1 /*
   2  * Copyright (c) 1997, 2019, 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/classLoaderDataGraph.inline.hpp"
  27 #include "classfile/dictionary.hpp"
  28 #include "classfile/stringTable.hpp"
  29 #include "classfile/symbolTable.hpp"
  30 #include "classfile/systemDictionary.hpp"
  31 #include "code/codeCache.hpp"
  32 #include "code/icBuffer.hpp"
  33 #include "code/nmethod.hpp"
  34 #include "code/pcDesc.hpp"
  35 #include "code/scopeDesc.hpp"
  36 #include "compiler/compilationPolicy.hpp"
  37 #include "gc/shared/collectedHeap.hpp"
  38 #include "gc/shared/gcLocker.hpp"
  39 #include "gc/shared/oopStorage.hpp"
  40 #include "gc/shared/strongRootsScope.hpp"
  41 #include "gc/shared/workgroup.hpp"
  42 #include "interpreter/interpreter.hpp"
  43 #include "jfr/jfrEvents.hpp"
  44 #include "logging/log.hpp"
  45 #include "logging/logStream.hpp"
  46 #include "memory/resourceArea.hpp"
  47 #include "memory/universe.hpp"
  48 #include "oops/oop.inline.hpp"
  49 #include "oops/symbol.hpp"
  50 #include "runtime/atomic.hpp"
  51 #include "runtime/deoptimization.hpp"
  52 #include "runtime/frame.inline.hpp"
  53 #include "runtime/handles.inline.hpp"
  54 #include "runtime/interfaceSupport.inline.hpp"
  55 #include "runtime/mutexLocker.hpp"
  56 #include "runtime/orderAccess.hpp"
  57 #include "runtime/osThread.hpp"
  58 #include "runtime/safepoint.hpp"
  59 #include "runtime/safepointMechanism.inline.hpp"
  60 #include "runtime/signature.hpp"
  61 #include "runtime/stubCodeGenerator.hpp"
  62 #include "runtime/stubRoutines.hpp"
  63 #include "runtime/sweeper.hpp"
  64 #include "runtime/synchronizer.hpp"
  65 #include "runtime/thread.inline.hpp"
  66 #include "runtime/threadSMR.hpp"
  67 #include "runtime/timerTrace.hpp"
  68 #include "services/runtimeService.hpp"
  69 #include "utilities/events.hpp"
  70 #include "utilities/macros.hpp"
  71 
  72 static void post_safepoint_begin_event(EventSafepointBegin& event,
  73                                        uint64_t safepoint_id,
  74                                        int thread_count,
  75                                        int critical_thread_count) {
  76   if (event.should_commit()) {
  77     event.set_safepointId(safepoint_id);
  78     event.set_totalThreadCount(thread_count);
  79     event.set_jniCriticalThreadCount(critical_thread_count);
  80     event.commit();
  81   }
  82 }
  83 
  84 static void post_safepoint_cleanup_event(EventSafepointCleanup& event, uint64_t safepoint_id) {
  85   if (event.should_commit()) {
  86     event.set_safepointId(safepoint_id);
  87     event.commit();
  88   }
  89 }
  90 
  91 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization& event,
  92                                              uint64_t safepoint_id,
  93                                              int initial_number_of_threads,
  94                                              int threads_waiting_to_block,
  95                                              uint64_t iterations) {
  96   if (event.should_commit()) {
  97     event.set_safepointId(safepoint_id);
  98     event.set_initialThreadCount(initial_number_of_threads);
  99     event.set_runningThreadCount(threads_waiting_to_block);
 100     event.set_iterations(iterations);
 101     event.commit();
 102   }
 103 }
 104 
 105 static void post_safepoint_cleanup_task_event(EventSafepointCleanupTask& event,
 106                                               uint64_t safepoint_id,
 107                                               const char* name) {
 108   if (event.should_commit()) {
 109     event.set_safepointId(safepoint_id);
 110     event.set_name(name);
 111     event.commit();
 112   }
 113 }
 114 
 115 static void post_safepoint_end_event(EventSafepointEnd& event, uint64_t safepoint_id) {
 116   if (event.should_commit()) {
 117     event.set_safepointId(safepoint_id);
 118     event.commit();
 119   }
 120 }
 121 
 122 // SafepointCheck
 123 SafepointStateTracker::SafepointStateTracker(uint64_t safepoint_id, bool at_safepoint)
 124   : _safepoint_id(safepoint_id), _at_safepoint(at_safepoint) {}
 125 
 126 bool SafepointStateTracker::safepoint_state_changed() {
 127   return _safepoint_id != SafepointSynchronize::safepoint_id() ||
 128     _at_safepoint != SafepointSynchronize::is_at_safepoint();
 129 }
 130 
 131 // --------------------------------------------------------------------------------------------------
 132 // Implementation of Safepoint begin/end
 133 
 134 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
 135 int SafepointSynchronize::_waiting_to_block = 0;
 136 volatile uint64_t SafepointSynchronize::_safepoint_counter = 0;
 137 uint64_t SafepointSynchronize::_safepoint_id = 0;
 138 const uint64_t SafepointSynchronize::InactiveSafepointCounter = 0;
 139 int SafepointSynchronize::_current_jni_active_count = 0;
 140 
 141 WaitBarrier* SafepointSynchronize::_wait_barrier;
 142 
 143 static volatile bool PageArmed = false;        // safepoint polling page is RO|RW vs PROT_NONE
 144 static bool timeout_error_printed = false;
 145 
 146 // Statistic related
 147 static jlong _safepoint_begin_time = 0;
 148 static volatile int _nof_threads_hit_polling_page = 0;
 149 
 150 void SafepointSynchronize::init(Thread* vmthread) {
 151   // WaitBarrier should never be destroyed since we will have
 152   // threads waiting on it while exiting.
