1 /*
2 * Copyright (c) 1998, 2016, 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/safepoint.hpp"
36 #include "runtime/thread.inline.hpp"
37 #include "runtime/vmThread.hpp"
38 #include "runtime/vm_operations.hpp"
39 #include "services/runtimeService.hpp"
40 #include "trace/tracing.hpp"
41 #include "utilities/dtrace.hpp"
42 #include "utilities/events.hpp"
43 #include "utilities/xmlstream.hpp"
44
45 // Dummy VM operation to act as first element in our circular double-linked list
46 class VM_Dummy: public VM_Operation {
47 VMOp_Type type() const { return VMOp_Dummy; }
48 void doit() {};
49 };
50
51 VMOperationQueue::VMOperationQueue() {
52 // The queue is a circular doubled-linked list, which always contains
53 // one element (i.e., one element means empty).
54 for(int i = 0; i < nof_priorities; i++) {
55 _queue_length[i] = 0;
56 _queue_counter = 0;
57 _queue[i] = new VM_Dummy();
58 _queue[i]->set_next(_queue[i]);
59 _queue[i]->set_prev(_queue[i]);
60 }
61 _drain_list = NULL;
62 }
63
64
65 bool VMOperationQueue::queue_empty(int prio) {
66 // It is empty if there is exactly one element
67 bool empty = (_queue[prio] == _queue[prio]->next());
68 assert( (_queue_length[prio] == 0 && empty) ||
69 (_queue_length[prio] > 0 && !empty), "sanity check");
70 return _queue_length[prio] == 0;
71 }
72
73 // Inserts an element to the right of the q element
74 void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) {
75 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
76 n->set_prev(q);
77 n->set_next(q->next());
78 q->next()->set_prev(n);
79 q->set_next(n);
80 }
81
82 void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) {
83 _queue_length[prio]++;
84 insert(_queue[prio]->next(), op);
85 }
86
87 void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) {
88 _queue_length[prio]++;
89 insert(_queue[prio]->prev(), op);
90 }
91
92
93 void VMOperationQueue::unlink(VM_Operation* q) {
94 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
95 q->prev()->set_next(q->next());
96 q->next()->set_prev(q->prev());
97 }
98
99 VM_Operation* VMOperationQueue::queue_remove_front(int prio) {
100 if (queue_empty(prio)) return NULL;
101 assert(_queue_length[prio] >= 0, "sanity check");
102 _queue_length[prio]--;
103 VM_Operation* r = _queue[prio]->next();
104 assert(r != _queue[prio], "cannot remove base element");
105 unlink(r);
106 return r;
107 }
108
109 VM_Operation* VMOperationQueue::queue_drain(int prio) {
110 if (queue_empty(prio)) return NULL;
111 DEBUG_ONLY(int length = _queue_length[prio];);
112 assert(length >= 0, "sanity check");
113 _queue_length[prio] = 0;
114 VM_Operation* r = _queue[prio]->next();
115 assert(r != _queue[prio], "cannot remove base element");
116 // remove links to base element from head and tail
117 r->set_prev(NULL);
118 _queue[prio]->prev()->set_next(NULL);
119 // restore queue to empty state
120 _queue[prio]->set_next(_queue[prio]);
121 _queue[prio]->set_prev(_queue[prio]);
122 assert(queue_empty(prio), "drain corrupted queue");
123 #ifdef ASSERT
124 int len = 0;
125 VM_Operation* cur;
126 for(cur = r; cur != NULL; cur=cur->next()) len++;
127 assert(len == length, "drain lost some ops");
128 #endif
129 return r;
130 }
131
132 void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) {
133 VM_Operation* cur = _queue[queue];
134 cur = cur->next();
135 while (cur != _queue[queue]) {
136 cur->oops_do(f);
137 cur = cur->next();
138 }
139 }
140
141 void VMOperationQueue::drain_list_oops_do(OopClosure* f) {
142 VM_Operation* cur = _drain_list;
143 while (cur != NULL) {
144 cur->oops_do(f);
145 cur = cur->next();
146 }
147 }
148
149 //-----------------------------------------------------------------
150 // High-level interface
151 bool VMOperationQueue::add(VM_Operation *op) {
152
153 HOTSPOT_VMOPS_REQUEST(
154 (char *) op->name(), strlen(op->name()),
155 op->evaluation_mode());
156
157 // Encapsulates VM queue policy. Currently, that
158 // only involves putting them on the right list
159 if (op->evaluate_at_safepoint()) {
160 queue_add_back(SafepointPriority, op);
161 return true;
162 }
163
164 queue_add_back(MediumPriority, op);
165 return true;
166 }
167
168 VM_Operation* VMOperationQueue::remove_next() {
169 // Assuming VMOperation queue is two-level priority queue. If there are
170 // more than two priorities, we need a different scheduling algorithm.
