1 /*
2 * Copyright (c) 1998, 2012, 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 "runtime/interfaceSupport.hpp"
32 #include "runtime/mutexLocker.hpp"
33 #include "runtime/os.hpp"
34 #include "runtime/thread.inline.hpp"
35 #include "runtime/vmThread.hpp"
36 #include "runtime/vm_operations.hpp"
37 #include "services/runtimeService.hpp"
38 #include "utilities/dtrace.hpp"
39 #include "utilities/events.hpp"
40 #include "utilities/xmlstream.hpp"
41
42 #ifndef USDT2
43 HS_DTRACE_PROBE_DECL3(hotspot, vmops__request, char *, uintptr_t, int);
44 HS_DTRACE_PROBE_DECL3(hotspot, vmops__begin, char *, uintptr_t, int);
45 HS_DTRACE_PROBE_DECL3(hotspot, vmops__end, char *, uintptr_t, int);
46 #endif /* !USDT2 */
47
48 // Dummy VM operation to act as first element in our circular double-linked list
49 class VM_Dummy: public VM_Operation {
50 VMOp_Type type() const { return VMOp_Dummy; }
51 void doit() {};
52 };
53
54 VMOperationQueue::VMOperationQueue() {
55 // The queue is a circular doubled-linked list, which always contains
56 // one element (i.e., one element means empty).
57 for(int i = 0; i < nof_priorities; i++) {
58 _queue_length[i] = 0;
59 _queue_counter = 0;
60 _queue[i] = new VM_Dummy();
61 _queue[i]->set_next(_queue[i]);
62 _queue[i]->set_prev(_queue[i]);
63 }
64 _drain_list = NULL;
65 }
66
67
68 bool VMOperationQueue::queue_empty(int prio) {
69 // It is empty if there is exactly one element
70 bool empty = (_queue[prio] == _queue[prio]->next());
71 assert( (_queue_length[prio] == 0 && empty) ||
72 (_queue_length[prio] > 0 && !empty), "sanity check");
73 return _queue_length[prio] == 0;
74 }
75
76 // Inserts an element to the right of the q element
77 void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) {
78 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
79 n->set_prev(q);
80 n->set_next(q->next());
81 q->next()->set_prev(n);
82 q->set_next(n);
83 }
84
85 void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) {
86 _queue_length[prio]++;
87 insert(_queue[prio]->next(), op);
88 }
89
90 void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) {
91 _queue_length[prio]++;
92 insert(_queue[prio]->prev(), op);
93 }
94
95
96 void VMOperationQueue::unlink(VM_Operation* q) {
97 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
98 q->prev()->set_next(q->next());
99 q->next()->set_prev(q->prev());
100 }
101
102 VM_Operation* VMOperationQueue::queue_remove_front(int prio) {
103 if (queue_empty(prio)) return NULL;
104 assert(_queue_length[prio] >= 0, "sanity check");
105 _queue_length[prio]--;
106 VM_Operation* r = _queue[prio]->next();
107 assert(r != _queue[prio], "cannot remove base element");
108 unlink(r);
109 return r;
110 }
111
112 VM_Operation* VMOperationQueue::queue_drain(int prio) {
113 if (queue_empty(prio)) return NULL;
114 DEBUG_ONLY(int length = _queue_length[prio];);
115 assert(length >= 0, "sanity check");
116 _queue_length[prio] = 0;
117 VM_Operation* r = _queue[prio]->next();
118 assert(r != _queue[prio], "cannot remove base element");
119 // remove links to base element from head and tail
120 r->set_prev(NULL);
121 _queue[prio]->prev()->set_next(NULL);
122 // restore queue to empty state
123 _queue[prio]->set_next(_queue[prio]);
124 _queue[prio]->set_prev(_queue[prio]);
125 assert(queue_empty(prio), "drain corrupted queue");
126 #ifdef DEBUG
127 int len = 0;
128 VM_Operation* cur;
129 for(cur = r; cur != NULL; cur=cur->next()) len++;
130 assert(len == length, "drain lost some ops");
131 #endif
132 return r;
133 }
134
135 void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) {
136 VM_Operation* cur = _queue[queue];
137 cur = cur->next();
138 while (cur != _queue[queue]) {
139 cur->oops_do(f);
140 cur = cur->next();
141 }
142 }
143
144 void VMOperationQueue::drain_list_oops_do(OopClosure* f) {
145 VM_Operation* cur = _drain_list;
146 while (cur != NULL) {
