1 /*
2 * Copyright (c) 2012, 2024, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 // A ClassLoaderData identifies the full set of class types that a class
26 // loader's name resolution strategy produces for a given configuration of the
27 // class loader.
28 // Class types in the ClassLoaderData may be defined by from class file binaries
29 // provided by the class loader, or from other class loader it interacts with
30 // according to its name resolution strategy.
31 //
32 // Class loaders that implement a deterministic name resolution strategy
33 // (including with respect to their delegation behavior), such as the boot, the
34 // platform, and the system loaders of the JDK's built-in class loader
35 // hierarchy, always produce the same linkset for a given configuration.
36 //
37 // ClassLoaderData carries information related to a linkset (e.g.,
38 // metaspace holding its klass definitions).
39 // The System Dictionary and related data structures (e.g., placeholder table,
40 // loader constraints table) as well as the runtime representation of classes
41 // only reference ClassLoaderData.
42 //
43 // Instances of java.lang.ClassLoader holds a pointer to a ClassLoaderData that
44 // that represent the loader's "linking domain" in the JVM.
45 //
46 // The bootstrap loader (represented by null) also has a ClassLoaderData,
47 // the singleton class the_null_class_loader_data().
48
49 #include "precompiled.hpp"
50 #include "classfile/classLoaderData.inline.hpp"
51 #include "classfile/classLoaderDataGraph.inline.hpp"
52 #include "classfile/dictionary.hpp"
53 #include "classfile/javaClasses.inline.hpp"
54 #include "classfile/moduleEntry.hpp"
55 #include "classfile/packageEntry.hpp"
56 #include "classfile/symbolTable.hpp"
57 #include "classfile/systemDictionary.hpp"
58 #include "classfile/systemDictionaryShared.hpp"
59 #include "classfile/vmClasses.hpp"
60 #include "logging/log.hpp"
61 #include "logging/logStream.hpp"
62 #include "memory/allocation.inline.hpp"
63 #include "memory/classLoaderMetaspace.hpp"
64 #include "memory/metadataFactory.hpp"
65 #include "memory/metaspace.hpp"
66 #include "memory/resourceArea.hpp"
67 #include "memory/universe.hpp"
68 #include "oops/access.inline.hpp"
69 #include "oops/inlineKlass.inline.hpp"
70 #include "oops/klass.inline.hpp"
71 #include "oops/oop.inline.hpp"
72 #include "oops/oopHandle.inline.hpp"
73 #include "oops/verifyOopClosure.hpp"
74 #include "oops/weakHandle.inline.hpp"
75 #include "runtime/arguments.hpp"
76 #include "runtime/atomic.hpp"
77 #include "runtime/handles.inline.hpp"
78 #include "runtime/mutex.hpp"
79 #include "runtime/safepoint.hpp"
80 #include "utilities/growableArray.hpp"
81 #include "utilities/macros.hpp"
82 #include "utilities/ostream.hpp"
83
84 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = 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 Atomic::release_store(&_head, next);
197 }
198 oop* handle = &_head->_data[_head->_size];
199 NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, o);
200 Atomic::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 = Atomic::load_acquire(&_head);
207 while (chunk != nullptr) {
208 count += Atomic::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 = Atomic::load_acquire(&_head);
222 if (head != nullptr) {
223 // Must be careful when reading size of head
224 oops_do_chunk(f, head, Atomic::load_acquire(&head->_size));
225 for (Chunk* c = head->_next; c != 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 = Atomic::load_acquire(&_head);
263 while (chunk != nullptr) {
264 if (&(chunk->_data[0]) <= oop_handle && oop_handle < &(chunk->_data[Atomic::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 = Atomic::load(&_claim);
276 if ((old_claim & claim) == 0) {
277 return;
278 }
279 int new_claim = old_claim & ~claim;
280 if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
281 return;
282 }
283 }
284 }
285
286 #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 bool ClassLoaderData::try_claim(int claim) {
293 for (;;) {
294 int old_claim = Atomic::load(&_claim);
295 if ((old_claim & claim) == claim) {
296 return false;
297 }
298 int new_claim = old_claim | claim;
299 if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
300 return true;
301 }
302 }
303 }
304
305 void ClassLoaderData::demote_strong_roots() {
306 // The oop handle area contains strong roots that the GC traces from. We are about
307 // to demote them to strong native oops that the GC does *not* trace from. Conceptually,
308 // we are retiring a rather normal strong root, and creating a strong non-root handle,
309 // which happens to reuse the same address as the normal strong root had.
