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 "memory/resourceArea.hpp"
  36 #include "memory/universe.inline.hpp"
  37 #include "oops/oop.inline.hpp"
  38 #include "oops/symbol.hpp"
  39 #include "runtime/compilationPolicy.hpp"
  40 #include "runtime/deoptimization.hpp"
  41 #include "runtime/frame.inline.hpp"
  42 #include "runtime/interfaceSupport.hpp"
  43 #include "runtime/mutexLocker.hpp"
  44 #include "runtime/orderAccess.inline.hpp"
  45 #include "runtime/osThread.hpp"
  46 #include "runtime/safepoint.hpp"
  47 #include "runtime/signature.hpp"
  48 #include "runtime/stubCodeGenerator.hpp"
  49 #include "runtime/stubRoutines.hpp"
  50 #include "runtime/sweeper.hpp"
  51 #include "runtime/synchronizer.hpp"
  52 #include "runtime/thread.inline.hpp"
  53 #include "services/runtimeService.hpp"
  54 #include "utilities/events.hpp"
  55 #include "utilities/macros.hpp"
  56 #ifdef TARGET_ARCH_x86
  57 # include "nativeInst_x86.hpp"
  58 # include "vmreg_x86.inline.hpp"
  59 #endif
  60 #ifdef TARGET_ARCH_sparc
  61 # include "nativeInst_sparc.hpp"
  62 # include "vmreg_sparc.inline.hpp"
  63 #endif
  64 #ifdef TARGET_ARCH_zero
  65 # include "nativeInst_zero.hpp"
  66 # include "vmreg_zero.inline.hpp"
  67 #endif
  68 #ifdef TARGET_ARCH_arm
  69 # include "nativeInst_arm.hpp"
  70 # include "vmreg_arm.inline.hpp"
  71 #endif
  72 #ifdef TARGET_ARCH_ppc
  73 # include "nativeInst_ppc.hpp"
  74 # include "vmreg_ppc.inline.hpp"
  75 #endif
  76 #if INCLUDE_ALL_GCS
  77 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
  78 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
  79 #endif // INCLUDE_ALL_GCS
  80 #ifdef COMPILER1
  81 #include "c1/c1_globals.hpp"
  82 #endif
  83 
  84 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
  85 
  86 // --------------------------------------------------------------------------------------------------
  87 // Implementation of Safepoint begin/end
  88 
  89 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
  90 volatile int  SafepointSynchronize::_waiting_to_block = 0;
  91 volatile int SafepointSynchronize::_safepoint_counter = 0;
  92 int SafepointSynchronize::_current_jni_active_count = 0;
  93 long  SafepointSynchronize::_end_of_last_safepoint = 0;
  94 static volatile int PageArmed = 0 ;        // safepoint polling page is RO|RW vs PROT_NONE
  95 static volatile int TryingToBlock = 0 ;    // proximate value -- for advisory use only
  96 static bool timeout_error_printed = false;
  97 
  98 // Roll all threads forward to a safepoint and suspend them all
  99 void SafepointSynchronize::begin() {
 100 
 101   Thread* myThread = Thread::current();
 102   assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
 103 
 104   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
 105     _safepoint_begin_time = os::javaTimeNanos();
 106     _ts_of_current_safepoint = tty->time_stamp().seconds();
 107   }
 108 
 109 #if INCLUDE_ALL_GCS
 110   if (UseConcMarkSweepGC) {
 111     // In the future we should investigate whether CMS can use the
 112     // more-general mechanism below.  DLD (01/05).
 113     ConcurrentMarkSweepThread::synchronize(false);
 114   } else if (UseG1GC) {
 115     SuspendibleThreadSet::synchronize();
 116   }
 117 #endif // INCLUDE_ALL_GCS
 118 
 119   // By getting the Threads_lock, we assure that no threads are about to start or
 120   // exit. It is released again in SafepointSynchronize::end().
 121   Threads_lock->lock();
 122 
 123   assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
 124 
 125   int nof_threads = Threads::number_of_threads();
 126 
 127   if (TraceSafepoint) {
 128     tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
 129   }
 130 
 131   RuntimeService::record_safepoint_begin();
 132 
 133   MutexLocker mu(Safepoint_lock);
 134 
 135   // Reset the count of active JNI critical threads
 136   _current_jni_active_count = 0;
 137 
 138   // Set number of threads to wait for, before we initiate the callbacks
 139   _waiting_to_block = nof_threads;
 140   TryingToBlock     = 0 ;
 141   int still_running = nof_threads;
 142 
 143   // Save the starting time, so that it can be compared to see if this has taken
 144   // too long to complete.
 145   jlong safepoint_limit_time = 0;
 146   timeout_error_printed = false;
 147 
 148   // PrintSafepointStatisticsTimeout can be specified separately. When
 149   // specified, PrintSafepointStatistics will be set to true in
 150   // deferred_initialize_stat method. The initialization has to be done
 151   // early enough to avoid any races. See bug 6880029 for details.
 152   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
 153     deferred_initialize_stat();
 154   }
 155 
 156   // Begin the process of bringing the system to a safepoint.
 157   // Java threads can be in several different states and are
 158   // stopped by different mechanisms:
 159   //
 160   //  1. Running interpreted
 161   //     The interpeter dispatch table is changed to force it to
 162   //     check for a safepoint condition between bytecodes.
 163   //  2. Running in native code
 164   //     When returning from the native code, a Java thread must check
 165   //     the safepoint _state to see if we must block.  If the
 166   //     VM thread sees a Java thread in native, it does
 167   //     not wait for this thread to block.  The order of the memory
 168   //     writes and reads of both the safepoint state and the Java
 169   //     threads state is critical.  In order to guarantee that the
 170   //     memory writes are serialized with respect to each other,
 171   //     the VM thread issues a memory barrier instruction
 172   //     (on MP systems).  In order to avoid the overhead of issuing
 173   //     a memory barrier for each Java thread making native calls, each Java
 174   //     thread performs a write to a single memory page after changing
 175   //     the thread state.  The VM thread performs a sequence of
 176   //     mprotect OS calls which forces all previous writes from all
 177   //     Java threads to be serialized.  This is done in the
 178   //     os::serialize_thread_states() call.  This has proven to be
 179   //     much more efficient than executing a membar instruction
 180   //     on every call to native code.
