1 /*
2 * Copyright (c) 2012, 2026, 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 "cds/heapShared.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/jmethodIDTable.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/atomicAccess.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 = nullptr;
85
86 void ClassLoaderData::init_null_class_loader_data() {
87 assert(_the_null_class_loader_data == nullptr, "cannot initialize twice");
88 assert(ClassLoaderDataGraph::_head == nullptr, "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 != nullptr) {
115 const char* cl_instance_name = java_lang_String::as_utf8_string(cl_name);
116
117 if (cl_instance_name != nullptr && 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 == nullptr) ? _class_loader_klass->external_name() :
132 java_lang_String::as_utf8_string(cl_name_and_id);
133 assert(cl_instance_name_and_id != nullptr && 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(nullptr),
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_ref_count((has_class_mirror_holder || h_class_loader.is_null()) ? 1 : 0),
146 _claim(0),
147 _handles(),
148 _klasses(nullptr), _packages(nullptr), _modules(nullptr), _unnamed_module(nullptr), _dictionary(nullptr),
149 _jmethod_ids(nullptr),
150 _deallocate_list(nullptr),
151 _next(nullptr),
152 _unloading_next(nullptr),
153 _class_loader_klass(nullptr), _name(nullptr), _name_and_id(nullptr) {
154
155 if (!h_class_loader.is_null()) {
156 _class_loader = _handles.add(h_class_loader());
157 _class_loader_klass = h_class_loader->klass();
158 initialize_name(h_class_loader);
159 }
160
161 if (!has_class_mirror_holder) {
162 // The holder is initialized later for non-strong hidden classes,
163 // and before calling anything that call class_loader().
164 initialize_holder(h_class_loader);
165
166 // A ClassLoaderData created solely for a non-strong hidden class should never
167 // have a ModuleEntryTable or PackageEntryTable created for it.
168 _packages = new PackageEntryTable();
169 if (h_class_loader.is_null()) {
170 // Create unnamed module for boot loader
171 _unnamed_module = ModuleEntry::create_boot_unnamed_module(this);
172 } else {
173 // Create unnamed module for all other loaders
174 _unnamed_module = ModuleEntry::create_unnamed_module(this);
175 }
176 _dictionary = create_dictionary();
177 }
178
179 NOT_PRODUCT(_dependency_count = 0); // number of class loader dependencies
180
181 JFR_ONLY(INIT_ID(this);)
182 }
183
184 ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {
185 Chunk* c = _head;
186 while (c != nullptr) {
187 Chunk* next = c->_next;
188 delete c;
189 c = next;
190 }
191 }
192
193 OopHandle ClassLoaderData::ChunkedHandleList::add(oop o) {
194 if (_head == nullptr || _head->_size == Chunk::CAPACITY) {
195 Chunk* next = new Chunk(_head);
196 AtomicAccess::release_store(&_head, next);
197 }
198 oop* handle = &_head->_data[_head->_size];
199 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, o);
200 AtomicAccess::release_store(&_head->_size, _head->_size + 1);
201 return OopHandle(handle);
202 }
203
204 int ClassLoaderData::ChunkedHandleList::count() const {
205 int count = 0;
206 Chunk* chunk = AtomicAccess::load_acquire(&_head);
207 while (chunk != nullptr) {
208 count += AtomicAccess::load(&chunk->_size);
209 chunk = chunk->_next;
210 }
211 return count;
212 }
213
214 inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {
215 for (juint i = 0; i < size; i++) {
216 f->do_oop(&c->_data[i]);
217 }
218 }
219
220 void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {
221 Chunk* head = AtomicAccess::load_acquire(&_head);
222 if (head != nullptr) {
223 // Must be careful when reading size of head
224 oops_do_chunk(f, head, AtomicAccess::load_acquire(&head->_size));
225 for (Chunk* c = head->_next; c != nullptr; c = c->_next) {
226 oops_do_chunk(f, c, c->_size);
227 }
228 }
229 }
230
231 class VerifyContainsOopClosure : public OopClosure {
232 oop _target;
233 bool _found;
234
235 public:
236 VerifyContainsOopClosure(oop target) : _target(target), _found(false) {}
237
238 void do_oop(oop* p) {
239 if (p != nullptr && NativeAccess<AS_NO_KEEPALIVE>::oop_load(p) == _target) {
240 _found = true;
241 }
242 }
243
244 void do_oop(narrowOop* p) {
245 // The ChunkedHandleList should not contain any narrowOop
246 ShouldNotReachHere();
247 }
248
249 bool found() const {
250 return _found;
251 }
252 };
253
254 bool ClassLoaderData::ChunkedHandleList::contains(oop p) {
255 VerifyContainsOopClosure cl(p);
