1 /*
   2  * Copyright (c) 1997, 2020, 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 bool timeout_error_printed = false;
 144 
 145 // Statistic related
 146 static jlong _safepoint_begin_time = 0;
 147 static volatile int _nof_threads_hit_polling_page = 0;
 148 
 149 void SafepointSynchronize::init(Thread* vmthread) {
 150   // WaitBarrier should never be destroyed since we will have
 151   // threads waiting on it while exiting.
 152   _wait_barrier = new WaitBarrier(vmthread);
 153   SafepointTracing::init();
 154 }
 155 
 156 void SafepointSynchronize::increment_jni_active_count() {
 157   assert(Thread::current()->is_VM_thread(), "Only VM thread may increment");
 158   ++_current_jni_active_count;
 159 }
 160 
 161 void SafepointSynchronize::decrement_waiting_to_block() {
 162   assert(_waiting_to_block > 0, "sanity check");
 163   assert(Thread::current()->is_VM_thread(), "Only VM thread may decrement");
 164   --_waiting_to_block;
 165 }
 166 
 167 bool SafepointSynchronize::thread_not_running(ThreadSafepointState *cur_state) {
 168   if (!cur_state->is_running()) {
 169     return true;
 170   }
 171   cur_state->examine_state_of_thread(SafepointSynchronize::safepoint_counter());
 172   if (!cur_state->is_running()) {
 173     return true;
 174   }
 175   LogTarget(Trace, safepoint) lt;
 176   if (lt.is_enabled()) {
 177     ResourceMark rm;
 178     LogStream ls(lt);
 179     cur_state->print_on(&ls);
 180   }
 181   return false;
 182 }
 183 
 184 #ifdef ASSERT
 185 static void assert_list_is_valid(const ThreadSafepointState* tss_head, int still_running) {
 186   int a = 0;
 187   const ThreadSafepointState *tmp_tss = tss_head;
 188   while (tmp_tss != NULL) {
 189     ++a;
 190     assert(tmp_tss->is_running(), "Illegal initial state");
 191     tmp_tss = tmp_tss->get_next();
 192   }
 193   assert(a == still_running, "Must be the same");
 194 }
 195 #endif // ASSERT
 196 
 197 static void back_off(int64_t start_time) {
 198   // We start with fine-grained nanosleeping until a millisecond has
 199   // passed, at which point we resort to plain naked_short_sleep.
 200   if (os::javaTimeNanos() - start_time < NANOSECS_PER_MILLISEC) {
 201     os::naked_short_nanosleep(10 * (NANOUNITS / MICROUNITS));
 202   } else {
 203     os::naked_short_sleep(1);
 204   }
 205 }
 206 
 207 int SafepointSynchronize::synchronize_threads(jlong safepoint_limit_time, int nof_threads, int* initial_running)
 208 {
 209   JavaThreadIteratorWithHandle jtiwh;
 210 
 211 #ifdef ASSERT
 212   for (; JavaThread *cur = jtiwh.next(); ) {
 213     assert(cur->safepoint_state()->is_running(), "Illegal initial state");
 214   }
 215   jtiwh.rewind();
 216 #endif // ASSERT
 217 
 218   // Iterate through all threads until it has been determined how to stop them all at a safepoint.
 219   int still_running = nof_threads;
 220   ThreadSafepointState *tss_head = NULL;
 221   ThreadSafepointState **p_prev = &tss_head;
 222   for (; JavaThread *cur = jtiwh.next(); ) {
 223     ThreadSafepointState *cur_tss = cur->safepoint_state();
 224     assert(cur_tss->get_next() == NULL, "Must be NULL");
 225     if (thread_not_running(cur_tss)) {
 226       --still_running;
 227     } else {
 228       *p_prev = cur_tss;
 229       p_prev = cur_tss->next_ptr();
 230     }
 231   }
 232   *p_prev = NULL;
 233 
 234   DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);)
 235 
 236   *initial_running = still_running;
 237 
 238   // If there is no thread still running, we are already done.
 239   if (still_running <= 0) {
 240     assert(tss_head == NULL, "Must be empty");
 241     return 1;
 242   }
 243 
 244   int iterations = 1; // The first iteration is above.
 245   int64_t start_time = os::javaTimeNanos();
 246 
 247   do {
 248     // Check if this has taken too long:
 249     if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
 250       print_safepoint_timeout();
 251     }
 252 
 253     p_prev = &tss_head;
 254     ThreadSafepointState *cur_tss = tss_head;
 255     while (cur_tss != NULL) {
 256       assert(cur_tss->is_running(), "Illegal initial state");
 257       if (thread_not_running(cur_tss)) {
 258         --still_running;
 259         *p_prev = NULL;
 260         ThreadSafepointState *tmp = cur_tss;
 261         cur_tss = cur_tss->get_next();
 262         tmp->set_next(NULL);
 263       } else {
 264         *p_prev = cur_tss;
 265         p_prev = cur_tss->next_ptr();
 266         cur_tss = cur_tss->get_next();
 267       }
 268     }
 269 
 270     DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);)
 271 
 272     if (still_running > 0) {
 273       back_off(start_time);
 274     }
 275 
 276     iterations++;
 277   } while (still_running > 0);
 278 
 279   assert(tss_head == NULL, "Must be empty");
 280 
 281   return iterations;
 282 }
 283 
 284 void SafepointSynchronize::arm_safepoint() {
 285   // Begin the process of bringing the system to a safepoint.
