1 /*
   2  * Copyright (c) 1997, 2012, 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/osThread.hpp"
  45 #include "runtime/safepoint.hpp"
  46 #include "runtime/signature.hpp"
  47 #include "runtime/stubCodeGenerator.hpp"
  48 #include "runtime/stubRoutines.hpp"
  49 #include "runtime/sweeper.hpp"
  50 #include "runtime/synchronizer.hpp"
  51 #include "services/memTracker.hpp"
  52 #include "services/runtimeService.hpp"
  53 #include "utilities/events.hpp"
  54 #ifdef TARGET_ARCH_x86
  55 # include "nativeInst_x86.hpp"
  56 # include "vmreg_x86.inline.hpp"
  57 #endif
  58 #ifdef TARGET_ARCH_sparc
  59 # include "nativeInst_sparc.hpp"
  60 # include "vmreg_sparc.inline.hpp"
  61 #endif
  62 #ifdef TARGET_ARCH_zero
  63 # include "nativeInst_zero.hpp"
  64 # include "vmreg_zero.inline.hpp"
  65 #endif
  66 #ifdef TARGET_ARCH_arm
  67 # include "nativeInst_arm.hpp"
  68 # include "vmreg_arm.inline.hpp"
  69 #endif
  70 #ifdef TARGET_ARCH_ppc
  71 # include "nativeInst_ppc.hpp"
  72 # include "vmreg_ppc.inline.hpp"
  73 #endif
  74 #ifdef TARGET_OS_FAMILY_linux
  75 # include "thread_linux.inline.hpp"
  76 #endif
  77 #ifdef TARGET_OS_FAMILY_solaris
  78 # include "thread_solaris.inline.hpp"
  79 #endif
  80 #ifdef TARGET_OS_FAMILY_windows
  81 # include "thread_windows.inline.hpp"
  82 #endif
  83 #ifdef TARGET_OS_FAMILY_bsd
  84 # include "thread_bsd.inline.hpp"
  85 #endif
  86 #ifndef SERIALGC
  87 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
  88 #include "gc_implementation/shared/concurrentGCThread.hpp"
  89 #endif
  90 #ifdef COMPILER1
  91 #include "c1/c1_globals.hpp"
  92 #endif
  93 
  94 // --------------------------------------------------------------------------------------------------
  95 // Implementation of Safepoint begin/end
  96 
  97 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
  98 volatile int  SafepointSynchronize::_waiting_to_block = 0;
  99 volatile int SafepointSynchronize::_safepoint_counter = 0;
 100 int SafepointSynchronize::_current_jni_active_count = 0;
 101 long  SafepointSynchronize::_end_of_last_safepoint = 0;
 102 static volatile int PageArmed = 0 ;        // safepoint polling page is RO|RW vs PROT_NONE
 103 static volatile int TryingToBlock = 0 ;    // proximate value -- for advisory use only
 104 static bool timeout_error_printed = false;
 105 
 106 // Roll all threads forward to a safepoint and suspend them all
 107 void SafepointSynchronize::begin() {
 108 
 109   Thread* myThread = Thread::current();
 110   assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
 111 
 112   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
 113     _safepoint_begin_time = os::javaTimeNanos();
 114     _ts_of_current_safepoint = tty->time_stamp().seconds();
 115   }
 116 
 117 #ifndef SERIALGC
 118   if (UseConcMarkSweepGC) {
 119     // In the future we should investigate whether CMS can use the
 120     // more-general mechanism below.  DLD (01/05).
 121     ConcurrentMarkSweepThread::synchronize(false);
 122   } else if (UseG1GC) {
 123     ConcurrentGCThread::safepoint_synchronize();
 124   }
 125 #endif // SERIALGC
 126 
 127   // By getting the Threads_lock, we assure that no threads are about to start or
 128   // exit. It is released again in SafepointSynchronize::end().
 129   Threads_lock->lock();
 130 
 131   assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
 132 
 133   int nof_threads = Threads::number_of_threads();
 134 
 135   if (TraceSafepoint) {
 136     tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
 137   }
 138 
 139   RuntimeService::record_safepoint_begin();
 140 
 141   MutexLocker mu(Safepoint_lock);
 142 
 143   // Reset the count of active JNI critical threads
 144   _current_jni_active_count = 0;
 145 
 146   // Set number of threads to wait for, before we initiate the callbacks
 147   _waiting_to_block = nof_threads;
 148   TryingToBlock     = 0 ;
 149   int still_running = nof_threads;
 150 
 151   // Save the starting time, so that it can be compared to see if this has taken
 152   // too long to complete.
 153   jlong safepoint_limit_time;
 154   timeout_error_printed = false;
 155 
 156   // PrintSafepointStatisticsTimeout can be specified separately. When
 157   // specified, PrintSafepointStatistics will be set to true in
 158   // deferred_initialize_stat method. The initialization has to be done
 159   // early enough to avoid any races. See bug 6880029 for details.
 160   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
 161     deferred_initialize_stat();
 162   }
 163 
 164   // Begin the process of bringing the system to a safepoint.
 165   // Java threads can be in several different states and are
 166   // stopped by different mechanisms:
 167   //
 168   //  1. Running interpreted
 169   //     The interpeter dispatch table is changed to force it to
 170   //     check for a safepoint condition between bytecodes.
 171   //  2. Running in native code
 172   //     When returning from the native code, a Java thread must check
 173   //     the safepoint _state to see if we must block.  If the
 174   //     VM thread sees a Java thread in native, it does
 175   //     not wait for this thread to block.  The order of the memory
 176   //     writes and reads of both the safepoint state and the Java
 177   //     threads state is critical.  In order to guarantee that the
 178   //     memory writes are serialized with respect to each other,
 179   //     the VM thread issues a memory barrier instruction
 180   //     (on MP systems).  In order to avoid the overhead of issuing
 181   //     a memory barrier for each Java thread making native calls, each Java
 182   //     thread performs a write to a single memory page after changing
 183   //     the thread state.  The VM thread performs a sequence of
 184   //     mprotect OS calls which forces all previous writes from all
 185   //     Java threads to be serialized.  This is done in the
 186   //     os::serialize_thread_states() call.  This has proven to be
 187   //     much more efficient than executing a membar instruction
 188   //     on every call to native code.
