1 /*
   2  * Copyright (c) 1997, 2017, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/stringTable.hpp"
  27 #include "classfile/symbolTable.hpp"
  28 #include "classfile/systemDictionary.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "code/nmethod.hpp"
  32 #include "code/pcDesc.hpp"
  33 #include "code/scopeDesc.hpp"
  34 #include "gc/shared/collectedHeap.hpp"
  35 #include "gc/shared/gcLocker.inline.hpp"
  36 #include "interpreter/interpreter.hpp"
  37 #include "logging/log.hpp"
  38 #include "memory/resourceArea.hpp"
  39 #include "memory/universe.inline.hpp"
  40 #include "oops/oop.inline.hpp"
  41 #include "oops/symbol.hpp"
  42 #include "runtime/atomic.hpp"
  43 #include "runtime/compilationPolicy.hpp"
  44 #include "runtime/deoptimization.hpp"
  45 #include "runtime/frame.inline.hpp"
  46 #include "runtime/interfaceSupport.hpp"
  47 #include "runtime/mutexLocker.hpp"
  48 #include "runtime/orderAccess.inline.hpp"
  49 #include "runtime/osThread.hpp"
  50 #include "runtime/safepoint.hpp"
  51 #include "runtime/signature.hpp"
  52 #include "runtime/stubCodeGenerator.hpp"
  53 #include "runtime/stubRoutines.hpp"
  54 #include "runtime/sweeper.hpp"
  55 #include "runtime/synchronizer.hpp"
  56 #include "runtime/thread.inline.hpp"
  57 #include "runtime/timerTrace.hpp"
  58 #include "services/runtimeService.hpp"
  59 #include "trace/tracing.hpp"
  60 #include "trace/traceMacros.hpp"
  61 #include "utilities/events.hpp"
  62 #include "utilities/macros.hpp"
  63 #if INCLUDE_ALL_GCS
  64 #include "gc/cms/concurrentMarkSweepThread.hpp"
  65 #include "gc/g1/suspendibleThreadSet.hpp"
  66 #endif // INCLUDE_ALL_GCS
  67 #ifdef COMPILER1
  68 #include "c1/c1_globals.hpp"
  69 #endif
  70 
  71 // --------------------------------------------------------------------------------------------------
  72 // Implementation of Safepoint begin/end
  73 
  74 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
  75 volatile int  SafepointSynchronize::_waiting_to_block = 0;
  76 volatile int SafepointSynchronize::_safepoint_counter = 0;
  77 int SafepointSynchronize::_current_jni_active_count = 0;
  78 long  SafepointSynchronize::_end_of_last_safepoint = 0;
  79 static volatile int PageArmed = 0 ;        // safepoint polling page is RO|RW vs PROT_NONE
  80 static volatile int TryingToBlock = 0 ;    // proximate value -- for advisory use only
  81 static bool timeout_error_printed = false;
  82 
  83 // Roll all threads forward to a safepoint and suspend them all
  84 void SafepointSynchronize::begin() {
  85   EventSafepointBegin begin_event;
  86   Thread* myThread = Thread::current();
  87   assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
  88 
  89   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
  90     _safepoint_begin_time = os::javaTimeNanos();
  91     _ts_of_current_safepoint = tty->time_stamp().seconds();
  92   }
  93 
  94 #if INCLUDE_ALL_GCS
  95   if (UseConcMarkSweepGC) {
  96     // In the future we should investigate whether CMS can use the
  97     // more-general mechanism below.  DLD (01/05).
  98     ConcurrentMarkSweepThread::synchronize(false);
  99   } else if (UseG1GC) {
 100     SuspendibleThreadSet::synchronize();
 101   }
 102 #endif // INCLUDE_ALL_GCS
 103 
 104   // By getting the Threads_lock, we assure that no threads are about to start or
 105   // exit. It is released again in SafepointSynchronize::end().
 106   Threads_lock->lock();
 107 
 108   assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
 109 
 110   int nof_threads = Threads::number_of_threads();
 111 
 112   log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
 113 
 114   RuntimeService::record_safepoint_begin();
 115 
 116   MutexLocker mu(Safepoint_lock);
 117 
 118   // Reset the count of active JNI critical threads
 119   _current_jni_active_count = 0;
 120 
 121   // Set number of threads to wait for, before we initiate the callbacks
 122   _waiting_to_block = nof_threads;
 123   TryingToBlock     = 0 ;
 124   int still_running = nof_threads;
 125 
 126   // Save the starting time, so that it can be compared to see if this has taken
 127   // too long to complete.
 128   jlong safepoint_limit_time = 0;
 129   timeout_error_printed = false;
 130 
 131   // PrintSafepointStatisticsTimeout can be specified separately. When
 132   // specified, PrintSafepointStatistics will be set to true in
 133   // deferred_initialize_stat method. The initialization has to be done
 134   // early enough to avoid any races. See bug 6880029 for details.
 135   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
 136     deferred_initialize_stat();
 137   }
 138 
 139   // Begin the process of bringing the system to a safepoint.
 140   // Java threads can be in several different states and are
 141   // stopped by different mechanisms:
 142   //
 143   //  1. Running interpreted
 144   //     The interpreter dispatch table is changed to force it to
 145   //     check for a safepoint condition between bytecodes.
 146   //  2. Running in native code
 147   //     When returning from the native code, a Java thread must check
 148   //     the safepoint _state to see if we must block.  If the
 149   //     VM thread sees a Java thread in native, it does
 150   //     not wait for this thread to block.  The order of the memory
 151   //     writes and reads of both the safepoint state and the Java
 152   //     threads state is critical.  In order to guarantee that the
 153   //     memory writes are serialized with respect to each other,
 154   //     the VM thread issues a memory barrier instruction
 155   //     (on MP systems).  In order to avoid the overhead of issuing
 156   //     a memory barrier for each Java thread making native calls, each Java
 157   //     thread performs a write to a single memory page after changing
 158   //     the thread state.  The VM thread performs a sequence of
 159   //     mprotect OS calls which forces all previous writes from all
 160   //     Java threads to be serialized.  This is done in the
 161   //     os::serialize_thread_states() call.  This has proven to be
 162   //     much more efficient than executing a membar instruction
 163   //     on every call to native code.
 164   //  3. Running compiled Code
 165   //     Compiled code reads a global (Safepoint Polling) page that
 166   //     is set to fault if we are trying to get to a safepoint.