256 oops_do(&cl);
257 return cl.found();
258 }
259
260 #ifndef PRODUCT
261 bool ClassLoaderData::ChunkedHandleList::owner_of(oop* oop_handle) {
262 Chunk* chunk = AtomicAccess::load_acquire(&_head);
263 while (chunk != nullptr) {
264 if (&(chunk->_data[0]) <= oop_handle && oop_handle < &(chunk->_data[AtomicAccess::load(&chunk->_size)])) {
265 return true;
266 }
267 chunk = chunk->_next;
268 }
269 return false;
270 }
271 #endif // PRODUCT
272
273 void ClassLoaderData::clear_claim(int claim) {
274 for (;;) {
275 int old_claim = AtomicAccess::load(&_claim);
276 if ((old_claim & claim) == 0) {
277 return;
278 }
279 int new_claim = old_claim & ~claim;
280 if (AtomicAccess::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
281 return;
282 }
283 }
284 }
285
286 #ifdef ASSERT
287 void ClassLoaderData::verify_not_claimed(int claim) {
288 assert((_claim & claim) == 0, "Found claim: %d bits in _claim: %d", claim, _claim);
289 }
290 #endif
291
292 void ClassLoaderData::demote_strong_roots() {
293 // The oop handle area contains strong roots that the GC traces from. We are about
294 // to demote them to strong native oops that the GC does *not* trace from. Conceptually,
295 // we are retiring a rather normal strong root, and creating a strong non-root handle,
296 // which happens to reuse the same address as the normal strong root had.
297 // Unless we invoke the right barriers, the GC might not notice that a strong root
298 // has been pulled from the system, and is left unprocessed by the GC. There can be
299 // several consequences:
300 // 1. A concurrently marking snapshot-at-the-beginning GC might assume that the contents
301 // of all strong roots get processed by the GC in order to keep them alive. Without
302 // barriers, some objects might not be kept alive.
303 // 2. A concurrently relocating GC might assume that after moving an object, a subsequent
304 // tracing from all roots can fix all the pointers in the system, which doesn't play
305 // well with roots racingly being pulled.
306 // 3. A concurrent GC using colored pointers, might assume that tracing the object graph
307 // from roots results in all pointers getting some particular color, which also doesn't
308 // play well with roots being pulled out from the system concurrently.
309
310 class TransitionRootsOopClosure : public OopClosure {
311 public:
312 virtual void do_oop(oop* p) {
313 // By loading the strong root with the access API, we can use the right barriers to
314 // store the oop as a strong non-root handle, that happens to reuse the same memory
315 // address as the strong root. The barriered store ensures that:
316 // 1. The concurrent SATB marking properties are satisfied as the store will keep
317 // the oop alive.
318 // 2. The concurrent object movement properties are satisfied as we store the address
319 // of the new location of the object, if any.
320 // 3. The colors if any will be stored as the new good colors.
321 oop obj = NativeAccess<>::oop_load(p); // Load the strong root
322 NativeAccess<>::oop_store(p, obj); // Store the strong non-root
323 }
324
325 virtual void do_oop(narrowOop* p) {
326 ShouldNotReachHere();
327 }
328 } cl;
329 oops_do(&cl, ClassLoaderData::_claim_none, false /* clear_mod_oops */);
330 }
331
332 // Non-strong hidden classes have their own ClassLoaderData that is marked to keep alive
333 // while the class is being parsed, and if the class appears on the module fixup list.
334 // Due to the uniqueness that no other class shares the hidden class' name or
335 // ClassLoaderData, no other non-GC thread has knowledge of the hidden class while
336 // it is being defined, therefore _keep_alive_ref_count is not volatile or atomic.
337 void ClassLoaderData::inc_keep_alive_ref_count() {
338 if (has_class_mirror_holder()) {
339 assert(_keep_alive_ref_count > 0, "Invalid keep alive increment count");
340 _keep_alive_ref_count++;
341 }
342 }
343
344 void ClassLoaderData::dec_keep_alive_ref_count() {
345 if (has_class_mirror_holder()) {
346 assert(_keep_alive_ref_count > 0, "Invalid keep alive decrement count");
347 if (_keep_alive_ref_count == 1) {
348 // When the keep_alive_ref_count counter is 1, the oop handle area is a strong root,
349 // acting as input to the GC tracing. Such strong roots are part of the
350 // snapshot-at-the-beginning, and can not just be pulled out from the
351 // system when concurrent GCs are running at the same time, without
352 // invoking the right barriers.