 181   //  3. Running compiled Code
 182   //     Compiled code reads a global (Safepoint Polling) page that
 183   //     is set to fault if we are trying to get to a safepoint.
 184   //  4. Blocked
 185   //     A thread which is blocked will not be allowed to return from the
 186   //     block condition until the safepoint operation is complete.
 187   //  5. In VM or Transitioning between states
 188   //     If a Java thread is currently running in the VM or transitioning
 189   //     between states, the safepointing code will wait for the thread to
 190   //     block itself when it attempts transitions to a new state.
 191   //
 192   _state            = _synchronizing;
 193   OrderAccess::fence();
 194 
 195   // Flush all thread states to memory
 196   if (!UseMembar) {
 197     os::serialize_thread_states();
 198   }
 199 
 200   // Make interpreter safepoint aware
 201   Interpreter::notice_safepoints();
 202 
 203   if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
 204     // Make polling safepoint aware
 205     guarantee (PageArmed == 0, "invariant") ;
 206     PageArmed = 1 ;
 207     os::make_polling_page_unreadable();
 208   }
 209 
 210   // Consider using active_processor_count() ... but that call is expensive.
 211   int ncpus = os::processor_count() ;
 212 
 213 #ifdef ASSERT
 214   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 215     assert(cur->safepoint_state()->is_running(), "Illegal initial state");
 216     // Clear the visited flag to ensure that the critical counts are collected properly.
 217     cur->set_visited_for_critical_count(false);
 218   }
 219 #endif // ASSERT
 220 
 221   if (SafepointTimeout)
 222     safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
 223 
 224   // Iterate through all threads until it have been determined how to stop them all at a safepoint
 225   unsigned int iterations = 0;
 226   int steps = 0 ;
 227   while(still_running > 0) {
 228     for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 229       assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
 230       ThreadSafepointState *cur_state = cur->safepoint_state();
 231       if (cur_state->is_running()) {
 232         cur_state->examine_state_of_thread();
 233         if (!cur_state->is_running()) {
 234            still_running--;
 235            // consider adjusting steps downward:
 236            //   steps = 0
 237            //   steps -= NNN
 238            //   steps >>= 1
 239            //   steps = MIN(steps, 2000-100)
 240            //   if (iterations != 0) steps -= NNN
 241         }
 242         if (TraceSafepoint && Verbose) cur_state->print();
 243       }
 244     }
 245 
 246     if (PrintSafepointStatistics && iterations == 0) {
 247       begin_statistics(nof_threads, still_running);
 248     }
 249 
 250     if (still_running > 0) {
 251       // Check for if it takes to long
 252       if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
 253         print_safepoint_timeout(_spinning_timeout);
 254       }
 255 
 256       // Spin to avoid context switching.
 257       // There's a tension between allowing the mutators to run (and rendezvous)
 258       // vs spinning.  As the VM thread spins, wasting cycles, it consumes CPU that
 259       // a mutator might otherwise use profitably to reach a safepoint.  Excessive
 260       // spinning by the VM thread on a saturated system can increase rendezvous latency.
 261       // Blocking or yielding incur their own penalties in the form of context switching
 262       // and the resultant loss of $ residency.
 263       //
 264       // Further complicating matters is that yield() does not work as naively expected
 265       // on many platforms -- yield() does not guarantee that any other ready threads
 266       // will run.   As such we revert yield_all() after some number of iterations.
 267       // Yield_all() is implemented as a short unconditional sleep on some platforms.
 268       // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
 269       // can actually increase the time it takes the VM thread to detect that a system-wide
 270       // stop-the-world safepoint has been reached.  In a pathological scenario such as that
 271       // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
 272       // In that case the mutators will be stalled waiting for the safepoint to complete and the
 273       // the VMthread will be sleeping, waiting for the mutators to rendezvous.  The VMthread
 274       // will eventually wake up and detect that all mutators are safe, at which point
 275       // we'll again make progress.
 276       //
 277       // Beware too that that the VMThread typically runs at elevated priority.
 278       // Its default priority is higher than the default mutator priority.
 279       // Obviously, this complicates spinning.
 280       //
 281       // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
 282       // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
 283       //
 284       // See the comments in synchronizer.cpp for additional remarks on spinning.
 285       //
 286       // In the future we might:
 287       // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
 288       //    This is tricky as the path used by a thread exiting the JVM (say on
 289       //    on JNI call-out) simply stores into its state field.  The burden
 290       //    is placed on the VM thread, which must poll (spin).
 291       // 2. Find something useful to do while spinning.  If the safepoint is GC-related
 292       //    we might aggressively scan the stacks of threads that are already safe.
 293       // 3. Use Solaris schedctl to examine the state of the still-running mutators.
 294       //    If all the mutators are ONPROC there's no reason to sleep or yield.
 295       // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
 296       // 5. Check system saturation.  If the system is not fully saturated then
 297       //    simply spin and avoid sleep/yield.
 298       // 6. As still-running mutators rendezvous they could unpark the sleeping
 299       //    VMthread.  This works well for still-running mutators that become
 300       //    safe.  The VMthread must still poll for mutators that call-out.
 301       // 7. Drive the policy on time-since-begin instead of iterations.
 302       // 8. Consider making the spin duration a function of the # of CPUs:
 303       //    Spin = (((ncpus-1) * M) + K) + F(still_running)
 304       //    Alternately, instead of counting iterations of the outer loop
 305       //    we could count the # of threads visited in the inner loop, above.
