safepoint.cpp revision 6760:22b98ab2a69f
1/* 2 * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25#include "precompiled.hpp" 26#include "classfile/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_interface/collectedHeap.hpp" 34#include "interpreter/interpreter.hpp" 35#include "memory/gcLocker.inline.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/memTracker.hpp" 56#include "services/runtimeService.hpp" 57#include "utilities/events.hpp" 58#include "utilities/macros.hpp" 59#if INCLUDE_ALL_GCS 60#include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" 61#include "gc_implementation/shared/suspendibleThreadSet.hpp" 62#endif // INCLUDE_ALL_GCS 63#ifdef COMPILER1 64#include "c1/c1_globals.hpp" 65#endif 66 67PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 68 69// -------------------------------------------------------------------------------------------------- 70// Implementation of Safepoint begin/end 71 72SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 73volatile int SafepointSynchronize::_waiting_to_block = 0; 74volatile int SafepointSynchronize::_safepoint_counter = 0; 75int SafepointSynchronize::_current_jni_active_count = 0; 76long SafepointSynchronize::_end_of_last_safepoint = 0; 77static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 78static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 79static bool timeout_error_printed = false; 80 81// Roll all threads forward to a safepoint and suspend them all 82void 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 } 100#endif // INCLUDE_ALL_GCS 101 102 // By getting the Threads_lock, we assure that no threads are about to start or 103 // exit. It is released again in SafepointSynchronize::end(). 104 Threads_lock->lock(); 105 106 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 107 108 int nof_threads = Threads::number_of_threads(); 109 110 if (TraceSafepoint) { 111 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); 112 } 113 114 RuntimeService::record_safepoint_begin(); 115 116 MutexLocker mu(Safepoint_lock); 117 118 // Reset the count of active JNI critical threads 119 _current_jni_active_count = 0; 120 121 // Set number of threads to wait for, before we initiate the callbacks 122 _waiting_to_block = nof_threads; 123 TryingToBlock = 0 ; 124 int still_running = nof_threads; 125 126 // Save the starting time, so that it can be compared to see if this has taken 127 // too long to complete. 128 jlong safepoint_limit_time; 129 timeout_error_printed = false; 130 131 // PrintSafepointStatisticsTimeout can be specified separately. When 132 // specified, PrintSafepointStatistics will be set to true in 133 // deferred_initialize_stat method. The initialization has to be done 134 // early enough to avoid any races. See bug 6880029 for details. 135 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 136 deferred_initialize_stat(); 137 } 138 139 // Begin the process of bringing the system to a safepoint. 140 // Java threads can be in several different states and are 141 // stopped by different mechanisms: 142 // 143 // 1. Running interpreted 144 // The interpreter dispatch table is changed to force it to 145 // check for a safepoint condition between bytecodes. 146 // 2. Running in native code 147 // When returning from the native code, a Java thread must check 148 // the safepoint _state to see if we must block. If the 149 // VM thread sees a Java thread in native, it does 150 // not wait for this thread to block. The order of the memory 151 // writes and reads of both the safepoint state and the Java 152 // threads state is critical. In order to guarantee that the 153 // memory writes are serialized with respect to each other, 154 // the VM thread issues a memory barrier instruction 155 // (on MP systems). In order to avoid the overhead of issuing 156 // a memory barrier for each Java thread making native calls, each Java 157 // thread performs a write to a single memory page after changing 158 // the thread state. The VM thread performs a sequence of 159 // mprotect OS calls which forces all previous writes from all 160 // Java threads to be serialized. This is done in the 161 // os::serialize_thread_states() call. This has proven to be 162 // much more efficient than executing a membar instruction 163 // on every call to native code. 164 // 3. Running compiled Code 165 // Compiled code reads a global (Safepoint Polling) page that 166 // is set to fault if we are trying to get to a safepoint. 167 // 4. Blocked 168 // A thread which is blocked will not be allowed to return from the 169 // block condition until the safepoint operation is complete. 170 // 5. In VM or Transitioning between states 171 // If a Java thread is currently running in the VM or transitioning 172 // between states, the safepointing code will wait for the thread to 173 // block itself when it attempts transitions to a new state. 174 // 175 _state = _synchronizing; 176 OrderAccess::fence(); 177 178 // Flush all thread states to memory 179 if (!UseMembar) { 180 os::serialize_thread_states(); 181 } 182 183 // Make interpreter safepoint aware 184 Interpreter::notice_safepoints(); 185 186 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) { 187 // Make polling safepoint aware 188 guarantee (PageArmed == 0, "invariant") ; 189 PageArmed = 1 ; 190 os::make_polling_page_unreadable(); 191 } 192 193 // Consider using active_processor_count() ... but that call is expensive. 194 int ncpus = os::processor_count() ; 195 196#ifdef ASSERT 197 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 198 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 199 // Clear the visited flag to ensure that the critical counts are collected properly. 