147 cur->oops_do(f);
148 cur = cur->next();
149 }
150 }
151
152 //-----------------------------------------------------------------
153 // High-level interface
154 bool VMOperationQueue::add(VM_Operation *op) {
155
156 #ifndef USDT2
157 HS_DTRACE_PROBE3(hotspot, vmops__request, op->name(), strlen(op->name()),
158 op->evaluation_mode());
159 #else /* USDT2 */
160 HOTSPOT_VMOPS_REQUEST(
161 (char *) op->name(), strlen(op->name()),
162 op->evaluation_mode());
163 #endif /* USDT2 */
164
165 // Encapsulates VM queue policy. Currently, that
166 // only involves putting them on the right list
167 if (op->evaluate_at_safepoint()) {
168 queue_add_back(SafepointPriority, op);
169 return true;
170 }
171
172 queue_add_back(MediumPriority, op);
173 return true;
174 }
175
176 VM_Operation* VMOperationQueue::remove_next() {
177 // Assuming VMOperation queue is two-level priority queue. If there are
178 // more than two priorities, we need a different scheduling algorithm.
179 assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2,
180 "current algorithm does not work");
181
182 // simple counter based scheduling to prevent starvation of lower priority
183 // queue. -- see 4390175
184 int high_prio, low_prio;
185 if (_queue_counter++ < 10) {
186 high_prio = SafepointPriority;
187 low_prio = MediumPriority;
188 } else {
189 _queue_counter = 0;
190 high_prio = MediumPriority;
191 low_prio = SafepointPriority;
192 }
193
194 return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio);
195 }
196
197 void VMOperationQueue::oops_do(OopClosure* f) {
198 for(int i = 0; i < nof_priorities; i++) {
199 queue_oops_do(i, f);
200 }
201 drain_list_oops_do(f);
202 }
203
204
205 //------------------------------------------------------------------------------------------------------------------
206 // Implementation of VMThread stuff
207
208 bool VMThread::_should_terminate = false;
209 bool VMThread::_terminated = false;
210 Monitor* VMThread::_terminate_lock = NULL;
211 VMThread* VMThread::_vm_thread = NULL;
212 VM_Operation* VMThread::_cur_vm_operation = NULL;
213 VMOperationQueue* VMThread::_vm_queue = NULL;
214 PerfCounter* VMThread::_perf_accumulated_vm_operation_time = NULL;
215
216
217 void VMThread::create() {
218 assert(vm_thread() == NULL, "we can only allocate one VMThread");
219 _vm_thread = new VMThread();
220
221 // Create VM operation queue
222 _vm_queue = new VMOperationQueue();
223 guarantee(_vm_queue != NULL, "just checking");
224
225 _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true);
226
227 if (UsePerfData) {
228 // jvmstat performance counters
229 Thread* THREAD = Thread::current();
230 _perf_accumulated_vm_operation_time =
231 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime",
232 PerfData::U_Ticks, CHECK);
233 }
234 }
235
236
237 VMThread::VMThread() : NamedThread() {
238 set_name("VM Thread");
239 }
240
241 void VMThread::destroy() {
242 if (_vm_thread != NULL) {
243 delete _vm_thread;
244 _vm_thread = NULL; // VM thread is gone
245 }
246 }
247
248 void VMThread::run() {
249 assert(this == vm_thread(), "check");
250
251 this->initialize_thread_local_storage();
252 this->record_stack_base_and_size();
253 // Notify_lock wait checks on active_handles() to rewait in
254 // case of spurious wakeup, it should wait on the last
255 // value set prior to the notify
256 this->set_active_handles(JNIHandleBlock::allocate_block());
257
258 {
259 MutexLocker ml(Notify_lock);
260 Notify_lock->notify();
261 }
262 // Notify_lock is destroyed by Threads::create_vm()
263
264 int prio = (VMThreadPriority == -1)
265 ? os::java_to_os_priority[NearMaxPriority]
266 : VMThreadPriority;
267 // Note that I cannot call os::set_priority because it expects Java
268 // priorities and I am *explicitly* using OS priorities so that it's
269 // possible to set the VM thread priority higher than any Java thread.
