1 /* 2 * Copyright (c) 1997, 2015, 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/stringTable.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/shared/collectedHeap.hpp" 34 #include "gc/shared/gcLocker.inline.hpp" 35 #include "interpreter/interpreter.hpp" 36 #include "memory/resourceArea.hpp" 37 #include "memory/universe.inline.hpp" 38 #include "oops/oop.inline.hpp" 39 #include "oops/symbol.hpp" 40 #include "runtime/atomic.inline.hpp" 41 #include "runtime/compilationPolicy.hpp" 42 #include "runtime/deoptimization.hpp" 43 #include "runtime/frame.inline.hpp" 44 #include "runtime/interfaceSupport.hpp" 45 #include "runtime/mutexLocker.hpp" 46 #include "runtime/orderAccess.inline.hpp" 47 #include "runtime/osThread.hpp" 48 #include "runtime/safepoint.hpp" 49 #include "runtime/signature.hpp" 50 #include "runtime/stubCodeGenerator.hpp" 51 #include "runtime/stubRoutines.hpp" 52 #include "runtime/sweeper.hpp" 53 #include "runtime/synchronizer.hpp" 54 #include "runtime/thread.inline.hpp" 55 #include "services/runtimeService.hpp" 56 #include "utilities/events.hpp" 57 #include "utilities/macros.hpp" 58 #if INCLUDE_ALL_GCS 59 #include "gc/cms/concurrentMarkSweepThread.hpp" 60 #include "gc/g1/suspendibleThreadSet.hpp" 61 #endif // INCLUDE_ALL_GCS 62 #ifdef COMPILER1 63 #include "c1/c1_globals.hpp" 64 #endif 65 66 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 67 68 // -------------------------------------------------------------------------------------------------- 69 // Implementation of Safepoint begin/end 70 71 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 72 volatile int SafepointSynchronize::_waiting_to_block = 0; 73 volatile int SafepointSynchronize::_safepoint_counter = 0; 74 int SafepointSynchronize::_current_jni_active_count = 0; 75 long SafepointSynchronize::_end_of_last_safepoint = 0; 76 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 77 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 78 static bool timeout_error_printed = false; 79 80 // Roll all threads forward to a safepoint and suspend them all 81 void SafepointSynchronize::begin() { 82 83 Thread* myThread = Thread::current(); 84 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); 85 86 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 87 _safepoint_begin_time = os::javaTimeNanos(); 88 _ts_of_current_safepoint = tty->time_stamp().seconds(); 89 } 90 91 #if INCLUDE_ALL_GCS 92 if (UseConcMarkSweepGC) { 93 // In the future we should investigate whether CMS can use the 94 // more-general mechanism below. DLD (01/05). 95 ConcurrentMarkSweepThread::synchronize(false); 96 } else if (UseG1GC) { 97 SuspendibleThreadSet::synchronize(); 98 } 99 #endif // INCLUDE_ALL_GCS 100 101 // By getting the Threads_lock, we assure that no threads are about to start or 102 // exit. It is released again in SafepointSynchronize::end(). 103 Threads_lock->lock(); 104 105 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 106 107 int nof_threads = Threads::number_of_threads(); 108 109 if (TraceSafepoint) { 110 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); 111 } 112 113 RuntimeService::record_safepoint_begin(); 114 115 MutexLocker mu(Safepoint_lock); 116 117 // Reset the count of active JNI critical threads 118 _current_jni_active_count = 0; 119 120 // Set number of threads to wait for, before we initiate the callbacks 121 _waiting_to_block = nof_threads; 122 TryingToBlock = 0 ; 123 int still_running = nof_threads; 124 125 // Save the starting time, so that it can be compared to see if this has taken 126 // too long to complete. 127 jlong safepoint_limit_time; 128 timeout_error_printed = false; 129 130 // PrintSafepointStatisticsTimeout can be specified separately. When 131 // specified, PrintSafepointStatistics will be set to true in 132 // deferred_initialize_stat method. The initialization has to be done 133 // early enough to avoid any races. See bug 6880029 for details. 134 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 135 deferred_initialize_stat(); 136 } 137 138 // Begin the process of bringing the system to a safepoint. 139 // Java threads can be in several different states and are 140 // stopped by different mechanisms: 141 // 142 // 1. Running interpreted 143 // The interpreter dispatch table is changed to force it to 144 // check for a safepoint condition between bytecodes. 145 // 2. Running in native code 146 // When returning from the native code, a Java thread must check 147 // the safepoint _state to see if we must block. If the 148 // VM thread sees a Java thread in native, it does 149 // not wait for this thread to block. The order of the memory 150 // writes and reads of both the safepoint state and the Java 151 // threads state is critical. In order to guarantee that the 152 // memory writes are serialized with respect to each other, 153 // the VM thread issues a memory barrier instruction 154 // (on MP systems). In order to avoid the overhead of issuing 155 // a memory barrier for each Java thread making native calls, each Java 156 // thread performs a write to a single memory page after changing 157 // the thread state. The VM thread performs a sequence of 158 // mprotect OS calls which forces all previous writes from all 159 // Java threads to be serialized. This is done in the 160 // os::serialize_thread_states() call. This has proven to be 161 // much more efficient than executing a membar instruction 162 // on every call to native code. 163 // 3. Running compiled Code 164 // Compiled code reads a global (Safepoint Polling) page that 165 // is set to fault if we are trying to get to a safepoint. 166 // 4. Blocked 167 // A thread which is blocked will not be allowed to return from the 168 // block condition until the safepoint operation is complete. 