 153   _wait_barrier = new WaitBarrier(vmthread);
 154   SafepointTracing::init();
 155 }
 156 
 157 void SafepointSynchronize::increment_jni_active_count() {
 158   assert(Thread::current()->is_VM_thread(), "Only VM thread may increment");
 159   ++_current_jni_active_count;
 160 }
 161 
 162 void SafepointSynchronize::decrement_waiting_to_block() {
 163   assert(_waiting_to_block > 0, "sanity check");
 164   assert(Thread::current()->is_VM_thread(), "Only VM thread may decrement");
 165   --_waiting_to_block;
 166 }
 167 
 168 bool SafepointSynchronize::thread_not_running(ThreadSafepointState *cur_state) {
 169   if (!cur_state->is_running()) {
 170     return true;
 171   }
 172   cur_state->examine_state_of_thread(SafepointSynchronize::safepoint_counter());
 173   if (!cur_state->is_running()) {
 174     return true;
 175   }
 176   LogTarget(Trace, safepoint) lt;
 177   if (lt.is_enabled()) {
 178     ResourceMark rm;
 179     LogStream ls(lt);
 180     cur_state->print_on(&ls);
 181   }
 182   return false;
 183 }
 184 
 185 #ifdef ASSERT
 186 static void assert_list_is_valid(const ThreadSafepointState* tss_head, int still_running) {
 187   int a = 0;
 188   const ThreadSafepointState *tmp_tss = tss_head;
 189   while (tmp_tss != NULL) {
 190     ++a;
 191     assert(tmp_tss->is_running(), "Illegal initial state");
 192     tmp_tss = tmp_tss->get_next();
 193   }
 194   assert(a == still_running, "Must be the same");
 195 }
 196 #endif // ASSERT
 197 
 198 static void back_off(int64_t start_time) {
 199   // We start with fine-grained nanosleeping until a millisecond has
 200   // passed, at which point we resort to plain naked_short_sleep.
 201   if (os::javaTimeNanos() - start_time < NANOSECS_PER_MILLISEC) {
 202     os::naked_short_nanosleep(10 * (NANOUNITS / MICROUNITS));
 203   } else {
 204     os::naked_short_sleep(1);
 205   }
 206 }
 207 
 208 int SafepointSynchronize::synchronize_threads(jlong safepoint_limit_time, int nof_threads, int* initial_running)
 209 {
 210   JavaThreadIteratorWithHandle jtiwh;
 211 
 212 #ifdef ASSERT
 213   for (; JavaThread *cur = jtiwh.next(); ) {
 214     assert(cur->safepoint_state()->is_running(), "Illegal initial state");
 215   }
 216   jtiwh.rewind();
 217 #endif // ASSERT
 218 
 219   // Iterate through all threads until it has been determined how to stop them all at a safepoint.
 220   int still_running = nof_threads;
 221   ThreadSafepointState *tss_head = NULL;
 222   ThreadSafepointState **p_prev = &tss_head;
 223   for (; JavaThread *cur = jtiwh.next(); ) {
 224     ThreadSafepointState *cur_tss = cur->safepoint_state();
 225     assert(cur_tss->get_next() == NULL, "Must be NULL");
 226     if (thread_not_running(cur_tss)) {
 227       --still_running;
 228     } else {
 229       *p_prev = cur_tss;
 230       p_prev = cur_tss->next_ptr();
 231     }
 232   }
 233   *p_prev = NULL;
 234 
 235   DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);)
 236 
 237   *initial_running = still_running;
 238 
 239   // If there is no thread still running, we are already done.
 240   if (still_running <= 0) {
 241     assert(tss_head == NULL, "Must be empty");
 242     return 1;
 243   }
 244 
 245   int iterations = 1; // The first iteration is above.
 246   int64_t start_time = os::javaTimeNanos();
 247 
 248   do {
 249     // Check if this has taken too long:
 250     if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
 251       print_safepoint_timeout();
 252     }
 253     if (int(iterations) == -1) { // overflow - something is wrong.
 254       // We can only overflow here when we are using global
 255       // polling pages. We keep this guarantee in its original
 256       // form so that searches of the bug database for this
 257       // failure mode find the right bugs.
 258       guarantee (!PageArmed, "invariant");
 259     }
 260 
 261     p_prev = &tss_head;
 262     ThreadSafepointState *cur_tss = tss_head;
 263     while (cur_tss != NULL) {
 264       assert(cur_tss->is_running(), "Illegal initial state");
 265       if (thread_not_running(cur_tss)) {
 266         --still_running;
 267         *p_prev = NULL;
 268         ThreadSafepointState *tmp = cur_tss;
 269         cur_tss = cur_tss->get_next();
 270         tmp->set_next(NULL);
 271       } else {
 272         *p_prev = cur_tss;
 273         p_prev = cur_tss->next_ptr();
 274         cur_tss = cur_tss->get_next();
 275       }
 276     }
 277 
 278     DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);)
 279 
 280     if (still_running > 0) {
 281       back_off(start_time);
 282     }
 283 
 284     iterations++;
 285   } while (still_running > 0);
 286 
 287   assert(tss_head == NULL, "Must be empty");
 288 
 289   return iterations;
 290 }
 291 
 292 void SafepointSynchronize::arm_safepoint() {
 293   // Begin the process of bringing the system to a safepoint.
 294   // Java threads can be in several different states and are
 295   // stopped by different mechanisms:
 296   //
 297   //  1. Running interpreted
 298   //     When executing branching/returning byte codes interpreter
 299   //     checks if the poll is armed, if so blocks in SS::block().
 300   //     When using global polling the interpreter dispatch table
 301   //     is changed to force it to check for a safepoint condition
 302   //     between bytecodes.
 303   //  2. Running in native code
 304   //     When returning from the native code, a Java thread must check
 305   //     the safepoint _state to see if we must block.  If the
 306   //     VM thread sees a Java thread in native, it does
 307   //     not wait for this thread to block.  The order of the memory
 308   //     writes and reads of both the safepoint state and the Java
 309   //     threads state is critical.  In order to guarantee that the
 310   //     memory writes are serialized with respect to each other,
 311   //     the VM thread issues a memory barrier instruction.
 312   //  3. Running compiled Code
 313   //     Compiled code reads the local polling page that
 314   //     is set to fault if we are trying to get to a safepoint.
 315   //  4. Blocked
 316   //     A thread which is blocked will not be allowed to return from the
 317   //     block condition until the safepoint operation is complete.
 318   //  5. In VM or Transitioning between states
 319   //     If a Java thread is currently running in the VM or transitioning
 320   //     between states, the safepointing code will poll the thread state
 321   //     until the thread blocks itself when it attempts transitions to a
 322   //     new state or locking a safepoint checked monitor.
 323 
 324   // We must never miss a thread with correct safepoint id, so we must make sure we arm
 325   // the wait barrier for the next safepoint id/counter.
 326   // Arming must be done after resetting _current_jni_active_count, _waiting_to_block.
 327   _wait_barrier->arm(static_cast<int>(_safepoint_counter + 1));
 328 
 329   assert((_safepoint_counter & 0x1) == 0, "must be even");
 330   // The store to _safepoint_counter must happen after any stores in arming.
