473 assert(allow_null_referent ?
474 _referent->is_oop_or_null()
475 : _referent->is_oop(),
476 "bad referent");
477 }
478
479 void DiscoveredListIterator::remove() {
480 assert(_ref->is_oop(), "Dropping a bad reference");
481 oop_store_raw(_discovered_addr, NULL);
482
483 // First _prev_next ref actually points into DiscoveredList (gross).
484 oop new_next;
485 if (_next == _ref) {
486 // At the end of the list, we should make _prev point to itself.
487 // If _ref is the first ref, then _prev_next will be in the DiscoveredList,
488 // and _prev will be NULL.
489 new_next = _prev;
490 } else {
491 new_next = _next;
492 }
493
494 if (UseCompressedOops) {
495 // Remove Reference object from list.
496 oopDesc::encode_store_heap_oop((narrowOop*)_prev_next, new_next);
497 } else {
498 // Remove Reference object from list.
499 oopDesc::store_heap_oop((oop*)_prev_next, new_next);
500 }
501 NOT_PRODUCT(_removed++);
502 _refs_list.dec_length(1);
503 }
504
505 // Make the Reference object active again.
506 void DiscoveredListIterator::make_active() {
507 // For G1 we don't want to use set_next - it
508 // will dirty the card for the next field of
509 // the reference object and will fail
510 // CT verification.
511 if (UseG1GC) {
512 HeapWord* next_addr = java_lang_ref_Reference::next_addr(_ref);
513 if (UseCompressedOops) {
514 oopDesc::bs()->write_ref_field_pre((narrowOop*)next_addr, NULL);
515 } else {
516 oopDesc::bs()->write_ref_field_pre((oop*)next_addr, NULL);
517 }
518 java_lang_ref_Reference::set_next_raw(_ref, NULL);
519 } else {
527
528 // NOTE: process_phase*() are largely similar, and at a high level
529 // merely iterate over the extant list applying a predicate to
530 // each of its elements and possibly removing that element from the
531 // list and applying some further closures to that element.
532 // We should consider the possibility of replacing these
533 // process_phase*() methods by abstracting them into
534 // a single general iterator invocation that receives appropriate
535 // closures that accomplish this work.
536
537 // (SoftReferences only) Traverse the list and remove any SoftReferences whose
538 // referents are not alive, but that should be kept alive for policy reasons.
539 // Keep alive the transitive closure of all such referents.
540 void
541 ReferenceProcessor::process_phase1(DiscoveredList& refs_list,
542 ReferencePolicy* policy,
543 BoolObjectClosure* is_alive,
544 OopClosure* keep_alive,
545 VoidClosure* complete_gc) {
546 assert(policy != NULL, "Must have a non-NULL policy");
547 DiscoveredListIterator iter(refs_list, keep_alive, is_alive);
548 // Decide which softly reachable refs should be kept alive.
549 while (iter.has_next()) {
550 iter.load_ptrs(DEBUG_ONLY(!discovery_is_atomic() /* allow_null_referent */));
551 bool referent_is_dead = (iter.referent() != NULL) && !iter.is_referent_alive();
552 if (referent_is_dead &&
553 !policy->should_clear_reference(iter.obj(), _soft_ref_timestamp_clock)) {
554 if (TraceReferenceGC) {
555 gclog_or_tty->print_cr("Dropping reference (" INTPTR_FORMAT ": %s" ") by policy",
556 (void *)iter.obj(), iter.obj()->klass()->internal_name());
557 }
558 // Remove Reference object from list
559 iter.remove();
560 // Make the Reference object active again
561 iter.make_active();
562 // keep the referent around
563 iter.make_referent_alive();
564 iter.move_to_next();
565 } else {
566 iter.next();
567 }
568 }
569 // Close the reachable set
570 complete_gc->do_void();
571 NOT_PRODUCT(
572 if (PrintGCDetails && TraceReferenceGC) {
573 gclog_or_tty->print_cr(" Dropped %d dead Refs out of %d "
574 "discovered Refs by policy, from list " INTPTR_FORMAT,
575 iter.removed(), iter.processed(), (address)refs_list.head());
576 }
577 )
578 }
579
580 // Traverse the list and remove any Refs that are not active, or
581 // whose referents are either alive or NULL.
