1 /*
2 * Copyright (c) 1998, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "compiler/compileBroker.hpp"
27 #include "gc_interface/collectedHeap.hpp"
28 #include "memory/resourceArea.hpp"
29 #include "oops/method.hpp"
30 #include "oops/oop.inline.hpp"
31 #include "oops/verifyOopClosure.hpp"
32 #include "runtime/interfaceSupport.hpp"
33 #include "runtime/mutexLocker.hpp"
34 #include "runtime/os.hpp"
35 #include "runtime/thread.inline.hpp"
36 #include "runtime/vmThread.hpp"
37 #include "runtime/vm_operations.hpp"
38 #include "services/runtimeService.hpp"
39 #include "trace/tracing.hpp"
40 #include "utilities/dtrace.hpp"
41 #include "utilities/events.hpp"
42 #include "utilities/xmlstream.hpp"
43
44 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
45
46 // Dummy VM operation to act as first element in our circular double-linked list
47 class VM_Dummy: public VM_Operation {
48 VMOp_Type type() const { return VMOp_Dummy; }
49 void doit() {};
50 };
51
52 VMOperationQueue::VMOperationQueue() {
53 // The queue is a circular doubled-linked list, which always contains
54 // one element (i.e., one element means empty).
55 for(int i = 0; i < nof_priorities; i++) {
56 _queue_length[i] = 0;
57 _queue_counter = 0;
58 _queue[i] = new VM_Dummy();
59 _queue[i]->set_next(_queue[i]);
60 _queue[i]->set_prev(_queue[i]);
61 }
62 _drain_list = NULL;
63 }
64
65
66 bool VMOperationQueue::queue_empty(int prio) {
67 // It is empty if there is exactly one element
68 bool empty = (_queue[prio] == _queue[prio]->next());
69 assert( (_queue_length[prio] == 0 && empty) ||
70 (_queue_length[prio] > 0 && !empty), "sanity check");
71 return _queue_length[prio] == 0;
72 }
73
74 // Inserts an element to the right of the q element
75 void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) {
76 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
77 n->set_prev(q);
78 n->set_next(q->next());
79 q->next()->set_prev(n);
80 q->set_next(n);
81 }
82
83 void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) {
84 _queue_length[prio]++;
85 insert(_queue[prio]->next(), op);
86 }
87
88 void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) {
89 _queue_length[prio]++;
90 insert(_queue[prio]->prev(), op);
91 }
92
93
94 void VMOperationQueue::unlink(VM_Operation* q) {
95 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
96 q->prev()->set_next(q->next());
97 q->next()->set_prev(q->prev());
98 }
99
100 VM_Operation* VMOperationQueue::queue_remove_front(int prio) {
101 if (queue_empty(prio)) return NULL;
102 assert(_queue_length[prio] >= 0, "sanity check");
103 _queue_length[prio]--;
104 VM_Operation* r = _queue[prio]->next();
105 assert(r != _queue[prio], "cannot remove base element");
106 unlink(r);
107 return r;
108 }
109
110 VM_Operation* VMOperationQueue::queue_drain(int prio) {
111 if (queue_empty(prio)) return NULL;
112 DEBUG_ONLY(int length = _queue_length[prio];);
113 assert(length >= 0, "sanity check");
114 _queue_length[prio] = 0;
115 VM_Operation* r = _queue[prio]->next();
116 assert(r != _queue[prio], "cannot remove base element");
117 // remove links to base element from head and tail
118 r->set_prev(NULL);
119 _queue[prio]->prev()->set_next(NULL);
120 // restore queue to empty state
121 _queue[prio]->set_next(_queue[prio]);
122 _queue[prio]->set_prev(_queue[prio]);
123 assert(queue_empty(prio), "drain corrupted queue");
124 #ifdef ASSERT
125 int len = 0;
126 VM_Operation* cur;
127 for(cur = r; cur != NULL; cur=cur->next()) len++;
128 assert(len == length, "drain lost some ops");
129 #endif
130 return r;
131 }
132
133 void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) {
134 VM_Operation* cur = _queue[queue];
135 cur = cur->next();
136 while (cur != _queue[queue]) {
137 cur->oops_do(f);
138 cur = cur->next();
139 }
140 }
141
142 void VMOperationQueue::drain_list_oops_do(OopClosure* f) {