169 // 5. In VM or Transitioning between states 170 // If a Java thread is currently running in the VM or transitioning 171 // between states, the safepointing code will wait for the thread to 172 // block itself when it attempts transitions to a new state. 173 // 174 _state = _synchronizing; 175 OrderAccess::fence(); 176 177 // Flush all thread states to memory 178 if (!UseMembar) { 179 os::serialize_thread_states(); 180 } 181 182 // Make interpreter safepoint aware 183 Interpreter::notice_safepoints(); 184 185 if (DeferPollingPageLoopCount < 0) { 186 // Make polling safepoint aware 187 guarantee (PageArmed == 0, "invariant") ; 188 PageArmed = 1 ; 189 os::make_polling_page_unreadable(); 190 } 191 192 // Consider using active_processor_count() ... but that call is expensive. 193 int ncpus = os::processor_count() ; 194 195 #ifdef ASSERT 196 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 197 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 198 // Clear the visited flag to ensure that the critical counts are collected properly. 199 cur->set_visited_for_critical_count(false); 200 } 201 #endif // ASSERT 202 203 if (SafepointTimeout) 204 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 205 206 // Iterate through all threads until it have been determined how to stop them all at a safepoint 207 unsigned int iterations = 0; 208 int steps = 0 ; 209 while(still_running > 0) { 210 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 211 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 212 ThreadSafepointState *cur_state = cur->safepoint_state(); 213 if (cur_state->is_running()) { 214 cur_state->examine_state_of_thread(); 215 if (!cur_state->is_running()) { 216 still_running--; 217 // consider adjusting steps downward: 218 // steps = 0 219 // steps -= NNN 220 // steps >>= 1 221 // steps = MIN(steps, 2000-100) 222 // if (iterations != 0) steps -= NNN 223 } 224 if (TraceSafepoint && Verbose) cur_state->print(); 225 } 226 } 227 228 if (PrintSafepointStatistics && iterations == 0) { 229 begin_statistics(nof_threads, still_running); 230 } 231 232 if (still_running > 0) { 233 // Check for if it takes to long 234 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 235 print_safepoint_timeout(_spinning_timeout); 236 } 237 238 // Spin to avoid context switching. 239 // There's a tension between allowing the mutators to run (and rendezvous) 240 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 241 // a mutator might otherwise use profitably to reach a safepoint. Excessive 242 // spinning by the VM thread on a saturated system can increase rendezvous latency. 243 // Blocking or yielding incur their own penalties in the form of context switching 244 // and the resultant loss of $ residency. 245 // 246 // Further complicating matters is that yield() does not work as naively expected 247 // on many platforms -- yield() does not guarantee that any other ready threads 248 // will run. As such we revert to naked_short_sleep() after some number of iterations. 249 // nakes_short_sleep() is implemented as a short unconditional sleep. 250 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 251 // can actually increase the time it takes the VM thread to detect that a system-wide 252 // stop-the-world safepoint has been reached. In a pathological scenario such as that 253 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 254 // In that case the mutators will be stalled waiting for the safepoint to complete and the 255 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 256 // will eventually wake up and detect that all mutators are safe, at which point 257 // we'll again make progress. 258 // 259 // Beware too that that the VMThread typically runs at elevated priority. 260 // Its default priority is higher than the default mutator priority. 261 // Obviously, this complicates spinning. 262 // 263 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 264 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 265 // 266 // See the comments in synchronizer.cpp for additional remarks on spinning. 267 // 268 // In the future we might: 269 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning. 270 // This is tricky as the path used by a thread exiting the JVM (say on 271 // on JNI call-out) simply stores into its state field. The burden 272 // is placed on the VM thread, which must poll (spin). 273 // 2. Find something useful to do while spinning. If the safepoint is GC-related 274 // we might aggressively scan the stacks of threads that are already safe. 275 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 276 // If all the mutators are ONPROC there's no reason to sleep or yield. 277 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 278 // 5. Check system saturation. If the system is not fully saturated then 279 // simply spin and avoid sleep/yield. 280 // 6. As still-running mutators rendezvous they could unpark the sleeping 281 // VMthread. This works well for still-running mutators that become 282 // safe. The VMthread must still poll for mutators that call-out. 283 // 7. Drive the policy on time-since-begin instead of iterations. 284 // 8. Consider making the spin duration a function of the # of CPUs: 285 // Spin = (((ncpus-1) * M) + K) + F(still_running) 286 // Alternately, instead of counting iterations of the outer loop 287 // we could count the # of threads visited in the inner loop, above. 