171 assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2,
172 "current algorithm does not work");
173
174 // simple counter based scheduling to prevent starvation of lower priority
175 // queue. -- see 4390175
176 int high_prio, low_prio;
177 if (_queue_counter++ < 10) {
178 high_prio = SafepointPriority;
179 low_prio = MediumPriority;
180 } else {
181 _queue_counter = 0;
182 high_prio = MediumPriority;
183 low_prio = SafepointPriority;
184 }
185
186 return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio);
187 }
188
189 void VMOperationQueue::oops_do(OopClosure* f) {
190 for(int i = 0; i < nof_priorities; i++) {
191 queue_oops_do(i, f);
192 }
193 drain_list_oops_do(f);
194 }
195
196
197 //------------------------------------------------------------------------------------------------------------------
198 // Implementation of VMThread stuff
199
200 bool VMThread::_should_terminate = false;
201 bool VMThread::_terminated = false;
202 Monitor* VMThread::_terminate_lock = NULL;
203 VMThread* VMThread::_vm_thread = NULL;
204 VM_Operation* VMThread::_cur_vm_operation = NULL;
205 VMOperationQueue* VMThread::_vm_queue = NULL;
206 PerfCounter* VMThread::_perf_accumulated_vm_operation_time = NULL;
207
208
209 void VMThread::create() {
210 assert(vm_thread() == NULL, "we can only allocate one VMThread");
211 _vm_thread = new VMThread();
212
213 // Create VM operation queue
214 _vm_queue = new VMOperationQueue();
215 guarantee(_vm_queue != NULL, "just checking");
216
217 _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true,
218 Monitor::_safepoint_check_never);
219
220 if (UsePerfData) {
221 // jvmstat performance counters
222 Thread* THREAD = Thread::current();
223 _perf_accumulated_vm_operation_time =
224 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime",
225 PerfData::U_Ticks, CHECK);
226 }
227 }
228
229 VMThread::VMThread() : NamedThread() {
230 set_name("VM Thread");
231 }
232
233 void VMThread::destroy() {
234 _vm_thread = NULL; // VM thread is gone
235 }
236
237 void VMThread::run() {
238 assert(this == vm_thread(), "check");
239
240 this->initialize_named_thread();
241 this->record_stack_base_and_size();
242 // Notify_lock wait checks on active_handles() to rewait in
243 // case of spurious wakeup, it should wait on the last
244 // value set prior to the notify
245 this->set_active_handles(JNIHandleBlock::allocate_block());
246
247 {
248 MutexLocker ml(Notify_lock);
249 Notify_lock->notify();
250 }
251 // Notify_lock is destroyed by Threads::create_vm()
252
253 int prio = (VMThreadPriority == -1)
254 ? os::java_to_os_priority[NearMaxPriority]
255 : VMThreadPriority;
256 // Note that I cannot call os::set_priority because it expects Java
257 // priorities and I am *explicitly* using OS priorities so that it's
258 // possible to set the VM thread priority higher than any Java thread.
259 os::set_native_priority( this, prio );
260
261 // Wait for VM_Operations until termination
262 this->loop();
263
264 // Note the intention to exit before safepointing.
265 // 6295565 This has the effect of waiting for any large tty
266 // outputs to finish.
267 if (xtty != NULL) {
268 ttyLocker ttyl;
269 xtty->begin_elem("destroy_vm");
270 xtty->stamp();
271 xtty->end_elem();
272 assert(should_terminate(), "termination flag must be set");
273 }
274
275 // 4526887 let VM thread exit at Safepoint
276 SafepointSynchronize::begin();
277
278 if (VerifyBeforeExit) {
279 HandleMark hm(VMThread::vm_thread());
280 // Among other things, this ensures that Eden top is correct.
281 Universe::heap()->prepare_for_verify();
282 os::check_heap();
283 // Silent verification so as not to pollute normal output,
284 // unless we really asked for it.
285 Universe::verify();
286 }
287
288 CompileBroker::set_should_block();
289
290 // wait for threads (compiler threads or daemon threads) in the
291 // _thread_in_native state to block.
292 VM_Exit::wait_for_threads_in_native_to_block();
293
294 // signal other threads that VM process is gone
295 {
296 // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows
297 // VM thread to enter any lock at Safepoint as long as its _owner is NULL.
