1 /*
2 * Copyright (c) 2001, 2013, 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
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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13 * accompanied this code).
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23 */
24
25 #ifndef SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP
26 #define SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP
27
28 #include "memory/referencePolicy.hpp"
29 #include "memory/referenceProcessorStats.hpp"
30 #include "memory/referenceType.hpp"
31 #include "oops/instanceRefKlass.hpp"
32
33 class GCTimer;
34
35 // ReferenceProcessor class encapsulates the per-"collector" processing
36 // of java.lang.Reference objects for GC. The interface is useful for supporting
37 // a generational abstraction, in particular when there are multiple
38 // generations that are being independently collected -- possibly
39 // concurrently and/or incrementally. Note, however, that the
40 // ReferenceProcessor class abstracts away from a generational setting
41 // by using only a heap interval (called "span" below), thus allowing
42 // its use in a straightforward manner in a general, non-generational
43 // setting.
44 //
45 // The basic idea is that each ReferenceProcessor object concerns
46 // itself with ("weak") reference processing in a specific "span"
47 // of the heap of interest to a specific collector. Currently,
48 // the span is a convex interval of the heap, but, efficiency
49 // apart, there seems to be no reason it couldn't be extended
50 // (with appropriate modifications) to any "non-convex interval".
51
52 // forward references
53 class ReferencePolicy;
54 class AbstractRefProcTaskExecutor;
55
56 // List of discovered references.
57 class DiscoveredList {
58 public:
59 DiscoveredList() : _len(0), _compressed_head(0), _oop_head(NULL) { }
60 oop head() const {
61 return UseCompressedOops ? oopDesc::decode_heap_oop(_compressed_head) :
62 _oop_head;
63 }
64 HeapWord* adr_head() {
65 return UseCompressedOops ? (HeapWord*)&_compressed_head :
66 (HeapWord*)&_oop_head;
67 }
68 void set_head(oop o) {
69 if (UseCompressedOops) {
70 // Must compress the head ptr.
71 _compressed_head = oopDesc::encode_heap_oop(o);
72 } else {
73 _oop_head = o;
74 }
75 }
76 bool is_empty() const { return head() == NULL; }
77 size_t length() { return _len; }
78 void set_length(size_t len) { _len = len; }
79 void inc_length(size_t inc) { _len += inc; assert(_len > 0, "Error"); }
80 void dec_length(size_t dec) { _len -= dec; }
81 private:
82 // Set value depending on UseCompressedOops. This could be a template class
83 // but then we have to fix all the instantiations and declarations that use this class.
84 oop _oop_head;
85 narrowOop _compressed_head;
86 size_t _len;
87 };
88
89 // Iterator for the list of discovered references.
90 class DiscoveredListIterator {
91 private:
92 DiscoveredList& _refs_list;
93 HeapWord* _prev_next;
94 oop _prev;
95 oop _ref;
96 HeapWord* _discovered_addr;
97 oop _next;
98 HeapWord* _referent_addr;
99 oop _referent;
100 OopClosure* _keep_alive;
101 BoolObjectClosure* _is_alive;
102 bool _discovered_list_needs_post_barrier;
103
104 DEBUG_ONLY(
105 oop _first_seen; // cyclic linked list check
106 )
107
108 NOT_PRODUCT(
109 size_t _processed;
110 size_t _removed;
111 )
112
113 public:
114 inline DiscoveredListIterator(DiscoveredList& refs_list,
115 OopClosure* keep_alive,
116 BoolObjectClosure* is_alive,
117 bool discovered_list_needs_post_barrier = false):
118 _refs_list(refs_list),
119 _prev_next(refs_list.adr_head()),
120 _prev(NULL),
121 _ref(refs_list.head()),
122 #ifdef ASSERT
123 _first_seen(refs_list.head()),
124 #endif
125 #ifndef PRODUCT
126 _processed(0),
127 _removed(0),
128 #endif
129 _next(NULL),
130 _keep_alive(keep_alive),
131 _is_alive(is_alive),
132 _discovered_list_needs_post_barrier(discovered_list_needs_post_barrier)
133 { }
134
135 // End Of List.
136 inline bool has_next() const { return _ref != NULL; }
137
138 // Get oop to the Reference object.