288 // 9. On windows consider using the return value from SwitchThreadTo() 289 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 290 291 if (int(iterations) == DeferPollingPageLoopCount) { 292 guarantee (PageArmed == 0, "invariant") ; 293 PageArmed = 1 ; 294 os::make_polling_page_unreadable(); 295 } 296 297 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 298 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 299 ++steps ; 300 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 301 SpinPause() ; // MP-Polite spin 302 } else 303 if (steps < DeferThrSuspendLoopCount) { 304 os::naked_yield() ; 305 } else { 306 os::naked_short_sleep(1); 307 } 308 309 iterations ++ ; 310 } 311 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 312 } 313 assert(still_running == 0, "sanity check"); 314 315 if (PrintSafepointStatistics) { 316 update_statistics_on_spin_end(); 317 } 318 319 // wait until all threads are stopped 320 while (_waiting_to_block > 0) { 321 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); 322 if (!SafepointTimeout || timeout_error_printed) { 323 Safepoint_lock->wait(true); // true, means with no safepoint checks 324 } else { 325 // Compute remaining time 326 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 327 328 // If there is no remaining time, then there is an error 329 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 330 print_safepoint_timeout(_blocking_timeout); 331 } 332 } 333 } 334 assert(_waiting_to_block == 0, "sanity check"); 335 336 #ifndef PRODUCT 337 if (SafepointTimeout) { 338 jlong current_time = os::javaTimeNanos(); 339 if (safepoint_limit_time < current_time) { 340 tty->print_cr("# SafepointSynchronize: Finished after " 341 INT64_FORMAT_W(6) " ms", 342 ((current_time - safepoint_limit_time) / MICROUNITS + 343 SafepointTimeoutDelay)); 344 } 345 } 346 #endif 347 348 assert((_safepoint_counter & 0x1) == 0, "must be even"); 349 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 350 _safepoint_counter ++; 351 352 // Record state 353 _state = _synchronized; 354 355 OrderAccess::fence(); 356 357 #ifdef ASSERT 358 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 359 // make sure all the threads were visited 360 assert(cur->was_visited_for_critical_count(), "missed a thread"); 361 } 362 #endif // ASSERT 363 364 // Update the count of active JNI critical regions 365 GC_locker::set_jni_lock_count(_current_jni_active_count); 366 367 if (TraceSafepoint) { 368 VM_Operation *op = VMThread::vm_operation(); 369 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); 370 } 371 372 RuntimeService::record_safepoint_synchronized(); 373 if (PrintSafepointStatistics) { 374 update_statistics_on_sync_end(os::javaTimeNanos()); 375 } 376 377 // Call stuff that needs to be run when a safepoint is just about to be completed 378 do_cleanup_tasks(); 379 380 if (PrintSafepointStatistics) { 381 // Record how much time spend on the above cleanup tasks 382 update_statistics_on_cleanup_end(os::javaTimeNanos()); 383 } 384 } 385 386 // Wake up all threads, so they are ready to resume execution after the safepoint 387 // operation has been carried out 388 void SafepointSynchronize::end() { 389 390 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 391 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 392 _safepoint_counter ++; 393 // memory fence isn't required here since an odd _safepoint_counter 394 // value can do no harm and a fence is issued below anyway. 395 396 DEBUG_ONLY(Thread* myThread = Thread::current();) 397 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 398 399 if (PrintSafepointStatistics) { 400 end_statistics(os::javaTimeNanos()); 401 } 402 403 #ifdef ASSERT 404 // A pending_exception cannot be installed during a safepoint. The threads 405 // may install an async exception after they come back from a safepoint into 406 // pending_exception after they unblock. But that should happen later. 407 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 408 assert (!(cur->has_pending_exception() && 409 cur->safepoint_state()->is_at_poll_safepoint()), 410 "safepoint installed a pending exception"); 411 } 412 #endif // ASSERT 413 414 if (PageArmed) { 415 // Make polling safepoint aware 416 os::make_polling_page_readable(); 417 PageArmed = 0 ; 418 } 419 420 // Remove safepoint check from interpreter 421 Interpreter::ignore_safepoints(); 422 423 { 424 MutexLocker mu(Safepoint_lock); 425 426 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 427 428 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 429 // when they get restarted. 430 _state = _not_synchronized; 431 OrderAccess::fence(); 432 433 if (TraceSafepoint) { 434 tty->print_cr("Leaving safepoint region"); 435 } 436 437 // Start suspended threads 438 for(JavaThread *current = Threads::first(); current; current = current->next()) { 439 // A problem occurring on Solaris is when attempting to restart threads 440 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 441 // to the next one (since it has been running the longest). We then have 442 // to wait for a cpu to become available before we can continue restarting 443 // threads. 444 // FIXME: This causes the performance of the VM to degrade when active and with 445 // large numbers of threads. Apparently this is due to the synchronous nature 446 // of suspending threads. 447 // 448 // TODO-FIXME: the comments above are vestigial and no longer apply. 449 // Furthermore, using solaris' schedctl in this particular context confers no benefit 450 if (VMThreadHintNoPreempt) { 451 os::hint_no_preempt(); 452 } 453 ThreadSafepointState* cur_state = current->safepoint_state(); 454 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 455 cur_state->restart(); 456 assert(cur_state->is_running(), "safepoint state has not been reset"); 457 } 458 459 RuntimeService::record_safepoint_end(); 460 461 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 462 // blocked in signal_thread_blocked 463 Threads_lock->unlock(); 464 465 } 466 #if INCLUDE_ALL_GCS 467 // If there are any concurrent GC threads resume them. 468 if (UseConcMarkSweepGC) { 469 ConcurrentMarkSweepThread::desynchronize(false); 470 } else if (UseG1GC) { 471 SuspendibleThreadSet::desynchronize(); 472 } 473 #endif // INCLUDE_ALL_GCS 474 // record this time so VMThread can keep track how much time has elapsed 475 // since last safepoint. 