200 cur->set_visited_for_critical_count(false); 201 } 202#endif // ASSERT 203 204 if (SafepointTimeout) 205 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 206 207 // Iterate through all threads until it have been determined how to stop them all at a safepoint 208 unsigned int iterations = 0; 209 int steps = 0 ; 210 while(still_running > 0) { 211 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 212 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 213 ThreadSafepointState *cur_state = cur->safepoint_state(); 214 if (cur_state->is_running()) { 215 cur_state->examine_state_of_thread(); 216 if (!cur_state->is_running()) { 217 still_running--; 218 // consider adjusting steps downward: 219 // steps = 0 220 // steps -= NNN 221 // steps >>= 1 222 // steps = MIN(steps, 2000-100) 223 // if (iterations != 0) steps -= NNN 224 } 225 if (TraceSafepoint && Verbose) cur_state->print(); 226 } 227 } 228 229 if (PrintSafepointStatistics && iterations == 0) { 230 begin_statistics(nof_threads, still_running); 231 } 232 233 if (still_running > 0) { 234 // Check for if it takes to long 235 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 236 print_safepoint_timeout(_spinning_timeout); 237 } 238 239 // Spin to avoid context switching. 240 // There's a tension between allowing the mutators to run (and rendezvous) 241 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 242 // a mutator might otherwise use profitably to reach a safepoint. Excessive 243 // spinning by the VM thread on a saturated system can increase rendezvous latency. 244 // Blocking or yielding incur their own penalties in the form of context switching 245 // and the resultant loss of $ residency. 246 // 247 // Further complicating matters is that yield() does not work as naively expected 248 // on many platforms -- yield() does not guarantee that any other ready threads 249 // will run. As such we revert to naked_short_sleep() after some number of iterations. 250 // nakes_short_sleep() is implemented as a short unconditional sleep. 251 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 252 // can actually increase the time it takes the VM thread to detect that a system-wide 253 // stop-the-world safepoint has been reached. In a pathological scenario such as that 254 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 255 // In that case the mutators will be stalled waiting for the safepoint to complete and the 256 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 257 // will eventually wake up and detect that all mutators are safe, at which point 258 // we'll again make progress. 259 // 260 // Beware too that that the VMThread typically runs at elevated priority. 261 // Its default priority is higher than the default mutator priority. 262 // Obviously, this complicates spinning. 263 // 264 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 265 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 266 // 267 // See the comments in synchronizer.cpp for additional remarks on spinning. 268 // 269 // In the future we might: 270 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning. 271 // This is tricky as the path used by a thread exiting the JVM (say on 272 // on JNI call-out) simply stores into its state field. The burden 273 // is placed on the VM thread, which must poll (spin). 274 // 2. Find something useful to do while spinning. If the safepoint is GC-related 275 // we might aggressively scan the stacks of threads that are already safe. 276 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 277 // If all the mutators are ONPROC there's no reason to sleep or yield. 278 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 279 // 5. Check system saturation. If the system is not fully saturated then 280 // simply spin and avoid sleep/yield. 281 // 6. As still-running mutators rendezvous they could unpark the sleeping 282 // VMthread. This works well for still-running mutators that become 283 // safe. The VMthread must still poll for mutators that call-out. 284 // 7. Drive the policy on time-since-begin instead of iterations. 285 // 8. Consider making the spin duration a function of the # of CPUs: 286 // Spin = (((ncpus-1) * M) + K) + F(still_running) 287 // Alternately, instead of counting iterations of the outer loop 288 // we could count the # of threads visited in the inner loop, above. 289 // 9. On windows consider using the return value from SwitchThreadTo() 290 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 291 292 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) { 293 guarantee (PageArmed == 0, "invariant") ; 294 PageArmed = 1 ; 295 os::make_polling_page_unreadable(); 296 } 297 298 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 299 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 300 ++steps ; 301 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 302 SpinPause() ; // MP-Polite spin 303 } else 304 if (steps < DeferThrSuspendLoopCount) { 305 os::NakedYield() ; 306 } else { 307 os::naked_short_sleep(1); 308 } 309 310 iterations ++ ; 311 } 312 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 313 } 314 assert(still_running == 0, "sanity check"); 315 316 if (PrintSafepointStatistics) { 317 update_statistics_on_spin_end(); 318 } 319 320 // wait until all threads are stopped 321 while (_waiting_to_block > 0) { 322 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); 323 if (!SafepointTimeout || timeout_error_printed) { 324 Safepoint_lock->wait(true); // true, means with no safepoint checks 325 } else { 326 // Compute remaining time 327 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 328 329 // If there is no remaining time, then there is an error 330 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 331 print_safepoint_timeout(_blocking_timeout); 332 } 333 } 334 } 335 assert(_waiting_to_block == 0, "sanity check"); 336 337#ifndef PRODUCT 338 if (SafepointTimeout) { 339 jlong current_time = os::javaTimeNanos(); 340 if (safepoint_limit_time < current_time) { 341 tty->print_cr("# SafepointSynchronize: Finished after " 342 INT64_FORMAT_W(6) " ms", 343 ((current_time - safepoint_limit_time) / MICROUNITS + 344 SafepointTimeoutDelay)); 345 } 346 } 347#endif 348 349 assert((_safepoint_counter & 0x1) == 0, "must be even"); 350 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 351 _safepoint_counter ++; 352 353 // Record state 354 _state = _synchronized; 355 356 OrderAccess::fence(); 357 358#ifdef ASSERT 359 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 360 // make sure all the threads were visited 361 assert(cur->was_visited_for_critical_count(), "missed a thread"); 362 } 363#endif // ASSERT 364 365 // Update the count of active JNI critical regions 366 GC_locker::set_jni_lock_count(_current_jni_active_count); 367 368 if (TraceSafepoint) { 369 VM_Operation *op = VMThread::vm_operation(); 370 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); 371 } 372 373 RuntimeService::record_safepoint_synchronized(); 374 if (PrintSafepointStatistics) { 375 update_statistics_on_sync_end(os::javaTimeNanos()); 376 } 377 378 // Call stuff that needs to be run when a safepoint is just about to be completed 379 do_cleanup_tasks(); 380 381 if (PrintSafepointStatistics) { 382 // Record how much time spend on the above cleanup tasks 383 update_statistics_on_cleanup_end(os::javaTimeNanos()); 384 } 385} 386 387// Wake up all threads, so they are ready to resume execution after the safepoint 388// operation has been carried out 389void SafepointSynchronize::end() { 390 391 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 392 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 393 _safepoint_counter ++; 394 // memory fence isn't required here since an odd _safepoint_counter 395 // value can do no harm and a fence is issued below anyway. 396 397 DEBUG_ONLY(Thread* myThread = Thread::current();) 398 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 399 400 if (PrintSafepointStatistics) { 401 end_statistics(os::javaTimeNanos()); 402 } 403 404#ifdef ASSERT 405 // A pending_exception cannot be installed during a safepoint. The threads 406 // may install an async exception after they come back from a safepoint into 407 // pending_exception after they unblock. But that should happen later. 408 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 409 assert (!(cur->has_pending_exception() && 410 cur->safepoint_state()->is_at_poll_safepoint()), 411 "safepoint installed a pending exception"); 412 } 413#endif // ASSERT 414 415 if (PageArmed) { 416 // Make polling safepoint aware 417 os::make_polling_page_readable(); 418 PageArmed = 0 ; 419 } 420 421 // Remove safepoint check from interpreter 422 Interpreter::ignore_safepoints(); 423 424 { 425 MutexLocker mu(Safepoint_lock); 426 427 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 428 429 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 430 // when they get restarted. 431 _state = _not_synchronized; 432 OrderAccess::fence(); 433 434 if (TraceSafepoint) { 435 tty->print_cr("Leaving safepoint region"); 436 } 437 438 // Start suspended threads 439 for(JavaThread *current = Threads::first(); current; current = current->next()) { 440 // A problem occurring on Solaris is when attempting to restart threads 441 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 442 // to the next one (since it has been running the longest). We then have 443 // to wait for a cpu to become available before we can continue restarting 444 // threads. 445 // FIXME: This causes the performance of the VM to degrade when active and with 446 // large numbers of threads. Apparently this is due to the synchronous nature 447 // of suspending threads. 448 // 449 // TODO-FIXME: the comments above are vestigial and no longer apply. 450 // Furthermore, using solaris' schedctl in this particular context confers no benefit 451 if (VMThreadHintNoPreempt) { 452 os::hint_no_preempt(); 453 } 454 ThreadSafepointState* cur_state = current->safepoint_state(); 455 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 456 cur_state->restart(); 457 assert(cur_state->is_running(), "safepoint state has not been reset"); 458 } 459 460 RuntimeService::record_safepoint_end(); 461 462 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 463 // blocked in signal_thread_blocked 464 Threads_lock->unlock(); 465 466 } 467#if INCLUDE_ALL_GCS 468 // If there are any concurrent GC threads resume them. 469 if (UseConcMarkSweepGC) { 470 ConcurrentMarkSweepThread::desynchronize(false); 471 } else if (UseG1GC) { 472 SuspendibleThreadSet::desynchronize(); 473 } 474#endif // INCLUDE_ALL_GCS 475 // record this time so VMThread can keep track how much time has elapsed 476 // since last safepoint. 