 331   Atomic::release_store(&_safepoint_counter, _safepoint_counter + 1);
 332 
 333   // We are synchronizing
 334   OrderAccess::storestore(); // Ordered with _safepoint_counter
 335   _state = _synchronizing;
 336 
 337   if (SafepointMechanism::uses_thread_local_poll()) {
 338     // Arming the per thread poll while having _state != _not_synchronized means safepointing
 339     log_trace(safepoint)("Setting thread local yield flag for threads");
 340     OrderAccess::storestore(); // storestore, global state -> local state
 341     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
 342       // Make sure the threads start polling, it is time to yield.
 343       SafepointMechanism::arm_local_poll(cur);
 344     }
 345   }
 346   OrderAccess::fence(); // storestore|storeload, global state -> local state
 347 
 348   if (SafepointMechanism::uses_global_page_poll()) {
 349     // Make interpreter safepoint aware
 350     Interpreter::notice_safepoints();
 351 
 352     // Make polling safepoint aware
 353     guarantee (!PageArmed, "invariant") ;
 354     PageArmed = true;
 355     os::make_polling_page_unreadable();
 356   }
 357 }
 358 
 359 // Roll all threads forward to a safepoint and suspend them all
 360 void SafepointSynchronize::begin() {
 361   assert(Thread::current()->is_VM_thread(), "Only VM thread may execute a safepoint");
 362 
 363   EventSafepointBegin begin_event;
 364   SafepointTracing::begin(VMThread::vm_op_type());
 365 
 366   Universe::heap()->safepoint_synchronize_begin();
 367 
 368   // By getting the Threads_lock, we assure that no threads are about to start or
 369   // exit. It is released again in SafepointSynchronize::end().
 370   Threads_lock->lock();
 371 
 372   assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
 373 
 374   int nof_threads = Threads::number_of_threads();
 375 
 376   _nof_threads_hit_polling_page = 0;
 377 
 378   log_debug(safepoint)("Safepoint synchronization initiated using %s wait barrier. (%d threads)", _wait_barrier->description(), nof_threads);
 379 
 380   // Reset the count of active JNI critical threads
 381   _current_jni_active_count = 0;
 382 
 383   // Set number of threads to wait for
 384   _waiting_to_block = nof_threads;
 385 
 386   jlong safepoint_limit_time = 0;
 387   if (SafepointTimeout) {
 388     // Set the limit time, so that it can be compared to see if this has taken
 389     // too long to complete.
 390     safepoint_limit_time = SafepointTracing::start_of_safepoint() + (jlong)SafepointTimeoutDelay * (NANOUNITS / MILLIUNITS);
 391     timeout_error_printed = false;
 392   }
 393 
 394   EventSafepointStateSynchronization sync_event;
 395   int initial_running = 0;
 396 
 397   // Arms the safepoint, _current_jni_active_count and _waiting_to_block must be set before.
 398   arm_safepoint();
 399 
 400   // Will spin until all threads are safe.
 401   int iterations = synchronize_threads(safepoint_limit_time, nof_threads, &initial_running);
 402   assert(_waiting_to_block == 0, "No thread should be running");
 403 
 404 #ifndef PRODUCT
 405   if (safepoint_limit_time != 0) {
 406     jlong current_time = os::javaTimeNanos();
 407     if (safepoint_limit_time < current_time) {
 408       log_warning(safepoint)("# SafepointSynchronize: Finished after "
 409                     INT64_FORMAT_W(6) " ms",
 410                     (int64_t)(current_time - SafepointTracing::start_of_safepoint()) / (NANOUNITS / MILLIUNITS));
 411     }
 412   }
 413 #endif
 414 
 415   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 416 
 417   // Record state
 418   _state = _synchronized;
 419 
 420   OrderAccess::fence();
 421 
 422   // Set the new id
 423   ++_safepoint_id;
 424 
 425 #ifdef ASSERT
 426   // Make sure all the threads were visited.
 427   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
 428     assert(cur->was_visited_for_critical_count(_safepoint_counter), "missed a thread");
 429   }
 430 #endif // ASSERT
 431 
 432   // Update the count of active JNI critical regions
 433   GCLocker::set_jni_lock_count(_current_jni_active_count);
 434 
 435   post_safepoint_synchronize_event(sync_event,
 436                                    _safepoint_id,
 437                                    initial_running,
 438                                    _waiting_to_block, iterations);
 439 
 440   SafepointTracing::synchronized(nof_threads, initial_running, _nof_threads_hit_polling_page);
 441 
 442   // We do the safepoint cleanup first since a GC related safepoint
 443   // needs cleanup to be completed before running the GC op.
 444   EventSafepointCleanup cleanup_event;
 445   do_cleanup_tasks();
 446   post_safepoint_cleanup_event(cleanup_event, _safepoint_id);
 447 
 448   post_safepoint_begin_event(begin_event, _safepoint_id, nof_threads, _current_jni_active_count);
 449   SafepointTracing::cleanup();
 450 }
 451 
 452 void SafepointSynchronize::disarm_safepoint() {
 453   uint64_t active_safepoint_counter = _safepoint_counter;
 454   {
 455     JavaThreadIteratorWithHandle jtiwh;
 456 #ifdef ASSERT
 457     // A pending_exception cannot be installed during a safepoint.  The threads
 458     // may install an async exception after they come back from a safepoint into
 459     // pending_exception after they unblock.  But that should happen later.
 460     for (; JavaThread *cur = jtiwh.next(); ) {
 461       assert (!(cur->has_pending_exception() &&
 462                 cur->safepoint_state()->is_at_poll_safepoint()),
 463               "safepoint installed a pending exception");
 464     }
 465 #endif // ASSERT
 466 
 467     if (SafepointMechanism::uses_global_page_poll()) {
 468       guarantee (PageArmed, "invariant");
 469       // Make polling safepoint aware
 470       os::make_polling_page_readable();
 471       PageArmed = false;
 472       // Remove safepoint check from interpreter
 473       Interpreter::ignore_safepoints();
 474     }
 475 
 476     OrderAccess::fence(); // keep read and write of _state from floating up
 477     assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
 478 
 479     // Change state first to _not_synchronized.
 480     // No threads should see _synchronized when running.
 481     _state = _not_synchronized;
 482 
 483     // Set the next dormant (even) safepoint id.
