hotspot/src/share/vm/runtime/safepoint.cpp
changeset 1 489c9b5090e2
child 1889 24b003a6fe46
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/runtime/safepoint.cpp	Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,1215 @@
+/*
+ * Copyright 1997-2007 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+# include "incls/_precompiled.incl"
+# include "incls/_safepoint.cpp.incl"
+
+// --------------------------------------------------------------------------------------------------
+// Implementation of Safepoint begin/end
+
+SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
+volatile int  SafepointSynchronize::_waiting_to_block = 0;
+jlong SafepointSynchronize::_last_safepoint = 0;
+volatile int SafepointSynchronize::_safepoint_counter = 0;
+static volatile int PageArmed = 0 ;        // safepoint polling page is RO|RW vs PROT_NONE
+static volatile int TryingToBlock = 0 ;    // proximate value -- for advisory use only
+static bool timeout_error_printed = false;
+
+// Roll all threads forward to a safepoint and suspend them all
+void SafepointSynchronize::begin() {
+
+  Thread* myThread = Thread::current();
+  assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
+
+  _last_safepoint = os::javaTimeNanos();
+
+#ifndef SERIALGC
+  if (UseConcMarkSweepGC) {
+    // In the future we should investigate whether CMS can use the
+    // more-general mechanism below.  DLD (01/05).
+    ConcurrentMarkSweepThread::synchronize(false);
+  } else {
+    ConcurrentGCThread::safepoint_synchronize();
+  }
+#endif // SERIALGC
+
+  // By getting the Threads_lock, we assure that no threads are about to start or
+  // exit. It is released again in SafepointSynchronize::end().
+  Threads_lock->lock();
+
+  assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
+
+  int nof_threads = Threads::number_of_threads();
+
+  if (TraceSafepoint) {
+    tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
+  }
+
+  RuntimeService::record_safepoint_begin();
+
+  {
+  MutexLocker mu(Safepoint_lock);
+
+  // Set number of threads to wait for, before we initiate the callbacks
+  _waiting_to_block = nof_threads;
+  TryingToBlock     = 0 ;
+  int still_running = nof_threads;
+
+  // Save the starting time, so that it can be compared to see if this has taken
+  // too long to complete.
+  jlong safepoint_limit_time;
+  timeout_error_printed = false;
+
+  // Begin the process of bringing the system to a safepoint.
+  // Java threads can be in several different states and are
+  // stopped by different mechanisms:
+  //
+  //  1. Running interpreted
+  //     The interpeter dispatch table is changed to force it to
+  //     check for a safepoint condition between bytecodes.
+  //  2. Running in native code
+  //     When returning from the native code, a Java thread must check
+  //     the safepoint _state to see if we must block.  If the
+  //     VM thread sees a Java thread in native, it does
+  //     not wait for this thread to block.  The order of the memory
+  //     writes and reads of both the safepoint state and the Java
+  //     threads state is critical.  In order to guarantee that the
+  //     memory writes are serialized with respect to each other,
+  //     the VM thread issues a memory barrier instruction
+  //     (on MP systems).  In order to avoid the overhead of issuing
+  //     a memory barrier for each Java thread making native calls, each Java
+  //     thread performs a write to a single memory page after changing
+  //     the thread state.  The VM thread performs a sequence of
+  //     mprotect OS calls which forces all previous writes from all
+  //     Java threads to be serialized.  This is done in the
+  //     os::serialize_thread_states() call.  This has proven to be
+  //     much more efficient than executing a membar instruction
+  //     on every call to native code.
+  //  3. Running compiled Code
+  //     Compiled code reads a global (Safepoint Polling) page that
+  //     is set to fault if we are trying to get to a safepoint.
+  //  4. Blocked
+  //     A thread which is blocked will not be allowed to return from the
+  //     block condition until the safepoint operation is complete.
+  //  5. In VM or Transitioning between states
+  //     If a Java thread is currently running in the VM or transitioning
+  //     between states, the safepointing code will wait for the thread to
+  //     block itself when it attempts transitions to a new state.
+  //
+  _state            = _synchronizing;
+  OrderAccess::fence();
+
+  // Flush all thread states to memory
+  if (!UseMembar) {
+    os::serialize_thread_states();
+  }
+
+  // Make interpreter safepoint aware
+  Interpreter::notice_safepoints();
+
+  if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
+    // Make polling safepoint aware
+    guarantee (PageArmed == 0, "invariant") ;
+    PageArmed = 1 ;
+    os::make_polling_page_unreadable();
+  }
+
+  // Consider using active_processor_count() ... but that call is expensive.