 286   // Java threads can be in several different states and are
 287   // stopped by different mechanisms:
 288   //
 289   //  1. Running interpreted
 290   //     When executing branching/returning byte codes interpreter
 291   //     checks if the poll is armed, if so blocks in SS::block().
 292   //  2. Running in native code
 293   //     When returning from the native code, a Java thread must check
 294   //     the safepoint _state to see if we must block.  If the
 295   //     VM thread sees a Java thread in native, it does
 296   //     not wait for this thread to block.  The order of the memory
 297   //     writes and reads of both the safepoint state and the Java
 298   //     threads state is critical.  In order to guarantee that the
 299   //     memory writes are serialized with respect to each other,
 300   //     the VM thread issues a memory barrier instruction.
 301   //  3. Running compiled Code
 302   //     Compiled code reads the local polling page that
 303   //     is set to fault if we are trying to get to a safepoint.
 304   //  4. Blocked
 305   //     A thread which is blocked will not be allowed to return from the
 306   //     block condition until the safepoint operation is complete.
 307   //  5. In VM or Transitioning between states
 308   //     If a Java thread is currently running in the VM or transitioning
 309   //     between states, the safepointing code will poll the thread state
 310   //     until the thread blocks itself when it attempts transitions to a
 311   //     new state or locking a safepoint checked monitor.
 312 
 313   // We must never miss a thread with correct safepoint id, so we must make sure we arm
 314   // the wait barrier for the next safepoint id/counter.
 315   // Arming must be done after resetting _current_jni_active_count, _waiting_to_block.
 316   _wait_barrier->arm(static_cast<int>(_safepoint_counter + 1));
 317 
 318   assert((_safepoint_counter & 0x1) == 0, "must be even");
 319   // The store to _safepoint_counter must happen after any stores in arming.
 320   Atomic::release_store(&_safepoint_counter, _safepoint_counter + 1);
 321 
 322   // We are synchronizing
 323   OrderAccess::storestore(); // Ordered with _safepoint_counter
 324   _state = _synchronizing;
 325 
 326   // Arming the per thread poll while having _state != _not_synchronized means safepointing
 327   log_trace(safepoint)("Setting thread local yield flag for threads");
 328   OrderAccess::storestore(); // storestore, global state -> local state
 329   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
 330     // Make sure the threads start polling, it is time to yield.
 331     SafepointMechanism::arm_local_poll(cur);
 332   }
 333 
 334   OrderAccess::fence(); // storestore|storeload, global state -> local state
 335 }
 336 
 337 // Roll all threads forward to a safepoint and suspend them all
 338 void SafepointSynchronize::begin() {
 339   assert(Thread::current()->is_VM_thread(), "Only VM thread may execute a safepoint");
 340 
 341   EventSafepointBegin begin_event;
 342   SafepointTracing::begin(VMThread::vm_op_type());
 343 
 344   Universe::heap()->safepoint_synchronize_begin();
 345 
 346   // By getting the Threads_lock, we assure that no threads are about to start or
 347   // exit. It is released again in SafepointSynchronize::end().
 348   Threads_lock->lock();
 349 
 350   assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
 351 
 352   int nof_threads = Threads::number_of_threads();
 353 
 354   _nof_threads_hit_polling_page = 0;
 355 
 356   log_debug(safepoint)("Safepoint synchronization initiated using %s wait barrier. (%d threads)", _wait_barrier->description(), nof_threads);
 357 
 358   // Reset the count of active JNI critical threads
 359   _current_jni_active_count = 0;
 360 
 361   // Set number of threads to wait for
 362   _waiting_to_block = nof_threads;
 363 
 364   jlong safepoint_limit_time = 0;
 365   if (SafepointTimeout) {
 366     // Set the limit time, so that it can be compared to see if this has taken
 367     // too long to complete.
 368     safepoint_limit_time = SafepointTracing::start_of_safepoint() + (jlong)SafepointTimeoutDelay * (NANOUNITS / MILLIUNITS);
 369     timeout_error_printed = false;
 370   }
 371 
 372   EventSafepointStateSynchronization sync_event;
 373   int initial_running = 0;
 374 
 375   // Arms the safepoint, _current_jni_active_count and _waiting_to_block must be set before.
 376   arm_safepoint();
 377 
 378   // Will spin until all threads are safe.
 379   int iterations = synchronize_threads(safepoint_limit_time, nof_threads, &initial_running);
 380   assert(_waiting_to_block == 0, "No thread should be running");
 381 
 382 #ifndef PRODUCT
 383   if (safepoint_limit_time != 0) {
 384     jlong current_time = os::javaTimeNanos();
 385     if (safepoint_limit_time < current_time) {
 386       log_warning(safepoint)("# SafepointSynchronize: Finished after "
 387                     INT64_FORMAT_W(6) " ms",
 388                     (int64_t)(current_time - SafepointTracing::start_of_safepoint()) / (NANOUNITS / MILLIUNITS));
 389     }
 390   }
 391 #endif
 392 
 393   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 394 
 395   // Record state
 396   _state = _synchronized;
 397 
 398   OrderAccess::fence();
 399 
 400   // Set the new id
 401   ++_safepoint_id;
 402 
 403 #ifdef ASSERT
 404   // Make sure all the threads were visited.