 167   //  4. Blocked
 168   //     A thread which is blocked will not be allowed to return from the
 169   //     block condition until the safepoint operation is complete.
 170   //  5. In VM or Transitioning between states
 171   //     If a Java thread is currently running in the VM or transitioning
 172   //     between states, the safepointing code will wait for the thread to
 173   //     block itself when it attempts transitions to a new state.
 174   //
 175   {
 176     EventSafepointStateSynchronization sync_event;
 177     int initial_running = 0;
 178 
 179     _state            = _synchronizing;
 180     OrderAccess::fence();
 181 
 182     // Flush all thread states to memory
 183     if (!UseMembar) {
 184       os::serialize_thread_states();
 185     }
 186 
 187     // Make interpreter safepoint aware
 188     Interpreter::notice_safepoints();
 189 
 190     if (DeferPollingPageLoopCount < 0) {
 191       // Make polling safepoint aware
 192       guarantee (PageArmed == 0, "invariant") ;
 193       PageArmed = 1 ;
 194       os::make_polling_page_unreadable();
 195     }
 196 
 197     // Consider using active_processor_count() ... but that call is expensive.
 198     int ncpus = os::processor_count() ;
 199 
 200 #ifdef ASSERT
 201     for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 202       assert(cur->safepoint_state()->is_running(), "Illegal initial state");
 203       // Clear the visited flag to ensure that the critical counts are collected properly.
 204       cur->set_visited_for_critical_count(false);
 205     }
 206 #endif // ASSERT
 207 
 208     if (SafepointTimeout)
 209       safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
 210 
 211     // Iterate through all threads until it have been determined how to stop them all at a safepoint
 212     unsigned int iterations = 0;
 213     int steps = 0 ;
 214     while(still_running > 0) {
 215       for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 216         assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
 217         ThreadSafepointState *cur_state = cur->safepoint_state();
 218         if (cur_state->is_running()) {
 219           cur_state->examine_state_of_thread();
 220           if (!cur_state->is_running()) {
 221             still_running--;
 222             // consider adjusting steps downward:
 223             //   steps = 0
 224             //   steps -= NNN
 225             //   steps >>= 1
 226             //   steps = MIN(steps, 2000-100)
 227             //   if (iterations != 0) steps -= NNN
 228           }
 229           if (log_is_enabled(Trace, safepoint)) {
 230             ResourceMark rm;
 231             cur_state->print_on(Log(safepoint)::trace_stream());
 232           }
 233         }
 234       }
 235 
 236       if (iterations == 0) {
 237         initial_running = still_running;
 238         if (PrintSafepointStatistics) {
 239           begin_statistics(nof_threads, still_running);
 240         }
 241       }
 242 
 243       if (still_running > 0) {
 244         // Check for if it takes to long
 245         if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
 246           print_safepoint_timeout(_spinning_timeout);
 247         }
 248 
 249         // Spin to avoid context switching.
 250         // There's a tension between allowing the mutators to run (and rendezvous)
 251         // vs spinning.  As the VM thread spins, wasting cycles, it consumes CPU that
 252         // a mutator might otherwise use profitably to reach a safepoint.  Excessive
 253         // spinning by the VM thread on a saturated system can increase rendezvous latency.
 254         // Blocking or yielding incur their own penalties in the form of context switching
 255         // and the resultant loss of $ residency.
 256         //
 257         // Further complicating matters is that yield() does not work as naively expected
 258         // on many platforms -- yield() does not guarantee that any other ready threads
 259         // will run.   As such we revert to naked_short_sleep() after some number of iterations.
 260         // nakes_short_sleep() is implemented as a short unconditional sleep.
 261         // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
 262         // can actually increase the time it takes the VM thread to detect that a system-wide
 263         // stop-the-world safepoint has been reached.  In a pathological scenario such as that
 264         // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
 265         // In that case the mutators will be stalled waiting for the safepoint to complete and the
 266         // the VMthread will be sleeping, waiting for the mutators to rendezvous.  The VMthread
 267         // will eventually wake up and detect that all mutators are safe, at which point
 268         // we'll again make progress.
 269         //
 270         // Beware too that that the VMThread typically runs at elevated priority.
 271         // Its default priority is higher than the default mutator priority.
 272         // Obviously, this complicates spinning.
 273         //
 274         // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
 275         // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
 276         //
 277         // See the comments in synchronizer.cpp for additional remarks on spinning.
 278         //
 279         // In the future we might:
 280         // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
 281         //    This is tricky as the path used by a thread exiting the JVM (say on
 282         //    on JNI call-out) simply stores into its state field.  The burden
 283         //    is placed on the VM thread, which must poll (spin).
 284         // 2. Find something useful to do while spinning.  If the safepoint is GC-related
 285         //    we might aggressively scan the stacks of threads that are already safe.
 286         // 3. Use Solaris schedctl to examine the state of the still-running mutators.
 287         //    If all the mutators are ONPROC there's no reason to sleep or yield.
 288         // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
 289         // 5. Check system saturation.  If the system is not fully saturated then
 290         //    simply spin and avoid sleep/yield.
 291         // 6. As still-running mutators rendezvous they could unpark the sleeping
 292         //    VMthread.  This works well for still-running mutators that become
 293         //    safe.  The VMthread must still poll for mutators that call-out.
 294         // 7. Drive the policy on time-since-begin instead of iterations.
 295         // 8. Consider making the spin duration a function of the # of CPUs:
 296         //    Spin = (((ncpus-1) * M) + K) + F(still_running)
 297         //    Alternately, instead of counting iterations of the outer loop
 298         //    we could count the # of threads visited in the inner loop, above.