 189   //  3. Running compiled Code
 190   //     Compiled code reads a global (Safepoint Polling) page that
 191   //     is set to fault if we are trying to get to a safepoint.
 192   //  4. Blocked
 193   //     A thread which is blocked will not be allowed to return from the
 194   //     block condition until the safepoint operation is complete.
 195   //  5. In VM or Transitioning between states
 196   //     If a Java thread is currently running in the VM or transitioning
 197   //     between states, the safepointing code will wait for the thread to
 198   //     block itself when it attempts transitions to a new state.
 199   //
 200   _state            = _synchronizing;
 201   OrderAccess::fence();
 202 
 203   // Flush all thread states to memory
 204   if (!UseMembar) {
 205     os::serialize_thread_states();
 206   }
 207 
 208   // Make interpreter safepoint aware
 209   Interpreter::notice_safepoints();
 210 
 211   if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
 212     // Make polling safepoint aware
 213     guarantee (PageArmed == 0, "invariant") ;
 214     PageArmed = 1 ;
 215     os::make_polling_page_unreadable();
 216   }
 217 
 218   // Consider using active_processor_count() ... but that call is expensive.
 219   int ncpus = os::processor_count() ;
 220 
 221 #ifdef ASSERT
 222   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 223     assert(cur->safepoint_state()->is_running(), "Illegal initial state");
 224     // Clear the visited flag to ensure that the critical counts are collected properly.
 225     cur->set_visited_for_critical_count(false);
 226   }
 227 #endif // ASSERT
 228 
 229   if (SafepointTimeout)
 230     safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
 231 
 232   // Iterate through all threads until it have been determined how to stop them all at a safepoint
 233   unsigned int iterations = 0;
 234   int steps = 0 ;
 235   while(still_running > 0) {
 236     for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 237       assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
 238       ThreadSafepointState *cur_state = cur->safepoint_state();
 239       if (cur_state->is_running()) {
 240         cur_state->examine_state_of_thread();
 241         if (!cur_state->is_running()) {
 242            still_running--;
 243            // consider adjusting steps downward:
 244            //   steps = 0
 245            //   steps -= NNN
 246            //   steps >>= 1
 247            //   steps = MIN(steps, 2000-100)
 248            //   if (iterations != 0) steps -= NNN
 249         }
 250         if (TraceSafepoint && Verbose) cur_state->print();
 251       }
 252     }
 253 
 254     if (PrintSafepointStatistics && iterations == 0) {
 255       begin_statistics(nof_threads, still_running);
 256     }
 257 
 258     if (still_running > 0) {
 259       // Check for if it takes to long
 260       if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
 261         print_safepoint_timeout(_spinning_timeout);
 262       }
 263 
 264       // Spin to avoid context switching.
 265       // There's a tension between allowing the mutators to run (and rendezvous)
 266       // vs spinning.  As the VM thread spins, wasting cycles, it consumes CPU that
 267       // a mutator might otherwise use profitably to reach a safepoint.  Excessive
 268       // spinning by the VM thread on a saturated system can increase rendezvous latency.
 269       // Blocking or yielding incur their own penalties in the form of context switching
 270       // and the resultant loss of $ residency.
 271       //
 272       // Further complicating matters is that yield() does not work as naively expected
 273       // on many platforms -- yield() does not guarantee that any other ready threads
 274       // will run.   As such we revert yield_all() after some number of iterations.
 275       // Yield_all() is implemented as a short unconditional sleep on some platforms.
 276       // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
 277       // can actually increase the time it takes the VM thread to detect that a system-wide
 278       // stop-the-world safepoint has been reached.  In a pathological scenario such as that
 279       // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
 280       // In that case the mutators will be stalled waiting for the safepoint to complete and the
 281       // the VMthread will be sleeping, waiting for the mutators to rendezvous.  The VMthread
 282       // will eventually wake up and detect that all mutators are safe, at which point
 283       // we'll again make progress.
 284       //
 285       // Beware too that that the VMThread typically runs at elevated priority.
 286       // Its default priority is higher than the default mutator priority.
 287       // Obviously, this complicates spinning.
 288       //
 289       // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
 290       // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
 291       //
 292       // See the comments in synchronizer.cpp for additional remarks on spinning.
 293       //
 294       // In the future we might:
 295       // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
 296       //    This is tricky as the path used by a thread exiting the JVM (say on
 297       //    on JNI call-out) simply stores into its state field.  The burden
 298       //    is placed on the VM thread, which must poll (spin).
 299       // 2. Find something useful to do while spinning.  If the safepoint is GC-related
 300       //    we might aggressively scan the stacks of threads that are already safe.
 301       // 3. Use Solaris schedctl to examine the state of the still-running mutators.
 302       //    If all the mutators are ONPROC there's no reason to sleep or yield.
 303       // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
 304       // 5. Check system saturation.  If the system is not fully saturated then
 305       //    simply spin and avoid sleep/yield.
 306       // 6. As still-running mutators rendezvous they could unpark the sleeping
 307       //    VMthread.  This works well for still-running mutators that become
 308       //    safe.  The VMthread must still poll for mutators that call-out.
 309       // 7. Drive the policy on time-since-begin instead of iterations.
 310       // 8. Consider making the spin duration a function of the # of CPUs:
 311       //    Spin = (((ncpus-1) * M) + K) + F(still_running)
 312       //    Alternately, instead of counting iterations of the outer loop
 313       //    we could count the # of threads visited in the inner loop, above.
 314       // 9. On windows consider using the return value from SwitchThreadTo()
 315       //    to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
 316 
 317       if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
 318          guarantee (PageArmed == 0, "invariant") ;
 319          PageArmed = 1 ;
 320          os::make_polling_page_unreadable();
 321       }
 322 
 323       // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
 324       // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
 325       ++steps ;
 326       if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
 327         SpinPause() ;     // MP-Polite spin
 328       } else
 329       if (steps < DeferThrSuspendLoopCount) {
 330         os::NakedYield() ;
 331       } else {
 332         os::yield_all(steps) ;
 333         // Alternately, the VM thread could transiently depress its scheduling priority or
 334         // transiently increase the priority of the tardy mutator(s).