 306       // 9. On windows consider using the return value from SwitchThreadTo()
 307       //    to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
 308 
 309       if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
 310          guarantee (PageArmed == 0, "invariant") ;
 311          PageArmed = 1 ;
 312          os::make_polling_page_unreadable();
 313       }
 314 
 315       // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
 316       // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
 317       ++steps ;
 318       if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
 319         SpinPause() ;     // MP-Polite spin
 320       } else
 321       if (steps < DeferThrSuspendLoopCount) {
 322         os::NakedYield() ;
 323       } else {
 324         os::yield_all(steps) ;
 325         // Alternately, the VM thread could transiently depress its scheduling priority or
 326         // transiently increase the priority of the tardy mutator(s).
 327       }
 328 
 329       iterations ++ ;
 330     }
 331     assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
 332   }
 333   assert(still_running == 0, "sanity check");
 334 
 335   if (PrintSafepointStatistics) {
 336     update_statistics_on_spin_end();
 337   }
 338 
 339   // wait until all threads are stopped
 340   while (_waiting_to_block > 0) {
 341     if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
 342     if (!SafepointTimeout || timeout_error_printed) {
 343       Safepoint_lock->wait(true);  // true, means with no safepoint checks
 344     } else {
 345       // Compute remaining time
 346       jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
 347 
 348       // If there is no remaining time, then there is an error
 349       if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
 350         print_safepoint_timeout(_blocking_timeout);
 351       }
 352     }
 353   }
 354   assert(_waiting_to_block == 0, "sanity check");
 355 
 356 #ifndef PRODUCT
 357   if (SafepointTimeout) {
 358     jlong current_time = os::javaTimeNanos();
 359     if (safepoint_limit_time < current_time) {
 360       tty->print_cr("# SafepointSynchronize: Finished after "
 361                     INT64_FORMAT_W(6) " ms",
 362                     ((current_time - safepoint_limit_time) / MICROUNITS +
 363                      SafepointTimeoutDelay));
 364     }
 365   }
 366 #endif
 367 
 368   assert((_safepoint_counter & 0x1) == 0, "must be even");
 369   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 370   _safepoint_counter ++;
 371 
 372   // Record state
 373   _state = _synchronized;
 374 
 375   OrderAccess::fence();
 376 
 377 #ifdef ASSERT
 378   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 379     // make sure all the threads were visited
 380     assert(cur->was_visited_for_critical_count(), "missed a thread");
 381   }
 382 #endif // ASSERT
 383 
 384   // Update the count of active JNI critical regions
 385   GC_locker::set_jni_lock_count(_current_jni_active_count);
 386 
 387   if (TraceSafepoint) {
 388     VM_Operation *op = VMThread::vm_operation();
 389     tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
 390   }
 391 
 392   RuntimeService::record_safepoint_synchronized();
 393   if (PrintSafepointStatistics) {
 394     update_statistics_on_sync_end(os::javaTimeNanos());
 395   }
 396 
 397   // Call stuff that needs to be run when a safepoint is just about to be completed
 398   do_cleanup_tasks();
 399 
 400   if (PrintSafepointStatistics) {
 401     // Record how much time spend on the above cleanup tasks
 402     update_statistics_on_cleanup_end(os::javaTimeNanos());
 403   }
 404 }
 405 
 406 // Wake up all threads, so they are ready to resume execution after the safepoint
 407 // operation has been carried out
 408 void SafepointSynchronize::end() {
 409 
 410   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 411   assert((_safepoint_counter & 0x1) == 1, "must be odd");
 412   _safepoint_counter ++;
 413   // memory fence isn't required here since an odd _safepoint_counter
 414   // value can do no harm and a fence is issued below anyway.
 415 
 416   DEBUG_ONLY(Thread* myThread = Thread::current();)
 417   assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
 418 
 419   if (PrintSafepointStatistics) {
 420     end_statistics(os::javaTimeNanos());
 421   }
 422 
 423 #ifdef ASSERT
 424   // A pending_exception cannot be installed during a safepoint.  The threads
 425   // may install an async exception after they come back from a safepoint into
 426   // pending_exception after they unblock.  But that should happen later.
 427   for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
 428     assert (!(cur->has_pending_exception() &&
 429               cur->safepoint_state()->is_at_poll_safepoint()),
 430             "safepoint installed a pending exception");
 431   }
 432 #endif // ASSERT
 433 
 434   if (PageArmed) {
 435     // Make polling safepoint aware
 436     os::make_polling_page_readable();
 437     PageArmed = 0 ;
 438   }
 439 
 440   // Remove safepoint check from interpreter
 441   Interpreter::ignore_safepoints();
 442 
 443   {
 444     MutexLocker mu(Safepoint_lock);
 445 
 446     assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
 447 
 448     // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
 449     // when they get restarted.
 450     _state = _not_synchronized;
 451     OrderAccess::fence();
 452 
 453     if (TraceSafepoint) {
 454        tty->print_cr("Leaving safepoint region");
 455     }
 456 
 457     // Start suspended threads
 458     for(JavaThread *current = Threads::first(); current; current = current->next()) {
 459       // A problem occurring on Solaris is when attempting to restart threads
 460       // the first #cpus - 1 go well, but then the VMThread is preempted when we get
 461       // to the next one (since it has been running the longest).  We then have
 462       // to wait for a cpu to become available before we can continue restarting
 463       // threads.
 464       // FIXME: This causes the performance of the VM to degrade when active and with
 465       // large numbers of threads.  Apparently this is due to the synchronous nature
 466       // of suspending threads.
 467       //
 468       // TODO-FIXME: the comments above are vestigial and no longer apply.