353 demote_strong_roots();
354 }
355 _keep_alive_ref_count--;
356 }
357 }
358
359 void ClassLoaderData::oops_do_slow(OopClosure* f, bool clear_mod_oops) {
360 // Only clear modified_oops after the ClassLoaderData is claimed.
361 if (clear_mod_oops) {
362 clear_modified_oops();
363 }
364
365 _handles.oops_do(f);
366 }
367
368 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
369 // Lock-free access requires load_acquire
370 for (Klass* k = AtomicAccess::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
371 klass_closure->do_klass(k);
372 assert(k != k->next_link(), "no loops!");
373 }
374 }
375
376 void ClassLoaderData::classes_do(void f(Klass * const)) {
377 // Lock-free access requires load_acquire
378 for (Klass* k = AtomicAccess::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
379 f(k);
380 assert(k != k->next_link(), "no loops!");
381 }
382 }
383
384 void ClassLoaderData::methods_do(void f(Method*)) {
385 // Lock-free access requires load_acquire
386 for (Klass* k = AtomicAccess::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
387 if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
388 InstanceKlass::cast(k)->methods_do(f);
389 }
390 }
391 }
392
393 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
394 // Lock-free access requires load_acquire
395 for (Klass* k = AtomicAccess::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
396 // Filter out InstanceKlasses (or their ObjArrayKlasses) that have not entered the
397 // loaded state.
398 if (k->is_instance_klass()) {
399 if (!InstanceKlass::cast(k)->is_loaded()) {
400 continue;
401 }
402 } else if (k->in_aot_cache() && k->is_objArray_klass()) {
403 Klass* bottom = ObjArrayKlass::cast(k)->bottom_klass();
404 if (bottom->is_instance_klass() && !InstanceKlass::cast(bottom)->is_loaded()) {
405 // This could happen if <bottom> is a shared class that has been restored
406 // but is not yet marked as loaded. All archived array classes of the
407 // bottom class are already restored and placed in the _klasses list.
408 continue;
409 }
410 }
411
412 #ifdef ASSERT
413 oop m = k->java_mirror();
414 assert(m != nullptr, "nullptr mirror");
415 assert(m->is_a(vmClasses::Class_klass()), "invalid mirror");
416 #endif
417 klass_closure->do_klass(k);
418 }
419 }
420
421 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
422 // Lock-free access requires load_acquire
423 for (Klass* k = AtomicAccess::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
424 if (k->is_instance_klass()) {
425 f(InstanceKlass::cast(k));
426 }
427 assert(k != k->next_link(), "no loops!");
428 }
429 }
430
431 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
432 assert_locked_or_safepoint(Module_lock);
433 if (_unnamed_module != nullptr) {
434 f(_unnamed_module);
435 }
436 if (_modules != nullptr) {
437 _modules->modules_do(f);
438 }
439 }
440
441 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
442 assert_locked_or_safepoint(Module_lock);
443 if (_packages != nullptr) {
444 _packages->packages_do(f);
445 }
446 }
447
448 void ClassLoaderData::record_dependency(const Klass* k) {
449 assert(k != nullptr, "invariant");
450
451 ClassLoaderData * const from_cld = this;
452 ClassLoaderData * const to_cld = k->class_loader_data();
453
454 // Do not need to record dependency if the dependency is to a class whose
455 // class loader data is never freed. (i.e. the dependency's class loader
456 // is one of the three builtin class loaders and the dependency's class
457 // loader data has a ClassLoader holder, not a Class holder.)
458 if (to_cld->is_permanent_class_loader_data()) {
459 return;
460 }
461
462 oop to;
463 if (to_cld->has_class_mirror_holder()) {
464 // Just return if a non-strong hidden class class is attempting to record a dependency
465 // to itself. (Note that every non-strong hidden class has its own unique class
466 // loader data.)
467 if (to_cld == from_cld) {
468 return;
469 }
470 // Hidden class dependencies are through the mirror.
471 to = k->java_mirror();
472 } else {
473 to = to_cld->class_loader();
474 oop from = from_cld->class_loader();
475
476 // Just return if this dependency is to a class with the same or a parent
477 // class_loader.
478 if (from == to || java_lang_ClassLoader::isAncestor(from, to)) {
479 return; // this class loader is in the parent list, no need to add it.
480 }
481 }
482
483 // It's a dependency we won't find through GC, add it.