+  int ncpus = os::processor_count() ;
+
+#ifdef ASSERT
+  for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
+    assert(cur->safepoint_state()->is_running(), "Illegal initial state");
+  }
+#endif // ASSERT
+
+  if (SafepointTimeout)
+    safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
+
+  // Iterate through all threads until it have been determined how to stop them all at a safepoint
+  unsigned int iterations = 0;
+  int steps = 0 ;
+  while(still_running > 0) {
+    for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
+      assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
+      ThreadSafepointState *cur_state = cur->safepoint_state();
+      if (cur_state->is_running()) {
+        cur_state->examine_state_of_thread();
+        if (!cur_state->is_running()) {
+           still_running--;
+           // consider adjusting steps downward:
+           //   steps = 0
+           //   steps -= NNN
+           //   steps >>= 1
+           //   steps = MIN(steps, 2000-100)
+           //   if (iterations != 0) steps -= NNN
+        }
+        if (TraceSafepoint && Verbose) cur_state->print();
+      }
+    }
+
+    if ( (PrintSafepointStatistics || (PrintSafepointStatisticsTimeout > 0))
+         && iterations == 0) {
+      begin_statistics(nof_threads, still_running);
+    }
+
+    if (still_running > 0) {
+      // Check for if it takes to long
+      if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
+        print_safepoint_timeout(_spinning_timeout);
+      }
+
+      // Spin to avoid context switching.
+      // There's a tension between allowing the mutators to run (and rendezvous)
+      // vs spinning.  As the VM thread spins, wasting cycles, it consumes CPU that
+      // a mutator might otherwise use profitably to reach a safepoint.  Excessive
+      // spinning by the VM thread on a saturated system can increase rendezvous latency.
+      // Blocking or yielding incur their own penalties in the form of context switching
+      // and the resultant loss of $ residency.
+      //
+      // Further complicating matters is that yield() does not work as naively expected
+      // on many platforms -- yield() does not guarantee that any other ready threads
+      // will run.   As such we revert yield_all() after some number of iterations.
+      // Yield_all() is implemented as a short unconditional sleep on some platforms.
+      // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
+      // can actually increase the time it takes the VM thread to detect that a system-wide
+      // stop-the-world safepoint has been reached.  In a pathological scenario such as that
+      // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
+      // In that case the mutators will be stalled waiting for the safepoint to complete and the
+      // the VMthread will be sleeping, waiting for the mutators to rendezvous.  The VMthread
+      // will eventually wake up and detect that all mutators are safe, at which point
+      // we'll again make progress.
+      //
+      // Beware too that that the VMThread typically runs at elevated priority.
+      // Its default priority is higher than the default mutator priority.
+      // Obviously, this complicates spinning.
+      //
+      // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
+      // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
+      //
+      // See the comments in synchronizer.cpp for additional remarks on spinning.
+      //
+      // In the future we might:
+      // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
+      //    This is tricky as the path used by a thread exiting the JVM (say on
+      //    on JNI call-out) simply stores into its state field.  The burden
+      //    is placed on the VM thread, which must poll (spin).
+      // 2. Find something useful to do while spinning.  If the safepoint is GC-related
+      //    we might aggressively scan the stacks of threads that are already safe.
+      // 3. Use Solaris schedctl to examine the state of the still-running mutators.
+      //    If all the mutators are ONPROC there's no reason to sleep or yield.
+      // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
+      // 5. Check system saturation.  If the system is not fully saturated then
+      //    simply spin and avoid sleep/yield.
+      // 6. As still-running mutators rendezvous they could unpark the sleeping
+      //    VMthread.  This works well for still-running mutators that become
+      //    safe.  The VMthread must still poll for mutators that call-out.
+      // 7. Drive the policy on time-since-begin instead of iterations.
+      // 8. Consider making the spin duration a function of the # of CPUs:
+      //    Spin = (((ncpus-1) * M) + K) + F(still_running)
+      //    Alternately, instead of counting iterations of the outer loop
+      //    we could count the # of threads visited in the inner loop, above.
+      // 9. On windows consider using the return value from SwitchThreadTo()
+      //    to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
+
+      if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
+         guarantee (PageArmed == 0, "invariant") ;
+         PageArmed = 1 ;
+         os::make_polling_page_unreadable();
+      }
+
+      // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
+      // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
+      ++steps ;
+      if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
+        SpinPause() ;     // MP-Polite spin
+      } else
+      if (steps < DeferThrSuspendLoopCount) {
+        os::NakedYield() ;
+      } else {
+        os::yield_all(steps) ;
+        // Alternately, the VM thread could transiently depress its scheduling priority or
+        // transiently increase the priority of the tardy mutator(s).
