1 /*
   2  * Copyright (c) 1997, 2015, 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/symbolTable.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "code/codeCache.hpp"
  29 #include "code/icBuffer.hpp"
  30 #include "code/nmethod.hpp"
  31 #include "code/pcDesc.hpp"
  32 #include "code/scopeDesc.hpp"
  33 #include "gc_interface/collectedHeap.hpp"
  34 #include "interpreter/interpreter.hpp"
  35 #include "jfr/jfrEvents.hpp"
  36 #include "memory/resourceArea.hpp"
  37 #include "memory/universe.inline.hpp"
  38 #include "oops/oop.inline.hpp"
  39 #include "oops/symbol.hpp"
  40 #include "runtime/compilationPolicy.hpp"
  41 #include "runtime/deoptimization.hpp"
  42 #include "runtime/frame.inline.hpp"
  43 #include "runtime/interfaceSupport.hpp"
  44 #include "runtime/mutexLocker.hpp"
  45 #include "runtime/orderAccess.inline.hpp"
  46 #include "runtime/osThread.hpp"
  47 #include "runtime/safepoint.hpp"
  48 #include "runtime/signature.hpp"
  49 #include "runtime/stubCodeGenerator.hpp"
  50 #include "runtime/stubRoutines.hpp"
  51 #include "runtime/sweeper.hpp"
  52 #include "runtime/synchronizer.hpp"
  53 #include "runtime/thread.inline.hpp"
  54 #include "services/runtimeService.hpp"
  55 #include "utilities/events.hpp"
  56 #include "utilities/macros.hpp"
  57 #ifdef TARGET_ARCH_x86
  58 # include "nativeInst_x86.hpp"
  59 # include "vmreg_x86.inline.hpp"
  60 #endif
  61 #ifdef TARGET_ARCH_sparc
  62 # include "nativeInst_sparc.hpp"
  63 # include "vmreg_sparc.inline.hpp"
  64 #endif
  65 #ifdef TARGET_ARCH_zero
  66 # include "nativeInst_zero.hpp"
  67 # include "vmreg_zero.inline.hpp"
  68 #endif
  69 #ifdef TARGET_ARCH_arm
  70 # include "nativeInst_arm.hpp"
  71 # include "vmreg_arm.inline.hpp"
  72 #endif
  73 #ifdef TARGET_ARCH_ppc
  74 # include "nativeInst_ppc.hpp"
  75 # include "vmreg_ppc.inline.hpp"
  76 #endif
  77 #if INCLUDE_ALL_GCS
  78 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
  79 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
  80 #endif // INCLUDE_ALL_GCS
  81 #ifdef COMPILER1
  82 #include "c1/c1_globals.hpp"
  83 #endif
  84 
  85 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  86 
  87 template <typename E>
  88 static void set_current_safepoint_id(E* event, int adjustment = 0) {
  89   assert(event != NULL, "invariant");
  90   event->set_safepointId(SafepointSynchronize::safepoint_counter() + adjustment);
  91 }
  92 
  93 static void post_safepoint_begin_event(EventSafepointBegin* event,
  94                                        int thread_count,
  95                                        int critical_thread_count) {
  96   assert(event != NULL, "invariant");
  97   assert(event->should_commit(), "invariant");
  98   set_current_safepoint_id(event);
  99   event->set_totalThreadCount(thread_count);
 100   event->set_jniCriticalThreadCount(critical_thread_count);
 101   event->commit();
 102 }
 103 
 104 static void post_safepoint_cleanup_event(EventSafepointCleanup* event) {
 105   assert(event != NULL, "invariant");
 106   assert(event->should_commit(), "invariant");
 107   set_current_safepoint_id(event);
 108   event->commit();
 109 }
 110 
 111 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization* event,
 112                                              int initial_number_of_threads,
 113                                              int threads_waiting_to_block,
 114                                              unsigned int iterations) {
 115   assert(event != NULL, "invariant");
 116   if (event->should_commit()) {
 117     // Group this event together with the ones committed after the counter is increased
 118     set_current_safepoint_id(event, 1);
 119     event->set_initialThreadCount(initial_number_of_threads);
 120     event->set_runningThreadCount(threads_waiting_to_block);
 121     event->set_iterations(iterations);
 122     event->commit();
 123   }
 124 }
 125 
 126 static void post_safepoint_wait_blocked_event(EventSafepointWaitBlocked* event,
 127                                               int initial_threads_waiting_to_block) {
 128   assert(event != NULL, "invariant");
 129   assert(event->should_commit(), "invariant");
 130   set_current_safepoint_id(event);
 131   event->set_runningThreadCount(initial_threads_waiting_to_block);
 132   event->commit();
 133 }
 134 
 135 static void post_safepoint_cleanup_task_event(EventSafepointCleanupTask* event,
 136                                               const char* name) {
 137   assert(event != NULL, "invariant");
 138   if (event->should_commit()) {
 139     set_current_safepoint_id(event);
 140     event->set_name(name);
 141     event->commit();
 142   }
 143 }
 144 
 145 static void post_safepoint_end_event(EventSafepointEnd* event) {
 146   assert(event != NULL, "invariant");
 147   if (event->should_commit()) {
 148     // Group this event together with the ones committed before the counter increased
 149     set_current_safepoint_id(event, -1);
 150     event->commit();
 151   }
 152 }
 153 
 154 // --------------------------------------------------------------------------------------------------
 155 // Implementation of Safepoint begin/end
 156 
 157 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
 158 volatile int  SafepointSynchronize::_waiting_to_block = 0;
 159 volatile int SafepointSynchronize::_safepoint_counter = 0;
 160 int SafepointSynchronize::_current_jni_active_count = 0;
 161 long  SafepointSynchronize::_end_of_last_safepoint = 0;
 162 static volatile int PageArmed = 0 ;        // safepoint polling page is RO|RW vs PROT_NONE
 163 static volatile int TryingToBlock = 0 ;    // proximate value -- for advisory use only
 164 static bool timeout_error_printed = false;
 165 
 166 // Roll all threads forward to a safepoint and suspend them all
 167 void SafepointSynchronize::begin() {
 168   EventSafepointBegin begin_event;
 169   Thread* myThread = Thread::current();
 170   assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
 171 
 172   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
 173     _safepoint_begin_time = os::javaTimeNanos();
 174     _ts_of_current_safepoint = tty->time_stamp().seconds();
 175   }
 176 
 177 #if INCLUDE_ALL_GCS
 178   if (UseConcMarkSweepGC) {
 179     // In the future we should investigate whether CMS can use the
 180     // more-general mechanism below.  DLD (01/05).