 335       }
 336 
 337       iterations ++ ;
 338     }
 339     assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
 340   }
 341   assert(still_running == 0, "sanity check");
 342 
 343   if (PrintSafepointStatistics) {
 344     update_statistics_on_spin_end();
 345   }
 346 
 347   // wait until all threads are stopped
 348   while (_waiting_to_block > 0) {
 349     if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
 350     if (!SafepointTimeout || timeout_error_printed) {
 351       Safepoint_lock->wait(true);  // true, means with no safepoint checks
 352     } else {
 353       // Compute remaining time
 354       jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
 355 
 356       // If there is no remaining time, then there is an error
 357       if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
 358         print_safepoint_timeout(_blocking_timeout);
 359       }
 360     }
 361   }
 362   assert(_waiting_to_block == 0, "sanity check");
 363 
 364 #ifndef PRODUCT
 365   if (SafepointTimeout) {
 366     jlong current_time = os::javaTimeNanos();
 367     if (safepoint_limit_time < current_time) {
 368       tty->print_cr("# SafepointSynchronize: Finished after "
 369                     INT64_FORMAT_W(6) " ms",
 370                     ((current_time - safepoint_limit_time) / MICROUNITS +
 371                      SafepointTimeoutDelay));
 372     }
 373   }
 374 #endif
 375 
 376   assert((_safepoint_counter & 0x1) == 0, "must be even");
 377   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 378   _safepoint_counter ++;
 379 
 380   // Record state
 381   _state = _synchronized;
 382 
 383   OrderAccess::fence();
 384 
 385 #ifdef ASSERT
 386   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 387     // make sure all the threads were visited
 388     assert(cur->was_visited_for_critical_count(), "missed a thread");
 389   }
 390 #endif // ASSERT
 391 
 392   // Update the count of active JNI critical regions
 393   GC_locker::set_jni_lock_count(_current_jni_active_count);
 394 
 395   if (TraceSafepoint) {
 396     VM_Operation *op = VMThread::vm_operation();
 397     tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
 398   }
 399 
 400   RuntimeService::record_safepoint_synchronized();
 401   if (PrintSafepointStatistics) {
 402     update_statistics_on_sync_end(os::javaTimeNanos());
 403   }
 404 
 405   // Call stuff that needs to be run when a safepoint is just about to be completed
 406   do_cleanup_tasks();
 407 
 408   if (PrintSafepointStatistics) {
 409     // Record how much time spend on the above cleanup tasks
 410     update_statistics_on_cleanup_end(os::javaTimeNanos());
 411   }
 412 }
 413 
 414 // Wake up all threads, so they are ready to resume execution after the safepoint
 415 // operation has been carried out
 416 void SafepointSynchronize::end() {
 417 
 418   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 419   assert((_safepoint_counter & 0x1) == 1, "must be odd");
 420   _safepoint_counter ++;
 421   // memory fence isn't required here since an odd _safepoint_counter
 422   // value can do no harm and a fence is issued below anyway.
 423 
 424   DEBUG_ONLY(Thread* myThread = Thread::current();)
 425   assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
 426 
 427   if (PrintSafepointStatistics) {
 428     end_statistics(os::javaTimeNanos());
 429   }
 430 
 431 #ifdef ASSERT
 432   // A pending_exception cannot be installed during a safepoint.  The threads
 433   // may install an async exception after they come back from a safepoint into
 434   // pending_exception after they unblock.  But that should happen later.
 435   for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
 436     assert (!(cur->has_pending_exception() &&
 437               cur->safepoint_state()->is_at_poll_safepoint()),
 438             "safepoint installed a pending exception");
 439   }
 440 #endif // ASSERT
 441 
 442   if (PageArmed) {
 443     // Make polling safepoint aware
 444     os::make_polling_page_readable();
 445     PageArmed = 0 ;
 446   }
 447 
 448   // Remove safepoint check from interpreter
 449   Interpreter::ignore_safepoints();
 450 
 451   {
 452     MutexLocker mu(Safepoint_lock);
 453 
 454     assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
 455 
 456     // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
 457     // when they get restarted.
 458     _state = _not_synchronized;
 459     OrderAccess::fence();
 460 
 461     if (TraceSafepoint) {
 462        tty->print_cr("Leaving safepoint region");
 463     }
 464 
 465     // Start suspended threads
 466     for(JavaThread *current = Threads::first(); current; current = current->next()) {
 467       // A problem occurring on Solaris is when attempting to restart threads
 468       // the first #cpus - 1 go well, but then the VMThread is preempted when we get
 469       // to the next one (since it has been running the longest).  We then have
 470       // to wait for a cpu to become available before we can continue restarting
 471       // threads.
 472       // FIXME: This causes the performance of the VM to degrade when active and with
 473       // large numbers of threads.  Apparently this is due to the synchronous nature
 474       // of suspending threads.
 475       //
 476       // TODO-FIXME: the comments above are vestigial and no longer apply.
 477       // Furthermore, using solaris' schedctl in this particular context confers no benefit
 478       if (VMThreadHintNoPreempt) {
 479         os::hint_no_preempt();
 480       }
 481       ThreadSafepointState* cur_state = current->safepoint_state();
 482       assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
 483       cur_state->restart();
 484       assert(cur_state->is_running(), "safepoint state has not been reset");
 485     }
 486 
 487     RuntimeService::record_safepoint_end();
 488 
 489     // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
 490     // blocked in signal_thread_blocked
 491     Threads_lock->unlock();
 492 
 493   }
 494 #ifndef SERIALGC
 495   // If there are any concurrent GC threads resume them.
 496   if (UseConcMarkSweepGC) {
 497     ConcurrentMarkSweepThread::desynchronize(false);
 498   } else if (UseG1GC) {
 499     ConcurrentGCThread::safepoint_desynchronize();
 500   }
 501 #endif // SERIALGC
 502   // record this time so VMThread can keep track how much time has elasped
 503   // since last safepoint.