484 if (!_handles.contains(to)) {
485 NOT_PRODUCT(AtomicAccess::inc(&_dependency_count));
486 LogTarget(Trace, class, loader, data) lt;
487 if (lt.is_enabled()) {
488 ResourceMark rm;
489 LogStream ls(lt);
490 ls.print("adding dependency from ");
491 print_value_on(&ls);
492 ls.print(" to ");
493 to_cld->print_value_on(&ls);
494 ls.cr();
495 }
496 Handle dependency(Thread::current(), to);
497 add_handle(dependency);
498 // Added a potentially young gen oop to the ClassLoaderData
499 record_modified_oops();
500 }
501 }
502
503 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
504 {
505 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
506 Klass* old_value = _klasses;
507 k->set_next_link(old_value);
508 // Link the new item into the list, making sure the linked class is stable
509 // since the list can be walked without a lock
510 AtomicAccess::release_store(&_klasses, k);
511 if (k->is_array_klass()) {
512 ClassLoaderDataGraph::inc_array_classes(1);
513 } else {
514 ClassLoaderDataGraph::inc_instance_classes(1);
515 }
516 }
517
518 if (publicize) {
519 LogTarget(Trace, class, loader, data) lt;
520 if (lt.is_enabled()) {
521 ResourceMark rm;
522 LogStream ls(lt);
523 ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());
524 print_value_on(&ls);
525 ls.cr();
526 }
527 }
528 }
529
530 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) {
531 if (loader_or_mirror() != nullptr) {
532 assert(_holder.is_null(), "never replace holders");
533 _holder = WeakHandle(Universe::vm_weak(), loader_or_mirror);
534 }
535 }
536
537 // Remove a klass from the _klasses list for scratch_class during redefinition
538 // or parsed class in the case of an error.
539 void ClassLoaderData::remove_class(Klass* scratch_class) {
540 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
541
542 Klass* prev = nullptr;
543 for (Klass* k = _klasses; k != nullptr; k = k->next_link()) {
544 if (k == scratch_class) {
545 if (prev == nullptr) {
546 _klasses = k->next_link();
547 } else {
548 Klass* next = k->next_link();
549 prev->set_next_link(next);
550 }
551
552 if (k->is_array_klass()) {
553 ClassLoaderDataGraph::dec_array_classes(1);
554 } else {
555 ClassLoaderDataGraph::dec_instance_classes(1);
556 }
557
558 return;
559 }
560 prev = k;
561 assert(k != k->next_link(), "no loops!");
562 }
563 ShouldNotReachHere(); // should have found this class!!
564 }
565
566 void ClassLoaderData::add_jmethod_id(jmethodID mid) {
567 MutexLocker m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
568 if (_jmethod_ids == nullptr) {
569 _jmethod_ids = new (mtClass) GrowableArray<jmethodID>(32, mtClass);
570 }
571 _jmethod_ids->push(mid);
572 }
573
574 // Method::remove_jmethod_ids removes jmethodID entries from the table which
575 // releases memory.
576 // Because native code (e.g., JVMTI agent) holding jmethod_ids may access them
577 // after the associated classes and class loader are unloaded, subsequent lookups
578 // for these ids will return null since they are no longer found in the table.
579 // 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".
583 void ClassLoaderData::remove_jmethod_ids() {
584 MutexLocker ml(JmethodIdCreation_lock, Mutex::_no_safepoint_check_flag);
585 for (int i = 0; i < _jmethod_ids->length(); i++) {
586 jmethodID mid = _jmethod_ids->at(i);
587 JmethodIDTable::remove(mid);
588 }
589 delete _jmethod_ids;
590 _jmethod_ids = nullptr;
591 }
592
593 void ClassLoaderData::unload() {
594 _unloading = true;
595
596 LogTarget(Trace, class, loader, data) lt;
597 if (lt.is_enabled()) {
598 ResourceMark rm;
599 LogStream ls(lt);
600 ls.print("unload");
601 print_value_on(&ls);
602 ls.cr();
603 }
604
605 // Some items on the _deallocate_list need to free their C heap structures
606 // if they are not already on the _klasses list.
607 free_deallocate_list_C_heap_structures();
608
609 // Clean up class dependencies and tell serviceability tools
610 // these classes are unloading. This must be called
611 // after erroneous classes are released.
612 classes_do(InstanceKlass::unload_class);
613
614 if (_jmethod_ids != nullptr) {
615 remove_jmethod_ids();
616 }
617 }
618
619 ModuleEntryTable* ClassLoaderData::modules() {
620 // Lazily create the module entry table at first request.
621 // Lock-free access requires load_acquire.
622 ModuleEntryTable* modules = AtomicAccess::load_acquire(&_modules);
623 if (modules == nullptr) {
624 MutexLocker m1(Module_lock);
625 // Check if _modules got allocated while we were waiting for this lock.
