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 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 #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; 102 103 DEBUG_ONLY( 104 oop _first_seen; // cyclic linked list check 105 ) 106 107 NOT_PRODUCT( 108 size_t _processed; 109 size_t _removed; 110 ) 111 112 public: 113 inline DiscoveredListIterator(DiscoveredList& refs_list, 114 OopClosure* keep_alive, 115 BoolObjectClosure* is_alive): 116 _refs_list(refs_list), 117 _prev_next(refs_list.adr_head()), 118 _prev(NULL), 119 _ref(refs_list.head()), 120 #ifdef ASSERT 121 _first_seen(refs_list.head()), 122 #endif 123 #ifndef PRODUCT 124 _processed(0), 125 _removed(0), 126 #endif 127 _next(NULL), 128 _keep_alive(keep_alive), 129 _is_alive(is_alive) 130 { } 131 132 // End Of List. 133 inline bool has_next() const { return _ref != NULL; } 134 135 // Get oop to the Reference object. 136 inline oop obj() const { return _ref; } 137 138 // Get oop to the referent object. 139 inline oop referent() const { return _referent; } 140 141 // Returns true if referent is alive. 142 inline bool is_referent_alive() const { 143 return _is_alive->do_object_b(_referent); 144 } 145 146 // Loads data for the current reference. 147 // The "allow_null_referent" argument tells us to allow for the possibility 148 // of a NULL referent in the discovered Reference object. This typically 149 // happens in the case of concurrent collectors that may have done the 150 // discovery concurrently, or interleaved, with mutator execution. 151 void load_ptrs(DEBUG_ONLY(bool allow_null_referent)); 152 153 // Move to the next discovered reference. 154 inline void next() { 155 _prev_next = _discovered_addr; 156 _prev = _ref; 157 move_to_next(); 158 } 159 160 // Remove the current reference from the list 161 void remove(); 162 163 // Make the Reference object active again. 164 void make_active(); 165 166 // Make the referent alive. 167 inline void make_referent_alive() { 168 if (UseCompressedOops) { 169 _keep_alive->do_oop((narrowOop*)_referent_addr); 170 } else { 171 _keep_alive->do_oop((oop*)_referent_addr); 172 } 173 } 174 175 // Update the discovered field. 176 inline void update_discovered() { 177 // First _prev_next ref actually points into DiscoveredList (gross). 178 if (UseCompressedOops) { 179 if (!oopDesc::is_null(*(narrowOop*)_prev_next)) { 180 _keep_alive->do_oop((narrowOop*)_prev_next); 181 } 182 } else { 183 if (!oopDesc::is_null(*(oop*)_prev_next)) { 184 _keep_alive->do_oop((oop*)_prev_next); 185 } 186 } 187 } 188 189 // NULL out referent pointer. 190 void clear_referent(); 191 192 // Statistics 193 NOT_PRODUCT( 194 inline size_t processed() const { return _processed; } 195 inline size_t removed() const { return _removed; } 196 ) 197 198 inline void move_to_next() { 199 if (_ref == _next) { 200 // End of the list. 201 _ref = NULL; 202 } else { 203 _ref = _next; 204 } 205 assert(_ref != _first_seen, "cyclic ref_list found"); 206 NOT_PRODUCT(_processed++); 207 } 208 }; 209 210 class ReferenceProcessor : public CHeapObj<mtGC> { 211 212 private: 213 size_t total_count(DiscoveredList lists[]); 214 215 protected: 216 // Compatibility with pre-4965777 JDK's 217 static bool _pending_list_uses_discovered_field; 218 219 // The SoftReference master timestamp clock 220 static jlong _soft_ref_timestamp_clock; 221 222 MemRegion _span; // (right-open) interval of heap 223 // subject to wkref discovery 224 225 bool _discovering_refs; // true when discovery enabled 226 bool _discovery_is_atomic; // if discovery is atomic wrt 227 // other collectors in configuration 228 bool _discovery_is_mt; // true if reference discovery is MT. 229 230 // If true, setting "next" field of a discovered refs list requires 231 // write barrier(s). (Must be true if used in a collector in which 232 // elements of a discovered list may be moved during discovery: for 233 // example, a collector like Garbage-First that moves objects during a 234 // long-term concurrent marking phase that does weak reference 235 // discovery.) 236 bool _discovered_list_needs_barrier; 237 238 BarrierSet* _bs; // Cached copy of BarrierSet. 239 bool _enqueuing_is_done; // true if all weak references enqueued 240 bool _processing_is_mt; // true during phases when 241 // reference processing is MT. 242 uint _next_id; // round-robin mod _num_q counter in 243 // support of work distribution 244 245 // For collectors that do not keep GC liveness information 246 // in the object header, this field holds a closure that 247 // helps the reference processor determine the reachability 248 // of an oop. It is currently initialized to NULL for all 249 // collectors except for CMS and G1. 250 BoolObjectClosure* _is_alive_non_header; 251 252 // Soft ref clearing policies 253 // . the default policy 254 static ReferencePolicy* _default_soft_ref_policy; 255 // . the "clear all" policy 256 static ReferencePolicy* _always_clear_soft_ref_policy; 257 // . the current policy below is either one of the above 258 ReferencePolicy* _current_soft_ref_policy; 259 260 // The discovered ref lists themselves 261 262 // The active MT'ness degree of the queues below 263 uint _num_q; 264 // The maximum MT'ness degree of the queues below 265 uint _max_num_q; 266 267 // Master array of discovered oops 268 DiscoveredList* _discovered_refs; 269 270 // Arrays of lists of oops, one per thread (pointers into master array above) 271 DiscoveredList* _discoveredSoftRefs; 272 DiscoveredList* _discoveredWeakRefs; 273 DiscoveredList* _discoveredFinalRefs; 274 DiscoveredList* _discoveredPhantomRefs; 275 276 public: 277 static int number_of_subclasses_of_ref() { return (REF_PHANTOM - REF_OTHER); } 278 279 uint num_q() { return _num_q; } 280 uint max_num_q() { return _max_num_q; } 281 void set_active_mt_degree(uint v) { _num_q = v; } 282 283 DiscoveredList* discovered_refs() { return _discovered_refs; } 284 285 ReferencePolicy* setup_policy(bool always_clear) { 286 _current_soft_ref_policy = always_clear ? 287 _always_clear_soft_ref_policy : _default_soft_ref_policy; 288 _current_soft_ref_policy->setup(); // snapshot the policy threshold 289 return _current_soft_ref_policy; 290 } 291 292 // Process references with a certain reachability level. 293 size_t process_discovered_reflist(DiscoveredList refs_lists[], 294 ReferencePolicy* policy, 295 bool clear_referent, 296 BoolObjectClosure* is_alive, 297 OopClosure* keep_alive, 298 VoidClosure* complete_gc, 299 AbstractRefProcTaskExecutor* task_executor); 300 301 void process_phaseJNI(BoolObjectClosure* is_alive, 302 OopClosure* keep_alive, 303 VoidClosure* complete_gc); 304 305 // Work methods used by the method process_discovered_reflist 306 // Phase1: keep alive all those referents that are otherwise 307 // dead but which must be kept alive by policy (and their closure). 308 void process_phase1(DiscoveredList& refs_list, 309 ReferencePolicy* policy, 310 BoolObjectClosure* is_alive, 311 OopClosure* keep_alive, 312 VoidClosure* complete_gc); 313 // Phase2: remove all those references whose referents are 314 // reachable. 