 469       // Furthermore, using solaris' schedctl in this particular context confers no benefit
 470       if (VMThreadHintNoPreempt) {
 471         os::hint_no_preempt();
 472       }
 473       ThreadSafepointState* cur_state = current->safepoint_state();
 474       assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
 475       cur_state->restart();
 476       assert(cur_state->is_running(), "safepoint state has not been reset");
 477     }
 478 
 479     RuntimeService::record_safepoint_end();
 480 
 481     // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
 482     // blocked in signal_thread_blocked
 483     Threads_lock->unlock();
 484 
 485   }
 486 #if INCLUDE_ALL_GCS
 487   // If there are any concurrent GC threads resume them.
 488   if (UseConcMarkSweepGC) {
 489     ConcurrentMarkSweepThread::desynchronize(false);
 490   } else if (UseG1GC) {
 491     SuspendibleThreadSet::desynchronize();
 492   }
 493 #endif // INCLUDE_ALL_GCS
 494   // record this time so VMThread can keep track how much time has elasped
 495   // since last safepoint.
 496   _end_of_last_safepoint = os::javaTimeMillis();
 497 }
 498 
 499 bool SafepointSynchronize::is_cleanup_needed() {
 500   // Need a safepoint if some inline cache buffers is non-empty
 501   if (!InlineCacheBuffer::is_empty()) return true;
 502   return false;
 503 }
 504 
 505 
 506 
 507 // Various cleaning tasks that should be done periodically at safepoints
 508 void SafepointSynchronize::do_cleanup_tasks() {
 509   {
 510     TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
 511     ObjectSynchronizer::deflate_idle_monitors();
 512   }
 513 
 514   {
 515     TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
 516     InlineCacheBuffer::update_inline_caches();
 517   }
 518   {
 519     TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
 520     CompilationPolicy::policy()->do_safepoint_work();
 521   }
 522 
 523   {
 524     TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
 525     NMethodSweeper::mark_active_nmethods();
 526   }
 527 
 528   if (SymbolTable::needs_rehashing()) {
 529     TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
 530     SymbolTable::rehash_table();
 531   }
 532 
 533   if (StringTable::needs_rehashing()) {
 534     TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
 535     StringTable::rehash_table();
 536   }
 537 
 538   // rotate log files?
 539   if (UseGCLogFileRotation) {
 540     TraceTime t8("rotating gc logs", TraceSafepointCleanupTime);
 541     gclog_or_tty->rotate_log(false);
 542   }
 543 
 544   {
 545     // CMS delays purging the CLDG until the beginning of the next safepoint and to
 546     // make sure concurrent sweep is done
 547     TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
 548     ClassLoaderDataGraph::purge_if_needed();
 549   }
 550 }
 551 
 552 
 553 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
 554   switch(state) {
 555   case _thread_in_native:
 556     // native threads are safe if they have no java stack or have walkable stack
 557     return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
 558 
 559    // blocked threads should have already have walkable stack
 560   case _thread_blocked:
 561     assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
 562     return true;
 563 
 564   default:
 565     return false;
 566   }
 567 }
 568 
 569 
 570 // See if the thread is running inside a lazy critical native and
 571 // update the thread critical count if so.  Also set a suspend flag to
 572 // cause the native wrapper to return into the JVM to do the unlock
 573 // once the native finishes.
 574 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
 575   if (state == _thread_in_native &&
 576       thread->has_last_Java_frame() &&
 577       thread->frame_anchor()->walkable()) {
 578     // This thread might be in a critical native nmethod so look at
 579     // the top of the stack and increment the critical count if it
 580     // is.
 581     frame wrapper_frame = thread->last_frame();
 582     CodeBlob* stub_cb = wrapper_frame.cb();
 583     if (stub_cb != NULL &&
 584         stub_cb->is_nmethod() &&
 585         stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
 586       // A thread could potentially be in a critical native across
 587       // more than one safepoint, so only update the critical state on
 588       // the first one.  When it returns it will perform the unlock.
 589       if (!thread->do_critical_native_unlock()) {
 590 #ifdef ASSERT
 591         if (!thread->in_critical()) {
 592           GC_locker::increment_debug_jni_lock_count();
 593         }
 594 #endif
 595         thread->enter_critical();
 596         // Make sure the native wrapper calls back on return to
 597         // perform the needed critical unlock.
 598         thread->set_critical_native_unlock();
 599       }
 600     }
 601   }
 602 }
 603 
 604 
 605 
 606 // -------------------------------------------------------------------------------------------------------
 607 // Implementation of Safepoint callback point
 608 
 609 void SafepointSynchronize::block(JavaThread *thread) {
 610   assert(thread != NULL, "thread must be set");
 611   assert(thread->is_Java_thread(), "not a Java thread");
 612 
 613   // Threads shouldn't block if they are in the middle of printing, but...
 614   ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
 615 
 616   // Only bail from the block() call if the thread is gone from the
 617   // thread list; starting to exit should still block.
 618   if (thread->is_terminated()) {
 619      // block current thread if we come here from native code when VM is gone
 620      thread->block_if_vm_exited();
 621 
 622      // otherwise do nothing
 623      return;
 624   }
 625 
 626   JavaThreadState state = thread->thread_state();
 627   thread->frame_anchor()->make_walkable(thread);
 628 
 629   // Check that we have a valid thread_state at this point
 630   switch(state) {
 631     case _thread_in_vm_trans:
 632     case _thread_in_Java:        // From compiled code
 633 
 634       // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
 635       // we pretend we are still in the VM.
 636       thread->set_thread_state(_thread_in_vm);
 637 
 638       if (is_synchronizing()) {
 639          Atomic::inc (&TryingToBlock) ;
 640       }
 641 
 642       // We will always be holding the Safepoint_lock when we are examine the state
 643       // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
 644       // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
 645       Safepoint_lock->lock_without_safepoint_check();
 646       if (is_synchronizing()) {
 647         // Decrement the number of threads to wait for and signal vm thread
 648         assert(_waiting_to_block > 0, "sanity check");
 649         _waiting_to_block--;
 650         thread->safepoint_state()->set_has_called_back(true);
 651 
 652         DEBUG_ONLY(thread->set_visited_for_critical_count(true));
 653         if (thread->in_critical()) {
 654           // Notice that this thread is in a critical section
 655           increment_jni_active_count();
 656         }
 657 
 658         // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
 659         if (_waiting_to_block == 0) {
 660           Safepoint_lock->notify_all();
 661         }
 662       }
 663 
 664       // We transition the thread to state _thread_blocked here, but
 665       // we can't do our usual check for external suspension and then
 666       // self-suspend after the lock_without_safepoint_check() call
 667       // below because we are often called during transitions while
 668       // we hold different locks. That would leave us suspended while
 669       // holding a resource which results in deadlocks.