+      }
+
+      iterations ++ ;
+    }
+    assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
+  }
+  assert(still_running == 0, "sanity check");
+
+  if (PrintSafepointStatistics) {
+    update_statistics_on_spin_end();
+  }
+
+  // wait until all threads are stopped
+  while (_waiting_to_block > 0) {
+    if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
+    if (!SafepointTimeout || timeout_error_printed) {
+      Safepoint_lock->wait(true);  // true, means with no safepoint checks
+    } else {
+      // Compute remaining time
+      jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
+
+      // If there is no remaining time, then there is an error
+      if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
+        print_safepoint_timeout(_blocking_timeout);
+      }
+    }
+  }
+  assert(_waiting_to_block == 0, "sanity check");
+
+#ifndef PRODUCT
+  if (SafepointTimeout) {
+    jlong current_time = os::javaTimeNanos();
+    if (safepoint_limit_time < current_time) {
+      tty->print_cr("# SafepointSynchronize: Finished after "
+                    INT64_FORMAT_W(6) " ms",
+                    ((current_time - safepoint_limit_time) / MICROUNITS +
+                     SafepointTimeoutDelay));
+    }
+  }
+#endif
+
+  assert((_safepoint_counter & 0x1) == 0, "must be even");
+  assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
+  _safepoint_counter ++;
+
+  // Record state
+  _state = _synchronized;
+
+  OrderAccess::fence();
+
+  if (TraceSafepoint) {
+    VM_Operation *op = VMThread::vm_operation();
+    tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
+  }
+
+  RuntimeService::record_safepoint_synchronized();
+  if (PrintSafepointStatistics) {
+    update_statistics_on_sync_end(os::javaTimeNanos());
+  }
+
+  // Call stuff that needs to be run when a safepoint is just about to be completed
+  do_cleanup_tasks();
+  }
+}
+
+// Wake up all threads, so they are ready to resume execution after the safepoint
+// operation has been carried out
+void SafepointSynchronize::end() {
+
+  assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
+  assert((_safepoint_counter & 0x1) == 1, "must be odd");
+  _safepoint_counter ++;
+  // memory fence isn't required here since an odd _safepoint_counter
+  // value can do no harm and a fence is issued below anyway.
+
+  DEBUG_ONLY(Thread* myThread = Thread::current();)
+  assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
+
+  if (PrintSafepointStatistics) {
+    end_statistics(os::javaTimeNanos());
+  }
+
+#ifdef ASSERT
+  // A pending_exception cannot be installed during a safepoint.  The threads
+  // may install an async exception after they come back from a safepoint into
+  // pending_exception after they unblock.  But that should happen later.
+  for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
+    assert (!(cur->has_pending_exception() &&
+              cur->safepoint_state()->is_at_poll_safepoint()),
+            "safepoint installed a pending exception");
+  }
+#endif // ASSERT
+
+  if (PageArmed) {
+    // Make polling safepoint aware
+    os::make_polling_page_readable();
+    PageArmed = 0 ;
+  }
+
+  // Remove safepoint check from interpreter
+  Interpreter::ignore_safepoints();
+
+  {
+    MutexLocker mu(Safepoint_lock);
+
+    assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
+
+    // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
+    // when they get restarted.
+    _state = _not_synchronized;
+    OrderAccess::fence();
+
+    if (TraceSafepoint) {
+       tty->print_cr("Leaving safepoint region");
+    }
+
+    // Start suspended threads
+    for(JavaThread *current = Threads::first(); current; current = current->next()) {
+      // A problem occuring on Solaris is when attempting to restart threads
+      // the first #cpus - 1 go well, but then the VMThread is preempted when we get
+      // to the next one (since it has been running the longest).  We then have
+      // to wait for a cpu to become available before we can continue restarting
+      // threads.
+      // FIXME: This causes the performance of the VM to degrade when active and with
+      // large numbers of threads.  Apparently this is due to the synchronous nature
+      // of suspending threads.
+      //
+      // TODO-FIXME: the comments above are vestigial and no longer apply.
+      // Furthermore, using solaris' schedctl in this particular context confers no benefit
+      if (VMThreadHintNoPreempt) {
+        os::hint_no_preempt();
+      }
+      ThreadSafepointState* cur_state = current->safepoint_state();
+      assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
+      cur_state->restart();
+      assert(cur_state->is_running(), "safepoint state has not been reset");
+    }
+
+    RuntimeService::record_safepoint_end();
+
+    // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
+    // blocked in signal_thread_blocked
+    Threads_lock->unlock();
+
+  }
+#ifndef SERIALGC
+  // If there are any concurrent GC threads resume them.
+  if (UseConcMarkSweepGC) {
+    ConcurrentMarkSweepThread::desynchronize(false);
+  } else {
+    ConcurrentGCThread::safepoint_desynchronize();
+  }
+#endif // SERIALGC
+}
+
+bool SafepointSynchronize::is_cleanup_needed() {
+  // Need a safepoint if some inline cache buffers is non-empty
+  if (!InlineCacheBuffer::is_empty()) return true;
+  return false;
+}
+
+jlong CounterDecay::_last_timestamp = 0;
+
+static void do_method(methodOop m) {
+  m->invocation_counter()->decay();
+}
+
+void CounterDecay::decay() {
+  _last_timestamp = os::javaTimeMillis();
+
+  // This operation is going to be performed only at the end of a safepoint
+  // and hence GC's will not be going on, all Java mutators are suspended
+  // at this point and hence SystemDictionary_lock is also not needed.
+  assert(SafepointSynchronize::is_at_safepoint(), "can only be executed at a safepoint");
+  int nclasses = SystemDictionary::number_of_classes();
+  double classes_per_tick = nclasses * (CounterDecayMinIntervalLength * 1e-3 /
+                                        CounterHalfLifeTime);
+  for (int i = 0; i < classes_per_tick; i++) {
+    klassOop k = SystemDictionary::try_get_next_class();
+    if (k != NULL && k->klass_part()->oop_is_instance()) {
+      instanceKlass::cast(k)->methods_do(do_method);
+    }
+  }
+}
+
+// Various cleaning tasks that should be done periodically at safepoints
+void SafepointSynchronize::do_cleanup_tasks() {
+  jlong cleanup_time;
+
+  // Update fat-monitor pool, since this is a safepoint.