582 void
583 ReferenceProcessor::pp2_work(DiscoveredList& refs_list,
584 BoolObjectClosure* is_alive,
585 OopClosure* keep_alive) {
586 assert(discovery_is_atomic(), "Error");
587 DiscoveredListIterator iter(refs_list, keep_alive, is_alive);
588 while (iter.has_next()) {
589 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */));
590 DEBUG_ONLY(oop next = java_lang_ref_Reference::next(iter.obj());)
591 assert(next == NULL, "Should not discover inactive Reference");
592 if (iter.is_referent_alive()) {
593 if (TraceReferenceGC) {
594 gclog_or_tty->print_cr("Dropping strongly reachable reference (" INTPTR_FORMAT ": %s)",
595 (void *)iter.obj(), iter.obj()->klass()->internal_name());
596 }
597 // The referent is reachable after all.
598 // Remove Reference object from list.
599 iter.remove();
600 // Update the referent pointer as necessary: Note that this
601 // should not entail any recursive marking because the
602 // referent must already have been traversed.
603 iter.make_referent_alive();
604 iter.move_to_next();
605 } else {
606 iter.next();
607 }
608 }
609 NOT_PRODUCT(
610 if (PrintGCDetails && TraceReferenceGC && (iter.processed() > 0)) {
611 gclog_or_tty->print_cr(" Dropped %d active Refs out of %d "
612 "Refs in discovered list " INTPTR_FORMAT,
613 iter.removed(), iter.processed(), (address)refs_list.head());
614 }
615 )
616 }
617
618 void
619 ReferenceProcessor::pp2_work_concurrent_discovery(DiscoveredList& refs_list,
620 BoolObjectClosure* is_alive,
621 OopClosure* keep_alive,
622 VoidClosure* complete_gc) {
623 assert(!discovery_is_atomic(), "Error");
624 DiscoveredListIterator iter(refs_list, keep_alive, is_alive);
625 while (iter.has_next()) {
626 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */));
627 HeapWord* next_addr = java_lang_ref_Reference::next_addr(iter.obj());
628 oop next = java_lang_ref_Reference::next(iter.obj());
629 if ((iter.referent() == NULL || iter.is_referent_alive() ||
630 next != NULL)) {
631 assert(next->is_oop_or_null(), "bad next field");
632 // Remove Reference object from list
633 iter.remove();
634 // Trace the cohorts
635 iter.make_referent_alive();
636 if (UseCompressedOops) {
637 keep_alive->do_oop((narrowOop*)next_addr);
638 } else {
639 keep_alive->do_oop((oop*)next_addr);
640 }
641 iter.move_to_next();
642 } else {
643 iter.next();
644 }
647 complete_gc->do_void();
648 NOT_PRODUCT(
649 if (PrintGCDetails && TraceReferenceGC && (iter.processed() > 0)) {
650 gclog_or_tty->print_cr(" Dropped %d active Refs out of %d "
651 "Refs in discovered list " INTPTR_FORMAT,
652 iter.removed(), iter.processed(), (address)refs_list.head());
653 }
654 )
655 }
656
657 // Traverse the list and process the referents, by either
658 // clearing them or keeping them (and their reachable
659 // closure) alive.
660 void
661 ReferenceProcessor::process_phase3(DiscoveredList& refs_list,
662 bool clear_referent,
663 BoolObjectClosure* is_alive,
664 OopClosure* keep_alive,
665 VoidClosure* complete_gc) {
666 ResourceMark rm;
667 DiscoveredListIterator iter(refs_list, keep_alive, is_alive);
668 while (iter.has_next()) {
669 iter.update_discovered();
670 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */));
671 if (clear_referent) {
672 // NULL out referent pointer
673 iter.clear_referent();
674 } else {
675 // keep the referent around
676 iter.make_referent_alive();
677 }
678 if (TraceReferenceGC) {
679 gclog_or_tty->print_cr("Adding %sreference (" INTPTR_FORMAT ": %s) as pending",
680 clear_referent ? "cleared " : "",
681 (void *)iter.obj(), iter.obj()->klass()->internal_name());
682 }
683 assert(iter.obj()->is_oop(UseConcMarkSweepGC), "Adding a bad reference");
684 iter.next();
685 }
686 // Remember to update the next pointer of the last ref.