270 os::set_native_priority( this, prio );
271
272 // Wait for VM_Operations until termination
273 this->loop();
274
275 // Note the intention to exit before safepointing.
276 // 6295565 This has the effect of waiting for any large tty
277 // outputs to finish.
278 if (xtty != NULL) {
279 ttyLocker ttyl;
280 xtty->begin_elem("destroy_vm");
281 xtty->stamp();
282 xtty->end_elem();
283 assert(should_terminate(), "termination flag must be set");
284 }
285
286 // 4526887 let VM thread exit at Safepoint
287 SafepointSynchronize::begin();
288
289 if (VerifyBeforeExit) {
290 HandleMark hm(VMThread::vm_thread());
291 // Among other things, this ensures that Eden top is correct.
292 Universe::heap()->prepare_for_verify();
293 os::check_heap();
294 // Silent verification so as not to pollute normal output,
295 // unless we really asked for it.
296 Universe::verify(!(PrintGCDetails || Verbose));
297 }
298
299 CompileBroker::set_should_block();
300
301 // wait for threads (compiler threads or daemon threads) in the
302 // _thread_in_native state to block.
303 VM_Exit::wait_for_threads_in_native_to_block();
304
305 // signal other threads that VM process is gone
306 {
307 // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows
308 // VM thread to enter any lock at Safepoint as long as its _owner is NULL.
309 // If that happens after _terminate_lock->wait() has unset _owner
310 // but before it actually drops the lock and waits, the notification below
311 // may get lost and we will have a hang. To avoid this, we need to use
312 // Mutex::lock_without_safepoint_check().
313 MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
314 _terminated = true;
315 _terminate_lock->notify();
316 }
317
318 // Deletion must be done synchronously by the JNI DestroyJavaVM thread
319 // so that the VMThread deletion completes before the main thread frees
320 // up the CodeHeap.
321
322 }
323
324
325 // Notify the VMThread that the last non-daemon JavaThread has terminated,
326 // and wait until operation is performed.
327 void VMThread::wait_for_vm_thread_exit() {
328 { MutexLocker mu(VMOperationQueue_lock);
329 _should_terminate = true;
330 VMOperationQueue_lock->notify();
331 }
332
333 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint
334 // because this thread has been removed from the threads list. But anything
335 // that could get blocked by Safepoint should not be used after this point,
336 // otherwise we will hang, since there is no one can end the safepoint.
337
338 // Wait until VM thread is terminated
339 // Note: it should be OK to use Terminator_lock here. But this is called
340 // at a very delicate time (VM shutdown) and we are operating in non- VM
341 // thread at Safepoint. It's safer to not share lock with other threads.
