1 /* 2 * Copyright (c) 2012, 2023, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 // A ClassLoaderData identifies the full set of class types that a class 26 // loader's name resolution strategy produces for a given configuration of the 27 // class loader. 28 // Class types in the ClassLoaderData may be defined by from class file binaries 29 // provided by the class loader, or from other class loader it interacts with 30 // according to its name resolution strategy. 31 // 32 // Class loaders that implement a deterministic name resolution strategy 33 // (including with respect to their delegation behavior), such as the boot, the 34 // platform, and the system loaders of the JDK's built-in class loader 35 // hierarchy, always produce the same linkset for a given configuration. 36 // 37 // ClassLoaderData carries information related to a linkset (e.g., 38 // metaspace holding its klass definitions). 39 // The System Dictionary and related data structures (e.g., placeholder table, 40 // loader constraints table) as well as the runtime representation of classes 41 // only reference ClassLoaderData. 42 // 43 // Instances of java.lang.ClassLoader holds a pointer to a ClassLoaderData that 44 // that represent the loader's "linking domain" in the JVM. 45 // 46 // The bootstrap loader (represented by null) also has a ClassLoaderData, 47 // the singleton class the_null_class_loader_data(). 48 49 #include "precompiled.hpp" 50 #include "classfile/classLoaderData.inline.hpp" 51 #include "classfile/classLoaderDataGraph.inline.hpp" 52 #include "classfile/dictionary.hpp" 53 #include "classfile/javaClasses.inline.hpp" 54 #include "classfile/moduleEntry.hpp" 55 #include "classfile/packageEntry.hpp" 56 #include "classfile/symbolTable.hpp" 57 #include "classfile/systemDictionary.hpp" 58 #include "classfile/systemDictionaryShared.hpp" 59 #include "classfile/vmClasses.hpp" 60 #include "logging/log.hpp" 61 #include "logging/logStream.hpp" 62 #include "memory/allocation.inline.hpp" 63 #include "memory/classLoaderMetaspace.hpp" 64 #include "memory/metadataFactory.hpp" 65 #include "memory/metaspace.hpp" 66 #include "memory/resourceArea.hpp" 67 #include "memory/universe.hpp" 68 #include "oops/access.inline.hpp" 69 #include "oops/inlineKlass.inline.hpp" 70 #include "oops/klass.inline.hpp" 71 #include "oops/oop.inline.hpp" 72 #include "oops/oopHandle.inline.hpp" 73 #include "oops/verifyOopClosure.hpp" 74 #include "oops/weakHandle.inline.hpp" 75 #include "runtime/arguments.hpp" 76 #include "runtime/atomic.hpp" 77 #include "runtime/handles.inline.hpp" 78 #include "runtime/mutex.hpp" 79 #include "runtime/safepoint.hpp" 80 #include "utilities/growableArray.hpp" 81 #include "utilities/macros.hpp" 82 #include "utilities/ostream.hpp" 83 84 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = 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((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 = _head; 207 while (chunk != nullptr) { 208 count += 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 = _head; 263 while (chunk != nullptr) { 264 if (&(chunk->_data[0]) <= oop_handle && oop_handle < &(chunk->_data[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 is not volatile or atomic. 350 void ClassLoaderData::inc_keep_alive() { 351 if (has_class_mirror_holder()) { 352 assert(_keep_alive > 0, "Invalid keep alive increment count"); 353 _keep_alive++; 354 } 355 } 356 357 void ClassLoaderData::dec_keep_alive() { 358 if (has_class_mirror_holder()) { 359 assert(_keep_alive > 0, "Invalid keep alive decrement count"); 360 if (_keep_alive == 1) { 361 // When the keep_alive 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--; 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 // To call this, one must have the MultiArray_lock held, but the _klasses list still has lock free reads. 412 assert_locked_or_safepoint(MultiArray_lock); 413 414 // Lock-free access requires load_acquire 415 for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) { 416 // Filter out InstanceKlasses (or their ObjArrayKlasses) that have not entered the 417 // loaded state. 