 504   _end_of_last_safepoint = os::javaTimeMillis();
 505 }
 506 
 507 bool SafepointSynchronize::is_cleanup_needed() {
 508   // Need a safepoint if some inline cache buffers is non-empty
 509   if (!InlineCacheBuffer::is_empty()) return true;
 510   return false;
 511 }
 512 
 513 
 514 
 515 // Various cleaning tasks that should be done periodically at safepoints
 516 void SafepointSynchronize::do_cleanup_tasks() {
 517   {
 518     TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
 519     ObjectSynchronizer::deflate_idle_monitors();
 520   }
 521 
 522   {
 523     TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
 524     InlineCacheBuffer::update_inline_caches();
 525   }
 526   {
 527     TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
 528     CompilationPolicy::policy()->do_safepoint_work();
 529   }
 530 
 531   {
 532     TraceTime t4("sweeping nmethods", TraceSafepointCleanupTime);
 533     NMethodSweeper::scan_stacks();
 534   }
 535 
 536   if (SymbolTable::needs_rehashing()) {
 537     TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
 538     SymbolTable::rehash_table();
 539   }
 540 
 541   if (StringTable::needs_rehashing()) {
 542     TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
 543     StringTable::rehash_table();
 544   }
 545 
 546   // rotate log files?
 547   if (UseGCLogFileRotation) {
 548     gclog_or_tty->rotate_log();
 549   }
 550 
 551   if (MemTracker::is_on()) {
 552     MemTracker::sync();
 553   }
 554 }
 555 
 556 
 557 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
 558   switch(state) {
 559   case _thread_in_native:
 560     // native threads are safe if they have no java stack or have walkable stack
 561     return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
 562 
 563    // blocked threads should have already have walkable stack
 564   case _thread_blocked:
 565     assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
 566     return true;
 567 
 568   default:
 569     return false;
 570   }
 571 }
 572 
 573 
 574 // See if the thread is running inside a lazy critical native and
 575 // update the thread critical count if so.  Also set a suspend flag to
 576 // cause the native wrapper to return into the JVM to do the unlock
 577 // once the native finishes.
 578 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
 579   if (state == _thread_in_native &&
 580       thread->has_last_Java_frame() &&
 581       thread->frame_anchor()->walkable()) {
 582     // This thread might be in a critical native nmethod so look at
 583     // the top of the stack and increment the critical count if it
 584     // is.
 585     frame wrapper_frame = thread->last_frame();
 586     CodeBlob* stub_cb = wrapper_frame.cb();
 587     if (stub_cb != NULL &&
 588         stub_cb->is_nmethod() &&
 589         stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
 590       // A thread could potentially be in a critical native across
 591       // more than one safepoint, so only update the critical state on
 592       // the first one.  When it returns it will perform the unlock.
 593       if (!thread->do_critical_native_unlock()) {
 594 #ifdef ASSERT
 595         if (!thread->in_critical()) {
 596           GC_locker::increment_debug_jni_lock_count();
 597         }
 598 #endif
 599         thread->enter_critical();
 600         // Make sure the native wrapper calls back on return to
 601         // perform the needed critical unlock.
 602         thread->set_critical_native_unlock();
 603       }
 604     }
 605   }
 606 }
 607 
 608 
 609 
 610 // -------------------------------------------------------------------------------------------------------
 611 // Implementation of Safepoint callback point
 612 
 613 void SafepointSynchronize::block(JavaThread *thread) {
 614   assert(thread != NULL, "thread must be set");
 615   assert(thread->is_Java_thread(), "not a Java thread");
 616 
 617   // Threads shouldn't block if they are in the middle of printing, but...
 618   ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
 619 
 620   // Only bail from the block() call if the thread is gone from the
 621   // thread list; starting to exit should still block.
 622   if (thread->is_terminated()) {
 623      // block current thread if we come here from native code when VM is gone
 624      thread->block_if_vm_exited();
 625 
 626      // otherwise do nothing
 627      return;
 628   }
 629 
 630   JavaThreadState state = thread->thread_state();
 631   thread->frame_anchor()->make_walkable(thread);
 632 
 633   // Check that we have a valid thread_state at this point
 634   switch(state) {
 635     case _thread_in_vm_trans:
 636     case _thread_in_Java:        // From compiled code
 637 
 638       // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
 639       // we pretend we are still in the VM.
 640       thread->set_thread_state(_thread_in_vm);
 641 
 642       if (is_synchronizing()) {
 643          Atomic::inc (&TryingToBlock) ;
 644       }
 645 
 646       // We will always be holding the Safepoint_lock when we are examine the state
 647       // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
 648       // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
 649       Safepoint_lock->lock_without_safepoint_check();
 650       if (is_synchronizing()) {
 651         // Decrement the number of threads to wait for and signal vm thread
 652         assert(_waiting_to_block > 0, "sanity check");
 653         _waiting_to_block--;
 654         thread->safepoint_state()->set_has_called_back(true);
 655 
 656         DEBUG_ONLY(thread->set_visited_for_critical_count(true));
 657         if (thread->in_critical()) {
 658           // Notice that this thread is in a critical section
 659           increment_jni_active_count();
 660         }
 661 
 662         // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
 663         if (_waiting_to_block == 0) {
 664           Safepoint_lock->notify_all();
 665         }
 666       }
 667 
 668       // We transition the thread to state _thread_blocked here, but
 669       // we can't do our usual check for external suspension and then
 670       // self-suspend after the lock_without_safepoint_check() call
 671       // below because we are often called during transitions while
 672       // we hold different locks. That would leave us suspended while
 673       // holding a resource which results in deadlocks.
 674       thread->set_thread_state(_thread_blocked);
 675       Safepoint_lock->unlock();
 676 
 677       // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
 678       // the entire safepoint, the threads will all line up here during the safepoint.
 679       Threads_lock->lock_without_safepoint_check();
 680       // restore original state. This is important if the thread comes from compiled code, so it
 681       // will continue to execute with the _thread_in_Java state.