 484     assert((_safepoint_counter & 0x1) == 1, "must be odd");
 485     Atomic::release_store(&_safepoint_counter, _safepoint_counter + 1);
 486 
 487     OrderAccess::fence(); // Keep the local state from floating up.
 488 
 489     jtiwh.rewind();
 490     for (; JavaThread *current = jtiwh.next(); ) {
 491       // Clear the visited flag to ensure that the critical counts are collected properly.
 492       DEBUG_ONLY(current->reset_visited_for_critical_count(active_safepoint_counter);)
 493       ThreadSafepointState* cur_state = current->safepoint_state();
 494       assert(!cur_state->is_running(), "Thread not suspended at safepoint");
 495       cur_state->restart(); // TSS _running
 496       assert(cur_state->is_running(), "safepoint state has not been reset");
 497 
 498       SafepointMechanism::disarm_if_needed(current, false /* NO release */);
 499     }
 500   } // ~JavaThreadIteratorWithHandle
 501 
 502   // Release threads lock, so threads can be created/destroyed again.
 503   Threads_lock->unlock();
 504 
 505   // Wake threads after local state is correctly set.
 506   _wait_barrier->disarm();
 507 }
 508 
 509 // Wake up all threads, so they are ready to resume execution after the safepoint
 510 // operation has been carried out
 511 void SafepointSynchronize::end() {
 512   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 513   EventSafepointEnd event;
 514   assert(Thread::current()->is_VM_thread(), "Only VM thread can execute a safepoint");
 515 
 516   disarm_safepoint();
 517 
 518   Universe::heap()->safepoint_synchronize_end();
 519 
 520   SafepointTracing::end();
 521 
 522   post_safepoint_end_event(event, safepoint_id());
 523 }
 524 
 525 bool SafepointSynchronize::is_cleanup_needed() {
 526   // Need a safepoint if there are many monitors to deflate.
 527   if (ObjectSynchronizer::is_cleanup_needed()) return true;
 528   // Need a safepoint if some inline cache buffers is non-empty
 529   if (!InlineCacheBuffer::is_empty()) return true;
 530   if (StringTable::needs_rehashing()) return true;
 531   if (SymbolTable::needs_rehashing()) return true;
 532   return false;
 533 }
 534 
 535 bool SafepointSynchronize::is_forced_cleanup_needed() {
 536   return ObjectSynchronizer::needs_monitor_scavenge();
 537 }
 538 
 539 class ParallelSPCleanupThreadClosure : public ThreadClosure {
 540 private:
 541   CodeBlobClosure* _nmethod_cl;
 542   DeflateMonitorCounters* _counters;
 543 
 544 public:
 545   ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
 546     _nmethod_cl(UseCodeAging ? NMethodSweeper::prepare_reset_hotness_counters() : NULL),
 547     _counters(counters) {}
 548 
 549   void do_thread(Thread* thread) {
 550     ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
 551     if (_nmethod_cl != NULL && thread->is_Java_thread() &&
 552         ! thread->is_Code_cache_sweeper_thread()) {
 553       JavaThread* jt = (JavaThread*) thread;
 554       jt->nmethods_do(_nmethod_cl);
 555     }
 556   }
 557 };
 558 
 559 class ParallelSPCleanupTask : public AbstractGangTask {
 560 private:
 561   SubTasksDone _subtasks;
 562   ParallelSPCleanupThreadClosure _cleanup_threads_cl;
 563   uint _num_workers;
 564   DeflateMonitorCounters* _counters;
 565 public:
 566   ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
 567     AbstractGangTask("Parallel Safepoint Cleanup"),
 568     _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
 569     _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
 570     _num_workers(num_workers),
 571     _counters(counters) {}
 572 
 573   void work(uint worker_id) {
 574     uint64_t safepoint_id = SafepointSynchronize::safepoint_id();
 575     // All threads deflate monitors and mark nmethods (if necessary).
 576     Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
 577 
 578     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
 579       const char* name = "deflating global idle monitors";
 580       EventSafepointCleanupTask event;
 581       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 582       ObjectSynchronizer::deflate_idle_monitors(_counters);
 583 
 584       post_safepoint_cleanup_task_event(event, safepoint_id, name);
 585     }
 586 
 587     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
 588       const char* name = "updating inline caches";
 589       EventSafepointCleanupTask event;
 590       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 591       InlineCacheBuffer::update_inline_caches();
 592 
 593       post_safepoint_cleanup_task_event(event, safepoint_id, name);
 594     }
 595 
 596     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
 597       const char* name = "compilation policy safepoint handler";
 598       EventSafepointCleanupTask event;
 599       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 600       CompilationPolicy::policy()->do_safepoint_work();
 601 
 602       post_safepoint_cleanup_task_event(event, safepoint_id, name);
 603     }
 604 
 605     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
 606       if (SymbolTable::needs_rehashing()) {
 607         const char* name = "rehashing symbol table";
 608         EventSafepointCleanupTask event;
 609         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 610         SymbolTable::rehash_table();
 611 
 612         post_safepoint_cleanup_task_event(event, safepoint_id, name);
 613       }
 614     }
 615 
 616     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
 617       if (StringTable::needs_rehashing()) {
 618         const char* name = "rehashing string table";
 619         EventSafepointCleanupTask event;
 620         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 621         StringTable::rehash_table();
 622 
 623         post_safepoint_cleanup_task_event(event, safepoint_id, name);
 624       }
 625     }
 626 
 627     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
 628       if (Dictionary::does_any_dictionary_needs_resizing()) {
 629         const char* name = "resizing system dictionaries";
 630         EventSafepointCleanupTask event;
 631         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 632         ClassLoaderDataGraph::resize_dictionaries();
 633 
 634         post_safepoint_cleanup_task_event(event, safepoint_id, name);
 635       }
 636     }
 637 
 638     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_REQUEST_OOPSTORAGE_CLEANUP)) {
 639       // Don't bother reporting event or time for this very short operation.
 640       // To have any utility we'd also want to report whether needed.
 641       OopStorage::trigger_cleanup_if_needed();
 642     }
 643 
 644     _subtasks.all_tasks_completed(_num_workers);
 645   }
 646 };
 647 
 648 // Various cleaning tasks that should be done periodically at safepoints.
 649 void SafepointSynchronize::do_cleanup_tasks() {
 650 
 651   TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
 652 
 653   // Prepare for monitor deflation.
 654   DeflateMonitorCounters deflate_counters;
 655   ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
 656 
 657   CollectedHeap* heap = Universe::heap();
 658   assert(heap != NULL, "heap not initialized yet?");
 659   WorkGang* cleanup_workers = heap->get_safepoint_workers();
 660   if (cleanup_workers != NULL) {
 661     // Parallel cleanup using GC provided thread pool.
