages() {
2280   if (_stack_guard_state == stack_guard_unused) return;
2281   address low_addr = stack_base() - stack_size();
2282   size_t len = (StackYellowPages + StackRedPages) * os::vm_page_size();
2283 
2284   if (os::allocate_stack_guard_pages()) {
2285     if (os::remove_stack_guard_pages((char *) low_addr, len)) {
2286       _stack_guard_state = stack_guard_unused;
2287     } else {
2288       warning("Attempt to deallocate stack guard pages failed.");
2289     }
2290   } else {
2291     if (_stack_guard_state == stack_guard_unused) return;
2292     if (os::unguard_memory((char *) low_addr, len)) {
2293       _stack_guard_state = stack_guard_unused;
2294     } else {
2295         warning("Attempt to unprotect stack guard pages failed.");
2296     }
2297   }
2298 }
2299 
2300 void JavaThread::enable_stack_yellow_zone() {
2301   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2302   assert(_stack_guard_state != stack_guard_enabled, "already enabled");
2303 
2304   // The base notation is from the stacks point of view, growing downward.
2305   // We need to adjust it to work correctly with guard_memory()
2306   address base = stack_yellow_zone_base() - stack_yellow_zone_size();
2307 
2308   guarantee(base < stack_base(),"Error calculating stack yellow zone");
2309   guarantee(base < os::current_stack_pointer(),"Error calculating stack yellow zone");
2310 
2311   if (os::guard_memory((char *) base, stack_yellow_zone_size())) {
2312     _stack_guard_state = stack_guard_enabled;
2313   } else {
2314     warning("Attempt to guard stack yellow zone failed.");
2315   }
2316   enable_register_stack_guard();
2317 }
2318 
2319 void JavaThread::disable_stack_yellow_zone() {
2320   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2321   assert(_stack_guard_state != stack_guard_yellow_disabled, "already disabled");
2322 
2323   // Simply return if called for a thread that does not use guard pages.
2324   if (_stack_guard_state == stack_guard_unused) return;
2325 
2326   // The base notation is from the stacks point of view, growing downward.
2327   // We need to adjust it to work correctly with guard_memory()
2328   address base = stack_yellow_zone_base() - stack_yellow_zone_size();
2329 
2330   if (os::unguard_memory((char *)base, stack_yellow_zone_size())) {
2331     _stack_guard_state = stack_guard_yellow_disabled;
2332   } else {
2333     warning("Attempt to unguard stack yellow zone failed.");
2334   }
2335   disable_register_stack_guard();
2336 }
2337 
2338 void JavaThread::enable_stack_red_zone() {
2339   // The base notation is from the stacks point of view, growing downward.
2340   // We need to adjust it to work correctly with guard_memory()
2341   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2342   address base = stack_red_zone_base() - stack_red_zone_size();
2343 
2344   guarantee(base < stack_base(),"Error calculating stack red zone");
2345   guarantee(base < os::current_stack_pointer(),"Error calculating stack red zone");
2346 
2347   if(!os::guard_memory((char *) base, stack_red_zone_size())) {
2348     warning("Attempt to guard stack red zone failed.");
2349   }
2350 }
2351 
2352 void JavaThread::disable_stack_red_zone() {
2353   // The base notation is from the stacks point of view, growing downward.
2354   // We need to adjust it to work correctly with guard_memory()
2355   assert(_stack_guard_state != stack_guard_unused, "must be using guard pages.");
2356   address base = stack_red_zone_base() - stack_red_zone_size();
2357   if (!os::unguard_memory((char *)base, stack_red_zone_size())) {
2358     warning("Attempt to unguard stack red zone failed.");
2359   }
2360 }
2361 
2362 void JavaThread::frames_do(void f(frame*, const RegisterMap* map)) {
2363   // ignore is there is no stack
2364   if (!has_last_Java_frame()) return;
2365   // traverse the stack frames. Starts from top frame.
2366   for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2367     frame* fr = fst.current();
2368     f(fr, fst.register_map());
2369   }
2370 }
2371 
2372 
2373 #ifndef PRODUCT
2374 // Deoptimization
2375 // Function for testing deoptimization
2376 void JavaThread::deoptimize() {
2377   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2378   StackFrameStream fst(this, UseBiasedLocking);
2379   bool deopt = false;           // Dump stack only if a deopt actually happens.
2380   bool only_at = strlen(DeoptimizeOnlyAt) > 0;
2381   // Iterate over all frames in the thread and deoptimize
2382   for(; !fst.is_done(); fst.next()) {
2383     if(fst.current()->can_be_deoptimized()) {
2384 
2385       if (only_at) {
2386         // Deoptimize only at particular bcis.  DeoptimizeOnlyAt
2387         // consists of comma or carriage return separated numbers so
2388         // search for the current bci in that string.
2389         address pc = fst.current()->pc();
2390         nmethod* nm =  (nmethod*) fst.current()->cb();
2391         ScopeDesc* sd = nm->scope_desc_at( pc);
2392         char buffer[8];
2393         jio_snprintf(buffer, sizeof(buffer), "%d", sd->bci());
2394         size_t len = strlen(buffer);
2395         const char * found = strstr(DeoptimizeOnlyAt, buffer);
2396         while (found != NULL) {
2397           if ((found[len] == ',' || found[len] == '\n' || found[len] == '\0') &&
2398               (found == DeoptimizeOnlyAt || found[-1] == ',' || found[-1] == '\n')) {
2399             // Check that the bci found is bracketed by terminators.
2400             break;
2401           }
2402           found = strstr(found + 1, buffer);
2403         }
2404         if (!found) {
2405           continue;
2406         }
2407       }
2408 
2409       if (DebugDeoptimization && !deopt) {
2410         deopt = true; // One-time only print before deopt
2411         tty->print_cr("[BEFORE Deoptimization]");
2412         trace_frames();
2413         trace_stack();
2414       }
2415       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2416     }
2417   }
2418 
2419   if (DebugDeoptimization && deopt) {
2420     tty->print_cr("[AFTER Deoptimization]");
2421     trace_frames();
2422   }
2423 }
2424 
2425 
2426 // Make zombies
2427 void JavaThread::make_zombies() {
2428   for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2429     if (fst.current()->can_be_deoptimized()) {
2430       // it is a Java nmethod
2431       nmethod* nm = CodeCache::find_nmethod(fst.current()->pc());
2432       nm->make_not_entrant();
2433     }
2434   }
2435 }
2436 #endif // PRODUCT
2437 
2438 
2439 void JavaThread::deoptimized_wrt_marked_nmethods() {
2440   if (!has_last_Java_frame()) return;
2441   // BiasedLocking needs an updated RegisterMap for the revoke monitors pass
2442   StackFrameStream fst(this, UseBiasedLocking);
2443   for(; !fst.is_done(); fst.next()) {
2444     if (fst.current()->should_be_deoptimized()) {
2445       Deoptimization::deoptimize(this, *fst.current(), fst.register_map());
2446     }
2447   }
2448 }
2449 
2450 
2451 // GC support
2452 static void frame_gc_epilogue(frame* f, const RegisterMap* map) { f->gc_epilogue(); }
2453 
2454 void JavaThread::gc_epilogue() {
2455   frames_do(frame_gc_epilogue);
2456 }
2457 
2458 
2459 static void frame_gc_prologue(frame* f, const RegisterMap* map) { f->gc_prologue(); }
2460 
2461 void JavaThread::gc_prologue() {
2462   frames_do(frame_gc_prologue);
2463 }
2464 
2465 // If the caller is a NamedThread, then remember, in the current scope,
2466 // the given JavaThread in its _processed_thread field.
2467 class RememberProcessedThread: public StackObj {
2468   NamedThread* _cur_thr;
2469 public:
2470   RememberProcessedThread(JavaThread* jthr) {
2471     Thread* thread = Thread::current();
2472     if (thread->is_Named_thread()) {
2473       _cur_thr = (NamedThread *)thread;
2474       _cur_thr->set_processed_thread(jthr);
2475     } else {
2476       _cur_thr = NULL;
2477     }
2478   }
2479 
2480   ~RememberProcessedThread() {
2481     if (_cur_thr) {
2482       _cur_thr->set_processed_thread(NULL);
2483     }
2484   }
2485 };
2486 
2487 void JavaThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
2488   // Verify that the deferred card marks have been flushed.
2489   assert(deferred_card_mark().is_empty(), "Should be empty during GC");
2490 
2491   // The ThreadProfiler oops_do is done from FlatProfiler::oops_do
2492   // since there may be more than one thread using each ThreadProfiler.
2493 
2494   // Traverse the GCHandles
2495   Thread::oops_do(f, cf);
2496 
2497   assert( (!has_last_Java_frame() && java_call_counter() == 0) ||
2498           (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2499 
2500   if (has_last_Java_frame()) {
2501     // Record JavaThread to GC thread
2502     RememberProcessedThread rpt(this);
2503 
2504     // Traverse the privileged stack
2505     if (_privileged_stack_top != NULL) {
2506       _privileged_stack_top->oops_do(f);
2507     }
2508 
2509     // traverse the registered growable array
2510     if (_array_for_gc != NULL) {
2511       for (int index = 0; index < _array_for_gc->length(); index++) {
2512         f->do_oop(_array_for_gc->adr_at(index));
2513       }
2514     }
2515 
2516     // Traverse the monitor chunks
2517     for (MonitorChunk* chunk = monitor_chunks(); chunk != NULL; chunk = chunk->next()) {
2518       chunk->oops_do(f);
2519     }
2520 
2521     // Traverse the execution stack
2522     for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2523       fst.current()->oops_do(f, cf, fst.register_map());
2524     }
2525   }
2526 
2527   // callee_target is never live across a gc point so NULL it here should
2528   // it still contain a methdOop.
2529 
2530   set_callee_target(NULL);
2531 
2532   assert(vframe_array_head() == NULL, "deopt in progress at a safepoint!");
2533   // If we have deferred set_locals there might be oops waiting to be
2534   // written
2535   GrowableArray<jvmtiDeferredLocalVariableSet*>* list = deferred_locals();
2536   if (list != NULL) {
2537     for (int i = 0; i < list->length(); i++) {
2538       list->at(i)->oops_do(f);
2539     }
2540   }
2541 
2542   // Traverse instance variables at the end since the GC may be moving things
2543   // around using this function
2544   f->do_oop((oop*) &_threadObj);
2545   f->do_oop((oop*) &_vm_result);
2546   f->do_oop((oop*) &_vm_result_2);
2547   f->do_oop((oop*) &_exception_oop);
2548   f->do_oop((oop*) &_pending_async_exception);
2549 
2550   if (jvmti_thread_state() != NULL) {
2551     jvmti_thread_state()->oops_do(f);
2552   }
2553 }
2554 
2555 void JavaThread::nmethods_do(CodeBlobClosure* cf) {
2556   Thread::nmethods_do(cf);  // (super method is a no-op)
2557 
2558   assert( (!has_last_Java_frame() && java_call_counter() == 0) ||
2559           (has_last_Java_frame() && java_call_counter() > 0), "wrong java_sp info!");
2560 
2561   if (has_last_Java_frame()) {
2562     // Traverse the execution stack
2563     for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2564       fst.current()->nmethods_do(cf);
2565     }
2566   }
2567 }
2568 
2569 // Printing
2570 const char* _get_thread_state_name(JavaThreadState _thread_state) {
2571   switch (_thread_state) {
2572   case _thread_uninitialized:     return "_thread_uninitialized";
2573   case _thread_new:               return "_thread_new";
2574   case _thread_new_trans:         return "_thread_new_trans";
2575   case _thread_in_native:         return "_thread_in_native";
2576   case _thread_in_native_trans:   return "_thread_in_native_trans";
2577   case _thread_in_vm:             return "_thread_in_vm";
2578   case _thread_in_vm_trans:       return "_thread_in_vm_trans";
2579   case _thread_in_Java:           return "_thread_in_Java";
2580   case _thread_in_Java_trans:     return "_thread_in_Java_trans";
2581   case _thread_blocked:           return "_thread_blocked";
2582   case _thread_blocked_trans:     return "_thread_blocked_trans";
2583   default:                        return "unknown thread state";
2584   }
2585 }
2586 
2587 #ifndef PRODUCT
2588 void JavaThread::print_thread_state_on(outputStream *st) const {
2589   st->print_cr("   JavaThread state: %s", _get_thread_state_name(_thread_state));
2590 };
2591 void JavaThread::print_thread_state() const {
2592   print_thread_state_on(tty);
2593 };
2594 #endif // PRODUCT
2595 
2596 // Called by Threads::print() for VM_PrintThreads operation
2597 void JavaThread::print_on(outputStream *st) const {
2598   st->print("\"%s\" ", get_thread_name());
2599   oop thread_oop = threadObj();
2600   if (thread_oop != NULL && java_lang_Thread::is_daemon(thread_oop))  st->print("daemon ");
2601   Thread::print_on(st);
2602   // print guess for valid stack memory region (assume 4K pages); helps lock debugging
2603   st->print_cr("[" INTPTR_FORMAT "]", (intptr_t)last_Java_sp() & ~right_n_bits(12));
2604   if (thread_oop != NULL && JDK_Version::is_gte_jdk15x_version()) {
2605     st->print_cr("   java.lang.Thread.State: %s", java_lang_Thread::thread_status_name(thread_oop));
2606   }
2607 #ifndef PRODUCT
2608   print_thread_state_on(st);
2609   _safepoint_state->print_on(st);
2610 #endif // PRODUCT
2611 }
2612 
2613 // Called by fatal error handler. The difference between this and
2614 // JavaThread::print() is that we can't grab lock or allocate memory.
2615 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
2616   st->print("JavaThread \"%s\"",  get_thread_name_string(buf, buflen));
2617   oop thread_obj = threadObj();
2618   if (thread_obj != NULL) {
2619      if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
2620   }
2621   st->print(" [");
2622   st->print("%s", _get_thread_state_name(_thread_state));
2623   if (osthread()) {
2624     st->print(", id=%d", osthread()->thread_id());
2625   }
2626   st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
2627             _stack_base - _stack_size, _stack_base);
2628   st->print("]");
2629   return;
2630 }
2631 
2632 // Verification
2633 
2634 static void frame_verify(frame* f, const RegisterMap *map) { f->verify(map); }
2635 
2636 void JavaThread::verify() {
2637   // Verify oops in the thread.
2638   oops_do(&VerifyOopClosure::verify_oop, NULL);
2639 
2640   // Verify the stack frames.
2641   frames_do(frame_verify);
2642 }
2643 
2644 // CR 6300358 (sub-CR 2137150)
2645 // Most callers of this method assume that it can't return NULL but a
2646 // thread may not have a name whilst it is in the process of attaching to
2647 // the VM - see CR 6412693, and there are places where a JavaThread can be
2648 // seen prior to having it's threadObj set (eg JNI attaching threads and
2649 // if vm exit occurs during initialization). These cases can all be accounted
2650 // for such that this method never returns NULL.
2651 const char* JavaThread::get_thread_name() const {
2652 #ifdef ASSERT
2653   // early safepoints can hit while current thread does not yet have TLS
2654   if (!SafepointSynchronize::is_at_safepoint()) {
2655     Thread *cur = Thread::current();
2656     if (!(cur->is_Java_thread() && cur == this)) {
2657       // Current JavaThreads are allowed to get their own name without
2658       // the Threads_lock.
2659       assert_locked_or_safepoint(Threads_lock);
2660     }
2661   }
2662 #endif // ASSERT
2663     return get_thread_name_string();
2664 }
2665 
2666 // Returns a non-NULL representation of this thread's name, or a suitable
2667 // descriptive string if there is no set name
2668 const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
2669   const char* name_str;
2670   oop thread_obj = threadObj();
2671   if (thread_obj != NULL) {
2672     typeArrayOop name = java_lang_Thread::name(thread_obj);
2673     if (name != NULL) {
2674       if (buf == NULL) {
2675         name_str = UNICODE::as_utf8((jchar*) name->base(T_CHAR), name->length());
2676       }
2677       else {
2678         name_str = UNICODE::as_utf8((jchar*) name->base(T_CHAR), name->length(), buf, buflen);
2679       }
2680     }
2681     else if (is_attaching()) { // workaround for 6412693 - see 6404306
2682       name_str = "<no-name - thread is attaching>";
2683     }
2684     else {
2685       name_str = Thread::name();
2686     }
2687   }
2688   else {
2689     name_str = Thread::name();
2690   }
2691   assert(name_str != NULL, "unexpected NULL thread name");
2692   return name_str;
2693 }
2694 
2695 
2696 const char* JavaThread::get_threadgroup_name() const {
2697   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
2698   oop thread_obj = threadObj();
2699   if (thread_obj != NULL) {
2700     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
2701     if (thread_group != NULL) {
2702       typeArrayOop name = java_lang_ThreadGroup::name(thread_group);
2703       // ThreadGroup.name can be null
2704       if (name != NULL) {
2705         const char* str = UNICODE::as_utf8((jchar*) name->base(T_CHAR), name->length());
2706         return str;
2707       }
2708     }
2709   }
2710   return NULL;
2711 }
2712 
2713 const char* JavaThread::get_parent_name() const {
2714   debug_only(if (JavaThread::current() != this) assert_locked_or_safepoint(Threads_lock);)
2715   oop thread_obj = threadObj();
2716   if (thread_obj != NULL) {
2717     oop thread_group = java_lang_Thread::threadGroup(thread_obj);
2718     if (thread_group != NULL) {
2719       oop parent = java_lang_ThreadGroup::parent(thread_group);
2720       if (parent != NULL) {
2721         typeArrayOop name = java_lang_ThreadGroup::name(parent);
2722         // ThreadGroup.name can be null
2723         if (name != NULL) {
2724           const char* str = UNICODE::as_utf8((jchar*) name->base(T_CHAR), name->length());
2725           return str;
2726         }
2727       }
2728     }
2729   }
2730   return NULL;
2731 }
2732 
2733 ThreadPriority JavaThread::java_priority() const {
2734   oop thr_oop = threadObj();
2735   if (thr_oop == NULL) return NormPriority; // Bootstrapping
2736   ThreadPriority priority = java_lang_Thread::priority(thr_oop);
2737   assert(MinPriority <= priority && priority <= MaxPriority, "sanity check");
2738   return priority;
2739 }
2740 
2741 void JavaThread::prepare(jobject jni_thread, ThreadPriority prio) {
2742 
2743   assert(Threads_lock->owner() == Thread::current(), "must have threads lock");
2744   // Link Java Thread object <-> C++ Thread
2745 
2746   // Get the C++ thread object (an oop) from the JNI handle (a jthread)
2747   // and put it into a new Handle.  The Handle "thread_oop" can then
2748   // be used to pass the C++ thread object to other methods.
2749 
2750   // Set the Java level thread object (jthread) field of the
2751   // new thread (a JavaThread *) to C++ thread object using the
2752   // "thread_oop" handle.
2753 
2754   // Set the thread field (a JavaThread *) of the
2755   // oop representing the java_lang_Thread to the new thread (a JavaThread *).
2756 
2757   Handle thread_oop(Thread::current(),
2758                     JNIHandles::resolve_non_null(jni_thread));
2759   assert(instanceKlass::cast(thread_oop->klass())->is_linked(),
2760     "must be initialized");
2761   set_threadObj(thread_oop());
2762   java_lang_Thread::set_thread(thread_oop(), this);
2763 
2764   if (prio == NoPriority) {
2765     prio = java_lang_Thread::priority(thread_oop());
2766     assert(prio != NoPriority, "A valid priority should be present");
2767   }
2768 
2769   // Push the Java priority down to the native thread; needs Threads_lock
2770   Thread::set_priority(this, prio);
2771 
2772   // Add the new thread to the Threads list and set it in motion.
2773   // We must have threads lock in order to call Threads::add.
2774   // It is crucial that we do not block before the thread is
2775   // added to the Threads list for if a GC happens, then the java_thread oop
2776   // will not be visited by GC.
2777   Threads::add(this);
2778 }
2779 
2780 oop JavaThread::current_park_blocker() {
2781   // Support for JSR-166 locks
2782   oop thread_oop = threadObj();
2783   if (thread_oop != NULL &&
2784       JDK_Version::current().supports_thread_park_blocker()) {
2785     return java_lang_Thread::park_blocker(thread_oop);
2786   }
2787   return NULL;
2788 }
2789 
2790 
2791 void JavaThread::print_stack_on(outputStream* st) {
2792   if (!has_last_Java_frame()) return;
2793   ResourceMark rm;
2794   HandleMark   hm;
2795 
2796   RegisterMap reg_map(this);
2797   vframe* start_vf = last_java_vframe(&reg_map);
2798   int count = 0;
2799   for (vframe* f = start_vf; f; f = f->sender() ) {
2800     if (f->is_java_frame()) {
2801       javaVFrame* jvf = javaVFrame::cast(f);
2802       java_lang_Throwable::print_stack_element(st, jvf->method(), jvf->bci());
2803 
2804       // Print out lock information
2805       if (JavaMonitorsInStackTrace) {
2806         jvf->print_lock_info_on(st, count);
2807       }
2808     } else {
2809       // Ignore non-Java frames
2810     }
2811 
2812     // Bail-out case for too deep stacks
2813     count++;
2814     if (MaxJavaStackTraceDepth == count) return;
2815   }
2816 }
2817 
2818 
2819 // JVMTI PopFrame support
2820 void JavaThread::popframe_preserve_args(ByteSize size_in_bytes, void* start) {
2821   assert(_popframe_preserved_args == NULL, "should not wipe out old PopFrame preserved arguments");
2822   if (in_bytes(size_in_bytes) != 0) {
2823     _popframe_preserved_args = NEW_C_HEAP_ARRAY(char, in_bytes(size_in_bytes));
2824     _popframe_preserved_args_size = in_bytes(size_in_bytes);
2825     Copy::conjoint_jbytes(start, _popframe_preserved_args, _popframe_preserved_args_size);
2826   }
2827 }
2828 
2829 void* JavaThread::popframe_preserved_args() {
2830   return _popframe_preserved_args;
2831 }
2832 
2833 ByteSize JavaThread::popframe_preserved_args_size() {
2834   return in_ByteSize(_popframe_preserved_args_size);
2835 }
2836 
2837 WordSize JavaThread::popframe_preserved_args_size_in_words() {
2838   int sz = in_bytes(popframe_preserved_args_size());
2839   assert(sz % wordSize == 0, "argument size must be multiple of wordSize");
2840   return in_WordSize(sz / wordSize);
2841 }
2842 
2843 void JavaThread::popframe_free_preserved_args() {
2844   assert(_popframe_preserved_args != NULL, "should not free PopFrame preserved arguments twice");
2845   FREE_C_HEAP_ARRAY(char, (char*) _popframe_preserved_args);
2846   _popframe_preserved_args = NULL;
2847   _popframe_preserved_args_size = 0;
2848 }
2849 
2850 #ifndef PRODUCT
2851 
2852 void JavaThread::trace_frames() {
2853   tty->print_cr("[Describe stack]");
2854   int frame_no = 1;
2855   for(StackFrameStream fst(this); !fst.is_done(); fst.next()) {
2856     tty->print("  %d. ", frame_no++);
2857     fst.current()->print_value_on(tty,this);
2858     tty->cr();
2859   }
2860 }
2861 
2862 
2863 void JavaThread::trace_stack_from(vframe* start_vf) {
2864   ResourceMark rm;
2865   int vframe_no = 1;
2866   for (vframe* f = start_vf; f; f = f->sender() ) {
2867     if (f->is_java_frame()) {
2868       javaVFrame::cast(f)->print_activation(vframe_no++);
2869     } else {
2870       f->print();
2871     }
2872     if (vframe_no > StackPrintLimit) {
2873       tty->print_cr("...<more frames>...");
2874       return;
2875     }
2876   }
2877 }
2878 
2879 
2880 void JavaThread::trace_stack() {
2881   if (!has_last_Java_frame()) return;
2882   ResourceMark rm;
2883   HandleMark   hm;
2884   RegisterMap reg_map(this);
2885   trace_stack_from(last_java_vframe(&reg_map));
2886 }
2887 
2888 
2889 #endif // PRODUCT
2890 
2891 
2892 javaVFrame* JavaThread::last_java_vframe(RegisterMap *reg_map) {
2893   assert(reg_map != NULL, "a map must be given");
2894   frame f = last_frame();
2895   for (vframe* vf = vframe::new_vframe(&f, reg_map, this); vf; vf = vf->sender() ) {
2896     if (vf->is_java_frame()) return javaVFrame::cast(vf);
2897   }
2898   return NULL;
2899 }
2900 
2901 
2902 klassOop JavaThread::security_get_caller_class(int depth) {
2903   vframeStream vfst(this);
2904   vfst.security_get_caller_frame(depth);
2905   if (!vfst.at_end()) {
2906     return vfst.method()->method_holder();
2907   }
2908   return NULL;
2909 }
2910 
2911 static void compiler_thread_entry(JavaThread* thread, TRAPS) {
2912   assert(thread->is_Compiler_thread(), "must be compiler thread");
2913   CompileBroker::compiler_thread_loop();
2914 }
2915 
2916 // Create a CompilerThread
2917 CompilerThread::CompilerThread(CompileQueue* queue, CompilerCounters* counters)
2918 : JavaThread(&compiler_thread_entry) {
2919   _env   = NULL;
2920   _log   = NULL;
2921   _task  = NULL;
2922   _queue = queue;
2923   _counters = counters;
2924   _buffer_blob = NULL;
2925 
2926 #ifndef PRODUCT
2927   _ideal_graph_printer = NULL;
2928 #endif
2929 }
2930 
2931 
2932 // ======= Threads ========
2933 
2934 // The Threads class links together all active threads, and provides
2935 // operations over all threads.  It is protected by its own Mutex
2936 // lock, which is also used in other contexts to protect thread
2937 // operations from having the thread being operated on from exiting
2938 // and going away unexpectedly (e.g., safepoint synchronization)
2939 
2940 JavaThread* Threads::_thread_list = NULL;
2941 int         Threads::_number_of_threads = 0;
2942 int         Threads::_number_of_non_daemon_threads = 0;
2943 int         Threads::_return_code = 0;
2944 size_t      JavaThread::_stack_size_at_create = 0;
2945 
2946 // All JavaThreads
2947 #define ALL_JAVA_THREADS(X) for (JavaThread* X = _thread_list; X; X = X->next())
2948 
2949 void os_stream();
2950 
2951 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system)
2952 void Threads::threads_do(ThreadClosure* tc) {
2953   assert_locked_or_safepoint(Threads_lock);
2954   // ALL_JAVA_THREADS iterates through all JavaThreads
2955   ALL_JAVA_THREADS(p) {
2956     tc->do_thread(p);
2957   }
2958   // Someday we could have a table or list of all non-JavaThreads.
2959   // For now, just manually iterate through them.
2960   tc->do_thread(VMThread::vm_thread());
2961   Universe::heap()->gc_threads_do(tc);
2962   WatcherThread *wt = WatcherThread::watcher_thread();
2963   // Strictly speaking, the following NULL check isn't sufficient to make sure
2964   // the data for WatcherThread is still valid upon being examined. However,
2965   // considering that WatchThread terminates when the VM is on the way to
2966   // exit at safepoint, the chance of the above is extremely small. The right
2967   // way to prevent termination of WatcherThread would be to acquire
2968   // Terminator_lock, but we can't do that without violating the lock rank
2969   // checking in some cases.
2970   if (wt != NULL)
2971     tc->do_thread(wt);
2972 
2973   // If CompilerThreads ever become non-JavaThreads, add them here
2974 }
2975 
2976 jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
2977 
2978   extern void JDK_Version_init();
2979 
2980   // Check version
2981   if (!is_supported_jni_version(args->version)) return JNI_EVERSION;
2982 
2983   // Initialize the output stream module
2984   ostream_init();
2985 
2986   // Process java launcher properties.
2987   Arguments::process_sun_java_launcher_properties(args);
2988 
2989   // Initialize the os module before using TLS
2990   os::init();
2991 
2992   // Initialize system properties.
2993   Arguments::init_system_properties();
2994 
2995   // So that JDK version can be used as a discrimintor when parsing arguments
2996   JDK_Version_init();
2997 
2998   // Update/Initialize System properties after JDK version number is known
2999   Arguments::init_version_specific_system_properties();
3000 
3001   // Parse arguments
3002   jint parse_result = Arguments::parse(args);
3003   if (parse_result != JNI_OK) return parse_result;
3004 
3005   if (PauseAtStartup) {
3006     os::pause();
3007   }
3008 
3009   HS_DTRACE_PROBE(hotspot, vm__init__begin);
3010 
3011   // Record VM creation timing statistics
3012   TraceVmCreationTime create_vm_timer;
3013   create_vm_timer.start();
3014 
3015   // Timing (must come after argument parsing)
3016   TraceTime timer("Create VM", TraceStartupTime);
3017 
3018   // Initialize the os module after parsing the args
3019   jint os_init_2_result = os::init_2();
3020   if (os_init_2_result != JNI_OK) return os_init_2_result;
3021 
3022   // Initialize output stream logging
3023   ostream_init_log();
3024 
3025   // Convert -Xrun to -agentlib: if there is no JVM_OnLoad
3026   // Must be before create_vm_init_agents()
3027   if (Arguments::init_libraries_at_startup()) {
3028     convert_vm_init_libraries_to_agents();
3029   }
3030 
3031   // Launch -agentlib/-agentpath and converted -Xrun agents
3032   if (Arguments::init_agents_at_startup()) {
3033     create_vm_init_agents();
3034   }
3035 
3036   // Initialize Threads state
3037   _thread_list = NULL;
3038   _number_of_threads = 0;
3039   _number_of_non_daemon_threads = 0;
3040 
3041   // Initialize TLS
3042   ThreadLocalStorage::init();
3043 
3044   // Initialize global data structures and create system classes in heap
3045   vm_init_globals();
3046 
3047   // Attach the main thread to this os thread
3048   JavaThread* main_thread = new JavaThread();
3049   main_thread->set_thread_state(_thread_in_vm);
3050   // must do this before set_active_handles and initialize_thread_local_storage
3051   // Note: on solaris initialize_thread_local_storage() will (indirectly)
3052   // change the stack size recorded here to one based on the java thread
3053   // stacksize. This adjusted size is what is used to figure the placement
3054   // of the guard pages.
3055   main_thread->record_stack_base_and_size();
3056   main_thread->initialize_thread_local_storage();
3057 
3058   main_thread->set_active_handles(JNIHandleBlock::allocate_block());
3059 
3060   if (!main_thread->set_as_starting_thread()) {
3061     vm_shutdown_during_initialization(
3062       "Failed necessary internal allocation. Out of swap space");
3063     delete main_thread;
3064     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3065     return JNI_ENOMEM;
3066   }
3067 
3068   // Enable guard page *after* os::create_main_thread(), otherwise it would
3069   // crash Linux VM, see notes in os_linux.cpp.
3070   main_thread->create_stack_guard_pages();
3071 
3072   // Initialize Java-Level synchronization subsystem
3073   ObjectMonitor::Initialize() ;
3074 
3075   // Initialize global modules
3076   jint status = init_globals();
3077   if (status != JNI_OK) {
3078     delete main_thread;
3079     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
3080     return status;
3081   }
3082 
3083   // Should be done after the heap is fully created
3084   main_thread->cache_global_variables();
3085 
3086   HandleMark hm;
3087 
3088   { MutexLocker mu(Threads_lock);
3089     Threads::add(main_thread);
3090   }
3091 
3092   // Any JVMTI raw monitors entered in onload will transition into
3093   // real raw monitor. VM is setup enough here for raw monitor enter.
3094   JvmtiExport::transition_pending_onload_raw_monitors();
3095 
3096   if (VerifyBeforeGC &&
3097       Universe::heap()->total_collections() >= VerifyGCStartAt) {
3098     Universe::heap()->prepare_for_verify();
3099     Universe::verify();   // make sure we're starting with a clean slate
3100   }
3101 
3102   // Create the VMThread
3103   { TraceTime timer("Start VMThread", TraceStartupTime);
3104     VMThread::create();
3105     Thread* vmthread = VMThread::vm_thread();
3106 
3107     if (!os::create_thread(vmthread, os::vm_thread))
3108       vm_exit_during_initialization("Cannot create VM thread. Out of system resources.");
3109 
3110     // Wait for the VM thread to become ready, and VMThread::run to initialize
3111     // Monitors can have spurious returns, must always check another state flag
3112     {
3113       MutexLocker ml(Notify_lock);
3114       os::start_thread(vmthread);
3115       while (vmthread->active_handles() == NULL) {
3116         Notify_lock->wait();
3117       }
3118     }
3119   }
3120 
3121   assert (Universe::is_fully_initialized(), "not initialized");
3122   EXCEPTION_MARK;
3123 
3124   // At this point, the Universe is initialized, but we have not executed
3125   // any byte code.  Now is a good time (the only time) to dump out the
3126   // internal state of the JVM for sharing.
3127 
3128   if (DumpSharedSpaces) {
3129     Universe::heap()->preload_and_dump(CHECK_0);
3130     ShouldNotReachHere();
3131   }
3132 
3133   // Always call even when there are not JVMTI environments yet, since environments
3134   // may be attached late and JVMTI must track phases of VM execution
3135   JvmtiExport::enter_start_phase();
3136 
3137   // Notify JVMTI agents that VM has started (JNI is up) - nop if no agents.
3138   JvmtiExport::post_vm_start();
3139 
3140   {
3141     TraceTime timer("Initialize java.lang classes", TraceStartupTime);
3142 
3143     if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
3144       create_vm_init_libraries();
3145     }
3146 
3147     if (InitializeJavaLangString) {
3148       initialize_class(vmSymbols::java_lang_String(), CHECK_0);
3149     } else {
3150       warning("java.lang.String not initialized");
3151     }
3152 
3153     if (AggressiveOpts) {
3154       {
3155         // Forcibly initialize java/util/HashMap and mutate the private
3156         // static final "frontCacheEnabled" field before we start creating instances
3157 #ifdef ASSERT
3158         klassOop tmp_k = SystemDictionary::find(vmSymbols::java_util_HashMap(), Handle(), Handle(), CHECK_0);
3159         assert(tmp_k == NULL, "java/util/HashMap should not be loaded yet");
3160 #endif
3161         klassOop k_o = SystemDictionary::resolve_or_null(vmSymbols::java_util_HashMap(), Handle(), Handle(), CHECK_0);
3162         KlassHandle k = KlassHandle(THREAD, k_o);
3163         guarantee(k.not_null(), "Must find java/util/HashMap");
3164         instanceKlassHandle ik = instanceKlassHandle(THREAD, k());
3165         ik->initialize(CHECK_0);
3166         fieldDescriptor fd;
3167         // Possible we might not find this field; if so, don't break
3168         if (ik->find_local_field(vmSymbols::frontCacheEnabled_name(), vmSymbols::bool_signature(), &fd)) {
3169           k()->bool_field_put(fd.offset(), true);
3170         }
3171       }
3172 
3173       if (UseStringCache) {
3174         // Forcibly initialize java/lang/StringValue and mutate the private
3175         // static final "stringCacheEnabled" field before we start creating instances
3176         klassOop k_o = SystemDictionary::resolve_or_null(vmSymbols::java_lang_StringValue(), Handle(), Handle(), CHECK_0);
3177         // Possible that StringValue isn't present: if so, silently don't break
3178         if (k_o != NULL) {
3179           KlassHandle k = KlassHandle(THREAD, k_o);
3180           instanceKlassHandle ik = instanceKlassHandle(THREAD, k());
3181           ik->initialize(CHECK_0);
3182           fieldDescriptor fd;
3183           // Possible we might not find this field: if so, silently don't break
3184           if (ik->find_local_field(vmSymbols::stringCacheEnabled_name(), vmSymbols::bool_signature(), &fd)) {
3185             k()->bool_field_put(fd.offset(), true);
3186           }
3187         }
3188       }
3189     }
3190 
3191     // Initialize java_lang.System (needed before creating the thread)
3192     if (InitializeJavaLangSystem) {
3193       initialize_class(vmSymbols::java_lang_System(), CHECK_0);
3194       initialize_class(vmSymbols::java_lang_ThreadGroup(), CHECK_0);
3195       Handle thread_group = create_initial_thread_group(CHECK_0);
3196       Universe::set_main_thread_group(thread_group());
3197       initialize_class(vmSymbols::java_lang_Thread(), CHECK_0);
3198       oop thread_object = create_initial_thread(thread_group, main_thread, CHECK_0);
3199       main_thread->set_threadObj(thread_object);
3200       // Set thread status to running since main thread has
3201       // been started and running.
3202       java_lang_Thread::set_thread_status(thread_object,
3203                                           java_lang_Thread::RUNNABLE);
3204 
3205       // The VM preresolve methods to these classes. Make sure that get initialized
3206       initialize_class(vmSymbols::java_lang_reflect_Method(), CHECK_0);
3207       initialize_class(vmSymbols::java_lang_ref_Finalizer(),  CHECK_0);
3208       // The VM creates & returns objects of this class. Make sure it's initialized.
3209       initialize_class(vmSymbols::java_lang_Class(), CHECK_0);
3210       call_initializeSystemClass(CHECK_0);
3211     } else {
3212       warning("java.lang.System not initialized");
3213     }
3214 
3215     // an instance of OutOfMemory exception has been allocated earlier
3216     if (InitializeJavaLangExceptionsErrors) {
3217       initialize_class(vmSymbols::java_lang_OutOfMemoryError(), CHECK_0);
3218       initialize_class(vmSymbols::java_lang_NullPointerException(), CHECK_0);
3219       initialize_class(vmSymbols::java_lang_ClassCastException(), CHECK_0);
3220       initialize_class(vmSymbols::java_lang_ArrayStoreException(), CHECK_0);
3221       initialize_class(vmSymbols::java_lang_ArithmeticException(), CHECK_0);
3222       initialize_class(vmSymbols::java_lang_StackOverflowError(), CHECK_0);
3223       initialize_class(vmSymbols::java_lang_IllegalMonitorStateException(), CHECK_0);
3224     } else {
3225       warning("java.lang.OutOfMemoryError has not been initialized");
3226       warning("java.lang.NullPointerException has not been initialized");
3227       warning("java.lang.ClassCastException has not been initialized");
3228       warning("java.lang.ArrayStoreException has not been initialized");
3229       warning("java.lang.ArithmeticException has not been initialized");
3230       warning("java.lang.StackOverflowError has not been initialized");
3231     }
3232     }
3233 
3234   // See        : bugid 4211085.
3235   // Background : the static initializer of java.lang.Compiler tries to read
3236   //              property"java.compiler" and read & write property "java.vm.info".
3237   //              When a security manager is installed through the command line
3238   //              option "-Djava.security.manager", the above properties are not
3239   //              readable and the static initializer for java.lang.Compiler fails
3240   //              resulting in a NoClassDefFoundError.  This can happen in any
3241   //              user code which calls methods in java.lang.Compiler.
3242   // Hack :       the hack is to pre-load and initialize this class, so that only
3243   //              system domains are on the stack when the properties are read.
3244   //              Currently even the AWT code has calls to methods in java.lang.Compiler.
3245   //              On the classic VM, java.lang.Compiler is loaded very early to load the JIT.
3246   // Future Fix : the best fix is to grant everyone permissions to read "java.compiler" and
3247   //              read and write"java.vm.info" in the default policy file. See bugid 4211383
3248   //              Once that is done, we should remove this hack.
3249   initialize_class(vmSymbols::java_lang_Compiler(), CHECK_0);
3250 
3251   // More hackery - the static initializer of java.lang.Compiler adds the string "nojit" to
3252   // the java.vm.info property if no jit gets loaded through java.lang.Compiler (the hotspot
3253   // compiler does not get loaded through java.lang.Compiler).  "java -version" with the
3254   // hotspot vm says "nojit" all the time which is confusing.  So, we reset it here.
3255   // This should also be taken out as soon as 4211383 gets fixed.
3256   reset_vm_info_property(CHECK_0);
3257 
3258   quicken_jni_functions();
3259 
3260   // Set flag that basic initialization has completed. Used by exceptions and various
3261   // debug stuff, that does not work until all basic classes have been initialized.
3262   set_init_completed();
3263 
3264   HS_DTRACE_PROBE(hotspot, vm__init__end);
3265 
3266   // record VM initialization completion time
3267   Management::record_vm_init_completed();
3268 
3269   // Compute system loader. Note that this has to occur after set_init_completed, since
3270   // valid exceptions may be thrown in the process.
3271   // Note that we do not use CHECK_0 here since we are inside an EXCEPTION_MARK and
3272   // set_init_completed has just been called, causing exceptions not to be shortcut
3273   // anymore. We call vm_exit_during_initialization directly instead.
3274   SystemDictionary::compute_java_system_loader(THREAD);
3275   if (HAS_PENDING_EXCEPTION) {
3276     vm_exit_during_initialization(Handle(THREAD, PENDING_EXCEPTION));
3277   }
3278 
3279 #ifndef SERIALGC
3280   // Support for ConcurrentMarkSweep. This should be cleaned up
3281   // and better encapsulated. The ugly nested if test would go away
3282   // once things are properly refactored. XXX YSR
3283   if (UseConcMarkSweepGC || UseG1GC) {
3284     if (UseConcMarkSweepGC) {
3285       ConcurrentMarkSweepThread::makeSurrogateLockerThread(THREAD);
3286     } else {
3287       ConcurrentMarkThread::makeSurrogateLockerThread(THREAD);
3288     }
3289     if (HAS_PENDING_EXCEPTION) {
3290       vm_exit_during_initialization(Handle(THREAD, PENDING_EXCEPTION));
3291     }
3292   }
3293 #endif // SERIALGC
3294 
3295   // Always call even when there are not JVMTI environments yet, since environments
3296   // may be attached late and JVMTI must track phases of VM execution
3297   JvmtiExport::enter_live_phase();
3298 
3299   // Signal Dispatcher needs to be started before VMInit event is posted
3300   os::signal_init();
3301 
3302   // Start Attach Listener if +StartAttachListener or it can't be started lazily
3303   if (!DisableAttachMechanism) {
3304     if (StartAttachListener || AttachListener::init_at_startup()) {
3305       AttachListener::init();
3306     }
3307   }
3308 
3309   // Launch -Xrun agents
3310   // Must be done in the JVMTI live phase so that for backward compatibility the JDWP
3311   // back-end can launch with -Xdebug -Xrunjdwp.
3312   if (!EagerXrunInit && Arguments::init_libraries_at_startup()) {
3313     create_vm_init_libraries();
3314   }
3315 
3316   // Notify JVMTI agents that VM initialization is complete - nop if no agents.
3317   JvmtiExport::post_vm_initialized();
3318 
3319   Chunk::start_chunk_pool_cleaner_task();
3320 
3321   // initialize compiler(s)
3322   CompileBroker::compilation_init();
3323 
3324   Management::initialize(THREAD);
3325   if (HAS_PENDING_EXCEPTION) {
3326     // management agent fails to start possibly due to
3327     // configuration problem and is responsible for printing
3328     // stack trace if appropriate. Simply exit VM.
3329     vm_exit(1);
3330   }
3331 
3332   if (Arguments::has_profile())       FlatProfiler::engage(main_thread, true);
3333   if (Arguments::has_alloc_profile()) AllocationProfiler::engage();
3334   if (MemProfiling)                   MemProfiler::engage();
3335   StatSampler::engage();
3336   if (CheckJNICalls)                  JniPeriodicChecker::engage();
3337 
3338   BiasedLocking::init();
3339 
3340   if (JDK_Version::current().post_vm_init_hook_enabled()) {
3341     call_postVMInitHook(THREAD);
3342     // The Java side of PostVMInitHook.run must deal with all
3343     // exceptions and provide means of diagnosis.
3344     if (HAS_PENDING_EXCEPTION) {
3345       CLEAR_PENDING_EXCEPTION;
3346     }
3347   }
3348 
3349   // Start up the WatcherThread if there are any periodic tasks
3350   // NOTE:  All PeriodicTasks should be registered by now. If they
3351   //   aren't, late joiners might appear to start slowly (we might
3352   //   take a while to process their first tick).
3353   if (PeriodicTask::num_tasks() > 0) {
3354     WatcherThread::start();
3355   }
3356 
3357   // Give os specific code one last chance to start
3358   os::init_3();
3359 
3360   create_vm_timer.end();
3361   return JNI_OK;
3362 }
3363 
3364 // type for the Agent_OnLoad and JVM_OnLoad entry points
3365 extern "C" {
3366   typedef jint (JNICALL *OnLoadEntry_t)(JavaVM *, char *, void *);
3367 }
3368 // Find a command line agent library and return its entry point for
3369 //         -agentlib:  -agentpath:   -Xrun
3370 // num_symbol_entries must be passed-in since only the caller knows the number of symbols in the array.
3371 static OnLoadEntry_t lookup_on_load(AgentLibrary* agent, const char *on_load_symbols[], size_t num_symbol_entries) {
3372   OnLoadEntry_t on_load_entry = NULL;
3373   void *library = agent->os_lib();  // check if we have looked it up before
3374 
3375   if (library == NULL) {
3376     char buffer[JVM_MAXPATHLEN];
3377     char ebuf[1024];
3378     const char *name = agent->name();
3379     const char *msg = "Could not find agent library ";
3380 
3381     if (agent->is_absolute_path()) {
3382       library = os::dll_load(name, ebuf, sizeof ebuf);
3383       if (library == NULL) {
3384         const char *sub_msg = " in absolute path, with error: ";
3385         size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3386         char *buf = NEW_C_HEAP_ARRAY(char, len);
3387         jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
3388         // If we can't find the agent, exit.
3389         vm_exit_during_initialization(buf, NULL);
3390         FREE_C_HEAP_ARRAY(char, buf);
3391       }
3392     } else {
3393       // Try to load the agent from the standard dll directory
3394       os::dll_build_name(buffer, sizeof(buffer), Arguments::get_dll_dir(), name);
3395       library = os::dll_load(buffer, ebuf, sizeof ebuf);
3396 #ifdef KERNEL
3397       // Download instrument dll
3398       if (library == NULL && strcmp(name, "instrument") == 0) {
3399         char *props = Arguments::get_kernel_properties();
3400         char *home  = Arguments::get_java_home();
3401         const char *fmt   = "%s/bin/java %s -Dkernel.background.download=false"
3402                       " sun.jkernel.DownloadManager -download client_jvm";
3403         size_t length = strlen(props) + strlen(home) + strlen(fmt) + 1;
3404         char *cmd = NEW_C_HEAP_ARRAY(char, length);
3405         jio_snprintf(cmd, length, fmt, home, props);
3406         int status = os::fork_and_exec(cmd);
3407         FreeHeap(props);
3408         if (status == -1) {
3409           warning(cmd);
3410           vm_exit_during_initialization("fork_and_exec failed: %s",
3411                                          strerror(errno));
3412         }
3413         FREE_C_HEAP_ARRAY(char, cmd);
3414         // when this comes back the instrument.dll should be where it belongs.
3415         library = os::dll_load(buffer, ebuf, sizeof ebuf);
3416       }
3417 #endif // KERNEL
3418       if (library == NULL) { // Try the local directory
3419         char ns[1] = {0};
3420         os::dll_build_name(buffer, sizeof(buffer), ns, name);
3421         library = os::dll_load(buffer, ebuf, sizeof ebuf);
3422         if (library == NULL) {
3423           const char *sub_msg = " on the library path, with error: ";
3424           size_t len = strlen(msg) + strlen(name) + strlen(sub_msg) + strlen(ebuf) + 1;
3425           char *buf = NEW_C_HEAP_ARRAY(char, len);
3426           jio_snprintf(buf, len, "%s%s%s%s", msg, name, sub_msg, ebuf);
3427           // If we can't find the agent, exit.
3428           vm_exit_during_initialization(buf, NULL);
3429           FREE_C_HEAP_ARRAY(char, buf);
3430         }
3431       }
3432     }
3433     agent->set_os_lib(library);
3434   }
3435 
3436   // Find the OnLoad function.
3437   for (size_t symbol_index = 0; symbol_index < num_symbol_entries; symbol_index++) {
3438     on_load_entry = CAST_TO_FN_PTR(OnLoadEntry_t, os::dll_lookup(library, on_load_symbols[symbol_index]));
3439     if (on_load_entry != NULL) break;
3440   }
3441   return on_load_entry;
3442 }
3443 
3444 // Find the JVM_OnLoad entry point
3445 static OnLoadEntry_t lookup_jvm_on_load(AgentLibrary* agent) {
3446   const char *on_load_symbols[] = JVM_ONLOAD_SYMBOLS;
3447   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
3448 }
3449 
3450 // Find the Agent_OnLoad entry point
3451 static OnLoadEntry_t lookup_agent_on_load(AgentLibrary* agent) {
3452   const char *on_load_symbols[] = AGENT_ONLOAD_SYMBOLS;
3453   return lookup_on_load(agent, on_load_symbols, sizeof(on_load_symbols) / sizeof(char*));
3454 }
3455 
3456 // For backwards compatibility with -Xrun
3457 // Convert libraries with no JVM_OnLoad, but which have Agent_OnLoad to be
3458 // treated like -agentpath:
3459 // Must be called before agent libraries are created
3460 void Threads::convert_vm_init_libraries_to_agents() {
3461   AgentLibrary* agent;
3462   AgentLibrary* next;
3463 
3464   for (agent = Arguments::libraries(); agent != NULL; agent = next) {
3465     next = agent->next();  // cache the next agent now as this agent may get moved off this list
3466     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
3467 
3468     // If there is an JVM_OnLoad function it will get called later,
3469     // otherwise see if there is an Agent_OnLoad
3470     if (on_load_entry == NULL) {
3471       on_load_entry = lookup_agent_on_load(agent);
3472       if (on_load_entry != NULL) {
3473         // switch it to the agent list -- so that Agent_OnLoad will be called,
3474         // JVM_OnLoad won't be attempted and Agent_OnUnload will
3475         Arguments::convert_library_to_agent(agent);
3476       } else {
3477         vm_exit_during_initialization("Could not find JVM_OnLoad or Agent_OnLoad function in the library", agent->name());
3478       }
3479     }
3480   }
3481 }
3482 
3483 // Create agents for -agentlib:  -agentpath:  and converted -Xrun
3484 // Invokes Agent_OnLoad
3485 // Called very early -- before JavaThreads exist
3486 void Threads::create_vm_init_agents() {
3487   extern struct JavaVM_ main_vm;
3488   AgentLibrary* agent;
3489 
3490   JvmtiExport::enter_onload_phase();
3491   for (agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
3492     OnLoadEntry_t  on_load_entry = lookup_agent_on_load(agent);
3493 
3494     if (on_load_entry != NULL) {
3495       // Invoke the Agent_OnLoad function
3496       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
3497       if (err != JNI_OK) {
3498         vm_exit_during_initialization("agent library failed to init", agent->name());
3499       }
3500     } else {
3501       vm_exit_during_initialization("Could not find Agent_OnLoad function in the agent library", agent->name());
3502     }
3503   }
3504   JvmtiExport::enter_primordial_phase();
3505 }
3506 
3507 extern "C" {
3508   typedef void (JNICALL *Agent_OnUnload_t)(JavaVM *);
3509 }
3510 
3511 void Threads::shutdown_vm_agents() {
3512   // Send any Agent_OnUnload notifications
3513   const char *on_unload_symbols[] = AGENT_ONUNLOAD_SYMBOLS;
3514   extern struct JavaVM_ main_vm;
3515   for (AgentLibrary* agent = Arguments::agents(); agent != NULL; agent = agent->next()) {
3516 
3517     // Find the Agent_OnUnload function.
3518     for (uint symbol_index = 0; symbol_index < ARRAY_SIZE(on_unload_symbols); symbol_index++) {
3519       Agent_OnUnload_t unload_entry = CAST_TO_FN_PTR(Agent_OnUnload_t,
3520                os::dll_lookup(agent->os_lib(), on_unload_symbols[symbol_index]));
3521 
3522       // Invoke the Agent_OnUnload function
3523       if (unload_entry != NULL) {
3524         JavaThread* thread = JavaThread::current();
3525         ThreadToNativeFromVM ttn(thread);
3526         HandleMark hm(thread);
3527         (*unload_entry)(&main_vm);
3528         break;
3529       }
3530     }
3531   }
3532 }
3533 
3534 // Called for after the VM is initialized for -Xrun libraries which have not been converted to agent libraries
3535 // Invokes JVM_OnLoad
3536 void Threads::create_vm_init_libraries() {
3537   extern struct JavaVM_ main_vm;
3538   AgentLibrary* agent;
3539 
3540   for (agent = Arguments::libraries(); agent != NULL; agent = agent->next()) {
3541     OnLoadEntry_t on_load_entry = lookup_jvm_on_load(agent);
3542 
3543     if (on_load_entry != NULL) {
3544       // Invoke the JVM_OnLoad function
3545       JavaThread* thread = JavaThread::current();
3546       ThreadToNativeFromVM ttn(thread);
3547       HandleMark hm(thread);
3548       jint err = (*on_load_entry)(&main_vm, agent->options(), NULL);
3549       if (err != JNI_OK) {
3550         vm_exit_during_initialization("-Xrun library failed to init", agent->name());
3551       }
3552     } else {
3553       vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
3554     }
3555   }
3556 }
3557 
3558 // Last thread running calls java.lang.Shutdown.shutdown()
3559 void JavaThread::invoke_shutdown_hooks() {
3560   HandleMark hm(this);
3561 
3562   // We could get here with a pending exception, if so clear it now.
3563   if (this->has_pending_exception()) {
3564     this->clear_pending_exception();
3565   }
3566 
3567   EXCEPTION_MARK;
3568   klassOop k =
3569     SystemDictionary::resolve_or_null(vmSymbols::java_lang_Shutdown(),
3570                                       THREAD);
3571   if (k != NULL) {
3572     // SystemDictionary::resolve_or_null will return null if there was
3573     // an exception.  If we cannot load the Shutdown class, just don't
3574     // call Shutdown.shutdown() at all.  This will mean the shutdown hooks
3575     // and finalizers (if runFinalizersOnExit is set) won't be run.
3576     // Note that if a shutdown hook was registered or runFinalizersOnExit
3577     // was called, the Shutdown class would have already been loaded
3578     // (Runtime.addShutdownHook and runFinalizersOnExit will load it).
3579     instanceKlassHandle shutdown_klass (THREAD, k);
3580     JavaValue result(T_VOID);
3581     JavaCalls::call_static(&result,
3582                            shutdown_klass,
3583                            vmSymbols::shutdown_method_name(),
3584                            vmSymbols::void_method_signature(),
3585                            THREAD);
3586   }
3587   CLEAR_PENDING_EXCEPTION;
3588 }
3589 
3590 // Threads::destroy_vm() is normally called from jni_DestroyJavaVM() when
3591 // the program falls off the end of main(). Another VM exit path is through
3592 // vm_exit() when the program calls System.exit() to return a value or when
3593 // there is a serious error in VM. The two shutdown paths are not exactly
3594 // the same, but they share Shutdown.shutdown() at Java level and before_exit()
3595 // and VM_Exit op at VM level.
3596 //
3597 // Shutdown sequence:
3598 //   + Wait until we are the last non-daemon thread to execute
3599 //     <-- every thing is still working at this moment -->
3600 //   + Call java.lang.Shutdown.shutdown(), which will invoke Java level
3601 //        shutdown hooks, run finalizers if finalization-on-exit
3602 //   + Call before_exit(), prepare for VM exit
3603 //      > run VM level shutdown hooks (they are registered through JVM_OnExit(),
3604 //        currently the only user of this mechanism is File.deleteOnExit())
3605 //      > stop flat profiler, StatSampler, watcher thread, CMS threads,
3606 //        post thread end and vm death events to JVMTI,
3607 //        stop signal thread
3608 //   + Call JavaThread::exit(), it will:
3609 //      > release JNI handle blocks, remove stack guard pages
3610 //      > remove this thread from Threads list
3611 //     <-- no more Java code from this thread after this point -->
3612 //   + Stop VM thread, it will bring the remaining VM to a safepoint and stop
3613 //     the compiler threads at safepoint
3614 //     <-- do not use anything that could get blocked by Safepoint -->
3615 //   + Disable tracing at JNI/JVM barriers
3616 //   + Set _vm_exited flag for threads that are still running native code
3617 //   + Delete this thread
3618 //   + Call exit_globals()
3619 //      > deletes tty
3620 //      > deletes PerfMemory resources
3621 //   + Return to caller
3622 
3623 bool Threads::destroy_vm() {
3624   JavaThread* thread = JavaThread::current();
3625 
3626   // Wait until we are the last non-daemon thread to execute
3627   { MutexLocker nu(Threads_lock);
3628     while (Threads::number_of_non_daemon_threads() > 1 )
3629       // This wait should make safepoint checks, wait without a timeout,
3630       // and wait as a suspend-equivalent condition.
3631       //
3632       // Note: If the FlatProfiler is running and this thread is waiting
3633       // for another non-daemon thread to finish, then the FlatProfiler
3634       // is waiting for the external suspend request on this thread to
3635       // complete. wait_for_ext_suspend_completion() will eventually
3636       // timeout, but that takes time. Making this wait a suspend-
3637       // equivalent condition solves that timeout problem.
3638       //
3639       Threads_lock->wait(!Mutex::_no_safepoint_check_flag, 0,
3640                          Mutex::_as_suspend_equivalent_flag);
3641   }
3642 
3643   // Hang forever on exit if we are reporting an error.
3644   if (ShowMessageBoxOnError && is_error_reported()) {
3645     os::infinite_sleep();
3646   }
3647   os::check_for_debugger_and_wait();
3648 
3649   if (JDK_Version::is_jdk12x_version()) {
3650     // We are the last thread running, so check if finalizers should be run.
3651     // For 1.3 or later this is done in thread->invoke_shutdown_hooks()
3652     HandleMark rm(thread);
3653     Universe::run_finalizers_on_exit();
3654   } else {
3655     // run Java level shutdown hooks
3656     thread->invoke_shutdown_hooks();
3657   }
3658 
3659   before_exit(thread);
3660 
3661   thread->exit(true);
3662 
3663   // Stop VM thread.
3664   {
3665     // 4945125 The vm thread comes to a safepoint during exit.
3666     // GC vm_operations can get caught at the safepoint, and the
3667     // heap is unparseable if they are caught. Grab the Heap_lock
3668     // to prevent this. The GC vm_operations will not be able to
3669     // queue until after the vm thread is dead.
3670     MutexLocker ml(Heap_lock);
3671 
3672     VMThread::wait_for_vm_thread_exit();
3673     assert(SafepointSynchronize::is_at_safepoint(), "VM thread should exit at Safepoint");
3674     VMThread::destroy();
3675   }
3676 
3677   // clean up ideal graph printers
3678 #if defined(COMPILER2) && !defined(PRODUCT)
3679   IdealGraphPrinter::clean_up();
3680 #endif
3681 
3682   // Now, all Java threads are gone except daemon threads. Daemon threads
3683   // running Java code or in VM are stopped by the Safepoint. However,
3684   // daemon threads executing native code are still running.  But they
3685   // will be stopped at native=>Java/VM barriers. Note that we can't
3686   // simply kill or suspend them, as it is inherently deadlock-prone.
3687 
3688 #ifndef PRODUCT
3689   // disable function tracing at JNI/JVM barriers
3690   TraceJNICalls = false;
3691   TraceJVMCalls = false;
3692   TraceRuntimeCalls = false;
3693 #endif
3694 
3695   VM_Exit::set_vm_exited();
3696 
3697   notify_vm_shutdown();
3698 
3699   delete thread;
3700 
3701   // exit_globals() will delete tty
3702   exit_globals();
3703 
3704   return true;
3705 }
3706 
3707 
3708 jboolean Threads::is_supported_jni_version_including_1_1(jint version) {
3709   if (version == JNI_VERSION_1_1) return JNI_TRUE;
3710   return is_supported_jni_version(version);
3711 }
3712 
3713 
3714 jboolean Threads::is_supported_jni_version(jint version) {
3715   if (version == JNI_VERSION_1_2) return JNI_TRUE;
3716   if (version == JNI_VERSION_1_4) return JNI_TRUE;
3717   if (version == JNI_VERSION_1_6) return JNI_TRUE;
3718   return JNI_FALSE;
3719 }
3720 
3721 
3722 void Threads::add(JavaThread* p, bool force_daemon) {
3723   // The threads lock must be owned at this point
3724   assert_locked_or_safepoint(Threads_lock);
3725 
3726   // See the comment for this method in thread.hpp for its purpose and
3727   // why it is called here.
3728   p->initialize_queues();
3729   p->set_next(_thread_list);
3730   _thread_list = p;
3731   _number_of_threads++;
3732   oop threadObj = p->threadObj();
3733   bool daemon = true;
3734   // Bootstrapping problem: threadObj can be null for initial
3735   // JavaThread (or for threads attached via JNI)
3736   if ((!force_daemon) && (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj))) {
3737     _number_of_non_daemon_threads++;
3738     daemon = false;
3739   }
3740 
3741   ThreadService::add_thread(p, daemon);
3742 
3743   // Possible GC point.
3744   Events::log("Thread added: " INTPTR_FORMAT, p);
3745 }
3746 
3747 void Threads::remove(JavaThread* p) {
3748   // Extra scope needed for Thread_lock, so we can check
3749   // that we do not remove thread without safepoint code notice
3750   { MutexLocker ml(Threads_lock);
3751 
3752     assert(includes(p), "p must be present");
3753 
3754     JavaThread* current = _thread_list;
3755     JavaThread* prev    = NULL;
3756 
3757     while (current != p) {
3758       prev    = current;
3759       current = current->next();
3760     }
3761 
3762     if (prev) {
3763       prev->set_next(current->next());
3764     } else {
3765       _thread_list = p->next();
3766     }
3767     _number_of_threads--;
3768     oop threadObj = p->threadObj();
3769     bool daemon = true;
3770     if (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj)) {
3771       _number_of_non_daemon_threads--;
3772       daemon = false;
3773 
3774       // Only one thread left, do a notify on the Threads_lock so a thread waiting
3775       // on destroy_vm will wake up.
3776       if (number_of_non_daemon_threads() == 1)
3777         Threads_lock->notify_all();
3778     }
3779     ThreadService::remove_thread(p, daemon);
3780 
3781     // Make sure that safepoint code disregard this thread. This is needed since
3782     // the thread might mess around with locks after this point. This can cause it
3783     // to do callbacks into the safepoint code. However, the safepoint code is not aware
3784     // of this thread since it is removed from the queue.
3785     p->set_terminated_value();
3786   } // unlock Threads_lock
3787 
3788   // Since Events::log uses a lock, we grab it outside the Threads_lock
3789   Events::log("Thread exited: " INTPTR_FORMAT, p);
3790 }
3791 
3792 // Threads_lock must be held when this is called (or must be called during a safepoint)
3793 bool Threads::includes(JavaThread* p) {
3794   assert(Threads_lock->is_locked(), "sanity check");
3795   ALL_JAVA_THREADS(q) {
3796     if (q == p ) {
3797       return true;
3798     }
3799   }
3800   return false;
3801 }
3802 
3803 // Operations on the Threads list for GC.  These are not explicitly locked,
3804 // but the garbage collector must provide a safe context for them to run.
3805 // In particular, these things should never be called when the Threads_lock
3806 // is held by some other thread. (Note: the Safepoint abstraction also
3807 // uses the Threads_lock to gurantee this property. It also makes sure that
3808 // all threads gets blocked when exiting or starting).
3809 
3810 void Threads::oops_do(OopClosure* f, CodeBlobClosure* cf) {
3811   ALL_JAVA_THREADS(p) {
3812     p->oops_do(f, cf);
3813   }
3814   VMThread::vm_thread()->oops_do(f, cf);
3815 }
3816 
3817 void Threads::possibly_parallel_oops_do(OopClosure* f, CodeBlobClosure* cf) {
3818   // Introduce a mechanism allowing parallel threads to claim threads as
3819   // root groups.  Overhead should be small enough to use all the time,
3820   // even in sequential code.
3821   SharedHeap* sh = SharedHeap::heap();
3822   bool is_par = (sh->n_par_threads() > 0);
3823   int cp = SharedHeap::heap()->strong_roots_parity();
3824   ALL_JAVA_THREADS(p) {
3825     if (p->claim_oops_do(is_par, cp)) {
3826       p->oops_do(f, cf);
3827     }
3828   }
3829   VMThread* vmt = VMThread::vm_thread();
3830   if (vmt->claim_oops_do(is_par, cp))
3831     vmt->oops_do(f, cf);
3832 }
3833 
3834 #ifndef SERIALGC
3835 // Used by ParallelScavenge
3836 void Threads::create_thread_roots_tasks(GCTaskQueue* q) {
3837   ALL_JAVA_THREADS(p) {
3838     q->enqueue(new ThreadRootsTask(p));
3839   }
3840   q->enqueue(new ThreadRootsTask(VMThread::vm_thread()));
3841 }
3842 
3843 // Used by Parallel Old
3844 void Threads::create_thread_roots_marking_tasks(GCTaskQueue* q) {
3845   ALL_JAVA_THREADS(p) {
3846     q->enqueue(new ThreadRootsMarkingTask(p));
3847   }
3848   q->enqueue(new ThreadRootsMarkingTask(VMThread::vm_thread()));
3849 }
3850 #endif // SERIALGC
3851 
3852 void Threads::nmethods_do(CodeBlobClosure* cf) {
3853   ALL_JAVA_THREADS(p) {
3854     p->nmethods_do(cf);
3855   }
3856   VMThread::vm_thread()->nmethods_do(cf);
3857 }
3858 
3859 void Threads::gc_epilogue() {
3860   ALL_JAVA_THREADS(p) {
3861     p->gc_epilogue();
3862   }
3863 }
3864 
3865 void Threads::gc_prologue() {
3866   ALL_JAVA_THREADS(p) {
3867     p->gc_prologue();
3868   }
3869 }
3870 
3871 void Threads::deoptimized_wrt_marked_nmethods() {
3872   ALL_JAVA_THREADS(p) {
3873     p->deoptimized_wrt_marked_nmethods();
3874   }
3875 }
3876 
3877 
3878 // Get count Java threads that are waiting to enter the specified monitor.
3879 GrowableArray<JavaThread*>* Threads::get_pending_threads(int count,
3880   address monitor, bool doLock) {
3881   assert(doLock || SafepointSynchronize::is_at_safepoint(),
3882     "must grab Threads_lock or be at safepoint");
3883   GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
3884 
3885   int i = 0;
3886   {
3887     MutexLockerEx ml(doLock ? Threads_lock : NULL);
3888     ALL_JAVA_THREADS(p) {
3889       if (p->is_Compiler_thread()) continue;
3890 
3891       address pending = (address)p->current_pending_monitor();
3892       if (pending == monitor) {             // found a match
3893         if (i < count) result->append(p);   // save the first count matches
3894         i++;
3895       }
3896     }
3897   }
3898   return result;
3899 }
3900 
3901 
3902 JavaThread *Threads::owning_thread_from_monitor_owner(address owner, bool doLock) {
3903   assert(doLock ||
3904          Threads_lock->owned_by_self() ||
3905          SafepointSynchronize::is_at_safepoint(),
3906          "must grab Threads_lock or be at safepoint");
3907 
3908   // NULL owner means not locked so we can skip the search
3909   if (owner == NULL) return NULL;
3910 
3911   {
3912     MutexLockerEx ml(doLock ? Threads_lock : NULL);
3913     ALL_JAVA_THREADS(p) {
3914       // first, see if owner is the address of a Java thread
3915       if (owner == (address)p) return p;
3916     }
3917   }
3918   assert(UseHeavyMonitors == false, "Did not find owning Java thread with UseHeavyMonitors enabled");
3919   if (UseHeavyMonitors) return NULL;
3920 
3921   //
3922   // If we didn't find a matching Java thread and we didn't force use of
3923   // heavyweight monitors, then the owner is the stack address of the
3924   // Lock Word in the owning Java thread's stack.
3925   //
3926   JavaThread* the_owner = NULL;
3927   {
3928     MutexLockerEx ml(doLock ? Threads_lock : NULL);
3929     ALL_JAVA_THREADS(q) {
3930       if (q->is_lock_owned(owner)) {
3931         the_owner = q;
3932         break;
3933       }
3934     }
3935   }
3936   assert(the_owner != NULL, "Did not find owning Java thread for lock word address");
3937   return the_owner;
3938 }
3939 
3940 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
3941 void Threads::print_on(outputStream* st, bool print_stacks, bool internal_format, bool print_concurrent_locks) {
3942   char buf[32];
3943   st->print_cr(os::local_time_string(buf, sizeof(buf)));
3944 
3945   st->print_cr("Full thread dump %s (%s %s):",
3946                 Abstract_VM_Version::vm_name(),
3947                 Abstract_VM_Version::vm_release(),
3948                 Abstract_VM_Version::vm_info_string()
3949                );
3950   st->cr();
3951 
3952 #ifndef SERIALGC
3953   // Dump concurrent locks
3954   ConcurrentLocksDump concurrent_locks;
3955   if (print_concurrent_locks) {
3956     concurrent_locks.dump_at_safepoint();
3957   }
3958 #endif // SERIALGC
3959 
3960   ALL_JAVA_THREADS(p) {
3961     ResourceMark rm;
3962     p->print_on(st);
3963     if (print_stacks) {
3964       if (internal_format) {
3965         p->trace_stack();
3966       } else {
3967         p->print_stack_on(st);
3968       }
3969     }
3970     st->cr();
3971 #ifndef SERIALGC
3972     if (print_concurrent_locks) {
3973       concurrent_locks.print_locks_on(p, st);
3974     }
3975 #endif // SERIALGC
3976   }
3977 
3978   VMThread::vm_thread()->print_on(st);
3979   st->cr();
3980   Universe::heap()->print_gc_threads_on(st);
3981   WatcherThread* wt = WatcherThread::watcher_thread();
3982   if (wt != NULL) wt->print_on(st);
3983   st->cr();
3984   CompileBroker::print_compiler_threads_on(st);
3985   st->flush();
3986 }
3987 
3988 // Threads::print_on_error() is called by fatal error handler. It's possible
3989 // that VM is not at safepoint and/or current thread is inside signal handler.
3990 // Don't print stack trace, as the stack may not be walkable. Don't allocate
3991 // memory (even in resource area), it might deadlock the error handler.
3992 void Threads::print_on_error(outputStream* st, Thread* current, char* buf, int buflen) {
3993   bool found_current = false;
3994   st->print_cr("Java Threads: ( => current thread )");
3995   ALL_JAVA_THREADS(thread) {
3996     bool is_current = (current == thread);
3997     found_current = found_current || is_current;
3998 
3999     st->print("%s", is_current ? "=>" : "  ");
4000 
4001     st->print(PTR_FORMAT, thread);
4002     st->print(" ");
4003     thread->print_on_error(st, buf, buflen);
4004     st->cr();
4005   }
4006   st->cr();
4007 
4008   st->print_cr("Other Threads:");
4009   if (VMThread::vm_thread()) {
4010     bool is_current = (current == VMThread::vm_thread());
4011     found_current = found_current || is_current;
4012     st->print("%s", current == VMThread::vm_thread() ? "=>" : "  ");
4013 
4014     st->print(PTR_FORMAT, VMThread::vm_thread());
4015     st->print(" ");
4016     VMThread::vm_thread()->print_on_error(st, buf, buflen);
4017     st->cr();
4018   }
4019   WatcherThread* wt = WatcherThread::watcher_thread();
4020   if (wt != NULL) {
4021     bool is_current = (current == wt);
4022     found_current = found_current || is_current;
4023     st->print("%s", is_current ? "=>" : "  ");
4024 
4025     st->print(PTR_FORMAT, wt);
4026     st->print(" ");
4027     wt->print_on_error(st, buf, buflen);
4028     st->cr();
4029   }
4030   if (!found_current) {
4031     st->cr();
4032     st->print("=>" PTR_FORMAT " (exited) ", current);
4033     current->print_on_error(st, buf, buflen);
4034     st->cr();
4035   }
4036 }
4037 
4038 // Internal SpinLock and Mutex
4039 // Based on ParkEvent
4040 
4041 // Ad-hoc mutual exclusion primitives: SpinLock and Mux
4042 //
4043 // We employ SpinLocks _only for low-contention, fixed-length
4044 // short-duration critical sections where we're concerned
4045 // about native mutex_t or HotSpot Mutex:: latency.
4046 // The mux construct provides a spin-then-block mutual exclusion
4047 // mechanism.
4048 //
4049 // Testing has shown that contention on the ListLock guarding gFreeList
4050 // is common.  If we implement ListLock as a simple SpinLock it's common
4051 // for the JVM to devolve to yielding with little progress.  This is true
4052 // despite the fact that the critical sections protected by ListLock are
4053 // extremely short.
4054 //
4055 // TODO-FIXME: ListLock should be of type SpinLock.
4056 // We should make this a 1st-class type, integrated into the lock
4057 // hierarchy as leaf-locks.  Critically, the SpinLock structure
4058 // should have sufficient padding to avoid false-sharing and excessive
4059 // cache-coherency traffic.
