1 /* 2 * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/stringTable.hpp" 27 #include "classfile/systemDictionary.hpp" 28 #include "code/codeCache.hpp" 29 #include "code/icBuffer.hpp" 30 #include "code/nmethod.hpp" 31 #include "code/pcDesc.hpp" 32 #include "code/scopeDesc.hpp" 33 #include "gc_interface/collectedHeap.hpp" 34 #include "interpreter/interpreter.hpp" 35 #include "memory/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/orderAccess.inline.hpp" 45 #include "runtime/osThread.hpp" 46 #include "runtime/safepoint.hpp" 47 #include "runtime/signature.hpp" 48 #include "runtime/stubCodeGenerator.hpp" 49 #include "runtime/stubRoutines.hpp" 50 #include "runtime/sweeper.hpp" 51 #include "runtime/synchronizer.hpp" 52 #include "runtime/thread.inline.hpp" 53 #include "services/memTracker.hpp" 54 #include "services/runtimeService.hpp" 55 #include "utilities/events.hpp" 56 #include "utilities/macros.hpp" 57 #ifdef TARGET_ARCH_x86 58 # include "nativeInst_x86.hpp" 59 # include "vmreg_x86.inline.hpp" 60 #endif 61 #ifdef TARGET_ARCH_sparc 62 # include "nativeInst_sparc.hpp" 63 # include "vmreg_sparc.inline.hpp" 64 #endif 65 #ifdef TARGET_ARCH_zero 66 # include "nativeInst_zero.hpp" 67 # include "vmreg_zero.inline.hpp" 68 #endif 69 #ifdef TARGET_ARCH_arm 70 # include "nativeInst_arm.hpp" 71 # include "vmreg_arm.inline.hpp" 72 #endif 73 #ifdef TARGET_ARCH_ppc 74 # include "nativeInst_ppc.hpp" 75 # include "vmreg_ppc.inline.hpp" 76 #endif 77 #if INCLUDE_ALL_GCS 78 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" 79 #include "gc_implementation/shared/suspendibleThreadSet.hpp" 80 #endif // INCLUDE_ALL_GCS 81 #ifdef COMPILER1 82 #include "c1/c1_globals.hpp" 83 #endif 84 85 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 86 87 // -------------------------------------------------------------------------------------------------- 88 // Implementation of Safepoint begin/end 89 90 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 91 volatile int SafepointSynchronize::_waiting_to_block = 0; 92 volatile int SafepointSynchronize::_safepoint_counter = 0; 93 int SafepointSynchronize::_current_jni_active_count = 0; 94 long SafepointSynchronize::_end_of_last_safepoint = 0; 95 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 96 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 97 static bool timeout_error_printed = false; 98 99 // Roll all threads forward to a safepoint and suspend them all 100 void SafepointSynchronize::begin() { 101 102 Thread* myThread = Thread::current(); 103 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); 104 105 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 106 _safepoint_begin_time = os::javaTimeNanos(); 107 _ts_of_current_safepoint = tty->time_stamp().seconds(); 108 } 109 110 #if INCLUDE_ALL_GCS 111 if (UseConcMarkSweepGC) { 112 // In the future we should investigate whether CMS can use the 113 // more-general mechanism below. DLD (01/05). 114 ConcurrentMarkSweepThread::synchronize(false); 115 } else if (UseG1GC) { 116 SuspendibleThreadSet::synchronize(); 117 } 118 #endif // INCLUDE_ALL_GCS 119 120 // By getting the Threads_lock, we assure that no threads are about to start or 121 // exit. It is released again in SafepointSynchronize::end(). 122 Threads_lock->lock(); 123 124 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 125 126 int nof_threads = Threads::number_of_threads(); 127 128 if (TraceSafepoint) { 129 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); 130 } 131 132 RuntimeService::record_safepoint_begin(); 133 134 MutexLocker mu(Safepoint_lock); 135 136 // Reset the count of active JNI critical threads 137 _current_jni_active_count = 0; 138 139 // Set number of threads to wait for, before we initiate the callbacks 140 _waiting_to_block = nof_threads; 141 TryingToBlock = 0 ; 142 int still_running = nof_threads; 143 144 // Save the starting time, so that it can be compared to see if this has taken 145 // too long to complete. 146 jlong safepoint_limit_time; 147 timeout_error_printed = false; 148 149 // PrintSafepointStatisticsTimeout can be specified separately. When 150 // specified, PrintSafepointStatistics will be set to true in 151 // deferred_initialize_stat method. The initialization has to be done 152 // early enough to avoid any races. See bug 6880029 for details. 153 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 154 deferred_initialize_stat(); 155 } 156 157 // Begin the process of bringing the system to a safepoint. 158 // Java threads can be in several different states and are 159 // stopped by different mechanisms: 160 // 161 // 1. Running interpreted 162 // The interpreter dispatch table is changed to force it to 163 // check for a safepoint condition between bytecodes. 