 181     ConcurrentMarkSweepThread::synchronize(false);
 182   } else if (UseG1GC) {
 183     SuspendibleThreadSet::synchronize();
 184   }
 185 #endif // INCLUDE_ALL_GCS
 186 
 187   // By getting the Threads_lock, we assure that no threads are about to start or
 188   // exit. It is released again in SafepointSynchronize::end().
 189   Threads_lock->lock();
 190 
 191   assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
 192 
 193   int nof_threads = Threads::number_of_threads();
 194 
 195   if (TraceSafepoint) {
 196     tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
 197   }
 198 
 199   RuntimeService::record_safepoint_begin();
 200 
 201   MutexLocker mu(Safepoint_lock);
 202 
 203   // Reset the count of active JNI critical threads
 204   _current_jni_active_count = 0;
 205 
 206   // Set number of threads to wait for, before we initiate the callbacks
 207   _waiting_to_block = nof_threads;
 208   TryingToBlock     = 0 ;
 209   int still_running = nof_threads;
 210 
 211   // Save the starting time, so that it can be compared to see if this has taken
 212   // too long to complete.
 213   jlong safepoint_limit_time = 0;
 214   timeout_error_printed = false;
 215 
 216   // PrintSafepointStatisticsTimeout can be specified separately. When
 217   // specified, PrintSafepointStatistics will be set to true in
 218   // deferred_initialize_stat method. The initialization has to be done
 219   // early enough to avoid any races. See bug 6880029 for details.
 220   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
 221     deferred_initialize_stat();
 222   }
 223 
 224   // Begin the process of bringing the system to a safepoint.
 225   // Java threads can be in several different states and are
 226   // stopped by different mechanisms:
 227   //
 228   //  1. Running interpreted
 229   //     The interpeter dispatch table is changed to force it to
 230   //     check for a safepoint condition between bytecodes.
 231   //  2. Running in native code
 232   //     When returning from the native code, a Java thread must check
 233   //     the safepoint _state to see if we must block.  If the
 234   //     VM thread sees a Java thread in native, it does
 235   //     not wait for this thread to block.  The order of the memory
 236   //     writes and reads of both the safepoint state and the Java
 237   //     threads state is critical.  In order to guarantee that the
 238   //     memory writes are serialized with respect to each other,
 239   //     the VM thread issues a memory barrier instruction
 240   //     (on MP systems).  In order to avoid the overhead of issuing
 241   //     a memory barrier for each Java thread making native calls, each Java
 242   //     thread performs a write to a single memory page after changing
 243   //     the thread state.  The VM thread performs a sequence of
 244   //     mprotect OS calls which forces all previous writes from all
 245   //     Java threads to be serialized.  This is done in the
 246   //     os::serialize_thread_states() call.  This has proven to be
 247   //     much more efficient than executing a membar instruction
 248   //     on every call to native code.
 249   //  3. Running compiled Code
 250   //     Compiled code reads a global (Safepoint Polling) page that
 251   //     is set to fault if we are trying to get to a safepoint.
 252   //  4. Blocked
 253   //     A thread which is blocked will not be allowed to return from the
 254   //     block condition until the safepoint operation is complete.
 255   //  5. In VM or Transitioning between states
 256   //     If a Java thread is currently running in the VM or transitioning
 257   //     between states, the safepointing code will wait for the thread to
 258   //     block itself when it attempts transitions to a new state.
 259   //
 260   EventSafepointStateSynchronization sync_event;
 261   int initial_running = 0;
 262 
 263   _state            = _synchronizing;
 264   OrderAccess::fence();
 265 
 266   // Flush all thread states to memory
 267   if (!UseMembar) {
 268     os::serialize_thread_states();
 269   }
 270 
 271   // Make interpreter safepoint aware
 272   Interpreter::notice_safepoints();
 273 
 274   if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
 275     // Make polling safepoint aware
 276     guarantee (PageArmed == 0, "invariant") ;
 277     PageArmed = 1 ;
 278     os::make_polling_page_unreadable();
 279   }
 280 
 281   // Consider using active_processor_count() ... but that call is expensive.
 282   int ncpus = os::processor_count() ;
 283 
 284 #ifdef ASSERT
 285   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 286     assert(cur->safepoint_state()->is_running(), "Illegal initial state");
 287     // Clear the visited flag to ensure that the critical counts are collected properly.
 288     cur->set_visited_for_critical_count(false);
 289   }
 290 #endif // ASSERT
 291 
 292   if (SafepointTimeout)
 293     safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
 294 
 295   // Iterate through all threads until it have been determined how to stop them all at a safepoint
 296   unsigned int iterations = 0;
 297   int steps = 0 ;
 298   while(still_running > 0) {
 299     for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 300       assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
 301       ThreadSafepointState *cur_state = cur->safepoint_state();
 302       if (cur_state->is_running()) {
 303         cur_state->examine_state_of_thread();
 304         if (!cur_state->is_running()) {
 305            still_running--;
 306            // consider adjusting steps downward:
 307            //   steps = 0
 308            //   steps -= NNN
 309            //   steps >>= 1
 310            //   steps = MIN(steps, 2000-100)
 311            //   if (iterations != 0) steps -= NNN
 312         }
 313         if (TraceSafepoint && Verbose) cur_state->print();
 314       }
 315     }
 316 
 317     if (iterations == 0) {
 318       initial_running = still_running;
 319       if (PrintSafepointStatistics) {
 320         begin_statistics(nof_threads, still_running);
 321       }
 322     }
 323 
 324     if (still_running > 0) {
 325       // Check for if it takes to long
 326       if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
 327         print_safepoint_timeout(_spinning_timeout);
 328       }
 329 
 330       // Spin to avoid context switching.
 331       // There's a tension between allowing the mutators to run (and rendezvous)
 332       // vs spinning.  As the VM thread spins, wasting cycles, it consumes CPU that
 333       // a mutator might otherwise use profitably to reach a safepoint.  Excessive
 334       // spinning by the VM thread on a saturated system can increase rendezvous latency.
 335       // Blocking or yielding incur their own penalties in the form of context switching
 336       // and the resultant loss of $ residency.
 337       //
 338       // Further complicating matters is that yield() does not work as naively expected
 339       // on many platforms -- yield() does not guarantee that any other ready threads
 340       // will run.   As such we revert yield_all() after some number of iterations.
 341       // Yield_all() is implemented as a short unconditional sleep on some platforms.
