1 /*
   2  * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/symbolTable.hpp"
  27 #include "classfile/systemDictionary.hpp"
  28 #include "code/codeCache.hpp"
  29 #include "code/icBuffer.hpp"
  30 #include "code/nmethod.hpp"
  31 #include "code/pcDesc.hpp"
  32 #include "code/scopeDesc.hpp"
  33 #include "gc_interface/collectedHeap.hpp"
  34 #include "interpreter/interpreter.hpp"
  35 #include "memory/resourceArea.hpp"
  36 #include "memory/universe.inline.hpp"
  37 #include "oops/oop.inline.hpp"
  38 #include "oops/symbol.hpp"
  39 #include "runtime/compilationPolicy.hpp"
  40 #include "runtime/deoptimization.hpp"
  41 #include "runtime/frame.inline.hpp"
  42 #include "runtime/interfaceSupport.hpp"
  43 #include "runtime/mutexLocker.hpp"
  44 #include "runtime/osThread.hpp"
  45 #include "runtime/safepoint.hpp"
  46 #include "runtime/signature.hpp"
  47 #include "runtime/stubCodeGenerator.hpp"
  48 #include "runtime/stubRoutines.hpp"
  49 #include "runtime/sweeper.hpp"
  50 #include "runtime/synchronizer.hpp"
  51 #include "runtime/thread.inline.hpp"
  52 #include "services/memTracker.hpp"
  53 #include "services/runtimeService.hpp"
  54 #include "utilities/events.hpp"
  55 #include "utilities/macros.hpp"
  56 #ifdef TARGET_ARCH_x86
  57 # include "nativeInst_x86.hpp"
  58 # include "vmreg_x86.inline.hpp"
  59 #endif
  60 #ifdef TARGET_ARCH_sparc
  61 # include "nativeInst_sparc.hpp"
  62 # include "vmreg_sparc.inline.hpp"
  63 #endif
  64 #ifdef TARGET_ARCH_zero
  65 # include "nativeInst_zero.hpp"
  66 # include "vmreg_zero.inline.hpp"
  67 #endif
  68 #ifdef TARGET_ARCH_arm
  69 # include "nativeInst_arm.hpp"
  70 # include "vmreg_arm.inline.hpp"
  71 #endif
  72 #ifdef TARGET_ARCH_ppc
  73 # include "nativeInst_ppc.hpp"
  74 # include "vmreg_ppc.inline.hpp"
  75 #endif
  76 #if INCLUDE_ALL_GCS
  77 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
  78 #include "gc_implementation/shared/concurrentGCThread.hpp"
  79 #endif // INCLUDE_ALL_GCS
  80 #ifdef COMPILER1
  81 #include "c1/c1_globals.hpp"
  82 #endif
  83 
  84 // --------------------------------------------------------------------------------------------------
  85 // Implementation of Safepoint begin/end
  86 
  87 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
  88 volatile int  SafepointSynchronize::_waiting_to_block = 0;
  89 volatile int SafepointSynchronize::_safepoint_counter = 0;
  90 int SafepointSynchronize::_current_jni_active_count = 0;
  91 long  SafepointSynchronize::_end_of_last_safepoint = 0;
  92 static volatile int PageArmed = 0 ;        // safepoint polling page is RO|RW vs PROT_NONE
  93 static volatile int TryingToBlock = 0 ;    // proximate value -- for advisory use only
  94 static bool timeout_error_printed = false;
  95 
  96 // Roll all threads forward to a safepoint and suspend them all
  97 void SafepointSynchronize::begin() {
  98 
  99   Thread* myThread = Thread::current();
 100   assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
 101 
 102   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
 103     _safepoint_begin_time = os::javaTimeNanos();
 104     _ts_of_current_safepoint = tty->time_stamp().seconds();
 105   }
 106 
 107 #if INCLUDE_ALL_GCS
 108   if (UseConcMarkSweepGC) {
 109     // In the future we should investigate whether CMS can use the
 110     // more-general mechanism below.  DLD (01/05).
 111     ConcurrentMarkSweepThread::synchronize(false);
 112   } else if (UseG1GC) {
 113     ConcurrentGCThread::safepoint_synchronize();
 114   }
 115 #endif // INCLUDE_ALL_GCS
 116 
 117   // By getting the Threads_lock, we assure that no threads are about to start or
 118   // exit. It is released again in SafepointSynchronize::end().
 119   Threads_lock->lock();
 120 
 121   assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
 122 
 123   int nof_threads = Threads::number_of_threads();
 124 
 125   if (TraceSafepoint) {
 126     tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
 127   }
 128 
 129   RuntimeService::record_safepoint_begin();
 130 
 131   MutexLocker mu(Safepoint_lock);
 132 
 133   // Reset the count of active JNI critical threads
 134   _current_jni_active_count = 0;
 135 
 136   // Set number of threads to wait for, before we initiate the callbacks
 137   _waiting_to_block = nof_threads;
 138   TryingToBlock     = 0 ;
 139   int still_running = nof_threads;
 140 
 141   // Save the starting time, so that it can be compared to see if this has taken
 142   // too long to complete.
 143   jlong safepoint_limit_time;
 144   timeout_error_printed = false;
 145 
 146   // PrintSafepointStatisticsTimeout can be specified separately. When
 147   // specified, PrintSafepointStatistics will be set to true in
 148   // deferred_initialize_stat method. The initialization has to be done
 149   // early enough to avoid any races. See bug 6880029 for details.
 150   if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
 151     deferred_initialize_stat();
 152   }
 153 
 154   // Begin the process of bringing the system to a safepoint.
 155   // Java threads can be in several different states and are
 156   // stopped by different mechanisms:
 157   //
 158   //  1. Running interpreted
 159   //     The interpeter dispatch table is changed to force it to
 160   //     check for a safepoint condition between bytecodes.
