vmThread.cpp revision 3602:da91efe96a93
1/* 2 * Copyright (c) 1998, 2012, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25#include "precompiled.hpp" 26#include "compiler/compileBroker.hpp" 27#include "gc_interface/collectedHeap.hpp" 28#include "memory/resourceArea.hpp" 29#include "oops/method.hpp" 30#include "oops/oop.inline.hpp" 31#include "runtime/interfaceSupport.hpp" 32#include "runtime/mutexLocker.hpp" 33#include "runtime/os.hpp" 34#include "runtime/vmThread.hpp" 35#include "runtime/vm_operations.hpp" 36#include "services/runtimeService.hpp" 37#include "utilities/dtrace.hpp" 38#include "utilities/events.hpp" 39#include "utilities/xmlstream.hpp" 40#ifdef TARGET_OS_FAMILY_linux 41# include "thread_linux.inline.hpp" 42#endif 43#ifdef TARGET_OS_FAMILY_solaris 44# include "thread_solaris.inline.hpp" 45#endif 46#ifdef TARGET_OS_FAMILY_windows 47# include "thread_windows.inline.hpp" 48#endif 49#ifdef TARGET_OS_FAMILY_bsd 50# include "thread_bsd.inline.hpp" 51#endif 52 53#ifndef USDT2 54HS_DTRACE_PROBE_DECL3(hotspot, vmops__request, char *, uintptr_t, int); 55HS_DTRACE_PROBE_DECL3(hotspot, vmops__begin, char *, uintptr_t, int); 56HS_DTRACE_PROBE_DECL3(hotspot, vmops__end, char *, uintptr_t, int); 57#endif /* !USDT2 */ 58 59// Dummy VM operation to act as first element in our circular double-linked list 60class VM_Dummy: public VM_Operation { 61 VMOp_Type type() const { return VMOp_Dummy; } 62 void doit() {}; 63}; 64 65VMOperationQueue::VMOperationQueue() { 66 // The queue is a circular doubled-linked list, which always contains 67 // one element (i.e., one element means empty). 68 for(int i = 0; i < nof_priorities; i++) { 69 _queue_length[i] = 0; 70 _queue_counter = 0; 71 _queue[i] = new VM_Dummy(); 72 _queue[i]->set_next(_queue[i]); 73 _queue[i]->set_prev(_queue[i]); 74 } 75 _drain_list = NULL; 76} 77 78 79bool VMOperationQueue::queue_empty(int prio) { 80 // It is empty if there is exactly one element 81 bool empty = (_queue[prio] == _queue[prio]->next()); 82 assert( (_queue_length[prio] == 0 && empty) || 83 (_queue_length[prio] > 0 && !empty), "sanity check"); 84 return _queue_length[prio] == 0; 85} 86 87// Inserts an element to the right of the q element 88void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) { 89 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check"); 90 n->set_prev(q); 91 n->set_next(q->next()); 92 q->next()->set_prev(n); 93 q->set_next(n); 94} 95 96void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) { 97 _queue_length[prio]++; 98 insert(_queue[prio]->next(), op); 99} 100 101void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) { 102 _queue_length[prio]++; 103 insert(_queue[prio]->prev(), op); 104} 105 106 107void VMOperationQueue::unlink(VM_Operation* q) { 108 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check"); 109 q->prev()->set_next(q->next()); 110 q->next()->set_prev(q->prev()); 111} 112 113VM_Operation* VMOperationQueue::queue_remove_front(int prio) { 114 if (queue_empty(prio)) return NULL; 115 assert(_queue_length[prio] >= 0, "sanity check"); 116 _queue_length[prio]--; 117 VM_Operation* r = _queue[prio]->next(); 118 assert(r != _queue[prio], "cannot remove base element"); 119 unlink(r); 120 return r; 121} 122 123VM_Operation* VMOperationQueue::queue_drain(int prio) { 124 if (queue_empty(prio)) return NULL; 125 DEBUG_ONLY(int length = _queue_length[prio];); 126 assert(length >= 0, "sanity check"); 127 _queue_length[prio] = 0; 128 VM_Operation* r = _queue[prio]->next(); 129 assert(r != _queue[prio], "cannot remove base element"); 130 // remove links to base element from head and tail 131 r->set_prev(NULL); 132 _queue[prio]->prev()->set_next(NULL); 133 // restore queue to empty state 134 _queue[prio]->set_next(_queue[prio]); 135 _queue[prio]->set_prev(_queue[prio]); 136 assert(queue_empty(prio), "drain corrupted queue"); 137#ifdef DEBUG 138 int len = 0; 139 VM_Operation* cur; 140 for(cur = r; cur != NULL; cur=cur->next()) len++; 141 assert(len == length, "drain lost some ops"); 142#endif 143 return r; 144} 145 146void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) { 147 VM_Operation* cur = _queue[queue]; 148 cur = cur->next(); 149 while (cur != _queue[queue]) { 150 cur->oops_do(f); 151 cur = cur->next(); 152 } 153} 154 155void VMOperationQueue::drain_list_oops_do(OopClosure* f) { 156 VM_Operation* cur = _drain_list; 157 while (cur != NULL) { 158 cur->oops_do(f); 159 cur = cur->next(); 160 } 161} 162 163//----------------------------------------------------------------- 164// High-level interface 165bool VMOperationQueue::add(VM_Operation *op) { 166 167#ifndef USDT2 168 HS_DTRACE_PROBE3(hotspot, vmops__request, op->name(), strlen(op->name()), 169 op->evaluation_mode()); 170#else /* USDT2 */ 171 HOTSPOT_VMOPS_REQUEST( 172 (char *) op->name(), strlen(op->name()), 173 op->evaluation_mode()); 174#endif /* USDT2 */ 175 176 // Encapsulates VM queue policy. Currently, that 177 // only involves putting them on the right list 178 if (op->evaluate_at_safepoint()) { 179 queue_add_back(SafepointPriority, op); 180 return true; 181 } 182 183 queue_add_back(MediumPriority, op); 184 return true; 185} 186 187VM_Operation* VMOperationQueue::remove_next() { 188 // Assuming VMOperation queue is two-level priority queue. If there are 189 // more than two priorities, we need a different scheduling algorithm. 190 assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2, 191 "current algorithm does not work"); 192 193 // simple counter based scheduling to prevent starvation of lower priority 194 // queue. -- see 4390175 195 int high_prio, low_prio; 196 if (_queue_counter++ < 10) { 197 high_prio = SafepointPriority; 198 low_prio = MediumPriority; 199 } else { 200 _queue_counter = 0; 201 high_prio = MediumPriority; 202 low_prio = SafepointPriority; 203 } 204 205 return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio); 206} 207 208void VMOperationQueue::oops_do(OopClosure* f) { 209 for(int i = 0; i < nof_priorities; i++) { 210 queue_oops_do(i, f); 211 } 212 drain_list_oops_do(f); 213} 214 215 216//------------------------------------------------------------------------------------------------------------------ 217// Implementation of VMThread stuff 218 219bool VMThread::_should_terminate = false; 220bool VMThread::_terminated = false; 221Monitor* VMThread::_terminate_lock = NULL; 222VMThread* VMThread::_vm_thread = NULL; 223VM_Operation* VMThread::_cur_vm_operation = NULL; 224VMOperationQueue* VMThread::_vm_queue = NULL; 225PerfCounter* VMThread::_perf_accumulated_vm_operation_time = NULL; 226 227 228void VMThread::create() { 229 assert(vm_thread() == NULL, "we can only allocate one VMThread"); 230 _vm_thread = new VMThread(); 231 232 // Create VM operation queue 233 _vm_queue = new VMOperationQueue(); 234 guarantee(_vm_queue != NULL, "just checking"); 235 236 _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true); 237 238 if (UsePerfData) { 239 // jvmstat performance counters 240 Thread* THREAD = Thread::current(); 241 _perf_accumulated_vm_operation_time = 242 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime", 243 PerfData::U_Ticks, CHECK); 244 } 245} 246 247 248VMThread::VMThread() : NamedThread() { 249 set_name("VM Thread"); 250} 251 252void VMThread::destroy() { 253 if (_vm_thread != NULL) { 254 delete _vm_thread; 255 _vm_thread = NULL; // VM thread is gone 256 } 257} 258 259void VMThread::run() { 260 assert(this == vm_thread(), "check"); 261 262 this->initialize_thread_local_storage(); 263 this->record_stack_base_and_size(); 264 // Notify_lock wait checks on active_handles() to rewait in 265 // case of spurious wakeup, it should wait on the last 266 // value set prior to the notify 267 this->set_active_handles(JNIHandleBlock::allocate_block()); 268 269 { 270 MutexLocker ml(Notify_lock); 271 Notify_lock->notify(); 272 } 273 // Notify_lock is destroyed by Threads::create_vm() 274 275 int prio = (VMThreadPriority == -1) 276 ? os::java_to_os_priority[NearMaxPriority] 277 : VMThreadPriority; 278 // Note that I cannot call os::set_priority because it expects Java 279 // priorities and I am *explicitly* using OS priorities so that it's 280 // possible to set the VM thread priority higher than any Java thread. 281 os::set_native_priority( this, prio ); 282 283 // Wait for VM_Operations until termination 284 this->loop(); 285 286 // Note the intention to exit before safepointing. 287 // 6295565 This has the effect of waiting for any large tty 288 // outputs to finish. 289 if (xtty != NULL) { 290 ttyLocker ttyl; 291 xtty->begin_elem("destroy_vm"); 292 xtty->stamp(); 293 xtty->end_elem(); 294 assert(should_terminate(), "termination flag must be set"); 295 } 296 297 // 4526887 let VM thread exit at Safepoint 298 SafepointSynchronize::begin(); 299 300 if (VerifyBeforeExit) { 301 HandleMark hm(VMThread::vm_thread()); 302 // Among other things, this ensures that Eden top is correct. 303 Universe::heap()->prepare_for_verify(); 304 os::check_heap(); 305 // Silent verification so as not to pollute normal output, 306 // unless we really asked for it. 307 Universe::verify(!(PrintGCDetails || Verbose)); 308 } 309 310 CompileBroker::set_should_block(); 311 312 // wait for threads (compiler threads or daemon threads) in the 313 // _thread_in_native state to block. 314 VM_Exit::wait_for_threads_in_native_to_block(); 315 316 // signal other threads that VM process is gone 317 { 318 // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows 319 // VM thread to enter any lock at Safepoint as long as its _owner is NULL. 320 // If that happens after _terminate_lock->wait() has unset _owner 321 // but before it actually drops the lock and waits, the notification below 322 // may get lost and we will have a hang. To avoid this, we need to use 323 // Mutex::lock_without_safepoint_check(). 324 MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag); 325 _terminated = true; 326 _terminate_lock->notify(); 327 } 328 329 // Deletion must be done synchronously by the JNI DestroyJavaVM thread 330 // so that the VMThread deletion completes before the main thread frees 331 // up the CodeHeap. 332 333} 334 335 336// Notify the VMThread that the last non-daemon JavaThread has terminated, 337// and wait until operation is performed. 338void VMThread::wait_for_vm_thread_exit() { 339 { MutexLocker mu(VMOperationQueue_lock); 340 _should_terminate = true; 341 VMOperationQueue_lock->notify(); 342 } 343 344 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint 345 // because this thread has been removed from the threads list. But anything 346 // that could get blocked by Safepoint should not be used after this point, 347 // otherwise we will hang, since there is no one can end the safepoint. 348 349 // Wait until VM thread is terminated 350 // Note: it should be OK to use Terminator_lock here. But this is called 351 // at a very delicate time (VM shutdown) and we are operating in non- VM 352 // thread at Safepoint. It's safer to not share lock with other threads. 353 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag); 354 while(!VMThread::is_terminated()) { 355 _terminate_lock->wait(Mutex::_no_safepoint_check_flag); 356 } 357 } 358} 359 360void VMThread::print_on(outputStream* st) const { 361 st->print("\"%s\" ", name()); 362 Thread::print_on(st); 363 st->cr(); 364} 365 366void VMThread::evaluate_operation(VM_Operation* op) { 367 ResourceMark rm; 368 369 { 370 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time()); 371#ifndef USDT2 372 HS_DTRACE_PROBE3(hotspot, vmops__begin, op->name(), strlen(op->name()), 373 op->evaluation_mode()); 374#else /* USDT2 */ 375 HOTSPOT_VMOPS_BEGIN( 376 (char *) op->name(), strlen(op->name()), 377 op->evaluation_mode()); 378#endif /* USDT2 */ 379 op->evaluate(); 380#ifndef USDT2 381 HS_DTRACE_PROBE3(hotspot, vmops__end, op->name(), strlen(op->name()), 382 op->evaluation_mode()); 383#else /* USDT2 */ 384 HOTSPOT_VMOPS_END( 385 (char *) op->name(), strlen(op->name()), 386 op->evaluation_mode()); 387#endif /* USDT2 */ 388 } 389 390 // Last access of info in _cur_vm_operation! 391 bool c_heap_allocated = op->is_cheap_allocated(); 392 393 // Mark as completed 394 if (!op->evaluate_concurrently()) { 395 op->calling_thread()->increment_vm_operation_completed_count(); 396 } 397 // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call, 398 // since if it is stack allocated the calling thread might have deallocated 399 if (c_heap_allocated) { 400 delete _cur_vm_operation; 401 } 402} 403 404 405void VMThread::loop() { 406 assert(_cur_vm_operation == NULL, "no current one should be executing"); 407 408 while(true) { 409 VM_Operation* safepoint_ops = NULL; 410 // 411 // Wait for VM operation 412 // 413 // use no_safepoint_check to get lock without attempting to "sneak" 414 { MutexLockerEx mu_queue(VMOperationQueue_lock, 415 Mutex::_no_safepoint_check_flag); 416 417 // Look for new operation 418 assert(_cur_vm_operation == NULL, "no current one should be executing"); 419 _cur_vm_operation = _vm_queue->remove_next(); 420 421 // Stall time tracking code 422 if (PrintVMQWaitTime && _cur_vm_operation != NULL && 423 !_cur_vm_operation->evaluate_concurrently()) { 424 long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp(); 425 if (stall > 0) 426 tty->print_cr("%s stall: %Ld", _cur_vm_operation->name(), stall); 427 } 428 429 while (!should_terminate() && _cur_vm_operation == NULL) { 430 // wait with a timeout to guarantee safepoints at regular intervals 431 bool timedout = 432 VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag, 433 GuaranteedSafepointInterval); 434 435 // Support for self destruction 436 if ((SelfDestructTimer != 0) && !is_error_reported() && 437 (os::elapsedTime() > SelfDestructTimer * 60)) { 438 tty->print_cr("VM self-destructed"); 439 exit(-1); 440 } 441 442 if (timedout && (SafepointALot || 443 SafepointSynchronize::is_cleanup_needed())) { 444 MutexUnlockerEx mul(VMOperationQueue_lock, 445 Mutex::_no_safepoint_check_flag); 446 // Force a safepoint since we have not had one for at least 447 // 'GuaranteedSafepointInterval' milliseconds. This will run all 448 // the clean-up processing that needs to be done regularly at a 449 // safepoint 450 SafepointSynchronize::begin(); 451 #ifdef ASSERT 452 if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot(); 453 #endif 454 SafepointSynchronize::end(); 455 } 456 _cur_vm_operation = _vm_queue->remove_next(); 457 458 // If we are at a safepoint we will evaluate all the operations that 459 // follow that also require a safepoint 460 if (_cur_vm_operation != NULL && 461 _cur_vm_operation->evaluate_at_safepoint()) { 462 safepoint_ops = _vm_queue->drain_at_safepoint_priority(); 463 } 464 } 465 466 if (should_terminate()) break; 467 } // Release mu_queue_lock 468 469 // 470 // Execute VM operation 471 // 472 { HandleMark hm(VMThread::vm_thread()); 473 474 EventMark em("Executing VM operation: %s", vm_operation()->name()); 475 assert(_cur_vm_operation != NULL, "we should have found an operation to execute"); 476 477 // Give the VM thread an extra quantum. Jobs tend to be bursty and this 478 // helps the VM thread to finish up the job. 479 // FIXME: When this is enabled and there are many threads, this can degrade 480 // performance significantly. 481 if( VMThreadHintNoPreempt ) 482 os::hint_no_preempt(); 483 484 // If we are at a safepoint we will evaluate all the operations that 485 // follow that also require a safepoint 486 if (_cur_vm_operation->evaluate_at_safepoint()) { 487 488 _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned 489 490 SafepointSynchronize::begin(); 491 evaluate_operation(_cur_vm_operation); 492 // now process all queued safepoint ops, iteratively draining 493 // the queue until there are none left 494 do { 495 _cur_vm_operation = safepoint_ops; 496 if (_cur_vm_operation != NULL) { 497 do { 498 // evaluate_operation deletes the op object so we have 499 // to grab the next op now 500 VM_Operation* next = _cur_vm_operation->next(); 501 _vm_queue->set_drain_list(next); 502 evaluate_operation(_cur_vm_operation); 503 _cur_vm_operation = next; 504 if (PrintSafepointStatistics) { 505 SafepointSynchronize::inc_vmop_coalesced_count(); 506 } 507 } while (_cur_vm_operation != NULL); 508 } 509 // There is a chance that a thread enqueued a safepoint op 510 // since we released the op-queue lock and initiated the safepoint. 511 // So we drain the queue again if there is anything there, as an 512 // optimization to try and reduce the number of safepoints. 513 // As the safepoint synchronizes us with JavaThreads we will see 514 // any enqueue made by a JavaThread, but the peek will not 515 // necessarily detect a concurrent enqueue by a GC thread, but 516 // that simply means the op will wait for the next major cycle of the 517 // VMThread - just as it would if the GC thread lost the race for 518 // the lock. 519 if (_vm_queue->peek_at_safepoint_priority()) { 520 // must hold lock while draining queue 521 MutexLockerEx mu_queue(VMOperationQueue_lock, 522 Mutex::_no_safepoint_check_flag); 523 safepoint_ops = _vm_queue->drain_at_safepoint_priority(); 524 } else { 525 safepoint_ops = NULL; 526 } 527 } while(safepoint_ops != NULL); 528 529 _vm_queue->set_drain_list(NULL); 530 531 // Complete safepoint synchronization 532 SafepointSynchronize::end(); 533 534 } else { // not a safepoint operation 535 if (TraceLongCompiles) { 536 elapsedTimer t; 537 t.start(); 538 evaluate_operation(_cur_vm_operation); 539 t.stop(); 540 double secs = t.seconds(); 541 if (secs * 1e3 > LongCompileThreshold) { 542 // XXX - _cur_vm_operation should not be accessed after 543 // the completed count has been incremented; the waiting 544 // thread may have already freed this memory. 545 tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs); 546 } 547 } else { 548 evaluate_operation(_cur_vm_operation); 549 } 550 551 _cur_vm_operation = NULL; 552 } 553 } 554 555 // 556 // Notify (potential) waiting Java thread(s) - lock without safepoint 557 // check so that sneaking is not possible 558 { MutexLockerEx mu(VMOperationRequest_lock, 559 Mutex::_no_safepoint_check_flag); 560 VMOperationRequest_lock->notify_all(); 561 } 562 563 // 564 // We want to make sure that we get to a safepoint regularly. 565 // 566 if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) { 567 long interval = SafepointSynchronize::last_non_safepoint_interval(); 568 bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval); 569 if (SafepointALot || max_time_exceeded) { 570 HandleMark hm(VMThread::vm_thread()); 571 SafepointSynchronize::begin(); 572 SafepointSynchronize::end(); 573 } 574 } 575 } 576} 577 578void VMThread::execute(VM_Operation* op) { 579 Thread* t = Thread::current(); 580 581 if (!t->is_VM_thread()) { 582 SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot 583 // JavaThread or WatcherThread 584 t->check_for_valid_safepoint_state(true); 585 586 // New request from Java thread, evaluate prologue 587 if (!op->doit_prologue()) { 588 return; // op was cancelled 589 } 590 591 // Setup VM_operations for execution 592 op->set_calling_thread(t, Thread::get_priority(t)); 593 594 // It does not make sense to execute the epilogue, if the VM operation object is getting 595 // deallocated by the VM thread. 596 bool concurrent = op->evaluate_concurrently(); 597 bool execute_epilog = !op->is_cheap_allocated(); 598 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated"); 599 600 // Get ticket number for non-concurrent VM operations 601 int ticket = 0; 602 if (!concurrent) { 603 ticket = t->vm_operation_ticket(); 604 } 605 606 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the 607 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests 608 // to be queued up during a safepoint synchronization. 609 { 610 VMOperationQueue_lock->lock_without_safepoint_check(); 611 bool ok = _vm_queue->add(op); 612 op->set_timestamp(os::javaTimeMillis()); 613 VMOperationQueue_lock->notify(); 614 VMOperationQueue_lock->unlock(); 615 // VM_Operation got skipped 616 if (!ok) { 617 assert(concurrent, "can only skip concurrent tasks"); 618 if (op->is_cheap_allocated()) delete op; 619 return; 620 } 621 } 622 623 if (!concurrent) { 624 // Wait for completion of request (non-concurrent) 625 // Note: only a JavaThread triggers the safepoint check when locking 626 MutexLocker mu(VMOperationRequest_lock); 627 while(t->vm_operation_completed_count() < ticket) { 628 VMOperationRequest_lock->wait(!t->is_Java_thread()); 629 } 630 } 631 632 if (execute_epilog) { 633 op->doit_epilogue(); 634 } 635 } else { 636 // invoked by VM thread; usually nested VM operation 637 assert(t->is_VM_thread(), "must be a VM thread"); 638 VM_Operation* prev_vm_operation = vm_operation(); 639 if (prev_vm_operation != NULL) { 640 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler 641 // does not allow nested scavenges or compiles. 642 if (!prev_vm_operation->allow_nested_vm_operations()) { 643 fatal(err_msg("Nested VM operation %s requested by operation %s", 644 op->name(), vm_operation()->name())); 645 } 646 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority()); 647 } 648 649 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name()); 650 651 // Release all internal handles after operation is evaluated 652 HandleMark hm(t); 653 _cur_vm_operation = op; 654 655 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) { 656 SafepointSynchronize::begin(); 657 op->evaluate(); 658 SafepointSynchronize::end(); 659 } else { 660 op->evaluate(); 661 } 662 663 // Free memory if needed 664 if (op->is_cheap_allocated()) delete op; 665 666 _cur_vm_operation = prev_vm_operation; 667 } 668} 669 670 671void VMThread::oops_do(OopClosure* f, CodeBlobClosure* cf) { 672 Thread::oops_do(f, cf); 673 _vm_queue->oops_do(f); 674} 675 676//------------------------------------------------------------------------------------------------------------------ 677#ifndef PRODUCT 678 679void VMOperationQueue::verify_queue(int prio) { 680 // Check that list is correctly linked 681 int length = _queue_length[prio]; 682 VM_Operation *cur = _queue[prio]; 683 int i; 684 685 // Check forward links 686 for(i = 0; i < length; i++) { 687 cur = cur->next(); 688 assert(cur != _queue[prio], "list to short (forward)"); 689 } 690 assert(cur->next() == _queue[prio], "list to long (forward)"); 691 692 // Check backwards links 693 cur = _queue[prio]; 694 for(i = 0; i < length; i++) { 695 cur = cur->prev(); 696 assert(cur != _queue[prio], "list to short (backwards)"); 697 } 698 assert(cur->prev() == _queue[prio], "list to long (backwards)"); 699} 700 701#endif 702 703void VMThread::verify() { 704 oops_do(&VerifyOopClosure::verify_oop, NULL); 705} 706