 662     uint num_cleanup_workers = cleanup_workers->active_workers();
 663     ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
 664     StrongRootsScope srs(num_cleanup_workers);
 665     cleanup_workers->run_task(&cleanup);
 666   } else {
 667     // Serial cleanup using VMThread.
 668     ParallelSPCleanupTask cleanup(1, &deflate_counters);
 669     StrongRootsScope srs(1);
 670     cleanup.work(0);
 671   }
 672 
 673   // Needs to be done single threaded by the VMThread.  This walks
 674   // the thread stacks looking for references to metadata before
 675   // deciding to remove it from the metaspaces.
 676   if (ClassLoaderDataGraph::should_clean_metaspaces_and_reset()) {
 677     const char* name = "cleanup live ClassLoaderData metaspaces";
 678     TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 679     ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces();
 680   }
 681 
 682   // Finish monitor deflation.
 683   ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
 684 
 685   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
 686 }
 687 
 688 // Methods for determining if a JavaThread is safepoint safe.
 689 
 690 // False means unsafe with undetermined state.
 691 // True means a determined state, but it may be an unsafe state.
 692 // If called from a non-safepoint context safepoint_count MUST be InactiveSafepointCounter.
 693 bool SafepointSynchronize::try_stable_load_state(JavaThreadState *state, JavaThread *thread, uint64_t safepoint_count) {
 694   assert((safepoint_count != InactiveSafepointCounter &&
 695           Thread::current() == (Thread*)VMThread::vm_thread() &&
 696           SafepointSynchronize::_state != _not_synchronized)
 697          || safepoint_count == InactiveSafepointCounter, "Invalid check");
 698 
 699   // To handle the thread_blocked state on the backedge of the WaitBarrier from
 700   // previous safepoint and reading the reset value (0/InactiveSafepointCounter) we
 701   // re-read state after we read thread safepoint id. The JavaThread changes its
 702   // thread state from thread_blocked before resetting safepoint id to 0.
 703   // This guarantees the second read will be from an updated thread state. It can
 704   // either be different state making this an unsafe state or it can see blocked
 705   // again. When we see blocked twice with a 0 safepoint id, either:
 706   // - It is normally blocked, e.g. on Mutex, TBIVM.
 707   // - It was in SS:block(), looped around to SS:block() and is blocked on the WaitBarrier.
 708   // - It was in SS:block() but now on a Mutex.
 709   // All of these cases are safe.
 710 
 711   *state = thread->thread_state();
 712   OrderAccess::loadload();
 713   uint64_t sid = thread->safepoint_state()->get_safepoint_id();  // Load acquire
 714   if (sid != InactiveSafepointCounter && sid != safepoint_count) {
 715     // In an old safepoint, state not relevant.
 716     return false;
 717   }
 718   return *state == thread->thread_state();
 719 }
 720 
 721 static bool safepoint_safe_with(JavaThread *thread, JavaThreadState state) {
 722   switch(state) {
 723   case _thread_in_native:
 724     // native threads are safe if they have no java stack or have walkable stack
 725     return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
 726 
 727   case _thread_blocked:
 728     // On wait_barrier or blocked.
 729     // Blocked threads should already have walkable stack.
 730     assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
 731     return true;
 732 
 733   default:
 734     return false;
 735   }
 736 }
 737 
 738 bool SafepointSynchronize::handshake_safe(JavaThread *thread) {
 739   assert(Thread::current()->is_VM_thread(), "Must be VMThread");
 740   if (thread->is_ext_suspended() || thread->is_terminated()) {
 741     return true;
 742   }
 743   JavaThreadState stable_state;
 744   if (try_stable_load_state(&stable_state, thread, InactiveSafepointCounter)) {
 745     return safepoint_safe_with(thread, stable_state);
 746   }
 747   return false;
 748 }
 749 
 750 // See if the thread is running inside a lazy critical native and
 751 // update the thread critical count if so.  Also set a suspend flag to
 752 // cause the native wrapper to return into the JVM to do the unlock
 753 // once the native finishes.
 754 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
 755   if (state == _thread_in_native &&
 756       thread->has_last_Java_frame() &&
 757       thread->frame_anchor()->walkable()) {
 758     // This thread might be in a critical native nmethod so look at
 759     // the top of the stack and increment the critical count if it
 760     // is.
 761     frame wrapper_frame = thread->last_frame();
 762     CodeBlob* stub_cb = wrapper_frame.cb();
 763     if (stub_cb != NULL &&
 764         stub_cb->is_nmethod() &&
 765         stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
 766       // A thread could potentially be in a critical native across
 767       // more than one safepoint, so only update the critical state on
 768       // the first one.  When it returns it will perform the unlock.
 769       if (!thread->do_critical_native_unlock()) {
 770 #ifdef ASSERT
 771         if (!thread->in_critical()) {
 772           GCLocker::increment_debug_jni_lock_count();
 773         }
 774 #endif
 775         thread->enter_critical();
 776         // Make sure the native wrapper calls back on return to
 777         // perform the needed critical unlock.
 778         thread->set_critical_native_unlock();
 779       }
 780     }
 781   }
 782 }
 783 
 784 // -------------------------------------------------------------------------------------------------------
 785 // Implementation of Safepoint blocking point
 786 
 787 void SafepointSynchronize::block(JavaThread *thread) {
 788   assert(thread != NULL, "thread must be set");
 789   assert(thread->is_Java_thread(), "not a Java thread");
 790 
 791   // Threads shouldn't block if they are in the middle of printing, but...
 792   ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
 793 
 794   // Only bail from the block() call if the thread is gone from the
 795   // thread list; starting to exit should still block.
 796   if (thread->is_terminated()) {
 797      // block current thread if we come here from native code when VM is gone
 798      thread->block_if_vm_exited();
 799 
 800      // otherwise do nothing
 801      return;
 802   }
 803 
 804   JavaThreadState state = thread->thread_state();
 805   thread->frame_anchor()->make_walkable(thread);
 806 
 807   uint64_t safepoint_id = SafepointSynchronize::safepoint_counter();
 808   // Check that we have a valid thread_state at this point
 809   switch(state) {
 810     case _thread_in_vm_trans:
 811     case _thread_in_Java:        // From compiled code
 812     case _thread_in_native_trans:
 813     case _thread_blocked_trans:
 814     case _thread_new_trans:
 815 
 816       // We have no idea where the VMThread is, it might even be at next safepoint.