 161   //  2. Running in native code
 162   //     When returning from the native code, a Java thread must check
 163   //     the safepoint _state to see if we must block.  If the
 164   //     VM thread sees a Java thread in native, it does
 165   //     not wait for this thread to block.  The order of the memory
 166   //     writes and reads of both the safepoint state and the Java
 167   //     threads state is critical.  In order to guarantee that the
 168   //     memory writes are serialized with respect to each other,
 169   //     the VM thread issues a memory barrier instruction
 170   //     (on MP systems).  In order to avoid the overhead of issuing
 171   //     a memory barrier for each Java thread making native calls, each Java
 172   //     thread performs a write to a single memory page after changing
 173   //     the thread state.  The VM thread performs a sequence of
 174   //     mprotect OS calls which forces all previous writes from all
 175   //     Java threads to be serialized.  This is done in the
 176   //     os::serialize_thread_states() call.  This has proven to be
 177   //     much more efficient than executing a membar instruction
 178   //     on every call to native code.
 179   //  3. Running compiled Code
 180   //     Compiled code reads a global (Safepoint Polling) page that
 181   //     is set to fault if we are trying to get to a safepoint.
 182   //  4. Blocked
 183   //     A thread which is blocked will not be allowed to return from the
 184   //     block condition until the safepoint operation is complete.
 185   //  5. In VM or Transitioning between states
 186   //     If a Java thread is currently running in the VM or transitioning
 187   //     between states, the safepointing code will wait for the thread to
 188   //     block itself when it attempts transitions to a new state.
 189   //
 190   _state            = _synchronizing;
 191   OrderAccess::fence();
 192 
 193   // Flush all thread states to memory
 194   if (!UseMembar) {
 195     os::serialize_thread_states();
 196   }
 197 
 198   // Make interpreter safepoint aware
 199   Interpreter::notice_safepoints();
 200 
 201   if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
 202     // Make polling safepoint aware
 203     guarantee (PageArmed == 0, "invariant") ;
 204     PageArmed = 1 ;
 205     os::make_polling_page_unreadable();
 206   }
 207 
 208   // Consider using active_processor_count() ... but that call is expensive.
 209   int ncpus = os::processor_count() ;
 210 
 211 #ifdef ASSERT
 212   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 213     assert(cur->safepoint_state()->is_running(), "Illegal initial state");
 214     // Clear the visited flag to ensure that the critical counts are collected properly.
 215     cur->set_visited_for_critical_count(false);
 216   }
 217 #endif // ASSERT
 218 
 219   if (SafepointTimeout)
 220     safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
 221 
 222   // Iterate through all threads until it have been determined how to stop them all at a safepoint
 223   unsigned int iterations = 0;
 224   int steps = 0 ;
 225   while(still_running > 0) {
 226     for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 227       assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
 228       ThreadSafepointState *cur_state = cur->safepoint_state();
 229       if (cur_state->is_running()) {
 230         cur_state->examine_state_of_thread();
 231         if (!cur_state->is_running()) {
 232            still_running--;
 233            // consider adjusting steps downward:
 234            //   steps = 0
 235            //   steps -= NNN
 236            //   steps >>= 1
 237            //   steps = MIN(steps, 2000-100)
 238            //   if (iterations != 0) steps -= NNN
 239         }
 240         if (TraceSafepoint && Verbose) cur_state->print();
 241       }
 242     }
 243 
 244     if (PrintSafepointStatistics && iterations == 0) {
 245       begin_statistics(nof_threads, still_running);
 246     }
 247 
 248     if (still_running > 0) {
 249       // Check for if it takes to long
 250       if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
 251         print_safepoint_timeout(_spinning_timeout);
 252       }
 253 
 254       // Spin to avoid context switching.
 255       // There's a tension between allowing the mutators to run (and rendezvous)
 256       // vs spinning.  As the VM thread spins, wasting cycles, it consumes CPU that
 257       // a mutator might otherwise use profitably to reach a safepoint.  Excessive
 258       // spinning by the VM thread on a saturated system can increase rendezvous latency.
 259       // Blocking or yielding incur their own penalties in the form of context switching
 260       // and the resultant loss of $ residency.
 261       //
 262       // Further complicating matters is that yield() does not work as naively expected
 263       // on many platforms -- yield() does not guarantee that any other ready threads
 264       // will run.   As such we revert yield_all() after some number of iterations.
 265       // Yield_all() is implemented as a short unconditional sleep on some platforms.
 266       // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
 267       // can actually increase the time it takes the VM thread to detect that a system-wide
 268       // stop-the-world safepoint has been reached.  In a pathological scenario such as that
 269       // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
 270       // In that case the mutators will be stalled waiting for the safepoint to complete and the
 271       // the VMthread will be sleeping, waiting for the mutators to rendezvous.  The VMthread
 272       // will eventually wake up and detect that all mutators are safe, at which point
 273       // we'll again make progress.
 274       //
 275       // Beware too that that the VMThread typically runs at elevated priority.
 276       // Its default priority is higher than the default mutator priority.
 277       // Obviously, this complicates spinning.
 278       //
 279       // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
 280       // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
 281       //
 282       // See the comments in synchronizer.cpp for additional remarks on spinning.
 283       //
 284       // In the future we might:
 285       // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
 286       //    This is tricky as the path used by a thread exiting the JVM (say on
 287       //    on JNI call-out) simply stores into its state field.  The burden
 288       //    is placed on the VM thread, which must poll (spin).
 289       // 2. Find something useful to do while spinning.  If the safepoint is GC-related
 290       //    we might aggressively scan the stacks of threads that are already safe.
 291       // 3. Use Solaris schedctl to examine the state of the still-running mutators.
 292       //    If all the mutators are ONPROC there's no reason to sleep or yield.
 293       // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
 294       // 5. Check system saturation.  If the system is not fully saturated then
 295       //    simply spin and avoid sleep/yield.
 296       // 6. As still-running mutators rendezvous they could unpark the sleeping
 297       //    VMthread.  This works well for still-running mutators that become
 298       //    safe.  The VMthread must still poll for mutators that call-out.
 299       // 7. Drive the policy on time-since-begin instead of iterations.
 300       // 8. Consider making the spin duration a function of the # of CPUs:
 301       //    Spin = (((ncpus-1) * M) + K) + F(still_running)
 302       //    Alternately, instead of counting iterations of the outer loop
 303       //    we could count the # of threads visited in the inner loop, above.