 405   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
 406     assert(cur->was_visited_for_critical_count(_safepoint_counter), "missed a thread");
 407   }
 408 #endif // ASSERT
 409 
 410   // Update the count of active JNI critical regions
 411   GCLocker::set_jni_lock_count(_current_jni_active_count);
 412 
 413   post_safepoint_synchronize_event(sync_event,
 414                                    _safepoint_id,
 415                                    initial_running,
 416                                    _waiting_to_block, iterations);
 417 
 418   SafepointTracing::synchronized(nof_threads, initial_running, _nof_threads_hit_polling_page);
 419 
 420   // We do the safepoint cleanup first since a GC related safepoint
 421   // needs cleanup to be completed before running the GC op.
 422   EventSafepointCleanup cleanup_event;
 423   do_cleanup_tasks();
 424   post_safepoint_cleanup_event(cleanup_event, _safepoint_id);
 425 
 426   post_safepoint_begin_event(begin_event, _safepoint_id, nof_threads, _current_jni_active_count);
 427   SafepointTracing::cleanup();
 428 }
 429 
 430 void SafepointSynchronize::disarm_safepoint() {
 431   uint64_t active_safepoint_counter = _safepoint_counter;
 432   {
 433     JavaThreadIteratorWithHandle jtiwh;
 434 #ifdef ASSERT
 435     // A pending_exception cannot be installed during a safepoint.  The threads
 436     // may install an async exception after they come back from a safepoint into
 437     // pending_exception after they unblock.  But that should happen later.
 438     for (; JavaThread *cur = jtiwh.next(); ) {
 439       assert (!(cur->has_pending_exception() &&
 440                 cur->safepoint_state()->is_at_poll_safepoint()),
 441               "safepoint installed a pending exception");
 442     }
 443 #endif // ASSERT
 444 
 445     OrderAccess::fence(); // keep read and write of _state from floating up
 446     assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
 447 
 448     // Change state first to _not_synchronized.
 449     // No threads should see _synchronized when running.
 450     _state = _not_synchronized;
 451 
 452     // Set the next dormant (even) safepoint id.
 453     assert((_safepoint_counter & 0x1) == 1, "must be odd");
 454     Atomic::release_store(&_safepoint_counter, _safepoint_counter + 1);
 455 
 456     OrderAccess::fence(); // Keep the local state from floating up.
 457 
 458     jtiwh.rewind();
 459     for (; JavaThread *current = jtiwh.next(); ) {
 460       // Clear the visited flag to ensure that the critical counts are collected properly.
 461       DEBUG_ONLY(current->reset_visited_for_critical_count(active_safepoint_counter);)
 462       ThreadSafepointState* cur_state = current->safepoint_state();
 463       assert(!cur_state->is_running(), "Thread not suspended at safepoint");
 464       cur_state->restart(); // TSS _running
 465       assert(cur_state->is_running(), "safepoint state has not been reset");
 466     }
 467   } // ~JavaThreadIteratorWithHandle
 468 
 469   // Release threads lock, so threads can be created/destroyed again.
 470   Threads_lock->unlock();
 471 
 472   // Wake threads after local state is correctly set.
 473   _wait_barrier->disarm();
 474 }
 475 
 476 // Wake up all threads, so they are ready to resume execution after the safepoint
 477 // operation has been carried out
 478 void SafepointSynchronize::end() {
 479   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 480   EventSafepointEnd event;
 481   assert(Thread::current()->is_VM_thread(), "Only VM thread can execute a safepoint");
 482 
 483   disarm_safepoint();
 484 
 485   Universe::heap()->safepoint_synchronize_end();
 486 
 487   SafepointTracing::end();
 488 
 489   post_safepoint_end_event(event, safepoint_id());
 490 }
 491 
 492 bool SafepointSynchronize::is_cleanup_needed() {
 493   // Need a safepoint if some inline cache buffers is non-empty
 494   if (!InlineCacheBuffer::is_empty()) return true;
 495   if (StringTable::needs_rehashing()) return true;
 496   if (SymbolTable::needs_rehashing()) return true;
 497   return false;
 498 }
 499 
 500 class ParallelSPCleanupTask : public AbstractGangTask {
 501 private:
 502   SubTasksDone _subtasks;
 503   uint _num_workers;
 504 public:
 505   ParallelSPCleanupTask(uint num_workers) :
 506     AbstractGangTask("Parallel Safepoint Cleanup"),
 507     _subtasks(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS),
 508     _num_workers(num_workers) {}
 509 
 510   void work(uint worker_id) {
 511     uint64_t safepoint_id = SafepointSynchronize::safepoint_id();
 512 
 513     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
 514       const char* name = "deflating idle monitors";
 515       EventSafepointCleanupTask event;
 516       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 517       ObjectSynchronizer::do_safepoint_work();
 518 
 519       post_safepoint_cleanup_task_event(event, safepoint_id, name);
 520     }
 521 
 522     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
 523       const char* name = "updating inline caches";
 524       EventSafepointCleanupTask event;
 525       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 526       InlineCacheBuffer::update_inline_caches();
 527 
 528       post_safepoint_cleanup_task_event(event, safepoint_id, name);
 529     }
 530 
 531     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
 532       const char* name = "compilation policy safepoint handler";
 533       EventSafepointCleanupTask event;
 534       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 535       CompilationPolicy::policy()->do_safepoint_work();
 536 
 537       post_safepoint_cleanup_task_event(event, safepoint_id, name);
 538     }
 539 
 540     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
 541       if (SymbolTable::needs_rehashing()) {
 542         const char* name = "rehashing symbol table";
 543         EventSafepointCleanupTask event;
 544         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 545         SymbolTable::rehash_table();
 546 
 547         post_safepoint_cleanup_task_event(event, safepoint_id, name);
 548       }
 549     }
 550 
 551     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
 552       if (StringTable::needs_rehashing()) {
 553         const char* name = "rehashing string table";
 554         EventSafepointCleanupTask event;
 555         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 556         StringTable::rehash_table();
 557 
 558         post_safepoint_cleanup_task_event(event, safepoint_id, name);
 559       }
 560     }
 561 
 562     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
 563       if (Dictionary::does_any_dictionary_needs_resizing()) {
 564         const char* name = "resizing system dictionaries";
 565         EventSafepointCleanupTask event;
 566         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 567         ClassLoaderDataGraph::resize_dictionaries();
 568 
 569         post_safepoint_cleanup_task_event(event, safepoint_id, name);
 570       }
 571     }
 572 
 573     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_REQUEST_OOPSTORAGE_CLEANUP)) {
 574       // Don't bother reporting event or time for this very short operation.