 670       thread->set_thread_state(_thread_blocked);
 671       Safepoint_lock->unlock();
 672 
 673       // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
 674       // the entire safepoint, the threads will all line up here during the safepoint.
 675       Threads_lock->lock_without_safepoint_check();
 676       // restore original state. This is important if the thread comes from compiled code, so it
 677       // will continue to execute with the _thread_in_Java state.
 678       thread->set_thread_state(state);
 679       Threads_lock->unlock();
 680       break;
 681 
 682     case _thread_in_native_trans:
 683     case _thread_blocked_trans:
 684     case _thread_new_trans:
 685       if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
 686         thread->print_thread_state();
 687         fatal("Deadlock in safepoint code.  "
 688               "Should have called back to the VM before blocking.");
 689       }
 690 
 691       // We transition the thread to state _thread_blocked here, but
 692       // we can't do our usual check for external suspension and then
 693       // self-suspend after the lock_without_safepoint_check() call
 694       // below because we are often called during transitions while
 695       // we hold different locks. That would leave us suspended while
 696       // holding a resource which results in deadlocks.
 697       thread->set_thread_state(_thread_blocked);
 698 
 699       // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
 700       // the safepoint code might still be waiting for it to block. We need to change the state here,
 701       // so it can see that it is at a safepoint.
 702 
 703       // Block until the safepoint operation is completed.
 704       Threads_lock->lock_without_safepoint_check();
 705 
 706       // Restore state
 707       thread->set_thread_state(state);
 708 
 709       Threads_lock->unlock();
 710       break;
 711 
 712     default:
 713      fatal(err_msg("Illegal threadstate encountered: %d", state));
 714   }
 715 
 716   // Check for pending. async. exceptions or suspends - except if the
 717   // thread was blocked inside the VM. has_special_runtime_exit_condition()
 718   // is called last since it grabs a lock and we only want to do that when
 719   // we must.
 720   //
 721   // Note: we never deliver an async exception at a polling point as the
 722   // compiler may not have an exception handler for it. The polling
 723   // code will notice the async and deoptimize and the exception will
 724   // be delivered. (Polling at a return point is ok though). Sure is
 725   // a lot of bother for a deprecated feature...
 726   //
 727   // We don't deliver an async exception if the thread state is
 728   // _thread_in_native_trans so JNI functions won't be called with
 729   // a surprising pending exception. If the thread state is going back to java,
 730   // async exception is checked in check_special_condition_for_native_trans().
 731 
 732   if (state != _thread_blocked_trans &&
 733       state != _thread_in_vm_trans &&
 734       thread->has_special_runtime_exit_condition()) {
 735     thread->handle_special_runtime_exit_condition(
 736       !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
 737   }
 738 }
 739 
 740 // ------------------------------------------------------------------------------------------------------
 741 // Exception handlers
 742 
 743 
 744 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
 745   assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
 746   assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
 747   assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
 748 
 749   if (ShowSafepointMsgs) {
 750     tty->print("handle_polling_page_exception: ");
 751   }
 752 
 753   if (PrintSafepointStatistics) {
 754     inc_page_trap_count();
 755   }
 756 
 757   ThreadSafepointState* state = thread->safepoint_state();
 758 
 759   state->handle_polling_page_exception();
 760 }
 761 
 762 
 763 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
 764   if (!timeout_error_printed) {
 765     timeout_error_printed = true;
 766     // Print out the thread infor which didn't reach the safepoint for debugging
 767     // purposes (useful when there are lots of threads in the debugger).
 768     tty->cr();
 769     tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
 770     if (reason ==  _spinning_timeout) {
 771       tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
 772     } else if (reason == _blocking_timeout) {
 773       tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
 774     }
 775 
 776     tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
 777     ThreadSafepointState *cur_state;
 778     ResourceMark rm;
 779     for(JavaThread *cur_thread = Threads::first(); cur_thread;
 780         cur_thread = cur_thread->next()) {
 781       cur_state = cur_thread->safepoint_state();
 782 
 783       if (cur_thread->thread_state() != _thread_blocked &&
 784           ((reason == _spinning_timeout && cur_state->is_running()) ||
 785            (reason == _blocking_timeout && !cur_state->has_called_back()))) {
 786         tty->print("# ");
 787         cur_thread->print();
 788         tty->cr();
 789       }
 790     }
 791     tty->print_cr("# SafepointSynchronize::begin: (End of list)");
 792   }
 793 
 794   // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
 795   // ShowMessageBoxOnError.
 796   if (AbortVMOnSafepointTimeout) {
 797     char msg[1024];
 798     VM_Operation *op = VMThread::vm_operation();
 799     sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
 800             SafepointTimeoutDelay,
 801             op != NULL ? op->name() : "no vm operation");
 802     fatal(msg);
 803   }
 804 }
 805 
 806 
 807 // -------------------------------------------------------------------------------------------------------
 808 // Implementation of ThreadSafepointState
 809 
 810 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
 811   _thread = thread;
 812   _type   = _running;
 813   _has_called_back = false;
 814   _at_poll_safepoint = false;
 815 }
 816 
 817 void ThreadSafepointState::create(JavaThread *thread) {
 818   ThreadSafepointState *state = new ThreadSafepointState(thread);
 819   thread->set_safepoint_state(state);
 820 }
 821 
 822 void ThreadSafepointState::destroy(JavaThread *thread) {
 823   if (thread->safepoint_state()) {
 824     delete(thread->safepoint_state());
 825     thread->set_safepoint_state(NULL);
 826   }
 827 }
 828 
 829 void ThreadSafepointState::examine_state_of_thread() {
 830   assert(is_running(), "better be running or just have hit safepoint poll");
 831 
 832   JavaThreadState state = _thread->thread_state();
 833 
 834   // Save the state at the start of safepoint processing.