315 inline void process_phase2(DiscoveredList& refs_list, 316 BoolObjectClosure* is_alive, 317 OopClosure* keep_alive, 318 VoidClosure* complete_gc) { 319 if (discovery_is_atomic()) { 320 // complete_gc is ignored in this case for this phase 321 pp2_work(refs_list, is_alive, keep_alive); 322 } else { 323 assert(complete_gc != NULL, "Error"); 324 pp2_work_concurrent_discovery(refs_list, is_alive, 325 keep_alive, complete_gc); 326 } 327 } 328 // Work methods in support of process_phase2 329 void pp2_work(DiscoveredList& refs_list, 330 BoolObjectClosure* is_alive, 331 OopClosure* keep_alive); 332 void pp2_work_concurrent_discovery( 333 DiscoveredList& refs_list, 334 BoolObjectClosure* is_alive, 335 OopClosure* keep_alive, 336 VoidClosure* complete_gc); 337 // Phase3: process the referents by either clearing them 338 // or keeping them alive (and their closure) 339 void process_phase3(DiscoveredList& refs_list, 340 bool clear_referent, 341 BoolObjectClosure* is_alive, 342 OopClosure* keep_alive, 343 VoidClosure* complete_gc); 344 345 // Enqueue references with a certain reachability level 346 void enqueue_discovered_reflist(DiscoveredList& refs_list, HeapWord* pending_list_addr); 347 348 // "Preclean" all the discovered reference lists 349 // by removing references with strongly reachable referents. 350 // The first argument is a predicate on an oop that indicates 351 // its (strong) reachability and the second is a closure that 352 // may be used to incrementalize or abort the precleaning process. 353 // The caller is responsible for taking care of potential 354 // interference with concurrent operations on these lists 355 // (or predicates involved) by other threads. Currently 356 // only used by the CMS collector. 357 void preclean_discovered_references(BoolObjectClosure* is_alive, 358 OopClosure* keep_alive, 359 VoidClosure* complete_gc, 360 YieldClosure* yield, 361 GCTimer* gc_timer); 362 363 // Delete entries in the discovered lists that have 364 // either a null referent or are not active. Such 365 // Reference objects can result from the clearing 366 // or enqueueing of Reference objects concurrent 367 // with their discovery by a (concurrent) collector. 368 // For a definition of "active" see java.lang.ref.Reference; 369 // Refs are born active, become inactive when enqueued, 370 // and never become active again. The state of being 371 // active is encoded as follows: A Ref is active 372 // if and only if its "next" field is NULL. 373 void clean_up_discovered_references(); 374 void clean_up_discovered_reflist(DiscoveredList& refs_list); 375 376 // Returns the name of the discovered reference list 377 // occupying the i / _num_q slot. 378 const char* list_name(uint i); 379 380 void enqueue_discovered_reflists(HeapWord* pending_list_addr, AbstractRefProcTaskExecutor* task_executor); 381 382 protected: 383 // Set the 'discovered' field of the given reference to 384 // the given value - emitting barriers depending upon 385 // the value of _discovered_list_needs_barrier. 386 void set_discovered(oop ref, oop value); 387 388 // "Preclean" the given discovered reference list 389 // by removing references with strongly reachable referents. 