       1 /*
       2  * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
       3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
       4  *
       5  * This code is free software; you can redistribute it and/or modify it
       6  * under the terms of the GNU General Public License version 2 only, as
       7  * published by the Free Software Foundation.
       8  *
       9  * This code is distributed in the hope that it will be useful, but WITHOUT
      10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
      11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      12  * version 2 for more details (a copy is included in the LICENSE file that
      13  * accompanied this code).
      14  *
      15  * You should have received a copy of the GNU General Public License version
      16  * 2 along with this work; if not, write to the Free Software Foundation,
      17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
      18  *
      19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
      20  * or visit www.oracle.com if you need additional information or have any
      21  * questions.
      22  *
      23  */
      24
      25 #include "precompiled.hpp"
      26 #include "classfile/symbolTable.hpp"
      27 #include "classfile/systemDictionary.hpp"
      28 #include "code/codeCache.hpp"
      29 #include "code/icBuffer.hpp"
      30 #include "code/nmethod.hpp"
      31 #include "code/pcDesc.hpp"
      32 #include "code/scopeDesc.hpp"
      33 #include "gc_interface/collectedHeap.hpp"
      34 #include "interpreter/interpreter.hpp"
      35 #include "memory/resourceArea.hpp"
      36 #include "memory/universe.inline.hpp"
      37 #include "oops/oop.inline.hpp"
      38 #include "oops/symbol.hpp"
      39 #include "runtime/compilationPolicy.hpp"
      40 #include "runtime/deoptimization.hpp"
      41 #include "runtime/frame.inline.hpp"
      42 #include "runtime/interfaceSupport.hpp"
      43 #include "runtime/mutexLocker.hpp"
      44 #include "runtime/orderAccess.inline.hpp"
      45 #include "runtime/osThread.hpp"
      46 #include "runtime/safepoint.hpp"
      47 #include "runtime/signature.hpp"
      48 #include "runtime/stubCodeGenerator.hpp"
      49 #include "runtime/stubRoutines.hpp"
      50 #include "runtime/sweeper.hpp"
      51 #include "runtime/synchronizer.hpp"
      52 #include "runtime/thread.inline.hpp"
      53 #include "services/runtimeService.hpp"
      54 #include "trace/tracing.hpp"
      55 #include "utilities/events.hpp"
      56 #include "utilities/macros.hpp"
      57 #ifdef TARGET_ARCH_x86
      58 # include "nativeInst_x86.hpp"
      59 # include "vmreg_x86.inline.hpp"
      60 #endif
      61 #ifdef TARGET_ARCH_sparc
      62 # include "nativeInst_sparc.hpp"
      63 # include "vmreg_sparc.inline.hpp"
      64 #endif
      65 #ifdef TARGET_ARCH_zero
      66 # include "nativeInst_zero.hpp"
      67 # include "vmreg_zero.inline.hpp"
      68 #endif
      69 #ifdef TARGET_ARCH_arm
      70 # include "nativeInst_arm.hpp"
      71 # include "vmreg_arm.inline.hpp"
      72 #endif
      73 #ifdef TARGET_ARCH_ppc
      74 # include "nativeInst_ppc.hpp"
      75 # include "vmreg_ppc.inline.hpp"
      76 #endif
      77 #if INCLUDE_ALL_GCS
      78 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
      79 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
      80 #endif // INCLUDE_ALL_GCS
      81 #ifdef COMPILER1
      82 #include "c1/c1_globals.hpp"
      83 #endif
      84
      85 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
      86
      87 // --------------------------------------------------------------------------------------------------
      88 // Implementation of Safepoint begin/end
      89
      90 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
      91 volatile int  SafepointSynchronize::_waiting_to_block = 0;
      92 volatile int SafepointSynchronize::_safepoint_counter = 0;
      93 int SafepointSynchronize::_current_jni_active_count = 0;
      94 long  SafepointSynchronize::_end_of_last_safepoint = 0;
      95 static volatile int PageArmed = 0 ;        // safepoint polling page is RO|RW vs PROT_NONE
      96 static volatile int TryingToBlock = 0 ;    // proximate value -- for advisory use only
      97 static bool timeout_error_printed = false;
      98
      99 // Roll all threads forward to a safepoint and suspend them all
     100 void SafepointSynchronize::begin() {
     101
     102   Thread* myThread = Thread::current();
     103   assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
     104
     105   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
     106     _safepoint_begin_time = os::javaTimeNanos();
     107     _ts_of_current_safepoint = tty->time_stamp().seconds();
     108   }
     109
     110 #if INCLUDE_ALL_GCS
     111   if (UseConcMarkSweepGC) {
     112     // In the future we should investigate whether CMS can use the
     113     // more-general mechanism below.  DLD (01/05).
     114     ConcurrentMarkSweepThread::synchronize(false);
     115   } else if (UseG1GC) {
     116     SuspendibleThreadSet::synchronize();
     117   }
     118 #endif // INCLUDE_ALL_GCS
     119
     120   // By getting the Threads_lock, we assure that no threads are about to start or
     121   // exit. It is released again in SafepointSynchronize::end().
     122   Threads_lock->lock();
     123
     124   assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
     125
     126   int nof_threads = Threads::number_of_threads();
     127
     128   if (TraceSafepoint) {
     129     tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
     130   }
     131
     132   RuntimeService::record_safepoint_begin();
     133
     134   MutexLocker mu(Safepoint_lock);
     135
     136   // Reset the count of active JNI critical threads
     137   _current_jni_active_count = 0;
     138
     139   // Set number of threads to wait for, before we initiate the callbacks
     140   _waiting_to_block = nof_threads;
     141   TryingToBlock     = 0 ;
     142   int still_running = nof_threads;
     143
     144   // Save the starting time, so that it can be compared to see if this has taken
     145   // too long to complete.
     146   jlong safepoint_limit_time;
     147   timeout_error_printed = false;
     148
     149   // PrintSafepointStatisticsTimeout can be specified separately. When
     150   // specified, PrintSafepointStatistics will be set to true in
     151   // deferred_initialize_stat method. The initialization has to be done
     152   // early enough to avoid any races. See bug 6880029 for details.
     153   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
     154     deferred_initialize_stat();
     155   }
     156
     157   // Begin the process of bringing the system to a safepoint.
     158   // Java threads can be in several different states and are
     159   // stopped by different mechanisms:
     160   //
     161   //  1. Running interpreted
     162   //     The interpeter dispatch table is changed to force it to
     163   //     check for a safepoint condition between bytecodes.
     164   //  2. Running in native code
     165   //     When returning from the native code, a Java thread must check
     166   //     the safepoint _state to see if we must block.  If the
     167   //     VM thread sees a Java thread in native, it does
     168   //     not wait for this thread to block.  The order of the memory
     169   //     writes and reads of both the safepoint state and the Java
     170   //     threads state is critical.  In order to guarantee that the
     171   //     memory writes are serialized with respect to each other,
     172   //     the VM thread issues a memory barrier instruction
     173   //     (on MP systems).  In order to avoid the overhead of issuing
     174   //     a memory barrier for each Java thread making native calls, each Java
     175   //     thread performs a write to a single memory page after changing
     176   //     the thread state.  The VM thread performs a sequence of
     177   //     mprotect OS calls which forces all previous writes from all
     178   //     Java threads to be serialized.  This is done in the
     179   //     os::serialize_thread_states() call.  This has proven to be
     180   //     much more efficient than executing a membar instruction
     181   //     on every call to native code.
