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src/hotspot/share/runtime/safepoint.cpp

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rev 47794 : Port 09.17.Thread_SMR_logging_update from JDK9 to JDK10
rev 47796 : eosterlund, stefank CR - refactor code into threadSMR.cpp and threadSMR.hpp
rev 47799 : stefank, coleenp CR - refactor most JavaThreadIterator usage to use JavaThreadIteratorWithHandle.


  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


 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         }


 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     }


 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();


 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) {


 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 }


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


  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/threadSMR.hpp"
  62 #include "runtime/timerTrace.hpp"
  63 #include "services/runtimeService.hpp"
  64 #include "trace/tracing.hpp"
  65 #include "trace/traceMacros.hpp"
  66 #include "utilities/events.hpp"
  67 #include "utilities/macros.hpp"
  68 #ifdef COMPILER1
  69 #include "c1/c1_globals.hpp"
  70 #endif
  71 
  72 // --------------------------------------------------------------------------------------------------
  73 // Implementation of Safepoint begin/end
  74 
  75 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
  76 volatile int  SafepointSynchronize::_waiting_to_block = 0;
  77 volatile int SafepointSynchronize::_safepoint_counter = 0;
  78 int SafepointSynchronize::_current_jni_active_count = 0;
  79 long  SafepointSynchronize::_end_of_last_safepoint = 0;
  80 static volatile int PageArmed = 0 ;        // safepoint polling page is RO|RW vs PROT_NONE
  81 static volatile int TryingToBlock = 0 ;    // proximate value -- for advisory use only


 172     _state            = _synchronizing;
 173     OrderAccess::fence();
 174 
 175     // Flush all thread states to memory
 176     if (!UseMembar) {
 177       os::serialize_thread_states();
 178     }
 179 
 180     // Make interpreter safepoint aware
 181     Interpreter::notice_safepoints();
 182 
 183     if (DeferPollingPageLoopCount < 0) {
 184       // Make polling safepoint aware
 185       guarantee (PageArmed == 0, "invariant") ;
 186       PageArmed = 1 ;
 187       os::make_polling_page_unreadable();
 188     }
 189 
 190     // Consider using active_processor_count() ... but that call is expensive.
 191     int ncpus = os::processor_count() ;
 192     unsigned int iterations = 0;
 193 
 194     {
 195       JavaThreadIteratorWithHandle jtiwh;
 196 #ifdef ASSERT
 197       for (; JavaThread *cur = jtiwh.next(); ) {
 198         assert(cur->safepoint_state()->is_running(), "Illegal initial state");
 199         // Clear the visited flag to ensure that the critical counts are collected properly.
 200         cur->set_visited_for_critical_count(false);
 201       }
 202 #endif // ASSERT
 203 
 204       if (SafepointTimeout)
 205         safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
 206 
 207       // Iterate through all threads until it have been determined how to stop them all at a safepoint

 208       int steps = 0 ;
 209       while(still_running > 0) {
 210         jtiwh.rewind();
 211         for (; JavaThread *cur = jtiwh.next(); ) {
 212           assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
 213           ThreadSafepointState *cur_state = cur->safepoint_state();
 214           if (cur_state->is_running()) {
 215             cur_state->examine_state_of_thread();
 216             if (!cur_state->is_running()) {
 217               still_running--;
 218               // consider adjusting steps downward:
 219               //   steps = 0
 220               //   steps -= NNN
 221               //   steps >>= 1
 222               //   steps = MIN(steps, 2000-100)
 223               //   if (iterations != 0) steps -= NNN
 224             }
 225             LogTarget(Trace, safepoint) lt;
 226             if (lt.is_enabled()) {
 227               ResourceMark rm;
 228               LogStream ls(lt);
 229               cur_state->print_on(&ls);
 230             }
 231           }


 302             PageArmed = 1 ;
 303             os::make_polling_page_unreadable();
 304           }
 305 
 306           // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
 307           // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
 308           ++steps ;
 309           if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
 310             SpinPause() ;     // MP-Polite spin
 311           } else
 312             if (steps < DeferThrSuspendLoopCount) {
 313               os::naked_yield() ;
 314             } else {
 315               os::naked_short_sleep(1);
 316             }
 317 
 318           iterations ++ ;
 319         }
 320         assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
 321       }
 322     } // ThreadsListHandle destroyed here.
 323     assert(still_running == 0, "sanity check");
 324 
 325     if (PrintSafepointStatistics) {
 326       update_statistics_on_spin_end();
 327     }
 328 
 329     if (sync_event.should_commit()) {
 330       // Group this event together with the ones committed after the counter is increased
 331       sync_event.set_safepointId(safepoint_counter() + 1);
 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   } // EventSafepointStateSynchronization destroyed here.
 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     }


 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   // Make sure all the threads were visited.
 390   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
 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();