 817       // So we can miss this poll, but stop at next.
 818 
 819       // Load dependent store, it must not pass loading of safepoint_id.
 820       thread->safepoint_state()->set_safepoint_id(safepoint_id); // Release store
 821 
 822       // This part we can skip if we notice we miss or are in a future safepoint.
 823       OrderAccess::storestore();
 824       // Load in wait barrier should not float up
 825       thread->set_thread_state_fence(_thread_blocked);
 826 
 827       _wait_barrier->wait(static_cast<int>(safepoint_id));
 828       assert(_state != _synchronized, "Can't be");
 829 
 830       // If barrier is disarmed stop store from floating above loads in barrier.
 831       OrderAccess::loadstore();
 832       thread->set_thread_state(state);
 833 
 834       // Then we reset the safepoint id to inactive.
 835       thread->safepoint_state()->reset_safepoint_id(); // Release store
 836 
 837       OrderAccess::fence();
 838 
 839       break;
 840 
 841     default:
 842      fatal("Illegal threadstate encountered: %d", state);
 843   }
 844   guarantee(thread->safepoint_state()->get_safepoint_id() == InactiveSafepointCounter,
 845             "The safepoint id should be set only in block path");
 846 
 847   // Check for pending. async. exceptions or suspends - except if the
 848   // thread was blocked inside the VM. has_special_runtime_exit_condition()
 849   // is called last since it grabs a lock and we only want to do that when
 850   // we must.
 851   //
 852   // Note: we never deliver an async exception at a polling point as the
 853   // compiler may not have an exception handler for it. The polling
 854   // code will notice the async and deoptimize and the exception will
 855   // be delivered. (Polling at a return point is ok though). Sure is
 856   // a lot of bother for a deprecated feature...
 857   //
 858   // We don't deliver an async exception if the thread state is
 859   // _thread_in_native_trans so JNI functions won't be called with
 860   // a surprising pending exception. If the thread state is going back to java,
 861   // async exception is checked in check_special_condition_for_native_trans().
 862 
 863   if (state != _thread_blocked_trans &&
 864       state != _thread_in_vm_trans &&
 865       thread->has_special_runtime_exit_condition()) {
 866     thread->handle_special_runtime_exit_condition(
 867       !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
 868   }
 869 
 870   // cross_modify_fence is done by SafepointMechanism::block_if_requested_slow
 871   // which is the only caller here.
 872 }
 873 
 874 // ------------------------------------------------------------------------------------------------------
 875 // Exception handlers
 876 
 877 
 878 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
 879   assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
 880   assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
 881   if (!SafepointMechanism::uses_thread_local_poll()) {
 882     assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
 883   }
 884 
 885   if (log_is_enabled(Info, safepoint, stats)) {
 886     Atomic::inc(&_nof_threads_hit_polling_page);
 887   }
 888 
 889   ThreadSafepointState* state = thread->safepoint_state();
 890 
 891   state->handle_polling_page_exception();
 892 }
 893 
 894 
 895 void SafepointSynchronize::print_safepoint_timeout() {
 896   if (!timeout_error_printed) {
 897     timeout_error_printed = true;
 898     // Print out the thread info which didn't reach the safepoint for debugging
 899     // purposes (useful when there are lots of threads in the debugger).
 900     LogTarget(Warning, safepoint) lt;
 901     if (lt.is_enabled()) {
 902       ResourceMark rm;
 903       LogStream ls(lt);
 904 
 905       ls.cr();
 906       ls.print_cr("# SafepointSynchronize::begin: Timeout detected:");
 907       ls.print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
 908       ls.print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
 909       for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
 910         if (cur_thread->safepoint_state()->is_running()) {
 911           ls.print("# ");
 912           cur_thread->print_on(&ls);
 913           ls.cr();
 914         }
 915       }
 916       ls.print_cr("# SafepointSynchronize::begin: (End of list)");
 917     }
 918   }
 919 
 920   // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
 921   // ShowMessageBoxOnError.
 922   if (AbortVMOnSafepointTimeout) {
 923     // Send the blocking thread a signal to terminate and write an error file.
 924     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
 925       if (cur_thread->safepoint_state()->is_running()) {
 926         if (!os::signal_thread(cur_thread, SIGILL, "blocking a safepoint")) {
 927           break; // Could not send signal. Report fatal error.
 928         }
 929         // Give cur_thread a chance to report the error and terminate the VM.
 930         os::naked_sleep(3000);
 931       }
 932     }
 933     fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
 934           SafepointTimeoutDelay, VMThread::vm_operation()->name());
 935   }
 936 }
 937 
 938 // -------------------------------------------------------------------------------------------------------
 939 // Implementation of ThreadSafepointState
 940 
 941 ThreadSafepointState::ThreadSafepointState(JavaThread *thread)
 942   : _at_poll_safepoint(false), _thread(thread), _safepoint_safe(false),
 943     _safepoint_id(SafepointSynchronize::InactiveSafepointCounter), _next(NULL) {
 944 }
 945 
 946 void ThreadSafepointState::create(JavaThread *thread) {
 947   ThreadSafepointState *state = new ThreadSafepointState(thread);
 948   thread->set_safepoint_state(state);
 949 }
 950 
 951 void ThreadSafepointState::destroy(JavaThread *thread) {
 952   if (thread->safepoint_state()) {
 953     delete(thread->safepoint_state());
 954     thread->set_safepoint_state(NULL);
 955   }
 956 }
 957 
 958 uint64_t ThreadSafepointState::get_safepoint_id() const {
 959   return Atomic::load_acquire(&_safepoint_id);
 960 }
 961 
 962 void ThreadSafepointState::reset_safepoint_id() {
 963   Atomic::release_store(&_safepoint_id, SafepointSynchronize::InactiveSafepointCounter);
 964 }
 965 
 966 void ThreadSafepointState::set_safepoint_id(uint64_t safepoint_id) {
 967   Atomic::release_store(&_safepoint_id, safepoint_id);
 968 }
 969 
 970 void ThreadSafepointState::examine_state_of_thread(uint64_t safepoint_count) {
 971   assert(is_running(), "better be running or just have hit safepoint poll");
 972 
 973   JavaThreadState stable_state;
 974   if (!SafepointSynchronize::try_stable_load_state(&stable_state, _thread, safepoint_count)) {
 975     // We could not get stable state of the JavaThread.
 976     // Consider it running and just return.
