1 /* 2 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/symbolTable.hpp" 27 #include "classfile/systemDictionary.hpp" 28 #include "code/codeCache.hpp" 29 #include "code/icBuffer.hpp" 30 #include "code/nmethod.hpp" 31 #include "code/pcDesc.hpp" 32 #include "code/scopeDesc.hpp" 33 #include "gc_interface/collectedHeap.hpp" 34 #include "interpreter/interpreter.hpp" 35 #include "memory/resourceArea.hpp" 36 #include "memory/universe.inline.hpp" 37 #include "oops/oop.inline.hpp" 38 #include "oops/symbol.hpp" 39 #include "runtime/compilationPolicy.hpp" 40 #include "runtime/deoptimization.hpp" 41 #include "runtime/frame.inline.hpp" 42 #include "runtime/interfaceSupport.hpp" 43 #include "runtime/mutexLocker.hpp" 44 #include "runtime/osThread.hpp" 45 #include "runtime/safepoint.hpp" 46 #include "runtime/signature.hpp" 47 #include "runtime/stubCodeGenerator.hpp" 48 #include "runtime/stubRoutines.hpp" 49 #include "runtime/sweeper.hpp" 50 #include "runtime/synchronizer.hpp" 51 #include "services/memTracker.hpp" 52 #include "services/runtimeService.hpp" 53 #include "utilities/events.hpp" 54 #ifdef TARGET_ARCH_x86 55 # include "nativeInst_x86.hpp" 56 # include "vmreg_x86.inline.hpp" 57 #endif 58 #ifdef TARGET_ARCH_sparc 59 # include "nativeInst_sparc.hpp" 60 # include "vmreg_sparc.inline.hpp" 61 #endif 62 #ifdef TARGET_ARCH_zero 63 # include "nativeInst_zero.hpp" 64 # include "vmreg_zero.inline.hpp" 65 #endif 66 #ifdef TARGET_ARCH_arm 67 # include "nativeInst_arm.hpp" 68 # include "vmreg_arm.inline.hpp" 69 #endif 70 #ifdef TARGET_ARCH_ppc 71 # include "nativeInst_ppc.hpp" 72 # include "vmreg_ppc.inline.hpp" 73 #endif 74 #ifdef TARGET_OS_FAMILY_linux 75 # include "thread_linux.inline.hpp" 76 #endif 77 #ifdef TARGET_OS_FAMILY_solaris 78 # include "thread_solaris.inline.hpp" 79 #endif 80 #ifdef TARGET_OS_FAMILY_windows 81 # include "thread_windows.inline.hpp" 82 #endif 83 #ifdef TARGET_OS_FAMILY_bsd 84 # include "thread_bsd.inline.hpp" 85 #endif 86 #ifndef SERIALGC 87 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" 88 #include "gc_implementation/shared/concurrentGCThread.hpp" 89 #endif 90 #ifdef COMPILER1 91 #include "c1/c1_globals.hpp" 92 #endif 93 94 // -------------------------------------------------------------------------------------------------- 95 // Implementation of Safepoint begin/end 96 97 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 98 volatile int SafepointSynchronize::_waiting_to_block = 0; 99 volatile int SafepointSynchronize::_safepoint_counter = 0; 100 int SafepointSynchronize::_current_jni_active_count = 0; 101 long SafepointSynchronize::_end_of_last_safepoint = 0; 102 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 103 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 104 static bool timeout_error_printed = false; 105 106 // Roll all threads forward to a safepoint and suspend them all 107 void SafepointSynchronize::begin() { 108 109 Thread* myThread = Thread::current(); 110 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); 111 112 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 113 _safepoint_begin_time = os::javaTimeNanos(); 114 _ts_of_current_safepoint = tty->time_stamp().seconds(); 115 } 116 117 #ifndef SERIALGC 118 if (UseConcMarkSweepGC) { 119 // In the future we should investigate whether CMS can use the 120 // more-general mechanism below. DLD (01/05). 121 ConcurrentMarkSweepThread::synchronize(false); 122 } else if (UseG1GC) { 123 ConcurrentGCThread::safepoint_synchronize(); 124 } 125 #endif // SERIALGC 126 127 // By getting the Threads_lock, we assure that no threads are about to start or 128 // exit. It is released again in SafepointSynchronize::end(). 129 Threads_lock->lock(); 130 131 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 132 133 int nof_threads = Threads::number_of_threads(); 134 135 if (TraceSafepoint) { 136 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); 137 } 138 139 RuntimeService::record_safepoint_begin(); 140 141 MutexLocker mu(Safepoint_lock); 142 143 // Reset the count of active JNI critical threads 144 _current_jni_active_count = 0; 145 146 // Set number of threads to wait for, before we initiate the callbacks 147 _waiting_to_block = nof_threads; 148 TryingToBlock = 0 ; 149 int still_running = nof_threads; 150 151 // Save the starting time, so that it can be compared to see if this has taken 152 // too long to complete. 153 jlong safepoint_limit_time; 154 timeout_error_printed = false; 155 156 // PrintSafepointStatisticsTimeout can be specified separately. When 157 // specified, PrintSafepointStatistics will be set to true in 158 // deferred_initialize_stat method. The initialization has to be done 159 // early enough to avoid any races. See bug 6880029 for details. 160 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 161 deferred_initialize_stat(); 162 } 163 164 // Begin the process of bringing the system to a safepoint. 165 // Java threads can be in several different states and are 166 // stopped by different mechanisms: 167 // 168 // 1. Running interpreted 169 // The interpeter dispatch table is changed to force it to 170 // check for a safepoint condition between bytecodes. 171 // 2. Running in native code 172 // When returning from the native code, a Java thread must check 173 // the safepoint _state to see if we must block. If the 174 // VM thread sees a Java thread in native, it does 175 // not wait for this thread to block. The order of the memory 176 // writes and reads of both the safepoint state and the Java 177 // threads state is critical. In order to guarantee that the 178 // memory writes are serialized with respect to each other, 179 // the VM thread issues a memory barrier instruction 180 // (on MP systems). In order to avoid the overhead of issuing 181 // a memory barrier for each Java thread making native calls, each Java 182 // thread performs a write to a single memory page after changing 183 // the thread state. The VM thread performs a sequence of 184 // mprotect OS calls which forces all previous writes from all 185 // Java threads to be serialized. This is done in the 186 // os::serialize_thread_states() call. This has proven to be 187 // much more efficient than executing a membar instruction 188 // on every call to native code. 189 // 3. Running compiled Code 190 // Compiled code reads a global (Safepoint Polling) page that 191 // is set to fault if we are trying to get to a safepoint. 