 304       // 9. On windows consider using the return value from SwitchThreadTo()
 305       //    to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
 306 
 307       if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
 308          guarantee (PageArmed == 0, "invariant") ;
 309          PageArmed = 1 ;
 310          os::make_polling_page_unreadable();
 311       }
 312 
 313       // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
 314       // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
 315       ++steps ;
 316       if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
 317         SpinPause() ;     // MP-Polite spin
 318       } else
 319       if (steps < DeferThrSuspendLoopCount) {
 320         os::NakedYield() ;
 321       } else {
 322         os::yield_all(steps) ;
 323         // Alternately, the VM thread could transiently depress its scheduling priority or
 324         // transiently increase the priority of the tardy mutator(s).
 325       }
 326 
 327       iterations ++ ;
 328     }
 329     assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
 330   }
 331   assert(still_running == 0, "sanity check");
 332 
 333   if (PrintSafepointStatistics) {
 334     update_statistics_on_spin_end();
 335   }
 336 
 337   // wait until all threads are stopped
 338   while (_waiting_to_block > 0) {
 339     if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
 340     if (!SafepointTimeout || timeout_error_printed) {
 341       Safepoint_lock->wait(true);  // true, means with no safepoint checks
 342     } else {
 343       // Compute remaining time
 344       jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
 345 
 346       // If there is no remaining time, then there is an error
 347       if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
 348         print_safepoint_timeout(_blocking_timeout);
 349       }
 350     }
 351   }
 352   assert(_waiting_to_block == 0, "sanity check");
 353 
 354 #ifndef PRODUCT
 355   if (SafepointTimeout) {
 356     jlong current_time = os::javaTimeNanos();
 357     if (safepoint_limit_time < current_time) {
 358       tty->print_cr("# SafepointSynchronize: Finished after "
 359                     INT64_FORMAT_W(6) " ms",
 360                     ((current_time - safepoint_limit_time) / MICROUNITS +
 361                      SafepointTimeoutDelay));
 362     }
 363   }
 364 #endif
 365 
 366   assert((_safepoint_counter & 0x1) == 0, "must be even");
 367   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 368   _safepoint_counter ++;
 369 
 370   // Record state
 371   _state = _synchronized;
 372 
 373   OrderAccess::fence();
 374 
 375 #ifdef ASSERT
 376   for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
 377     // make sure all the threads were visited
 378     assert(cur->was_visited_for_critical_count(), "missed a thread");
 379   }
 380 #endif // ASSERT
 381 
 382   // Update the count of active JNI critical regions
 383   GC_locker::set_jni_lock_count(_current_jni_active_count);
 384 
 385   if (TraceSafepoint) {
 386     VM_Operation *op = VMThread::vm_operation();
 387     tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
 388   }
 389 
 390   RuntimeService::record_safepoint_synchronized();
 391   if (PrintSafepointStatistics) {
 392     update_statistics_on_sync_end(os::javaTimeNanos());
 393   }
 394 
 395   // Call stuff that needs to be run when a safepoint is just about to be completed
 396   do_cleanup_tasks();
 397 
 398   if (PrintSafepointStatistics) {
 399     // Record how much time spend on the above cleanup tasks
 400     update_statistics_on_cleanup_end(os::javaTimeNanos());
 401   }
 402 }
 403 
 404 // Wake up all threads, so they are ready to resume execution after the safepoint
 405 // operation has been carried out
 406 void SafepointSynchronize::end() {
 407 
 408   assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
 409   assert((_safepoint_counter & 0x1) == 1, "must be odd");
 410   _safepoint_counter ++;
 411   // memory fence isn't required here since an odd _safepoint_counter
 412   // value can do no harm and a fence is issued below anyway.
 413 
 414   DEBUG_ONLY(Thread* myThread = Thread::current();)
 415   assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
 416 
 417   if (PrintSafepointStatistics) {
 418     end_statistics(os::javaTimeNanos());
 419   }
 420 
 421 #ifdef ASSERT
 422   // A pending_exception cannot be installed during a safepoint.  The threads
 423   // may install an async exception after they come back from a safepoint into
 424   // pending_exception after they unblock.  But that should happen later.
 425   for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
 426     assert (!(cur->has_pending_exception() &&
 427               cur->safepoint_state()->is_at_poll_safepoint()),
 428             "safepoint installed a pending exception");
 429   }
 430 #endif // ASSERT
 431 
 432   if (PageArmed) {
 433     // Make polling safepoint aware
 434     os::make_polling_page_readable();
 435     PageArmed = 0 ;
 436   }
 437 
 438   // Remove safepoint check from interpreter
 439   Interpreter::ignore_safepoints();
 440 
 441   {
 442     MutexLocker mu(Safepoint_lock);
 443 
 444     assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
 445 
 446     // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
 447     // when they get restarted.
 448     _state = _not_synchronized;
 449     OrderAccess::fence();
 450 
 451     if (TraceSafepoint) {
 452        tty->print_cr("Leaving safepoint region");
 453     }
 454 
 455     // Start suspended threads
 456     for(JavaThread *current = Threads::first(); current; current = current->next()) {
 457       // A problem occurring on Solaris is when attempting to restart threads
 458       // the first #cpus - 1 go well, but then the VMThread is preempted when we get
 459       // to the next one (since it has been running the longest).  We then have
 460       // to wait for a cpu to become available before we can continue restarting
 461       // threads.
 462       // FIXME: This causes the performance of the VM to degrade when active and with
 463       // large numbers of threads.  Apparently this is due to the synchronous nature
 464       // of suspending threads.
 465       //
 466       // TODO-FIXME: the comments above are vestigial and no longer apply.
 467       // Furthermore, using solaris' schedctl in this particular context confers no benefit
 468       if (VMThreadHintNoPreempt) {
 469         os::hint_no_preempt();
 470       }
 471       ThreadSafepointState* cur_state = current->safepoint_state();
 472       assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
 473       cur_state->restart();
 474       assert(cur_state->is_running(), "safepoint state has not been reset");
 475     }
 476 
 477     RuntimeService::record_safepoint_end();
 478 
 479     // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
 480     // blocked in signal_thread_blocked
 481     Threads_lock->unlock();
 482 
 483   }
 484 #if INCLUDE_ALL_GCS
 485   // If there are any concurrent GC threads resume them.
