1 /*
2 * Copyright (c) 1998, 2017, 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/vmError.hpp"
44 #include "utilities/xmlstream.hpp"
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 const char* VMThread::_no_op_reason = NULL;
209
210
211 void VMThread::create() {
212 assert(vm_thread() == NULL, "we can only allocate one VMThread");
213 _vm_thread = new VMThread();
214
215 // Create VM operation queue
216 _vm_queue = new VMOperationQueue();
217 guarantee(_vm_queue != NULL, "just checking");
218
219 _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true,
220 Monitor::_safepoint_check_never);
221
222 if (UsePerfData) {
223 // jvmstat performance counters
224 Thread* THREAD = Thread::current();
225 _perf_accumulated_vm_operation_time =
226 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime",
227 PerfData::U_Ticks, CHECK);
228 }
229 }
230
231 VMThread::VMThread() : NamedThread() {
232 set_name("VM Thread");
233 }
234
235 void VMThread::destroy() {
236 _vm_thread = NULL; // VM thread is gone
237 }
238
239 void VMThread::run() {
240 assert(this == vm_thread(), "check");
241
242 this->initialize_named_thread();
243 this->record_stack_base_and_size();
244 // Notify_lock wait checks on active_handles() to rewait in
245 // case of spurious wakeup, it should wait on the last
246 // value set prior to the notify
247 this->set_active_handles(JNIHandleBlock::allocate_block());
248
249 {
250 MutexLocker ml(Notify_lock);
251 Notify_lock->notify();
252 }
253 // Notify_lock is destroyed by Threads::create_vm()
254
255 int prio = (VMThreadPriority == -1)
256 ? os::java_to_os_priority[NearMaxPriority]
257 : VMThreadPriority;
258 // Note that I cannot call os::set_priority because it expects Java
259 // priorities and I am *explicitly* using OS priorities so that it's
260 // possible to set the VM thread priority higher than any Java thread.
261 os::set_native_priority( this, prio );
262
263 // Wait for VM_Operations until termination
264 this->loop();
265
266 // Note the intention to exit before safepointing.
267 // 6295565 This has the effect of waiting for any large tty
268 // outputs to finish.
269 if (xtty != NULL) {
270 ttyLocker ttyl;
271 xtty->begin_elem("destroy_vm");
272 xtty->stamp();
273 xtty->end_elem();
274 assert(should_terminate(), "termination flag must be set");
275 }
276
277 // 4526887 let VM thread exit at Safepoint
278 _no_op_reason = "Halt";
279 SafepointSynchronize::begin();
280
281 if (VerifyBeforeExit) {
282 HandleMark hm(VMThread::vm_thread());
283 // Among other things, this ensures that Eden top is correct.
284 Universe::heap()->prepare_for_verify();
285 // Silent verification so as not to pollute normal output,
286 // unless we really asked for it.
287 Universe::verify();
288 }
289
290 CompileBroker::set_should_block();
291
292 // wait for threads (compiler threads or daemon threads) in the
293 // _thread_in_native state to block.
294 VM_Exit::wait_for_threads_in_native_to_block();
295
296 // signal other threads that VM process is gone
297 {
298 // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows
299 // VM thread to enter any lock at Safepoint as long as its _owner is NULL.
300 // If that happens after _terminate_lock->wait() has unset _owner
301 // but before it actually drops the lock and waits, the notification below
302 // may get lost and we will have a hang. To avoid this, we need to use
303 // Mutex::lock_without_safepoint_check().
304 MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
305 _terminated = true;
306 _terminate_lock->notify();
307 }
308
309 // We are now racing with the VM termination being carried out in
310 // another thread, so we don't "delete this". Numerous threads don't
311 // get deleted when the VM terminates
312
313 }
314
315
316 // Notify the VMThread that the last non-daemon JavaThread has terminated,
317 // and wait until operation is performed.
318 void VMThread::wait_for_vm_thread_exit() {
319 { MutexLocker mu(VMOperationQueue_lock);
320 _should_terminate = true;
321 VMOperationQueue_lock->notify();
322 }
323
324 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint
325 // because this thread has been removed from the threads list. But anything
326 // that could get blocked by Safepoint should not be used after this point,
327 // otherwise we will hang, since there is no one can end the safepoint.
