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