     182   //  3. Running compiled Code
     183   //     Compiled code reads a global (Safepoint Polling) page that
     184   //     is set to fault if we are trying to get to a safepoint.
     185   //  4. Blocked
     186   //     A thread which is blocked will not be allowed to return from the
     187   //     block condition until the safepoint operation is complete.
     188   //  5. In VM or Transitioning between states
     189   //     If a Java thread is currently running in the VM or transitioning
     190   //     between states, the safepointing code will wait for the thread to
     191   //     block itself when it attempts transitions to a new state.
     192   //
     193   _state            = _synchronizing;
     194   OrderAccess::fence();
     195
     196   // Flush all thread states to memory
     197   if (!UseMembar) {
     198     os::serialize_thread_states();
     199   }
     200
     201   // Make interpreter safepoint aware
     202   Interpreter::notice_safepoints();
     203
     204   if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
     205     // Make polling safepoint aware
     206     guarantee (PageArmed == 0, "invariant") ;
     207     PageArmed = 1 ;
     208     os::make_polling_page_unreadable();
     209   }
     210
     211   // Consider using active_processor_count() ... but that call is expensive.
     212   int ncpus = os::processor_count() ;
     213
     214 #ifdef ASSERT
     215   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
     216     assert(cur->safepoint_state()->is_running(), "Illegal initial state");
     217     // Clear the visited flag to ensure that the critical counts are collected properly.
     218     cur->set_visited_for_critical_count(false);
     219   }
     220 #endif // ASSERT
     221
     222   if (SafepointTimeout)
     223     safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
     224
     225   // Iterate through all threads until it have been determined how to stop them all at a safepoint
     226   unsigned int iterations = 0;
     227   int steps = 0 ;
     228   while(still_running > 0) {
     229     for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
     230       assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
     231       ThreadSafepointState *cur_state = cur->safepoint_state();
     232       if (cur_state->is_running()) {
     233         cur_state->examine_state_of_thread();
     234         if (!cur_state->is_running()) {
     235            still_running--;
     236            // consider adjusting steps downward:
     237            //   steps = 0
     238            //   steps -= NNN
     239            //   steps >>= 1
     240            //   steps = MIN(steps, 2000-100)
     241            //   if (iterations != 0) steps -= NNN
     242         }
     243         if (TraceSafepoint && Verbose) cur_state->print();
     244       }
     245     }
     246
     247     if (PrintSafepointStatistics && iterations == 0) {
     248       begin_statistics(nof_threads, still_running);
     249     }
     250
     251     if (still_running > 0) {
     252       // Check for if it takes to long
     253       if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
     254         print_safepoint_timeout(_spinning_timeout);
     255       }
     256
     257       // Spin to avoid context switching.
     258       // There's a tension between allowing the mutators to run (and rendezvous)
     259       // vs spinning.  As the VM thread spins, wasting cycles, it consumes CPU that
     260       // a mutator might otherwise use profitably to reach a safepoint.  Excessive
     261       // spinning by the VM thread on a saturated system can increase rendezvous latency.
     262       // Blocking or yielding incur their own penalties in the form of context switching
     263       // and the resultant loss of $ residency.
     264       //
     265       // Further complicating matters is that yield() does not work as naively expected
     266       // on many platforms -- yield() does not guarantee that any other ready threads
     267       // will run.   As such we revert yield_all() after some number of iterations.
     268       // Yield_all() is implemented as a short unconditional sleep on some platforms.
     269       // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
     270       // can actually increase the time it takes the VM thread to detect that a system-wide
     271       // stop-the-world safepoint has been reached.  In a pathological scenario such as that
     272       // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
     273       // In that case the mutators will be stalled waiting for the safepoint to complete and the
     274       // the VMthread will be sleeping, waiting for the mutators to rendezvous.  The VMthread
     275       // will eventually wake up and detect that all mutators are safe, at which point
     276       // we'll again make progress.
     277       //
     278       // Beware too that that the VMThread typically runs at elevated priority.
     279       // Its default priority is higher than the default mutator priority.
     280       // Obviously, this complicates spinning.
     281       //
     282       // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
     283       // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
     284       //
     285       // See the comments in synchronizer.cpp for additional remarks on spinning.
     286       //
     287       // In the future we might:
     288       // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
     289       //    This is tricky as the path used by a thread exiting the JVM (say on
     290       //    on JNI call-out) simply stores into its state field.  The burden
     291       //    is placed on the VM thread, which must poll (spin).
     292       // 2. Find something useful to do while spinning.  If the safepoint is GC-related
     293       //    we might aggressively scan the stacks of threads that are already safe.
     294       // 3. Use Solaris schedctl to examine the state of the still-running mutators.
     295       //    If all the mutators are ONPROC there's no reason to sleep or yield.
     296       // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
     297       // 5. Check system saturation.  If the system is not fully saturated then
     298       //    simply spin and avoid sleep/yield.
     299       // 6. As still-running mutators rendezvous they could unpark the sleeping
     300       //    VMthread.  This works well for still-running mutators that become
     301       //    safe.  The VMthread must still poll for mutators that call-out.
     302       // 7. Drive the policy on time-since-begin instead of iterations.
     303       // 8. Consider making the spin duration a function of the # of CPUs:
     304       //    Spin = (((ncpus-1) * M) + K) + F(still_running)
     305       //    Alternately, instead of counting iterations of the outer loop
     306       //    we could count the # of threads visited in the inner loop, above.
     307       // 9. On windows consider using the return value from SwitchThreadTo()
     308       //    to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
     309
     310       if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
     311          guarantee (PageArmed == 0, "invariant") ;
     312          PageArmed = 1 ;
     313          os::make_polling_page_unreadable();
     314       }
     315
     316       // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
     317       // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
     318       ++steps ;
     319       if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
     320         SpinPause() ;     // MP-Polite spin
     321       } else
     322       if (steps < DeferThrSuspendLoopCount) {
     323         os::NakedYield() ;
     324       } else {
     325         os::yield_all(steps) ;
     326         // Alternately, the VM thread could transiently depress its scheduling priority or
     327         // transiently increase the priority of the tardy mutator(s).