390 // Currently used in support of CMS only. 391 void preclean_discovered_reflist(DiscoveredList& refs_list, 392 BoolObjectClosure* is_alive, 393 OopClosure* keep_alive, 394 VoidClosure* complete_gc, 395 YieldClosure* yield); 396 397 // round-robin mod _num_q (not: _not_ mode _max_num_q) 398 uint next_id() { 399 uint id = _next_id; 400 if (++_next_id == _num_q) { 401 _next_id = 0; 402 } 403 return id; 404 } 405 DiscoveredList* get_discovered_list(ReferenceType rt); 406 inline void add_to_discovered_list_mt(DiscoveredList& refs_list, oop obj, 407 HeapWord* discovered_addr); 408 void verify_ok_to_handle_reflists() PRODUCT_RETURN; 409 410 void clear_discovered_references(DiscoveredList& refs_list); 411 void abandon_partial_discovered_list(DiscoveredList& refs_list); 412 413 // Calculate the number of jni handles. 414 unsigned int count_jni_refs(); 415 416 // Balances reference queues. 417 void balance_queues(DiscoveredList ref_lists[]); 418 419 // Update (advance) the soft ref master clock field. 420 void update_soft_ref_master_clock(); 421 422 public: 423 // constructor 424 ReferenceProcessor(): 425 _span((HeapWord*)NULL, (HeapWord*)NULL), 426 _discovered_refs(NULL), 427 _discoveredSoftRefs(NULL), _discoveredWeakRefs(NULL), 428 _discoveredFinalRefs(NULL), _discoveredPhantomRefs(NULL), 429 _discovering_refs(false), 430 _discovery_is_atomic(true), 431 _enqueuing_is_done(false), 432 _discovery_is_mt(false), 433 _discovered_list_needs_barrier(false), 434 _bs(NULL), 435 _is_alive_non_header(NULL), 436 _num_q(0), 437 _max_num_q(0), 438 _processing_is_mt(false), 439 _next_id(0) 440 { } 441 442 // Default parameters give you a vanilla reference processor. 443 ReferenceProcessor(MemRegion span, 444 bool mt_processing = false, uint mt_processing_degree = 1, 445 bool mt_discovery = false, uint mt_discovery_degree = 1, 446 bool atomic_discovery = true, 447 BoolObjectClosure* is_alive_non_header = NULL, 448 bool discovered_list_needs_barrier = false); 449 450 // RefDiscoveryPolicy values 451 enum DiscoveryPolicy { 452 ReferenceBasedDiscovery = 0, 453 ReferentBasedDiscovery = 1, 454 DiscoveryPolicyMin = ReferenceBasedDiscovery, 455 DiscoveryPolicyMax = ReferentBasedDiscovery 456 }; 457 458 static void init_statics(); 459 460 public: 461 // get and set "is_alive_non_header" field 462 BoolObjectClosure* is_alive_non_header() { 463 return _is_alive_non_header; 464 } 465 void set_is_alive_non_header(BoolObjectClosure* is_alive_non_header) { 466 _is_alive_non_header = is_alive_non_header; 467 } 468 469 // get and set span 470 MemRegion span() { return _span; } 471 void set_span(MemRegion span) { _span = span; } 472 473 // start and stop weak ref discovery 474 void enable_discovery(bool verify_disabled, bool check_no_refs); 475 void disable_discovery() { _discovering_refs = false; } 476 bool discovery_enabled() { return _discovering_refs; } 477 478 // whether discovery is atomic wrt other collectors 479 bool discovery_is_atomic() const { return _discovery_is_atomic; } 480 void set_atomic_discovery(bool atomic) { _discovery_is_atomic = atomic; } 481 482 // whether the JDK in which we are embedded is a pre-4965777 JDK, 483 // and thus whether or not it uses the discovered field to chain 484 // the entries in the pending list. 485 static bool pending_list_uses_discovered_field() { 486 return _pending_list_uses_discovered_field; 487 } 488 489 // whether discovery is done by multiple threads same-old-timeously 490 bool discovery_is_mt() const { return _discovery_is_mt; } 491 void set_mt_discovery(bool mt) { _discovery_is_mt = mt; } 492 493 // Whether we are in a phase when _processing_ is MT. 494 bool processing_is_mt() const { return _processing_is_mt; } 495 void set_mt_processing(bool mt) { _processing_is_mt = mt; } 496 497 // whether all enqueueing of weak references is complete 498 bool enqueuing_is_done() { return _enqueuing_is_done; } 499 void set_enqueuing_is_done(bool v) { _enqueuing_is_done = v; } 500 501 // iterate over oops 502 void weak_oops_do(OopClosure* f); // weak roots 503 504 // Balance each of the discovered lists. 