328
329 // Wait until VM thread is terminated
330 // Note: it should be OK to use Terminator_lock here. But this is called
331 // at a very delicate time (VM shutdown) and we are operating in non- VM
332 // thread at Safepoint. It's safer to not share lock with other threads.
333 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
334 while(!VMThread::is_terminated()) {
335 _terminate_lock->wait(Mutex::_no_safepoint_check_flag);
336 }
337 }
338 }
339
340 void VMThread::evaluate_operation(VM_Operation* op) {
341 ResourceMark rm;
342
343 {
344 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time());
345 HOTSPOT_VMOPS_BEGIN(
346 (char *) op->name(), strlen(op->name()),
347 op->evaluation_mode());
348
349 EventExecuteVMOperation event;
350
351 op->evaluate();
352
353 if (event.should_commit()) {
354 const bool is_concurrent = op->evaluate_concurrently();
355 const bool evaluate_at_safepoint = op->evaluate_at_safepoint();
356 event.set_operation(op->type());
357 event.set_safepoint(evaluate_at_safepoint);
358 event.set_blocking(!is_concurrent);
359 // Only write caller thread information for non-concurrent vm operations.
360 // For concurrent vm operations, the thread id is set to 0 indicating thread is unknown.
361 // This is because the caller thread could have exited already.
362 event.set_caller(is_concurrent ? 0 : THREAD_TRACE_ID(op->calling_thread()));
363 event.set_safepointId(evaluate_at_safepoint ? SafepointSynchronize::safepoint_counter() : 0);
364 event.commit();
365 }
366
367 HOTSPOT_VMOPS_END(
368 (char *) op->name(), strlen(op->name()),
369 op->evaluation_mode());
370 }
371
372 // Last access of info in _cur_vm_operation!
373 bool c_heap_allocated = op->is_cheap_allocated();
374
375 // Mark as completed
376 if (!op->evaluate_concurrently()) {
377 op->calling_thread()->increment_vm_operation_completed_count();
378 }
379 // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call,
380 // since if it is stack allocated the calling thread might have deallocated
381 if (c_heap_allocated) {
382 delete _cur_vm_operation;
383 }
384 }
385
386 bool VMThread::no_op_safepoint_needed(bool check_time) {
387 if (SafepointALot) {
388 _no_op_reason = "SafepointALot";
389 return true;
390 }
391 if (!SafepointSynchronize::is_cleanup_needed()) {
392 return false;
393 }
394 if (check_time) {
395 long interval = SafepointSynchronize::last_non_safepoint_interval();
396 bool max_time_exceeded = GuaranteedSafepointInterval != 0 &&
397 (interval > GuaranteedSafepointInterval);
398 if (!max_time_exceeded) {
399 return false;
400 }
401 }
402 _no_op_reason = "Cleanup";
403 return true;
404 }
405
406 void VMThread::loop() {
407 assert(_cur_vm_operation == NULL, "no current one should be executing");
408
409 while(true) {
410 VM_Operation* safepoint_ops = NULL;
411 //
412 // Wait for VM operation
413 //
414 // use no_safepoint_check to get lock without attempting to "sneak"
415 { MutexLockerEx mu_queue(VMOperationQueue_lock,
416 Mutex::_no_safepoint_check_flag);
417
418 // Look for new operation
419 assert(_cur_vm_operation == NULL, "no current one should be executing");
420 _cur_vm_operation = _vm_queue->remove_next();
421
422 // Stall time tracking code
423 if (PrintVMQWaitTime && _cur_vm_operation != NULL &&
424 !_cur_vm_operation->evaluate_concurrently()) {
425 long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp();
426 if (stall > 0)
427 tty->print_cr("%s stall: %ld", _cur_vm_operation->name(), stall);
428 }
429
430 while (!should_terminate() && _cur_vm_operation == NULL) {
431 // wait with a timeout to guarantee safepoints at regular intervals
432 bool timedout =
433 VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag,
434 GuaranteedSafepointInterval);
435
436 // Support for self destruction
437 if ((SelfDestructTimer != 0) && !VMError::is_error_reported() &&
438 (os::elapsedTime() > (double)SelfDestructTimer * 60.0)) {
439 tty->print_cr("VM self-destructed");
440 exit(-1);
441 }
442
443 if (timedout && VMThread::no_op_safepoint_needed(false)) {
444 MutexUnlockerEx mul(VMOperationQueue_lock,
445 Mutex::_no_safepoint_check_flag);
446 // Force a safepoint since we have not had one for at least
447 // 'GuaranteedSafepointInterval' milliseconds. This will run all
448 // the clean-up processing that needs to be done regularly at a
449 // safepoint
450 SafepointSynchronize::begin();
451 #ifdef ASSERT
452 if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot();
453 #endif
454 SafepointSynchronize::end();
455 }
456 _cur_vm_operation = _vm_queue->remove_next();
457
458 // If we are at a safepoint we will evaluate all the operations that
459 // follow that also require a safepoint
460 if (_cur_vm_operation != NULL &&
461 _cur_vm_operation->evaluate_at_safepoint()) {
462 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
463 }
464 }
465
466 if (should_terminate()) break;
467 } // Release mu_queue_lock
468
469 //
470 // Execute VM operation
471 //
472 { HandleMark hm(VMThread::vm_thread());
473
474 EventMark em("Executing VM operation: %s", vm_operation()->name());
475 assert(_cur_vm_operation != NULL, "we should have found an operation to execute");
476
477 // Give the VM thread an extra quantum. Jobs tend to be bursty and this
478 // helps the VM thread to finish up the job.