 342       // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
 343       // can actually increase the time it takes the VM thread to detect that a system-wide
 344       // stop-the-world safepoint has been reached.  In a pathological scenario such as that
 345       // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
 346       // In that case the mutators will be stalled waiting for the safepoint to complete and the
 347       // the VMthread will be sleeping, waiting for the mutators to rendezvous.  The VMthread
 348       // will eventually wake up and detect that all mutators are safe, at which point
 349       // we'll again make progress.
 350       //
 351       // Beware too that that the VMThread typically runs at elevated priority.
 352       // Its default priority is higher than the default mutator priority.
 353       // Obviously, this complicates spinning.
 354       //
 355       // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
 356       // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
 357       //
 358       // See the comments in synchronizer.cpp for additional remarks on spinning.
 359       //
 360       // In the future we might:
 361       // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
 362       //    This is tricky as the path used by a thread exiting the JVM (say on
 363       //    on JNI call-out) simply stores into its state field.  The burden
 364       //    is placed on the VM thread, which must poll (spin).
 365       // 2. Find something useful to do while spinning.  If the safepoint is GC-related
 366       //    we might aggressively scan the stacks of threads that are already safe.
 367       // 3. Use Solaris schedctl to examine the state of the still-running mutators.
 368       //    If all the mutators are ONPROC there's no reason to sleep or yield.
 369       // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
 370       // 5. Check system saturation.  If the system is not fully saturated then
 371       //    simply spin and avoid sleep/yield.
 372       // 6. As still-running mutators rendezvous they could unpark the sleeping
 373       //    VMthread.  This works well for still-running mutators that become
 374       //    safe.  The VMthread must still poll for mutators that call-out.
 375       // 7. Drive the policy on time-since-begin instead of iterations.
 376       // 8. Consider making the spin duration a function of the # of CPUs:
 377       //    Spin = (((ncpus-1) * M) + K) + F(still_running)
 378       //    Alternately, instead of counting iterations of the outer loop
 379       //    we could count the # of threads visited in the inner loop, above.
 380       // 9. On windows consider using the return value from SwitchThreadTo()
 381       //    to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
 382 
 383       if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
 384          guarantee (PageArmed == 0, "invariant") ;
 385          PageArmed = 1 ;
 386          os::make_polling_page_unreadable();
 387       }
 388 
 389       // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
 390       // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
 391       ++steps ;
 392       if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
 393         SpinPause() ;     // MP-Polite spin
 394       } else
 395       if (steps < DeferThrSuspendLoopCount) {
 396         os::NakedYield() ;
 397       } else {
 398         os::yield_all(steps) ;
 399         // Alternately, the VM thread could transiently depress its scheduling priority or
 400         // transiently increase the priority of the tardy mutator(s).
 401       }
 402 
 403       iterations ++ ;
 404     }
 405     assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
 406   }
 407   assert(still_running == 0, "sanity check");
 408 
 409   if (PrintSafepointStatistics) {
 410     update_statistics_on_spin_end();
 411   }
 412 
 413   if (sync_event.should_commit()) {
 414     post_safepoint_synchronize_event(&sync_event, initial_running, _waiting_to_block, iterations);
 415   }
 416 
 417   // wait until all threads are stopped
 418   {
 419     EventSafepointWaitBlocked wait_blocked_event;
 420     int initial_waiting_to_block = _waiting_to_block;
 421 
 422     while (_waiting_to_block > 0) {
 423       if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
 424       if (!SafepointTimeout || timeout_error_printed) {
 425         Safepoint_lock->wait(true);  // true, means with no safepoint checks
 426       } else {
 427         // Compute remaining time
 428         jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
 429 
 430         // If there is no remaining time, then there is an error
 431         if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
 432           print_safepoint_timeout(_blocking_timeout);
 433         }
 434       }
 435     }
 436     assert(_waiting_to_block == 0, "sanity check");
 437 
 438 #ifndef PRODUCT
 439     if (SafepointTimeout) {
 440       jlong current_time = os::javaTimeNanos();
 441       if (safepoint_limit_time < current_time) {
 442         tty->print_cr("# SafepointSynchronize: Finished after "
 443                       INT64_FORMAT_W(6) " ms",
 444                       ((current_time - safepoint_limit_time) / MICROUNITS +
 445                        SafepointTimeoutDelay));
 446       }
 447     }
 448 #endif
 449 
 450     assert((_safepoint_counter & 0x1) == 0, "must be even");
 451     assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 452     _safepoint_counter ++;
 453 
 454     // Record state
 455     _state = _synchronized;
 456 
 457     OrderAccess::fence();
 458 
 459     if (wait_blocked_event.should_commit()) {
 460       post_safepoint_wait_blocked_event(&wait_blocked_event, initial_waiting_to_block);
 461     }
 462   }
 463 
 464 #ifdef ASSERT
 465   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 466     // make sure all the threads were visited
 467     assert(cur->was_visited_for_critical_count(), "missed a thread");
 468   }
 469 #endif // ASSERT
 470 
 471   // Update the count of active JNI critical regions
 472   GC_locker::set_jni_lock_count(_current_jni_active_count);
 473 
 474   if (TraceSafepoint) {
 475     VM_Operation *op = VMThread::vm_operation();
 476     tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
 477   }
 478 
 479   RuntimeService::record_safepoint_synchronized();
 480   if (PrintSafepointStatistics) {
 481     update_statistics_on_sync_end(os::javaTimeNanos());
 482   }
 483 
 484   // Call stuff that needs to be run when a safepoint is just about to be completed
 485   {
 486     EventSafepointCleanup cleanup_event;
 487     do_cleanup_tasks();
 488     if (cleanup_event.should_commit()) {
 489       post_safepoint_cleanup_event(&cleanup_event);
 490     }
 491   }
 492 
 493   if (PrintSafepointStatistics) {
 494     // Record how much time spend on the above cleanup tasks
 495     update_statistics_on_cleanup_end(os::javaTimeNanos());
 496   }
 497 
 498   if (begin_event.should_commit()) {
 499     post_safepoint_begin_event(&begin_event, nof_threads, _current_jni_active_count);
 500   }
 501 }
 502 
 503 // Wake up all threads, so they are ready to resume execution after the safepoint
 504 // operation has been carried out
 505 void SafepointSynchronize::end() {
 506 
 507   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 508   assert((_safepoint_counter & 0x1) == 1, "must be odd");
 509   EventSafepointEnd event;
 510   _safepoint_counter ++;
 511   // memory fence isn't required here since an odd _safepoint_counter
 512   // value can do no harm and a fence is issued below anyway.