+  if (TraceSafepoint) {
+    cleanup_time = os::javaTimeNanos();
+  }
+
+  ObjectSynchronizer::deflate_idle_monitors();
+  InlineCacheBuffer::update_inline_caches();
+  if(UseCounterDecay && CounterDecay::is_decay_needed()) {
+    CounterDecay::decay();
+  }
+  NMethodSweeper::sweep();
+
+  if (TraceSafepoint) {
+    tty->print_cr("do_cleanup_tasks takes "INT64_FORMAT_W(6) "ms",
+                  (os::javaTimeNanos() - cleanup_time) / MICROUNITS);
+  }
+}
+
+
+bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
+  switch(state) {
+  case _thread_in_native:
+    // native threads are safe if they have no java stack or have walkable stack
+    return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
+
+   // blocked threads should have already have walkable stack
+  case _thread_blocked:
+    assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
+    return true;
+
+  default:
+    return false;
+  }
+}
+
+
+// -------------------------------------------------------------------------------------------------------
+// Implementation of Safepoint callback point
+
+void SafepointSynchronize::block(JavaThread *thread) {
+  assert(thread != NULL, "thread must be set");
+  assert(thread->is_Java_thread(), "not a Java thread");
+
+  // Threads shouldn't block if they are in the middle of printing, but...
+  ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
+
+  // Only bail from the block() call if the thread is gone from the
+  // thread list; starting to exit should still block.
+  if (thread->is_terminated()) {
+     // block current thread if we come here from native code when VM is gone
+     thread->block_if_vm_exited();
+
+     // otherwise do nothing
+     return;
+  }
+
+  JavaThreadState state = thread->thread_state();
+  thread->frame_anchor()->make_walkable(thread);
+
+  // Check that we have a valid thread_state at this point
+  switch(state) {
+    case _thread_in_vm_trans:
+    case _thread_in_Java:        // From compiled code
+
+      // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
+      // we pretend we are still in the VM.
+      thread->set_thread_state(_thread_in_vm);
+
+      if (is_synchronizing()) {
+         Atomic::inc (&TryingToBlock) ;
+      }
+
+      // We will always be holding the Safepoint_lock when we are examine the state
+      // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
+      // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
+      Safepoint_lock->lock_without_safepoint_check();
+      if (is_synchronizing()) {
+        // Decrement the number of threads to wait for and signal vm thread
+        assert(_waiting_to_block > 0, "sanity check");
+        _waiting_to_block--;
+        thread->safepoint_state()->set_has_called_back(true);
+
+        // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
+        if (_waiting_to_block == 0) {
+          Safepoint_lock->notify_all();
+        }
+      }
+
+      // We transition the thread to state _thread_blocked here, but
+      // we can't do our usual check for external suspension and then
+      // self-suspend after the lock_without_safepoint_check() call
+      // below because we are often called during transitions while
+      // we hold different locks. That would leave us suspended while
+      // holding a resource which results in deadlocks.
+      thread->set_thread_state(_thread_blocked);
+      Safepoint_lock->unlock();
+
+      // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
+      // the entire safepoint, the threads will all line up here during the safepoint.
+      Threads_lock->lock_without_safepoint_check();
+      // restore original state. This is important if the thread comes from compiled code, so it
+      // will continue to execute with the _thread_in_Java state.
+      thread->set_thread_state(state);
+      Threads_lock->unlock();
+      break;
+
+    case _thread_in_native_trans:
+    case _thread_blocked_trans:
+    case _thread_new_trans:
+      if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
+        thread->print_thread_state();
+        fatal("Deadlock in safepoint code.  "
+              "Should have called back to the VM before blocking.");
+      }
+
+      // We transition the thread to state _thread_blocked here, but
+      // we can't do our usual check for external suspension and then
+      // self-suspend after the lock_without_safepoint_check() call
+      // below because we are often called during transitions while
+      // we hold different locks. That would leave us suspended while
+      // holding a resource which results in deadlocks.
+      thread->set_thread_state(_thread_blocked);
+
+      // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
+      // the safepoint code might still be waiting for it to block. We need to change the state here,
+      // so it can see that it is at a safepoint.
+
+      // Block until the safepoint operation is completed.
+      Threads_lock->lock_without_safepoint_check();
+
+      // Restore state
+      thread->set_thread_state(state);
+
+      Threads_lock->unlock();
+      break;
+
+    default:
+     fatal1("Illegal threadstate encountered: %d", state);
+  }
+
+  // Check for pending. async. exceptions or suspends - except if the
+  // thread was blocked inside the VM. has_special_runtime_exit_condition()
+  // is called last since it grabs a lock and we only want to do that when
+  // we must.
+  //
+  // Note: we never deliver an async exception at a polling point as the
+  // compiler may not have an exception handler for it. The polling
+  // code will notice the async and deoptimize and the exception will
+  // be delivered. (Polling at a return point is ok though). Sure is
+  // a lot of bother for a deprecated feature...
