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