 299         // 9. On windows consider using the return value from SwitchThreadTo()
 300         //    to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
 301 
 302         if (int(iterations) == DeferPollingPageLoopCount) {
 303           guarantee (PageArmed == 0, "invariant") ;
 304           PageArmed = 1 ;
 305           os::make_polling_page_unreadable();
 306         }
 307 
 308         // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
 309         // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
 310         ++steps ;
 311         if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
 312           SpinPause() ;     // MP-Polite spin
 313         } else
 314           if (steps < DeferThrSuspendLoopCount) {
 315             os::naked_yield() ;
 316           } else {
 317             os::naked_short_sleep(1);
 318           }
 319 
 320         iterations ++ ;
 321       }
 322       assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
 323     }
 324     assert(still_running == 0, "sanity check");
 325 
 326     if (PrintSafepointStatistics) {
 327       update_statistics_on_spin_end();
 328     }
 329 
 330     if (sync_event.should_commit()) {
 331       sync_event.set_safepointId(safepoint_counter());
 332       sync_event.set_initialThreadCount(initial_running);
 333       sync_event.set_runningThreadCount(_waiting_to_block);
 334       sync_event.set_iterations(iterations);
 335       sync_event.commit();
 336     }
 337   } //EventSafepointStateSync
 338 
 339   // wait until all threads are stopped
 340   {
 341     EventSafepointWaitBlocked wait_blocked_event;
 342     int initial_waiting_to_block = _waiting_to_block;
 343 
 344     while (_waiting_to_block > 0) {
 345       log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
 346       if (!SafepointTimeout || timeout_error_printed) {
 347         Safepoint_lock->wait(true);  // true, means with no safepoint checks
 348       } else {
 349         // Compute remaining time
 350         jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
 351 
 352         // If there is no remaining time, then there is an error
 353         if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
 354           print_safepoint_timeout(_blocking_timeout);
 355         }
 356       }
 357     }
 358     assert(_waiting_to_block == 0, "sanity check");
 359 
 360 #ifndef PRODUCT
 361     if (SafepointTimeout) {
 362       jlong current_time = os::javaTimeNanos();
 363       if (safepoint_limit_time < current_time) {
 364         tty->print_cr("# SafepointSynchronize: Finished after "
 365                       INT64_FORMAT_W(6) " ms",
 366                       ((current_time - safepoint_limit_time) / MICROUNITS +
 367                        (jlong)SafepointTimeoutDelay));
 368       }
 369     }
 370 #endif
 371 
 372     assert((_safepoint_counter & 0x1) == 0, "must be even");
 373     assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 374     _safepoint_counter ++;
 375 
 376     // Record state
 377     _state = _synchronized;
 378 
 379     OrderAccess::fence();
 380 
 381     if (wait_blocked_event.should_commit()) {
 382       wait_blocked_event.set_safepointId(safepoint_counter());
 383       wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
 384       wait_blocked_event.commit();
 385     }
 386   } // EventSafepointWaitBlocked
 387 
 388 #ifdef ASSERT
 389   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 390     // make sure all the threads were visited
 391     assert(cur->was_visited_for_critical_count(), "missed a thread");
 392   }
 393 #endif // ASSERT
 394 
 395   // Update the count of active JNI critical regions
 396   GCLocker::set_jni_lock_count(_current_jni_active_count);
 397 
 398   if (log_is_enabled(Debug, safepoint)) {
 399     log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
 400   }
 401 
 402   RuntimeService::record_safepoint_synchronized();
 403   if (PrintSafepointStatistics) {
 404     update_statistics_on_sync_end(os::javaTimeNanos());
 405   }
 406 
 407   // Call stuff that needs to be run when a safepoint is just about to be completed
 408   {
 409     EventSafepointCleanup cleanup_event;
 410     do_cleanup_tasks();
 411     if (cleanup_event.should_commit()) {
 412       cleanup_event.set_safepointId(safepoint_counter());
 413       cleanup_event.commit();
 414     }
 415   }
 416 
 417   if (PrintSafepointStatistics) {
 418     // Record how much time spend on the above cleanup tasks
 419     update_statistics_on_cleanup_end(os::javaTimeNanos());
 420   }
 421   if (begin_event.should_commit()) {
 422     begin_event.set_safepointId(safepoint_counter());
 423     begin_event.set_totalThreadCount(nof_threads);
 424     begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
 425     begin_event.commit();
 426   }
 427 }
 428 
 429 // Wake up all threads, so they are ready to resume execution after the safepoint
 430 // operation has been carried out
 431 void SafepointSynchronize::end() {
 432   EventSafepointEnd event;
 433   int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
 434 
 435   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 436   assert((_safepoint_counter & 0x1) == 1, "must be odd");
 437   _safepoint_counter ++;
 438   // memory fence isn't required here since an odd _safepoint_counter
 439   // value can do no harm and a fence is issued below anyway.
 440 
 441   DEBUG_ONLY(Thread* myThread = Thread::current();)
 442   assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
 443 
 444   if (PrintSafepointStatistics) {
 445     end_statistics(os::javaTimeNanos());
 446   }
 447 
 448 #ifdef ASSERT
 449   // A pending_exception cannot be installed during a safepoint.  The threads
 450   // may install an async exception after they come back from a safepoint into
 451   // pending_exception after they unblock.  But that should happen later.
 452   for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
 453     assert (!(cur->has_pending_exception() &&
 454               cur->safepoint_state()->is_at_poll_safepoint()),
 455             "safepoint installed a pending exception");
 456   }
 457 #endif // ASSERT
 458 
 459   if (PageArmed) {
 460     // Make polling safepoint aware
 461     os::make_polling_page_readable();
 462     PageArmed = 0 ;
 463   }
 464 
 465   // Remove safepoint check from interpreter
 466   Interpreter::ignore_safepoints();
 467 
 468   {
 469     MutexLocker mu(Safepoint_lock);
 470 
 471     assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
 472 
 473     // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
 474     // when they get restarted.
 475     _state = _not_synchronized;
 476     OrderAccess::fence();
 477 
 478     log_debug(safepoint)("Leaving safepoint region");
 479 
 480     // Start suspended threads
 481     for(JavaThread *current = Threads::first(); current; current = current->next()) {
 482       // A problem occurring on Solaris is when attempting to restart threads
 483       // the first #cpus - 1 go well, but then the VMThread is preempted when we get
 484       // to the next one (since it has been running the longest).  We then have
 485       // to wait for a cpu to become available before we can continue restarting
 486       // threads.
 487       // FIXME: This causes the performance of the VM to degrade when active and with
 488       // large numbers of threads.  Apparently this is due to the synchronous nature
 489       // of suspending threads.
 490       //
 491       // TODO-FIXME: the comments above are vestigial and no longer apply.
 492       // Furthermore, using solaris' schedctl in this particular context confers no benefit
 493       if (VMThreadHintNoPreempt) {
 494         os::hint_no_preempt();
 495       }
 496       ThreadSafepointState* cur_state = current->safepoint_state();
 497       assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
 498       cur_state->restart();
 499       assert(cur_state->is_running(), "safepoint state has not been reset");
 500     }
 501 
 502     RuntimeService::record_safepoint_end();
 503 
 504     // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
 505     // blocked in signal_thread_blocked
 506     Threads_lock->unlock();
 507 
 508   }
 509 #if INCLUDE_ALL_GCS
 510   // If there are any concurrent GC threads resume them.