     328       }
     329
     330       iterations ++ ;
     331     }
     332     assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
     333   }
     334   assert(still_running == 0, "sanity check");
     335
     336   if (PrintSafepointStatistics) {
     337     update_statistics_on_spin_end();
     338   }
     339
     340   // wait until all threads are stopped
     341   while (_waiting_to_block > 0) {
     342     if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
     343     if (!SafepointTimeout || timeout_error_printed) {
     344       Safepoint_lock->wait(true);  // true, means with no safepoint checks
     345     } else {
     346       // Compute remaining time
     347       jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
     348
     349       // If there is no remaining time, then there is an error
     350       if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
     351         print_safepoint_timeout(_blocking_timeout);
     352       }
     353     }
     354   }
     355   assert(_waiting_to_block == 0, "sanity check");
     356
     357 #ifndef PRODUCT
     358   if (SafepointTimeout) {
     359     jlong current_time = os::javaTimeNanos();
     360     if (safepoint_limit_time < current_time) {
     361       tty->print_cr("# SafepointSynchronize: Finished after "
     362                     INT64_FORMAT_W(6) " ms",
     363                     ((current_time - safepoint_limit_time) / MICROUNITS +
     364                      SafepointTimeoutDelay));
     365     }
     366   }
     367 #endif
     368
     369   assert((_safepoint_counter & 0x1) == 0, "must be even");
     370   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
     371   _safepoint_counter ++;
     372
     373   // Record state
     374   _state = _synchronized;
     375
     376   OrderAccess::fence();
     377
     378 #ifdef ASSERT
     379   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
     380     // make sure all the threads were visited
     381     assert(cur->was_visited_for_critical_count(), "missed a thread");
     382   }
     383 #endif // ASSERT
     384
     385   // Update the count of active JNI critical regions
     386   GC_locker::set_jni_lock_count(_current_jni_active_count);
     387
     388   if (TraceSafepoint) {
     389     VM_Operation *op = VMThread::vm_operation();
     390     tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
     391   }
     392
     393   RuntimeService::record_safepoint_synchronized();
     394   if (PrintSafepointStatistics) {
     395     update_statistics_on_sync_end(os::javaTimeNanos());
     396   }
     397
     398   // Call stuff that needs to be run when a safepoint is just about to be completed
     399   do_cleanup_tasks();
     400
     401   if (PrintSafepointStatistics) {
     402     // Record how much time spend on the above cleanup tasks
     403     update_statistics_on_cleanup_end(os::javaTimeNanos());
     404   }
     405 }
     406
     407 // Wake up all threads, so they are ready to resume execution after the safepoint
     408 // operation has been carried out
     409 void SafepointSynchronize::end() {
     410
     411   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
     412   assert((_safepoint_counter & 0x1) == 1, "must be odd");
     413   _safepoint_counter ++;
     414   // memory fence isn't required here since an odd _safepoint_counter
     415   // value can do no harm and a fence is issued below anyway.
     416
     417   DEBUG_ONLY(Thread* myThread = Thread::current();)
     418   assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
     419
     420   if (PrintSafepointStatistics) {
     421     end_statistics(os::javaTimeNanos());
     422   }
     423
     424 #ifdef ASSERT
     425   // A pending_exception cannot be installed during a safepoint.  The threads
     426   // may install an async exception after they come back from a safepoint into
     427   // pending_exception after they unblock.  But that should happen later.
     428   for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
     429     assert (!(cur->has_pending_exception() &&
     430               cur->safepoint_state()->is_at_poll_safepoint()),
     431             "safepoint installed a pending exception");
     432   }
     433 #endif // ASSERT
     434
     435   if (PageArmed) {
     436     // Make polling safepoint aware
     437     os::make_polling_page_readable();
     438     PageArmed = 0 ;
     439   }
     440
     441   // Remove safepoint check from interpreter
     442   Interpreter::ignore_safepoints();
     443
     444   {
     445     MutexLocker mu(Safepoint_lock);
     446
     447     assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
     448
     449     // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
     450     // when they get restarted.
     451     _state = _not_synchronized;
     452     OrderAccess::fence();
     453
     454     if (TraceSafepoint) {
     455        tty->print_cr("Leaving safepoint region");
     456     }
     457
     458     // Start suspended threads
     459     for(JavaThread *current = Threads::first(); current; current = current->next()) {
     460       // A problem occurring on Solaris is when attempting to restart threads
     461       // the first #cpus - 1 go well, but then the VMThread is preempted when we get
     462       // to the next one (since it has been running the longest).  We then have
     463       // to wait for a cpu to become available before we can continue restarting
     464       // threads.
     465       // FIXME: This causes the performance of the VM to degrade when active and with
     466       // large numbers of threads.  Apparently this is due to the synchronous nature
     467       // of suspending threads.
     468       //
     469       // TODO-FIXME: the comments above are vestigial and no longer apply.
     470       // Furthermore, using solaris' schedctl in this particular context confers no benefit
     471       if (VMThreadHintNoPreempt) {
     472         os::hint_no_preempt();
     473       }
     474       ThreadSafepointState* cur_state = current->safepoint_state();
     475       assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
     476       cur_state->restart();
     477       assert(cur_state->is_running(), "safepoint state has not been reset");
     478     }
     479
     480     RuntimeService::record_safepoint_end();
     481
     482     // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
     483     // blocked in signal_thread_blocked
     484     Threads_lock->unlock();
     485
     486   }
     487 #if INCLUDE_ALL_GCS
     488   // If there are any concurrent GC threads resume them.
     489   if (UseConcMarkSweepGC) {
     490     ConcurrentMarkSweepThread::desynchronize(false);
     491   } else if (UseG1GC) {
     492     SuspendibleThreadSet::desynchronize();
     493   }
     494 #endif // INCLUDE_ALL_GCS
     495   // record this time so VMThread can keep track how much time has elasped
     496   // since last safepoint.