418 if (k->is_instance_klass()) { 419 if (!InstanceKlass::cast(k)->is_loaded()) { 420 continue; 421 } 422 } else if (k->is_shared() && k->is_objArray_klass()) { 423 Klass* bottom = ObjArrayKlass::cast(k)->bottom_klass(); 424 if (bottom->is_instance_klass() && !InstanceKlass::cast(bottom)->is_loaded()) { 425 // This could happen if <bottom> is a shared class that has been restored 426 // but is not yet marked as loaded. All archived array classes of the 427 // bottom class are already restored and placed in the _klasses list. 428 continue; 429 } 430 } 431 432 #ifdef ASSERT 433 oop m = k->java_mirror(); 434 assert(m != nullptr, "nullptr mirror"); 435 assert(m->is_a(vmClasses::Class_klass()), "invalid mirror"); 436 #endif 437 klass_closure->do_klass(k); 438 } 439 } 440 441 void ClassLoaderData::classes_do(void f(InstanceKlass*)) { 442 // Lock-free access requires load_acquire 443 for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) { 444 if (k->is_instance_klass()) { 445 f(InstanceKlass::cast(k)); 446 } 447 assert(k != k->next_link(), "no loops!"); 448 } 449 } 450 451 void ClassLoaderData::inline_classes_do(void f(InlineKlass*)) { 452 // Lock-free access requires load_acquire 453 for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) { 454 if (k->is_inline_klass()) { 455 f(InlineKlass::cast(k)); 456 } 457 assert(k != k->next_link(), "no loops!"); 458 } 459 } 460 461 void ClassLoaderData::modules_do(void f(ModuleEntry*)) { 462 assert_locked_or_safepoint(Module_lock); 463 if (_unnamed_module != nullptr) { 464 f(_unnamed_module); 465 } 466 if (_modules != nullptr) { 467 _modules->modules_do(f); 468 } 469 } 470 471 void ClassLoaderData::packages_do(void f(PackageEntry*)) { 472 assert_locked_or_safepoint(Module_lock); 473 if (_packages != nullptr) { 474 _packages->packages_do(f); 475 } 476 } 477 478 void ClassLoaderData::record_dependency(const Klass* k) { 479 assert(k != nullptr, "invariant"); 480 481 ClassLoaderData * const from_cld = this; 482 ClassLoaderData * const to_cld = k->class_loader_data(); 483 484 // Do not need to record dependency if the dependency is to a class whose 485 // class loader data is never freed. (i.e. the dependency's class loader 486 // is one of the three builtin class loaders and the dependency's class 487 // loader data has a ClassLoader holder, not a Class holder.) 488 if (to_cld->is_permanent_class_loader_data()) { 489 return; 490 } 491 492 oop to; 493 if (to_cld->has_class_mirror_holder()) { 494 // Just return if a non-strong hidden class class is attempting to record a dependency 495 // to itself. (Note that every non-strong hidden class has its own unique class 496 // loader data.) 497 if (to_cld == from_cld) { 498 return; 499 } 500 // Hidden class dependencies are through the mirror. 501 to = k->java_mirror(); 502 } else { 503 to = to_cld->class_loader(); 504 oop from = from_cld->class_loader(); 505 506 // Just return if this dependency is to a class with the same or a parent 507 // class_loader. 508 if (from == to || java_lang_ClassLoader::isAncestor(from, to)) { 509 return; // this class loader is in the parent list, no need to add it. 510 } 511 } 512 513 // It's a dependency we won't find through GC, add it. 514 if (!_handles.contains(to)) { 515 NOT_PRODUCT(Atomic::inc(&_dependency_count)); 516 LogTarget(Trace, class, loader, data) lt; 517 if (lt.is_enabled()) { 518 ResourceMark rm; 519 LogStream ls(lt); 520 ls.print("adding dependency from "); 521 print_value_on(&ls); 522 ls.print(" to "); 523 to_cld->print_value_on(&ls); 524 ls.cr(); 525 } 526 Handle dependency(Thread::current(), to); 527 add_handle(dependency); 528 // Added a potentially young gen oop to the ClassLoaderData 529 record_modified_oops(); 530 } 531 } 532 533 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) { 534 { 535 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag); 536 Klass* old_value = _klasses; 537 k->set_next_link(old_value); 538 // Link the new item into the list, making sure the linked class is stable 539 // since the list can be walked without a lock 540 Atomic::release_store(&_klasses, k); 541 if (k->is_array_klass()) { 542 ClassLoaderDataGraph::inc_array_classes(1); 543 } else { 544 ClassLoaderDataGraph::inc_instance_classes(1); 545 } 546 } 547 548 if (publicize) { 549 LogTarget(Trace, class, loader, data) lt; 550 if (lt.is_enabled()) { 551 ResourceMark rm; 552 LogStream ls(lt); 553 ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name()); 554 print_value_on(&ls); 555 ls.cr(); 556 } 557 } 558 } 559 560 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) { 561 if (loader_or_mirror() != nullptr) { 562 assert(_holder.is_null(), "never replace holders"); 563 _holder = WeakHandle(Universe::vm_weak(), loader_or_mirror); 564 } 565 } 566 567 // Remove a klass from the _klasses list for scratch_class during redefinition 568 // or parsed class in the case of an error. 569 void ClassLoaderData::remove_class(Klass* scratch_class) { 570 assert_locked_or_safepoint(ClassLoaderDataGraph_lock); 571 572 Klass* prev = nullptr; 573 for (Klass* k = _klasses; k != nullptr; k = k->next_link()) { 574 if (k == scratch_class) { 575 if (prev == nullptr) { 576 _klasses = k->next_link(); 577 } else { 578 Klass* next = k->next_link(); 579 prev->set_next_link(next); 580 } 581 582 if (k->is_array_klass()) { 583 ClassLoaderDataGraph::dec_array_classes(1); 584 } else { 585 ClassLoaderDataGraph::dec_instance_classes(1); 586 } 587 588 return; 589 } 590 prev = k; 591 assert(k != k->next_link(), "no loops!"); 592 } 593 ShouldNotReachHere(); // should have found this class!! 594 } 595 596 void ClassLoaderData::unload() { 597 _unloading = true; 598 599 LogTarget(Trace, class, loader, data) lt; 600 if (lt.is_enabled()) { 601 ResourceMark rm; 602 LogStream ls(lt); 603 ls.print("unload"); 604 print_value_on(&ls); 605 ls.cr(); 606 } 607 608 // Some items on the _deallocate_list need to free their C heap structures 609 // if they are not already on the _klasses list. 610 free_deallocate_list_C_heap_structures(); 611 612 inline_classes_do(InlineKlass::cleanup); 613 614 // Clean up class dependencies and tell serviceability tools 615 // these classes are unloading. This must be called 616 // after erroneous classes are released. 617 classes_do(InstanceKlass::unload_class); 618 619 // Method::clear_jmethod_ids only sets the jmethod_ids to null without 620 // releasing the memory for related JNIMethodBlocks and JNIMethodBlockNodes. 621 // This is done intentionally because native code (e.g. JVMTI agent) holding 622 // jmethod_ids may access them after the associated classes and class loader 623 // are unloaded. The Java Native Interface Specification says "method ID 624 // does not prevent the VM from unloading the class from which the ID has 625 // been derived. After the class is unloaded, the method or field ID becomes 626 // invalid". In real world usages, the native code may rely on jmethod_ids 627 // being null after class unloading. Hence, it is unsafe to free the memory 628 // from the VM side without knowing when native code is going to stop using 629 // them. 630 if (_jmethod_ids != nullptr) { 631 Method::clear_jmethod_ids(this); 632 } 633 } 634 635 ModuleEntryTable* ClassLoaderData::modules() { 636 // Lazily create the module entry table at first request. 637 // Lock-free access requires load_acquire. 638 ModuleEntryTable* modules = Atomic::load_acquire(&_modules); 639 if (modules == nullptr) { 640 MutexLocker m1(Module_lock); 641 // Check if _modules got allocated while we were waiting for this lock. 642 if ((modules = _modules) == nullptr) { 643 modules = new ModuleEntryTable(); 644 645 { 646 MutexLocker m1(metaspace_lock(), Mutex::_no_safepoint_check_flag); 647 // Ensure _modules is stable, since it is examined without a lock 648 Atomic::release_store(&_modules, modules); 649 } 650 } 651 } 652 return modules; 653 } 654 655 const int _boot_loader_dictionary_size = 1009; 656 const int _default_loader_dictionary_size = 107; 657 658 Dictionary* ClassLoaderData::create_dictionary() { 659 assert(!has_class_mirror_holder(), "class mirror holder cld does not have a dictionary"); 660 int size; 661 if (_the_null_class_loader_data == nullptr) { 662 size = _boot_loader_dictionary_size; 663 } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) { 664 size = 1; // there's only one class in relection class loader and no initiated classes 665 } else if (is_system_class_loader_data()) { 666 size = _boot_loader_dictionary_size; 667 } else { 668 size = _default_loader_dictionary_size; 669 } 670 return new Dictionary(this, size); 671 } 672 673 // Tell the GC to keep this klass alive. Needed while iterating ClassLoaderDataGraph, 674 // and any runtime code that uses klasses. 675 oop ClassLoaderData::holder() const { 676 // A klass that was previously considered dead can be looked up in the 677 // CLD/SD, and its _java_mirror or _class_loader can be stored in a root 678 // or a reachable object making it alive again. The SATB part of G1 needs 679 // to get notified about this potential resurrection, otherwise the marking 680 // might not find the object. 681 if (!_holder.is_null()) { // null class_loader 682 return _holder.resolve(); 683 } else { 684 return nullptr; 685 } 686 } 687 688 // Let the GC read the holder without keeping it alive. 689 oop ClassLoaderData::holder_no_keepalive() const { 690 if (!_holder.is_null()) { // null class_loader 691 return _holder.peek(); 692 } else { 693 return nullptr; 694 } 695 } 696 697 // Unloading support 698 bool ClassLoaderData::is_alive() const { 699 bool alive = keep_alive() // null class loader and incomplete non-strong hidden class. 700 || (_holder.peek() != nullptr); // and not cleaned by the GC weak handle processing. 701 702 return alive; 703 } 704 705 class ReleaseKlassClosure: public KlassClosure { 706 private: 707 size_t _instance_class_released; 708 size_t _array_class_released; 709 public: 710 ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { } 711 712 size_t instance_class_released() const { return _instance_class_released; } 713 size_t array_class_released() const { return _array_class_released; } 714 715 void do_klass(Klass* k) { 716 if (k->is_array_klass()) { 717 _array_class_released ++; 718 } else { 719 assert(k->is_instance_klass(), "Must be"); 720 _instance_class_released ++; 721 } 722 k->release_C_heap_structures(); 723 } 724 }; 725 726 ClassLoaderData::~ClassLoaderData() { 727 // Release C heap structures for all the classes. 728 ReleaseKlassClosure cl; 729 classes_do(&cl); 730 731 ClassLoaderDataGraph::dec_array_classes(cl.array_class_released()); 732 ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released()); 733 734 // Release the WeakHandle 735 _holder.release(Universe::vm_weak()); 736 737 // Release C heap allocated hashtable for all the packages. 738 if (_packages != nullptr) { 739 // Destroy the table itself 740 delete _packages; 741 _packages = nullptr; 742 } 743 744 // Release C heap allocated hashtable for all the modules. 745 if (_modules != nullptr) { 746 // Destroy the table itself 747 delete _modules; 748 _modules = nullptr; 749 } 750 751 // Release C heap allocated hashtable for the dictionary 752 if (_dictionary != nullptr) { 753 // Destroy the table itself 754 delete _dictionary; 755 _dictionary = nullptr; 756 } 757 758 if (_unnamed_module != nullptr) { 759 delete _unnamed_module; 760 _unnamed_module = nullptr; 761 } 762 763 // release the metaspace 764 ClassLoaderMetaspace *m = _metaspace; 765 if (m != nullptr) { 766 _metaspace = nullptr; 767 delete m; 768 } 769 770 // Delete lock 771 delete _metaspace_lock; 772 773 // Delete free list 774 if (_deallocate_list != nullptr) { 775 delete _deallocate_list; 776 } 777 778 // Decrement refcounts of Symbols if created. 779 if (_name != nullptr) { 780 _name->decrement_refcount(); 781 } 782 if (_name_and_id != nullptr) { 783 _name_and_id->decrement_refcount(); 784 } 785 } 786 787 // Returns true if this class loader data is for the app class loader 788 // or a user defined system class loader. (Note that the class loader 789 // data may have a Class holder.) 790 bool ClassLoaderData::is_system_class_loader_data() const { 791 return SystemDictionary::is_system_class_loader(class_loader()); 792 } 793 794 // Returns true if this class loader data is for the platform class loader. 795 // (Note that the class loader data may have a Class holder.) 796 bool ClassLoaderData::is_platform_class_loader_data() const { 797 return SystemDictionary::is_platform_class_loader(class_loader()); 798 } 799 800 // Returns true if the class loader for this class loader data is one of 801 // the 3 builtin (boot application/system or platform) class loaders, 802 // including a user-defined system class loader. Note that if the class 803 // loader data is for a non-strong hidden class then it may 804 // get freed by a GC even if its class loader is one of these loaders. 805 bool ClassLoaderData::is_builtin_class_loader_data() const { 806 return (is_boot_class_loader_data() || 807 SystemDictionary::is_system_class_loader(class_loader()) || 808 SystemDictionary::is_platform_class_loader(class_loader())); 809 } 810 811 // Returns true if this class loader data is a class loader data 812 // that is not ever freed by a GC. It must be the CLD for one of the builtin 813 // class loaders and not the CLD for a non-strong hidden class. 814 bool ClassLoaderData::is_permanent_class_loader_data() const { 815 return is_builtin_class_loader_data() && !has_class_mirror_holder(); 816 } 817 818 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() { 819 // If the metaspace has not been allocated, create a new one. Might want 820 // to create smaller arena for Reflection class loaders also. 821 // The reason for the delayed allocation is because some class loaders are 822 // simply for delegating with no metadata of their own. 823 // Lock-free access requires load_acquire. 