477 _end_of_last_safepoint = os::javaTimeMillis(); 478} 479 480bool SafepointSynchronize::is_cleanup_needed() { 481 // Need a safepoint if some inline cache buffers is non-empty 482 if (!InlineCacheBuffer::is_empty()) return true; 483 return false; 484} 485 486 487 488// Various cleaning tasks that should be done periodically at safepoints 489void SafepointSynchronize::do_cleanup_tasks() { 490 { 491 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime); 492 ObjectSynchronizer::deflate_idle_monitors(); 493 } 494 495 { 496 TraceTime t2("updating inline caches", TraceSafepointCleanupTime); 497 InlineCacheBuffer::update_inline_caches(); 498 } 499 { 500 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime); 501 CompilationPolicy::policy()->do_safepoint_work(); 502 } 503 504 { 505 TraceTime t4("mark nmethods", TraceSafepointCleanupTime); 506 NMethodSweeper::mark_active_nmethods(); 507 } 508 509 if (SymbolTable::needs_rehashing()) { 510 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime); 511 SymbolTable::rehash_table(); 512 } 513 514 if (StringTable::needs_rehashing()) { 515 TraceTime t6("rehashing string table", TraceSafepointCleanupTime); 516 StringTable::rehash_table(); 517 } 518 519 // rotate log files? 520 if (UseGCLogFileRotation) { 521 gclog_or_tty->rotate_log(false); 522 } 523 524 { 525 // CMS delays purging the CLDG until the beginning of the next safepoint and to 526 // make sure concurrent sweep is done 527 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime); 528 ClassLoaderDataGraph::purge_if_needed(); 529 } 530 531 if (MemTracker::is_on()) { 532 MemTracker::sync(); 533 } 534} 535 536 537bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 538 switch(state) { 539 case _thread_in_native: 540 // native threads are safe if they have no java stack or have walkable stack 541 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 542 543 // blocked threads should have already have walkable stack 544 case _thread_blocked: 545 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 546 return true; 547 548 default: 549 return false; 550 } 551} 552 553 554// See if the thread is running inside a lazy critical native and 555// update the thread critical count if so. Also set a suspend flag to 556// cause the native wrapper to return into the JVM to do the unlock 557// once the native finishes. 558void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 559 if (state == _thread_in_native && 560 thread->has_last_Java_frame() && 561 thread->frame_anchor()->walkable()) { 562 // This thread might be in a critical native nmethod so look at 563 // the top of the stack and increment the critical count if it 564 // is. 565 frame wrapper_frame = thread->last_frame(); 566 CodeBlob* stub_cb = wrapper_frame.cb(); 567 if (stub_cb != NULL && 568 stub_cb->is_nmethod() && 569 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 570 // A thread could potentially be in a critical native across 571 // more than one safepoint, so only update the critical state on 572 // the first one. When it returns it will perform the unlock. 573 if (!thread->do_critical_native_unlock()) { 574#ifdef ASSERT 575 if (!thread->in_critical()) { 576 GC_locker::increment_debug_jni_lock_count(); 577 } 578#endif 579 thread->enter_critical(); 580 // Make sure the native wrapper calls back on return to 581 // perform the needed critical unlock. 582 thread->set_critical_native_unlock(); 583 } 584 } 585 } 586} 587 588 589 590// ------------------------------------------------------------------------------------------------------- 591// Implementation of Safepoint callback point 592 593void SafepointSynchronize::block(JavaThread *thread) { 594 assert(thread != NULL, "thread must be set"); 595 assert(thread->is_Java_thread(), "not a Java thread"); 596 597 // Threads shouldn't block if they are in the middle of printing, but... 598 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 599 600 // Only bail from the block() call if the thread is gone from the 601 // thread list; starting to exit should still block. 602 if (thread->is_terminated()) { 603 // block current thread if we come here from native code when VM is gone 604 thread->block_if_vm_exited(); 605 606 // otherwise do nothing 607 return; 608 } 609 610 JavaThreadState state = thread->thread_state(); 611 thread->frame_anchor()->make_walkable(thread); 612 613 // Check that we have a valid thread_state at this point 614 switch(state) { 615 case _thread_in_vm_trans: 616 case _thread_in_Java: // From compiled code 617 618 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 619 // we pretend we are still in the VM. 620 thread->set_thread_state(_thread_in_vm); 621 622 if (is_synchronizing()) { 623 Atomic::inc (&TryingToBlock) ; 624 } 625 626 // We will always be holding the Safepoint_lock when we are examine the state 627 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 628 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 629 Safepoint_lock->lock_without_safepoint_check(); 630 if (is_synchronizing()) { 631 // Decrement the number of threads to wait for and signal vm thread 632 assert(_waiting_to_block > 0, "sanity check"); 633 _waiting_to_block--; 634 thread->safepoint_state()->set_has_called_back(true); 635 636 DEBUG_ONLY(thread->set_visited_for_critical_count(true)); 637 if (thread->in_critical()) { 638 // Notice that this thread is in a critical section 639 increment_jni_active_count(); 640 } 641 642 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 643 if (_waiting_to_block == 0) { 644 Safepoint_lock->notify_all(); 645 } 646 } 647 648 // We transition the thread to state _thread_blocked here, but 649 // we can't do our usual check for external suspension and then 650 // self-suspend after the lock_without_safepoint_check() call 651 // below because we are often called during transitions while 652 // we hold different locks. That would leave us suspended while 653 // holding a resource which results in deadlocks. 654 thread->set_thread_state(_thread_blocked); 655 Safepoint_lock->unlock(); 656 657 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 658 // the entire safepoint, the threads will all line up here during the safepoint. 