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/classLoaderData.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "classfile/systemDictionary.hpp"
  30 #include "code/codeCache.hpp"
  31 #include "code/icBuffer.hpp"
  32 #include "code/nmethod.hpp"
  33 #include "code/pcDesc.hpp"
  34 #include "code/scopeDesc.hpp"
  35 #include "gc/shared/collectedHeap.hpp"
  36 #include "gc/shared/gcLocker.inline.hpp"
  37 #include "gc/shared/strongRootsScope.hpp"
  38 #include "gc/shared/workgroup.hpp"
  39 #include "interpreter/interpreter.hpp"
  40 #include "logging/log.hpp"
  41 #include "logging/logStream.hpp"
  42 #include "memory/resourceArea.hpp"
  43 #include "memory/universe.inline.hpp"
  44 #include "oops/oop.inline.hpp"
  45 #include "oops/symbol.hpp"
  46 #include "runtime/atomic.hpp"
  47 #include "runtime/compilationPolicy.hpp"
  48 #include "runtime/deoptimization.hpp"
  49 #include "runtime/frame.inline.hpp"
  50 #include "runtime/interfaceSupport.hpp"
  51 #include "runtime/mutexLocker.hpp"
  52 #include "runtime/orderAccess.inline.hpp"
  53 #include "runtime/osThread.hpp"
  54 #include "runtime/safepoint.hpp"
  55 #include "runtime/signature.hpp"
  56 #include "runtime/stubCodeGenerator.hpp"
  57 #include "runtime/stubRoutines.hpp"
  58 #include "runtime/sweeper.hpp"
  59 #include "runtime/synchronizer.hpp"
  60 #include "runtime/thread.inline.hpp"
  61 #include "runtime/timerTrace.hpp"
  62 #include "services/runtimeService.hpp"
  63 #include "trace/tracing.hpp"
  64 #include "trace/traceMacros.hpp"
  65 #include "utilities/events.hpp"
  66 #include "utilities/macros.hpp"
  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   Universe::heap()->safepoint_synchronize_begin();
  95 
  96   // By getting the Threads_lock, we assure that no threads are about to start or
  97   // exit. It is released again in SafepointSynchronize::end().
  98   Threads_lock->lock();
  99 
 100   assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
 101 
 102   int nof_threads = Threads::number_of_threads();
 103 
 104   log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
 105 
 106   RuntimeService::record_safepoint_begin();
 107 
 108   MutexLocker mu(Safepoint_lock);
 109 
 110   // Reset the count of active JNI critical threads
 111   _current_jni_active_count = 0;
 112 
 113   // Set number of threads to wait for, before we initiate the callbacks
 114   _waiting_to_block = nof_threads;
 115   TryingToBlock     = 0 ;
 116   int still_running = nof_threads;
 117 
 118   // Save the starting time, so that it can be compared to see if this has taken
 119   // too long to complete.
 120   jlong safepoint_limit_time = 0;
 121   timeout_error_printed = false;
 122 
 123   // PrintSafepointStatisticsTimeout can be specified separately. When
 124   // specified, PrintSafepointStatistics will be set to true in
 125   // deferred_initialize_stat method. The initialization has to be done
 126   // early enough to avoid any races. See bug 6880029 for details.
 127   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
 128     deferred_initialize_stat();
 129   }
 130 
 131   // Begin the process of bringing the system to a safepoint.
 132   // Java threads can be in several different states and are
 133   // stopped by different mechanisms:
 134   //
 135   //  1. Running interpreted
 136   //     The interpreter dispatch table is changed to force it to
 137   //     check for a safepoint condition between bytecodes.
 138   //  2. Running in native code
 139   //     When returning from the native code, a Java thread must check
 140   //     the safepoint _state to see if we must block.  If the
 141   //     VM thread sees a Java thread in native, it does
 142   //     not wait for this thread to block.  The order of the memory
 143   //     writes and reads of both the safepoint state and the Java
 144   //     threads state is critical.  In order to guarantee that the
 145   //     memory writes are serialized with respect to each other,
 146   //     the VM thread issues a memory barrier instruction
 147   //     (on MP systems).  In order to avoid the overhead of issuing
 148   //     a memory barrier for each Java thread making native calls, each Java
 149   //     thread performs a write to a single memory page after changing
 150   //     the thread state.  The VM thread performs a sequence of
 151   //     mprotect OS calls which forces all previous writes from all
 152   //     Java threads to be serialized.  This is done in the
 153   //     os::serialize_thread_states() call.  This has proven to be
 154   //     much more efficient than executing a membar instruction
 155   //     on every call to native code.
 156   //  3. Running compiled Code
 157   //     Compiled code reads a global (Safepoint Polling) page that
 158   //     is set to fault if we are trying to get to a safepoint.
 159   //  4. Blocked
 160   //     A thread which is blocked will not be allowed to return from the
 161   //     block condition until the safepoint operation is complete.
 162   //  5. In VM or Transitioning between states
 163   //     If a Java thread is currently running in the VM or transitioning
 164   //     between states, the safepointing code will wait for the thread to
 165   //     block itself when it attempts transitions to a new state.
 166   //
 167   {
 168     EventSafepointStateSynchronization sync_event;
 169     int initial_running = 0;
 170 
 171     _state            = _synchronizing;
 172     OrderAccess::fence();
 173 
 174     // Flush all thread states to memory
 175     if (!UseMembar) {
 176       os::serialize_thread_states();
 177     }
 178 
 179     // Make interpreter safepoint aware
 180     Interpreter::notice_safepoints();
 181 
 182     if (DeferPollingPageLoopCount < 0) {
 183       // Make polling safepoint aware
 184       guarantee (PageArmed == 0, "invariant") ;
 185       PageArmed = 1 ;
 186       os::make_polling_page_unreadable();
 187     }
 188 
 189     // Consider using active_processor_count() ... but that call is expensive.
 190     int ncpus = os::processor_count() ;
 191 
 192 #ifdef ASSERT
 193     for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 194       assert(cur->safepoint_state()->is_running(), "Illegal initial state");
 195       // Clear the visited flag to ensure that the critical counts are collected properly.
