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_oops_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_oops_do(CLDClosure* cl) {
263 assert_locked_or_safepoint_weak(ClassLoaderDataGraph_lock);
264 if (ClassUnloading) {
265 roots_cld_do(cl, NULL);
266 } else {
267 cld_oops_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::cld_do(CLDClosure* cl) {
319 ClassLoaderDataGraphIterator iter;
320 while (ClassLoaderData* cld = iter.get_next()) {
321 cl->do_cld(cld);
322 }
323 }
324
325 void ClassLoaderDataGraph::always_strong_cld_do(CLDClosure* cl) {
326 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
327 if (ClassUnloading) {
328 // The keep_alive bits are only so GC doesn't unload the classes prematurely,
329 // not for tools to find.
330 cl->do_cld(ClassLoaderData::the_null_class_loader_data());
331 } else {
332 cld_do(cl);
333 }
334 }
335
336 // These functions assume that the caller has locked the ClassLoaderDataGraph_lock
337 // if they are not calling the function from a safepoint.
338 void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
339 ClassLoaderDataGraphIterator iter;
340 while (ClassLoaderData* cld = iter.get_next()) {
341 cld->classes_do(klass_closure);
342 }
343 }
344
345 void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
346 ClassLoaderDataGraphIterator iter;
347 while (ClassLoaderData* cld = iter.get_next()) {
348 cld->classes_do(f);
349 }
350 }
351
352 void ClassLoaderDataGraph::methods_do(void f(Method*)) {
353 ClassLoaderDataGraphIterator iter;
354 while (ClassLoaderData* cld = iter.get_next()) {
355 cld->methods_do(f);
356 }
357 }
358
359 void ClassLoaderDataGraph::modules_do(void f(ModuleEntry*)) {
360 assert_locked_or_safepoint(Module_lock);
361 ClassLoaderDataGraphIterator iter;
362 while (ClassLoaderData* cld = iter.get_next()) {
363 cld->modules_do(f);
364 }
365 }
366
367 void ClassLoaderDataGraph::modules_unloading_do(void f(ModuleEntry*)) {
368 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
369 // Only walk the head until any clds not purged from prior unloading
370 // (CMS doesn't purge right away).
371 for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
372 assert(cld->is_unloading(), "invariant");
373 cld->modules_do(f);
374 }
375 }
376
377 void ClassLoaderDataGraph::packages_do(void f(PackageEntry*)) {
378 assert_locked_or_safepoint(Module_lock);
379 ClassLoaderDataGraphIterator iter;
380 while (ClassLoaderData* cld = iter.get_next()) {
381 cld->packages_do(f);
382 }
383 }
384
385 void ClassLoaderDataGraph::packages_unloading_do(void f(PackageEntry*)) {
386 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
387 // Only walk the head until any clds not purged from prior unloading
388 // (CMS doesn't purge right away).
389 for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
390 assert(cld->is_unloading(), "invariant");
391 cld->packages_do(f);
392 }
393 }
394
395 void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
396 ClassLoaderDataGraphIterator iter;
397 while (ClassLoaderData* cld = iter.get_next()) {
398 cld->loaded_classes_do(klass_closure);
399 }
400 }
401
402 // This case can block but cannot do unloading (called from CDS)
403 void ClassLoaderDataGraph::unlocked_loaded_classes_do(KlassClosure* klass_closure) {
404 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
405 cld->loaded_classes_do(klass_closure);
406 }
407 }
408
409
410 void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
411 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
412 // Only walk the head until any clds not purged from prior unloading
413 // (CMS doesn't purge right away).
414 for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
415 assert(cld->is_unloading(), "invariant");
416 cld->classes_do(f);
417 }
418 }
419
420 #define FOR_ALL_DICTIONARY(X) ClassLoaderDataGraphIterator iter; \
421 while (ClassLoaderData* X = iter.get_next()) \
422 if (X->dictionary() != NULL)
423
424 // Walk classes in the loaded class dictionaries in various forms.
425 // Only walks the classes defined in this class loader.
426 void ClassLoaderDataGraph::dictionary_classes_do(void f(InstanceKlass*)) {
427 FOR_ALL_DICTIONARY(cld) {
428 cld->dictionary()->classes_do(f);
429 }
430 }
431
432 // Only walks the classes defined in this class loader.
433 void ClassLoaderDataGraph::dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS) {
434 FOR_ALL_DICTIONARY(cld) {
435 cld->dictionary()->classes_do(f, CHECK);
436 }
437 }
438
439 void ClassLoaderDataGraph::verify_dictionary() {
440 FOR_ALL_DICTIONARY(cld) {
441 cld->dictionary()->verify();
442 }
443 }
444
445 void ClassLoaderDataGraph::print_dictionary(outputStream* st) {
446 FOR_ALL_DICTIONARY(cld) {
447 st->print("Dictionary for ");
448 cld->print_value_on(st);
449 st->cr();
450 cld->dictionary()->print_on(st);
451 st->cr();
452 }
453 }
454
455 void ClassLoaderDataGraph::print_dictionary_statistics(outputStream* st) {
456 FOR_ALL_DICTIONARY(cld) {
457 ResourceMark rm;
458 stringStream tempst;
459 tempst.print("System Dictionary for %s class loader", cld->loader_name_and_id());
460 cld->dictionary()->print_table_statistics(st, tempst.as_string());
461 }
462 }
463
464 GrowableArray<ClassLoaderData*>* ClassLoaderDataGraph::new_clds() {
465 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
466 assert(_head == NULL || _saved_head != NULL, "remember_new_clds(true) not called?");
467
468 GrowableArray<ClassLoaderData*>* array = new GrowableArray<ClassLoaderData*>();
469
470 // The CLDs in [_head, _saved_head] were all added during last call to remember_new_clds(true);
471 ClassLoaderData* curr = _head;
472 while (curr != _saved_head) {
473 if (!curr->claimed()) {
474 array->push(curr);
475 LogTarget(Debug, class, loader, data) lt;
476 if (lt.is_enabled()) {
477 LogStream ls(lt);
478 ls.print("found new CLD: ");
479 curr->print_value_on(&ls);
480 ls.cr();
481 }
482 }
483
484 curr = curr->_next;
485 }
486
487 return array;
488 }
489
490 #ifndef PRODUCT
491 bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {
492 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
493 for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
494 if (loader_data == data) {
495 return true;
496 }
497 }
498
499 return false;
500 }
501 #endif // PRODUCT
502
503 bool ClassLoaderDataGraph::is_valid(ClassLoaderData* loader_data) {
504 DEBUG_ONLY( if (!VMError::is_error_reported()) { assert_locked_or_safepoint(ClassLoaderDataGraph_lock); } )
505 if (loader_data != NULL) {
506 if (loader_data == ClassLoaderData::the_null_class_loader_data()) {
507 return true;
508 }
509 for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
510 if (loader_data == data) {
511 return true;
512 }
513 }
514 }
515 return false;
516 }
517
518 // Move class loader data from main list to the unloaded list for unloading
519 // and deallocation later.
520 bool ClassLoaderDataGraph::do_unloading(bool do_cleaning) {
521 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
522
523 // Indicate whether safepoint cleanup is needed.
524 _safepoint_cleanup_needed |= do_cleaning;
525
526 ClassLoaderData* data = _head;
527 ClassLoaderData* prev = NULL;
528 bool seen_dead_loader = false;
529 uint loaders_processed = 0;
530 uint loaders_removed = 0;
531
532 // Save previous _unloading pointer for CMS which may add to unloading list before
533 // purging and we don't want to rewalk the previously unloaded class loader data.
534 _saved_unloading = _unloading;
535
536 data = _head;
537 while (data != NULL) {
538 if (data->is_alive()) {
539 prev = data;
540 data = data->next();
541 loaders_processed++;
542 continue;
543 }
544 seen_dead_loader = true;
545 loaders_removed++;
546 ClassLoaderData* dead = data;
547 dead->unload();
548 data = data->next();
549 // Remove from loader list.
550 // This class loader data will no longer be found
551 // in the ClassLoaderDataGraph.
552 if (prev != NULL) {
553 prev->set_next(data);
554 } else {
555 assert(dead == _head, "sanity check");
556 _head = data;
557 }
558 dead->set_next(_unloading);
559 _unloading = dead;
560 }
561
562 log_debug(class, loader, data)("do_unloading: loaders processed %u, loaders removed %u", loaders_processed, loaders_removed);
563
564 return seen_dead_loader;
565 }
566
567 // There's at least one dead class loader. Purge refererences of healthy module
568 // reads lists and package export lists to modules belonging to dead loaders.
569 void ClassLoaderDataGraph::clean_module_and_package_info() {
570 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
571
572 ClassLoaderData* data = _head;
573 while (data != NULL) {
574 // Remove entries in the dictionary of live class loader that have
575 // initiated loading classes in a dead class loader.
576 if (data->dictionary() != NULL) {
577 data->dictionary()->do_unloading();
578 }
579 // Walk a ModuleEntry's reads, and a PackageEntry's exports
580 // lists to determine if there are modules on those lists that are now
581 // dead and should be removed. A module's life cycle is equivalent
582 // to its defining class loader's life cycle. Since a module is
583 // considered dead if its class loader is dead, these walks must
584 // occur after each class loader's aliveness is determined.
585 if (data->packages() != NULL) {
586 data->packages()->purge_all_package_exports();
587 }
588 if (data->modules_defined()) {
589 data->modules()->purge_all_module_reads();
590 }
591 data = data->next();
592 }
593 }
594
595 void ClassLoaderDataGraph::purge() {
596 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
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 }
612
613 int ClassLoaderDataGraph::resize_if_needed() {
614 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
615 int resized = 0;
616 if (Dictionary::does_any_dictionary_needs_resizing()) {
617 FOR_ALL_DICTIONARY(cld) {
618 if (cld->dictionary()->resize_if_needed()) {
619 resized++;
620 }
621 }
622 }
623 return resized;
624 }
625
626 ClassLoaderDataGraphKlassIteratorAtomic::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
644 Klass* 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
664 Klass* 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
684 ClassLoaderDataGraphMetaspaceIterator::ClassLoaderDataGraphMetaspaceIterator() {
685 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
686 _data = ClassLoaderDataGraph::_head;
687 }
688
689 ClassLoaderDataGraphMetaspaceIterator::~ClassLoaderDataGraphMetaspaceIterator() {}
690
691 ClassLoaderMetaspace* 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
704 extern "C" int print_loader_data_graph() {
705 ResourceMark rm;
706 ClassLoaderDataGraph::print_on(tty);
707 return 0;
708 }
709
710 void ClassLoaderDataGraph::verify() {
711 ClassLoaderDataGraphIterator iter;
712 while (ClassLoaderData* cld = iter.get_next()) {
713 cld->verify();
714 }
715 }
716
717 void 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