626 if ((modules = _modules) == nullptr) {
627 modules = new ModuleEntryTable();
628
629 {
630 MutexLocker m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
631 // Ensure _modules is stable, since it is examined without a lock
632 AtomicAccess::release_store(&_modules, modules);
633 }
634 }
635 }
636 return modules;
637 }
638
639 const int _boot_loader_dictionary_size = 1009;
640 const int _default_loader_dictionary_size = 107;
641
642 Dictionary* ClassLoaderData::create_dictionary() {
643 assert(!has_class_mirror_holder(), "class mirror holder cld does not have a dictionary");
644 int size;
645 if (_the_null_class_loader_data == nullptr) {
646 size = _boot_loader_dictionary_size;
647 } else if (is_system_class_loader_data()) {
648 size = _boot_loader_dictionary_size;
649 } else {
650 size = _default_loader_dictionary_size;
651 }
652 return new Dictionary(this, size);
653 }
654
655 // Tell the GC to keep this klass alive. Needed while iterating ClassLoaderDataGraph,
656 // and any runtime code that uses klasses.
657 oop ClassLoaderData::holder() const {
658 // A klass that was previously considered dead can be looked up in the
659 // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
660 // or a reachable object making it alive again. The SATB part of G1 needs
661 // to get notified about this potential resurrection, otherwise the marking
662 // might not find the object.
663 if (!_holder.is_null()) { // null class_loader
664 return _holder.resolve();
665 } else {
666 return nullptr;
667 }
668 }
669
670 // Let the GC read the holder without keeping it alive.
671 oop ClassLoaderData::holder_no_keepalive() const {
672 if (!_holder.is_null()) { // null class_loader
673 return _holder.peek();
674 } else {
675 return nullptr;
676 }
677 }
678
679 // Unloading support
680 bool ClassLoaderData::is_alive() const {
681 bool alive = (_keep_alive_ref_count > 0) // null class loader and incomplete non-strong hidden class.
682 || (_holder.peek() != nullptr); // and not cleaned by the GC weak handle processing.
683
684 return alive;
685 }
686
687 class ReleaseKlassClosure: public KlassClosure {
688 private:
689 size_t _instance_class_released;
690 size_t _array_class_released;
691 public:
692 ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { }
693
694 size_t instance_class_released() const { return _instance_class_released; }
695 size_t array_class_released() const { return _array_class_released; }
696
697 void do_klass(Klass* k) {
698 if (k->is_array_klass()) {
699 _array_class_released ++;
700 } else {
701 assert(k->is_instance_klass(), "Must be");
702 _instance_class_released ++;
703 }
704 k->release_C_heap_structures();
705 }
706 };
707
708 ClassLoaderData::~ClassLoaderData() {
709 // Release C heap structures for all the classes.
710 ReleaseKlassClosure cl;
711 classes_do(&cl);
712
713 ClassLoaderDataGraph::dec_array_classes(cl.array_class_released());
714 ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released());
715
716 // Release the WeakHandle
717 _holder.release(Universe::vm_weak());
718
719 // Release C heap allocated hashtable for all the packages.
720 if (_packages != nullptr) {
721 // Destroy the table itself
722 delete _packages;
723 _packages = nullptr;
724 }
725
726 // Release C heap allocated hashtable for all the modules.
727 if (_modules != nullptr) {
728 // Destroy the table itself
729 delete _modules;
730 _modules = nullptr;
731 }
732
733 // Release C heap allocated hashtable for the dictionary
734 if (_dictionary != nullptr) {
735 // Destroy the table itself
736 delete _dictionary;
737 _dictionary = nullptr;
738 }
739
740 if (_unnamed_module != nullptr) {
741 delete _unnamed_module;
742 _unnamed_module = nullptr;
743 }
744
745 // release the metaspace
746 ClassLoaderMetaspace *m = _metaspace;
747 if (m != nullptr) {
748 _metaspace = nullptr;
749 delete m;
750 }
751
752 // Delete lock
753 delete _metaspace_lock;
754
755 // Delete free list
756 if (_deallocate_list != nullptr) {
757 delete _deallocate_list;
758 }
759
760 // Decrement refcounts of Symbols if created.
761 if (_name != nullptr) {
762 _name->decrement_refcount();
763 }
764 if (_name_and_id != nullptr) {
765 _name_and_id->decrement_refcount();
766 }
767 }
768
769 // Returns true if this class loader data is for the app class loader
770 // or a user defined system class loader. (Note that the class loader
771 // data may have a Class holder.)
772 bool ClassLoaderData::is_system_class_loader_data() const {
773 return SystemDictionary::is_system_class_loader(class_loader());
774 }
775
776 // Returns true if this class loader data is for the platform class loader.
777 // (Note that the class loader data may have a Class holder.)
