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