 575       // To have any utility we'd also want to report whether needed.
 576       OopStorage::trigger_cleanup_if_needed();
 577     }
 578 
 579     _subtasks.all_tasks_completed(_num_workers);
 580   }
 581 };
 582 
 583 // Various cleaning tasks that should be done periodically at safepoints.
 584 void SafepointSynchronize::do_cleanup_tasks() {
 585 
 586   TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
 587 
 588   CollectedHeap* heap = Universe::heap();
 589   assert(heap != NULL, "heap not initialized yet?");
 590   WorkGang* cleanup_workers = heap->safepoint_workers();
 591   if (cleanup_workers != NULL) {
 592     // Parallel cleanup using GC provided thread pool.
 593     uint num_cleanup_workers = cleanup_workers->active_workers();
 594     ParallelSPCleanupTask cleanup(num_cleanup_workers);
 595     cleanup_workers->run_task(&cleanup);
 596   } else {
 597     // Serial cleanup using VMThread.
 598     ParallelSPCleanupTask cleanup(1);
 599     cleanup.work(0);
 600   }
 601 
 602   // Needs to be done single threaded by the VMThread.  This walks
 603   // the thread stacks looking for references to metadata before
 604   // deciding to remove it from the metaspaces.
 605   if (ClassLoaderDataGraph::should_clean_metaspaces_and_reset()) {
 606     const char* name = "cleanup live ClassLoaderData metaspaces";
 607     TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 608     ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces();
 609   }
 610 
 611   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
 612 }
 613 
 614 // Methods for determining if a JavaThread is safepoint safe.
 615 
 616 // False means unsafe with undetermined state.
 617 // True means a determined state, but it may be an unsafe state.
 618 // If called from a non-safepoint context safepoint_count MUST be InactiveSafepointCounter.
 619 bool SafepointSynchronize::try_stable_load_state(JavaThreadState *state, JavaThread *thread, uint64_t safepoint_count) {
 620   assert((safepoint_count != InactiveSafepointCounter &&
 621           Thread::current() == (Thread*)VMThread::vm_thread() &&
 622           SafepointSynchronize::_state != _not_synchronized)
 623          || safepoint_count == InactiveSafepointCounter, "Invalid check");
 624 
 625   // To handle the thread_blocked state on the backedge of the WaitBarrier from
 626   // previous safepoint and reading the reset value (0/InactiveSafepointCounter) we
 627   // re-read state after we read thread safepoint id. The JavaThread changes its
 628   // thread state from thread_blocked before resetting safepoint id to 0.
 629   // This guarantees the second read will be from an updated thread state. It can
 630   // either be different state making this an unsafe state or it can see blocked
 631   // again. When we see blocked twice with a 0 safepoint id, either:
 632   // - It is normally blocked, e.g. on Mutex, TBIVM.
 633   // - It was in SS:block(), looped around to SS:block() and is blocked on the WaitBarrier.
 634   // - It was in SS:block() but now on a Mutex.
 635   // All of these cases are safe.
 636 
 637   *state = thread->thread_state();
 638   OrderAccess::loadload();
 639   uint64_t sid = thread->safepoint_state()->get_safepoint_id();  // Load acquire
 640   if (sid != InactiveSafepointCounter && sid != safepoint_count) {
 641     // In an old safepoint, state not relevant.
 642     return false;
 643   }
 644   return *state == thread->thread_state();
 645 }
 646 
 647 static bool safepoint_safe_with(JavaThread *thread, JavaThreadState state) {
 648   switch(state) {
 649   case _thread_in_native:
 650     // native threads are safe if they have no java stack or have walkable stack
 651     return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
 652 
 653   case _thread_blocked:
 654     // On wait_barrier or blocked.
 655     // Blocked threads should already have walkable stack.
 656     assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
 657     return true;
 658 
 659   default:
 660     return false;
 661   }
 662 }
 663 
 664 bool SafepointSynchronize::handshake_safe(JavaThread *thread) {
 665   if (thread->is_ext_suspended() || thread->is_terminated()) {
 666     return true;
 667   }
 668   JavaThreadState stable_state;
 669   if (try_stable_load_state(&stable_state, thread, InactiveSafepointCounter)) {
 670     return safepoint_safe_with(thread, stable_state);
 671   }
 672   return false;
 673 }
 674 
 675 // See if the thread is running inside a lazy critical native and
 676 // update the thread critical count if so.  Also set a suspend flag to
 677 // cause the native wrapper to return into the JVM to do the unlock
 678 // once the native finishes.