476 _end_of_last_safepoint = os::javaTimeMillis(); 477 } 478 479 bool SafepointSynchronize::is_cleanup_needed() { 480 // Need a safepoint if some inline cache buffers is non-empty 481 if (!InlineCacheBuffer::is_empty()) return true; 482 return false; 483 } 484 485 486 487 // Various cleaning tasks that should be done periodically at safepoints 488 void SafepointSynchronize::do_cleanup_tasks() { 489 { 490 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime); 491 ObjectSynchronizer::deflate_idle_monitors(); 492 } 493 494 { 495 TraceTime t2("updating inline caches", TraceSafepointCleanupTime); 496 InlineCacheBuffer::update_inline_caches(); 497 } 498 { 499 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime); 500 CompilationPolicy::policy()->do_safepoint_work(); 501 } 502 503 { 504 TraceTime t4("mark nmethods", TraceSafepointCleanupTime); 505 NMethodSweeper::mark_active_nmethods(); 506 } 507 508 if (SymbolTable::needs_rehashing()) { 509 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime); 510 SymbolTable::rehash_table(); 511 } 512 513 if (StringTable::needs_rehashing()) { 514 TraceTime t6("rehashing string table", TraceSafepointCleanupTime); 515 StringTable::rehash_table(); 516 } 517 518 // rotate log files? 519 if (UseGCLogFileRotation) { 520 gclog_or_tty->rotate_log(false); 521 } 522 523 { 524 // CMS delays purging the CLDG until the beginning of the next safepoint and to 525 // make sure concurrent sweep is done 526 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime); 527 ClassLoaderDataGraph::purge_if_needed(); 528 } 529 } 530 531 532 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 533 switch(state) { 534 case _thread_in_native: 535 // native threads are safe if they have no java stack or have walkable stack 536 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 537 538 // blocked threads should have already have walkable stack 539 case _thread_blocked: 540 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 541 return true; 542 543 default: 544 return false; 545 } 546 } 547 548 549 // See if the thread is running inside a lazy critical native and 550 // update the thread critical count if so. Also set a suspend flag to 551 // cause the native wrapper to return into the JVM to do the unlock 552 // once the native finishes. 553 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 554 if (state == _thread_in_native && 555 thread->has_last_Java_frame() && 556 thread->frame_anchor()->walkable()) { 557 // This thread might be in a critical native nmethod so look at 558 // the top of the stack and increment the critical count if it 559 // is. 560 frame wrapper_frame = thread->last_frame(); 561 CodeBlob* stub_cb = wrapper_frame.cb(); 562 if (stub_cb != NULL && 563 stub_cb->is_nmethod() && 564 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 565 // A thread could potentially be in a critical native across 566 // more than one safepoint, so only update the critical state on 567 // the first one. When it returns it will perform the unlock. 568 if (!thread->do_critical_native_unlock()) { 569 #ifdef ASSERT 570 if (!thread->in_critical()) { 571 GC_locker::increment_debug_jni_lock_count(); 572 } 573 #endif 574 thread->enter_critical(); 575 // Make sure the native wrapper calls back on return to 576 // perform the needed critical unlock. 577 thread->set_critical_native_unlock(); 578 } 579 } 580 } 581 } 582 583 584 585 // ------------------------------------------------------------------------------------------------------- 586 // Implementation of Safepoint callback point 587 588 void SafepointSynchronize::block(JavaThread *thread) { 589 assert(thread != NULL, "thread must be set"); 590 assert(thread->is_Java_thread(), "not a Java thread"); 591 592 // Threads shouldn't block if they are in the middle of printing, but... 593 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 594 595 // Only bail from the block() call if the thread is gone from the 596 // thread list; starting to exit should still block. 597 if (thread->is_terminated()) { 598 // block current thread if we come here from native code when VM is gone 599 thread->block_if_vm_exited(); 600 601 // otherwise do nothing 602 return; 603 } 604 605 JavaThreadState state = thread->thread_state(); 606 thread->frame_anchor()->make_walkable(thread); 607 608 // Check that we have a valid thread_state at this point 609 switch(state) { 610 case _thread_in_vm_trans: 611 case _thread_in_Java: // From compiled code 612 613 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 614 // we pretend we are still in the VM. 615 thread->set_thread_state(_thread_in_vm); 616 617 if (is_synchronizing()) { 618 Atomic::inc (&TryingToBlock) ; 619 } 620 621 // We will always be holding the Safepoint_lock when we are examine the state 622 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 623 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 624 Safepoint_lock->lock_without_safepoint_check(); 625 if (is_synchronizing()) { 626 // Decrement the number of threads to wait for and signal vm thread 627 assert(_waiting_to_block > 0, "sanity check"); 628 _waiting_to_block--; 629 thread->safepoint_state()->set_has_called_back(true); 630 631 DEBUG_ONLY(thread->set_visited_for_critical_count(true)); 632 if (thread->in_critical()) { 633 // Notice that this thread is in a critical section 634 increment_jni_active_count(); 635 } 636 637 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 638 if (_waiting_to_block == 0) { 639 Safepoint_lock->notify_all(); 640 } 641 } 642 643 // We transition the thread to state _thread_blocked here, but 644 // we can't do our usual check for external suspension and then 645 // self-suspend after the lock_without_safepoint_check() call 646 // below because we are often called during transitions while 647 // we hold different locks. That would leave us suspended while 648 // holding a resource which results in deadlocks. 