298 // If that happens after _terminate_lock->wait() has unset _owner
299 // but before it actually drops the lock and waits, the notification below
300 // may get lost and we will have a hang. To avoid this, we need to use
301 // Mutex::lock_without_safepoint_check().
302 MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
303 _terminated = true;
304 _terminate_lock->notify();
305 }
306
307 // We are now racing with the VM termination being carried out in
308 // another thread, so we don't "delete this". Numerous threads don't
309 // get deleted when the VM terminates
310
311 }
312
313
314 // Notify the VMThread that the last non-daemon JavaThread has terminated,
315 // and wait until operation is performed.
316 void VMThread::wait_for_vm_thread_exit() {
317 { MutexLocker mu(VMOperationQueue_lock);
318 _should_terminate = true;
319 VMOperationQueue_lock->notify();
320 }
321
322 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint
323 // because this thread has been removed from the threads list. But anything
324 // that could get blocked by Safepoint should not be used after this point,
325 // otherwise we will hang, since there is no one can end the safepoint.
326
327 // Wait until VM thread is terminated
328 // Note: it should be OK to use Terminator_lock here. But this is called
329 // at a very delicate time (VM shutdown) and we are operating in non- VM
330 // thread at Safepoint. It's safer to not share lock with other threads.
331 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
332 while(!VMThread::is_terminated()) {
333 _terminate_lock->wait(Mutex::_no_safepoint_check_flag);
334 }
335 }
336 }
337
338 void VMThread::evaluate_operation(VM_Operation* op) {
339 ResourceMark rm;
340
341 {
342 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time());
343 HOTSPOT_VMOPS_BEGIN(
344 (char *) op->name(), strlen(op->name()),
345 op->evaluation_mode());
346
347 EventExecuteVMOperation event;
348
349 op->evaluate();
350
351 if (event.should_commit()) {
352 const bool is_concurrent = op->evaluate_concurrently();
353 const bool evaluate_at_safepoint = op->evaluate_at_safepoint();
354 event.set_operation(op->type());
355 event.set_safepoint(evaluate_at_safepoint);
356 event.set_blocking(!is_concurrent);
357 // Only write caller thread information for non-concurrent vm operations.
358 // For concurrent vm operations, the thread id is set to 0 indicating thread is unknown.
359 // This is because the caller thread could have exited already.
360 event.set_caller(is_concurrent ? 0 : THREAD_TRACE_ID(op->calling_thread()));
361 event.set_safepointId(evaluate_at_safepoint ? SafepointSynchronize::safepoint_counter() : 0);
362 event.commit();
363 }
364
365 HOTSPOT_VMOPS_END(
366 (char *) op->name(), strlen(op->name()),
367 op->evaluation_mode());
368 }
369
370 // Last access of info in _cur_vm_operation!
371 bool c_heap_allocated = op->is_cheap_allocated();
372
373 // Mark as completed
374 if (!op->evaluate_concurrently()) {
375 op->calling_thread()->increment_vm_operation_completed_count();
376 }
377 // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call,
378 // since if it is stack allocated the calling thread might have deallocated
379 if (c_heap_allocated) {
380 delete _cur_vm_operation;
381 }
382 }
383
384
385 void VMThread::loop() {
386 assert(_cur_vm_operation == NULL, "no current one should be executing");
387
388 while(true) {
389 VM_Operation* safepoint_ops = NULL;
390 //
391 // Wait for VM operation
392 //
393 // use no_safepoint_check to get lock without attempting to "sneak"
394 { MutexLockerEx mu_queue(VMOperationQueue_lock,
395 Mutex::_no_safepoint_check_flag);
396
397 // Look for new operation
398 assert(_cur_vm_operation == NULL, "no current one should be executing");
399 _cur_vm_operation = _vm_queue->remove_next();
400
401 // Stall time tracking code
402 if (PrintVMQWaitTime && _cur_vm_operation != NULL &&
403 !_cur_vm_operation->evaluate_concurrently()) {
404 long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp();
405 if (stall > 0)
406 tty->print_cr("%s stall: %ld", _cur_vm_operation->name(), stall);
407 }
408
409 while (!should_terminate() && _cur_vm_operation == NULL) {
410 // wait with a timeout to guarantee safepoints at regular intervals
411 bool timedout =
412 VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag,
413 GuaranteedSafepointInterval);
414
415 // Support for self destruction
416 if ((SelfDestructTimer != 0) && !is_error_reported() &&
417 (os::elapsedTime() > (double)SelfDestructTimer * 60.0)) {
