Fri, 15 Apr 2011 09:36:28 -0400
7032407: Crash in LinkResolver::runtime_resolve_virtual_method()
Summary: Make CDS reorder vtables so that dump time vtables match run time order, so when redefine classes reinitializes them, they aren't in the wrong order.
Reviewed-by: dcubed, acorn
1 /*
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25 #ifndef SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP
26 #define SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP
28 #include "memory/referencePolicy.hpp"
29 #include "oops/instanceRefKlass.hpp"
31 // ReferenceProcessor class encapsulates the per-"collector" processing
32 // of java.lang.Reference objects for GC. The interface is useful for supporting
33 // a generational abstraction, in particular when there are multiple
34 // generations that are being independently collected -- possibly
35 // concurrently and/or incrementally. Note, however, that the
36 // ReferenceProcessor class abstracts away from a generational setting
37 // by using only a heap interval (called "span" below), thus allowing
38 // its use in a straightforward manner in a general, non-generational
39 // setting.
40 //
41 // The basic idea is that each ReferenceProcessor object concerns
42 // itself with ("weak") reference processing in a specific "span"
43 // of the heap of interest to a specific collector. Currently,
44 // the span is a convex interval of the heap, but, efficiency
45 // apart, there seems to be no reason it couldn't be extended
46 // (with appropriate modifications) to any "non-convex interval".
48 // forward references
49 class ReferencePolicy;
50 class AbstractRefProcTaskExecutor;
51 class DiscoveredList;
53 class ReferenceProcessor : public CHeapObj {
54 protected:
55 // End of list marker
56 static oop _sentinelRef;
57 MemRegion _span; // (right-open) interval of heap
58 // subject to wkref discovery
59 bool _discovering_refs; // true when discovery enabled
60 bool _discovery_is_atomic; // if discovery is atomic wrt
61 // other collectors in configuration
62 bool _discovery_is_mt; // true if reference discovery is MT.
63 // If true, setting "next" field of a discovered refs list requires
64 // write barrier(s). (Must be true if used in a collector in which
65 // elements of a discovered list may be moved during discovery: for
66 // example, a collector like Garbage-First that moves objects during a
67 // long-term concurrent marking phase that does weak reference
68 // discovery.)
69 bool _discovered_list_needs_barrier;
70 BarrierSet* _bs; // Cached copy of BarrierSet.
71 bool _enqueuing_is_done; // true if all weak references enqueued
72 bool _processing_is_mt; // true during phases when
73 // reference processing is MT.
74 int _next_id; // round-robin mod _num_q counter in
75 // support of work distribution
77 // For collectors that do not keep GC marking information
78 // in the object header, this field holds a closure that
79 // helps the reference processor determine the reachability
80 // of an oop (the field is currently initialized to NULL for
81 // all collectors but the CMS collector).
82 BoolObjectClosure* _is_alive_non_header;
84 // Soft ref clearing policies
85 // . the default policy
86 static ReferencePolicy* _default_soft_ref_policy;
87 // . the "clear all" policy
88 static ReferencePolicy* _always_clear_soft_ref_policy;
89 // . the current policy below is either one of the above
90 ReferencePolicy* _current_soft_ref_policy;
92 // The discovered ref lists themselves
94 // The active MT'ness degree of the queues below
95 int _num_q;
96 // The maximum MT'ness degree of the queues below
97 int _max_num_q;
98 // Arrays of lists of oops, one per thread
99 DiscoveredList* _discoveredSoftRefs;
100 DiscoveredList* _discoveredWeakRefs;
101 DiscoveredList* _discoveredFinalRefs;
102 DiscoveredList* _discoveredPhantomRefs;
104 public:
105 int num_q() { return _num_q; }
106 int max_num_q() { return _max_num_q; }
107 void set_active_mt_degree(int v) { _num_q = v; }
108 DiscoveredList* discovered_soft_refs() { return _discoveredSoftRefs; }
109 static oop sentinel_ref() { return _sentinelRef; }
110 static oop* adr_sentinel_ref() { return &_sentinelRef; }
111 ReferencePolicy* setup_policy(bool always_clear) {
112 _current_soft_ref_policy = always_clear ?