 511   if (UseConcMarkSweepGC) {
 512     ConcurrentMarkSweepThread::desynchronize(false);
 513   } else if (UseG1GC) {
 514     SuspendibleThreadSet::desynchronize();
 515   }
 516 #endif // INCLUDE_ALL_GCS
 517   // record this time so VMThread can keep track how much time has elapsed
 518   // since last safepoint.
 519   _end_of_last_safepoint = os::javaTimeMillis();
 520 
 521   if (event.should_commit()) {
 522     event.set_safepointId(safepoint_id);
 523     event.commit();
 524   }
 525 }
 526 
 527 bool SafepointSynchronize::is_cleanup_needed() {
 528   // Need a safepoint if there are many monitors to deflate.
 529   if (ObjectSynchronizer::is_cleanup_needed()) return true;
 530   // Need a safepoint if some inline cache buffers is non-empty
 531   if (!InlineCacheBuffer::is_empty()) return true;
 532   return false;
 533 }
 534 
 535 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
 536   if (event.should_commit()) {
 537     event.set_safepointId(SafepointSynchronize::safepoint_counter());
 538     event.set_name(name);
 539     event.commit();
 540   }
 541 }
 542 
 543 class ParallelSPCleanupThreadClosure : public ThreadClosure {
 544 private:
 545   CodeBlobClosure* _nmethod_cl;
 546   DeflateMonitorCounters* _counters;
 547 
 548 public:
 549   ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
 550     _counters(counters),
 551     _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
 552 
 553   void do_thread(Thread* thread) {
 554     ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
 555     if (_nmethod_cl != NULL && thread->is_Java_thread() &&
 556         ! thread->is_Code_cache_sweeper_thread()) {
 557       JavaThread* jt = (JavaThread*) thread;
 558       jt->nmethods_do(_nmethod_cl);
 559     }
 560   }
 561 };
 562 
 563 class ParallelSPCleanupTask : public AbstractGangTask {
 564 private:
 565   SubTasksDone _subtasks;
 566   ParallelSPCleanupThreadClosure _cleanup_threads_cl;
 567   uint _num_workers;
 568   DeflateMonitorCounters* _counters;
 569 public:
 570   ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
 571     AbstractGangTask("Parallel Safepoint Cleanup"),
 572     _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
 573     _num_workers(num_workers),
 574     _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
 575     _counters(counters) {}
 576 
 577   void work(uint worker_id) {
 578     // All threads deflate monitors and mark nmethods (if necessary).
 579     Threads::parallel_java_threads_do(&_cleanup_threads_cl);
 580 
 581     if (! _subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
 582       const char* name = "deflating idle monitors";
 583       EventSafepointCleanupTask event;
 584       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 585       ObjectSynchronizer::deflate_idle_monitors(_counters);
 586       event_safepoint_cleanup_task_commit(event, name);
 587     }
 588 
 589     if (! _subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
 590       const char* name = "updating inline caches";
 591       EventSafepointCleanupTask event;
 592       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 593       InlineCacheBuffer::update_inline_caches();
 594       event_safepoint_cleanup_task_commit(event, name);
 595     }
 596 
 597     if (! _subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
 598       const char* name = "compilation policy safepoint handler";
 599       EventSafepointCleanupTask event;
 600       TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepoint, cleanup));
 601       CompilationPolicy::policy()->do_safepoint_work();
 602       event_safepoint_cleanup_task_commit(event, name);
 603     }
 604 
 605     if (! _subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
 606       if (SymbolTable::needs_rehashing()) {
 607         const char* name = "rehashing symbol table";
 608         EventSafepointCleanupTask event;
 609         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 610         SymbolTable::rehash_table();
 611         event_safepoint_cleanup_task_commit(event, name);
 612       }
 613     }
 614 
 615     if (! _subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
 616       if (StringTable::needs_rehashing()) {
 617         const char* name = "rehashing string table";
 618         EventSafepointCleanupTask event;
 619         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 620         StringTable::rehash_table();
 621         event_safepoint_cleanup_task_commit(event, name);
 622       }
 623     }
 624 
 625     if (! _subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
 626       // CMS delays purging the CLDG until the beginning of the next safepoint and to
 627       // make sure concurrent sweep is done
 628       const char* name = "purging class loader data graph";
 629       EventSafepointCleanupTask event;
 630       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 631       ClassLoaderDataGraph::purge_if_needed();
 632       event_safepoint_cleanup_task_commit(event, name);
 633     }
 634     _subtasks.all_tasks_completed(_num_workers);
 635   }
 636 };
 637 
 638 // Various cleaning tasks that should be done periodically at safepoints
 639 void SafepointSynchronize::do_cleanup_tasks() {
 640 
 641   // Prepare for monitor deflation
 642   DeflateMonitorCounters deflate_counters;
 643   ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
 644 
 645   CollectedHeap* heap = Universe::heap();
 646   assert(heap != NULL, "heap not initialized yet?");
 647   WorkGang* cleanup_workers = heap->get_safepoint_workers();
 648   if (cleanup_workers != NULL) {
 649     // Parallel cleanup using GC provided thread pool.
 650     uint num_cleanup_workers = cleanup_workers->active_workers();
 651     ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
 652     StrongRootsScope srs(num_cleanup_workers);
 653     cleanup_workers->run_task(&cleanup);
 654   } else {
 655     // Serial cleanup using VMThread.
 656     ParallelSPCleanupTask cleanup(1, &deflate_counters);
 657     StrongRootsScope srs(1);
 658     cleanup.work(0);
 659   }
 660 
 661   // Finish monitor deflation.
 662   ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
 663 }
 664 
 665 
 666 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
 667   switch(state) {
 668   case _thread_in_native:
 669     // native threads are safe if they have no java stack or have walkable stack
 670     return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
 671 
 672    // blocked threads should have already have walkable stack
 673   case _thread_blocked:
 674     assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
 675     return true;
 676 
 677   default:
 678     return false;
 679   }
 680 }
 681 
 682 
 683 // See if the thread is running inside a lazy critical native and
 684 // update the thread critical count if so.  Also set a suspend flag to
 685 // cause the native wrapper to return into the JVM to do the unlock
 686 // once the native finishes.
