1 /*
2 * Copyright (c) 2012, 2021, 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 "classfile/vmClasses.hpp"
59 #include "logging/log.hpp"
60 #include "logging/logStream.hpp"
61 #include "memory/allocation.inline.hpp"
62 #include "memory/classLoaderMetaspace.hpp"
63 #include "memory/metadataFactory.hpp"
64 #include "memory/metaspace.hpp"
65 #include "memory/resourceArea.hpp"
66 #include "memory/universe.hpp"
67 #include "oops/access.inline.hpp"
68 #include "oops/klass.inline.hpp"
69 #include "oops/oop.inline.hpp"
70 #include "oops/oopHandle.inline.hpp"
71 #include "oops/inlineKlass.inline.hpp"
72 #include "oops/weakHandle.inline.hpp"
73 #include "runtime/arguments.hpp"
74 #include "runtime/atomic.hpp"
75 #include "runtime/handles.inline.hpp"
76 #include "runtime/mutex.hpp"
77 #include "runtime/safepoint.hpp"
78 #include "utilities/growableArray.hpp"
79 #include "utilities/macros.hpp"
80 #include "utilities/ostream.hpp"
81
82 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
83
84 void ClassLoaderData::init_null_class_loader_data() {
85 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
86 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
87
88 _the_null_class_loader_data = new ClassLoaderData(Handle(), false);
89 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
90 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
91
92 LogTarget(Trace, class, loader, data) lt;
93 if (lt.is_enabled()) {
94 ResourceMark rm;
95 LogStream ls(lt);
96 ls.print("create ");
97 _the_null_class_loader_data->print_value_on(&ls);
98 ls.cr();
99 }
100 }
101
102 // Obtain and set the class loader's name within the ClassLoaderData so
103 // it will be available for error messages, logging, JFR, etc. The name
104 // and klass are available after the class_loader oop is no longer alive,
105 // during unloading.
106 void ClassLoaderData::initialize_name(Handle class_loader) {
107 ResourceMark rm;
108
109 // Obtain the class loader's name. If the class loader's name was not
110 // explicitly set during construction, the CLD's _name field will be null.
111 oop cl_name = java_lang_ClassLoader::name(class_loader());
112 if (cl_name != NULL) {
113 const char* cl_instance_name = java_lang_String::as_utf8_string(cl_name);
114
115 if (cl_instance_name != NULL && cl_instance_name[0] != '\0') {
116 _name = SymbolTable::new_symbol(cl_instance_name);
117 }
118 }
119
120 // Obtain the class loader's name and identity hash. If the class loader's
121 // name was not explicitly set during construction, the class loader's name and id
122 // will be set to the qualified class name of the class loader along with its
123 // identity hash.
124 // If for some reason the ClassLoader's constructor has not been run, instead of
125 // leaving the _name_and_id field null, fall back to the external qualified class
126 // name. Thus CLD's _name_and_id field should never have a null value.
127 oop cl_name_and_id = java_lang_ClassLoader::nameAndId(class_loader());
128 const char* cl_instance_name_and_id =
129 (cl_name_and_id == NULL) ? _class_loader_klass->external_name() :
130 java_lang_String::as_utf8_string(cl_name_and_id);
131 assert(cl_instance_name_and_id != NULL && cl_instance_name_and_id[0] != '\0', "class loader has no name and id");
132 _name_and_id = SymbolTable::new_symbol(cl_instance_name_and_id);
133 }
134
135 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool has_class_mirror_holder) :
136 _metaspace(NULL),
137 _metaspace_lock(new Mutex(Mutex::nosafepoint-2, "MetaspaceAllocation_lock",
138 Mutex::_safepoint_check_never)),
139 _unloading(false), _has_class_mirror_holder(has_class_mirror_holder),
140 _modified_oops(true),
141 // A non-strong hidden class loader data doesn't have anything to keep
142 // it from being unloaded during parsing of the non-strong hidden class.
143 // The null-class-loader should always be kept alive.
144 _keep_alive((has_class_mirror_holder || h_class_loader.is_null()) ? 1 : 0),
145 _claim(0),
146 _handles(),
147 _klasses(NULL), _packages(NULL), _modules(NULL), _unnamed_module(NULL), _dictionary(NULL),
148 _jmethod_ids(NULL),
149 _deallocate_list(NULL),
150 _next(NULL),
151 _class_loader_klass(NULL), _name(NULL), _name_and_id(NULL) {
152
153 if (!h_class_loader.is_null()) {
154 _class_loader = _handles.add(h_class_loader());
155 _class_loader_klass = h_class_loader->klass();
156 initialize_name(h_class_loader);
157 }
158
159 if (!has_class_mirror_holder) {
160 // The holder is initialized later for non-strong hidden classes,
161 // and before calling anything that call class_loader().
162 initialize_holder(h_class_loader);
163
164 // A ClassLoaderData created solely for a non-strong hidden class should never
165 // have a ModuleEntryTable or PackageEntryTable created for it.
166 _packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);
167 if (h_class_loader.is_null()) {
168 // Create unnamed module for boot loader
169 _unnamed_module = ModuleEntry::create_boot_unnamed_module(this);
170 } else {
171 // Create unnamed module for all other loaders
172 _unnamed_module = ModuleEntry::create_unnamed_module(this);
173 }
174 _dictionary = create_dictionary();
175 }
176
177 NOT_PRODUCT(_dependency_count = 0); // number of class loader dependencies
178
179 JFR_ONLY(INIT_ID(this);)
180 }
181
182 ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {
183 Chunk* c = _head;
184 while (c != NULL) {
185 Chunk* next = c->_next;
186 delete c;
187 c = next;
188 }
189 }
190
191 OopHandle ClassLoaderData::ChunkedHandleList::add(oop o) {
192 if (_head == NULL || _head->_size == Chunk::CAPACITY) {
193 Chunk* next = new Chunk(_head);
194 Atomic::release_store(&_head, next);
195 }
196 oop* handle = &_head->_data[_head->_size];
197 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, o);
198 Atomic::release_store(&_head->_size, _head->_size + 1);
199 return OopHandle(handle);
200 }
201
202 int ClassLoaderData::ChunkedHandleList::count() const {
203 int count = 0;
204 Chunk* chunk = _head;
205 while (chunk != NULL) {
206 count += chunk->_size;
207 chunk = chunk->_next;
208 }
209 return count;
210 }
211
212 inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {
213 for (juint i = 0; i < size; i++) {
214 if (c->_data[i] != NULL) {
215 f->do_oop(&c->_data[i]);
216 }
217 }
218 }
219
220 void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {
221 Chunk* head = Atomic::load_acquire(&_head);
222 if (head != NULL) {
223 // Must be careful when reading size of head
224 oops_do_chunk(f, head, Atomic::load_acquire(&head->_size));
225 for (Chunk* c = head->_next; c != NULL; c = c->_next) {
226 oops_do_chunk(f, c, c->_size);
227 }
228 }
229 }
230
231 class VerifyContainsOopClosure : public OopClosure {
232 oop _target;
233 bool _found;
234
235 public:
236 VerifyContainsOopClosure(oop target) : _target(target), _found(false) {}
237
238 void do_oop(oop* p) {
239 if (p != NULL && NativeAccess<AS_NO_KEEPALIVE>::oop_load(p) == _target) {
240 _found = true;
241 }
242 }
243
244 void do_oop(narrowOop* p) {
245 // The ChunkedHandleList should not contain any narrowOop
246 ShouldNotReachHere();
247 }
248
249 bool found() const {
250 return _found;
251 }
252 };
253
254 bool ClassLoaderData::ChunkedHandleList::contains(oop p) {
255 VerifyContainsOopClosure cl(p);
256 oops_do(&cl);
257 return cl.found();
258 }
259
260 #ifndef PRODUCT
261 bool ClassLoaderData::ChunkedHandleList::owner_of(oop* oop_handle) {
262 Chunk* chunk = _head;
263 while (chunk != NULL) {
264 if (&(chunk->_data[0]) <= oop_handle && oop_handle < &(chunk->_data[chunk->_size])) {
265 return true;
266 }
267 chunk = chunk->_next;
268 }
269 return false;
270 }
271 #endif // PRODUCT
272
273 void ClassLoaderData::clear_claim(int claim) {
274 for (;;) {
275 int old_claim = Atomic::load(&_claim);
276 if ((old_claim & claim) == 0) {
277 return;
278 }
279 int new_claim = old_claim & ~claim;
280 if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
281 return;
282 }
283 }
284 }
285
286 bool ClassLoaderData::try_claim(int claim) {
287 for (;;) {
288 int old_claim = Atomic::load(&_claim);
289 if ((old_claim & claim) == claim) {
290 return false;
291 }
292 int new_claim = old_claim | claim;
293 if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
294 return true;
295 }
296 }
297 }
298
299 // Non-strong hidden classes have their own ClassLoaderData that is marked to keep alive
300 // while the class is being parsed, and if the class appears on the module fixup list.
301 // Due to the uniqueness that no other class shares the hidden class' name or
302 // ClassLoaderData, no other non-GC thread has knowledge of the hidden class while
303 // it is being defined, therefore _keep_alive is not volatile or atomic.
304 void ClassLoaderData::inc_keep_alive() {
305 if (has_class_mirror_holder()) {
306 assert(_keep_alive > 0, "Invalid keep alive increment count");
307 _keep_alive++;
308 }
309 }
310
311 void ClassLoaderData::dec_keep_alive() {
312 if (has_class_mirror_holder()) {
313 assert(_keep_alive > 0, "Invalid keep alive decrement count");
314 _keep_alive--;
315 }
316 }
317
318 void ClassLoaderData::oops_do(OopClosure* f, int claim_value, bool clear_mod_oops) {
319 if (claim_value != ClassLoaderData::_claim_none && !try_claim(claim_value)) {
320 return;
321 }
322
323 // Only clear modified_oops after the ClassLoaderData is claimed.
324 if (clear_mod_oops) {
325 clear_modified_oops();
326 }
327
328 _handles.oops_do(f);
329 }
330
331 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
332 // Lock-free access requires load_acquire
333 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
334 klass_closure->do_klass(k);
335 assert(k != k->next_link(), "no loops!");
336 }
337 }
338
339 void ClassLoaderData::classes_do(void f(Klass * const)) {
340 // Lock-free access requires load_acquire
341 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
342 f(k);
343 assert(k != k->next_link(), "no loops!");
344 }
345 }
346
347 void ClassLoaderData::methods_do(void f(Method*)) {
348 // Lock-free access requires load_acquire
349 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
350 if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
351 InstanceKlass::cast(k)->methods_do(f);
352 }
353 }
354 }
355
356 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
357 // Lock-free access requires load_acquire
358 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
359 // Do not filter ArrayKlass oops here...
360 if (k->is_array_klass() || (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded())) {
361 #ifdef ASSERT
362 oop m = k->java_mirror();
363 assert(m != NULL, "NULL mirror");
364 assert(m->is_a(vmClasses::Class_klass()), "invalid mirror");
365 #endif
366 klass_closure->do_klass(k);
367 }
368 }
369 }
370
371 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
372 // Lock-free access requires load_acquire
373 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
374 if (k->is_instance_klass()) {
375 f(InstanceKlass::cast(k));
376 }
377 assert(k != k->next_link(), "no loops!");
378 }
379 }
380
381 void ClassLoaderData::inline_classes_do(void f(InlineKlass*)) {
382 // Lock-free access requires load_acquire
383 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
384 if (k->is_inline_klass()) {
385 f(InlineKlass::cast(k));
386 }
387 assert(k != k->next_link(), "no loops!");
388 }
389 }
390
391 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
392 assert_locked_or_safepoint(Module_lock);
393 if (_unnamed_module != NULL) {
394 f(_unnamed_module);
395 }
396 if (_modules != NULL) {
397 for (int i = 0; i < _modules->table_size(); i++) {
398 for (ModuleEntry* entry = _modules->bucket(i);
399 entry != NULL;
400 entry = entry->next()) {
401 f(entry);
402 }
403 }
404 }
405 }
406
407 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
408 assert_locked_or_safepoint(Module_lock);
409 if (_packages != NULL) {
410 for (int i = 0; i < _packages->table_size(); i++) {
411 for (PackageEntry* entry = _packages->bucket(i);
412 entry != NULL;
413 entry = entry->next()) {
414 f(entry);
415 }
416 }
417 }
418 }
419
420 void ClassLoaderData::record_dependency(const Klass* k) {
421 assert(k != NULL, "invariant");
422
423 ClassLoaderData * const from_cld = this;
424 ClassLoaderData * const to_cld = k->class_loader_data();
425
426 // Do not need to record dependency if the dependency is to a class whose
427 // class loader data is never freed. (i.e. the dependency's class loader
428 // is one of the three builtin class loaders and the dependency's class
429 // loader data has a ClassLoader holder, not a Class holder.)
430 if (to_cld->is_permanent_class_loader_data()) {
431 return;
432 }
433
434 oop to;
435 if (to_cld->has_class_mirror_holder()) {
436 // Just return if a non-strong hidden class class is attempting to record a dependency
437 // to itself. (Note that every non-strong hidden class has its own unique class
438 // loader data.)
439 if (to_cld == from_cld) {
440 return;
441 }
442 // Hidden class dependencies are through the mirror.
443 to = k->java_mirror();
444 } else {
445 to = to_cld->class_loader();
446 oop from = from_cld->class_loader();
447
448 // Just return if this dependency is to a class with the same or a parent
449 // class_loader.
450 if (from == to || java_lang_ClassLoader::isAncestor(from, to)) {
451 return; // this class loader is in the parent list, no need to add it.
452 }
453 }
454
455 // It's a dependency we won't find through GC, add it.
456 if (!_handles.contains(to)) {
457 NOT_PRODUCT(Atomic::inc(&_dependency_count));
458 LogTarget(Trace, class, loader, data) lt;
459 if (lt.is_enabled()) {
460 ResourceMark rm;
461 LogStream ls(lt);
462 ls.print("adding dependency from ");
463 print_value_on(&ls);
464 ls.print(" to ");
465 to_cld->print_value_on(&ls);
466 ls.cr();
467 }
468 Handle dependency(Thread::current(), to);
469 add_handle(dependency);
470 // Added a potentially young gen oop to the ClassLoaderData
471 record_modified_oops();
472 }
473 }
474
475 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
476 {
477 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
478 Klass* old_value = _klasses;
479 k->set_next_link(old_value);
480 // Link the new item into the list, making sure the linked class is stable
481 // since the list can be walked without a lock
482 Atomic::release_store(&_klasses, k);
483 if (k->is_array_klass()) {
484 ClassLoaderDataGraph::inc_array_classes(1);
485 } else {
486 ClassLoaderDataGraph::inc_instance_classes(1);
487 }
488 }
489
490 if (publicize) {
491 LogTarget(Trace, class, loader, data) lt;
492 if (lt.is_enabled()) {
493 ResourceMark rm;
494 LogStream ls(lt);
495 ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());
496 print_value_on(&ls);
497 ls.cr();
498 }
499 }
500 }
501
502 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) {
503 if (loader_or_mirror() != NULL) {
504 assert(_holder.is_null(), "never replace holders");
505 _holder = WeakHandle(Universe::vm_weak(), loader_or_mirror);
506 }
507 }
508
509 // Remove a klass from the _klasses list for scratch_class during redefinition
510 // or parsed class in the case of an error.
511 void ClassLoaderData::remove_class(Klass* scratch_class) {
512 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
513
514 // Adjust global class iterator.
515 ClassLoaderDataGraph::adjust_saved_class(scratch_class);
516
517 Klass* prev = NULL;
518 for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
519 if (k == scratch_class) {
520 if (prev == NULL) {
521 _klasses = k->next_link();
522 } else {
523 Klass* next = k->next_link();
524 prev->set_next_link(next);
525 }
526
527 if (k->is_array_klass()) {
528 ClassLoaderDataGraph::dec_array_classes(1);
529 } else {
530 ClassLoaderDataGraph::dec_instance_classes(1);
531 }
532
533 return;
534 }
535 prev = k;
536 assert(k != k->next_link(), "no loops!");
537 }
538 ShouldNotReachHere(); // should have found this class!!
539 }
540
541 void ClassLoaderData::unload() {
542 _unloading = true;
543
544 LogTarget(Trace, class, loader, data) lt;
545 if (lt.is_enabled()) {
546 ResourceMark rm;
547 LogStream ls(lt);
548 ls.print("unload");
549 print_value_on(&ls);
550 ls.cr();
551 }
552
553 // Some items on the _deallocate_list need to free their C heap structures
554 // if they are not already on the _klasses list.
555 free_deallocate_list_C_heap_structures();
556
557 inline_classes_do(InlineKlass::cleanup);
558
559 // Clean up class dependencies and tell serviceability tools
560 // these classes are unloading. Must be called
561 // after erroneous classes are released.
562 classes_do(InstanceKlass::unload_class);
563
564 // Method::clear_jmethod_ids only sets the jmethod_ids to NULL without
565 // releasing the memory for related JNIMethodBlocks and JNIMethodBlockNodes.
566 // This is done intentionally because native code (e.g. JVMTI agent) holding
567 // jmethod_ids may access them after the associated classes and class loader
568 // are unloaded. The Java Native Interface Specification says "method ID
569 // does not prevent the VM from unloading the class from which the ID has
570 // been derived. After the class is unloaded, the method or field ID becomes
571 // invalid". In real world usages, the native code may rely on jmethod_ids
572 // being NULL after class unloading. Hence, it is unsafe to free the memory
573 // from the VM side without knowing when native code is going to stop using
574 // them.
575 if (_jmethod_ids != NULL) {
576 Method::clear_jmethod_ids(this);
577 }
578
579 // Clean up global class iterator for compiler
580 ClassLoaderDataGraph::adjust_saved_class(this);
581 }
582
583 ModuleEntryTable* ClassLoaderData::modules() {
584 // Lazily create the module entry table at first request.
585 // Lock-free access requires load_acquire.
586 ModuleEntryTable* modules = Atomic::load_acquire(&_modules);
587 if (modules == NULL) {
588 MutexLocker m1(Module_lock);
589 // Check if _modules got allocated while we were waiting for this lock.
590 if ((modules = _modules) == NULL) {
591 modules = new ModuleEntryTable(ModuleEntryTable::_moduletable_entry_size);
592
593 {
594 MutexLocker m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
595 // Ensure _modules is stable, since it is examined without a lock
596 Atomic::release_store(&_modules, modules);
597 }
598 }
599 }
600 return modules;
601 }
602
603 const int _boot_loader_dictionary_size = 1009;
604 const int _default_loader_dictionary_size = 107;
605
606 Dictionary* ClassLoaderData::create_dictionary() {
607 assert(!has_class_mirror_holder(), "class mirror holder cld does not have a dictionary");
608 int size;
609 bool resizable = false;
610 if (_the_null_class_loader_data == NULL) {
611 size = _boot_loader_dictionary_size;
612 resizable = true;
613 } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) {
614 size = 1; // there's only one class in relection class loader and no initiated classes
615 } else if (is_system_class_loader_data()) {
616 size = _boot_loader_dictionary_size;
617 resizable = true;
618 } else {
619 size = _default_loader_dictionary_size;
620 resizable = true;
621 }
622 if (!DynamicallyResizeSystemDictionaries || DumpSharedSpaces) {
623 resizable = false;
624 }
625 return new Dictionary(this, size, resizable);
626 }
627
628 // Tell the GC to keep this klass alive while iterating ClassLoaderDataGraph
629 oop ClassLoaderData::holder_phantom() const {
630 // A klass that was previously considered dead can be looked up in the
631 // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
632 // or a reachable object making it alive again. The SATB part of G1 needs
633 // to get notified about this potential resurrection, otherwise the marking
634 // might not find the object.
635 if (!_holder.is_null()) { // NULL class_loader
636 return _holder.resolve();
637 } else {
638 return NULL;
639 }
640 }
641
642 // Let the GC read the holder without keeping it alive.
643 oop ClassLoaderData::holder_no_keepalive() const {
644 if (!_holder.is_null()) { // NULL class_loader
645 return _holder.peek();
646 } else {
647 return NULL;
648 }
649 }
650
651 // Unloading support
652 bool ClassLoaderData::is_alive() const {
653 bool alive = keep_alive() // null class loader and incomplete non-strong hidden class.
654 || (_holder.peek() != NULL); // and not cleaned by the GC weak handle processing.
655
656 return alive;
657 }
658
659 class ReleaseKlassClosure: public KlassClosure {
660 private:
661 size_t _instance_class_released;
662 size_t _array_class_released;
663 public:
664 ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { }
665
666 size_t instance_class_released() const { return _instance_class_released; }
667 size_t array_class_released() const { return _array_class_released; }
668
669 void do_klass(Klass* k) {
670 if (k->is_array_klass()) {
671 _array_class_released ++;
672 } else {
673 assert(k->is_instance_klass(), "Must be");
674 _instance_class_released ++;
675 }
676 k->release_C_heap_structures();
677 }
678 };
679
680 ClassLoaderData::~ClassLoaderData() {
681 // Release C heap structures for all the classes.
682 ReleaseKlassClosure cl;
683 classes_do(&cl);
684
685 ClassLoaderDataGraph::dec_array_classes(cl.array_class_released());
686 ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released());
687
688 // Release the WeakHandle
689 _holder.release(Universe::vm_weak());
690
691 // Release C heap allocated hashtable for all the packages.
692 if (_packages != NULL) {
693 // Destroy the table itself
694 delete _packages;
695 _packages = NULL;
696 }
697
698 // Release C heap allocated hashtable for all the modules.
699 if (_modules != NULL) {
700 // Destroy the table itself
701 delete _modules;
702 _modules = NULL;
703 }
704
705 // Release C heap allocated hashtable for the dictionary
706 if (_dictionary != NULL) {
707 // Destroy the table itself
708 delete _dictionary;
709 _dictionary = NULL;
710 }
711
712 if (_unnamed_module != NULL) {
713 _unnamed_module->delete_unnamed_module();
714 _unnamed_module = NULL;
715 }
716
717 // release the metaspace
718 ClassLoaderMetaspace *m = _metaspace;
719 if (m != NULL) {
720 _metaspace = NULL;
721 delete m;
722 }
723
724 // Delete lock
725 delete _metaspace_lock;
726
727 // Delete free list
728 if (_deallocate_list != NULL) {
729 delete _deallocate_list;
730 }
731
732 // Decrement refcounts of Symbols if created.
733 if (_name != NULL) {
734 _name->decrement_refcount();
735 }
736 if (_name_and_id != NULL) {
737 _name_and_id->decrement_refcount();
738 }
739 }
740
741 // Returns true if this class loader data is for the app class loader
742 // or a user defined system class loader. (Note that the class loader
743 // data may have a Class holder.)
744 bool ClassLoaderData::is_system_class_loader_data() const {
745 return SystemDictionary::is_system_class_loader(class_loader());
746 }
747
748 // Returns true if this class loader data is for the platform class loader.
749 // (Note that the class loader data may have a Class holder.)
750 bool ClassLoaderData::is_platform_class_loader_data() const {
751 return SystemDictionary::is_platform_class_loader(class_loader());
752 }
753
754 // Returns true if the class loader for this class loader data is one of
755 // the 3 builtin (boot application/system or platform) class loaders,
756 // including a user-defined system class loader. Note that if the class
757 // loader data is for a non-strong hidden class then it may
758 // get freed by a GC even if its class loader is one of these loaders.
759 bool ClassLoaderData::is_builtin_class_loader_data() const {
760 return (is_boot_class_loader_data() ||
761 SystemDictionary::is_system_class_loader(class_loader()) ||
762 SystemDictionary::is_platform_class_loader(class_loader()));
763 }
764
765 // Returns true if this class loader data is a class loader data
766 // that is not ever freed by a GC. It must be the CLD for one of the builtin
767 // class loaders and not the CLD for a non-strong hidden class.
768 bool ClassLoaderData::is_permanent_class_loader_data() const {
769 return is_builtin_class_loader_data() && !has_class_mirror_holder();
770 }
771
772 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() {
773 // If the metaspace has not been allocated, create a new one. Might want
774 // to create smaller arena for Reflection class loaders also.
775 // The reason for the delayed allocation is because some class loaders are
776 // simply for delegating with no metadata of their own.
777 // Lock-free access requires load_acquire.
778 ClassLoaderMetaspace* metaspace = Atomic::load_acquire(&_metaspace);
779 if (metaspace == NULL) {
780 MutexLocker ml(_metaspace_lock, Mutex::_no_safepoint_check_flag);
781 // Check if _metaspace got allocated while we were waiting for this lock.
782 if ((metaspace = _metaspace) == NULL) {
783 if (this == the_null_class_loader_data()) {
784 assert (class_loader() == NULL, "Must be");
785 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
786 } else if (has_class_mirror_holder()) {
787 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ClassMirrorHolderMetaspaceType);
788 } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) {
789 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
790 } else {
791 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
792 }
793 // Ensure _metaspace is stable, since it is examined without a lock
794 Atomic::release_store(&_metaspace, metaspace);
795 }
796 }
797 return metaspace;
798 }
799
800 OopHandle ClassLoaderData::add_handle(Handle h) {
801 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
802 record_modified_oops();
803 return _handles.add(h());
804 }
805
806 void ClassLoaderData::remove_handle(OopHandle h) {
807 assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading");
808 oop* ptr = h.ptr_raw();
809 if (ptr != NULL) {
810 assert(_handles.owner_of(ptr), "Got unexpected handle " PTR_FORMAT, p2i(ptr));
811 NativeAccess<>::oop_store(ptr, oop(NULL));
812 }
813 }
814
815 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
816 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
817 if (dest.resolve() != NULL) {
818 return;
819 } else {
820 record_modified_oops();
821 dest = _handles.add(h());
822 }
823 }
824
825 // Add this metadata pointer to be freed when it's safe. This is only during
826 // a safepoint which checks if handles point to this metadata field.
827 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
828 // Metadata in shared region isn't deleted.
829 if (!m->is_shared()) {
830 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
831 if (_deallocate_list == NULL) {
832 _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, mtClass);
833 }
834 _deallocate_list->append_if_missing(m);
835 log_debug(class, loader, data)("deallocate added for %s", m->print_value_string());
836 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
837 }
838 }
839
840 // Deallocate free metadata on the free list. How useful the PermGen was!
841 void ClassLoaderData::free_deallocate_list() {
842 // This must be called at a safepoint because it depends on metadata walking at
843 // safepoint cleanup time.
844 assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
845 assert(!is_unloading(), "only called for ClassLoaderData that are not unloading");
846 if (_deallocate_list == NULL) {
847 return;
848 }
849 // Go backwards because this removes entries that are freed.
850 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
851 Metadata* m = _deallocate_list->at(i);
852 if (!m->on_stack()) {
853 _deallocate_list->remove_at(i);
854 // There are only three types of metadata that we deallocate directly.
855 // Cast them so they can be used by the template function.
856 if (m->is_method()) {
857 MetadataFactory::free_metadata(this, (Method*)m);
858 } else if (m->is_constantPool()) {
859 MetadataFactory::free_metadata(this, (ConstantPool*)m);
860 } else if (m->is_klass()) {
861 if (!((Klass*)m)->is_inline_klass()) {
862 MetadataFactory::free_metadata(this, (InstanceKlass*)m);
863 } else {
864 MetadataFactory::free_metadata(this, (InlineKlass*)m);
865 }
866 } else {
867 ShouldNotReachHere();
868 }
869 } else {
870 // Metadata is alive.
871 // If scratch_class is on stack then it shouldn't be on this list!
872 assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
873 "scratch classes on this list should be dead");
874 // Also should assert that other metadata on the list was found in handles.
875 // Some cleaning remains.
876 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
877 }
878 }
879 }
880
881 // This is distinct from free_deallocate_list. For class loader data that are
882 // unloading, this frees the C heap memory for items on the list, and unlinks
883 // scratch or error classes so that unloading events aren't triggered for these
884 // classes. The metadata is removed with the unloading metaspace.
885 // There isn't C heap memory allocated for methods, so nothing is done for them.
886 void ClassLoaderData::free_deallocate_list_C_heap_structures() {
887 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
888 assert(is_unloading(), "only called for ClassLoaderData that are 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 _deallocate_list->remove_at(i);
896 if (m->is_constantPool()) {
897 ((ConstantPool*)m)->release_C_heap_structures();
898 } else if (m->is_klass()) {
899 InstanceKlass* ik = (InstanceKlass*)m;
900 // also releases ik->constants() C heap memory
901 ik->release_C_heap_structures();
902 // Remove the class so unloading events aren't triggered for
903 // this class (scratch or error class) in do_unloading().
904 remove_class(ik);
905 }
906 }
907 }
908
909 // Caller needs ResourceMark
910 // If the class loader's _name has not been explicitly set, the class loader's
911 // qualified class name is returned.
912 const char* ClassLoaderData::loader_name() const {
913 if (_class_loader_klass == NULL) {
914 return BOOTSTRAP_LOADER_NAME;
915 } else if (_name != NULL) {
916 return _name->as_C_string();
917 } else {
918 return _class_loader_klass->external_name();
919 }
920 }
921
922 // Caller needs ResourceMark
923 // Format of the _name_and_id is as follows:
924 // If the defining loader has a name explicitly set then '<loader-name>' @<id>
925 // If the defining loader has no name then <qualified-class-name> @<id>
926 // If built-in loader, then omit '@<id>' as there is only one instance.
927 const char* ClassLoaderData::loader_name_and_id() const {
928 if (_class_loader_klass == NULL) {
929 return "'" BOOTSTRAP_LOADER_NAME "'";
930 } else if (_name_and_id != NULL) {
931 return _name_and_id->as_C_string();
932 } else {
933 // May be called in a race before _name_and_id is initialized.
934 return _class_loader_klass->external_name();
935 }
936 }
937
938 void ClassLoaderData::print_value_on(outputStream* out) const {
939 if (!is_unloading() && class_loader() != NULL) {
940 out->print("loader data: " INTPTR_FORMAT " for instance ", p2i(this));
941 class_loader()->print_value_on(out); // includes loader_name_and_id() and address of class loader instance
942 } else {
943 // loader data: 0xsomeaddr of 'bootstrap'
944 out->print("loader data: " INTPTR_FORMAT " of %s", p2i(this), loader_name_and_id());
945 }
946 if (_has_class_mirror_holder) {
947 out->print(" has a class holder");
948 }
949 }
950
951 void ClassLoaderData::print_value() const { print_value_on(tty); }
952
953 #ifndef PRODUCT
954 class PrintKlassClosure: public KlassClosure {
955 outputStream* _out;
956 public:
957 PrintKlassClosure(outputStream* out): _out(out) { }
958
959 void do_klass(Klass* k) {
960 ResourceMark rm;
961 _out->print("%s,", k->external_name());
962 }
963 };
964
965 void ClassLoaderData::print_on(outputStream* out) const {
966 ResourceMark rm;
967 out->print_cr("ClassLoaderData(" INTPTR_FORMAT ")", p2i(this));
968 out->print_cr(" - name %s", loader_name_and_id());
969 if (!_holder.is_null()) {
970 out->print (" - holder ");
971 _holder.print_on(out);
972 out->print_cr("");
973 }
974 out->print_cr(" - class loader " INTPTR_FORMAT, p2i(_class_loader.ptr_raw()));
975 out->print_cr(" - metaspace " INTPTR_FORMAT, p2i(_metaspace));
976 out->print_cr(" - unloading %s", _unloading ? "true" : "false");
977 out->print_cr(" - class mirror holder %s", _has_class_mirror_holder ? "true" : "false");
978 out->print_cr(" - modified oops %s", _modified_oops ? "true" : "false");
979 out->print_cr(" - keep alive %d", _keep_alive);
980 out->print (" - claim ");
981 switch(_claim) {
982 case _claim_none: out->print_cr("none"); break;
983 case _claim_finalizable: out->print_cr("finalizable"); break;
984 case _claim_strong: out->print_cr("strong"); break;
985 case _claim_other: out->print_cr("other"); break;
986 case _claim_other | _claim_finalizable: out->print_cr("other and finalizable"); break;
987 case _claim_other | _claim_strong: out->print_cr("other and strong"); break;
988 default: ShouldNotReachHere();
989 }
990 out->print_cr(" - handles %d", _handles.count());
991 out->print_cr(" - dependency count %d", _dependency_count);
992 out->print (" - klasses {");
993 PrintKlassClosure closure(out);
994 ((ClassLoaderData*)this)->classes_do(&closure);
995 out->print_cr(" }");
996 out->print_cr(" - packages " INTPTR_FORMAT, p2i(_packages));
997 out->print_cr(" - module " INTPTR_FORMAT, p2i(_modules));
998 out->print_cr(" - unnamed module " INTPTR_FORMAT, p2i(_unnamed_module));
999 out->print_cr(" - dictionary " INTPTR_FORMAT, p2i(_dictionary));
1000 if (_jmethod_ids != NULL) {
1001 out->print (" - jmethod count ");
1002 Method::print_jmethod_ids_count(this, out);
1003 out->print_cr("");
1004 }
1005 out->print_cr(" - deallocate list " INTPTR_FORMAT, p2i(_deallocate_list));
1006 out->print_cr(" - next CLD " INTPTR_FORMAT, p2i(_next));
1007 }
1008 #endif // PRODUCT
1009
1010 void ClassLoaderData::print() const { print_on(tty); }
1011
1012 void ClassLoaderData::verify() {
1013 assert_locked_or_safepoint(_metaspace_lock);
1014 oop cl = class_loader();
1015
1016 guarantee(this == class_loader_data(cl) || has_class_mirror_holder(), "Must be the same");
1017 guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || has_class_mirror_holder(), "must be");
1018
1019 // Verify the integrity of the allocated space.
1020 #ifdef ASSERT
1021 if (metaspace_or_null() != NULL) {
1022 metaspace_or_null()->verify();
1023 }
1024 #endif
1025
1026 for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
1027 guarantee(k->class_loader_data() == this, "Must be the same");
1028 k->verify();
1029 assert(k != k->next_link(), "no loops!");
1030 }
1031 }
1032
1033 bool ClassLoaderData::contains_klass(Klass* klass) {
1034 // Lock-free access requires load_acquire
1035 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
1036 if (k == klass) return true;
1037 }
1038 return false;
1039 }