+  //
+  // We don't deliver an async exception if the thread state is
+  // _thread_in_native_trans so JNI functions won't be called with
+  // a surprising pending exception. If the thread state is going back to java,
+  // async exception is checked in check_special_condition_for_native_trans().
+
+  if (state != _thread_blocked_trans &&
+      state != _thread_in_vm_trans &&
+      thread->has_special_runtime_exit_condition()) {
+    thread->handle_special_runtime_exit_condition(
+      !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
+  }
+}
+
+// ------------------------------------------------------------------------------------------------------
+// Exception handlers
+
+#ifndef PRODUCT
+#ifdef _LP64
+#define PTR_PAD ""
+#else
+#define PTR_PAD "        "
+#endif
+
+static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
+  bool is_oop = newptr ? ((oop)newptr)->is_oop() : false;
+  tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
+                oldptr, wasoop?"oop":"   ", oldptr == newptr ? ' ' : '!',
+                newptr, is_oop?"oop":"   ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":"     "));
+}
+
+static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
+  bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false;
+  tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
+                oldptr, wasoop?"oop":"   ", oldptr == newptr ? ' ' : '!',
+                newptr, is_oop?"oop":"   ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":"     "));
+}
+
+#ifdef SPARC
+static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
+#ifdef _LP64
+  tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
+  const int incr = 1;           // Increment to skip a long, in units of intptr_t
+#else
+  tty->print_cr("--------+--address-+------before-----------+-------after----------+");
+  const int incr = 2;           // Increment to skip a long, in units of intptr_t
+#endif
+  tty->print_cr("---SP---|");
+  for( int i=0; i<16; i++ ) {
+    tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
+  tty->print_cr("--------|");
+  for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
+    tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
+  tty->print("     pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
+  tty->print_cr("--------|");
+  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;
+  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;
+  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;
+  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;
+  tty->print_cr(" FSR    |"PTR_FORMAT" "PTR64_FORMAT"       "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
+  old_sp += incr; new_sp += incr; was_oops += incr;
+  // Skip the floats
+  tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
+  tty->print_cr("---FP---|");
+  old_sp += incr*32;  new_sp += incr*32;  was_oops += incr*32;
+  for( int i2=0; i2<16; i2++ ) {
+    tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
+  tty->print_cr("");
+}
+#endif  // SPARC
+#endif  // PRODUCT
+
+
+void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
+  assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
+  assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
+  assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
+
+  // Uncomment this to get some serious before/after printing of the
+  // Sparc safepoint-blob frame structure.
+  /*
+  intptr_t* sp = thread->last_Java_sp();
+  intptr_t stack_copy[150];
+  for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
+  bool was_oops[150];
+  for( int i=0; i<150; i++ )
+    was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
+  */
+
+  if (ShowSafepointMsgs) {
+    tty->print("handle_polling_page_exception: ");
+  }
+
+  if (PrintSafepointStatistics) {
+    inc_page_trap_count();
+  }
+
+  ThreadSafepointState* state = thread->safepoint_state();
+
+  state->handle_polling_page_exception();
+  // print_me(sp,stack_copy,was_oops);
+}
+
+
+void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
+  if (!timeout_error_printed) {
+    timeout_error_printed = true;
+    // Print out the thread infor which didn't reach the safepoint for debugging
+    // purposes (useful when there are lots of threads in the debugger).
+    tty->print_cr("");
+    tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
+    if (reason ==  _spinning_timeout) {
+      tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
+    } else if (reason == _blocking_timeout) {
+      tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
+    }
+
+    tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
+    ThreadSafepointState *cur_state;
+    ResourceMark rm;
+    for(JavaThread *cur_thread = Threads::first(); cur_thread;
+        cur_thread = cur_thread->next()) {
+      cur_state = cur_thread->safepoint_state();
+
+      if (cur_thread->thread_state() != _thread_blocked &&
+          ((reason == _spinning_timeout && cur_state->is_running()) ||
+           (reason == _blocking_timeout && !cur_state->has_called_back()))) {
+        tty->print("# ");
+        cur_thread->print();
+        tty->print_cr("");
+      }
+    }
+    tty->print_cr("# SafepointSynchronize::begin: (End of list)");
+  }
+
+  // To debug the long safepoint, specify both DieOnSafepointTimeout &
+  // ShowMessageBoxOnError.
+  if (DieOnSafepointTimeout) {
+    char msg[1024];
+    VM_Operation *op = VMThread::vm_operation();
+    sprintf(msg, "Safepoint sync time longer than %d ms detected when executing %s.",
+            SafepointTimeoutDelay,
+            op != NULL ? op->name() : "no vm operation");
+    fatal(msg);
+  }
+}
+
+
+// -------------------------------------------------------------------------------------------------------
+// Implementation of ThreadSafepointState
+
+ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
+  _thread = thread;
+  _type   = _running;
+  _has_called_back = false;
+  _at_poll_safepoint = false;
+}
+
+void ThreadSafepointState::create(JavaThread *thread) {
+  ThreadSafepointState *state = new ThreadSafepointState(thread);
+  thread->set_safepoint_state(state);
+}
+
+void ThreadSafepointState::destroy(JavaThread *thread) {
+  if (thread->safepoint_state()) {
+    delete(thread->safepoint_state());
+    thread->set_safepoint_state(NULL);
+  }
+}
+
+void ThreadSafepointState::examine_state_of_thread() {
+  assert(is_running(), "better be running or just have hit safepoint poll");
+
+  JavaThreadState state = _thread->thread_state();
+
+  // Check for a thread that is suspended. Note that thread resume tries
+  // to grab the Threads_lock which we own here, so a thread cannot be
+  // resumed during safepoint synchronization.