     497   _end_of_last_safepoint = os::javaTimeMillis();
     498 }
     499
     500 bool SafepointSynchronize::is_cleanup_needed() {
     501   // Need a safepoint if some inline cache buffers is non-empty
     502   if (!InlineCacheBuffer::is_empty()) return true;
     503   return false;
     504 }
     505

     506 // Various cleaning tasks that should be done periodically at safepoints
     507 void SafepointSynchronize::do_cleanup_tasks() {
     508   {
     509     TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
     510     ObjectSynchronizer::deflate_idle_monitors();
     511   }
     512
     513   {
     514     TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
     515     InlineCacheBuffer::update_inline_caches();
     516   }
     517
     518   {
     519     TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
     520     CompilationPolicy::policy()->do_safepoint_work();
     521   }
     522
     523   {
     524     TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
     525     NMethodSweeper::mark_active_nmethods();
     526   }
     527
     528 //#define PRINT_RESIZE
     529
     530   if (HashtablesResizeSymbolTable == true) {
     531     ResizeHashtableStats stats;
     532     {
     533       //tty->print("SymbolTable      ");
     534       TraceTime t5("resize_table for SymbolTable", TraceSafepointCleanupTime);
     535       EventSymbolTableResize event;
     536       stats = SymbolTable::the_table()->resize_table(SymbolTable_lock,
     537                                                       HashtablesResizeSymbolTableTriggerLoadFactor,
     538                                                         HashtablesResizeSymbolTableDesiredLoadFactor);
     539       if (stats.resized == true) {
     540         if (PrintSymbolTableStatisticsTimeline == true) {
     541           tty->print("-------------------------------------------------------------------------------\n");
     542           tty->print("SymbolTable resized from %d to %d\n", stats.old_size, stats.new_size);
     543           tty->print("-------------------------------------------------------------------------------\n");
     544         }
     545         if (event.should_commit() == true) {
     546           event.set_oldSize(stats.old_size);
     547           event.set_newSize(stats.new_size);
     548           event.commit();
     549         }
     550       }
     551     }
     552   }
     553
     554   if (HashtablesResizeStringTable == true) {
     555     ResizeHashtableStats stats;
     556     {
     557       //tty->print("StringTable      ");
     558       TraceTime t6("resize_table for StringTable", TraceSafepointCleanupTime);
     559       EventStringTableResize event;
     560       stats = StringTable::the_table()->resize_table(StringTable_lock,
     561                                                       HashtablesResizeStringTableTriggerLoadFactor,
     562                                                         HashtablesResizeStringTableDesiredLoadFactor);
     563       if (stats.resized == true) {
     564         if (PrintStringTableStatisticsTimeline == true) {
     565           tty->print("-------------------------------------------------------------------------------\n");
     566           tty->print("StringTable resized from %d to %d\n", stats.old_size, stats.new_size);
     567           tty->print("-------------------------------------------------------------------------------\n");
     568         }
     569         if (event.should_commit() == true) {
     570           event.set_oldSize(stats.old_size);
     571           event.set_newSize(stats.new_size);
     572           event.commit();
     573         }
     574       }
     575     }
     576   }
     577
     578   if (HashtablesResizeSystemDictionary == true) {
     579     ResizeHashtableStats stats;
     580     {
     581       //tty->print("SystemDictionary ");
     582       TraceTime t6("resize_table for SystemDictionary", TraceSafepointCleanupTime);
     583       EventSystemDictionaryResize event;
     584       stats = SystemDictionary::the_table()->resize_table(SystemDictionary_lock,
     585                                                             HashtablesResizeSystemDictionaryTriggerLoadFactor,
     586                                                               HashtablesResizeSystemDictionaryDesiredLoadFactor);
     587       if (stats.resized == true) {
     588         if (PrintStringTableStatisticsTimeline == true) {
     589           tty->print("-------------------------------------------------------------------------------\n");
     590           tty->print("SystemDictionary resized from %d to %d\n", stats.old_size, stats.new_size);
     591           tty->print("-------------------------------------------------------------------------------\n");
     592         }
     593         if (event.should_commit() == true) {
     594           event.set_oldSize(stats.old_size);
     595           event.set_newSize(stats.new_size);
     596           event.commit();
     597         }
     598       }
     599     }
     600   }
     601
     602   {
     603     bool wants = false;
     604     bool reported = false;
     605     static int skip = 1000;
     606     if (PrintSymbolTableStatisticsTimeline == true) {
     607       wants = true;
     608       static int number_of_entries = 0;
     609       if (SymbolTable::the_table()->number_of_entries() > (skip+number_of_entries)) {
     610         number_of_entries = SymbolTable::the_table()->number_of_entries();
     611         tty->print("SymbolTable      %9d:%6.3f:%lld\n", number_of_entries, (float)number_of_entries/(float)SymbolTable::the_table()->table_size(), os::javaTimeNanos());
     612         reported = true;
     613       }
     614     }
     615     if (PrintStringTableStatisticsTimeline == true) {
     616       wants = true;
     617       static int number_of_entries = 0;
     618       if (StringTable::the_table()->number_of_entries() > (skip+number_of_entries)) {
     619         number_of_entries = StringTable::the_table()->number_of_entries();
     620         tty->print("StringTable      %9d:%6.3f:%lld\n", number_of_entries, (float)number_of_entries/(float)SymbolTable::the_table()->table_size(), os::javaTimeNanos());
     621         reported = true;
     622       }
     623     }
     624     if (PrintSystemDictionaryStatisticsTimeline == true) {
     625       wants = true;
     626       static int number_of_entries = 0;
     627       if (SystemDictionary::the_table()->number_of_entries() > (skip+number_of_entries)) {
     628         number_of_entries = SystemDictionary::the_table()->number_of_entries();
     629         tty->print("SystemDictionary %9d:%6.3f:%lld\n", number_of_entries, (float)number_of_entries/(float)SymbolTable::the_table()->table_size(), os::javaTimeNanos());
     630         reported = true;
     631       }
     632     }
     633     if ((wants == true) && (reported == false)) {
     634       tty->print(".\n");
     635     }
     636   }
     637
     638   if (SymbolTable::needs_rehashing()) {
     639     TraceTime t8("rehashing symbol table", TraceSafepointCleanupTime);
     640     SymbolTable::rehash_table();
     641   }
     642
     643   if (StringTable::needs_rehashing()) {
     644     TraceTime t9("rehashing string table", TraceSafepointCleanupTime);
     645     StringTable::rehash_table();
     646   }
     647
     648   // rotate log files?
     649   if (UseGCLogFileRotation) {
     650     gclog_or_tty->rotate_log(false);
     651   }
     652
     653   {
     654     // CMS delays purging the CLDG until the beginning of the next safepoint and to
     655     // make sure concurrent sweep is done
     656     TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
     657     ClassLoaderDataGraph::purge_if_needed();
     658   }
     659 }
     660
     661
     662 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
     663   switch(state) {
     664   case _thread_in_native:
     665     // native threads are safe if they have no java stack or have walkable stack
     666     return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
     667
     668    // blocked threads should have already have walkable stack
     669   case _thread_blocked:
     670     assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
     671     return true;
     672
     673   default:
     674     return false;
     675   }
     676 }
     677
     678
     679 // See if the thread is running inside a lazy critical native and
     680 // update the thread critical count if so.  Also set a suspend flag to
     681 // cause the native wrapper to return into the JVM to do the unlock
     682 // once the native finishes.
     683 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
     684   if (state == _thread_in_native &&
     685       thread->has_last_Java_frame() &&
     686       thread->frame_anchor()->walkable()) {
     687     // This thread might be in a critical native nmethod so look at
     688     // the top of the stack and increment the critical count if it
     689     // is.
     690     frame wrapper_frame = thread->last_frame();
     691     CodeBlob* stub_cb = wrapper_frame.cb();
     692     if (stub_cb != NULL &&
     693         stub_cb->is_nmethod() &&
     694         stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
     695       // A thread could potentially be in a critical native across
     696       // more than one safepoint, so only update the critical state on
     697       // the first one.  When it returns it will perform the unlock.
     698       if (!thread->do_critical_native_unlock()) {
     699 #ifdef ASSERT
     700         if (!thread->in_critical()) {
     701           GC_locker::increment_debug_jni_lock_count();
     702         }
     703 #endif
     704         thread->enter_critical();
     705         // Make sure the native wrapper calls back on return to
     706         // perform the needed critical unlock.
     707         thread->set_critical_native_unlock();
     708       }
     709     }
     710   }
     711 }
     712
     713
     714
     715 // -------------------------------------------------------------------------------------------------------
     716 // Implementation of Safepoint callback point
     717
     718 void SafepointSynchronize::block(JavaThread *thread) {
     719   assert(thread != NULL, "thread must be set");
     720   assert(thread->is_Java_thread(), "not a Java thread");
     721
     722   // Threads shouldn't block if they are in the middle of printing, but...
     723   ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
     724
     725   // Only bail from the block() call if the thread is gone from the
     726   // thread list; starting to exit should still block.