113 _always_clear_soft_ref_policy : _default_soft_ref_policy;
114 _current_soft_ref_policy->setup(); // snapshot the policy threshold
115 return _current_soft_ref_policy;
116 }
118 public:
119 // Process references with a certain reachability level.
120 void process_discovered_reflist(DiscoveredList refs_lists[],
121 ReferencePolicy* policy,
122 bool clear_referent,
123 BoolObjectClosure* is_alive,
124 OopClosure* keep_alive,
125 VoidClosure* complete_gc,
126 AbstractRefProcTaskExecutor* task_executor);
128 void process_phaseJNI(BoolObjectClosure* is_alive,
129 OopClosure* keep_alive,
130 VoidClosure* complete_gc);
132 // Work methods used by the method process_discovered_reflist
133 // Phase1: keep alive all those referents that are otherwise
134 // dead but which must be kept alive by policy (and their closure).
135 void process_phase1(DiscoveredList& refs_list,
136 ReferencePolicy* policy,
137 BoolObjectClosure* is_alive,
138 OopClosure* keep_alive,
139 VoidClosure* complete_gc);
140 // Phase2: remove all those references whose referents are
141 // reachable.
142 inline void process_phase2(DiscoveredList& refs_list,
143 BoolObjectClosure* is_alive,
144 OopClosure* keep_alive,
145 VoidClosure* complete_gc) {
146 if (discovery_is_atomic()) {
147 // complete_gc is ignored in this case for this phase
148 pp2_work(refs_list, is_alive, keep_alive);
149 } else {
150 assert(complete_gc != NULL, "Error");
151 pp2_work_concurrent_discovery(refs_list, is_alive,
152 keep_alive, complete_gc);
153 }
154 }
155 // Work methods in support of process_phase2
156 void pp2_work(DiscoveredList& refs_list,
157 BoolObjectClosure* is_alive,
158 OopClosure* keep_alive);
159 void pp2_work_concurrent_discovery(
160 DiscoveredList& refs_list,
161 BoolObjectClosure* is_alive,
162 OopClosure* keep_alive,
163 VoidClosure* complete_gc);
164 // Phase3: process the referents by either clearing them
165 // or keeping them alive (and their closure)
166 void process_phase3(DiscoveredList& refs_list,
167 bool clear_referent,
168 BoolObjectClosure* is_alive,
169 OopClosure* keep_alive,
170 VoidClosure* complete_gc);
172 // Enqueue references with a certain reachability level
173 void enqueue_discovered_reflist(DiscoveredList& refs_list, HeapWord* pending_list_addr);
175 // "Preclean" all the discovered reference lists
176 // by removing references with strongly reachable referents.
177 // The first argument is a predicate on an oop that indicates
178 // its (strong) reachability and the second is a closure that
179 // may be used to incrementalize or abort the precleaning process.
180 // The caller is responsible for taking care of potential
181 // interference with concurrent operations on these lists
182 // (or predicates involved) by other threads. Currently
183 // only used by the CMS collector. should_unload_classes is
184 // used to aid assertion checking when classes are collected.
185 void preclean_discovered_references(BoolObjectClosure* is_alive,
186 OopClosure* keep_alive,
187 VoidClosure* complete_gc,
188 YieldClosure* yield,
189 bool should_unload_classes);
191 // Delete entries in the discovered lists that have
192 // either a null referent or are not active. Such
193 // Reference objects can result from the clearing
194 // or enqueueing of Reference objects concurrent
195 // with their discovery by a (concurrent) collector.
196 // For a definition of "active" see java.lang.ref.Reference;
197 // Refs are born active, become inactive when enqueued,
198 // and never become active again. The state of being
199 // active is encoded as follows: A Ref is active
200 // if and only if its "next" field is NULL.
201 void clean_up_discovered_references();
202 void clean_up_discovered_reflist(DiscoveredList& refs_list);
204 // Returns the name of the discovered reference list
205 // occupying the i / _num_q slot.