 977     return;
 978   }
 979 
 980   // Check for a thread that is suspended. Note that thread resume tries
 981   // to grab the Threads_lock which we own here, so a thread cannot be
 982   // resumed during safepoint synchronization.
 983 
 984   // We check to see if this thread is suspended without locking to
 985   // avoid deadlocking with a third thread that is waiting for this
 986   // thread to be suspended. The third thread can notice the safepoint
 987   // that we're trying to start at the beginning of its SR_lock->wait()
 988   // call. If that happens, then the third thread will block on the
 989   // safepoint while still holding the underlying SR_lock. We won't be
 990   // able to get the SR_lock and we'll deadlock.
 991   //
 992   // We don't need to grab the SR_lock here for two reasons:
 993   // 1) The suspend flags are both volatile and are set with an
 994   //    Atomic::cmpxchg() call so we should see the suspended
 995   //    state right away.
 996   // 2) We're being called from the safepoint polling loop; if
 997   //    we don't see the suspended state on this iteration, then
 998   //    we'll come around again.
 999   //
1000   bool is_suspended = _thread->is_ext_suspended();
1001   if (is_suspended) {
1002     account_safe_thread();
1003     return;
1004   }
1005 
1006   if (safepoint_safe_with(_thread, stable_state)) {
1007     check_for_lazy_critical_native(_thread, stable_state);
1008     account_safe_thread();
1009     return;
1010   }
1011 
1012   // All other thread states will continue to run until they
1013   // transition and self-block in state _blocked
1014   // Safepoint polling in compiled code causes the Java threads to do the same.
1015   // Note: new threads may require a malloc so they must be allowed to finish
1016 
1017   assert(is_running(), "examine_state_of_thread on non-running thread");
1018   return;
1019 }
1020 
1021 void ThreadSafepointState::account_safe_thread() {
1022   SafepointSynchronize::decrement_waiting_to_block();
1023   if (_thread->in_critical()) {
1024     // Notice that this thread is in a critical section
1025     SafepointSynchronize::increment_jni_active_count();
1026   }
1027   DEBUG_ONLY(_thread->set_visited_for_critical_count(SafepointSynchronize::safepoint_counter());)
1028   assert(!_safepoint_safe, "Must be unsafe before safe");
1029   _safepoint_safe = true;
1030 }
1031 
1032 void ThreadSafepointState::restart() {
1033   assert(_safepoint_safe, "Must be safe before unsafe");
1034   _safepoint_safe = false;
1035 }
1036 
1037 void ThreadSafepointState::print_on(outputStream *st) const {
1038   const char *s = _safepoint_safe ? "_at_safepoint" : "_running";
1039 
1040   st->print_cr("Thread: " INTPTR_FORMAT
1041               "  [0x%2x] State: %s _at_poll_safepoint %d",
1042                p2i(_thread), _thread->osthread()->thread_id(), s, _at_poll_safepoint);
1043 
1044   _thread->print_thread_state_on(st);
1045 }
1046 
1047 // ---------------------------------------------------------------------------------------------------------------------
1048 
1049 // Block the thread at poll or poll return for safepoint/handshake.
1050 void ThreadSafepointState::handle_polling_page_exception() {
1051 
1052   // If we're using a global poll, then the thread should not be
1053   // marked as safepoint safe yet.
1054   assert(!SafepointMechanism::uses_global_page_poll() || !_safepoint_safe,
1055          "polling page exception on thread safepoint safe");
1056 
1057   // Step 1: Find the nmethod from the return address
1058   address real_return_addr = thread()->saved_exception_pc();
1059 
1060   CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1061   assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1062   CompiledMethod* nm = (CompiledMethod*)cb;
1063 
1064   // Find frame of caller
1065   frame stub_fr = thread()->last_frame();
1066   CodeBlob* stub_cb = stub_fr.cb();
1067   assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1068   RegisterMap map(thread(), true);
1069   frame caller_fr = stub_fr.sender(&map);
1070 
1071   // Should only be poll_return or poll
1072   assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1073 
1074   // This is a poll immediately before a return. The exception handling code
1075   // has already had the effect of causing the return to occur, so the execution
1076   // will continue immediately after the call. In addition, the oopmap at the
1077   // return point does not mark the return value as an oop (if it is), so
1078   // it needs a handle here to be updated.
1079   if( nm->is_at_poll_return(real_return_addr) ) {
1080     // See if return type is an oop.
1081     bool return_oop = nm->method()->is_returning_oop();
1082     Handle return_value;
1083     if (return_oop) {
1084       // The oop result has been saved on the stack together with all
1085       // the other registers. In order to preserve it over GCs we need
1086       // to keep it in a handle.
1087       oop result = caller_fr.saved_oop_result(&map);
1088       assert(oopDesc::is_oop_or_null(result), "must be oop");
1089       return_value = Handle(thread(), result);
1090       assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1091     }
1092 
1093     // Block the thread
1094     SafepointMechanism::block_if_requested(thread());
1095 
1096     // restore oop result, if any
1097     if (return_oop) {
1098       caller_fr.set_saved_oop_result(&map, return_value());
1099     }
1100   }
1101 
1102   // This is a safepoint poll. Verify the return address and block.
1103   else {
1104     set_at_poll_safepoint(true);
1105 
1106     // verify the blob built the "return address" correctly
1107     assert(real_return_addr == caller_fr.pc(), "must match");
1108 
1109     // Block the thread
1110     SafepointMechanism::block_if_requested(thread());
1111     set_at_poll_safepoint(false);
1112 
1113     // If we have a pending async exception deoptimize the frame
1114     // as otherwise we may never deliver it.
1115     if (thread()->has_async_condition()) {
1116       ThreadInVMfromJavaNoAsyncException __tiv(thread());
1117       Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1118     }
1119 
1120     // If an exception has been installed we must check for a pending deoptimization
1121     // Deoptimize frame if exception has been thrown.
1122 
1123     if (thread()->has_pending_exception() ) {
1124       RegisterMap map(thread(), true);
1125       frame caller_fr = stub_fr.sender(&map);
1126       if (caller_fr.is_deoptimized_frame()) {
1127         // The exception patch will destroy registers that are still
1128         // live and will be needed during deoptimization. Defer the
1129         // Async exception should have deferred the exception until the
1130         // next safepoint which will be detected when we get into
1131         // the interpreter so if we have an exception now things
1132         // are messed up.
