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 "oops/inlineKlass.hpp" 46 #include "runtime/atomic.hpp" 47 #include "runtime/deoptimization.hpp" 48 #include "runtime/frame.inline.hpp" 49 #include "runtime/globals.hpp" 50 #include "runtime/handles.inline.hpp" 51 #include "runtime/interfaceSupport.inline.hpp" 52 #include "runtime/javaThread.inline.hpp" 53 #include "runtime/mutexLocker.hpp" 54 #include "runtime/orderAccess.hpp" 55 #include "runtime/osThread.hpp" 56 #include "runtime/safepoint.hpp" 57 #include "runtime/safepointMechanism.inline.hpp" 58 #include "runtime/signature.hpp" 59 #include "runtime/stackWatermarkSet.inline.hpp" 60 #include "runtime/stubCodeGenerator.hpp" 61 #include "runtime/stubRoutines.hpp" 62 #include "runtime/synchronizer.hpp" 63 #include "runtime/threads.hpp" 64 #include "runtime/threadSMR.hpp" 65 #include "runtime/threadWXSetters.inline.hpp" 66 #include "runtime/timerTrace.hpp" 67 #include "services/runtimeService.hpp" 68 #include "utilities/events.hpp" 69 #include "utilities/macros.hpp" 70 #include "utilities/systemMemoryBarrier.hpp" 71 72 static void post_safepoint_begin_event(EventSafepointBegin& event, 73 uint64_t safepoint_id, 74 int thread_count, 75 int critical_thread_count) { 76 if (event.should_commit()) { 77 event.set_safepointId(safepoint_id); 78 event.set_totalThreadCount(thread_count); 79 event.set_jniCriticalThreadCount(critical_thread_count); 80 event.commit(); 81 } 82 } 83 84 85 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization& event, 86 uint64_t safepoint_id, 87 int initial_number_of_threads, 88 int threads_waiting_to_block, 89 int iterations) { 90 if (event.should_commit()) { 91 event.set_safepointId(safepoint_id); 92 event.set_initialThreadCount(initial_number_of_threads); 93 event.set_runningThreadCount(threads_waiting_to_block); 94 event.set_iterations(checked_cast<u4>(iterations)); 95 event.commit(); 96 } 97 } 98 99 static void post_safepoint_end_event(EventSafepointEnd& event, uint64_t safepoint_id) { 100 if (event.should_commit()) { 101 event.set_safepointId(safepoint_id); 102 event.commit(); 103 } 104 } 105 106 // SafepointCheck 107 SafepointStateTracker::SafepointStateTracker(uint64_t safepoint_id, bool at_safepoint) 108 : _safepoint_id(safepoint_id), _at_safepoint(at_safepoint) {} 109 110 bool SafepointStateTracker::safepoint_state_changed() { 111 return _safepoint_id != SafepointSynchronize::safepoint_id() || 112 _at_safepoint != SafepointSynchronize::is_at_safepoint(); 113 } 114 115 // -------------------------------------------------------------------------------------------------- 116 // Implementation of Safepoint begin/end 117 118 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 119 int SafepointSynchronize::_waiting_to_block = 0; 120 volatile uint64_t SafepointSynchronize::_safepoint_counter = 0; 121 uint64_t SafepointSynchronize::_safepoint_id = 0; 122 const uint64_t SafepointSynchronize::InactiveSafepointCounter = 0; 123 int SafepointSynchronize::_current_jni_active_count = 0; 124 125 WaitBarrier* SafepointSynchronize::_wait_barrier; 126 127 static bool timeout_error_printed = false; 128 129 // Statistic related 130 static jlong _safepoint_begin_time = 0; 131 static volatile int _nof_threads_hit_polling_page = 0; 132 133 void SafepointSynchronize::init(Thread* vmthread) { 134 // WaitBarrier should never be destroyed since we will have 135 // threads waiting on it while exiting. 136 _wait_barrier = new WaitBarrier(vmthread); 137 SafepointTracing::init(); 138 } 139 140 void SafepointSynchronize::increment_jni_active_count() { 141 assert(Thread::current()->is_VM_thread(), "Only VM thread may increment"); 142 ++_current_jni_active_count; 143 } 144 145 void SafepointSynchronize::decrement_waiting_to_block() { 146 assert(_waiting_to_block > 0, "sanity check"); 147 assert(Thread::current()->is_VM_thread(), "Only VM thread may decrement"); 148 --_waiting_to_block; 149 } 150 151 bool SafepointSynchronize::thread_not_running(ThreadSafepointState *cur_state) { 152 if (!cur_state->is_running()) { 153 // Robustness: asserted in the caller, but handle/tolerate it for release bits. 154 LogTarget(Error, safepoint) lt; 155 if (lt.is_enabled()) { 156 ResourceMark rm; 157 LogStream ls(lt); 158 ls.print("Illegal initial state detected: "); 159 cur_state->print_on(&ls); 160 } 161 return true; 162 } 163 cur_state->examine_state_of_thread(SafepointSynchronize::safepoint_counter()); 164 if (!cur_state->is_running()) { 165 return true; 166 } 167 LogTarget(Trace, safepoint) lt; 168 if (lt.is_enabled()) { 169 ResourceMark rm; 170 LogStream ls(lt); 171 cur_state->print_on(&ls); 172 } 173 return false; 174 } 175 176 #ifdef ASSERT 177 static void assert_list_is_valid(const ThreadSafepointState* tss_head, int still_running) { 178 int a = 0; 179 const ThreadSafepointState *tmp_tss = tss_head; 180 while (tmp_tss != nullptr) { 181 ++a; 182 assert(tmp_tss->is_running(), "Illegal initial state"); 183 tmp_tss = tmp_tss->get_next(); 184 } 185 assert(a == still_running, "Must be the same"); 186 } 187 #endif // ASSERT 188 189 static void back_off(int64_t start_time) { 190 // We start with fine-grained nanosleeping until a millisecond has 191 // passed, at which point we resort to plain naked_short_sleep. 192 if (os::javaTimeNanos() - start_time < NANOSECS_PER_MILLISEC) { 193 os::naked_short_nanosleep(10 * (NANOUNITS / MICROUNITS)); 194 } else { 195 os::naked_short_sleep(1); 196 } 197 } 198 199 int SafepointSynchronize::synchronize_threads(jlong safepoint_limit_time, int nof_threads, int* initial_running) 200 { 201 JavaThreadIteratorWithHandle jtiwh; 202 203 #ifdef ASSERT 204 for (; JavaThread *cur = jtiwh.next(); ) { 205 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 206 } 207 jtiwh.rewind(); 208 #endif // ASSERT 209 210 // Iterate through all threads until it has been determined how to stop them all at a safepoint. 211 int still_running = nof_threads; 212 ThreadSafepointState *tss_head = nullptr; 213 ThreadSafepointState **p_prev = &tss_head; 214 for (; JavaThread *cur = jtiwh.next(); ) { 215 ThreadSafepointState *cur_tss = cur->safepoint_state(); 216 assert(cur_tss->get_next() == nullptr, "Must be null"); 217 if (thread_not_running(cur_tss)) { 218 --still_running; 219 } else { 220 *p_prev = cur_tss; 221 p_prev = cur_tss->next_ptr(); 222 } 223 } 224 *p_prev = nullptr; 225 226 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);) 227 228 *initial_running = still_running; 229 230 // If there is no thread still running, we are already done. 231 if (still_running <= 0) { 232 assert(tss_head == nullptr, "Must be empty"); 233 return 1; 234 } 235 236 int iterations = 1; // The first iteration is above. 237 int64_t start_time = os::javaTimeNanos(); 238 239 do { 240 // Check if this has taken too long: 241 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 242 print_safepoint_timeout(); 243 } 244 245 p_prev = &tss_head; 246 ThreadSafepointState *cur_tss = tss_head; 247 while (cur_tss != nullptr) { 248 assert(cur_tss->is_running(), "Illegal initial state"); 249 if (thread_not_running(cur_tss)) { 250 --still_running; 251 *p_prev = nullptr; 252 ThreadSafepointState *tmp = cur_tss; 253 cur_tss = cur_tss->get_next(); 254 tmp->set_next(nullptr); 255 } else { 256 *p_prev = cur_tss; 257 p_prev = cur_tss->next_ptr(); 258 cur_tss = cur_tss->get_next(); 259 } 260 } 261 262 DEBUG_ONLY(assert_list_is_valid(tss_head, still_running);) 263 264 if (still_running > 0) { 265 back_off(start_time); 266 } 267 268 iterations++; 269 } while (still_running > 0); 270 271 assert(tss_head == nullptr, "Must be empty"); 272 273 return iterations; 274 } 275 276 void SafepointSynchronize::arm_safepoint() { 277 // Begin the process of bringing the system to a safepoint. 278 // Java threads can be in several different states and are 279 // stopped by different mechanisms: 280 // 281 // 1. Running interpreted 282 // When executing branching/returning byte codes interpreter 283 // checks if the poll is armed, if so blocks in SS::block(). 284 // 2. Running in native code 285 // When returning from the native code, a Java thread must check 286 // the safepoint _state to see if we must block. If the 287 // VM thread sees a Java thread in native, it does 288 // not wait for this thread to block. The order of the memory 289 // writes and reads of both the safepoint state and the Java 290 // threads state is critical. In order to guarantee that the 291 // memory writes are serialized with respect to each other, 292 // the VM thread issues a memory barrier instruction. 293 // 3. Running compiled Code 294 // Compiled code reads the local polling page that 295 // is set to fault if we are trying to get to a safepoint. 296 // 4. Blocked 297 // A thread which is blocked will not be allowed to return from the 298 // block condition until the safepoint operation is complete. 299 // 5. In VM or Transitioning between states 300 // If a Java thread is currently running in the VM or transitioning 301 // between states, the safepointing code will poll the thread state 302 // until the thread blocks itself when it attempts transitions to a 303 // new state or locking a safepoint checked monitor. 304 305 // We must never miss a thread with correct safepoint id, so we must make sure we arm 306 // the wait barrier for the next safepoint id/counter. 307 // Arming must be done after resetting _current_jni_active_count, _waiting_to_block. 308 _wait_barrier->arm(static_cast<int>(_safepoint_counter + 1)); 309 310 assert((_safepoint_counter & 0x1) == 0, "must be even"); 311 // The store to _safepoint_counter must happen after any stores in arming. 312 Atomic::release_store(&_safepoint_counter, _safepoint_counter + 1); 313 314 // We are synchronizing 315 OrderAccess::storestore(); // Ordered with _safepoint_counter 316 _state = _synchronizing; 317 318 // Arming the per thread poll while having _state != _not_synchronized means safepointing 319 log_trace(safepoint)("Setting thread local yield flag for threads"); 320 OrderAccess::storestore(); // storestore, global state -> local state 321 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) { 322 // Make sure the threads start polling, it is time to yield. 323 SafepointMechanism::arm_local_poll(cur); 324 } 325 if (UseSystemMemoryBarrier) { 326 SystemMemoryBarrier::emit(); // storestore|storeload, global state -> local state 327 } else { 328 OrderAccess::fence(); // storestore|storeload, global state -> local state 329 } 330 } 331 332 // Roll all threads forward to a safepoint and suspend them all 333 void SafepointSynchronize::begin() { 334 assert(Thread::current()->is_VM_thread(), "Only VM thread may execute a safepoint"); 335 336 EventSafepointBegin begin_event; 337 SafepointTracing::begin(VMThread::vm_op_type()); 338 339 Universe::heap()->safepoint_synchronize_begin(); 340 341 // By getting the Threads_lock, we assure that no threads are about to start or 342 // exit. It is released again in SafepointSynchronize::end(). 343 Threads_lock->lock(); 344 345 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 346 347 int nof_threads = Threads::number_of_threads(); 348 349 _nof_threads_hit_polling_page = 0; 350 351 log_debug(safepoint)("Safepoint synchronization initiated using %s wait barrier. (%d threads)", _wait_barrier->description(), nof_threads); 352 353 // Reset the count of active JNI critical threads 354 _current_jni_active_count = 0; 355 356 // Set number of threads to wait for 357 _waiting_to_block = nof_threads; 358 359 jlong safepoint_limit_time = 0; 360 if (SafepointTimeout) { 361 // Set the limit time, so that it can be compared to see if this has taken 362 // too long to complete. 363 safepoint_limit_time = SafepointTracing::start_of_safepoint() + (jlong)(SafepointTimeoutDelay * NANOSECS_PER_MILLISEC); 364 timeout_error_printed = false; 365 } 366 367 EventSafepointStateSynchronization sync_event; 368 int initial_running = 0; 369 370 // Arms the safepoint, _current_jni_active_count and _waiting_to_block must be set before. 371 arm_safepoint(); 372 373 // Will spin until all threads are safe. 374 int iterations = synchronize_threads(safepoint_limit_time, nof_threads, &initial_running); 375 assert(_waiting_to_block == 0, "No thread should be running"); 376 377 #ifndef PRODUCT 378 // Mark all threads 379 if (VerifyCrossModifyFence) { 380 JavaThreadIteratorWithHandle jtiwh; 381 for (; JavaThread *cur = jtiwh.next(); ) { 382 cur->set_requires_cross_modify_fence(true); 383 } 384 } 385 386 if (safepoint_limit_time != 0) { 387 jlong current_time = os::javaTimeNanos(); 388 if (safepoint_limit_time < current_time) { 389 log_warning(safepoint)("# SafepointSynchronize: Finished after " 390 INT64_FORMAT_W(6) " ms", 391 (int64_t)(current_time - SafepointTracing::start_of_safepoint()) / (NANOUNITS / MILLIUNITS)); 392 } 393 } 394 #endif 395 396 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 397 398 // Record state 399 _state = _synchronized; 400 401 OrderAccess::fence(); 402 403 // Set the new id 404 ++_safepoint_id; 405 406 #ifdef ASSERT 407 // Make sure all the threads were visited. 408 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) { 409 assert(cur->was_visited_for_critical_count(_safepoint_counter), "missed a thread"); 410 } 411 #endif // ASSERT 412 413 // Update the count of active JNI critical regions 414 GCLocker::set_jni_lock_count(_current_jni_active_count); 415 416 post_safepoint_synchronize_event(sync_event, 417 _safepoint_id, 418 initial_running, 419 _waiting_to_block, iterations); 420 421 SafepointTracing::synchronized(nof_threads, initial_running, _nof_threads_hit_polling_page); 422 423 post_safepoint_begin_event(begin_event, _safepoint_id, nof_threads, _current_jni_active_count); 424 } 425 426 void SafepointSynchronize::disarm_safepoint() { 427 uint64_t active_safepoint_counter = _safepoint_counter; 428 { 429 JavaThreadIteratorWithHandle jtiwh; 430 #ifdef ASSERT 431 // A pending_exception cannot be installed during a safepoint. The threads 432 // may install an async exception after they come back from a safepoint into 433 // pending_exception after they unblock. But that should happen later. 434 for (; JavaThread *cur = jtiwh.next(); ) { 435 assert (!(cur->has_pending_exception() && 436 cur->safepoint_state()->is_at_poll_safepoint()), 437 "safepoint installed a pending exception"); 438 } 439 #endif // ASSERT 440 441 OrderAccess::fence(); // keep read and write of _state from floating up 442 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 443 444 // Change state first to _not_synchronized. 445 // No threads should see _synchronized when running. 446 _state = _not_synchronized; 447 448 // Set the next dormant (even) safepoint id. 449 assert((_safepoint_counter & 0x1) == 1, "must be odd"); 450 Atomic::release_store(&_safepoint_counter, _safepoint_counter + 1); 451 452 OrderAccess::fence(); // Keep the local state from floating up. 453 454 jtiwh.rewind(); 455 for (; JavaThread *current = jtiwh.next(); ) { 456 // Clear the visited flag to ensure that the critical counts are collected properly. 457 DEBUG_ONLY(current->reset_visited_for_critical_count(active_safepoint_counter);) 458 ThreadSafepointState* cur_state = current->safepoint_state(); 459 assert(!cur_state->is_running(), "Thread not suspended at safepoint"); 460 cur_state->restart(); // TSS _running 461 assert(cur_state->is_running(), "safepoint state has not been reset"); 462 } 463 } // ~JavaThreadIteratorWithHandle 464 465 // Release threads lock, so threads can be created/destroyed again. 466 Threads_lock->unlock(); 467 468 // Wake threads after local state is correctly set. 469 _wait_barrier->disarm(); 470 } 471 472 // Wake up all threads, so they are ready to resume execution after the safepoint 473 // operation has been carried out 474 void SafepointSynchronize::end() { 475 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 476 EventSafepointEnd event; 477 assert(Thread::current()->is_VM_thread(), "Only VM thread can execute a safepoint"); 478 479 disarm_safepoint(); 480 481 Universe::heap()->safepoint_synchronize_end(); 482 483 SafepointTracing::end(); 484 485 post_safepoint_end_event(event, safepoint_id()); 486 } 487 488 // Methods for determining if a JavaThread is safepoint safe. 489 490 // False means unsafe with undetermined state. 491 // True means a determined state, but it may be an unsafe state. 492 // If called from a non-safepoint context safepoint_count MUST be InactiveSafepointCounter. 493 bool SafepointSynchronize::try_stable_load_state(JavaThreadState *state, JavaThread *thread, uint64_t safepoint_count) { 494 assert((safepoint_count != InactiveSafepointCounter && 495 Thread::current() == (Thread*)VMThread::vm_thread() && 496 SafepointSynchronize::_state != _not_synchronized) 497 || safepoint_count == InactiveSafepointCounter, "Invalid check"); 498 499 // To handle the thread_blocked state on the backedge of the WaitBarrier from 500 // previous safepoint and reading the reset value (0/InactiveSafepointCounter) we 501 // re-read state after we read thread safepoint id. The JavaThread changes its 502 // thread state from thread_blocked before resetting safepoint id to 0. 503 // This guarantees the second read will be from an updated thread state. It can 504 // either be different state making this an unsafe state or it can see blocked 505 // again. When we see blocked twice with a 0 safepoint id, either: 506 // - It is normally blocked, e.g. on Mutex, TBIVM. 507 // - It was in SS:block(), looped around to SS:block() and is blocked on the WaitBarrier. 508 // - It was in SS:block() but now on a Mutex. 509 // All of these cases are safe. 510 511 *state = thread->thread_state(); 512 OrderAccess::loadload(); 513 uint64_t sid = thread->safepoint_state()->get_safepoint_id(); // Load acquire 514 if (sid != InactiveSafepointCounter && sid != safepoint_count) { 515 // In an old safepoint, state not relevant. 516 return false; 517 } 518 return *state == thread->thread_state(); 519 } 520 521 static bool safepoint_safe_with(JavaThread *thread, JavaThreadState state) { 522 switch(state) { 523 case _thread_in_native: 524 // native threads are safe if they have no java stack or have walkable stack 525 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 526 527 case _thread_blocked: 528 // On wait_barrier or blocked. 529 // Blocked threads should already have walkable stack. 530 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 531 return true; 532 533 default: 534 return false; 535 } 536 } 537 538 bool SafepointSynchronize::handshake_safe(JavaThread *thread) { 539 if (thread->is_terminated()) { 540 return true; 541 } 542 JavaThreadState stable_state; 543 if (try_stable_load_state(&stable_state, thread, InactiveSafepointCounter)) { 544 return safepoint_safe_with(thread, stable_state); 545 } 546 return false; 547 } 548 549 550 // ------------------------------------------------------------------------------------------------------- 551 // Implementation of Safepoint blocking point 552 553 void SafepointSynchronize::block(JavaThread *thread) { 554 assert(thread != nullptr, "thread must be set"); 555 556 // Threads shouldn't block if they are in the middle of printing, but... 557 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 558 559 // Only bail from the block() call if the thread is gone from the 560 // thread list; starting to exit should still block. 561 if (thread->is_terminated()) { 562 // block current thread if we come here from native code when VM is gone 563 thread->block_if_vm_exited(); 564 565 // otherwise do nothing 566 return; 567 } 568 569 JavaThreadState state = thread->thread_state(); 570 thread->frame_anchor()->make_walkable(); 571 572 uint64_t safepoint_id = SafepointSynchronize::safepoint_counter(); 573 574 // We have no idea where the VMThread is, it might even be at next safepoint. 575 // So we can miss this poll, but stop at next. 576 577 // Load dependent store, it must not pass loading of safepoint_id. 578 thread->safepoint_state()->set_safepoint_id(safepoint_id); // Release store 579 580 // This part we can skip if we notice we miss or are in a future safepoint. 581 OrderAccess::storestore(); 582 // Load in wait barrier should not float up 583 thread->set_thread_state_fence(_thread_blocked); 584 585 _wait_barrier->wait(static_cast<int>(safepoint_id)); 586 assert(_state != _synchronized, "Can't be"); 587 588 // If barrier is disarmed stop store from floating above loads in barrier. 589 OrderAccess::loadstore(); 590 thread->set_thread_state(state); 591 592 // Then we reset the safepoint id to inactive. 593 thread->safepoint_state()->reset_safepoint_id(); // Release store 594 595 OrderAccess::fence(); 596 597 guarantee(thread->safepoint_state()->get_safepoint_id() == InactiveSafepointCounter, 598 "The safepoint id should be set only in block path"); 599 600 // cross_modify_fence is done by SafepointMechanism::process_if_requested 601 // which is the only caller here. 602 } 603 604 // ------------------------------------------------------------------------------------------------------ 605 // Exception handlers 606 607 608 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 609 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 610 thread->set_thread_state(_thread_in_vm); 611 612 // Enable WXWrite: the function is called implicitly from java code. 613 MACOS_AARCH64_ONLY(ThreadWXEnable wx(WXWrite, thread)); 614 615 if (log_is_enabled(Info, safepoint, stats)) { 616 Atomic::inc(&_nof_threads_hit_polling_page); 617 } 618 619 ThreadSafepointState* state = thread->safepoint_state(); 620 621 state->handle_polling_page_exception(); 622 623 thread->set_thread_state(_thread_in_Java); 624 } 625 626 627 void SafepointSynchronize::print_safepoint_timeout() { 628 if (!timeout_error_printed) { 629 timeout_error_printed = true; 630 // Print out the thread info which didn't reach the safepoint for debugging 631 // purposes (useful when there are lots of threads in the debugger). 632 LogTarget(Warning, safepoint) lt; 633 if (lt.is_enabled()) { 634 ResourceMark rm; 635 LogStream ls(lt); 636 637 ls.cr(); 638 ls.print_cr("# SafepointSynchronize::begin: Timeout detected:"); 639 ls.print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 640 ls.print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 641 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) { 642 if (cur_thread->safepoint_state()->is_running()) { 643 ls.print("# "); 644 cur_thread->print_on(&ls); 645 ls.cr(); 646 } 647 } 648 ls.print_cr("# SafepointSynchronize::begin: (End of list)"); 649 } 650 } 651 652 // To debug the long safepoint, specify both AbortVMOnSafepointTimeout & 653 // ShowMessageBoxOnError. 654 if (AbortVMOnSafepointTimeout && (os::elapsedTime() * MILLIUNITS > AbortVMOnSafepointTimeoutDelay)) { 655 // Send the blocking thread a signal to terminate and write an error file. 656 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) { 657 if (cur_thread->safepoint_state()->is_running()) { 658 if (!os::signal_thread(cur_thread, SIGILL, "blocking a safepoint")) { 659 break; // Could not send signal. Report fatal error. 660 } 661 // Give cur_thread a chance to report the error and terminate the VM. 662 os::naked_sleep(3000); 663 } 664 } 665 fatal("Safepoint sync time longer than %.6f ms detected when executing %s.", 666 SafepointTimeoutDelay, VMThread::vm_operation()->name()); 667 } 668 } 669 670 // ------------------------------------------------------------------------------------------------------- 671 // Implementation of ThreadSafepointState 672 673 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) 674 : _at_poll_safepoint(false), _thread(thread), _safepoint_safe(false), 675 _safepoint_id(SafepointSynchronize::InactiveSafepointCounter), _next(nullptr) { 676 } 677 678 void ThreadSafepointState::create(JavaThread *thread) { 679 ThreadSafepointState *state = new ThreadSafepointState(thread); 680 thread->set_safepoint_state(state); 681 } 682 683 void ThreadSafepointState::destroy(JavaThread *thread) { 684 if (thread->safepoint_state()) { 685 delete(thread->safepoint_state()); 686 thread->set_safepoint_state(nullptr); 687 } 688 } 689 690 uint64_t ThreadSafepointState::get_safepoint_id() const { 691 return Atomic::load_acquire(&_safepoint_id); 692 } 693 694 void ThreadSafepointState::reset_safepoint_id() { 695 Atomic::release_store(&_safepoint_id, SafepointSynchronize::InactiveSafepointCounter); 696 } 697 698 void ThreadSafepointState::set_safepoint_id(uint64_t safepoint_id) { 699 Atomic::release_store(&_safepoint_id, safepoint_id); 700 } 701 702 void ThreadSafepointState::examine_state_of_thread(uint64_t safepoint_count) { 703 assert(is_running(), "better be running or just have hit safepoint poll"); 704 705 JavaThreadState stable_state; 706 if (!SafepointSynchronize::try_stable_load_state(&stable_state, _thread, safepoint_count)) { 707 // We could not get stable state of the JavaThread. 708 // Consider it running and just return. 709 return; 710 } 711 712 if (safepoint_safe_with(_thread, stable_state)) { 713 account_safe_thread(); 714 return; 715 } 716 717 // All other thread states will continue to run until they 718 // transition and self-block in state _blocked 719 // Safepoint polling in compiled code causes the Java threads to do the same. 720 // Note: new threads may require a malloc so they must be allowed to finish 721 722 assert(is_running(), "examine_state_of_thread on non-running thread"); 723 return; 724 } 725 726 void ThreadSafepointState::account_safe_thread() { 727 SafepointSynchronize::decrement_waiting_to_block(); 728 if (_thread->in_critical()) { 729 // Notice that this thread is in a critical section 730 SafepointSynchronize::increment_jni_active_count(); 731 } 732 DEBUG_ONLY(_thread->set_visited_for_critical_count(SafepointSynchronize::safepoint_counter());) 733 assert(!_safepoint_safe, "Must be unsafe before safe"); 734 _safepoint_safe = true; 735 736 // The oops in the monitor cache are cleared to prevent stale cache entries 737 // from keeping dead objects alive. Because these oops are always cleared 738 // before safepoint operations they are not visited in JavaThread::oops_do. 739 _thread->om_clear_monitor_cache(); 740 } 741 742 void ThreadSafepointState::restart() { 743 assert(_safepoint_safe, "Must be safe before unsafe"); 744 _safepoint_safe = false; 745 } 746 747 void ThreadSafepointState::print_on(outputStream *st) const { 748 const char *s = _safepoint_safe ? "_at_safepoint" : "_running"; 749 750 st->print_cr("Thread: " INTPTR_FORMAT 751 " [0x%2x] State: %s _at_poll_safepoint %d", 752 p2i(_thread), _thread->osthread()->thread_id(), s, _at_poll_safepoint); 753 754 _thread->print_thread_state_on(st); 755 } 756 757 // --------------------------------------------------------------------------------------------------------------------- 758 759 // Process pending operation. 760 void ThreadSafepointState::handle_polling_page_exception() { 761 JavaThread* self = thread(); 762 assert(self == JavaThread::current(), "must be self"); 763 764 // Step 1: Find the nmethod from the return address 765 address real_return_addr = self->saved_exception_pc(); 766 767 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 768 assert(cb != nullptr && cb->is_nmethod(), "return address should be in nmethod"); 769 nmethod* nm = cb->as_nmethod(); 770 771 // Find frame of caller 772 frame stub_fr = self->last_frame(); 773 CodeBlob* stub_cb = stub_fr.cb(); 774 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 775 RegisterMap map(self, 776 RegisterMap::UpdateMap::include, 777 RegisterMap::ProcessFrames::skip, 778 RegisterMap::WalkContinuation::skip); 779 frame caller_fr = stub_fr.sender(&map); 780 781 // Should only be poll_return or poll 782 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 783 784 // This is a poll immediately before a return. The exception handling code 785 // has already had the effect of causing the return to occur, so the execution 786 // will continue immediately after the call. In addition, the oopmap at the 787 // return point does not mark the return value as an oop (if it is), so 788 // it needs a handle here to be updated. 789 if( nm->is_at_poll_return(real_return_addr) ) { 790 ResourceMark rm; 791 // See if return type is an oop. 792 Method* method = nm->method(); 793 bool return_oop = method->is_returning_oop(); 794 HandleMark hm(self); 795 GrowableArray<Handle> return_values; 796 InlineKlass* vk = nullptr; 797 if (return_oop && InlineTypeReturnedAsFields && 798 (method->result_type() == T_OBJECT)) { 799 // Check if an inline type is returned as fields 800 vk = InlineKlass::returned_inline_klass(map); 801 if (vk != nullptr) { 802 // We're at a safepoint at the return of a method that returns 803 // multiple values. We must make sure we preserve the oop values 804 // across the safepoint. 805 assert(vk == method->returns_inline_type(thread()), "bad inline klass"); 806 vk->save_oop_fields(map, return_values); 807 return_oop = false; 808 } 809 } 810 811 if (return_oop) { 812 // The oop result has been saved on the stack together with all 813 // the other registers. In order to preserve it over GCs we need 814 // to keep it in a handle. 815 oop result = caller_fr.saved_oop_result(&map); 816 assert(oopDesc::is_oop_or_null(result), "must be oop"); 817 return_values.push(Handle(self, result)); 818 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 819 } 820 821 // We get here if compiled return polls found a reason to call into the VM. 822 // One condition for that is that the top frame is not yet safe to use. 823 // The following stack watermark barrier poll will catch such situations. 824 StackWatermarkSet::after_unwind(self); 825 826 // Process pending operation 827 SafepointMechanism::process_if_requested_with_exit_check(self, true /* check asyncs */); 828 829 // restore oop result, if any 830 if (return_oop) { 831 assert(return_values.length() == 1, "only one return value"); 832 caller_fr.set_saved_oop_result(&map, return_values.pop()()); 833 } else if (vk != nullptr) { 834 vk->restore_oop_results(map, return_values); 835 } 836 } 837 838 // This is a safepoint poll. Verify the return address and block. 839 else { 840 841 // verify the blob built the "return address" correctly 842 assert(real_return_addr == caller_fr.pc(), "must match"); 843 844 set_at_poll_safepoint(true); 845 // Process pending operation 846 // We never deliver an async exception at a polling point as the 847 // compiler may not have an exception handler for it (polling at 848 // a return point is ok though). We will check for a pending async 849 // exception below and deoptimize if needed. We also cannot deoptimize 850 // and still install the exception here because live registers needed 851 // during deoptimization are clobbered by the exception path. The 852 // exception will just be delivered once we get into the interpreter. 853 SafepointMechanism::process_if_requested_with_exit_check(self, false /* check asyncs */); 854 set_at_poll_safepoint(false); 855 856 if (self->has_async_exception_condition()) { 857 Deoptimization::deoptimize_frame(self, caller_fr.id()); 858 log_info(exceptions)("deferred async exception at compiled safepoint"); 859 } 860 861 // If an exception has been installed we must verify that the top frame wasn't deoptimized. 862 if (self->has_pending_exception() ) { 863 RegisterMap map(self, 864 RegisterMap::UpdateMap::include, 865 RegisterMap::ProcessFrames::skip, 866 RegisterMap::WalkContinuation::skip); 867 frame caller_fr = stub_fr.sender(&map); 868 if (caller_fr.is_deoptimized_frame()) { 869 // The exception path will destroy registers that are still 870 // live and will be needed during deoptimization, so if we 871 // have an exception now things are messed up. We only check 872 // at this scope because for a poll return it is ok to deoptimize 873 // while having a pending exception since the call we are returning 874 // from already collides with exception handling registers and 875 // so there is no issue (the exception handling path kills call 876 // result registers but this is ok since the exception kills 877 // the result anyway). 878 fatal("Exception installed and deoptimization is pending"); 879 } 880 } 881 } 882 } 883 884 885 // ------------------------------------------------------------------------------------------------------- 886 // Implementation of SafepointTracing 887 888 jlong SafepointTracing::_last_safepoint_begin_time_ns = 0; 889 jlong SafepointTracing::_last_safepoint_sync_time_ns = 0; 890 jlong SafepointTracing::_last_safepoint_end_time_ns = 0; 891 jlong SafepointTracing::_last_app_time_ns = 0; 892 int SafepointTracing::_nof_threads = 0; 893 int SafepointTracing::_nof_running = 0; 894 int SafepointTracing::_page_trap = 0; 895 VM_Operation::VMOp_Type SafepointTracing::_current_type; 896 jlong SafepointTracing::_max_sync_time = 0; 897 jlong SafepointTracing::_max_vmop_time = 0; 898 uint64_t SafepointTracing::_op_count[VM_Operation::VMOp_Terminating] = {0}; 899 900 void SafepointTracing::init() { 901 // Application start 902 _last_safepoint_end_time_ns = os::javaTimeNanos(); 903 } 904 905 // Helper method to print the header. 906 static void print_header(outputStream* st) { 907 // The number of spaces is significant here, and should match the format 908 // specifiers in print_statistics(). 909 910 st->print("VM Operation " 911 "[ threads: total initial_running ]" 912 "[ time: sync vmop total ]"); 913 914 st->print_cr(" page_trap_count"); 915 } 916 917 // This prints a nice table. To get the statistics to not shift due to the logging uptime 918 // decorator, use the option as: -Xlog:safepoint+stats:[outputfile]:none 919 void SafepointTracing::statistics_log() { 920 LogTarget(Info, safepoint, stats) lt; 921 assert (lt.is_enabled(), "should only be called when printing statistics is enabled"); 922 LogStream ls(lt); 923 924 static int _cur_stat_index = 0; 925 926 // Print header every 30 entries 927 if ((_cur_stat_index % 30) == 0) { 928 print_header(&ls); 929 _cur_stat_index = 1; // wrap 930 } else { 931 _cur_stat_index++; 932 } 933 934 ls.print("%-28s [ " 935 INT32_FORMAT_W(8) " " INT32_FORMAT_W(8) " " 936 "]", 937 VM_Operation::name(_current_type), 938 _nof_threads, 939 _nof_running); 940 ls.print("[ " 941 INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " " INT64_FORMAT_W(10) " ]", 942 (int64_t)(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns), 943 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns), 944 (int64_t)(_last_safepoint_end_time_ns - _last_safepoint_begin_time_ns)); 945 946 ls.print_cr(INT32_FORMAT_W(16), _page_trap); 947 } 948 949 // This method will be called when VM exits. This tries to summarize the sampling. 950 // Current thread may already be deleted, so don't use ResourceMark. 951 void SafepointTracing::statistics_exit_log() { 952 if (!log_is_enabled(Info, safepoint, stats)) { 953 return; 954 } 955 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 956 if (_op_count[index] != 0) { 957 log_info(safepoint, stats)("%-28s" UINT64_FORMAT_W(10), VM_Operation::name(index), 958 _op_count[index]); 959 } 960 } 961 962 log_info(safepoint, stats)("Maximum sync time " INT64_FORMAT" ns", 963 (int64_t)(_max_sync_time)); 964 log_info(safepoint, stats)("Maximum vm operation time (except for Exit VM operation) " 965 INT64_FORMAT " ns", 966 (int64_t)(_max_vmop_time)); 967 } 968 969 void SafepointTracing::begin(VM_Operation::VMOp_Type type) { 970 _op_count[type]++; 971 _current_type = type; 972 973 // update the time stamp to begin recording safepoint time 974 _last_safepoint_begin_time_ns = os::javaTimeNanos(); 975 _last_safepoint_sync_time_ns = 0; 976 977 _last_app_time_ns = _last_safepoint_begin_time_ns - _last_safepoint_end_time_ns; 978 _last_safepoint_end_time_ns = 0; 979 980 RuntimeService::record_safepoint_begin(_last_app_time_ns); 981 } 982 983 void SafepointTracing::synchronized(int nof_threads, int nof_running, int traps) { 984 _last_safepoint_sync_time_ns = os::javaTimeNanos(); 985 _nof_threads = nof_threads; 986 _nof_running = nof_running; 987 _page_trap = traps; 988 RuntimeService::record_safepoint_synchronized(_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns); 989 } 990 991 void SafepointTracing::end() { 992 _last_safepoint_end_time_ns = os::javaTimeNanos(); 993 994 if (_max_sync_time < (_last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns)) { 995 _max_sync_time = _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns; 996 } 997 if (_max_vmop_time < (_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns)) { 998 _max_vmop_time = _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns; 999 } 1000 if (log_is_enabled(Info, safepoint, stats)) { 1001 statistics_log(); 1002 } 1003 1004 log_info(safepoint)( 1005 "Safepoint \"%s\", " 1006 "Time since last: " JLONG_FORMAT " ns, " 1007 "Reaching safepoint: " JLONG_FORMAT " ns, " 1008 "At safepoint: " JLONG_FORMAT " ns, " 1009 "Total: " JLONG_FORMAT " ns", 1010 VM_Operation::name(_current_type), 1011 _last_app_time_ns, 1012 _last_safepoint_sync_time_ns - _last_safepoint_begin_time_ns, 1013 _last_safepoint_end_time_ns - _last_safepoint_sync_time_ns, 1014 _last_safepoint_end_time_ns - _last_safepoint_begin_time_ns 1015 ); 1016 1017 RuntimeService::record_safepoint_end(_last_safepoint_end_time_ns - _last_safepoint_sync_time_ns); 1018 } --- EOF ---