1/*
2 * Copyright (c) 2018, 2019, 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#include "precompiled.hpp"
26#include "classfile/classLoaderDataGraph.inline.hpp"
27#include "classfile/dictionary.hpp"
28#include "classfile/javaClasses.hpp"
29#include "classfile/metadataOnStackMark.hpp"
30#include "classfile/moduleEntry.hpp"
31#include "classfile/packageEntry.hpp"
32#include "code/dependencyContext.hpp"
33#include "logging/log.hpp"
34#include "logging/logStream.hpp"
35#include "memory/allocation.inline.hpp"
36#include "memory/metaspace.hpp"
37#include "memory/resourceArea.hpp"
38#include "runtime/atomic.hpp"
39#include "runtime/handles.inline.hpp"
40#include "runtime/mutex.hpp"
41#include "runtime/orderAccess.hpp"
42#include "runtime/safepoint.hpp"
43#include "runtime/safepointVerifiers.hpp"
44#include "utilities/growableArray.hpp"
45#include "utilities/macros.hpp"
46#include "utilities/ostream.hpp"
47
48volatile size_t ClassLoaderDataGraph::_num_array_classes = 0;
49volatile size_t ClassLoaderDataGraph::_num_instance_classes = 0;
50
51void ClassLoaderDataGraph::clear_claimed_marks() {
52 // The claimed marks of the CLDs in the ClassLoaderDataGraph are cleared
53 // outside a safepoint and without locking the ClassLoaderDataGraph_lock.
54 // This is required to avoid a deadlock between concurrent GC threads and safepointing.
55 //
56 // We need to make sure that the CLD contents are fully visible to the
57 // reader thread. This is accomplished by acquire/release of the _head,
58 // and is sufficient.
59 //
60 // Any ClassLoaderData added after or during walking the list are prepended to
61 // _head. Their claim mark need not be handled here.
62 for (ClassLoaderData* cld = OrderAccess::load_acquire(&_head); cld != NULL; cld = cld->next()) {
63 cld->clear_claim();
64 }
65}
66
67void ClassLoaderDataGraph::clear_claimed_marks(int claim) {
68 for (ClassLoaderData* cld = OrderAccess::load_acquire(&_head); cld != NULL; cld = cld->next()) {
69 cld->clear_claim(claim);
70 }
71}
72// Class iterator used by the compiler. It gets some number of classes at
73// a safepoint to decay invocation counters on the methods.
74class ClassLoaderDataGraphKlassIteratorStatic {
75 ClassLoaderData* _current_loader_data;
76 Klass* _current_class_entry;
77 public:
78
79 ClassLoaderDataGraphKlassIteratorStatic() : _current_loader_data(NULL), _current_class_entry(NULL) {}
80
81 InstanceKlass* try_get_next_class() {
82 assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
83 size_t max_classes = ClassLoaderDataGraph::num_instance_classes();
84 assert(max_classes > 0, "should not be called with no instance classes");
85 for (size_t i = 0; i < max_classes; ) {
86
87 if (_current_class_entry != NULL) {
88 Klass* k = _current_class_entry;
89 _current_class_entry = _current_class_entry->next_link();
90
91 if (k->is_instance_klass()) {
92 InstanceKlass* ik = InstanceKlass::cast(k);
93 i++; // count all instance classes found
94 // Not yet loaded classes are counted in max_classes
95 // but only return loaded classes.
96 if (ik->is_loaded()) {
97 return ik;
98 }
99 }
100 } else {
101 // Go to next CLD
102 if (_current_loader_data != NULL) {
103 _current_loader_data = _current_loader_data->next();
104 }
105 // Start at the beginning
106 if (_current_loader_data == NULL) {
107 _current_loader_data = ClassLoaderDataGraph::_head;
108 }
109
110 _current_class_entry = _current_loader_data->klasses();
111 }
112 }
113 // Should never be reached unless all instance classes have failed or are not fully loaded.
114 // Caller handles NULL.
115 return NULL;
116 }
117
118 // If the current class for the static iterator is a class being unloaded or
119 // deallocated, adjust the current class.
120 void adjust_saved_class(ClassLoaderData* cld) {
121 if (_current_loader_data == cld) {
122 _current_loader_data = cld->next();
123 if (_current_loader_data != NULL) {
124 _current_class_entry = _current_loader_data->klasses();
125 } // else try_get_next_class will start at the head
126 }
127 }
128
129 void adjust_saved_class(Klass* klass) {
130 if (_current_class_entry == klass) {
131 _current_class_entry = klass->next_link();
132 }
133 }
134};
135
136static ClassLoaderDataGraphKlassIteratorStatic static_klass_iterator;
137
138InstanceKlass* ClassLoaderDataGraph::try_get_next_class() {
139 assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
140 return static_klass_iterator.try_get_next_class();
141}
142
143void ClassLoaderDataGraph::adjust_saved_class(ClassLoaderData* cld) {
144 return static_klass_iterator.adjust_saved_class(cld);
145}
146
147void ClassLoaderDataGraph::adjust_saved_class(Klass* klass) {
148 return static_klass_iterator.adjust_saved_class(klass);
149}
150
151void ClassLoaderDataGraph::clean_deallocate_lists(bool walk_previous_versions) {
152 assert(SafepointSynchronize::is_at_safepoint(), "must only be called at safepoint");
153 uint loaders_processed = 0;
154 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
155 // is_alive check will be necessary for concurrent class unloading.
156 if (cld->is_alive()) {
157 // clean metaspace
158 if (walk_previous_versions) {
159 cld->classes_do(InstanceKlass::purge_previous_versions);
160 }
161 cld->free_deallocate_list();
162 loaders_processed++;
163 }
164 }
165 log_debug(class, loader, data)("clean_deallocate_lists: loaders processed %u %s",
166 loaders_processed, walk_previous_versions ? "walk_previous_versions" : "");
167}
168
169void ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces() {
170 assert(SafepointSynchronize::is_at_safepoint(), "must only be called at safepoint");
171
172 _should_clean_deallocate_lists = false; // assume everything gets cleaned
173
174 // Mark metadata seen on the stack so we can delete unreferenced entries.
175 // Walk all metadata, including the expensive code cache walk, only for class redefinition.
176 // The MetadataOnStackMark walk during redefinition saves previous versions if it finds old methods
177 // on the stack or in the code cache, so we only have to repeat the full walk if
178 // they were found at that time.
179 // TODO: have redefinition clean old methods out of the code cache. They still exist in some places.
180 bool walk_all_metadata = InstanceKlass::has_previous_versions_and_reset();
181
182 MetadataOnStackMark md_on_stack(walk_all_metadata, /*redefinition_walk*/false);
183 clean_deallocate_lists(walk_all_metadata);
184}
185
186// GC root of class loader data created.
187ClassLoaderData* volatile ClassLoaderDataGraph::_head = NULL;
188ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;
189ClassLoaderData* ClassLoaderDataGraph::_saved_unloading = NULL;
190ClassLoaderData* ClassLoaderDataGraph::_saved_head = NULL;
191
192bool ClassLoaderDataGraph::_should_purge = false;
193bool ClassLoaderDataGraph::_should_clean_deallocate_lists = false;
194bool ClassLoaderDataGraph::_safepoint_cleanup_needed = false;
195bool ClassLoaderDataGraph::_metaspace_oom = false;
196
197// Add a new class loader data node to the list. Assign the newly created
198// ClassLoaderData into the java/lang/ClassLoader object as a hidden field
199ClassLoaderData* ClassLoaderDataGraph::add_to_graph(Handle loader, bool is_unsafe_anonymous) {
200
201 assert_lock_strong(ClassLoaderDataGraph_lock);
202
203 ClassLoaderData* cld;
204
205 // First check if another thread beat us to creating the CLD and installing
206 // it into the loader while we were waiting for the lock.
207 if (!is_unsafe_anonymous && loader.not_null()) {
208 cld = java_lang_ClassLoader::loader_data_acquire(loader());
209 if (cld != NULL) {
210 return cld;
211 }
212 }
213
214 // We mustn't GC until we've installed the ClassLoaderData in the Graph since the CLD
215 // contains oops in _handles that must be walked. GC doesn't walk CLD from the
216 // loader oop in all collections, particularly young collections.
217 NoSafepointVerifier no_safepoints;
218
219 cld = new ClassLoaderData(loader, is_unsafe_anonymous);
220
221 // First install the new CLD to the Graph.
222 cld->set_next(_head);
223 OrderAccess::release_store(&_head, cld);
224
225 // Next associate with the class_loader.
226 if (!is_unsafe_anonymous) {
227 // Use OrderAccess, since readers need to get the loader_data only after
228 // it's added to the Graph
229 java_lang_ClassLoader::release_set_loader_data(loader(), cld);
230 }
231
232 // Lastly log, if requested
233 LogTarget(Trace, class, loader, data) lt;
234 if (lt.is_enabled()) {
235 ResourceMark rm;
236 LogStream ls(lt);
237 ls.print("create ");
238 cld->print_value_on(&ls);
239 ls.cr();
240 }
241 return cld;
242}
243
244ClassLoaderData* ClassLoaderDataGraph::add(Handle loader, bool is_unsafe_anonymous) {
245 MutexLocker ml(ClassLoaderDataGraph_lock);
246 ClassLoaderData* loader_data = add_to_graph(loader, is_unsafe_anonymous);
247 return loader_data;
248}
249
250void ClassLoaderDataGraph::cld_unloading_do(CLDClosure* cl) {
251 assert_locked_or_safepoint_weak(ClassLoaderDataGraph_lock);
252 // Only walk the head until any clds not purged from prior unloading
253 // (CMS doesn't purge right away).
254 for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
255 assert(cld->is_unloading(), "invariant");
256 cl->do_cld(cld);
257 }
258}
259
260// These are functions called by the GC, which require all of the CLDs, including the
261// unloading ones.
262void ClassLoaderDataGraph::cld_do(CLDClosure* cl) {
263 assert_locked_or_safepoint_weak(ClassLoaderDataGraph_lock);
264 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->_next) {
265 cl->do_cld(cld);
266 }
267}
268
269void ClassLoaderDataGraph::roots_cld_do(CLDClosure* strong, CLDClosure* weak) {
270 assert_locked_or_safepoint_weak(ClassLoaderDataGraph_lock);
271 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->_next) {
272 CLDClosure* closure = cld->keep_alive() ? strong : weak;
273 if (closure != NULL) {
274 closure->do_cld(cld);
275 }
276 }
277}
278
279void ClassLoaderDataGraph::always_strong_cld_do(CLDClosure* cl) {
280 assert_locked_or_safepoint_weak(ClassLoaderDataGraph_lock);
281 if (ClassUnloading) {
282 roots_cld_do(cl, NULL);
283 } else {
284 cld_do(cl);
285 }
286}
287
288// Closure for locking and iterating through classes.
289LockedClassesDo::LockedClassesDo(classes_do_func_t f) : _function(f) {
290 ClassLoaderDataGraph_lock->lock();
291}
292
293LockedClassesDo::LockedClassesDo() : _function(NULL) {
294 // callers provide their own do_klass
295 ClassLoaderDataGraph_lock->lock();
296}
297
298LockedClassesDo::~LockedClassesDo() { ClassLoaderDataGraph_lock->unlock(); }
299
300
301// Iterating over the CLDG needs to be locked because
302// unloading can remove entries concurrently soon.
303class ClassLoaderDataGraphIterator : public StackObj {
304 ClassLoaderData* _next;
305 HandleMark _hm; // clean up handles when this is done.
306 Handle _holder;
307 Thread* _thread;
308 NoSafepointVerifier _nsv; // No safepoints allowed in this scope
309 // unless verifying at a safepoint.
310
311public:
312 ClassLoaderDataGraphIterator() : _next(ClassLoaderDataGraph::_head),
313 _nsv(true, !SafepointSynchronize::is_at_safepoint()) {
314 _thread = Thread::current();
315 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
316 }
317
318 ClassLoaderData* get_next() {
319 ClassLoaderData* cld = _next;
320 // Skip already unloaded CLD for concurrent unloading.
321 while (cld != NULL && !cld->is_alive()) {
322 cld = cld->next();
323 }
324 if (cld != NULL) {
325 // Keep cld that is being returned alive.
326 _holder = Handle(_thread, cld->holder_phantom());
327 _next = cld->next();
328 } else {
329 _next = NULL;
330 }
331 return cld;
332 }
333};
334
335void ClassLoaderDataGraph::loaded_cld_do(CLDClosure* cl) {
336 ClassLoaderDataGraphIterator iter;
337 while (ClassLoaderData* cld = iter.get_next()) {
338 cl->do_cld(cld);
339 }
340}
341
342// These functions assume that the caller has locked the ClassLoaderDataGraph_lock
343// if they are not calling the function from a safepoint.
344void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
345 ClassLoaderDataGraphIterator iter;
346 while (ClassLoaderData* cld = iter.get_next()) {
347 cld->classes_do(klass_closure);
348 }
349}
350
351void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
352 ClassLoaderDataGraphIterator iter;
353 while (ClassLoaderData* cld = iter.get_next()) {
354 cld->classes_do(f);
355 }
356}
357
358void ClassLoaderDataGraph::methods_do(void f(Method*)) {
359 ClassLoaderDataGraphIterator iter;
360 while (ClassLoaderData* cld = iter.get_next()) {
361 cld->methods_do(f);
362 }
363}
364
365void ClassLoaderDataGraph::modules_do(void f(ModuleEntry*)) {
366 assert_locked_or_safepoint(Module_lock);
367 ClassLoaderDataGraphIterator iter;
368 while (ClassLoaderData* cld = iter.get_next()) {
369 cld->modules_do(f);
370 }
371}
372
373void ClassLoaderDataGraph::modules_unloading_do(void f(ModuleEntry*)) {
374 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
375 // Only walk the head until any clds not purged from prior unloading
376 // (CMS doesn't purge right away).
377 for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
378 assert(cld->is_unloading(), "invariant");
379 cld->modules_do(f);
380 }
381}
382
383void ClassLoaderDataGraph::packages_do(void f(PackageEntry*)) {
384 assert_locked_or_safepoint(Module_lock);
385 ClassLoaderDataGraphIterator iter;
386 while (ClassLoaderData* cld = iter.get_next()) {
387 cld->packages_do(f);
388 }
389}
390
391void ClassLoaderDataGraph::packages_unloading_do(void f(PackageEntry*)) {
392 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
393 // Only walk the head until any clds not purged from prior unloading
394 // (CMS doesn't purge right away).
395 for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
396 assert(cld->is_unloading(), "invariant");
397 cld->packages_do(f);
398 }
399}
400
401void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
402 ClassLoaderDataGraphIterator iter;
403 while (ClassLoaderData* cld = iter.get_next()) {
404 cld->loaded_classes_do(klass_closure);
405 }
406}
407
408// This case can block but cannot do unloading (called from CDS)
409void ClassLoaderDataGraph::unlocked_loaded_classes_do(KlassClosure* klass_closure) {
410 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
411 cld->loaded_classes_do(klass_closure);
412 }
413}
414
415
416void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
417 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
418 // Only walk the head until any clds not purged from prior unloading
419 // (CMS doesn't purge right away).
420 for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
421 assert(cld->is_unloading(), "invariant");
422 cld->classes_do(f);
423 }
424}
425
426#define FOR_ALL_DICTIONARY(X) ClassLoaderDataGraphIterator iter; \
427 while (ClassLoaderData* X = iter.get_next()) \
428 if (X->dictionary() != NULL)
429
430// Walk classes in the loaded class dictionaries in various forms.
431// Only walks the classes defined in this class loader.
432void ClassLoaderDataGraph::dictionary_classes_do(void f(InstanceKlass*)) {
433 FOR_ALL_DICTIONARY(cld) {
434 cld->dictionary()->classes_do(f);
435 }
436}
437
438// Only walks the classes defined in this class loader.
439void ClassLoaderDataGraph::dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS) {
440 FOR_ALL_DICTIONARY(cld) {
441 cld->dictionary()->classes_do(f, CHECK);
442 }
443}
444
445void ClassLoaderDataGraph::verify_dictionary() {
446 FOR_ALL_DICTIONARY(cld) {
447 cld->dictionary()->verify();
448 }
449}
450
451void ClassLoaderDataGraph::print_dictionary(outputStream* st) {
452 FOR_ALL_DICTIONARY(cld) {
453 st->print("Dictionary for ");
454 cld->print_value_on(st);
455 st->cr();
456 cld->dictionary()->print_on(st);
457 st->cr();
458 }
459}
460
461void ClassLoaderDataGraph::print_table_statistics(outputStream* st) {
462 FOR_ALL_DICTIONARY(cld) {
463 ResourceMark rm;
464 stringStream tempst;
465 tempst.print("System Dictionary for %s class loader", cld->loader_name_and_id());
466 cld->dictionary()->print_table_statistics(st, tempst.as_string());
467 }
468}
469
470GrowableArray<ClassLoaderData*>* ClassLoaderDataGraph::new_clds() {
471 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
472 assert(_head == NULL || _saved_head != NULL, "remember_new_clds(true) not called?");
473
474 GrowableArray<ClassLoaderData*>* array = new GrowableArray<ClassLoaderData*>();
475
476 // The CLDs in [_head, _saved_head] were all added during last call to remember_new_clds(true);
477 ClassLoaderData* curr = _head;
478 while (curr != _saved_head) {
479 if (!curr->claimed(ClassLoaderData::_claim_strong)) {
480 array->push(curr);
481 LogTarget(Debug, class, loader, data) lt;
482 if (lt.is_enabled()) {
483 LogStream ls(lt);
484 ls.print("found new CLD: ");
485 curr->print_value_on(&ls);
486 ls.cr();
487 }
488 }
489
490 curr = curr->_next;
491 }
492
493 return array;
494}
495
496#ifndef PRODUCT
497bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {
498 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
499 for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
500 if (loader_data == data) {
501 return true;
502 }
503 }
504
505 return false;
506}
507#endif // PRODUCT
508
509bool ClassLoaderDataGraph::is_valid(ClassLoaderData* loader_data) {
510 DEBUG_ONLY( if (!VMError::is_error_reported()) { assert_locked_or_safepoint(ClassLoaderDataGraph_lock); } )
511 if (loader_data != NULL) {
512 if (loader_data == ClassLoaderData::the_null_class_loader_data()) {
513 return true;
514 }
515 for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
516 if (loader_data == data) {
517 return true;
518 }
519 }
520 }
521 return false;
522}
523
524// Move class loader data from main list to the unloaded list for unloading
525// and deallocation later.
526bool ClassLoaderDataGraph::do_unloading() {
527 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
528
529 // Indicate whether safepoint cleanup is needed.
530 _safepoint_cleanup_needed = true;
531
532 ClassLoaderData* data = _head;
533 ClassLoaderData* prev = NULL;
534 bool seen_dead_loader = false;
535 uint loaders_processed = 0;
536 uint loaders_removed = 0;
537
538 // Save previous _unloading pointer for CMS which may add to unloading list before
539 // purging and we don't want to rewalk the previously unloaded class loader data.
540 _saved_unloading = _unloading;
541
542 data = _head;
543 while (data != NULL) {
544 if (data->is_alive()) {
545 prev = data;
546 data = data->next();
547 loaders_processed++;
548 continue;
549 }
550 seen_dead_loader = true;
551 loaders_removed++;
552 ClassLoaderData* dead = data;
553 dead->unload();
554 data = data->next();
555 // Remove from loader list.
556 // This class loader data will no longer be found
557 // in the ClassLoaderDataGraph.
558 if (prev != NULL) {
559 prev->set_next(data);
560 } else {
561 assert(dead == _head, "sanity check");
562 _head = data;
563 }
564 dead->set_next(_unloading);
565 _unloading = dead;
566 }
567
568 log_debug(class, loader, data)("do_unloading: loaders processed %u, loaders removed %u", loaders_processed, loaders_removed);
569
570 return seen_dead_loader;
571}
572
573// There's at least one dead class loader. Purge refererences of healthy module
574// reads lists and package export lists to modules belonging to dead loaders.
575void ClassLoaderDataGraph::clean_module_and_package_info() {
576 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
577
578 ClassLoaderData* data = _head;
579 while (data != NULL) {
580 // Walk a ModuleEntry's reads, and a PackageEntry's exports
581 // lists to determine if there are modules on those lists that are now
582 // dead and should be removed. A module's life cycle is equivalent
583 // to its defining class loader's life cycle. Since a module is
584 // considered dead if its class loader is dead, these walks must
585 // occur after each class loader's aliveness is determined.
586 if (data->packages() != NULL) {
587 data->packages()->purge_all_package_exports();
588 }
589 if (data->modules_defined()) {
590 data->modules()->purge_all_module_reads();
591 }
592 data = data->next();
593 }
594}
595
596void ClassLoaderDataGraph::purge() {
597 ClassLoaderData* list = _unloading;
598 _unloading = NULL;
599 ClassLoaderData* next = list;
600 bool classes_unloaded = false;
601 while (next != NULL) {
602 ClassLoaderData* purge_me = next;
603 next = purge_me->next();
604 delete purge_me;
605 classes_unloaded = true;
606 }
607 if (classes_unloaded) {
608 Metaspace::purge();
609 set_metaspace_oom(false);
610 }
611 DependencyContext::purge_dependency_contexts();
612}
613
614int ClassLoaderDataGraph::resize_dictionaries() {
615 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
616 int resized = 0;
617 assert (Dictionary::does_any_dictionary_needs_resizing(), "some dictionary should need resizing");
618 FOR_ALL_DICTIONARY(cld) {
619 if (cld->dictionary()->resize_if_needed()) {
620 resized++;
621 }
622 }
623 return resized;
624}
625
626ClassLoaderDataGraphKlassIteratorAtomic::ClassLoaderDataGraphKlassIteratorAtomic()
627 : _next_klass(NULL) {
628 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
629 ClassLoaderData* cld = ClassLoaderDataGraph::_head;
630 Klass* klass = NULL;
631
632 // Find the first klass in the CLDG.
633 while (cld != NULL) {
634 assert_locked_or_safepoint(cld->metaspace_lock());
635 klass = cld->_klasses;
636 if (klass != NULL) {
637 _next_klass = klass;
638 return;
639 }
640 cld = cld->next();
641 }
642}
643
644Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass_in_cldg(Klass* klass) {
645 Klass* next = klass->next_link();
646 if (next != NULL) {
647 return next;
648 }
649
650 // No more klasses in the current CLD. Time to find a new CLD.
651 ClassLoaderData* cld = klass->class_loader_data();
652 assert_locked_or_safepoint(cld->metaspace_lock());
653 while (next == NULL) {
654 cld = cld->next();
655 if (cld == NULL) {
656 break;
657 }
658 next = cld->_klasses;
659 }
660
661 return next;
662}
663
664Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass() {
665 Klass* head = _next_klass;
666
667 while (head != NULL) {
668 Klass* next = next_klass_in_cldg(head);
669
670 Klass* old_head = Atomic::cmpxchg(next, &_next_klass, head);
671
672 if (old_head == head) {
673 return head; // Won the CAS.
674 }
675
676 head = old_head;
677 }
678
679 // Nothing more for the iterator to hand out.
680 assert(head == NULL, "head is " PTR_FORMAT ", expected not null:", p2i(head));
681 return NULL;
682}
683
684ClassLoaderDataGraphMetaspaceIterator::ClassLoaderDataGraphMetaspaceIterator() {
685 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
686 _data = ClassLoaderDataGraph::_head;
687}
688
689ClassLoaderDataGraphMetaspaceIterator::~ClassLoaderDataGraphMetaspaceIterator() {}
690
691ClassLoaderMetaspace* ClassLoaderDataGraphMetaspaceIterator::get_next() {
692 assert(_data != NULL, "Should not be NULL in call to the iterator");
693 ClassLoaderMetaspace* result = _data->metaspace_or_null();
694 _data = _data->next();
695 // This result might be NULL for class loaders without metaspace
696 // yet. It would be nice to return only non-null results but
697 // there is no guarantee that there will be a non-null result
698 // down the list so the caller is going to have to check.
699 return result;
700}
701
702#ifndef PRODUCT
703// callable from debugger
704extern "C" int print_loader_data_graph() {
705 ResourceMark rm;
706 ClassLoaderDataGraph::print_on(tty);
707 return 0;
708}
709
710void ClassLoaderDataGraph::verify() {
711 ClassLoaderDataGraphIterator iter;
712 while (ClassLoaderData* cld = iter.get_next()) {
713 cld->verify();
714 }
715}
716
717void ClassLoaderDataGraph::print_on(outputStream * const out) {
718 ClassLoaderDataGraphIterator iter;
719 while (ClassLoaderData* cld = iter.get_next()) {
720 cld->print_on(out);
721 }
722}
723#endif // PRODUCT
724
725void ClassLoaderDataGraph::print() { print_on(tty); }
726