164 // 2. Running in native code 165 // When returning from the native code, a Java thread must check 166 // the safepoint _state to see if we must block. If the 167 // VM thread sees a Java thread in native, it does 168 // not wait for this thread to block. The order of the memory 169 // writes and reads of both the safepoint state and the Java 170 // threads state is critical. In order to guarantee that the 171 // memory writes are serialized with respect to each other, 172 // the VM thread issues a memory barrier instruction 173 // (on MP systems). In order to avoid the overhead of issuing 174 // a memory barrier for each Java thread making native calls, each Java 175 // thread performs a write to a single memory page after changing 176 // the thread state. The VM thread performs a sequence of 177 // mprotect OS calls which forces all previous writes from all 178 // Java threads to be serialized. This is done in the 179 // os::serialize_thread_states() call. This has proven to be 180 // much more efficient than executing a membar instruction 181 // on every call to native code. 182 // 3. Running compiled Code 183 // Compiled code reads a global (Safepoint Polling) page that 184 // is set to fault if we are trying to get to a safepoint. 185 // 4. Blocked 186 // A thread which is blocked will not be allowed to return from the 187 // block condition until the safepoint operation is complete. 188 // 5. In VM or Transitioning between states 189 // If a Java thread is currently running in the VM or transitioning 190 // between states, the safepointing code will wait for the thread to 191 // block itself when it attempts transitions to a new state. 192 // 193 _state = _synchronizing; 194 OrderAccess::fence(); 195 196 // Flush all thread states to memory 197 if (!UseMembar) { 198 os::serialize_thread_states(); 199 } 200 201 // Make interpreter safepoint aware 202 Interpreter::notice_safepoints(); 203 204 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) { 205 // Make polling safepoint aware 206 guarantee (PageArmed == 0, "invariant") ; 207 PageArmed = 1 ; 208 os::make_polling_page_unreadable(); 209 } 210 211 // Consider using active_processor_count() ... but that call is expensive. 212 int ncpus = os::processor_count() ; 213 214 #ifdef ASSERT 215 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 216 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 217 // Clear the visited flag to ensure that the critical counts are collected properly. 218 cur->set_visited_for_critical_count(false); 219 } 220 #endif // ASSERT 221 222 if (SafepointTimeout) 223 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 224 225 // Iterate through all threads until it have been determined how to stop them all at a safepoint 226 unsigned int iterations = 0; 227 int steps = 0 ; 228 while(still_running > 0) { 229 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 230 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 231 ThreadSafepointState *cur_state = cur->safepoint_state(); 232 if (cur_state->is_running()) { 233 cur_state->examine_state_of_thread(); 234 if (!cur_state->is_running()) { 235 still_running--; 236 // consider adjusting steps downward: 237 // steps = 0 238 // steps -= NNN 239 // steps >>= 1 240 // steps = MIN(steps, 2000-100) 241 // if (iterations != 0) steps -= NNN 242 } 243 if (TraceSafepoint && Verbose) cur_state->print(); 244 } 245 } 246 247 if (PrintSafepointStatistics && iterations == 0) { 248 begin_statistics(nof_threads, still_running); 249 } 250 251 if (still_running > 0) { 252 // Check for if it takes to long 253 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 254 print_safepoint_timeout(_spinning_timeout); 255 } 256 257 // Spin to avoid context switching. 258 // There's a tension between allowing the mutators to run (and rendezvous) 259 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 260 // a mutator might otherwise use profitably to reach a safepoint. Excessive 261 // spinning by the VM thread on a saturated system can increase rendezvous latency. 262 // Blocking or yielding incur their own penalties in the form of context switching 263 // and the resultant loss of $ residency. 264 // 265 // Further complicating matters is that yield() does not work as naively expected 266 // on many platforms -- yield() does not guarantee that any other ready threads 267 // will run. As such we revert yield_all() after some number of iterations. 268 // Yield_all() is implemented as a short unconditional sleep on some platforms. 269 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 270 // can actually increase the time it takes the VM thread to detect that a system-wide 271 // stop-the-world safepoint has been reached. In a pathological scenario such as that 272 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 273 // In that case the mutators will be stalled waiting for the safepoint to complete and the 274 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 275 // will eventually wake up and detect that all mutators are safe, at which point 276 // we'll again make progress. 277 // 278 // Beware too that that the VMThread typically runs at elevated priority. 279 // Its default priority is higher than the default mutator priority. 280 // Obviously, this complicates spinning. 281 // 282 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 283 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 284 // 285 // See the comments in synchronizer.cpp for additional remarks on spinning. 286 // 287 // In the future we might: 288 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning. 289 // This is tricky as the path used by a thread exiting the JVM (say on 290 // on JNI call-out) simply stores into its state field. The burden 291 // is placed on the VM thread, which must poll (spin). 