1 /* 2 * Copyright (c) 1998, 2015, 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 "compiler/compileBroker.hpp" 27 #include "gc/shared/collectedHeap.hpp" 28 #include "memory/resourceArea.hpp" 29 #include "oops/method.hpp" 30 #include "oops/oop.inline.hpp" 31 #include "oops/verifyOopClosure.hpp" 32 #include "runtime/interfaceSupport.hpp" 33 #include "runtime/mutexLocker.hpp" 34 #include "runtime/os.hpp" 35 #include "runtime/thread.inline.hpp" 36 #include "runtime/vmThread.hpp" 37 #include "runtime/vm_operations.hpp" 38 #include "services/runtimeService.hpp" 39 #include "trace/tracing.hpp" 40 #include "utilities/dtrace.hpp" 41 #include "utilities/events.hpp" 42 #include "utilities/xmlstream.hpp" 43 44 // Dummy VM operation to act as first element in our circular double-linked list 45 class VM_Dummy: public VM_Operation { 46 VMOp_Type type() const { return VMOp_Dummy; } 47 void doit() {}; 48 }; 49 50 VMOperationQueue::VMOperationQueue() { 51 // The queue is a circular doubled-linked list, which always contains 52 // one element (i.e., one element means empty). 53 for(int i = 0; i < nof_priorities; i++) { 54 _queue_length[i] = 0; 55 _queue_counter = 0; 56 _queue[i] = new VM_Dummy(); 57 _queue[i]->set_next(_queue[i]); 58 _queue[i]->set_prev(_queue[i]); 59 } 60 _drain_list = NULL; 61 } 62 63 64 bool VMOperationQueue::queue_empty(int prio) { 65 // It is empty if there is exactly one element 66 bool empty = (_queue[prio] == _queue[prio]->next()); 67 assert( (_queue_length[prio] == 0 && empty) || 68 (_queue_length[prio] > 0 && !empty), "sanity check"); 69 return _queue_length[prio] == 0; 70 } 71 72 // Inserts an element to the right of the q element 73 void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) { 74 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check"); 75 n->set_prev(q); 76 n->set_next(q->next()); 77 q->next()->set_prev(n); 78 q->set_next(n); 79 } 80 81 void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) { 82 _queue_length[prio]++; 83 insert(_queue[prio]->next(), op); 84 } 85 86 void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) { 87 _queue_length[prio]++; 88 insert(_queue[prio]->prev(), op); 89 } 90 91 92 void VMOperationQueue::unlink(VM_Operation* q) { 93 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check"); 94 q->prev()->set_next(q->next()); 95 q->next()->set_prev(q->prev()); 96 } 97 98 VM_Operation* VMOperationQueue::queue_remove_front(int prio) { 99 if (queue_empty(prio)) return NULL; 100 assert(_queue_length[prio] >= 0, "sanity check"); 101 _queue_length[prio]--; 102 VM_Operation* r = _queue[prio]->next(); 103 assert(r != _queue[prio], "cannot remove base element"); 104 unlink(r); 105 return r; 106 } 107 108 VM_Operation* VMOperationQueue::queue_drain(int prio) { 109 if (queue_empty(prio)) return NULL; 110 DEBUG_ONLY(int length = _queue_length[prio];); 111 assert(length >= 0, "sanity check"); 112 _queue_length[prio] = 0; 113 VM_Operation* r = _queue[prio]->next(); 114 assert(r != _queue[prio], "cannot remove base element"); 115 // remove links to base element from head and tail 116 r->set_prev(NULL); 117 _queue[prio]->prev()->set_next(NULL); 118 // restore queue to empty state 119 _queue[prio]->set_next(_queue[prio]); 120 _queue[prio]->set_prev(_queue[prio]); 121 assert(queue_empty(prio), "drain corrupted queue"); 122 #ifdef ASSERT 123 int len = 0; 124 VM_Operation* cur; 125 for(cur = r; cur != NULL; cur=cur->next()) len++; 126 assert(len == length, "drain lost some ops"); 127 #endif 128 return r; 129 } 130 131 void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) { 132 VM_Operation* cur = _queue[queue]; 133 cur = cur->next(); 134 while (cur != _queue[queue]) { 135 cur->oops_do(f); 136 cur = cur->next(); 137 } 138 } 139 140 void VMOperationQueue::drain_list_oops_do(OopClosure* f) { 141 VM_Operation* cur = _drain_list; 142 while (cur != NULL) { 143 cur->oops_do(f); 144 cur = cur->next(); 145 } 146 } 147 148 //----------------------------------------------------------------- 149 // High-level interface 150 bool VMOperationQueue::add(VM_Operation *op) { 151 152 HOTSPOT_VMOPS_REQUEST( 153 (char *) op->name(), strlen(op->name()), 154 op->evaluation_mode()); 155 156 // Encapsulates VM queue policy. Currently, that 157 // only involves putting them on the right list 158 if (op->evaluate_at_safepoint()) { 159 queue_add_back(SafepointPriority, op); 160 return true; 161 } 162 163 queue_add_back(MediumPriority, op); 164 return true; 165 } 166 167 VM_Operation* VMOperationQueue::remove_next() { 168 // Assuming VMOperation queue is two-level priority queue. If there are 169 // more than two priorities, we need a different scheduling algorithm. 170 assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2, 171 "current algorithm does not work"); 172 173 // simple counter based scheduling to prevent starvation of lower priority 174 // queue. -- see 4390175 175 int high_prio, low_prio; 176 if (_queue_counter++ < 10) { 177 high_prio = SafepointPriority; 178 low_prio = MediumPriority; 179 } else { 180 _queue_counter = 0; 181 high_prio = MediumPriority; 182 low_prio = SafepointPriority; 183 } 184 185 return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio); 186 } 187 188 void VMOperationQueue::oops_do(OopClosure* f) { 189 for(int i = 0; i < nof_priorities; i++) { 190 queue_oops_do(i, f); 191 } 192 drain_list_oops_do(f); 193 } 194 195 196 //------------------------------------------------------------------------------------------------------------------ 197 // Implementation of VMThread stuff 198 199 bool VMThread::_should_terminate = false; 200 bool VMThread::_terminated = false; 201 Monitor* VMThread::_terminate_lock = NULL; 202 VMThread* VMThread::_vm_thread = NULL; 203 VM_Operation* VMThread::_cur_vm_operation = NULL; 204 VMOperationQueue* VMThread::_vm_queue = NULL; 205 PerfCounter* VMThread::_perf_accumulated_vm_operation_time = NULL; 206 207 208 void VMThread::create() { 209 assert(vm_thread() == NULL, "we can only allocate one VMThread"); 210 _vm_thread = new VMThread(); 211 212 // Create VM operation queue 213 _vm_queue = new VMOperationQueue(); 214 guarantee(_vm_queue != NULL, "just checking"); 215 216 _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true, 217 Monitor::_safepoint_check_never); 218 219 if (UsePerfData) { 220 // jvmstat performance counters 221 Thread* THREAD = Thread::current(); 222 _perf_accumulated_vm_operation_time = 223 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime", 224 PerfData::U_Ticks, CHECK); 225 } 226 } 227 228 229 VMThread::VMThread() : NamedThread() { 230 set_name("VM Thread"); 231 } 232 233 void VMThread::destroy() { 234 if (_vm_thread != NULL) { 235 delete _vm_thread; 236 _vm_thread = NULL; // VM thread is gone 237 } 238 } 239 240 void VMThread::run() { 241 assert(this == vm_thread(), "check"); 242 243 this->initialize_thread_local_storage(); 244 this->initialize_named_thread(); 245 this->record_stack_base_and_size(); 246 // Notify_lock wait checks on active_handles() to rewait in 247 // case of spurious wakeup, it should wait on the last 248 // value set prior to the notify 249 this->set_active_handles(JNIHandleBlock::allocate_block()); 250 251 { 252 MutexLocker ml(Notify_lock); 253 Notify_lock->notify(); 254 } 255 // Notify_lock is destroyed by Threads::create_vm() 256 257 int prio = (VMThreadPriority == -1) 258 ? os::java_to_os_priority[NearMaxPriority] 259 : VMThreadPriority; 260 // Note that I cannot call os::set_priority because it expects Java 261 // priorities and I am *explicitly* using OS priorities so that it's 262 // possible to set the VM thread priority higher than any Java thread. 263 os::set_native_priority( this, prio ); 264 265 // Wait for VM_Operations until termination 266 this->loop(); 267 268 // Note the intention to exit before safepointing. 269 // 6295565 This has the effect of waiting for any large tty 270 // outputs to finish. 271 if (xtty != NULL) { 272 ttyLocker ttyl; 273 xtty->begin_elem("destroy_vm"); 274 xtty->stamp(); 275 xtty->end_elem(); 276 assert(should_terminate(), "termination flag must be set"); 277 } 278 279 // 4526887 let VM thread exit at Safepoint 280 SafepointSynchronize::begin(); 281 282 if (VerifyBeforeExit) { 283 HandleMark hm(VMThread::vm_thread()); 284 // Among other things, this ensures that Eden top is correct. 285 Universe::heap()->prepare_for_verify(); 286 os::check_heap(); 287 // Silent verification so as not to pollute normal output, 288 // unless we really asked for it. 289 Universe::verify(!(PrintGCDetails || Verbose) || VerifySilently); 290 } 291 292 CompileBroker::set_should_block(); 293 294 // wait for threads (compiler threads or daemon threads) in the 295 // _thread_in_native state to block. 296 VM_Exit::wait_for_threads_in_native_to_block(); 297 298 // signal other threads that VM process is gone 299 { 300 // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows 301 // VM thread to enter any lock at Safepoint as long as its _owner is NULL. 302 // If that happens after _terminate_lock->wait() has unset _owner 303 // but before it actually drops the lock and waits, the notification below 304 // may get lost and we will have a hang. To avoid this, we need to use 305 // Mutex::lock_without_safepoint_check(). 306 MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag); 307 _terminated = true; 308 _terminate_lock->notify(); 309 } 310 311 // Thread destructor usually does this. 312 ThreadLocalStorage::set_thread(NULL); 313 314 // Deletion must be done synchronously by the JNI DestroyJavaVM thread 315 // so that the VMThread deletion completes before the main thread frees 316 // up the CodeHeap. 317 318 } 319 320 321 // Notify the VMThread that the last non-daemon JavaThread has terminated, 322 // and wait until operation is performed. 323 void VMThread::wait_for_vm_thread_exit() { 324 { MutexLocker mu(VMOperationQueue_lock); 325 _should_terminate = true; 326 VMOperationQueue_lock->notify(); 327 } 328 329 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint 330 // because this thread has been removed from the threads list. But anything 331 // that could get blocked by Safepoint should not be used after this point, 332 // otherwise we will hang, since there is no one can end the safepoint. 333 334 // Wait until VM thread is terminated 335 // Note: it should be OK to use Terminator_lock here. But this is called 336 // at a very delicate time (VM shutdown) and we are operating in non- VM 337 // thread at Safepoint. It's safer to not share lock with other threads. 338 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag); 339 while(!VMThread::is_terminated()) { 340 _terminate_lock->wait(Mutex::_no_safepoint_check_flag); 341 } 342 } 343 } 344 345 void VMThread::evaluate_operation(VM_Operation* op) { 346 ResourceMark rm; 347 348 { 349 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time()); 350 HOTSPOT_VMOPS_BEGIN( 351 (char *) op->name(), strlen(op->name()), 352 op->evaluation_mode()); 353 354 EventExecuteVMOperation event; 355 356 op->evaluate(); 357 358 if (event.should_commit()) { 359 bool is_concurrent = op->evaluate_concurrently(); 360 event.set_operation(op->type()); 361 event.set_safepoint(op->evaluate_at_safepoint()); 362 event.set_blocking(!is_concurrent); 363 // Only write caller thread information for non-concurrent vm operations. 364 // For concurrent vm operations, the thread id is set to 0 indicating thread is unknown. 365 // This is because the caller thread could have exited already. 366 event.set_caller(is_concurrent ? 0 : op->calling_thread()->osthread()->thread_id()); 367 event.commit(); 368 } 369 370 HOTSPOT_VMOPS_END( 371 (char *) op->name(), strlen(op->name()), 372 op->evaluation_mode()); 373 } 374 375 // Last access of info in _cur_vm_operation! 376 bool c_heap_allocated = op->is_cheap_allocated(); 377 378 // Mark as completed 379 if (!op->evaluate_concurrently()) { 380 op->calling_thread()->increment_vm_operation_completed_count(); 381 } 382 // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call, 383 // since if it is stack allocated the calling thread might have deallocated 384 if (c_heap_allocated) { 385 delete _cur_vm_operation; 386 } 387 } 388 389 390 void VMThread::loop() { 391 assert(_cur_vm_operation == NULL, "no current one should be executing"); 392 393 while(true) { 394 VM_Operation* safepoint_ops = NULL; 395 // 396 // Wait for VM operation 397 // 398 // use no_safepoint_check to get lock without attempting to "sneak" 399 { MutexLockerEx mu_queue(VMOperationQueue_lock, 400 Mutex::_no_safepoint_check_flag); 401 402 // Look for new operation 403 assert(_cur_vm_operation == NULL, "no current one should be executing"); 404 _cur_vm_operation = _vm_queue->remove_next(); 405 406 // Stall time tracking code 407 if (PrintVMQWaitTime && _cur_vm_operation != NULL && 408 !_cur_vm_operation->evaluate_concurrently()) { 409 long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp(); 410 if (stall > 0) 411 tty->print_cr("%s stall: %ld", _cur_vm_operation->name(), stall); 412 } 413 414 while (!should_terminate() && _cur_vm_operation == NULL) { 415 // wait with a timeout to guarantee safepoints at regular intervals 416 bool timedout = 417 VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag, 418 GuaranteedSafepointInterval); 419 420 // Support for self destruction 421 if ((SelfDestructTimer != 0) && !is_error_reported() && 422 (os::elapsedTime() > (double)SelfDestructTimer * 60.0)) { 423 tty->print_cr("VM self-destructed"); 424 exit(-1); 425 } 426 427 if (timedout && (SafepointALot || 428 SafepointSynchronize::is_cleanup_needed())) { 429 MutexUnlockerEx mul(VMOperationQueue_lock, 430 Mutex::_no_safepoint_check_flag); 431 // Force a safepoint since we have not had one for at least 432 // 'GuaranteedSafepointInterval' milliseconds. This will run all 433 // the clean-up processing that needs to be done regularly at a 434 // safepoint 435 SafepointSynchronize::begin(); 436 #ifdef ASSERT 437 if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot(); 438 #endif 439 SafepointSynchronize::end(); 440 } 441 _cur_vm_operation = _vm_queue->remove_next(); 442 443 // If we are at a safepoint we will evaluate all the operations that 444 // follow that also require a safepoint 445 if (_cur_vm_operation != NULL && 446 _cur_vm_operation->evaluate_at_safepoint()) { 447 safepoint_ops = _vm_queue->drain_at_safepoint_priority(); 448 } 449 } 450 451 if (should_terminate()) break; 452 } // Release mu_queue_lock 453 454 // 455 // Execute VM operation 456 // 457 { HandleMark hm(VMThread::vm_thread()); 458 459 EventMark em("Executing VM operation: %s", vm_operation()->name()); 460 assert(_cur_vm_operation != NULL, "we should have found an operation to execute"); 461 462 // Give the VM thread an extra quantum. Jobs tend to be bursty and this 463 // helps the VM thread to finish up the job. 464 // FIXME: When this is enabled and there are many threads, this can degrade 465 // performance significantly. 466 if( VMThreadHintNoPreempt ) 467 os::hint_no_preempt(); 468 469 // If we are at a safepoint we will evaluate all the operations that 470 // follow that also require a safepoint 471 if (_cur_vm_operation->evaluate_at_safepoint()) { 472 473 _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned 474 475 SafepointSynchronize::begin(); 476 evaluate_operation(_cur_vm_operation); 477 // now process all queued safepoint ops, iteratively draining 478 // the queue until there are none left 479 do { 480 _cur_vm_operation = safepoint_ops; 481 if (_cur_vm_operation != NULL) { 482 do { 483 // evaluate_operation deletes the op object so we have 484 // to grab the next op now 485 VM_Operation* next = _cur_vm_operation->next(); 486 _vm_queue->set_drain_list(next); 487 evaluate_operation(_cur_vm_operation); 488 _cur_vm_operation = next; 489 if (PrintSafepointStatistics) { 490 SafepointSynchronize::inc_vmop_coalesced_count(); 491 } 492 } while (_cur_vm_operation != NULL); 493 } 494 // There is a chance that a thread enqueued a safepoint op 495 // since we released the op-queue lock and initiated the safepoint. 496 // So we drain the queue again if there is anything there, as an 497 // optimization to try and reduce the number of safepoints. 498 // As the safepoint synchronizes us with JavaThreads we will see 499 // any enqueue made by a JavaThread, but the peek will not 500 // necessarily detect a concurrent enqueue by a GC thread, but 501 // that simply means the op will wait for the next major cycle of the 502 // VMThread - just as it would if the GC thread lost the race for 503 // the lock. 504 if (_vm_queue->peek_at_safepoint_priority()) { 505 // must hold lock while draining queue 506 MutexLockerEx mu_queue(VMOperationQueue_lock, 507 Mutex::_no_safepoint_check_flag); 508 safepoint_ops = _vm_queue->drain_at_safepoint_priority(); 509 } else { 510 safepoint_ops = NULL; 511 } 512 } while(safepoint_ops != NULL); 513 514 _vm_queue->set_drain_list(NULL); 515 516 // Complete safepoint synchronization 517 SafepointSynchronize::end(); 518 519 } else { // not a safepoint operation 520 if (TraceLongCompiles) { 521 elapsedTimer t; 522 t.start(); 523 evaluate_operation(_cur_vm_operation); 524 t.stop(); 525 double secs = t.seconds(); 526 if (secs * 1e3 > LongCompileThreshold) { 527 // XXX - _cur_vm_operation should not be accessed after 528 // the completed count has been incremented; the waiting 529 // thread may have already freed this memory. 530 tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs); 531 } 532 } else { 533 evaluate_operation(_cur_vm_operation); 534 } 535 536 _cur_vm_operation = NULL; 537 } 538 } 539 540 // 541 // Notify (potential) waiting Java thread(s) - lock without safepoint 542 // check so that sneaking is not possible 543 { MutexLockerEx mu(VMOperationRequest_lock, 544 Mutex::_no_safepoint_check_flag); 545 VMOperationRequest_lock->notify_all(); 546 } 547 548 // 549 // We want to make sure that we get to a safepoint regularly. 550 // 551 if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) { 552 long interval = SafepointSynchronize::last_non_safepoint_interval(); 553 bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval); 554 if (SafepointALot || max_time_exceeded) { 555 HandleMark hm(VMThread::vm_thread()); 556 SafepointSynchronize::begin(); 557 SafepointSynchronize::end(); 558 } 559 } 560 } 561 } 562 563 void VMThread::execute(VM_Operation* op) { 564 Thread* t = Thread::current(); 565 566 if (!t->is_VM_thread()) { 567 SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot 568 // JavaThread or WatcherThread 569 bool concurrent = op->evaluate_concurrently(); 570 // only blocking VM operations need to verify the caller's safepoint state: 571 if (!concurrent) { 572 t->check_for_valid_safepoint_state(true); 573 } 574 575 // New request from Java thread, evaluate prologue 576 if (!op->doit_prologue()) { 577 return; // op was cancelled 578 } 579 580 // Setup VM_operations for execution 581 op->set_calling_thread(t, Thread::get_priority(t)); 582 583 // It does not make sense to execute the epilogue, if the VM operation object is getting 584 // deallocated by the VM thread. 585 bool execute_epilog = !op->is_cheap_allocated(); 586 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated"); 587 588 // Get ticket number for non-concurrent VM operations 589 int ticket = 0; 590 if (!concurrent) { 591 ticket = t->vm_operation_ticket(); 592 } 593 594 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the 595 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests 596 // to be queued up during a safepoint synchronization. 597 { 598 VMOperationQueue_lock->lock_without_safepoint_check(); 599 bool ok = _vm_queue->add(op); 600 op->set_timestamp(os::javaTimeMillis()); 601 VMOperationQueue_lock->notify(); 602 VMOperationQueue_lock->unlock(); 603 // VM_Operation got skipped 604 if (!ok) { 605 assert(concurrent, "can only skip concurrent tasks"); 606 if (op->is_cheap_allocated()) delete op; 607 return; 608 } 609 } 610 611 if (!concurrent) { 612 // Wait for completion of request (non-concurrent) 613 // Note: only a JavaThread triggers the safepoint check when locking 614 MutexLocker mu(VMOperationRequest_lock); 615 while(t->vm_operation_completed_count() < ticket) { 616 VMOperationRequest_lock->wait(!t->is_Java_thread()); 617 } 618 } 619 620 if (execute_epilog) { 621 op->doit_epilogue(); 622 } 623 } else { 624 // invoked by VM thread; usually nested VM operation 625 assert(t->is_VM_thread(), "must be a VM thread"); 626 VM_Operation* prev_vm_operation = vm_operation(); 627 if (prev_vm_operation != NULL) { 628 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler 629 // does not allow nested scavenges or compiles. 630 if (!prev_vm_operation->allow_nested_vm_operations()) { 631 fatal("Nested VM operation %s requested by operation %s", 632 op->name(), vm_operation()->name()); 633 } 634 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority()); 635 } 636 637 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name()); 638 639 // Release all internal handles after operation is evaluated 640 HandleMark hm(t); 641 _cur_vm_operation = op; 642 643 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) { 644 SafepointSynchronize::begin(); 645 op->evaluate(); 646 SafepointSynchronize::end(); 647 } else { 648 op->evaluate(); 649 } 650 651 // Free memory if needed 652 if (op->is_cheap_allocated()) delete op; 653 654 _cur_vm_operation = prev_vm_operation; 655 } 656 } 657 658 659 void VMThread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) { 660 Thread::oops_do(f, cld_f, cf); 661 _vm_queue->oops_do(f); 662 } 663 664 //------------------------------------------------------------------------------------------------------------------ 665 #ifndef PRODUCT 666 667 void VMOperationQueue::verify_queue(int prio) { 668 // Check that list is correctly linked 669 int length = _queue_length[prio]; 670 VM_Operation *cur = _queue[prio]; 671 int i; 672 673 // Check forward links 674 for(i = 0; i < length; i++) { 675 cur = cur->next(); 676 assert(cur != _queue[prio], "list to short (forward)"); 677 } 678 assert(cur->next() == _queue[prio], "list to long (forward)"); 679 680 // Check backwards links 681 cur = _queue[prio]; 682 for(i = 0; i < length; i++) { 683 cur = cur->prev(); 684 assert(cur != _queue[prio], "list to short (backwards)"); 685 } 686 assert(cur->prev() == _queue[prio], "list to long (backwards)"); 687 } 688 689 #endif 690 691 void VMThread::verify() { 692 oops_do(&VerifyOopClosure::verify_oop, NULL, NULL); 693 }