192 // 4. Blocked 193 // A thread which is blocked will not be allowed to return from the 194 // block condition until the safepoint operation is complete. 195 // 5. In VM or Transitioning between states 196 // If a Java thread is currently running in the VM or transitioning 197 // between states, the safepointing code will wait for the thread to 198 // block itself when it attempts transitions to a new state. 199 // 200 _state = _synchronizing; 201 OrderAccess::fence(); 202 203 // Flush all thread states to memory 204 if (!UseMembar) { 205 os::serialize_thread_states(); 206 } 207 208 // Make interpreter safepoint aware 209 Interpreter::notice_safepoints(); 210 211 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) { 212 // Make polling safepoint aware 213 guarantee (PageArmed == 0, "invariant") ; 214 PageArmed = 1 ; 215 os::make_polling_page_unreadable(); 216 } 217 218 // Consider using active_processor_count() ... but that call is expensive. 219 int ncpus = os::processor_count() ; 220 221 #ifdef ASSERT 222 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 223 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 224 // Clear the visited flag to ensure that the critical counts are collected properly. 225 cur->set_visited_for_critical_count(false); 226 } 227 #endif // ASSERT 228 229 if (SafepointTimeout) 230 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 231 232 // Iterate through all threads until it have been determined how to stop them all at a safepoint 233 unsigned int iterations = 0; 234 int steps = 0 ; 235 while(still_running > 0) { 236 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 237 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 238 ThreadSafepointState *cur_state = cur->safepoint_state(); 239 if (cur_state->is_running()) { 240 cur_state->examine_state_of_thread(); 241 if (!cur_state->is_running()) { 242 still_running--; 243 // consider adjusting steps downward: 244 // steps = 0 245 // steps -= NNN 246 // steps >>= 1 247 // steps = MIN(steps, 2000-100) 248 // if (iterations != 0) steps -= NNN 249 } 250 if (TraceSafepoint && Verbose) cur_state->print(); 251 } 252 } 253 254 if (PrintSafepointStatistics && iterations == 0) { 255 begin_statistics(nof_threads, still_running); 256 } 257 258 if (still_running > 0) { 259 // Check for if it takes to long 260 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 261 print_safepoint_timeout(_spinning_timeout); 262 } 263 264 // Spin to avoid context switching. 265 // There's a tension between allowing the mutators to run (and rendezvous) 266 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 267 // a mutator might otherwise use profitably to reach a safepoint. Excessive 268 // spinning by the VM thread on a saturated system can increase rendezvous latency. 269 // Blocking or yielding incur their own penalties in the form of context switching 270 // and the resultant loss of $ residency. 271 // 272 // Further complicating matters is that yield() does not work as naively expected 273 // on many platforms -- yield() does not guarantee that any other ready threads 274 // will run. As such we revert yield_all() after some number of iterations. 275 // Yield_all() is implemented as a short unconditional sleep on some platforms. 276 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 277 // can actually increase the time it takes the VM thread to detect that a system-wide 278 // stop-the-world safepoint has been reached. In a pathological scenario such as that 279 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 280 // In that case the mutators will be stalled waiting for the safepoint to complete and the 281 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 282 // will eventually wake up and detect that all mutators are safe, at which point 283 // we'll again make progress. 284 // 285 // Beware too that that the VMThread typically runs at elevated priority. 286 // Its default priority is higher than the default mutator priority. 287 // Obviously, this complicates spinning. 288 // 289 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 290 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 291 // 292 // See the comments in synchronizer.cpp for additional remarks on spinning. 293 // 294 // In the future we might: 295 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning. 296 // This is tricky as the path used by a thread exiting the JVM (say on 297 // on JNI call-out) simply stores into its state field. The burden 298 // is placed on the VM thread, which must poll (spin). 299 // 2. Find something useful to do while spinning. If the safepoint is GC-related 300 // we might aggressively scan the stacks of threads that are already safe. 301 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 302 // If all the mutators are ONPROC there's no reason to sleep or yield. 303 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 304 // 5. Check system saturation. If the system is not fully saturated then 305 // simply spin and avoid sleep/yield. 306 // 6. As still-running mutators rendezvous they could unpark the sleeping 307 // VMthread. This works well for still-running mutators that become 308 // safe. The VMthread must still poll for mutators that call-out. 309 // 7. Drive the policy on time-since-begin instead of iterations. 310 // 8. Consider making the spin duration a function of the # of CPUs: 311 // Spin = (((ncpus-1) * M) + K) + F(still_running) 312 // Alternately, instead of counting iterations of the outer loop 313 // we could count the # of threads visited in the inner loop, above. 314 // 9. On windows consider using the return value from SwitchThreadTo() 315 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 316 317 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) { 318 guarantee (PageArmed == 0, "invariant") ; 319 PageArmed = 1 ; 320 os::make_polling_page_unreadable(); 321 } 322 323 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 324 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 325 ++steps ; 326 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 327 SpinPause() ; // MP-Polite spin 328 } else 329 if (steps < DeferThrSuspendLoopCount) { 330 os::NakedYield() ; 331 } else { 332 os::yield_all(steps) ; 333 // Alternately, the VM thread could transiently depress its scheduling priority or 334 // transiently increase the priority of the tardy mutator(s). 