687 iter.update_discovered();
766 { }
767 virtual void work(unsigned int i, BoolObjectClosure& is_alive,
768 OopClosure& keep_alive,
769 VoidClosure& complete_gc)
770 {
771 // Don't use "refs_list_index" calculated in this way because
772 // balance_queues() has moved the Ref's into the first n queues.
773 // Thread* thr = Thread::current();
774 // int refs_list_index = ((WorkerThread*)thr)->id();
775 // _ref_processor.process_phase3(_refs_lists[refs_list_index], _clear_referent,
776 _ref_processor.process_phase3(_refs_lists[i], _clear_referent,
777 &is_alive, &keep_alive, &complete_gc);
778 }
779 private:
780 bool _clear_referent;
781 };
782
783 void ReferenceProcessor::set_discovered(oop ref, oop value) {
784 java_lang_ref_Reference::set_discovered_raw(ref, value);
785 if (_discovered_list_needs_barrier) {
786 oopDesc::bs()->write_ref_field(ref, value);
787 }
788 }
789
790 // Balances reference queues.
791 // Move entries from all queues[0, 1, ..., _max_num_q-1] to
792 // queues[0, 1, ..., _num_q-1] because only the first _num_q
793 // corresponding to the active workers will be processed.
794 void ReferenceProcessor::balance_queues(DiscoveredList ref_lists[])
795 {
796 // calculate total length
797 size_t total_refs = 0;
798 if (TraceReferenceGC && PrintGCDetails) {
799 gclog_or_tty->print_cr("\nBalance ref_lists ");
800 }
801
802 for (uint i = 0; i < _max_num_q; ++i) {
803 total_refs += ref_lists[i].length();
804 if (TraceReferenceGC && PrintGCDetails) {
805 gclog_or_tty->print("%d ", ref_lists[i].length());
806 }
963 }
964 }
965
966 return total_list_count;
967 }
968
969 void ReferenceProcessor::clean_up_discovered_references() {
970 // loop over the lists
971 for (uint i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) {
972 if (TraceReferenceGC && PrintGCDetails && ((i % _max_num_q) == 0)) {
973 gclog_or_tty->print_cr(
974 "\nScrubbing %s discovered list of Null referents",
975 list_name(i));
976 }
977 clean_up_discovered_reflist(_discovered_refs[i]);
978 }
979 }
980
981 void ReferenceProcessor::clean_up_discovered_reflist(DiscoveredList& refs_list) {
982 assert(!discovery_is_atomic(), "Else why call this method?");
983 DiscoveredListIterator iter(refs_list, NULL, NULL);
984 while (iter.has_next()) {
985 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */));
986 oop next = java_lang_ref_Reference::next(iter.obj());
987 assert(next->is_oop_or_null(), "bad next field");
988 // If referent has been cleared or Reference is not active,
989 // drop it.
990 if (iter.referent() == NULL || next != NULL) {
991 debug_only(
992 if (PrintGCDetails && TraceReferenceGC) {
993 gclog_or_tty->print_cr("clean_up_discovered_list: Dropping Reference: "
994 INTPTR_FORMAT " with next field: " INTPTR_FORMAT
995 " and referent: " INTPTR_FORMAT,
996 (void *)iter.obj(), (void *)next, (void *)iter.referent());
997 }
998 )
999 // Remove Reference object from list
1000 iter.remove();
1001 iter.move_to_next();
1002 } else {
1003 iter.next();
1334 preclean_discovered_reflist(_discoveredPhantomRefs[i], is_alive,
1335 keep_alive, complete_gc, yield);
1336 }
1337 }
1338 }
1339
1340 // Walk the given discovered ref list, and remove all reference objects
1341 // whose referents are still alive, whose referents are NULL or which
1342 // are not active (have a non-NULL next field). NOTE: When we are
1343 // thus precleaning the ref lists (which happens single-threaded today),
1344 // we do not disable refs discovery to honor the correct semantics of
1345 // java.lang.Reference. As a result, we need to be careful below
1346 // that ref removal steps interleave safely with ref discovery steps
1347 // (in this thread).
1348 void
1349 ReferenceProcessor::preclean_discovered_reflist(DiscoveredList& refs_list,
1350 BoolObjectClosure* is_alive,
1351 OopClosure* keep_alive,
1352 VoidClosure* complete_gc,
1353 YieldClosure* yield) {
1354 DiscoveredListIterator iter(refs_list, keep_alive, is_alive);
1355 while (iter.has_next()) {
1356 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */));
1357 oop obj = iter.obj();
1358 oop next = java_lang_ref_Reference::next(obj);
1359 if (iter.referent() == NULL || iter.is_referent_alive() ||
1360 next != NULL) {
1361 // The referent has been cleared, or is alive, or the Reference is not
1362 // active; we need to trace and mark its cohort.
1363 if (TraceReferenceGC) {
1364 gclog_or_tty->print_cr("Precleaning Reference (" INTPTR_FORMAT ": %s)",
1365 (void *)iter.obj(), iter.obj()->klass()->internal_name());
1366 }
1367 // Remove Reference object from list
1368 iter.remove();
1369 // Keep alive its cohort.
1370 iter.make_referent_alive();
1371 if (UseCompressedOops) {
1372 narrowOop* next_addr = (narrowOop*)java_lang_ref_Reference::next_addr(obj);
1373 keep_alive->do_oop(next_addr);
1374 } else {
|
473 assert(allow_null_referent ?
474 _referent->is_oop_or_null()
475 : _referent->is_oop(),
476 "bad referent");
477 }
478
479 void DiscoveredListIterator::remove() {
480 assert(_ref->is_oop(), "Dropping a bad reference");
481 oop_store_raw(_discovered_addr, NULL);
482
483 // First _prev_next ref actually points into DiscoveredList (gross).
484 oop new_next;
485 if (_next == _ref) {
486 // At the end of the list, we should make _prev point to itself.
487 // If _ref is the first ref, then _prev_next will be in the DiscoveredList,
488 // and _prev will be NULL.
489 new_next = _prev;
490 } else {
491 new_next = _next;
492 }
493 // Remove Reference object from list.
494 oop_store_raw(_prev_next, new_next);
495 if (_discovered_list_needs_barrier && _prev_next != _refs_list.adr_head()) {
496 // Needs post-barrier and this is not the list head (which is not on the heap)
497 oopDesc::bs()->write_ref_field(_prev_next, new_next);
498 }
499 NOT_PRODUCT(_removed++);
500 _refs_list.dec_length(1);
501 }
502
503 // Make the Reference object active again.
504 void DiscoveredListIterator::make_active() {
505 // For G1 we don't want to use set_next - it
506 // will dirty the card for the next field of
507 // the reference object and will fail
508 // CT verification.
509 if (UseG1GC) {
510 HeapWord* next_addr = java_lang_ref_Reference::next_addr(_ref);
511 if (UseCompressedOops) {
512 oopDesc::bs()->write_ref_field_pre((narrowOop*)next_addr, NULL);
513 } else {
514 oopDesc::bs()->write_ref_field_pre((oop*)next_addr, NULL);
515 }
516 java_lang_ref_Reference::set_next_raw(_ref, NULL);
517 } else {
525
526 // NOTE: process_phase*() are largely similar, and at a high level
527 // merely iterate over the extant list applying a predicate to
528 // each of its elements and possibly removing that element from the
529 // list and applying some further closures to that element.
530 // We should consider the possibility of replacing these
531 // process_phase*() methods by abstracting them into
532 // a single general iterator invocation that receives appropriate
533 // closures that accomplish this work.
534
535 // (SoftReferences only) Traverse the list and remove any SoftReferences whose
536 // referents are not alive, but that should be kept alive for policy reasons.
537 // Keep alive the transitive closure of all such referents.
538 void
539 ReferenceProcessor::process_phase1(DiscoveredList& refs_list,
540 ReferencePolicy* policy,
541 BoolObjectClosure* is_alive,
542 OopClosure* keep_alive,
543 VoidClosure* complete_gc) {
544 assert(policy != NULL, "Must have a non-NULL policy");
545 DiscoveredListIterator iter(refs_list, keep_alive, is_alive, _discovered_list_needs_barrier);
546 // Decide which softly reachable refs should be kept alive.
547 while (iter.has_next()) {
548 iter.load_ptrs(DEBUG_ONLY(!discovery_is_atomic() /* allow_null_referent */));
549 bool referent_is_dead = (iter.referent() != NULL) && !iter.is_referent_alive();
550 if (referent_is_dead &&
551 !policy->should_clear_reference(iter.obj(), _soft_ref_timestamp_clock)) {
552 if (TraceReferenceGC) {
553 gclog_or_tty->print_cr("Dropping reference (" INTPTR_FORMAT ": %s" ") by policy",
554 (void *)iter.obj(), iter.obj()->klass()->internal_name());
555 }
556 // Remove Reference object from list
557 iter.remove();
558 // Make the Reference object active again
559 iter.make_active();
560 // keep the referent around
561 iter.make_referent_alive();
562 iter.move_to_next();
563 } else {
564 iter.next();
565 }
566 }
567 // Close the reachable set
568 complete_gc->do_void();
569 NOT_PRODUCT(
570 if (PrintGCDetails && TraceReferenceGC) {
571 gclog_or_tty->print_cr(" Dropped %d dead Refs out of %d "
572 "discovered Refs by policy, from list " INTPTR_FORMAT,
573 iter.removed(), iter.processed(), (address)refs_list.head());
574 }
575 )
576 }
577
578 // Traverse the list and remove any Refs that are not active, or
579 // whose referents are either alive or NULL.
580 void
581 ReferenceProcessor::pp2_work(DiscoveredList& refs_list,
582 BoolObjectClosure* is_alive,
583 OopClosure* keep_alive) {
584 assert(discovery_is_atomic(), "Error");
585 DiscoveredListIterator iter(refs_list, keep_alive, is_alive, _discovered_list_needs_barrier);
586 while (iter.has_next()) {
587 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */));
588 DEBUG_ONLY(oop next = java_lang_ref_Reference::next(iter.obj());)
589 assert(next == NULL, "Should not discover inactive Reference");
590 if (iter.is_referent_alive()) {
591 if (TraceReferenceGC) {
592 gclog_or_tty->print_cr("Dropping strongly reachable reference (" INTPTR_FORMAT ": %s)",
593 (void *)iter.obj(), iter.obj()->klass()->internal_name());
594 }
595 // The referent is reachable after all.
596 // Remove Reference object from list.
597 iter.remove();
598 // Update the referent pointer as necessary: Note that this
599 // should not entail any recursive marking because the
600 // referent must already have been traversed.
601 iter.make_referent_alive();
602 iter.move_to_next();
603 } else {
604 iter.next();
605 }
606 }
607 NOT_PRODUCT(
608 if (PrintGCDetails && TraceReferenceGC && (iter.processed() > 0)) {
609 gclog_or_tty->print_cr(" Dropped %d active Refs out of %d "
610 "Refs in discovered list " INTPTR_FORMAT,
611 iter.removed(), iter.processed(), (address)refs_list.head());
612 }
613 )
614 }
615
616 void
617 ReferenceProcessor::pp2_work_concurrent_discovery(DiscoveredList& refs_list,
618 BoolObjectClosure* is_alive,
619 OopClosure* keep_alive,
620 VoidClosure* complete_gc) {
621 assert(!discovery_is_atomic(), "Error");
622 DiscoveredListIterator iter(refs_list, keep_alive, is_alive, _discovered_list_needs_barrier);
623 while (iter.has_next()) {
624 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */));
625 HeapWord* next_addr = java_lang_ref_Reference::next_addr(iter.obj());
626 oop next = java_lang_ref_Reference::next(iter.obj());
627 if ((iter.referent() == NULL || iter.is_referent_alive() ||
628 next != NULL)) {
629 assert(next->is_oop_or_null(), "bad next field");
630 // Remove Reference object from list
631 iter.remove();
632 // Trace the cohorts
633 iter.make_referent_alive();
634 if (UseCompressedOops) {
635 keep_alive->do_oop((narrowOop*)next_addr);
636 } else {
637 keep_alive->do_oop((oop*)next_addr);
638 }
639 iter.move_to_next();
640 } else {
641 iter.next();
642 }
645 complete_gc->do_void();
646 NOT_PRODUCT(
647 if (PrintGCDetails && TraceReferenceGC && (iter.processed() > 0)) {
648 gclog_or_tty->print_cr(" Dropped %d active Refs out of %d "
649 "Refs in discovered list " INTPTR_FORMAT,
650 iter.removed(), iter.processed(), (address)refs_list.head());
651 }
652 )
653 }
654
655 // Traverse the list and process the referents, by either
656 // clearing them or keeping them (and their reachable
657 // closure) alive.
658 void
659 ReferenceProcessor::process_phase3(DiscoveredList& refs_list,
660 bool clear_referent,
661 BoolObjectClosure* is_alive,
662 OopClosure* keep_alive,
663 VoidClosure* complete_gc) {
664 ResourceMark rm;
665 DiscoveredListIterator iter(refs_list, keep_alive, is_alive, _discovered_list_needs_barrier);
666 while (iter.has_next()) {
667 iter.update_discovered();
668 iter.load_ptrs(DEBUG_ONLY(false /* allow_null_referent */));
669 if (clear_referent) {
670 // NULL out referent pointer
671 iter.clear_referent();
672 } else {
673 // keep the referent around
674 iter.make_referent_alive();
675 }
676 if (TraceReferenceGC) {
677 gclog_or_tty->print_cr("Adding %sreference (" INTPTR_FORMAT ": %s) as pending",
678 clear_referent ? "cleared " : "",
679 (void *)iter.obj(), iter.obj()->klass()->internal_name());
680 }
681 assert(iter.obj()->is_oop(UseConcMarkSweepGC), "Adding a bad reference");
682 iter.next();
683 }
684 // Remember to update the next pointer of the last ref.
685 iter.update_discovered();
764 { }
765 virtual void work(unsigned int i, BoolObjectClosure& is_alive,
766 OopClosure& keep_alive,
767 VoidClosure& complete_gc)
768 {
769 // Don't use "refs_list_index" calculated in this way because
770 // balance_queues() has moved the Ref's into the first n queues.
771 // Thread* thr = Thread::current();
772 // int refs_list_index = ((WorkerThread*)thr)->id();
773 // _ref_processor.process_phase3(_refs_lists[refs_list_index], _clear_referent,
774 _ref_processor.process_phase3(_refs_lists[i], _clear_referent,
775 &is_alive, &keep_alive, &complete_gc);
776 }
777 private:
778 bool _clear_referent;
779 };
780
781 void ReferenceProcessor::set_discovered(oop ref, oop value) {
782 java_lang_ref_Reference::set_discovered_raw(ref, value);
783 if (_discovered_list_needs_barrier) {
784 oopDesc::bs()->write_ref_field(java_lang_ref_Reference::discovered_addr(ref), value);
785 }
786 }
787
788 // Balances reference queues.
789 // Move entries from all queues[0, 1, ..., _max_num_q-1] to
790 // queues[0, 1, ..., _num_q-1] because only the first _num_q
791 // corresponding to the active workers will be processed.
792 void ReferenceProcessor::balance_queues(DiscoveredList ref_lists[])
793 {
794 // calculate total length
795 size_t total_refs = 0;
796 if (TraceReferenceGC && PrintGCDetails) {
797 gclog_or_tty->print_cr("\nBalance ref_lists ");
798 }
799
800 for (uint i = 0; i < _max_num_q; ++i) {
801 total_refs += ref_lists[i].length();
802 if (TraceReferenceGC && PrintGCDetails) {
803 gclog_or_tty->print("%d ", ref_lists[i].length());
804 }
961 }
962 }
963
964 return total_list_count;
965 }
966
967 void ReferenceProcessor::clean_up_discovered_references() {
968 // loop over the lists
969 for (uint i = 0; i < _max_num_q * number_of_subclasses_of_ref(); i++) {
970 if (TraceReferenceGC && PrintGCDetails && ((i % _max_num_q) == 0)) {
971 gclog_or_tty->print_cr(
972 "\nScrubbing %s discovered list of Null referents",
973 list_name(i));
974 }
975 clean_up_discovered_reflist(_discovered_refs[i]);
976 }
977 }
978
979 void ReferenceProcessor::clean_up_discovered_reflist(DiscoveredList& refs_list) {
980 assert(!discovery_is_atomic(), "Else why call this method?");
981 DiscoveredListIterator iter(refs_list, NULL, NULL, _discovered_list_needs_barrier);
982 while (iter.has_next()) {
983 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */));
984 oop next = java_lang_ref_Reference::next(iter.obj());
985 assert(next->is_oop_or_null(), "bad next field");
986 // If referent has been cleared or Reference is not active,
987 // drop it.
988 if (iter.referent() == NULL || next != NULL) {
989 debug_only(
990 if (PrintGCDetails && TraceReferenceGC) {
991 gclog_or_tty->print_cr("clean_up_discovered_list: Dropping Reference: "
992 INTPTR_FORMAT " with next field: " INTPTR_FORMAT
993 " and referent: " INTPTR_FORMAT,
994 (void *)iter.obj(), (void *)next, (void *)iter.referent());
995 }
996 )
997 // Remove Reference object from list
998 iter.remove();
999 iter.move_to_next();
1000 } else {
1001 iter.next();
1332 preclean_discovered_reflist(_discoveredPhantomRefs[i], is_alive,
1333 keep_alive, complete_gc, yield);
1334 }
1335 }
1336 }
1337
1338 // Walk the given discovered ref list, and remove all reference objects
1339 // whose referents are still alive, whose referents are NULL or which
1340 // are not active (have a non-NULL next field). NOTE: When we are
1341 // thus precleaning the ref lists (which happens single-threaded today),
1342 // we do not disable refs discovery to honor the correct semantics of
1343 // java.lang.Reference. As a result, we need to be careful below
1344 // that ref removal steps interleave safely with ref discovery steps
1345 // (in this thread).
1346 void
1347 ReferenceProcessor::preclean_discovered_reflist(DiscoveredList& refs_list,
1348 BoolObjectClosure* is_alive,
1349 OopClosure* keep_alive,
1350 VoidClosure* complete_gc,
1351 YieldClosure* yield) {
1352 DiscoveredListIterator iter(refs_list, keep_alive, is_alive, _discovered_list_needs_barrier);
1353 while (iter.has_next()) {
1354 iter.load_ptrs(DEBUG_ONLY(true /* allow_null_referent */));
1355 oop obj = iter.obj();
1356 oop next = java_lang_ref_Reference::next(obj);
1357 if (iter.referent() == NULL || iter.is_referent_alive() ||
1358 next != NULL) {
1359 // The referent has been cleared, or is alive, or the Reference is not
1360 // active; we need to trace and mark its cohort.
1361 if (TraceReferenceGC) {
1362 gclog_or_tty->print_cr("Precleaning Reference (" INTPTR_FORMAT ": %s)",
1363 (void *)iter.obj(), iter.obj()->klass()->internal_name());
1364 }
1365 // Remove Reference object from list
1366 iter.remove();
1367 // Keep alive its cohort.
1368 iter.make_referent_alive();
1369 if (UseCompressedOops) {
1370 narrowOop* next_addr = (narrowOop*)java_lang_ref_Reference::next_addr(obj);
1371 keep_alive->do_oop(next_addr);
1372 } else {
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