310 // Unless we invoke the right barriers, the GC might not notice that a strong root
311 // has been pulled from the system, and is left unprocessed by the GC. There can be
312 // several consequences:
313 // 1. A concurrently marking snapshot-at-the-beginning GC might assume that the contents
314 // of all strong roots get processed by the GC in order to keep them alive. Without
315 // barriers, some objects might not be kept alive.
316 // 2. A concurrently relocating GC might assume that after moving an object, a subsequent
317 // tracing from all roots can fix all the pointers in the system, which doesn't play
318 // well with roots racingly being pulled.
319 // 3. A concurrent GC using colored pointers, might assume that tracing the object graph
320 // from roots results in all pointers getting some particular color, which also doesn't
321 // play well with roots being pulled out from the system concurrently.
322
323 class TransitionRootsOopClosure : public OopClosure {
324 public:
325 virtual void do_oop(oop* p) {
326 // By loading the strong root with the access API, we can use the right barriers to
327 // store the oop as a strong non-root handle, that happens to reuse the same memory
328 // address as the strong root. The barriered store ensures that:
329 // 1. The concurrent SATB marking properties are satisfied as the store will keep
330 // the oop alive.
331 // 2. The concurrent object movement properties are satisfied as we store the address
332 // of the new location of the object, if any.
333 // 3. The colors if any will be stored as the new good colors.
334 oop obj = NativeAccess<>::oop_load(p); // Load the strong root
335 NativeAccess<>::oop_store(p, obj); // Store the strong non-root
336 }
337
338 virtual void do_oop(narrowOop* p) {
339 ShouldNotReachHere();
340 }
341 } cl;
342 oops_do(&cl, ClassLoaderData::_claim_none, false /* clear_mod_oops */);
343 }
344
345 // Non-strong hidden classes have their own ClassLoaderData that is marked to keep alive
346 // while the class is being parsed, and if the class appears on the module fixup list.
347 // Due to the uniqueness that no other class shares the hidden class' name or
348 // ClassLoaderData, no other non-GC thread has knowledge of the hidden class while
349 // it is being defined, therefore _keep_alive_ref_count is not volatile or atomic.
350 void ClassLoaderData::inc_keep_alive_ref_count() {
351 if (has_class_mirror_holder()) {
352 assert(_keep_alive_ref_count > 0, "Invalid keep alive increment count");
353 _keep_alive_ref_count++;
354 }
355 }
356
357 void ClassLoaderData::dec_keep_alive_ref_count() {
358 if (has_class_mirror_holder()) {
359 assert(_keep_alive_ref_count > 0, "Invalid keep alive decrement count");
360 if (_keep_alive_ref_count == 1) {
361 // When the keep_alive_ref_count counter is 1, the oop handle area is a strong root,
362 // acting as input to the GC tracing. Such strong roots are part of the
363 // snapshot-at-the-beginning, and can not just be pulled out from the
364 // system when concurrent GCs are running at the same time, without
365 // invoking the right barriers.
366 demote_strong_roots();
367 }
368 _keep_alive_ref_count--;
369 }
370 }
371
372 void ClassLoaderData::oops_do(OopClosure* f, int claim_value, bool clear_mod_oops) {
373 if (claim_value != ClassLoaderData::_claim_none && !try_claim(claim_value)) {
374 return;
375 }
376
377 // Only clear modified_oops after the ClassLoaderData is claimed.
378 if (clear_mod_oops) {
379 clear_modified_oops();
380 }
381
382 _handles.oops_do(f);
383 }
384
385 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
386 // Lock-free access requires load_acquire
387 for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
388 klass_closure->do_klass(k);
389 assert(k != k->next_link(), "no loops!");
390 }
391 }
392
393 void ClassLoaderData::classes_do(void f(Klass * const)) {
394 // Lock-free access requires load_acquire
395 for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
396 f(k);
397 assert(k != k->next_link(), "no loops!");
398 }
399 }
400
401 void ClassLoaderData::methods_do(void f(Method*)) {
402 // Lock-free access requires load_acquire
403 for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
404 if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
405 InstanceKlass::cast(k)->methods_do(f);
406 }
407 }
408 }
409
410 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
411 // Lock-free access requires load_acquire
412 for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
413 // Filter out InstanceKlasses (or their ObjArrayKlasses) that have not entered the
414 // loaded state.
