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
230 VMThread::VMThread() : NamedThread() {
231 set_name("VM Thread");
232 }
233
234 void VMThread::destroy() {
235 if (_vm_thread != NULL) {
236 delete _vm_thread;
237 _vm_thread = NULL; // VM thread is gone
238 }
239 }
240
241 void VMThread::run() {
242 assert(this == vm_thread(), "check");
243
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();
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 // Deletion must be done synchronously by the JNI DestroyJavaVM thread
312 // so that the VMThread deletion completes before the main thread frees
313 // up the CodeHeap.
314
315 }
316
317
318 // Notify the VMThread that the last non-daemon JavaThread has terminated,
319 // and wait until operation is performed.
320 void VMThread::wait_for_vm_thread_exit() {
321 { MutexLocker mu(VMOperationQueue_lock);
322 _should_terminate = true;
323 VMOperationQueue_lock->notify();
324 }
325
326 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint
327 // because this thread has been removed from the threads list. But anything
328 // that could get blocked by Safepoint should not be used after this point,
329 // otherwise we will hang, since there is no one can end the safepoint.
330
331 // Wait until VM thread is terminated
332 // Note: it should be OK to use Terminator_lock here. But this is called
333 // at a very delicate time (VM shutdown) and we are operating in non- VM
334 // thread at Safepoint. It's safer to not share lock with other threads.
335 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
336 while(!VMThread::is_terminated()) {
337 _terminate_lock->wait(Mutex::_no_safepoint_check_flag);
338 }
339 }
340 }
341
342 void VMThread::evaluate_operation(VM_Operation* op) {
343 ResourceMark rm;
344
345 {
346 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time());
347 HOTSPOT_VMOPS_BEGIN(
348 (char *) op->name(), strlen(op->name()),
349 op->evaluation_mode());
350
351 EventExecuteVMOperation event;
352
353 op->evaluate();
354
355 if (event.should_commit()) {
356 const bool is_concurrent = op->evaluate_concurrently();
357 const bool evaluate_at_safepoint = op->evaluate_at_safepoint();
358 event.set_operation(op->type());
359 event.set_safepoint(evaluate_at_safepoint);
360 event.set_blocking(!is_concurrent);
361 // Only write caller thread information for non-concurrent vm operations.
362 // For concurrent vm operations, the thread id is set to 0 indicating thread is unknown.
363 // This is because the caller thread could have exited already.
364 event.set_caller(is_concurrent ? 0 : THREAD_TRACE_ID(op->calling_thread()));
365 event.set_safepointId(evaluate_at_safepoint ? SafepointSynchronize::safepoint_counter() : 0);
366 event.commit();
367 }
368
369 HOTSPOT_VMOPS_END(
370 (char *) op->name(), strlen(op->name()),
371 op->evaluation_mode());
372 }
373
374 // Last access of info in _cur_vm_operation!
375 bool c_heap_allocated = op->is_cheap_allocated();
376
377 // Mark as completed
378 if (!op->evaluate_concurrently()) {
379 op->calling_thread()->increment_vm_operation_completed_count();
380 }
381 // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call,
382 // since if it is stack allocated the calling thread might have deallocated
383 if (c_heap_allocated) {
384 delete _cur_vm_operation;
385 }
386 }
387
388
389 void VMThread::loop() {
390 assert(_cur_vm_operation == NULL, "no current one should be executing");
391
392 while(true) {
393 VM_Operation* safepoint_ops = NULL;
394 //
395 // Wait for VM operation
396 //
397 // use no_safepoint_check to get lock without attempting to "sneak"
398 { MutexLockerEx mu_queue(VMOperationQueue_lock,
399 Mutex::_no_safepoint_check_flag);
400
401 // Look for new operation
402 assert(_cur_vm_operation == NULL, "no current one should be executing");
403 _cur_vm_operation = _vm_queue->remove_next();
404
405 // Stall time tracking code
406 if (PrintVMQWaitTime && _cur_vm_operation != NULL &&
407 !_cur_vm_operation->evaluate_concurrently()) {
408 long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp();
409 if (stall > 0)
410 tty->print_cr("%s stall: %ld", _cur_vm_operation->name(), stall);
411 }
412
413 while (!should_terminate() && _cur_vm_operation == NULL) {
414 // wait with a timeout to guarantee safepoints at regular intervals
415 bool timedout =
416 VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag,
417 GuaranteedSafepointInterval);
418
419 // Support for self destruction
420 if ((SelfDestructTimer != 0) && !is_error_reported() &&