 196       cur->set_visited_for_critical_count(false);
 197     }
 198 #endif // ASSERT
 199 
 200     if (SafepointTimeout)
 201       safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
 202 
 203     // Iterate through all threads until it have been determined how to stop them all at a safepoint
 204     unsigned int iterations = 0;
 205     int steps = 0 ;
 206     while(still_running > 0) {
 207       for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 208         assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
 209         ThreadSafepointState *cur_state = cur->safepoint_state();
 210         if (cur_state->is_running()) {
 211           cur_state->examine_state_of_thread();
 212           if (!cur_state->is_running()) {
 213             still_running--;
 214             // consider adjusting steps downward:
 215             //   steps = 0
 216             //   steps -= NNN
 217             //   steps >>= 1
 218             //   steps = MIN(steps, 2000-100)
 219             //   if (iterations != 0) steps -= NNN
 220           }
 221           LogTarget(Trace, safepoint) lt;
 222           if (lt.is_enabled()) {
 223             ResourceMark rm;
 224             LogStream ls(lt);
 225             cur_state->print_on(&ls);
 226           }
 227         }
 228       }
 229 
 230       if (iterations == 0) {
 231         initial_running = still_running;
 232         if (PrintSafepointStatistics) {
 233           begin_statistics(nof_threads, still_running);
 234         }
 235       }
 236 
 237       if (still_running > 0) {
 238         // Check for if it takes to long
 239         if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
 240           print_safepoint_timeout(_spinning_timeout);
 241         }
 242 
 243         // Spin to avoid context switching.
 244         // There's a tension between allowing the mutators to run (and rendezvous)
 245         // vs spinning.  As the VM thread spins, wasting cycles, it consumes CPU that
 246         // a mutator might otherwise use profitably to reach a safepoint.  Excessive
 247         // spinning by the VM thread on a saturated system can increase rendezvous latency.
 248         // Blocking or yielding incur their own penalties in the form of context switching
 249         // and the resultant loss of $ residency.
 250         //
 251         // Further complicating matters is that yield() does not work as naively expected
 252         // on many platforms -- yield() does not guarantee that any other ready threads
 253         // will run.   As such we revert to naked_short_sleep() after some number of iterations.
 254         // nakes_short_sleep() is implemented as a short unconditional sleep.
 255         // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
 256         // can actually increase the time it takes the VM thread to detect that a system-wide
 257         // stop-the-world safepoint has been reached.  In a pathological scenario such as that
 258         // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
 259         // In that case the mutators will be stalled waiting for the safepoint to complete and the
 260         // the VMthread will be sleeping, waiting for the mutators to rendezvous.  The VMthread
 261         // will eventually wake up and detect that all mutators are safe, at which point
 262         // we'll again make progress.
 263         //
 264         // Beware too that that the VMThread typically runs at elevated priority.
 265         // Its default priority is higher than the default mutator priority.
 266         // Obviously, this complicates spinning.
 267         //
 268         // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
 269         // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
 270         //
 271         // See the comments in synchronizer.cpp for additional remarks on spinning.
 272         //
 273         // In the future we might:
 274         // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
 275         //    This is tricky as the path used by a thread exiting the JVM (say on
 276         //    on JNI call-out) simply stores into its state field.  The burden
 277         //    is placed on the VM thread, which must poll (spin).
 278         // 2. Find something useful to do while spinning.  If the safepoint is GC-related
 279         //    we might aggressively scan the stacks of threads that are already safe.
 280         // 3. Use Solaris schedctl to examine the state of the still-running mutators.
 281         //    If all the mutators are ONPROC there's no reason to sleep or yield.
 282         // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
 283         // 5. Check system saturation.  If the system is not fully saturated then
 284         //    simply spin and avoid sleep/yield.
 285         // 6. As still-running mutators rendezvous they could unpark the sleeping
 286         //    VMthread.  This works well for still-running mutators that become
 287         //    safe.  The VMthread must still poll for mutators that call-out.
 288         // 7. Drive the policy on time-since-begin instead of iterations.
 289         // 8. Consider making the spin duration a function of the # of CPUs:
 290         //    Spin = (((ncpus-1) * M) + K) + F(still_running)
 291         //    Alternately, instead of counting iterations of the outer loop
 292         //    we could count the # of threads visited in the inner loop, above.
 293         // 9. On windows consider using the return value from SwitchThreadTo()
 294         //    to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
 295 
 296         if (int(iterations) == DeferPollingPageLoopCount) {
 297           guarantee (PageArmed == 0, "invariant") ;
 298           PageArmed = 1 ;
 299           os::make_polling_page_unreadable();
 300         }
 301 
 302         // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
 303         // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
 304         ++steps ;
 305         if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
 306           SpinPause() ;     // MP-Polite spin
 307         } else
 308           if (steps < DeferThrSuspendLoopCount) {
 309             os::naked_yield() ;
 310           } else {
 311             os::naked_short_sleep(1);
 312           }
 313 
 314         iterations ++ ;
 315       }
 316       assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
 317     }
 318     assert(still_running == 0, "sanity check");
 319 
 320     if (PrintSafepointStatistics) {
 321       update_statistics_on_spin_end();
 322     }
 323 
 324     if (sync_event.should_commit()) {
 325       // Group this event together with the ones committed after the counter is increased
 326       sync_event.set_safepointId(safepoint_counter() + 1);
 327       sync_event.set_initialThreadCount(initial_running);
 328       sync_event.set_runningThreadCount(_waiting_to_block);
 329       sync_event.set_iterations(iterations);
 330       sync_event.commit();
 331     }
 332   } //EventSafepointStateSync
 333 
 334   // wait until all threads are stopped
 335   {