778 bool ClassLoaderData::is_platform_class_loader_data() const {
779 return SystemDictionary::is_platform_class_loader(class_loader());
780 }
781
782 // Returns true if the class loader for this class loader data is one of
783 // the 3 builtin (boot application/system or platform) class loaders,
784 // including a user-defined system class loader. Note that if the class
785 // loader data is for a non-strong hidden class then it may
786 // get freed by a GC even if its class loader is one of these loaders.
787 bool ClassLoaderData::is_builtin_class_loader_data() const {
788 return (is_boot_class_loader_data() ||
789 SystemDictionary::is_system_class_loader(class_loader()) ||
790 SystemDictionary::is_platform_class_loader(class_loader()));
791 }
792
793 // Returns true if this class loader data is a class loader data
794 // that is not ever freed by a GC. It must be the CLD for one of the builtin
795 // class loaders and not the CLD for a non-strong hidden class.
796 bool ClassLoaderData::is_permanent_class_loader_data() const {
797 return is_builtin_class_loader_data() && !has_class_mirror_holder();
798 }
799
800 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() {
801 // If the metaspace has not been allocated, create a new one. Might want
802 // to create smaller arena for Reflection class loaders also.
803 // The reason for the delayed allocation is because some class loaders are
804 // simply for delegating with no metadata of their own.
805 // Lock-free access requires load_acquire.
806 ClassLoaderMetaspace* metaspace = AtomicAccess::load_acquire(&_metaspace);
807 if (metaspace == nullptr) {
808 MutexLocker ml(_metaspace_lock, Mutex::_no_safepoint_check_flag);
809 // Check if _metaspace got allocated while we were waiting for this lock.
810 if ((metaspace = _metaspace) == nullptr) {
811 if (this == the_null_class_loader_data()) {
812 assert (class_loader() == nullptr, "Must be");
813 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
814 } else if (has_class_mirror_holder()) {
815 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ClassMirrorHolderMetaspaceType);
816 } else {
817 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
818 }
819 // Ensure _metaspace is stable, since it is examined without a lock
820 AtomicAccess::release_store(&_metaspace, metaspace);
821 }
822 }
823 return metaspace;
824 }
825
826 OopHandle ClassLoaderData::add_handle(Handle h) {
827 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
828 record_modified_oops();
829 return _handles.add(h());
830 }
831
832 void ClassLoaderData::remove_handle(OopHandle h) {
833 assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading");
834 if (!h.is_empty()) {
835 assert(_handles.owner_of(h.ptr_raw()),
836 "Got unexpected handle " PTR_FORMAT, p2i(h.ptr_raw()));
837 h.replace(oop(nullptr));
838 }
839 }
840
841 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
842 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
843 if (dest.resolve() != nullptr) {
844 return;
845 } else {
846 record_modified_oops();
847 dest = _handles.add(h());
848 }
849 }
850
851 // Add this metadata pointer to be freed when it's safe. This is only during
852 // a safepoint which checks if handles point to this metadata field.
853 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
854 // Metadata in shared region isn't deleted.
855 if (!m->in_aot_cache()) {
856 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
857 if (_deallocate_list == nullptr) {
858 _deallocate_list = new (mtClass) GrowableArray<Metadata*>(100, mtClass);
859 }
860 _deallocate_list->append_if_missing(m);
861 ResourceMark rm;
862 log_debug(class, loader, data)("deallocate added for %s", m->print_value_string());
863 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
864 }
865 }
866
867 // Deallocate free metadata on the free list. How useful the PermGen was!
868 void ClassLoaderData::free_deallocate_list() {
869 // This must be called at a safepoint because it depends on metadata walking at
870 // safepoint cleanup time.
871 assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
872 assert(!is_unloading(), "only called for ClassLoaderData that are not unloading");
873 if (_deallocate_list == nullptr) {
874 return;
875 }
876 // Go backwards because this removes entries that are freed.
877 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
878 Metadata* m = _deallocate_list->at(i);
879 if (!m->on_stack()) {
880 _deallocate_list->remove_at(i);
881 // There are only three types of metadata that we deallocate directly.
882 // Cast them so they can be used by the template function.
883 if (m->is_method()) {
884 MetadataFactory::free_metadata(this, (Method*)m);
885 } else if (m->is_constantPool()) {
886 HeapShared::remove_scratch_resolved_references((ConstantPool*)m);
887 MetadataFactory::free_metadata(this, (ConstantPool*)m);
888 } else if (m->is_klass()) {
889 MetadataFactory::free_metadata(this, (InstanceKlass*)m);
890 } else {
891 ShouldNotReachHere();
892 }
893 } else {
894 // Metadata is alive.
895 // If scratch_class is on stack then it shouldn't be on this list!
