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