 336     EventSafepointWaitBlocked wait_blocked_event;
 337     int initial_waiting_to_block = _waiting_to_block;
 338 
 339     while (_waiting_to_block > 0) {
 340       log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
 341       if (!SafepointTimeout || timeout_error_printed) {
 342         Safepoint_lock->wait(true);  // true, means with no safepoint checks
 343       } else {
 344         // Compute remaining time
 345         jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
 346 
 347         // If there is no remaining time, then there is an error
 348         if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
 349           print_safepoint_timeout(_blocking_timeout);
 350         }
 351       }
 352     }
 353     assert(_waiting_to_block == 0, "sanity check");
 354 
 355 #ifndef PRODUCT
 356     if (SafepointTimeout) {
 357       jlong current_time = os::javaTimeNanos();
 358       if (safepoint_limit_time < current_time) {
 359         tty->print_cr("# SafepointSynchronize: Finished after "
 360                       INT64_FORMAT_W(6) " ms",
 361                       (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
 362                                 (jlong)SafepointTimeoutDelay));
 363       }
 364     }
 365 #endif
 366 
 367     assert((_safepoint_counter & 0x1) == 0, "must be even");
 368     assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 369     _safepoint_counter ++;
 370 
 371     // Record state
 372     _state = _synchronized;
 373 
 374     OrderAccess::fence();
 375 
 376     if (wait_blocked_event.should_commit()) {
 377       wait_blocked_event.set_safepointId(safepoint_counter());
 378       wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
 379       wait_blocked_event.commit();
 380     }
 381   } // EventSafepointWaitBlocked
 382 
 383 #ifdef ASSERT
 384   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 385     // make sure all the threads were visited
 386     assert(cur->was_visited_for_critical_count(), "missed a thread");
 387   }
 388 #endif // ASSERT
 389 
 390   // Update the count of active JNI critical regions
 391   GCLocker::set_jni_lock_count(_current_jni_active_count);
 392 
 393   if (log_is_enabled(Debug, safepoint)) {
 394     log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
 395   }
 396 
 397   RuntimeService::record_safepoint_synchronized();
 398   if (PrintSafepointStatistics) {
 399     update_statistics_on_sync_end(os::javaTimeNanos());
 400   }
 401 
 402   // Call stuff that needs to be run when a safepoint is just about to be completed
 403   {
 404     EventSafepointCleanup cleanup_event;
 405     do_cleanup_tasks();
 406     if (cleanup_event.should_commit()) {
 407       cleanup_event.set_safepointId(safepoint_counter());
 408       cleanup_event.commit();
 409     }
 410   }
 411 
 412   if (PrintSafepointStatistics) {
 413     // Record how much time spend on the above cleanup tasks
 414     update_statistics_on_cleanup_end(os::javaTimeNanos());
 415   }
 416   if (begin_event.should_commit()) {
 417     begin_event.set_safepointId(safepoint_counter());
 418     begin_event.set_totalThreadCount(nof_threads);
 419     begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
 420     begin_event.commit();
 421   }
 422 }
 423 
 424 // Wake up all threads, so they are ready to resume execution after the safepoint
 425 // operation has been carried out
 426 void SafepointSynchronize::end() {
 427   EventSafepointEnd event;
 428   int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
 429 
 430   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 431   assert((_safepoint_counter & 0x1) == 1, "must be odd");
 432   _safepoint_counter ++;
 433   // memory fence isn't required here since an odd _safepoint_counter
 434   // value can do no harm and a fence is issued below anyway.
 435 
 436   DEBUG_ONLY(Thread* myThread = Thread::current();)
 437   assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
 438 
 439   if (PrintSafepointStatistics) {
 440     end_statistics(os::javaTimeNanos());
 441   }
 442 
 443 #ifdef ASSERT
 444   // A pending_exception cannot be installed during a safepoint.  The threads
 445   // may install an async exception after they come back from a safepoint into
 446   // pending_exception after they unblock.  But that should happen later.
 447   for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
 448     assert (!(cur->has_pending_exception() &&
 449               cur->safepoint_state()->is_at_poll_safepoint()),
 450             "safepoint installed a pending exception");
 451   }
 452 #endif // ASSERT
 453 
 454   if (PageArmed) {
 455     // Make polling safepoint aware
 456     os::make_polling_page_readable();
 457     PageArmed = 0 ;
 458   }
 459 
 460   // Remove safepoint check from interpreter
 461   Interpreter::ignore_safepoints();
 462 
 463   {
 464     MutexLocker mu(Safepoint_lock);
 465 
 466     assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
 467 
 468     // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
 469     // when they get restarted.
 470     _state = _not_synchronized;
 471     OrderAccess::fence();
 472 
 473     log_debug(safepoint)("Leaving safepoint region");
 474 
 475     // Start suspended threads
 476     for(JavaThread *current = Threads::first(); current; current = current->next()) {
 477       // A problem occurring on Solaris is when attempting to restart threads
 478       // the first #cpus - 1 go well, but then the VMThread is preempted when we get
 479       // to the next one (since it has been running the longest).  We then have
 480       // to wait for a cpu to become available before we can continue restarting
 481       // threads.
 482       // FIXME: This causes the performance of the VM to degrade when active and with
 483       // large numbers of threads.  Apparently this is due to the synchronous nature
 484       // of suspending threads.
 485       //
 486       // TODO-FIXME: the comments above are vestigial and no longer apply.
 487       // Furthermore, using solaris' schedctl in this particular context confers no benefit
 488       if (VMThreadHintNoPreempt) {
 489         os::hint_no_preempt();
 490       }
 491       ThreadSafepointState* cur_state = current->safepoint_state();
 492       assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
 493       cur_state->restart();
 494       assert(cur_state->is_running(), "safepoint state has not been reset");
 495     }
 496 
 497     RuntimeService::record_safepoint_end();
 498 
 499     // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
 500     // blocked in signal_thread_blocked
 501     Threads_lock->unlock();
 502 
 503   }
 504   Universe::heap()->safepoint_synchronize_end();
 505   // record this time so VMThread can keep track how much time has elapsed
 506   // since last safepoint.
 507   _end_of_last_safepoint = os::javaTimeMillis();
 508 
 509   if (event.should_commit()) {
 510     event.set_safepointId(safepoint_id);
 511     event.commit();
 512   }
 513 }
 514 
 515 bool SafepointSynchronize::is_cleanup_needed() {
 516   // Need a safepoint if there are many monitors to deflate.
 517   if (ObjectSynchronizer::is_cleanup_needed()) return true;
 518   // Need a safepoint if some inline cache buffers is non-empty
 519   if (!InlineCacheBuffer::is_empty()) return true;
 520   return false;
 521 }
 522 
 523 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
 524   if (event.should_commit()) {
 525     event.set_safepointId(SafepointSynchronize::safepoint_counter());
 526     event.set_name(name);
 527     event.commit();
 528   }
 529 }
 530 
 531 class ParallelSPCleanupThreadClosure : public ThreadClosure {
 532 private:
 533   CodeBlobClosure* _nmethod_cl;
 534   DeflateMonitorCounters* _counters;
 535 
 536 public:
 537   ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
 538     _counters(counters),
 539     _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
 540 
 541   void do_thread(Thread* thread) {
 542     ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
 543     if (_nmethod_cl != NULL && thread->is_Java_thread() &&
 544         ! thread->is_Code_cache_sweeper_thread()) {
 545       JavaThread* jt = (JavaThread*) thread;
 546       jt->nmethods_do(_nmethod_cl);
 547     }
 548   }
 549 };
 550 
 551 class ParallelSPCleanupTask : public AbstractGangTask {
 552 private:
 553   SubTasksDone _subtasks;
 554   ParallelSPCleanupThreadClosure _cleanup_threads_cl;
 555   uint _num_workers;
 556   DeflateMonitorCounters* _counters;
 557 public:
 558   ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
 559     AbstractGangTask("Parallel Safepoint Cleanup"),
 560     _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
 561     _num_workers(num_workers),
 562     _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
 563     _counters(counters) {}
 564 
 565   void work(uint worker_id) {
 566     // All threads deflate monitors and mark nmethods (if necessary).
 567     Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
 568 
 569     if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
 570       const char* name = "deflating idle monitors";
 571       EventSafepointCleanupTask event;
 572       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 573       ObjectSynchronizer::deflate_idle_monitors(_counters);
 574       event_safepoint_cleanup_task_commit(event, name);
 575     }
 576 
 577     if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
 578       const char* name = "updating inline caches";
 579       EventSafepointCleanupTask event;
 580       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 581       InlineCacheBuffer::update_inline_caches();
 582       event_safepoint_cleanup_task_commit(event, name);
 583     }
 584 
 585     if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
 586       const char* name = "compilation policy safepoint handler";
 587       EventSafepointCleanupTask event;
 588       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 589       CompilationPolicy::policy()->do_safepoint_work();
 590       event_safepoint_cleanup_task_commit(event, name);
 591     }
 592 
 593     if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
 594       if (SymbolTable::needs_rehashing()) {
 595         const char* name = "rehashing symbol table";
 596         EventSafepointCleanupTask event;
 597         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 598         SymbolTable::rehash_table();
 599         event_safepoint_cleanup_task_commit(event, name);
 600       }
 601     }
 602 
 603     if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
 604       if (StringTable::needs_rehashing()) {
 605         const char* name = "rehashing string table";
 606         EventSafepointCleanupTask event;
 607         TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 608         StringTable::rehash_table();
 609         event_safepoint_cleanup_task_commit(event, name);
 610       }
 611     }
 612 
 613     if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
 614       // CMS delays purging the CLDG until the beginning of the next safepoint and to
 615       // make sure concurrent sweep is done
 616       const char* name = "purging class loader data graph";
 617       EventSafepointCleanupTask event;
 618       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 619       ClassLoaderDataGraph::purge_if_needed();
 620       event_safepoint_cleanup_task_commit(event, name);
 621     }
 622 
 623     if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
 624       const char* name = "resizing system dictionaries";
 625       EventSafepointCleanupTask event;
 626       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
 627       ClassLoaderDataGraph::resize_if_needed();
 628       event_safepoint_cleanup_task_commit(event, name);
 629     }
 630     _subtasks.all_tasks_completed(_num_workers);
 631   }
 632 };
 633 
 634 // Various cleaning tasks that should be done periodically at safepoints.
 635 void SafepointSynchronize::do_cleanup_tasks() {
 636 
 637   TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
 638 
 639   // Prepare for monitor deflation.
 640   DeflateMonitorCounters deflate_counters;
 641   ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
 642 
 643   CollectedHeap* heap = Universe::heap();
 644   assert(heap != NULL, "heap not initialized yet?");
 645   WorkGang* cleanup_workers = heap->get_safepoint_workers();
 646   if (cleanup_workers != NULL) {
 647     // Parallel cleanup using GC provided thread pool.
 648     uint num_cleanup_workers = cleanup_workers->active_workers();
 649     ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
 650     StrongRootsScope srs(num_cleanup_workers);
 651     cleanup_workers->run_task(&cleanup);
 652   } else {
 653     // Serial cleanup using VMThread.
 654     ParallelSPCleanupTask cleanup(1, &deflate_counters);
 655     StrongRootsScope srs(1);
 656     cleanup.work(0);
 657   }
 658 
 659   // Finish monitor deflation.
 660   ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
 661 }
 662 
 663 
 664 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
 665   switch(state) {
 666   case _thread_in_native:
 667     // native threads are safe if they have no java stack or have walkable stack
 668     return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
 669 
 670    // blocked threads should have already have walkable stack
 671   case _thread_blocked:
 672     assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
 673     return true;
 674 
 675   default:
 676     return false;
 677   }
 678 }
 679 
 680 
 681 // See if the thread is running inside a lazy critical native and
 682 // update the thread critical count if so.  Also set a suspend flag to
 683 // cause the native wrapper to return into the JVM to do the unlock
 684 // once the native finishes.
 685 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
 686   if (state == _thread_in_native &&
 687       thread->has_last_Java_frame() &&
 688       thread->frame_anchor()->walkable()) {
 689     // This thread might be in a critical native nmethod so look at
 690     // the top of the stack and increment the critical count if it
 691     // is.
 692     frame wrapper_frame = thread->last_frame();
 693     CodeBlob* stub_cb = wrapper_frame.cb();
 694     if (stub_cb != NULL &&
 695         stub_cb->is_nmethod() &&
 696         stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
 697       // A thread could potentially be in a critical native across
 698       // more than one safepoint, so only update the critical state on
 699       // the first one.  When it returns it will perform the unlock.
 700       if (!thread->do_critical_native_unlock()) {
 701 #ifdef ASSERT
 702         if (!thread->in_critical()) {
 703           GCLocker::increment_debug_jni_lock_count();
 704         }
 705 #endif
 706         thread->enter_critical();
 707         // Make sure the native wrapper calls back on return to
 708         // perform the needed critical unlock.
 709         thread->set_critical_native_unlock();
 710       }
 711     }
 712   }
 713 }
 714 
 715 
 716 
 717 // -------------------------------------------------------------------------------------------------------
 718 // Implementation of Safepoint callback point
 719 
 720 void SafepointSynchronize::block(JavaThread *thread) {
 721   assert(thread != NULL, "thread must be set");
 722   assert(thread->is_Java_thread(), "not a Java thread");
 723 
 724   // Threads shouldn't block if they are in the middle of printing, but...
 725   ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
 726 
 727   // Only bail from the block() call if the thread is gone from the
 728   // thread list; starting to exit should still block.
 729   if (thread->is_terminated()) {
 730      // block current thread if we come here from native code when VM is gone
 731      thread->block_if_vm_exited();
 732 
 733      // otherwise do nothing
 734      return;
 735   }
 736 
 737   JavaThreadState state = thread->thread_state();
 738   thread->frame_anchor()->make_walkable(thread);
 739 
 740   // Check that we have a valid thread_state at this point
 741   switch(state) {
 742     case _thread_in_vm_trans:
 743     case _thread_in_Java:        // From compiled code
 744 
 745       // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
 746       // we pretend we are still in the VM.
 747       thread->set_thread_state(_thread_in_vm);
 748 
 749       if (is_synchronizing()) {
 750          Atomic::inc (&TryingToBlock) ;
 751       }
 752 
 753       // We will always be holding the Safepoint_lock when we are examine the state
 754       // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
 755       // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
 756       Safepoint_lock->lock_without_safepoint_check();
 757       if (is_synchronizing()) {
 758         // Decrement the number of threads to wait for and signal vm thread
 759         assert(_waiting_to_block > 0, "sanity check");
 760         _waiting_to_block--;
 761         thread->safepoint_state()->set_has_called_back(true);
 762 
 763         DEBUG_ONLY(thread->set_visited_for_critical_count(true));
 764         if (thread->in_critical()) {
 765           // Notice that this thread is in a critical section
 766           increment_jni_active_count();
 767         }
 768 
 769         // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
 770         if (_waiting_to_block == 0) {
 771           Safepoint_lock->notify_all();
 772         }
 773       }
 774 
 775       // We transition the thread to state _thread_blocked here, but
 776       // we can't do our usual check for external suspension and then
 777       // self-suspend after the lock_without_safepoint_check() call
 778       // below because we are often called during transitions while
 779       // we hold different locks. That would leave us suspended while
 780       // holding a resource which results in deadlocks.
 781       thread->set_thread_state(_thread_blocked);
 782       Safepoint_lock->unlock();
 783 
 784       // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
 785       // the entire safepoint, the threads will all line up here during the safepoint.
 786       Threads_lock->lock_without_safepoint_check();
 787       // restore original state. This is important if the thread comes from compiled code, so it
 788       // will continue to execute with the _thread_in_Java state.
 789       thread->set_thread_state(state);
 790       Threads_lock->unlock();
 791       break;
 792 
 793     case _thread_in_native_trans:
 794     case _thread_blocked_trans:
 795     case _thread_new_trans:
 796       if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
 797         thread->print_thread_state();
 798         fatal("Deadlock in safepoint code.  "
 799               "Should have called back to the VM before blocking.");
 800       }
 801 
 802       // We transition the thread to state _thread_blocked here, but
 803       // we can't do our usual check for external suspension and then
 804       // self-suspend after the lock_without_safepoint_check() call
 805       // below because we are often called during transitions while
 806       // we hold different locks. That would leave us suspended while
 807       // holding a resource which results in deadlocks.
 808       thread->set_thread_state(_thread_blocked);
 809 
 810       // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
 811       // the safepoint code might still be waiting for it to block. We need to change the state here,
 812       // so it can see that it is at a safepoint.
 813 
 814       // Block until the safepoint operation is completed.
 815       Threads_lock->lock_without_safepoint_check();
 816 
 817       // Restore state
 818       thread->set_thread_state(state);
 819 
 820       Threads_lock->unlock();
 821       break;
 822 
 823     default:
 824      fatal("Illegal threadstate encountered: %d", state);
 825   }
 826 
 827   // Check for pending. async. exceptions or suspends - except if the
 828   // thread was blocked inside the VM. has_special_runtime_exit_condition()
 829   // is called last since it grabs a lock and we only want to do that when
 830   // we must.
 831   //
 832   // Note: we never deliver an async exception at a polling point as the
 833   // compiler may not have an exception handler for it. The polling
 834   // code will notice the async and deoptimize and the exception will
 835   // be delivered. (Polling at a return point is ok though). Sure is
 836   // a lot of bother for a deprecated feature...
 837   //
 838   // We don't deliver an async exception if the thread state is
 839   // _thread_in_native_trans so JNI functions won't be called with
 840   // a surprising pending exception. If the thread state is going back to java,
 841   // async exception is checked in check_special_condition_for_native_trans().
 842 
 843   if (state != _thread_blocked_trans &&
 844       state != _thread_in_vm_trans &&
 845       thread->has_special_runtime_exit_condition()) {
 846     thread->handle_special_runtime_exit_condition(
 847       !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
 848   }
 849 }
 850 
 851 // ------------------------------------------------------------------------------------------------------
 852 // Exception handlers
 853 
 854 
 855 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
 856   assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
 857   assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
 858   assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
 859 
 860   if (ShowSafepointMsgs) {
 861     tty->print("handle_polling_page_exception: ");
 862   }
 863 
 864   if (PrintSafepointStatistics) {
 865     inc_page_trap_count();
 866   }
 867 
 868   ThreadSafepointState* state = thread->safepoint_state();
 869 
 870   state->handle_polling_page_exception();
 871 }
 872 
 873 
 874 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
 875   if (!timeout_error_printed) {
 876     timeout_error_printed = true;
 877     // Print out the thread info which didn't reach the safepoint for debugging
 878     // purposes (useful when there are lots of threads in the debugger).