292 // 2. Find something useful to do while spinning. If the safepoint is GC-related 293 // we might aggressively scan the stacks of threads that are already safe. 294 // 3. Use Solaris schedctl to examine the state of the still-running mutators. 295 // If all the mutators are ONPROC there's no reason to sleep or yield. 296 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 297 // 5. Check system saturation. If the system is not fully saturated then 298 // simply spin and avoid sleep/yield. 299 // 6. As still-running mutators rendezvous they could unpark the sleeping 300 // VMthread. This works well for still-running mutators that become 301 // safe. The VMthread must still poll for mutators that call-out. 302 // 7. Drive the policy on time-since-begin instead of iterations. 303 // 8. Consider making the spin duration a function of the # of CPUs: 304 // Spin = (((ncpus-1) * M) + K) + F(still_running) 305 // Alternately, instead of counting iterations of the outer loop 306 // we could count the # of threads visited in the inner loop, above. 307 // 9. On windows consider using the return value from SwitchThreadTo() 308 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 309 310 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) { 311 guarantee (PageArmed == 0, "invariant") ; 312 PageArmed = 1 ; 313 os::make_polling_page_unreadable(); 314 } 315 316 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 317 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 318 ++steps ; 319 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 320 SpinPause() ; // MP-Polite spin 321 } else 322 if (steps < DeferThrSuspendLoopCount) { 323 os::NakedYield() ; 324 } else { 325 os::yield_all() ; 326 // Alternately, the VM thread could transiently depress its scheduling priority or 327 // transiently increase the priority of the tardy mutator(s). 328 } 329 330 iterations ++ ; 331 } 332 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 333 } 334 assert(still_running == 0, "sanity check"); 335 336 if (PrintSafepointStatistics) { 337 update_statistics_on_spin_end(); 338 } 339 340 // wait until all threads are stopped 341 while (_waiting_to_block > 0) { 342 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); 343 if (!SafepointTimeout || timeout_error_printed) { 344 Safepoint_lock->wait(true); // true, means with no safepoint checks 345 } else { 346 // Compute remaining time 347 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 348 349 // If there is no remaining time, then there is an error 350 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 351 print_safepoint_timeout(_blocking_timeout); 352 } 353 } 354 } 355 assert(_waiting_to_block == 0, "sanity check"); 356 357 #ifndef PRODUCT 358 if (SafepointTimeout) { 359 jlong current_time = os::javaTimeNanos(); 360 if (safepoint_limit_time < current_time) { 361 tty->print_cr("# SafepointSynchronize: Finished after " 362 INT64_FORMAT_W(6) " ms", 363 ((current_time - safepoint_limit_time) / MICROUNITS + 364 SafepointTimeoutDelay)); 365 } 366 } 367 #endif 368 369 assert((_safepoint_counter & 0x1) == 0, "must be even"); 370 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 371 _safepoint_counter ++; 372 373 // Record state 374 _state = _synchronized; 375 376 OrderAccess::fence(); 377 378 #ifdef ASSERT 379 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 380 // make sure all the threads were visited 381 assert(cur->was_visited_for_critical_count(), "missed a thread"); 382 } 383 #endif // ASSERT 384 385 // Update the count of active JNI critical regions 386 GC_locker::set_jni_lock_count(_current_jni_active_count); 387 388 if (TraceSafepoint) { 389 VM_Operation *op = VMThread::vm_operation(); 390 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); 391 } 392 393 RuntimeService::record_safepoint_synchronized(); 394 if (PrintSafepointStatistics) { 395 update_statistics_on_sync_end(os::javaTimeNanos()); 396 } 397 398 // Call stuff that needs to be run when a safepoint is just about to be completed 399 do_cleanup_tasks(); 400 401 if (PrintSafepointStatistics) { 402 // Record how much time spend on the above cleanup tasks 403 update_statistics_on_cleanup_end(os::javaTimeNanos()); 404 } 405 } 406 407 // Wake up all threads, so they are ready to resume execution after the safepoint 408 // operation has been carried out 409 void SafepointSynchronize::end() { 410 411 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 412 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 413 _safepoint_counter ++; 414 // memory fence isn't required here since an odd _safepoint_counter 415 // value can do no harm and a fence is issued below anyway. 416 417 DEBUG_ONLY(Thread* myThread = Thread::current();) 418 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 419 420 if (PrintSafepointStatistics) { 421 end_statistics(os::javaTimeNanos()); 422 } 423 424 #ifdef ASSERT 425 // A pending_exception cannot be installed during a safepoint. The threads 426 // may install an async exception after they come back from a safepoint into 427 // pending_exception after they unblock. But that should happen later. 428 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 429 assert (!(cur->has_pending_exception() && 430 cur->safepoint_state()->is_at_poll_safepoint()), 431 "safepoint installed a pending exception"); 432 } 433 #endif // ASSERT 434 435 if (PageArmed) { 436 // Make polling safepoint aware 437 os::make_polling_page_readable(); 438 PageArmed = 0 ; 439 } 440 441 // Remove safepoint check from interpreter 442 Interpreter::ignore_safepoints(); 443 444 { 445 MutexLocker mu(Safepoint_lock); 446 447 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 448 449 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 450 // when they get restarted. 451 _state = _not_synchronized; 452 OrderAccess::fence(); 453 454 if (TraceSafepoint) { 455 tty->print_cr("Leaving safepoint region"); 456 } 457 458 // Start suspended threads 459 for(JavaThread *current = Threads::first(); current; current = current->next()) { 460 // A problem occurring on Solaris is when attempting to restart threads 461 // the first #cpus - 1 go well, but then the VMThread is preempted when we get 462 // to the next one (since it has been running the longest). We then have 463 // to wait for a cpu to become available before we can continue restarting 464 // threads. 465 // FIXME: This causes the performance of the VM to degrade when active and with 466 // large numbers of threads. Apparently this is due to the synchronous nature 467 // of suspending threads. 468 // 469 // TODO-FIXME: the comments above are vestigial and no longer apply. 470 // Furthermore, using solaris' schedctl in this particular context confers no benefit 471 if (VMThreadHintNoPreempt) { 472 os::hint_no_preempt(); 473 } 474 ThreadSafepointState* cur_state = current->safepoint_state(); 475 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 476 cur_state->restart(); 477 assert(cur_state->is_running(), "safepoint state has not been reset"); 478 } 479 480 RuntimeService::record_safepoint_end(); 481 482 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 483 // blocked in signal_thread_blocked 484 Threads_lock->unlock(); 485 486 } 487 #if INCLUDE_ALL_GCS 488 // If there are any concurrent GC threads resume them. 489 if (UseConcMarkSweepGC) { 490 ConcurrentMarkSweepThread::desynchronize(false); 491 } else if (UseG1GC) { 492 SuspendibleThreadSet::desynchronize(); 493 } 494 #endif // INCLUDE_ALL_GCS 495 // record this time so VMThread can keep track how much time has elapsed 496 // since last safepoint. 497 _end_of_last_safepoint = os::javaTimeMillis(); 498 } 499 500 bool SafepointSynchronize::is_cleanup_needed() { 501 // Need a safepoint if some inline cache buffers is non-empty 502 if (!InlineCacheBuffer::is_empty()) return true; 503 return false; 504 } 505 506 507 508 // Various cleaning tasks that should be done periodically at safepoints 509 void SafepointSynchronize::do_cleanup_tasks() { 510 { 511 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime); 512 ObjectSynchronizer::deflate_idle_monitors(); 513 } 514 515 { 516 TraceTime t2("updating inline caches", TraceSafepointCleanupTime); 517 InlineCacheBuffer::update_inline_caches(); 518 } 519 { 520 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime); 521 CompilationPolicy::policy()->do_safepoint_work(); 522 } 523 524 { 525 TraceTime t4("mark nmethods", TraceSafepointCleanupTime); 526 NMethodSweeper::mark_active_nmethods(); 527 } 528 529 if (SymbolTable::needs_rehashing()) { 530 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime); 531 SymbolTable::rehash_table(); 532 } 533 534 if (StringTable::needs_rehashing()) { 535 TraceTime t6("rehashing string table", TraceSafepointCleanupTime); 536 StringTable::rehash_table(); 537 } 538 539 // rotate log files? 540 if (UseGCLogFileRotation) { 541 gclog_or_tty->rotate_log(false); 542 } 543 544 { 545 // CMS delays purging the CLDG until the beginning of the next safepoint and to 546 // make sure concurrent sweep is done 547 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime); 548 ClassLoaderDataGraph::purge_if_needed(); 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 748 749 #ifdef SPARC 750 751 #ifdef _LP64 752 #define PTR_PAD "" 753 #else 754 #define PTR_PAD " " 755 #endif 756 757 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) { 758 bool is_oop = newptr ? (cast_to_oop(newptr))->is_oop() : false; 759 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s", 760 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', 761 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); 762 } 763 764 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) { 765 bool is_oop = newptr ? (cast_to_oop(newptr))->is_oop() : false; 766 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s", 767 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', 768 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); 769 } 770 771 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) { 772 #ifdef _LP64 773 tty->print_cr("--------+------address-----+------before-----------+-------after----------+"); 774 const int incr = 1; // Increment to skip a long, in units of intptr_t 775 #else 776 tty->print_cr("--------+--address-+------before-----------+-------after----------+"); 777 const int incr = 2; // Increment to skip a long, in units of intptr_t 778 #endif 779 tty->print_cr("---SP---|"); 780 for( int i=0; i<16; i++ ) { 781 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 782 tty->print_cr("--------|"); 783 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) { 784 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 785 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); 786 tty->print_cr("--------|"); 787 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; 788 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; 789 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; 790 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; 791 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp); 792 old_sp += incr; new_sp += incr; was_oops += incr; 793 // Skip the floats 794 tty->print_cr("--Float-|"PTR_FORMAT,new_sp); 795 tty->print_cr("---FP---|"); 796 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32; 797 for( int i2=0; i2<16; i2++ ) { 798 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } 799 tty->cr(); 800 } 801 #endif // SPARC 802 #endif // PRODUCT 803 804 805 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 806 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 807 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 808 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 809 810 // Uncomment this to get some serious before/after printing of the 811 // Sparc safepoint-blob frame structure. 812 /* 813 intptr_t* sp = thread->last_Java_sp(); 814 intptr_t stack_copy[150]; 815 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i]; 816 bool was_oops[150]; 817 for( int i=0; i<150; i++ ) 818 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false; 819 */ 820 821 if (ShowSafepointMsgs) { 822 tty->print("handle_polling_page_exception: "); 823 } 824 825 if (PrintSafepointStatistics) { 826 inc_page_trap_count(); 827 } 828 829 ThreadSafepointState* state = thread->safepoint_state(); 830 831 state->handle_polling_page_exception(); 832 // print_me(sp,stack_copy,was_oops); 833 } 834 835 836 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 837 if (!timeout_error_printed) { 838 timeout_error_printed = true; 839 // Print out the thread info which didn't reach the safepoint for debugging 840 // purposes (useful when there are lots of threads in the debugger). 841 tty->cr(); 842 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 843 if (reason == _spinning_timeout) { 844 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 845 } else if (reason == _blocking_timeout) { 846 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 847 } 848 849 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 850 ThreadSafepointState *cur_state; 851 ResourceMark rm; 852 for(JavaThread *cur_thread = Threads::first(); cur_thread; 853 cur_thread = cur_thread->next()) { 854 cur_state = cur_thread->safepoint_state(); 855 856 if (cur_thread->thread_state() != _thread_blocked && 857 ((reason == _spinning_timeout && cur_state->is_running()) || 858 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 859 tty->print("# "); 860 cur_thread->print(); 861 tty->cr(); 862 } 863 } 864 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 865 } 866 867 // To debug the long safepoint, specify both DieOnSafepointTimeout & 868 // ShowMessageBoxOnError. 869 if (DieOnSafepointTimeout) { 870 char msg[1024]; 871 VM_Operation *op = VMThread::vm_operation(); 872 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 873 SafepointTimeoutDelay, 874 op != NULL ? op->name() : "no vm operation"); 875 fatal(msg); 876 } 877 } 878 879 880 // ------------------------------------------------------------------------------------------------------- 881 // Implementation of ThreadSafepointState 882 883 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 884 _thread = thread; 885 _type = _running; 886 _has_called_back = false; 887 _at_poll_safepoint = false; 888 } 889 890 void ThreadSafepointState::create(JavaThread *thread) { 891 ThreadSafepointState *state = new ThreadSafepointState(thread); 892 thread->set_safepoint_state(state); 893 } 894 895 void ThreadSafepointState::destroy(JavaThread *thread) { 896 if (thread->safepoint_state()) { 897 delete(thread->safepoint_state()); 898 thread->set_safepoint_state(NULL); 899 } 900 } 901 902 void ThreadSafepointState::examine_state_of_thread() { 903 assert(is_running(), "better be running or just have hit safepoint poll"); 904 905 JavaThreadState state = _thread->thread_state(); 906 907 // Save the state at the start of safepoint processing. 908 _orig_thread_state = state; 909 910 // Check for a thread that is suspended. Note that thread resume tries 911 // to grab the Threads_lock which we own here, so a thread cannot be 912 // resumed during safepoint synchronization. 913 914 // We check to see if this thread is suspended without locking to 915 // avoid deadlocking with a third thread that is waiting for this 916 // thread to be suspended. The third thread can notice the safepoint 917 // that we're trying to start at the beginning of its SR_lock->wait() 918 // call. If that happens, then the third thread will block on the 919 // safepoint while still holding the underlying SR_lock. We won't be 920 // able to get the SR_lock and we'll deadlock. 921 // 922 // We don't need to grab the SR_lock here for two reasons: 923 // 1) The suspend flags are both volatile and are set with an 924 // Atomic::cmpxchg() call so we should see the suspended 925 // state right away. 926 // 2) We're being called from the safepoint polling loop; if 927 // we don't see the suspended state on this iteration, then 928 // we'll come around again. 929 // 930 bool is_suspended = _thread->is_ext_suspended(); 931 if (is_suspended) { 932 roll_forward(_at_safepoint); 933 return; 934 } 935 936 // Some JavaThread states have an initial safepoint state of 937 // running, but are actually at a safepoint. We will happily 938 // agree and update the safepoint state here. 939 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 940 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 941 roll_forward(_at_safepoint); 942 return; 943 } 944 945 if (state == _thread_in_vm) { 946 roll_forward(_call_back); 947 return; 948 } 949 950 // All other thread states will continue to run until they 951 // transition and self-block in state _blocked 952 // Safepoint polling in compiled code causes the Java threads to do the same. 953 // Note: new threads may require a malloc so they must be allowed to finish 954 955 assert(is_running(), "examine_state_of_thread on non-running thread"); 956 return; 957 } 958 959 // Returns true is thread could not be rolled forward at present position. 960 void ThreadSafepointState::roll_forward(suspend_type type) { 961 _type = type; 962 963 switch(_type) { 964 case _at_safepoint: 965 SafepointSynchronize::signal_thread_at_safepoint(); 966 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 967 if (_thread->in_critical()) { 968 // Notice that this thread is in a critical section 969 SafepointSynchronize::increment_jni_active_count(); 970 } 971 break; 972 973 case _call_back: 974 set_has_called_back(false); 975 break; 976 977 case _running: 978 default: 979 ShouldNotReachHere(); 980 } 981 } 982 983 void ThreadSafepointState::restart() { 984 switch(type()) { 985 case _at_safepoint: 986 case _call_back: 987 break; 988 989 case _running: 990 default: 991 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d", 992 _thread, _type); 993 _thread->print(); 994 ShouldNotReachHere(); 995 } 996 _type = _running; 997 set_has_called_back(false); 998 } 999 1000 1001 void ThreadSafepointState::print_on(outputStream *st) const { 1002 const char *s; 1003 1004 switch(_type) { 1005 case _running : s = "_running"; break; 1006 case _at_safepoint : s = "_at_safepoint"; break; 1007 case _call_back : s = "_call_back"; break; 1008 default: 1009 ShouldNotReachHere(); 1010 } 1011 1012 st->print_cr("Thread: " INTPTR_FORMAT 1013 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 1014 _thread, _thread->osthread()->thread_id(), s, _has_called_back, 1015 _at_poll_safepoint); 1016 1017 _thread->print_thread_state_on(st); 1018 } 1019 1020 1021 // --------------------------------------------------------------------------------------------------------------------- 1022 1023 // Block the thread at the safepoint poll or poll return. 1024 void ThreadSafepointState::handle_polling_page_exception() { 1025 1026 // Check state. block() will set thread state to thread_in_vm which will 1027 // cause the safepoint state _type to become _call_back. 1028 assert(type() == ThreadSafepointState::_running, 1029 "polling page exception on thread not running state"); 1030 1031 // Step 1: Find the nmethod from the return address 1032 if (ShowSafepointMsgs && Verbose) { 1033 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); 1034 } 1035 address real_return_addr = thread()->saved_exception_pc(); 1036 1037 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 1038 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); 1039 nmethod* nm = (nmethod*)cb; 1040 1041 // Find frame of caller 1042 frame stub_fr = thread()->last_frame(); 1043 CodeBlob* stub_cb = stub_fr.cb(); 1044 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 1045 RegisterMap map(thread(), true); 1046 frame caller_fr = stub_fr.sender(&map); 1047 1048 // Should only be poll_return or poll 1049 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 1050 1051 // This is a poll immediately before a return. The exception handling code 1052 // has already had the effect of causing the return to occur, so the execution 1053 // will continue immediately after the call. In addition, the oopmap at the 1054 // return point does not mark the return value as an oop (if it is), so 1055 // it needs a handle here to be updated. 1056 if( nm->is_at_poll_return(real_return_addr) ) { 1057 // See if return type is an oop. 1058 bool return_oop = nm->method()->is_returning_oop(); 1059 Handle return_value; 1060 if (return_oop) { 1061 // The oop result has been saved on the stack together with all 1062 // the other registers. In order to preserve it over GCs we need 1063 // to keep it in a handle. 1064 oop result = caller_fr.saved_oop_result(&map); 1065 assert(result == NULL || result->is_oop(), "must be oop"); 1066 return_value = Handle(thread(), result); 1067 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 1068 } 1069 1070 // Block the thread 1071 SafepointSynchronize::block(thread()); 1072 1073 // restore oop result, if any 1074 if (return_oop) { 1075 caller_fr.set_saved_oop_result(&map, return_value()); 1076 } 1077 } 1078 1079 // This is a safepoint poll. Verify the return address and block. 1080 else { 1081 set_at_poll_safepoint(true); 1082 1083 // verify the blob built the "return address" correctly 1084 assert(real_return_addr == caller_fr.pc(), "must match"); 1085 1086 // Block the thread 1087 SafepointSynchronize::block(thread()); 1088 set_at_poll_safepoint(false); 1089 1090 // If we have a pending async exception deoptimize the frame 1091 // as otherwise we may never deliver it. 1092 if (thread()->has_async_condition()) { 1093 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1094 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1095 } 1096 1097 // If an exception has been installed we must check for a pending deoptimization 1098 // Deoptimize frame if exception has been thrown. 1099 1100 if (thread()->has_pending_exception() ) { 1101 RegisterMap map(thread(), true); 1102 frame caller_fr = stub_fr.sender(&map); 1103 if (caller_fr.is_deoptimized_frame()) { 1104 // The exception patch will destroy registers that are still 1105 // live and will be needed during deoptimization. Defer the 1106 // Async exception should have deferred the exception until the 1107 // next safepoint which will be detected when we get into 1108 // the interpreter so if we have an exception now things 1109 // are messed up. 1110 1111 fatal("Exception installed and deoptimization is pending"); 1112 } 1113 } 1114 } 1115 } 1116 1117 1118 // 1119 // Statistics & Instrumentations 1120 // 1121 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1122 jlong SafepointSynchronize::_safepoint_begin_time = 0; 1123 int SafepointSynchronize::_cur_stat_index = 0; 1124 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1125 julong SafepointSynchronize::_coalesced_vmop_count = 0; 1126 jlong SafepointSynchronize::_max_sync_time = 0; 1127 jlong SafepointSynchronize::_max_vmop_time = 0; 1128 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1129 1130 static jlong cleanup_end_time = 0; 1131 static bool need_to_track_page_armed_status = false; 1132 static bool init_done = false; 1133 1134 // Helper method to print the header. 1135 static void print_header() { 1136 tty->print(" vmop " 1137 "[threads: total initially_running wait_to_block] "); 1138 tty->print("[time: spin block sync cleanup vmop] "); 1139 1140 // no page armed status printed out if it is always armed. 1141 if (need_to_track_page_armed_status) { 1142 tty->print("page_armed "); 1143 } 1144 1145 tty->print_cr("page_trap_count"); 1146 } 1147 1148 void SafepointSynchronize::deferred_initialize_stat() { 1149 if (init_done) return; 1150 1151 if (PrintSafepointStatisticsCount <= 0) { 1152 fatal("Wrong PrintSafepointStatisticsCount"); 1153 } 1154 1155 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1156 // be printed right away, in which case, _safepoint_stats will regress to 1157 // a single element array. Otherwise, it is a circular ring buffer with default 1158 // size of PrintSafepointStatisticsCount. 1159 int stats_array_size; 1160 if (PrintSafepointStatisticsTimeout > 0) { 1161 stats_array_size = 1; 1162 PrintSafepointStatistics = true; 1163 } else { 1164 stats_array_size = PrintSafepointStatisticsCount; 1165 } 1166 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1167 * sizeof(SafepointStats), mtInternal); 1168 guarantee(_safepoint_stats != NULL, 1169 "not enough memory for safepoint instrumentation data"); 1170 1171 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) { 1172 need_to_track_page_armed_status = true; 1173 } 1174 init_done = true; 1175 } 1176 1177 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1178 assert(init_done, "safepoint statistics array hasn't been initialized"); 1179 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1180 1181 spstat->_time_stamp = _ts_of_current_safepoint; 1182 1183 VM_Operation *op = VMThread::vm_operation(); 1184 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1185 if (op != NULL) { 1186 _safepoint_reasons[spstat->_vmop_type]++; 1187 } 1188 1189 spstat->_nof_total_threads = nof_threads; 1190 spstat->_nof_initial_running_threads = nof_running; 1191 spstat->_nof_threads_hit_page_trap = 0; 1192 1193 // Records the start time of spinning. The real time spent on spinning 1194 // will be adjusted when spin is done. Same trick is applied for time 1195 // spent on waiting for threads to block. 1196 if (nof_running != 0) { 1197 spstat->_time_to_spin = os::javaTimeNanos(); 1198 } else { 1199 spstat->_time_to_spin = 0; 1200 } 1201 } 1202 1203 void SafepointSynchronize::update_statistics_on_spin_end() { 1204 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1205 1206 jlong cur_time = os::javaTimeNanos(); 1207 1208 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1209 if (spstat->_nof_initial_running_threads != 0) { 1210 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1211 } 1212 1213 if (need_to_track_page_armed_status) { 1214 spstat->_page_armed = (PageArmed == 1); 1215 } 1216 1217 // Records the start time of waiting for to block. Updated when block is done. 1218 if (_waiting_to_block != 0) { 1219 spstat->_time_to_wait_to_block = cur_time; 1220 } else { 1221 spstat->_time_to_wait_to_block = 0; 1222 } 1223 } 1224 1225 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1226 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1227 1228 if (spstat->_nof_threads_wait_to_block != 0) { 1229 spstat->_time_to_wait_to_block = end_time - 1230 spstat->_time_to_wait_to_block; 1231 } 1232 1233 // Records the end time of sync which will be used to calculate the total 1234 // vm operation time. Again, the real time spending in syncing will be deducted 1235 // from the start of the sync time later when end_statistics is called. 1236 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1237 if (spstat->_time_to_sync > _max_sync_time) { 1238 _max_sync_time = spstat->_time_to_sync; 1239 } 1240 1241 spstat->_time_to_do_cleanups = end_time; 1242 } 1243 1244 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1245 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1246 1247 // Record how long spent in cleanup tasks. 1248 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1249 1250 cleanup_end_time = end_time; 1251 } 1252 1253 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1254 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1255 1256 // Update the vm operation time. 1257 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1258 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1259 _max_vmop_time = spstat->_time_to_exec_vmop; 1260 } 1261 // Only the sync time longer than the specified 1262 // PrintSafepointStatisticsTimeout will be printed out right away. 1263 // By default, it is -1 meaning all samples will be put into the list. 1264 if ( PrintSafepointStatisticsTimeout > 0) { 1265 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1266 print_statistics(); 1267 } 1268 } else { 1269 // The safepoint statistics will be printed out when the _safepoin_stats 1270 // array fills up. 1271 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1272 print_statistics(); 1273 _cur_stat_index = 0; 1274 } else { 1275 _cur_stat_index++; 1276 } 1277 } 1278 } 1279 1280 void SafepointSynchronize::print_statistics() { 1281 SafepointStats* sstats = _safepoint_stats; 1282 1283 for (int index = 0; index <= _cur_stat_index; index++) { 1284 if (index % 30 == 0) { 1285 print_header(); 1286 } 1287 sstats = &_safepoint_stats[index]; 1288 tty->print("%.3f: ", sstats->_time_stamp); 1289 tty->print("%-26s [" 1290 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15) 1291 " ] ", 1292 sstats->_vmop_type == -1 ? "no vm operation" : 1293 VM_Operation::name(sstats->_vmop_type), 1294 sstats->_nof_total_threads, 1295 sstats->_nof_initial_running_threads, 1296 sstats->_nof_threads_wait_to_block); 1297 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1298 tty->print(" [" 1299 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1300 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1301 INT64_FORMAT_W(6)" ] ", 1302 sstats->_time_to_spin / MICROUNITS, 1303 sstats->_time_to_wait_to_block / MICROUNITS, 1304 sstats->_time_to_sync / MICROUNITS, 1305 sstats->_time_to_do_cleanups / MICROUNITS, 1306 sstats->_time_to_exec_vmop / MICROUNITS); 1307 1308 if (need_to_track_page_armed_status) { 1309 tty->print(INT32_FORMAT" ", sstats->_page_armed); 1310 } 1311 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap); 1312 } 1313 } 1314 1315 // This method will be called when VM exits. It will first call 1316 // print_statistics to print out the rest of the sampling. Then 1317 // it tries to summarize the sampling. 1318 void SafepointSynchronize::print_stat_on_exit() { 1319 if (_safepoint_stats == NULL) return; 1320 1321 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1322 1323 // During VM exit, end_statistics may not get called and in that 1324 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1325 // don't print it out. 1326 // Approximate the vm op time. 1327 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1328 os::javaTimeNanos() - cleanup_end_time; 1329 1330 if ( PrintSafepointStatisticsTimeout < 0 || 1331 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1332 print_statistics(); 1333 } 1334 tty->cr(); 1335 1336 // Print out polling page sampling status. 1337 if (!need_to_track_page_armed_status) { 1338 if (UseCompilerSafepoints) { 1339 tty->print_cr("Polling page always armed"); 1340 } 1341 } else { 1342 tty->print_cr("Defer polling page loop count = %d\n", 1343 DeferPollingPageLoopCount); 1344 } 1345 1346 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1347 if (_safepoint_reasons[index] != 0) { 1348 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index), 1349 _safepoint_reasons[index]); 1350 } 1351 } 1352 1353 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint", 1354 _coalesced_vmop_count); 1355 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms", 1356 _max_sync_time / MICROUNITS); 1357 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1358 INT64_FORMAT_W(5)" ms", 1359 _max_vmop_time / MICROUNITS); 1360 } 1361 1362 // ------------------------------------------------------------------------------------------------ 1363 // Non-product code 1364 1365 #ifndef PRODUCT 1366 1367 void SafepointSynchronize::print_state() { 1368 if (_state == _not_synchronized) { 1369 tty->print_cr("not synchronized"); 1370 } else if (_state == _synchronizing || _state == _synchronized) { 1371 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1372 "synchronized"); 1373 1374 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1375 cur->safepoint_state()->print(); 1376 } 1377 } 1378 } 1379 1380 void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1381 if (ShowSafepointMsgs) { 1382 va_list ap; 1383 va_start(ap, format); 1384 tty->vprint_cr(format, ap); 1385 va_end(ap); 1386 } 1387 } 1388 1389 #endif // !PRODUCT