342 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
343 while(!VMThread::is_terminated()) {
344 _terminate_lock->wait(Mutex::_no_safepoint_check_flag);
345 }
346 }
347 }
348
349 void VMThread::print_on(outputStream* st) const {
350 st->print("\"%s\" ", name());
351 Thread::print_on(st);
352 st->cr();
353 }
354
355 void VMThread::evaluate_operation(VM_Operation* op) {
356 ResourceMark rm;
357
358 {
359 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time());
360 #ifndef USDT2
361 HS_DTRACE_PROBE3(hotspot, vmops__begin, op->name(), strlen(op->name()),
362 op->evaluation_mode());
363 #else /* USDT2 */
364 HOTSPOT_VMOPS_BEGIN(
365 (char *) op->name(), strlen(op->name()),
366 op->evaluation_mode());
367 #endif /* USDT2 */
368 op->evaluate();
369 #ifndef USDT2
370 HS_DTRACE_PROBE3(hotspot, vmops__end, op->name(), strlen(op->name()),
371 op->evaluation_mode());
372 #else /* USDT2 */
373 HOTSPOT_VMOPS_END(
374 (char *) op->name(), strlen(op->name()),
375 op->evaluation_mode());
376 #endif /* USDT2 */
377 }
378
379 // Last access of info in _cur_vm_operation!
380 bool c_heap_allocated = op->is_cheap_allocated();
381
382 // Mark as completed
383 if (!op->evaluate_concurrently()) {
384 op->calling_thread()->increment_vm_operation_completed_count();
385 }
386 // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call,
387 // since if it is stack allocated the calling thread might have deallocated
388 if (c_heap_allocated) {
389 delete _cur_vm_operation;
390 }
391 }
392
393
394 void VMThread::loop() {
395 assert(_cur_vm_operation == NULL, "no current one should be executing");
396
397 while(true) {
398 VM_Operation* safepoint_ops = NULL;
399 //
400 // Wait for VM operation
401 //
402 // use no_safepoint_check to get lock without attempting to "sneak"
403 { MutexLockerEx mu_queue(VMOperationQueue_lock,
404 Mutex::_no_safepoint_check_flag);
405
406 // Look for new operation
407 assert(_cur_vm_operation == NULL, "no current one should be executing");
408 _cur_vm_operation = _vm_queue->remove_next();
409
410 // Stall time tracking code
411 if (PrintVMQWaitTime && _cur_vm_operation != NULL &&
412 !_cur_vm_operation->evaluate_concurrently()) {
413 long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp();
414 if (stall > 0)
415 tty->print_cr("%s stall: %Ld", _cur_vm_operation->name(), stall);
416 }
417
418 while (!should_terminate() && _cur_vm_operation == NULL) {
419 // wait with a timeout to guarantee safepoints at regular intervals
420 bool timedout =
421 VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag,
422 GuaranteedSafepointInterval);
423
424 // Support for self destruction
425 if ((SelfDestructTimer != 0) && !is_error_reported() &&
426 (os::elapsedTime() > SelfDestructTimer * 60)) {
427 tty->print_cr("VM self-destructed");
428 exit(-1);
429 }
430
431 if (timedout && (SafepointALot ||
432 SafepointSynchronize::is_cleanup_needed())) {
433 MutexUnlockerEx mul(VMOperationQueue_lock,
434 Mutex::_no_safepoint_check_flag);
435 // Force a safepoint since we have not had one for at least
436 // 'GuaranteedSafepointInterval' milliseconds. This will run all
437 // the clean-up processing that needs to be done regularly at a
438 // safepoint
439 SafepointSynchronize::begin();
440 #ifdef ASSERT
441 if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot();
442 #endif
443 SafepointSynchronize::end();
444 }
445 _cur_vm_operation = _vm_queue->remove_next();
446
447 // If we are at a safepoint we will evaluate all the operations that
448 // follow that also require a safepoint
449 if (_cur_vm_operation != NULL &&
450 _cur_vm_operation->evaluate_at_safepoint()) {
451 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
452 }
453 }
454
455 if (should_terminate()) break;
456 } // Release mu_queue_lock
457
458 //
459 // Execute VM operation
460 //
461 { HandleMark hm(VMThread::vm_thread());
462
463 EventMark em("Executing VM operation: %s", vm_operation()->name());
464 assert(_cur_vm_operation != NULL, "we should have found an operation to execute");
465
466 // Give the VM thread an extra quantum. Jobs tend to be bursty and this
467 // helps the VM thread to finish up the job.
