1 /* 2 * Copyright (c) 1997, 2024, 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 "code/codeCache.hpp" 27 #include "code/nmethod.hpp" 28 #include "code/pcDesc.hpp" 29 #include "code/scopeDesc.hpp" 30 #include "compiler/compilationPolicy.hpp" 31 #include "gc/shared/collectedHeap.hpp" 32 #include "gc/shared/gcLocker.hpp" 33 #include "gc/shared/oopStorage.hpp" 34 #include "gc/shared/strongRootsScope.hpp" 35 #include "gc/shared/workerThread.hpp" 36 #include "gc/shared/workerUtils.hpp" 37 #include "interpreter/interpreter.hpp" 38 #include "jfr/jfrEvents.hpp" 39 #include "logging/log.hpp" 40 #include "logging/logStream.hpp" 41 #include "memory/resourceArea.hpp" 42 #include "memory/universe.hpp" 43 #include "oops/oop.inline.hpp" 44 #include "oops/symbol.hpp" 45 #include "runtime/atomic.hpp" 46 #include "runtime/deoptimization.hpp" 47 #include "runtime/frame.inline.hpp" 48 #include "runtime/globals.hpp" 49 #include "runtime/handles.inline.hpp" 50 #include "runtime/interfaceSupport.inline.hpp" 51 #include "runtime/javaThread.inline.hpp" 52 #include "runtime/mutexLocker.hpp" 53 #include "runtime/orderAccess.hpp" 54 #include "runtime/osThread.hpp" 55 #include "runtime/safepoint.hpp" 56 #include "runtime/safepointMechanism.inline.hpp" 57 #include "runtime/signature.hpp" 58 #include "runtime/stackWatermarkSet.inline.hpp" 59 #include "runtime/stubCodeGenerator.hpp" 60 #include "runtime/stubRoutines.hpp" 61 #include "runtime/synchronizer.hpp" 62 #include "runtime/threads.hpp" 63 #include "runtime/threadSMR.hpp" 64 #include "runtime/threadWXSetters.inline.hpp" 65 #include "runtime/timerTrace.hpp" 66 #include "services/runtimeService.hpp" 67 #include "utilities/events.hpp" 68 #include "utilities/macros.hpp" 69 #include "utilities/systemMemoryBarrier.hpp" 70 71 static void post_safepoint_begin_event(EventSafepointBegin& event, 72 uint64_t safepoint_id, 73 int thread_count, 74 int critical_thread_count) { 75 if (event.should_commit()) { 76 event.set_safepointId(safepoint_id); 77 event.set_totalThreadCount(thread_count); 78 event.set_jniCriticalThreadCount(critical_thread_count); 79 event.commit(); 80 } 81 } 82 83 84 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization& event, 85 uint64_t safepoint_id, 86 int initial_number_of_threads, 87 int threads_waiting_to_block, 88 int iterations) { 89 if (event.should_commit()) { 90 event.set_safepointId(safepoint_id); 91 event.set_initialThreadCount(initial_number_of_threads); 92 event.set_runningThreadCount(threads_waiting_to_block); 93 event.set_iterations(checked_cast<u4>(iterations)); 94 event.commit(); 95 } 96 } 97 98 static void post_safepoint_end_event(EventSafepointEnd& event, uint64_t safepoint_id) { 99 if (event.should_commit()) { 100 event.set_safepointId(safepoint_id); 101 event.commit(); 102 } 103 } 104 105 // SafepointCheck 106 SafepointStateTracker::SafepointStateTracker(uint64_t safepoint_id, bool at_safepoint) 107 : _safepoint_id(safepoint_id), _at_safepoint(at_safepoint) {} 108 109 bool SafepointStateTracker::safepoint_state_changed() { 110 return _safepoint_id != SafepointSynchronize::safepoint_id() || 111 _at_safepoint != SafepointSynchronize::is_at_safepoint(); 112 } 113 114 // -------------------------------------------------------------------------------------------------- 115 // Implementation of Safepoint begin/end 116 117 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 118 int SafepointSynchronize::_waiting_to_block = 0; 119 volatile uint64_t SafepointSynchronize::_safepoint_counter = 0; 120 uint64_t SafepointSynchronize::_safepoint_id = 0; 121 const uint64_t SafepointSynchronize::InactiveSafepointCounter = 0; 122 int SafepointSynchronize::_current_jni_active_count = 0; 123 124 WaitBarrier* SafepointSynchronize::_wait_barrier; 125 126 static bool timeout_error_printed = false; 127 128 // Statistic related 129 static jlong _safepoint_begin_time = 0; 130 static volatile int _nof_threads_hit_polling_page = 0; 131 132 void SafepointSynchronize::init(Thread* vmthread) { 133 // WaitBarrier should never be destroyed since we will have 134 // threads waiting on it while exiting. 