 513 
 514   DEBUG_ONLY(Thread* myThread = Thread::current();)
 515   assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
 516 
 517   if (PrintSafepointStatistics) {
 518     end_statistics(os::javaTimeNanos());
 519   }
 520 
 521 #ifdef ASSERT
 522   // A pending_exception cannot be installed during a safepoint.  The threads
 523   // may install an async exception after they come back from a safepoint into
 524   // pending_exception after they unblock.  But that should happen later.
 525   for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
 526     assert (!(cur->has_pending_exception() &&
 527               cur->safepoint_state()->is_at_poll_safepoint()),
 528             "safepoint installed a pending exception");
 529   }
 530 #endif // ASSERT
 531 
 532   if (PageArmed) {
 533     // Make polling safepoint aware
 534     os::make_polling_page_readable();
 535     PageArmed = 0 ;
 536   }
 537 
 538   // Remove safepoint check from interpreter
 539   Interpreter::ignore_safepoints();
 540 
 541   {
 542     MutexLocker mu(Safepoint_lock);
 543 
 544     assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
 545 
 546     // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
 547     // when they get restarted.
 548     _state = _not_synchronized;
 549     OrderAccess::fence();
 550 
 551     if (TraceSafepoint) {
 552        tty->print_cr("Leaving safepoint region");
 553     }
 554 
 555     // Start suspended threads
 556     for(JavaThread *current = Threads::first(); current; current = current->next()) {
 557       // A problem occurring on Solaris is when attempting to restart threads
 558       // the first #cpus - 1 go well, but then the VMThread is preempted when we get
 559       // to the next one (since it has been running the longest).  We then have
 560       // to wait for a cpu to become available before we can continue restarting
 561       // threads.
 562       // FIXME: This causes the performance of the VM to degrade when active and with
 563       // large numbers of threads.  Apparently this is due to the synchronous nature
 564       // of suspending threads.
 565       //
 566       // TODO-FIXME: the comments above are vestigial and no longer apply.
 567       // Furthermore, using solaris' schedctl in this particular context confers no benefit
 568       if (VMThreadHintNoPreempt) {
 569         os::hint_no_preempt();
 570       }
 571       ThreadSafepointState* cur_state = current->safepoint_state();
 572       assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
 573       cur_state->restart();
 574       assert(cur_state->is_running(), "safepoint state has not been reset");
 575     }
 576 
 577     RuntimeService::record_safepoint_end();
 578 
 579     // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
 580     // blocked in signal_thread_blocked
 581     Threads_lock->unlock();
 582 
 583   }
 584 #if INCLUDE_ALL_GCS
 585   // If there are any concurrent GC threads resume them.
 586   if (UseConcMarkSweepGC) {
 587     ConcurrentMarkSweepThread::desynchronize(false);
 588   } else if (UseG1GC) {
 589     SuspendibleThreadSet::desynchronize();
 590   }
 591 #endif // INCLUDE_ALL_GCS
 592   // record this time so VMThread can keep track how much time has elasped
 593   // since last safepoint.
 594   _end_of_last_safepoint = os::javaTimeMillis();
 595   if (event.should_commit()) {
 596     post_safepoint_end_event(&event);
 597   }
 598 }
 599 
 600 bool SafepointSynchronize::is_cleanup_needed() {
 601   // Need a safepoint if some inline cache buffers is non-empty
 602   if (!InlineCacheBuffer::is_empty()) return true;
 603   return false;
 604 }
 605 
 606 
 607 
 608 // Various cleaning tasks that should be done periodically at safepoints
 609 void SafepointSynchronize::do_cleanup_tasks() {
 610   {
 611     const char* name = "deflating idle monitors";
 612     EventSafepointCleanupTask event;
 613     TraceTime t1(name, TraceSafepointCleanupTime);
 614     ObjectSynchronizer::deflate_idle_monitors();
 615     if (event.should_commit()) {
 616       post_safepoint_cleanup_task_event(&event, name);
 617     }
 618   }
 619 
 620   {
 621     const char* name = "updating inline caches";
 622     EventSafepointCleanupTask event;
 623     TraceTime t2(name, TraceSafepointCleanupTime);
 624     InlineCacheBuffer::update_inline_caches();
 625     if (event.should_commit()) {
 626       post_safepoint_cleanup_task_event(&event, name);
 627     }
 628   }
 629   {
 630     const char* name = "compilation policy safepoint handler";
 631     EventSafepointCleanupTask event;
 632     TraceTime t3(name, TraceSafepointCleanupTime);
 633     CompilationPolicy::policy()->do_safepoint_work();
 634     if (event.should_commit()) {
 635       post_safepoint_cleanup_task_event(&event, name);
 636     }
 637   }
 638 
 639   {
 640     const char* name = "mark nmethods";
 641     EventSafepointCleanupTask event;
 642     TraceTime t4(name, TraceSafepointCleanupTime);
 643     NMethodSweeper::mark_active_nmethods();
 644     if (event.should_commit()) {
 645       post_safepoint_cleanup_task_event(&event, name);
 646     }
 647   }
 648 
 649   if (SymbolTable::needs_rehashing()) {
 650     const char* name = "rehashing symbol table";
 651     EventSafepointCleanupTask event;
 652     TraceTime t5(name, TraceSafepointCleanupTime);
 653     SymbolTable::rehash_table();
 654     if (event.should_commit()) {
 655       post_safepoint_cleanup_task_event(&event, name);
 656     }
 657   }
 658 
 659   if (StringTable::needs_rehashing()) {
 660     const char* name = "rehashing string table";
 661     EventSafepointCleanupTask event;
 662     TraceTime t6(name, TraceSafepointCleanupTime);
 663     StringTable::rehash_table();
 664     if (event.should_commit()) {
 665       post_safepoint_cleanup_task_event(&event, name);
 666     }
 667   }
 668 
 669   // rotate log files?
 670   if (UseGCLogFileRotation) {
 671     gclog_or_tty->rotate_log(false);
 672   }
 673 
 674   {
 675     // CMS delays purging the CLDG until the beginning of the next safepoint and to
 676     // make sure concurrent sweep is done
 677     TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
 678     ClassLoaderDataGraph::purge_if_needed();
 679   }
 680 }
 681 
 682 
 683 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
 684   switch(state) {
 685   case _thread_in_native:
 686     // native threads are safe if they have no java stack or have walkable stack
 687     return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
 688 
 689    // blocked threads should have already have walkable stack
 690   case _thread_blocked:
 691     assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
 692     return true;
 693 
 694   default:
 695     return false;
 696   }
 697 }
 698 
 699 
 700 // See if the thread is running inside a lazy critical native and
 701 // update the thread critical count if so.  Also set a suspend flag to
 702 // cause the native wrapper to return into the JVM to do the unlock
 703 // once the native finishes.
 704 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
 705   if (state == _thread_in_native &&
 706       thread->has_last_Java_frame() &&
 707       thread->frame_anchor()->walkable()) {
 708     // This thread might be in a critical native nmethod so look at
 709     // the top of the stack and increment the critical count if it
 710     // is.
 711     frame wrapper_frame = thread->last_frame();
 712     CodeBlob* stub_cb = wrapper_frame.cb();
 713     if (stub_cb != NULL &&
 714         stub_cb->is_nmethod() &&
 715         stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
 716       // A thread could potentially be in a critical native across
 717       // more than one safepoint, so only update the critical state on
 718       // the first one.  When it returns it will perform the unlock.
 719       if (!thread->do_critical_native_unlock()) {
 720 #ifdef ASSERT
 721         if (!thread->in_critical()) {
 722           GC_locker::increment_debug_jni_lock_count();
 723         }
 724 #endif
 725         thread->enter_critical();
 726         // Make sure the native wrapper calls back on return to
 727         // perform the needed critical unlock.
 728         thread->set_critical_native_unlock();
 729       }
 730     }
 731   }
 732 }
 733 
 734 
 735 
 736 // -------------------------------------------------------------------------------------------------------
 737 // Implementation of Safepoint callback point
 738 
 739 void SafepointSynchronize::block(JavaThread *thread) {
 740   assert(thread != NULL, "thread must be set");
 741   assert(thread->is_Java_thread(), "not a Java thread");
 742 
 743   // Threads shouldn't block if they are in the middle of printing, but...
 744   ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
 745 
 746   // Only bail from the block() call if the thread is gone from the
 747   // thread list; starting to exit should still block.
 748   if (thread->is_terminated()) {
 749      // block current thread if we come here from native code when VM is gone
 750      thread->block_if_vm_exited();
 751 
 752      // otherwise do nothing
 753      return;
 754   }
 755 
 756   JavaThreadState state = thread->thread_state();
 757   thread->frame_anchor()->make_walkable(thread);
 758 
 759   // Check that we have a valid thread_state at this point
 760   switch(state) {
 761     case _thread_in_vm_trans:
 762     case _thread_in_Java:        // From compiled code
 763 
 764       // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
 765       // we pretend we are still in the VM.
 766       thread->set_thread_state(_thread_in_vm);
 767 
 768       if (is_synchronizing()) {
 769          Atomic::inc (&TryingToBlock) ;
 770       }
 771 
 772       // We will always be holding the Safepoint_lock when we are examine the state
 773       // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
 774       // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
 775       Safepoint_lock->lock_without_safepoint_check();
 776       if (is_synchronizing()) {
 777         // Decrement the number of threads to wait for and signal vm thread
 778         assert(_waiting_to_block > 0, "sanity check");
 779         _waiting_to_block--;
 780         thread->safepoint_state()->set_has_called_back(true);
 781 
 782         DEBUG_ONLY(thread->set_visited_for_critical_count(true));
 783         if (thread->in_critical()) {
 784           // Notice that this thread is in a critical section
 785           increment_jni_active_count();
 786         }
 787 
 788         // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
 789         if (_waiting_to_block == 0) {
 790           Safepoint_lock->notify_all();
 791         }
 792       }
 793 
 794       // We transition the thread to state _thread_blocked here, but
 795       // we can't do our usual check for external suspension and then
 796       // self-suspend after the lock_without_safepoint_check() call
 797       // below because we are often called during transitions while
 798       // we hold different locks. That would leave us suspended while
 799       // holding a resource which results in deadlocks.
 800       thread->set_thread_state(_thread_blocked);
 801       Safepoint_lock->unlock();
 802 
 803       // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
 804       // the entire safepoint, the threads will all line up here during the safepoint.
 805       Threads_lock->lock_without_safepoint_check();
 806       // restore original state. This is important if the thread comes from compiled code, so it
 807       // will continue to execute with the _thread_in_Java state.
 808       thread->set_thread_state(state);
 809       Threads_lock->unlock();
 810       break;
 811 
 812     case _thread_in_native_trans:
 813     case _thread_blocked_trans:
 814     case _thread_new_trans:
 815       if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
 816         thread->print_thread_state();
 817         fatal("Deadlock in safepoint code.  "
 818               "Should have called back to the VM before blocking.");
 819       }
 820 
 821       // We transition the thread to state _thread_blocked here, but
 822       // we can't do our usual check for external suspension and then
 823       // self-suspend after the lock_without_safepoint_check() call
 824       // below because we are often called during transitions while
 825       // we hold different locks. That would leave us suspended while
 826       // holding a resource which results in deadlocks.
 827       thread->set_thread_state(_thread_blocked);
 828 
 829       // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
 830       // the safepoint code might still be waiting for it to block. We need to change the state here,
 831       // so it can see that it is at a safepoint.
 832 
 833       // Block until the safepoint operation is completed.
 834       Threads_lock->lock_without_safepoint_check();
 835 
 836       // Restore state
 837       thread->set_thread_state(state);
 838 
 839       Threads_lock->unlock();
 840       break;
 841 
 842     default:
 843      fatal(err_msg("Illegal threadstate encountered: %d", state));
 844   }
 845 
 846   // Check for pending. async. exceptions or suspends - except if the
 847   // thread was blocked inside the VM. has_special_runtime_exit_condition()
 848   // is called last since it grabs a lock and we only want to do that when
 849   // we must.
 850   //
 851   // Note: we never deliver an async exception at a polling point as the
 852   // compiler may not have an exception handler for it. The polling
 853   // code will notice the async and deoptimize and the exception will
 854   // be delivered. (Polling at a return point is ok though). Sure is
 855   // a lot of bother for a deprecated feature...
 856   //
 857   // We don't deliver an async exception if the thread state is
 858   // _thread_in_native_trans so JNI functions won't be called with
 859   // a surprising pending exception. If the thread state is going back to java,
 860   // async exception is checked in check_special_condition_for_native_trans().
 861 
 862   if (state != _thread_blocked_trans &&
 863       state != _thread_in_vm_trans &&
 864       thread->has_special_runtime_exit_condition()) {
 865     thread->handle_special_runtime_exit_condition(
 866       !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
 867   }
 868 }
 869 
 870 // ------------------------------------------------------------------------------------------------------
 871 // Exception handlers
 872 
 873 
 874 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
 875   assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
 876   assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
 877   assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
 878 
 879   if (ShowSafepointMsgs) {
 880     tty->print("handle_polling_page_exception: ");
 881   }
 882 
 883   if (PrintSafepointStatistics) {
 884     inc_page_trap_count();
 885   }
 886 
 887   ThreadSafepointState* state = thread->safepoint_state();
 888 
 889   state->handle_polling_page_exception();
 890 }
 891 
 892 
 893 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
 894   if (!timeout_error_printed) {
 895     timeout_error_printed = true;
 896     // Print out the thread infor which didn't reach the safepoint for debugging
 897     // purposes (useful when there are lots of threads in the debugger).
 898     tty->cr();
 899     tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
 900     if (reason ==  _spinning_timeout) {
 901       tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
 902     } else if (reason == _blocking_timeout) {
 903       tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
 904     }
 905 
 906     tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
 907     ThreadSafepointState *cur_state;
 908     ResourceMark rm;
 909     for(JavaThread *cur_thread = Threads::first(); cur_thread;
 910         cur_thread = cur_thread->next()) {
 911       cur_state = cur_thread->safepoint_state();
 912 
 913       if (cur_thread->thread_state() != _thread_blocked &&
 914           ((reason == _spinning_timeout && cur_state->is_running()) ||
 915            (reason == _blocking_timeout && !cur_state->has_called_back()))) {
 916         tty->print("# ");
 917         cur_thread->print();
 918         tty->cr();
 919       }
 920     }
 921     tty->print_cr("# SafepointSynchronize::begin: (End of list)");
 922   }
 923 
 924   // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
 925   // ShowMessageBoxOnError.
 926   if (AbortVMOnSafepointTimeout) {
 927     char msg[1024];
 928     VM_Operation *op = VMThread::vm_operation();
 929     sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
 930             SafepointTimeoutDelay,
 931             op != NULL ? op->name() : "no vm operation");
 932     fatal(msg);
 933   }
 934 }
 935 
 936 
 937 // -------------------------------------------------------------------------------------------------------
 938 // Implementation of ThreadSafepointState
 939 
 940 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
 941   _thread = thread;
 942   _type   = _running;
 943   _has_called_back = false;
 944   _at_poll_safepoint = false;
 945 }
 946 
 947 void ThreadSafepointState::create(JavaThread *thread) {
 948   ThreadSafepointState *state = new ThreadSafepointState(thread);
 949   thread->set_safepoint_state(state);
 950 }
 951 
 952 void ThreadSafepointState::destroy(JavaThread *thread) {
 953   if (thread->safepoint_state()) {
 954     delete(thread->safepoint_state());
 955     thread->set_safepoint_state(NULL);
 956   }
 957 }
 958 
 959 void ThreadSafepointState::examine_state_of_thread() {
 960   assert(is_running(), "better be running or just have hit safepoint poll");
 961 
 962   JavaThreadState state = _thread->thread_state();
 963 
 964   // Save the state at the start of safepoint processing.
 965   _orig_thread_state = state;
 966 
 967   // Check for a thread that is suspended. Note that thread resume tries
 968   // to grab the Threads_lock which we own here, so a thread cannot be
 969   // resumed during safepoint synchronization.
 970 
 971   // We check to see if this thread is suspended without locking to
 972   // avoid deadlocking with a third thread that is waiting for this
 973   // thread to be suspended. The third thread can notice the safepoint
 974   // that we're trying to start at the beginning of its SR_lock->wait()
 975   // call. If that happens, then the third thread will block on the
 976   // safepoint while still holding the underlying SR_lock. We won't be
 977   // able to get the SR_lock and we'll deadlock.
 978   //
 979   // We don't need to grab the SR_lock here for two reasons:
 980   // 1) The suspend flags are both volatile and are set with an
 981   //    Atomic::cmpxchg() call so we should see the suspended
 982   //    state right away.
 983   // 2) We're being called from the safepoint polling loop; if
 984   //    we don't see the suspended state on this iteration, then
 985   //    we'll come around again.
 986   //
 987   bool is_suspended = _thread->is_ext_suspended();
 988   if (is_suspended) {
 989     roll_forward(_at_safepoint);
 990     return;
 991   }
 992 
 993   // Some JavaThread states have an initial safepoint state of
 994   // running, but are actually at a safepoint. We will happily
 995   // agree and update the safepoint state here.
 996   if (SafepointSynchronize::safepoint_safe(_thread, state)) {
 997     SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
 998     roll_forward(_at_safepoint);
 999     return;
1000   }
1001 
1002   if (state == _thread_in_vm) {
1003     roll_forward(_call_back);
1004     return;
1005   }
1006 
1007   // All other thread states will continue to run until they
1008   // transition and self-block in state _blocked
1009   // Safepoint polling in compiled code causes the Java threads to do the same.
1010   // Note: new threads may require a malloc so they must be allowed to finish
1011 
1012   assert(is_running(), "examine_state_of_thread on non-running thread");
1013   return;
1014 }
1015 
1016 // Returns true is thread could not be rolled forward at present position.
1017 void ThreadSafepointState::roll_forward(suspend_type type) {
1018   _type = type;
1019 
1020   switch(_type) {
1021     case _at_safepoint:
1022       SafepointSynchronize::signal_thread_at_safepoint();
1023       DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1024       if (_thread->in_critical()) {
1025         // Notice that this thread is in a critical section
1026         SafepointSynchronize::increment_jni_active_count();
1027       }
1028       break;
1029 
1030     case _call_back:
1031       set_has_called_back(false);
1032       break;
1033 
1034     case _running:
1035     default:
1036       ShouldNotReachHere();
1037   }
1038 }
1039 
1040 void ThreadSafepointState::restart() {
1041   switch(type()) {
1042     case _at_safepoint:
1043     case _call_back:
1044       break;
1045 
1046     case _running:
1047     default:
1048        tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1049                       _thread, _type);
1050        _thread->print();
1051       ShouldNotReachHere();
1052   }
1053   _type = _running;
1054   set_has_called_back(false);
1055 }
1056 
1057 
1058 void ThreadSafepointState::print_on(outputStream *st) const {
1059   const char *s = NULL;
1060 
1061   switch(_type) {
1062     case _running                : s = "_running";              break;
1063     case _at_safepoint           : s = "_at_safepoint";         break;
1064     case _call_back              : s = "_call_back";            break;
1065     default:
1066       ShouldNotReachHere();
1067   }
1068 
1069   st->print_cr("Thread: " INTPTR_FORMAT
1070               "  [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1071                _thread, _thread->osthread()->thread_id(), s, _has_called_back,
1072                _at_poll_safepoint);
1073 
1074   _thread->print_thread_state_on(st);
1075 }
1076 
1077 
1078 // ---------------------------------------------------------------------------------------------------------------------
1079 
1080 // Block the thread at the safepoint poll or poll return.
1081 void ThreadSafepointState::handle_polling_page_exception() {
1082 
1083   // Check state.  block() will set thread state to thread_in_vm which will
1084   // cause the safepoint state _type to become _call_back.
1085   assert(type() == ThreadSafepointState::_running,
1086          "polling page exception on thread not running state");
1087 
1088   // Step 1: Find the nmethod from the return address
1089   if (ShowSafepointMsgs && Verbose) {
1090     tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
1091   }
1092   address real_return_addr = thread()->saved_exception_pc();
1093 
1094   CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1095   assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
1096   nmethod* nm = (nmethod*)cb;
1097 
1098   // Find frame of caller
1099   frame stub_fr = thread()->last_frame();
1100   CodeBlob* stub_cb = stub_fr.cb();
1101   assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1102   RegisterMap map(thread(), true);
1103   frame caller_fr = stub_fr.sender(&map);
1104 
1105   // Should only be poll_return or poll
1106   assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1107 
1108   // This is a poll immediately before a return. The exception handling code
1109   // has already had the effect of causing the return to occur, so the execution
1110   // will continue immediately after the call. In addition, the oopmap at the
1111   // return point does not mark the return value as an oop (if it is), so
1112   // it needs a handle here to be updated.
1113   if( nm->is_at_poll_return(real_return_addr) ) {
1114     // See if return type is an oop.
1115     bool return_oop = nm->method()->is_returning_oop();
1116     Handle return_value;
1117     if (return_oop) {
1118       // The oop result has been saved on the stack together with all
1119       // the other registers. In order to preserve it over GCs we need
1120       // to keep it in a handle.
1121       oop result = caller_fr.saved_oop_result(&map);
1122       assert(result == NULL || result->is_oop(), "must be oop");
1123       return_value = Handle(thread(), result);
1124       assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1125     }
1126 
1127     // Block the thread
1128     SafepointSynchronize::block(thread());
1129 
1130     // restore oop result, if any
1131     if (return_oop) {
1132       caller_fr.set_saved_oop_result(&map, return_value());
1133     }
1134   }
1135 
1136   // This is a safepoint poll. Verify the return address and block.
1137   else {
1138     set_at_poll_safepoint(true);
1139 
1140     // verify the blob built the "return address" correctly
1141     assert(real_return_addr == caller_fr.pc(), "must match");
1142 
1143     // Block the thread
1144     SafepointSynchronize::block(thread());
1145     set_at_poll_safepoint(false);
1146 
1147     // If we have a pending async exception deoptimize the frame
1148     // as otherwise we may never deliver it.
1149     if (thread()->has_async_condition()) {
1150       ThreadInVMfromJavaNoAsyncException __tiv(thread());
1151       Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1152     }
1153 
1154     // If an exception has been installed we must check for a pending deoptimization
1155     // Deoptimize frame if exception has been thrown.
1156 
1157     if (thread()->has_pending_exception() ) {
1158       RegisterMap map(thread(), true);
1159       frame caller_fr = stub_fr.sender(&map);
1160       if (caller_fr.is_deoptimized_frame()) {
1161         // The exception patch will destroy registers that are still
1162         // live and will be needed during deoptimization. Defer the
1163         // Async exception should have defered the exception until the
1164         // next safepoint which will be detected when we get into
1165         // the interpreter so if we have an exception now things
1166         // are messed up.
1167 
1168         fatal("Exception installed and deoptimization is pending");
1169       }
1170     }
1171   }
1172 }
1173 
1174 
1175 //
1176 //                     Statistics & Instrumentations
1177 //
1178 SafepointSynchronize::SafepointStats*  SafepointSynchronize::_safepoint_stats = NULL;
1179 jlong  SafepointSynchronize::_safepoint_begin_time = 0;
1180 int    SafepointSynchronize::_cur_stat_index = 0;
1181 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1182 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1183 jlong  SafepointSynchronize::_max_sync_time = 0;
1184 jlong  SafepointSynchronize::_max_vmop_time = 0;
1185 float  SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1186 
1187 static jlong  cleanup_end_time = 0;
1188 static bool   need_to_track_page_armed_status = false;
1189 static bool   init_done = false;
1190 
1191 // Helper method to print the header.
1192 static void print_header() {
1193   tty->print("         vmop                    "
1194              "[threads: total initially_running wait_to_block]    ");
1195   tty->print("[time: spin block sync cleanup vmop] ");
1196 
1197   // no page armed status printed out if it is always armed.
1198   if (need_to_track_page_armed_status) {
1199     tty->print("page_armed ");
1200   }
1201 
1202   tty->print_cr("page_trap_count");
1203 }
1204 
1205 void SafepointSynchronize::deferred_initialize_stat() {
1206   if (init_done) return;
1207 
1208   if (PrintSafepointStatisticsCount <= 0) {
1209     fatal("Wrong PrintSafepointStatisticsCount");
1210   }
1211 
1212   // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1213   // be printed right away, in which case, _safepoint_stats will regress to
1214   // a single element array. Otherwise, it is a circular ring buffer with default
1215   // size of PrintSafepointStatisticsCount.
1216   int stats_array_size;
1217   if (PrintSafepointStatisticsTimeout > 0) {
1218     stats_array_size = 1;
1219     PrintSafepointStatistics = true;
1220   } else {
1221     stats_array_size = PrintSafepointStatisticsCount;
1222   }
1223   _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1224                                                  * sizeof(SafepointStats), mtInternal);
1225   guarantee(_safepoint_stats != NULL,
1226             "not enough memory for safepoint instrumentation data");
1227 
1228   if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1229     need_to_track_page_armed_status = true;
1230   }
1231   init_done = true;
1232 }
1233 
1234 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1235   assert(init_done, "safepoint statistics array hasn't been initialized");
1236   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1237 
1238   spstat->_time_stamp = _ts_of_current_safepoint;
1239 
1240   VM_Operation *op = VMThread::vm_operation();
1241   spstat->_vmop_type = (op != NULL ? op->type() : -1);
1242   if (op != NULL) {
1243     _safepoint_reasons[spstat->_vmop_type]++;
1244   }
1245 
1246   spstat->_nof_total_threads = nof_threads;
1247   spstat->_nof_initial_running_threads = nof_running;
1248   spstat->_nof_threads_hit_page_trap = 0;
1249 
1250   // Records the start time of spinning. The real time spent on spinning
1251   // will be adjusted when spin is done. Same trick is applied for time
1252   // spent on waiting for threads to block.
1253   if (nof_running != 0) {
1254     spstat->_time_to_spin = os::javaTimeNanos();
1255   }  else {
1256     spstat->_time_to_spin = 0;
1257   }
1258 }
1259 
1260 void SafepointSynchronize::update_statistics_on_spin_end() {
1261   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1262 
1263   jlong cur_time = os::javaTimeNanos();
1264 
1265   spstat->_nof_threads_wait_to_block = _waiting_to_block;
1266   if (spstat->_nof_initial_running_threads != 0) {
1267     spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1268   }
1269 
1270   if (need_to_track_page_armed_status) {
1271     spstat->_page_armed = (PageArmed == 1);
1272   }
1273 
1274   // Records the start time of waiting for to block. Updated when block is done.
1275   if (_waiting_to_block != 0) {
1276     spstat->_time_to_wait_to_block = cur_time;
1277   } else {
1278     spstat->_time_to_wait_to_block = 0;
1279   }
1280 }
1281 
1282 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1283   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1284 
1285   if (spstat->_nof_threads_wait_to_block != 0) {
1286     spstat->_time_to_wait_to_block = end_time -
1287       spstat->_time_to_wait_to_block;
1288   }
1289 
1290   // Records the end time of sync which will be used to calculate the total
1291   // vm operation time. Again, the real time spending in syncing will be deducted
1292   // from the start of the sync time later when end_statistics is called.
1293   spstat->_time_to_sync = end_time - _safepoint_begin_time;
1294   if (spstat->_time_to_sync > _max_sync_time) {
1295     _max_sync_time = spstat->_time_to_sync;
1296   }
1297 
1298   spstat->_time_to_do_cleanups = end_time;
1299 }
1300 
1301 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1302   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1303 
1304   // Record how long spent in cleanup tasks.
1305   spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1306 
1307   cleanup_end_time = end_time;
1308 }
1309 
1310 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1311   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1312 
1313   // Update the vm operation time.
1314   spstat->_time_to_exec_vmop = vmop_end_time -  cleanup_end_time;
1315   if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1316     _max_vmop_time = spstat->_time_to_exec_vmop;
1317   }
1318   // Only the sync time longer than the specified
1319   // PrintSafepointStatisticsTimeout will be printed out right away.
1320   // By default, it is -1 meaning all samples will be put into the list.
1321   if ( PrintSafepointStatisticsTimeout > 0) {
1322     if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1323       print_statistics();
1324     }
1325   } else {
1326     // The safepoint statistics will be printed out when the _safepoin_stats
1327     // array fills up.
1328     if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1329       print_statistics();
1330       _cur_stat_index = 0;
1331     } else {
1332       _cur_stat_index++;
1333     }
1334   }
1335 }
1336 
1337 void SafepointSynchronize::print_statistics() {
1338   SafepointStats* sstats = _safepoint_stats;
1339 
1340   for (int index = 0; index <= _cur_stat_index; index++) {
1341     if (index % 30 == 0) {
1342       print_header();
1343     }
1344     sstats = &_safepoint_stats[index];
1345     tty->print("%.3f: ", sstats->_time_stamp);
1346     tty->print("%-26s       ["
1347                INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1348                "    ]    ",
1349                sstats->_vmop_type == -1 ? "no vm operation" :
1350                VM_Operation::name(sstats->_vmop_type),
1351                sstats->_nof_total_threads,
1352                sstats->_nof_initial_running_threads,
1353                sstats->_nof_threads_wait_to_block);
1354     // "/ MICROUNITS " is to convert the unit from nanos to millis.
1355     tty->print("  ["
1356                INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1357                INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1358                INT64_FORMAT_W(6) "    ]  ",
1359                sstats->_time_to_spin / MICROUNITS,
1360                sstats->_time_to_wait_to_block / MICROUNITS,
1361                sstats->_time_to_sync / MICROUNITS,
1362                sstats->_time_to_do_cleanups / MICROUNITS,
1363                sstats->_time_to_exec_vmop / MICROUNITS);
1364 
1365     if (need_to_track_page_armed_status) {
1366       tty->print(INT32_FORMAT "         ", sstats->_page_armed);
1367     }
1368     tty->print_cr(INT32_FORMAT "   ", sstats->_nof_threads_hit_page_trap);
1369   }
1370 }
1371 
1372 // This method will be called when VM exits. It will first call
1373 // print_statistics to print out the rest of the sampling.  Then
1374 // it tries to summarize the sampling.
1375 void SafepointSynchronize::print_stat_on_exit() {
1376   if (_safepoint_stats == NULL) return;
1377 
1378   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1379 
1380   // During VM exit, end_statistics may not get called and in that
1381   // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1382   // don't print it out.
1383   // Approximate the vm op time.
1384   _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1385     os::javaTimeNanos() - cleanup_end_time;
1386 
1387   if ( PrintSafepointStatisticsTimeout < 0 ||
1388        spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1389     print_statistics();
1390   }
1391   tty->cr();
1392 
1393   // Print out polling page sampling status.
1394   if (!need_to_track_page_armed_status) {
1395     if (UseCompilerSafepoints) {
1396       tty->print_cr("Polling page always armed");
1397     }
1398   } else {
1399     tty->print_cr("Defer polling page loop count = %d\n",
1400                  DeferPollingPageLoopCount);
1401   }
1402 
1403   for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1404     if (_safepoint_reasons[index] != 0) {
1405       tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1406                     _safepoint_reasons[index]);
1407     }
1408   }
1409 
1410   tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1411                 _coalesced_vmop_count);
1412   tty->print_cr("Maximum sync time  " INT64_FORMAT_W(5) " ms",
1413                 _max_sync_time / MICROUNITS);
1414   tty->print_cr("Maximum vm operation time (except for Exit VM operation)  "
1415                 INT64_FORMAT_W(5) " ms",
1416                 _max_vmop_time / MICROUNITS);
1417 }
1418 
1419 // ------------------------------------------------------------------------------------------------
1420 // Non-product code
1421 
1422 #ifndef PRODUCT
1423 
1424 void SafepointSynchronize::print_state() {
1425   if (_state == _not_synchronized) {
1426     tty->print_cr("not synchronized");
1427   } else if (_state == _synchronizing || _state == _synchronized) {
1428     tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1429                   "synchronized");
1430 
1431     for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1432        cur->safepoint_state()->print();
1433     }
1434   }
1435 }
1436 
1437 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1438   if (ShowSafepointMsgs) {
1439     va_list ap;
1440     va_start(ap, format);
1441     tty->vprint_cr(format, ap);
1442     va_end(ap);
1443   }
1444 }
1445 
1446 #endif // !PRODUCT