659 Threads_lock->lock_without_safepoint_check(); 660 // restore original state. This is important if the thread comes from compiled code, so it 661 // will continue to execute with the _thread_in_Java state. 662 thread->set_thread_state(state); 663 Threads_lock->unlock(); 664 break; 665 666 case _thread_in_native_trans: 667 case _thread_blocked_trans: 668 case _thread_new_trans: 669 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 670 thread->print_thread_state(); 671 fatal("Deadlock in safepoint code. " 672 "Should have called back to the VM before blocking."); 673 } 674 675 // We transition the thread to state _thread_blocked here, but 676 // we can't do our usual check for external suspension and then 677 // self-suspend after the lock_without_safepoint_check() call 678 // below because we are often called during transitions while 679 // we hold different locks. That would leave us suspended while 680 // holding a resource which results in deadlocks. 681 thread->set_thread_state(_thread_blocked); 682 683 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 684 // the safepoint code might still be waiting for it to block. We need to change the state here, 685 // so it can see that it is at a safepoint. 686 687 // Block until the safepoint operation is completed. 688 Threads_lock->lock_without_safepoint_check(); 689 690 // Restore state 691 thread->set_thread_state(state); 692 693 Threads_lock->unlock(); 694 break; 695 696 default: 697 fatal(err_msg("Illegal threadstate encountered: %d", state)); 698 } 699 700 // Check for pending. async. exceptions or suspends - except if the 701 // thread was blocked inside the VM. has_special_runtime_exit_condition() 702 // is called last since it grabs a lock and we only want to do that when 703 // we must. 704 // 705 // Note: we never deliver an async exception at a polling point as the 706 // compiler may not have an exception handler for it. The polling 707 // code will notice the async and deoptimize and the exception will 708 // be delivered. (Polling at a return point is ok though). Sure is 709 // a lot of bother for a deprecated feature... 710 // 711 // We don't deliver an async exception if the thread state is 712 // _thread_in_native_trans so JNI functions won't be called with 713 // a surprising pending exception. If the thread state is going back to java, 714 // async exception is checked in check_special_condition_for_native_trans(). 715 716 if (state != _thread_blocked_trans && 717 state != _thread_in_vm_trans && 718 thread->has_special_runtime_exit_condition()) { 719 thread->handle_special_runtime_exit_condition( 720 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 721 } 722} 723 724// ------------------------------------------------------------------------------------------------------ 725// Exception handlers 726 727 728void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 729 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 730 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 731 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 732 733 if (ShowSafepointMsgs) { 734 tty->print("handle_polling_page_exception: "); 735 } 736 737 if (PrintSafepointStatistics) { 738 inc_page_trap_count(); 739 } 740 741 ThreadSafepointState* state = thread->safepoint_state(); 742 743 state->handle_polling_page_exception(); 744} 745 746 747void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 748 if (!timeout_error_printed) { 749 timeout_error_printed = true; 750 // Print out the thread info which didn't reach the safepoint for debugging 751 // purposes (useful when there are lots of threads in the debugger). 752 tty->cr(); 753 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 754 if (reason == _spinning_timeout) { 755 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 756 } else if (reason == _blocking_timeout) { 757 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 758 } 759 760 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 761 ThreadSafepointState *cur_state; 762 ResourceMark rm; 763 for(JavaThread *cur_thread = Threads::first(); cur_thread; 764 cur_thread = cur_thread->next()) { 765 cur_state = cur_thread->safepoint_state(); 766 767 if (cur_thread->thread_state() != _thread_blocked && 768 ((reason == _spinning_timeout && cur_state->is_running()) || 769 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 770 tty->print("# "); 771 cur_thread->print(); 772 tty->cr(); 773 } 774 } 775 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 776 } 777 778 // To debug the long safepoint, specify both DieOnSafepointTimeout & 779 // ShowMessageBoxOnError. 780 if (DieOnSafepointTimeout) { 781 char msg[1024]; 782 VM_Operation *op = VMThread::vm_operation(); 783 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 784 SafepointTimeoutDelay, 785 op != NULL ? op->name() : "no vm operation"); 786 fatal(msg); 787 } 788} 789 790 791// ------------------------------------------------------------------------------------------------------- 792// Implementation of ThreadSafepointState 793 794ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 795 _thread = thread; 796 _type = _running; 797 _has_called_back = false; 798 _at_poll_safepoint = false; 799} 800 801void ThreadSafepointState::create(JavaThread *thread) { 802 ThreadSafepointState *state = new ThreadSafepointState(thread); 803 thread->set_safepoint_state(state); 804} 805 806void ThreadSafepointState::destroy(JavaThread *thread) { 807 if (thread->safepoint_state()) { 808 delete(thread->safepoint_state()); 809 thread->set_safepoint_state(NULL); 810 } 811} 812 813void ThreadSafepointState::examine_state_of_thread() { 814 assert(is_running(), "better be running or just have hit safepoint poll"); 815 816 JavaThreadState state = _thread->thread_state(); 817 818 // Save the state at the start of safepoint processing. 