+
+  // We check with locking because another thread that has not yet
+  // synchronized may be trying to suspend this one.
+  bool is_suspended = _thread->is_any_suspended_with_lock();
+  if (is_suspended) {
+    roll_forward(_at_safepoint);
+    return;
+  }
+
+  // Some JavaThread states have an initial safepoint state of
+  // running, but are actually at a safepoint. We will happily
+  // agree and update the safepoint state here.
+  if (SafepointSynchronize::safepoint_safe(_thread, state)) {
+      roll_forward(_at_safepoint);
+      return;
+  }
+
+  if (state == _thread_in_vm) {
+    roll_forward(_call_back);
+    return;
+  }
+
+  // All other thread states will continue to run until they
+  // transition and self-block in state _blocked
+  // Safepoint polling in compiled code causes the Java threads to do the same.
+  // Note: new threads may require a malloc so they must be allowed to finish
+
+  assert(is_running(), "examine_state_of_thread on non-running thread");
+  return;
+}
+
+// Returns true is thread could not be rolled forward at present position.
+void ThreadSafepointState::roll_forward(suspend_type type) {
+  _type = type;
+
+  switch(_type) {
+    case _at_safepoint:
+      SafepointSynchronize::signal_thread_at_safepoint();
+      break;
+
+    case _call_back:
+      set_has_called_back(false);
+      break;
+
+    case _running:
+    default:
+      ShouldNotReachHere();
+  }
+}
+
+void ThreadSafepointState::restart() {
+  switch(type()) {
+    case _at_safepoint:
+    case _call_back:
+      break;
+
+    case _running:
+    default:
+       tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
+                      _thread, _type);
+       _thread->print();
+      ShouldNotReachHere();
+  }
+  _type = _running;
+  set_has_called_back(false);
+}
+
+
+void ThreadSafepointState::print_on(outputStream *st) const {
+  const char *s;
+
+  switch(_type) {
+    case _running                : s = "_running";              break;
+    case _at_safepoint           : s = "_at_safepoint";         break;
+    case _call_back              : s = "_call_back";            break;
+    default:
+      ShouldNotReachHere();
+  }
+
+  st->print_cr("Thread: " INTPTR_FORMAT
+              "  [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
+               _thread, _thread->osthread()->thread_id(), s, _has_called_back,
+               _at_poll_safepoint);
+
+  _thread->print_thread_state_on(st);
+}
+
+
+// ---------------------------------------------------------------------------------------------------------------------
+
+// Block the thread at the safepoint poll or poll return.
+void ThreadSafepointState::handle_polling_page_exception() {
+
+  // Check state.  block() will set thread state to thread_in_vm which will
+  // cause the safepoint state _type to become _call_back.
+  assert(type() == ThreadSafepointState::_running,
+         "polling page exception on thread not running state");
+
+  // Step 1: Find the nmethod from the return address
+  if (ShowSafepointMsgs && Verbose) {
+    tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
+  }
+  address real_return_addr = thread()->saved_exception_pc();
+
+  CodeBlob *cb = CodeCache::find_blob(real_return_addr);
+  assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
+  nmethod* nm = (nmethod*)cb;
+
+  // Find frame of caller
+  frame stub_fr = thread()->last_frame();
+  CodeBlob* stub_cb = stub_fr.cb();
+  assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
+  RegisterMap map(thread(), true);
+  frame caller_fr = stub_fr.sender(&map);
+
+  // Should only be poll_return or poll
+  assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
+
+  // This is a poll immediately before a return. The exception handling code
+  // has already had the effect of causing the return to occur, so the execution
+  // will continue immediately after the call. In addition, the oopmap at the
+  // return point does not mark the return value as an oop (if it is), so
+  // it needs a handle here to be updated.
+  if( nm->is_at_poll_return(real_return_addr) ) {
+    // See if return type is an oop.
+    bool return_oop = nm->method()->is_returning_oop();
+    Handle return_value;
+    if (return_oop) {
+      // The oop result has been saved on the stack together with all
+      // the other registers. In order to preserve it over GCs we need
+      // to keep it in a handle.
+      oop result = caller_fr.saved_oop_result(&map);
+      assert(result == NULL || result->is_oop(), "must be oop");
+      return_value = Handle(thread(), result);
+      assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
+    }
+
+    // Block the thread
+    SafepointSynchronize::block(thread());
+
+    // restore oop result, if any
+    if (return_oop) {
+      caller_fr.set_saved_oop_result(&map, return_value());
+    }
+  }
+
+  // This is a safepoint poll. Verify the return address and block.