 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   {
 449     JavaThreadIteratorWithHandle jtiwh;
 450 #ifdef ASSERT
 451     // A pending_exception cannot be installed during a safepoint.  The threads
 452     // may install an async exception after they come back from a safepoint into
 453     // pending_exception after they unblock.  But that should happen later.
 454     for (; JavaThread *cur = jtiwh.next(); ) {
 455       assert (!(cur->has_pending_exception() &&
 456                 cur->safepoint_state()->is_at_poll_safepoint()),
 457               "safepoint installed a pending exception");
 458     }
 459 #endif // ASSERT
 460 
 461     if (PageArmed) {
 462       // Make polling safepoint aware
 463       os::make_polling_page_readable();
 464       PageArmed = 0 ;
 465     }
 466 
 467     // Remove safepoint check from interpreter
 468     Interpreter::ignore_safepoints();
 469 
 470     {
 471       MutexLocker mu(Safepoint_lock);
 472 
 473       assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
 474 
 475       // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
 476       // when they get restarted.
 477       _state = _not_synchronized;
 478       OrderAccess::fence();
 479 
 480       log_debug(safepoint)("Leaving safepoint region");
 481 
 482       // Start suspended threads
 483       jtiwh.rewind();
 484       for (; JavaThread *current = jtiwh.next(); ) {
 485         // A problem occurring on Solaris is when attempting to restart threads
 486         // the first #cpus - 1 go well, but then the VMThread is preempted when we get
 487         // to the next one (since it has been running the longest).  We then have
 488         // to wait for a cpu to become available before we can continue restarting
 489         // threads.
 490         // FIXME: This causes the performance of the VM to degrade when active and with
 491         // large numbers of threads.  Apparently this is due to the synchronous nature
 492         // of suspending threads.
 493         //
 494         // TODO-FIXME: the comments above are vestigial and no longer apply.
 495         // Furthermore, using solaris' schedctl in this particular context confers no benefit
 496         if (VMThreadHintNoPreempt) {
 497           os::hint_no_preempt();
 498         }
 499         ThreadSafepointState* cur_state = current->safepoint_state();
 500         assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
 501         cur_state->restart();
 502         assert(cur_state->is_running(), "safepoint state has not been reset");
 503       }
 504 
 505       RuntimeService::record_safepoint_end();
 506 
 507       // Release threads lock, so threads can be created/destroyed again.
 508       // It will also release all threads blocked in signal_thread_blocked.
 509       Threads_lock->unlock();

 510     }
 511   } // ThreadsListHandle destroyed here.
 512 
 513   Universe::heap()->safepoint_synchronize_end();
 514   // record this time so VMThread can keep track how much time has elapsed
 515   // since last safepoint.
 516   _end_of_last_safepoint = os::javaTimeMillis();
 517 
 518   if (event.should_commit()) {
 519     event.set_safepointId(safepoint_id);
 520     event.commit();
 521   }
 522 }
 523 
 524 bool SafepointSynchronize::is_cleanup_needed() {
 525   // Need a safepoint if there are many monitors to deflate.
 526   if (ObjectSynchronizer::is_cleanup_needed()) return true;
 527   // Need a safepoint if some inline cache buffers is non-empty
 528   if (!InlineCacheBuffer::is_empty()) return true;
 529   return false;
 530 }
 531 
 532 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {


 879   state->handle_polling_page_exception();
 880 }
 881 
 882 
 883 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
 884   if (!timeout_error_printed) {
 885     timeout_error_printed = true;
 886     // Print out the thread info which didn't reach the safepoint for debugging
 887     // purposes (useful when there are lots of threads in the debugger).
 888     tty->cr();
 889     tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
 890     if (reason ==  _spinning_timeout) {
 891       tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
 892     } else if (reason == _blocking_timeout) {
 893       tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
 894     }
 895 
 896     tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
 897     ThreadSafepointState *cur_state;
 898     ResourceMark rm;
 899     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {

 900       cur_state = cur_thread->safepoint_state();
 901 
 902       if (cur_thread->thread_state() != _thread_blocked &&
 903         ((reason == _spinning_timeout && cur_state->is_running()) ||
 904            (reason == _blocking_timeout && !cur_state->has_called_back()))) {
 905         tty->print("# ");
 906         cur_thread->print();
 907         tty->cr();
 908       }
 909     }
 910     tty->print_cr("# SafepointSynchronize::begin: (End of list)");
 911   }
 912 
 913   // To debug the long safepoint, specify both DieOnSafepointTimeout &
 914   // ShowMessageBoxOnError.
 915   if (DieOnSafepointTimeout) {
 916     fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
 917           SafepointTimeoutDelay, VMThread::vm_safepoint_description());
 918   }
 919 }


1389                 _coalesced_vmop_count);
1390   tty->print_cr("Maximum sync time  " INT64_FORMAT_W(5) " ms",
1391                 (int64_t)(_max_sync_time / MICROUNITS));
1392   tty->print_cr("Maximum vm operation time (except for Exit VM operation)  "
1393                 INT64_FORMAT_W(5) " ms",
1394                 (int64_t)(_max_vmop_time / MICROUNITS));
1395 }
1396 
1397 // ------------------------------------------------------------------------------------------------
1398 // Non-product code
1399 
1400 #ifndef PRODUCT
1401 
1402 void SafepointSynchronize::print_state() {
1403   if (_state == _not_synchronized) {
1404     tty->print_cr("not synchronized");
1405   } else if (_state == _synchronizing || _state == _synchronized) {
1406     tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1407                   "synchronized");
1408 
1409     for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
1410        cur->safepoint_state()->print();
1411     }
1412   }
1413 }
1414 
1415 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1416   if (ShowSafepointMsgs) {
1417     va_list ap;
1418     va_start(ap, format);
1419     tty->vprint_cr(format, ap);
1420     va_end(ap);
1421   }
1422 }
1423 
1424 #endif // !PRODUCT
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