335 } 336 337 iterations ++ ; 338 } 339 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 340 } 341 assert(still_running == 0, "sanity check"); 342 343 if (PrintSafepointStatistics) { 344 update_statistics_on_spin_end(); 345 } 346 347 // wait until all threads are stopped 348 while (_waiting_to_block > 0) { 349 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); 350 if (!SafepointTimeout || timeout_error_printed) { 351 Safepoint_lock->wait(true); // true, means with no safepoint checks 352 } else { 353 // Compute remaining time 354 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 355 356 // If there is no remaining time, then there is an error 357 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 358 print_safepoint_timeout(_blocking_timeout); 359 } 360 } 361 } 362 assert(_waiting_to_block == 0, "sanity check"); 363 364 #ifndef PRODUCT 365 if (SafepointTimeout) { 366 jlong current_time = os::javaTimeNanos(); 367 if (safepoint_limit_time < current_time) { 368 tty->print_cr("# SafepointSynchronize: Finished after " 369 INT64_FORMAT_W(6) " ms", 370 ((current_time - safepoint_limit_time) / MICROUNITS + 371 SafepointTimeoutDelay)); 372 } 373 } 374 #endif 375 376 assert((_safepoint_counter & 0x1) == 0, "must be even"); 377 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 378 _safepoint_counter ++; 379 380 // Record state 381 _state = _synchronized; 382 383 OrderAccess::fence(); 384 385 #ifdef ASSERT 386 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 387 // make sure all the threads were visited 388 assert(cur->was_visited_for_critical_count(), "missed a thread"); 389 } 390 #endif // ASSERT 391 392 // Update the count of active JNI critical regions 393 GC_locker::set_jni_lock_count(_current_jni_active_count); 394 395 if (TraceSafepoint) { 396 VM_Operation *op = VMThread::vm_operation(); 397 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); 398 } 399 400 RuntimeService::record_safepoint_synchronized(); 401 if (PrintSafepointStatistics) { 402 update_statistics_on_sync_end(os::javaTimeNanos()); 403 } 404 405 // Call stuff that needs to be run when a safepoint is just about to be completed 406 do_cleanup_tasks(); 407 408 if (PrintSafepointStatistics) { 409 // Record how much time spend on the above cleanup tasks 410 update_statistics_on_cleanup_end(os::javaTimeNanos()); 411 } 412 } 413 414 // Wake up all threads, so they are ready to resume execution after the safepoint 415 // operation has been carried out 416 void SafepointSynchronize::end() { 417 418 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 419 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 420 _safepoint_counter ++; 421 // memory fence isn't required here since an odd _safepoint_counter 422 // value can do no harm and a fence is issued below anyway. 423 424 DEBUG_ONLY(Thread* myThread = Thread::current();) 425 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 426 427 if (PrintSafepointStatistics) { 428 end_statistics(os::javaTimeNanos()); 429 } 430 431 #ifdef ASSERT 432 // A pending_exception cannot be installed during a safepoint. The threads 433 // may install an async exception after they come back from a safepoint into 434 // pending_exception after they unblock. But that should happen later. 435 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 436 assert (!(cur->has_pending_exception() && 437 cur->safepoint_state()->is_at_poll_safepoint()), 438 "safepoint installed a pending exception"); 439 } 440 #endif // ASSERT 441 442 if (PageArmed) { 443 // Make polling safepoint aware 444 os::make_polling_page_readable(); 445 PageArmed = 0 ; 446 } 447 448 // Remove safepoint check from interpreter 449 Interpreter::ignore_safepoints(); 450 451 { 452 MutexLocker mu(Safepoint_lock); 453 454 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 455 456 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 457 // when they get restarted. 458 _state = _not_synchronized; 459 OrderAccess::fence(); 460 461 if (TraceSafepoint) { 462 tty->print_cr("Leaving safepoint region"); 463 } 464 465 // Start suspended threads 466 for(JavaThread *current = Threads::first(); current; current = current->next()) { 467 // A problem occurring on Solaris is when attempting to restart threads 468 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 469 // to the next one (since it has been running the longest). We then have 470 // to wait for a cpu to become available before we can continue restarting 471 // threads. 472 // FIXME: This causes the performance of the VM to degrade when active and with 473 // large numbers of threads. Apparently this is due to the synchronous nature 474 // of suspending threads. 475 // 476 // TODO-FIXME: the comments above are vestigial and no longer apply. 477 // Furthermore, using solaris' schedctl in this particular context confers no benefit 478 if (VMThreadHintNoPreempt) { 479 os::hint_no_preempt(); 480 } 481 ThreadSafepointState* cur_state = current->safepoint_state(); 482 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 483 cur_state->restart(); 484 assert(cur_state->is_running(), "safepoint state has not been reset"); 485 } 486 487 RuntimeService::record_safepoint_end(); 488 489 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 490 // blocked in signal_thread_blocked 491 Threads_lock->unlock(); 492 493 } 494 #ifndef SERIALGC 495 // If there are any concurrent GC threads resume them. 496 if (UseConcMarkSweepGC) { 497 ConcurrentMarkSweepThread::desynchronize(false); 498 } else if (UseG1GC) { 499 ConcurrentGCThread::safepoint_desynchronize(); 500 } 501 #endif // SERIALGC 502 // record this time so VMThread can keep track how much time has elasped 503 // since last safepoint. 