1 /*
2 * Copyright (c) 2012, 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 // A ClassLoaderData identifies the full set of class types that a class
26 // loader's name resolution strategy produces for a given configuration of the
27 // class loader.
28 // Class types in the ClassLoaderData may be defined by from class file binaries
29 // provided by the class loader, or from other class loader it interacts with
30 // according to its name resolution strategy.
31 //
32 // Class loaders that implement a deterministic name resolution strategy
33 // (including with respect to their delegation behavior), such as the boot, the
34 // platform, and the system loaders of the JDK's built-in class loader
35 // hierarchy, always produce the same linkset for a given configuration.
36 //
37 // ClassLoaderData carries information related to a linkset (e.g.,
38 // metaspace holding its klass definitions).
39 // The System Dictionary and related data structures (e.g., placeholder table,
40 // loader constraints table) as well as the runtime representation of classes
41 // only reference ClassLoaderData.
42 //
43 // Instances of java.lang.ClassLoader holds a pointer to a ClassLoaderData that
44 // that represent the loader's "linking domain" in the JVM.
45 //
46 // The bootstrap loader (represented by NULL) also has a ClassLoaderData,
47 // the singleton class the_null_class_loader_data().
48
49 #include "precompiled.hpp"
50 #include "classfile/classLoaderData.hpp"
51 #include "classfile/classLoaderData.inline.hpp"
52 #include "classfile/dictionary.hpp"
53 #include "classfile/javaClasses.hpp"
54 #include "classfile/metadataOnStackMark.hpp"
55 #include "classfile/moduleEntry.hpp"
56 #include "classfile/packageEntry.hpp"
57 #include "classfile/symbolTable.hpp"
58 #include "classfile/systemDictionary.hpp"
59 #include "logging/log.hpp"
60 #include "logging/logStream.hpp"
61 #include "memory/allocation.inline.hpp"
62 #include "memory/metadataFactory.hpp"
63 #include "memory/metaspaceShared.hpp"
64 #include "memory/resourceArea.hpp"
65 #include "memory/universe.hpp"
66 #include "oops/access.inline.hpp"
67 #include "oops/oop.inline.hpp"
68 #include "oops/oopHandle.inline.hpp"
69 #include "oops/weakHandle.inline.hpp"
70 #include "runtime/atomic.hpp"
71 #include "runtime/handles.inline.hpp"
72 #include "runtime/mutex.hpp"
73 #include "runtime/orderAccess.hpp"
74 #include "runtime/safepoint.hpp"
75 #include "runtime/safepointVerifiers.hpp"
76 #include "utilities/growableArray.hpp"
77 #include "utilities/macros.hpp"
78 #include "utilities/ostream.hpp"
79 #include "utilities/ticks.hpp"
80 #if INCLUDE_JFR
81 #include "jfr/jfr.hpp"
82 #include "jfr/jfrEvents.hpp"
83 #endif
84
85 volatile size_t ClassLoaderDataGraph::_num_array_classes = 0;
86 volatile size_t ClassLoaderDataGraph::_num_instance_classes = 0;
87
88 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
89
90 void ClassLoaderData::init_null_class_loader_data() {
91 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
92 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
93
94 _the_null_class_loader_data = new ClassLoaderData(Handle(), false);
95 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
96 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
97
98 LogTarget(Trace, class, loader, data) lt;
99 if (lt.is_enabled()) {
100 ResourceMark rm;
101 LogStream ls(lt);
102 ls.print("create ");
103 _the_null_class_loader_data->print_value_on(&ls);
104 ls.cr();
105 }
106 }
107
108 // Obtain and set the class loader's name within the ClassLoaderData so
109 // it will be available for error messages, logging, JFR, etc. The name
110 // and klass are available after the class_loader oop is no longer alive,
111 // during unloading.
112 void ClassLoaderData::initialize_name(Handle class_loader) {
113 Thread* THREAD = Thread::current();
114 ResourceMark rm(THREAD);
115
116 // Obtain the class loader's name. If the class loader's name was not
117 // explicitly set during construction, the CLD's _name field will be null.
118 oop cl_name = java_lang_ClassLoader::name(class_loader());
119 if (cl_name != NULL) {
120 const char* cl_instance_name = java_lang_String::as_utf8_string(cl_name);
121
122 if (cl_instance_name != NULL && cl_instance_name[0] != '\0') {
123 // Can't throw InternalError and SymbolTable doesn't throw OOM anymore.
124 _name = SymbolTable::new_symbol(cl_instance_name, CATCH);
125 }
126 }
127
128 // Obtain the class loader's name and identity hash. If the class loader's
129 // name was not explicitly set during construction, the class loader's name and id
130 // will be set to the qualified class name of the class loader along with its
131 // identity hash.
132 // If for some reason the ClassLoader's constructor has not been run, instead of
133 // leaving the _name_and_id field null, fall back to the external qualified class
134 // name. Thus CLD's _name_and_id field should never have a null value.
135 oop cl_name_and_id = java_lang_ClassLoader::nameAndId(class_loader());
136 const char* cl_instance_name_and_id =
137 (cl_name_and_id == NULL) ? _class_loader_klass->external_name() :
138 java_lang_String::as_utf8_string(cl_name_and_id);
139 assert(cl_instance_name_and_id != NULL && cl_instance_name_and_id[0] != '\0', "class loader has no name and id");
140 // Can't throw InternalError and SymbolTable doesn't throw OOM anymore.
141 _name_and_id = SymbolTable::new_symbol(cl_instance_name_and_id, CATCH);
142 }
143
144 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool is_anonymous) :
145 _metaspace(NULL),
146 _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true,
147 Monitor::_safepoint_check_never)),
148 _unloading(false), _is_anonymous(is_anonymous),
149 _modified_oops(true), _accumulated_modified_oops(false),
150 // An anonymous class loader data doesn't have anything to keep
151 // it from being unloaded during parsing of the anonymous class.
152 // The null-class-loader should always be kept alive.
153 _keep_alive((is_anonymous || h_class_loader.is_null()) ? 1 : 0),
154 _claimed(0),
155 _handles(),
156 _klasses(NULL), _packages(NULL), _modules(NULL), _unnamed_module(NULL), _dictionary(NULL),
157 _jmethod_ids(NULL),
158 _deallocate_list(NULL),
159 _next(NULL),
160 _class_loader_klass(NULL), _name(NULL), _name_and_id(NULL) {
161
162 if (!h_class_loader.is_null()) {
163 _class_loader = _handles.add(h_class_loader());
164 _class_loader_klass = h_class_loader->klass();
165 }
166
167 if (!is_anonymous) {
168 // The holder is initialized later for anonymous classes, and before calling anything
169 // that call class_loader().
170 initialize_holder(h_class_loader);
171
172 // A ClassLoaderData created solely for an anonymous class should never have a
173 // ModuleEntryTable or PackageEntryTable created for it. The defining package
174 // and module for an anonymous class will be found in its host class.
175 _packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);
176 if (h_class_loader.is_null()) {
177 // Create unnamed module for boot loader
178 _unnamed_module = ModuleEntry::create_boot_unnamed_module(this);
179 } else {
180 // Create unnamed module for all other loaders
181 _unnamed_module = ModuleEntry::create_unnamed_module(this);
182 }
183 _dictionary = create_dictionary();
184 }
185
186 NOT_PRODUCT(_dependency_count = 0); // number of class loader dependencies
187
188 JFR_ONLY(INIT_ID(this);)
189 }
190
191 ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {
192 Chunk* c = _head;
193 while (c != NULL) {
194 Chunk* next = c->_next;
195 delete c;
196 c = next;
197 }
198 }
199
200 oop* ClassLoaderData::ChunkedHandleList::add(oop o) {
201 if (_head == NULL || _head->_size == Chunk::CAPACITY) {
202 Chunk* next = new Chunk(_head);
203 OrderAccess::release_store(&_head, next);
204 }
205 oop* handle = &_head->_data[_head->_size];
206 *handle = o;
207 OrderAccess::release_store(&_head->_size, _head->_size + 1);
208 return handle;
209 }
210
211 int ClassLoaderData::ChunkedHandleList::count() const {
212 int count = 0;
213 Chunk* chunk = _head;
214 while (chunk != NULL) {
215 count += chunk->_size;
216 chunk = chunk->_next;
217 }
218 return count;
219 }
220
221 inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {
222 for (juint i = 0; i < size; i++) {
223 if (c->_data[i] != NULL) {
224 f->do_oop(&c->_data[i]);
225 }
226 }
227 }
228
229 void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {
230 Chunk* head = OrderAccess::load_acquire(&_head);
231 if (head != NULL) {
232 // Must be careful when reading size of head
233 oops_do_chunk(f, head, OrderAccess::load_acquire(&head->_size));
234 for (Chunk* c = head->_next; c != NULL; c = c->_next) {
235 oops_do_chunk(f, c, c->_size);
236 }
237 }
238 }
239
240 class VerifyContainsOopClosure : public OopClosure {
241 oop _target;
242 bool _found;
243
244 public:
245 VerifyContainsOopClosure(oop target) : _target(target), _found(false) {}
246
247 void do_oop(oop* p) {
248 if (p != NULL && oopDesc::equals(RawAccess<>::oop_load(p), _target)) {
249 _found = true;
250 }
251 }
252
253 void do_oop(narrowOop* p) {
254 // The ChunkedHandleList should not contain any narrowOop
255 ShouldNotReachHere();
256 }
257
258 bool found() const {
259 return _found;
260 }
261 };
262
263 bool ClassLoaderData::ChunkedHandleList::contains(oop p) {
264 VerifyContainsOopClosure cl(p);
265 oops_do(&cl);
266 return cl.found();
267 }
268
269 #ifndef PRODUCT
270 bool ClassLoaderData::ChunkedHandleList::owner_of(oop* oop_handle) {
271 Chunk* chunk = _head;
272 while (chunk != NULL) {
273 if (&(chunk->_data[0]) <= oop_handle && oop_handle < &(chunk->_data[chunk->_size])) {
274 return true;
275 }
276 chunk = chunk->_next;
277 }
278 return false;
279 }
280 #endif // PRODUCT
281
282 bool ClassLoaderData::claim(bool finalizable) {
283 for (;;) {
284 int old_claim = Atomic::load(&_claimed);
285 int claim_mask = finalizable ? 1 : 3;
286 if ((old_claim & claim_mask) == claim_mask) {
287 return false;
288 }
289 int new_claim = old_claim | claim_mask;
290 if (Atomic::cmpxchg(new_claim, &_claimed, old_claim) == old_claim) {
291 return true;
292 }
293 }
294 }
295
296 // Anonymous classes have their own ClassLoaderData that is marked to keep alive
297 // while the class is being parsed, and if the class appears on the module fixup list.
298 // Due to the uniqueness that no other class shares the anonymous class' name or
299 // ClassLoaderData, no other non-GC thread has knowledge of the anonymous class while
300 // it is being defined, therefore _keep_alive is not volatile or atomic.
301 void ClassLoaderData::inc_keep_alive() {
302 if (is_anonymous()) {
303 assert(_keep_alive >= 0, "Invalid keep alive increment count");
304 _keep_alive++;
305 }
306 }
307
308 void ClassLoaderData::dec_keep_alive() {
309 if (is_anonymous()) {
310 assert(_keep_alive > 0, "Invalid keep alive decrement count");
311 _keep_alive--;
312 }
313 }
314
315 void ClassLoaderData::oops_do(OopClosure* f, bool must_claim, bool clear_mod_oops) {
316 if (must_claim && !claim()) {
317 return;
318 }
319
320 // Only clear modified_oops after the ClassLoaderData is claimed.
321 if (clear_mod_oops) {
322 clear_modified_oops();
323 }
324
325 _handles.oops_do(f);
326 }
327
328 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
329 // Lock-free access requires load_acquire
330 for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
331 klass_closure->do_klass(k);
332 assert(k != k->next_link(), "no loops!");
333 }
334 }
335
336 void ClassLoaderData::classes_do(void f(Klass * const)) {
337 // Lock-free access requires load_acquire
338 for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
339 f(k);
340 assert(k != k->next_link(), "no loops!");
341 }
342 }
343
344 void ClassLoaderData::methods_do(void f(Method*)) {
345 // Lock-free access requires load_acquire
346 for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
347 if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
348 InstanceKlass::cast(k)->methods_do(f);
349 }
350 }
351 }
352
353 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
354 // Lock-free access requires load_acquire
355 for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
356 // Do not filter ArrayKlass oops here...
357 if (k->is_array_klass() || (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded())) {
358 klass_closure->do_klass(k);
359 }
360 }
361 }
362
363 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
364 // Lock-free access requires load_acquire
365 for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
366 if (k->is_instance_klass()) {
367 f(InstanceKlass::cast(k));
368 }
369 assert(k != k->next_link(), "no loops!");
370 }
371 }
372
373 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
374 assert_locked_or_safepoint(Module_lock);
375 if (_unnamed_module != NULL) {
376 f(_unnamed_module);
377 }
378 if (_modules != NULL) {
379 for (int i = 0; i < _modules->table_size(); i++) {
380 for (ModuleEntry* entry = _modules->bucket(i);
381 entry != NULL;
382 entry = entry->next()) {
383 f(entry);
384 }
385 }
386 }
387 }
388
389 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
390 assert_locked_or_safepoint(Module_lock);
391 if (_packages != NULL) {
392 for (int i = 0; i < _packages->table_size(); i++) {
393 for (PackageEntry* entry = _packages->bucket(i);
394 entry != NULL;
395 entry = entry->next()) {
396 f(entry);
397 }
398 }
399 }
400 }
401
402 void ClassLoaderData::record_dependency(const Klass* k) {
403 assert(k != NULL, "invariant");
404
405 ClassLoaderData * const from_cld = this;
406 ClassLoaderData * const to_cld = k->class_loader_data();
407
408 // Do not need to record dependency if the dependency is to a class whose
409 // class loader data is never freed. (i.e. the dependency's class loader
410 // is one of the three builtin class loaders and the dependency is not
411 // anonymous.)
412 if (to_cld->is_permanent_class_loader_data()) {
413 return;
414 }
415
416 oop to;
417 if (to_cld->is_anonymous()) {
418 // Just return if an anonymous class is attempting to record a dependency
419 // to itself. (Note that every anonymous class has its own unique class
420 // loader data.)
421 if (to_cld == from_cld) {
422 return;
423 }
424 // Anonymous class dependencies are through the mirror.
425 to = k->java_mirror();
426 } else {
427 to = to_cld->class_loader();
428 oop from = from_cld->class_loader();
429
430 // Just return if this dependency is to a class with the same or a parent
431 // class_loader.
432 if (oopDesc::equals(from, to) || java_lang_ClassLoader::isAncestor(from, to)) {
433 return; // this class loader is in the parent list, no need to add it.
434 }
435 }
436
437 // It's a dependency we won't find through GC, add it.
438 if (!_handles.contains(to)) {
439 NOT_PRODUCT(Atomic::inc(&_dependency_count));
440 LogTarget(Trace, class, loader, data) lt;
441 if (lt.is_enabled()) {
442 ResourceMark rm;
443 LogStream ls(lt);
444 ls.print("adding dependency from ");
445 print_value_on(&ls);
446 ls.print(" to ");
447 to_cld->print_value_on(&ls);
448 ls.cr();
449 }
450 Handle dependency(Thread::current(), to);
451 add_handle(dependency);
452 // Added a potentially young gen oop to the ClassLoaderData
453 record_modified_oops();
454 }
455 }
456
457
458 void ClassLoaderDataGraph::clear_claimed_marks() {
459 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
460 cld->clear_claimed();
461 }
462 }
463
464 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
465 {
466 MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
467 Klass* old_value = _klasses;
468 k->set_next_link(old_value);
469 // Link the new item into the list, making sure the linked class is stable
470 // since the list can be walked without a lock
471 OrderAccess::release_store(&_klasses, k);
472 if (k->is_array_klass()) {
473 ClassLoaderDataGraph::inc_array_classes(1);
474 } else {
475 ClassLoaderDataGraph::inc_instance_classes(1);
476 }
477 }
478
479 if (publicize) {
480 LogTarget(Trace, class, loader, data) lt;
481 if (lt.is_enabled()) {
482 ResourceMark rm;
483 LogStream ls(lt);
484 ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());
485 print_value_on(&ls);
486 ls.cr();
487 }
488 }
489 }
490
491 // Class iterator used by the compiler. It gets some number of classes at
492 // a safepoint to decay invocation counters on the methods.
493 class ClassLoaderDataGraphKlassIteratorStatic {
494 ClassLoaderData* _current_loader_data;
495 Klass* _current_class_entry;
496 public:
497
498 ClassLoaderDataGraphKlassIteratorStatic() : _current_loader_data(NULL), _current_class_entry(NULL) {}
499
500 InstanceKlass* try_get_next_class() {
501 assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
502 size_t max_classes = ClassLoaderDataGraph::num_instance_classes();
503 assert(max_classes > 0, "should not be called with no instance classes");
504 for (size_t i = 0; i < max_classes; ) {
505
506 if (_current_class_entry != NULL) {
507 Klass* k = _current_class_entry;
508 _current_class_entry = _current_class_entry->next_link();
509
510 if (k->is_instance_klass()) {
511 InstanceKlass* ik = InstanceKlass::cast(k);
512 i++; // count all instance classes found
513 // Not yet loaded classes are counted in max_classes
514 // but only return loaded classes.
515 if (ik->is_loaded()) {
516 return ik;
517 }
518 }
519 } else {
520 // Go to next CLD
521 if (_current_loader_data != NULL) {
522 _current_loader_data = _current_loader_data->next();
523 }
524 // Start at the beginning
525 if (_current_loader_data == NULL) {
526 _current_loader_data = ClassLoaderDataGraph::_head;
527 }
528
529 _current_class_entry = _current_loader_data->klasses();
530 }
531 }
532 // Should never be reached unless all instance classes have failed or are not fully loaded.
533 // Caller handles NULL.
534 return NULL;
535 }
536
537 // If the current class for the static iterator is a class being unloaded or
538 // deallocated, adjust the current class.
539 void adjust_saved_class(ClassLoaderData* cld) {
540 if (_current_loader_data == cld) {
541 _current_loader_data = cld->next();
542 if (_current_loader_data != NULL) {
543 _current_class_entry = _current_loader_data->klasses();
544 } // else try_get_next_class will start at the head
545 }
546 }
547
548 void adjust_saved_class(Klass* klass) {
549 if (_current_class_entry == klass) {
550 _current_class_entry = klass->next_link();
551 }
552 }
553 };
554
555 static ClassLoaderDataGraphKlassIteratorStatic static_klass_iterator;
556
557 InstanceKlass* ClassLoaderDataGraph::try_get_next_class() {
558 return static_klass_iterator.try_get_next_class();
559 }
560
561 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) {
562 if (loader_or_mirror() != NULL) {
563 assert(_holder.is_null(), "never replace holders");
564 _holder = WeakHandle<vm_class_loader_data>::create(loader_or_mirror);
565 }
566 }
567
568 // Remove a klass from the _klasses list for scratch_class during redefinition
569 // or parsed class in the case of an error.
570 void ClassLoaderData::remove_class(Klass* scratch_class) {
571 assert(UseZGC || SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
572
573 // Adjust global class iterator.
574 static_klass_iterator.adjust_saved_class(scratch_class);
575
576 Klass* prev = NULL;
577 for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
578 if (k == scratch_class) {
579 if (prev == NULL) {
580 _klasses = k->next_link();
581 } else {
582 Klass* next = k->next_link();
583 prev->set_next_link(next);
584 }
585
586 if (k->is_array_klass()) {
587 ClassLoaderDataGraph::dec_array_classes(1);
588 } else {
589 ClassLoaderDataGraph::dec_instance_classes(1);
590 }
591
592 return;
593 }
594 prev = k;
595 assert(k != k->next_link(), "no loops!");
596 }
597 ShouldNotReachHere(); // should have found this class!!
598 }
599
600 void ClassLoaderData::unload() {
601 MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
602 _unloading = true;
603
604 LogTarget(Trace, class, loader, data) lt;
605 if (lt.is_enabled()) {
606 ResourceMark rm;
607 LogStream ls(lt);
608 ls.print("unload");
609 print_value_on(&ls);
610 ls.cr();
611 }
612
613 // Some items on the _deallocate_list need to free their C heap structures
614 // if they are not already on the _klasses list.
615 free_deallocate_list_C_heap_structures();
616
617 // Tell serviceability tools these classes are unloading
618 // after erroneous classes are released.
619 classes_do(InstanceKlass::notify_unload_class);
620
621 // Clean up global class iterator for compiler
622 static_klass_iterator.adjust_saved_class(this);
623 }
624
625 ModuleEntryTable* ClassLoaderData::modules() {
626 // Lazily create the module entry table at first request.
627 // Lock-free access requires load_acquire.
628 ModuleEntryTable* modules = OrderAccess::load_acquire(&_modules);
629 if (modules == NULL) {
630 MutexLocker m1(Module_lock);
631 // Check if _modules got allocated while we were waiting for this lock.
632 if ((modules = _modules) == NULL) {
633 modules = new ModuleEntryTable(ModuleEntryTable::_moduletable_entry_size);
634
635 {
636 MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
637 // Ensure _modules is stable, since it is examined without a lock
638 OrderAccess::release_store(&_modules, modules);
639 }
640 }
641 }
642 return modules;
643 }
644
645 const int _boot_loader_dictionary_size = 1009;
646 const int _default_loader_dictionary_size = 107;
647
648 Dictionary* ClassLoaderData::create_dictionary() {
649 assert(!is_anonymous(), "anonymous class loader data do not have a dictionary");
650 int size;
651 bool resizable = false;
652 if (_the_null_class_loader_data == NULL) {
653 size = _boot_loader_dictionary_size;
654 resizable = true;
655 } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
656 size = 1; // there's only one class in relection class loader and no initiated classes
657 } else if (is_system_class_loader_data()) {
658 size = _boot_loader_dictionary_size;
659 resizable = true;
660 } else {
661 size = _default_loader_dictionary_size;
662 resizable = true;
663 }
664 if (!DynamicallyResizeSystemDictionaries || DumpSharedSpaces || UseSharedSpaces) {
665 resizable = false;
666 }
667 return new Dictionary(this, size, resizable);
668 }
669
670 // Tell the GC to keep this klass alive while iterating ClassLoaderDataGraph
671 oop ClassLoaderData::holder_phantom() const {
672 // A klass that was previously considered dead can be looked up in the
673 // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
674 // or a reachable object making it alive again. The SATB part of G1 needs
675 // to get notified about this potential resurrection, otherwise the marking
676 // might not find the object.
677 if (!_holder.is_null()) { // NULL class_loader
678 return _holder.resolve();
679 } else {
680 return NULL;
681 }
682 }
683
684 oop ClassLoaderData::holder_no_keepalive() const {
685 if (!_holder.is_null()) { // NULL class_loader
686 return _holder.peek();
687 } else {
688 return NULL;
689 }
690 }
691
692 // Unloading support
693 bool ClassLoaderData::is_alive() const {
694 bool alive = keep_alive() // null class loader and incomplete anonymous klasses.
695 || (_holder.peek() != NULL); // and not cleaned by the GC weak handle processing.
696
697 return alive;
698 }
699
700 class ReleaseKlassClosure: public KlassClosure {
701 private:
702 size_t _instance_class_released;
703 size_t _array_class_released;
704 public:
705 ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { }
706
707 size_t instance_class_released() const { return _instance_class_released; }
708 size_t array_class_released() const { return _array_class_released; }
709
710 void do_klass(Klass* k) {
711 if (k->is_array_klass()) {
712 _array_class_released ++;
713 } else {
714 assert(k->is_instance_klass(), "Must be");
715 _instance_class_released ++;
716 InstanceKlass::release_C_heap_structures(InstanceKlass::cast(k));
717 }
718 }
719 };
720
721 ClassLoaderData::~ClassLoaderData() {
722 {
723 MutexLockerEx m(SafepointSynchronize::is_at_safepoint() ? NULL : CodeCache_lock,
724 Mutex::_no_safepoint_check_flag);
725 // Release C heap structures for all the classes.
726 ReleaseKlassClosure cl;
727 classes_do(&cl);
728
729 ClassLoaderDataGraph::dec_array_classes(cl.array_class_released());
730 ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released());
731 }
732
733 // Release the WeakHandle
734 _holder.release();
735
736 // Release C heap allocated hashtable for all the packages.
737 if (_packages != NULL) {
738 // Destroy the table itself
739 delete _packages;
740 _packages = NULL;
741 }
742
743 // Release C heap allocated hashtable for all the modules.
744 if (_modules != NULL) {
745 // Destroy the table itself
746 delete _modules;
747 _modules = NULL;
748 }
749
750 // Release C heap allocated hashtable for the dictionary
751 if (_dictionary != NULL) {
752 // Destroy the table itself
753 delete _dictionary;
754 _dictionary = NULL;
755 }
756
757 if (_unnamed_module != NULL) {
758 _unnamed_module->delete_unnamed_module();
759 _unnamed_module = NULL;
760 }
761
762 // release the metaspace
763 ClassLoaderMetaspace *m = _metaspace;
764 if (m != NULL) {
765 _metaspace = NULL;
766 delete m;
767 }
768 // Clear all the JNI handles for methods
769 // These aren't deallocated and are going to look like a leak, but that's
770 // needed because we can't really get rid of jmethodIDs because we don't
771 // know when native code is going to stop using them. The spec says that
772 // they're "invalid" but existing programs likely rely on their being
773 // NULL after class unloading.
774 if (_jmethod_ids != NULL) {
775 Method::clear_jmethod_ids(this);
776 }
777 // Delete lock
778 delete _metaspace_lock;
779
780 // Delete free list
781 if (_deallocate_list != NULL) {
782 delete _deallocate_list;
783 }
784 }
785
786 // Returns true if this class loader data is for the app class loader
787 // or a user defined system class loader. (Note that the class loader
788 // data may be anonymous.)
789 bool ClassLoaderData::is_system_class_loader_data() const {
790 return SystemDictionary::is_system_class_loader(class_loader());
791 }
792
793 // Returns true if this class loader data is for the platform class loader.
794 // (Note that the class loader data may be anonymous.)
795 bool ClassLoaderData::is_platform_class_loader_data() const {
796 return SystemDictionary::is_platform_class_loader(class_loader());
797 }
798
799 // Returns true if the class loader for this class loader data is one of
800 // the 3 builtin (boot application/system or platform) class loaders,
801 // including a user-defined system class loader. Note that if the class
802 // loader data is for an anonymous class then it may get freed by a GC
803 // even if its class loader is one of these loaders.
804 bool ClassLoaderData::is_builtin_class_loader_data() const {
805 return (is_boot_class_loader_data() ||
806 SystemDictionary::is_system_class_loader(class_loader()) ||
807 SystemDictionary::is_platform_class_loader(class_loader()));
808 }
809
810 // Returns true if this class loader data is a class loader data
811 // that is not ever freed by a GC. It must be one of the builtin
812 // class loaders and not anonymous.
813 bool ClassLoaderData::is_permanent_class_loader_data() const {
814 return is_builtin_class_loader_data() && !is_anonymous();
815 }
816
817 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() {
818 // If the metaspace has not been allocated, create a new one. Might want
819 // to create smaller arena for Reflection class loaders also.
820 // The reason for the delayed allocation is because some class loaders are
821 // simply for delegating with no metadata of their own.
822 // Lock-free access requires load_acquire.
823 ClassLoaderMetaspace* metaspace = OrderAccess::load_acquire(&_metaspace);
824 if (metaspace == NULL) {
825 MutexLockerEx ml(_metaspace_lock, Mutex::_no_safepoint_check_flag);
826 // Check if _metaspace got allocated while we were waiting for this lock.
827 if ((metaspace = _metaspace) == NULL) {
828 if (this == the_null_class_loader_data()) {
829 assert (class_loader() == NULL, "Must be");
830 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
831 } else if (is_anonymous()) {
832 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType);
833 } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
834 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
835 } else {
836 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
837 }
838 // Ensure _metaspace is stable, since it is examined without a lock
839 OrderAccess::release_store(&_metaspace, metaspace);
840 }
841 }
842 return metaspace;
843 }
844
845 OopHandle ClassLoaderData::add_handle(Handle h) {
846 MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
847 record_modified_oops();
848 return OopHandle(_handles.add(h()));
849 }
850
851 void ClassLoaderData::remove_handle(OopHandle h) {
852 assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading");
853 oop* ptr = h.ptr_raw();
854 if (ptr != NULL) {
855 assert(_handles.owner_of(ptr), "Got unexpected handle " PTR_FORMAT, p2i(ptr));
856 NativeAccess<>::oop_store(ptr, oop(NULL));
857 }
858 }
859
860 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
861 MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
862 if (dest.resolve() != NULL) {
863 return;
864 } else {
865 dest = _handles.add(h());
866 }
867 }
868
869 // Add this metadata pointer to be freed when it's safe. This is only during
870 // a safepoint which checks if handles point to this metadata field.
871 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
872 // Metadata in shared region isn't deleted.
873 if (!m->is_shared()) {
874 MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
875 if (_deallocate_list == NULL) {
876 _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, true);
877 }
878 _deallocate_list->append_if_missing(m);
879 log_debug(class, loader, data)("deallocate added for %s", m->print_value_string());
880 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
881 }
882 }
883
884 // Deallocate free metadata on the free list. How useful the PermGen was!
885 void ClassLoaderData::free_deallocate_list() {
886 MutexLockerEx ml(SafepointSynchronize::is_at_safepoint() ? NULL : metaspace_lock(),
887 Mutex::_no_safepoint_check_flag);
888 assert(!is_unloading(), "only called for ClassLoaderData that are not unloading");
889 if (_deallocate_list == NULL) {
890 return;
891 }
892 // Go backwards because this removes entries that are freed.
893 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
894 Metadata* m = _deallocate_list->at(i);
895 if (!m->on_stack()) {
896 _deallocate_list->remove_at(i);
897 // There are only three types of metadata that we deallocate directly.
898 // Cast them so they can be used by the template function.
899 if (m->is_method()) {
900 MetadataFactory::free_metadata(this, (Method*)m);
901 } else if (m->is_constantPool()) {
902 MetadataFactory::free_metadata(this, (ConstantPool*)m);
903 } else if (m->is_klass()) {
904 MetadataFactory::free_metadata(this, (InstanceKlass*)m);
905 } else {
906 ShouldNotReachHere();
907 }
908 } else {
909 // Metadata is alive.
910 // If scratch_class is on stack then it shouldn't be on this list!
911 assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
912 "scratch classes on this list should be dead");
913 // Also should assert that other metadata on the list was found in handles.
914 // Some cleaning remains.
915 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
916 }
917 }
918 }
919
920 void ClassLoaderDataGraph::clean_deallocate_lists(bool walk_previous_versions) {
921 uint loaders_processed = 0;
922 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
923 // is_alive check will be necessary for concurrent class unloading.
924 if (cld->is_alive()) {
925 // clean metaspace
926 if (walk_previous_versions) {
927 cld->classes_do(InstanceKlass::purge_previous_versions);
928 }
929 cld->free_deallocate_list();
930 loaders_processed++;
931 }
932 }
933 log_debug(class, loader, data)("clean_deallocate_lists: loaders processed %u %s",
934 loaders_processed, walk_previous_versions ? "walk_previous_versions" : "");
935 }
936
937 void ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces() {
938 assert(SafepointSynchronize::is_at_safepoint(), "must only be called at safepoint");
939
940 _should_clean_deallocate_lists = false; // assume everything gets cleaned
941
942 // Mark metadata seen on the stack so we can delete unreferenced entries.
943 // Walk all metadata, including the expensive code cache walk, only for class redefinition.
944 // The MetadataOnStackMark walk during redefinition saves previous versions if it finds old methods
945 // on the stack or in the code cache, so we only have to repeat the full walk if
946 // they were found at that time.
947 // TODO: have redefinition clean old methods out of the code cache. They still exist in some places.
948 bool walk_all_metadata = InstanceKlass::has_previous_versions_and_reset();
949
950 MetadataOnStackMark md_on_stack(walk_all_metadata);
951 clean_deallocate_lists(walk_all_metadata);
952 }
953
954 // This is distinct from free_deallocate_list. For class loader data that are
955 // unloading, this frees the C heap memory for items on the list, and unlinks
956 // scratch or error classes so that unloading events aren't triggered for these
957 // classes. The metadata is removed with the unloading metaspace.
958 // There isn't C heap memory allocated for methods, so nothing is done for them.
959 void ClassLoaderData::free_deallocate_list_C_heap_structures() {
960 // Don't need lock, at safepoint
961 assert(UseZGC || SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
962 assert(is_unloading(), "only called for ClassLoaderData that are unloading");
963 if (_deallocate_list == NULL) {
964 return;
965 }
966 // Go backwards because this removes entries that are freed.
967 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
968 Metadata* m = _deallocate_list->at(i);
969 _deallocate_list->remove_at(i);
970 if (m->is_constantPool()) {
971 ((ConstantPool*)m)->release_C_heap_structures();
972 } else if (m->is_klass()) {
973 InstanceKlass* ik = (InstanceKlass*)m;
974 // also releases ik->constants() C heap memory
975 InstanceKlass::release_C_heap_structures(ik);
976 // Remove the class so unloading events aren't triggered for
977 // this class (scratch or error class) in do_unloading().
978 remove_class(ik);
979 }
980 }
981 }
982
983 // These anonymous class loaders are to contain classes used for JSR292
984 ClassLoaderData* ClassLoaderData::anonymous_class_loader_data(Handle loader) {
985 // Add a new class loader data to the graph.
986 return ClassLoaderDataGraph::add(loader, true);
987 }
988
989 // Caller needs ResourceMark
990 // If the class loader's _name has not been explicitly set, the class loader's
991 // qualified class name is returned.
992 const char* ClassLoaderData::loader_name() const {
993 if (_class_loader_klass == NULL) {
994 return BOOTSTRAP_LOADER_NAME;
995 } else if (_name != NULL) {
996 return _name->as_C_string();
997 } else {
998 return _class_loader_klass->external_name();
999 }
1000 }
1001
1002 // Caller needs ResourceMark
1003 // Format of the _name_and_id is as follows:
1004 // If the defining loader has a name explicitly set then '<loader-name>' @<id>
1005 // If the defining loader has no name then <qualified-class-name> @<id>
1006 // If built-in loader, then omit '@<id>' as there is only one instance.
1007 const char* ClassLoaderData::loader_name_and_id() const {
1008 if (_class_loader_klass == NULL) {
1009 return "'" BOOTSTRAP_LOADER_NAME "'";
1010 } else if (_name_and_id != NULL) {
1011 return _name_and_id->as_C_string();
1012 } else {
1013 // May be called in a race before _name_and_id is initialized.
1014 return _class_loader_klass->external_name();
1015 }
1016 }
1017
1018 void ClassLoaderData::print_value_on(outputStream* out) const {
1019 if (!is_unloading() && class_loader() != NULL) {
1020 out->print("loader data: " INTPTR_FORMAT " for instance ", p2i(this));
1021 class_loader()->print_value_on(out); // includes loader_name_and_id() and address of class loader instance
1022 } else {
1023 // loader data: 0xsomeaddr of 'bootstrap'
1024 out->print("loader data: " INTPTR_FORMAT " of %s", p2i(this), loader_name_and_id());
1025 }
1026 if (is_anonymous()) {
1027 out->print(" anonymous");
1028 }
1029 }
1030
1031 #ifndef PRODUCT
1032 void ClassLoaderData::print_on(outputStream* out) const {
1033 out->print("ClassLoaderData CLD: " PTR_FORMAT ", loader: " PTR_FORMAT ", loader_klass: %s {",
1034 p2i(this), p2i(_class_loader.ptr_raw()), loader_name_and_id());
1035 if (is_anonymous()) out->print(" anonymous");
1036 if (claimed()) out->print(" claimed");
1037 if (is_unloading()) out->print(" unloading");
1038 out->print(" metaspace: " INTPTR_FORMAT, p2i(metaspace_or_null()));
1039
1040 if (_jmethod_ids != NULL) {
1041 Method::print_jmethod_ids(this, out);
1042 }
1043 out->print(" handles count %d", _handles.count());
1044 out->print(" dependencies %d", _dependency_count);
1045 out->print_cr("}");
1046 }
1047 #endif // PRODUCT
1048
1049 void ClassLoaderData::verify() {
1050 assert_locked_or_safepoint(_metaspace_lock);
1051 oop cl = class_loader();
1052
1053 guarantee(this == class_loader_data(cl) || is_anonymous(), "Must be the same");
1054 guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || is_anonymous(), "must be");
1055
1056 // Verify the integrity of the allocated space.
1057 if (metaspace_or_null() != NULL) {
1058 metaspace_or_null()->verify();
1059 }
1060
1061 for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
1062 guarantee(k->class_loader_data() == this, "Must be the same");
1063 k->verify();
1064 assert(k != k->next_link(), "no loops!");
1065 }
1066 }
1067
1068 bool ClassLoaderData::contains_klass(Klass* klass) {
1069 // Lock-free access requires load_acquire
1070 for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
1071 if (k == klass) return true;
1072 }
1073 return false;
1074 }
1075
1076
1077 // GC root of class loader data created.
1078 ClassLoaderData* ClassLoaderDataGraph::_head = NULL;
1079 ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;
1080 ClassLoaderData* ClassLoaderDataGraph::_saved_unloading = NULL;
1081 ClassLoaderData* ClassLoaderDataGraph::_saved_head = NULL;
1082
1083 bool ClassLoaderDataGraph::_should_purge = false;
1084 bool ClassLoaderDataGraph::_should_clean_deallocate_lists = false;
1085 bool ClassLoaderDataGraph::_safepoint_cleanup_needed = false;
1086 bool ClassLoaderDataGraph::_metaspace_oom = false;
1087
1088 // Add a new class loader data node to the list. Assign the newly created
1089 // ClassLoaderData into the java/lang/ClassLoader object as a hidden field
1090 ClassLoaderData* ClassLoaderDataGraph::add_to_graph(Handle loader, bool is_anonymous) {
1091 NoSafepointVerifier no_safepoints; // we mustn't GC until we've installed the
1092 // ClassLoaderData in the graph since the CLD
1093 // contains oops in _handles that must be walked.
1094
1095 ClassLoaderData* cld = new ClassLoaderData(loader, is_anonymous);
1096
1097 if (!is_anonymous) {
1098 // First, Atomically set it
1099 ClassLoaderData* old = java_lang_ClassLoader::cmpxchg_loader_data(cld, loader(), NULL);
1100 if (old != NULL) {
1101 delete cld;
1102 // Returns the data.
1103 return old;
1104 }
1105 }
1106
1107 // We won the race, and therefore the task of adding the data to the list of
1108 // class loader data
1109 ClassLoaderData** list_head = &_head;
1110 ClassLoaderData* next = _head;
1111
1112 do {
1113 cld->set_next(next);
1114 ClassLoaderData* exchanged = Atomic::cmpxchg(cld, list_head, next);
1115 if (exchanged == next) {
1116 LogTarget(Trace, class, loader, data) lt;
1117 if (lt.is_enabled()) {
1118 ResourceMark rm;
1119 LogStream ls(lt);
1120 ls.print("create ");
1121 cld->print_value_on(&ls);
1122 ls.cr();
1123 }
1124 return cld;
1125 }
1126 next = exchanged;
1127 } while (true);
1128 }
1129
1130 ClassLoaderData* ClassLoaderDataGraph::add(Handle loader, bool is_anonymous) {
1131 ClassLoaderData* loader_data = add_to_graph(loader, is_anonymous);
1132 // Initialize _name and _name_and_id after the loader data is added to the
1133 // CLDG because adding the Symbol for _name and _name_and_id might safepoint.
1134 if (loader.not_null()) {
1135 loader_data->initialize_name(loader);
1136 }
1137 return loader_data;
1138 }
1139
1140 void ClassLoaderDataGraph::oops_do(OopClosure* f, bool must_claim) {
1141 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1142 cld->oops_do(f, must_claim);
1143 }
1144 }
1145
1146 void ClassLoaderDataGraph::keep_alive_oops_do(OopClosure* f, bool must_claim) {
1147 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1148 if (cld->keep_alive()) {
1149 cld->oops_do(f, must_claim);
1150 }
1151 }
1152 }
1153
1154 void ClassLoaderDataGraph::always_strong_oops_do(OopClosure* f, bool must_claim) {
1155 if (ClassUnloading) {
1156 keep_alive_oops_do(f, must_claim);
1157 } else {
1158 oops_do(f, must_claim);
1159 }
1160 }
1161
1162 void ClassLoaderDataGraph::cld_do(CLDClosure* cl) {
1163 for (ClassLoaderData* cld = _head; cl != NULL && cld != NULL; cld = cld->next()) {
1164 cl->do_cld(cld);
1165 }
1166 }
1167
1168 void ClassLoaderDataGraph::cld_unloading_do(CLDClosure* cl) {
1169 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1170 // Only walk the head until any clds not purged from prior unloading
1171 // (CMS doesn't purge right away).
1172 for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
1173 assert(cld->is_unloading(), "invariant");
1174 cl->do_cld(cld);
1175 }
1176 }
1177
1178 void ClassLoaderDataGraph::roots_cld_do(CLDClosure* strong, CLDClosure* weak) {
1179 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->_next) {
1180 CLDClosure* closure = cld->keep_alive() ? strong : weak;
1181 if (closure != NULL) {
1182 closure->do_cld(cld);
1183 }
1184 }
1185 }
1186
1187 void ClassLoaderDataGraph::keep_alive_cld_do(CLDClosure* cl) {
1188 roots_cld_do(cl, NULL);
1189 }
1190
1191 void ClassLoaderDataGraph::always_strong_cld_do(CLDClosure* cl) {
1192 if (ClassUnloading) {
1193 keep_alive_cld_do(cl);
1194 } else {
1195 cld_do(cl);
1196 }
1197 }
1198
1199 void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
1200 Thread* thread = Thread::current();
1201 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1202 Handle holder(thread, cld->holder_phantom());
1203 cld->classes_do(klass_closure);
1204 }
1205 }
1206
1207 void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
1208 Thread* thread = Thread::current();
1209 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1210 Handle holder(thread, cld->holder_phantom());
1211 cld->classes_do(f);
1212 }
1213 }
1214
1215 void ClassLoaderDataGraph::methods_do(void f(Method*)) {
1216 Thread* thread = Thread::current();
1217 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1218 Handle holder(thread, cld->holder_phantom());
1219 cld->methods_do(f);
1220 }
1221 }
1222
1223 void ClassLoaderDataGraph::modules_do(void f(ModuleEntry*)) {
1224 assert_locked_or_safepoint(Module_lock);
1225 Thread* thread = Thread::current();
1226 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1227 Handle holder(thread, cld->holder_phantom());
1228 cld->modules_do(f);
1229 }
1230 }
1231
1232 void ClassLoaderDataGraph::modules_unloading_do(void f(ModuleEntry*)) {
1233 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1234 // Only walk the head until any clds not purged from prior unloading
1235 // (CMS doesn't purge right away).
1236 for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
1237 assert(cld->is_unloading(), "invariant");
1238 cld->modules_do(f);
1239 }
1240 }
1241
1242 void ClassLoaderDataGraph::packages_do(void f(PackageEntry*)) {
1243 assert_locked_or_safepoint(Module_lock);
1244 Thread* thread = Thread::current();
1245 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1246 Handle holder(thread, cld->holder_phantom());
1247 cld->packages_do(f);
1248 }
1249 }
1250
1251 void ClassLoaderDataGraph::packages_unloading_do(void f(PackageEntry*)) {
1252 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1253 // Only walk the head until any clds not purged from prior unloading
1254 // (CMS doesn't purge right away).
1255 for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
1256 assert(cld->is_unloading(), "invariant");
1257 cld->packages_do(f);
1258 }
1259 }
1260
1261 void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
1262 Thread* thread = Thread::current();
1263 for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1264 Handle holder(thread, cld->holder_phantom());
1265 cld->loaded_classes_do(klass_closure);
1266 }
1267 }
1268
1269 void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
1270 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1271 // Only walk the head until any clds not purged from prior unloading
1272 // (CMS doesn't purge right away).
1273 for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
1274 assert(cld->is_unloading(), "invariant");
1275 cld->classes_do(f);
1276 }
1277 }
1278
1279 #define FOR_ALL_DICTIONARY(X) for (ClassLoaderData* X = _head; X != NULL; X = X->next()) \
1280 if (X->dictionary() != NULL)
1281
1282 // Walk classes in the loaded class dictionaries in various forms.
1283 // Only walks the classes defined in this class loader.
1284 void ClassLoaderDataGraph::dictionary_classes_do(void f(InstanceKlass*)) {
1285 Thread* thread = Thread::current();
1286 FOR_ALL_DICTIONARY(cld) {
1287 Handle holder(thread, cld->holder_phantom());
1288 cld->dictionary()->classes_do(f);
1289 }
1290 }
1291
1292 // Only walks the classes defined in this class loader.
1293 void ClassLoaderDataGraph::dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS) {
1294 Thread* thread = Thread::current();
1295 FOR_ALL_DICTIONARY(cld) {
1296 Handle holder(thread, cld->holder_phantom());
1297 cld->dictionary()->classes_do(f, CHECK);
1298 }
1299 }
1300
1301 // Walks all entries in the dictionary including entries initiated by this class loader.
1302 void ClassLoaderDataGraph::dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*)) {
1303 Thread* thread = Thread::current();
1304 FOR_ALL_DICTIONARY(cld) {
1305 Handle holder(thread, cld->holder_phantom());
1306 cld->dictionary()->all_entries_do(f);
1307 }
1308 }
1309
1310 void ClassLoaderDataGraph::verify_dictionary() {
1311 FOR_ALL_DICTIONARY(cld) {
1312 cld->dictionary()->verify();
1313 }
1314 }
1315
1316 void ClassLoaderDataGraph::print_dictionary(outputStream* st) {
1317 FOR_ALL_DICTIONARY(cld) {
1318 st->print("Dictionary for ");
1319 cld->print_value_on(st);
1320 st->cr();
1321 cld->dictionary()->print_on(st);
1322 st->cr();
1323 }
1324 }
1325
1326 void ClassLoaderDataGraph::print_dictionary_statistics(outputStream* st) {
1327 FOR_ALL_DICTIONARY(cld) {
1328 ResourceMark rm;
1329 stringStream tempst;
1330 tempst.print("System Dictionary for %s class loader", cld->loader_name_and_id());
1331 cld->dictionary()->print_table_statistics(st, tempst.as_string());
1332 }
1333 }
1334
1335 GrowableArray<ClassLoaderData*>* ClassLoaderDataGraph::new_clds() {
1336 assert(_head == NULL || _saved_head != NULL, "remember_new_clds(true) not called?");
1337
1338 GrowableArray<ClassLoaderData*>* array = new GrowableArray<ClassLoaderData*>();
1339
1340 // The CLDs in [_head, _saved_head] were all added during last call to remember_new_clds(true);
1341 ClassLoaderData* curr = _head;
1342 while (curr != _saved_head) {
1343 if (!curr->claimed()) {
1344 array->push(curr);
1345 LogTarget(Debug, class, loader, data) lt;
1346 if (lt.is_enabled()) {
1347 LogStream ls(lt);
1348 ls.print("found new CLD: ");
1349 curr->print_value_on(&ls);
1350 ls.cr();
1351 }
1352 }
1353
1354 curr = curr->_next;
1355 }
1356
1357 return array;
1358 }
1359
1360 #ifndef PRODUCT
1361 bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {
1362 for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
1363 if (loader_data == data) {
1364 return true;
1365 }
1366 }
1367
1368 return false;
1369 }
1370 #endif // PRODUCT
1371
1372 #if INCLUDE_JFR
1373 static Ticks class_unload_time;
1374 static void post_class_unload_event(Klass* const k) {
1375 assert(k != NULL, "invariant");
1376 EventClassUnload event(UNTIMED);
1377 event.set_endtime(class_unload_time);
1378 event.set_unloadedClass(k);
1379 event.set_definingClassLoader(k->class_loader_data());
1380 event.commit();
1381 }
1382
1383 static void post_class_unload_events() {
1384 assert(UseZGC || SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1385 if (Jfr::is_enabled()) {
1386 if (EventClassUnload::is_enabled()) {
1387 class_unload_time = Ticks::now();
1388 ClassLoaderDataGraph::classes_unloading_do(&post_class_unload_event);
1389 }
1390 Jfr::on_unloading_classes();
1391 }
1392 }
1393 #endif // INCLUDE_JFR
1394
1395 // Move class loader data from main list to the unloaded list for unloading
1396 // and deallocation later.
1397 bool ClassLoaderDataGraph::do_unloading(bool do_cleaning) {
1398
1399 // Indicate whether safepoint cleanup is needed.
1400 _safepoint_cleanup_needed |= do_cleaning;
1401
1402 ClassLoaderData* data = _head;
1403 ClassLoaderData* prev = NULL;
1404 bool seen_dead_loader = false;
1405 uint loaders_processed = 0;
1406 uint loaders_removed = 0;
1407
1408 // Save previous _unloading pointer for CMS which may add to unloading list before
1409 // purging and we don't want to rewalk the previously unloaded class loader data.
1410 _saved_unloading = _unloading;
1411
1412 data = _head;
1413 while (data != NULL) {
1414 if (data->is_alive()) {
1415 prev = data;
1416 data = data->next();
1417 loaders_processed++;
1418 continue;
1419 }
1420 seen_dead_loader = true;
1421 loaders_removed++;
1422 ClassLoaderData* dead = data;
1423 dead->unload();
1424 data = data->next();
1425 // Remove from loader list.
1426 // This class loader data will no longer be found
1427 // in the ClassLoaderDataGraph.
1428 if (prev != NULL) {
1429 prev->set_next(data);
1430 } else {
1431 assert(dead == _head, "sanity check");
1432 _head = data;
1433 }
1434 dead->set_next(_unloading);
1435 _unloading = dead;
1436 }
1437
1438 if (seen_dead_loader) {
1439 data = _head;
1440 while (data != NULL) {
1441 // Remove entries in the dictionary of live class loader that have
1442 // initiated loading classes in a dead class loader.
1443 if (data->dictionary() != NULL) {
1444 data->dictionary()->do_unloading();
1445 }
1446 // Walk a ModuleEntry's reads, and a PackageEntry's exports
1447 // lists to determine if there are modules on those lists that are now
1448 // dead and should be removed. A module's life cycle is equivalent
1449 // to its defining class loader's life cycle. Since a module is
1450 // considered dead if its class loader is dead, these walks must
1451 // occur after each class loader's aliveness is determined.
1452 MutexLockerEx ml(UseZGC ? Module_lock : NULL);
1453 if (data->packages() != NULL) {
1454 data->packages()->purge_all_package_exports();
1455 }
1456 if (data->modules_defined()) {
1457 data->modules()->purge_all_module_reads();
1458 }
1459 data = data->next();
1460 }
1461 if (!UseZGC) {
1462 SymbolTable::do_check_concurrent_work();
1463 }
1464 JFR_ONLY(post_class_unload_events();)
1465 }
1466
1467 log_debug(class, loader, data)("do_unloading: loaders processed %u, loaders removed %u", loaders_processed, loaders_removed);
1468
1469 return seen_dead_loader;
1470 }
1471
1472 // There's at least one dead class loader. Purge refererences of healthy module
1473 // reads lists and package export lists to modules belonging to dead loaders.
1474 void ClassLoaderDataGraph::clean_module_and_package_info() {
1475 ClassLoaderData* data = _head;
1476 while (data != NULL) {
1477 // Remove entries in the dictionary of live class loader that have
1478 // initiated loading classes in a dead class loader.
1479 if (data->dictionary() != NULL) {
1480 data->dictionary()->do_unloading();
1481 }
1482 // Walk a ModuleEntry's reads, and a PackageEntry's exports
1483 // lists to determine if there are modules on those lists that are now
1484 // dead and should be removed. A module's life cycle is equivalent
1485 // to its defining class loader's life cycle. Since a module is
1486 // considered dead if its class loader is dead, these walks must
1487 // occur after each class loader's aliveness is determined.
1488 MutexLockerEx ml(UseZGC ? Module_lock : NULL);
1489 if (data->packages() != NULL) {
1490 data->packages()->purge_all_package_exports();
1491 }
1492 if (data->modules_defined()) {
1493 data->modules()->purge_all_module_reads();
1494 }
1495 data = data->next();
1496 }
1497 }
1498
1499 void ClassLoaderDataGraph::purge() {
1500 assert(UseZGC || SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1501 ClassLoaderData* list = _unloading;
1502 _unloading = NULL;
1503 ClassLoaderData* next = list;
1504 bool classes_unloaded = false;
1505 while (next != NULL) {
1506 ClassLoaderData* purge_me = next;
1507 next = purge_me->next();
1508 delete purge_me;
1509 classes_unloaded = true;
1510 }
1511 if (classes_unloaded) {
1512 Metaspace::purge();
1513 set_metaspace_oom(false);
1514 }
1515 }
1516
1517 int ClassLoaderDataGraph::resize_if_needed() {
1518 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1519 int resized = 0;
1520 if (Dictionary::does_any_dictionary_needs_resizing()) {
1521 FOR_ALL_DICTIONARY(cld) {
1522 if (cld->dictionary()->resize_if_needed()) {
1523 resized++;
1524 }
1525 }
1526 }
1527 return resized;
1528 }
1529
1530 ClassLoaderDataGraphKlassIteratorAtomic::ClassLoaderDataGraphKlassIteratorAtomic()
1531 : _next_klass(NULL) {
1532 ClassLoaderData* cld = ClassLoaderDataGraph::_head;
1533 Klass* klass = NULL;
1534
1535 // Find the first klass in the CLDG.
1536 while (cld != NULL) {
1537 assert_locked_or_safepoint(cld->metaspace_lock());
1538 klass = cld->_klasses;
1539 if (klass != NULL) {
1540 _next_klass = klass;
1541 return;
1542 }
1543 cld = cld->next();
1544 }
1545 }
1546
1547 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass_in_cldg(Klass* klass) {
1548 Klass* next = klass->next_link();
1549 if (next != NULL) {
1550 return next;
1551 }
1552
1553 // No more klasses in the current CLD. Time to find a new CLD.
1554 ClassLoaderData* cld = klass->class_loader_data();
1555 assert_locked_or_safepoint(cld->metaspace_lock());
1556 while (next == NULL) {
1557 cld = cld->next();
1558 if (cld == NULL) {
1559 break;
1560 }
1561 next = cld->_klasses;
1562 }
1563
1564 return next;
1565 }
1566
1567 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass() {
1568 Klass* head = _next_klass;
1569
1570 while (head != NULL) {
1571 Klass* next = next_klass_in_cldg(head);
1572
1573 Klass* old_head = Atomic::cmpxchg(next, &_next_klass, head);
1574
1575 if (old_head == head) {
1576 return head; // Won the CAS.
1577 }
1578
1579 head = old_head;
1580 }
1581
1582 // Nothing more for the iterator to hand out.
1583 assert(head == NULL, "head is " PTR_FORMAT ", expected not null:", p2i(head));
1584 return NULL;
1585 }
1586
1587 ClassLoaderDataGraphMetaspaceIterator::ClassLoaderDataGraphMetaspaceIterator() {
1588 _data = ClassLoaderDataGraph::_head;
1589 }
1590
1591 ClassLoaderDataGraphMetaspaceIterator::~ClassLoaderDataGraphMetaspaceIterator() {}
1592
1593 #ifndef PRODUCT
1594 // callable from debugger
1595 extern "C" int print_loader_data_graph() {
1596 ResourceMark rm;
1597 ClassLoaderDataGraph::print_on(tty);
1598 return 0;
1599 }
1600
1601 void ClassLoaderDataGraph::verify() {
1602 for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
1603 data->verify();
1604 }
1605 }
1606
1607 void ClassLoaderDataGraph::print_on(outputStream * const out) {
1608 for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
1609 data->print_on(out);
1610 }
1611 }
1612 #endif // PRODUCT