819 _orig_thread_state = state; 820 821 // Check for a thread that is suspended. Note that thread resume tries 822 // to grab the Threads_lock which we own here, so a thread cannot be 823 // resumed during safepoint synchronization. 824 825 // We check to see if this thread is suspended without locking to 826 // avoid deadlocking with a third thread that is waiting for this 827 // thread to be suspended. The third thread can notice the safepoint 828 // that we're trying to start at the beginning of its SR_lock->wait() 829 // call. If that happens, then the third thread will block on the 830 // safepoint while still holding the underlying SR_lock. We won't be 831 // able to get the SR_lock and we'll deadlock. 832 // 833 // We don't need to grab the SR_lock here for two reasons: 834 // 1) The suspend flags are both volatile and are set with an 835 // Atomic::cmpxchg() call so we should see the suspended 836 // state right away. 837 // 2) We're being called from the safepoint polling loop; if 838 // we don't see the suspended state on this iteration, then 839 // we'll come around again. 840 // 841 bool is_suspended = _thread->is_ext_suspended(); 842 if (is_suspended) { 843 roll_forward(_at_safepoint); 844 return; 845 } 846 847 // Some JavaThread states have an initial safepoint state of 848 // running, but are actually at a safepoint. We will happily 849 // agree and update the safepoint state here. 850 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 851 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 852 roll_forward(_at_safepoint); 853 return; 854 } 855 856 if (state == _thread_in_vm) { 857 roll_forward(_call_back); 858 return; 859 } 860 861 // All other thread states will continue to run until they 862 // transition and self-block in state _blocked 863 // Safepoint polling in compiled code causes the Java threads to do the same. 864 // Note: new threads may require a malloc so they must be allowed to finish 865 866 assert(is_running(), "examine_state_of_thread on non-running thread"); 867 return; 868} 869 870// Returns true is thread could not be rolled forward at present position. 871void ThreadSafepointState::roll_forward(suspend_type type) { 872 _type = type; 873 874 switch(_type) { 875 case _at_safepoint: 876 SafepointSynchronize::signal_thread_at_safepoint(); 877 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 878 if (_thread->in_critical()) { 879 // Notice that this thread is in a critical section 880 SafepointSynchronize::increment_jni_active_count(); 881 } 882 break; 883 884 case _call_back: 885 set_has_called_back(false); 886 break; 887 888 case _running: 889 default: 890 ShouldNotReachHere(); 891 } 892} 893 894void ThreadSafepointState::restart() { 895 switch(type()) { 896 case _at_safepoint: 897 case _call_back: 898 break; 899 900 case _running: 901 default: 902 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d", 903 _thread, _type); 904 _thread->print(); 905 ShouldNotReachHere(); 906 } 907 _type = _running; 908 set_has_called_back(false); 909} 910 911 912void ThreadSafepointState::print_on(outputStream *st) const { 913 const char *s; 914 915 switch(_type) { 916 case _running : s = "_running"; break; 917 case _at_safepoint : s = "_at_safepoint"; break; 918 case _call_back : s = "_call_back"; break; 919 default: 920 ShouldNotReachHere(); 921 } 922 923 st->print_cr("Thread: " INTPTR_FORMAT 924 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 925 _thread, _thread->osthread()->thread_id(), s, _has_called_back, 926 _at_poll_safepoint); 927 928 _thread->print_thread_state_on(st); 929} 930 931 932// --------------------------------------------------------------------------------------------------------------------- 933 934// Block the thread at the safepoint poll or poll return. 935void ThreadSafepointState::handle_polling_page_exception() { 936 937 // Check state. block() will set thread state to thread_in_vm which will 938 // cause the safepoint state _type to become _call_back. 939 assert(type() == ThreadSafepointState::_running, 940 "polling page exception on thread not running state"); 941 942 // Step 1: Find the nmethod from the return address 943 if (ShowSafepointMsgs && Verbose) { 944 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); 945 } 946 address real_return_addr = thread()->saved_exception_pc(); 947 948 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 949 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); 950 nmethod* nm = (nmethod*)cb; 951 952 // Find frame of caller 953 frame stub_fr = thread()->last_frame(); 954 CodeBlob* stub_cb = stub_fr.cb(); 955 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 956 RegisterMap map(thread(), true); 957 frame caller_fr = stub_fr.sender(&map); 958 959 // Should only be poll_return or poll 960 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 961 962 // This is a poll immediately before a return. The exception handling code 963 // has already had the effect of causing the return to occur, so the execution 964 // will continue immediately after the call. In addition, the oopmap at the 965 // return point does not mark the return value as an oop (if it is), so 966 // it needs a handle here to be updated. 967 if( nm->is_at_poll_return(real_return_addr) ) { 968 // See if return type is an oop. 969 bool return_oop = nm->method()->is_returning_oop(); 970 Handle return_value; 971 if (return_oop) { 972 // The oop result has been saved on the stack together with all 973 // the other registers. In order to preserve it over GCs we need 974 // to keep it in a handle. 