     727   if (thread->is_terminated()) {
     728      // block current thread if we come here from native code when VM is gone
     729      thread->block_if_vm_exited();
     730
     731      // otherwise do nothing
     732      return;
     733   }
     734
     735   JavaThreadState state = thread->thread_state();
     736   thread->frame_anchor()->make_walkable(thread);
     737
     738   // Check that we have a valid thread_state at this point
     739   switch(state) {
     740     case _thread_in_vm_trans:
     741     case _thread_in_Java:        // From compiled code
     742
     743       // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
     744       // we pretend we are still in the VM.
     745       thread->set_thread_state(_thread_in_vm);
     746
     747       if (is_synchronizing()) {
     748          Atomic::inc (&TryingToBlock) ;
     749       }
     750
     751       // We will always be holding the Safepoint_lock when we are examine the state
     752       // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
     753       // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
     754       Safepoint_lock->lock_without_safepoint_check();
     755       if (is_synchronizing()) {
     756         // Decrement the number of threads to wait for and signal vm thread
     757         assert(_waiting_to_block > 0, "sanity check");
     758         _waiting_to_block--;
     759         thread->safepoint_state()->set_has_called_back(true);
     760
     761         DEBUG_ONLY(thread->set_visited_for_critical_count(true));
     762         if (thread->in_critical()) {
     763           // Notice that this thread is in a critical section
     764           increment_jni_active_count();
     765         }
     766
     767         // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
     768         if (_waiting_to_block == 0) {
     769           Safepoint_lock->notify_all();
     770         }
     771       }
     772
     773       // We transition the thread to state _thread_blocked here, but
     774       // we can't do our usual check for external suspension and then
     775       // self-suspend after the lock_without_safepoint_check() call
     776       // below because we are often called during transitions while
     777       // we hold different locks. That would leave us suspended while
     778       // holding a resource which results in deadlocks.
     779       thread->set_thread_state(_thread_blocked);
     780       Safepoint_lock->unlock();
     781
     782       // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
     783       // the entire safepoint, the threads will all line up here during the safepoint.
     784       Threads_lock->lock_without_safepoint_check();
     785       // restore original state. This is important if the thread comes from compiled code, so it
     786       // will continue to execute with the _thread_in_Java state.
     787       thread->set_thread_state(state);
     788       Threads_lock->unlock();
     789       break;
     790
     791     case _thread_in_native_trans:
     792     case _thread_blocked_trans:
     793     case _thread_new_trans:
     794       if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
     795         thread->print_thread_state();
     796         fatal("Deadlock in safepoint code.  "
     797               "Should have called back to the VM before blocking.");
     798       }
     799
     800       // We transition the thread to state _thread_blocked here, but
     801       // we can't do our usual check for external suspension and then
     802       // self-suspend after the lock_without_safepoint_check() call
     803       // below because we are often called during transitions while
     804       // we hold different locks. That would leave us suspended while
     805       // holding a resource which results in deadlocks.
     806       thread->set_thread_state(_thread_blocked);
     807
     808       // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
     809       // the safepoint code might still be waiting for it to block. We need to change the state here,
     810       // so it can see that it is at a safepoint.
     811
     812       // Block until the safepoint operation is completed.
     813       Threads_lock->lock_without_safepoint_check();
     814
     815       // Restore state
     816       thread->set_thread_state(state);
     817
     818       Threads_lock->unlock();
     819       break;
     820
     821     default:
     822      fatal(err_msg("Illegal threadstate encountered: %d", state));
     823   }
     824
     825   // Check for pending. async. exceptions or suspends - except if the
     826   // thread was blocked inside the VM. has_special_runtime_exit_condition()
     827   // is called last since it grabs a lock and we only want to do that when
     828   // we must.
     829   //
     830   // Note: we never deliver an async exception at a polling point as the
     831   // compiler may not have an exception handler for it. The polling
     832   // code will notice the async and deoptimize and the exception will
     833   // be delivered. (Polling at a return point is ok though). Sure is
     834   // a lot of bother for a deprecated feature...
     835   //
     836   // We don't deliver an async exception if the thread state is
     837   // _thread_in_native_trans so JNI functions won't be called with
     838   // a surprising pending exception. If the thread state is going back to java,
     839   // async exception is checked in check_special_condition_for_native_trans().
     840
     841   if (state != _thread_blocked_trans &&
     842       state != _thread_in_vm_trans &&
     843       thread->has_special_runtime_exit_condition()) {
     844     thread->handle_special_runtime_exit_condition(
     845       !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
     846   }
     847 }
     848
     849 // ------------------------------------------------------------------------------------------------------
     850 // Exception handlers
     851
     852 #ifndef PRODUCT
     853
     854 #ifdef SPARC
     855
     856 #ifdef _LP64
     857 #define PTR_PAD ""
     858 #else
     859 #define PTR_PAD "        "
     860 #endif
     861
     862 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
     863   bool is_oop = newptr ? (cast_to_oop(newptr))->is_oop() : false;
     864   tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
     865                 oldptr, wasoop?"oop":"   ", oldptr == newptr ? ' ' : '!',
     866                 newptr, is_oop?"oop":"   ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":"     "));
     867 }
     868
     869 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
     870   bool is_oop = newptr ? (cast_to_oop(newptr))->is_oop() : false;
     871   tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
     872                 oldptr, wasoop?"oop":"   ", oldptr == newptr ? ' ' : '!',
     873                 newptr, is_oop?"oop":"   ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":"     "));
     874 }
     875
     876 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
     877 #ifdef _LP64
     878   tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
     879   const int incr = 1;           // Increment to skip a long, in units of intptr_t
     880 #else
     881   tty->print_cr("--------+--address-+------before-----------+-------after----------+");
     882   const int incr = 2;           // Increment to skip a long, in units of intptr_t
     883 #endif
     884   tty->print_cr("---SP---|");
     885   for( int i=0; i<16; i++ ) {
     886     tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
     887   tty->print_cr("--------|");
     888   for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
     889     tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
     890   tty->print("     pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
     891   tty->print_cr("--------|");
     892   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;
     893   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;
     894   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;
     895   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;
     896   tty->print_cr(" FSR    |"PTR_FORMAT" "PTR64_FORMAT"       "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
     897   old_sp += incr; new_sp += incr; was_oops += incr;
     898   // Skip the floats
     899   tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
     900   tty->print_cr("---FP---|");
     901   old_sp += incr*32;  new_sp += incr*32;  was_oops += incr*32;
     902   for( int i2=0; i2<16; i2++ ) {
     903     tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
     904   tty->cr();
     905 }
     906 #endif  // SPARC
     907 #endif  // PRODUCT
     908
     909
     910 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
     911   assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
     912   assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
     913   assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
     914
     915   // Uncomment this to get some serious before/after printing of the
     916   // Sparc safepoint-blob frame structure.
     917   /*
     918   intptr_t* sp = thread->last_Java_sp();
     919   intptr_t stack_copy[150];
     920   for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
     921   bool was_oops[150];
     922   for( int i=0; i<150; i++ )
     923     was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
     924   */
     925
     926   if (ShowSafepointMsgs) {
     927     tty->print("handle_polling_page_exception: ");
     928   }
     929
     930   if (PrintSafepointStatistics) {
     931     inc_page_trap_count();
     932   }
     933
     934   ThreadSafepointState* state = thread->safepoint_state();
     935
     936   state->handle_polling_page_exception();
     937   // print_me(sp,stack_copy,was_oops);
     938 }
     939
     940
     941 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
     942   if (!timeout_error_printed) {
     943     timeout_error_printed = true;
     944     // Print out the thread infor which didn't reach the safepoint for debugging
     945     // purposes (useful when there are lots of threads in the debugger).
     946     tty->cr();
     947     tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
     948     if (reason ==  _spinning_timeout) {
     949       tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
     950     } else if (reason == _blocking_timeout) {
     951       tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
     952     }
     953
     954     tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
     955     ThreadSafepointState *cur_state;
     956     ResourceMark rm;
     957     for(JavaThread *cur_thread = Threads::first(); cur_thread;
     958         cur_thread = cur_thread->next()) {
     959       cur_state = cur_thread->safepoint_state();
     960
     961       if (cur_thread->thread_state() != _thread_blocked &&
     962           ((reason == _spinning_timeout && cur_state->is_running()) ||
     963            (reason == _blocking_timeout && !cur_state->has_called_back()))) {
     964         tty->print("# ");
     965         cur_thread->print();
     966         tty->cr();
     967       }
     968     }
     969     tty->print_cr("# SafepointSynchronize::begin: (End of list)");
     970   }
     971
     972   // To debug the long safepoint, specify both DieOnSafepointTimeout &
     973   // ShowMessageBoxOnError.
     974   if (DieOnSafepointTimeout) {
     975     char msg[1024];
     976     VM_Operation *op = VMThread::vm_operation();
     977     sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
     978             SafepointTimeoutDelay,
     979             op != NULL ? op->name() : "no vm operation");
     980     fatal(msg);
     981   }
     982 }
     983
     984
     985 // -------------------------------------------------------------------------------------------------------
     986 // Implementation of ThreadSafepointState
     987
     988 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
     989   _thread = thread;
     990   _type   = _running;
     991   _has_called_back = false;
     992   _at_poll_safepoint = false;
     993 }
     994
     995 void ThreadSafepointState::create(JavaThread *thread) {
     996   ThreadSafepointState *state = new ThreadSafepointState(thread);
     997   thread->set_safepoint_state(state);
     998 }
     999
    1000 void ThreadSafepointState::destroy(JavaThread *thread) {
    1001   if (thread->safepoint_state()) {
    1002     delete(thread->safepoint_state());
    1003     thread->set_safepoint_state(NULL);
    1004   }
    1005 }
    1006
    1007 void ThreadSafepointState::examine_state_of_thread() {
    1008   assert(is_running(), "better be running or just have hit safepoint poll");
    1009
    1010   JavaThreadState state = _thread->thread_state();
    1011
    1012   // Save the state at the start of safepoint processing.
    1013   _orig_thread_state = state;
    1014
    1015   // Check for a thread that is suspended. Note that thread resume tries
    1016   // to grab the Threads_lock which we own here, so a thread cannot be
    1017   // resumed during safepoint synchronization.
    1018
    1019   // We check to see if this thread is suspended without locking to
    1020   // avoid deadlocking with a third thread that is waiting for this
    1021   // thread to be suspended. The third thread can notice the safepoint
    1022   // that we're trying to start at the beginning of its SR_lock->wait()
    1023   // call. If that happens, then the third thread will block on the
    1024   // safepoint while still holding the underlying SR_lock. We won't be
    1025   // able to get the SR_lock and we'll deadlock.
    1026   //
    1027   // We don't need to grab the SR_lock here for two reasons:
    1028   // 1) The suspend flags are both volatile and are set with an
    1029   //    Atomic::cmpxchg() call so we should see the suspended
    1030   //    state right away.
    1031   // 2) We're being called from the safepoint polling loop; if
    1032   //    we don't see the suspended state on this iteration, then
    1033   //    we'll come around again.
    1034   //
    1035   bool is_suspended = _thread->is_ext_suspended();
    1036   if (is_suspended) {
    1037     roll_forward(_at_safepoint);
    1038     return;
    1039   }
    1040
    1041   // Some JavaThread states have an initial safepoint state of
    1042   // running, but are actually at a safepoint. We will happily
    1043   // agree and update the safepoint state here.
    1044   if (SafepointSynchronize::safepoint_safe(_thread, state)) {
    1045     SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
    1046     roll_forward(_at_safepoint);
    1047     return;
    1048   }
    1049
    1050   if (state == _thread_in_vm) {
    1051     roll_forward(_call_back);
    1052     return;
    1053   }
    1054
    1055   // All other thread states will continue to run until they
    1056   // transition and self-block in state _blocked
    1057   // Safepoint polling in compiled code causes the Java threads to do the same.
    1058   // Note: new threads may require a malloc so they must be allowed to finish
    1059
    1060   assert(is_running(), "examine_state_of_thread on non-running thread");
    1061   return;
    1062 }
    1063
    1064 // Returns true is thread could not be rolled forward at present position.
    1065 void ThreadSafepointState::roll_forward(suspend_type type) {
    1066   _type = type;
    1067
    1068   switch(_type) {
    1069     case _at_safepoint:
    1070       SafepointSynchronize::signal_thread_at_safepoint();
    1071       DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
    1072       if (_thread->in_critical()) {
    1073         // Notice that this thread is in a critical section
    1074         SafepointSynchronize::increment_jni_active_count();
    1075       }
    1076       break;
    1077
    1078     case _call_back:
    1079       set_has_called_back(false);
    1080       break;
    1081
    1082     case _running:
    1083     default:
    1084       ShouldNotReachHere();
    1085   }
    1086 }
    1087
    1088 void ThreadSafepointState::restart() {
    1089   switch(type()) {
    1090     case _at_safepoint:
    1091     case _call_back:
    1092       break;
    1093
    1094     case _running:
    1095     default:
    1096        tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
    1097                       _thread, _type);
    1098        _thread->print();
    1099       ShouldNotReachHere();
    1100   }
    1101   _type = _running;
    1102   set_has_called_back(false);
    1103 }
    1104
    1105
    1106 void ThreadSafepointState::print_on(outputStream *st) const {
    1107   const char *s;
    1108
    1109   switch(_type) {
    1110     case _running                : s = "_running";              break;
    1111     case _at_safepoint           : s = "_at_safepoint";         break;
    1112     case _call_back              : s = "_call_back";            break;
    1113     default:
    1114       ShouldNotReachHere();
    1115   }
    1116
    1117   st->print_cr("Thread: " INTPTR_FORMAT
    1118               "  [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
    1119                _thread, _thread->osthread()->thread_id(), s, _has_called_back,
    1120                _at_poll_safepoint);
    1121
    1122   _thread->print_thread_state_on(st);
    1123 }
    1124
    1125
    1126 // ---------------------------------------------------------------------------------------------------------------------
    1127
    1128 // Block the thread at the safepoint poll or poll return.
    1129 void ThreadSafepointState::handle_polling_page_exception() {
    1130
    1131   // Check state.  block() will set thread state to thread_in_vm which will
    1132   // cause the safepoint state _type to become _call_back.