 679 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
 680   if (state == _thread_in_native &&
 681       thread->has_last_Java_frame() &&
 682       thread->frame_anchor()->walkable()) {
 683     // This thread might be in a critical native nmethod so look at
 684     // the top of the stack and increment the critical count if it
 685     // is.
 686     frame wrapper_frame = thread->last_frame();
 687     CodeBlob* stub_cb = wrapper_frame.cb();
 688     if (stub_cb != NULL &&
 689         stub_cb->is_nmethod() &&
 690         stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
 691       // A thread could potentially be in a critical native across
 692       // more than one safepoint, so only update the critical state on
 693       // the first one.  When it returns it will perform the unlock.
 694       if (!thread->do_critical_native_unlock()) {
 695 #ifdef ASSERT
 696         if (!thread->in_critical()) {
 697           GCLocker::increment_debug_jni_lock_count();
 698         }
 699 #endif
 700         thread->enter_critical();
 701         // Make sure the native wrapper calls back on return to
 702         // perform the needed critical unlock.
 703         thread->set_critical_native_unlock();
 704       }
 705     }
 706   }
 707 }
 708 
 709 // -------------------------------------------------------------------------------------------------------
 710 // Implementation of Safepoint blocking point
 711 
 712 void SafepointSynchronize::block(JavaThread *thread) {
 713   assert(thread != NULL, "thread must be set");
 714   assert(thread->is_Java_thread(), "not a Java thread");
 715 
 716   // Threads shouldn't block if they are in the middle of printing, but...
 717   ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
 718 
 719   // Only bail from the block() call if the thread is gone from the
 720   // thread list; starting to exit should still block.
 721   if (thread->is_terminated()) {
 722      // block current thread if we come here from native code when VM is gone
 723      thread->block_if_vm_exited();
 724 
 725      // otherwise do nothing
 726      return;
 727   }
 728 
 729   JavaThreadState state = thread->thread_state();
 730   thread->frame_anchor()->make_walkable(thread);
 731 
 732   uint64_t safepoint_id = SafepointSynchronize::safepoint_counter();
 733   // Check that we have a valid thread_state at this point
 734   switch(state) {
 735     case _thread_in_vm_trans:
 736     case _thread_in_Java:        // From compiled code
 737     case _thread_in_native_trans:
 738     case _thread_blocked_trans:
 739     case _thread_new_trans:
 740 
 741       // We have no idea where the VMThread is, it might even be at next safepoint.
 742       // So we can miss this poll, but stop at next.
 743 
 744       // Load dependent store, it must not pass loading of safepoint_id.
 745       thread->safepoint_state()->set_safepoint_id(safepoint_id); // Release store
 746 
 747       // This part we can skip if we notice we miss or are in a future safepoint.
 748       OrderAccess::storestore();
 749       // Load in wait barrier should not float up
 750       thread->set_thread_state_fence(_thread_blocked);
 751 
 752       _wait_barrier->wait(static_cast<int>(safepoint_id));
 753       assert(_state != _synchronized, "Can't be");
 754 
 755       // If barrier is disarmed stop store from floating above loads in barrier.
 756       OrderAccess::loadstore();
 757       thread->set_thread_state(state);
 758 
 759       // Then we reset the safepoint id to inactive.
 760       thread->safepoint_state()->reset_safepoint_id(); // Release store
 761 
 762       OrderAccess::fence();
 763 
 764       break;
 765 
 766     default:
 767      fatal("Illegal threadstate encountered: %d", state);
 768   }
 769   guarantee(thread->safepoint_state()->get_safepoint_id() == InactiveSafepointCounter,
 770             "The safepoint id should be set only in block path");
 771 
 772   // Check for pending. async. exceptions or suspends - except if the
 773   // thread was blocked inside the VM. has_special_runtime_exit_condition()
 774   // is called last since it grabs a lock and we only want to do that when
 775   // we must.
 776   //
 777   // Note: we never deliver an async exception at a polling point as the
 778   // compiler may not have an exception handler for it. The polling
 779   // code will notice the async and deoptimize and the exception will
 780   // be delivered. (Polling at a return point is ok though). Sure is
 781   // a lot of bother for a deprecated feature...
 782   //
 783   // We don't deliver an async exception if the thread state is
 784   // _thread_in_native_trans so JNI functions won't be called with
 785   // a surprising pending exception. If the thread state is going back to java,
 786   // async exception is checked in check_special_condition_for_native_trans().
 787 
 788   if (state != _thread_blocked_trans &&
 789       state != _thread_in_vm_trans &&
 790       thread->has_special_runtime_exit_condition()) {
 791     thread->handle_special_runtime_exit_condition(
 792       !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
 793   }
 794 
 795   // cross_modify_fence is done by SafepointMechanism::block_if_requested_slow
 796   // which is the only caller here.