135 _wait_barrier = new WaitBarrier(vmthread); 136 SafepointTracing::init(); 137 } 138 139 void SafepointSynchronize::increment_jni_active_count() { 140 assert(Thread::current()->is_VM_thread(), "Only VM thread may increment"); 141 ++_current_jni_active_count; 142 } 143 144 void SafepointSynchronize::decrement_waiting_to_block() { 145 assert(_waiting_to_block > 0, "sanity check"); 146 assert(Thread::current()->is_VM_thread(), "Only VM thread may decrement"); 147 --_waiting_to_block; 148 } 149 150 bool SafepointSynchronize::thread_not_running(ThreadSafepointState *cur_state) { 151 if (!cur_state->is_running()) { 152 // Robustness: asserted in the caller, but handle/tolerate it for release bits. 153 LogTarget(Error, safepoint) lt; 154 if (lt.is_enabled()) { 155 ResourceMark rm; 156 LogStream ls(lt); 157 ls.print("Illegal initial state detected: "); 158 cur_state->print_on(&ls); 159 } 160 return true; 161 } 162 cur_state->examine_state_of_thread(SafepointSynchronize::safepoint_counter()); 163 if (!cur_state->is_running()) { 164 return true; 165 } 166 LogTarget(Trace, safepoint) lt; 167 if (lt.is_enabled()) { 168 ResourceMark rm; 169 LogStream ls(lt); 170 cur_state->print_on(&ls); 171 } 172 return false; 173 } 174 175 #ifdef ASSERT 176 static void assert_list_is_valid(const ThreadSafepointState* tss_head, int still_running) { 177 int a = 0; 178 const ThreadSafepointState *tmp_tss = tss_head; 179 while (tmp_tss != nullptr) { 180 ++a; 181 assert(tmp_tss->is_running(), "Illegal initial state"); 182 tmp_tss = tmp_tss->get_next(); 183 } 184 assert(a == still_running, "Must be the same"); 185 } 186 #endif // ASSERT 187 188 static void back_off(int64_t start_time) { 189 // We start with fine-grained nanosleeping until a millisecond has 190 // passed, at which point we resort to plain naked_short_sleep. 191 if (os::javaTimeNanos() - start_time < NANOSECS_PER_MILLISEC) { 192 os::naked_short_nanosleep(10 * (NANOUNITS / MICROUNITS)); 193 } else { 194 os::naked_short_sleep(1); 195 } 196 } 197 198 int SafepointSynchronize::synchronize_threads(jlong safepoint_limit_time, int nof_threads, int* initial_running) 199 { 200 JavaThreadIteratorWithHandle jtiwh; 201 202 #ifdef ASSERT 203 for (; JavaThread *cur = jtiwh.next(); ) { 204 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 205 } 206 jtiwh.rewind(); 207 #endif // ASSERT 208 209 // Iterate through all threads until it has been determined how to stop them all at a safepoint. 210 int still_running = nof_threads; 211 ThreadSafepointState *tss_head = nullptr; 212 ThreadSafepointState **p_prev = &tss_head; 213 for (; JavaThread *cur = jtiwh.next(); ) { 214 ThreadSafepointState *cur_tss = cur->safepoint_state(); 215 assert(cur_tss->get_next() == nullptr, "Must be null"); 216 if (thread_not_running(cur_tss)) { 217 --still_running; 218 } else { 219 *p_prev = cur_tss; 220 p_prev = cur_tss->next_ptr(); 221 } 222 } 223 *p_prev = nullptr; 224 225 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);) 226 227 *initial_running = still_running; 228 229 // If there is no thread still running, we are already done. 230 if (still_running <= 0) { 231 assert(tss_head == nullptr, "Must be empty"); 232 return 1; 233 } 234 235 int iterations = 1; // The first iteration is above. 236 int64_t start_time = os::javaTimeNanos(); 237 238 do { 239 // Check if this has taken too long: 240 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 241 print_safepoint_timeout(); 242 } 243 244 p_prev = &tss_head; 245 ThreadSafepointState *cur_tss = tss_head; 246 while (cur_tss != nullptr) { 247 assert(cur_tss->is_running(), "Illegal initial state"); 248 if (thread_not_running(cur_tss)) { 249 --still_running; 250 *p_prev = nullptr; 251 ThreadSafepointState *tmp = cur_tss; 252 cur_tss = cur_tss->get_next(); 253 tmp->set_next(nullptr); 254 } else { 255 *p_prev = cur_tss; 256 p_prev = cur_tss->next_ptr(); 257 cur_tss = cur_tss->get_next(); 258 } 259 } 260 261 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);) 262 263 if (still_running > 0) { 264 back_off(start_time); 265 } 266 267 iterations++; 268 } while (still_running > 0); 269 270 assert(tss_head == nullptr, "Must be empty"); 271 272 return iterations; 273 } 274 275 void SafepointSynchronize::arm_safepoint() { 276 // Begin the process of bringing the system to a safepoint. 277 // Java threads can be in several different states and are 278 // stopped by different mechanisms: 279 // 280 // 1. Running interpreted 281 // When executing branching/returning byte codes interpreter 282 // checks if the poll is armed, if so blocks in SS::block(). 283 // 2. Running in native code 284 // When returning from the native code, a Java thread must check 285 // the safepoint _state to see if we must block. If the 286 // VM thread sees a Java thread in native, it does 287 // not wait for this thread to block. The order of the memory 288 // writes and reads of both the safepoint state and the Java 289 // threads state is critical. In order to guarantee that the 290 // memory writes are serialized with respect to each other, 291 // the VM thread issues a memory barrier instruction. 