1 /*
2 * Copyright (c) 1998, 2010, 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/methodOop.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 HS_DTRACE_PROBE_DECL3(hotspot, vmops__request, char *, uintptr_t, int);
54 HS_DTRACE_PROBE_DECL3(hotspot, vmops__begin, char *, uintptr_t, int);
55 HS_DTRACE_PROBE_DECL3(hotspot, vmops__end, char *, uintptr_t, int);
56
57 // Dummy VM operation to act as first element in our circular double-linked list
58 class VM_Dummy: public VM_Operation {
59 VMOp_Type type() const { return VMOp_Dummy; }
60 void doit() {};
61 };
62
63 VMOperationQueue::VMOperationQueue() {
64 // The queue is a circular doubled-linked list, which always contains
65 // one element (i.e., one element means empty).
66 for(int i = 0; i < nof_priorities; i++) {
67 _queue_length[i] = 0;
68 _queue_counter = 0;
69 _queue[i] = new VM_Dummy();
70 _queue[i]->set_next(_queue[i]);
71 _queue[i]->set_prev(_queue[i]);
72 }
73 _drain_list = NULL;
74 }
75
76
77 bool VMOperationQueue::queue_empty(int prio) {
78 // It is empty if there is exactly one element
79 bool empty = (_queue[prio] == _queue[prio]->next());
80 assert( (_queue_length[prio] == 0 && empty) ||
81 (_queue_length[prio] > 0 && !empty), "sanity check");
82 return _queue_length[prio] == 0;
83 }
84
85 // Inserts an element to the right of the q element
86 void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) {
87 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
88 n->set_prev(q);
89 n->set_next(q->next());
90 q->next()->set_prev(n);
91 q->set_next(n);
92 }
93
94 void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) {
95 _queue_length[prio]++;
96 insert(_queue[prio]->next(), op);
97 }
98
99 void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) {
100 _queue_length[prio]++;
101 insert(_queue[prio]->prev(), op);
102 }
103
104
105 void VMOperationQueue::unlink(VM_Operation* q) {
106 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
107 q->prev()->set_next(q->next());
108 q->next()->set_prev(q->prev());
109 }
110
111 VM_Operation* VMOperationQueue::queue_remove_front(int prio) {
112 if (queue_empty(prio)) return NULL;
113 assert(_queue_length[prio] >= 0, "sanity check");
114 _queue_length[prio]--;
115 VM_Operation* r = _queue[prio]->next();
116 assert(r != _queue[prio], "cannot remove base element");
117 unlink(r);
118 return r;
119 }
120
121 VM_Operation* VMOperationQueue::queue_drain(int prio) {
122 if (queue_empty(prio)) return NULL;
123 DEBUG_ONLY(int length = _queue_length[prio];);
124 assert(length >= 0, "sanity check");
125 _queue_length[prio] = 0;
126 VM_Operation* r = _queue[prio]->next();
127 assert(r != _queue[prio], "cannot remove base element");
128 // remove links to base element from head and tail
129 r->set_prev(NULL);
130 _queue[prio]->prev()->set_next(NULL);
131 // restore queue to empty state
132 _queue[prio]->set_next(_queue[prio]);
133 _queue[prio]->set_prev(_queue[prio]);
134 assert(queue_empty(prio), "drain corrupted queue");
135 #ifdef DEBUG
136 int len = 0;
137 VM_Operation* cur;
138 for(cur = r; cur != NULL; cur=cur->next()) len++;
139 assert(len == length, "drain lost some ops");
140 #endif
141 return r;
142 }
143
144 void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) {
145 VM_Operation* cur = _queue[queue];
146 cur = cur->next();
147 while (cur != _queue[queue]) {
148 cur->oops_do(f);
149 cur = cur->next();
150 }
151 }
152
153 void VMOperationQueue::drain_list_oops_do(OopClosure* f) {
154 VM_Operation* cur = _drain_list;
155 while (cur != NULL) {
156 cur->oops_do(f);
157 cur = cur->next();
158 }
159 }
160
161 //-----------------------------------------------------------------
162 // High-level interface
163 bool VMOperationQueue::add(VM_Operation *op) {
164
165 HS_DTRACE_PROBE3(hotspot, vmops__request, op->name(), strlen(op->name()),
166 op->evaluation_mode());
167
168 // Encapsulates VM queue policy. Currently, that
169 // only involves putting them on the right list
170 if (op->evaluate_at_safepoint()) {
171 queue_add_back(SafepointPriority, op);
172 return true;
173 }
174
175 queue_add_back(MediumPriority, op);
176 return true;
177 }
178
179 VM_Operation* VMOperationQueue::remove_next() {
180 // Assuming VMOperation queue is two-level priority queue. If there are
181 // more than two priorities, we need a different scheduling algorithm.
182 assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2,
183 "current algorithm does not work");
184
185 // simple counter based scheduling to prevent starvation of lower priority
186 // queue. -- see 4390175
187 int high_prio, low_prio;
188 if (_queue_counter++ < 10) {
189 high_prio = SafepointPriority;
190 low_prio = MediumPriority;
191 } else {
192 _queue_counter = 0;
193 high_prio = MediumPriority;
194 low_prio = SafepointPriority;
195 }
196
197 return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio);
198 }
199
200 void VMOperationQueue::oops_do(OopClosure* f) {
201 for(int i = 0; i < nof_priorities; i++) {
202 queue_oops_do(i, f);
203 }
204 drain_list_oops_do(f);
205 }
206
207
208 //------------------------------------------------------------------------------------------------------------------
209 // Implementation of VMThread stuff
210
211 bool VMThread::_should_terminate = false;
212 bool VMThread::_terminated = false;
213 Monitor* VMThread::_terminate_lock = NULL;
214 VMThread* VMThread::_vm_thread = NULL;
215 VM_Operation* VMThread::_cur_vm_operation = NULL;
216 VMOperationQueue* VMThread::_vm_queue = NULL;
217 PerfCounter* VMThread::_perf_accumulated_vm_operation_time = NULL;
218
219
220 void VMThread::create() {
221 assert(vm_thread() == NULL, "we can only allocate one VMThread");
222 _vm_thread = new VMThread();
223
224 // Create VM operation queue
225 _vm_queue = new VMOperationQueue();
226 guarantee(_vm_queue != NULL, "just checking");
227
228 _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true);
229
230 if (UsePerfData) {
231 // jvmstat performance counters
232 Thread* THREAD = Thread::current();
233 _perf_accumulated_vm_operation_time =
234 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime",
235 PerfData::U_Ticks, CHECK);
236 }
237 }
238
239
240 VMThread::VMThread() : NamedThread() {
241 set_name("VM Thread");
242 }
243
244 void VMThread::destroy() {
245 if (_vm_thread != NULL) {
246 delete _vm_thread;
247 _vm_thread = NULL; // VM thread is gone
248 }
249 }
250
251 void VMThread::run() {
252 assert(this == vm_thread(), "check");
253
254 this->initialize_thread_local_storage();
255 this->record_stack_base_and_size();
256 // Notify_lock wait checks on active_handles() to rewait in
257 // case of spurious wakeup, it should wait on the last
258 // value set prior to the notify
259 this->set_active_handles(JNIHandleBlock::allocate_block());
260
261 {
262 MutexLocker ml(Notify_lock);
263 Notify_lock->notify();
264 }
265 // Notify_lock is destroyed by Threads::create_vm()
266
267 int prio = (VMThreadPriority == -1)
268 ? os::java_to_os_priority[NearMaxPriority]
269 : VMThreadPriority;
270 // Note that I cannot call os::set_priority because it expects Java
271 // priorities and I am *explicitly* using OS priorities so that it's
272 // possible to set the VM thread priority higher than any Java thread.
273 os::set_native_priority( this, prio );
274
275 // Wait for VM_Operations until termination
276 this->loop();
277
278 // Note the intention to exit before safepointing.
279 // 6295565 This has the effect of waiting for any large tty
280 // outputs to finish.
281 if (xtty != NULL) {
282 ttyLocker ttyl;
283 xtty->begin_elem("destroy_vm");
284 xtty->stamp();
285 xtty->end_elem();
286 assert(should_terminate(), "termination flag must be set");
287 }
288
289 // 4526887 let VM thread exit at Safepoint
290 SafepointSynchronize::begin();
291
292 if (VerifyBeforeExit) {
293 HandleMark hm(VMThread::vm_thread());
294 // Among other things, this ensures that Eden top is correct.
295 Universe::heap()->prepare_for_verify();
296 os::check_heap();
297 // Silent verification so as not to pollute normal output,
298 // unless we really asked for it.
299 Universe::verify(true, !(PrintGCDetails || Verbose));
300 }
301
302 CompileBroker::set_should_block();
303
304 // wait for threads (compiler threads or daemon threads) in the
305 // _thread_in_native state to block.
306 VM_Exit::wait_for_threads_in_native_to_block();
307
308 // signal other threads that VM process is gone
309 {
310 // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows
311 // VM thread to enter any lock at Safepoint as long as its _owner is NULL.
312 // If that happens after _terminate_lock->wait() has unset _owner
313 // but before it actually drops the lock and waits, the notification below
314 // may get lost and we will have a hang. To avoid this, we need to use
315 // Mutex::lock_without_safepoint_check().
316 MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
317 _terminated = true;
318 _terminate_lock->notify();
319 }
320
321 // Deletion must be done synchronously by the JNI DestroyJavaVM thread
322 // so that the VMThread deletion completes before the main thread frees
323 // up the CodeHeap.
324
325 }
326
327
328 // Notify the VMThread that the last non-daemon JavaThread has terminated,
329 // and wait until operation is performed.
330 void VMThread::wait_for_vm_thread_exit() {
331 { MutexLocker mu(VMOperationQueue_lock);
332 _should_terminate = true;
333 VMOperationQueue_lock->notify();
334 }
335
336 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint
337 // because this thread has been removed from the threads list. But anything
338 // that could get blocked by Safepoint should not be used after this point,
339 // otherwise we will hang, since there is no one can end the safepoint.
340
341 // Wait until VM thread is terminated
342 // Note: it should be OK to use Terminator_lock here. But this is called
343 // at a very delicate time (VM shutdown) and we are operating in non- VM
344 // thread at Safepoint. It's safer to not share lock with other threads.
345 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
346 while(!VMThread::is_terminated()) {
347 _terminate_lock->wait(Mutex::_no_safepoint_check_flag);
348 }
349 }
350 }
351
352 void VMThread::print_on(outputStream* st) const {
353 st->print("\"%s\" ", name());
354 Thread::print_on(st);
355 st->cr();
356 }
357
358 void VMThread::evaluate_operation(VM_Operation* op) {
359 ResourceMark rm;
360
361 {
362 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time());
363 HS_DTRACE_PROBE3(hotspot, vmops__begin, op->name(), strlen(op->name()),
364 op->evaluation_mode());
365 op->evaluate();
366 HS_DTRACE_PROBE3(hotspot, vmops__end, 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() > SelfDestructTimer * 60)) {
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 t->check_for_valid_safepoint_state(true);
565
566 // New request from Java thread, evaluate prologue
567 if (!op->doit_prologue()) {
568 return; // op was cancelled
569 }
570
571 // Setup VM_operations for execution
572 op->set_calling_thread(t, Thread::get_priority(t));
573
574 // It does not make sense to execute the epilogue, if the VM operation object is getting
575 // deallocated by the VM thread.
576 bool concurrent = op->evaluate_concurrently();
577 bool execute_epilog = !op->is_cheap_allocated();
578 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated");
579
580 // Get ticket number for non-concurrent VM operations
581 int ticket = 0;
582 if (!concurrent) {
583 ticket = t->vm_operation_ticket();
584 }
585
586 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the
587 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests
588 // to be queued up during a safepoint synchronization.
589 {
590 VMOperationQueue_lock->lock_without_safepoint_check();
591 bool ok = _vm_queue->add(op);
592 op->set_timestamp(os::javaTimeMillis());
593 VMOperationQueue_lock->notify();
594 VMOperationQueue_lock->unlock();
595 // VM_Operation got skipped
596 if (!ok) {
597 assert(concurrent, "can only skip concurrent tasks");
598 if (op->is_cheap_allocated()) delete op;
599 return;
600 }
601 }
602
603 if (!concurrent) {
604 // Wait for completion of request (non-concurrent)
605 // Note: only a JavaThread triggers the safepoint check when locking
606 MutexLocker mu(VMOperationRequest_lock);
607 while(t->vm_operation_completed_count() < ticket) {
608 VMOperationRequest_lock->wait(!t->is_Java_thread());
609 }
610 }
611
612 if (execute_epilog) {
613 op->doit_epilogue();
614 }
615 } else {
616 // invoked by VM thread; usually nested VM operation
617 assert(t->is_VM_thread(), "must be a VM thread");
618 VM_Operation* prev_vm_operation = vm_operation();
619 if (prev_vm_operation != NULL) {
620 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler
621 // does not allow nested scavenges or compiles.
622 if (!prev_vm_operation->allow_nested_vm_operations()) {
623 fatal(err_msg("Nested VM operation %s requested by operation %s",
624 op->name(), vm_operation()->name()));
625 }
626 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority());
627 }
628
629 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name());
630
631 // Release all internal handles after operation is evaluated
632 HandleMark hm(t);
633 _cur_vm_operation = op;
634
635 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) {
636 SafepointSynchronize::begin();
637 op->evaluate();
638 SafepointSynchronize::end();
639 } else {
640 op->evaluate();
641 }
642
643 // Free memory if needed
644 if (op->is_cheap_allocated()) delete op;
645
646 _cur_vm_operation = prev_vm_operation;
647 }
648 }
649
650
651 void VMThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
652 Thread::oops_do(f, cf);
653 _vm_queue->oops_do(f);
654 }
655
656 //------------------------------------------------------------------------------------------------------------------
657 #ifndef PRODUCT
658
659 void VMOperationQueue::verify_queue(int prio) {
660 // Check that list is correctly linked
661 int length = _queue_length[prio];
662 VM_Operation *cur = _queue[prio];
663 int i;
664
665 // Check forward links
666 for(i = 0; i < length; i++) {
667 cur = cur->next();
668 assert(cur != _queue[prio], "list to short (forward)");
669 }
670 assert(cur->next() == _queue[prio], "list to long (forward)");
671
672 // Check backwards links
673 cur = _queue[prio];
674 for(i = 0; i < length; i++) {
675 cur = cur->prev();
676 assert(cur != _queue[prio], "list to short (backwards)");
677 }
678 assert(cur->prev() == _queue[prio], "list to long (backwards)");
679 }
680
681 #endif
682
683 void VMThread::verify() {
684 oops_do(&VerifyOopClosure::verify_oop, NULL);
685 }