418 tty->print_cr("VM self-destructed");
419 exit(-1);
420 }
421
422 if (timedout && (SafepointALot ||
423 SafepointSynchronize::is_cleanup_needed())) {
424 MutexUnlockerEx mul(VMOperationQueue_lock,
425 Mutex::_no_safepoint_check_flag);
426 // Force a safepoint since we have not had one for at least
427 // 'GuaranteedSafepointInterval' milliseconds. This will run all
428 // the clean-up processing that needs to be done regularly at a
429 // safepoint
430 SafepointSynchronize::begin();
431 #ifdef ASSERT
432 if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot();
433 #endif
434 SafepointSynchronize::end();
435 }
436 _cur_vm_operation = _vm_queue->remove_next();
437
438 // If we are at a safepoint we will evaluate all the operations that
439 // follow that also require a safepoint
440 if (_cur_vm_operation != NULL &&
441 _cur_vm_operation->evaluate_at_safepoint()) {
442 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
443 }
444 }
445
446 if (should_terminate()) break;
447 } // Release mu_queue_lock
448
449 //
450 // Execute VM operation
451 //
452 { HandleMark hm(VMThread::vm_thread());
453
454 EventMark em("Executing VM operation: %s", vm_operation()->name());
455 assert(_cur_vm_operation != NULL, "we should have found an operation to execute");
456
457 // Give the VM thread an extra quantum. Jobs tend to be bursty and this
458 // helps the VM thread to finish up the job.
459 // FIXME: When this is enabled and there are many threads, this can degrade
460 // performance significantly.
461 if( VMThreadHintNoPreempt )
462 os::hint_no_preempt();
463
464 // If we are at a safepoint we will evaluate all the operations that
465 // follow that also require a safepoint
466 if (_cur_vm_operation->evaluate_at_safepoint()) {
467
468 _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned
469
470 SafepointSynchronize::begin();
471 evaluate_operation(_cur_vm_operation);
472 // now process all queued safepoint ops, iteratively draining
473 // the queue until there are none left
474 do {
475 _cur_vm_operation = safepoint_ops;
476 if (_cur_vm_operation != NULL) {
477 do {
478 // evaluate_operation deletes the op object so we have
479 // to grab the next op now
480 VM_Operation* next = _cur_vm_operation->next();
481 _vm_queue->set_drain_list(next);
482 evaluate_operation(_cur_vm_operation);
483 _cur_vm_operation = next;
484 if (PrintSafepointStatistics) {
485 SafepointSynchronize::inc_vmop_coalesced_count();
486 }
487 } while (_cur_vm_operation != NULL);
488 }
489 // There is a chance that a thread enqueued a safepoint op
490 // since we released the op-queue lock and initiated the safepoint.
491 // So we drain the queue again if there is anything there, as an
492 // optimization to try and reduce the number of safepoints.
493 // As the safepoint synchronizes us with JavaThreads we will see
494 // any enqueue made by a JavaThread, but the peek will not
495 // necessarily detect a concurrent enqueue by a GC thread, but
496 // that simply means the op will wait for the next major cycle of the
497 // VMThread - just as it would if the GC thread lost the race for
498 // the lock.
499 if (_vm_queue->peek_at_safepoint_priority()) {
500 // must hold lock while draining queue
501 MutexLockerEx mu_queue(VMOperationQueue_lock,
502 Mutex::_no_safepoint_check_flag);
503 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
504 } else {
505 safepoint_ops = NULL;
506 }
507 } while(safepoint_ops != NULL);
508
509 _vm_queue->set_drain_list(NULL);
510
511 // Complete safepoint synchronization
512 SafepointSynchronize::end();
513
514 } else { // not a safepoint operation
515 if (TraceLongCompiles) {
516 elapsedTimer t;
517 t.start();
518 evaluate_operation(_cur_vm_operation);
519 t.stop();
520 double secs = t.seconds();
521 if (secs * 1e3 > LongCompileThreshold) {
522 // XXX - _cur_vm_operation should not be accessed after
523 // the completed count has been incremented; the waiting
524 // thread may have already freed this memory.
525 tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs);
526 }
527 } else {
528 evaluate_operation(_cur_vm_operation);
529 }
530
531 _cur_vm_operation = NULL;
532 }
533 }
534
535 //
536 // Notify (potential) waiting Java thread(s) - lock without safepoint
537 // check so that sneaking is not possible
538 { MutexLockerEx mu(VMOperationRequest_lock,
539 Mutex::_no_safepoint_check_flag);
540 VMOperationRequest_lock->notify_all();
541 }
542
543 //
544 // We want to make sure that we get to a safepoint regularly.