504 _end_of_last_safepoint = os::javaTimeMillis(); 505 } 506 507 bool SafepointSynchronize::is_cleanup_needed() { 508 // Need a safepoint if some inline cache buffers is non-empty 509 if (!InlineCacheBuffer::is_empty()) return true; 510 return false; 511 } 512 513 514 515 // Various cleaning tasks that should be done periodically at safepoints 516 void SafepointSynchronize::do_cleanup_tasks() { 517 { 518 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime); 519 ObjectSynchronizer::deflate_idle_monitors(); 520 } 521 522 { 523 TraceTime t2("updating inline caches", TraceSafepointCleanupTime); 524 InlineCacheBuffer::update_inline_caches(); 525 } 526 { 527 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime); 528 CompilationPolicy::policy()->do_safepoint_work(); 529 } 530 531 { 532 TraceTime t4("sweeping nmethods", TraceSafepointCleanupTime); 533 NMethodSweeper::scan_stacks(); 534 } 535 536 if (SymbolTable::needs_rehashing()) { 537 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime); 538 SymbolTable::rehash_table(); 539 } 540 541 if (StringTable::needs_rehashing()) { 542 TraceTime t6("rehashing string table", TraceSafepointCleanupTime); 543 StringTable::rehash_table(); 544 } 545 546 // rotate log files? 547 if (UseGCLogFileRotation) { 548 gclog_or_tty->rotate_log(); 549 } 550 551 if (MemTracker::is_on()) { 552 MemTracker::sync(); 553 } 554 } 555 556 557 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 558 switch(state) { 559 case _thread_in_native: 560 // native threads are safe if they have no java stack or have walkable stack 561 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 562 563 // blocked threads should have already have walkable stack 564 case _thread_blocked: 565 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 566 return true; 567 568 default: 569 return false; 570 } 571 } 572 573 574 // See if the thread is running inside a lazy critical native and 575 // update the thread critical count if so. Also set a suspend flag to 576 // cause the native wrapper to return into the JVM to do the unlock 577 // once the native finishes. 578 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 579 if (state == _thread_in_native && 580 thread->has_last_Java_frame() && 581 thread->frame_anchor()->walkable()) { 582 // This thread might be in a critical native nmethod so look at 583 // the top of the stack and increment the critical count if it 584 // is. 585 frame wrapper_frame = thread->last_frame(); 586 CodeBlob* stub_cb = wrapper_frame.cb(); 587 if (stub_cb != NULL && 588 stub_cb->is_nmethod() && 589 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 590 // A thread could potentially be in a critical native across 591 // more than one safepoint, so only update the critical state on 592 // the first one. When it returns it will perform the unlock. 593 if (!thread->do_critical_native_unlock()) { 594 #ifdef ASSERT 595 if (!thread->in_critical()) { 596 GC_locker::increment_debug_jni_lock_count(); 597 } 598 #endif 599 thread->enter_critical(); 600 // Make sure the native wrapper calls back on return to 601 // perform the needed critical unlock. 602 thread->set_critical_native_unlock(); 603 } 604 } 605 } 606 } 607 608 609 610 // ------------------------------------------------------------------------------------------------------- 611 // Implementation of Safepoint callback point 612 613 void SafepointSynchronize::block(JavaThread *thread) { 614 assert(thread != NULL, "thread must be set"); 615 assert(thread->is_Java_thread(), "not a Java thread"); 616 617 // Threads shouldn't block if they are in the middle of printing, but... 618 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 619 620 // Only bail from the block() call if the thread is gone from the 621 // thread list; starting to exit should still block. 622 if (thread->is_terminated()) { 623 // block current thread if we come here from native code when VM is gone 624 thread->block_if_vm_exited(); 625 626 // otherwise do nothing 627 return; 628 } 629 630 JavaThreadState state = thread->thread_state(); 631 thread->frame_anchor()->make_walkable(thread); 632 633 // Check that we have a valid thread_state at this point 634 switch(state) { 635 case _thread_in_vm_trans: 636 case _thread_in_Java: // From compiled code 637 638 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 639 // we pretend we are still in the VM. 640 thread->set_thread_state(_thread_in_vm); 641 642 if (is_synchronizing()) { 643 Atomic::inc (&TryingToBlock) ; 644 } 645 646 // We will always be holding the Safepoint_lock when we are examine the state 647 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 648 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 649 Safepoint_lock->lock_without_safepoint_check(); 650 if (is_synchronizing()) { 651 // Decrement the number of threads to wait for and signal vm thread 652 assert(_waiting_to_block > 0, "sanity check"); 653 _waiting_to_block--; 654 thread->safepoint_state()->set_has_called_back(true); 655 656 DEBUG_ONLY(thread->set_visited_for_critical_count(true)); 657 if (thread->in_critical()) { 658 // Notice that this thread is in a critical section 659 increment_jni_active_count(); 660 } 661 662 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 663 if (_waiting_to_block == 0) { 664 Safepoint_lock->notify_all(); 665 } 666 } 667 668 // We transition the thread to state _thread_blocked here, but 669 // we can't do our usual check for external suspension and then 670 // self-suspend after the lock_without_safepoint_check() call 671 // below because we are often called during transitions while 672 // we hold different locks. That would leave us suspended while 673 // holding a resource which results in deadlocks. 674 thread->set_thread_state(_thread_blocked); 675 Safepoint_lock->unlock(); 676 677 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 678 // the entire safepoint, the threads will all line up here during the safepoint. 679 Threads_lock->lock_without_safepoint_check(); 680 // restore original state. This is important if the thread comes from compiled code, so it 681 // will continue to execute with the _thread_in_Java state. 