 835   _orig_thread_state = state;
 836 
 837   // Check for a thread that is suspended. Note that thread resume tries
 838   // to grab the Threads_lock which we own here, so a thread cannot be
 839   // resumed during safepoint synchronization.
 840 
 841   // We check to see if this thread is suspended without locking to
 842   // avoid deadlocking with a third thread that is waiting for this
 843   // thread to be suspended. The third thread can notice the safepoint
 844   // that we're trying to start at the beginning of its SR_lock->wait()
 845   // call. If that happens, then the third thread will block on the
 846   // safepoint while still holding the underlying SR_lock. We won't be
 847   // able to get the SR_lock and we'll deadlock.
 848   //
 849   // We don't need to grab the SR_lock here for two reasons:
 850   // 1) The suspend flags are both volatile and are set with an
 851   //    Atomic::cmpxchg() call so we should see the suspended
 852   //    state right away.
 853   // 2) We're being called from the safepoint polling loop; if
 854   //    we don't see the suspended state on this iteration, then
 855   //    we'll come around again.
 856   //
 857   bool is_suspended = _thread->is_ext_suspended();
 858   if (is_suspended) {
 859     roll_forward(_at_safepoint);
 860     return;
 861   }
 862 
 863   // Some JavaThread states have an initial safepoint state of
 864   // running, but are actually at a safepoint. We will happily
 865   // agree and update the safepoint state here.
 866   if (SafepointSynchronize::safepoint_safe(_thread, state)) {
 867     SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
 868     roll_forward(_at_safepoint);
 869     return;
 870   }
 871 
 872   if (state == _thread_in_vm) {
 873     roll_forward(_call_back);
 874     return;
 875   }
 876 
 877   // All other thread states will continue to run until they
 878   // transition and self-block in state _blocked
 879   // Safepoint polling in compiled code causes the Java threads to do the same.
 880   // Note: new threads may require a malloc so they must be allowed to finish
 881 
 882   assert(is_running(), "examine_state_of_thread on non-running thread");
 883   return;
 884 }
 885 
 886 // Returns true is thread could not be rolled forward at present position.
 887 void ThreadSafepointState::roll_forward(suspend_type type) {
 888   _type = type;
 889 
 890   switch(_type) {
 891     case _at_safepoint:
 892       SafepointSynchronize::signal_thread_at_safepoint();
 893       DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
 894       if (_thread->in_critical()) {
 895         // Notice that this thread is in a critical section
 896         SafepointSynchronize::increment_jni_active_count();
 897       }
 898       break;
 899 
 900     case _call_back:
 901       set_has_called_back(false);
 902       break;
 903 
 904     case _running:
 905     default:
 906       ShouldNotReachHere();
 907   }
 908 }
 909 
 910 void ThreadSafepointState::restart() {
 911   switch(type()) {
 912     case _at_safepoint:
 913     case _call_back:
 914       break;
 915 
 916     case _running:
 917     default:
 918        tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
 919                       _thread, _type);
 920        _thread->print();
 921       ShouldNotReachHere();
 922   }
 923   _type = _running;
 924   set_has_called_back(false);
 925 }
 926 
 927 
 928 void ThreadSafepointState::print_on(outputStream *st) const {
 929   const char *s = NULL;
 930 
 931   switch(_type) {
 932     case _running                : s = "_running";              break;
 933     case _at_safepoint           : s = "_at_safepoint";         break;
 934     case _call_back              : s = "_call_back";            break;
 935     default:
 936       ShouldNotReachHere();
 937   }
 938 
 939   st->print_cr("Thread: " INTPTR_FORMAT
 940               "  [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
 941                _thread, _thread->osthread()->thread_id(), s, _has_called_back,
 942                _at_poll_safepoint);
 943 
 944   _thread->print_thread_state_on(st);
 945 }
 946 
 947 
 948 // ---------------------------------------------------------------------------------------------------------------------
 949 
 950 // Block the thread at the safepoint poll or poll return.
 951 void ThreadSafepointState::handle_polling_page_exception() {
 952 
 953   // Check state.  block() will set thread state to thread_in_vm which will
 954   // cause the safepoint state _type to become _call_back.
 955   assert(type() == ThreadSafepointState::_running,
 956          "polling page exception on thread not running state");
 957 
 958   // Step 1: Find the nmethod from the return address
 959   if (ShowSafepointMsgs && Verbose) {
 960     tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
 961   }
 962   address real_return_addr = thread()->saved_exception_pc();
 963 
 964   CodeBlob *cb = CodeCache::find_blob(real_return_addr);
 965   assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
 966   nmethod* nm = (nmethod*)cb;
 967 
 968   // Find frame of caller
 969   frame stub_fr = thread()->last_frame();
 970   CodeBlob* stub_cb = stub_fr.cb();
 971   assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
 972   RegisterMap map(thread(), true);
 973   frame caller_fr = stub_fr.sender(&map);
 974 
 975   // Should only be poll_return or poll
 976   assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
 977 
 978   // This is a poll immediately before a return. The exception handling code
 979   // has already had the effect of causing the return to occur, so the execution
 980   // will continue immediately after the call. In addition, the oopmap at the
 981   // return point does not mark the return value as an oop (if it is), so
 982   // it needs a handle here to be updated.
 983   if( nm->is_at_poll_return(real_return_addr) ) {
 984     // See if return type is an oop.