479 // FIXME: When this is enabled and there are many threads, this can degrade
480 // performance significantly.
481 if( VMThreadHintNoPreempt )
482 os::hint_no_preempt();
483
484 // If we are at a safepoint we will evaluate all the operations that
485 // follow that also require a safepoint
486 if (_cur_vm_operation->evaluate_at_safepoint()) {
487
488 _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned
489
490 SafepointSynchronize::begin();
491 evaluate_operation(_cur_vm_operation);
492 // now process all queued safepoint ops, iteratively draining
493 // the queue until there are none left
494 do {
495 _cur_vm_operation = safepoint_ops;
496 if (_cur_vm_operation != NULL) {
497 do {
498 // evaluate_operation deletes the op object so we have
499 // to grab the next op now
500 VM_Operation* next = _cur_vm_operation->next();
501 _vm_queue->set_drain_list(next);
502 evaluate_operation(_cur_vm_operation);
503 _cur_vm_operation = next;
504 if (PrintSafepointStatistics) {
505 SafepointSynchronize::inc_vmop_coalesced_count();
506 }
507 } while (_cur_vm_operation != NULL);
508 }
509 // There is a chance that a thread enqueued a safepoint op
510 // since we released the op-queue lock and initiated the safepoint.
511 // So we drain the queue again if there is anything there, as an
512 // optimization to try and reduce the number of safepoints.
513 // As the safepoint synchronizes us with JavaThreads we will see
514 // any enqueue made by a JavaThread, but the peek will not
515 // necessarily detect a concurrent enqueue by a GC thread, but
516 // that simply means the op will wait for the next major cycle of the
517 // VMThread - just as it would if the GC thread lost the race for
518 // the lock.
519 if (_vm_queue->peek_at_safepoint_priority()) {
520 // must hold lock while draining queue
521 MutexLockerEx mu_queue(VMOperationQueue_lock,
522 Mutex::_no_safepoint_check_flag);
523 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
524 } else {
525 safepoint_ops = NULL;
526 }
527 } while(safepoint_ops != NULL);
528
529 _vm_queue->set_drain_list(NULL);
530
531 // Complete safepoint synchronization
532 SafepointSynchronize::end();
533
534 } else { // not a safepoint operation
535 if (TraceLongCompiles) {
536 elapsedTimer t;
537 t.start();
538 evaluate_operation(_cur_vm_operation);
539 t.stop();
540 double secs = t.seconds();
541 if (secs * 1e3 > LongCompileThreshold) {
542 // XXX - _cur_vm_operation should not be accessed after
543 // the completed count has been incremented; the waiting
544 // thread may have already freed this memory.
545 tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs);
546 }
547 } else {
548 evaluate_operation(_cur_vm_operation);
549 }
550
551 _cur_vm_operation = NULL;
552 }
553 }
554
555 //
556 // Notify (potential) waiting Java thread(s) - lock without safepoint
557 // check so that sneaking is not possible
558 { MutexLockerEx mu(VMOperationRequest_lock,
559 Mutex::_no_safepoint_check_flag);
560 VMOperationRequest_lock->notify_all();
561 }
562
563 //
564 // We want to make sure that we get to a safepoint regularly.