649 thread->set_thread_state(_thread_blocked); 650 Safepoint_lock->unlock(); 651 652 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 653 // the entire safepoint, the threads will all line up here during the safepoint. 654 Threads_lock->lock_without_safepoint_check(); 655 // restore original state. This is important if the thread comes from compiled code, so it 656 // will continue to execute with the _thread_in_Java state. 657 thread->set_thread_state(state); 658 Threads_lock->unlock(); 659 break; 660 661 case _thread_in_native_trans: 662 case _thread_blocked_trans: 663 case _thread_new_trans: 664 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 665 thread->print_thread_state(); 666 fatal("Deadlock in safepoint code. " 667 "Should have called back to the VM before blocking."); 668 } 669 670 // We transition the thread to state _thread_blocked here, but 671 // we can't do our usual check for external suspension and then 672 // self-suspend after the lock_without_safepoint_check() call 673 // below because we are often called during transitions while 674 // we hold different locks. That would leave us suspended while 675 // holding a resource which results in deadlocks. 676 thread->set_thread_state(_thread_blocked); 677 678 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 679 // the safepoint code might still be waiting for it to block. We need to change the state here, 680 // so it can see that it is at a safepoint. 681 682 // Block until the safepoint operation is completed. 683 Threads_lock->lock_without_safepoint_check(); 684 685 // Restore state 686 thread->set_thread_state(state); 687 688 Threads_lock->unlock(); 689 break; 690 691 default: 692 fatal(err_msg("Illegal threadstate encountered: %d", state)); 693 } 694 695 // Check for pending. async. exceptions or suspends - except if the 696 // thread was blocked inside the VM. has_special_runtime_exit_condition() 697 // is called last since it grabs a lock and we only want to do that when 698 // we must. 699 // 700 // Note: we never deliver an async exception at a polling point as the 701 // compiler may not have an exception handler for it. The polling 702 // code will notice the async and deoptimize and the exception will 703 // be delivered. (Polling at a return point is ok though). Sure is 704 // a lot of bother for a deprecated feature... 705 // 706 // We don't deliver an async exception if the thread state is 707 // _thread_in_native_trans so JNI functions won't be called with 708 // a surprising pending exception. If the thread state is going back to java, 709 // async exception is checked in check_special_condition_for_native_trans(). 710 711 if (state != _thread_blocked_trans && 712 state != _thread_in_vm_trans && 713 thread->has_special_runtime_exit_condition()) { 714 thread->handle_special_runtime_exit_condition( 715 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 716 } 717 } 718 719 // ------------------------------------------------------------------------------------------------------ 720 // Exception handlers 721 722 723 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 724 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 725 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 726 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 727 728 if (ShowSafepointMsgs) { 729 tty->print("handle_polling_page_exception: "); 730 } 731 732 if (PrintSafepointStatistics) { 733 inc_page_trap_count(); 734 } 735 736 ThreadSafepointState* state = thread->safepoint_state(); 737 738 state->handle_polling_page_exception(); 739 } 740 741 742 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 743 if (!timeout_error_printed) { 744 timeout_error_printed = true; 745 // Print out the thread info which didn't reach the safepoint for debugging 746 // purposes (useful when there are lots of threads in the debugger). 747 tty->cr(); 748 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 749 if (reason == _spinning_timeout) { 750 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 751 } else if (reason == _blocking_timeout) { 752 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 753 } 754 755 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 756 ThreadSafepointState *cur_state; 757 ResourceMark rm; 758 for(JavaThread *cur_thread = Threads::first(); cur_thread; 759 cur_thread = cur_thread->next()) { 760 cur_state = cur_thread->safepoint_state(); 761 762 if (cur_thread->thread_state() != _thread_blocked && 763 ((reason == _spinning_timeout && cur_state->is_running()) || 764 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 765 tty->print("# "); 766 cur_thread->print(); 767 tty->cr(); 768 } 769 } 770 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 771 } 772 773 // To debug the long safepoint, specify both DieOnSafepointTimeout & 774 // ShowMessageBoxOnError. 775 if (DieOnSafepointTimeout) { 776 char msg[1024]; 777 VM_Operation *op = VMThread::vm_operation(); 778 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 779 SafepointTimeoutDelay, 780 op != NULL ? op->name() : "no vm operation"); 781 fatal(msg); 782 } 783 } 784 785 786 // ------------------------------------------------------------------------------------------------------- 787 // Implementation of ThreadSafepointState 788 789 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 790 _thread = thread; 791 _type = _running; 792 _has_called_back = false; 793 _at_poll_safepoint = false; 794 } 795 796 void ThreadSafepointState::create(JavaThread *thread) { 797 ThreadSafepointState *state = new ThreadSafepointState(thread); 798 thread->set_safepoint_state(state); 799 } 800 801 void ThreadSafepointState::destroy(JavaThread *thread) { 802 if (thread->safepoint_state()) { 803 delete(thread->safepoint_state()); 804 thread->set_safepoint_state(NULL); 805 } 806 } 807 808 void ThreadSafepointState::examine_state_of_thread() { 809 assert(is_running(), "better be running or just have hit safepoint poll"); 810 811 JavaThreadState state = _thread->thread_state(); 812 813 // Save the state at the start of safepoint processing. 