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 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 cleanup safepoint if there are too many monitors in use
 527   // and the monitor deflation needs to be done at a safepoint.
 528   if (ObjectSynchronizer::is_safepoint_deflation_needed()) return true;
 529   // Need a safepoint if some inline cache buffers is non-empty
 530   if (!InlineCacheBuffer::is_empty()) return true;
 531   if (StringTable::needs_rehashing()) return true;
 532   if (SymbolTable::needs_rehashing()) return true;
 533   return false;
 534 }
 535 
 536 bool SafepointSynchronize::is_forced_cleanup_needed() {
 537   return ObjectSynchronizer::needs_monitor_scavenge();
 538 }
 539 
 540 class ParallelSPCleanupThreadClosure : public ThreadClosure {
 541 private:
 542   CodeBlobClosure* _nmethod_cl;
 543   DeflateMonitorCounters* _counters;
 544 
 545 public:
 546   ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
 547     _nmethod_cl(UseCodeAging ? NMethodSweeper::prepare_reset_hotness_counters() : NULL),
 548     _counters(counters) {}
 549 
 550   void do_thread(Thread* thread) {
 551     // deflate_thread_local_monitors() handles or requests deflation of
 552     // this thread's idle monitors. If !AsyncDeflateIdleMonitors or if
 553     // there is a special cleanup request, deflation is handled now.
 554     // Otherwise, async deflation is requested via a flag.
 555     ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
 556     if (_nmethod_cl != NULL && thread->is_Java_thread() &&
 557         ! thread->is_Code_cache_sweeper_thread()) {
 558       JavaThread* jt = (JavaThread*) thread;
 559       jt->nmethods_do(_nmethod_cl);
 560     }
 561   }
 562 };
 563 
 564 class ParallelSPCleanupTask : public AbstractGangTask {
 565 private:
 566   SubTasksDone _subtasks;
 567   ParallelSPCleanupThreadClosure _cleanup_threads_cl;
 568   uint _num_workers;
 569   DeflateMonitorCounters* _counters;
 570 public:
 571   ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
 572     AbstractGangTask("Parallel Safepoint Cleanup"),
 573     _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
 574     _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
 575     _num_workers(num_workers),
 576     _counters(counters) {}
 577 
 578   void work(uint worker_id) {
 579     uint64_t safepoint_id = SafepointSynchronize::safepoint_id();
 580     // All threads deflate monitors and mark nmethods (if necessary).
 581     Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
 582 
 583     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
 584       const char* name = "deflating global idle monitors";
 585       EventSafepointCleanupTask event;
 586       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 587       // AsyncDeflateIdleMonitors only uses DeflateMonitorCounters
 588       // when a special cleanup has been requested.
 589       // Note: This logging output will include global idle monitor
 590       // elapsed times, but not global idle monitor deflation count.
 591       ObjectSynchronizer::do_safepoint_work(_counters);
 592 
 593       post_safepoint_cleanup_task_event(event, safepoint_id, name);
 594     }
 595 
 596     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
 597       const char* name = "updating inline caches";
 598       EventSafepointCleanupTask event;
 599       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 600       InlineCacheBuffer::update_inline_caches();
 601 
 602       post_safepoint_cleanup_task_event(event, safepoint_id, name);
 603     }
 604 
 605     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
 606       const char* name = "compilation policy safepoint handler";
 607       EventSafepointCleanupTask event;
 608       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 609       CompilationPolicy::policy()->do_safepoint_work();
 610 
 611       post_safepoint_cleanup_task_event(event, safepoint_id, name);
 612     }
 613 
 614     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
 615       if (SymbolTable::needs_rehashing()) {
 616         const char* name = "rehashing symbol table";
 617         EventSafepointCleanupTask event;
 618         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 619         SymbolTable::rehash_table();
 620 
 621         post_safepoint_cleanup_task_event(event, safepoint_id, name);
 622       }
 623     }
 624 
 625     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
 626       if (StringTable::needs_rehashing()) {
 627         const char* name = "rehashing string table";
 628         EventSafepointCleanupTask event;
 629         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 630         StringTable::rehash_table();
 631 
 632         post_safepoint_cleanup_task_event(event, safepoint_id, name);
 633       }
 634     }
 635 
 636     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
 637       if (Dictionary::does_any_dictionary_needs_resizing()) {
 638         const char* name = "resizing system dictionaries";
 639         EventSafepointCleanupTask event;
 640         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 641         ClassLoaderDataGraph::resize_dictionaries();
 642 
 643         post_safepoint_cleanup_task_event(event, safepoint_id, name);
 644       }
 645     }
 646 
 647     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_REQUEST_OOPSTORAGE_CLEANUP)) {
 648       // Don't bother reporting event or time for this very short operation.