 486   if (UseConcMarkSweepGC) {
 487     ConcurrentMarkSweepThread::desynchronize(false);
 488   } else if (UseG1GC) {
 489     ConcurrentGCThread::safepoint_desynchronize();
 490   }
 491 #endif // INCLUDE_ALL_GCS
 492   // record this time so VMThread can keep track how much time has elasped
 493   // since last safepoint.
 494   _end_of_last_safepoint = os::javaTimeMillis();
 495 }
 496 
 497 bool SafepointSynchronize::is_cleanup_needed() {
 498   // Need a safepoint if some inline cache buffers is non-empty
 499   if (!InlineCacheBuffer::is_empty()) return true;
 500   return false;
 501 }
 502 
 503 
 504 
 505 // Various cleaning tasks that should be done periodically at safepoints
 506 void SafepointSynchronize::do_cleanup_tasks() {
 507   {
 508     TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
 509     ObjectSynchronizer::deflate_idle_monitors();
 510   }
 511 
 512   {
 513     TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
 514     InlineCacheBuffer::update_inline_caches();
 515   }
 516   {
 517     TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
 518     CompilationPolicy::policy()->do_safepoint_work();
 519   }
 520 
 521   {
 522     TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
 523     NMethodSweeper::mark_active_nmethods();
 524   }
 525 
 526   if (SymbolTable::needs_rehashing()) {
 527     TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
 528     SymbolTable::rehash_table();
 529   }
 530 
 531   if (StringTable::needs_rehashing()) {
 532     TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
 533     StringTable::rehash_table();
 534   }
 535 
 536   // rotate log files?
 537   if (UseGCLogFileRotation) {
 538     gclog_or_tty->rotate_log();
 539   }
 540 
 541   if (MemTracker::is_on()) {
 542     MemTracker::sync();
 543   }
 544 }
 545 
 546 
 547 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
 548   switch(state) {
 549   case _thread_in_native:
 550     // native threads are safe if they have no java stack or have walkable stack
 551     return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
 552 
 553    // blocked threads should have already have walkable stack
 554   case _thread_blocked:
 555     assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
 556     return true;
 557 
 558   default:
 559     return false;
 560   }
 561 }
 562 
 563 
 564 // See if the thread is running inside a lazy critical native and
 565 // update the thread critical count if so.  Also set a suspend flag to
 566 // cause the native wrapper to return into the JVM to do the unlock
 567 // once the native finishes.
 568 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
 569   if (state == _thread_in_native &&
 570       thread->has_last_Java_frame() &&
 571       thread->frame_anchor()->walkable()) {
 572     // This thread might be in a critical native nmethod so look at
 573     // the top of the stack and increment the critical count if it
 574     // is.
 575     frame wrapper_frame = thread->last_frame();
 576     CodeBlob* stub_cb = wrapper_frame.cb();
 577     if (stub_cb != NULL &&
 578         stub_cb->is_nmethod() &&
 579         stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
 580       // A thread could potentially be in a critical native across
 581       // more than one safepoint, so only update the critical state on
 582       // the first one.  When it returns it will perform the unlock.
 583       if (!thread->do_critical_native_unlock()) {
 584 #ifdef ASSERT
 585         if (!thread->in_critical()) {
 586           GC_locker::increment_debug_jni_lock_count();
 587         }
 588 #endif
 589         thread->enter_critical();
 590         // Make sure the native wrapper calls back on return to
 591         // perform the needed critical unlock.
 592         thread->set_critical_native_unlock();
 593       }
 594     }
 595   }
 596 }
 597 
 598 
 599 
 600 // -------------------------------------------------------------------------------------------------------
 601 // Implementation of Safepoint callback point
 602 
 603 void SafepointSynchronize::block(JavaThread *thread) {
 604   assert(thread != NULL, "thread must be set");
 605   assert(thread->is_Java_thread(), "not a Java thread");
 606 
 607   // Threads shouldn't block if they are in the middle of printing, but...
 608   ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
 609 
 610   // Only bail from the block() call if the thread is gone from the
 611   // thread list; starting to exit should still block.
 612   if (thread->is_terminated()) {
 613      // block current thread if we come here from native code when VM is gone
 614      thread->block_if_vm_exited();
 615 
 616      // otherwise do nothing
 617      return;
 618   }
 619 
 620   JavaThreadState state = thread->thread_state();
 621   thread->frame_anchor()->make_walkable(thread);
 622 
 623   // Check that we have a valid thread_state at this point
 624   switch(state) {
 625     case _thread_in_vm_trans:
 626     case _thread_in_Java:        // From compiled code
 627 
 628       // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
 629       // we pretend we are still in the VM.
 630       thread->set_thread_state(_thread_in_vm);
 631 
 632       if (is_synchronizing()) {
 633          Atomic::inc (&TryingToBlock) ;
 634       }
 635 
 636       // We will always be holding the Safepoint_lock when we are examine the state
 637       // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
 638       // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
 639       Safepoint_lock->lock_without_safepoint_check();
 640       if (is_synchronizing()) {
 641         // Decrement the number of threads to wait for and signal vm thread
 642         assert(_waiting_to_block > 0, "sanity check");
 643         _waiting_to_block--;
 644         thread->safepoint_state()->set_has_called_back(true);
 645 
 646         DEBUG_ONLY(thread->set_visited_for_critical_count(true));
 647         if (thread->in_critical()) {
 648           // Notice that this thread is in a critical section
 649           increment_jni_active_count();
 650         }
 651 
 652         // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
 653         if (_waiting_to_block == 0) {
 654           Safepoint_lock->notify_all();
 655         }
 656       }
 657 
 658       // We transition the thread to state _thread_blocked here, but
 659       // we can't do our usual check for external suspension and then
 660       // self-suspend after the lock_without_safepoint_check() call
 661       // below because we are often called during transitions while
 662       // we hold different locks. That would leave us suspended while
 663       // holding a resource which results in deadlocks.
 664       thread->set_thread_state(_thread_blocked);
 665       Safepoint_lock->unlock();
 666 
 667       // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
 668       // the entire safepoint, the threads will all line up here during the safepoint.
 669       Threads_lock->lock_without_safepoint_check();
 670       // restore original state. This is important if the thread comes from compiled code, so it
 671       // will continue to execute with the _thread_in_Java state.