143 VM_Operation* cur = _drain_list;
144 while (cur != NULL) {
145 cur->oops_do(f);
146 cur = cur->next();
147 }
148 }
149
150 //-----------------------------------------------------------------
151 // High-level interface
152 bool VMOperationQueue::add(VM_Operation *op) {
153
154 HOTSPOT_VMOPS_REQUEST(
155 (char *) op->name(), strlen(op->name()),
156 op->evaluation_mode());
157
158 // Encapsulates VM queue policy. Currently, that
159 // only involves putting them on the right list
160 if (op->evaluate_at_safepoint()) {
161 queue_add_back(SafepointPriority, op);
162 return true;
163 }
164
165 queue_add_back(MediumPriority, op);
166 return true;
167 }
168
169 VM_Operation* VMOperationQueue::remove_next() {
170 // Assuming VMOperation queue is two-level priority queue. If there are
171 // more than two priorities, we need a different scheduling algorithm.
172 assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2,
173 "current algorithm does not work");
174
175 // simple counter based scheduling to prevent starvation of lower priority
176 // queue. -- see 4390175
177 int high_prio, low_prio;
178 if (_queue_counter++ < 10) {
179 high_prio = SafepointPriority;
180 low_prio = MediumPriority;
181 } else {
182 _queue_counter = 0;
183 high_prio = MediumPriority;
184 low_prio = SafepointPriority;
185 }
186
187 return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio);
188 }
189
190 void VMOperationQueue::oops_do(OopClosure* f) {
191 for(int i = 0; i < nof_priorities; i++) {
192 queue_oops_do(i, f);
193 }
194 drain_list_oops_do(f);
195 }
196
197
198 //------------------------------------------------------------------------------------------------------------------
199 // Implementation of VMThread stuff
200
201 bool VMThread::_should_terminate = false;
202 bool VMThread::_terminated = false;
203 Monitor* VMThread::_terminate_lock = NULL;
204 VMThread* VMThread::_vm_thread = NULL;
205 VM_Operation* VMThread::_cur_vm_operation = NULL;
206 VMOperationQueue* VMThread::_vm_queue = NULL;
207 PerfCounter* VMThread::_perf_accumulated_vm_operation_time = NULL;
208
209
210 void VMThread::create() {
211 assert(vm_thread() == NULL, "we can only allocate one VMThread");
212 _vm_thread = new VMThread();
213
214 // Create VM operation queue
215 _vm_queue = new VMOperationQueue();
216 guarantee(_vm_queue != NULL, "just checking");
217
218 _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true,
219 Monitor::_safepoint_check_never);
220
221 if (UsePerfData) {
222 // jvmstat performance counters
223 Thread* THREAD = Thread::current();
224 _perf_accumulated_vm_operation_time =
225 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime",
226 PerfData::U_Ticks, CHECK);
227 }
228 }
229
230
231 VMThread::VMThread() : NamedThread() {
232 set_name("VM Thread");
233 }
234
235 void VMThread::destroy() {
236 if (_vm_thread != NULL) {
237 delete _vm_thread;
238 _vm_thread = NULL; // VM thread is gone
239 }
240 }
241
242 void VMThread::run() {
243 assert(this == vm_thread(), "check");
244
245 this->initialize_thread_local_storage();
246 this->initialize_named_thread();
247 this->record_stack_base_and_size();
248 // Notify_lock wait checks on active_handles() to rewait in
249 // case of spurious wakeup, it should wait on the last
250 // value set prior to the notify
251 this->set_active_handles(JNIHandleBlock::allocate_block());
252
253 {
254 MutexLocker ml(Notify_lock);
255 Notify_lock->notify();
256 }
257 // Notify_lock is destroyed by Threads::create_vm()
258
259 int prio = (VMThreadPriority == -1)
260 ? os::java_to_os_priority[NearMaxPriority]
261 : VMThreadPriority;
262 // Note that I cannot call os::set_priority because it expects Java
263 // priorities and I am *explicitly* using OS priorities so that it's
264 // possible to set the VM thread priority higher than any Java thread.
265 os::set_native_priority( this, prio );
266
267 // Wait for VM_Operations until termination
268 this->loop();
269
270 // Note the intention to exit before safepointing.
271 // 6295565 This has the effect of waiting for any large tty
272 // outputs to finish.
273 if (xtty != NULL) {
274 ttyLocker ttyl;
275 xtty->begin_elem("destroy_vm");
276 xtty->stamp();
277 xtty->end_elem();
278 assert(should_terminate(), "termination flag must be set");
279 }
280
281 // 4526887 let VM thread exit at Safepoint
282 SafepointSynchronize::begin();
283
284 if (VerifyBeforeExit) {
285 HandleMark hm(VMThread::vm_thread());
286 // Among other things, this ensures that Eden top is correct.
287 Universe::heap()->prepare_for_verify();
288 os::check_heap();
289 // Silent verification so as not to pollute normal output,
290 // unless we really asked for it.
291 Universe::verify(!(PrintGCDetails || Verbose) || VerifySilently);
292 }
293
294 CompileBroker::set_should_block();
295
296 // wait for threads (compiler threads or daemon threads) in the
297 // _thread_in_native state to block.
298 VM_Exit::wait_for_threads_in_native_to_block();
299
300 // signal other threads that VM process is gone
301 {
302 // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows
303 // VM thread to enter any lock at Safepoint as long as its _owner is NULL.
304 // If that happens after _terminate_lock->wait() has unset _owner
305 // but before it actually drops the lock and waits, the notification below
306 // may get lost and we will have a hang. To avoid this, we need to use
307 // Mutex::lock_without_safepoint_check().
308 MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
309 _terminated = true;
310 _terminate_lock->notify();
311 }
312
313 // Thread destructor usually does this.
314 ThreadLocalStorage::set_thread(NULL);
315
316 // Deletion must be done synchronously by the JNI DestroyJavaVM thread
317 // so that the VMThread deletion completes before the main thread frees
318 // up the CodeHeap.
319
320 }
321
322
323 // Notify the VMThread that the last non-daemon JavaThread has terminated,
324 // and wait until operation is performed.
325 void VMThread::wait_for_vm_thread_exit() {
326 { MutexLocker mu(VMOperationQueue_lock);
327 _should_terminate = true;
328 VMOperationQueue_lock->notify();
329 }
330
331 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint
332 // because this thread has been removed from the threads list. But anything
333 // that could get blocked by Safepoint should not be used after this point,
334 // otherwise we will hang, since there is no one can end the safepoint.
335
336 // Wait until VM thread is terminated
337 // Note: it should be OK to use Terminator_lock here. But this is called
338 // at a very delicate time (VM shutdown) and we are operating in non- VM
339 // thread at Safepoint. It's safer to not share lock with other threads.
340 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
341 while(!VMThread::is_terminated()) {
342 _terminate_lock->wait(Mutex::_no_safepoint_check_flag);
343 }
344 }
345 }
346
347 void VMThread::evaluate_operation(VM_Operation* op) {
348 ResourceMark rm;
349
350 {
351 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time());
352 HOTSPOT_VMOPS_BEGIN(
353 (char *) op->name(), strlen(op->name()),
354 op->evaluation_mode());
355
356 EventExecuteVMOperation event;
357
358 op->evaluate();
359
360 if (event.should_commit()) {
361 bool is_concurrent = op->evaluate_concurrently();
362 event.set_operation(op->type());
363 event.set_safepoint(op->evaluate_at_safepoint());
364 event.set_blocking(!is_concurrent);
365 // Only write caller thread information for non-concurrent vm operations.
366 // For concurrent vm operations, the thread id is set to 0 indicating thread is unknown.
367 // This is because the caller thread could have exited already.
368 event.set_caller(is_concurrent ? 0 : op->calling_thread()->osthread()->thread_id());
369 event.commit();
370 }
371
372 HOTSPOT_VMOPS_END(
373 (char *) op->name(), strlen(op->name()),
374 op->evaluation_mode());
375 }
376
377 // Last access of info in _cur_vm_operation!
378 bool c_heap_allocated = op->is_cheap_allocated();
379
380 // Mark as completed
381 if (!op->evaluate_concurrently()) {
382 op->calling_thread()->increment_vm_operation_completed_count();
383 }
384 // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call,
385 // since if it is stack allocated the calling thread might have deallocated
386 if (c_heap_allocated) {
387 delete _cur_vm_operation;
388 }
389 }
390
391
392 void VMThread::loop() {
393 assert(_cur_vm_operation == NULL, "no current one should be executing");
394
395 while(true) {
396 VM_Operation* safepoint_ops = NULL;
397 //
398 // Wait for VM operation
399 //
400 // use no_safepoint_check to get lock without attempting to "sneak"
401 { MutexLockerEx mu_queue(VMOperationQueue_lock,
402 Mutex::_no_safepoint_check_flag);
403
404 // Look for new operation
405 assert(_cur_vm_operation == NULL, "no current one should be executing");
406 _cur_vm_operation = _vm_queue->remove_next();
407
408 // Stall time tracking code
409 if (PrintVMQWaitTime && _cur_vm_operation != NULL &&
410 !_cur_vm_operation->evaluate_concurrently()) {
411 long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp();
412 if (stall > 0)
413 tty->print_cr("%s stall: %Ld", _cur_vm_operation->name(), stall);
414 }
415
416 while (!should_terminate() && _cur_vm_operation == NULL) {
417 // wait with a timeout to guarantee safepoints at regular intervals
418 bool timedout =
419 VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag,
420 GuaranteedSafepointInterval);
421
422 // Support for self destruction
423 if ((SelfDestructTimer != 0) && !is_error_reported() &&
424 (os::elapsedTime() > SelfDestructTimer * 60)) {
425 tty->print_cr("VM self-destructed");
426 exit(-1);
427 }
428
429 if (timedout && (SafepointALot ||
430 SafepointSynchronize::is_cleanup_needed())) {
431 MutexUnlockerEx mul(VMOperationQueue_lock,
432 Mutex::_no_safepoint_check_flag);
433 // Force a safepoint since we have not had one for at least
434 // 'GuaranteedSafepointInterval' milliseconds. This will run all
435 // the clean-up processing that needs to be done regularly at a
436 // safepoint
437 SafepointSynchronize::begin();
438 #ifdef ASSERT
439 if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot();
440 #endif
441 SafepointSynchronize::end();
442 }
443 _cur_vm_operation = _vm_queue->remove_next();
444
445 // If we are at a safepoint we will evaluate all the operations that
446 // follow that also require a safepoint
447 if (_cur_vm_operation != NULL &&
448 _cur_vm_operation->evaluate_at_safepoint()) {
449 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
450 }
451 }
452
453 if (should_terminate()) break;
454 } // Release mu_queue_lock
455
456 //
457 // Execute VM operation
458 //
459 { HandleMark hm(VMThread::vm_thread());
460
461 EventMark em("Executing VM operation: %s", vm_operation()->name());
462 assert(_cur_vm_operation != NULL, "we should have found an operation to execute");
463
464 // Give the VM thread an extra quantum. Jobs tend to be bursty and this
465 // helps the VM thread to finish up the job.