468 // FIXME: When this is enabled and there are many threads, this can degrade
469 // performance significantly.
470 if( VMThreadHintNoPreempt )
471 os::hint_no_preempt();
472
473 // If we are at a safepoint we will evaluate all the operations that
474 // follow that also require a safepoint
475 if (_cur_vm_operation->evaluate_at_safepoint()) {
476
477 _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned
478
479 SafepointSynchronize::begin();
480 evaluate_operation(_cur_vm_operation);
481 // now process all queued safepoint ops, iteratively draining
482 // the queue until there are none left
483 do {
484 _cur_vm_operation = safepoint_ops;
485 if (_cur_vm_operation != NULL) {
486 do {
487 // evaluate_operation deletes the op object so we have
488 // to grab the next op now
489 VM_Operation* next = _cur_vm_operation->next();
490 _vm_queue->set_drain_list(next);
491 evaluate_operation(_cur_vm_operation);
492 _cur_vm_operation = next;
493 if (PrintSafepointStatistics) {
494 SafepointSynchronize::inc_vmop_coalesced_count();
495 }
496 } while (_cur_vm_operation != NULL);
497 }
498 // There is a chance that a thread enqueued a safepoint op
499 // since we released the op-queue lock and initiated the safepoint.
500 // So we drain the queue again if there is anything there, as an
501 // optimization to try and reduce the number of safepoints.
502 // As the safepoint synchronizes us with JavaThreads we will see
503 // any enqueue made by a JavaThread, but the peek will not
504 // necessarily detect a concurrent enqueue by a GC thread, but
505 // that simply means the op will wait for the next major cycle of the
506 // VMThread - just as it would if the GC thread lost the race for
507 // the lock.
508 if (_vm_queue->peek_at_safepoint_priority()) {
509 // must hold lock while draining queue
510 MutexLockerEx mu_queue(VMOperationQueue_lock,
511 Mutex::_no_safepoint_check_flag);
512 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
513 } else {
514 safepoint_ops = NULL;
515 }
516 } while(safepoint_ops != NULL);
517
518 _vm_queue->set_drain_list(NULL);
519
520 // Complete safepoint synchronization
521 SafepointSynchronize::end();
522
523 } else { // not a safepoint operation
524 if (TraceLongCompiles) {
525 elapsedTimer t;
526 t.start();
527 evaluate_operation(_cur_vm_operation);
528 t.stop();
529 double secs = t.seconds();
530 if (secs * 1e3 > LongCompileThreshold) {
531 // XXX - _cur_vm_operation should not be accessed after
532 // the completed count has been incremented; the waiting
533 // thread may have already freed this memory.
534 tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs);
535 }
536 } else {
537 evaluate_operation(_cur_vm_operation);
538 }
539
540 _cur_vm_operation = NULL;
541 }
542 }
543
544 //
545 // Notify (potential) waiting Java thread(s) - lock without safepoint
546 // check so that sneaking is not possible
547 { MutexLockerEx mu(VMOperationRequest_lock,
548 Mutex::_no_safepoint_check_flag);
549 VMOperationRequest_lock->notify_all();
550 }
551
552 //
553 // We want to make sure that we get to a safepoint regularly.
554 //
555 if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) {
556 long interval = SafepointSynchronize::last_non_safepoint_interval();
557 bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval);
558 if (SafepointALot || max_time_exceeded) {
559 HandleMark hm(VMThread::vm_thread());
560 SafepointSynchronize::begin();
561 SafepointSynchronize::end();
562 }
563 }
564 }
565 }
566
567 void VMThread::execute(VM_Operation* op) {
568 Thread* t = Thread::current();
569
570 if (!t->is_VM_thread()) {
571 SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot
572 // JavaThread or WatcherThread
573 t->check_for_valid_safepoint_state(true);
574
575 // New request from Java thread, evaluate prologue
576 if (!op->doit_prologue()) {
577 return; // op was cancelled
578 }
579
580 // Setup VM_operations for execution
581 op->set_calling_thread(t, Thread::get_priority(t));
582
583 // It does not make sense to execute the epilogue, if the VM operation object is getting
584 // deallocated by the VM thread.
585 bool concurrent = op->evaluate_concurrently();
586 bool execute_epilog = !op->is_cheap_allocated();
587 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated");
588
589 // Get ticket number for non-concurrent VM operations
590 int ticket = 0;
591 if (!concurrent) {
592 ticket = t->vm_operation_ticket();
593 }
594
595 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the
596 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests
597 // to be queued up during a safepoint synchronization.
598 {
599 VMOperationQueue_lock->lock_without_safepoint_check();
600 bool ok = _vm_queue->add(op);
601 op->set_timestamp(os::javaTimeMillis());
602 VMOperationQueue_lock->notify();
603 VMOperationQueue_lock->unlock();
604 // VM_Operation got skipped
605 if (!ok) {
606 assert(concurrent, "can only skip concurrent tasks");
607 if (op->is_cheap_allocated()) delete op;
608 return;
609 }
610 }
611
612 if (!concurrent) {
613 // Wait for completion of request (non-concurrent)
614 // Note: only a JavaThread triggers the safepoint check when locking
615 MutexLocker mu(VMOperationRequest_lock);
616 while(t->vm_operation_completed_count() < ticket) {
617 VMOperationRequest_lock->wait(!t->is_Java_thread());
618 }
619 }
620
621 if (execute_epilog) {
622 op->doit_epilogue();
623 }
624 } else {
625 // invoked by VM thread; usually nested VM operation
626 assert(t->is_VM_thread(), "must be a VM thread");
627 VM_Operation* prev_vm_operation = vm_operation();
628 if (prev_vm_operation != NULL) {
629 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler
630 // does not allow nested scavenges or compiles.
631 if (!prev_vm_operation->allow_nested_vm_operations()) {
632 fatal(err_msg("Nested VM operation %s requested by operation %s",
633 op->name(), vm_operation()->name()));
634 }
635 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority());
636 }
637
638 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name());
639
640 // Release all internal handles after operation is evaluated
641 HandleMark hm(t);
642 _cur_vm_operation = op;
643
644 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) {
645 SafepointSynchronize::begin();
646 op->evaluate();
647 SafepointSynchronize::end();
648 } else {
649 op->evaluate();
650 }
651
652 // Free memory if needed
653 if (op->is_cheap_allocated()) delete op;
654
655 _cur_vm_operation = prev_vm_operation;
656 }
657 }
658
659
660 void VMThread::oops_do(OopClosure* f, CLDToOopClosure* cld_f, CodeBlobClosure* cf) {
661 Thread::oops_do(f, cld_f, cf);
662 _vm_queue->oops_do(f);
663 }
664
665 //------------------------------------------------------------------------------------------------------------------
666 #ifndef PRODUCT
667
668 void VMOperationQueue::verify_queue(int prio) {
669 // Check that list is correctly linked
670 int length = _queue_length[prio];
671 VM_Operation *cur = _queue[prio];
672 int i;
673
674 // Check forward links
675 for(i = 0; i < length; i++) {
676 cur = cur->next();
677 assert(cur != _queue[prio], "list to short (forward)");
678 }
679 assert(cur->next() == _queue[prio], "list to long (forward)");
680
681 // Check backwards links
682 cur = _queue[prio];
683 for(i = 0; i < length; i++) {
684 cur = cur->prev();
685 assert(cur != _queue[prio], "list to short (backwards)");
686 }
687 assert(cur->prev() == _queue[prio], "list to long (backwards)");
688 }
689
690 #endif
691
692 void VMThread::verify() {
693 oops_do(&VerifyOopClosure::verify_oop, NULL, NULL);
694 }