139 inline oop obj() const { return _ref; }
140
141 // Get oop to the referent object.
142 inline oop referent() const { return _referent; }
143
144 // Returns true if referent is alive.
145 inline bool is_referent_alive() const {
146 return _is_alive->do_object_b(_referent);
147 }
148
149 // Loads data for the current reference.
150 // The "allow_null_referent" argument tells us to allow for the possibility
151 // of a NULL referent in the discovered Reference object. This typically
152 // happens in the case of concurrent collectors that may have done the
153 // discovery concurrently, or interleaved, with mutator execution.
154 void load_ptrs(DEBUG_ONLY(bool allow_null_referent));
155
156 // Move to the next discovered reference.
157 inline void next() {
158 _prev_next = _discovered_addr;
159 _prev = _ref;
160 move_to_next();
161 }
162
163 // Remove the current reference from the list
164 void remove();
165
166 // Make the Reference object active again.
167 void make_active();
168
169 // Make the referent alive.
170 inline void make_referent_alive() {
171 if (UseCompressedOops) {
172 _keep_alive->do_oop((narrowOop*)_referent_addr);
173 } else {
174 _keep_alive->do_oop((oop*)_referent_addr);
175 }
176 }
177
178 // Update the discovered field.
179 inline void update_discovered() {
180 // First _prev_next ref actually points into DiscoveredList (gross).
181 if (UseCompressedOops) {
182 if (!oopDesc::is_null(*(narrowOop*)_prev_next)) {
183 _keep_alive->do_oop((narrowOop*)_prev_next);
184 }
185 } else {
186 if (!oopDesc::is_null(*(oop*)_prev_next)) {
187 _keep_alive->do_oop((oop*)_prev_next);
188 }
189 }
190 }
191
192 // NULL out referent pointer.
193 void clear_referent();
194
195 // Statistics
196 NOT_PRODUCT(
197 inline size_t processed() const { return _processed; }
198 inline size_t removed() const { return _removed; }
199 )
200
201 inline void move_to_next() {
202 if (_ref == _next) {
203 // End of the list.
204 _ref = NULL;
205 } else {
206 _ref = _next;
207 }
208 assert(_ref != _first_seen, "cyclic ref_list found");
209 NOT_PRODUCT(_processed++);
210 }
211 };
212
213 class ReferenceProcessor : public CHeapObj<mtGC> {
214
215 private:
216 size_t total_count(DiscoveredList lists[]);
217
218 protected:
219 // Compatibility with pre-4965777 JDK's
220 static bool _pending_list_uses_discovered_field;
221
222 // The SoftReference master timestamp clock
223 static jlong _soft_ref_timestamp_clock;
224
225 MemRegion _span; // (right-open) interval of heap
226 // subject to wkref discovery
227
228 bool _discovering_refs; // true when discovery enabled
229 bool _discovery_is_atomic; // if discovery is atomic wrt
230 // other collectors in configuration
231 bool _discovery_is_mt; // true if reference discovery is MT.
232
233 // If true, setting "next" field of a discovered refs list requires
234 // write post barrier. (Must be true if used in a collector in which
235 // elements of a discovered list may be moved during discovery: for
236 // example, a collector like Garbage-First that moves objects during a
237 // long-term concurrent marking phase that does weak reference
238 // discovery.)
239 bool _discovered_list_needs_post_barrier;
240
241 bool _enqueuing_is_done; // true if all weak references enqueued
242 bool _processing_is_mt; // true during phases when
243 // reference processing is MT.
244 uint _next_id; // round-robin mod _num_q counter in
245 // support of work distribution
246
247 // For collectors that do not keep GC liveness information
248 // in the object header, this field holds a closure that
249 // helps the reference processor determine the reachability
250 // of an oop. It is currently initialized to NULL for all
251 // collectors except for CMS and G1.