 672       thread->set_thread_state(state);
 673       Threads_lock->unlock();
 674       break;
 675 
 676     case _thread_in_native_trans:
 677     case _thread_blocked_trans:
 678     case _thread_new_trans:
 679       if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
 680         thread->print_thread_state();
 681         fatal("Deadlock in safepoint code.  "
 682               "Should have called back to the VM before blocking.");
 683       }
 684 
 685       // We transition the thread to state _thread_blocked here, but
 686       // we can't do our usual check for external suspension and then
 687       // self-suspend after the lock_without_safepoint_check() call
 688       // below because we are often called during transitions while
 689       // we hold different locks. That would leave us suspended while
 690       // holding a resource which results in deadlocks.
 691       thread->set_thread_state(_thread_blocked);
 692 
 693       // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
 694       // the safepoint code might still be waiting for it to block. We need to change the state here,
 695       // so it can see that it is at a safepoint.
 696 
 697       // Block until the safepoint operation is completed.
 698       Threads_lock->lock_without_safepoint_check();
 699 
 700       // Restore state
 701       thread->set_thread_state(state);
 702 
 703       Threads_lock->unlock();
 704       break;
 705 
 706     default:
 707      fatal(err_msg("Illegal threadstate encountered: %d", state));
 708   }
 709 
 710   // Check for pending. async. exceptions or suspends - except if the
 711   // thread was blocked inside the VM. has_special_runtime_exit_condition()
 712   // is called last since it grabs a lock and we only want to do that when
 713   // we must.
 714   //
 715   // Note: we never deliver an async exception at a polling point as the
 716   // compiler may not have an exception handler for it. The polling
 717   // code will notice the async and deoptimize and the exception will
 718   // be delivered. (Polling at a return point is ok though). Sure is
 719   // a lot of bother for a deprecated feature...
 720   //
 721   // We don't deliver an async exception if the thread state is
 722   // _thread_in_native_trans so JNI functions won't be called with
 723   // a surprising pending exception. If the thread state is going back to java,
 724   // async exception is checked in check_special_condition_for_native_trans().
 725 
 726   if (state != _thread_blocked_trans &&
 727       state != _thread_in_vm_trans &&
 728       thread->has_special_runtime_exit_condition()) {
 729     thread->handle_special_runtime_exit_condition(
 730       !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
 731   }
 732 }
 733 
 734 // ------------------------------------------------------------------------------------------------------
 735 // Exception handlers
 736 
 737 #ifndef PRODUCT
 738 
 739 #ifdef SPARC
 740 
 741 #ifdef _LP64
 742 #define PTR_PAD ""
 743 #else
 744 #define PTR_PAD "        "
 745 #endif
 746 
 747 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
 748   bool is_oop = newptr ? ((oop)newptr)->is_oop() : false;
 749   tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
 750                 oldptr, wasoop?"oop":"   ", oldptr == newptr ? ' ' : '!',
 751                 newptr, is_oop?"oop":"   ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":"     "));
 752 }
 753 
 754 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
 755   bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false;
 756   tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
 757                 oldptr, wasoop?"oop":"   ", oldptr == newptr ? ' ' : '!',
 758                 newptr, is_oop?"oop":"   ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":"     "));
 759 }
 760 
 761 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
 762 #ifdef _LP64
 763   tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
 764   const int incr = 1;           // Increment to skip a long, in units of intptr_t
 765 #else
 766   tty->print_cr("--------+--address-+------before-----------+-------after----------+");
 767   const int incr = 2;           // Increment to skip a long, in units of intptr_t
 768 #endif
 769   tty->print_cr("---SP---|");
 770   for( int i=0; i<16; i++ ) {
 771     tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
 772   tty->print_cr("--------|");
 773   for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
 774     tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
 775   tty->print("     pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
 776   tty->print_cr("--------|");
 777   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;
 778   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;
 779   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;
 780   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;
 781   tty->print_cr(" FSR    |"PTR_FORMAT" "PTR64_FORMAT"       "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
 782   old_sp += incr; new_sp += incr; was_oops += incr;
 783   // Skip the floats
 784   tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
 785   tty->print_cr("---FP---|");
 786   old_sp += incr*32;  new_sp += incr*32;  was_oops += incr*32;
 787   for( int i2=0; i2<16; i2++ ) {
 788     tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
 789   tty->print_cr("");
 790 }
 791 #endif  // SPARC
 792 #endif  // PRODUCT
 793 
 794 
 795 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
 796   assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
 797   assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
 798   assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
 799 
 800   // Uncomment this to get some serious before/after printing of the
 801   // Sparc safepoint-blob frame structure.
 802   /*
 803   intptr_t* sp = thread->last_Java_sp();
 804   intptr_t stack_copy[150];
 805   for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
 806   bool was_oops[150];
 807   for( int i=0; i<150; i++ )
 808     was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
 809   */
 810 
 811   if (ShowSafepointMsgs) {
 812     tty->print("handle_polling_page_exception: ");
 813   }
 814 
 815   if (PrintSafepointStatistics) {
 816     inc_page_trap_count();
 817   }
 818 
 819   ThreadSafepointState* state = thread->safepoint_state();
 820 
 821   state->handle_polling_page_exception();
 822   // print_me(sp,stack_copy,was_oops);
 823 }
 824 
 825 
 826 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
 827   if (!timeout_error_printed) {
 828     timeout_error_printed = true;
 829     // Print out the thread infor which didn't reach the safepoint for debugging
 830     // purposes (useful when there are lots of threads in the debugger).
 831     tty->print_cr("");
 832     tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
 833     if (reason ==  _spinning_timeout) {
 834       tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
 835     } else if (reason == _blocking_timeout) {
 836       tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
 837     }
 838 
 839     tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
 840     ThreadSafepointState *cur_state;
 841     ResourceMark rm;
 842     for(JavaThread *cur_thread = Threads::first(); cur_thread;
 843         cur_thread = cur_thread->next()) {
 844       cur_state = cur_thread->safepoint_state();
 845 
 846       if (cur_thread->thread_state() != _thread_blocked &&
 847           ((reason == _spinning_timeout && cur_state->is_running()) ||
 848            (reason == _blocking_timeout && !cur_state->has_called_back()))) {
 849         tty->print("# ");
 850         cur_thread->print();
 851         tty->print_cr("");
 852       }
 853     }
 854     tty->print_cr("# SafepointSynchronize::begin: (End of list)");
 855   }
 856 
 857   // To debug the long safepoint, specify both DieOnSafepointTimeout &
 858   // ShowMessageBoxOnError.