682 thread->set_thread_state(state); 683 Threads_lock->unlock(); 684 break; 685 686 case _thread_in_native_trans: 687 case _thread_blocked_trans: 688 case _thread_new_trans: 689 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 690 thread->print_thread_state(); 691 fatal("Deadlock in safepoint code. " 692 "Should have called back to the VM before blocking."); 693 } 694 695 // We transition the thread to state _thread_blocked here, but 696 // we can't do our usual check for external suspension and then 697 // self-suspend after the lock_without_safepoint_check() call 698 // below because we are often called during transitions while 699 // we hold different locks. That would leave us suspended while 700 // holding a resource which results in deadlocks. 701 thread->set_thread_state(_thread_blocked); 702 703 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 704 // the safepoint code might still be waiting for it to block. We need to change the state here, 705 // so it can see that it is at a safepoint. 706 707 // Block until the safepoint operation is completed. 708 Threads_lock->lock_without_safepoint_check(); 709 710 // Restore state 711 thread->set_thread_state(state); 712 713 Threads_lock->unlock(); 714 break; 715 716 default: 717 fatal(err_msg("Illegal threadstate encountered: %d", state)); 718 } 719 720 // Check for pending. async. exceptions or suspends - except if the 721 // thread was blocked inside the VM. has_special_runtime_exit_condition() 722 // is called last since it grabs a lock and we only want to do that when 723 // we must. 724 // 725 // Note: we never deliver an async exception at a polling point as the 726 // compiler may not have an exception handler for it. The polling 727 // code will notice the async and deoptimize and the exception will 728 // be delivered. (Polling at a return point is ok though). Sure is 729 // a lot of bother for a deprecated feature... 730 // 731 // We don't deliver an async exception if the thread state is 732 // _thread_in_native_trans so JNI functions won't be called with 733 // a surprising pending exception. If the thread state is going back to java, 734 // async exception is checked in check_special_condition_for_native_trans(). 735 736 if (state != _thread_blocked_trans && 737 state != _thread_in_vm_trans && 738 thread->has_special_runtime_exit_condition()) { 739 thread->handle_special_runtime_exit_condition( 740 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 741 } 742 } 743 744 // ------------------------------------------------------------------------------------------------------ 745 // Exception handlers 746 747 #ifndef PRODUCT 748 #ifdef _LP64 749 #define PTR_PAD "" 750 #else 751 #define PTR_PAD " " 752 #endif 753 754 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) { 755 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false; 756 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s", 757 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', 758 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); 759 } 760 761 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) { 762 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false; 763 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s", 764 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', 765 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); 766 } 767 768 #ifdef SPARC 769 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) { 770 #ifdef _LP64 771 tty->print_cr("--------+------address-----+------before-----------+-------after----------+"); 772 const int incr = 1; // Increment to skip a long, in units of intptr_t 773 #else 774 tty->print_cr("--------+--address-+------before-----------+-------after----------+"); 775 const int incr = 2; // Increment to skip a long, in units of intptr_t 776 #endif 777 tty->print_cr("---SP---|"); 778 for( int i=0; i<16; i++ ) { 779 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 780 tty->print_cr("--------|"); 781 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) { 782 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 783 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); 784 tty->print_cr("--------|"); 785 tty->print(" G1 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 786 tty->print(" G3 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 787 tty->print(" G4 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 788 tty->print(" G5 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; 789 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp); 790 old_sp += incr; new_sp += incr; was_oops += incr; 791 // Skip the floats 792 tty->print_cr("--Float-|"PTR_FORMAT,new_sp); 793 tty->print_cr("---FP---|"); 794 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32; 795 for( int i2=0; i2<16; i2++ ) { 796 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 797 tty->print_cr(""); 798 } 799 #endif // SPARC 800 #endif // PRODUCT 801 802 803 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 804 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 805 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 806 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 807 808 // Uncomment this to get some serious before/after printing of the 809 // Sparc safepoint-blob frame structure. 810 /* 811 intptr_t* sp = thread->last_Java_sp(); 812 intptr_t stack_copy[150]; 813 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i]; 814 bool was_oops[150]; 815 for( int i=0; i<150; i++ ) 816 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false; 817 */ 818 819 if (ShowSafepointMsgs) { 820 tty->print("handle_polling_page_exception: "); 821 } 822 823 if (PrintSafepointStatistics) { 824 inc_page_trap_count(); 825 } 826 827 ThreadSafepointState* state = thread->safepoint_state(); 828 829 state->handle_polling_page_exception(); 830 // print_me(sp,stack_copy,was_oops); 831 } 832 833 834 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 835 if (!timeout_error_printed) { 836 timeout_error_printed = true; 837 // Print out the thread infor which didn't reach the safepoint for debugging 838 // purposes (useful when there are lots of threads in the debugger). 