252 BoolObjectClosure* _is_alive_non_header;
253
254 // Soft ref clearing policies
255 // . the default policy
256 static ReferencePolicy* _default_soft_ref_policy;
257 // . the "clear all" policy
258 static ReferencePolicy* _always_clear_soft_ref_policy;
259 // . the current policy below is either one of the above
260 ReferencePolicy* _current_soft_ref_policy;
261
262 // The discovered ref lists themselves
263
264 // The active MT'ness degree of the queues below
265 uint _num_q;
266 // The maximum MT'ness degree of the queues below
267 uint _max_num_q;
268
269 // Master array of discovered oops
270 DiscoveredList* _discovered_refs;
271
272 // Arrays of lists of oops, one per thread (pointers into master array above)
273 DiscoveredList* _discoveredSoftRefs;
274 DiscoveredList* _discoveredWeakRefs;
275 DiscoveredList* _discoveredFinalRefs;
276 DiscoveredList* _discoveredPhantomRefs;
277
278 public:
279 static int number_of_subclasses_of_ref() { return (REF_PHANTOM - REF_OTHER); }
280
281 uint num_q() { return _num_q; }
282 uint max_num_q() { return _max_num_q; }
283 void set_active_mt_degree(uint v) { _num_q = v; }
284
285 DiscoveredList* discovered_refs() { return _discovered_refs; }
286
287 ReferencePolicy* setup_policy(bool always_clear) {
288 _current_soft_ref_policy = always_clear ?
289 _always_clear_soft_ref_policy : _default_soft_ref_policy;
290 _current_soft_ref_policy->setup(); // snapshot the policy threshold
291 return _current_soft_ref_policy;
292 }
293
294 // Process references with a certain reachability level.
295 size_t process_discovered_reflist(DiscoveredList refs_lists[],
296 ReferencePolicy* policy,
297 bool clear_referent,
298 BoolObjectClosure* is_alive,
299 OopClosure* keep_alive,
300 VoidClosure* complete_gc,
301 AbstractRefProcTaskExecutor* task_executor);
302
303 void process_phaseJNI(BoolObjectClosure* is_alive,
304 OopClosure* keep_alive,
305 VoidClosure* complete_gc);
306
307 // Work methods used by the method process_discovered_reflist
308 // Phase1: keep alive all those referents that are otherwise
309 // dead but which must be kept alive by policy (and their closure).
310 void process_phase1(DiscoveredList& refs_list,
311 ReferencePolicy* policy,
312 BoolObjectClosure* is_alive,
313 OopClosure* keep_alive,
314 VoidClosure* complete_gc);
315 // Phase2: remove all those references whose referents are
316 // reachable.
317 inline void process_phase2(DiscoveredList& refs_list,
318 BoolObjectClosure* is_alive,
319 OopClosure* keep_alive,
320 VoidClosure* complete_gc) {
321 if (discovery_is_atomic()) {
322 // complete_gc is ignored in this case for this phase
323 pp2_work(refs_list, is_alive, keep_alive);
324 } else {
325 assert(complete_gc != NULL, "Error");
326 pp2_work_concurrent_discovery(refs_list, is_alive,
327 keep_alive, complete_gc);
328 }
329 }
330 // Work methods in support of process_phase2
331 void pp2_work(DiscoveredList& refs_list,
332 BoolObjectClosure* is_alive,
333 OopClosure* keep_alive);
334 void pp2_work_concurrent_discovery(
335 DiscoveredList& refs_list,
336 BoolObjectClosure* is_alive,
337 OopClosure* keep_alive,
338 VoidClosure* complete_gc);
339 // Phase3: process the referents by either clearing them
340 // or keeping them alive (and their closure)
341 void process_phase3(DiscoveredList& refs_list,
342 bool clear_referent,
343 BoolObjectClosure* is_alive,
344 OopClosure* keep_alive,
345 VoidClosure* complete_gc);
346
347 // Enqueue references with a certain reachability level
348 void enqueue_discovered_reflist(DiscoveredList& refs_list, HeapWord* pending_list_addr);
349
350 // "Preclean" all the discovered reference lists
351 // by removing references with strongly reachable referents.
352 // The first argument is a predicate on an oop that indicates
353 // its (strong) reachability and the second is a closure that
354 // may be used to incrementalize or abort the precleaning process.
355 // The caller is responsible for taking care of potential
356 // interference with concurrent operations on these lists
357 // (or predicates involved) by other threads. Currently
358 // only used by the CMS collector.
359 void preclean_discovered_references(BoolObjectClosure* is_alive,
360 OopClosure* keep_alive,
361 VoidClosure* complete_gc,
362 YieldClosure* yield,
363 GCTimer* gc_timer);
364
365 // Delete entries in the discovered lists that have
366 // either a null referent or are not active. Such
367 // Reference objects can result from the clearing
368 // or enqueueing of Reference objects concurrent
369 // with their discovery by a (concurrent) collector.
