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/shenandoah/shenandoahConcurrentThread.hpp" 60 #include "gc/cms/concurrentMarkSweepThread.hpp" 61 #include "gc/g1/suspendibleThreadSet.hpp" 62 #endif // INCLUDE_ALL_GCS 63 #ifdef COMPILER1 64 #include "c1/c1_globals.hpp" 65 #endif 66 67 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 68 69 // -------------------------------------------------------------------------------------------------- 70 // Implementation of Safepoint begin/end 71 72 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 73 volatile int SafepointSynchronize::_waiting_to_block = 0; 74 volatile int SafepointSynchronize::_safepoint_counter = 0; 75 int SafepointSynchronize::_current_jni_active_count = 0; 76 long SafepointSynchronize::_end_of_last_safepoint = 0; 77 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 78 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 79 static bool timeout_error_printed = false; 80 81 // Roll all threads forward to a safepoint and suspend them all 82 void SafepointSynchronize::begin() { 83 84 Thread* myThread = Thread::current(); 85 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); 86 87 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 88 _safepoint_begin_time = os::javaTimeNanos(); 89 _ts_of_current_safepoint = tty->time_stamp().seconds(); 90 } 91 92 #if INCLUDE_ALL_GCS 93 if (UseConcMarkSweepGC) { 94 // In the future we should investigate whether CMS can use the 95 // more-general mechanism below. DLD (01/05). 96 ConcurrentMarkSweepThread::synchronize(false); 97 } else if (UseG1GC) { 98 SuspendibleThreadSet::synchronize(); 99 } else if (UseShenandoahGC) { 100 ShenandoahConcurrentThread::safepoint_synchronize(); 101 } 102 103 #endif // INCLUDE_ALL_GCS 104 105 // By getting the Threads_lock, we assure that no threads are about to start or 106 // exit. It is released again in SafepointSynchronize::end(). 107 Threads_lock->lock(); 108 109 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 110 111 int nof_threads = Threads::number_of_threads(); 112 113 if (TraceSafepoint) { 114 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); 115 } 116 117 RuntimeService::record_safepoint_begin(); 118 119 MutexLocker mu(Safepoint_lock); 120 121 // Reset the count of active JNI critical threads 122 _current_jni_active_count = 0; 123 124 // Set number of threads to wait for, before we initiate the callbacks 125 _waiting_to_block = nof_threads; 126 TryingToBlock = 0 ; 127 int still_running = nof_threads; 128 129 // Save the starting time, so that it can be compared to see if this has taken 130 // too long to complete. 131 jlong safepoint_limit_time; 132 timeout_error_printed = false; 133 134 // PrintSafepointStatisticsTimeout can be specified separately. When 135 // specified, PrintSafepointStatistics will be set to true in 136 // deferred_initialize_stat method. The initialization has to be done 137 // early enough to avoid any races. See bug 6880029 for details. 138 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 139 deferred_initialize_stat(); 140 } 141 142 // Begin the process of bringing the system to a safepoint. 143 // Java threads can be in several different states and are 144 // stopped by different mechanisms: 145 // 146 // 1. Running interpreted 147 // The interpreter dispatch table is changed to force it to 148 // check for a safepoint condition between bytecodes. 149 // 2. Running in native code 150 // When returning from the native code, a Java thread must check 151 // the safepoint _state to see if we must block. If the 152 // VM thread sees a Java thread in native, it does 153 // not wait for this thread to block. The order of the memory 154 // writes and reads of both the safepoint state and the Java 155 // threads state is critical. In order to guarantee that the 156 // memory writes are serialized with respect to each other, 157 // the VM thread issues a memory barrier instruction 158 // (on MP systems). In order to avoid the overhead of issuing 159 // a memory barrier for each Java thread making native calls, each Java 160 // thread performs a write to a single memory page after changing 161 // the thread state. The VM thread performs a sequence of 162 // mprotect OS calls which forces all previous writes from all 163 // Java threads to be serialized. This is done in the 164 // os::serialize_thread_states() call. This has proven to be 165 // much more efficient than executing a membar instruction 166 // on every call to native code. 167 // 3. Running compiled Code 168 // Compiled code reads a global (Safepoint Polling) page that 169 // is set to fault if we are trying to get to a safepoint. 170 // 4. Blocked 171 // A thread which is blocked will not be allowed to return from the 172 // block condition until the safepoint operation is complete. 173 // 5. In VM or Transitioning between states 174 // If a Java thread is currently running in the VM or transitioning 175 // between states, the safepointing code will wait for the thread to 176 // block itself when it attempts transitions to a new state. 177 // 178 _state = _synchronizing; 179 OrderAccess::fence(); 180 181 // Flush all thread states to memory 182 if (!UseMembar) { 183 os::serialize_thread_states(); 184 } 185 186 // Make interpreter safepoint aware 187 Interpreter::notice_safepoints(); 188 189 if (DeferPollingPageLoopCount < 0) { 190 // Make polling safepoint aware 191 guarantee (PageArmed == 0, "invariant") ; 192 PageArmed = 1 ; 193 os::make_polling_page_unreadable(); 194 } 195 196 // Consider using active_processor_count() ... but that call is expensive. 