 859   if (DieOnSafepointTimeout) {
 860     char msg[1024];
 861     VM_Operation *op = VMThread::vm_operation();
 862     sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
 863             SafepointTimeoutDelay,
 864             op != NULL ? op->name() : "no vm operation");
 865     fatal(msg);
 866   }
 867 }
 868 
 869 
 870 // -------------------------------------------------------------------------------------------------------
 871 // Implementation of ThreadSafepointState
 872 
 873 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
 874   _thread = thread;
 875   _type   = _running;
 876   _has_called_back = false;
 877   _at_poll_safepoint = false;
 878 }
 879 
 880 void ThreadSafepointState::create(JavaThread *thread) {
 881   ThreadSafepointState *state = new ThreadSafepointState(thread);
 882   thread->set_safepoint_state(state);
 883 }
 884 
 885 void ThreadSafepointState::destroy(JavaThread *thread) {
 886   if (thread->safepoint_state()) {
 887     delete(thread->safepoint_state());
 888     thread->set_safepoint_state(NULL);
 889   }
 890 }
 891 
 892 void ThreadSafepointState::examine_state_of_thread() {
 893   assert(is_running(), "better be running or just have hit safepoint poll");
 894 
 895   JavaThreadState state = _thread->thread_state();
 896 
 897   // Save the state at the start of safepoint processing.
 898   _orig_thread_state = state;
 899 
 900   // Check for a thread that is suspended. Note that thread resume tries
 901   // to grab the Threads_lock which we own here, so a thread cannot be
 902   // resumed during safepoint synchronization.
 903 
 904   // We check to see if this thread is suspended without locking to
 905   // avoid deadlocking with a third thread that is waiting for this
 906   // thread to be suspended. The third thread can notice the safepoint
 907   // that we're trying to start at the beginning of its SR_lock->wait()
 908   // call. If that happens, then the third thread will block on the
 909   // safepoint while still holding the underlying SR_lock. We won't be
 910   // able to get the SR_lock and we'll deadlock.
 911   //
 912   // We don't need to grab the SR_lock here for two reasons:
 913   // 1) The suspend flags are both volatile and are set with an
 914   //    Atomic::cmpxchg() call so we should see the suspended
 915   //    state right away.
 916   // 2) We're being called from the safepoint polling loop; if
 917   //    we don't see the suspended state on this iteration, then
 918   //    we'll come around again.
 919   //
 920   bool is_suspended = _thread->is_ext_suspended();
 921   if (is_suspended) {
 922     roll_forward(_at_safepoint);
 923     return;
 924   }
 925 
 926   // Some JavaThread states have an initial safepoint state of
 927   // running, but are actually at a safepoint. We will happily
 928   // agree and update the safepoint state here.
 929   if (SafepointSynchronize::safepoint_safe(_thread, state)) {
 930     SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
 931     roll_forward(_at_safepoint);
 932     return;
 933   }
 934 
 935   if (state == _thread_in_vm) {
 936     roll_forward(_call_back);
 937     return;
 938   }
 939 
 940   // All other thread states will continue to run until they
 941   // transition and self-block in state _blocked
 942   // Safepoint polling in compiled code causes the Java threads to do the same.
 943   // Note: new threads may require a malloc so they must be allowed to finish
 944 
 945   assert(is_running(), "examine_state_of_thread on non-running thread");
 946   return;
 947 }
 948 
 949 // Returns true is thread could not be rolled forward at present position.
 950 void ThreadSafepointState::roll_forward(suspend_type type) {
 951   _type = type;
 952 
 953   switch(_type) {
 954     case _at_safepoint:
 955       SafepointSynchronize::signal_thread_at_safepoint();
 956       DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
 957       if (_thread->in_critical()) {
 958         // Notice that this thread is in a critical section
 959         SafepointSynchronize::increment_jni_active_count();
 960       }
 961       break;
 962 
 963     case _call_back:
 964       set_has_called_back(false);
 965       break;
 966 
 967     case _running:
 968     default:
 969       ShouldNotReachHere();
 970   }
 971 }
 972 
 973 void ThreadSafepointState::restart() {
 974   switch(type()) {
 975     case _at_safepoint:
 976     case _call_back:
 977       break;
 978 
 979     case _running:
 980     default:
 981        tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
 982                       _thread, _type);
 983        _thread->print();
 984       ShouldNotReachHere();
 985   }
 986   _type = _running;
 987   set_has_called_back(false);
 988 }
 989 
 990 
 991 void ThreadSafepointState::print_on(outputStream *st) const {
 992   const char *s;
 993 
 994   switch(_type) {
 995     case _running                : s = "_running";              break;
 996     case _at_safepoint           : s = "_at_safepoint";         break;
 997     case _call_back              : s = "_call_back";            break;
 998     default:
 999       ShouldNotReachHere();
1000   }
1001 
1002   st->print_cr("Thread: " INTPTR_FORMAT
1003               "  [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1004                _thread, _thread->osthread()->thread_id(), s, _has_called_back,
1005                _at_poll_safepoint);
1006 
1007   _thread->print_thread_state_on(st);
1008 }
1009 
1010 
1011 // ---------------------------------------------------------------------------------------------------------------------
1012 
1013 // Block the thread at the safepoint poll or poll return.
1014 void ThreadSafepointState::handle_polling_page_exception() {
1015 
1016   // Check state.  block() will set thread state to thread_in_vm which will
1017   // cause the safepoint state _type to become _call_back.
1018   assert(type() == ThreadSafepointState::_running,
1019          "polling page exception on thread not running state");
1020 
1021   // Step 1: Find the nmethod from the return address
1022   if (ShowSafepointMsgs && Verbose) {
1023     tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
1024   }
1025   address real_return_addr = thread()->saved_exception_pc();
1026 
1027   CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1028   assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
1029   nmethod* nm = (nmethod*)cb;
1030 
1031   // Find frame of caller
1032   frame stub_fr = thread()->last_frame();
1033   CodeBlob* stub_cb = stub_fr.cb();
1034   assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1035   RegisterMap map(thread(), true);
1036   frame caller_fr = stub_fr.sender(&map);
1037 
1038   // Should only be poll_return or poll
1039   assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1040 
1041   // This is a poll immediately before a return. The exception handling code
1042   // has already had the effect of causing the return to occur, so the execution
1043   // will continue immediately after the call. In addition, the oopmap at the
1044   // return point does not mark the return value as an oop (if it is), so
1045   // it needs a handle here to be updated.
1046   if( nm->is_at_poll_return(real_return_addr) ) {
1047     // See if return type is an oop.
1048     bool return_oop = nm->method()->is_returning_oop();
1049     Handle return_value;
1050     if (return_oop) {
1051       // The oop result has been saved on the stack together with all
1052       // the other registers. In order to preserve it over GCs we need
1053       // to keep it in a handle.
1054       oop result = caller_fr.saved_oop_result(&map);
1055       assert(result == NULL || result->is_oop(), "must be oop");
1056       return_value = Handle(thread(), result);
1057       assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1058     }
1059 
1060     // Block the thread
1061     SafepointSynchronize::block(thread());
1062 
1063     // restore oop result, if any
1064     if (return_oop) {
1065       caller_fr.set_saved_oop_result(&map, return_value());
1066     }
1067   }
1068 
1069   // This is a safepoint poll. Verify the return address and block.
1070   else {
1071     set_at_poll_safepoint(true);
1072 
1073     // verify the blob built the "return address" correctly
1074     assert(real_return_addr == caller_fr.pc(), "must match");
1075 
1076     // Block the thread
1077     SafepointSynchronize::block(thread());
1078     set_at_poll_safepoint(false);
1079 
1080     // If we have a pending async exception deoptimize the frame
1081     // as otherwise we may never deliver it.
1082     if (thread()->has_async_condition()) {
1083       ThreadInVMfromJavaNoAsyncException __tiv(thread());
1084       Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1085     }
1086 
1087     // If an exception has been installed we must check for a pending deoptimization
1088     // Deoptimize frame if exception has been thrown.
1089 
1090     if (thread()->has_pending_exception() ) {
1091       RegisterMap map(thread(), true);
1092       frame caller_fr = stub_fr.sender(&map);
1093       if (caller_fr.is_deoptimized_frame()) {
1094         // The exception patch will destroy registers that are still
1095         // live and will be needed during deoptimization. Defer the
1096         // Async exception should have defered the exception until the
1097         // next safepoint which will be detected when we get into
1098         // the interpreter so if we have an exception now things
1099         // are messed up.
1100 
1101         fatal("Exception installed and deoptimization is pending");
1102       }
1103     }
1104   }
1105 }
1106 
1107 
1108 //
1109 //                     Statistics & Instrumentations
1110 //
1111 SafepointSynchronize::SafepointStats*  SafepointSynchronize::_safepoint_stats = NULL;
1112 jlong  SafepointSynchronize::_safepoint_begin_time = 0;
1113 int    SafepointSynchronize::_cur_stat_index = 0;
1114 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1115 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1116 jlong  SafepointSynchronize::_max_sync_time = 0;
1117 jlong  SafepointSynchronize::_max_vmop_time = 0;
1118 float  SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1119 
1120 static jlong  cleanup_end_time = 0;
1121 static bool   need_to_track_page_armed_status = false;
1122 static bool   init_done = false;
1123 
1124 // Helper method to print the header.
1125 static void print_header() {
1126   tty->print("         vmop                    "
1127              "[threads: total initially_running wait_to_block]    ");
1128   tty->print("[time: spin block sync cleanup vmop] ");
1129 
1130   // no page armed status printed out if it is always armed.
1131   if (need_to_track_page_armed_status) {
1132     tty->print("page_armed ");
1133   }
1134 
1135   tty->print_cr("page_trap_count");
1136 }
1137 
1138 void SafepointSynchronize::deferred_initialize_stat() {
1139   if (init_done) return;
1140 
1141   if (PrintSafepointStatisticsCount <= 0) {
1142     fatal("Wrong PrintSafepointStatisticsCount");
1143   }
1144 
1145   // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1146   // be printed right away, in which case, _safepoint_stats will regress to
1147   // a single element array. Otherwise, it is a circular ring buffer with default
1148   // size of PrintSafepointStatisticsCount.
1149   int stats_array_size;
1150   if (PrintSafepointStatisticsTimeout > 0) {
1151     stats_array_size = 1;
1152     PrintSafepointStatistics = true;
1153   } else {
1154     stats_array_size = PrintSafepointStatisticsCount;
1155   }
1156   _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1157                                                  * sizeof(SafepointStats), mtInternal);
1158   guarantee(_safepoint_stats != NULL,
1159             "not enough memory for safepoint instrumentation data");
1160 
1161   if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1162     need_to_track_page_armed_status = true;
1163   }
1164   init_done = true;
1165 }
1166 
1167 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1168   assert(init_done, "safepoint statistics array hasn't been initialized");
1169   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1170 
1171   spstat->_time_stamp = _ts_of_current_safepoint;
1172 
1173   VM_Operation *op = VMThread::vm_operation();
1174   spstat->_vmop_type = (op != NULL ? op->type() : -1);
1175   if (op != NULL) {
1176     _safepoint_reasons[spstat->_vmop_type]++;
1177   }
1178 
1179   spstat->_nof_total_threads = nof_threads;
1180   spstat->_nof_initial_running_threads = nof_running;
1181   spstat->_nof_threads_hit_page_trap = 0;
1182 
1183   // Records the start time of spinning. The real time spent on spinning
1184   // will be adjusted when spin is done. Same trick is applied for time
1185   // spent on waiting for threads to block.
1186   if (nof_running != 0) {
1187     spstat->_time_to_spin = os::javaTimeNanos();
1188   }  else {
1189     spstat->_time_to_spin = 0;
1190   }
1191 }
1192 
1193 void SafepointSynchronize::update_statistics_on_spin_end() {
1194   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1195 
1196   jlong cur_time = os::javaTimeNanos();
1197 
1198   spstat->_nof_threads_wait_to_block = _waiting_to_block;
1199   if (spstat->_nof_initial_running_threads != 0) {
1200     spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1201   }
1202 
1203   if (need_to_track_page_armed_status) {
1204     spstat->_page_armed = (PageArmed == 1);
1205   }
1206 
1207   // Records the start time of waiting for to block. Updated when block is done.