292 // 3. Running compiled Code 293 // Compiled code reads the local polling page that 294 // is set to fault if we are trying to get to a safepoint. 295 // 4. Blocked 296 // A thread which is blocked will not be allowed to return from the 297 // block condition until the safepoint operation is complete. 298 // 5. In VM or Transitioning between states 299 // If a Java thread is currently running in the VM or transitioning 300 // between states, the safepointing code will poll the thread state 301 // until the thread blocks itself when it attempts transitions to a 302 // new state or locking a safepoint checked monitor. 303 304 // We must never miss a thread with correct safepoint id, so we must make sure we arm 305 // the wait barrier for the next safepoint id/counter. 306 // Arming must be done after resetting _current_jni_active_count, _waiting_to_block. 307 _wait_barrier->arm(static_cast<int>(_safepoint_counter + 1)); 308 309 assert((_safepoint_counter & 0x1) == 0, "must be even"); 310 // The store to _safepoint_counter must happen after any stores in arming. 311 Atomic::release_store(&_safepoint_counter, _safepoint_counter + 1); 312 313 // We are synchronizing 314 OrderAccess::storestore(); // Ordered with _safepoint_counter 315 _state = _synchronizing; 316 317 // Arming the per thread poll while having _state != _not_synchronized means safepointing 318 log_trace(safepoint)("Setting thread local yield flag for threads"); 319 OrderAccess::storestore(); // storestore, global state -> local state 320 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) { 321 // Make sure the threads start polling, it is time to yield. 322 SafepointMechanism::arm_local_poll(cur); 323 } 324 if (UseSystemMemoryBarrier) { 325 SystemMemoryBarrier::emit(); // storestore|storeload, global state -> local state 326 } else { 327 OrderAccess::fence(); // storestore|storeload, global state -> local state 328 } 329 } 330 331 // Roll all threads forward to a safepoint and suspend them all 332 void SafepointSynchronize::begin() { 333 assert(Thread::current()->is_VM_thread(), "Only VM thread may execute a safepoint"); 334 335 EventSafepointBegin begin_event; 336 SafepointTracing::begin(VMThread::vm_op_type()); 337 338 Universe::heap()->safepoint_synchronize_begin(); 339 340 // By getting the Threads_lock, we assure that no threads are about to start or 341 // exit. It is released again in SafepointSynchronize::end(). 342 Threads_lock->lock(); 343 344 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 345 346 int nof_threads = Threads::number_of_threads(); 347 348 _nof_threads_hit_polling_page = 0; 349 350 log_debug(safepoint)("Safepoint synchronization initiated using %s wait barrier. (%d threads)", _wait_barrier->description(), nof_threads); 351 352 // Reset the count of active JNI critical threads 353 _current_jni_active_count = 0; 354 355 // Set number of threads to wait for 356 _waiting_to_block = nof_threads; 357 358 jlong safepoint_limit_time = 0; 359 if (SafepointTimeout) { 360 // Set the limit time, so that it can be compared to see if this has taken 361 // too long to complete. 362 safepoint_limit_time = SafepointTracing::start_of_safepoint() + (jlong)(SafepointTimeoutDelay * NANOSECS_PER_MILLISEC); 363 timeout_error_printed = false; 364 } 365 366 EventSafepointStateSynchronization sync_event; 367 int initial_running = 0; 368 369 // Arms the safepoint, _current_jni_active_count and _waiting_to_block must be set before. 370 arm_safepoint(); 371 372 // Will spin until all threads are safe. 373 int iterations = synchronize_threads(safepoint_limit_time, nof_threads, &initial_running); 374 assert(_waiting_to_block == 0, "No thread should be running"); 375 376 #ifndef PRODUCT 377 // Mark all threads 378 if (VerifyCrossModifyFence) { 379 JavaThreadIteratorWithHandle jtiwh; 380 for (; JavaThread *cur = jtiwh.next(); ) { 381 cur->set_requires_cross_modify_fence(true); 382 } 383 } 384 385 if (safepoint_limit_time != 0) { 386 jlong current_time = os::javaTimeNanos(); 387 if (safepoint_limit_time < current_time) { 388 log_warning(safepoint)("# SafepointSynchronize: Finished after " 389 INT64_FORMAT_W(6) " ms", 390 (int64_t)(current_time - SafepointTracing::start_of_safepoint()) / (NANOUNITS / MILLIUNITS)); 391 } 392 } 393 #endif 394 395 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 396 397 // Record state 398 _state = _synchronized; 399 400 OrderAccess::fence(); 401 402 // Set the new id 403 ++_safepoint_id; 404 405 #ifdef ASSERT 406 // Make sure all the threads were visited. 