    1133   assert(type() == ThreadSafepointState::_running,
    1134          "polling page exception on thread not running state");
    1135
    1136   // Step 1: Find the nmethod from the return address
    1137   if (ShowSafepointMsgs && Verbose) {
    1138     tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
    1139   }
    1140   address real_return_addr = thread()->saved_exception_pc();
    1141
    1142   CodeBlob *cb = CodeCache::find_blob(real_return_addr);
    1143   assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
    1144   nmethod* nm = (nmethod*)cb;
    1145
    1146   // Find frame of caller
    1147   frame stub_fr = thread()->last_frame();
    1148   CodeBlob* stub_cb = stub_fr.cb();
    1149   assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
    1150   RegisterMap map(thread(), true);
    1151   frame caller_fr = stub_fr.sender(&map);
    1152
    1153   // Should only be poll_return or poll
    1154   assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
    1155
    1156   // This is a poll immediately before a return. The exception handling code
    1157   // has already had the effect of causing the return to occur, so the execution
    1158   // will continue immediately after the call. In addition, the oopmap at the
    1159   // return point does not mark the return value as an oop (if it is), so
    1160   // it needs a handle here to be updated.
    1161   if( nm->is_at_poll_return(real_return_addr) ) {
    1162     // See if return type is an oop.
    1163     bool return_oop = nm->method()->is_returning_oop();
    1164     Handle return_value;
    1165     if (return_oop) {
    1166       // The oop result has been saved on the stack together with all
    1167       // the other registers. In order to preserve it over GCs we need
    1168       // to keep it in a handle.
    1169       oop result = caller_fr.saved_oop_result(&map);
    1170       assert(result == NULL || result->is_oop(), "must be oop");
    1171       return_value = Handle(thread(), result);
    1172       assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
    1173     }
    1174
    1175     // Block the thread
    1176     SafepointSynchronize::block(thread());
    1177
    1178     // restore oop result, if any
    1179     if (return_oop) {
    1180       caller_fr.set_saved_oop_result(&map, return_value());
    1181     }
    1182   }
    1183
    1184   // This is a safepoint poll. Verify the return address and block.
    1185   else {
    1186     set_at_poll_safepoint(true);
    1187
    1188     // verify the blob built the "return address" correctly
    1189     assert(real_return_addr == caller_fr.pc(), "must match");
    1190
    1191     // Block the thread
    1192     SafepointSynchronize::block(thread());
    1193     set_at_poll_safepoint(false);
    1194
    1195     // If we have a pending async exception deoptimize the frame
    1196     // as otherwise we may never deliver it.
    1197     if (thread()->has_async_condition()) {
    1198       ThreadInVMfromJavaNoAsyncException __tiv(thread());
    1199       Deoptimization::deoptimize_frame(thread(), caller_fr.id());
    1200     }
    1201
    1202     // If an exception has been installed we must check for a pending deoptimization
    1203     // Deoptimize frame if exception has been thrown.
    1204
    1205     if (thread()->has_pending_exception() ) {
    1206       RegisterMap map(thread(), true);
    1207       frame caller_fr = stub_fr.sender(&map);
    1208       if (caller_fr.is_deoptimized_frame()) {
    1209         // The exception patch will destroy registers that are still
    1210         // live and will be needed during deoptimization. Defer the
    1211         // Async exception should have defered the exception until the
    1212         // next safepoint which will be detected when we get into
    1213         // the interpreter so if we have an exception now things
    1214         // are messed up.
    1215
    1216         fatal("Exception installed and deoptimization is pending");
    1217       }
    1218     }
    1219   }
    1220 }
    1221
    1222
    1223 //
    1224 //                     Statistics & Instrumentations
    1225 //
    1226 SafepointSynchronize::SafepointStats*  SafepointSynchronize::_safepoint_stats = NULL;
    1227 jlong  SafepointSynchronize::_safepoint_begin_time = 0;
    1228 int    SafepointSynchronize::_cur_stat_index = 0;
    1229 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
    1230 julong SafepointSynchronize::_coalesced_vmop_count = 0;
    1231 jlong  SafepointSynchronize::_max_sync_time = 0;
    1232 jlong  SafepointSynchronize::_max_vmop_time = 0;
    1233 float  SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
    1234
    1235 static jlong  cleanup_end_time = 0;
    1236 static bool   need_to_track_page_armed_status = false;
    1237 static bool   init_done = false;
    1238
    1239 // Helper method to print the header.
    1240 static void print_header() {
    1241   tty->print("         vmop                    "
    1242              "[threads: total initially_running wait_to_block]    ");
    1243   tty->print("[time: spin block sync cleanup vmop] ");
    1244
    1245   // no page armed status printed out if it is always armed.
    1246   if (need_to_track_page_armed_status) {
    1247     tty->print("page_armed ");
    1248   }
    1249
    1250   tty->print_cr("page_trap_count");
    1251 }
    1252
    1253 void SafepointSynchronize::deferred_initialize_stat() {
    1254   if (init_done) return;
    1255
    1256   if (PrintSafepointStatisticsCount <= 0) {
    1257     fatal("Wrong PrintSafepointStatisticsCount");
    1258   }
    1259
    1260   // If PrintSafepointStatisticsTimeout is specified, the statistics data will
    1261   // be printed right away, in which case, _safepoint_stats will regress to
    1262   // a single element array. Otherwise, it is a circular ring buffer with default
    1263   // size of PrintSafepointStatisticsCount.
    1264   int stats_array_size;
    1265   if (PrintSafepointStatisticsTimeout > 0) {
    1266     stats_array_size = 1;
    1267     PrintSafepointStatistics = true;
    1268   } else {
    1269     stats_array_size = PrintSafepointStatisticsCount;
    1270   }
    1271   _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
    1272                                                  * sizeof(SafepointStats), mtInternal);
    1273   guarantee(_safepoint_stats != NULL,
    1274             "not enough memory for safepoint instrumentation data");
    1275
    1276   if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
    1277     need_to_track_page_armed_status = true;
    1278   }
    1279   init_done = true;
    1280 }
    1281
    1282 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
    1283   assert(init_done, "safepoint statistics array hasn't been initialized");
    1284   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
    1285
    1286   spstat->_time_stamp = _ts_of_current_safepoint;
    1287
    1288   VM_Operation *op = VMThread::vm_operation();
    1289   spstat->_vmop_type = (op != NULL ? op->type() : -1);
    1290   if (op != NULL) {
    1291     _safepoint_reasons[spstat->_vmop_type]++;
    1292   }
    1293
    1294   spstat->_nof_total_threads = nof_threads;
    1295   spstat->_nof_initial_running_threads = nof_running;
    1296   spstat->_nof_threads_hit_page_trap = 0;
    1297
    1298   // Records the start time of spinning. The real time spent on spinning
    1299   // will be adjusted when spin is done. Same trick is applied for time
    1300   // spent on waiting for threads to block.
