1 /*
2 * Copyright (c) 2012, 2023, 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.inline.hpp"
54 #include "classfile/moduleEntry.hpp"
55 #include "classfile/packageEntry.hpp"
56 #include "classfile/symbolTable.hpp"
57 #include "classfile/systemDictionary.hpp"
58 #include "classfile/systemDictionaryShared.hpp"
59 #include "classfile/vmClasses.hpp"
60 #include "logging/log.hpp"
61 #include "logging/logStream.hpp"
62 #include "memory/allocation.inline.hpp"
63 #include "memory/classLoaderMetaspace.hpp"
64 #include "memory/metadataFactory.hpp"
65 #include "memory/metaspace.hpp"
66 #include "memory/resourceArea.hpp"
67 #include "memory/universe.hpp"
68 #include "oops/access.inline.hpp"
69 #include "oops/inlineKlass.inline.hpp"
70 #include "oops/klass.inline.hpp"
71 #include "oops/oop.inline.hpp"
72 #include "oops/oopHandle.inline.hpp"
73 #include "oops/verifyOopClosure.hpp"
74 #include "oops/weakHandle.inline.hpp"
75 #include "runtime/arguments.hpp"
76 #include "runtime/atomic.hpp"
77 #include "runtime/handles.inline.hpp"
78 #include "runtime/mutex.hpp"
79 #include "runtime/safepoint.hpp"
80 #include "utilities/growableArray.hpp"
81 #include "utilities/macros.hpp"
82 #include "utilities/ostream.hpp"
83
84 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
85
86 void ClassLoaderData::init_null_class_loader_data() {
87 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
88 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
89
90 _the_null_class_loader_data = new ClassLoaderData(Handle(), false);
91 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
92 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
93
94 LogTarget(Trace, class, loader, data) lt;
95 if (lt.is_enabled()) {
96 ResourceMark rm;
97 LogStream ls(lt);
98 ls.print("create ");
99 _the_null_class_loader_data->print_value_on(&ls);
100 ls.cr();
101 }
102 }
103
104 // Obtain and set the class loader's name within the ClassLoaderData so
105 // it will be available for error messages, logging, JFR, etc. The name
106 // and klass are available after the class_loader oop is no longer alive,
107 // during unloading.
108 void ClassLoaderData::initialize_name(Handle class_loader) {
109 ResourceMark rm;
110
111 // Obtain the class loader's name. If the class loader's name was not
112 // explicitly set during construction, the CLD's _name field will be null.
113 oop cl_name = java_lang_ClassLoader::name(class_loader());
114 if (cl_name != NULL) {
115 const char* cl_instance_name = java_lang_String::as_utf8_string(cl_name);
116
117 if (cl_instance_name != NULL && cl_instance_name[0] != '\0') {
118 _name = SymbolTable::new_symbol(cl_instance_name);
119 }
120 }
121
122 // Obtain the class loader's name and identity hash. If the class loader's
123 // name was not explicitly set during construction, the class loader's name and id
124 // will be set to the qualified class name of the class loader along with its
125 // identity hash.
126 // If for some reason the ClassLoader's constructor has not been run, instead of
127 // leaving the _name_and_id field null, fall back to the external qualified class
128 // name. Thus CLD's _name_and_id field should never have a null value.
129 oop cl_name_and_id = java_lang_ClassLoader::nameAndId(class_loader());
130 const char* cl_instance_name_and_id =
131 (cl_name_and_id == NULL) ? _class_loader_klass->external_name() :
132 java_lang_String::as_utf8_string(cl_name_and_id);
133 assert(cl_instance_name_and_id != NULL && cl_instance_name_and_id[0] != '\0', "class loader has no name and id");
134 _name_and_id = SymbolTable::new_symbol(cl_instance_name_and_id);
135 }
136
137 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool has_class_mirror_holder) :
138 _metaspace(NULL),
139 _metaspace_lock(new Mutex(Mutex::nosafepoint-2, "MetaspaceAllocation_lock")),
140 _unloading(false), _has_class_mirror_holder(has_class_mirror_holder),
141 _modified_oops(true),
142 // A non-strong hidden class loader data doesn't have anything to keep
143 // it from being unloaded during parsing of the non-strong hidden class.
144 // The null-class-loader should always be kept alive.
145 _keep_alive((has_class_mirror_holder || h_class_loader.is_null()) ? 1 : 0),
146 _claim(0),
147 _handles(),
148 _klasses(NULL), _packages(NULL), _modules(NULL), _unnamed_module(NULL), _dictionary(NULL),
149 _jmethod_ids(NULL),
150 _deallocate_list(NULL),
151 _next(NULL),
152 _class_loader_klass(NULL), _name(NULL), _name_and_id(NULL) {
153
154 if (!h_class_loader.is_null()) {
155 _class_loader = _handles.add(h_class_loader());
156 _class_loader_klass = h_class_loader->klass();
157 initialize_name(h_class_loader);
158 }
159
160 if (!has_class_mirror_holder) {
161 // The holder is initialized later for non-strong hidden classes,
162 // and before calling anything that call class_loader().