814 _orig_thread_state = state; 815 816 // Check for a thread that is suspended. Note that thread resume tries 817 // to grab the Threads_lock which we own here, so a thread cannot be 818 // resumed during safepoint synchronization. 819 820 // We check to see if this thread is suspended without locking to 821 // avoid deadlocking with a third thread that is waiting for this 822 // thread to be suspended. The third thread can notice the safepoint 823 // that we're trying to start at the beginning of its SR_lock->wait() 824 // call. If that happens, then the third thread will block on the 825 // safepoint while still holding the underlying SR_lock. We won't be 826 // able to get the SR_lock and we'll deadlock. 827 // 828 // We don't need to grab the SR_lock here for two reasons: 829 // 1) The suspend flags are both volatile and are set with an 830 // Atomic::cmpxchg() call so we should see the suspended 831 // state right away. 832 // 2) We're being called from the safepoint polling loop; if 833 // we don't see the suspended state on this iteration, then 834 // we'll come around again. 835 // 836 bool is_suspended = _thread->is_ext_suspended(); 837 if (is_suspended) { 838 roll_forward(_at_safepoint); 839 return; 840 } 841 842 // Some JavaThread states have an initial safepoint state of 843 // running, but are actually at a safepoint. We will happily 844 // agree and update the safepoint state here. 845 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 846 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 847 roll_forward(_at_safepoint); 848 return; 849 } 850 851 if (state == _thread_in_vm) { 852 roll_forward(_call_back); 853 return; 854 } 855 856 // All other thread states will continue to run until they 857 // transition and self-block in state _blocked 858 // Safepoint polling in compiled code causes the Java threads to do the same. 859 // Note: new threads may require a malloc so they must be allowed to finish 860 861 assert(is_running(), "examine_state_of_thread on non-running thread"); 862 return; 863 } 864 865 // Returns true is thread could not be rolled forward at present position. 866 void ThreadSafepointState::roll_forward(suspend_type type) { 867 _type = type; 868 869 switch(_type) { 870 case _at_safepoint: 871 SafepointSynchronize::signal_thread_at_safepoint(); 872 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 873 if (_thread->in_critical()) { 874 // Notice that this thread is in a critical section 875 SafepointSynchronize::increment_jni_active_count(); 876 } 877 break; 878 879 case _call_back: 880 set_has_called_back(false); 881 break; 882 883 case _running: 884 default: 885 ShouldNotReachHere(); 886 } 887 } 888 889 void ThreadSafepointState::restart() { 890 switch(type()) { 891 case _at_safepoint: 892 case _call_back: 893 break; 894 895 case _running: 896 default: 897 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d", 898 _thread, _type); 899 _thread->print(); 900 ShouldNotReachHere(); 901 } 902 _type = _running; 903 set_has_called_back(false); 904 } 905 906 907 void ThreadSafepointState::print_on(outputStream *st) const { 908 const char *s; 909 910 switch(_type) { 911 case _running : s = "_running"; break; 912 case _at_safepoint : s = "_at_safepoint"; break; 913 case _call_back : s = "_call_back"; break; 914 default: 915 ShouldNotReachHere(); 916 } 917 918 st->print_cr("Thread: " INTPTR_FORMAT 919 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 920 _thread, _thread->osthread()->thread_id(), s, _has_called_back, 921 _at_poll_safepoint); 922 923 _thread->print_thread_state_on(st); 924 } 925 926 927 // --------------------------------------------------------------------------------------------------------------------- 928 929 // Block the thread at the safepoint poll or poll return. 930 void ThreadSafepointState::handle_polling_page_exception() { 931 932 // Check state. block() will set thread state to thread_in_vm which will 933 // cause the safepoint state _type to become _call_back. 934 assert(type() == ThreadSafepointState::_running, 935 "polling page exception on thread not running state"); 936 937 // Step 1: Find the nmethod from the return address 938 if (ShowSafepointMsgs && Verbose) { 939 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); 940 } 941 address real_return_addr = thread()->saved_exception_pc(); 942 943 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 944 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); 945 nmethod* nm = (nmethod*)cb; 946 947 // Find frame of caller 948 frame stub_fr = thread()->last_frame(); 949 CodeBlob* stub_cb = stub_fr.cb(); 950 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 951 RegisterMap map(thread(), true); 952 frame caller_fr = stub_fr.sender(&map); 953 954 // Should only be poll_return or poll 955 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 956 957 // This is a poll immediately before a return. The exception handling code 958 // has already had the effect of causing the return to occur, so the execution 959 // will continue immediately after the call. In addition, the oopmap at the 960 // return point does not mark the return value as an oop (if it is), so 961 // it needs a handle here to be updated. 962 if( nm->is_at_poll_return(real_return_addr) ) { 963 // See if return type is an oop. 964 bool return_oop = nm->method()->is_returning_oop(); 965 Handle return_value; 966 if (return_oop) { 967 // The oop result has been saved on the stack together with all 968 // the other registers. In order to preserve it over GCs we need 969 // to keep it in a handle. 970 oop result = caller_fr.saved_oop_result(&map); 971 assert(result == NULL || result->is_oop(), "must be oop"); 972 return_value = Handle(thread(), result); 973 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 974 } 975 976 // Block the thread 977 SafepointSynchronize::block(thread()); 978 979 // restore oop result, if any 980 if (return_oop) { 981 caller_fr.set_saved_oop_result(&map, return_value()); 982 } 983 } 984 985 // This is a safepoint poll. Verify the return address and block. 986 else { 987 set_at_poll_safepoint(true); 988 989 // verify the blob built the "return address" correctly 990 assert(real_return_addr == caller_fr.pc(), "must match"); 991 992 // Block the thread 993 SafepointSynchronize::block(thread()); 994 set_at_poll_safepoint(false); 995 996 // If we have a pending async exception deoptimize the frame 997 // as otherwise we may never deliver it. 998 if (thread()->has_async_condition()) { 999 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1000 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1001 } 1002 1003 // If an exception has been installed we must check for a pending deoptimization 1004 // Deoptimize frame if exception has been thrown. 1005 1006 if (thread()->has_pending_exception() ) { 1007 RegisterMap map(thread(), true); 1008 frame caller_fr = stub_fr.sender(&map); 1009 if (caller_fr.is_deoptimized_frame()) { 1010 // The exception patch will destroy registers that are still 1011 // live and will be needed during deoptimization. Defer the 1012 // Async exception should have deferred the exception until the 1013 // next safepoint which will be detected when we get into 1014 // the interpreter so if we have an exception now things 1015 // are messed up. 1016 1017 fatal("Exception installed and deoptimization is pending"); 1018 } 1019 } 1020 } 1021 } 1022 1023 1024 // 1025 // Statistics & Instrumentations 1026 // 1027 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1028 jlong SafepointSynchronize::_safepoint_begin_time = 0; 1029 int SafepointSynchronize::_cur_stat_index = 0; 1030 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1031 julong SafepointSynchronize::_coalesced_vmop_count = 0; 1032 jlong SafepointSynchronize::_max_sync_time = 0; 1033 jlong SafepointSynchronize::_max_vmop_time = 0; 1034 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1035 1036 static jlong cleanup_end_time = 0; 1037 static bool need_to_track_page_armed_status = false; 1038 static bool init_done = false; 1039 1040 // Helper method to print the header. 1041 static void print_header() { 1042 tty->print(" vmop " 1043 "[threads: total initially_running wait_to_block] "); 1044 tty->print("[time: spin block sync cleanup vmop] "); 1045 1046 // no page armed status printed out if it is always armed. 1047 if (need_to_track_page_armed_status) { 1048 tty->print("page_armed "); 1049 } 1050 1051 tty->print_cr("page_trap_count"); 1052 } 1053 1054 void SafepointSynchronize::deferred_initialize_stat() { 1055 if (init_done) return; 1056 1057 if (PrintSafepointStatisticsCount <= 0) { 1058 fatal("Wrong PrintSafepointStatisticsCount"); 1059 } 1060 1061 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1062 // be printed right away, in which case, _safepoint_stats will regress to 1063 // a single element array. Otherwise, it is a circular ring buffer with default 1064 // size of PrintSafepointStatisticsCount. 1065 int stats_array_size; 1066 if (PrintSafepointStatisticsTimeout > 0) { 1067 stats_array_size = 1; 1068 PrintSafepointStatistics = true; 1069 } else { 1070 stats_array_size = PrintSafepointStatisticsCount; 1071 } 1072 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1073 * sizeof(SafepointStats), mtInternal); 1074 guarantee(_safepoint_stats != NULL, 1075 "not enough memory for safepoint instrumentation data"); 1076 1077 if (DeferPollingPageLoopCount >= 0) { 1078 need_to_track_page_armed_status = true; 1079 } 1080 init_done = true; 1081 } 1082 1083 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1084 assert(init_done, "safepoint statistics array hasn't been initialized"); 1085 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1086 1087 spstat->_time_stamp = _ts_of_current_safepoint; 1088 1089 VM_Operation *op = VMThread::vm_operation(); 1090 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1091 if (op != NULL) { 1092 _safepoint_reasons[spstat->_vmop_type]++; 1093 } 1094 1095 spstat->_nof_total_threads = nof_threads; 1096 spstat->_nof_initial_running_threads = nof_running; 1097 spstat->_nof_threads_hit_page_trap = 0; 1098 1099 // Records the start time of spinning. The real time spent on spinning 1100 // will be adjusted when spin is done. Same trick is applied for time 1101 // spent on waiting for threads to block. 1102 if (nof_running != 0) { 1103 spstat->_time_to_spin = os::javaTimeNanos(); 1104 } else { 1105 spstat->_time_to_spin = 0; 1106 } 1107 } 1108 1109 void SafepointSynchronize::update_statistics_on_spin_end() { 1110 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1111 1112 jlong cur_time = os::javaTimeNanos(); 1113 1114 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1115 if (spstat->_nof_initial_running_threads != 0) { 1116 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1117 } 1118 1119 if (need_to_track_page_armed_status) { 1120 spstat->_page_armed = (PageArmed == 1); 1121 } 1122 1123 // Records the start time of waiting for to block. Updated when block is done. 1124 if (_waiting_to_block != 0) { 1125 spstat->_time_to_wait_to_block = cur_time; 1126 } else { 1127 spstat->_time_to_wait_to_block = 0; 1128 } 1129 } 1130 1131 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1132 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1133 1134 if (spstat->_nof_threads_wait_to_block != 0) { 1135 spstat->_time_to_wait_to_block = end_time - 1136 spstat->_time_to_wait_to_block; 1137 } 1138 1139 // Records the end time of sync which will be used to calculate the total 1140 // vm operation time. Again, the real time spending in syncing will be deducted 1141 // from the start of the sync time later when end_statistics is called. 1142 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1143 if (spstat->_time_to_sync > _max_sync_time) { 1144 _max_sync_time = spstat->_time_to_sync; 1145 } 1146 1147 spstat->_time_to_do_cleanups = end_time; 1148 } 1149 1150 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1151 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1152 1153 // Record how long spent in cleanup tasks. 1154 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1155 1156 cleanup_end_time = end_time; 1157 } 1158 1159 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1160 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1161 1162 // Update the vm operation time. 1163 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1164 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1165 _max_vmop_time = spstat->_time_to_exec_vmop; 1166 } 1167 // Only the sync time longer than the specified 1168 // PrintSafepointStatisticsTimeout will be printed out right away. 1169 // By default, it is -1 meaning all samples will be put into the list. 1170 if ( PrintSafepointStatisticsTimeout > 0) { 1171 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1172 print_statistics(); 1173 } 1174 } else { 1175 // The safepoint statistics will be printed out when the _safepoin_stats 1176 // array fills up. 1177 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1178 print_statistics(); 1179 _cur_stat_index = 0; 1180 } else { 1181 _cur_stat_index++; 1182 } 1183 } 1184 } 1185 1186 void SafepointSynchronize::print_statistics() { 1187 SafepointStats* sstats = _safepoint_stats; 1188 1189 for (int index = 0; index <= _cur_stat_index; index++) { 1190 if (index % 30 == 0) { 1191 print_header(); 1192 } 1193 sstats = &_safepoint_stats[index]; 1194 tty->print("%.3f: ", sstats->_time_stamp); 1195 tty->print("%-26s [" 1196 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15) 1197 " ] ", 1198 sstats->_vmop_type == -1 ? "no vm operation" : 1199 VM_Operation::name(sstats->_vmop_type), 1200 sstats->_nof_total_threads, 1201 sstats->_nof_initial_running_threads, 1202 sstats->_nof_threads_wait_to_block); 1203 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1204 tty->print(" [" 1205 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1206 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1207 INT64_FORMAT_W(6)" ] ", 1208 sstats->_time_to_spin / MICROUNITS, 1209 sstats->_time_to_wait_to_block / MICROUNITS, 1210 sstats->_time_to_sync / MICROUNITS, 1211 sstats->_time_to_do_cleanups / MICROUNITS, 1212 sstats->_time_to_exec_vmop / MICROUNITS); 1213 1214 if (need_to_track_page_armed_status) { 1215 tty->print(INT32_FORMAT" ", sstats->_page_armed); 1216 } 1217 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap); 1218 } 1219 } 1220 1221 // This method will be called when VM exits. It will first call 1222 // print_statistics to print out the rest of the sampling. Then 1223 // it tries to summarize the sampling. 1224 void SafepointSynchronize::print_stat_on_exit() { 1225 if (_safepoint_stats == NULL) return; 1226 1227 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1228 1229 // During VM exit, end_statistics may not get called and in that 1230 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1231 // don't print it out. 1232 // Approximate the vm op time. 1233 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1234 os::javaTimeNanos() - cleanup_end_time; 1235 1236 if ( PrintSafepointStatisticsTimeout < 0 || 1237 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1238 print_statistics(); 1239 } 1240 tty->cr(); 1241 1242 // Print out polling page sampling status. 1243 if (!need_to_track_page_armed_status) { 1244 tty->print_cr("Polling page always armed"); 1245 } else { 1246 tty->print_cr("Defer polling page loop count = %d\n", 1247 DeferPollingPageLoopCount); 1248 } 1249 1250 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1251 if (_safepoint_reasons[index] != 0) { 1252 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index), 1253 _safepoint_reasons[index]); 1254 } 1255 } 1256 1257 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint", 1258 _coalesced_vmop_count); 1259 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms", 1260 _max_sync_time / MICROUNITS); 1261 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1262 INT64_FORMAT_W(5)" ms", 1263 _max_vmop_time / MICROUNITS); 1264 } 1265 1266 // ------------------------------------------------------------------------------------------------ 1267 // Non-product code 1268 1269 #ifndef PRODUCT 1270 1271 void SafepointSynchronize::print_state() { 1272 if (_state == _not_synchronized) { 1273 tty->print_cr("not synchronized"); 1274 } else if (_state == _synchronizing || _state == _synchronized) { 1275 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1276 "synchronized"); 1277 1278 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1279 cur->safepoint_state()->print(); 1280 } 1281 } 1282 } 1283 1284 void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1285 if (ShowSafepointMsgs) { 1286 va_list ap; 1287 va_start(ap, format); 1288 tty->vprint_cr(format, ap); 1289 va_end(ap); 1290 } 1291 } 1292 1293 #endif // !PRODUCT