565 //
566 if (VMThread::no_op_safepoint_needed(true)) {
567 HandleMark hm(VMThread::vm_thread());
568 SafepointSynchronize::begin();
569 SafepointSynchronize::end();
570 }
571 }
572 }
573
574 void VMThread::execute(VM_Operation* op) {
575 Thread* t = Thread::current();
576
577 if (!t->is_VM_thread()) {
578 SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot
579 // JavaThread or WatcherThread
580 bool concurrent = op->evaluate_concurrently();
581 // only blocking VM operations need to verify the caller's safepoint state:
582 if (!concurrent) {
583 t->check_for_valid_safepoint_state(true);
584 }
585
586 // New request from Java thread, evaluate prologue
587 if (!op->doit_prologue()) {
588 return; // op was cancelled
589 }
590
591 // Setup VM_operations for execution
592 op->set_calling_thread(t, Thread::get_priority(t));
593
594 // It does not make sense to execute the epilogue, if the VM operation object is getting
595 // deallocated by the VM thread.
596 bool execute_epilog = !op->is_cheap_allocated();
597 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated");
598
599 // Get ticket number for non-concurrent VM operations
600 int ticket = 0;
601 if (!concurrent) {
602 ticket = t->vm_operation_ticket();
603 }
604
605 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the
606 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests
607 // to be queued up during a safepoint synchronization.
608 {
609 VMOperationQueue_lock->lock_without_safepoint_check();
610 bool ok = _vm_queue->add(op);
611 op->set_timestamp(os::javaTimeMillis());
612 VMOperationQueue_lock->notify();
613 VMOperationQueue_lock->unlock();
614 // VM_Operation got skipped
615 if (!ok) {
616 assert(concurrent, "can only skip concurrent tasks");
617 if (op->is_cheap_allocated()) delete op;
618 return;
619 }
620 }
621
622 if (!concurrent) {
623 // Wait for completion of request (non-concurrent)
624 // Note: only a JavaThread triggers the safepoint check when locking
625 MutexLocker mu(VMOperationRequest_lock);
626 while(t->vm_operation_completed_count() < ticket) {
627 VMOperationRequest_lock->wait(!t->is_Java_thread());
628 }
629 }
630
631 if (execute_epilog) {
632 op->doit_epilogue();
633 }
634 } else {
635 // invoked by VM thread; usually nested VM operation
636 assert(t->is_VM_thread(), "must be a VM thread");
637 VM_Operation* prev_vm_operation = vm_operation();
638 if (prev_vm_operation != NULL) {
639 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler
640 // does not allow nested scavenges or compiles.
641 if (!prev_vm_operation->allow_nested_vm_operations()) {
642 fatal("Nested VM operation %s requested by operation %s",
643 op->name(), vm_operation()->name());
644 }
645 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority());
646 }
647
648 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name());
649
650 // Release all internal handles after operation is evaluated
651 HandleMark hm(t);
652 _cur_vm_operation = op;
653
654 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) {
655 SafepointSynchronize::begin();
656 op->evaluate();
657 SafepointSynchronize::end();
658 } else {
659 op->evaluate();
660 }
661
662 // Free memory if needed
663 if (op->is_cheap_allocated()) delete op;
664
665 _cur_vm_operation = prev_vm_operation;
666 }
667 }
668
669
670 void VMThread::oops_do(OopClosure* f, CodeBlobClosure* cf) {
671 Thread::oops_do(f, cf);
672 _vm_queue->oops_do(f);
673 }
674
675 //------------------------------------------------------------------------------------------------------------------
676 #ifndef PRODUCT
677
678 void VMOperationQueue::verify_queue(int prio) {
679 // Check that list is correctly linked
680 int length = _queue_length[prio];
681 VM_Operation *cur = _queue[prio];
682 int i;
683
684 // Check forward links
685 for(i = 0; i < length; i++) {
686 cur = cur->next();
687 assert(cur != _queue[prio], "list to short (forward)");
688 }
689 assert(cur->next() == _queue[prio], "list to long (forward)");
690
691 // Check backwards links
692 cur = _queue[prio];
693 for(i = 0; i < length; i++) {
694 cur = cur->prev();
695 assert(cur != _queue[prio], "list to short (backwards)");
696 }
697 assert(cur->prev() == _queue[prio], "list to long (backwards)");
698 }
699
700 #endif
701
702 void VMThread::verify() {
703 oops_do(&VerifyOopClosure::verify_oop, NULL);
704 }