 649       // To have any utility we'd also want to report whether needed.
 650       OopStorage::trigger_cleanup_if_needed();
 651     }
 652 
 653     _subtasks.all_tasks_completed(_num_workers);
 654   }
 655 };
 656 
 657 // Various cleaning tasks that should be done periodically at safepoints.
 658 void SafepointSynchronize::do_cleanup_tasks() {
 659 
 660   TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
 661 
 662   // Prepare for monitor deflation.
 663   DeflateMonitorCounters deflate_counters;
 664   ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
 665 
 666   CollectedHeap* heap = Universe::heap();
 667   assert(heap != NULL, "heap not initialized yet?");
 668   WorkGang* cleanup_workers = heap->get_safepoint_workers();
 669   if (cleanup_workers != NULL) {
 670     // Parallel cleanup using GC provided thread pool.
 671     uint num_cleanup_workers = cleanup_workers->active_workers();
 672     ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
 673     StrongRootsScope srs(num_cleanup_workers);
 674     cleanup_workers->run_task(&cleanup);
 675   } else {
 676     // Serial cleanup using VMThread.
 677     ParallelSPCleanupTask cleanup(1, &deflate_counters);
 678     StrongRootsScope srs(1);
 679     cleanup.work(0);
 680   }
 681 
 682   // Needs to be done single threaded by the VMThread.  This walks
 683   // the thread stacks looking for references to metadata before
 684   // deciding to remove it from the metaspaces.
 685   if (ClassLoaderDataGraph::should_clean_metaspaces_and_reset()) {
 686     const char* name = "cleanup live ClassLoaderData metaspaces";
 687     TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 688     ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces();
 689   }
 690 
 691   // Finish monitor deflation.
 692   ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
 693 
 694   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
 695 }
 696 
 697 // Methods for determining if a JavaThread is safepoint safe.
 698 
 699 // False means unsafe with undetermined state.
 700 // True means a determined state, but it may be an unsafe state.
 701 // If called from a non-safepoint context safepoint_count MUST be InactiveSafepointCounter.
 702 bool SafepointSynchronize::try_stable_load_state(JavaThreadState *state, JavaThread *thread, uint64_t safepoint_count) {
 703   assert((safepoint_count != InactiveSafepointCounter &&
 704           Thread::current() == (Thread*)VMThread::vm_thread() &&
 705           SafepointSynchronize::_state != _not_synchronized)
 706          || safepoint_count == InactiveSafepointCounter, "Invalid check");
 707 
 708   // To handle the thread_blocked state on the backedge of the WaitBarrier from
 709   // previous safepoint and reading the reset value (0/InactiveSafepointCounter) we
 710   // re-read state after we read thread safepoint id. The JavaThread changes its
 711   // thread state from thread_blocked before resetting safepoint id to 0.
 712   // This guarantees the second read will be from an updated thread state. It can
 713   // either be different state making this an unsafe state or it can see blocked
 714   // again. When we see blocked twice with a 0 safepoint id, either:
 715   // - It is normally blocked, e.g. on Mutex, TBIVM.
 716   // - It was in SS:block(), looped around to SS:block() and is blocked on the WaitBarrier.
 717   // - It was in SS:block() but now on a Mutex.
 718   // All of these cases are safe.
 719 
 720   *state = thread->thread_state();
 721   OrderAccess::loadload();
 722   uint64_t sid = thread->safepoint_state()->get_safepoint_id();  // Load acquire
 723   if (sid != InactiveSafepointCounter && sid != safepoint_count) {
 724     // In an old safepoint, state not relevant.
 725     return false;
 726   }
 727   return *state == thread->thread_state();
 728 }
 729 
 730 static bool safepoint_safe_with(JavaThread *thread, JavaThreadState state) {
 731   switch(state) {
 732   case _thread_in_native:
 733     // native threads are safe if they have no java stack or have walkable stack
 734     return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
 735 
 736   case _thread_blocked:
 737     // On wait_barrier or blocked.
 738     // Blocked threads should already have walkable stack.
 739     assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
 740     return true;
 741 
 742   default:
 743     return false;
 744   }
 745 }
 746 
 747 bool SafepointSynchronize::handshake_safe(JavaThread *thread) {
 748   assert(Thread::current()->is_VM_thread(), "Must be VMThread");
 749   if (thread->is_ext_suspended() || thread->is_terminated()) {
 750     return true;
 751   }
 752   JavaThreadState stable_state;
 753   if (try_stable_load_state(&stable_state, thread, InactiveSafepointCounter)) {
 754     return safepoint_safe_with(thread, stable_state);
 755   }
 756   return false;
 757 }
 758 
 759 // See if the thread is running inside a lazy critical native and
 760 // update the thread critical count if so.  Also set a suspend flag to
 761 // cause the native wrapper to return into the JVM to do the unlock
 762 // once the native finishes.
 763 static void check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
 764   if (state == _thread_in_native &&
 765       thread->has_last_Java_frame() &&
 766       thread->frame_anchor()->walkable()) {
 767     // This thread might be in a critical native nmethod so look at
 768     // the top of the stack and increment the critical count if it
 769     // is.
 770     frame wrapper_frame = thread->last_frame();
 771     CodeBlob* stub_cb = wrapper_frame.cb();
 772     if (stub_cb != NULL &&
 773         stub_cb->is_nmethod() &&
 774         stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
 775       // A thread could potentially be in a critical native across
 776       // more than one safepoint, so only update the critical state on
 777       // the first one.  When it returns it will perform the unlock.
 778       if (!thread->do_critical_native_unlock()) {
 779 #ifdef ASSERT
 780         if (!thread->in_critical()) {
 781           GCLocker::increment_debug_jni_lock_count();
 782         }
 783 #endif
 784         thread->enter_critical();
 785         // Make sure the native wrapper calls back on return to
 786         // perform the needed critical unlock.
 787         thread->set_critical_native_unlock();
 788       }
 789     }
 790   }
 791 }
 792 
 793 // -------------------------------------------------------------------------------------------------------
 794 // Implementation of Safepoint blocking point
 795 
 796 void SafepointSynchronize::block(JavaThread *thread) {
 797   assert(thread != NULL, "thread must be set");
 798   assert(thread->is_Java_thread(), "not a Java thread");
 799 
 800   // Threads shouldn't block if they are in the middle of printing, but...
 801   ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
 802 
 803   // Only bail from the block() call if the thread is gone from the
 804   // thread list; starting to exit should still block.
 805   if (thread->is_terminated()) {
 806      // block current thread if we come here from native code when VM is gone
 807      thread->block_if_vm_exited();
 808 
 809      // otherwise do nothing
 810      return;
 811   }
 812 
 813   JavaThreadState state = thread->thread_state();
 814   thread->frame_anchor()->make_walkable(thread);
 815 
 816   uint64_t safepoint_id = SafepointSynchronize::safepoint_counter();
 817   // Check that we have a valid thread_state at this point
 818   switch(state) {
 819     case _thread_in_vm_trans:
 820     case _thread_in_Java:        // From compiled code
 821     case _thread_in_native_trans:
 822     case _thread_blocked_trans:
 823     case _thread_new_trans:
 824 
 825       // We have no idea where the VMThread is, it might even be at next safepoint.
 826       // So we can miss this poll, but stop at next.
 827 
 828       // Load dependent store, it must not pass loading of safepoint_id.
 829       thread->safepoint_state()->set_safepoint_id(safepoint_id); // Release store
 830 
 831       // This part we can skip if we notice we miss or are in a future safepoint.
 832       OrderAccess::storestore();
 833       // Load in wait barrier should not float up
 834       thread->set_thread_state_fence(_thread_blocked);
 835 
 836       _wait_barrier->wait(static_cast<int>(safepoint_id));
 837       assert(_state != _synchronized, "Can't be");
 838 
 839       // If barrier is disarmed stop store from floating above loads in barrier.
 840       OrderAccess::loadstore();
 841       thread->set_thread_state(state);
 842 
 843       // Then we reset the safepoint id to inactive.
 844       thread->safepoint_state()->reset_safepoint_id(); // Release store
 845 
 846       OrderAccess::fence();
 847 
 848       break;
 849 
 850     default:
 851      fatal("Illegal threadstate encountered: %d", state);
 852   }
 853   guarantee(thread->safepoint_state()->get_safepoint_id() == InactiveSafepointCounter,
 854             "The safepoint id should be set only in block path");
 855 
 856   // Check for pending. async. exceptions or suspends - except if the
 857   // thread was blocked inside the VM. has_special_runtime_exit_condition()
 858   // is called last since it grabs a lock and we only want to do that when
 859   // we must.
 860   //
 861   // Note: we never deliver an async exception at a polling point as the
 862   // compiler may not have an exception handler for it. The polling
 863   // code will notice the async and deoptimize and the exception will
 864   // be delivered. (Polling at a return point is ok though). Sure is
 865   // a lot of bother for a deprecated feature...
 866   //
 867   // We don't deliver an async exception if the thread state is
 868   // _thread_in_native_trans so JNI functions won't be called with
 869   // a surprising pending exception. If the thread state is going back to java,
 870   // async exception is checked in check_special_condition_for_native_trans().
 871 
 872   if (state != _thread_blocked_trans &&
 873       state != _thread_in_vm_trans &&
 874       thread->has_special_runtime_exit_condition()) {
 875     thread->handle_special_runtime_exit_condition(
 876       !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
 877   }
 878 
 879   // cross_modify_fence is done by SafepointMechanism::block_if_requested_slow
 880   // which is the only caller here.
 881 }
 882 
 883 // ------------------------------------------------------------------------------------------------------
 884 // Exception handlers
 885 
 886 
 887 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
 888   assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
 889   assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
 890   if (!SafepointMechanism::uses_thread_local_poll()) {
 891     assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
 892   }
 893 
 894   if (log_is_enabled(Info, safepoint, stats)) {
 895     Atomic::inc(&_nof_threads_hit_polling_page);
 896   }
 897 
 898   ThreadSafepointState* state = thread->safepoint_state();
 899 
 900   state->handle_polling_page_exception();
 901 }
 902 
 903 
 904 void SafepointSynchronize::print_safepoint_timeout() {
 905   if (!timeout_error_printed) {
 906     timeout_error_printed = true;
 907     // Print out the thread info which didn't reach the safepoint for debugging
 908     // purposes (useful when there are lots of threads in the debugger).
 909     LogTarget(Warning, safepoint) lt;
 910     if (lt.is_enabled()) {
 911       ResourceMark rm;
 912       LogStream ls(lt);
 913 
 914       ls.cr();
 915       ls.print_cr("# SafepointSynchronize::begin: Timeout detected:");
 916       ls.print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
 917       ls.print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
 918       for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
 919         if (cur_thread->safepoint_state()->is_running()) {
 920           ls.print("# ");
 921           cur_thread->print_on(&ls);
 922           ls.cr();
 923         }
 924       }
 925       ls.print_cr("# SafepointSynchronize::begin: (End of list)");
 926     }
 927   }
 928 
 929   // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
 930   // ShowMessageBoxOnError.
 931   if (AbortVMOnSafepointTimeout) {
 932     // Send the blocking thread a signal to terminate and write an error file.
 933     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
 934       if (cur_thread->safepoint_state()->is_running()) {
 935         if (!os::signal_thread(cur_thread, SIGILL, "blocking a safepoint")) {
 936           break; // Could not send signal. Report fatal error.
 937         }
 938         // Give cur_thread a chance to report the error and terminate the VM.
 939         os::naked_sleep(3000);
 940       }
 941     }
 942     fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
 943           SafepointTimeoutDelay, VMThread::vm_operation()->name());
 944   }
 945 }
 946 
 947 // -------------------------------------------------------------------------------------------------------
 948 // Implementation of ThreadSafepointState
 949 
 950 ThreadSafepointState::ThreadSafepointState(JavaThread *thread)
 951   : _at_poll_safepoint(false), _thread(thread), _safepoint_safe(false),
 952     _safepoint_id(SafepointSynchronize::InactiveSafepointCounter), _next(NULL) {
 953 }
 954 
 955 void ThreadSafepointState::create(JavaThread *thread) {
 956   ThreadSafepointState *state = new ThreadSafepointState(thread);
 957   thread->set_safepoint_state(state);
 958 }
 959 
 960 void ThreadSafepointState::destroy(JavaThread *thread) {
 961   if (thread->safepoint_state()) {
 962     delete(thread->safepoint_state());
 963     thread->set_safepoint_state(NULL);
 964   }
 965 }
 966 
 967 uint64_t ThreadSafepointState::get_safepoint_id() const {
 968   return Atomic::load_acquire(&_safepoint_id);
 969 }
 970 
 971 void ThreadSafepointState::reset_safepoint_id() {
 972   Atomic::release_store(&_safepoint_id, SafepointSynchronize::InactiveSafepointCounter);
 973 }
 974 
 975 void ThreadSafepointState::set_safepoint_id(uint64_t safepoint_id) {
 976   Atomic::release_store(&_safepoint_id, safepoint_id);
 977 }
 978 
 979 void ThreadSafepointState::examine_state_of_thread(uint64_t safepoint_count) {
 980   assert(is_running(), "better be running or just have hit safepoint poll");
 981 
 982   JavaThreadState stable_state;
 983   if (!SafepointSynchronize::try_stable_load_state(&stable_state, _thread, safepoint_count)) {
 984     // We could not get stable state of the JavaThread.
 985     // Consider it running and just return.
 986     return;
 987   }
 988 
 989   // Check for a thread that is suspended. Note that thread resume tries
 990   // to grab the Threads_lock which we own here, so a thread cannot be
 991   // resumed during safepoint synchronization.
 992 
 993   // We check to see if this thread is suspended without locking to
 994   // avoid deadlocking with a third thread that is waiting for this
 995   // thread to be suspended. The third thread can notice the safepoint
 996   // that we're trying to start at the beginning of its SR_lock->wait()
 997   // call. If that happens, then the third thread will block on the
 998   // safepoint while still holding the underlying SR_lock. We won't be
 999   // able to get the SR_lock and we'll deadlock.
1000   //
1001   // We don't need to grab the SR_lock here for two reasons:
1002   // 1) The suspend flags are both volatile and are set with an
1003   //    Atomic::cmpxchg() call so we should see the suspended
1004   //    state right away.
1005   // 2) We're being called from the safepoint polling loop; if
1006   //    we don't see the suspended state on this iteration, then
1007   //    we'll come around again.
1008   //
1009   bool is_suspended = _thread->is_ext_suspended();
1010   if (is_suspended) {
1011     account_safe_thread();
1012     return;
1013   }
1014 
1015   if (safepoint_safe_with(_thread, stable_state)) {
1016     check_for_lazy_critical_native(_thread, stable_state);
1017     account_safe_thread();
1018     return;
1019   }
1020 
1021   // All other thread states will continue to run until they
1022   // transition and self-block in state _blocked
1023   // Safepoint polling in compiled code causes the Java threads to do the same.
1024   // Note: new threads may require a malloc so they must be allowed to finish
1025 
1026   assert(is_running(), "examine_state_of_thread on non-running thread");
1027   return;
1028 }
1029 
1030 void ThreadSafepointState::account_safe_thread() {
1031   SafepointSynchronize::decrement_waiting_to_block();
1032   if (_thread->in_critical()) {
1033     // Notice that this thread is in a critical section
1034     SafepointSynchronize::increment_jni_active_count();
1035   }
1036   DEBUG_ONLY(_thread->set_visited_for_critical_count(SafepointSynchronize::safepoint_counter());)
1037   assert(!_safepoint_safe, "Must be unsafe before safe");
1038   _safepoint_safe = true;
1039 }
1040 
1041 void ThreadSafepointState::restart() {
1042   assert(_safepoint_safe, "Must be safe before unsafe");
1043   _safepoint_safe = false;
1044 }
1045 
1046 void ThreadSafepointState::print_on(outputStream *st) const {
1047   const char *s = _safepoint_safe ? "_at_safepoint" : "_running";
1048 
1049   st->print_cr("Thread: " INTPTR_FORMAT
1050               "  [0x%2x] State: %s _at_poll_safepoint %d",
1051                p2i(_thread), _thread->osthread()->thread_id(), s, _at_poll_safepoint);
1052 
1053   _thread->print_thread_state_on(st);
1054 }
1055 
1056 // ---------------------------------------------------------------------------------------------------------------------
1057 
1058 // Block the thread at poll or poll return for safepoint/handshake.
1059 void ThreadSafepointState::handle_polling_page_exception() {
1060 
1061   // If we're using a global poll, then the thread should not be
1062   // marked as safepoint safe yet.
1063   assert(!SafepointMechanism::uses_global_page_poll() || !_safepoint_safe,
1064          "polling page exception on thread safepoint safe");
1065 
1066   // Step 1: Find the nmethod from the return address
1067   address real_return_addr = thread()->saved_exception_pc();
1068 
1069   CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1070   assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1071   CompiledMethod* nm = (CompiledMethod*)cb;
1072 
1073   // Find frame of caller
1074   frame stub_fr = thread()->last_frame();
1075   CodeBlob* stub_cb = stub_fr.cb();
1076   assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1077   RegisterMap map(thread(), true);
1078   frame caller_fr = stub_fr.sender(&map);
1079 
1080   // Should only be poll_return or poll
1081   assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1082 
1083   // This is a poll immediately before a return. The exception handling code
1084   // has already had the effect of causing the return to occur, so the execution
1085   // will continue immediately after the call. In addition, the oopmap at the
1086   // return point does not mark the return value as an oop (if it is), so
1087   // it needs a handle here to be updated.
1088   if( nm->is_at_poll_return(real_return_addr) ) {
1089     // See if return type is an oop.
1090     bool return_oop = nm->method()->is_returning_oop();
1091     Handle return_value;
1092     if (return_oop) {
1093       // The oop result has been saved on the stack together with all
1094       // the other registers. In order to preserve it over GCs we need
1095       // to keep it in a handle.
1096       oop result = caller_fr.saved_oop_result(&map);
1097       assert(oopDesc::is_oop_or_null(result), "must be oop");
1098       return_value = Handle(thread(), result);
1099       assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1100     }
1101 
1102     // Block the thread
1103     SafepointMechanism::block_if_requested(thread());
1104 
1105     // restore oop result, if any
1106     if (return_oop) {
1107       caller_fr.set_saved_oop_result(&map, return_value());
1108     }
1109   }
1110 
1111   // This is a safepoint poll. Verify the return address and block.
1112   else {
1113     set_at_poll_safepoint(true);
1114 
1115     // verify the blob built the "return address" correctly
1116     assert(real_return_addr == caller_fr.pc(), "must match");
1117 
1118     // Block the thread
1119     SafepointMechanism::block_if_requested(thread());
1120     set_at_poll_safepoint(false);
1121 
1122     // If we have a pending async exception deoptimize the frame
1123     // as otherwise we may never deliver it.
1124     if (thread()->has_async_condition()) {
1125       ThreadInVMfromJavaNoAsyncException __tiv(thread());
1126       Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1127     }
1128 
1129     // If an exception has been installed we must check for a pending deoptimization
1130     // Deoptimize frame if exception has been thrown.
1131 
1132     if (thread()->has_pending_exception() ) {
1133       RegisterMap map(thread(), true);
1134       frame caller_fr = stub_fr.sender(&map);
1135       if (caller_fr.is_deoptimized_frame()) {
1136         // The exception patch will destroy registers that are still
1137         // live and will be needed during deoptimization. Defer the
1138         // Async exception should have deferred the exception until the
1139         // next safepoint which will be detected when we get into
1140         // the interpreter so if we have an exception now things
1141         // are messed up.
1142 
1143         fatal("Exception installed and deoptimization is pending");
1144       }
1145     }
1146   }
1147 }
1148 
1149 
1150 // -------------------------------------------------------------------------------------------------------
1151 // Implementation of SafepointTracing
1152 
1153 jlong SafepointTracing::_last_safepoint_begin_time_ns = 0;
1154 jlong SafepointTracing::_last_safepoint_sync_time_ns = 0;
1155 jlong SafepointTracing::_last_safepoint_cleanup_time_ns = 0;
1156 jlong SafepointTracing::_last_safepoint_end_time_ns = 0;
1157 jlong SafepointTracing::_last_app_time_ns = 0;
1158 int SafepointTracing::_nof_threads = 0;
1159 int SafepointTracing::_nof_running = 0;
1160 int SafepointTracing::_page_trap = 0;
1161 VM_Operation::VMOp_Type SafepointTracing::_current_type;
1162 jlong     SafepointTracing::_max_sync_time = 0;
1163 jlong     SafepointTracing::_max_vmop_time = 0;
1164 uint64_t  SafepointTracing::_op_count[VM_Operation::VMOp_Terminating] = {0};
1165 
1166 void SafepointTracing::init() {
1167   // Application start
1168   _last_safepoint_end_time_ns = os::javaTimeNanos();
1169 }
1170 
1171 // Helper method to print the header.
1172 static void print_header(outputStream* st) {
1173   // The number of spaces is significant here, and should match the format
1174   // specifiers in print_statistics().
1175 
1176   st->print("VM Operation                 "
1177             "[ threads: total initial_running ]"
1178             "[ time:       sync    cleanup       vmop      total ]");
1179 
1180   st->print_cr(" page_trap_count");
1181 }
1182 
1183 // This prints a nice table.  To get the statistics to not shift due to the logging uptime
1184 // decorator, use the option as: -Xlog:safepoint+stats:[outputfile]:none
1185 void SafepointTracing::statistics_log() {
1186   LogTarget(Info, safepoint, stats) lt;
1187   assert (lt.is_enabled(), "should only be called when printing statistics is enabled");
1188   LogStream ls(lt);
1189 
1190   static int _cur_stat_index = 0;
1191 
1192   // Print header every 30 entries
1193   if ((_cur_stat_index % 30) == 0) {
1194     print_header(&ls);
1195     _cur_stat_index = 1;  // wrap
1196   } else {
1197     _cur_stat_index++;
1198   }
1199 
1200   ls.print("%-28s [       "
1201            INT32_FORMAT_W(8) "        " INT32_FORMAT_W(8) " "
1202            "]",
1203            VM_Operation::name(_current_type),
1204            _nof_threads,
1205            _nof_running);
1206   ls.print("[       "
1207            INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " "
1208            INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " ]",
1209            (int64_t)(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns),
1210            (int64_t)(_last_safepoint_cleanup_time_ns - _last_safepoint_sync_time_ns),
1211            (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns),
1212            (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_begin_time_ns));
1213 
1214   ls.print_cr(INT32_FORMAT_W(16), _page_trap);
1215 }
1216 
1217 // This method will be called when VM exits. This tries to summarize the sampling.
