1 /*
2 * Copyright (c) 2012, 2022, 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/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/klass.inline.hpp"
70 #include "oops/objArrayKlass.hpp"
71 #include "oops/oop.inline.hpp"
72 #include "oops/oopHandle.inline.hpp"
73 #include "oops/inlineKlass.inline.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 bool ClassLoaderData::try_claim(int claim) {
288 for (;;) {
289 int old_claim = Atomic::load(&_claim);
290 if ((old_claim & claim) == claim) {
291 return false;
292 }
293 int new_claim = old_claim | claim;
294 if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
295 return true;
296 }
297 }
298 }
299
300 // Non-strong hidden classes have their own ClassLoaderData that is marked to keep alive
301 // while the class is being parsed, and if the class appears on the module fixup list.
302 // Due to the uniqueness that no other class shares the hidden class' name or
303 // ClassLoaderData, no other non-GC thread has knowledge of the hidden class while
304 // it is being defined, therefore _keep_alive is not volatile or atomic.
305 void ClassLoaderData::inc_keep_alive() {
306 if (has_class_mirror_holder()) {
307 assert(_keep_alive > 0, "Invalid keep alive increment count");
308 _keep_alive++;
309 }
310 }
311
312 void ClassLoaderData::dec_keep_alive() {
313 if (has_class_mirror_holder()) {
314 assert(_keep_alive > 0, "Invalid keep alive decrement count");
315 _keep_alive--;
316 }
317 }
318
319 void ClassLoaderData::oops_do(OopClosure* f, int claim_value, bool clear_mod_oops) {
320 if (claim_value != ClassLoaderData::_claim_none && !try_claim(claim_value)) {
321 return;
322 }
323
324 // Only clear modified_oops after the ClassLoaderData is claimed.
325 if (clear_mod_oops) {
326 clear_modified_oops();
327 }
328
329 _handles.oops_do(f);
330 }
331
332 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
333 // Lock-free access requires load_acquire
334 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
335 klass_closure->do_klass(k);
336 assert(k != k->next_link(), "no loops!");
337 }
338 }
339
340 void ClassLoaderData::classes_do(void f(Klass * const)) {
341 // Lock-free access requires load_acquire
342 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
343 f(k);
344 assert(k != k->next_link(), "no loops!");
345 }
346 }
347
348 void ClassLoaderData::methods_do(void f(Method*)) {
349 // Lock-free access requires load_acquire
350 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
351 if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
352 InstanceKlass::cast(k)->methods_do(f);
353 }
354 }
355 }
356
357 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
358 // To call this, one must have the MultiArray_lock held, but the _klasses list still has lock free reads.
359 assert_locked_or_safepoint(MultiArray_lock);
360
361 // Lock-free access requires load_acquire
362 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
363 // Filter out InstanceKlasses (or their ObjArrayKlasses) that have not entered the
364 // loaded state.
365 if (k->is_instance_klass()) {
366 if (!InstanceKlass::cast(k)->is_loaded()) {
367 continue;
368 }
369 } else if (k->is_shared() && k->is_objArray_klass()) {
370 Klass* bottom = ObjArrayKlass::cast(k)->bottom_klass();
371 if (bottom->is_instance_klass() && !InstanceKlass::cast(bottom)->is_loaded()) {
372 // This could happen if <bottom> is a shared class that has been restored
373 // but is not yet marked as loaded. All archived array classes of the
374 // bottom class are already restored and placed in the _klasses list.
375 continue;
376 }
377 }
378
379 #ifdef ASSERT
380 oop m = k->java_mirror();
381 assert(m != NULL, "NULL mirror");
382 assert(m->is_a(vmClasses::Class_klass()), "invalid mirror");
383 #endif
384 klass_closure->do_klass(k);
385 }
386 }
387
388 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
389 // Lock-free access requires load_acquire
390 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
391 if (k->is_instance_klass()) {
392 f(InstanceKlass::cast(k));
393 }
394 assert(k != k->next_link(), "no loops!");
395 }
396 }
397
398 void ClassLoaderData::inline_classes_do(void f(InlineKlass*)) {
399 // Lock-free access requires load_acquire
400 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
401 if (k->is_inline_klass()) {
402 f(InlineKlass::cast(k));
403 }
404 assert(k != k->next_link(), "no loops!");
405 }
406 }
407
408 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
409 assert_locked_or_safepoint(Module_lock);
410 if (_unnamed_module != NULL) {
411 f(_unnamed_module);
412 }
413 if (_modules != NULL) {
414 _modules->modules_do(f);
415 }
416 }
417
418 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
419 assert_locked_or_safepoint(Module_lock);
420 if (_packages != NULL) {
421 _packages->packages_do(f);
422 }
423 }
424
425 void ClassLoaderData::record_dependency(const Klass* k) {
426 assert(k != NULL, "invariant");
427
428 ClassLoaderData * const from_cld = this;
429 ClassLoaderData * const to_cld = k->class_loader_data();
430
431 // Do not need to record dependency if the dependency is to a class whose
432 // class loader data is never freed. (i.e. the dependency's class loader
433 // is one of the three builtin class loaders and the dependency's class
434 // loader data has a ClassLoader holder, not a Class holder.)
435 if (to_cld->is_permanent_class_loader_data()) {
436 return;
437 }
438
439 oop to;
440 if (to_cld->has_class_mirror_holder()) {
441 // Just return if a non-strong hidden class class is attempting to record a dependency
442 // to itself. (Note that every non-strong hidden class has its own unique class
443 // loader data.)
444 if (to_cld == from_cld) {
445 return;
446 }
447 // Hidden class dependencies are through the mirror.
448 to = k->java_mirror();
449 } else {
450 to = to_cld->class_loader();
451 oop from = from_cld->class_loader();
452
453 // Just return if this dependency is to a class with the same or a parent
454 // class_loader.
455 if (from == to || java_lang_ClassLoader::isAncestor(from, to)) {
456 return; // this class loader is in the parent list, no need to add it.
457 }
458 }
459
460 // It's a dependency we won't find through GC, add it.
461 if (!_handles.contains(to)) {
462 NOT_PRODUCT(Atomic::inc(&_dependency_count));
463 LogTarget(Trace, class, loader, data) lt;
464 if (lt.is_enabled()) {
465 ResourceMark rm;
466 LogStream ls(lt);
467 ls.print("adding dependency from ");
468 print_value_on(&ls);
469 ls.print(" to ");
470 to_cld->print_value_on(&ls);
471 ls.cr();
472 }
473 Handle dependency(Thread::current(), to);
474 add_handle(dependency);
475 // Added a potentially young gen oop to the ClassLoaderData
476 record_modified_oops();
477 }
478 }
479
480 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
481 {
482 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
483 Klass* old_value = _klasses;
484 k->set_next_link(old_value);
485 // Link the new item into the list, making sure the linked class is stable
486 // since the list can be walked without a lock
487 Atomic::release_store(&_klasses, k);
488 if (k->is_array_klass()) {
489 ClassLoaderDataGraph::inc_array_classes(1);
490 } else {
491 ClassLoaderDataGraph::inc_instance_classes(1);
492 }
493 }
494
495 if (publicize) {
496 LogTarget(Trace, class, loader, data) lt;
497 if (lt.is_enabled()) {
498 ResourceMark rm;
499 LogStream ls(lt);
500 ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());
501 print_value_on(&ls);
502 ls.cr();
503 }
504 }
505 }
506
507 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) {
508 if (loader_or_mirror() != NULL) {
509 assert(_holder.is_null(), "never replace holders");
510 _holder = WeakHandle(Universe::vm_weak(), loader_or_mirror);
511 }
512 }
513
514 // Remove a klass from the _klasses list for scratch_class during redefinition
515 // or parsed class in the case of an error.
516 void ClassLoaderData::remove_class(Klass* scratch_class) {
517 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
518
519 // Adjust global class iterator.
520 ClassLoaderDataGraph::adjust_saved_class(scratch_class);
521
522 Klass* prev = NULL;
523 for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
524 if (k == scratch_class) {
525 if (prev == NULL) {
526 _klasses = k->next_link();
527 } else {
528 Klass* next = k->next_link();
529 prev->set_next_link(next);
530 }
531
532 if (k->is_array_klass()) {
533 ClassLoaderDataGraph::dec_array_classes(1);
534 } else {
535 ClassLoaderDataGraph::dec_instance_classes(1);
536 }
537
538 return;
539 }
540 prev = k;
541 assert(k != k->next_link(), "no loops!");
542 }
543 ShouldNotReachHere(); // should have found this class!!
544 }
545
546 void ClassLoaderData::unload() {
547 _unloading = true;
548
549 LogTarget(Trace, class, loader, data) lt;
550 if (lt.is_enabled()) {
551 ResourceMark rm;
552 LogStream ls(lt);
553 ls.print("unload");
554 print_value_on(&ls);
555 ls.cr();
556 }
557
558 // Some items on the _deallocate_list need to free their C heap structures
559 // if they are not already on the _klasses list.
560 free_deallocate_list_C_heap_structures();
561
562 inline_classes_do(InlineKlass::cleanup);
563
564 // Clean up class dependencies and tell serviceability tools
565 // these classes are unloading. Must be called
566 // after erroneous classes are released.
567 classes_do(InstanceKlass::unload_class);
568
569 // Method::clear_jmethod_ids only sets the jmethod_ids to NULL without
570 // releasing the memory for related JNIMethodBlocks and JNIMethodBlockNodes.
571 // This is done intentionally because native code (e.g. JVMTI agent) holding
572 // jmethod_ids may access them after the associated classes and class loader
573 // are unloaded. The Java Native Interface Specification says "method ID
574 // does not prevent the VM from unloading the class from which the ID has
575 // been derived. After the class is unloaded, the method or field ID becomes
576 // invalid". In real world usages, the native code may rely on jmethod_ids
577 // being NULL after class unloading. Hence, it is unsafe to free the memory
578 // from the VM side without knowing when native code is going to stop using
579 // them.
580 if (_jmethod_ids != NULL) {
581 Method::clear_jmethod_ids(this);
582 }
583
584 // Clean up global class iterator for compiler
585 ClassLoaderDataGraph::adjust_saved_class(this);
586 }
587
588 ModuleEntryTable* ClassLoaderData::modules() {
589 // Lazily create the module entry table at first request.
590 // Lock-free access requires load_acquire.
591 ModuleEntryTable* modules = Atomic::load_acquire(&_modules);
592 if (modules == NULL) {
593 MutexLocker m1(Module_lock);
594 // Check if _modules got allocated while we were waiting for this lock.
595 if ((modules = _modules) == NULL) {
596 modules = new ModuleEntryTable();
597
598 {
599 MutexLocker m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
600 // Ensure _modules is stable, since it is examined without a lock
601 Atomic::release_store(&_modules, modules);
602 }
603 }
604 }
605 return modules;
606 }
607
608 const int _boot_loader_dictionary_size = 1009;
609 const int _default_loader_dictionary_size = 107;
610
611 Dictionary* ClassLoaderData::create_dictionary() {
612 assert(!has_class_mirror_holder(), "class mirror holder cld does not have a dictionary");
613 int size;
614 bool resizable = false;
615 if (_the_null_class_loader_data == NULL) {
616 size = _boot_loader_dictionary_size;
617 resizable = true;
618 } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) {
619 size = 1; // there's only one class in relection class loader and no initiated classes
620 } else if (is_system_class_loader_data()) {
621 size = _boot_loader_dictionary_size;
622 resizable = true;
623 } else {
624 size = _default_loader_dictionary_size;
625 resizable = true;
626 }
627 if (!DynamicallyResizeSystemDictionaries || DumpSharedSpaces) {
628 resizable = false;
629 }
630 return new Dictionary(this, size, resizable);
631 }
632
633 // Tell the GC to keep this klass alive. Needed while iterating ClassLoaderDataGraph,
634 // and any runtime code that uses klasses.
635 oop ClassLoaderData::holder() const {
636 // A klass that was previously considered dead can be looked up in the
637 // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
638 // or a reachable object making it alive again. The SATB part of G1 needs
639 // to get notified about this potential resurrection, otherwise the marking
640 // might not find the object.
641 if (!_holder.is_null()) { // NULL class_loader
642 return _holder.resolve();
643 } else {
644 return NULL;
645 }
646 }
647
648 // Let the GC read the holder without keeping it alive.
649 oop ClassLoaderData::holder_no_keepalive() const {
650 if (!_holder.is_null()) { // NULL class_loader
651 return _holder.peek();
652 } else {
653 return NULL;
654 }
655 }
656
657 // Unloading support
658 bool ClassLoaderData::is_alive() const {
659 bool alive = keep_alive() // null class loader and incomplete non-strong hidden class.
660 || (_holder.peek() != NULL); // and not cleaned by the GC weak handle processing.
661
662 return alive;
663 }
664
665 class ReleaseKlassClosure: public KlassClosure {
666 private:
667 size_t _instance_class_released;
668 size_t _array_class_released;
669 public:
670 ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { }
671
672 size_t instance_class_released() const { return _instance_class_released; }
673 size_t array_class_released() const { return _array_class_released; }
674
675 void do_klass(Klass* k) {
676 if (k->is_array_klass()) {
677 _array_class_released ++;
678 } else {
679 assert(k->is_instance_klass(), "Must be");
680 _instance_class_released ++;
681 }
682 k->release_C_heap_structures();
683 }
684 };
685
686 ClassLoaderData::~ClassLoaderData() {
687 // Release C heap structures for all the classes.
688 ReleaseKlassClosure cl;
689 classes_do(&cl);
690
691 ClassLoaderDataGraph::dec_array_classes(cl.array_class_released());
692 ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released());
693
694 // Release the WeakHandle
695 _holder.release(Universe::vm_weak());
696
697 // Release C heap allocated hashtable for all the packages.
698 if (_packages != NULL) {
699 // Destroy the table itself
700 delete _packages;
701 _packages = NULL;
702 }
703
704 // Release C heap allocated hashtable for all the modules.
705 if (_modules != NULL) {
706 // Destroy the table itself
707 delete _modules;
708 _modules = NULL;
709 }
710
711 // Release C heap allocated hashtable for the dictionary
712 if (_dictionary != NULL) {
713 // Destroy the table itself
714 delete _dictionary;
715 _dictionary = NULL;
716 }
717
718 if (_unnamed_module != NULL) {
719 delete _unnamed_module;
720 _unnamed_module = NULL;
721 }
722
723 // release the metaspace
724 ClassLoaderMetaspace *m = _metaspace;
725 if (m != NULL) {
726 _metaspace = NULL;
727 delete m;
728 }
729
730 // Delete lock
731 delete _metaspace_lock;
732
733 // Delete free list
734 if (_deallocate_list != NULL) {
735 delete _deallocate_list;
736 }
737
738 // Decrement refcounts of Symbols if created.
739 if (_name != NULL) {
740 _name->decrement_refcount();
741 }
742 if (_name_and_id != NULL) {
743 _name_and_id->decrement_refcount();
744 }
745 }
746
747 // Returns true if this class loader data is for the app class loader
748 // or a user defined system class loader. (Note that the class loader
749 // data may have a Class holder.)
750 bool ClassLoaderData::is_system_class_loader_data() const {
751 return SystemDictionary::is_system_class_loader(class_loader());
752 }
753
754 // Returns true if this class loader data is for the platform class loader.
755 // (Note that the class loader data may have a Class holder.)
756 bool ClassLoaderData::is_platform_class_loader_data() const {
757 return SystemDictionary::is_platform_class_loader(class_loader());
758 }
759
760 // Returns true if the class loader for this class loader data is one of
761 // the 3 builtin (boot application/system or platform) class loaders,
762 // including a user-defined system class loader. Note that if the class
763 // loader data is for a non-strong hidden class then it may
764 // get freed by a GC even if its class loader is one of these loaders.
765 bool ClassLoaderData::is_builtin_class_loader_data() const {
766 return (is_boot_class_loader_data() ||
767 SystemDictionary::is_system_class_loader(class_loader()) ||
768 SystemDictionary::is_platform_class_loader(class_loader()));
769 }
770
771 // Returns true if this class loader data is a class loader data
772 // that is not ever freed by a GC. It must be the CLD for one of the builtin
773 // class loaders and not the CLD for a non-strong hidden class.
774 bool ClassLoaderData::is_permanent_class_loader_data() const {
775 return is_builtin_class_loader_data() && !has_class_mirror_holder();
776 }
777
778 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() {
779 // If the metaspace has not been allocated, create a new one. Might want
780 // to create smaller arena for Reflection class loaders also.
781 // The reason for the delayed allocation is because some class loaders are
782 // simply for delegating with no metadata of their own.
783 // Lock-free access requires load_acquire.
784 ClassLoaderMetaspace* metaspace = Atomic::load_acquire(&_metaspace);
785 if (metaspace == NULL) {
786 MutexLocker ml(_metaspace_lock, Mutex::_no_safepoint_check_flag);
787 // Check if _metaspace got allocated while we were waiting for this lock.
788 if ((metaspace = _metaspace) == NULL) {
789 if (this == the_null_class_loader_data()) {
790 assert (class_loader() == NULL, "Must be");
791 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
792 } else if (has_class_mirror_holder()) {
793 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ClassMirrorHolderMetaspaceType);
794 } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) {
795 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
796 } else {
797 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
798 }
799 // Ensure _metaspace is stable, since it is examined without a lock
800 Atomic::release_store(&_metaspace, metaspace);
801 }
802 }
803 return metaspace;
804 }
805
806 OopHandle ClassLoaderData::add_handle(Handle h) {
807 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
808 record_modified_oops();
809 return _handles.add(h());
810 }
811
812 void ClassLoaderData::remove_handle(OopHandle h) {
813 assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading");
814 oop* ptr = h.ptr_raw();
815 if (ptr != NULL) {
816 assert(_handles.owner_of(ptr), "Got unexpected handle " PTR_FORMAT, p2i(ptr));
817 NativeAccess<>::oop_store(ptr, oop(NULL));
818 }
819 }
820
821 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
822 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
823 if (dest.resolve() != NULL) {
824 return;
825 } else {
826 record_modified_oops();
827 dest = _handles.add(h());
828 }
829 }
830
831 // Add this metadata pointer to be freed when it's safe. This is only during
832 // a safepoint which checks if handles point to this metadata field.
833 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
834 // Metadata in shared region isn't deleted.
835 if (!m->is_shared()) {
836 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
837 if (_deallocate_list == NULL) {
838 _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, mtClass);
839 }
840 _deallocate_list->append_if_missing(m);
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_other: out->print_cr("other"); break;
994 case _claim_other | _claim_finalizable: out->print_cr("other and finalizable"); break;
995 case _claim_other | _claim_strong: out->print_cr("other and strong"); break;
996 default: ShouldNotReachHere();
997 }
998 out->print_cr(" - handles %d", _handles.count());
999 out->print_cr(" - dependency count %d", _dependency_count);
1000 out->print (" - klasses { ");
1001 if (Verbose) {
1002 PrintKlassClosure closure(out);
1003 ((ClassLoaderData*)this)->classes_do(&closure);
1004 } else {
1005 out->print("...");
1006 }
1007 out->print_cr(" }");
1008 out->print_cr(" - packages " INTPTR_FORMAT, p2i(_packages));
1009 out->print_cr(" - module " INTPTR_FORMAT, p2i(_modules));
1010 out->print_cr(" - unnamed module " INTPTR_FORMAT, p2i(_unnamed_module));
1011 if (_dictionary != nullptr) {
1012 out->print (" - dictionary " INTPTR_FORMAT " ", p2i(_dictionary));
1013 _dictionary->print_size(out);
1014 } else {
1015 out->print_cr(" - dictionary " INTPTR_FORMAT, p2i(_dictionary));
1016 }
1017 if (_jmethod_ids != NULL) {
1018 out->print (" - jmethod count ");
1019 Method::print_jmethod_ids_count(this, out);
1020 out->print_cr("");
1021 }
1022 out->print_cr(" - deallocate list " INTPTR_FORMAT, p2i(_deallocate_list));
1023 out->print_cr(" - next CLD " INTPTR_FORMAT, p2i(_next));
1024 }
1025 #endif // PRODUCT
1026
1027 void ClassLoaderData::print() const { print_on(tty); }
1028
1029 void ClassLoaderData::verify() {
1030 assert_locked_or_safepoint(_metaspace_lock);
1031 oop cl = class_loader();
1032
1033 guarantee(this == class_loader_data(cl) || has_class_mirror_holder(), "Must be the same");
1034 guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || has_class_mirror_holder(), "must be");
1035
1036 // Verify the integrity of the allocated space.
1037 #ifdef ASSERT
1038 if (metaspace_or_null() != NULL) {
1039 metaspace_or_null()->verify();
1040 }
1041 #endif
1042
1043 for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
1044 guarantee(k->class_loader_data() == this, "Must be the same");
1045 k->verify();
1046 assert(k != k->next_link(), "no loops!");
1047 }
1048
1049 if (_modules != NULL) {
1050 _modules->verify();
1051 }
1052 }
1053
1054 bool ClassLoaderData::contains_klass(Klass* klass) {
1055 // Lock-free access requires load_acquire
1056 for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
1057 if (k == klass) return true;
1058 }
1059 return false;
1060 }