415 if (k->is_instance_klass()) {
416 if (!InstanceKlass::cast(k)->is_loaded()) {
417 continue;
418 }
419 } else if (k->is_shared() && k->is_objArray_klass()) {
420 Klass* bottom = ObjArrayKlass::cast(k)->bottom_klass();
421 if (bottom->is_instance_klass() && !InstanceKlass::cast(bottom)->is_loaded()) {
422 // This could happen if <bottom> is a shared class that has been restored
423 // but is not yet marked as loaded. All archived array classes of the
424 // bottom class are already restored and placed in the _klasses list.
425 continue;
426 }
427 }
428
429 #ifdef ASSERT
430 oop m = k->java_mirror();
431 assert(m != nullptr, "nullptr mirror");
432 assert(m->is_a(vmClasses::Class_klass()), "invalid mirror");
433 #endif
434 klass_closure->do_klass(k);
435 }
436 }
437
438 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
439 // Lock-free access requires load_acquire
440 for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
441 if (k->is_instance_klass()) {
442 f(InstanceKlass::cast(k));
443 }
444 assert(k != k->next_link(), "no loops!");
445 }
446 }
447
448 void ClassLoaderData::inline_classes_do(void f(InlineKlass*)) {
449 // Lock-free access requires load_acquire
450 for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
451 if (k->is_inline_klass()) {
452 f(InlineKlass::cast(k));
453 }
454 assert(k != k->next_link(), "no loops!");
455 }
456 }
457
458 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
459 assert_locked_or_safepoint(Module_lock);
460 if (_unnamed_module != nullptr) {
461 f(_unnamed_module);
462 }
463 if (_modules != nullptr) {
464 _modules->modules_do(f);
465 }
466 }
467
468 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
469 assert_locked_or_safepoint(Module_lock);
470 if (_packages != nullptr) {
471 _packages->packages_do(f);
472 }
473 }
474
475 void ClassLoaderData::record_dependency(const Klass* k) {
476 assert(k != nullptr, "invariant");
477
478 ClassLoaderData * const from_cld = this;
479 ClassLoaderData * const to_cld = k->class_loader_data();
480
481 // Do not need to record dependency if the dependency is to a class whose
482 // class loader data is never freed. (i.e. the dependency's class loader
483 // is one of the three builtin class loaders and the dependency's class
484 // loader data has a ClassLoader holder, not a Class holder.)
485 if (to_cld->is_permanent_class_loader_data()) {
486 return;
487 }
488
489 oop to;
490 if (to_cld->has_class_mirror_holder()) {
491 // Just return if a non-strong hidden class class is attempting to record a dependency
492 // to itself. (Note that every non-strong hidden class has its own unique class
493 // loader data.)
494 if (to_cld == from_cld) {
495 return;
496 }
497 // Hidden class dependencies are through the mirror.
498 to = k->java_mirror();
499 } else {
500 to = to_cld->class_loader();
501 oop from = from_cld->class_loader();
502
503 // Just return if this dependency is to a class with the same or a parent
504 // class_loader.
505 if (from == to || java_lang_ClassLoader::isAncestor(from, to)) {
506 return; // this class loader is in the parent list, no need to add it.
507 }
508 }
509
510 // It's a dependency we won't find through GC, add it.
511 if (!_handles.contains(to)) {
512 NOT_PRODUCT(Atomic::inc(&_dependency_count));
513 LogTarget(Trace, class, loader, data) lt;
514 if (lt.is_enabled()) {
515 ResourceMark rm;
516 LogStream ls(lt);
517 ls.print("adding dependency from ");
518 print_value_on(&ls);
519 ls.print(" to ");
520 to_cld->print_value_on(&ls);
521 ls.cr();
522 }
523 Handle dependency(Thread::current(), to);
524 add_handle(dependency);
525 // Added a potentially young gen oop to the ClassLoaderData
526 record_modified_oops();
527 }
528 }
529
530 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
531 {
532 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
533 Klass* old_value = _klasses;
534 k->set_next_link(old_value);
535 // Link the new item into the list, making sure the linked class is stable
536 // since the list can be walked without a lock
537 Atomic::release_store(&_klasses, k);
538 if (k->is_array_klass()) {
539 ClassLoaderDataGraph::inc_array_classes(1);
540 } else {
541 ClassLoaderDataGraph::inc_instance_classes(1);
542 }
543 }
544
545 if (publicize) {
546 LogTarget(Trace, class, loader, data) lt;
547 if (lt.is_enabled()) {
548 ResourceMark rm;
549 LogStream ls(lt);
550 ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());
551 print_value_on(&ls);
552 ls.cr();
553 }
554 }
555 }
556
557 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) {
558 if (loader_or_mirror() != nullptr) {
559 assert(_holder.is_null(), "never replace holders");
560 _holder = WeakHandle(Universe::vm_weak(), loader_or_mirror);
561 }
562 }
563
564 // Remove a klass from the _klasses list for scratch_class during redefinition
565 // or parsed class in the case of an error.