4060 
4061 
4062 typedef volatile int SpinLockT ;
4063 
4064 void Thread::SpinAcquire (volatile int * adr, const char * LockName) {
4065   if (Atomic::cmpxchg (1, adr, 0) == 0) {
4066      return ;   // normal fast-path return
4067   }
4068 
4069   // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
4070   TEVENT (SpinAcquire - ctx) ;
4071   int ctr = 0 ;
4072   int Yields = 0 ;
4073   for (;;) {
4074      while (*adr != 0) {
4075         ++ctr ;
4076         if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
4077            if (Yields > 5) {
4078              // Consider using a simple NakedSleep() instead.
4079              // Then SpinAcquire could be called by non-JVM threads
4080              Thread::current()->_ParkEvent->park(1) ;
4081            } else {
4082              os::NakedYield() ;
4083              ++Yields ;
4084            }
4085         } else {
4086            SpinPause() ;
4087         }
4088      }
4089      if (Atomic::cmpxchg (1, adr, 0) == 0) return ;
4090   }
4091 }
4092 
4093 void Thread::SpinRelease (volatile int * adr) {
4094   assert (*adr != 0, "invariant") ;
4095   OrderAccess::fence() ;      // guarantee at least release consistency.
4096   // Roach-motel semantics.
4097   // It's safe if subsequent LDs and STs float "up" into the critical section,
4098   // but prior LDs and STs within the critical section can't be allowed
4099   // to reorder or float past the ST that releases the lock.
4100   *adr = 0 ;
4101 }
4102 
4103 // muxAcquire and muxRelease:
4104 //
4105 // *  muxAcquire and muxRelease support a single-word lock-word construct.
4106 //    The LSB of the word is set IFF the lock is held.
4107 //    The remainder of the word points to the head of a singly-linked list
4108 //    of threads blocked on the lock.
4109 //
4110 // *  The current implementation of muxAcquire-muxRelease uses its own
4111 //    dedicated Thread._MuxEvent instance.  If we're interested in
4112 //    minimizing the peak number of extant ParkEvent instances then
4113 //    we could eliminate _MuxEvent and "borrow" _ParkEvent as long
4114 //    as certain invariants were satisfied.  Specifically, care would need
4115 //    to be taken with regards to consuming unpark() "permits".
4116 //    A safe rule of thumb is that a thread would never call muxAcquire()
4117 //    if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
4118 //    park().  Otherwise the _ParkEvent park() operation in muxAcquire() could
4119 //    consume an unpark() permit intended for monitorenter, for instance.
4120 //    One way around this would be to widen the restricted-range semaphore
4121 //    implemented in park().  Another alternative would be to provide
4122 //    multiple instances of the PlatformEvent() for each thread.  One
4123 //    instance would be dedicated to muxAcquire-muxRelease, for instance.
4124 //
4125 // *  Usage:
4126 //    -- Only as leaf locks
4127 //    -- for short-term locking only as muxAcquire does not perform
4128 //       thread state transitions.
4129 //
4130 // Alternatives:
4131 // *  We could implement muxAcquire and muxRelease with MCS or CLH locks
4132 //    but with parking or spin-then-park instead of pure spinning.
4133 // *  Use Taura-Oyama-Yonenzawa locks.
4134 // *  It's possible to construct a 1-0 lock if we encode the lockword as
4135 //    (List,LockByte).  Acquire will CAS the full lockword while Release
4136 //    will STB 0 into the LockByte.  The 1-0 scheme admits stranding, so
4137 //    acquiring threads use timers (ParkTimed) to detect and recover from
4138 //    the stranding window.  Thread/Node structures must be aligned on 256-byte
4139 //    boundaries by using placement-new.
4140 // *  Augment MCS with advisory back-link fields maintained with CAS().
4141 //    Pictorially:  LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
4142 //    The validity of the backlinks must be ratified before we trust the value.
4143 //    If the backlinks are invalid the exiting thread must back-track through the
4144 //    the forward links, which are always trustworthy.
4145 // *  Add a successor indication.  The LockWord is currently encoded as
4146 //    (List, LOCKBIT:1).  We could also add a SUCCBIT or an explicit _succ variable
4147 //    to provide the usual futile-wakeup optimization.
4148 //    See RTStt for details.
4149 // *  Consider schedctl.sc_nopreempt to cover the critical section.
4150 //
4151 
4152 
4153 typedef volatile intptr_t MutexT ;      // Mux Lock-word
4154 enum MuxBits { LOCKBIT = 1 } ;
4155 
4156 void Thread::muxAcquire (volatile intptr_t * Lock, const char * LockName) {
4157   intptr_t w = Atomic::cmpxchg_ptr (LOCKBIT, Lock, 0) ;
4158   if (w == 0) return ;
4159   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4160      return ;
4161   }
4162 
4163   TEVENT (muxAcquire - Contention) ;
4164   ParkEvent * const Self = Thread::current()->_MuxEvent ;
4165   assert ((intptr_t(Self) & LOCKBIT) == 0, "invariant") ;
4166   for (;;) {
4167      int its = (os::is_MP() ? 100 : 0) + 1 ;
4168 
4169      // Optional spin phase: spin-then-park strategy
4170      while (--its >= 0) {
4171        w = *Lock ;
4172        if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4173           return ;
4174        }
4175      }
4176 
4177      Self->reset() ;
4178      Self->OnList = intptr_t(Lock) ;
4179      // The following fence() isn't _strictly necessary as the subsequent
4180      // CAS() both serializes execution and ratifies the fetched *Lock value.
4181      OrderAccess::fence();
4182      for (;;) {
4183         w = *Lock ;
4184         if ((w & LOCKBIT) == 0) {
4185             if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4186                 Self->OnList = 0 ;   // hygiene - allows stronger asserts
4187                 return ;
4188             }
4189             continue ;      // Interference -- *Lock changed -- Just retry
4190         }
4191         assert (w & LOCKBIT, "invariant") ;
4192         Self->ListNext = (ParkEvent *) (w & ~LOCKBIT );
4193         if (Atomic::cmpxchg_ptr (intptr_t(Self)|LOCKBIT, Lock, w) == w) break ;
4194      }
4195 
4196      while (Self->OnList != 0) {
4197         Self->park() ;
4198      }
4199   }
4200 }
4201 
4202 void Thread::muxAcquireW (volatile intptr_t * Lock, ParkEvent * ev) {
4203   intptr_t w = Atomic::cmpxchg_ptr (LOCKBIT, Lock, 0) ;
4204   if (w == 0) return ;
4205   if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4206     return ;
4207   }
4208 
4209   TEVENT (muxAcquire - Contention) ;
4210   ParkEvent * ReleaseAfter = NULL ;
4211   if (ev == NULL) {
4212     ev = ReleaseAfter = ParkEvent::Allocate (NULL) ;
4213   }
4214   assert ((intptr_t(ev) & LOCKBIT) == 0, "invariant") ;
4215   for (;;) {
4216     guarantee (ev->OnList == 0, "invariant") ;
4217     int its = (os::is_MP() ? 100 : 0) + 1 ;
4218 
4219     // Optional spin phase: spin-then-park strategy
4220     while (--its >= 0) {
4221       w = *Lock ;
4222       if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4223         if (ReleaseAfter != NULL) {
4224           ParkEvent::Release (ReleaseAfter) ;
4225         }
4226         return ;
4227       }
4228     }
4229 
4230     ev->reset() ;
4231     ev->OnList = intptr_t(Lock) ;
4232     // The following fence() isn't _strictly necessary as the subsequent
4233     // CAS() both serializes execution and ratifies the fetched *Lock value.
4234     OrderAccess::fence();
4235     for (;;) {
4236       w = *Lock ;
4237       if ((w & LOCKBIT) == 0) {
4238         if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
4239           ev->OnList = 0 ;
4240           // We call ::Release while holding the outer lock, thus
4241           // artificially lengthening the critical section.
4242           // Consider deferring the ::Release() until the subsequent unlock(),
4243           // after we've dropped the outer lock.
4244           if (ReleaseAfter != NULL) {
4245             ParkEvent::Release (ReleaseAfter) ;
4246           }
4247           return ;
4248         }
4249         continue ;      // Interference -- *Lock changed -- Just retry
4250       }
4251       assert (w & LOCKBIT, "invariant") ;
4252       ev->ListNext = (ParkEvent *) (w & ~LOCKBIT );
4253       if (Atomic::cmpxchg_ptr (intptr_t(ev)|LOCKBIT, Lock, w) == w) break ;
4254     }
4255 
4256     while (ev->OnList != 0) {
4257       ev->park() ;
4258     }
4259   }
4260 }
4261 
4262 // Release() must extract a successor from the list and then wake that thread.
4263 // It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
4264 // similar to that used by ParkEvent::Allocate() and ::Release().  DMR-based
4265 // Release() would :
4266 // (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
4267 // (B) Extract a successor from the private list "in-hand"
4268 // (C) attempt to CAS() the residual back into *Lock over null.
4269 //     If there were any newly arrived threads and the CAS() would fail.
4270 //     In that case Release() would detach the RATs, re-merge the list in-hand
4271 //     with the RATs and repeat as needed.  Alternately, Release() might
4272 //     detach and extract a successor, but then pass the residual list to the wakee.
4273 //     The wakee would be responsible for reattaching and remerging before it
4274 //     competed for the lock.
4275 //
4276 // Both "pop" and DMR are immune from ABA corruption -- there can be
4277 // multiple concurrent pushers, but only one popper or detacher.
4278 // This implementation pops from the head of the list.  This is unfair,
4279 // but tends to provide excellent throughput as hot threads remain hot.
4280 // (We wake recently run threads first).
4281 
4282 void Thread::muxRelease (volatile intptr_t * Lock)  {
4283   for (;;) {
4284     const intptr_t w = Atomic::cmpxchg_ptr (0, Lock, LOCKBIT) ;
4285     assert (w & LOCKBIT, "invariant") ;
4286     if (w == LOCKBIT) return ;
4287     ParkEvent * List = (ParkEvent *) (w & ~LOCKBIT) ;
4288     assert (List != NULL, "invariant") ;
4289     assert (List->OnList == intptr_t(Lock), "invariant") ;
4290     ParkEvent * nxt = List->ListNext ;
4291 
4292     // The following CAS() releases the lock and pops the head element.
4293     if (Atomic::cmpxchg_ptr (intptr_t(nxt), Lock, w) != w) {
4294       continue ;
4295     }
4296     List->OnList = 0 ;
4297     OrderAccess::fence() ;
4298     List->unpark () ;
4299     return ;
4300   }
4301 }
4302 
4303 
4304 void Threads::verify() {
4305   ALL_JAVA_THREADS(p) {
4306     p->verify();
4307   }
4308   VMThread* thread = VMThread::vm_thread();
4309   if (thread != NULL) thread->verify();
4310 }
--- EOF ---