1208   if (_waiting_to_block != 0) {
1209     spstat->_time_to_wait_to_block = cur_time;
1210   } else {
1211     spstat->_time_to_wait_to_block = 0;
1212   }
1213 }
1214 
1215 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1216   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1217 
1218   if (spstat->_nof_threads_wait_to_block != 0) {
1219     spstat->_time_to_wait_to_block = end_time -
1220       spstat->_time_to_wait_to_block;
1221   }
1222 
1223   // Records the end time of sync which will be used to calculate the total
1224   // vm operation time. Again, the real time spending in syncing will be deducted
1225   // from the start of the sync time later when end_statistics is called.
1226   spstat->_time_to_sync = end_time - _safepoint_begin_time;
1227   if (spstat->_time_to_sync > _max_sync_time) {
1228     _max_sync_time = spstat->_time_to_sync;
1229   }
1230 
1231   spstat->_time_to_do_cleanups = end_time;
1232 }
1233 
1234 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1235   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1236 
1237   // Record how long spent in cleanup tasks.
1238   spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1239 
1240   cleanup_end_time = end_time;
1241 }
1242 
1243 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1244   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1245 
1246   // Update the vm operation time.
1247   spstat->_time_to_exec_vmop = vmop_end_time -  cleanup_end_time;
1248   if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1249     _max_vmop_time = spstat->_time_to_exec_vmop;
1250   }
1251   // Only the sync time longer than the specified
1252   // PrintSafepointStatisticsTimeout will be printed out right away.
1253   // By default, it is -1 meaning all samples will be put into the list.
1254   if ( PrintSafepointStatisticsTimeout > 0) {
1255     if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1256       print_statistics();
1257     }
1258   } else {
1259     // The safepoint statistics will be printed out when the _safepoin_stats
1260     // array fills up.
1261     if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1262       print_statistics();
1263       _cur_stat_index = 0;
1264     } else {
1265       _cur_stat_index++;
1266     }
1267   }
1268 }
1269 
1270 void SafepointSynchronize::print_statistics() {
1271   SafepointStats* sstats = _safepoint_stats;
1272 
1273   for (int index = 0; index <= _cur_stat_index; index++) {
1274     if (index % 30 == 0) {
1275       print_header();
1276     }
1277     sstats = &_safepoint_stats[index];
1278     tty->print("%.3f: ", sstats->_time_stamp);
1279     tty->print("%-26s       ["
1280                INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1281                "    ]    ",
1282                sstats->_vmop_type == -1 ? "no vm operation" :
1283                VM_Operation::name(sstats->_vmop_type),
1284                sstats->_nof_total_threads,
1285                sstats->_nof_initial_running_threads,
1286                sstats->_nof_threads_wait_to_block);
1287     // "/ MICROUNITS " is to convert the unit from nanos to millis.
1288     tty->print("  ["
1289                INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1290                INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1291                INT64_FORMAT_W(6)"    ]  ",
1292                sstats->_time_to_spin / MICROUNITS,
1293                sstats->_time_to_wait_to_block / MICROUNITS,
1294                sstats->_time_to_sync / MICROUNITS,
1295                sstats->_time_to_do_cleanups / MICROUNITS,
1296                sstats->_time_to_exec_vmop / MICROUNITS);
1297 
1298     if (need_to_track_page_armed_status) {
1299       tty->print(INT32_FORMAT"         ", sstats->_page_armed);
1300     }
1301     tty->print_cr(INT32_FORMAT"   ", sstats->_nof_threads_hit_page_trap);
1302   }
1303 }
1304 
1305 // This method will be called when VM exits. It will first call
1306 // print_statistics to print out the rest of the sampling.  Then
1307 // it tries to summarize the sampling.
1308 void SafepointSynchronize::print_stat_on_exit() {
1309   if (_safepoint_stats == NULL) return;
1310 
1311   SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1312 
1313   // During VM exit, end_statistics may not get called and in that
1314   // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1315   // don't print it out.
1316   // Approximate the vm op time.
1317   _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1318     os::javaTimeNanos() - cleanup_end_time;
1319 
1320   if ( PrintSafepointStatisticsTimeout < 0 ||
1321        spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1322     print_statistics();
1323   }
1324   tty->print_cr("");
1325 
1326   // Print out polling page sampling status.
1327   if (!need_to_track_page_armed_status) {
1328     if (UseCompilerSafepoints) {
1329       tty->print_cr("Polling page always armed");
1330     }
1331   } else {
1332     tty->print_cr("Defer polling page loop count = %d\n",
1333                  DeferPollingPageLoopCount);
1334   }
1335 
1336   for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1337     if (_safepoint_reasons[index] != 0) {
1338       tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1339                     _safepoint_reasons[index]);
1340     }
1341   }
1342 
1343   tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1344                 _coalesced_vmop_count);
1345   tty->print_cr("Maximum sync time  "INT64_FORMAT_W(5)" ms",
1346                 _max_sync_time / MICROUNITS);
1347   tty->print_cr("Maximum vm operation time (except for Exit VM operation)  "
1348                 INT64_FORMAT_W(5)" ms",
1349                 _max_vmop_time / MICROUNITS);
1350 }
1351 
1352 // ------------------------------------------------------------------------------------------------
1353 // Non-product code
1354 
1355 #ifndef PRODUCT
1356 
1357 void SafepointSynchronize::print_state() {
1358   if (_state == _not_synchronized) {
1359     tty->print_cr("not synchronized");
1360   } else if (_state == _synchronizing || _state == _synchronized) {
1361     tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1362                   "synchronized");
1363 
1364     for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1365        cur->safepoint_state()->print();
1366     }
1367   }
1368 }
1369 
1370 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1371   if (ShowSafepointMsgs) {
1372     va_list ap;
1373     va_start(ap, format);
1374     tty->vprint_cr(format, ap);
1375     va_end(ap);
1376   }
1377 }
1378 
1379 #endif // !PRODUCT