 797 }
 798 
 799 // ------------------------------------------------------------------------------------------------------
 800 // Exception handlers
 801 
 802 
 803 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
 804   assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
 805   assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
 806 
 807   if (log_is_enabled(Info, safepoint, stats)) {
 808     Atomic::inc(&_nof_threads_hit_polling_page);
 809   }
 810 
 811   ThreadSafepointState* state = thread->safepoint_state();
 812 
 813   state->handle_polling_page_exception();
 814 }
 815 
 816 
 817 void SafepointSynchronize::print_safepoint_timeout() {
 818   if (!timeout_error_printed) {
 819     timeout_error_printed = true;
 820     // Print out the thread info which didn't reach the safepoint for debugging
 821     // purposes (useful when there are lots of threads in the debugger).
 822     LogTarget(Warning, safepoint) lt;
 823     if (lt.is_enabled()) {
 824       ResourceMark rm;
 825       LogStream ls(lt);
 826 
 827       ls.cr();
 828       ls.print_cr("# SafepointSynchronize::begin: Timeout detected:");
 829       ls.print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
 830       ls.print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
 831       for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
 832         if (cur_thread->safepoint_state()->is_running()) {
 833           ls.print("# ");
 834           cur_thread->print_on(&ls);
 835           ls.cr();
 836         }
 837       }
 838       ls.print_cr("# SafepointSynchronize::begin: (End of list)");
 839     }
 840   }
 841 
 842   // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
 843   // ShowMessageBoxOnError.
 844   if (AbortVMOnSafepointTimeout) {
 845     // Send the blocking thread a signal to terminate and write an error file.
 846     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
 847       if (cur_thread->safepoint_state()->is_running()) {
 848         if (!os::signal_thread(cur_thread, SIGILL, "blocking a safepoint")) {
 849           break; // Could not send signal. Report fatal error.
 850         }
 851         // Give cur_thread a chance to report the error and terminate the VM.
 852         os::naked_sleep(3000);
 853       }
 854     }
 855     fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
 856           SafepointTimeoutDelay, VMThread::vm_operation()->name());
 857   }
 858 }
 859 
 860 // -------------------------------------------------------------------------------------------------------
 861 // Implementation of ThreadSafepointState
 862 
 863 ThreadSafepointState::ThreadSafepointState(JavaThread *thread)
 864   : _at_poll_safepoint(false), _thread(thread), _safepoint_safe(false),
 865     _safepoint_id(SafepointSynchronize::InactiveSafepointCounter), _next(NULL) {
 866 }
 867 
 868 void ThreadSafepointState::create(JavaThread *thread) {
 869   ThreadSafepointState *state = new ThreadSafepointState(thread);
 870   thread->set_safepoint_state(state);
 871 }
 872 
 873 void ThreadSafepointState::destroy(JavaThread *thread) {
 874   if (thread->safepoint_state()) {
 875     delete(thread->safepoint_state());
 876     thread->set_safepoint_state(NULL);
 877   }
 878 }
 879 
 880 uint64_t ThreadSafepointState::get_safepoint_id() const {
 881   return Atomic::load_acquire(&_safepoint_id);
 882 }
 883 
 884 void ThreadSafepointState::reset_safepoint_id() {
 885   Atomic::release_store(&_safepoint_id, SafepointSynchronize::InactiveSafepointCounter);
 886 }
 887 
 888 void ThreadSafepointState::set_safepoint_id(uint64_t safepoint_id) {
 889   Atomic::release_store(&_safepoint_id, safepoint_id);
 890 }
 891 
 892 void ThreadSafepointState::examine_state_of_thread(uint64_t safepoint_count) {
 893   assert(is_running(), "better be running or just have hit safepoint poll");
 894 
 895   JavaThreadState stable_state;
 896   if (!SafepointSynchronize::try_stable_load_state(&stable_state, _thread, safepoint_count)) {
 897     // We could not get stable state of the JavaThread.
 898     // Consider it running and just return.
 899     return;
 900   }
 901 
 902   // Check for a thread that is suspended. Note that thread resume tries
 903   // to grab the Threads_lock which we own here, so a thread cannot be
 904   // resumed during safepoint synchronization.
 905 
 906   // We check to see if this thread is suspended without locking to
 907   // avoid deadlocking with a third thread that is waiting for this
 908   // thread to be suspended. The third thread can notice the safepoint
 909   // that we're trying to start at the beginning of its SR_lock->wait()
 910   // call. If that happens, then the third thread will block on the
 911   // safepoint while still holding the underlying SR_lock. We won't be
 912   // able to get the SR_lock and we'll deadlock.
 913   //
 914   // We don't need to grab the SR_lock here for two reasons:
 915   // 1) The suspend flags are both volatile and are set with an
 916   //    Atomic::cmpxchg() call so we should see the suspended
 917   //    state right away.
 918   // 2) We're being called from the safepoint polling loop; if
 919   //    we don't see the suspended state on this iteration, then
 920   //    we'll come around again.
 921   //
 922   bool is_suspended = _thread->is_ext_suspended();
 923   if (is_suspended) {
 924     account_safe_thread();
 925     return;
 926   }
 927 
 928   if (safepoint_safe_with(_thread, stable_state)) {
 929     check_for_lazy_critical_native(_thread, stable_state);
 930     account_safe_thread();
 931     return;
 932   }
 933 
 934   // All other thread states will continue to run until they
 935   // transition and self-block in state _blocked
 936   // Safepoint polling in compiled code causes the Java threads to do the same.