    1301   if (nof_running != 0) {
    1302     spstat->_time_to_spin = os::javaTimeNanos();
    1303   }  else {
    1304     spstat->_time_to_spin = 0;
    1305   }
    1306 }
    1307
    1308 void SafepointSynchronize::update_statistics_on_spin_end() {
    1309   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
    1310
    1311   jlong cur_time = os::javaTimeNanos();
    1312
    1313   spstat->_nof_threads_wait_to_block = _waiting_to_block;
    1314   if (spstat->_nof_initial_running_threads != 0) {
    1315     spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
    1316   }
    1317
    1318   if (need_to_track_page_armed_status) {
    1319     spstat->_page_armed = (PageArmed == 1);
    1320   }
    1321
    1322   // Records the start time of waiting for to block. Updated when block is done.
    1323   if (_waiting_to_block != 0) {
    1324     spstat->_time_to_wait_to_block = cur_time;
    1325   } else {
    1326     spstat->_time_to_wait_to_block = 0;
    1327   }
    1328 }
    1329
    1330 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
    1331   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
    1332
    1333   if (spstat->_nof_threads_wait_to_block != 0) {
    1334     spstat->_time_to_wait_to_block = end_time -
    1335       spstat->_time_to_wait_to_block;
    1336   }
    1337
    1338   // Records the end time of sync which will be used to calculate the total
    1339   // vm operation time. Again, the real time spending in syncing will be deducted
    1340   // from the start of the sync time later when end_statistics is called.
    1341   spstat->_time_to_sync = end_time - _safepoint_begin_time;
    1342   if (spstat->_time_to_sync > _max_sync_time) {
    1343     _max_sync_time = spstat->_time_to_sync;
    1344   }
    1345
    1346   spstat->_time_to_do_cleanups = end_time;
    1347 }
    1348
    1349 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
    1350   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
    1351
    1352   // Record how long spent in cleanup tasks.
    1353   spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
    1354
    1355   cleanup_end_time = end_time;
    1356 }
    1357
    1358 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
    1359   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
    1360
    1361   // Update the vm operation time.
    1362   spstat->_time_to_exec_vmop = vmop_end_time -  cleanup_end_time;
    1363   if (spstat->_time_to_exec_vmop > _max_vmop_time) {
    1364     _max_vmop_time = spstat->_time_to_exec_vmop;
    1365   }
    1366   // Only the sync time longer than the specified
    1367   // PrintSafepointStatisticsTimeout will be printed out right away.
    1368   // By default, it is -1 meaning all samples will be put into the list.
    1369   if ( PrintSafepointStatisticsTimeout > 0) {
    1370     if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
    1371       print_statistics();
    1372     }
    1373   } else {
    1374     // The safepoint statistics will be printed out when the _safepoin_stats
    1375     // array fills up.
    1376     if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
    1377       print_statistics();
    1378       _cur_stat_index = 0;
    1379     } else {
    1380       _cur_stat_index++;
    1381     }
    1382   }
    1383 }
    1384
    1385 void SafepointSynchronize::print_statistics() {
    1386   SafepointStats* sstats = _safepoint_stats;
    1387
    1388   for (int index = 0; index <= _cur_stat_index; index++) {
    1389     if (index % 30 == 0) {
    1390       print_header();
    1391     }
    1392     sstats = &_safepoint_stats[index];
    1393     tty->print("%.3f: ", sstats->_time_stamp);
    1394     tty->print("%-26s       ["
    1395                INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
    1396                "    ]    ",
    1397                sstats->_vmop_type == -1 ? "no vm operation" :
    1398                VM_Operation::name(sstats->_vmop_type),
    1399                sstats->_nof_total_threads,
    1400                sstats->_nof_initial_running_threads,
    1401                sstats->_nof_threads_wait_to_block);
    1402     // "/ MICROUNITS " is to convert the unit from nanos to millis.
    1403     tty->print("  ["
    1404                INT64_FORMAT_W(6)INT64_FORMAT_W(6)
    1405                INT64_FORMAT_W(6)INT64_FORMAT_W(6)
    1406                INT64_FORMAT_W(6)"    ]  ",
    1407                sstats->_time_to_spin / MICROUNITS,
    1408                sstats->_time_to_wait_to_block / MICROUNITS,
    1409                sstats->_time_to_sync / MICROUNITS,
    1410                sstats->_time_to_do_cleanups / MICROUNITS,
    1411                sstats->_time_to_exec_vmop / MICROUNITS);
    1412
    1413     if (need_to_track_page_armed_status) {
    1414       tty->print(INT32_FORMAT"         ", sstats->_page_armed);
    1415     }
    1416     tty->print_cr(INT32_FORMAT"   ", sstats->_nof_threads_hit_page_trap);
    1417   }
    1418 }
    1419
    1420 // This method will be called when VM exits. It will first call
    1421 // print_statistics to print out the rest of the sampling.  Then
    1422 // it tries to summarize the sampling.
    1423 void SafepointSynchronize::print_stat_on_exit() {
    1424   if (_safepoint_stats == NULL) return;
    1425
    1426   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
    1427
    1428   // During VM exit, end_statistics may not get called and in that
    1429   // case, if the sync time is less than PrintSafepointStatisticsTimeout,
    1430   // don't print it out.
    1431   // Approximate the vm op time.
    1432   _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
    1433     os::javaTimeNanos() - cleanup_end_time;
    1434
    1435   if ( PrintSafepointStatisticsTimeout < 0 ||
    1436        spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
    1437     print_statistics();
    1438   }
    1439   tty->cr();
    1440
    1441   // Print out polling page sampling status.
    1442   if (!need_to_track_page_armed_status) {
    1443     if (UseCompilerSafepoints) {
    1444       tty->print_cr("Polling page always armed");
    1445     }
    1446   } else {
    1447     tty->print_cr("Defer polling page loop count = %d\n",
    1448                  DeferPollingPageLoopCount);
    1449   }
    1450
    1451   for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
    1452     if (_safepoint_reasons[index] != 0) {
    1453       tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
    1454                     _safepoint_reasons[index]);
    1455     }
    1456   }
    1457
    1458   tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
    1459                 _coalesced_vmop_count);
    1460   tty->print_cr("Maximum sync time  "INT64_FORMAT_W(5)" ms",
    1461                 _max_sync_time / MICROUNITS);
    1462   tty->print_cr("Maximum vm operation time (except for Exit VM operation)  "
    1463                 INT64_FORMAT_W(5)" ms",
    1464                 _max_vmop_time / MICROUNITS);
    1465 }
    1466
    1467 // ------------------------------------------------------------------------------------------------
    1468 // Non-product code
    1469
    1470 #ifndef PRODUCT
    1471
    1472 void SafepointSynchronize::print_state() {
    1473   if (_state == _not_synchronized) {
    1474     tty->print_cr("not synchronized");
    1475   } else if (_state == _synchronizing || _state == _synchronized) {
    1476     tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
    1477                   "synchronized");
    1478
    1479     for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
    1480        cur->safepoint_state()->print();
    1481     }
    1482   }
    1483 }
    1484
    1485 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
    1486   if (ShowSafepointMsgs) {
    1487     va_list ap;
    1488     va_start(ap, format);
    1489     tty->vprint_cr(format, ap);
    1490     va_end(ap);
    1491   }
    1492 }
    1493
    1494 #endif // !PRODUCT
    --- EOF ---