566 void ClassLoaderData::remove_class(Klass* scratch_class) {
567 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
568
569 Klass* prev = nullptr;
570 for (Klass* k = _klasses; k != nullptr; k = k->next_link()) {
571 if (k == scratch_class) {
572 if (prev == nullptr) {
573 _klasses = k->next_link();
574 } else {
575 Klass* next = k->next_link();
576 prev->set_next_link(next);
577 }
578
579 if (k->is_array_klass()) {
580 ClassLoaderDataGraph::dec_array_classes(1);
581 } else {
582 ClassLoaderDataGraph::dec_instance_classes(1);
583 }
584
585 return;
586 }
587 prev = k;
588 assert(k != k->next_link(), "no loops!");
589 }
590 ShouldNotReachHere(); // should have found this class!!
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 inline_classes_do(InlineKlass::cleanup);
610
611 // Clean up class dependencies and tell serviceability tools
612 // these classes are unloading. This must be called
613 // after erroneous classes are released.
614 classes_do(InstanceKlass::unload_class);
615
616 // Method::clear_jmethod_ids only sets the jmethod_ids to null without
617 // releasing the memory for related JNIMethodBlocks and JNIMethodBlockNodes.
618 // This is done intentionally because native code (e.g. JVMTI agent) holding
619 // jmethod_ids may access them after the associated classes and class loader
620 // are unloaded. The Java Native Interface Specification says "method ID
621 // does not prevent the VM from unloading the class from which the ID has
622 // been derived. After the class is unloaded, the method or field ID becomes
623 // invalid". In real world usages, the native code may rely on jmethod_ids
624 // being null after class unloading. Hence, it is unsafe to free the memory
625 // from the VM side without knowing when native code is going to stop using
626 // them.
627 if (_jmethod_ids != nullptr) {
628 Method::clear_jmethod_ids(this);
629 }
630 }
631
632 ModuleEntryTable* ClassLoaderData::modules() {
633 // Lazily create the module entry table at first request.
634 // Lock-free access requires load_acquire.
635 ModuleEntryTable* modules = Atomic::load_acquire(&_modules);
636 if (modules == nullptr) {
637 MutexLocker m1(Module_lock);
638 // Check if _modules got allocated while we were waiting for this lock.
639 if ((modules = _modules) == nullptr) {
640 modules = new ModuleEntryTable();
641
642 {
643 MutexLocker m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
644 // Ensure _modules is stable, since it is examined without a lock
645 Atomic::release_store(&_modules, modules);
646 }
647 }
648 }
649 return modules;
650 }
651
652 const int _boot_loader_dictionary_size = 1009;
653 const int _default_loader_dictionary_size = 107;
654
655 Dictionary* ClassLoaderData::create_dictionary() {
656 assert(!has_class_mirror_holder(), "class mirror holder cld does not have a dictionary");
657 int size;
658 if (_the_null_class_loader_data == nullptr) {
659 size = _boot_loader_dictionary_size;
660 } else if (is_system_class_loader_data()) {
661 size = _boot_loader_dictionary_size;
662 } else {
663 size = _default_loader_dictionary_size;
664 }
665 return new Dictionary(this, size);
666 }
667
668 // Tell the GC to keep this klass alive. Needed while iterating ClassLoaderDataGraph,
669 // and any runtime code that uses klasses.
670 oop ClassLoaderData::holder() const {
671 // A klass that was previously considered dead can be looked up in the
672 // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
673 // or a reachable object making it alive again. The SATB part of G1 needs
674 // to get notified about this potential resurrection, otherwise the marking
675 // might not find the object.
676 if (!_holder.is_null()) { // null class_loader
677 return _holder.resolve();
678 } else {
679 return nullptr;
680 }
681 }
682
683 // Let the GC read the holder without keeping it alive.
684 oop ClassLoaderData::holder_no_keepalive() const {
685 if (!_holder.is_null()) { // null class_loader
686 return _holder.peek();
687 } else {
688 return nullptr;
689 }
690 }
691
692 // Unloading support
693 bool ClassLoaderData::is_alive() const {
694 bool alive = (_keep_alive_ref_count > 0) // null class loader and incomplete non-strong hidden class.
695 || (_holder.peek() != nullptr); // and not cleaned by the GC weak handle processing.
696
697 return alive;
698 }
699
700 class ReleaseKlassClosure: public KlassClosure {
701 private:
702 size_t _instance_class_released;
703 size_t _array_class_released;
704 public:
705 ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { }
706
707 size_t instance_class_released() const { return _instance_class_released; }
708 size_t array_class_released() const { return _array_class_released; }
709
710 void do_klass(Klass* k) {
711 if (k->is_array_klass()) {
712 _array_class_released ++;
713 } else {
714 assert(k->is_instance_klass(), "Must be");
715 _instance_class_released ++;
716 }
717 k->release_C_heap_structures();
718 }
719 };
720
721 ClassLoaderData::~ClassLoaderData() {
722 // Release C heap structures for all the classes.
723 ReleaseKlassClosure cl;
724 classes_do(&cl);
725
726 ClassLoaderDataGraph::dec_array_classes(cl.array_class_released());
727 ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released());
728
729 // Release the WeakHandle
730 _holder.release(Universe::vm_weak());
731
732 // Release C heap allocated hashtable for all the packages.
733 if (_packages != nullptr) {
734 // Destroy the table itself
735 delete _packages;
736 _packages = nullptr;
737 }
738
739 // Release C heap allocated hashtable for all the modules.
740 if (_modules != nullptr) {
741 // Destroy the table itself
742 delete _modules;
743 _modules = nullptr;
744 }
745
746 // Release C heap allocated hashtable for the dictionary
747 if (_dictionary != nullptr) {
748 // Destroy the table itself
749 delete _dictionary;
750 _dictionary = nullptr;
751 }
752
753 if (_unnamed_module != nullptr) {
754 delete _unnamed_module;
755 _unnamed_module = nullptr;
756 }
757
758 // release the metaspace
759 ClassLoaderMetaspace *m = _metaspace;
760 if (m != nullptr) {
761 _metaspace = nullptr;
762 delete m;
763 }
764
765 // Delete lock
766 delete _metaspace_lock;
767
768 // Delete free list
769 if (_deallocate_list != nullptr) {
770 delete _deallocate_list;
771 }
772
773 // Decrement refcounts of Symbols if created.
774 if (_name != nullptr) {
775 _name->decrement_refcount();
776 }
777 if (_name_and_id != nullptr) {
778 _name_and_id->decrement_refcount();
779 }
780 }
781
782 // Returns true if this class loader data is for the app class loader
783 // or a user defined system class loader. (Note that the class loader
784 // data may have a Class holder.)
785 bool ClassLoaderData::is_system_class_loader_data() const {
786 return SystemDictionary::is_system_class_loader(class_loader());
787 }
788
789 // Returns true if this class loader data is for the platform class loader.
790 // (Note that the class loader data may have a Class holder.)
791 bool ClassLoaderData::is_platform_class_loader_data() const {
792 return SystemDictionary::is_platform_class_loader(class_loader());
793 }
794
795 // Returns true if the class loader for this class loader data is one of
796 // the 3 builtin (boot application/system or platform) class loaders,
797 // including a user-defined system class loader. Note that if the class
798 // loader data is for a non-strong hidden class then it may
799 // get freed by a GC even if its class loader is one of these loaders.
800 bool ClassLoaderData::is_builtin_class_loader_data() const {
801 return (is_boot_class_loader_data() ||
802 SystemDictionary::is_system_class_loader(class_loader()) ||
803 SystemDictionary::is_platform_class_loader(class_loader()));
804 }
805
806 // Returns true if this class loader data is a class loader data
807 // that is not ever freed by a GC. It must be the CLD for one of the builtin
808 // class loaders and not the CLD for a non-strong hidden class.
809 bool ClassLoaderData::is_permanent_class_loader_data() const {
810 return is_builtin_class_loader_data() && !has_class_mirror_holder();
811 }
812
813 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() {
814 // If the metaspace has not been allocated, create a new one. Might want
815 // to create smaller arena for Reflection class loaders also.