 879     tty->cr();
 880     tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
 881     if (reason ==  _spinning_timeout) {
 882       tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
 883     } else if (reason == _blocking_timeout) {
 884       tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
 885     }
 886 
 887     tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
 888     ThreadSafepointState *cur_state;
 889     ResourceMark rm;
 890     for(JavaThread *cur_thread = Threads::first(); cur_thread;
 891         cur_thread = cur_thread->next()) {
 892       cur_state = cur_thread->safepoint_state();
 893 
 894       if (cur_thread->thread_state() != _thread_blocked &&
 895           ((reason == _spinning_timeout && cur_state->is_running()) ||
 896            (reason == _blocking_timeout && !cur_state->has_called_back()))) {
 897         tty->print("# ");
 898         cur_thread->print();
 899         tty->cr();
 900       }
 901     }
 902     tty->print_cr("# SafepointSynchronize::begin: (End of list)");
 903   }
 904 
 905   // To debug the long safepoint, specify both DieOnSafepointTimeout &
 906   // ShowMessageBoxOnError.
 907   if (DieOnSafepointTimeout) {
 908     fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
 909           SafepointTimeoutDelay, VMThread::vm_safepoint_description());
 910   }
 911 }
 912 
 913 
 914 // -------------------------------------------------------------------------------------------------------
 915 // Implementation of ThreadSafepointState
 916 
 917 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
 918   _thread = thread;
 919   _type   = _running;
 920   _has_called_back = false;
 921   _at_poll_safepoint = false;
 922 }
 923 
 924 void ThreadSafepointState::create(JavaThread *thread) {
 925   ThreadSafepointState *state = new ThreadSafepointState(thread);
 926   thread->set_safepoint_state(state);
 927 }
 928 
 929 void ThreadSafepointState::destroy(JavaThread *thread) {
 930   if (thread->safepoint_state()) {
 931     delete(thread->safepoint_state());
 932     thread->set_safepoint_state(NULL);
 933   }
 934 }
 935 
 936 void ThreadSafepointState::examine_state_of_thread() {
 937   assert(is_running(), "better be running or just have hit safepoint poll");
 938 
 939   JavaThreadState state = _thread->thread_state();
 940 
 941   // Save the state at the start of safepoint processing.
 942   _orig_thread_state = state;
 943 
 944   // Check for a thread that is suspended. Note that thread resume tries
 945   // to grab the Threads_lock which we own here, so a thread cannot be
 946   // resumed during safepoint synchronization.
 947 
 948   // We check to see if this thread is suspended without locking to
 949   // avoid deadlocking with a third thread that is waiting for this
 950   // thread to be suspended. The third thread can notice the safepoint
 951   // that we're trying to start at the beginning of its SR_lock->wait()
 952   // call. If that happens, then the third thread will block on the
 953   // safepoint while still holding the underlying SR_lock. We won't be
 954   // able to get the SR_lock and we'll deadlock.
 955   //
 956   // We don't need to grab the SR_lock here for two reasons:
 957   // 1) The suspend flags are both volatile and are set with an
 958   //    Atomic::cmpxchg() call so we should see the suspended
 959   //    state right away.
 960   // 2) We're being called from the safepoint polling loop; if
 961   //    we don't see the suspended state on this iteration, then
 962   //    we'll come around again.
 963   //
 964   bool is_suspended = _thread->is_ext_suspended();
 965   if (is_suspended) {
 966     roll_forward(_at_safepoint);
 967     return;
 968   }
 969 
 970   // Some JavaThread states have an initial safepoint state of
 971   // running, but are actually at a safepoint. We will happily
 972   // agree and update the safepoint state here.
 973   if (SafepointSynchronize::safepoint_safe(_thread, state)) {
 974     SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
 975     roll_forward(_at_safepoint);
 976     return;
 977   }
 978 
 979   if (state == _thread_in_vm) {
 980     roll_forward(_call_back);
 981     return;
 982   }
 983 
 984   // All other thread states will continue to run until they
 985   // transition and self-block in state _blocked
 986   // Safepoint polling in compiled code causes the Java threads to do the same.
 987   // Note: new threads may require a malloc so they must be allowed to finish
 988 
 989   assert(is_running(), "examine_state_of_thread on non-running thread");
 990   return;
 991 }
 992 
 993 // Returns true is thread could not be rolled forward at present position.
 994 void ThreadSafepointState::roll_forward(suspend_type type) {
 995   _type = type;
 996 
 997   switch(_type) {
 998     case _at_safepoint:
 999       SafepointSynchronize::signal_thread_at_safepoint();
1000       DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1001       if (_thread->in_critical()) {
1002         // Notice that this thread is in a critical section
1003         SafepointSynchronize::increment_jni_active_count();
1004       }
1005       break;
1006 
1007     case _call_back:
1008       set_has_called_back(false);
1009       break;
1010 
1011     case _running:
1012     default:
1013       ShouldNotReachHere();
1014   }
1015 }
1016 
1017 void ThreadSafepointState::restart() {
1018   switch(type()) {
1019     case _at_safepoint:
1020     case _call_back:
1021       break;
1022 
1023     case _running:
1024     default:
1025        tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1026                      p2i(_thread), _type);
1027        _thread->print();
1028       ShouldNotReachHere();
1029   }
1030   _type = _running;
1031   set_has_called_back(false);
1032 }
1033 
1034 
1035 void ThreadSafepointState::print_on(outputStream *st) const {
1036   const char *s = NULL;
1037 
1038   switch(_type) {
1039     case _running                : s = "_running";              break;
1040     case _at_safepoint           : s = "_at_safepoint";         break;
1041     case _call_back              : s = "_call_back";            break;
1042     default:
1043       ShouldNotReachHere();
1044   }
1045 
1046   st->print_cr("Thread: " INTPTR_FORMAT
1047               "  [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1048                p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1049                _at_poll_safepoint);
1050 
1051   _thread->print_thread_state_on(st);
1052 }
1053 
1054 // ---------------------------------------------------------------------------------------------------------------------
1055 
1056 // Block the thread at the safepoint poll or poll return.
1057 void ThreadSafepointState::handle_polling_page_exception() {
1058 
1059   // Check state.  block() will set thread state to thread_in_vm which will
1060   // cause the safepoint state _type to become _call_back.