1133 
1134         fatal("Exception installed and deoptimization is pending");
1135       }
1136     }
1137   }
1138 }
1139 
1140 
1141 // -------------------------------------------------------------------------------------------------------
1142 // Implementation of SafepointTracing
1143 
1144 jlong SafepointTracing::_last_safepoint_begin_time_ns = 0;
1145 jlong SafepointTracing::_last_safepoint_sync_time_ns = 0;
1146 jlong SafepointTracing::_last_safepoint_cleanup_time_ns = 0;
1147 jlong SafepointTracing::_last_safepoint_end_time_ns = 0;
1148 jlong SafepointTracing::_last_app_time_ns = 0;
1149 int SafepointTracing::_nof_threads = 0;
1150 int SafepointTracing::_nof_running = 0;
1151 int SafepointTracing::_page_trap = 0;
1152 VM_Operation::VMOp_Type SafepointTracing::_current_type;
1153 jlong     SafepointTracing::_max_sync_time = 0;
1154 jlong     SafepointTracing::_max_vmop_time = 0;
1155 uint64_t  SafepointTracing::_op_count[VM_Operation::VMOp_Terminating] = {0};
1156 
1157 void SafepointTracing::init() {
1158   // Application start
1159   _last_safepoint_end_time_ns = os::javaTimeNanos();
1160 }
1161 
1162 // Helper method to print the header.
1163 static void print_header(outputStream* st) {
1164   // The number of spaces is significant here, and should match the format
1165   // specifiers in print_statistics().
1166 
1167   st->print("VM Operation                 "
1168             "[ threads: total initial_running ]"
1169             "[ time:       sync    cleanup       vmop      total ]");
1170 
1171   st->print_cr(" page_trap_count");
1172 }
1173 
1174 // This prints a nice table.  To get the statistics to not shift due to the logging uptime
1175 // decorator, use the option as: -Xlog:safepoint+stats:[outputfile]:none
1176 void SafepointTracing::statistics_log() {
1177   LogTarget(Info, safepoint, stats) lt;
1178   assert (lt.is_enabled(), "should only be called when printing statistics is enabled");
1179   LogStream ls(lt);
1180 
1181   static int _cur_stat_index = 0;
1182 
1183   // Print header every 30 entries
1184   if ((_cur_stat_index % 30) == 0) {
1185     print_header(&ls);
1186     _cur_stat_index = 1;  // wrap
1187   } else {
1188     _cur_stat_index++;
1189   }
1190 
1191   ls.print("%-28s [       "
1192            INT32_FORMAT_W(8) "        " INT32_FORMAT_W(8) " "
1193            "]",
1194            VM_Operation::name(_current_type),
1195            _nof_threads,
1196            _nof_running);
1197   ls.print("[       "
1198            INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " "
1199            INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " ]",
1200            (int64_t)(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns),
1201            (int64_t)(_last_safepoint_cleanup_time_ns - _last_safepoint_sync_time_ns),
1202            (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns),
1203            (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_begin_time_ns));
1204 
1205   ls.print_cr(INT32_FORMAT_W(16), _page_trap);
1206 }
1207 
1208 // This method will be called when VM exits. This tries to summarize the sampling.
1209 // Current thread may already be deleted, so don't use ResourceMark.
1210 void SafepointTracing::statistics_exit_log() {
1211   if (!log_is_enabled(Info, safepoint, stats)) {
1212     return;
1213   }
1214   for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1215     if (_op_count[index] != 0) {
1216       log_info(safepoint, stats)("%-28s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1217                _op_count[index]);
1218     }
1219   }
1220 
1221   log_info(safepoint, stats)("VM operations coalesced during safepoint " INT64_FORMAT,
1222                               VMThread::get_coalesced_count());
1223   log_info(safepoint, stats)("Maximum sync time  " INT64_FORMAT" ns",
1224                               (int64_t)(_max_sync_time));
1225   log_info(safepoint, stats)("Maximum vm operation time (except for Exit VM operation)  "
1226                               INT64_FORMAT " ns",
1227                               (int64_t)(_max_vmop_time));
1228 }
1229 
1230 void SafepointTracing::begin(VM_Operation::VMOp_Type type) {
1231   _op_count[type]++;
1232   _current_type = type;
1233 
1234   // update the time stamp to begin recording safepoint time
1235   _last_safepoint_begin_time_ns = os::javaTimeNanos();
1236   _last_safepoint_sync_time_ns = 0;
1237   _last_safepoint_cleanup_time_ns = 0;
1238 
1239   _last_app_time_ns = _last_safepoint_begin_time_ns - _last_safepoint_end_time_ns;
1240   _last_safepoint_end_time_ns = 0;
1241 
1242   RuntimeService::record_safepoint_begin(_last_app_time_ns);
1243 }
1244 
1245 void SafepointTracing::synchronized(int nof_threads, int nof_running, int traps) {
1246   _last_safepoint_sync_time_ns = os::javaTimeNanos();
1247   _nof_threads = nof_threads;
1248   _nof_running = nof_running;
1249   _page_trap   = traps;
1250   RuntimeService::record_safepoint_synchronized(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns);
1251 }
1252 
1253 void SafepointTracing::cleanup() {
1254   _last_safepoint_cleanup_time_ns = os::javaTimeNanos();
1255 }
1256 
1257 void SafepointTracing::end() {
1258   _last_safepoint_end_time_ns = os::javaTimeNanos();
1259 
1260   if (_max_sync_time < (_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns)) {
1261     _max_sync_time = _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns;
1262   }
1263   if (_max_vmop_time < (_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns)) {
1264     _max_vmop_time = _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns;
1265   }
1266   if (log_is_enabled(Info, safepoint, stats)) {
1267     statistics_log();
1268   }
1269 
1270   log_info(safepoint)(
1271      "Safepoint \"%s\", "
1272      "Time since last: " JLONG_FORMAT " ns, "
1273      "Reaching safepoint: " JLONG_FORMAT " ns, "
1274      "At safepoint: " JLONG_FORMAT " ns, "
1275      "Total: " JLONG_FORMAT " ns",
1276       VM_Operation::name(_current_type),
1277       _last_app_time_ns,
1278       _last_safepoint_cleanup_time_ns - _last_safepoint_begin_time_ns,
1279       _last_safepoint_end_time_ns     - _last_safepoint_cleanup_time_ns,
1280       _last_safepoint_end_time_ns     - _last_safepoint_begin_time_ns
1281      );
1282 
1283   RuntimeService::record_safepoint_end(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns);
1284 }