 687 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
 688   if (state == _thread_in_native &&
 689       thread->has_last_Java_frame() &&
 690       thread->frame_anchor()->walkable()) {
 691     // This thread might be in a critical native nmethod so look at
 692     // the top of the stack and increment the critical count if it
 693     // is.
 694     frame wrapper_frame = thread->last_frame();
 695     CodeBlob* stub_cb = wrapper_frame.cb();
 696     if (stub_cb != NULL &&
 697         stub_cb->is_nmethod() &&
 698         stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
 699       // A thread could potentially be in a critical native across
 700       // more than one safepoint, so only update the critical state on
 701       // the first one.  When it returns it will perform the unlock.
 702       if (!thread->do_critical_native_unlock()) {
 703 #ifdef ASSERT
 704         if (!thread->in_critical()) {
 705           GCLocker::increment_debug_jni_lock_count();
 706         }
 707 #endif
 708         thread->enter_critical();
 709         // Make sure the native wrapper calls back on return to
 710         // perform the needed critical unlock.
 711         thread->set_critical_native_unlock();
 712       }
 713     }
 714   }
 715 }
 716 
 717 
 718 
 719 // -------------------------------------------------------------------------------------------------------
 720 // Implementation of Safepoint callback point
 721 
 722 void SafepointSynchronize::block(JavaThread *thread) {
 723   assert(thread != NULL, "thread must be set");
 724   assert(thread->is_Java_thread(), "not a Java thread");
 725 
 726   // Threads shouldn't block if they are in the middle of printing, but...
 727   ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
 728 
 729   // Only bail from the block() call if the thread is gone from the
 730   // thread list; starting to exit should still block.
 731   if (thread->is_terminated()) {
 732      // block current thread if we come here from native code when VM is gone
 733      thread->block_if_vm_exited();
 734 
 735      // otherwise do nothing
 736      return;
 737   }
 738 
 739   JavaThreadState state = thread->thread_state();
 740   thread->frame_anchor()->make_walkable(thread);
 741 
 742   // Check that we have a valid thread_state at this point
 743   switch(state) {
 744     case _thread_in_vm_trans:
 745     case _thread_in_Java:        // From compiled code
 746 
 747       // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
 748       // we pretend we are still in the VM.
 749       thread->set_thread_state(_thread_in_vm);
 750 
 751       if (is_synchronizing()) {
 752          Atomic::inc (&TryingToBlock) ;
 753       }
 754 
 755       // We will always be holding the Safepoint_lock when we are examine the state
 756       // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
 757       // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
 758       Safepoint_lock->lock_without_safepoint_check();
 759       if (is_synchronizing()) {
 760         // Decrement the number of threads to wait for and signal vm thread
 761         assert(_waiting_to_block > 0, "sanity check");
 762         _waiting_to_block--;
 763         thread->safepoint_state()->set_has_called_back(true);
 764 
 765         DEBUG_ONLY(thread->set_visited_for_critical_count(true));
 766         if (thread->in_critical()) {
 767           // Notice that this thread is in a critical section
 768           increment_jni_active_count();
 769         }
 770 
 771         // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
 772         if (_waiting_to_block == 0) {
 773           Safepoint_lock->notify_all();
 774         }
 775       }
 776 
 777       // We transition the thread to state _thread_blocked here, but
 778       // we can't do our usual check for external suspension and then
 779       // self-suspend after the lock_without_safepoint_check() call
 780       // below because we are often called during transitions while
 781       // we hold different locks. That would leave us suspended while
 782       // holding a resource which results in deadlocks.
 783       thread->set_thread_state(_thread_blocked);
 784       Safepoint_lock->unlock();
 785 
 786       // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
 787       // the entire safepoint, the threads will all line up here during the safepoint.
 788       Threads_lock->lock_without_safepoint_check();
 789       // restore original state. This is important if the thread comes from compiled code, so it
 790       // will continue to execute with the _thread_in_Java state.
 791       thread->set_thread_state(state);
 792       Threads_lock->unlock();
 793       break;
 794 
 795     case _thread_in_native_trans:
 796     case _thread_blocked_trans:
 797     case _thread_new_trans:
 798       if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
 799         thread->print_thread_state();
 800         fatal("Deadlock in safepoint code.  "
 801               "Should have called back to the VM before blocking.");
 802       }
 803 
 804       // We transition the thread to state _thread_blocked here, but
 805       // we can't do our usual check for external suspension and then
 806       // self-suspend after the lock_without_safepoint_check() call
 807       // below because we are often called during transitions while
 808       // we hold different locks. That would leave us suspended while
 809       // holding a resource which results in deadlocks.
 810       thread->set_thread_state(_thread_blocked);
 811 
 812       // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
 813       // the safepoint code might still be waiting for it to block. We need to change the state here,
 814       // so it can see that it is at a safepoint.
 815 
 816       // Block until the safepoint operation is completed.
 817       Threads_lock->lock_without_safepoint_check();
 818 
 819       // Restore state
 820       thread->set_thread_state(state);
 821 
 822       Threads_lock->unlock();
 823       break;
 824 
 825     default:
 826      fatal("Illegal threadstate encountered: %d", state);
 827   }
 828 
 829   // Check for pending. async. exceptions or suspends - except if the
 830   // thread was blocked inside the VM. has_special_runtime_exit_condition()
 831   // is called last since it grabs a lock and we only want to do that when
 832   // we must.
 833   //
 834   // Note: we never deliver an async exception at a polling point as the
 835   // compiler may not have an exception handler for it. The polling
 836   // code will notice the async and deoptimize and the exception will
 837   // be delivered. (Polling at a return point is ok though). Sure is
 838   // a lot of bother for a deprecated feature...
 839   //
 840   // We don't deliver an async exception if the thread state is
 841   // _thread_in_native_trans so JNI functions won't be called with
 842   // a surprising pending exception. If the thread state is going back to java,
 843   // async exception is checked in check_special_condition_for_native_trans().
 844 
 845   if (state != _thread_blocked_trans &&
 846       state != _thread_in_vm_trans &&
 847       thread->has_special_runtime_exit_condition()) {
 848     thread->handle_special_runtime_exit_condition(
 849       !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
 850   }
 851 }
 852 
 853 // ------------------------------------------------------------------------------------------------------
 854 // Exception handlers
 855 
 856 
 857 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
 858   assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
 859   assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
 860   assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
 861 
 862   if (ShowSafepointMsgs) {
 863     tty->print("handle_polling_page_exception: ");
 864   }
 865 
 866   if (PrintSafepointStatistics) {
 867     inc_page_trap_count();
 868   }
 869 
 870   ThreadSafepointState* state = thread->safepoint_state();
 871 
 872   state->handle_polling_page_exception();
 873 }
 874 
 875 
 876 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
 877   if (!timeout_error_printed) {
 878     timeout_error_printed = true;
 879     // Print out the thread info which didn't reach the safepoint for debugging
 880     // purposes (useful when there are lots of threads in the debugger).
 881     tty->cr();
 882     tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
 883     if (reason ==  _spinning_timeout) {
 884       tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
 885     } else if (reason == _blocking_timeout) {
 886       tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
 887     }
 888 
 889     tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
 890     ThreadSafepointState *cur_state;
 891     ResourceMark rm;
 892     for(JavaThread *cur_thread = Threads::first(); cur_thread;
 893         cur_thread = cur_thread->next()) {
 894       cur_state = cur_thread->safepoint_state();
 895 
 896       if (cur_thread->thread_state() != _thread_blocked &&
 897           ((reason == _spinning_timeout && cur_state->is_running()) ||
 898            (reason == _blocking_timeout && !cur_state->has_called_back()))) {
 899         tty->print("# ");
 900         cur_thread->print();
 901         tty->cr();
 902       }
 903     }
 904     tty->print_cr("# SafepointSynchronize::begin: (End of list)");
 905   }
 906 
 907   // To debug the long safepoint, specify both DieOnSafepointTimeout &
 908   // ShowMessageBoxOnError.
 909   if (DieOnSafepointTimeout) {
 910     fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
 911           SafepointTimeoutDelay, VMThread::vm_safepoint_description());
 912   }
 913 }
 914 
 915 
 916 // -------------------------------------------------------------------------------------------------------
 917 // Implementation of ThreadSafepointState
 918 
 919 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
 920   _thread = thread;
 921   _type   = _running;
 922   _has_called_back = false;
 923   _at_poll_safepoint = false;
 924 }
 925 
 926 void ThreadSafepointState::create(JavaThread *thread) {
 927   ThreadSafepointState *state = new ThreadSafepointState(thread);
 928   thread->set_safepoint_state(state);
 929 }
 930 
 931 void ThreadSafepointState::destroy(JavaThread *thread) {
 932   if (thread->safepoint_state()) {
 933     delete(thread->safepoint_state());
 934     thread->set_safepoint_state(NULL);
 935   }
 936 }
 937 
 938 void ThreadSafepointState::examine_state_of_thread() {
 939   assert(is_running(), "better be running or just have hit safepoint poll");
 940 
 941   JavaThreadState state = _thread->thread_state();
 942 
 943   // Save the state at the start of safepoint processing.
 944   _orig_thread_state = state;
 945 
 946   // Check for a thread that is suspended. Note that thread resume tries
 947   // to grab the Threads_lock which we own here, so a thread cannot be
 948   // resumed during safepoint synchronization.
 949 
 950   // We check to see if this thread is suspended without locking to
 951   // avoid deadlocking with a third thread that is waiting for this
 952   // thread to be suspended. The third thread can notice the safepoint
 953   // that we're trying to start at the beginning of its SR_lock->wait()
 954   // call. If that happens, then the third thread will block on the
 955   // safepoint while still holding the underlying SR_lock. We won't be
 956   // able to get the SR_lock and we'll deadlock.
 957   //
 958   // We don't need to grab the SR_lock here for two reasons:
 959   // 1) The suspend flags are both volatile and are set with an
 960   //    Atomic::cmpxchg() call so we should see the suspended
 961   //    state right away.
 962   // 2) We're being called from the safepoint polling loop; if
 963   //    we don't see the suspended state on this iteration, then
 964   //    we'll come around again.
 965   //
 966   bool is_suspended = _thread->is_ext_suspended();
 967   if (is_suspended) {
 968     roll_forward(_at_safepoint);
 969     return;
 970   }
 971 
 972   // Some JavaThread states have an initial safepoint state of
 973   // running, but are actually at a safepoint. We will happily
 974   // agree and update the safepoint state here.
 975   if (SafepointSynchronize::safepoint_safe(_thread, state)) {
 976     SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
 977     roll_forward(_at_safepoint);
 978     return;
 979   }
 980 
 981   if (state == _thread_in_vm) {
 982     roll_forward(_call_back);
 983     return;
 984   }
 985 
 986   // All other thread states will continue to run until they
 987   // transition and self-block in state _blocked
 988   // Safepoint polling in compiled code causes the Java threads to do the same.
 989   // Note: new threads may require a malloc so they must be allowed to finish
 990 
 991   assert(is_running(), "examine_state_of_thread on non-running thread");
 992   return;
 993 }
 994 
 995 // Returns true is thread could not be rolled forward at present position.
 996 void ThreadSafepointState::roll_forward(suspend_type type) {
 997   _type = type;
 998 
 999   switch(_type) {
1000     case _at_safepoint:
1001       SafepointSynchronize::signal_thread_at_safepoint();
1002       DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1003       if (_thread->in_critical()) {
1004         // Notice that this thread is in a critical section
1005         SafepointSynchronize::increment_jni_active_count();
1006       }
1007       break;
1008 
1009     case _call_back:
1010       set_has_called_back(false);
1011       break;
1012 
1013     case _running:
1014     default:
1015       ShouldNotReachHere();
1016   }
1017 }
1018 
1019 void ThreadSafepointState::restart() {
1020   switch(type()) {
1021     case _at_safepoint:
1022     case _call_back:
1023       break;
1024 
1025     case _running:
1026     default:
1027        tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1028                      p2i(_thread), _type);
1029        _thread->print();
1030       ShouldNotReachHere();
1031   }
1032   _type = _running;
1033   set_has_called_back(false);
1034 }
1035 
1036 
1037 void ThreadSafepointState::print_on(outputStream *st) const {
1038   const char *s = NULL;
1039 
1040   switch(_type) {
1041     case _running                : s = "_running";              break;
1042     case _at_safepoint           : s = "_at_safepoint";         break;
1043     case _call_back              : s = "_call_back";            break;
1044     default:
1045       ShouldNotReachHere();
1046   }
1047 
1048   st->print_cr("Thread: " INTPTR_FORMAT
1049               "  [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1050                p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1051                _at_poll_safepoint);
1052 
1053   _thread->print_thread_state_on(st);
1054 }
1055 
1056 // ---------------------------------------------------------------------------------------------------------------------
1057 
1058 // Block the thread at the safepoint poll or poll return.
1059 void ThreadSafepointState::handle_polling_page_exception() {
1060 
1061   // Check state.  block() will set thread state to thread_in_vm which will
1062   // cause the safepoint state _type to become _call_back.
1063   assert(type() == ThreadSafepointState::_running,
1064          "polling page exception on thread not running state");
1065 
1066   // Step 1: Find the nmethod from the return address
1067   if (ShowSafepointMsgs && Verbose) {
1068     tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1069   }
1070   address real_return_addr = thread()->saved_exception_pc();
1071 
1072   CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1073   assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1074   CompiledMethod* nm = (CompiledMethod*)cb;
1075 
1076   // Find frame of caller
1077   frame stub_fr = thread()->last_frame();
1078   CodeBlob* stub_cb = stub_fr.cb();
1079   assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1080   RegisterMap map(thread(), true);
1081   frame caller_fr = stub_fr.sender(&map);
1082 
1083   // Should only be poll_return or poll
1084   assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1085 
1086   // This is a poll immediately before a return. The exception handling code
1087   // has already had the effect of causing the return to occur, so the execution
1088   // will continue immediately after the call. In addition, the oopmap at the
1089   // return point does not mark the return value as an oop (if it is), so
1090   // it needs a handle here to be updated.
1091   if( nm->is_at_poll_return(real_return_addr) ) {
1092     // See if return type is an oop.
1093     bool return_oop = nm->method()->is_returning_oop();
1094     Handle return_value;
1095     if (return_oop) {
1096       // The oop result has been saved on the stack together with all
1097       // the other registers. In order to preserve it over GCs we need
1098       // to keep it in a handle.
1099       oop result = caller_fr.saved_oop_result(&map);
1100       assert(result == NULL || result->is_oop(), "must be oop");
1101       return_value = Handle(thread(), result);
1102       assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1103     }
1104 
1105     // Block the thread
1106     SafepointSynchronize::block(thread());
1107 
1108     // restore oop result, if any
1109     if (return_oop) {
1110       caller_fr.set_saved_oop_result(&map, return_value());
1111     }
1112   }
1113 
1114   // This is a safepoint poll. Verify the return address and block.
1115   else {
1116     set_at_poll_safepoint(true);
1117 
1118     // verify the blob built the "return address" correctly
1119     assert(real_return_addr == caller_fr.pc(), "must match");
1120 
1121     // Block the thread
1122     SafepointSynchronize::block(thread());
1123     set_at_poll_safepoint(false);
1124 
1125     // If we have a pending async exception deoptimize the frame
1126     // as otherwise we may never deliver it.
1127     if (thread()->has_async_condition()) {
1128       ThreadInVMfromJavaNoAsyncException __tiv(thread());
1129       Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1130     }
1131 
1132     // If an exception has been installed we must check for a pending deoptimization
1133     // Deoptimize frame if exception has been thrown.
1134 
1135     if (thread()->has_pending_exception() ) {
1136       RegisterMap map(thread(), true);
1137       frame caller_fr = stub_fr.sender(&map);
1138       if (caller_fr.is_deoptimized_frame()) {
1139         // The exception patch will destroy registers that are still
1140         // live and will be needed during deoptimization. Defer the
1141         // Async exception should have deferred the exception until the
1142         // next safepoint which will be detected when we get into
1143         // the interpreter so if we have an exception now things
1144         // are messed up.
1145 
1146         fatal("Exception installed and deoptimization is pending");
1147       }
1148     }
1149   }
1150 }
1151 
1152 
1153 //
1154 //                     Statistics & Instrumentations
1155 //
1156 SafepointSynchronize::SafepointStats*  SafepointSynchronize::_safepoint_stats = NULL;
1157 jlong  SafepointSynchronize::_safepoint_begin_time = 0;
1158 int    SafepointSynchronize::_cur_stat_index = 0;
1159 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1160 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1161 jlong  SafepointSynchronize::_max_sync_time = 0;
1162 jlong  SafepointSynchronize::_max_vmop_time = 0;
1163 float  SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1164 
1165 static jlong  cleanup_end_time = 0;
1166 static bool   need_to_track_page_armed_status = false;
1167 static bool   init_done = false;
1168 
1169 // Helper method to print the header.
1170 static void print_header() {
1171   // The number of spaces is significant here, and should match the format
1172   // specifiers in print_statistics().
1173 
1174   tty->print("          vmop                            "
1175              "[ threads:    total initially_running wait_to_block ]"
1176              "[ time:    spin   block    sync cleanup    vmop ] ");
1177 
1178   // no page armed status printed out if it is always armed.
1179   if (need_to_track_page_armed_status) {
1180     tty->print("page_armed ");
1181   }
1182 
1183   tty->print_cr("page_trap_count");
1184 }
1185 
1186 void SafepointSynchronize::deferred_initialize_stat() {
1187   if (init_done) return;
1188 
1189   // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1190   // be printed right away, in which case, _safepoint_stats will regress to
1191   // a single element array. Otherwise, it is a circular ring buffer with default
1192   // size of PrintSafepointStatisticsCount.
1193   int stats_array_size;
1194   if (PrintSafepointStatisticsTimeout > 0) {
1195     stats_array_size = 1;
1196     PrintSafepointStatistics = true;
1197   } else {
1198     stats_array_size = PrintSafepointStatisticsCount;
1199   }
1200   _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1201                                                  * sizeof(SafepointStats), mtInternal);
1202   guarantee(_safepoint_stats != NULL,
1203             "not enough memory for safepoint instrumentation data");
1204 
1205   if (DeferPollingPageLoopCount >= 0) {
1206     need_to_track_page_armed_status = true;
1207   }
1208   init_done = true;
1209 }
1210 
1211 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1212   assert(init_done, "safepoint statistics array hasn't been initialized");
1213   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1214 
1215   spstat->_time_stamp = _ts_of_current_safepoint;
1216 
1217   VM_Operation *op = VMThread::vm_operation();
1218   spstat->_vmop_type = (op != NULL ? op->type() : -1);
1219   if (op != NULL) {
1220     _safepoint_reasons[spstat->_vmop_type]++;
1221   }
1222 
1223   spstat->_nof_total_threads = nof_threads;
1224   spstat->_nof_initial_running_threads = nof_running;
1225   spstat->_nof_threads_hit_page_trap = 0;
1226 
1227   // Records the start time of spinning. The real time spent on spinning
1228   // will be adjusted when spin is done. Same trick is applied for time
1229   // spent on waiting for threads to block.