197 int ncpus = os::processor_count() ; 198 199 #ifdef ASSERT 200 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 201 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 202 // Clear the visited flag to ensure that the critical counts are collected properly. 203 cur->set_visited_for_critical_count(false); 204 } 205 #endif // ASSERT 206 207 if (SafepointTimeout) 208 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 209 210 // Iterate through all threads until it have been determined how to stop them all at a safepoint 211 unsigned int iterations = 0; 212 int steps = 0 ; 213 while(still_running > 0) { 214 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 215 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 216 ThreadSafepointState *cur_state = cur->safepoint_state(); 217 if (cur_state->is_running()) { 218 cur_state->examine_state_of_thread(); 219 if (!cur_state->is_running()) { 220 still_running--; 221 // consider adjusting steps downward: 222 // steps = 0 223 // steps -= NNN 224 // steps >>= 1 225 // steps = MIN(steps, 2000-100) 226 // if (iterations != 0) steps -= NNN 227 } 228 if (TraceSafepoint && Verbose) cur_state->print(); 229 } 230 } 231 232 if (PrintSafepointStatistics && iterations == 0) { 233 begin_statistics(nof_threads, still_running); 234 } 235 236 if (still_running > 0) { 237 // Check for if it takes to long 238 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 239 print_safepoint_timeout(_spinning_timeout); 240 } 241 242 // Spin to avoid context switching. 243 // There's a tension between allowing the mutators to run (and rendezvous) 244 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 245 // a mutator might otherwise use profitably to reach a safepoint. Excessive 246 // spinning by the VM thread on a saturated system can increase rendezvous latency. 247 // Blocking or yielding incur their own penalties in the form of context switching 248 // and the resultant loss of $ residency. 249 // 250 // Further complicating matters is that yield() does not work as naively expected 251 // on many platforms -- yield() does not guarantee that any other ready threads 252 // will run. As such we revert to naked_short_sleep() after some number of iterations. 253 // nakes_short_sleep() is implemented as a short unconditional sleep. 254 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 255 // can actually increase the time it takes the VM thread to detect that a system-wide 256 // stop-the-world safepoint has been reached. In a pathological scenario such as that 257 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 258 // In that case the mutators will be stalled waiting for the safepoint to complete and the 259 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 260 // will eventually wake up and detect that all mutators are safe, at which point 261 // we'll again make progress. 262 // 263 // Beware too that that the VMThread typically runs at elevated priority. 264 // Its default priority is higher than the default mutator priority. 265 // Obviously, this complicates spinning. 266 // 267 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 268 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 269 // 270 // See the comments in synchronizer.cpp for additional remarks on spinning. 271 // 272 // In the future we might: 273 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning. 274 // This is tricky as the path used by a thread exiting the JVM (say on 275 // on JNI call-out) simply stores into its state field. The burden 276 // is placed on the VM thread, which must poll (spin). 277 // 2. Find something useful to do while spinning. If the safepoint is GC-related 278 // we might aggressively scan the stacks of threads that are already safe. 279 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 280 // If all the mutators are ONPROC there's no reason to sleep or yield. 281 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 282 // 5. Check system saturation. If the system is not fully saturated then 283 // simply spin and avoid sleep/yield. 284 // 6. As still-running mutators rendezvous they could unpark the sleeping 285 // VMthread. This works well for still-running mutators that become 286 // safe. The VMthread must still poll for mutators that call-out. 287 // 7. Drive the policy on time-since-begin instead of iterations. 288 // 8. Consider making the spin duration a function of the # of CPUs: 289 // Spin = (((ncpus-1) * M) + K) + F(still_running) 290 // Alternately, instead of counting iterations of the outer loop 291 // we could count the # of threads visited in the inner loop, above. 292 // 9. On windows consider using the return value from SwitchThreadTo() 293 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 294 295 if (int(iterations) == DeferPollingPageLoopCount) { 296 guarantee (PageArmed == 0, "invariant") ; 297 PageArmed = 1 ; 298 os::make_polling_page_unreadable(); 299 } 300 301 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 302 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 303 ++steps ; 304 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 305 SpinPause() ; // MP-Polite spin 306 } else 307 if (steps < DeferThrSuspendLoopCount) { 308 os::naked_yield() ; 309 } else { 310 os::naked_short_sleep(1); 311 } 312 313 iterations ++ ; 314 } 315 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 316 } 317 assert(still_running == 0, "sanity check"); 318 319 if (PrintSafepointStatistics) { 320 update_statistics_on_spin_end(); 321 } 322 323 // wait until all threads are stopped 324 while (_waiting_to_block > 0) { 325 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); 326 if (!SafepointTimeout || timeout_error_printed) { 327 Safepoint_lock->wait(true); // true, means with no safepoint checks 328 } else { 329 // Compute remaining time 330 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 331 332 // If there is no remaining time, then there is an error 333 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 334 print_safepoint_timeout(_blocking_timeout); 335 } 336 } 337 } 338 assert(_waiting_to_block == 0, "sanity check"); 339 340 #ifndef PRODUCT 341 if (SafepointTimeout) { 342 jlong current_time = os::javaTimeNanos(); 343 if (safepoint_limit_time < current_time) { 344 tty->print_cr("# SafepointSynchronize: Finished after " 345 INT64_FORMAT_W(6) " ms", 346 ((current_time - safepoint_limit_time) / MICROUNITS + 347 SafepointTimeoutDelay)); 348 } 349 } 350 #endif 351 352 assert((_safepoint_counter & 0x1) == 0, "must be even"); 353 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 354 _safepoint_counter ++; 355 356 // Record state 357 _state = _synchronized; 358 359 OrderAccess::fence(); 360 361 #ifdef ASSERT 362 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 363 // make sure all the threads were visited 364 assert(cur->was_visited_for_critical_count(), "missed a thread"); 365 } 366 #endif // ASSERT 367 368 // Update the count of active JNI critical regions 369 GC_locker::set_jni_lock_count(_current_jni_active_count); 370 371 if (TraceSafepoint) { 372 VM_Operation *op = VMThread::vm_operation(); 373 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); 374 } 375 376 RuntimeService::record_safepoint_synchronized(); 377 if (PrintSafepointStatistics) { 378 update_statistics_on_sync_end(os::javaTimeNanos()); 379 } 380 381 // Call stuff that needs to be run when a safepoint is just about to be completed 382 do_cleanup_tasks(); 383 384 if (PrintSafepointStatistics) { 385 // Record how much time spend on the above cleanup tasks 386 update_statistics_on_cleanup_end(os::javaTimeNanos()); 387 } 388 } 389 390 // Wake up all threads, so they are ready to resume execution after the safepoint 391 // operation has been carried out 392 void SafepointSynchronize::end() { 393 394 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 395 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 396 _safepoint_counter ++; 397 // memory fence isn't required here since an odd _safepoint_counter 398 // value can do no harm and a fence is issued below anyway. 399 400 DEBUG_ONLY(Thread* myThread = Thread::current();) 401 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 402 403 if (PrintSafepointStatistics) { 404 end_statistics(os::javaTimeNanos()); 405 } 406 407 #ifdef ASSERT 408 // A pending_exception cannot be installed during a safepoint. The threads 409 // may install an async exception after they come back from a safepoint into 410 // pending_exception after they unblock. But that should happen later. 411 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 412 assert (!(cur->has_pending_exception() && 413 cur->safepoint_state()->is_at_poll_safepoint()), 414 "safepoint installed a pending exception"); 415 } 416 #endif // ASSERT 417 418 if (PageArmed) { 419 // Make polling safepoint aware 420 os::make_polling_page_readable(); 421 PageArmed = 0 ; 422 } 423 424 // Remove safepoint check from interpreter 425 Interpreter::ignore_safepoints(); 426 427 { 428 MutexLocker mu(Safepoint_lock); 429 430 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 431 432 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 433 // when they get restarted. 434 _state = _not_synchronized; 435 OrderAccess::fence(); 436 437 if (TraceSafepoint) { 438 tty->print_cr("Leaving safepoint region"); 439 } 440 441 // Start suspended threads 442 for(JavaThread *current = Threads::first(); current; current = current->next()) { 443 // A problem occurring on Solaris is when attempting to restart threads 444 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 445 // to the next one (since it has been running the longest). We then have 446 // to wait for a cpu to become available before we can continue restarting 447 // threads. 448 // FIXME: This causes the performance of the VM to degrade when active and with 449 // large numbers of threads. Apparently this is due to the synchronous nature 450 // of suspending threads. 451 // 452 // TODO-FIXME: the comments above are vestigial and no longer apply. 453 // Furthermore, using solaris' schedctl in this particular context confers no benefit 454 if (VMThreadHintNoPreempt) { 455 os::hint_no_preempt(); 456 } 457 ThreadSafepointState* cur_state = current->safepoint_state(); 458 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 459 cur_state->restart(); 460 assert(cur_state->is_running(), "safepoint state has not been reset"); 461 } 462 463 RuntimeService::record_safepoint_end(); 464 465 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 466 // blocked in signal_thread_blocked 467 Threads_lock->unlock(); 468 469 } 470 #if INCLUDE_ALL_GCS 471 // If there are any concurrent GC threads resume them. 472 if (UseConcMarkSweepGC) { 473 ConcurrentMarkSweepThread::desynchronize(false); 474 } else if (UseG1GC) { 475 SuspendibleThreadSet::desynchronize(); 476 } else if (UseShenandoahGC) { 477 ShenandoahConcurrentThread::safepoint_desynchronize(); 478 } 479 #endif // INCLUDE_ALL_GCS 480 // record this time so VMThread can keep track how much time has elapsed 481 // since last safepoint. 482 _end_of_last_safepoint = os::javaTimeMillis(); 483 } 484 485 bool SafepointSynchronize::is_cleanup_needed() { 486 // Need a safepoint if some inline cache buffers is non-empty 487 if (!InlineCacheBuffer::is_empty()) return true; 488 return false; 489 } 490 491 492 493 // Various cleaning tasks that should be done periodically at safepoints 494 void SafepointSynchronize::do_cleanup_tasks() { 495 { 496 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime); 497 ObjectSynchronizer::deflate_idle_monitors(); 498 } 499 500 { 501 TraceTime t2("updating inline caches", TraceSafepointCleanupTime); 502 InlineCacheBuffer::update_inline_caches(); 503 } 504 { 505 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime); 506 CompilationPolicy::policy()->do_safepoint_work(); 507 } 508 509 { 510 TraceTime t4("mark nmethods", TraceSafepointCleanupTime); 511 NMethodSweeper::mark_active_nmethods(); 512 } 513 514 if (SymbolTable::needs_rehashing()) { 515 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime); 516 SymbolTable::rehash_table(); 517 } 518 519 if (StringTable::needs_rehashing()) { 520 TraceTime t6("rehashing string table", TraceSafepointCleanupTime); 521 StringTable::rehash_table(); 522 } 523 524 // rotate log files? 525 if (UseGCLogFileRotation) { 526 gclog_or_tty->rotate_log(false); 527 } 528 529 { 530 // CMS delays purging the CLDG until the beginning of the next safepoint and to 531 // make sure concurrent sweep is done 532 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime); 533 ClassLoaderDataGraph::purge_if_needed(); 534 } 535 } 536 537 538 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 539 switch(state) { 540 case _thread_in_native: 541 // native threads are safe if they have no java stack or have walkable stack 542 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 543 544 // blocked threads should have already have walkable stack 545 case _thread_blocked: 546 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 547 return true; 548 549 default: 550 return false; 551 } 552 } 553 554 555 // See if the thread is running inside a lazy critical native and 556 // update the thread critical count if so. Also set a suspend flag to 557 // cause the native wrapper to return into the JVM to do the unlock 558 // once the native finishes. 559 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 560 if (state == _thread_in_native && 561 thread->has_last_Java_frame() && 562 thread->frame_anchor()->walkable()) { 563 // This thread might be in a critical native nmethod so look at 564 // the top of the stack and increment the critical count if it 565 // is. 566 frame wrapper_frame = thread->last_frame(); 567 CodeBlob* stub_cb = wrapper_frame.cb(); 568 if (stub_cb != NULL && 569 stub_cb->is_nmethod() && 570 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 571 // A thread could potentially be in a critical native across 572 // more than one safepoint, so only update the critical state on 573 // the first one. When it returns it will perform the unlock. 574 if (!thread->do_critical_native_unlock()) { 575 #ifdef ASSERT 576 if (!thread->in_critical()) { 577 GC_locker::increment_debug_jni_lock_count(); 578 } 579 #endif 580 thread->enter_critical(); 581 // Make sure the native wrapper calls back on return to 582 // perform the needed critical unlock. 583 thread->set_critical_native_unlock(); 584 } 585 } 586 } 587 } 588 589 590 591 // ------------------------------------------------------------------------------------------------------- 592 // Implementation of Safepoint callback point 593 594 void SafepointSynchronize::block(JavaThread *thread) { 595 assert(thread != NULL, "thread must be set"); 596 assert(thread->is_Java_thread(), "not a Java thread"); 597 598 // Threads shouldn't block if they are in the middle of printing, but... 599 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 600 601 // Only bail from the block() call if the thread is gone from the 602 // thread list; starting to exit should still block. 603 if (thread->is_terminated()) { 604 // block current thread if we come here from native code when VM is gone 605 thread->block_if_vm_exited(); 606 607 // otherwise do nothing 608 return; 609 } 610 611 JavaThreadState state = thread->thread_state(); 612 thread->frame_anchor()->make_walkable(thread); 613 614 // Check that we have a valid thread_state at this point 615 switch(state) { 616 case _thread_in_vm_trans: 617 case _thread_in_Java: // From compiled code 618 619 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 620 // we pretend we are still in the VM. 621 thread->set_thread_state(_thread_in_vm); 622 623 if (is_synchronizing()) { 624 Atomic::inc (&TryingToBlock) ; 625 } 626 627 // We will always be holding the Safepoint_lock when we are examine the state 628 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 629 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 630 Safepoint_lock->lock_without_safepoint_check(); 631 if (is_synchronizing()) { 632 // Decrement the number of threads to wait for and signal vm thread 633 assert(_waiting_to_block > 0, "sanity check"); 634 _waiting_to_block--; 635 thread->safepoint_state()->set_has_called_back(true); 636 637 DEBUG_ONLY(thread->set_visited_for_critical_count(true)); 638 if (thread->in_critical()) { 639 // Notice that this thread is in a critical section 640 increment_jni_active_count(); 641 } 642 643 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 644 if (_waiting_to_block == 0) { 645 Safepoint_lock->notify_all(); 646 } 647 } 648 649 // We transition the thread to state _thread_blocked here, but 650 // we can't do our usual check for external suspension and then 651 // self-suspend after the lock_without_safepoint_check() call 652 // below because we are often called during transitions while 653 // we hold different locks. That would leave us suspended while 654 // holding a resource which results in deadlocks. 655 thread->set_thread_state(_thread_blocked); 656 Safepoint_lock->unlock(); 657 658 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 659 // the entire safepoint, the threads will all line up here during the safepoint. 660 Threads_lock->lock_without_safepoint_check(); 661 // restore original state. This is important if the thread comes from compiled code, so it 662 // will continue to execute with the _thread_in_Java state. 663 thread->set_thread_state(state); 664 Threads_lock->unlock(); 665 break; 666 667 case _thread_in_native_trans: 668 case _thread_blocked_trans: 669 case _thread_new_trans: 670 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 671 thread->print_thread_state(); 672 fatal("Deadlock in safepoint code. " 673 "Should have called back to the VM before blocking."); 674 } 675 676 // We transition the thread to state _thread_blocked here, but 677 // we can't do our usual check for external suspension and then 678 // self-suspend after the lock_without_safepoint_check() call 679 // below because we are often called during transitions while 680 // we hold different locks. That would leave us suspended while 681 // holding a resource which results in deadlocks. 682 thread->set_thread_state(_thread_blocked); 683 684 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 685 // the safepoint code might still be waiting for it to block. We need to change the state here, 686 // so it can see that it is at a safepoint. 687 688 // Block until the safepoint operation is completed. 689 Threads_lock->lock_without_safepoint_check(); 690 691 // Restore state 692 thread->set_thread_state(state); 693 694 Threads_lock->unlock(); 695 break; 696 697 default: 698 fatal(err_msg("Illegal threadstate encountered: %d", state)); 699 } 700 701 // Check for pending. async. exceptions or suspends - except if the 702 // thread was blocked inside the VM. has_special_runtime_exit_condition() 703 // is called last since it grabs a lock and we only want to do that when 704 // we must. 705 // 706 // Note: we never deliver an async exception at a polling point as the 707 // compiler may not have an exception handler for it. The polling 708 // code will notice the async and deoptimize and the exception will 709 // be delivered. (Polling at a return point is ok though). Sure is 710 // a lot of bother for a deprecated feature... 711 // 712 // We don't deliver an async exception if the thread state is 713 // _thread_in_native_trans so JNI functions won't be called with 714 // a surprising pending exception. If the thread state is going back to java, 715 // async exception is checked in check_special_condition_for_native_trans(). 716 717 if (state != _thread_blocked_trans && 718 state != _thread_in_vm_trans && 719 thread->has_special_runtime_exit_condition()) { 720 thread->handle_special_runtime_exit_condition( 721 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 722 } 723 } 724 725 // ------------------------------------------------------------------------------------------------------ 726 // Exception handlers 727 728 729 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 730 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 731 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 732 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 733 734 if (ShowSafepointMsgs) { 735 tty->print("handle_polling_page_exception: "); 736 } 737 738 if (PrintSafepointStatistics) { 739 inc_page_trap_count(); 740 } 741 742 ThreadSafepointState* state = thread->safepoint_state(); 743 744 state->handle_polling_page_exception(); 745 } 746 747 748 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 749 if (!timeout_error_printed) { 750 timeout_error_printed = true; 751 // Print out the thread info which didn't reach the safepoint for debugging 752 // purposes (useful when there are lots of threads in the debugger). 753 tty->cr(); 754 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 755 if (reason == _spinning_timeout) { 756 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 757 } else if (reason == _blocking_timeout) { 758 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 759 } 760 761 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 762 ThreadSafepointState *cur_state; 763 ResourceMark rm; 764 for(JavaThread *cur_thread = Threads::first(); cur_thread; 765 cur_thread = cur_thread->next()) { 766 cur_state = cur_thread->safepoint_state(); 767 768 if (cur_thread->thread_state() != _thread_blocked && 769 ((reason == _spinning_timeout && cur_state->is_running()) || 770 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 771 tty->print("# "); 772 cur_thread->print(); 773 tty->cr(); 774 } 775 } 776 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 777 } 778 779 // To debug the long safepoint, specify both DieOnSafepointTimeout & 780 // ShowMessageBoxOnError. 781 if (DieOnSafepointTimeout) { 782 char msg[1024]; 783 VM_Operation *op = VMThread::vm_operation(); 784 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 785 SafepointTimeoutDelay, 786 op != NULL ? op->name() : "no vm operation"); 787 fatal(msg); 788 } 789 } 790 791 792 // ------------------------------------------------------------------------------------------------------- 793 // Implementation of ThreadSafepointState 794 795 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 796 _thread = thread; 797 _type = _running; 798 _has_called_back = false; 799 _at_poll_safepoint = false; 800 } 801 802 void ThreadSafepointState::create(JavaThread *thread) { 803 ThreadSafepointState *state = new ThreadSafepointState(thread); 804 thread->set_safepoint_state(state); 805 } 806 807 void ThreadSafepointState::destroy(JavaThread *thread) { 808 if (thread->safepoint_state()) { 809 delete(thread->safepoint_state()); 810 thread->set_safepoint_state(NULL); 811 } 812 } 813 814 void ThreadSafepointState::examine_state_of_thread() { 815 assert(is_running(), "better be running or just have hit safepoint poll"); 816 817 JavaThreadState state = _thread->thread_state(); 818 819 // Save the state at the start of safepoint processing. 820 _orig_thread_state = state; 821 822 // Check for a thread that is suspended. Note that thread resume tries 823 // to grab the Threads_lock which we own here, so a thread cannot be 824 // resumed during safepoint synchronization. 825 826 // We check to see if this thread is suspended without locking to 827 // avoid deadlocking with a third thread that is waiting for this 828 // thread to be suspended. The third thread can notice the safepoint 829 // that we're trying to start at the beginning of its SR_lock->wait() 830 // call. If that happens, then the third thread will block on the 831 // safepoint while still holding the underlying SR_lock. We won't be 832 // able to get the SR_lock and we'll deadlock. 833 // 834 // We don't need to grab the SR_lock here for two reasons: 835 // 1) The suspend flags are both volatile and are set with an 836 // Atomic::cmpxchg() call so we should see the suspended 837 // state right away. 838 // 2) We're being called from the safepoint polling loop; if 839 // we don't see the suspended state on this iteration, then 840 // we'll come around again. 841 // 842 bool is_suspended = _thread->is_ext_suspended(); 843 if (is_suspended) { 844 roll_forward(_at_safepoint); 845 return; 846 } 847 848 // Some JavaThread states have an initial safepoint state of 849 // running, but are actually at a safepoint. We will happily 850 // agree and update the safepoint state here. 851 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 852 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 853 roll_forward(_at_safepoint); 854 return; 855 } 856 857 if (state == _thread_in_vm) { 858 roll_forward(_call_back); 859 return; 860 } 861 862 // All other thread states will continue to run until they 863 // transition and self-block in state _blocked 864 // Safepoint polling in compiled code causes the Java threads to do the same. 865 // Note: new threads may require a malloc so they must be allowed to finish 866 867 assert(is_running(), "examine_state_of_thread on non-running thread"); 868 return; 869 } 870 871 // Returns true is thread could not be rolled forward at present position. 872 void ThreadSafepointState::roll_forward(suspend_type type) { 873 _type = type; 874 875 switch(_type) { 876 case _at_safepoint: 877 SafepointSynchronize::signal_thread_at_safepoint(); 878 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 879 if (_thread->in_critical()) { 880 // Notice that this thread is in a critical section 881 SafepointSynchronize::increment_jni_active_count(); 882 } 883 break; 884 885 case _call_back: 886 set_has_called_back(false); 887 break; 888 889 case _running: 890 default: 891 ShouldNotReachHere(); 892 } 893 } 894 895 void ThreadSafepointState::restart() { 896 switch(type()) { 897 case _at_safepoint: 898 case _call_back: 899 break; 900 901 case _running: 902 default: 903 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d", 904 _thread, _type); 905 _thread->print(); 906 ShouldNotReachHere(); 907 } 908 _type = _running; 909 set_has_called_back(false); 910 } 911 912 913 void ThreadSafepointState::print_on(outputStream *st) const { 914 const char *s; 915 916 switch(_type) { 917 case _running : s = "_running"; break; 918 case _at_safepoint : s = "_at_safepoint"; break; 919 case _call_back : s = "_call_back"; break; 920 default: 921 ShouldNotReachHere(); 922 } 923 924 st->print_cr("Thread: " INTPTR_FORMAT 925 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 926 _thread, _thread->osthread()->thread_id(), s, _has_called_back, 927 _at_poll_safepoint); 928 929 _thread->print_thread_state_on(st); 930 } 931 932 933 // --------------------------------------------------------------------------------------------------------------------- 934 935 // Block the thread at the safepoint poll or poll return. 936 void ThreadSafepointState::handle_polling_page_exception() { 937 938 // Check state. block() will set thread state to thread_in_vm which will 939 // cause the safepoint state _type to become _call_back. 940 assert(type() == ThreadSafepointState::_running, 941 "polling page exception on thread not running state"); 942 943 // Step 1: Find the nmethod from the return address 944 if (ShowSafepointMsgs && Verbose) { 945 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); 946 } 947 address real_return_addr = thread()->saved_exception_pc(); 948 949 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 950 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); 951 nmethod* nm = (nmethod*)cb; 952 953 // Find frame of caller 954 frame stub_fr = thread()->last_frame(); 955 CodeBlob* stub_cb = stub_fr.cb(); 956 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 957 RegisterMap map(thread(), true); 958 frame caller_fr = stub_fr.sender(&map); 959 960 // Should only be poll_return or poll 961 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 962 963 // This is a poll immediately before a return. The exception handling code 964 // has already had the effect of causing the return to occur, so the execution 965 // will continue immediately after the call. In addition, the oopmap at the 966 // return point does not mark the return value as an oop (if it is), so 967 // it needs a handle here to be updated. 968 if( nm->is_at_poll_return(real_return_addr) ) { 969 // See if return type is an oop. 970 bool return_oop = nm->method()->is_returning_oop(); 971 Handle return_value; 972 if (return_oop) { 973 // The oop result has been saved on the stack together with all 974 // the other registers. In order to preserve it over GCs we need 975 // to keep it in a handle. 976 oop result = caller_fr.saved_oop_result(&map); 977 if (ShenandoahVerifyReadsToFromSpace) { 978 result = oopDesc::bs()->read_barrier(result); 979 } 980 assert(result == NULL || result->is_oop(), "must be oop"); 981 return_value = Handle(thread(), result); 982 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 983 } 984 985 // Block the thread 986 SafepointSynchronize::block(thread()); 987 988 // restore oop result, if any 989 if (return_oop) { 990 caller_fr.set_saved_oop_result(&map, return_value()); 991 } 992 } 993 994 // This is a safepoint poll. Verify the return address and block. 995 else { 996 set_at_poll_safepoint(true); 997 998 // verify the blob built the "return address" correctly 999 assert(real_return_addr == caller_fr.pc(), "must match"); 1000 1001 // Block the thread 1002 SafepointSynchronize::block(thread()); 1003 set_at_poll_safepoint(false); 1004 1005 // If we have a pending async exception deoptimize the frame 1006 // as otherwise we may never deliver it. 1007 if (thread()->has_async_condition()) { 1008 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1009 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1010 } 1011 1012 // If an exception has been installed we must check for a pending deoptimization 1013 // Deoptimize frame if exception has been thrown. 1014 1015 if (thread()->has_pending_exception() ) { 1016 RegisterMap map(thread(), true); 1017 frame caller_fr = stub_fr.sender(&map); 1018 if (caller_fr.is_deoptimized_frame()) { 1019 // The exception patch will destroy registers that are still 1020 // live and will be needed during deoptimization. Defer the 1021 // Async exception should have deferred the exception until the 1022 // next safepoint which will be detected when we get into 1023 // the interpreter so if we have an exception now things 1024 // are messed up. 1025 1026 fatal("Exception installed and deoptimization is pending"); 1027 } 1028 } 1029 } 1030 } 1031 1032 1033 // 1034 // Statistics & Instrumentations 1035 // 1036 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1037 jlong SafepointSynchronize::_safepoint_begin_time = 0; 1038 int SafepointSynchronize::_cur_stat_index = 0; 1039 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1040 julong SafepointSynchronize::_coalesced_vmop_count = 0; 1041 jlong SafepointSynchronize::_max_sync_time = 0; 1042 jlong SafepointSynchronize::_max_vmop_time = 0; 1043 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1044 1045 static jlong cleanup_end_time = 0; 1046 static bool need_to_track_page_armed_status = false; 1047 static bool init_done = false; 1048 1049 // Helper method to print the header. 1050 static void print_header() { 1051 tty->print(" vmop " 1052 "[threads: total initially_running wait_to_block] "); 1053 tty->print("[time: spin block sync cleanup vmop] "); 1054 1055 // no page armed status printed out if it is always armed. 1056 if (need_to_track_page_armed_status) { 1057 tty->print("page_armed "); 1058 } 1059 1060 tty->print_cr("page_trap_count"); 1061 } 1062 1063 void SafepointSynchronize::deferred_initialize_stat() { 1064 if (init_done) return; 1065 1066 if (PrintSafepointStatisticsCount <= 0) { 1067 fatal("Wrong PrintSafepointStatisticsCount"); 1068 } 1069 1070 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1071 // be printed right away, in which case, _safepoint_stats will regress to 1072 // a single element array. Otherwise, it is a circular ring buffer with default 1073 // size of PrintSafepointStatisticsCount. 1074 int stats_array_size; 1075 if (PrintSafepointStatisticsTimeout > 0) { 1076 stats_array_size = 1; 1077 PrintSafepointStatistics = true; 1078 } else { 1079 stats_array_size = PrintSafepointStatisticsCount; 1080 } 1081 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1082 * sizeof(SafepointStats), mtInternal); 1083 guarantee(_safepoint_stats != NULL, 1084 "not enough memory for safepoint instrumentation data"); 1085 1086 if (DeferPollingPageLoopCount >= 0) { 1087 need_to_track_page_armed_status = true; 1088 } 1089 init_done = true; 1090 } 1091 1092 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1093 assert(init_done, "safepoint statistics array hasn't been initialized"); 1094 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1095 1096 spstat->_time_stamp = _ts_of_current_safepoint; 1097 1098 VM_Operation *op = VMThread::vm_operation(); 1099 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1100 if (op != NULL) { 1101 _safepoint_reasons[spstat->_vmop_type]++; 1102 } 1103 1104 spstat->_nof_total_threads = nof_threads; 1105 spstat->_nof_initial_running_threads = nof_running; 1106 spstat->_nof_threads_hit_page_trap = 0; 1107 1108 // Records the start time of spinning. The real time spent on spinning 1109 // will be adjusted when spin is done. Same trick is applied for time 1110 // spent on waiting for threads to block. 1111 if (nof_running != 0) { 1112 spstat->_time_to_spin = os::javaTimeNanos(); 1113 } else { 1114 spstat->_time_to_spin = 0; 1115 } 1116 } 1117 1118 void SafepointSynchronize::update_statistics_on_spin_end() { 1119 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1120 1121 jlong cur_time = os::javaTimeNanos(); 1122 1123 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1124 if (spstat->_nof_initial_running_threads != 0) { 1125 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1126 } 1127 1128 if (need_to_track_page_armed_status) { 1129 spstat->_page_armed = (PageArmed == 1); 1130 } 1131 1132 // Records the start time of waiting for to block. Updated when block is done. 1133 if (_waiting_to_block != 0) { 1134 spstat->_time_to_wait_to_block = cur_time; 1135 } else { 1136 spstat->_time_to_wait_to_block = 0; 1137 } 1138 } 1139 1140 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1141 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1142 1143 if (spstat->_nof_threads_wait_to_block != 0) { 1144 spstat->_time_to_wait_to_block = end_time - 1145 spstat->_time_to_wait_to_block; 1146 } 1147 1148 // Records the end time of sync which will be used to calculate the total 1149 // vm operation time. Again, the real time spending in syncing will be deducted 1150 // from the start of the sync time later when end_statistics is called. 1151 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1152 if (spstat->_time_to_sync > _max_sync_time) { 1153 _max_sync_time = spstat->_time_to_sync; 1154 } 1155 1156 spstat->_time_to_do_cleanups = end_time; 1157 } 1158 1159 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1160 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1161 1162 // Record how long spent in cleanup tasks. 1163 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1164 1165 cleanup_end_time = end_time; 1166 } 1167 1168 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1169 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1170 1171 // Update the vm operation time. 1172 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1173 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1174 _max_vmop_time = spstat->_time_to_exec_vmop; 1175 } 1176 // Only the sync time longer than the specified 1177 // PrintSafepointStatisticsTimeout will be printed out right away. 1178 // By default, it is -1 meaning all samples will be put into the list. 1179 if ( PrintSafepointStatisticsTimeout > 0) { 1180 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1181 print_statistics(); 1182 } 1183 } else { 1184 // The safepoint statistics will be printed out when the _safepoin_stats 1185 // array fills up. 1186 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1187 print_statistics(); 1188 _cur_stat_index = 0; 1189 } else { 1190 _cur_stat_index++; 1191 } 1192 } 1193 } 1194 1195 void SafepointSynchronize::print_statistics() { 1196 SafepointStats* sstats = _safepoint_stats; 1197 1198 for (int index = 0; index <= _cur_stat_index; index++) { 1199 if (index % 30 == 0) { 1200 print_header(); 1201 } 1202 sstats = &_safepoint_stats[index]; 1203 tty->print("%.3f: ", sstats->_time_stamp); 1204 tty->print("%-26s [" 1205 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15) 1206 " ] ", 1207 sstats->_vmop_type == -1 ? "no vm operation" : 1208 VM_Operation::name(sstats->_vmop_type), 1209 sstats->_nof_total_threads, 1210 sstats->_nof_initial_running_threads, 1211 sstats->_nof_threads_wait_to_block); 1212 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1213 tty->print(" [" 1214 INT64_FORMAT_W(6) INT64_FORMAT_W(6) 1215 INT64_FORMAT_W(6) INT64_FORMAT_W(6) 1216 INT64_FORMAT_W(6) " ] ", 1217 sstats->_time_to_spin / MICROUNITS, 1218 sstats->_time_to_wait_to_block / MICROUNITS, 1219 sstats->_time_to_sync / MICROUNITS, 1220 sstats->_time_to_do_cleanups / MICROUNITS, 1221 sstats->_time_to_exec_vmop / MICROUNITS); 1222 1223 if (need_to_track_page_armed_status) { 1224 tty->print(INT32_FORMAT " ", sstats->_page_armed); 1225 } 1226 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap); 1227 } 1228 } 1229 1230 // This method will be called when VM exits. It will first call 1231 // print_statistics to print out the rest of the sampling. Then 1232 // it tries to summarize the sampling. 1233 void SafepointSynchronize::print_stat_on_exit() { 1234 if (_safepoint_stats == NULL) return; 1235 1236 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1237 1238 // During VM exit, end_statistics may not get called and in that 1239 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1240 // don't print it out. 1241 // Approximate the vm op time. 1242 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1243 os::javaTimeNanos() - cleanup_end_time; 1244 1245 if ( PrintSafepointStatisticsTimeout < 0 || 1246 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1247 print_statistics(); 1248 } 1249 tty->cr(); 1250 1251 // Print out polling page sampling status. 1252 if (!need_to_track_page_armed_status) { 1253 tty->print_cr("Polling page always armed"); 1254 } else { 1255 tty->print_cr("Defer polling page loop count = %d\n", 1256 DeferPollingPageLoopCount); 1257 } 1258 1259 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1260 if (_safepoint_reasons[index] != 0) { 1261 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index), 1262 _safepoint_reasons[index]); 1263 } 1264 } 1265 1266 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint", 1267 _coalesced_vmop_count); 1268 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms", 1269 _max_sync_time / MICROUNITS); 1270 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1271 INT64_FORMAT_W(5) " ms", 1272 _max_vmop_time / MICROUNITS); 1273 } 1274 1275 // ------------------------------------------------------------------------------------------------ 1276 // Non-product code 1277 1278 #ifndef PRODUCT 1279 1280 void SafepointSynchronize::print_state() { 1281 if (_state == _not_synchronized) { 1282 tty->print_cr("not synchronized"); 1283 } else if (_state == _synchronizing || _state == _synchronized) { 1284 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1285 "synchronized"); 1286 1287 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1288 cur->safepoint_state()->print(); 1289 } 1290 } 1291 } 1292 1293 void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1294 if (ShowSafepointMsgs) { 1295 va_list ap; 1296 va_start(ap, format); 1297 tty->vprint_cr(format, ap); 1298 va_end(ap); 1299 } 1300 } 1301 1302 #endif // !PRODUCT