 985     bool return_oop = nm->method()->is_returning_oop();
 986     Handle return_value;
 987     if (return_oop) {
 988       // The oop result has been saved on the stack together with all
 989       // the other registers. In order to preserve it over GCs we need
 990       // to keep it in a handle.
 991       oop result = caller_fr.saved_oop_result(&map);
 992       assert(result == NULL || result->is_oop(), "must be oop");
 993       return_value = Handle(thread(), result);
 994       assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
 995     }
 996 
 997     // Block the thread
 998     SafepointSynchronize::block(thread());
 999 
1000     // restore oop result, if any
1001     if (return_oop) {
1002       caller_fr.set_saved_oop_result(&map, return_value());
1003     }
1004   }
1005 
1006   // This is a safepoint poll. Verify the return address and block.
1007   else {
1008     set_at_poll_safepoint(true);
1009 
1010     // verify the blob built the "return address" correctly
1011     assert(real_return_addr == caller_fr.pc(), "must match");
1012 
1013     // Block the thread
1014     SafepointSynchronize::block(thread());
1015     set_at_poll_safepoint(false);
1016 
1017     // If we have a pending async exception deoptimize the frame
1018     // as otherwise we may never deliver it.
1019     if (thread()->has_async_condition()) {
1020       ThreadInVMfromJavaNoAsyncException __tiv(thread());
1021       Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1022     }
1023 
1024     // If an exception has been installed we must check for a pending deoptimization
1025     // Deoptimize frame if exception has been thrown.
1026 
1027     if (thread()->has_pending_exception() ) {
1028       RegisterMap map(thread(), true);
1029       frame caller_fr = stub_fr.sender(&map);
1030       if (caller_fr.is_deoptimized_frame()) {
1031         // The exception patch will destroy registers that are still
1032         // live and will be needed during deoptimization. Defer the
1033         // Async exception should have defered the exception until the
1034         // next safepoint which will be detected when we get into
1035         // the interpreter so if we have an exception now things
1036         // are messed up.
1037 
1038         fatal("Exception installed and deoptimization is pending");
1039       }
1040     }
1041   }
1042 }
1043 
1044 
1045 //
1046 //                     Statistics & Instrumentations
1047 //
1048 SafepointSynchronize::SafepointStats*  SafepointSynchronize::_safepoint_stats = NULL;
1049 jlong  SafepointSynchronize::_safepoint_begin_time = 0;
1050 int    SafepointSynchronize::_cur_stat_index = 0;
1051 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1052 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1053 jlong  SafepointSynchronize::_max_sync_time = 0;
1054 jlong  SafepointSynchronize::_max_vmop_time = 0;
1055 float  SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1056 
1057 static jlong  cleanup_end_time = 0;
1058 static bool   need_to_track_page_armed_status = false;
1059 static bool   init_done = false;
1060 
1061 // Helper method to print the header.
1062 static void print_header() {
1063   tty->print("         vmop                    "
1064              "[threads: total initially_running wait_to_block]    ");
1065   tty->print("[time: spin block sync cleanup vmop] ");
1066 
1067   // no page armed status printed out if it is always armed.
1068   if (need_to_track_page_armed_status) {
1069     tty->print("page_armed ");
1070   }
1071 
1072   tty->print_cr("page_trap_count");
1073 }
1074 
1075 void SafepointSynchronize::deferred_initialize_stat() {
1076   if (init_done) return;
1077 
1078   if (PrintSafepointStatisticsCount <= 0) {
1079     fatal("Wrong PrintSafepointStatisticsCount");
1080   }
1081 
1082   // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1083   // be printed right away, in which case, _safepoint_stats will regress to
1084   // a single element array. Otherwise, it is a circular ring buffer with default
1085   // size of PrintSafepointStatisticsCount.
1086   int stats_array_size;
1087   if (PrintSafepointStatisticsTimeout > 0) {
1088     stats_array_size = 1;
1089     PrintSafepointStatistics = true;
1090   } else {
1091     stats_array_size = PrintSafepointStatisticsCount;
1092   }
1093   _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1094                                                  * sizeof(SafepointStats), mtInternal);
1095   guarantee(_safepoint_stats != NULL,
1096             "not enough memory for safepoint instrumentation data");
1097 
1098   if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1099     need_to_track_page_armed_status = true;
1100   }
1101   init_done = true;
1102 }
1103 
1104 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1105   assert(init_done, "safepoint statistics array hasn't been initialized");
1106   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1107 
1108   spstat->_time_stamp = _ts_of_current_safepoint;
1109 
1110   VM_Operation *op = VMThread::vm_operation();
1111   spstat->_vmop_type = (op != NULL ? op->type() : -1);
1112   if (op != NULL) {
1113     _safepoint_reasons[spstat->_vmop_type]++;
1114   }
1115 
1116   spstat->_nof_total_threads = nof_threads;
1117   spstat->_nof_initial_running_threads = nof_running;
1118   spstat->_nof_threads_hit_page_trap = 0;
1119 
1120   // Records the start time of spinning. The real time spent on spinning
1121   // will be adjusted when spin is done. Same trick is applied for time
1122   // spent on waiting for threads to block.
1123   if (nof_running != 0) {
1124     spstat->_time_to_spin = os::javaTimeNanos();
1125   }  else {
1126     spstat->_time_to_spin = 0;
1127   }
1128 }
1129 
1130 void SafepointSynchronize::update_statistics_on_spin_end() {
1131   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1132 
1133   jlong cur_time = os::javaTimeNanos();
1134 
1135   spstat->_nof_threads_wait_to_block = _waiting_to_block;
1136   if (spstat->_nof_initial_running_threads != 0) {
1137     spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1138   }
1139 
1140   if (need_to_track_page_armed_status) {
1141     spstat->_page_armed = (PageArmed == 1);
1142   }
1143 
1144   // Records the start time of waiting for to block. Updated when block is done.
1145   if (_waiting_to_block != 0) {
1146     spstat->_time_to_wait_to_block = cur_time;
1147   } else {
1148     spstat->_time_to_wait_to_block = 0;
1149   }
1150 }
1151 
1152 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1153   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1154 
1155   if (spstat->_nof_threads_wait_to_block != 0) {
1156     spstat->_time_to_wait_to_block = end_time -
1157       spstat->_time_to_wait_to_block;
1158   }
1159 
1160   // Records the end time of sync which will be used to calculate the total
1161   // vm operation time. Again, the real time spending in syncing will be deducted
1162   // from the start of the sync time later when end_statistics is called.
1163   spstat->_time_to_sync = end_time - _safepoint_begin_time;
1164   if (spstat->_time_to_sync > _max_sync_time) {
1165     _max_sync_time = spstat->_time_to_sync;
1166   }
1167 
1168   spstat->_time_to_do_cleanups = end_time;
1169 }
1170 
1171 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1172   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1173 
1174   // Record how long spent in cleanup tasks.
1175   spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1176 
1177   cleanup_end_time = end_time;
1178 }
1179 
1180 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1181   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1182 
1183   // Update the vm operation time.
1184   spstat->_time_to_exec_vmop = vmop_end_time -  cleanup_end_time;
1185   if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1186     _max_vmop_time = spstat->_time_to_exec_vmop;
1187   }
1188   // Only the sync time longer than the specified
1189   // PrintSafepointStatisticsTimeout will be printed out right away.
1190   // By default, it is -1 meaning all samples will be put into the list.
1191   if ( PrintSafepointStatisticsTimeout > 0) {
1192     if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1193       print_statistics();
1194     }
1195   } else {
1196     // The safepoint statistics will be printed out when the _safepoin_stats
1197     // array fills up.
1198     if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1199       print_statistics();
1200       _cur_stat_index = 0;
1201     } else {
1202       _cur_stat_index++;
1203     }
1204   }
1205 }
1206 
1207 void SafepointSynchronize::print_statistics() {
1208   SafepointStats* sstats = _safepoint_stats;
1209 
1210   for (int index = 0; index <= _cur_stat_index; index++) {
1211     if (index % 30 == 0) {
1212       print_header();
1213     }
1214     sstats = &_safepoint_stats[index];
1215     tty->print("%.3f: ", sstats->_time_stamp);
1216     tty->print("%-26s       ["
1217                INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1218                "    ]    ",
1219                sstats->_vmop_type == -1 ? "no vm operation" :
1220                VM_Operation::name(sstats->_vmop_type),
1221                sstats->_nof_total_threads,
1222                sstats->_nof_initial_running_threads,
1223                sstats->_nof_threads_wait_to_block);
1224     // "/ MICROUNITS " is to convert the unit from nanos to millis.
1225     tty->print("  ["
1226                INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1227                INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1228                INT64_FORMAT_W(6) "    ]  ",
1229                sstats->_time_to_spin / MICROUNITS,
1230                sstats->_time_to_wait_to_block / MICROUNITS,
1231                sstats->_time_to_sync / MICROUNITS,
1232                sstats->_time_to_do_cleanups / MICROUNITS,
1233                sstats->_time_to_exec_vmop / MICROUNITS);
1234 
1235     if (need_to_track_page_armed_status) {
1236       tty->print(INT32_FORMAT "         ", sstats->_page_armed);
1237     }
1238     tty->print_cr(INT32_FORMAT "   ", sstats->_nof_threads_hit_page_trap);
1239   }
1240 }
1241 
1242 // This method will be called when VM exits. It will first call
1243 // print_statistics to print out the rest of the sampling.  Then
1244 // it tries to summarize the sampling.
1245 void SafepointSynchronize::print_stat_on_exit() {
1246   if (_safepoint_stats == NULL) return;
1247 
1248   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1249 
1250   // During VM exit, end_statistics may not get called and in that
1251   // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1252   // don't print it out.
1253   // Approximate the vm op time.
1254   _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1255     os::javaTimeNanos() - cleanup_end_time;
1256 
1257   if ( PrintSafepointStatisticsTimeout < 0 ||
1258        spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1259     print_statistics();
1260   }
1261   tty->cr();
1262 
1263   // Print out polling page sampling status.
1264   if (!need_to_track_page_armed_status) {
1265     if (UseCompilerSafepoints) {
1266       tty->print_cr("Polling page always armed");
1267     }
1268   } else {
1269     tty->print_cr("Defer polling page loop count = %d\n",
1270                  DeferPollingPageLoopCount);
1271   }
1272 
1273   for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1274     if (_safepoint_reasons[index] != 0) {
1275       tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1276                     _safepoint_reasons[index]);
1277     }
1278   }
1279 
1280   tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1281                 _coalesced_vmop_count);
1282   tty->print_cr("Maximum sync time  " INT64_FORMAT_W(5) " ms",
1283                 _max_sync_time / MICROUNITS);
1284   tty->print_cr("Maximum vm operation time (except for Exit VM operation)  "
1285                 INT64_FORMAT_W(5) " ms",
1286                 _max_vmop_time / MICROUNITS);
1287 }
1288 
1289 // ------------------------------------------------------------------------------------------------
1290 // Non-product code
1291 
1292 #ifndef PRODUCT
1293 
1294 void SafepointSynchronize::print_state() {
1295   if (_state == _not_synchronized) {
1296     tty->print_cr("not synchronized");
1297   } else if (_state == _synchronizing || _state == _synchronized) {
1298     tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1299                   "synchronized");
1300 
1301     for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1302        cur->safepoint_state()->print();
1303     }
1304   }
1305 }
1306 
1307 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1308   if (ShowSafepointMsgs) {
1309     va_list ap;
1310     va_start(ap, format);
1311     tty->vprint_cr(format, ap);
1312     va_end(ap);
1313   }
1314 }
1315 
1316 #endif // !PRODUCT