 682       thread->set_thread_state(state);
 683       Threads_lock->unlock();
 684       break;
 685 
 686     case _thread_in_native_trans:
 687     case _thread_blocked_trans:
 688     case _thread_new_trans:
 689       if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
 690         thread->print_thread_state();
 691         fatal("Deadlock in safepoint code.  "
 692               "Should have called back to the VM before blocking.");
 693       }
 694 
 695       // We transition the thread to state _thread_blocked here, but
 696       // we can't do our usual check for external suspension and then
 697       // self-suspend after the lock_without_safepoint_check() call
 698       // below because we are often called during transitions while
 699       // we hold different locks. That would leave us suspended while
 700       // holding a resource which results in deadlocks.
 701       thread->set_thread_state(_thread_blocked);
 702 
 703       // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
 704       // the safepoint code might still be waiting for it to block. We need to change the state here,
 705       // so it can see that it is at a safepoint.
 706 
 707       // Block until the safepoint operation is completed.
 708       Threads_lock->lock_without_safepoint_check();
 709 
 710       // Restore state
 711       thread->set_thread_state(state);
 712 
 713       Threads_lock->unlock();
 714       break;
 715 
 716     default:
 717      fatal(err_msg("Illegal threadstate encountered: %d", state));
 718   }
 719 
 720   // Check for pending. async. exceptions or suspends - except if the
 721   // thread was blocked inside the VM. has_special_runtime_exit_condition()
 722   // is called last since it grabs a lock and we only want to do that when
 723   // we must.
 724   //
 725   // Note: we never deliver an async exception at a polling point as the
 726   // compiler may not have an exception handler for it. The polling
 727   // code will notice the async and deoptimize and the exception will
 728   // be delivered. (Polling at a return point is ok though). Sure is
 729   // a lot of bother for a deprecated feature...
 730   //
 731   // We don't deliver an async exception if the thread state is
 732   // _thread_in_native_trans so JNI functions won't be called with
 733   // a surprising pending exception. If the thread state is going back to java,
 734   // async exception is checked in check_special_condition_for_native_trans().
 735 
 736   if (state != _thread_blocked_trans &&
 737       state != _thread_in_vm_trans &&
 738       thread->has_special_runtime_exit_condition()) {
 739     thread->handle_special_runtime_exit_condition(
 740       !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
 741   }
 742 }
 743 
 744 // ------------------------------------------------------------------------------------------------------
 745 // Exception handlers
 746 
 747 #ifndef PRODUCT
 748 #ifdef _LP64
 749 #define PTR_PAD ""
 750 #else
 751 #define PTR_PAD "        "
 752 #endif
 753 
 754 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
 755   bool is_oop = newptr ? ((oop)newptr)->is_oop() : false;
 756   tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
 757                 oldptr, wasoop?"oop":"   ", oldptr == newptr ? ' ' : '!',
 758                 newptr, is_oop?"oop":"   ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":"     "));
 759 }
 760 
 761 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
 762   bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false;
 763   tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
 764                 oldptr, wasoop?"oop":"   ", oldptr == newptr ? ' ' : '!',
 765                 newptr, is_oop?"oop":"   ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":"     "));
 766 }
 767 
 768 #ifdef SPARC
 769 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
 770 #ifdef _LP64
 771   tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
 772   const int incr = 1;           // Increment to skip a long, in units of intptr_t
 773 #else
 774   tty->print_cr("--------+--address-+------before-----------+-------after----------+");
 775   const int incr = 2;           // Increment to skip a long, in units of intptr_t
 776 #endif
 777   tty->print_cr("---SP---|");
 778   for( int i=0; i<16; i++ ) {
 779     tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
 780   tty->print_cr("--------|");
 781   for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
 782     tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
 783   tty->print("     pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
 784   tty->print_cr("--------|");
 785   tty->print(" G1     |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
 786   tty->print(" G3     |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
 787   tty->print(" G4     |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
 788   tty->print(" G5     |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
 789   tty->print_cr(" FSR    |"PTR_FORMAT" "PTR64_FORMAT"       "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
 790   old_sp += incr; new_sp += incr; was_oops += incr;
 791   // Skip the floats
 792   tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
 793   tty->print_cr("---FP---|");
 794   old_sp += incr*32;  new_sp += incr*32;  was_oops += incr*32;
 795   for( int i2=0; i2<16; i2++ ) {
 796     tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
 797   tty->print_cr("");
 798 }
 799 #endif  // SPARC
 800 #endif  // PRODUCT
 801 
 802 
 803 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
 804   assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
 805   assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
 806   assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
 807 
 808   // Uncomment this to get some serious before/after printing of the
 809   // Sparc safepoint-blob frame structure.
 810   /*
 811   intptr_t* sp = thread->last_Java_sp();
 812   intptr_t stack_copy[150];
 813   for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
 814   bool was_oops[150];
 815   for( int i=0; i<150; i++ )
 816     was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
 817   */
 818 
 819   if (ShowSafepointMsgs) {
 820     tty->print("handle_polling_page_exception: ");
 821   }
 822 
 823   if (PrintSafepointStatistics) {
 824     inc_page_trap_count();
 825   }
 826 
 827   ThreadSafepointState* state = thread->safepoint_state();
 828 
 829   state->handle_polling_page_exception();
 830   // print_me(sp,stack_copy,was_oops);
 831 }
 832 
 833 
 834 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
 835   if (!timeout_error_printed) {
 836     timeout_error_printed = true;
 837     // Print out the thread infor which didn't reach the safepoint for debugging
 838     // purposes (useful when there are lots of threads in the debugger).
 839     tty->print_cr("");
 840     tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
 841     if (reason ==  _spinning_timeout) {
 842       tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
 843     } else if (reason == _blocking_timeout) {
 844       tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
 845     }
 846 
 847     tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
 848     ThreadSafepointState *cur_state;
 849     ResourceMark rm;
 850     for(JavaThread *cur_thread = Threads::first(); cur_thread;
 851         cur_thread = cur_thread->next()) {
 852       cur_state = cur_thread->safepoint_state();
 853 
 854       if (cur_thread->thread_state() != _thread_blocked &&
 855           ((reason == _spinning_timeout && cur_state->is_running()) ||
 856            (reason == _blocking_timeout && !cur_state->has_called_back()))) {
 857         tty->print("# ");
 858         cur_thread->print();
 859         tty->print_cr("");
 860       }
 861     }
 862     tty->print_cr("# SafepointSynchronize::begin: (End of list)");
 863   }
 864 
 865   // To debug the long safepoint, specify both DieOnSafepointTimeout &
 866   // ShowMessageBoxOnError.
 867   if (DieOnSafepointTimeout) {
 868     char msg[1024];
 869     VM_Operation *op = VMThread::vm_operation();
 870     sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
 871             SafepointTimeoutDelay,
 872             op != NULL ? op->name() : "no vm operation");
 873     fatal(msg);
 874   }
 875 }
 876 
 877 
 878 // -------------------------------------------------------------------------------------------------------
 879 // Implementation of ThreadSafepointState
 880 
 881 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
 882   _thread = thread;
 883   _type   = _running;
 884   _has_called_back = false;
 885   _at_poll_safepoint = false;
 886 }
 887 
 888 void ThreadSafepointState::create(JavaThread *thread) {
 889   ThreadSafepointState *state = new ThreadSafepointState(thread);
 890   thread->set_safepoint_state(state);
 891 }
 892 
 893 void ThreadSafepointState::destroy(JavaThread *thread) {
 894   if (thread->safepoint_state()) {
 895     delete(thread->safepoint_state());
 896     thread->set_safepoint_state(NULL);
 897   }
 898 }
 899 
 900 void ThreadSafepointState::examine_state_of_thread() {
 901   assert(is_running(), "better be running or just have hit safepoint poll");
 902 
 903   JavaThreadState state = _thread->thread_state();
 904 
 905   // Save the state at the start of safepoint processing.
 906   _orig_thread_state = state;
 907 
 908   // Check for a thread that is suspended. Note that thread resume tries
 909   // to grab the Threads_lock which we own here, so a thread cannot be
 910   // resumed during safepoint synchronization.
 911 
 912   // We check to see if this thread is suspended without locking to
 913   // avoid deadlocking with a third thread that is waiting for this
 914   // thread to be suspended. The third thread can notice the safepoint
 915   // that we're trying to start at the beginning of its SR_lock->wait()
 916   // call. If that happens, then the third thread will block on the
 917   // safepoint while still holding the underlying SR_lock. We won't be
 918   // able to get the SR_lock and we'll deadlock.
 919   //
 920   // We don't need to grab the SR_lock here for two reasons:
 921   // 1) The suspend flags are both volatile and are set with an
 922   //    Atomic::cmpxchg() call so we should see the suspended
 923   //    state right away.
 924   // 2) We're being called from the safepoint polling loop; if
 925   //    we don't see the suspended state on this iteration, then
 926   //    we'll come around again.
 927   //
 928   bool is_suspended = _thread->is_ext_suspended();
 929   if (is_suspended) {
 930     roll_forward(_at_safepoint);
 931     return;
 932   }
 933 
 934   // Some JavaThread states have an initial safepoint state of
 935   // running, but are actually at a safepoint. We will happily
 936   // agree and update the safepoint state here.
 937   if (SafepointSynchronize::safepoint_safe(_thread, state)) {
 938     SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
 939     roll_forward(_at_safepoint);
 940     return;
 941   }
 942 
 943   if (state == _thread_in_vm) {
 944     roll_forward(_call_back);
 945     return;
 946   }
 947 
 948   // All other thread states will continue to run until they
 949   // transition and self-block in state _blocked
 950   // Safepoint polling in compiled code causes the Java threads to do the same.
 951   // Note: new threads may require a malloc so they must be allowed to finish
 952 
 953   assert(is_running(), "examine_state_of_thread on non-running thread");
 954   return;
 955 }
 956 
 957 // Returns true is thread could not be rolled forward at present position.
 958 void ThreadSafepointState::roll_forward(suspend_type type) {
 959   _type = type;
 960 
 961   switch(_type) {
 962     case _at_safepoint:
 963       SafepointSynchronize::signal_thread_at_safepoint();
 964       DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
 965       if (_thread->in_critical()) {
 966         // Notice that this thread is in a critical section
 967         SafepointSynchronize::increment_jni_active_count();
 968       }
 969       break;
 970 
 971     case _call_back:
 972       set_has_called_back(false);
 973       break;
 974 
 975     case _running:
 976     default:
 977       ShouldNotReachHere();
 978   }
 979 }
 980 
 981 void ThreadSafepointState::restart() {
 982   switch(type()) {
 983     case _at_safepoint:
 984     case _call_back:
 985       break;
 986 
 987     case _running:
 988     default:
 989        tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
 990                       _thread, _type);
 991        _thread->print();
 992       ShouldNotReachHere();
 993   }
 994   _type = _running;
 995   set_has_called_back(false);
 996 }
 997 
 998 
 999 void ThreadSafepointState::print_on(outputStream *st) const {
1000   const char *s;
1001 
1002   switch(_type) {
1003     case _running                : s = "_running";              break;
1004     case _at_safepoint           : s = "_at_safepoint";         break;
1005     case _call_back              : s = "_call_back";            break;
1006     default:
1007       ShouldNotReachHere();
1008   }
1009 
1010   st->print_cr("Thread: " INTPTR_FORMAT
1011               "  [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1012                _thread, _thread->osthread()->thread_id(), s, _has_called_back,
1013                _at_poll_safepoint);
1014 
1015   _thread->print_thread_state_on(st);
1016 }
1017 
1018 
1019 // ---------------------------------------------------------------------------------------------------------------------
1020 
1021 // Block the thread at the safepoint poll or poll return.
1022 void ThreadSafepointState::handle_polling_page_exception() {
1023 
1024   // Check state.  block() will set thread state to thread_in_vm which will
1025   // cause the safepoint state _type to become _call_back.
1026   assert(type() == ThreadSafepointState::_running,
1027          "polling page exception on thread not running state");
1028 
1029   // Step 1: Find the nmethod from the return address
1030   if (ShowSafepointMsgs && Verbose) {
1031     tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
1032   }
1033   address real_return_addr = thread()->saved_exception_pc();
1034 
1035   CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1036   assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
1037   nmethod* nm = (nmethod*)cb;
1038 
1039   // Find frame of caller
1040   frame stub_fr = thread()->last_frame();
1041   CodeBlob* stub_cb = stub_fr.cb();
1042   assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1043   RegisterMap map(thread(), true);
1044   frame caller_fr = stub_fr.sender(&map);
1045 
1046   // Should only be poll_return or poll
1047   assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1048 
1049   // This is a poll immediately before a return. The exception handling code
1050   // has already had the effect of causing the return to occur, so the execution
1051   // will continue immediately after the call. In addition, the oopmap at the
1052   // return point does not mark the return value as an oop (if it is), so
1053   // it needs a handle here to be updated.
1054   if( nm->is_at_poll_return(real_return_addr) ) {
1055     // See if return type is an oop.
1056     bool return_oop = nm->method()->is_returning_oop();
1057     Handle return_value;
1058     if (return_oop) {
1059       // The oop result has been saved on the stack together with all
1060       // the other registers. In order to preserve it over GCs we need
1061       // to keep it in a handle.
1062       oop result = caller_fr.saved_oop_result(&map);
1063       assert(result == NULL || result->is_oop(), "must be oop");
1064       return_value = Handle(thread(), result);
1065       assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1066     }
1067 
1068     // Block the thread
1069     SafepointSynchronize::block(thread());
1070 
1071     // restore oop result, if any
1072     if (return_oop) {
1073       caller_fr.set_saved_oop_result(&map, return_value());
1074     }
1075   }
1076 
1077   // This is a safepoint poll. Verify the return address and block.
1078   else {
1079     set_at_poll_safepoint(true);
1080 
1081     // verify the blob built the "return address" correctly
1082     assert(real_return_addr == caller_fr.pc(), "must match");
1083 
1084     // Block the thread
1085     SafepointSynchronize::block(thread());
1086     set_at_poll_safepoint(false);
1087 
1088     // If we have a pending async exception deoptimize the frame
1089     // as otherwise we may never deliver it.
1090     if (thread()->has_async_condition()) {
1091       ThreadInVMfromJavaNoAsyncException __tiv(thread());
1092       Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1093     }
1094 
1095     // If an exception has been installed we must check for a pending deoptimization
1096     // Deoptimize frame if exception has been thrown.
1097 
1098     if (thread()->has_pending_exception() ) {
1099       RegisterMap map(thread(), true);
1100       frame caller_fr = stub_fr.sender(&map);
1101       if (caller_fr.is_deoptimized_frame()) {
1102         // The exception patch will destroy registers that are still
1103         // live and will be needed during deoptimization. Defer the
1104         // Async exception should have defered the exception until the
1105         // next safepoint which will be detected when we get into
1106         // the interpreter so if we have an exception now things
1107         // are messed up.
1108 
1109         fatal("Exception installed and deoptimization is pending");
1110       }
1111     }
1112   }
1113 }
1114 
1115 
1116 //
1117 //                     Statistics & Instrumentations
1118 //
1119 SafepointSynchronize::SafepointStats*  SafepointSynchronize::_safepoint_stats = NULL;
1120 jlong  SafepointSynchronize::_safepoint_begin_time = 0;
1121 int    SafepointSynchronize::_cur_stat_index = 0;
1122 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1123 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1124 jlong  SafepointSynchronize::_max_sync_time = 0;
1125 jlong  SafepointSynchronize::_max_vmop_time = 0;
1126 float  SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1127 
1128 static jlong  cleanup_end_time = 0;
1129 static bool   need_to_track_page_armed_status = false;
1130 static bool   init_done = false;
1131 
1132 // Helper method to print the header.
1133 static void print_header() {
1134   tty->print("         vmop                    "
1135              "[threads: total initially_running wait_to_block]    ");
1136   tty->print("[time: spin block sync cleanup vmop] ");
1137 
1138   // no page armed status printed out if it is always armed.
1139   if (need_to_track_page_armed_status) {
1140     tty->print("page_armed ");
1141   }
1142 
1143   tty->print_cr("page_trap_count");
1144 }
1145 
1146 void SafepointSynchronize::deferred_initialize_stat() {
1147   if (init_done) return;
1148 
1149   if (PrintSafepointStatisticsCount <= 0) {
1150     fatal("Wrong PrintSafepointStatisticsCount");
1151   }
1152 
1153   // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1154   // be printed right away, in which case, _safepoint_stats will regress to
1155   // a single element array. Otherwise, it is a circular ring buffer with default
1156   // size of PrintSafepointStatisticsCount.
1157   int stats_array_size;
1158   if (PrintSafepointStatisticsTimeout > 0) {
1159     stats_array_size = 1;
1160     PrintSafepointStatistics = true;
1161   } else {
1162     stats_array_size = PrintSafepointStatisticsCount;
1163   }
1164   _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1165                                                  * sizeof(SafepointStats), mtInternal);
1166   guarantee(_safepoint_stats != NULL,
1167             "not enough memory for safepoint instrumentation data");
1168 
1169   if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1170     need_to_track_page_armed_status = true;
1171   }
1172   init_done = true;
1173 }
1174 
1175 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1176   assert(init_done, "safepoint statistics array hasn't been initialized");
1177   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1178 
1179   spstat->_time_stamp = _ts_of_current_safepoint;
1180 
1181   VM_Operation *op = VMThread::vm_operation();
1182   spstat->_vmop_type = (op != NULL ? op->type() : -1);
1183   if (op != NULL) {
1184     _safepoint_reasons[spstat->_vmop_type]++;
1185   }
1186 
1187   spstat->_nof_total_threads = nof_threads;
1188   spstat->_nof_initial_running_threads = nof_running;
1189   spstat->_nof_threads_hit_page_trap = 0;
1190 
1191   // Records the start time of spinning. The real time spent on spinning
1192   // will be adjusted when spin is done. Same trick is applied for time
1193   // spent on waiting for threads to block.
1194   if (nof_running != 0) {
1195     spstat->_time_to_spin = os::javaTimeNanos();
1196   }  else {
1197     spstat->_time_to_spin = 0;
1198   }
1199 }
1200 
1201 void SafepointSynchronize::update_statistics_on_spin_end() {
1202   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1203 
1204   jlong cur_time = os::javaTimeNanos();
1205 
1206   spstat->_nof_threads_wait_to_block = _waiting_to_block;
1207   if (spstat->_nof_initial_running_threads != 0) {
1208     spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1209   }
1210 
1211   if (need_to_track_page_armed_status) {
1212     spstat->_page_armed = (PageArmed == 1);
1213   }
1214 
1215   // Records the start time of waiting for to block. Updated when block is done.