+  else {
+    set_at_poll_safepoint(true);
+
+    // verify the blob built the "return address" correctly
+    assert(real_return_addr == caller_fr.pc(), "must match");
+
+    // Block the thread
+    SafepointSynchronize::block(thread());
+    set_at_poll_safepoint(false);
+
+    // If we have a pending async exception deoptimize the frame
+    // as otherwise we may never deliver it.
+    if (thread()->has_async_condition()) {
+      ThreadInVMfromJavaNoAsyncException __tiv(thread());
+      VM_DeoptimizeFrame deopt(thread(), caller_fr.id());
+      VMThread::execute(&deopt);
+    }
+
+    // If an exception has been installed we must check for a pending deoptimization
+    // Deoptimize frame if exception has been thrown.
+
+    if (thread()->has_pending_exception() ) {
+      RegisterMap map(thread(), true);
+      frame caller_fr = stub_fr.sender(&map);
+      if (caller_fr.is_deoptimized_frame()) {
+        // The exception patch will destroy registers that are still
+        // live and will be needed during deoptimization. Defer the
+        // Async exception should have defered the exception until the
+        // next safepoint which will be detected when we get into
+        // the interpreter so if we have an exception now things
+        // are messed up.
+
+        fatal("Exception installed and deoptimization is pending");
+      }
+    }
+  }
+}
+
+
+//
+//                     Statistics & Instrumentations
+//
+SafepointSynchronize::SafepointStats*  SafepointSynchronize::_safepoint_stats = NULL;
+int    SafepointSynchronize::_cur_stat_index = 0;
+julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
+julong SafepointSynchronize::_coalesced_vmop_count = 0;
+jlong  SafepointSynchronize::_max_sync_time = 0;
+
+// last_safepoint_start_time records the start time of last safepoint.
+static jlong  last_safepoint_start_time = 0;
+static jlong  sync_end_time = 0;
+static bool   need_to_track_page_armed_status = false;
+static bool   init_done = false;
+
+void SafepointSynchronize::deferred_initialize_stat() {
+  if (init_done) return;
+
+  if (PrintSafepointStatisticsCount <= 0) {
+    fatal("Wrong PrintSafepointStatisticsCount");
+  }
+
+  // If PrintSafepointStatisticsTimeout is specified, the statistics data will
+  // be printed right away, in which case, _safepoint_stats will regress to
+  // a single element array. Otherwise, it is a circular ring buffer with default
+  // size of PrintSafepointStatisticsCount.
+  int stats_array_size;
+  if (PrintSafepointStatisticsTimeout > 0) {
+    stats_array_size = 1;
+    PrintSafepointStatistics = true;
+  } else {
+    stats_array_size = PrintSafepointStatisticsCount;
+  }
+  _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
+                                                 * sizeof(SafepointStats));
+  guarantee(_safepoint_stats != NULL,
+            "not enough memory for safepoint instrumentation data");
+
+  if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
+    need_to_track_page_armed_status = true;
+  }
+
+  tty->print("     vmop_name               "
+             "[threads: total initially_running wait_to_block] ");
+  tty->print("[time: spin block sync] "
+             "[vmop_time  time_elapsed] ");
+
+  // no page armed status printed out if it is always armed.
+  if (need_to_track_page_armed_status) {
+    tty->print("page_armed ");
+  }
+
+  tty->print_cr("page_trap_count");
+
+  init_done = true;
+}
+
+void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
+  deferred_initialize_stat();
+
+  SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
+
+  VM_Operation *op = VMThread::vm_operation();
+  spstat->_vmop_type = (op != NULL ? op->type() : -1);
+  if (op != NULL) {
+    _safepoint_reasons[spstat->_vmop_type]++;
+  }
+
+  spstat->_nof_total_threads = nof_threads;
+  spstat->_nof_initial_running_threads = nof_running;
+  spstat->_nof_threads_hit_page_trap = 0;
+
+  // Records the start time of spinning. The real time spent on spinning
+  // will be adjusted when spin is done. Same trick is applied for time
+  // spent on waiting for threads to block.
+  if (nof_running != 0) {
+    spstat->_time_to_spin = os::javaTimeNanos();
+  }  else {
+    spstat->_time_to_spin = 0;
+  }
+
+  if (last_safepoint_start_time == 0) {
+    spstat->_time_elapsed_since_last_safepoint = 0;
+  } else {
+    spstat->_time_elapsed_since_last_safepoint = _last_safepoint -
+      last_safepoint_start_time;
+  }
+  last_safepoint_start_time = _last_safepoint;
+}
+
+void SafepointSynchronize::update_statistics_on_spin_end() {
+  SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
+
+  jlong cur_time = os::javaTimeNanos();
+
+  spstat->_nof_threads_wait_to_block = _waiting_to_block;
+  if (spstat->_nof_initial_running_threads != 0) {
+    spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
+  }
+
+  if (need_to_track_page_armed_status) {
+    spstat->_page_armed = (PageArmed == 1);
+  }
+
+  // Records the start time of waiting for to block. Updated when block is done.