206 const char* list_name(int i);
208 void enqueue_discovered_reflists(HeapWord* pending_list_addr, AbstractRefProcTaskExecutor* task_executor);
210 protected:
211 // "Preclean" the given discovered reference list
212 // by removing references with strongly reachable referents.
213 // Currently used in support of CMS only.
214 void preclean_discovered_reflist(DiscoveredList& refs_list,
215 BoolObjectClosure* is_alive,
216 OopClosure* keep_alive,
217 VoidClosure* complete_gc,
218 YieldClosure* yield);
220 // round-robin mod _num_q (not: _not_ mode _max_num_q)
221 int next_id() {
222 int id = _next_id;
223 if (++_next_id == _num_q) {
224 _next_id = 0;
225 }
226 return id;
227 }
228 DiscoveredList* get_discovered_list(ReferenceType rt);
229 inline void add_to_discovered_list_mt(DiscoveredList& refs_list, oop obj,
230 HeapWord* discovered_addr);
231 void verify_ok_to_handle_reflists() PRODUCT_RETURN;
233 void abandon_partial_discovered_list(DiscoveredList& refs_list);
235 // Calculate the number of jni handles.
236 unsigned int count_jni_refs();
238 // Balances reference queues.
239 void balance_queues(DiscoveredList ref_lists[]);
241 // Update (advance) the soft ref master clock field.
242 void update_soft_ref_master_clock();
244 public:
245 // constructor
246 ReferenceProcessor():
247 _span((HeapWord*)NULL, (HeapWord*)NULL),
248 _discoveredSoftRefs(NULL), _discoveredWeakRefs(NULL),
249 _discoveredFinalRefs(NULL), _discoveredPhantomRefs(NULL),
250 _discovering_refs(false),
251 _discovery_is_atomic(true),
252 _enqueuing_is_done(false),
253 _discovery_is_mt(false),
254 _discovered_list_needs_barrier(false),
255 _bs(NULL),
256 _is_alive_non_header(NULL),
257 _num_q(0),
258 _max_num_q(0),
259 _processing_is_mt(false),
260 _next_id(0)
261 { }
263 // Default parameters give you a vanilla reference processor.
264 ReferenceProcessor(MemRegion span,
265 bool mt_processing = false, int mt_processing_degree = 1,
266 bool mt_discovery = false, int mt_discovery_degree = 1,
267 bool atomic_discovery = true,
268 BoolObjectClosure* is_alive_non_header = NULL,
269 bool discovered_list_needs_barrier = false);
271 // RefDiscoveryPolicy values
272 enum DiscoveryPolicy {
273 ReferenceBasedDiscovery = 0,
274 ReferentBasedDiscovery = 1,
275 DiscoveryPolicyMin = ReferenceBasedDiscovery,
276 DiscoveryPolicyMax = ReferentBasedDiscovery
277 };
279 static void init_statics();
281 public:
282 // get and set "is_alive_non_header" field
283 BoolObjectClosure* is_alive_non_header() {
284 return _is_alive_non_header;
285 }
286 void set_is_alive_non_header(BoolObjectClosure* is_alive_non_header) {
287 _is_alive_non_header = is_alive_non_header;
288 }
290 // get and set span
291 MemRegion span() { return _span; }
292 void set_span(MemRegion span) { _span = span; }
294 // start and stop weak ref discovery
295 void enable_discovery() { _discovering_refs = true; }
296 void disable_discovery() { _discovering_refs = false; }
297 bool discovery_enabled() { return _discovering_refs; }
299 // whether discovery is atomic wrt other collectors
300 bool discovery_is_atomic() const { return _discovery_is_atomic; }
301 void set_atomic_discovery(bool atomic) { _discovery_is_atomic = atomic; }
303 // whether discovery is done by multiple threads same-old-timeously
304 bool discovery_is_mt() const { return _discovery_is_mt; }
305 void set_mt_discovery(bool mt) { _discovery_is_mt = mt; }
307 // Whether we are in a phase when _processing_ is MT.
308 bool processing_is_mt() const { return _processing_is_mt; }
309 void set_mt_processing(bool mt) { _processing_is_mt = mt; }
311 // whether all enqueuing of weak references is complete
312 bool enqueuing_is_done() { return _enqueuing_is_done; }
313 void set_enqueuing_is_done(bool v) { _enqueuing_is_done = v; }
315 // iterate over oops
316 void weak_oops_do(OopClosure* f); // weak roots
317 static void oops_do(OopClosure* f); // strong root(s)
319 // Balance each of the discovered lists.
320 void balance_all_queues();
322 // Discover a Reference object, using appropriate discovery criteria
323 bool discover_reference(oop obj, ReferenceType rt);
325 // Process references found during GC (called by the garbage collector)
326 void process_discovered_references(BoolObjectClosure* is_alive,
327 OopClosure* keep_alive,
328 VoidClosure* complete_gc,
329 AbstractRefProcTaskExecutor* task_executor);
331 public:
332 // Enqueue references at end of GC (called by the garbage collector)
333 bool enqueue_discovered_references(AbstractRefProcTaskExecutor* task_executor = NULL);
335 // If a discovery is in process that is being superceded, abandon it: all
336 // the discovered lists will be empty, and all the objects on them will
337 // have NULL discovered fields. Must be called only at a safepoint.
338 void abandon_partial_discovery();
340 // debugging
341 void verify_no_references_recorded() PRODUCT_RETURN;
342 void verify_referent(oop obj) PRODUCT_RETURN;
343 static void verify();
345 // clear the discovered lists (unlinking each entry).
346 void clear_discovered_references() PRODUCT_RETURN;
347 };
349 // A utility class to disable reference discovery in
350 // the scope which contains it, for given ReferenceProcessor.
351 class NoRefDiscovery: StackObj {
352 private:
353 ReferenceProcessor* _rp;
354 bool _was_discovering_refs;
355 public:
356 NoRefDiscovery(ReferenceProcessor* rp) : _rp(rp) {
357 _was_discovering_refs = _rp->discovery_enabled();
358 if (_was_discovering_refs) {
359 _rp->disable_discovery();
360 }
361 }
363 ~NoRefDiscovery() {
364 if (_was_discovering_refs) {
365 _rp->enable_discovery();
366 }
367 }
368 };
371 // A utility class to temporarily mutate the span of the
372 // given ReferenceProcessor in the scope that contains it.
373 class ReferenceProcessorSpanMutator: StackObj {
374 private:
375 ReferenceProcessor* _rp;
376 MemRegion _saved_span;
378 public:
379 ReferenceProcessorSpanMutator(ReferenceProcessor* rp,
380 MemRegion span):
381 _rp(rp) {
382 _saved_span = _rp->span();
383 _rp->set_span(span);
384 }
386 ~ReferenceProcessorSpanMutator() {
387 _rp->set_span(_saved_span);
388 }
389 };
391 // A utility class to temporarily change the MT'ness of
392 // reference discovery for the given ReferenceProcessor
393 // in the scope that contains it.
394 class ReferenceProcessorMTDiscoveryMutator: StackObj {
395 private:
396 ReferenceProcessor* _rp;
397 bool _saved_mt;
399 public:
400 ReferenceProcessorMTDiscoveryMutator(ReferenceProcessor* rp,
401 bool mt):
402 _rp(rp) {
403 _saved_mt = _rp->discovery_is_mt();
404 _rp->set_mt_discovery(mt);
405 }
407 ~ReferenceProcessorMTDiscoveryMutator() {
408 _rp->set_mt_discovery(_saved_mt);
409 }
410 };
413 // A utility class to temporarily change the disposition
414 // of the "is_alive_non_header" closure field of the
415 // given ReferenceProcessor in the scope that contains it.
416 class ReferenceProcessorIsAliveMutator: StackObj {
417 private:
418 ReferenceProcessor* _rp;
419 BoolObjectClosure* _saved_cl;
421 public:
422 ReferenceProcessorIsAliveMutator(ReferenceProcessor* rp,
423 BoolObjectClosure* cl):
424 _rp(rp) {
425 _saved_cl = _rp->is_alive_non_header();
426 _rp->set_is_alive_non_header(cl);
427 }
429 ~ReferenceProcessorIsAliveMutator() {
430 _rp->set_is_alive_non_header(_saved_cl);
431 }
432 };
434 // A utility class to temporarily change the disposition
435 // of the "discovery_is_atomic" field of the
436 // given ReferenceProcessor in the scope that contains it.
437 class ReferenceProcessorAtomicMutator: StackObj {
438 private:
439 ReferenceProcessor* _rp;
440 bool _saved_atomic_discovery;
442 public:
443 ReferenceProcessorAtomicMutator(ReferenceProcessor* rp,
444 bool atomic):
445 _rp(rp) {
446 _saved_atomic_discovery = _rp->discovery_is_atomic();
447 _rp->set_atomic_discovery(atomic);
448 }
450 ~ReferenceProcessorAtomicMutator() {
451 _rp->set_atomic_discovery(_saved_atomic_discovery);
452 }
453 };
456 // A utility class to temporarily change the MT processing
457 // disposition of the given ReferenceProcessor instance
458 // in the scope that contains it.
459 class ReferenceProcessorMTProcMutator: StackObj {
460 private:
461 ReferenceProcessor* _rp;
462 bool _saved_mt;
464 public:
465 ReferenceProcessorMTProcMutator(ReferenceProcessor* rp,
466 bool mt):
467 _rp(rp) {
468 _saved_mt = _rp->processing_is_mt();
469 _rp->set_mt_processing(mt);
470 }
472 ~ReferenceProcessorMTProcMutator() {
473 _rp->set_mt_processing(_saved_mt);
474 }
475 };
478 // This class is an interface used to implement task execution for the
479 // reference processing.
480 class AbstractRefProcTaskExecutor {
481 public:
483 // Abstract tasks to execute.
484 class ProcessTask;
485 class EnqueueTask;
487 // Executes a task using worker threads.
488 virtual void execute(ProcessTask& task) = 0;
489 virtual void execute(EnqueueTask& task) = 0;
491 // Switch to single threaded mode.
492 virtual void set_single_threaded_mode() { };
493 };
495 // Abstract reference processing task to execute.
496 class AbstractRefProcTaskExecutor::ProcessTask {
497 protected:
498 ProcessTask(ReferenceProcessor& ref_processor,
499 DiscoveredList refs_lists[],
500 bool marks_oops_alive)
501 : _ref_processor(ref_processor),
502 _refs_lists(refs_lists),
503 _marks_oops_alive(marks_oops_alive)
504 { }
506 public:
507 virtual void work(unsigned int work_id, BoolObjectClosure& is_alive,
508 OopClosure& keep_alive,
509 VoidClosure& complete_gc) = 0;
511 // Returns true if a task marks some oops as alive.
512 bool marks_oops_alive() const
513 { return _marks_oops_alive; }
515 protected:
516 ReferenceProcessor& _ref_processor;
517 DiscoveredList* _refs_lists;
518 const bool _marks_oops_alive;
519 };
521 // Abstract reference processing task to execute.
522 class AbstractRefProcTaskExecutor::EnqueueTask {
523 protected:
524 EnqueueTask(ReferenceProcessor& ref_processor,
525 DiscoveredList refs_lists[],
526 HeapWord* pending_list_addr,
527 oop sentinel_ref,
528 int n_queues)
529 : _ref_processor(ref_processor),
530 _refs_lists(refs_lists),
531 _pending_list_addr(pending_list_addr),
532 _sentinel_ref(sentinel_ref),
533 _n_queues(n_queues)
534 { }
536 public:
537 virtual void work(unsigned int work_id) = 0;
539 protected:
540 ReferenceProcessor& _ref_processor;
541 DiscoveredList* _refs_lists;
542 HeapWord* _pending_list_addr;
543 oop _sentinel_ref;
544 int _n_queues;
545 };
547 #endif // SHARE_VM_MEMORY_REFERENCEPROCESSOR_HPP