1061   assert(type() == ThreadSafepointState::_running,
1062          "polling page exception on thread not running state");
1063 
1064   // Step 1: Find the nmethod from the return address
1065   if (ShowSafepointMsgs && Verbose) {
1066     tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1067   }
1068   address real_return_addr = thread()->saved_exception_pc();
1069 
1070   CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1071   assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1072   CompiledMethod* nm = (CompiledMethod*)cb;
1073 
1074   // Find frame of caller
1075   frame stub_fr = thread()->last_frame();
1076   CodeBlob* stub_cb = stub_fr.cb();
1077   assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1078   RegisterMap map(thread(), true);
1079   frame caller_fr = stub_fr.sender(&map);
1080 
1081   // Should only be poll_return or poll
1082   assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1083 
1084   // This is a poll immediately before a return. The exception handling code
1085   // has already had the effect of causing the return to occur, so the execution
1086   // will continue immediately after the call. In addition, the oopmap at the
1087   // return point does not mark the return value as an oop (if it is), so
1088   // it needs a handle here to be updated.
1089   if( nm->is_at_poll_return(real_return_addr) ) {
1090     // See if return type is an oop.
1091     bool return_oop = nm->method()->is_returning_oop();
1092     Handle return_value;
1093     if (return_oop) {
1094       // The oop result has been saved on the stack together with all
1095       // the other registers. In order to preserve it over GCs we need
1096       // to keep it in a handle.
1097       oop result = caller_fr.saved_oop_result(&map);
1098       assert(oopDesc::is_oop_or_null(result), "must be oop");
1099       return_value = Handle(thread(), result);
1100       assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1101     }
1102 
1103     // Block the thread
1104     SafepointSynchronize::block(thread());
1105 
1106     // restore oop result, if any
1107     if (return_oop) {
1108       caller_fr.set_saved_oop_result(&map, return_value());
1109     }
1110   }
1111 
1112   // This is a safepoint poll. Verify the return address and block.
1113   else {
1114     set_at_poll_safepoint(true);
1115 
1116     // verify the blob built the "return address" correctly
1117     assert(real_return_addr == caller_fr.pc(), "must match");
1118 
1119     // Block the thread
1120     SafepointSynchronize::block(thread());
1121     set_at_poll_safepoint(false);
1122 
1123     // If we have a pending async exception deoptimize the frame
1124     // as otherwise we may never deliver it.
1125     if (thread()->has_async_condition()) {
1126       ThreadInVMfromJavaNoAsyncException __tiv(thread());
1127       Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1128     }
1129 
1130     // If an exception has been installed we must check for a pending deoptimization
1131     // Deoptimize frame if exception has been thrown.
1132 
1133     if (thread()->has_pending_exception() ) {
1134       RegisterMap map(thread(), true);
1135       frame caller_fr = stub_fr.sender(&map);
1136       if (caller_fr.is_deoptimized_frame()) {
1137         // The exception patch will destroy registers that are still
1138         // live and will be needed during deoptimization. Defer the
1139         // Async exception should have deferred the exception until the
1140         // next safepoint which will be detected when we get into
1141         // the interpreter so if we have an exception now things
1142         // are messed up.
1143 
1144         fatal("Exception installed and deoptimization is pending");
1145       }
1146     }
1147   }
1148 }
1149 
1150 
1151 //
1152 //                     Statistics & Instrumentations
1153 //
1154 SafepointSynchronize::SafepointStats*  SafepointSynchronize::_safepoint_stats = NULL;
1155 jlong  SafepointSynchronize::_safepoint_begin_time = 0;
1156 int    SafepointSynchronize::_cur_stat_index = 0;
1157 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1158 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1159 jlong  SafepointSynchronize::_max_sync_time = 0;
1160 jlong  SafepointSynchronize::_max_vmop_time = 0;
1161 float  SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1162 
1163 static jlong  cleanup_end_time = 0;
1164 static bool   need_to_track_page_armed_status = false;
1165 static bool   init_done = false;
1166 
1167 // Helper method to print the header.
1168 static void print_header() {
1169   // The number of spaces is significant here, and should match the format
1170   // specifiers in print_statistics().
1171 
1172   tty->print("          vmop                            "
1173              "[ threads:    total initially_running wait_to_block ]"
1174              "[ time:    spin   block    sync cleanup    vmop ] ");
1175 
1176   // no page armed status printed out if it is always armed.
1177   if (need_to_track_page_armed_status) {
1178     tty->print("page_armed ");
1179   }
1180 
1181   tty->print_cr("page_trap_count");
1182 }
1183 
1184 void SafepointSynchronize::deferred_initialize_stat() {
1185   if (init_done) return;
1186 
1187   // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1188   // be printed right away, in which case, _safepoint_stats will regress to
1189   // a single element array. Otherwise, it is a circular ring buffer with default
1190   // size of PrintSafepointStatisticsCount.
1191   int stats_array_size;
1192   if (PrintSafepointStatisticsTimeout > 0) {
1193     stats_array_size = 1;
1194     PrintSafepointStatistics = true;
1195   } else {
1196     stats_array_size = PrintSafepointStatisticsCount;
1197   }
1198   _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1199                                                  * sizeof(SafepointStats), mtInternal);
1200   guarantee(_safepoint_stats != NULL,
1201             "not enough memory for safepoint instrumentation data");
1202 
1203   if (DeferPollingPageLoopCount >= 0) {
1204     need_to_track_page_armed_status = true;
1205   }
1206   init_done = true;
1207 }
1208 
1209 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1210   assert(init_done, "safepoint statistics array hasn't been initialized");
1211   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1212 
1213   spstat->_time_stamp = _ts_of_current_safepoint;
1214 
1215   VM_Operation *op = VMThread::vm_operation();
1216   spstat->_vmop_type = (op != NULL ? op->type() : -1);
1217   if (op != NULL) {
1218     _safepoint_reasons[spstat->_vmop_type]++;
1219   }
1220 
1221   spstat->_nof_total_threads = nof_threads;
1222   spstat->_nof_initial_running_threads = nof_running;
1223   spstat->_nof_threads_hit_page_trap = 0;
1224 
1225   // Records the start time of spinning. The real time spent on spinning
1226   // will be adjusted when spin is done. Same trick is applied for time
1227   // spent on waiting for threads to block.
1228   if (nof_running != 0) {
1229     spstat->_time_to_spin = os::javaTimeNanos();
1230   }  else {
1231     spstat->_time_to_spin = 0;
1232   }
1233 }
1234 
1235 void SafepointSynchronize::update_statistics_on_spin_end() {
1236   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1237 
1238   jlong cur_time = os::javaTimeNanos();
1239 
1240   spstat->_nof_threads_wait_to_block = _waiting_to_block;
1241   if (spstat->_nof_initial_running_threads != 0) {
1242     spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1243   }
1244 
1245   if (need_to_track_page_armed_status) {
1246     spstat->_page_armed = (PageArmed == 1);
1247   }
1248 
1249   // Records the start time of waiting for to block. Updated when block is done.
1250   if (_waiting_to_block != 0) {
1251     spstat->_time_to_wait_to_block = cur_time;
1252   } else {
1253     spstat->_time_to_wait_to_block = 0;
1254   }
1255 }
1256 
1257 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1258   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1259 
1260   if (spstat->_nof_threads_wait_to_block != 0) {
1261     spstat->_time_to_wait_to_block = end_time -
1262       spstat->_time_to_wait_to_block;
1263   }
1264 
1265   // Records the end time of sync which will be used to calculate the total
1266   // vm operation time. Again, the real time spending in syncing will be deducted
1267   // from the start of the sync time later when end_statistics is called.
1268   spstat->_time_to_sync = end_time - _safepoint_begin_time;
1269   if (spstat->_time_to_sync > _max_sync_time) {
1270     _max_sync_time = spstat->_time_to_sync;
1271   }
1272 
1273   spstat->_time_to_do_cleanups = end_time;
1274 }
1275 
1276 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1277   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1278 
1279   // Record how long spent in cleanup tasks.
1280   spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1281 
1282   cleanup_end_time = end_time;
1283 }
1284 
1285 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1286   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1287 
1288   // Update the vm operation time.
1289   spstat->_time_to_exec_vmop = vmop_end_time -  cleanup_end_time;
1290   if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1291     _max_vmop_time = spstat->_time_to_exec_vmop;
1292   }
1293   // Only the sync time longer than the specified
1294   // PrintSafepointStatisticsTimeout will be printed out right away.
1295   // By default, it is -1 meaning all samples will be put into the list.
1296   if ( PrintSafepointStatisticsTimeout > 0) {
1297     if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1298       print_statistics();
1299     }
1300   } else {
1301     // The safepoint statistics will be printed out when the _safepoin_stats
1302     // array fills up.
1303     if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1304       print_statistics();
1305       _cur_stat_index = 0;
1306     } else {
1307       _cur_stat_index++;
1308     }
1309   }
1310 }
1311 
1312 void SafepointSynchronize::print_statistics() {
1313   for (int index = 0; index <= _cur_stat_index; index++) {
1314     if (index % 30 == 0) {
1315       print_header();
1316     }
1317     SafepointStats* sstats = &_safepoint_stats[index];
1318     tty->print("%8.3f: ", sstats->_time_stamp);
1319     tty->print("%-30s  [          "
1320                INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1321                "]",
1322                (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1323                sstats->_nof_total_threads,
1324                sstats->_nof_initial_running_threads,
1325                sstats->_nof_threads_wait_to_block);
1326     // "/ MICROUNITS " is to convert the unit from nanos to millis.
1327     tty->print("[       "
1328                INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1329                INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1330                INT64_FORMAT_W(7) " ] ",
1331                (int64_t)(sstats->_time_to_spin / MICROUNITS),
1332                (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
1333                (int64_t)(sstats->_time_to_sync / MICROUNITS),
1334                (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
1335                (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
1336 
1337     if (need_to_track_page_armed_status) {
1338       tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1339     }
1340     tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1341   }
1342 }
1343 
1344 // This method will be called when VM exits. It will first call
1345 // print_statistics to print out the rest of the sampling.  Then
1346 // it tries to summarize the sampling.
1347 void SafepointSynchronize::print_stat_on_exit() {
1348   if (_safepoint_stats == NULL) return;
1349 
1350   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1351 
1352   // During VM exit, end_statistics may not get called and in that
1353   // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1354   // don't print it out.
1355   // Approximate the vm op time.
1356   _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1357     os::javaTimeNanos() - cleanup_end_time;
1358 
1359   if ( PrintSafepointStatisticsTimeout < 0 ||
1360        spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1361     print_statistics();
1362   }
1363   tty->cr();
1364 
1365   // Print out polling page sampling status.
1366   if (!need_to_track_page_armed_status) {
1367     tty->print_cr("Polling page always armed");
1368   } else {
1369     tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1370                   DeferPollingPageLoopCount);
1371   }
1372 
1373   for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1374     if (_safepoint_reasons[index] != 0) {
1375       tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1376                     _safepoint_reasons[index]);
1377     }
1378   }
1379 
1380   tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1381                 _coalesced_vmop_count);
1382   tty->print_cr("Maximum sync time  " INT64_FORMAT_W(5) " ms",
1383                 (int64_t)(_max_sync_time / MICROUNITS));
1384   tty->print_cr("Maximum vm operation time (except for Exit VM operation)  "
1385                 INT64_FORMAT_W(5) " ms",
1386                 (int64_t)(_max_vmop_time / MICROUNITS));
1387 }
1388 
1389 // ------------------------------------------------------------------------------------------------
1390 // Non-product code
1391 
1392 #ifndef PRODUCT
1393 
1394 void SafepointSynchronize::print_state() {
1395   if (_state == _not_synchronized) {
1396     tty->print_cr("not synchronized");
1397   } else if (_state == _synchronizing || _state == _synchronized) {
1398     tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1399                   "synchronized");
1400 
1401     for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1402        cur->safepoint_state()->print();
1403     }
1404   }
1405 }
1406 
1407 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1408   if (ShowSafepointMsgs) {
1409     va_list ap;
1410     va_start(ap, format);
1411     tty->vprint_cr(format, ap);
1412     va_end(ap);
1413   }
1414 }
1415 
1416 #endif // !PRODUCT
--- EOF ---