466 // FIXME: When this is enabled and there are many threads, this can degrade
467 // performance significantly.
468 if( VMThreadHintNoPreempt )
469 os::hint_no_preempt();
470
471 // If we are at a safepoint we will evaluate all the operations that
472 // follow that also require a safepoint
473 if (_cur_vm_operation->evaluate_at_safepoint()) {
474
475 _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned
476
477 SafepointSynchronize::begin();
478 evaluate_operation(_cur_vm_operation);
479 // now process all queued safepoint ops, iteratively draining
480 // the queue until there are none left
481 do {
482 _cur_vm_operation = safepoint_ops;
483 if (_cur_vm_operation != NULL) {
484 do {
485 // evaluate_operation deletes the op object so we have
486 // to grab the next op now
487 VM_Operation* next = _cur_vm_operation->next();
488 _vm_queue->set_drain_list(next);
489 evaluate_operation(_cur_vm_operation);
490 _cur_vm_operation = next;
491 if (PrintSafepointStatistics) {
492 SafepointSynchronize::inc_vmop_coalesced_count();
493 }
494 } while (_cur_vm_operation != NULL);
495 }
496 // There is a chance that a thread enqueued a safepoint op
497 // since we released the op-queue lock and initiated the safepoint.
498 // So we drain the queue again if there is anything there, as an
499 // optimization to try and reduce the number of safepoints.
500 // As the safepoint synchronizes us with JavaThreads we will see
501 // any enqueue made by a JavaThread, but the peek will not
502 // necessarily detect a concurrent enqueue by a GC thread, but
503 // that simply means the op will wait for the next major cycle of the
504 // VMThread - just as it would if the GC thread lost the race for
505 // the lock.
506 if (_vm_queue->peek_at_safepoint_priority()) {
507 // must hold lock while draining queue
508 MutexLockerEx mu_queue(VMOperationQueue_lock,
509 Mutex::_no_safepoint_check_flag);
510 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
511 } else {
512 safepoint_ops = NULL;
513 }
514 } while(safepoint_ops != NULL);
515
516 _vm_queue->set_drain_list(NULL);
517
518 // Complete safepoint synchronization
519 SafepointSynchronize::end();
520
521 } else { // not a safepoint operation
522 if (TraceLongCompiles) {
523 elapsedTimer t;
524 t.start();
525 evaluate_operation(_cur_vm_operation);
526 t.stop();
527 double secs = t.seconds();
528 if (secs * 1e3 > LongCompileThreshold) {
529 // XXX - _cur_vm_operation should not be accessed after
530 // the completed count has been incremented; the waiting
531 // thread may have already freed this memory.
532 tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs);
533 }
534 } else {
535 evaluate_operation(_cur_vm_operation);
536 }
537
538 _cur_vm_operation = NULL;
539 }
540 }
541
542 //
543 // Notify (potential) waiting Java thread(s) - lock without safepoint
544 // check so that sneaking is not possible
545 { MutexLockerEx mu(VMOperationRequest_lock,
546 Mutex::_no_safepoint_check_flag);
547 VMOperationRequest_lock->notify_all();
548 }
549
550 //
551 // We want to make sure that we get to a safepoint regularly.
552 //
553 if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) {
554 long interval = SafepointSynchronize::last_non_safepoint_interval();
555 bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval);
556 if (SafepointALot || max_time_exceeded) {
557 HandleMark hm(VMThread::vm_thread());
558 SafepointSynchronize::begin();
559 SafepointSynchronize::end();
560 }
561 }
562 }
563 }
564
565 void VMThread::execute(VM_Operation* op) {
566 Thread* t = Thread::current();
567
568 if (!t->is_VM_thread()) {
569 SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot
570 // JavaThread or WatcherThread
571 bool concurrent = op->evaluate_concurrently();
572 // only blocking VM operations need to verify the caller's safepoint state:
573 if (!concurrent) {
574 t->check_for_valid_safepoint_state(true);
575 }
576
577 // New request from Java thread, evaluate prologue
578 if (!op->doit_prologue()) {
579 return; // op was cancelled
580 }
581
582 // Setup VM_operations for execution
583 op->set_calling_thread(t, Thread::get_priority(t));
584
585 // It does not make sense to execute the epilogue, if the VM operation object is getting
586 // deallocated by the VM thread.
587 bool execute_epilog = !op->is_cheap_allocated();
588 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated");
589
590 // Get ticket number for non-concurrent VM operations
591 int ticket = 0;
592 if (!concurrent) {
593 ticket = t->vm_operation_ticket();
594 }
595
596 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the
597 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests
598 // to be queued up during a safepoint synchronization.
599 {
600 VMOperationQueue_lock->lock_without_safepoint_check();
601 bool ok = _vm_queue->add(op);
602 op->set_timestamp(os::javaTimeMillis());
603 VMOperationQueue_lock->notify();
604 VMOperationQueue_lock->unlock();
605 // VM_Operation got skipped
606 if (!ok) {
607 assert(concurrent, "can only skip concurrent tasks");
608 if (op->is_cheap_allocated()) delete op;
609 return;
610 }
611 }
612
613 if (!concurrent) {
614 // Wait for completion of request (non-concurrent)
615 // Note: only a JavaThread triggers the safepoint check when locking
616 MutexLocker mu(VMOperationRequest_lock);
617 while(t->vm_operation_completed_count() < ticket) {
618 VMOperationRequest_lock->wait(!t->is_Java_thread());
619 }
620 }
621
622 if (execute_epilog) {
623 op->doit_epilogue();
624 }
625 } else {
626 // invoked by VM thread; usually nested VM operation
627 assert(t->is_VM_thread(), "must be a VM thread");
628 VM_Operation* prev_vm_operation = vm_operation();
629 if (prev_vm_operation != NULL) {
630 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler
631 // does not allow nested scavenges or compiles.
632 if (!prev_vm_operation->allow_nested_vm_operations()) {
633 fatal(err_msg("Nested VM operation %s requested by operation %s",
634 op->name(), vm_operation()->name()));
635 }
636 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority());
637 }
638
639 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name());
640
641 // Release all internal handles after operation is evaluated
642 HandleMark hm(t);
643 _cur_vm_operation = op;
644
645 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) {
646 SafepointSynchronize::begin();
647 op->evaluate();
648 SafepointSynchronize::end();
649 } else {
650 op->evaluate();
651 }
652
653 // Free memory if needed
654 if (op->is_cheap_allocated()) delete op;
655
656 _cur_vm_operation = prev_vm_operation;
657 }
658 }
659
660
661 void VMThread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
662 Thread::oops_do(f, cld_f, cf);
663 _vm_queue->oops_do(f);
664 }
665
666 //------------------------------------------------------------------------------------------------------------------
667 #ifndef PRODUCT
668
669 void VMOperationQueue::verify_queue(int prio) {
670 // Check that list is correctly linked
671 int length = _queue_length[prio];
672 VM_Operation *cur = _queue[prio];
673 int i;
674
675 // Check forward links
676 for(i = 0; i < length; i++) {
677 cur = cur->next();
678 assert(cur != _queue[prio], "list to short (forward)");
679 }
680 assert(cur->next() == _queue[prio], "list to long (forward)");
681
682 // Check backwards links
683 cur = _queue[prio];
684 for(i = 0; i < length; i++) {
685 cur = cur->prev();
686 assert(cur != _queue[prio], "list to short (backwards)");
687 }
688 assert(cur->prev() == _queue[prio], "list to long (backwards)");
689 }
690
691 #endif
692
693 void VMThread::verify() {
694 oops_do(&VerifyOopClosure::verify_oop, NULL, NULL);
695 }