505 void balance_all_queues(); 506 void verify_list(DiscoveredList& ref_list); 507 508 // Discover a Reference object, using appropriate discovery criteria 509 bool discover_reference(oop obj, ReferenceType rt); 510 511 // Process references found during GC (called by the garbage collector) 512 ReferenceProcessorStats 513 process_discovered_references(BoolObjectClosure* is_alive, 514 OopClosure* keep_alive, 515 VoidClosure* complete_gc, 516 AbstractRefProcTaskExecutor* task_executor, 517 GCTimer *gc_timer); 518 519 // Enqueue references at end of GC (called by the garbage collector) 520 bool enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor = NULL); 521 522 // If a discovery is in process that is being superceded, abandon it: all 523 // the discovered lists will be empty, and all the objects on them will 524 // have NULL discovered fields. Must be called only at a safepoint. 525 void abandon_partial_discovery(); 526 527 // debugging 528 void verify_no_references_recorded() PRODUCT_RETURN; 529 void verify_referent(oop obj) PRODUCT_RETURN; 530 531 // clear the discovered lists (unlinking each entry). 532 void clear_discovered_references() PRODUCT_RETURN; 533 }; 534 535 // A utility class to disable reference discovery in 536 // the scope which contains it, for given ReferenceProcessor. 537 class NoRefDiscovery: StackObj { 538 private: 539 ReferenceProcessor* _rp; 540 bool _was_discovering_refs; 541 public: 542 NoRefDiscovery(ReferenceProcessor* rp) : _rp(rp) { 543 _was_discovering_refs = _rp->discovery_enabled(); 544 if (_was_discovering_refs) { 545 _rp->disable_discovery(); 546 } 547 } 548 549 ~NoRefDiscovery() { 550 if (_was_discovering_refs) { 551 _rp->enable_discovery(true /*verify_disabled*/, false /*check_no_refs*/); 552 } 553 } 554 }; 555 556 557 // A utility class to temporarily mutate the span of the 558 // given ReferenceProcessor in the scope that contains it. 559 class ReferenceProcessorSpanMutator: StackObj { 560 private: 561 ReferenceProcessor* _rp; 562 MemRegion _saved_span; 563 564 public: 565 ReferenceProcessorSpanMutator(ReferenceProcessor* rp, 566 MemRegion span): 567 _rp(rp) { 568 _saved_span = _rp->span(); 569 _rp->set_span(span); 570 } 571 572 ~ReferenceProcessorSpanMutator() { 573 _rp->set_span(_saved_span); 574 } 575 }; 576 577 // A utility class to temporarily change the MT'ness of 578 // reference discovery for the given ReferenceProcessor 579 // in the scope that contains it. 580 class ReferenceProcessorMTDiscoveryMutator: StackObj { 581 private: 582 ReferenceProcessor* _rp; 583 bool _saved_mt; 584 585 public: 586 ReferenceProcessorMTDiscoveryMutator(ReferenceProcessor* rp, 587 bool mt): 588 _rp(rp) { 589 _saved_mt = _rp->discovery_is_mt(); 590 _rp->set_mt_discovery(mt); 591 } 592 593 ~ReferenceProcessorMTDiscoveryMutator() { 594 _rp->set_mt_discovery(_saved_mt); 595 } 596 }; 597 598 599 // A utility class to temporarily change the disposition 600 // of the "is_alive_non_header" closure field of the 601 // given ReferenceProcessor in the scope that contains it. 602 class ReferenceProcessorIsAliveMutator: StackObj { 603 private: 604 ReferenceProcessor* _rp; 605 BoolObjectClosure* _saved_cl; 606 607 public: 608 ReferenceProcessorIsAliveMutator(ReferenceProcessor* rp, 609 BoolObjectClosure* cl): 610 _rp(rp) { 611 _saved_cl = _rp->is_alive_non_header(); 612 _rp->set_is_alive_non_header(cl); 613 } 614 615 ~ReferenceProcessorIsAliveMutator() { 616 _rp->set_is_alive_non_header(_saved_cl); 617 } 618 }; 619 620 // A utility class to temporarily change the disposition 621 // of the "discovery_is_atomic" field of the 622 // given ReferenceProcessor in the scope that contains it. 623 class ReferenceProcessorAtomicMutator: StackObj { 624 private: 625 ReferenceProcessor* _rp; 626 bool _saved_atomic_discovery; 627 628 public: 629 ReferenceProcessorAtomicMutator(ReferenceProcessor* rp, 630 bool atomic): 631 _rp(rp) { 632 _saved_atomic_discovery = _rp->discovery_is_atomic(); 633 _rp->set_atomic_discovery(atomic); 634 } 635 636 ~ReferenceProcessorAtomicMutator() { 637 _rp->set_atomic_discovery(_saved_atomic_discovery); 638 } 639 }; 640 641 642 // A utility class to temporarily change the MT processing 643 // disposition of the given ReferenceProcessor instance 644 // in the scope that contains it. 645 class ReferenceProcessorMTProcMutator: StackObj { 646 private: 647 ReferenceProcessor* _rp; 648 bool _saved_mt; 649 650 public: 651 ReferenceProcessorMTProcMutator(ReferenceProcessor* rp, 652 bool mt): 653 _rp(rp) { 654 _saved_mt = _rp->processing_is_mt(); 655 _rp->set_mt_processing(mt); 656 } 657 658 ~ReferenceProcessorMTProcMutator() { 659 _rp->set_mt_processing(_saved_mt); 660 } 661 }; 662 663 664 // This class is an interface used to implement task execution for the 665 // reference processing. 666 class AbstractRefProcTaskExecutor { 667 public: 668 669 // Abstract tasks to execute. 670 class ProcessTask; 671 class EnqueueTask; 672 673 // Executes a task using worker threads. 674 virtual void execute(ProcessTask& task) = 0; 675 virtual void execute(EnqueueTask& task) = 0; 676 677 // Switch to single threaded mode. 678 virtual void set_single_threaded_mode() { }; 679 }; 680 681 // Abstract reference processing task to execute. 682 class AbstractRefProcTaskExecutor::ProcessTask { 683 protected: 684 ProcessTask(ReferenceProcessor& ref_processor, 685 DiscoveredList refs_lists[], 686 bool marks_oops_alive) 687 : _ref_processor(ref_processor), 688 _refs_lists(refs_lists), 689 _marks_oops_alive(marks_oops_alive) 690 { } 691 692 public: 693 virtual void work(unsigned int work_id, BoolObjectClosure& is_alive, 694 OopClosure& keep_alive, 695 VoidClosure& complete_gc) = 0; 696 697 // Returns true if a task marks some oops as alive. 698 bool marks_oops_alive() const 699 { return _marks_oops_alive; } 700 701 protected: 702 ReferenceProcessor& _ref_processor; 703 DiscoveredList* _refs_lists; 704 const bool _marks_oops_alive; 705 }; 706 707 // Abstract reference processing task to execute. 708 class AbstractRefProcTaskExecutor::EnqueueTask { 709 protected: 710 EnqueueTask(ReferenceProcessor& ref_processor, 711 DiscoveredList refs_lists[], 712 HeapWord* pending_list_addr, 713 int n_queues) 714 : _ref_processor(ref_processor), 715 _refs_lists(refs_lists), 716 _pending_list_addr(pending_list_addr), 717 _n_queues(n_queues) 718 { } 719 720 public: 721 virtual void work(unsigned int work_id) = 0; 722 723 protected: 724 ReferenceProcessor& _ref_processor; 725 DiscoveredList* _refs_lists; 726 HeapWord* _pending_list_addr; 727 int _n_queues; 728 }; 729 730 #endif // SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP