1 /*
2 * Copyright (c) 2012, 2020, 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.inline.hpp"
51 #include "classfile/classLoaderDataGraph.inline.hpp"
52 #include "classfile/dictionary.hpp"
53 #include "classfile/javaClasses.hpp"
54 #include "classfile/moduleEntry.hpp"
55 #include "classfile/packageEntry.hpp"
56 #include "classfile/symbolTable.hpp"
57 #include "classfile/systemDictionary.hpp"
58 #include "logging/log.hpp"
59 #include "logging/logStream.hpp"
60 #include "memory/allocation.inline.hpp"
61 #include "memory/metadataFactory.hpp"
62 #include "memory/iterator.hpp"
63 #include "memory/resourceArea.hpp"
64 #include "memory/universe.hpp"
65 #include "oops/access.inline.hpp"
66 #include "oops/array.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/safepoint.hpp"
74 #include "utilities/growableArray.hpp"
75 #include "utilities/macros.hpp"
76 #include "utilities/ostream.hpp"
77
78 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
79
80 void ClassLoaderData::init_null_class_loader_data() {
81 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
82 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
83
84 _the_null_class_loader_data = new ClassLoaderData(Handle(), false);
85 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
86 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
87
88 LogTarget(Trace, class, loader, data) lt;
89 if (lt.is_enabled()) {
90 ResourceMark rm;
91 LogStream ls(lt);
92 ls.print("create ");
93 _the_null_class_loader_data->print_value_on(&ls);
94 ls.cr();
95 }
96 }
97
98 // Obtain and set the class loader's name within the ClassLoaderData so
99 // it will be available for error messages, logging, JFR, etc. The name
100 // and klass are available after the class_loader oop is no longer alive,
101 // during unloading.
102 void ClassLoaderData::initialize_name(Handle class_loader) {
103 Thread* THREAD = Thread::current();
104 ResourceMark rm(THREAD);
105
106 // Obtain the class loader's name. If the class loader's name was not
107 // explicitly set during construction, the CLD's _name field will be null.
108 oop cl_name = java_lang_ClassLoader::name(class_loader());
109 if (cl_name != NULL) {
110 const char* cl_instance_name = java_lang_String::as_utf8_string(cl_name);
111
112 if (cl_instance_name != NULL && cl_instance_name[0] != '\0') {
113 _name = SymbolTable::new_symbol(cl_instance_name);
114 }
115 }
116
117 // Obtain the class loader's name and identity hash. If the class loader's
118 // name was not explicitly set during construction, the class loader's name and id
119 // will be set to the qualified class name of the class loader along with its
120 // identity hash.
121 // If for some reason the ClassLoader's constructor has not been run, instead of
122 // leaving the _name_and_id field null, fall back to the external qualified class
123 // name. Thus CLD's _name_and_id field should never have a null value.
124 oop cl_name_and_id = java_lang_ClassLoader::nameAndId(class_loader());
125 const char* cl_instance_name_and_id =
126 (cl_name_and_id == NULL) ? _class_loader_klass->external_name() :
127 java_lang_String::as_utf8_string(cl_name_and_id);
128 assert(cl_instance_name_and_id != NULL && cl_instance_name_and_id[0] != '\0', "class loader has no name and id");
129 _name_and_id = SymbolTable::new_symbol(cl_instance_name_and_id);
130 }
131
132 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool has_class_mirror_holder) :
133 _metaspace(NULL),
134 _metaspace_lock(new Mutex(Mutex::leaf+1, "Metaspace allocation lock", true,
135 Mutex::_safepoint_check_never)),
136 _unloading(false), _has_class_mirror_holder(has_class_mirror_holder),
137 _modified_oops(true), _accumulated_modified_oops(false),
138 // An unsafe anonymous class loader data doesn't have anything to keep
139 // it from being unloaded during parsing of the unsafe anonymous class.
140 // The null-class-loader should always be kept alive.
141 _keep_alive((has_class_mirror_holder || h_class_loader.is_null()) ? 1 : 0),
142 _claim(0),
143 _handles(),
144 _klasses(NULL), _packages(NULL), _modules(NULL), _unnamed_module(NULL), _dictionary(NULL),
145 _jmethod_ids(NULL),
146 _deallocate_list(NULL),
147 _next(NULL),
148 _class_loader_klass(NULL), _name(NULL), _name_and_id(NULL) {
149
150 if (!h_class_loader.is_null()) {
151 _class_loader = _handles.add(h_class_loader());
152 _class_loader_klass = h_class_loader->klass();
153 initialize_name(h_class_loader);
154 }
155
156 if (!has_class_mirror_holder) {
157 // The holder is initialized later for non-strong hidden classes and unsafe anonymous classes,
158 // and before calling anything that call class_loader().
159 initialize_holder(h_class_loader);
160
161 // A ClassLoaderData created solely for a non-strong hidden class or unsafe anonymous class should
162 // never have a ModuleEntryTable or PackageEntryTable created for it. The defining package
163 // and module for an unsafe anonymous class will be found in its host class.
164 _packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);
165 if (h_class_loader.is_null()) {
166 // Create unnamed module for boot loader
167 _unnamed_module = ModuleEntry::create_boot_unnamed_module(this);
168 } else {
169 // Create unnamed module for all other loaders
170 _unnamed_module = ModuleEntry::create_unnamed_module(this);
171 }
172 _dictionary = create_dictionary();
173 }
174
175 NOT_PRODUCT(_dependency_count = 0); // number of class loader dependencies
176
177 JFR_ONLY(INIT_ID(this);)
178 }
179
180 ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {
181 Chunk* c = _head;
182 while (c != NULL) {
183 Chunk* next = c->_next;
184 delete c;
185 c = next;
186 }
187 }
188
189 OopHandle ClassLoaderData::ChunkedHandleList::add(oop o) {
190 if (_head == NULL || _head->_size == Chunk::CAPACITY) {
191 Chunk* next = new Chunk(_head);
192 Atomic::release_store(&_head, next);
193 }
194 oop* handle = &_head->_data[_head->_size];
195 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, o);
196 Atomic::release_store(&_head->_size, _head->_size + 1);
197 return OopHandle(handle);
198 }
199
200 int ClassLoaderData::ChunkedHandleList::count() const {
201 int count = 0;
202 Chunk* chunk = _head;
203 while (chunk != NULL) {
204 count += chunk->_size;
205 chunk = chunk->_next;
206 }
207 return count;
208 }
209
210 inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {
211 for (juint i = 0; i < size; i++) {
212 if (c->_data[i] != NULL) {
213 f->do_oop(&c->_data[i]);
214 }
215 }
216 }
217
218 void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {
219 Chunk* head = Atomic::load_acquire(&_head);
220 if (head != NULL) {
221 // Must be careful when reading size of head
222 oops_do_chunk(f, head, Atomic::load_acquire(&head->_size));
223 for (Chunk* c = head->_next; c != NULL; c = c->_next) {
224 oops_do_chunk(f, c, c->_size);
225 }
226 }
227 }
228
229 class VerifyContainsOopClosure : public OopClosure {
230 oop _target;
231 bool _found;
232
233 public:
234 VerifyContainsOopClosure(oop target) : _target(target), _found(false) {}
235
236 void do_oop(oop* p) {
237 if (p != NULL && NativeAccess<AS_NO_KEEPALIVE>::oop_load(p) == _target) {
238 _found = true;
239 }
240 }
241
242 void do_oop(narrowOop* p) {
243 // The ChunkedHandleList should not contain any narrowOop
244 ShouldNotReachHere();
245 }
246
247 bool found() const {
248 return _found;
249 }
250 };
251
252 bool ClassLoaderData::ChunkedHandleList::contains(oop p) {
253 VerifyContainsOopClosure cl(p);
254 oops_do(&cl);
255 return cl.found();
256 }
257
258 #ifndef PRODUCT
259 bool ClassLoaderData::ChunkedHandleList::owner_of(oop* oop_handle) {
260 Chunk* chunk = _head;
261 while (chunk != NULL) {
262 if (&(chunk->_data[0]) <= oop_handle && oop_handle < &(chunk->_data[chunk->_size])) {
263 return true;
264 }
265 chunk = chunk->_next;
266 }
267 return false;
268 }
269 #endif // PRODUCT
270
271 void ClassLoaderData::clear_claim(int claim) {
272 for (;;) {
273 int old_claim = Atomic::load(&_claim);
274 if ((old_claim & claim) == 0) {
275 return;
276 }
277 int new_claim = old_claim & ~claim;
278 if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
279 return;
280 }
281 }
282 }
283
284 bool ClassLoaderData::try_claim(int claim) {
285 for (;;) {
286 int old_claim = Atomic::load(&_claim);
287 if ((old_claim & claim) == claim) {
288 return false;
289 }
290 int new_claim = old_claim | claim;
291 if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
292 return true;
293 }
294 }
295 }
296
297 // Weak hidden and unsafe anonymous classes have their own ClassLoaderData that is marked to keep alive
298 // while the class is being parsed, and if the class appears on the module fixup list.
299 // Due to the uniqueness that no other class shares the hidden or unsafe anonymous class' name or
300 // ClassLoaderData, no other non-GC thread has knowledge of the hidden or unsafe anonymous class while
301 // it is being defined, therefore _keep_alive is not volatile or atomic.
302 void ClassLoaderData::inc_keep_alive() {
303 if (has_class_mirror_holder()) {
304 assert(_keep_alive > 0, "Invalid keep alive increment count");
305 _keep_alive++;
306 }
307 }
308
309 void ClassLoaderData::dec_keep_alive() {
310 if (has_class_mirror_holder()) {
311 assert(_keep_alive > 0, "Invalid keep alive decrement count");
312 _keep_alive--;
313 }
314 }
315
316 void ClassLoaderData::oops_do(OopClosure* f, int claim_value, bool clear_mod_oops) {
317 if (claim_value != ClassLoaderData::_claim_none && !try_claim(claim_value)) {
318 return;
319 }
320
321 // Only clear modified_oops after the ClassLoaderData is claimed.
322 if (clear_mod_oops) {
323 clear_modified_oops();
324 }
325
326 _handles.oops_do(f);
327 }
328
329 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
330 // Lock-free access requires load_acquire
331 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
332 klass_closure->do_klass(k);
333 assert(k != k->next_link(), "no loops!");
334 }
335 }
336
337 void ClassLoaderData::classes_do(void f(Klass * const)) {
338 // Lock-free access requires load_acquire
339 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
340 f(k);
341 assert(k != k->next_link(), "no loops!");
342 }
343 }
344
345 void ClassLoaderData::methods_do(void f(Method*)) {
346 // Lock-free access requires load_acquire
347 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
348 if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
349 InstanceKlass::cast(k)->methods_do(f);
350 }
351 }
352 }
353
354 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
355 // Lock-free access requires load_acquire
356 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
357 // Do not filter ArrayKlass oops here...
358 if (k->is_array_klass() || (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded())) {
359 #ifdef ASSERT
360 oop m = k->java_mirror();
361 assert(m != NULL, "NULL mirror");
362 assert(m->is_a(SystemDictionary::Class_klass()), "invalid mirror");
363 #endif
364 klass_closure->do_klass(k);
365 }
366 }
367 }
368
369 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
370 // Lock-free access requires load_acquire
371 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
372 if (k->is_instance_klass()) {
373 f(InstanceKlass::cast(k));
374 }
375 assert(k != k->next_link(), "no loops!");
376 }
377 }
378
379 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
380 assert_locked_or_safepoint(Module_lock);
381 if (_unnamed_module != NULL) {
382 f(_unnamed_module);
383 }
384 if (_modules != NULL) {
385 for (int i = 0; i < _modules->table_size(); i++) {
386 for (ModuleEntry* entry = _modules->bucket(i);
387 entry != NULL;
388 entry = entry->next()) {
389 f(entry);
390 }
391 }
392 }
393 }
394
395 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
396 assert_locked_or_safepoint(Module_lock);
397 if (_packages != NULL) {
398 for (int i = 0; i < _packages->table_size(); i++) {
399 for (PackageEntry* entry = _packages->bucket(i);
400 entry != NULL;
401 entry = entry->next()) {
402 f(entry);
403 }
404 }
405 }
406 }
407
408 void ClassLoaderData::record_dependency(const Klass* k) {
409 assert(k != NULL, "invariant");
410
411 ClassLoaderData * const from_cld = this;
412 ClassLoaderData * const to_cld = k->class_loader_data();
413
414 // Do not need to record dependency if the dependency is to a class whose
415 // class loader data is never freed. (i.e. the dependency's class loader
416 // is one of the three builtin class loaders and the dependency's class
417 // loader data has a ClassLoader holder, not a Class holder.)
418 if (to_cld->is_permanent_class_loader_data()) {
419 return;
420 }
421
422 oop to;
423 if (to_cld->has_class_mirror_holder()) {
424 // Just return if a non-strong hidden class or unsafe anonymous class is attempting to record a dependency
425 // to itself. (Note that every non-strong hidden class or unsafe anonymous class has its own unique class
426 // loader data.)
427 if (to_cld == from_cld) {
428 return;
429 }
430 // Hidden and unsafe anonymous class dependencies are through the mirror.
431 to = k->java_mirror();
432 } else {
433 to = to_cld->class_loader();
434 oop from = from_cld->class_loader();
435
436 // Just return if this dependency is to a class with the same or a parent
437 // class_loader.
438 if (from == to || java_lang_ClassLoader::isAncestor(from, to)) {
439 return; // this class loader is in the parent list, no need to add it.
440 }
441 }
442
443 // It's a dependency we won't find through GC, add it.
444 if (!_handles.contains(to)) {
445 NOT_PRODUCT(Atomic::inc(&_dependency_count));
446 LogTarget(Trace, class, loader, data) lt;
447 if (lt.is_enabled()) {
448 ResourceMark rm;
449 LogStream ls(lt);
450 ls.print("adding dependency from ");
451 print_value_on(&ls);
452 ls.print(" to ");
453 to_cld->print_value_on(&ls);
454 ls.cr();
455 }
456 Handle dependency(Thread::current(), to);
457 add_handle(dependency);
458 // Added a potentially young gen oop to the ClassLoaderData
459 record_modified_oops();
460 }
461 }
462
463 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
464 {
465 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
466 Klass* old_value = _klasses;
467 k->set_next_link(old_value);
468 // Link the new item into the list, making sure the linked class is stable
469 // since the list can be walked without a lock
470 Atomic::release_store(&_klasses, k);
471 if (k->is_array_klass()) {
472 ClassLoaderDataGraph::inc_array_classes(1);
473 } else {
474 ClassLoaderDataGraph::inc_instance_classes(1);
475 }
476 }
477
478 if (publicize) {
479 LogTarget(Trace, class, loader, data) lt;
480 if (lt.is_enabled()) {
481 ResourceMark rm;
482 LogStream ls(lt);
483 ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());
484 print_value_on(&ls);
485 ls.cr();
486 }
487 }
488 }
489
490 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) {
491 if (loader_or_mirror() != NULL) {
492 assert(_holder.is_null(), "never replace holders");
493 _holder = WeakHandle(Universe::vm_weak(), loader_or_mirror);
494 }
495 }
496
497 // Remove a klass from the _klasses list for scratch_class during redefinition
498 // or parsed class in the case of an error.
499 void ClassLoaderData::remove_class(Klass* scratch_class) {
500 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
501
502 // Adjust global class iterator.
503 ClassLoaderDataGraph::adjust_saved_class(scratch_class);
504
505 Klass* prev = NULL;
506 for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
507 if (k == scratch_class) {
508 if (prev == NULL) {
509 _klasses = k->next_link();
510 } else {
511 Klass* next = k->next_link();
512 prev->set_next_link(next);
513 }
514
515 if (k->is_array_klass()) {
516 ClassLoaderDataGraph::dec_array_classes(1);
517 } else {
518 ClassLoaderDataGraph::dec_instance_classes(1);
519 }
520
521 return;
522 }
523 prev = k;
524 assert(k != k->next_link(), "no loops!");
525 }
526 ShouldNotReachHere(); // should have found this class!!
527 }
528
529 void ClassLoaderData::unload() {
530 _unloading = true;
531
532 LogTarget(Trace, class, loader, data) lt;
533 if (lt.is_enabled()) {
534 ResourceMark rm;
535 LogStream ls(lt);
536 ls.print("unload");
537 print_value_on(&ls);
538 ls.cr();
539 }
540
541 // Some items on the _deallocate_list need to free their C heap structures
542 // if they are not already on the _klasses list.
543 free_deallocate_list_C_heap_structures();
544
545 // Clean up class dependencies and tell serviceability tools
546 // these classes are unloading. Must be called
547 // after erroneous classes are released.
548 classes_do(InstanceKlass::unload_class);
549
550 // Clean up global class iterator for compiler
551 ClassLoaderDataGraph::adjust_saved_class(this);
552 }
553
554 ModuleEntryTable* ClassLoaderData::modules() {
555 // Lazily create the module entry table at first request.
556 // Lock-free access requires load_acquire.
557 ModuleEntryTable* modules = Atomic::load_acquire(&_modules);
558 if (modules == NULL) {
559 MutexLocker m1(Module_lock);
560 // Check if _modules got allocated while we were waiting for this lock.
561 if ((modules = _modules) == NULL) {
562 modules = new ModuleEntryTable(ModuleEntryTable::_moduletable_entry_size);
563
564 {
565 MutexLocker m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
566 // Ensure _modules is stable, since it is examined without a lock
567 Atomic::release_store(&_modules, modules);
568 }
569 }
570 }
571 return modules;
572 }
573
574 const int _boot_loader_dictionary_size = 1009;
575 const int _default_loader_dictionary_size = 107;
576
577 Dictionary* ClassLoaderData::create_dictionary() {
578 assert(!has_class_mirror_holder(), "class mirror holder cld does not have a dictionary");
579 int size;
580 bool resizable = false;
581 if (_the_null_class_loader_data == NULL) {
582 size = _boot_loader_dictionary_size;
583 resizable = true;
584 } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
585 size = 1; // there's only one class in relection class loader and no initiated classes
586 } else if (is_system_class_loader_data()) {
587 size = _boot_loader_dictionary_size;
588 resizable = true;
589 } else {
590 size = _default_loader_dictionary_size;
591 resizable = true;
592 }
593 if (!DynamicallyResizeSystemDictionaries || DumpSharedSpaces) {
594 resizable = false;
595 }
596 return new Dictionary(this, size, resizable);
597 }
598
599 // Tell the GC to keep this klass alive while iterating ClassLoaderDataGraph
600 oop ClassLoaderData::holder_phantom() const {
601 // A klass that was previously considered dead can be looked up in the
602 // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
603 // or a reachable object making it alive again. The SATB part of G1 needs
604 // to get notified about this potential resurrection, otherwise the marking
605 // might not find the object.
606 if (!_holder.is_null()) { // NULL class_loader
607 return _holder.resolve();
608 } else {
609 return NULL;
610 }
611 }
612
613 // Let the GC read the holder without keeping it alive.
614 oop ClassLoaderData::holder_no_keepalive() const {
615 if (!_holder.is_null()) { // NULL class_loader
616 return _holder.peek();
617 } else {
618 return NULL;
619 }
620 }
621
622 // Unloading support
623 bool ClassLoaderData::is_alive() const {
624 bool alive = keep_alive() // null class loader and incomplete non-strong hidden class or unsafe anonymous class.
625 || (_holder.peek() != NULL); // and not cleaned by the GC weak handle processing.
626
627 return alive;
628 }
629
630 class ReleaseKlassClosure: public KlassClosure {
631 private:
632 size_t _instance_class_released;
633 size_t _array_class_released;
634 public:
635 ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { }
636
637 size_t instance_class_released() const { return _instance_class_released; }
638 size_t array_class_released() const { return _array_class_released; }
639
640 void do_klass(Klass* k) {
641 if (k->is_array_klass()) {
642 _array_class_released ++;
643 } else {
644 assert(k->is_instance_klass(), "Must be");
645 _instance_class_released ++;
646 }
647 k->release_C_heap_structures();
648 }
649 };
650
651 ClassLoaderData::~ClassLoaderData() {
652 // Release C heap structures for all the classes.
653 ReleaseKlassClosure cl;
654 classes_do(&cl);
655
656 ClassLoaderDataGraph::dec_array_classes(cl.array_class_released());
657 ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released());
658
659 // Release the WeakHandle
660 _holder.release(Universe::vm_weak());
661
662 // Release C heap allocated hashtable for all the packages.
663 if (_packages != NULL) {
664 // Destroy the table itself
665 delete _packages;
666 _packages = NULL;
667 }
668
669 // Release C heap allocated hashtable for all the modules.
670 if (_modules != NULL) {
671 // Destroy the table itself
672 delete _modules;
673 _modules = NULL;
674 }
675
676 // Release C heap allocated hashtable for the dictionary
677 if (_dictionary != NULL) {
678 // Destroy the table itself
679 delete _dictionary;
680 _dictionary = NULL;
681 }
682
683 if (_unnamed_module != NULL) {
684 _unnamed_module->delete_unnamed_module();
685 _unnamed_module = NULL;
686 }
687
688 // release the metaspace
689 ClassLoaderMetaspace *m = _metaspace;
690 if (m != NULL) {
691 _metaspace = NULL;
692 delete m;
693 }
694 // Clear all the JNI handles for methods
695 // These aren't deallocated and are going to look like a leak, but that's
696 // needed because we can't really get rid of jmethodIDs because we don't
697 // know when native code is going to stop using them. The spec says that
698 // they're "invalid" but existing programs likely rely on their being
699 // NULL after class unloading.
700 if (_jmethod_ids != NULL) {
701 Method::clear_jmethod_ids(this);
702 }
703 // Delete lock
704 delete _metaspace_lock;
705
706 // Delete free list
707 if (_deallocate_list != NULL) {
708 delete _deallocate_list;
709 }
710
711 // Decrement refcounts of Symbols if created.
712 if (_name != NULL) {
713 _name->decrement_refcount();
714 }
715 if (_name_and_id != NULL) {
716 _name_and_id->decrement_refcount();
717 }
718 }
719
720 // Returns true if this class loader data is for the app class loader
721 // or a user defined system class loader. (Note that the class loader
722 // data may have a Class holder.)
723 bool ClassLoaderData::is_system_class_loader_data() const {
724 return SystemDictionary::is_system_class_loader(class_loader());
725 }
726
727 // Returns true if this class loader data is for the platform class loader.
728 // (Note that the class loader data may have a Class holder.)
729 bool ClassLoaderData::is_platform_class_loader_data() const {
730 return SystemDictionary::is_platform_class_loader(class_loader());
731 }
732
733 // Returns true if the class loader for this class loader data is one of
734 // the 3 builtin (boot application/system or platform) class loaders,
735 // including a user-defined system class loader. Note that if the class
736 // loader data is for a non-strong hidden class or unsafe anonymous class then it may
737 // get freed by a GC even if its class loader is one of these loaders.
738 bool ClassLoaderData::is_builtin_class_loader_data() const {
739 return (is_boot_class_loader_data() ||
740 SystemDictionary::is_system_class_loader(class_loader()) ||
741 SystemDictionary::is_platform_class_loader(class_loader()));
742 }
743
744 // Returns true if this class loader data is a class loader data
745 // that is not ever freed by a GC. It must be the CLD for one of the builtin
746 // class loaders and not the CLD for a non-strong hidden class or unsafe anonymous class.
747 bool ClassLoaderData::is_permanent_class_loader_data() const {
748 return is_builtin_class_loader_data() && !has_class_mirror_holder();
749 }
750
751 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() {
752 // If the metaspace has not been allocated, create a new one. Might want
753 // to create smaller arena for Reflection class loaders also.
754 // The reason for the delayed allocation is because some class loaders are
755 // simply for delegating with no metadata of their own.
756 // Lock-free access requires load_acquire.
757 ClassLoaderMetaspace* metaspace = Atomic::load_acquire(&_metaspace);
758 if (metaspace == NULL) {
759 MutexLocker ml(_metaspace_lock, Mutex::_no_safepoint_check_flag);
760 // Check if _metaspace got allocated while we were waiting for this lock.
761 if ((metaspace = _metaspace) == NULL) {
762 if (this == the_null_class_loader_data()) {
763 assert (class_loader() == NULL, "Must be");
764 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
765 } else if (has_class_mirror_holder()) {
766 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ClassMirrorHolderMetaspaceType);
767 } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
768 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
769 } else {
770 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
771 }
772 // Ensure _metaspace is stable, since it is examined without a lock
773 Atomic::release_store(&_metaspace, metaspace);
774 }
775 }
776 return metaspace;
777 }
778
779 OopHandle ClassLoaderData::add_handle(Handle h) {
780 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
781 record_modified_oops();
782 return _handles.add(h());
783 }
784
785 void ClassLoaderData::remove_handle(OopHandle h) {
786 assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading");
787 oop* ptr = h.ptr_raw();
788 if (ptr != NULL) {
789 assert(_handles.owner_of(ptr), "Got unexpected handle " PTR_FORMAT, p2i(ptr));
790 NativeAccess<>::oop_store(ptr, oop(NULL));
791 }
792 }
793
794 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
795 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
796 if (dest.resolve() != NULL) {
797 return;
798 } else {
799 dest = _handles.add(h());
800 }
801 }
802
803 // Add this metadata pointer to be freed when it's safe. This is only during
804 // a safepoint which checks if handles point to this metadata field.
805 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
806 // Metadata in shared region isn't deleted.
807 if (!m->is_shared()) {
808 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
809 if (_deallocate_list == NULL) {
810 _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, mtClass);
811 }
812 _deallocate_list->append_if_missing(m);
813 log_debug(class, loader, data)("deallocate added for %s", m->print_value_string());
814 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
815 }
816 }
817
818 // Deallocate free metadata on the free list. How useful the PermGen was!
819 void ClassLoaderData::free_deallocate_list() {
820 // This must be called at a safepoint because it depends on metadata walking at
821 // safepoint cleanup time.
822 assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
823 assert(!is_unloading(), "only called for ClassLoaderData that are not unloading");
824 if (_deallocate_list == NULL) {
825 return;
826 }
827 // Go backwards because this removes entries that are freed.
828 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
829 Metadata* m = _deallocate_list->at(i);
830 if (!m->on_stack()) {
831 _deallocate_list->remove_at(i);
832 // There are only three types of metadata that we deallocate directly.
833 // Cast them so they can be used by the template function.
834 if (m->is_method()) {
835 MetadataFactory::free_metadata(this, (Method*)m);
836 } else if (m->is_constantPool()) {
837 MetadataFactory::free_metadata(this, (ConstantPool*)m);
838 } else if (m->is_klass()) {
839 MetadataFactory::free_metadata(this, (InstanceKlass*)m);
840 } else {
841 ShouldNotReachHere();
842 }
843 } else {
844 // Metadata is alive.
845 // If scratch_class is on stack then it shouldn't be on this list!
846 assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
847 "scratch classes on this list should be dead");
848 // Also should assert that other metadata on the list was found in handles.
849 // Some cleaning remains.
850 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
851 }
852 }
853 }
854
855 // This is distinct from free_deallocate_list. For class loader data that are
856 // unloading, this frees the C heap memory for items on the list, and unlinks
857 // scratch or error classes so that unloading events aren't triggered for these
858 // classes. The metadata is removed with the unloading metaspace.
859 // There isn't C heap memory allocated for methods, so nothing is done for them.
860 void ClassLoaderData::free_deallocate_list_C_heap_structures() {
861 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
862 assert(is_unloading(), "only called for ClassLoaderData that are unloading");
863 if (_deallocate_list == NULL) {
864 return;
865 }
866 // Go backwards because this removes entries that are freed.
867 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
868 Metadata* m = _deallocate_list->at(i);
869 _deallocate_list->remove_at(i);
870 if (m->is_constantPool()) {
871 ((ConstantPool*)m)->release_C_heap_structures();
872 } else if (m->is_klass()) {
873 InstanceKlass* ik = (InstanceKlass*)m;
874 // also releases ik->constants() C heap memory
875 ik->release_C_heap_structures();
876 // Remove the class so unloading events aren't triggered for
877 // this class (scratch or error class) in do_unloading().
878 remove_class(ik);
879 }
880 }
881 }
882
883 // Caller needs ResourceMark
884 // If the class loader's _name has not been explicitly set, the class loader's
885 // qualified class name is returned.
886 const char* ClassLoaderData::loader_name() const {
887 if (_class_loader_klass == NULL) {
888 return BOOTSTRAP_LOADER_NAME;
889 } else if (_name != NULL) {
890 return _name->as_C_string();
891 } else {
892 return _class_loader_klass->external_name();
893 }
894 }
895
896 // Caller needs ResourceMark
897 // Format of the _name_and_id is as follows:
898 // If the defining loader has a name explicitly set then '<loader-name>' @<id>
899 // If the defining loader has no name then <qualified-class-name> @<id>
900 // If built-in loader, then omit '@<id>' as there is only one instance.
901 const char* ClassLoaderData::loader_name_and_id() const {
902 if (_class_loader_klass == NULL) {
903 return "'" BOOTSTRAP_LOADER_NAME "'";
904 } else if (_name_and_id != NULL) {
905 return _name_and_id->as_C_string();
906 } else {
907 // May be called in a race before _name_and_id is initialized.
908 return _class_loader_klass->external_name();
909 }
910 }
911
912 void ClassLoaderData::print_value_on(outputStream* out) const {
913 if (!is_unloading() && class_loader() != NULL) {
914 out->print("loader data: " INTPTR_FORMAT " for instance ", p2i(this));
915 class_loader()->print_value_on(out); // includes loader_name_and_id() and address of class loader instance
916 } else {
917 // loader data: 0xsomeaddr of 'bootstrap'
918 out->print("loader data: " INTPTR_FORMAT " of %s", p2i(this), loader_name_and_id());
919 }
920 if (_has_class_mirror_holder) {
921 out->print(" has a class holder");
922 }
923 }
924
925 void ClassLoaderData::print_value() const { print_value_on(tty); }
926
927 #ifndef PRODUCT
928 void ClassLoaderData::print_on(outputStream* out) const {
929 out->print("ClassLoaderData CLD: " PTR_FORMAT ", loader: " PTR_FORMAT ", loader_klass: %s {",
930 p2i(this), p2i(_class_loader.ptr_raw()), loader_name_and_id());
931 if (has_class_mirror_holder()) out->print(" has a class holder");
932 if (claimed()) out->print(" claimed");
933 if (is_unloading()) out->print(" unloading");
934 out->print(" metaspace: " INTPTR_FORMAT, p2i(metaspace_or_null()));
935
936 if (_jmethod_ids != NULL) {
937 Method::print_jmethod_ids(this, out);
938 }
939 out->print(" handles count %d", _handles.count());
940 out->print(" dependencies %d", _dependency_count);
941 out->print_cr("}");
942 }
943 #endif // PRODUCT
944
945 void ClassLoaderData::print() const { print_on(tty); }
946
947 void ClassLoaderData::verify() {
948 assert_locked_or_safepoint(_metaspace_lock);
949 oop cl = class_loader();
950
951 guarantee(this == class_loader_data(cl) || has_class_mirror_holder(), "Must be the same");
952 guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || has_class_mirror_holder(), "must be");
953
954 // Verify the integrity of the allocated space.
955 if (metaspace_or_null() != NULL) {
956 metaspace_or_null()->verify();
957 }
958
959 for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
960 guarantee(k->class_loader_data() == this, "Must be the same");
961 k->verify();
962 assert(k != k->next_link(), "no loops!");
963 }
964 }
965
966 bool ClassLoaderData::contains_klass(Klass* klass) {
967 // Lock-free access requires load_acquire
968 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
969 if (k == klass) return true;
970 }
971 return false;
972 }