407 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) { 408 assert(cur->was_visited_for_critical_count(_safepoint_counter), "missed a thread"); 409 } 410 #endif // ASSERT 411 412 // Update the count of active JNI critical regions 413 GCLocker::set_jni_lock_count(_current_jni_active_count); 414 415 post_safepoint_synchronize_event(sync_event, 416 _safepoint_id, 417 initial_running, 418 _waiting_to_block, iterations); 419 420 SafepointTracing::synchronized(nof_threads, initial_running, _nof_threads_hit_polling_page); 421 422 post_safepoint_begin_event(begin_event, _safepoint_id, nof_threads, _current_jni_active_count); 423 } 424 425 void SafepointSynchronize::disarm_safepoint() { 426 uint64_t active_safepoint_counter = _safepoint_counter; 427 { 428 JavaThreadIteratorWithHandle jtiwh; 429 #ifdef ASSERT 430 // A pending_exception cannot be installed during a safepoint. The threads 431 // may install an async exception after they come back from a safepoint into 432 // pending_exception after they unblock. But that should happen later. 433 for (; JavaThread *cur = jtiwh.next(); ) { 434 assert (!(cur->has_pending_exception() && 435 cur->safepoint_state()->is_at_poll_safepoint()), 436 "safepoint installed a pending exception"); 437 } 438 #endif // ASSERT 439 440 OrderAccess::fence(); // keep read and write of _state from floating up 441 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 442 443 // Change state first to _not_synchronized. 444 // No threads should see _synchronized when running. 445 _state = _not_synchronized; 446 447 // Set the next dormant (even) safepoint id. 448 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 449 Atomic::release_store(&_safepoint_counter, _safepoint_counter + 1); 450 451 OrderAccess::fence(); // Keep the local state from floating up. 452 453 jtiwh.rewind(); 454 for (; JavaThread *current = jtiwh.next(); ) { 455 // Clear the visited flag to ensure that the critical counts are collected properly. 456 DEBUG_ONLY(current->reset_visited_for_critical_count(active_safepoint_counter);) 457 ThreadSafepointState* cur_state = current->safepoint_state(); 458 assert(!cur_state->is_running(), "Thread not suspended at safepoint"); 459 cur_state->restart(); // TSS _running 460 assert(cur_state->is_running(), "safepoint state has not been reset"); 461 } 462 } // ~JavaThreadIteratorWithHandle 463 464 // Release threads lock, so threads can be created/destroyed again. 465 Threads_lock->unlock(); 466 467 // Wake threads after local state is correctly set. 468 _wait_barrier->disarm(); 469 } 470 471 // Wake up all threads, so they are ready to resume execution after the safepoint 472 // operation has been carried out 473 void SafepointSynchronize::end() { 474 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 475 EventSafepointEnd event; 476 assert(Thread::current()->is_VM_thread(), "Only VM thread can execute a safepoint"); 477 478 disarm_safepoint(); 479 480 Universe::heap()->safepoint_synchronize_end(); 481 482 SafepointTracing::end(); 483 484 post_safepoint_end_event(event, safepoint_id()); 485 } 486 487 // Methods for determining if a JavaThread is safepoint safe. 488 489 // False means unsafe with undetermined state. 490 // True means a determined state, but it may be an unsafe state. 491 // If called from a non-safepoint context safepoint_count MUST be InactiveSafepointCounter. 492 bool SafepointSynchronize::try_stable_load_state(JavaThreadState *state, JavaThread *thread, uint64_t safepoint_count) { 493 assert((safepoint_count != InactiveSafepointCounter && 494 Thread::current() == (Thread*)VMThread::vm_thread() && 495 SafepointSynchronize::_state != _not_synchronized) 496 || safepoint_count == InactiveSafepointCounter, "Invalid check"); 497 498 // To handle the thread_blocked state on the backedge of the WaitBarrier from 499 // previous safepoint and reading the reset value (0/InactiveSafepointCounter) we 500 // re-read state after we read thread safepoint id. The JavaThread changes its 501 // thread state from thread_blocked before resetting safepoint id to 0. 502 // This guarantees the second read will be from an updated thread state. It can 503 // either be different state making this an unsafe state or it can see blocked 504 // again. When we see blocked twice with a 0 safepoint id, either: 505 // - It is normally blocked, e.g. on Mutex, TBIVM. 506 // - It was in SS:block(), looped around to SS:block() and is blocked on the WaitBarrier. 507 // - It was in SS:block() but now on a Mutex. 508 // All of these cases are safe. 509 510 *state = thread->thread_state(); 511 OrderAccess::loadload(); 512 uint64_t sid = thread->safepoint_state()->get_safepoint_id(); // Load acquire 513 if (sid != InactiveSafepointCounter && sid != safepoint_count) { 514 // In an old safepoint, state not relevant. 