163 initialize_holder(h_class_loader);
164
165 // A ClassLoaderData created solely for a non-strong hidden class should never
166 // have a ModuleEntryTable or PackageEntryTable created for it.
167 _packages = new PackageEntryTable();
168 if (h_class_loader.is_null()) {
169 // Create unnamed module for boot loader
170 _unnamed_module = ModuleEntry::create_boot_unnamed_module(this);
171 } else {
172 // Create unnamed module for all other loaders
173 _unnamed_module = ModuleEntry::create_unnamed_module(this);
174 }
175 _dictionary = create_dictionary();
176 }
177
178 NOT_PRODUCT(_dependency_count = 0); // number of class loader dependencies
179
180 JFR_ONLY(INIT_ID(this);)
181 }
182
183 ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {
184 Chunk* c = _head;
185 while (c != NULL) {
186 Chunk* next = c->_next;
187 delete c;
188 c = next;
189 }
190 }
191
192 OopHandle ClassLoaderData::ChunkedHandleList::add(oop o) {
193 if (_head == NULL || _head->_size == Chunk::CAPACITY) {
194 Chunk* next = new Chunk(_head);
195 Atomic::release_store(&_head, next);
196 }
197 oop* handle = &_head->_data[_head->_size];
198 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, o);
199 Atomic::release_store(&_head->_size, _head->_size + 1);
200 return OopHandle(handle);
201 }
202
203 int ClassLoaderData::ChunkedHandleList::count() const {
204 int count = 0;
205 Chunk* chunk = _head;
206 while (chunk != NULL) {
207 count += chunk->_size;
208 chunk = chunk->_next;
209 }
210 return count;
211 }
212
213 inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {
214 for (juint i = 0; i < size; i++) {
215 if (c->_data[i] != NULL) {
216 f->do_oop(&c->_data[i]);
217 }
218 }
219 }
220
221 void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {
222 Chunk* head = Atomic::load_acquire(&_head);
223 if (head != NULL) {
224 // Must be careful when reading size of head
225 oops_do_chunk(f, head, Atomic::load_acquire(&head->_size));
226 for (Chunk* c = head->_next; c != NULL; c = c->_next) {
227 oops_do_chunk(f, c, c->_size);
228 }
229 }
230 }
231
232 class VerifyContainsOopClosure : public OopClosure {
233 oop _target;
234 bool _found;
235
236 public:
237 VerifyContainsOopClosure(oop target) : _target(target), _found(false) {}
238
239 void do_oop(oop* p) {
240 if (p != NULL && NativeAccess<AS_NO_KEEPALIVE>::oop_load(p) == _target) {
241 _found = true;
242 }
243 }
244
245 void do_oop(narrowOop* p) {
246 // The ChunkedHandleList should not contain any narrowOop
247 ShouldNotReachHere();
248 }
249
250 bool found() const {
251 return _found;
252 }
253 };
254
255 bool ClassLoaderData::ChunkedHandleList::contains(oop p) {
256 VerifyContainsOopClosure cl(p);
257 oops_do(&cl);
258 return cl.found();
259 }
260
261 #ifndef PRODUCT
262 bool ClassLoaderData::ChunkedHandleList::owner_of(oop* oop_handle) {
263 Chunk* chunk = _head;
264 while (chunk != NULL) {
265 if (&(chunk->_data[0]) <= oop_handle && oop_handle < &(chunk->_data[chunk->_size])) {
266 return true;
267 }
268 chunk = chunk->_next;
269 }
270 return false;
271 }
272 #endif // PRODUCT
273
274 void ClassLoaderData::clear_claim(int claim) {
275 for (;;) {
276 int old_claim = Atomic::load(&_claim);
277 if ((old_claim & claim) == 0) {
278 return;
279 }
280 int new_claim = old_claim & ~claim;
281 if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
282 return;
283 }
284 }
285 }
286
287 #ifdef ASSERT
288 void ClassLoaderData::verify_not_claimed(int claim) {
289 assert((_claim & claim) == 0, "Found claim: %d bits in _claim: %d", claim, _claim);
290 }
291 #endif
292
293 bool ClassLoaderData::try_claim(int claim) {
294 for (;;) {
295 int old_claim = Atomic::load(&_claim);
296 if ((old_claim & claim) == claim) {
297 return false;
298 }
299 int new_claim = old_claim | claim;
300 if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
301 return true;
302 }
303 }
304 }
305
306 // Non-strong hidden classes have their own ClassLoaderData that is marked to keep alive
307 // while the class is being parsed, and if the class appears on the module fixup list.
308 // Due to the uniqueness that no other class shares the hidden class' name or
309 // ClassLoaderData, no other non-GC thread has knowledge of the hidden class while
310 // it is being defined, therefore _keep_alive is not volatile or atomic.
311 void ClassLoaderData::inc_keep_alive() {
312 if (has_class_mirror_holder()) {
313 assert(_keep_alive > 0, "Invalid keep alive increment count");
314 _keep_alive++;
315 }
316 }
317
318 void ClassLoaderData::dec_keep_alive() {
319 if (has_class_mirror_holder()) {
320 assert(_keep_alive > 0, "Invalid keep alive decrement count");
321 _keep_alive--;
322 }
323 }
324
325 void ClassLoaderData::oops_do(OopClosure* f, int claim_value, bool clear_mod_oops) {
326 if (claim_value != ClassLoaderData::_claim_none && !try_claim(claim_value)) {
327 return;
328 }
329
330 // Only clear modified_oops after the ClassLoaderData is claimed.
331 if (clear_mod_oops) {
332 clear_modified_oops();
333 }
334
335 _handles.oops_do(f);
336 }
337
338 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
339 // Lock-free access requires load_acquire
340 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
341 klass_closure->do_klass(k);
342 assert(k != k->next_link(), "no loops!");
343 }
344 }
345
346 void ClassLoaderData::classes_do(void f(Klass * const)) {
347 // Lock-free access requires load_acquire
348 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
349 f(k);
350 assert(k != k->next_link(), "no loops!");
351 }
352 }
353
354 void ClassLoaderData::methods_do(void f(Method*)) {
355 // Lock-free access requires load_acquire
356 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
357 if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
358 InstanceKlass::cast(k)->methods_do(f);
359 }
360 }
361 }
362
363 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
364 // To call this, one must have the MultiArray_lock held, but the _klasses list still has lock free reads.
365 assert_locked_or_safepoint(MultiArray_lock);
366
367 // Lock-free access requires load_acquire
368 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
369 // Filter out InstanceKlasses (or their ObjArrayKlasses) that have not entered the
370 // loaded state.
371 if (k->is_instance_klass()) {
372 if (!InstanceKlass::cast(k)->is_loaded()) {
373 continue;
374 }
375 } else if (k->is_shared() && k->is_objArray_klass()) {
376 Klass* bottom = ObjArrayKlass::cast(k)->bottom_klass();
377 if (bottom->is_instance_klass() && !InstanceKlass::cast(bottom)->is_loaded()) {
378 // This could happen if <bottom> is a shared class that has been restored
379 // but is not yet marked as loaded. All archived array classes of the
380 // bottom class are already restored and placed in the _klasses list.
381 continue;
382 }
383 }
384
385 #ifdef ASSERT
386 oop m = k->java_mirror();
387 assert(m != NULL, "NULL mirror");
388 assert(m->is_a(vmClasses::Class_klass()), "invalid mirror");
389 #endif
390 klass_closure->do_klass(k);
391 }
392 }
393
394 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
395 // Lock-free access requires load_acquire
396 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
397 if (k->is_instance_klass()) {
398 f(InstanceKlass::cast(k));
399 }
400 assert(k != k->next_link(), "no loops!");
401 }
402 }
403
404 void ClassLoaderData::inline_classes_do(void f(InlineKlass*)) {
405 // Lock-free access requires load_acquire
406 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
407 if (k->is_inline_klass()) {
408 f(InlineKlass::cast(k));
409 }
410 assert(k != k->next_link(), "no loops!");
411 }
412 }
413
414 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
415 assert_locked_or_safepoint(Module_lock);
416 if (_unnamed_module != NULL) {
417 f(_unnamed_module);
418 }
419 if (_modules != NULL) {
420 _modules->modules_do(f);
421 }
422 }
423
424 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
425 assert_locked_or_safepoint(Module_lock);
426 if (_packages != NULL) {
427 _packages->packages_do(f);
428 }
429 }
430
431 void ClassLoaderData::record_dependency(const Klass* k) {
432 assert(k != NULL, "invariant");
433
434 ClassLoaderData * const from_cld = this;
435 ClassLoaderData * const to_cld = k->class_loader_data();
436
437 // Do not need to record dependency if the dependency is to a class whose
438 // class loader data is never freed. (i.e. the dependency's class loader
439 // is one of the three builtin class loaders and the dependency's class
440 // loader data has a ClassLoader holder, not a Class holder.)
441 if (to_cld->is_permanent_class_loader_data()) {
442 return;
443 }
444
445 oop to;
446 if (to_cld->has_class_mirror_holder()) {
447 // Just return if a non-strong hidden class class is attempting to record a dependency
448 // to itself. (Note that every non-strong hidden class has its own unique class
449 // loader data.)
450 if (to_cld == from_cld) {
451 return;
452 }
453 // Hidden class dependencies are through the mirror.
454 to = k->java_mirror();
455 } else {
456 to = to_cld->class_loader();
457 oop from = from_cld->class_loader();
458
459 // Just return if this dependency is to a class with the same or a parent
460 // class_loader.
461 if (from == to || java_lang_ClassLoader::isAncestor(from, to)) {
462 return; // this class loader is in the parent list, no need to add it.
463 }
464 }
465
466 // It's a dependency we won't find through GC, add it.
467 if (!_handles.contains(to)) {
468 NOT_PRODUCT(Atomic::inc(&_dependency_count));
469 LogTarget(Trace, class, loader, data) lt;
470 if (lt.is_enabled()) {
471 ResourceMark rm;
472 LogStream ls(lt);
473 ls.print("adding dependency from ");
474 print_value_on(&ls);
475 ls.print(" to ");
476 to_cld->print_value_on(&ls);
477 ls.cr();
478 }
479 Handle dependency(Thread::current(), to);
480 add_handle(dependency);
481 // Added a potentially young gen oop to the ClassLoaderData
482 record_modified_oops();
483 }
484 }
485
486 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
487 {
488 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
489 Klass* old_value = _klasses;
490 k->set_next_link(old_value);
491 // Link the new item into the list, making sure the linked class is stable
492 // since the list can be walked without a lock
493 Atomic::release_store(&_klasses, k);
494 if (k->is_array_klass()) {
495 ClassLoaderDataGraph::inc_array_classes(1);
496 } else {
497 ClassLoaderDataGraph::inc_instance_classes(1);
498 }
499 }
500
501 if (publicize) {
502 LogTarget(Trace, class, loader, data) lt;
503 if (lt.is_enabled()) {
504 ResourceMark rm;
505 LogStream ls(lt);
506 ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());
507 print_value_on(&ls);
508 ls.cr();
509 }
510 }
511 }
512
513 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) {
514 if (loader_or_mirror() != NULL) {
515 assert(_holder.is_null(), "never replace holders");
516 _holder = WeakHandle(Universe::vm_weak(), loader_or_mirror);
517 }
518 }
519
520 // Remove a klass from the _klasses list for scratch_class during redefinition
521 // or parsed class in the case of an error.
522 void ClassLoaderData::remove_class(Klass* scratch_class) {
523 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
524
525 // Adjust global class iterator.
526 ClassLoaderDataGraph::adjust_saved_class(scratch_class);
527
528 Klass* prev = NULL;
529 for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
530 if (k == scratch_class) {
531 if (prev == NULL) {
532 _klasses = k->next_link();
533 } else {
534 Klass* next = k->next_link();
535 prev->set_next_link(next);
536 }
537
538 if (k->is_array_klass()) {
539 ClassLoaderDataGraph::dec_array_classes(1);
540 } else {
541 ClassLoaderDataGraph::dec_instance_classes(1);
542 }
543
544 return;
545 }
546 prev = k;
547 assert(k != k->next_link(), "no loops!");
548 }
549 ShouldNotReachHere(); // should have found this class!!
550 }
551
552 void ClassLoaderData::unload() {
553 _unloading = true;
554
555 LogTarget(Trace, class, loader, data) lt;
556 if (lt.is_enabled()) {
557 ResourceMark rm;
558 LogStream ls(lt);
559 ls.print("unload");
560 print_value_on(&ls);
561 ls.cr();
562 }
563
564 // Some items on the _deallocate_list need to free their C heap structures
565 // if they are not already on the _klasses list.
566 free_deallocate_list_C_heap_structures();
567
568 inline_classes_do(InlineKlass::cleanup);
569
570 // Clean up class dependencies and tell serviceability tools
571 // these classes are unloading. Must be called
572 // after erroneous classes are released.
573 classes_do(InstanceKlass::unload_class);
574
575 // Method::clear_jmethod_ids only sets the jmethod_ids to NULL without
576 // releasing the memory for related JNIMethodBlocks and JNIMethodBlockNodes.
577 // This is done intentionally because native code (e.g. JVMTI agent) holding
578 // jmethod_ids may access them after the associated classes and class loader
579 // are unloaded. The Java Native Interface Specification says "method ID
580 // does not prevent the VM from unloading the class from which the ID has
581 // been derived. After the class is unloaded, the method or field ID becomes
582 // invalid". In real world usages, the native code may rely on jmethod_ids
583 // being NULL after class unloading. Hence, it is unsafe to free the memory
584 // from the VM side without knowing when native code is going to stop using
585 // them.
586 if (_jmethod_ids != NULL) {
587 Method::clear_jmethod_ids(this);
588 }
589
590 // Clean up global class iterator for compiler
591 ClassLoaderDataGraph::adjust_saved_class(this);
592 }
593
594 ModuleEntryTable* ClassLoaderData::modules() {
595 // Lazily create the module entry table at first request.
596 // Lock-free access requires load_acquire.
597 ModuleEntryTable* modules = Atomic::load_acquire(&_modules);
598 if (modules == NULL) {
599 MutexLocker m1(Module_lock);
600 // Check if _modules got allocated while we were waiting for this lock.
601 if ((modules = _modules) == NULL) {
602 modules = new ModuleEntryTable();
603
604 {
605 MutexLocker m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
606 // Ensure _modules is stable, since it is examined without a lock
607 Atomic::release_store(&_modules, modules);
608 }
609 }
610 }
611 return modules;
612 }
613
614 const int _boot_loader_dictionary_size = 1009;
615 const int _default_loader_dictionary_size = 107;
616
617 Dictionary* ClassLoaderData::create_dictionary() {
618 assert(!has_class_mirror_holder(), "class mirror holder cld does not have a dictionary");
619 int size;
620 if (_the_null_class_loader_data == NULL) {
621 size = _boot_loader_dictionary_size;
622 } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) {
623 size = 1; // there's only one class in relection class loader and no initiated classes
624 } else if (is_system_class_loader_data()) {
625 size = _boot_loader_dictionary_size;
626 } else {
627 size = _default_loader_dictionary_size;
628 }
629 return new Dictionary(this, size);
630 }
631
632 // Tell the GC to keep this klass alive. Needed while iterating ClassLoaderDataGraph,
633 // and any runtime code that uses klasses.
634 oop ClassLoaderData::holder() const {
635 // A klass that was previously considered dead can be looked up in the
636 // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
637 // or a reachable object making it alive again. The SATB part of G1 needs
638 // to get notified about this potential resurrection, otherwise the marking
639 // might not find the object.
640 if (!_holder.is_null()) { // NULL class_loader
641 return _holder.resolve();
642 } else {
643 return NULL;
644 }
645 }
646
647 // Let the GC read the holder without keeping it alive.
648 oop ClassLoaderData::holder_no_keepalive() const {
649 if (!_holder.is_null()) { // NULL class_loader
650 return _holder.peek();
651 } else {
652 return NULL;
653 }
654 }
655
656 // Unloading support
657 bool ClassLoaderData::is_alive() const {
658 bool alive = keep_alive() // null class loader and incomplete non-strong hidden class.
659 || (_holder.peek() != NULL); // and not cleaned by the GC weak handle processing.
660
661 return alive;
662 }
663
664 class ReleaseKlassClosure: public KlassClosure {
665 private:
666 size_t _instance_class_released;
667 size_t _array_class_released;
668 public:
669 ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { }
670
671 size_t instance_class_released() const { return _instance_class_released; }
672 size_t array_class_released() const { return _array_class_released; }
673
674 void do_klass(Klass* k) {
675 if (k->is_array_klass()) {
676 _array_class_released ++;
677 } else {
678 assert(k->is_instance_klass(), "Must be");
679 _instance_class_released ++;
680 }
681 k->release_C_heap_structures();
682 }
683 };
684
685 ClassLoaderData::~ClassLoaderData() {
686 // Release C heap structures for all the classes.
687 ReleaseKlassClosure cl;
688 classes_do(&cl);
689
690 ClassLoaderDataGraph::dec_array_classes(cl.array_class_released());
691 ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released());
692
693 // Release the WeakHandle
694 _holder.release(Universe::vm_weak());
695
696 // Release C heap allocated hashtable for all the packages.
697 if (_packages != NULL) {
698 // Destroy the table itself
699 delete _packages;
700 _packages = NULL;
701 }
702
703 // Release C heap allocated hashtable for all the modules.
704 if (_modules != NULL) {
705 // Destroy the table itself
706 delete _modules;
707 _modules = NULL;
708 }
709
710 // Release C heap allocated hashtable for the dictionary
711 if (_dictionary != NULL) {
712 // Destroy the table itself
713 delete _dictionary;
714 _dictionary = NULL;
715 }
716
717 if (_unnamed_module != NULL) {
718 delete _unnamed_module;
719 _unnamed_module = NULL;
720 }
721
722 // release the metaspace
723 ClassLoaderMetaspace *m = _metaspace;
724 if (m != NULL) {
725 _metaspace = NULL;
726 delete m;
727 }
728
729 // Delete lock
730 delete _metaspace_lock;
731
732 // Delete free list
733 if (_deallocate_list != NULL) {
734 delete _deallocate_list;
735 }
736
737 // Decrement refcounts of Symbols if created.
738 if (_name != NULL) {
739 _name->decrement_refcount();
740 }
741 if (_name_and_id != NULL) {
742 _name_and_id->decrement_refcount();
743 }
744 }
745
746 // Returns true if this class loader data is for the app class loader
747 // or a user defined system class loader. (Note that the class loader
748 // data may have a Class holder.)
749 bool ClassLoaderData::is_system_class_loader_data() const {
750 return SystemDictionary::is_system_class_loader(class_loader());
751 }
752
753 // Returns true if this class loader data is for the platform class loader.
754 // (Note that the class loader data may have a Class holder.)
755 bool ClassLoaderData::is_platform_class_loader_data() const {
756 return SystemDictionary::is_platform_class_loader(class_loader());
757 }
758
759 // Returns true if the class loader for this class loader data is one of
760 // the 3 builtin (boot application/system or platform) class loaders,
761 // including a user-defined system class loader. Note that if the class
762 // loader data is for a non-strong hidden class then it may
763 // get freed by a GC even if its class loader is one of these loaders.
764 bool ClassLoaderData::is_builtin_class_loader_data() const {
765 return (is_boot_class_loader_data() ||
766 SystemDictionary::is_system_class_loader(class_loader()) ||
767 SystemDictionary::is_platform_class_loader(class_loader()));
768 }
769
770 // Returns true if this class loader data is a class loader data
771 // that is not ever freed by a GC. It must be the CLD for one of the builtin
772 // class loaders and not the CLD for a non-strong hidden class.
773 bool ClassLoaderData::is_permanent_class_loader_data() const {
774 return is_builtin_class_loader_data() && !has_class_mirror_holder();
775 }
776
777 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() {
778 // If the metaspace has not been allocated, create a new one. Might want
779 // to create smaller arena for Reflection class loaders also.
780 // The reason for the delayed allocation is because some class loaders are
781 // simply for delegating with no metadata of their own.
782 // Lock-free access requires load_acquire.
783 ClassLoaderMetaspace* metaspace = Atomic::load_acquire(&_metaspace);
784 if (metaspace == NULL) {
785 MutexLocker ml(_metaspace_lock, Mutex::_no_safepoint_check_flag);
786 // Check if _metaspace got allocated while we were waiting for this lock.
787 if ((metaspace = _metaspace) == NULL) {
788 if (this == the_null_class_loader_data()) {
789 assert (class_loader() == NULL, "Must be");
790 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
791 } else if (has_class_mirror_holder()) {
792 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ClassMirrorHolderMetaspaceType);
793 } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) {
794 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
795 } else {
796 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
797 }
798 // Ensure _metaspace is stable, since it is examined without a lock
799 Atomic::release_store(&_metaspace, metaspace);
800 }
801 }
802 return metaspace;
803 }
804
805 OopHandle ClassLoaderData::add_handle(Handle h) {
806 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
807 record_modified_oops();
808 return _handles.add(h());
809 }
810
811 void ClassLoaderData::remove_handle(OopHandle h) {
812 assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading");
813 oop* ptr = h.ptr_raw();
814 if (ptr != NULL) {
815 assert(_handles.owner_of(ptr), "Got unexpected handle " PTR_FORMAT, p2i(ptr));
816 NativeAccess<>::oop_store(ptr, oop(NULL));
817 }
818 }
819
820 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
821 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
822 if (dest.resolve() != NULL) {
823 return;
824 } else {
825 record_modified_oops();
826 dest = _handles.add(h());
827 }
828 }
829
830 // Add this metadata pointer to be freed when it's safe. This is only during
831 // a safepoint which checks if handles point to this metadata field.
832 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
833 // Metadata in shared region isn't deleted.
834 if (!m->is_shared()) {
835 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
836 if (_deallocate_list == NULL) {
837 _deallocate_list = new (mtClass) GrowableArray<Metadata*>(100, mtClass);
838 }
839 _deallocate_list->append_if_missing(m);
840 ResourceMark rm;
841 log_debug(class, loader, data)("deallocate added for %s", m->print_value_string());
842 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
843 }
844 }
845
846 // Deallocate free metadata on the free list. How useful the PermGen was!
847 void ClassLoaderData::free_deallocate_list() {
848 // This must be called at a safepoint because it depends on metadata walking at
849 // safepoint cleanup time.
850 assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
851 assert(!is_unloading(), "only called for ClassLoaderData that are not unloading");
852 if (_deallocate_list == NULL) {
853 return;
854 }
855 // Go backwards because this removes entries that are freed.
856 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
857 Metadata* m = _deallocate_list->at(i);
858 if (!m->on_stack()) {
859 _deallocate_list->remove_at(i);
860 // There are only three types of metadata that we deallocate directly.
861 // Cast them so they can be used by the template function.
862 if (m->is_method()) {
863 MetadataFactory::free_metadata(this, (Method*)m);
864 } else if (m->is_constantPool()) {
865 MetadataFactory::free_metadata(this, (ConstantPool*)m);
866 } else if (m->is_klass()) {
867 if (!((Klass*)m)->is_inline_klass()) {
868 MetadataFactory::free_metadata(this, (InstanceKlass*)m);
869 } else {
870 MetadataFactory::free_metadata(this, (InlineKlass*)m);
871 }
872 } else {
873 ShouldNotReachHere();
874 }
875 } else {
876 // Metadata is alive.
877 // If scratch_class is on stack then it shouldn't be on this list!
878 assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
879 "scratch classes on this list should be dead");
880 // Also should assert that other metadata on the list was found in handles.
881 // Some cleaning remains.
882 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
883 }
884 }
885 }
886
887 // This is distinct from free_deallocate_list. For class loader data that are
888 // unloading, this frees the C heap memory for items on the list, and unlinks
889 // scratch or error classes so that unloading events aren't triggered for these
890 // classes. The metadata is removed with the unloading metaspace.
891 // There isn't C heap memory allocated for methods, so nothing is done for them.
892 void ClassLoaderData::free_deallocate_list_C_heap_structures() {
893 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
894 assert(is_unloading(), "only called for ClassLoaderData that are unloading");
895 if (_deallocate_list == NULL) {
896 return;
897 }
898 // Go backwards because this removes entries that are freed.
899 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
900 Metadata* m = _deallocate_list->at(i);
901 _deallocate_list->remove_at(i);
902 if (m->is_constantPool()) {
903 ((ConstantPool*)m)->release_C_heap_structures();
904 } else if (m->is_klass()) {
905 InstanceKlass* ik = (InstanceKlass*)m;
906 // also releases ik->constants() C heap memory
907 ik->release_C_heap_structures();
908 // Remove the class so unloading events aren't triggered for
909 // this class (scratch or error class) in do_unloading().
910 remove_class(ik);
911 // But still have to remove it from the dumptime_table.
912 SystemDictionaryShared::handle_class_unloading(ik);
913 }
914 }
915 }
916
917 // Caller needs ResourceMark
918 // If the class loader's _name has not been explicitly set, the class loader's
919 // qualified class name is returned.
920 const char* ClassLoaderData::loader_name() const {
921 if (_class_loader_klass == NULL) {
922 return BOOTSTRAP_LOADER_NAME;
923 } else if (_name != NULL) {
924 return _name->as_C_string();
925 } else {
926 return _class_loader_klass->external_name();
927 }
928 }
929
930 // Caller needs ResourceMark
931 // Format of the _name_and_id is as follows:
932 // If the defining loader has a name explicitly set then '<loader-name>' @<id>
933 // If the defining loader has no name then <qualified-class-name> @<id>
934 // If built-in loader, then omit '@<id>' as there is only one instance.
935 const char* ClassLoaderData::loader_name_and_id() const {
936 if (_class_loader_klass == NULL) {
937 return "'" BOOTSTRAP_LOADER_NAME "'";
938 } else if (_name_and_id != NULL) {
939 return _name_and_id->as_C_string();
940 } else {
941 // May be called in a race before _name_and_id is initialized.
942 return _class_loader_klass->external_name();
943 }
944 }
945
946 void ClassLoaderData::print_value_on(outputStream* out) const {
947 if (!is_unloading() && class_loader() != NULL) {
948 out->print("loader data: " INTPTR_FORMAT " for instance ", p2i(this));
949 class_loader()->print_value_on(out); // includes loader_name_and_id() and address of class loader instance
950 } else {
951 // loader data: 0xsomeaddr of 'bootstrap'
952 out->print("loader data: " INTPTR_FORMAT " of %s", p2i(this), loader_name_and_id());
953 }
954 if (_has_class_mirror_holder) {
955 out->print(" has a class holder");
956 }
957 }
958
959 void ClassLoaderData::print_value() const { print_value_on(tty); }
960
961 #ifndef PRODUCT
962 class PrintKlassClosure: public KlassClosure {
963 outputStream* _out;
964 public:
965 PrintKlassClosure(outputStream* out): _out(out) { }
966
967 void do_klass(Klass* k) {
968 ResourceMark rm;
969 _out->print("%s,", k->external_name());
970 }
971 };
972
973 void ClassLoaderData::print_on(outputStream* out) const {
974 ResourceMark rm;
975 out->print_cr("ClassLoaderData(" INTPTR_FORMAT ")", p2i(this));
976 out->print_cr(" - name %s", loader_name_and_id());
977 if (!_holder.is_null()) {
978 out->print (" - holder ");
979 _holder.print_on(out);
980 out->print_cr("");
981 }
982 out->print_cr(" - class loader " INTPTR_FORMAT, p2i(_class_loader.ptr_raw()));
983 out->print_cr(" - metaspace " INTPTR_FORMAT, p2i(_metaspace));
984 out->print_cr(" - unloading %s", _unloading ? "true" : "false");
985 out->print_cr(" - class mirror holder %s", _has_class_mirror_holder ? "true" : "false");
986 out->print_cr(" - modified oops %s", _modified_oops ? "true" : "false");
987 out->print_cr(" - keep alive %d", _keep_alive);
988 out->print (" - claim ");
989 switch(_claim) {
990 case _claim_none: out->print_cr("none"); break;
991 case _claim_finalizable: out->print_cr("finalizable"); break;
992 case _claim_strong: out->print_cr("strong"); break;
993 case _claim_stw_fullgc_mark: out->print_cr("stw full gc mark"); break;
994 case _claim_stw_fullgc_adjust: out->print_cr("stw full gc adjust"); break;
995 case _claim_other: out->print_cr("other"); break;
996 case _claim_other | _claim_finalizable: out->print_cr("other and finalizable"); break;
997 case _claim_other | _claim_strong: out->print_cr("other and strong"); break;
998 default: ShouldNotReachHere();
999 }
1000 out->print_cr(" - handles %d", _handles.count());
1001 out->print_cr(" - dependency count %d", _dependency_count);
1002 out->print (" - klasses { ");
1003 if (Verbose) {
1004 PrintKlassClosure closure(out);
1005 ((ClassLoaderData*)this)->classes_do(&closure);
1006 } else {
1007 out->print("...");
1008 }
1009 out->print_cr(" }");
1010 out->print_cr(" - packages " INTPTR_FORMAT, p2i(_packages));
1011 out->print_cr(" - module " INTPTR_FORMAT, p2i(_modules));
1012 out->print_cr(" - unnamed module " INTPTR_FORMAT, p2i(_unnamed_module));
1013 if (_dictionary != nullptr) {
1014 out->print (" - dictionary " INTPTR_FORMAT " ", p2i(_dictionary));
1015 _dictionary->print_size(out);
1016 } else {
1017 out->print_cr(" - dictionary " INTPTR_FORMAT, p2i(_dictionary));
1018 }
1019 if (_jmethod_ids != NULL) {
1020 out->print (" - jmethod count ");
1021 Method::print_jmethod_ids_count(this, out);
1022 out->print_cr("");
1023 }
1024 out->print_cr(" - deallocate list " INTPTR_FORMAT, p2i(_deallocate_list));
1025 out->print_cr(" - next CLD " INTPTR_FORMAT, p2i(_next));
1026 }
1027 #endif // PRODUCT
1028
1029 void ClassLoaderData::print() const { print_on(tty); }
1030
1031 class VerifyHandleOops : public OopClosure {
1032 VerifyOopClosure vc;
1033 public:
1034 virtual void do_oop(oop* p) {
1035 if (p != nullptr && *p != nullptr) {
1036 oop o = *p;
1037 if (!java_lang_Class::is_instance(o)) {
1038 // is_instance will assert for an invalid oop.
1039 // Walk the resolved_references array and other assorted oops in the
1040 // CLD::_handles field. The mirror oops are followed by other heap roots.
1041 o->oop_iterate(&vc);
1042 }
1043 }
1044 }
1045 virtual void do_oop(narrowOop* o) { ShouldNotReachHere(); }
1046 };
1047
1048 void ClassLoaderData::verify() {
1049 assert_locked_or_safepoint(_metaspace_lock);
1050 oop cl = class_loader();
1051
1052 guarantee(this == class_loader_data(cl) || has_class_mirror_holder(), "Must be the same");
1053 guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || has_class_mirror_holder(), "must be");
1054
1055 // Verify the integrity of the allocated space.
1056 #ifdef ASSERT
1057 if (metaspace_or_null() != NULL) {
1058 metaspace_or_null()->verify();
1059 }
1060 #endif
1061
1062 for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
1063 guarantee(k->class_loader_data() == this, "Must be the same");
1064 k->verify();
1065 assert(k != k->next_link(), "no loops!");
1066 }
1067
1068 if (_modules != NULL) {
1069 _modules->verify();
1070 }
1071
1072 if (_deallocate_list != nullptr) {
1073 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
1074 Metadata* m = _deallocate_list->at(i);
1075 if (m->is_klass()) {
1076 ((Klass*)m)->verify();
1077 }
1078 }
1079 }
1080
1081 // Check the oops in the handles area
1082 VerifyHandleOops vho;
1083 oops_do(&vho, _claim_none, false);
1084 }
1085
1086 bool ClassLoaderData::contains_klass(Klass* klass) {
1087 // Lock-free access requires load_acquire
1088 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
1089 if (k == klass) return true;
1090 }
1091 return false;
1092 }