545 //
546 if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) {
547 long interval = SafepointSynchronize::last_non_safepoint_interval();
548 bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval);
549 if (SafepointALot || max_time_exceeded) {
550 HandleMark hm(VMThread::vm_thread());
551 SafepointSynchronize::begin();
552 SafepointSynchronize::end();
553 }
554 }
555 }
556 }
557
558 void VMThread::execute(VM_Operation* op) {
559 Thread* t = Thread::current();
560
561 if (!t->is_VM_thread()) {
562 SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot
563 // JavaThread or WatcherThread
564 bool concurrent = op->evaluate_concurrently();
565 // only blocking VM operations need to verify the caller's safepoint state:
566 if (!concurrent) {
567 t->check_for_valid_safepoint_state(true);
568 }
569
570 // New request from Java thread, evaluate prologue
571 if (!op->doit_prologue()) {
572 return; // op was cancelled
573 }
574
575 // Setup VM_operations for execution
576 op->set_calling_thread(t, Thread::get_priority(t));
577
578 // It does not make sense to execute the epilogue, if the VM operation object is getting
579 // deallocated by the VM thread.
580 bool execute_epilog = !op->is_cheap_allocated();
581 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated");
582
583 // Get ticket number for non-concurrent VM operations
584 int ticket = 0;
585 if (!concurrent) {
586 ticket = t->vm_operation_ticket();
587 }
588
589 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the
590 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests
591 // to be queued up during a safepoint synchronization.
592 {
593 VMOperationQueue_lock->lock_without_safepoint_check();
594 bool ok = _vm_queue->add(op);
595 op->set_timestamp(os::javaTimeMillis());
596 VMOperationQueue_lock->notify();
597 VMOperationQueue_lock->unlock();
598 // VM_Operation got skipped
599 if (!ok) {
600 assert(concurrent, "can only skip concurrent tasks");
601 if (op->is_cheap_allocated()) delete op;
602 return;
603 }
604 }
605
606 if (!concurrent) {
607 // Wait for completion of request (non-concurrent)
608 // Note: only a JavaThread triggers the safepoint check when locking
609 MutexLocker mu(VMOperationRequest_lock);
610 while(t->vm_operation_completed_count() < ticket) {
611 VMOperationRequest_lock->wait(!t->is_Java_thread());
612 }
613 }
614
615 if (execute_epilog) {
616 op->doit_epilogue();
617 }
618 } else {
619 // invoked by VM thread; usually nested VM operation
620 assert(t->is_VM_thread(), "must be a VM thread");
621 VM_Operation* prev_vm_operation = vm_operation();
622 if (prev_vm_operation != NULL) {
623 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler
624 // does not allow nested scavenges or compiles.
625 if (!prev_vm_operation->allow_nested_vm_operations()) {
626 fatal("Nested VM operation %s requested by operation %s",
627 op->name(), vm_operation()->name());
628 }
629 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority());
630 }
631
632 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name());
633
634 // Release all internal handles after operation is evaluated
635 HandleMark hm(t);
636 _cur_vm_operation = op;
637
638 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) {
639 SafepointSynchronize::begin();
640 op->evaluate();
641 SafepointSynchronize::end();
642 } else {
643 op->evaluate();
644 }
645
646 // Free memory if needed
647 if (op->is_cheap_allocated()) delete op;
648
649 _cur_vm_operation = prev_vm_operation;
650 }
651 }
652
653
654 void VMThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
655 Thread::oops_do(f, cf);
656 _vm_queue->oops_do(f);
657 }
658
659 //------------------------------------------------------------------------------------------------------------------
660 #ifndef PRODUCT
661
662 void VMOperationQueue::verify_queue(int prio) {
663 // Check that list is correctly linked
664 int length = _queue_length[prio];
665 VM_Operation *cur = _queue[prio];
666 int i;
667
668 // Check forward links
669 for(i = 0; i < length; i++) {
670 cur = cur->next();
671 assert(cur != _queue[prio], "list to short (forward)");
672 }
673 assert(cur->next() == _queue[prio], "list to long (forward)");
674
675 // Check backwards links
676 cur = _queue[prio];
677 for(i = 0; i < length; i++) {
678 cur = cur->prev();
679 assert(cur != _queue[prio], "list to short (backwards)");
680 }
681 assert(cur->prev() == _queue[prio], "list to long (backwards)");
682 }
683
684 #endif
685
686 void VMThread::verify() {
687 oops_do(&VerifyOopClosure::verify_oop, NULL);
688 }