515 return false; 516 } 517 return *state == thread->thread_state(); 518 } 519 520 static bool safepoint_safe_with(JavaThread *thread, JavaThreadState state) { 521 switch(state) { 522 case _thread_in_native: 523 // native threads are safe if they have no java stack or have walkable stack 524 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 525 526 case _thread_blocked: 527 // On wait_barrier or blocked. 528 // Blocked threads should already have walkable stack. 529 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 530 return true; 531 532 default: 533 return false; 534 } 535 } 536 537 bool SafepointSynchronize::handshake_safe(JavaThread *thread) { 538 if (thread->is_terminated()) { 539 return true; 540 } 541 JavaThreadState stable_state; 542 if (try_stable_load_state(&stable_state, thread, InactiveSafepointCounter)) { 543 return safepoint_safe_with(thread, stable_state); 544 } 545 return false; 546 } 547 548 549 // ------------------------------------------------------------------------------------------------------- 550 // Implementation of Safepoint blocking point 551 552 void SafepointSynchronize::block(JavaThread *thread) { 553 assert(thread != nullptr, "thread must be set"); 554 555 // Threads shouldn't block if they are in the middle of printing, but... 556 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 557 558 // Only bail from the block() call if the thread is gone from the 559 // thread list; starting to exit should still block. 560 if (thread->is_terminated()) { 561 // block current thread if we come here from native code when VM is gone 562 thread->block_if_vm_exited(); 563 564 // otherwise do nothing 565 return; 566 } 567 568 JavaThreadState state = thread->thread_state(); 569 thread->frame_anchor()->make_walkable(); 570 571 uint64_t safepoint_id = SafepointSynchronize::safepoint_counter(); 572 573 // We have no idea where the VMThread is, it might even be at next safepoint. 574 // So we can miss this poll, but stop at next. 575 576 // Load dependent store, it must not pass loading of safepoint_id. 577 thread->safepoint_state()->set_safepoint_id(safepoint_id); // Release store 578 579 // This part we can skip if we notice we miss or are in a future safepoint. 580 OrderAccess::storestore(); 581 // Load in wait barrier should not float up 582 thread->set_thread_state_fence(_thread_blocked); 583 584 _wait_barrier->wait(static_cast<int>(safepoint_id)); 585 assert(_state != _synchronized, "Can't be"); 586 587 // If barrier is disarmed stop store from floating above loads in barrier. 588 OrderAccess::loadstore(); 589 thread->set_thread_state(state); 590 591 // Then we reset the safepoint id to inactive. 592 thread->safepoint_state()->reset_safepoint_id(); // Release store 593 594 OrderAccess::fence(); 595 596 guarantee(thread->safepoint_state()->get_safepoint_id() == InactiveSafepointCounter, 597 "The safepoint id should be set only in block path"); 598 599 // cross_modify_fence is done by SafepointMechanism::process_if_requested 600 // which is the only caller here. 601 } 602 603 // ------------------------------------------------------------------------------------------------------ 604 // Exception handlers 605 606 607 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 608 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 609 thread->set_thread_state(_thread_in_vm); 610 611 // Enable WXWrite: the function is called implicitly from java code. 612 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXWrite, thread)); 613 614 if (log_is_enabled(Info, safepoint, stats)) { 615 Atomic::inc(&_nof_threads_hit_polling_page); 616 } 617 618 ThreadSafepointState* state = thread->safepoint_state(); 619 620 state->handle_polling_page_exception(); 621 622 thread->set_thread_state(_thread_in_Java); 623 } 624 625 626 void SafepointSynchronize::print_safepoint_timeout() { 627 if (!timeout_error_printed) { 628 timeout_error_printed = true; 629 // Print out the thread info which didn't reach the safepoint for debugging 630 // purposes (useful when there are lots of threads in the debugger). 631 LogTarget(Warning, safepoint) lt; 632 if (lt.is_enabled()) { 633 ResourceMark rm; 634 LogStream ls(lt); 635 636 ls.cr(); 637 ls.print_cr("# SafepointSynchronize::begin: Timeout detected:"); 638 ls.print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 639 ls.print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 640 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) { 641 if (cur_thread->safepoint_state()->is_running()) { 642 ls.print("# "); 643 cur_thread->print_on(&ls); 644 ls.cr(); 645 } 646 } 647 ls.print_cr("# SafepointSynchronize::begin: (End of list)"); 648 } 649 } 650 651 // To debug the long safepoint, specify both AbortVMOnSafepointTimeout & 652 // ShowMessageBoxOnError. 653 if (AbortVMOnSafepointTimeout && (os::elapsedTime() * MILLIUNITS > AbortVMOnSafepointTimeoutDelay)) { 654 // Send the blocking thread a signal to terminate and write an error file. 655 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) { 656 if (cur_thread->safepoint_state()->is_running()) { 657 if (!os::signal_thread(cur_thread, SIGILL, "blocking a safepoint")) { 658 break; // Could not send signal. Report fatal error. 659 } 660 // Give cur_thread a chance to report the error and terminate the VM. 661 os::naked_sleep(3000); 662 } 663 } 664 fatal("Safepoint sync time longer than %.6f ms detected when executing %s.", 665 SafepointTimeoutDelay, VMThread::vm_operation()->name()); 666 } 667 } 668 669 // ------------------------------------------------------------------------------------------------------- 670 // Implementation of ThreadSafepointState 671 672 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) 673 : _at_poll_safepoint(false), _thread(thread), _safepoint_safe(false), 674 _safepoint_id(SafepointSynchronize::InactiveSafepointCounter), _next(nullptr) { 675 } 676 677 void ThreadSafepointState::create(JavaThread *thread) { 678 ThreadSafepointState *state = new ThreadSafepointState(thread); 679 thread->set_safepoint_state(state); 680 } 681 682 void ThreadSafepointState::destroy(JavaThread *thread) { 683 if (thread->safepoint_state()) { 684 delete(thread->safepoint_state()); 685 thread->set_safepoint_state(nullptr); 686 } 687 } 688 689 uint64_t ThreadSafepointState::get_safepoint_id() const { 690 return Atomic::load_acquire(&_safepoint_id); 691 } 692 693 void ThreadSafepointState::reset_safepoint_id() { 694 Atomic::release_store(&_safepoint_id, SafepointSynchronize::InactiveSafepointCounter); 695 } 696 697 void ThreadSafepointState::set_safepoint_id(uint64_t safepoint_id) { 698 Atomic::release_store(&_safepoint_id, safepoint_id); 699 } 700 701 void ThreadSafepointState::examine_state_of_thread(uint64_t safepoint_count) { 702 assert(is_running(), "better be running or just have hit safepoint poll"); 703 704 JavaThreadState stable_state; 705 if (!SafepointSynchronize::try_stable_load_state(&stable_state, _thread, safepoint_count)) { 706 // We could not get stable state of the JavaThread. 707 // Consider it running and just return. 708 return; 709 } 710 711 if (safepoint_safe_with(_thread, stable_state)) { 712 account_safe_thread(); 713 return; 714 } 715 716 // All other thread states will continue to run until they 717 // transition and self-block in state _blocked 718 // Safepoint polling in compiled code causes the Java threads to do the same. 719 // Note: new threads may require a malloc so they must be allowed to finish 720 721 assert(is_running(), "examine_state_of_thread on non-running thread"); 722 return; 723 } 724 725 void ThreadSafepointState::account_safe_thread() { 726 SafepointSynchronize::decrement_waiting_to_block(); 727 if (_thread->in_critical()) { 728 // Notice that this thread is in a critical section 729 SafepointSynchronize::increment_jni_active_count(); 730 } 731 DEBUG_ONLY(_thread->set_visited_for_critical_count(SafepointSynchronize::safepoint_counter());) 732 assert(!_safepoint_safe, "Must be unsafe before safe"); 733 _safepoint_safe = true; 734 } 735 736 void ThreadSafepointState::restart() { 737 assert(_safepoint_safe, "Must be safe before unsafe"); 738 _safepoint_safe = false; 739 } 740 741 void ThreadSafepointState::print_on(outputStream *st) const { 742 const char *s = _safepoint_safe ? "_at_safepoint" : "_running"; 743 744 st->print_cr("Thread: " INTPTR_FORMAT 745 " [0x%2x] State: %s _at_poll_safepoint %d", 746 p2i(_thread), _thread->osthread()->thread_id(), s, _at_poll_safepoint); 747 748 _thread->print_thread_state_on(st); 749 } 750 751 // --------------------------------------------------------------------------------------------------------------------- 752 753 // Process pending operation. 754 void ThreadSafepointState::handle_polling_page_exception() { 755 JavaThread* self = thread(); 756 assert(self == JavaThread::current(), "must be self"); 757 758 // Step 1: Find the nmethod from the return address 759 address real_return_addr = self->saved_exception_pc(); 760 761 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 762 assert(cb != nullptr && cb->is_nmethod(), "return address should be in nmethod"); 763 nmethod* nm = cb->as_nmethod(); 764 765 // Find frame of caller 766 frame stub_fr = self->last_frame(); 767 CodeBlob* stub_cb = stub_fr.cb(); 768 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 769 RegisterMap map(self, 770 RegisterMap::UpdateMap::include, 771 RegisterMap::ProcessFrames::skip, 772 RegisterMap::WalkContinuation::skip); 773 frame caller_fr = stub_fr.sender(&map); 774 775 // Should only be poll_return or poll 776 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 777 778 // This is a poll immediately before a return. The exception handling code 779 // has already had the effect of causing the return to occur, so the execution 780 // will continue immediately after the call. In addition, the oopmap at the 781 // return point does not mark the return value as an oop (if it is), so 782 // it needs a handle here to be updated. 783 if( nm->is_at_poll_return(real_return_addr) ) { 784 // See if return type is an oop. 785 bool return_oop = nm->method()->is_returning_oop(); 786 HandleMark hm(self); 787 Handle return_value; 788 if (return_oop) { 789 // The oop result has been saved on the stack together with all 790 // the other registers. In order to preserve it over GCs we need 791 // to keep it in a handle. 792 oop result = caller_fr.saved_oop_result(&map); 793 assert(oopDesc::is_oop_or_null(result), "must be oop"); 794 return_value = Handle(self, result); 795 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 796 } 797 798 // We get here if compiled return polls found a reason to call into the VM. 799 // One condition for that is that the top frame is not yet safe to use. 800 // The following stack watermark barrier poll will catch such situations. 801 StackWatermarkSet::after_unwind(self); 802 803 // Process pending operation 804 SafepointMechanism::process_if_requested_with_exit_check(self, true /* check asyncs */); 805 806 // restore oop result, if any 807 if (return_oop) { 808 caller_fr.set_saved_oop_result(&map, return_value()); 809 } 810 } 811 812 // This is a safepoint poll. Verify the return address and block. 813 else { 814 815 // verify the blob built the "return address" correctly 816 assert(real_return_addr == caller_fr.pc(), "must match"); 817 818 set_at_poll_safepoint(true); 819 // Process pending operation 820 // We never deliver an async exception at a polling point as the 821 // compiler may not have an exception handler for it (polling at 822 // a return point is ok though). We will check for a pending async 823 // exception below and deoptimize if needed. We also cannot deoptimize 824 // and still install the exception here because live registers needed 825 // during deoptimization are clobbered by the exception path. The 826 // exception will just be delivered once we get into the interpreter. 827 SafepointMechanism::process_if_requested_with_exit_check(self, false /* check asyncs */); 828 set_at_poll_safepoint(false); 829 830 if (self->has_async_exception_condition()) { 831 Deoptimization::deoptimize_frame(self, caller_fr.id()); 832 log_info(exceptions)("deferred async exception at compiled safepoint"); 833 } 834 835 // If an exception has been installed we must verify that the top frame wasn't deoptimized. 836 if (self->has_pending_exception() ) { 837 RegisterMap map(self, 838 RegisterMap::UpdateMap::include, 839 RegisterMap::ProcessFrames::skip, 840 RegisterMap::WalkContinuation::skip); 841 frame caller_fr = stub_fr.sender(&map); 842 if (caller_fr.is_deoptimized_frame()) { 843 // The exception path will destroy registers that are still 844 // live and will be needed during deoptimization, so if we 845 // have an exception now things are messed up. We only check 846 // at this scope because for a poll return it is ok to deoptimize 847 // while having a pending exception since the call we are returning 848 // from already collides with exception handling registers and 849 // so there is no issue (the exception handling path kills call 850 // result registers but this is ok since the exception kills 851 // the result anyway). 852 fatal("Exception installed and deoptimization is pending"); 853 } 854 } 855 } 856 } 857 858 859 // ------------------------------------------------------------------------------------------------------- 860 // Implementation of SafepointTracing 861 862 jlong SafepointTracing::_last_safepoint_begin_time_ns = 0; 863 jlong SafepointTracing::_last_safepoint_sync_time_ns = 0; 864 jlong SafepointTracing::_last_safepoint_end_time_ns = 0; 865 jlong SafepointTracing::_last_app_time_ns = 0; 866 int SafepointTracing::_nof_threads = 0; 867 int SafepointTracing::_nof_running = 0; 868 int SafepointTracing::_page_trap = 0; 869 VM_Operation::VMOp_Type SafepointTracing::_current_type; 870 jlong SafepointTracing::_max_sync_time = 0; 871 jlong SafepointTracing::_max_vmop_time = 0; 872 uint64_t SafepointTracing::_op_count[VM_Operation::VMOp_Terminating] = {0}; 873 874 void SafepointTracing::init() { 875 // Application start 876 _last_safepoint_end_time_ns = os::javaTimeNanos(); 877 } 878 879 // Helper method to print the header. 880 static void print_header(outputStream* st) { 881 // The number of spaces is significant here, and should match the format 882 // specifiers in print_statistics(). 883 884 st->print("VM Operation " 885 "[ threads: total initial_running ]" 886 "[ time: sync vmop total ]"); 887 888 st->print_cr(" page_trap_count"); 889 } 890 891 // This prints a nice table. To get the statistics to not shift due to the logging uptime 892 // decorator, use the option as: -Xlog:safepoint+stats:[outputfile]:none 893 void SafepointTracing::statistics_log() { 894 LogTarget(Info, safepoint, stats) lt; 895 assert (lt.is_enabled(), "should only be called when printing statistics is enabled"); 896 LogStream ls(lt); 897 898 static int _cur_stat_index = 0; 899 900 // Print header every 30 entries 901 if ((_cur_stat_index % 30) == 0) { 902 print_header(&ls); 903 _cur_stat_index = 1; // wrap 904 } else { 905 _cur_stat_index++; 906 } 907 908 ls.print("%-28s [ " 909 INT32_FORMAT_W(8) " " INT32_FORMAT_W(8) " " 910 "]", 911 VM_Operation::name(_current_type), 912 _nof_threads, 913 _nof_running); 914 ls.print("[ " 915 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " ]", 916 (int64_t)(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns), 917 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns), 918 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_begin_time_ns)); 919 920 ls.print_cr(INT32_FORMAT_W(16), _page_trap); 921 } 922 923 // This method will be called when VM exits. This tries to summarize the sampling. 924 // Current thread may already be deleted, so don't use ResourceMark. 925 void SafepointTracing::statistics_exit_log() { 926 if (!log_is_enabled(Info, safepoint, stats)) { 927 return; 928 } 929 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 930 if (_op_count[index] != 0) { 931 log_info(safepoint, stats)("%-28s" UINT64_FORMAT_W(10), VM_Operation::name(index), 932 _op_count[index]); 933 } 934 } 935 936 log_info(safepoint, stats)("Maximum sync time " INT64_FORMAT" ns", 937 (int64_t)(_max_sync_time)); 938 log_info(safepoint, stats)("Maximum vm operation time (except for Exit VM operation) " 939 INT64_FORMAT " ns", 940 (int64_t)(_max_vmop_time)); 941 } 942 943 void SafepointTracing::begin(VM_Operation::VMOp_Type type) { 944 _op_count[type]++; 945 _current_type = type; 946 947 // update the time stamp to begin recording safepoint time 948 _last_safepoint_begin_time_ns = os::javaTimeNanos(); 949 _last_safepoint_sync_time_ns = 0; 950 951 _last_app_time_ns = _last_safepoint_begin_time_ns - _last_safepoint_end_time_ns; 952 _last_safepoint_end_time_ns = 0; 953 954 RuntimeService::record_safepoint_begin(_last_app_time_ns); 955 } 956 957 void SafepointTracing::synchronized(int nof_threads, int nof_running, int traps) { 958 _last_safepoint_sync_time_ns = os::javaTimeNanos(); 959 _nof_threads = nof_threads; 960 _nof_running = nof_running; 961 _page_trap = traps; 962 RuntimeService::record_safepoint_synchronized(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns); 963 } 964 965 void SafepointTracing::end() { 966 _last_safepoint_end_time_ns = os::javaTimeNanos(); 967 968 if (_max_sync_time < (_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns)) { 969 _max_sync_time = _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns; 970 } 971 if (_max_vmop_time < (_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns)) { 972 _max_vmop_time = _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns; 973 } 974 if (log_is_enabled(Info, safepoint, stats)) { 975 statistics_log(); 976 } 977 978 log_info(safepoint)( 979 "Safepoint \"%s\", " 980 "Time since last: " JLONG_FORMAT " ns, " 981 "Reaching safepoint: " JLONG_FORMAT " ns, " 982 "At safepoint: " JLONG_FORMAT " ns, " 983 "Total: " JLONG_FORMAT " ns", 984 VM_Operation::name(_current_type), 985 _last_app_time_ns, 986 _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns, 987 _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns, 988 _last_safepoint_end_time_ns - _last_safepoint_begin_time_ns 989 ); 990 991 RuntimeService::record_safepoint_end(_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns); 992 } --- EOF ---