+  if (_waiting_to_block != 0) {
+    spstat->_time_to_wait_to_block = cur_time;
+  } else {
+    spstat->_time_to_wait_to_block = 0;
+  }
+}
+
+void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
+  SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
+
+  if (spstat->_nof_threads_wait_to_block != 0) {
+    spstat->_time_to_wait_to_block = end_time -
+      spstat->_time_to_wait_to_block;
+  }
+
+  // Records the end time of sync which will be used to calculate the total
+  // vm operation time. Again, the real time spending in syncing will be deducted
+  // from the start of the sync time later when end_statistics is called.
+  spstat->_time_to_sync = end_time - _last_safepoint;
+  if (spstat->_time_to_sync > _max_sync_time) {
+    _max_sync_time = spstat->_time_to_sync;
+  }
+  sync_end_time = end_time;
+}
+
+void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
+  SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
+
+  // Update the vm operation time.
+  spstat->_time_to_exec_vmop = vmop_end_time -  sync_end_time;
+  // Only the sync time longer than the specified
+  // PrintSafepointStatisticsTimeout will be printed out right away.
+  // By default, it is -1 meaning all samples will be put into the list.
+  if ( PrintSafepointStatisticsTimeout > 0) {
+    if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
+      print_statistics();
+    }
+  } else {
+    // The safepoint statistics will be printed out when the _safepoin_stats
+    // array fills up.
+    if (_cur_stat_index != PrintSafepointStatisticsCount - 1) {
+      _cur_stat_index ++;
+    } else {
+      print_statistics();
+      _cur_stat_index = 0;
+      tty->print_cr("");
+    }
+  }
+}
+
+void SafepointSynchronize::print_statistics() {
+  int index;
+  SafepointStats* sstats = _safepoint_stats;
+
+  for (index = 0; index <= _cur_stat_index; index++) {
+    sstats = &_safepoint_stats[index];
+    tty->print("%-28s       ["
+               INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
+               "]   ",
+               sstats->_vmop_type == -1 ? "no vm operation" :
+               VM_Operation::name(sstats->_vmop_type),
+               sstats->_nof_total_threads,
+               sstats->_nof_initial_running_threads,
+               sstats->_nof_threads_wait_to_block);
+    // "/ MICROUNITS " is to convert the unit from nanos to millis.
+    tty->print("       ["
+               INT64_FORMAT_W(6)INT64_FORMAT_W(6)INT64_FORMAT_W(6)
+               "]     "
+               "["INT64_FORMAT_W(6)INT64_FORMAT_W(9) "]          ",
+               sstats->_time_to_spin / MICROUNITS,
+               sstats->_time_to_wait_to_block / MICROUNITS,
+               sstats->_time_to_sync / MICROUNITS,
+               sstats->_time_to_exec_vmop / MICROUNITS,
+               sstats->_time_elapsed_since_last_safepoint / MICROUNITS);
+
+    if (need_to_track_page_armed_status) {
+      tty->print(INT32_FORMAT"         ", sstats->_page_armed);
+    }
+    tty->print_cr(INT32_FORMAT"   ", sstats->_nof_threads_hit_page_trap);
+  }
+}
+
+// This method will be called when VM exits. It will first call
+// print_statistics to print out the rest of the sampling.  Then
+// it tries to summarize the sampling.
+void SafepointSynchronize::print_stat_on_exit() {
+  if (_safepoint_stats == NULL) return;
+
+  SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
+
+  // During VM exit, end_statistics may not get called and in that
+  // case, if the sync time is less than PrintSafepointStatisticsTimeout,
+  // don't print it out.
+  // Approximate the vm op time.
+  _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
+    os::javaTimeNanos() - sync_end_time;
+
+  if ( PrintSafepointStatisticsTimeout < 0 ||
+       spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
+    print_statistics();
+  }
+  tty->print_cr("");
+
+  // Print out polling page sampling status.
+  if (!need_to_track_page_armed_status) {
+    if (UseCompilerSafepoints) {
+      tty->print_cr("Polling page always armed");
+    }
+  } else {
+    tty->print_cr("Defer polling page loop count = %d\n",
+                 DeferPollingPageLoopCount);
+  }
+
+  for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
+    if (_safepoint_reasons[index] != 0) {
+      tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
+                    _safepoint_reasons[index]);
+    }
+  }
+
+  tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
+                _coalesced_vmop_count);
+  tty->print_cr("Maximum sync time  "INT64_FORMAT_W(5)" ms",
+                _max_sync_time / MICROUNITS);
+}
+
+// ------------------------------------------------------------------------------------------------
+// Non-product code
+
+#ifndef PRODUCT
+
+void SafepointSynchronize::print_state() {
+  if (_state == _not_synchronized) {
+    tty->print_cr("not synchronized");
+  } else if (_state == _synchronizing || _state == _synchronized) {
+    tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
+                  "synchronized");
+
+    for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
+       cur->safepoint_state()->print();
+    }
+  }
+}
+
+void SafepointSynchronize::safepoint_msg(const char* format, ...) {
+  if (ShowSafepointMsgs) {
+    va_list ap;
+    va_start(ap, format);
+    tty->vprint_cr(format, ap);
+    va_end(ap);
+  }
+}
+
+#endif // !PRODUCT