816 // The reason for the delayed allocation is because some class loaders are
817 // simply for delegating with no metadata of their own.
818 // Lock-free access requires load_acquire.
819 ClassLoaderMetaspace* metaspace = Atomic::load_acquire(&_metaspace);
820 if (metaspace == nullptr) {
821 MutexLocker ml(_metaspace_lock, Mutex::_no_safepoint_check_flag);
822 // Check if _metaspace got allocated while we were waiting for this lock.
823 if ((metaspace = _metaspace) == nullptr) {
824 if (this == the_null_class_loader_data()) {
825 assert (class_loader() == nullptr, "Must be");
826 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
827 } else if (has_class_mirror_holder()) {
828 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ClassMirrorHolderMetaspaceType);
829 } else {
830 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
831 }
832 // Ensure _metaspace is stable, since it is examined without a lock
833 Atomic::release_store(&_metaspace, metaspace);
834 }
835 }
836 return metaspace;
837 }
838
839 OopHandle ClassLoaderData::add_handle(Handle h) {
840 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
841 record_modified_oops();
842 return _handles.add(h());
843 }
844
845 void ClassLoaderData::remove_handle(OopHandle h) {
846 assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading");
847 if (!h.is_empty()) {
848 assert(_handles.owner_of(h.ptr_raw()),
849 "Got unexpected handle " PTR_FORMAT, p2i(h.ptr_raw()));
850 h.replace(oop(nullptr));
851 }
852 }
853
854 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
855 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
856 if (dest.resolve() != nullptr) {
857 return;
858 } else {
859 record_modified_oops();
860 dest = _handles.add(h());
861 }
862 }
863
864 // Add this metadata pointer to be freed when it's safe. This is only during
865 // a safepoint which checks if handles point to this metadata field.
866 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
867 // Metadata in shared region isn't deleted.
868 if (!m->is_shared()) {
869 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
870 if (_deallocate_list == nullptr) {
871 _deallocate_list = new (mtClass) GrowableArray<Metadata*>(100, mtClass);
872 }
873 _deallocate_list->append_if_missing(m);
874 ResourceMark rm;
875 log_debug(class, loader, data)("deallocate added for %s", m->print_value_string());
876 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
877 }
878 }
879
880 // Deallocate free metadata on the free list. How useful the PermGen was!
881 void ClassLoaderData::free_deallocate_list() {
882 // This must be called at a safepoint because it depends on metadata walking at
883 // safepoint cleanup time.
884 assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
885 assert(!is_unloading(), "only called for ClassLoaderData that are not unloading");
886 if (_deallocate_list == nullptr) {
887 return;
888 }
889 // Go backwards because this removes entries that are freed.
890 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
891 Metadata* m = _deallocate_list->at(i);
892 if (!m->on_stack()) {
893 _deallocate_list->remove_at(i);
894 // There are only three types of metadata that we deallocate directly.
895 // Cast them so they can be used by the template function.
896 if (m->is_method()) {
897 MetadataFactory::free_metadata(this, (Method*)m);
898 } else if (m->is_constantPool()) {
899 MetadataFactory::free_metadata(this, (ConstantPool*)m);
900 } else if (m->is_klass()) {
901 if (!((Klass*)m)->is_inline_klass()) {
902 MetadataFactory::free_metadata(this, (InstanceKlass*)m);
903 } else {
904 MetadataFactory::free_metadata(this, (InlineKlass*)m);
905 }
906 } else {
907 ShouldNotReachHere();
908 }
909 } else {
910 // Metadata is alive.
911 // If scratch_class is on stack then it shouldn't be on this list!
912 assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
913 "scratch classes on this list should be dead");
914 // Also should assert that other metadata on the list was found in handles.
915 // Some cleaning remains.
916 ClassLoaderDataGraph::set_should_clean_deallocate_lists();
917 }
918 }
919 }
920
921 // This is distinct from free_deallocate_list. For class loader data that are
922 // unloading, this frees the C heap memory for items on the list, and unlinks
923 // scratch or error classes so that unloading events aren't triggered for these
924 // classes. The metadata is removed with the unloading metaspace.
925 // There isn't C heap memory allocated for methods, so nothing is done for them.
926 void ClassLoaderData::free_deallocate_list_C_heap_structures() {
927 assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
928 assert(is_unloading(), "only called for ClassLoaderData that are unloading");
929 if (_deallocate_list == nullptr) {
930 return;
931 }
932 // Go backwards because this removes entries that are freed.
933 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
934 Metadata* m = _deallocate_list->at(i);
935 _deallocate_list->remove_at(i);
936 if (m->is_constantPool()) {
937 ((ConstantPool*)m)->release_C_heap_structures();
938 } else if (m->is_klass()) {
939 InstanceKlass* ik = (InstanceKlass*)m;
940 // also releases ik->constants() C heap memory
941 ik->release_C_heap_structures();
942 // Remove the class so unloading events aren't triggered for
943 // this class (scratch or error class) in do_unloading().
944 remove_class(ik);
945 // But still have to remove it from the dumptime_table.
946 SystemDictionaryShared::handle_class_unloading(ik);
947 }
948 }
949 }
950
951 // Caller needs ResourceMark
952 // If the class loader's _name has not been explicitly set, the class loader's
953 // qualified class name is returned.
954 const char* ClassLoaderData::loader_name() const {
955 if (_class_loader_klass == nullptr) {
956 return BOOTSTRAP_LOADER_NAME;
957 } else if (_name != nullptr) {
958 return _name->as_C_string();
959 } else {
960 return _class_loader_klass->external_name();
961 }
962 }
963
964 // Caller needs ResourceMark
965 // Format of the _name_and_id is as follows:
966 // If the defining loader has a name explicitly set then '<loader-name>' @<id>
967 // If the defining loader has no name then <qualified-class-name> @<id>
968 // If built-in loader, then omit '@<id>' as there is only one instance.
969 const char* ClassLoaderData::loader_name_and_id() const {
970 if (_class_loader_klass == nullptr) {
971 return "'" BOOTSTRAP_LOADER_NAME "'";
972 } else if (_name_and_id != nullptr) {
973 return _name_and_id->as_C_string();
974 } else {
975 // May be called in a race before _name_and_id is initialized.
976 return _class_loader_klass->external_name();
977 }
978 }
979
980 void ClassLoaderData::print_value_on(outputStream* out) const {
981 if (!is_unloading() && class_loader() != nullptr) {
982 out->print("loader data: " INTPTR_FORMAT " for instance ", p2i(this));
983 class_loader()->print_value_on(out); // includes loader_name_and_id() and address of class loader instance
984 } else {
985 // loader data: 0xsomeaddr of 'bootstrap'
986 out->print("loader data: " INTPTR_FORMAT " of %s", p2i(this), loader_name_and_id());
987 }
988 if (_has_class_mirror_holder) {
989 out->print(" has a class holder");
990 }
991 }
992
993 void ClassLoaderData::print_value() const { print_value_on(tty); }
994
995 #ifndef PRODUCT
996 class PrintKlassClosure: public KlassClosure {
997 outputStream* _out;
998 public:
999 PrintKlassClosure(outputStream* out): _out(out) { }
1000
1001 void do_klass(Klass* k) {
1002 ResourceMark rm;
1003 _out->print("%s,", k->external_name());
1004 }
1005 };
1006
1007 void ClassLoaderData::print_on(outputStream* out) const {
1008 ResourceMark rm;
1009 out->print_cr("ClassLoaderData(" INTPTR_FORMAT ")", p2i(this));
1010 out->print_cr(" - name %s", loader_name_and_id());
1011 if (!_holder.is_null()) {
1012 out->print (" - holder ");
1013 _holder.print_on(out);
1014 out->print_cr("");
1015 }
1016 if (!_unloading) {
1017 out->print_cr(" - class loader " INTPTR_FORMAT, p2i(_class_loader.peek()));
1018 } else {
1019 out->print_cr(" - class loader <unloading, oop is bad>");
1020 }
1021 out->print_cr(" - metaspace " INTPTR_FORMAT, p2i(_metaspace));
1022 out->print_cr(" - unloading %s", _unloading ? "true" : "false");
1023 out->print_cr(" - class mirror holder %s", _has_class_mirror_holder ? "true" : "false");
1024 out->print_cr(" - modified oops %s", _modified_oops ? "true" : "false");
1025 out->print_cr(" - _keep_alive_ref_count %d", _keep_alive_ref_count);
1026 out->print (" - claim ");
1027 switch(_claim) {
1028 case _claim_none: out->print_cr("none"); break;
1029 case _claim_finalizable: out->print_cr("finalizable"); break;
1030 case _claim_strong: out->print_cr("strong"); break;
1031 case _claim_stw_fullgc_mark: out->print_cr("stw full gc mark"); break;
1032 case _claim_stw_fullgc_adjust: out->print_cr("stw full gc adjust"); break;
1033 case _claim_other: out->print_cr("other"); break;
1034 case _claim_other | _claim_finalizable: out->print_cr("other and finalizable"); break;
1035 case _claim_other | _claim_strong: out->print_cr("other and strong"); break;
1036 default: ShouldNotReachHere();
1037 }
1038 out->print_cr(" - handles %d", _handles.count());
1039 out->print_cr(" - dependency count %d", _dependency_count);
1040 out->print (" - klasses { ");
1041 if (Verbose) {
1042 PrintKlassClosure closure(out);
1043 ((ClassLoaderData*)this)->classes_do(&closure);
1044 } else {
1045 out->print("...");
1046 }
1047 out->print_cr(" }");
1048 out->print_cr(" - packages " INTPTR_FORMAT, p2i(_packages));
1049 out->print_cr(" - module " INTPTR_FORMAT, p2i(_modules));
1050 out->print_cr(" - unnamed module " INTPTR_FORMAT, p2i(_unnamed_module));
1051 if (_dictionary != nullptr) {
1052 out->print (" - dictionary " INTPTR_FORMAT " ", p2i(_dictionary));
1053 _dictionary->print_size(out);
1054 } else {
1055 out->print_cr(" - dictionary " INTPTR_FORMAT, p2i(_dictionary));
1056 }
1057 if (_jmethod_ids != nullptr) {
1058 out->print (" - jmethod count ");
1059 Method::print_jmethod_ids_count(this, out);
1060 out->print_cr("");
1061 }
1062 out->print_cr(" - deallocate list " INTPTR_FORMAT, p2i(_deallocate_list));
1063 out->print_cr(" - next CLD " INTPTR_FORMAT, p2i(_next));
1064 }
1065 #endif // PRODUCT
1066
1067 void ClassLoaderData::print() const { print_on(tty); }
1068
1069 class VerifyHandleOops : public OopClosure {
1070 VerifyOopClosure vc;
1071 public:
1072 virtual void do_oop(oop* p) {
1073 if (p != nullptr && *p != nullptr) {
1074 oop o = *p;
1075 if (!java_lang_Class::is_instance(o)) {
1076 // is_instance will assert for an invalid oop.
1077 // Walk the resolved_references array and other assorted oops in the
1078 // CLD::_handles field. The mirror oops are followed by other heap roots.
1079 o->oop_iterate(&vc);
1080 }
1081 }
1082 }
1083 virtual void do_oop(narrowOop* o) { ShouldNotReachHere(); }
1084 };
1085
1086 void ClassLoaderData::verify() {
1087 assert_locked_or_safepoint(_metaspace_lock);
1088 oop cl = class_loader();
1089
1090 guarantee(this == class_loader_data(cl) || has_class_mirror_holder(), "Must be the same");
1091 guarantee(cl != nullptr || this == ClassLoaderData::the_null_class_loader_data() || has_class_mirror_holder(), "must be");
1092
1093 // Verify the integrity of the allocated space.
1094 #ifdef ASSERT
1095 if (metaspace_or_null() != nullptr) {
1096 metaspace_or_null()->verify();
1097 }
1098 #endif
1099
1100 for (Klass* k = _klasses; k != nullptr; k = k->next_link()) {
1101 guarantee(k->class_loader_data() == this, "Must be the same");
1102 k->verify();
1103 assert(k != k->next_link(), "no loops!");
1104 }
1105
1106 if (_modules != nullptr) {
1107 _modules->verify();
1108 }
1109
1110 if (_deallocate_list != nullptr) {
1111 for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
1112 Metadata* m = _deallocate_list->at(i);
1113 if (m->is_klass()) {
1114 ((Klass*)m)->verify();
1115 }
1116 }
1117 }
1118
1119 // Check the oops in the handles area
1120 VerifyHandleOops vho;
1121 oops_do(&vho, _claim_none, false);
1122 }
1123
1124 bool ClassLoaderData::contains_klass(Klass* klass) {
1125 // Lock-free access requires load_acquire
1126 for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
1127 if (k == klass) return true;
1128 }
1129 return false;
1130 }