 937   // Note: new threads may require a malloc so they must be allowed to finish
 938 
 939   assert(is_running(), "examine_state_of_thread on non-running thread");
 940   return;
 941 }
 942 
 943 void ThreadSafepointState::account_safe_thread() {
 944   SafepointSynchronize::decrement_waiting_to_block();
 945   if (_thread->in_critical()) {
 946     // Notice that this thread is in a critical section
 947     SafepointSynchronize::increment_jni_active_count();
 948   }
 949   DEBUG_ONLY(_thread->set_visited_for_critical_count(SafepointSynchronize::safepoint_counter());)
 950   assert(!_safepoint_safe, "Must be unsafe before safe");
 951   _safepoint_safe = true;
 952 }
 953 
 954 void ThreadSafepointState::restart() {
 955   assert(_safepoint_safe, "Must be safe before unsafe");
 956   _safepoint_safe = false;
 957 }
 958 
 959 void ThreadSafepointState::print_on(outputStream *st) const {
 960   const char *s = _safepoint_safe ? "_at_safepoint" : "_running";
 961 
 962   st->print_cr("Thread: " INTPTR_FORMAT
 963               "  [0x%2x] State: %s _at_poll_safepoint %d",
 964                p2i(_thread), _thread->osthread()->thread_id(), s, _at_poll_safepoint);
 965 
 966   _thread->print_thread_state_on(st);
 967 }
 968 
 969 // ---------------------------------------------------------------------------------------------------------------------
 970 
 971 // Block the thread at poll or poll return for safepoint/handshake.
 972 void ThreadSafepointState::handle_polling_page_exception() {
 973 
 974   // Step 1: Find the nmethod from the return address
 975   address real_return_addr = thread()->saved_exception_pc();
 976 
 977   CodeBlob *cb = CodeCache::find_blob(real_return_addr);
 978   assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
 979   CompiledMethod* nm = (CompiledMethod*)cb;
 980 
 981   // Find frame of caller
 982   frame stub_fr = thread()->last_frame();
 983   CodeBlob* stub_cb = stub_fr.cb();
 984   assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
 985   RegisterMap map(thread(), true);
 986   frame caller_fr = stub_fr.sender(&map);
 987 
 988   // Should only be poll_return or poll
 989   assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
 990 
 991   // This is a poll immediately before a return. The exception handling code
 992   // has already had the effect of causing the return to occur, so the execution
 993   // will continue immediately after the call. In addition, the oopmap at the
 994   // return point does not mark the return value as an oop (if it is), so
 995   // it needs a handle here to be updated.
 996   if( nm->is_at_poll_return(real_return_addr) ) {
 997     // See if return type is an oop.
 998     bool return_oop = nm->method()->is_returning_oop();
 999     Handle return_value;
1000     if (return_oop) {
1001       // The oop result has been saved on the stack together with all
1002       // the other registers. In order to preserve it over GCs we need
1003       // to keep it in a handle.
1004       oop result = caller_fr.saved_oop_result(&map);
1005       assert(oopDesc::is_oop_or_null(result), "must be oop");
1006       return_value = Handle(thread(), result);
1007       assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1008     }
1009 
1010     // Block the thread
1011     SafepointMechanism::block_if_requested(thread());
1012 
1013     // restore oop result, if any
1014     if (return_oop) {
1015       caller_fr.set_saved_oop_result(&map, return_value());
1016     }
1017   }
1018 
1019   // This is a safepoint poll. Verify the return address and block.
1020   else {
1021     set_at_poll_safepoint(true);
1022 
1023     // verify the blob built the "return address" correctly
1024     assert(real_return_addr == caller_fr.pc(), "must match");
1025 
1026     // Block the thread
1027     SafepointMechanism::block_if_requested(thread());
1028     set_at_poll_safepoint(false);
1029 
1030     // If we have a pending async exception deoptimize the frame
1031     // as otherwise we may never deliver it.
1032     if (thread()->has_async_condition()) {
1033       ThreadInVMfromJavaNoAsyncException __tiv(thread());
1034       Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1035     }
1036 
1037     // If an exception has been installed we must check for a pending deoptimization
1038     // Deoptimize frame if exception has been thrown.
1039 
1040     if (thread()->has_pending_exception() ) {
1041       RegisterMap map(thread(), true);
1042       frame caller_fr = stub_fr.sender(&map);
1043       if (caller_fr.is_deoptimized_frame()) {
1044         // The exception patch will destroy registers that are still
1045         // live and will be needed during deoptimization. Defer the
1046         // Async exception should have deferred the exception until the
1047         // next safepoint which will be detected when we get into
1048         // the interpreter so if we have an exception now things
1049         // are messed up.
1050 
1051         fatal("Exception installed and deoptimization is pending");
1052       }
1053     }
1054   }
1055 }
1056 
1057 
1058 // -------------------------------------------------------------------------------------------------------
1059 // Implementation of SafepointTracing
1060 
1061 jlong SafepointTracing::_last_safepoint_begin_time_ns = 0;
1062 jlong SafepointTracing::_last_safepoint_sync_time_ns = 0;
1063 jlong SafepointTracing::_last_safepoint_cleanup_time_ns = 0;
1064 jlong SafepointTracing::_last_safepoint_end_time_ns = 0;
1065 jlong SafepointTracing::_last_app_time_ns = 0;
1066 int SafepointTracing::_nof_threads = 0;
1067 int SafepointTracing::_nof_running = 0;
1068 int SafepointTracing::_page_trap = 0;
1069 VM_Operation::VMOp_Type SafepointTracing::_current_type;
1070 jlong     SafepointTracing::_max_sync_time = 0;
1071 jlong     SafepointTracing::_max_vmop_time = 0;
1072 uint64_t  SafepointTracing::_op_count[VM_Operation::VMOp_Terminating] = {0};
1073 
1074 void SafepointTracing::init() {
1075   // Application start
1076   _last_safepoint_end_time_ns = os::javaTimeNanos();
1077 }
1078 
1079 // Helper method to print the header.