1216   if (_waiting_to_block != 0) {
1217     spstat->_time_to_wait_to_block = cur_time;
1218   } else {
1219     spstat->_time_to_wait_to_block = 0;
1220   }
1221 }
1222 
1223 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1224   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1225 
1226   if (spstat->_nof_threads_wait_to_block != 0) {
1227     spstat->_time_to_wait_to_block = end_time -
1228       spstat->_time_to_wait_to_block;
1229   }
1230 
1231   // Records the end time of sync which will be used to calculate the total
1232   // vm operation time. Again, the real time spending in syncing will be deducted
1233   // from the start of the sync time later when end_statistics is called.
1234   spstat->_time_to_sync = end_time - _safepoint_begin_time;
1235   if (spstat->_time_to_sync > _max_sync_time) {
1236     _max_sync_time = spstat->_time_to_sync;
1237   }
1238 
1239   spstat->_time_to_do_cleanups = end_time;
1240 }
1241 
1242 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1243   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1244 
1245   // Record how long spent in cleanup tasks.
1246   spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1247 
1248   cleanup_end_time = end_time;
1249 }
1250 
1251 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1252   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1253 
1254   // Update the vm operation time.
1255   spstat->_time_to_exec_vmop = vmop_end_time -  cleanup_end_time;
1256   if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1257     _max_vmop_time = spstat->_time_to_exec_vmop;
1258   }
1259   // Only the sync time longer than the specified
1260   // PrintSafepointStatisticsTimeout will be printed out right away.
1261   // By default, it is -1 meaning all samples will be put into the list.
1262   if ( PrintSafepointStatisticsTimeout > 0) {
1263     if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1264       print_statistics();
1265     }
1266   } else {
1267     // The safepoint statistics will be printed out when the _safepoin_stats
1268     // array fills up.
1269     if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1270       print_statistics();
1271       _cur_stat_index = 0;
1272     } else {
1273       _cur_stat_index++;
1274     }
1275   }
1276 }
1277 
1278 void SafepointSynchronize::print_statistics() {
1279   SafepointStats* sstats = _safepoint_stats;
1280 
1281   for (int index = 0; index <= _cur_stat_index; index++) {
1282     if (index % 30 == 0) {
1283       print_header();
1284     }
1285     sstats = &_safepoint_stats[index];
1286     tty->print("%.3f: ", sstats->_time_stamp);
1287     tty->print("%-26s       ["
1288                INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1289                "    ]    ",
1290                sstats->_vmop_type == -1 ? "no vm operation" :
1291                VM_Operation::name(sstats->_vmop_type),
1292                sstats->_nof_total_threads,
1293                sstats->_nof_initial_running_threads,
1294                sstats->_nof_threads_wait_to_block);
1295     // "/ MICROUNITS " is to convert the unit from nanos to millis.
1296     tty->print("  ["
1297                INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1298                INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1299                INT64_FORMAT_W(6)"    ]  ",
1300                sstats->_time_to_spin / MICROUNITS,
1301                sstats->_time_to_wait_to_block / MICROUNITS,
1302                sstats->_time_to_sync / MICROUNITS,
1303                sstats->_time_to_do_cleanups / MICROUNITS,
1304                sstats->_time_to_exec_vmop / MICROUNITS);
1305 
1306     if (need_to_track_page_armed_status) {
1307       tty->print(INT32_FORMAT"         ", sstats->_page_armed);
1308     }
1309     tty->print_cr(INT32_FORMAT"   ", sstats->_nof_threads_hit_page_trap);
1310   }
1311 }
1312 
1313 // This method will be called when VM exits. It will first call
1314 // print_statistics to print out the rest of the sampling.  Then
1315 // it tries to summarize the sampling.
1316 void SafepointSynchronize::print_stat_on_exit() {
1317   if (_safepoint_stats == NULL) return;
1318 
1319   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1320 
1321   // During VM exit, end_statistics may not get called and in that
1322   // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1323   // don't print it out.
1324   // Approximate the vm op time.
1325   _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1326     os::javaTimeNanos() - cleanup_end_time;
1327 
1328   if ( PrintSafepointStatisticsTimeout < 0 ||
1329        spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1330     print_statistics();
1331   }
1332   tty->print_cr("");
1333 
1334   // Print out polling page sampling status.
1335   if (!need_to_track_page_armed_status) {
1336     if (UseCompilerSafepoints) {
1337       tty->print_cr("Polling page always armed");
1338     }
1339   } else {
1340     tty->print_cr("Defer polling page loop count = %d\n",
1341                  DeferPollingPageLoopCount);
1342   }
1343 
1344   for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1345     if (_safepoint_reasons[index] != 0) {
1346       tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1347                     _safepoint_reasons[index]);
1348     }
1349   }
1350 
1351   tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1352                 _coalesced_vmop_count);
1353   tty->print_cr("Maximum sync time  "INT64_FORMAT_W(5)" ms",
1354                 _max_sync_time / MICROUNITS);
1355   tty->print_cr("Maximum vm operation time (except for Exit VM operation)  "
1356                 INT64_FORMAT_W(5)" ms",
1357                 _max_vmop_time / MICROUNITS);
1358 }
1359 
1360 // ------------------------------------------------------------------------------------------------
1361 // Non-product code
1362 
1363 #ifndef PRODUCT
1364 
1365 void SafepointSynchronize::print_state() {
1366   if (_state == _not_synchronized) {
1367     tty->print_cr("not synchronized");
1368   } else if (_state == _synchronizing || _state == _synchronized) {
1369     tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1370                   "synchronized");
1371 
1372     for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1373        cur->safepoint_state()->print();
1374     }
1375   }
1376 }
1377 
1378 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1379   if (ShowSafepointMsgs) {
1380     va_list ap;
1381     va_start(ap, format);
1382     tty->vprint_cr(format, ap);
1383     va_end(ap);
1384   }
1385 }
1386 
1387 #endif // !PRODUCT