370 // For a definition of "active" see java.lang.ref.Reference;
371 // Refs are born active, become inactive when enqueued,
372 // and never become active again. The state of being
373 // active is encoded as follows: A Ref is active
374 // if and only if its "next" field is NULL.
375 void clean_up_discovered_references();
376 void clean_up_discovered_reflist(DiscoveredList& refs_list);
377
378 // Returns the name of the discovered reference list
379 // occupying the i / _num_q slot.
380 const char* list_name(uint i);
381
382 void enqueue_discovered_reflists(HeapWord* pending_list_addr, AbstractRefProcTaskExecutor* task_executor);
383
384 protected:
385 // Set the 'discovered' field of the given reference to
386 // the given value - emitting post barriers depending upon
387 // the value of _discovered_list_needs_post_barrier.
388 void set_discovered(oop ref, oop value);
389
390 // "Preclean" the given discovered reference list
391 // by removing references with strongly reachable referents.
392 // Currently used in support of CMS only.
393 void preclean_discovered_reflist(DiscoveredList& refs_list,
394 BoolObjectClosure* is_alive,
395 OopClosure* keep_alive,
396 VoidClosure* complete_gc,
397 YieldClosure* yield);
398
399 // round-robin mod _num_q (not: _not_ mode _max_num_q)
400 uint next_id() {
401 uint id = _next_id;
402 if (++_next_id == _num_q) {
403 _next_id = 0;
404 }
405 return id;
406 }
407 DiscoveredList* get_discovered_list(ReferenceType rt);
408 inline void add_to_discovered_list_mt(DiscoveredList& refs_list, oop obj,
409 HeapWord* discovered_addr);
410 void verify_ok_to_handle_reflists() PRODUCT_RETURN;
411
412 void clear_discovered_references(DiscoveredList& refs_list);
413 void abandon_partial_discovered_list(DiscoveredList& refs_list);
414
415 // Calculate the number of jni handles.
416 unsigned int count_jni_refs();
417
418 // Balances reference queues.
419 void balance_queues(DiscoveredList ref_lists[]);
420
421 // Update (advance) the soft ref master clock field.
422 void update_soft_ref_master_clock();
423
424 public:
425 // Default parameters give you a vanilla reference processor.
426 ReferenceProcessor(MemRegion span,
427 bool mt_processing = false, uint mt_processing_degree = 1,
428 bool mt_discovery = false, uint mt_discovery_degree = 1,
429 bool atomic_discovery = true,
430 BoolObjectClosure* is_alive_non_header = NULL,
431 bool discovered_list_needs_post_barrier = false);
432
433 // RefDiscoveryPolicy values
434 enum DiscoveryPolicy {
435 ReferenceBasedDiscovery = 0,
436 ReferentBasedDiscovery = 1,
437 DiscoveryPolicyMin = ReferenceBasedDiscovery,
438 DiscoveryPolicyMax = ReferentBasedDiscovery
439 };
440
441 static void init_statics();
442
443 public:
444 // get and set "is_alive_non_header" field
445 BoolObjectClosure* is_alive_non_header() {
446 return _is_alive_non_header;
447 }
448 void set_is_alive_non_header(BoolObjectClosure* is_alive_non_header) {
449 _is_alive_non_header = is_alive_non_header;
450 }
451
452 // get and set span
453 MemRegion span() { return _span; }
454 void set_span(MemRegion span) { _span = span; }
455
456 // start and stop weak ref discovery
457 void enable_discovery(bool verify_disabled, bool check_no_refs);
458 void disable_discovery() { _discovering_refs = false; }
459 bool discovery_enabled() { return _discovering_refs; }
460
461 // whether discovery is atomic wrt other collectors
462 bool discovery_is_atomic() const { return _discovery_is_atomic; }
463 void set_atomic_discovery(bool atomic) { _discovery_is_atomic = atomic; }
464
465 // whether the JDK in which we are embedded is a pre-4965777 JDK,
466 // and thus whether or not it uses the discovered field to chain
467 // the entries in the pending list.
468 static bool pending_list_uses_discovered_field() {
469 return _pending_list_uses_discovered_field;
470 }
471
472 // whether discovery is done by multiple threads same-old-timeously
473 bool discovery_is_mt() const { return _discovery_is_mt; }
474 void set_mt_discovery(bool mt) { _discovery_is_mt = mt; }
475
476 // Whether we are in a phase when _processing_ is MT.
477 bool processing_is_mt() const { return _processing_is_mt; }
478 void set_mt_processing(bool mt) { _processing_is_mt = mt; }
479
480 // whether all enqueueing of weak references is complete
481 bool enqueuing_is_done() { return _enqueuing_is_done; }
482 void set_enqueuing_is_done(bool v) { _enqueuing_is_done = v; }
483
484 // iterate over oops
485 void weak_oops_do(OopClosure* f); // weak roots
486
487 // Balance each of the discovered lists.
488 void balance_all_queues();
489 void verify_list(DiscoveredList& ref_list);
490
491 // Discover a Reference object, using appropriate discovery criteria
492 bool discover_reference(oop obj, ReferenceType rt);
493
494 // Process references found during GC (called by the garbage collector)
495 ReferenceProcessorStats
496 process_discovered_references(BoolObjectClosure* is_alive,
497 OopClosure* keep_alive,
498 VoidClosure* complete_gc,
499 AbstractRefProcTaskExecutor* task_executor,
500 GCTimer *gc_timer);
501
502 // Enqueue references at end of GC (called by the garbage collector)
503 bool enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor = NULL);
504
505 // If a discovery is in process that is being superceded, abandon it: all
506 // the discovered lists will be empty, and all the objects on them will
507 // have NULL discovered fields. Must be called only at a safepoint.
508 void abandon_partial_discovery();
509
510 // debugging
511 void verify_no_references_recorded() PRODUCT_RETURN;
512 void verify_referent(oop obj) PRODUCT_RETURN;
513
514 // clear the discovered lists (unlinking each entry).
515 void clear_discovered_references() PRODUCT_RETURN;
516 };
517
518 // A utility class to disable reference discovery in
519 // the scope which contains it, for given ReferenceProcessor.
520 class NoRefDiscovery: StackObj {
521 private:
522 ReferenceProcessor* _rp;
523 bool _was_discovering_refs;
524 public:
525 NoRefDiscovery(ReferenceProcessor* rp) : _rp(rp) {
526 _was_discovering_refs = _rp->discovery_enabled();
527 if (_was_discovering_refs) {
528 _rp->disable_discovery();
529 }
530 }
531
532 ~NoRefDiscovery() {
533 if (_was_discovering_refs) {
534 _rp->enable_discovery(true /*verify_disabled*/, false /*check_no_refs*/);
535 }
536 }
537 };
538
539
540 // A utility class to temporarily mutate the span of the
541 // given ReferenceProcessor in the scope that contains it.
542 class ReferenceProcessorSpanMutator: StackObj {
543 private:
544 ReferenceProcessor* _rp;
545 MemRegion _saved_span;
546
547 public:
548 ReferenceProcessorSpanMutator(ReferenceProcessor* rp,
549 MemRegion span):
550 _rp(rp) {
551 _saved_span = _rp->span();
552 _rp->set_span(span);
553 }
554
555 ~ReferenceProcessorSpanMutator() {
556 _rp->set_span(_saved_span);
557 }
558 };
559
560 // A utility class to temporarily change the MT'ness of
561 // reference discovery for the given ReferenceProcessor
562 // in the scope that contains it.
563 class ReferenceProcessorMTDiscoveryMutator: StackObj {
564 private:
565 ReferenceProcessor* _rp;
566 bool _saved_mt;
567
568 public:
569 ReferenceProcessorMTDiscoveryMutator(ReferenceProcessor* rp,
570 bool mt):
571 _rp(rp) {
572 _saved_mt = _rp->discovery_is_mt();
573 _rp->set_mt_discovery(mt);
574 }
575
576 ~ReferenceProcessorMTDiscoveryMutator() {
577 _rp->set_mt_discovery(_saved_mt);
578 }
579 };
580
581
582 // A utility class to temporarily change the disposition
583 // of the "is_alive_non_header" closure field of the
584 // given ReferenceProcessor in the scope that contains it.
585 class ReferenceProcessorIsAliveMutator: StackObj {
586 private:
587 ReferenceProcessor* _rp;
588 BoolObjectClosure* _saved_cl;
589
590 public:
591 ReferenceProcessorIsAliveMutator(ReferenceProcessor* rp,
592 BoolObjectClosure* cl):
593 _rp(rp) {
594 _saved_cl = _rp->is_alive_non_header();
595 _rp->set_is_alive_non_header(cl);
596 }
597
598 ~ReferenceProcessorIsAliveMutator() {
599 _rp->set_is_alive_non_header(_saved_cl);
600 }
601 };
602
603 // A utility class to temporarily change the disposition
604 // of the "discovery_is_atomic" field of the
605 // given ReferenceProcessor in the scope that contains it.
606 class ReferenceProcessorAtomicMutator: StackObj {
607 private:
608 ReferenceProcessor* _rp;
609 bool _saved_atomic_discovery;
610
611 public:
612 ReferenceProcessorAtomicMutator(ReferenceProcessor* rp,
613 bool atomic):
614 _rp(rp) {
615 _saved_atomic_discovery = _rp->discovery_is_atomic();
616 _rp->set_atomic_discovery(atomic);
617 }
618
619 ~ReferenceProcessorAtomicMutator() {
620 _rp->set_atomic_discovery(_saved_atomic_discovery);
621 }
622 };
623
624
625 // A utility class to temporarily change the MT processing
626 // disposition of the given ReferenceProcessor instance
627 // in the scope that contains it.
628 class ReferenceProcessorMTProcMutator: StackObj {
629 private:
630 ReferenceProcessor* _rp;
631 bool _saved_mt;
632
633 public:
634 ReferenceProcessorMTProcMutator(ReferenceProcessor* rp,
635 bool mt):
636 _rp(rp) {
637 _saved_mt = _rp->processing_is_mt();
638 _rp->set_mt_processing(mt);
639 }
640
641 ~ReferenceProcessorMTProcMutator() {
642 _rp->set_mt_processing(_saved_mt);
643 }
644 };
645
646
647 // This class is an interface used to implement task execution for the
648 // reference processing.
649 class AbstractRefProcTaskExecutor {
650 public:
651
652 // Abstract tasks to execute.
653 class ProcessTask;
654 class EnqueueTask;
655
656 // Executes a task using worker threads.
657 virtual void execute(ProcessTask& task) = 0;
658 virtual void execute(EnqueueTask& task) = 0;
659
660 // Switch to single threaded mode.
661 virtual void set_single_threaded_mode() { };
662 };
663
664 // Abstract reference processing task to execute.
665 class AbstractRefProcTaskExecutor::ProcessTask {
666 protected:
667 ProcessTask(ReferenceProcessor& ref_processor,
668 DiscoveredList refs_lists[],
669 bool marks_oops_alive)
670 : _ref_processor(ref_processor),
671 _refs_lists(refs_lists),
672 _marks_oops_alive(marks_oops_alive)
673 { }
674
675 public:
676 virtual void work(unsigned int work_id, BoolObjectClosure& is_alive,
677 OopClosure& keep_alive,
678 VoidClosure& complete_gc) = 0;
679
680 // Returns true if a task marks some oops as alive.
681 bool marks_oops_alive() const
682 { return _marks_oops_alive; }
683
684 protected:
685 ReferenceProcessor& _ref_processor;
686 DiscoveredList* _refs_lists;
687 const bool _marks_oops_alive;
688 };
689
690 // Abstract reference processing task to execute.
691 class AbstractRefProcTaskExecutor::EnqueueTask {
692 protected:
693 EnqueueTask(ReferenceProcessor& ref_processor,
694 DiscoveredList refs_lists[],
695 HeapWord* pending_list_addr,
696 int n_queues)
697 : _ref_processor(ref_processor),
698 _refs_lists(refs_lists),
699 _pending_list_addr(pending_list_addr),
700 _n_queues(n_queues)
701 { }
702
703 public:
704 virtual void work(unsigned int work_id) = 0;
705
706 protected:
707 ReferenceProcessor& _ref_processor;
708 DiscoveredList* _refs_lists;
709 HeapWord* _pending_list_addr;
710 int _n_queues;
711 };
712
713 #endif // SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP