Mon, 09 Mar 2020 12:54:53 +0000
8240295: hs_err elapsed time in seconds is not accurate enough
Reviewed-by: dholmes, sspitsyn
1 /*
2 * Copyright (c) 1998, 2014, 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.
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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
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23 */
25 #include "precompiled.hpp"
26 #include "compiler/compileBroker.hpp"
27 #include "gc_interface/collectedHeap.hpp"
28 #include "jfr/jfrEvents.hpp"
29 #include "jfr/support/jfrThreadId.hpp"
30 #include "memory/resourceArea.hpp"
31 #include "oops/method.hpp"
32 #include "oops/oop.inline.hpp"
33 #include "runtime/interfaceSupport.hpp"
34 #include "runtime/mutexLocker.hpp"
35 #include "runtime/os.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 "utilities/dtrace.hpp"
41 #include "utilities/events.hpp"
42 #include "utilities/xmlstream.hpp"
44 #ifndef USDT2
45 HS_DTRACE_PROBE_DECL3(hotspot, vmops__request, char *, uintptr_t, int);
46 HS_DTRACE_PROBE_DECL3(hotspot, vmops__begin, char *, uintptr_t, int);
47 HS_DTRACE_PROBE_DECL3(hotspot, vmops__end, char *, uintptr_t, int);
48 #endif /* !USDT2 */
50 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
52 // Dummy VM operation to act as first element in our circular double-linked list
53 class VM_Dummy: public VM_Operation {
54 VMOp_Type type() const { return VMOp_Dummy; }
55 void doit() {};
56 };
58 VMOperationQueue::VMOperationQueue() {
59 // The queue is a circular doubled-linked list, which always contains
60 // one element (i.e., one element means empty).
61 for(int i = 0; i < nof_priorities; i++) {
62 _queue_length[i] = 0;
63 _queue_counter = 0;
64 _queue[i] = new VM_Dummy();
65 _queue[i]->set_next(_queue[i]);
66 _queue[i]->set_prev(_queue[i]);
67 }
68 _drain_list = NULL;
69 }
72 bool VMOperationQueue::queue_empty(int prio) {
73 // It is empty if there is exactly one element
74 bool empty = (_queue[prio] == _queue[prio]->next());
75 assert( (_queue_length[prio] == 0 && empty) ||
76 (_queue_length[prio] > 0 && !empty), "sanity check");
77 return _queue_length[prio] == 0;
78 }
80 // Inserts an element to the right of the q element
81 void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) {
82 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
83 n->set_prev(q);
84 n->set_next(q->next());
85 q->next()->set_prev(n);
86 q->set_next(n);
87 }
89 void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) {
90 _queue_length[prio]++;
91 insert(_queue[prio]->next(), op);
92 }
94 void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) {
95 _queue_length[prio]++;
96 insert(_queue[prio]->prev(), op);
97 }
100 void VMOperationQueue::unlink(VM_Operation* q) {
101 assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
102 q->prev()->set_next(q->next());
103 q->next()->set_prev(q->prev());
104 }
106 VM_Operation* VMOperationQueue::queue_remove_front(int prio) {
107 if (queue_empty(prio)) return NULL;
108 assert(_queue_length[prio] >= 0, "sanity check");
109 _queue_length[prio]--;
110 VM_Operation* r = _queue[prio]->next();
111 assert(r != _queue[prio], "cannot remove base element");
112 unlink(r);
113 return r;
114 }
116 VM_Operation* VMOperationQueue::queue_drain(int prio) {
117 if (queue_empty(prio)) return NULL;
118 DEBUG_ONLY(int length = _queue_length[prio];);
119 assert(length >= 0, "sanity check");
120 _queue_length[prio] = 0;
121 VM_Operation* r = _queue[prio]->next();
122 assert(r != _queue[prio], "cannot remove base element");
123 // remove links to base element from head and tail
124 r->set_prev(NULL);
125 _queue[prio]->prev()->set_next(NULL);
126 // restore queue to empty state
127 _queue[prio]->set_next(_queue[prio]);
128 _queue[prio]->set_prev(_queue[prio]);
129 assert(queue_empty(prio), "drain corrupted queue");
130 #ifdef ASSERT
131 int len = 0;
132 VM_Operation* cur;
133 for(cur = r; cur != NULL; cur=cur->next()) len++;
134 assert(len == length, "drain lost some ops");
135 #endif
136 return r;
137 }
139 void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) {
140 VM_Operation* cur = _queue[queue];
141 cur = cur->next();
142 while (cur != _queue[queue]) {
143 cur->oops_do(f);
144 cur = cur->next();
145 }
146 }
148 void VMOperationQueue::drain_list_oops_do(OopClosure* f) {
149 VM_Operation* cur = _drain_list;
150 while (cur != NULL) {
151 cur->oops_do(f);
152 cur = cur->next();
153 }
154 }
156 //-----------------------------------------------------------------
157 // High-level interface
158 bool VMOperationQueue::add(VM_Operation *op) {
160 #ifndef USDT2
161 HS_DTRACE_PROBE3(hotspot, vmops__request, op->name(), strlen(op->name()),
162 op->evaluation_mode());
163 #else /* USDT2 */
164 HOTSPOT_VMOPS_REQUEST(
165 (char *) op->name(), strlen(op->name()),
166 op->evaluation_mode());
167 #endif /* USDT2 */
169 // Encapsulates VM queue policy. Currently, that
170 // only involves putting them on the right list
171 if (op->evaluate_at_safepoint()) {
172 queue_add_back(SafepointPriority, op);
173 return true;
174 }
176 queue_add_back(MediumPriority, op);
177 return true;
178 }
180 VM_Operation* VMOperationQueue::remove_next() {
181 // Assuming VMOperation queue is two-level priority queue. If there are
182 // more than two priorities, we need a different scheduling algorithm.
183 assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2,
184 "current algorithm does not work");
186 // simple counter based scheduling to prevent starvation of lower priority
187 // queue. -- see 4390175
188 int high_prio, low_prio;
189 if (_queue_counter++ < 10) {
190 high_prio = SafepointPriority;
191 low_prio = MediumPriority;
192 } else {
193 _queue_counter = 0;
194 high_prio = MediumPriority;
195 low_prio = SafepointPriority;
196 }
198 return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio);
199 }
201 void VMOperationQueue::oops_do(OopClosure* f) {
202 for(int i = 0; i < nof_priorities; i++) {
203 queue_oops_do(i, f);
204 }
205 drain_list_oops_do(f);
206 }
209 //------------------------------------------------------------------------------------------------------------------
210 // Implementation of VMThread stuff
212 bool VMThread::_should_terminate = false;
213 bool VMThread::_terminated = false;
214 bool VMThread::_gclog_reentry = false;
215 Monitor* VMThread::_terminate_lock = NULL;
216 VMThread* VMThread::_vm_thread = NULL;
217 VM_Operation* VMThread::_cur_vm_operation = NULL;
218 VMOperationQueue* VMThread::_vm_queue = NULL;
219 PerfCounter* VMThread::_perf_accumulated_vm_operation_time = NULL;
222 void VMThread::create() {
223 assert(vm_thread() == NULL, "we can only allocate one VMThread");
224 _vm_thread = new VMThread();
226 // Create VM operation queue
227 _vm_queue = new VMOperationQueue();
228 guarantee(_vm_queue != NULL, "just checking");
230 _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true);
232 if (UsePerfData) {
233 // jvmstat performance counters
234 Thread* THREAD = Thread::current();
235 _perf_accumulated_vm_operation_time =
236 PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime",
237 PerfData::U_Ticks, CHECK);
238 }
239 }
242 VMThread::VMThread() : NamedThread() {
243 set_name("VM Thread");
244 }
246 void VMThread::destroy() {
247 if (_vm_thread != NULL) {
248 delete _vm_thread;
249 _vm_thread = NULL; // VM thread is gone
250 }
251 }
253 void VMThread::run() {
254 assert(this == vm_thread(), "check");
256 this->initialize_thread_local_storage();
257 this->set_native_thread_name(this->name());
258 this->record_stack_base_and_size();
259 // Notify_lock wait checks on active_handles() to rewait in
260 // case of spurious wakeup, it should wait on the last
261 // value set prior to the notify
262 this->set_active_handles(JNIHandleBlock::allocate_block());
264 {
265 MutexLocker ml(Notify_lock);
266 Notify_lock->notify();
267 }
268 // Notify_lock is destroyed by Threads::create_vm()
270 int prio = (VMThreadPriority == -1)
271 ? os::java_to_os_priority[NearMaxPriority]
272 : VMThreadPriority;
273 // Note that I cannot call os::set_priority because it expects Java
274 // priorities and I am *explicitly* using OS priorities so that it's
275 // possible to set the VM thread priority higher than any Java thread.
276 os::set_native_priority( this, prio );
278 // Wait for VM_Operations until termination
279 this->loop();
281 // Note the intention to exit before safepointing.
282 // 6295565 This has the effect of waiting for any large tty
283 // outputs to finish.
284 if (xtty != NULL) {
285 ttyLocker ttyl;
286 xtty->begin_elem("destroy_vm");
287 xtty->stamp();
288 xtty->end_elem();
289 assert(should_terminate(), "termination flag must be set");
290 }
292 // 4526887 let VM thread exit at Safepoint
293 SafepointSynchronize::begin();
295 if (VerifyBeforeExit) {
296 HandleMark hm(VMThread::vm_thread());
297 // Among other things, this ensures that Eden top is correct.
298 Universe::heap()->prepare_for_verify();
299 os::check_heap();
300 // Silent verification so as not to pollute normal output,
301 // unless we really asked for it.
302 Universe::verify(!(PrintGCDetails || Verbose) || VerifySilently);
303 }
305 CompileBroker::set_should_block();
307 // wait for threads (compiler threads or daemon threads) in the
308 // _thread_in_native state to block.
309 VM_Exit::wait_for_threads_in_native_to_block();
311 // signal other threads that VM process is gone
312 {
313 // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows
314 // VM thread to enter any lock at Safepoint as long as its _owner is NULL.
315 // If that happens after _terminate_lock->wait() has unset _owner
316 // but before it actually drops the lock and waits, the notification below
317 // may get lost and we will have a hang. To avoid this, we need to use
318 // Mutex::lock_without_safepoint_check().
319 MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
320 _terminated = true;
321 _terminate_lock->notify();
322 }
324 // Thread destructor usually does this.
325 ThreadLocalStorage::set_thread(NULL);
327 // Deletion must be done synchronously by the JNI DestroyJavaVM thread
328 // so that the VMThread deletion completes before the main thread frees
329 // up the CodeHeap.
331 }
334 // Notify the VMThread that the last non-daemon JavaThread has terminated,
335 // and wait until operation is performed.
336 void VMThread::wait_for_vm_thread_exit() {
337 { MutexLocker mu(VMOperationQueue_lock);
338 _should_terminate = true;
339 VMOperationQueue_lock->notify();
340 }
342 // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint
343 // because this thread has been removed from the threads list. But anything
344 // that could get blocked by Safepoint should not be used after this point,
345 // otherwise we will hang, since there is no one can end the safepoint.
347 // Wait until VM thread is terminated
348 // Note: it should be OK to use Terminator_lock here. But this is called
349 // at a very delicate time (VM shutdown) and we are operating in non- VM
350 // thread at Safepoint. It's safer to not share lock with other threads.
351 { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
352 while(!VMThread::is_terminated()) {
353 _terminate_lock->wait(Mutex::_no_safepoint_check_flag);
354 }
355 }
356 }
358 void VMThread::print_on(outputStream* st) const {
359 st->print("\"%s\" ", name());
360 Thread::print_on(st);
361 st->cr();
362 }
364 static void post_vm_operation_event(EventExecuteVMOperation* event, VM_Operation* op) {
365 assert(event != NULL, "invariant");
366 assert(event->should_commit(), "invariant");
367 assert(op != NULL, "invariant");
368 const bool is_concurrent = op->evaluate_concurrently();
369 const bool evaluate_at_safepoint = op->evaluate_at_safepoint();
370 event->set_operation(op->type());
371 event->set_safepoint(evaluate_at_safepoint);
372 event->set_blocking(!is_concurrent);
373 // Only write caller thread information for non-concurrent vm operations.
374 // For concurrent vm operations, the thread id is set to 0 indicating thread is unknown.
375 // This is because the caller thread could have exited already.
376 event->set_caller(is_concurrent ? 0 : JFR_THREAD_ID(op->calling_thread()));
377 event->set_safepointId(evaluate_at_safepoint ? SafepointSynchronize::safepoint_counter() : 0);
378 event->commit();
379 }
381 void VMThread::evaluate_operation(VM_Operation* op) {
382 ResourceMark rm;
384 {
385 PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time());
386 #ifndef USDT2
387 HS_DTRACE_PROBE3(hotspot, vmops__begin, op->name(), strlen(op->name()),
388 op->evaluation_mode());
389 #else /* USDT2 */
390 HOTSPOT_VMOPS_BEGIN(
391 (char *) op->name(), strlen(op->name()),
392 op->evaluation_mode());
393 #endif /* USDT2 */
395 EventExecuteVMOperation event;
396 op->evaluate();
397 if (event.should_commit()) {
398 post_vm_operation_event(&event, op);
399 }
401 #ifndef USDT2
402 HS_DTRACE_PROBE3(hotspot, vmops__end, op->name(), strlen(op->name()),
403 op->evaluation_mode());
404 #else /* USDT2 */
405 HOTSPOT_VMOPS_END(
406 (char *) op->name(), strlen(op->name()),
407 op->evaluation_mode());
408 #endif /* USDT2 */
409 }
411 // Last access of info in _cur_vm_operation!
412 bool c_heap_allocated = op->is_cheap_allocated();
414 // Mark as completed
415 if (!op->evaluate_concurrently()) {
416 op->calling_thread()->increment_vm_operation_completed_count();
417 }
418 // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call,
419 // since if it is stack allocated the calling thread might have deallocated
420 if (c_heap_allocated) {
421 delete _cur_vm_operation;
422 }
423 }
426 void VMThread::loop() {
427 assert(_cur_vm_operation == NULL, "no current one should be executing");
429 while(true) {
430 VM_Operation* safepoint_ops = NULL;
431 //
432 // Wait for VM operation
433 //
434 // use no_safepoint_check to get lock without attempting to "sneak"
435 { MutexLockerEx mu_queue(VMOperationQueue_lock,
436 Mutex::_no_safepoint_check_flag);
438 // Look for new operation
439 assert(_cur_vm_operation == NULL, "no current one should be executing");
440 _cur_vm_operation = _vm_queue->remove_next();
442 // Stall time tracking code
443 if (PrintVMQWaitTime && _cur_vm_operation != NULL &&
444 !_cur_vm_operation->evaluate_concurrently()) {
445 long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp();
446 if (stall > 0)
447 tty->print_cr("%s stall: %Ld", _cur_vm_operation->name(), stall);
448 }
450 while (!should_terminate() && _cur_vm_operation == NULL) {
451 // wait with a timeout to guarantee safepoints at regular intervals
452 bool timedout =
453 VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag,
454 GuaranteedSafepointInterval);
456 // Support for self destruction
457 if ((SelfDestructTimer != 0) && !is_error_reported() &&
458 (os::elapsedTime() > SelfDestructTimer * 60)) {
459 tty->print_cr("VM self-destructed");
460 exit(-1);
461 }
463 if (timedout && (SafepointALot ||
464 SafepointSynchronize::is_cleanup_needed())) {
465 MutexUnlockerEx mul(VMOperationQueue_lock,
466 Mutex::_no_safepoint_check_flag);
467 // Force a safepoint since we have not had one for at least
468 // 'GuaranteedSafepointInterval' milliseconds. This will run all
469 // the clean-up processing that needs to be done regularly at a
470 // safepoint
471 SafepointSynchronize::begin();
472 #ifdef ASSERT
473 if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot();
474 #endif
475 SafepointSynchronize::end();
476 }
477 _cur_vm_operation = _vm_queue->remove_next();
479 // If we are at a safepoint we will evaluate all the operations that
480 // follow that also require a safepoint
481 if (_cur_vm_operation != NULL &&
482 _cur_vm_operation->evaluate_at_safepoint()) {
483 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
484 }
485 }
487 if (should_terminate()) break;
488 } // Release mu_queue_lock
490 //
491 // Execute VM operation
492 //
493 { HandleMark hm(VMThread::vm_thread());
495 EventMark em("Executing VM operation: %s", vm_operation()->name());
496 assert(_cur_vm_operation != NULL, "we should have found an operation to execute");
498 // Give the VM thread an extra quantum. Jobs tend to be bursty and this
499 // helps the VM thread to finish up the job.
500 // FIXME: When this is enabled and there are many threads, this can degrade
501 // performance significantly.
502 if( VMThreadHintNoPreempt )
503 os::hint_no_preempt();
505 // If we are at a safepoint we will evaluate all the operations that
506 // follow that also require a safepoint
507 if (_cur_vm_operation->evaluate_at_safepoint()) {
509 _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned
511 SafepointSynchronize::begin();
512 evaluate_operation(_cur_vm_operation);
513 // now process all queued safepoint ops, iteratively draining
514 // the queue until there are none left
515 do {
516 _cur_vm_operation = safepoint_ops;
517 if (_cur_vm_operation != NULL) {
518 do {
519 EventMark em("Executing coalesced safepoint VM operation: %s", _cur_vm_operation->name());
520 // evaluate_operation deletes the op object so we have
521 // to grab the next op now
522 VM_Operation* next = _cur_vm_operation->next();
523 _vm_queue->set_drain_list(next);
524 evaluate_operation(_cur_vm_operation);
525 _cur_vm_operation = next;
526 if (PrintSafepointStatistics) {
527 SafepointSynchronize::inc_vmop_coalesced_count();
528 }
529 } while (_cur_vm_operation != NULL);
530 }
531 // There is a chance that a thread enqueued a safepoint op
532 // since we released the op-queue lock and initiated the safepoint.
533 // So we drain the queue again if there is anything there, as an
534 // optimization to try and reduce the number of safepoints.
535 // As the safepoint synchronizes us with JavaThreads we will see
536 // any enqueue made by a JavaThread, but the peek will not
537 // necessarily detect a concurrent enqueue by a GC thread, but
538 // that simply means the op will wait for the next major cycle of the
539 // VMThread - just as it would if the GC thread lost the race for
540 // the lock.
541 if (_vm_queue->peek_at_safepoint_priority()) {
542 // must hold lock while draining queue
543 MutexLockerEx mu_queue(VMOperationQueue_lock,
544 Mutex::_no_safepoint_check_flag);
545 safepoint_ops = _vm_queue->drain_at_safepoint_priority();
546 } else {
547 safepoint_ops = NULL;
548 }
549 } while(safepoint_ops != NULL);
551 _vm_queue->set_drain_list(NULL);
553 // Complete safepoint synchronization
554 SafepointSynchronize::end();
556 } else { // not a safepoint operation
557 if (TraceLongCompiles) {
558 elapsedTimer t;
559 t.start();
560 evaluate_operation(_cur_vm_operation);
561 t.stop();
562 double secs = t.seconds();
563 if (secs * 1e3 > LongCompileThreshold) {
564 // XXX - _cur_vm_operation should not be accessed after
565 // the completed count has been incremented; the waiting
566 // thread may have already freed this memory.
567 tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs);
568 }
569 } else {
570 evaluate_operation(_cur_vm_operation);
571 }
573 _cur_vm_operation = NULL;
574 }
575 }
577 //
578 // Notify (potential) waiting Java thread(s) - lock without safepoint
579 // check so that sneaking is not possible
580 { MutexLockerEx mu(VMOperationRequest_lock,
581 Mutex::_no_safepoint_check_flag);
582 VMOperationRequest_lock->notify_all();
583 }
585 //
586 // We want to make sure that we get to a safepoint regularly.
587 //
588 if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) {
589 long interval = SafepointSynchronize::last_non_safepoint_interval();
590 bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval);
591 if (SafepointALot || max_time_exceeded) {
592 HandleMark hm(VMThread::vm_thread());
593 SafepointSynchronize::begin();
594 SafepointSynchronize::end();
595 }
596 }
597 }
598 }
600 void VMThread::execute(VM_Operation* op) {
601 Thread* t = Thread::current();
603 if (!t->is_VM_thread()) {
604 SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot
605 // JavaThread or WatcherThread
606 bool concurrent = op->evaluate_concurrently();
607 // only blocking VM operations need to verify the caller's safepoint state:
608 if (!concurrent) {
609 t->check_for_valid_safepoint_state(true);
610 }
612 // New request from Java thread, evaluate prologue
613 if (!op->doit_prologue()) {
614 return; // op was cancelled
615 }
617 // Setup VM_operations for execution
618 op->set_calling_thread(t, Thread::get_priority(t));
620 // It does not make sense to execute the epilogue, if the VM operation object is getting
621 // deallocated by the VM thread.
622 bool execute_epilog = !op->is_cheap_allocated();
623 assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated");
625 // Get ticket number for non-concurrent VM operations
626 int ticket = 0;
627 if (!concurrent) {
628 ticket = t->vm_operation_ticket();
629 }
631 // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the
632 // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests
633 // to be queued up during a safepoint synchronization.
634 {
635 VMOperationQueue_lock->lock_without_safepoint_check();
636 bool ok = _vm_queue->add(op);
637 op->set_timestamp(os::javaTimeMillis());
638 VMOperationQueue_lock->notify();
639 VMOperationQueue_lock->unlock();
640 // VM_Operation got skipped
641 if (!ok) {
642 assert(concurrent, "can only skip concurrent tasks");
643 if (op->is_cheap_allocated()) delete op;
644 return;
645 }
646 }
648 if (!concurrent) {
649 // Wait for completion of request (non-concurrent)
650 // Note: only a JavaThread triggers the safepoint check when locking
651 MutexLocker mu(VMOperationRequest_lock);
652 while(t->vm_operation_completed_count() < ticket) {
653 VMOperationRequest_lock->wait(!t->is_Java_thread());
654 }
655 }
657 if (execute_epilog) {
658 op->doit_epilogue();
659 }
660 } else {
661 // invoked by VM thread; usually nested VM operation
662 assert(t->is_VM_thread(), "must be a VM thread");
663 VM_Operation* prev_vm_operation = vm_operation();
664 if (prev_vm_operation != NULL) {
665 // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler
666 // does not allow nested scavenges or compiles.
667 if (!prev_vm_operation->allow_nested_vm_operations()) {
668 fatal(err_msg("Nested VM operation %s requested by operation %s",
669 op->name(), vm_operation()->name()));
670 }
671 op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority());
672 }
674 EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name());
676 // Release all internal handles after operation is evaluated
677 HandleMark hm(t);
678 _cur_vm_operation = op;
680 if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) {
681 SafepointSynchronize::begin();
682 op->evaluate();
683 SafepointSynchronize::end();
684 } else {
685 op->evaluate();
686 }
688 // Free memory if needed
689 if (op->is_cheap_allocated()) delete op;
691 _cur_vm_operation = prev_vm_operation;
692 }
693 }
696 void VMThread::oops_do(OopClosure* f, CLDClosure* cld_f, CodeBlobClosure* cf) {
697 Thread::oops_do(f, cld_f, cf);
698 _vm_queue->oops_do(f);
699 }
701 //------------------------------------------------------------------------------------------------------------------
702 #ifndef PRODUCT
704 void VMOperationQueue::verify_queue(int prio) {
705 // Check that list is correctly linked
706 int length = _queue_length[prio];
707 VM_Operation *cur = _queue[prio];
708 int i;
710 // Check forward links
711 for(i = 0; i < length; i++) {
712 cur = cur->next();
713 assert(cur != _queue[prio], "list to short (forward)");
714 }
715 assert(cur->next() == _queue[prio], "list to long (forward)");
717 // Check backwards links
718 cur = _queue[prio];
719 for(i = 0; i < length; i++) {
720 cur = cur->prev();
721 assert(cur != _queue[prio], "list to short (backwards)");
722 }
723 assert(cur->prev() == _queue[prio], "list to long (backwards)");
724 }
726 #endif
728 void VMThread::verify() {
729 oops_do(&VerifyOopClosure::verify_oop, NULL, NULL);
730 }