975 oop result = caller_fr.saved_oop_result(&map); 976 assert(result == NULL || result->is_oop(), "must be oop"); 977 return_value = Handle(thread(), result); 978 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 979 } 980 981 // Block the thread 982 SafepointSynchronize::block(thread()); 983 984 // restore oop result, if any 985 if (return_oop) { 986 caller_fr.set_saved_oop_result(&map, return_value()); 987 } 988 } 989 990 // This is a safepoint poll. Verify the return address and block. 991 else { 992 set_at_poll_safepoint(true); 993 994 // verify the blob built the "return address" correctly 995 assert(real_return_addr == caller_fr.pc(), "must match"); 996 997 // Block the thread 998 SafepointSynchronize::block(thread()); 999 set_at_poll_safepoint(false); 1000 1001 // If we have a pending async exception deoptimize the frame 1002 // as otherwise we may never deliver it. 1003 if (thread()->has_async_condition()) { 1004 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1005 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1006 } 1007 1008 // If an exception has been installed we must check for a pending deoptimization 1009 // Deoptimize frame if exception has been thrown. 1010 1011 if (thread()->has_pending_exception() ) { 1012 RegisterMap map(thread(), true); 1013 frame caller_fr = stub_fr.sender(&map); 1014 if (caller_fr.is_deoptimized_frame()) { 1015 // The exception patch will destroy registers that are still 1016 // live and will be needed during deoptimization. Defer the 1017 // Async exception should have deferred the exception until the 1018 // next safepoint which will be detected when we get into 1019 // the interpreter so if we have an exception now things 1020 // are messed up. 1021 1022 fatal("Exception installed and deoptimization is pending"); 1023 } 1024 } 1025 } 1026} 1027 1028 1029// 1030// Statistics & Instrumentations 1031// 1032SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1033jlong SafepointSynchronize::_safepoint_begin_time = 0; 1034int SafepointSynchronize::_cur_stat_index = 0; 1035julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1036julong SafepointSynchronize::_coalesced_vmop_count = 0; 1037jlong SafepointSynchronize::_max_sync_time = 0; 1038jlong SafepointSynchronize::_max_vmop_time = 0; 1039float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1040 1041static jlong cleanup_end_time = 0; 1042static bool need_to_track_page_armed_status = false; 1043static bool init_done = false; 1044 1045// Helper method to print the header. 1046static void print_header() { 1047 tty->print(" vmop " 1048 "[threads: total initially_running wait_to_block] "); 1049 tty->print("[time: spin block sync cleanup vmop] "); 1050 1051 // no page armed status printed out if it is always armed. 1052 if (need_to_track_page_armed_status) { 1053 tty->print("page_armed "); 1054 } 1055 1056 tty->print_cr("page_trap_count"); 1057} 1058 1059void SafepointSynchronize::deferred_initialize_stat() { 1060 if (init_done) return; 1061 1062 if (PrintSafepointStatisticsCount <= 0) { 1063 fatal("Wrong PrintSafepointStatisticsCount"); 1064 } 1065 1066 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1067 // be printed right away, in which case, _safepoint_stats will regress to 1068 // a single element array. Otherwise, it is a circular ring buffer with default 1069 // size of PrintSafepointStatisticsCount. 1070 int stats_array_size; 1071 if (PrintSafepointStatisticsTimeout > 0) { 1072 stats_array_size = 1; 1073 PrintSafepointStatistics = true; 1074 } else { 1075 stats_array_size = PrintSafepointStatisticsCount; 1076 } 1077 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1078 * sizeof(SafepointStats), mtInternal); 1079 guarantee(_safepoint_stats != NULL, 1080 "not enough memory for safepoint instrumentation data"); 1081 1082 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) { 1083 need_to_track_page_armed_status = true; 1084 } 1085 init_done = true; 1086} 1087 1088void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1089 assert(init_done, "safepoint statistics array hasn't been initialized"); 1090 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1091 1092 spstat->_time_stamp = _ts_of_current_safepoint; 1093 1094 VM_Operation *op = VMThread::vm_operation(); 1095 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1096 if (op != NULL) { 1097 _safepoint_reasons[spstat->_vmop_type]++; 1098 } 1099 1100 spstat->_nof_total_threads = nof_threads; 1101 spstat->_nof_initial_running_threads = nof_running; 1102 spstat->_nof_threads_hit_page_trap = 0; 1103 1104 // Records the start time of spinning. The real time spent on spinning 1105 // will be adjusted when spin is done. Same trick is applied for time 1106 // spent on waiting for threads to block. 1107 if (nof_running != 0) { 1108 spstat->_time_to_spin = os::javaTimeNanos(); 1109 } else { 1110 spstat->_time_to_spin = 0; 1111 } 1112} 1113 1114void SafepointSynchronize::update_statistics_on_spin_end() { 1115 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1116 1117 jlong cur_time = os::javaTimeNanos(); 1118 1119 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1120 if (spstat->_nof_initial_running_threads != 0) { 1121 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1122 } 1123 1124 if (need_to_track_page_armed_status) { 1125 spstat->_page_armed = (PageArmed == 1); 1126 } 1127 1128 // Records the start time of waiting for to block. Updated when block is done. 1129 if (_waiting_to_block != 0) { 1130 spstat->_time_to_wait_to_block = cur_time; 1131 } else { 1132 spstat->_time_to_wait_to_block = 0; 1133 } 1134} 1135 1136void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1137 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1138 1139 if (spstat->_nof_threads_wait_to_block != 0) { 1140 spstat->_time_to_wait_to_block = end_time - 1141 spstat->_time_to_wait_to_block; 1142 } 1143 1144 // Records the end time of sync which will be used to calculate the total 1145 // vm operation time. Again, the real time spending in syncing will be deducted 1146 // from the start of the sync time later when end_statistics is called. 1147 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1148 if (spstat->_time_to_sync > _max_sync_time) { 1149 _max_sync_time = spstat->_time_to_sync; 1150 } 1151 1152 spstat->_time_to_do_cleanups = end_time; 1153} 1154 1155void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1156 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1157 1158 // Record how long spent in cleanup tasks. 1159 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1160 1161 cleanup_end_time = end_time; 1162} 1163 1164void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1165 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1166 1167 // Update the vm operation time. 1168 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1169 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1170 _max_vmop_time = spstat->_time_to_exec_vmop; 1171 } 1172 // Only the sync time longer than the specified 1173 // PrintSafepointStatisticsTimeout will be printed out right away. 1174 // By default, it is -1 meaning all samples will be put into the list. 1175 if ( PrintSafepointStatisticsTimeout > 0) { 1176 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1177 print_statistics(); 1178 } 1179 } else { 1180 // The safepoint statistics will be printed out when the _safepoin_stats 1181 // array fills up. 1182 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1183 print_statistics(); 1184 _cur_stat_index = 0; 1185 } else { 1186 _cur_stat_index++; 1187 } 1188 } 1189} 1190 1191void SafepointSynchronize::print_statistics() { 1192 SafepointStats* sstats = _safepoint_stats; 1193 1194 for (int index = 0; index <= _cur_stat_index; index++) { 1195 if (index % 30 == 0) { 1196 print_header(); 1197 } 1198 sstats = &_safepoint_stats[index]; 1199 tty->print("%.3f: ", sstats->_time_stamp); 1200 tty->print("%-26s [" 1201 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15) 1202 " ] ", 1203 sstats->_vmop_type == -1 ? "no vm operation" : 1204 VM_Operation::name(sstats->_vmop_type), 1205 sstats->_nof_total_threads, 1206 sstats->_nof_initial_running_threads, 1207 sstats->_nof_threads_wait_to_block); 1208 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1209 tty->print(" [" 1210 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1211 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1212 INT64_FORMAT_W(6)" ] ", 1213 sstats->_time_to_spin / MICROUNITS, 1214 sstats->_time_to_wait_to_block / MICROUNITS, 1215 sstats->_time_to_sync / MICROUNITS, 1216 sstats->_time_to_do_cleanups / MICROUNITS, 1217 sstats->_time_to_exec_vmop / MICROUNITS); 1218 1219 if (need_to_track_page_armed_status) { 1220 tty->print(INT32_FORMAT" ", sstats->_page_armed); 1221 } 1222 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap); 1223 } 1224} 1225 1226// This method will be called when VM exits. It will first call 1227// print_statistics to print out the rest of the sampling. Then 1228// it tries to summarize the sampling. 1229void SafepointSynchronize::print_stat_on_exit() { 1230 if (_safepoint_stats == NULL) return; 1231 1232 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1233 1234 // During VM exit, end_statistics may not get called and in that 1235 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1236 // don't print it out. 1237 // Approximate the vm op time. 1238 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1239 os::javaTimeNanos() - cleanup_end_time; 1240 1241 if ( PrintSafepointStatisticsTimeout < 0 || 1242 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1243 print_statistics(); 1244 } 1245 tty->cr(); 1246 1247 // Print out polling page sampling status. 1248 if (!need_to_track_page_armed_status) { 1249 if (UseCompilerSafepoints) { 1250 tty->print_cr("Polling page always armed"); 1251 } 1252 } else { 1253 tty->print_cr("Defer polling page loop count = %d\n", 1254 DeferPollingPageLoopCount); 1255 } 1256 1257 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1258 if (_safepoint_reasons[index] != 0) { 1259 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index), 1260 _safepoint_reasons[index]); 1261 } 1262 } 1263 1264 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint", 1265 _coalesced_vmop_count); 1266 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms", 1267 _max_sync_time / MICROUNITS); 1268 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1269 INT64_FORMAT_W(5)" ms", 1270 _max_vmop_time / MICROUNITS); 1271} 1272 1273// ------------------------------------------------------------------------------------------------ 1274// Non-product code 1275 1276#ifndef PRODUCT 1277 1278void SafepointSynchronize::print_state() { 1279 if (_state == _not_synchronized) { 1280 tty->print_cr("not synchronized"); 1281 } else if (_state == _synchronizing || _state == _synchronized) { 1282 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1283 "synchronized"); 1284 1285 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1286 cur->safepoint_state()->print(); 1287 } 1288 } 1289} 1290 1291void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1292 if (ShowSafepointMsgs) { 1293 va_list ap; 1294 va_start(ap, format); 1295 tty->vprint_cr(format, ap); 1296 va_end(ap); 1297 } 1298} 1299 1300#endif // !PRODUCT 1301