1218 // Current thread may already be deleted, so don't use ResourceMark.
1219 void SafepointTracing::statistics_exit_log() {
1220   if (!log_is_enabled(Info, safepoint, stats)) {
1221     return;
1222   }
1223   for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1224     if (_op_count[index] != 0) {
1225       log_info(safepoint, stats)("%-28s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1226                _op_count[index]);
1227     }
1228   }
1229 
1230   log_info(safepoint, stats)("VM operations coalesced during safepoint " INT64_FORMAT,
1231                               VMThread::get_coalesced_count());
1232   log_info(safepoint, stats)("Maximum sync time  " INT64_FORMAT" ns",
1233                               (int64_t)(_max_sync_time));
1234   log_info(safepoint, stats)("Maximum vm operation time (except for Exit VM operation)  "
1235                               INT64_FORMAT " ns",
1236                               (int64_t)(_max_vmop_time));
1237 }
1238 
1239 void SafepointTracing::begin(VM_Operation::VMOp_Type type) {
1240   _op_count[type]++;
1241   _current_type = type;
1242 
1243   // update the time stamp to begin recording safepoint time
1244   _last_safepoint_begin_time_ns = os::javaTimeNanos();
1245   _last_safepoint_sync_time_ns = 0;
1246   _last_safepoint_cleanup_time_ns = 0;
1247 
1248   _last_app_time_ns = _last_safepoint_begin_time_ns - _last_safepoint_end_time_ns;
1249   _last_safepoint_end_time_ns = 0;
1250 
1251   RuntimeService::record_safepoint_begin(_last_app_time_ns);
1252 }
1253 
1254 void SafepointTracing::synchronized(int nof_threads, int nof_running, int traps) {
1255   _last_safepoint_sync_time_ns = os::javaTimeNanos();
1256   _nof_threads = nof_threads;
1257   _nof_running = nof_running;
1258   _page_trap   = traps;
1259   RuntimeService::record_safepoint_synchronized(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns);
1260 }
1261 
1262 void SafepointTracing::cleanup() {
1263   _last_safepoint_cleanup_time_ns = os::javaTimeNanos();
1264 }
1265 
1266 void SafepointTracing::end() {
1267   _last_safepoint_end_time_ns = os::javaTimeNanos();
1268 
1269   if (_max_sync_time < (_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns)) {
1270     _max_sync_time = _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns;
1271   }
1272   if (_max_vmop_time < (_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns)) {
1273     _max_vmop_time = _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns;
1274   }
1275   if (log_is_enabled(Info, safepoint, stats)) {
1276     statistics_log();
1277   }
1278 
1279   log_info(safepoint)(
1280      "Safepoint \"%s\", "
1281      "Time since last: " JLONG_FORMAT " ns, "
1282      "Reaching safepoint: " JLONG_FORMAT " ns, "
1283      "At safepoint: " JLONG_FORMAT " ns, "
1284      "Total: " JLONG_FORMAT " ns",
1285       VM_Operation::name(_current_type),
1286       _last_app_time_ns,
1287       _last_safepoint_cleanup_time_ns - _last_safepoint_begin_time_ns,
1288       _last_safepoint_end_time_ns     - _last_safepoint_cleanup_time_ns,
1289       _last_safepoint_end_time_ns     - _last_safepoint_begin_time_ns
1290      );
1291 
1292   RuntimeService::record_safepoint_end(_last_safepoint_end_time_ns - _last_safepoint_cleanup_time_ns);
1293 }