896 assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
897 "scratch classes on this list should be dead");
898 // Also should assert that other metadata on the list was found in handles.
899 // Some cleaning remains.
900 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
901 }
902 }
903 }
904
905 // This is distinct from free_deallocate_list. For class loader data that are
906 // unloading, this frees the C heap memory for items on the list, and unlinks
907 // scratch or error classes so that unloading events aren't triggered for these
908 // classes. The metadata is removed with the unloading metaspace.
909 // There isn't C heap memory allocated for methods, so nothing is done for them.
910 void ClassLoaderData::free_deallocate_list_C_heap_structures() {
911 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
912 assert(is_unloading(), "only called for ClassLoaderData that are unloading");
913 if (_deallocate_list == nullptr) {
914 return;
915 }
916 // Go backwards because this removes entries that are freed.
917 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
918 Metadata* m = _deallocate_list->at(i);
919 _deallocate_list->remove_at(i);
920 if (m->is_constantPool()) {
921 ((ConstantPool*)m)->release_C_heap_structures();
922 } else if (m->is_klass()) {
923 InstanceKlass* ik = (InstanceKlass*)m;
924 // also releases ik->constants() C heap memory
925 ik->release_C_heap_structures();
926 // Remove the class so unloading events aren't triggered for
927 // this class (scratch or error class) in do_unloading().
928 remove_class(ik);
929 // But still have to remove it from the dumptime_table.
930 SystemDictionaryShared::handle_class_unloading(ik);
931 }
932 }
933 }
934
935 // Caller needs ResourceMark
936 // If the class loader's _name has not been explicitly set, the class loader's
937 // qualified class name is returned.
938 const char* ClassLoaderData::loader_name() const {
939 if (_class_loader_klass == nullptr) {
940 return BOOTSTRAP_LOADER_NAME;
941 } else if (_name != nullptr) {
942 return _name->as_C_string();
943 } else {
944 return _class_loader_klass->external_name();
945 }
946 }
947
948 // Caller needs ResourceMark
949 // Format of the _name_and_id is as follows:
950 // If the defining loader has a name explicitly set then '<loader-name>' @<id>
951 // If the defining loader has no name then <qualified-class-name> @<id>
952 // If built-in loader, then omit '@<id>' as there is only one instance.
953 const char* ClassLoaderData::loader_name_and_id() const {
954 if (_class_loader_klass == nullptr) {
955 return "'" BOOTSTRAP_LOADER_NAME "'";
956 } else if (_name_and_id != nullptr) {
957 return _name_and_id->as_C_string();
958 } else {
959 // May be called in a race before _name_and_id is initialized.
960 return _class_loader_klass->external_name();
961 }
962 }
963
964 void ClassLoaderData::print_value_on(outputStream* out) const {
965 if (!is_unloading() && class_loader() != nullptr) {
966 out->print("loader data: " INTPTR_FORMAT " for instance ", p2i(this));
967 class_loader()->print_value_on(out); // includes loader_name_and_id() and address of class loader instance
968 } else {
969 // loader data: 0xsomeaddr of 'bootstrap'
970 out->print("loader data: " INTPTR_FORMAT " of %s", p2i(this), loader_name_and_id());
971 }
972 if (_has_class_mirror_holder) {
973 out->print(" has a class holder");
974 }
975 }
976
977 void ClassLoaderData::print_value() const { print_value_on(tty); }
978
979 #ifndef PRODUCT
980 class PrintKlassClosure: public KlassClosure {
981 outputStream* _out;
982 public:
983 PrintKlassClosure(outputStream* out): _out(out) { }
984
985 void do_klass(Klass* k) {
986 ResourceMark rm;
987 _out->print("%s,", k->external_name());
988 }
989 };
990
991 void ClassLoaderData::print_on(outputStream* out) const {
992 ResourceMark rm;
993 out->print_cr("ClassLoaderData(" INTPTR_FORMAT ")", p2i(this));
994 out->print_cr(" - name %s", loader_name_and_id());
995 if (!_holder.is_null()) {
996 out->print (" - holder ");
997 _holder.print_on(out);
998 out->print_cr("");
999 }
1000 if (!_unloading) {
1001 out->print_cr(" - class loader " INTPTR_FORMAT, p2i(_class_loader.peek()));
1002 } else {
1003 out->print_cr(" - class loader <unloading, oop is bad>");
1004 }
1005 out->print_cr(" - metaspace " INTPTR_FORMAT, p2i(_metaspace));
1006 out->print_cr(" - unloading %s", _unloading ? "true" : "false");
1007 out->print_cr(" - class mirror holder %s", _has_class_mirror_holder ? "true" : "false");
1008 out->print_cr(" - modified oops %s", _modified_oops ? "true" : "false");
1009 out->print_cr(" - _keep_alive_ref_count %d", _keep_alive_ref_count);
1010 out->print (" - claim ");
1011 switch(_claim) {
1012 case _claim_none: out->print_cr("none"); break;
1013 case _claim_finalizable: out->print_cr("finalizable"); break;
1014 case _claim_strong: out->print_cr("strong"); break;
1015 case _claim_stw_fullgc_mark: out->print_cr("stw full gc mark"); break;
1016 case _claim_stw_fullgc_adjust: out->print_cr("stw full gc adjust"); break;
1017 case _claim_other: out->print_cr("other"); break;
1018 case _claim_other | _claim_finalizable: out->print_cr("other and finalizable"); break;
1019 case _claim_other | _claim_strong: out->print_cr("other and strong"); break;
1020 default: ShouldNotReachHere();
1021 }
1022 out->print_cr(" - handles %d", _handles.count());
1023 out->print_cr(" - dependency count %d", _dependency_count);
1024 out->print (" - klasses { ");
1025 if (Verbose) {
1026 PrintKlassClosure closure(out);
1027 ((ClassLoaderData*)this)->classes_do(&closure);
1028 } else {
1029 out->print("...");
1030 }
1031 out->print_cr(" }");
1032 out->print_cr(" - packages " INTPTR_FORMAT, p2i(_packages));
1033 out->print_cr(" - module " INTPTR_FORMAT, p2i(_modules));
1034 out->print_cr(" - unnamed module " INTPTR_FORMAT, p2i(_unnamed_module));
1035 if (_dictionary != nullptr) {
1036 out->print (" - dictionary " INTPTR_FORMAT " ", p2i(_dictionary));
1037 _dictionary->print_size(out);
1038 } else {
1039 out->print_cr(" - dictionary " INTPTR_FORMAT, p2i(_dictionary));
1040 }
1041 if (_jmethod_ids != nullptr) {
1042 out->print_cr(" - jmethod count %d", _jmethod_ids->length());
1043 }
1044 out->print_cr(" - deallocate list " INTPTR_FORMAT, p2i(_deallocate_list));
1045 out->print_cr(" - next CLD " INTPTR_FORMAT, p2i(_next));
1046 }
1047 #endif // PRODUCT
1048
1049 void ClassLoaderData::print() const { print_on(tty); }
1050
1051 class VerifyHandleOops : public OopClosure {
1052 VerifyOopClosure vc;
1053 public:
1054 virtual void do_oop(oop* p) {
1055 if (p != nullptr && *p != nullptr) {
1056 oop o = *p;
1057 if (!java_lang_Class::is_instance(o)) {
1058 // is_instance will assert for an invalid oop.
1059 // Walk the resolved_references array and other assorted oops in the
1060 // CLD::_handles field. The mirror oops are followed by other heap roots.
1061 o->oop_iterate(&vc);
1062 }
1063 }
1064 }
1065 virtual void do_oop(narrowOop* o) { ShouldNotReachHere(); }
1066 };
1067
1068 void ClassLoaderData::verify() {
1069 assert_locked_or_safepoint(_metaspace_lock);
1070 oop cl = class_loader();
1071
1072 guarantee(this == class_loader_data(cl) || has_class_mirror_holder(), "Must be the same");
1073 guarantee(cl != nullptr || this == ClassLoaderData::the_null_class_loader_data() || has_class_mirror_holder(), "must be");
1074
1075 // Verify the integrity of the allocated space.
1076 #ifdef ASSERT
1077 if (metaspace_or_null() != nullptr) {
1078 metaspace_or_null()->verify();
1079 }
1080 #endif
1081
1082 for (Klass* k = _klasses; k != nullptr; k = k->next_link()) {
1083 guarantee(k->class_loader_data() == this, "Must be the same");
1084 k->verify();
1085 assert(k != k->next_link(), "no loops!");
1086 }
1087
1088 if (_modules != nullptr) {
1089 _modules->verify();
1090 }
1091
1092 if (_deallocate_list != nullptr) {
1093 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
1094 Metadata* m = _deallocate_list->at(i);
1095 if (m->is_klass()) {
1096 ((Klass*)m)->verify();
1097 }
1098 }
1099 }
1100
1101 // Check the oops in the handles area
1102 VerifyHandleOops vho;
1103 oops_do(&vho, _claim_none, false);
1104 }
1105
1106 bool ClassLoaderData::contains_klass(Klass* klass) {
1107 // Lock-free access requires load_acquire
1108 for (Klass* k = AtomicAccess::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
1109 if (k == klass) return true;
1110 }
1111 return false;
1112 }