421 (os::elapsedTime() > (double)SelfDestructTimer * 60.0)) {
422 tty->print_cr("VM self-destructed");
423 exit(-1);
424 }
425
426 if (timedout && (SafepointALot ||
427 SafepointSynchronize::is_cleanup_needed())) {
428 MutexUnlockerEx mul(VMOperationQueue_lock,
429 Mutex::_no_safepoint_check_flag);
430 // Force a safepoint since we have not had one for at least
431 // 'GuaranteedSafepointInterval' milliseconds. This will run all
432 // the clean-up processing that needs to be done regularly at a
433 // safepoint
434 SafepointSynchronize::begin();
435 #ifdef ASSERT
436 if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot();
437 #endif
438 SafepointSynchronize::end();
439 }
440 _cur_vm_operation = _vm_queue->remove_next();
441
442 // If we are at a safepoint we will evaluate all the operations that
443 // follow that also require a safepoint
444 if (_cur_vm_operation != NULL &&
445 _cur_vm_operation->evaluate_at_safepoint()) {
446 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
447 }
448 }
449
450 if (should_terminate()) break;
451 } // Release mu_queue_lock
452
453 //
454 // Execute VM operation
455 //
456 { HandleMark hm(VMThread::vm_thread());
457
458 EventMark em("Executing VM operation: %s", vm_operation()->name());
459 assert(_cur_vm_operation != NULL, "we should have found an operation to execute");
460
461 // Give the VM thread an extra quantum. Jobs tend to be bursty and this
462 // helps the VM thread to finish up the job.
463 // FIXME: When this is enabled and there are many threads, this can degrade
464 // performance significantly.
465 if( VMThreadHintNoPreempt )
466 os::hint_no_preempt();
467
468 // If we are at a safepoint we will evaluate all the operations that
469 // follow that also require a safepoint
470 if (_cur_vm_operation->evaluate_at_safepoint()) {
471
472 _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned
473
474 SafepointSynchronize::begin();
475 evaluate_operation(_cur_vm_operation);
476 // now process all queued safepoint ops, iteratively draining
477 // the queue until there are none left
478 do {
479 _cur_vm_operation = safepoint_ops;
480 if (_cur_vm_operation != NULL) {
481 do {
482 // evaluate_operation deletes the op object so we have
483 // to grab the next op now
484 VM_Operation* next = _cur_vm_operation->next();
485 _vm_queue->set_drain_list(next);
486 evaluate_operation(_cur_vm_operation);
487 _cur_vm_operation = next;
488 if (PrintSafepointStatistics) {
489 SafepointSynchronize::inc_vmop_coalesced_count();
490 }
491 } while (_cur_vm_operation != NULL);
492 }
493 // There is a chance that a thread enqueued a safepoint op
494 // since we released the op-queue lock and initiated the safepoint.
495 // So we drain the queue again if there is anything there, as an
496 // optimization to try and reduce the number of safepoints.
497 // As the safepoint synchronizes us with JavaThreads we will see
498 // any enqueue made by a JavaThread, but the peek will not
499 // necessarily detect a concurrent enqueue by a GC thread, but
500 // that simply means the op will wait for the next major cycle of the
501 // VMThread - just as it would if the GC thread lost the race for
502 // the lock.
503 if (_vm_queue->peek_at_safepoint_priority()) {
504 // must hold lock while draining queue
505 MutexLockerEx mu_queue(VMOperationQueue_lock,
506 Mutex::_no_safepoint_check_flag);
507 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
508 } else {
509 safepoint_ops = NULL;
510 }
511 } while(safepoint_ops != NULL);
512
513 _vm_queue->set_drain_list(NULL);
514
515 // Complete safepoint synchronization
516 SafepointSynchronize::end();
517
518 } else { // not a safepoint operation
519 if (TraceLongCompiles) {
520 elapsedTimer t;
521 t.start();
522 evaluate_operation(_cur_vm_operation);
523 t.stop();
524 double secs = t.seconds();
525 if (secs * 1e3 > LongCompileThreshold) {
526 // XXX - _cur_vm_operation should not be accessed after
527 // the completed count has been incremented; the waiting
528 // thread may have already freed this memory.
529 tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs);
530 }
531 } else {
532 evaluate_operation(_cur_vm_operation);
533 }
534
535 _cur_vm_operation = NULL;
536 }
537 }
538
539 //
540 // Notify (potential) waiting Java thread(s) - lock without safepoint
541 // check so that sneaking is not possible
542 { MutexLockerEx mu(VMOperationRequest_lock,
543 Mutex::_no_safepoint_check_flag);
544 VMOperationRequest_lock->notify_all();
545 }
546
547 //
548 // We want to make sure that we get to a safepoint regularly.
549 //
550 if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) {
551 long interval = SafepointSynchronize::last_non_safepoint_interval();
552 bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval);
553 if (SafepointALot || max_time_exceeded) {
554 HandleMark hm(VMThread::vm_thread());
555 SafepointSynchronize::begin();
556 SafepointSynchronize::end();
557 }
558 }
559 }
560 }
561
562 void VMThread::execute(VM_Operation* op) {
563 Thread* t = Thread::current();
564
565 if (!t->is_VM_thread()) {
566 SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot
567 // JavaThread or WatcherThread
568 bool concurrent = op->evaluate_concurrently();
569 // only blocking VM operations need to verify the caller's safepoint state:
570 if (!concurrent) {
571 t->check_for_valid_safepoint_state(true);
572 }
573
574 // New request from Java thread, evaluate prologue
575 if (!op->doit_prologue()) {
576 return; // op was cancelled
577 }
578
579 // Setup VM_operations for execution
580 op->set_calling_thread(t, Thread::get_priority(t));
581
582 // It does not make sense to execute the epilogue, if the VM operation object is getting
583 // deallocated by the VM thread.
584 bool execute_epilog = !op->is_cheap_allocated();
585 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated");
586
587 // Get ticket number for non-concurrent VM operations
588 int ticket = 0;
589 if (!concurrent) {
590 ticket = t->vm_operation_ticket();
591 }
592
593 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the
594 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests
595 // to be queued up during a safepoint synchronization.
596 {
597 VMOperationQueue_lock->lock_without_safepoint_check();
598 bool ok = _vm_queue->add(op);
599 op->set_timestamp(os::javaTimeMillis());
600 VMOperationQueue_lock->notify();
601 VMOperationQueue_lock->unlock();
602 // VM_Operation got skipped
603 if (!ok) {
604 assert(concurrent, "can only skip concurrent tasks");
605 if (op->is_cheap_allocated()) delete op;
606 return;
607 }
608 }
609
610 if (!concurrent) {
611 // Wait for completion of request (non-concurrent)
612 // Note: only a JavaThread triggers the safepoint check when locking
613 MutexLocker mu(VMOperationRequest_lock);
614 while(t->vm_operation_completed_count() < ticket) {
615 VMOperationRequest_lock->wait(!t->is_Java_thread());
616 }
617 }
618
619 if (execute_epilog) {
620 op->doit_epilogue();
621 }
622 } else {
623 // invoked by VM thread; usually nested VM operation
624 assert(t->is_VM_thread(), "must be a VM thread");
625 VM_Operation* prev_vm_operation = vm_operation();
626 if (prev_vm_operation != NULL) {
627 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler
628 // does not allow nested scavenges or compiles.
629 if (!prev_vm_operation->allow_nested_vm_operations()) {
630 fatal("Nested VM operation %s requested by operation %s",
631 op->name(), vm_operation()->name());
632 }
633 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority());
634 }
635
636 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name());
637
638 // Release all internal handles after operation is evaluated
639 HandleMark hm(t);
640 _cur_vm_operation = op;
641
642 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) {
643 SafepointSynchronize::begin();
644 op->evaluate();
645 SafepointSynchronize::end();
646 } else {
647 op->evaluate();
648 }
649
650 // Free memory if needed
651 if (op->is_cheap_allocated()) delete op;
652
653 _cur_vm_operation = prev_vm_operation;
654 }
655 }
656
657
658 void VMThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
659 Thread::oops_do(f, cf);
660 _vm_queue->oops_do(f);
661 }
662
663 //------------------------------------------------------------------------------------------------------------------
664 #ifndef PRODUCT
665
666 void VMOperationQueue::verify_queue(int prio) {
667 // Check that list is correctly linked
668 int length = _queue_length[prio];
669 VM_Operation *cur = _queue[prio];
670 int i;
671
672 // Check forward links
673 for(i = 0; i < length; i++) {
674 cur = cur->next();
675 assert(cur != _queue[prio], "list to short (forward)");
676 }
677 assert(cur->next() == _queue[prio], "list to long (forward)");
678
679 // Check backwards links
680 cur = _queue[prio];
681 for(i = 0; i < length; i++) {
682 cur = cur->prev();
683 assert(cur != _queue[prio], "list to short (backwards)");
684 }
685 assert(cur->prev() == _queue[prio], "list to long (backwards)");
686 }
687
688 #endif
689
690 void VMThread::verify() {
691 oops_do(&VerifyOopClosure::verify_oop, NULL);
692 }