839 tty->print_cr(""); 840 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 841 if (reason == _spinning_timeout) { 842 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 843 } else if (reason == _blocking_timeout) { 844 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 845 } 846 847 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 848 ThreadSafepointState *cur_state; 849 ResourceMark rm; 850 for(JavaThread *cur_thread = Threads::first(); cur_thread; 851 cur_thread = cur_thread->next()) { 852 cur_state = cur_thread->safepoint_state(); 853 854 if (cur_thread->thread_state() != _thread_blocked && 855 ((reason == _spinning_timeout && cur_state->is_running()) || 856 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 857 tty->print("# "); 858 cur_thread->print(); 859 tty->print_cr(""); 860 } 861 } 862 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 863 } 864 865 // To debug the long safepoint, specify both DieOnSafepointTimeout & 866 // ShowMessageBoxOnError. 867 if (DieOnSafepointTimeout) { 868 char msg[1024]; 869 VM_Operation *op = VMThread::vm_operation(); 870 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 871 SafepointTimeoutDelay, 872 op != NULL ? op->name() : "no vm operation"); 873 fatal(msg); 874 } 875 } 876 877 878 // ------------------------------------------------------------------------------------------------------- 879 // Implementation of ThreadSafepointState 880 881 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 882 _thread = thread; 883 _type = _running; 884 _has_called_back = false; 885 _at_poll_safepoint = false; 886 } 887 888 void ThreadSafepointState::create(JavaThread *thread) { 889 ThreadSafepointState *state = new ThreadSafepointState(thread); 890 thread->set_safepoint_state(state); 891 } 892 893 void ThreadSafepointState::destroy(JavaThread *thread) { 894 if (thread->safepoint_state()) { 895 delete(thread->safepoint_state()); 896 thread->set_safepoint_state(NULL); 897 } 898 } 899 900 void ThreadSafepointState::examine_state_of_thread() { 901 assert(is_running(), "better be running or just have hit safepoint poll"); 902 903 JavaThreadState state = _thread->thread_state(); 904 905 // Save the state at the start of safepoint processing. 906 _orig_thread_state = state; 907 908 // Check for a thread that is suspended. Note that thread resume tries 909 // to grab the Threads_lock which we own here, so a thread cannot be 910 // resumed during safepoint synchronization. 911 912 // We check to see if this thread is suspended without locking to 913 // avoid deadlocking with a third thread that is waiting for this 914 // thread to be suspended. The third thread can notice the safepoint 915 // that we're trying to start at the beginning of its SR_lock->wait() 916 // call. If that happens, then the third thread will block on the 917 // safepoint while still holding the underlying SR_lock. We won't be 918 // able to get the SR_lock and we'll deadlock. 919 // 920 // We don't need to grab the SR_lock here for two reasons: 921 // 1) The suspend flags are both volatile and are set with an 922 // Atomic::cmpxchg() call so we should see the suspended 923 // state right away. 924 // 2) We're being called from the safepoint polling loop; if 925 // we don't see the suspended state on this iteration, then 926 // we'll come around again. 927 // 928 bool is_suspended = _thread->is_ext_suspended(); 929 if (is_suspended) { 930 roll_forward(_at_safepoint); 931 return; 932 } 933 934 // Some JavaThread states have an initial safepoint state of 935 // running, but are actually at a safepoint. We will happily 936 // agree and update the safepoint state here. 937 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 938 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 939 roll_forward(_at_safepoint); 940 return; 941 } 942 943 if (state == _thread_in_vm) { 944 roll_forward(_call_back); 945 return; 946 } 947 948 // All other thread states will continue to run until they 949 // transition and self-block in state _blocked 950 // Safepoint polling in compiled code causes the Java threads to do the same. 951 // Note: new threads may require a malloc so they must be allowed to finish 952 953 assert(is_running(), "examine_state_of_thread on non-running thread"); 954 return; 955 } 956 957 // Returns true is thread could not be rolled forward at present position. 958 void ThreadSafepointState::roll_forward(suspend_type type) { 959 _type = type; 960 961 switch(_type) { 962 case _at_safepoint: 963 SafepointSynchronize::signal_thread_at_safepoint(); 964 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 965 if (_thread->in_critical()) { 966 // Notice that this thread is in a critical section 967 SafepointSynchronize::increment_jni_active_count(); 968 } 969 break; 970 971 case _call_back: 972 set_has_called_back(false); 973 break; 974 975 case _running: 976 default: 977 ShouldNotReachHere(); 978 } 979 } 980 981 void ThreadSafepointState::restart() { 982 switch(type()) { 983 case _at_safepoint: 984 case _call_back: 985 break; 986 987 case _running: 988 default: 989 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d", 990 _thread, _type); 991 _thread->print(); 992 ShouldNotReachHere(); 993 } 994 _type = _running; 995 set_has_called_back(false); 996 } 997 998 999 void ThreadSafepointState::print_on(outputStream *st) const { 1000 const char *s; 1001 1002 switch(_type) { 1003 case _running : s = "_running"; break; 1004 case _at_safepoint : s = "_at_safepoint"; break; 1005 case _call_back : s = "_call_back"; break; 1006 default: 1007 ShouldNotReachHere(); 1008 } 1009 1010 st->print_cr("Thread: " INTPTR_FORMAT 1011 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 1012 _thread, _thread->osthread()->thread_id(), s, _has_called_back, 1013 _at_poll_safepoint); 1014 1015 _thread->print_thread_state_on(st); 1016 } 1017 1018 1019 // --------------------------------------------------------------------------------------------------------------------- 1020 1021 // Block the thread at the safepoint poll or poll return. 1022 void ThreadSafepointState::handle_polling_page_exception() { 1023 1024 // Check state. block() will set thread state to thread_in_vm which will 1025 // cause the safepoint state _type to become _call_back. 1026 assert(type() == ThreadSafepointState::_running, 1027 "polling page exception on thread not running state"); 1028 1029 // Step 1: Find the nmethod from the return address 1030 if (ShowSafepointMsgs && Verbose) { 1031 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); 1032 } 1033 address real_return_addr = thread()->saved_exception_pc(); 1034 1035 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 1036 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); 1037 nmethod* nm = (nmethod*)cb; 1038 1039 // Find frame of caller 1040 frame stub_fr = thread()->last_frame(); 1041 CodeBlob* stub_cb = stub_fr.cb(); 1042 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 1043 RegisterMap map(thread(), true); 1044 frame caller_fr = stub_fr.sender(&map); 1045 1046 // Should only be poll_return or poll 1047 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 1048 1049 // This is a poll immediately before a return. The exception handling code 1050 // has already had the effect of causing the return to occur, so the execution 1051 // will continue immediately after the call. In addition, the oopmap at the 1052 // return point does not mark the return value as an oop (if it is), so 1053 // it needs a handle here to be updated. 1054 if( nm->is_at_poll_return(real_return_addr) ) { 1055 // See if return type is an oop. 1056 bool return_oop = nm->method()->is_returning_oop(); 1057 Handle return_value; 1058 if (return_oop) { 1059 // The oop result has been saved on the stack together with all 1060 // the other registers. In order to preserve it over GCs we need 1061 // to keep it in a handle. 1062 oop result = caller_fr.saved_oop_result(&map); 1063 assert(result == NULL || result->is_oop(), "must be oop"); 1064 return_value = Handle(thread(), result); 1065 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 1066 } 1067 1068 // Block the thread 1069 SafepointSynchronize::block(thread()); 1070 1071 // restore oop result, if any 1072 if (return_oop) { 1073 caller_fr.set_saved_oop_result(&map, return_value()); 1074 } 1075 } 1076 1077 // This is a safepoint poll. Verify the return address and block. 1078 else { 1079 set_at_poll_safepoint(true); 1080 1081 // verify the blob built the "return address" correctly 1082 assert(real_return_addr == caller_fr.pc(), "must match"); 1083 1084 // Block the thread 1085 SafepointSynchronize::block(thread()); 1086 set_at_poll_safepoint(false); 1087 1088 // If we have a pending async exception deoptimize the frame 1089 // as otherwise we may never deliver it. 1090 if (thread()->has_async_condition()) { 1091 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1092 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1093 } 1094 1095 // If an exception has been installed we must check for a pending deoptimization 1096 // Deoptimize frame if exception has been thrown. 1097 1098 if (thread()->has_pending_exception() ) { 1099 RegisterMap map(thread(), true); 1100 frame caller_fr = stub_fr.sender(&map); 1101 if (caller_fr.is_deoptimized_frame()) { 1102 // The exception patch will destroy registers that are still 1103 // live and will be needed during deoptimization. Defer the 1104 // Async exception should have defered the exception until the 1105 // next safepoint which will be detected when we get into 1106 // the interpreter so if we have an exception now things 1107 // are messed up. 1108 1109 fatal("Exception installed and deoptimization is pending"); 1110 } 1111 } 1112 } 1113 } 1114 1115 1116 // 1117 // Statistics & Instrumentations 1118 // 1119 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1120 jlong SafepointSynchronize::_safepoint_begin_time = 0; 1121 int SafepointSynchronize::_cur_stat_index = 0; 1122 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1123 julong SafepointSynchronize::_coalesced_vmop_count = 0; 1124 jlong SafepointSynchronize::_max_sync_time = 0; 1125 jlong SafepointSynchronize::_max_vmop_time = 0; 1126 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1127 1128 static jlong cleanup_end_time = 0; 1129 static bool need_to_track_page_armed_status = false; 1130 static bool init_done = false; 1131 1132 // Helper method to print the header. 1133 static void print_header() { 1134 tty->print(" vmop " 1135 "[threads: total initially_running wait_to_block] "); 1136 tty->print("[time: spin block sync cleanup vmop] "); 1137 1138 // no page armed status printed out if it is always armed. 1139 if (need_to_track_page_armed_status) { 1140 tty->print("page_armed "); 1141 } 1142 1143 tty->print_cr("page_trap_count"); 1144 } 1145 1146 void SafepointSynchronize::deferred_initialize_stat() { 1147 if (init_done) return; 1148 1149 if (PrintSafepointStatisticsCount <= 0) { 1150 fatal("Wrong PrintSafepointStatisticsCount"); 1151 } 1152 1153 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1154 // be printed right away, in which case, _safepoint_stats will regress to 1155 // a single element array. Otherwise, it is a circular ring buffer with default 1156 // size of PrintSafepointStatisticsCount. 1157 int stats_array_size; 1158 if (PrintSafepointStatisticsTimeout > 0) { 1159 stats_array_size = 1; 1160 PrintSafepointStatistics = true; 1161 } else { 1162 stats_array_size = PrintSafepointStatisticsCount; 1163 } 1164 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1165 * sizeof(SafepointStats), mtInternal); 1166 guarantee(_safepoint_stats != NULL, 1167 "not enough memory for safepoint instrumentation data"); 1168 1169 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) { 1170 need_to_track_page_armed_status = true; 1171 } 1172 init_done = true; 1173 } 1174 1175 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1176 assert(init_done, "safepoint statistics array hasn't been initialized"); 1177 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1178 1179 spstat->_time_stamp = _ts_of_current_safepoint; 1180 1181 VM_Operation *op = VMThread::vm_operation(); 1182 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1183 if (op != NULL) { 1184 _safepoint_reasons[spstat->_vmop_type]++; 1185 } 1186 1187 spstat->_nof_total_threads = nof_threads; 1188 spstat->_nof_initial_running_threads = nof_running; 1189 spstat->_nof_threads_hit_page_trap = 0; 1190 1191 // Records the start time of spinning. The real time spent on spinning 1192 // will be adjusted when spin is done. Same trick is applied for time 1193 // spent on waiting for threads to block. 1194 if (nof_running != 0) { 1195 spstat->_time_to_spin = os::javaTimeNanos(); 1196 } else { 1197 spstat->_time_to_spin = 0; 1198 } 1199 } 1200 1201 void SafepointSynchronize::update_statistics_on_spin_end() { 1202 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1203 1204 jlong cur_time = os::javaTimeNanos(); 1205 1206 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1207 if (spstat->_nof_initial_running_threads != 0) { 1208 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1209 } 1210 1211 if (need_to_track_page_armed_status) { 1212 spstat->_page_armed = (PageArmed == 1); 1213 } 1214 1215 // Records the start time of waiting for to block. Updated when block is done. 1216 if (_waiting_to_block != 0) { 1217 spstat->_time_to_wait_to_block = cur_time; 1218 } else { 1219 spstat->_time_to_wait_to_block = 0; 1220 } 1221 } 1222 1223 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1224 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1225 1226 if (spstat->_nof_threads_wait_to_block != 0) { 1227 spstat->_time_to_wait_to_block = end_time - 1228 spstat->_time_to_wait_to_block; 1229 } 1230 1231 // Records the end time of sync which will be used to calculate the total 1232 // vm operation time. Again, the real time spending in syncing will be deducted 1233 // from the start of the sync time later when end_statistics is called. 1234 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1235 if (spstat->_time_to_sync > _max_sync_time) { 1236 _max_sync_time = spstat->_time_to_sync; 1237 } 1238 1239 spstat->_time_to_do_cleanups = end_time; 1240 } 1241 1242 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1243 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1244 1245 // Record how long spent in cleanup tasks. 1246 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1247 1248 cleanup_end_time = end_time; 1249 } 1250 1251 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1252 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1253 1254 // Update the vm operation time. 1255 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1256 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1257 _max_vmop_time = spstat->_time_to_exec_vmop; 1258 } 1259 // Only the sync time longer than the specified 1260 // PrintSafepointStatisticsTimeout will be printed out right away. 1261 // By default, it is -1 meaning all samples will be put into the list. 1262 if ( PrintSafepointStatisticsTimeout > 0) { 1263 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1264 print_statistics(); 1265 } 1266 } else { 1267 // The safepoint statistics will be printed out when the _safepoin_stats 1268 // array fills up. 1269 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1270 print_statistics(); 1271 _cur_stat_index = 0; 1272 } else { 1273 _cur_stat_index++; 1274 } 1275 } 1276 } 1277 1278 void SafepointSynchronize::print_statistics() { 1279 SafepointStats* sstats = _safepoint_stats; 1280 1281 for (int index = 0; index <= _cur_stat_index; index++) { 1282 if (index % 30 == 0) { 1283 print_header(); 1284 } 1285 sstats = &_safepoint_stats[index]; 1286 tty->print("%.3f: ", sstats->_time_stamp); 1287 tty->print("%-26s [" 1288 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15) 1289 " ] ", 1290 sstats->_vmop_type == -1 ? "no vm operation" : 1291 VM_Operation::name(sstats->_vmop_type), 1292 sstats->_nof_total_threads, 1293 sstats->_nof_initial_running_threads, 1294 sstats->_nof_threads_wait_to_block); 1295 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1296 tty->print(" [" 1297 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1298 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1299 INT64_FORMAT_W(6)" ] ", 1300 sstats->_time_to_spin / MICROUNITS, 1301 sstats->_time_to_wait_to_block / MICROUNITS, 1302 sstats->_time_to_sync / MICROUNITS, 1303 sstats->_time_to_do_cleanups / MICROUNITS, 1304 sstats->_time_to_exec_vmop / MICROUNITS); 1305 1306 if (need_to_track_page_armed_status) { 1307 tty->print(INT32_FORMAT" ", sstats->_page_armed); 1308 } 1309 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap); 1310 } 1311 } 1312 1313 // This method will be called when VM exits. It will first call 1314 // print_statistics to print out the rest of the sampling. Then 1315 // it tries to summarize the sampling. 1316 void SafepointSynchronize::print_stat_on_exit() { 1317 if (_safepoint_stats == NULL) return; 1318 1319 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1320 1321 // During VM exit, end_statistics may not get called and in that 1322 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1323 // don't print it out. 1324 // Approximate the vm op time. 1325 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1326 os::javaTimeNanos() - cleanup_end_time; 1327 1328 if ( PrintSafepointStatisticsTimeout < 0 || 1329 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1330 print_statistics(); 1331 } 1332 tty->print_cr(""); 1333 1334 // Print out polling page sampling status. 1335 if (!need_to_track_page_armed_status) { 1336 if (UseCompilerSafepoints) { 1337 tty->print_cr("Polling page always armed"); 1338 } 1339 } else { 1340 tty->print_cr("Defer polling page loop count = %d\n", 1341 DeferPollingPageLoopCount); 1342 } 1343 1344 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1345 if (_safepoint_reasons[index] != 0) { 1346 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index), 1347 _safepoint_reasons[index]); 1348 } 1349 } 1350 1351 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint", 1352 _coalesced_vmop_count); 1353 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms", 1354 _max_sync_time / MICROUNITS); 1355 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1356 INT64_FORMAT_W(5)" ms", 1357 _max_vmop_time / MICROUNITS); 1358 } 1359 1360 // ------------------------------------------------------------------------------------------------ 1361 // Non-product code 1362 1363 #ifndef PRODUCT 1364 1365 void SafepointSynchronize::print_state() { 1366 if (_state == _not_synchronized) { 1367 tty->print_cr("not synchronized"); 1368 } else if (_state == _synchronizing || _state == _synchronized) { 1369 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1370 "synchronized"); 1371 1372 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1373 cur->safepoint_state()->print(); 1374 } 1375 } 1376 } 1377 1378 void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1379 if (ShowSafepointMsgs) { 1380 va_list ap; 1381 va_start(ap, format); 1382 tty->vprint_cr(format, ap); 1383 va_end(ap); 1384 } 1385 } 1386 1387 #endif // !PRODUCT