1080 static void print_header(outputStream* st) {
1081   // The number of spaces is significant here, and should match the format
1082   // specifiers in print_statistics().
1083 
1084   st->print("VM Operation                 "
1085             "[ threads: total initial_running ]"
1086             "[ time:       sync    cleanup       vmop      total ]");
1087 
1088   st->print_cr(" page_trap_count");
1089 }
1090 
1091 // This prints a nice table.  To get the statistics to not shift due to the logging uptime
1092 // decorator, use the option as: -Xlog:safepoint+stats:[outputfile]:none
1093 void SafepointTracing::statistics_log() {
1094   LogTarget(Info, safepoint, stats) lt;
1095   assert (lt.is_enabled(), "should only be called when printing statistics is enabled");
1096   LogStream ls(lt);
1097 
1098   static int _cur_stat_index = 0;
1099 
1100   // Print header every 30 entries
1101   if ((_cur_stat_index % 30) == 0) {
1102     print_header(&ls);
1103     _cur_stat_index = 1;  // wrap
1104   } else {
1105     _cur_stat_index++;
1106   }
1107 
1108   ls.print("%-28s [       "
1109            INT32_FORMAT_W(8) "        " INT32_FORMAT_W(8) " "
1110            "]",
1111            VM_Operation::name(_current_type),
1112            _nof_threads,
1113            _nof_running);
1114   ls.print("[       "
1115            INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " "
1116            INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " ]",
1117            (int64_t)(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns),
1118            (int64_t)(_last_safepoint_cleanup_time_ns - _last_safepoint_sync_time_ns),
1119            (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns),
1120            (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_begin_time_ns));
1121 
1122   ls.print_cr(INT32_FORMAT_W(16), _page_trap);
1123 }
1124 
1125 // This method will be called when VM exits. This tries to summarize the sampling.
1126 // Current thread may already be deleted, so don't use ResourceMark.
1127 void SafepointTracing::statistics_exit_log() {
1128   if (!log_is_enabled(Info, safepoint, stats)) {
1129     return;
1130   }
1131   for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1132     if (_op_count[index] != 0) {
1133       log_info(safepoint, stats)("%-28s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1134                _op_count[index]);
1135     }
1136   }
1137 
1138   log_info(safepoint, stats)("Maximum sync time  " INT64_FORMAT" ns",
1139                               (int64_t)(_max_sync_time));
1140   log_info(safepoint, stats)("Maximum vm operation time (except for Exit VM operation)  "
1141                               INT64_FORMAT " ns",
1142                               (int64_t)(_max_vmop_time));
1143 }
1144 
1145 void SafepointTracing::begin(VM_Operation::VMOp_Type type) {
1146   _op_count[type]++;
1147   _current_type = type;
1148 
1149   // update the time stamp to begin recording safepoint time
1150   _last_safepoint_begin_time_ns = os::javaTimeNanos();
1151   _last_safepoint_sync_time_ns = 0;
1152   _last_safepoint_cleanup_time_ns = 0;
1153 
1154   _last_app_time_ns = _last_safepoint_begin_time_ns - _last_safepoint_end_time_ns;
1155   _last_safepoint_end_time_ns = 0;
1156 
1157   RuntimeService::record_safepoint_begin(_last_app_time_ns);
1158 }
1159 
1160 void SafepointTracing::synchronized(int nof_threads, int nof_running, int traps) {
1161   _last_safepoint_sync_time_ns = os::javaTimeNanos();
1162   _nof_threads = nof_threads;
1163   _nof_running = nof_running;
1164   _page_trap   = traps;
1165   RuntimeService::record_safepoint_synchronized(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns);
1166 }
1167 
1168 void SafepointTracing::cleanup() {
1169   _last_safepoint_cleanup_time_ns = os::javaTimeNanos();
1170 }
1171 
1172 void SafepointTracing::end() {
1173   _last_safepoint_end_time_ns = os::javaTimeNanos();
1174 
1175   if (_max_sync_time < (_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns)) {
1176     _max_sync_time = _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns;
1177   }
1178   if (_max_vmop_time < (_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns)) {
1179     _max_vmop_time = _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns;
1180   }
1181   if (log_is_enabled(Info, safepoint, stats)) {
1182     statistics_log();
1183   }
1184 
1185   log_info(safepoint)(
1186      "Safepoint \"%s\", "
1187      "Time since last: " JLONG_FORMAT " ns, "
1188      "Reaching safepoint: " JLONG_FORMAT " ns, "
1189      "At safepoint: " JLONG_FORMAT " ns, "
1190      "Total: " JLONG_FORMAT " ns",
1191       VM_Operation::name(_current_type),
1192       _last_app_time_ns,
1193       _last_safepoint_cleanup_time_ns - _last_safepoint_begin_time_ns,
1194       _last_safepoint_end_time_ns     - _last_safepoint_cleanup_time_ns,
1195       _last_safepoint_end_time_ns     - _last_safepoint_begin_time_ns
1196      );
1197 
1198   RuntimeService::record_safepoint_end(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns);
1199 }