1230   if (nof_running != 0) {
1231     spstat->_time_to_spin = os::javaTimeNanos();
1232   }  else {
1233     spstat->_time_to_spin = 0;
1234   }
1235 }
1236 
1237 void SafepointSynchronize::update_statistics_on_spin_end() {
1238   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1239 
1240   jlong cur_time = os::javaTimeNanos();
1241 
1242   spstat->_nof_threads_wait_to_block = _waiting_to_block;
1243   if (spstat->_nof_initial_running_threads != 0) {
1244     spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1245   }
1246 
1247   if (need_to_track_page_armed_status) {
1248     spstat->_page_armed = (PageArmed == 1);
1249   }
1250 
1251   // Records the start time of waiting for to block. Updated when block is done.
1252   if (_waiting_to_block != 0) {
1253     spstat->_time_to_wait_to_block = cur_time;
1254   } else {
1255     spstat->_time_to_wait_to_block = 0;
1256   }
1257 }
1258 
1259 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1260   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1261 
1262   if (spstat->_nof_threads_wait_to_block != 0) {
1263     spstat->_time_to_wait_to_block = end_time -
1264       spstat->_time_to_wait_to_block;
1265   }
1266 
1267   // Records the end time of sync which will be used to calculate the total
1268   // vm operation time. Again, the real time spending in syncing will be deducted
1269   // from the start of the sync time later when end_statistics is called.
1270   spstat->_time_to_sync = end_time - _safepoint_begin_time;
1271   if (spstat->_time_to_sync > _max_sync_time) {
1272     _max_sync_time = spstat->_time_to_sync;
1273   }
1274 
1275   spstat->_time_to_do_cleanups = end_time;
1276 }
1277 
1278 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1279   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1280 
1281   // Record how long spent in cleanup tasks.
1282   spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1283 
1284   cleanup_end_time = end_time;
1285 }
1286 
1287 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1288   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1289 
1290   // Update the vm operation time.
1291   spstat->_time_to_exec_vmop = vmop_end_time -  cleanup_end_time;
1292   if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1293     _max_vmop_time = spstat->_time_to_exec_vmop;
1294   }
1295   // Only the sync time longer than the specified
1296   // PrintSafepointStatisticsTimeout will be printed out right away.
1297   // By default, it is -1 meaning all samples will be put into the list.
1298   if ( PrintSafepointStatisticsTimeout > 0) {
1299     if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1300       print_statistics();
1301     }
1302   } else {
1303     // The safepoint statistics will be printed out when the _safepoin_stats
1304     // array fills up.
1305     if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1306       print_statistics();
1307       _cur_stat_index = 0;
1308     } else {
1309       _cur_stat_index++;
1310     }
1311   }
1312 }
1313 
1314 void SafepointSynchronize::print_statistics() {
1315   for (int index = 0; index <= _cur_stat_index; index++) {
1316     if (index % 30 == 0) {
1317       print_header();
1318     }
1319     SafepointStats* sstats = &_safepoint_stats[index];
1320     tty->print("%8.3f: ", sstats->_time_stamp);
1321     tty->print("%-30s  [          "
1322                INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1323                "]",
1324                (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1325                sstats->_nof_total_threads,
1326                sstats->_nof_initial_running_threads,
1327                sstats->_nof_threads_wait_to_block);
1328     // "/ MICROUNITS " is to convert the unit from nanos to millis.
1329     tty->print("[       "
1330                INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1331                INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1332                INT64_FORMAT_W(7) " ] ",
1333                sstats->_time_to_spin / MICROUNITS,
1334                sstats->_time_to_wait_to_block / MICROUNITS,
1335                sstats->_time_to_sync / MICROUNITS,
1336                sstats->_time_to_do_cleanups / MICROUNITS,
1337                sstats->_time_to_exec_vmop / MICROUNITS);
1338 
1339     if (need_to_track_page_armed_status) {
1340       tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1341     }
1342     tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1343   }
1344 }
1345 
1346 // This method will be called when VM exits. It will first call
1347 // print_statistics to print out the rest of the sampling.  Then
1348 // it tries to summarize the sampling.
1349 void SafepointSynchronize::print_stat_on_exit() {
1350   if (_safepoint_stats == NULL) return;
1351 
1352   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1353 
1354   // During VM exit, end_statistics may not get called and in that
1355   // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1356   // don't print it out.
1357   // Approximate the vm op time.
1358   _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1359     os::javaTimeNanos() - cleanup_end_time;
1360 
1361   if ( PrintSafepointStatisticsTimeout < 0 ||
1362        spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1363     print_statistics();
1364   }
1365   tty->cr();
1366 
1367   // Print out polling page sampling status.
1368   if (!need_to_track_page_armed_status) {
1369     tty->print_cr("Polling page always armed");
1370   } else {
1371     tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1372                   DeferPollingPageLoopCount);
1373   }
1374 
1375   for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1376     if (_safepoint_reasons[index] != 0) {
1377       tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1378                     _safepoint_reasons[index]);
1379     }
1380   }
1381 
1382   tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1383                 _coalesced_vmop_count);
1384   tty->print_cr("Maximum sync time  " INT64_FORMAT_W(5) " ms",
1385                 _max_sync_time / MICROUNITS);
1386   tty->print_cr("Maximum vm operation time (except for Exit VM operation)  "
1387                 INT64_FORMAT_W(5) " ms",
1388                 _max_vmop_time / MICROUNITS);
1389 }
1390 
1391 // ------------------------------------------------------------------------------------------------
1392 // Non-product code
1393 
1394 #ifndef PRODUCT
1395 
1396 void SafepointSynchronize::print_state() {
1397   if (_state == _not_synchronized) {
1398     tty->print_cr("not synchronized");
1399   } else if (_state == _synchronizing || _state == _synchronized) {
1400     tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1401                   "synchronized");
1402 
1403     for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1404        cur->safepoint_state()->print();
1405     }
1406   }
1407 }
1408 
1409 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1410   if (ShowSafepointMsgs) {
1411     va_list ap;
1412     va_start(ap, format);
1413     tty->vprint_cr(format, ap);
1414     va_end(ap);
1415   }
1416 }
1417 
1418 #endif // !PRODUCT