824 ClassLoaderMetaspace* metaspace = Atomic::load_acquire(&_metaspace); 825 if (metaspace == nullptr) { 826 MutexLocker ml(_metaspace_lock, Mutex::_no_safepoint_check_flag); 827 // Check if _metaspace got allocated while we were waiting for this lock. 828 if ((metaspace = _metaspace) == nullptr) { 829 if (this == the_null_class_loader_data()) { 830 assert (class_loader() == nullptr, "Must be"); 831 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType); 832 } else if (has_class_mirror_holder()) { 833 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ClassMirrorHolderMetaspaceType); 834 } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) { 835 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType); 836 } else { 837 metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType); 838 } 839 // Ensure _metaspace is stable, since it is examined without a lock 840 Atomic::release_store(&_metaspace, metaspace); 841 } 842 } 843 return metaspace; 844 } 845 846 OopHandle ClassLoaderData::add_handle(Handle h) { 847 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag); 848 record_modified_oops(); 849 return _handles.add(h()); 850 } 851 852 void ClassLoaderData::remove_handle(OopHandle h) { 853 assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading"); 854 oop* ptr = h.ptr_raw(); 855 if (ptr != nullptr) { 856 assert(_handles.owner_of(ptr), "Got unexpected handle " PTR_FORMAT, p2i(ptr)); 857 NativeAccess<>::oop_store(ptr, oop(nullptr)); 858 } 859 } 860 861 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) { 862 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag); 863 if (dest.resolve() != nullptr) { 864 return; 865 } else { 866 record_modified_oops(); 867 dest = _handles.add(h()); 868 } 869 } 870 871 // Add this metadata pointer to be freed when it's safe. This is only during 872 // a safepoint which checks if handles point to this metadata field. 873 void ClassLoaderData::add_to_deallocate_list(Metadata* m) { 874 // Metadata in shared region isn't deleted. 875 if (!m->is_shared()) { 876 MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag); 877 if (_deallocate_list == nullptr) { 878 _deallocate_list = new (mtClass) GrowableArray<Metadata*>(100, mtClass); 879 } 880 _deallocate_list->append_if_missing(m); 881 ResourceMark rm; 882 log_debug(class, loader, data)("deallocate added for %s", m->print_value_string()); 883 ClassLoaderDataGraph::set_should_clean_deallocate_lists(); 884 } 885 } 886 887 // Deallocate free metadata on the free list. How useful the PermGen was! 888 void ClassLoaderData::free_deallocate_list() { 889 // This must be called at a safepoint because it depends on metadata walking at 890 // safepoint cleanup time. 891 assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint"); 892 assert(!is_unloading(), "only called for ClassLoaderData that are not unloading"); 893 if (_deallocate_list == nullptr) { 894 return; 895 } 896 // Go backwards because this removes entries that are freed. 897 for (int i = _deallocate_list->length() - 1; i >= 0; i--) { 898 Metadata* m = _deallocate_list->at(i); 899 if (!m->on_stack()) { 900 _deallocate_list->remove_at(i); 901 // There are only three types of metadata that we deallocate directly. 902 // Cast them so they can be used by the template function. 903 if (m->is_method()) { 904 MetadataFactory::free_metadata(this, (Method*)m); 905 } else if (m->is_constantPool()) { 906 MetadataFactory::free_metadata(this, (ConstantPool*)m); 907 } else if (m->is_klass()) { 908 if (!((Klass*)m)->is_inline_klass()) { 909 MetadataFactory::free_metadata(this, (InstanceKlass*)m); 910 } else { 911 MetadataFactory::free_metadata(this, (InlineKlass*)m); 912 } 913 } else { 914 ShouldNotReachHere(); 915 } 916 } else { 917 // Metadata is alive. 918 // If scratch_class is on stack then it shouldn't be on this list! 919 assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(), 920 "scratch classes on this list should be dead"); 921 // Also should assert that other metadata on the list was found in handles. 922 // Some cleaning remains. 923 ClassLoaderDataGraph::set_should_clean_deallocate_lists(); 924 } 925 } 926 } 927 928 // This is distinct from free_deallocate_list. For class loader data that are 929 // unloading, this frees the C heap memory for items on the list, and unlinks 930 // scratch or error classes so that unloading events aren't triggered for these 931 // classes. The metadata is removed with the unloading metaspace. 932 // There isn't C heap memory allocated for methods, so nothing is done for them. 933 void ClassLoaderData::free_deallocate_list_C_heap_structures() { 934 assert_locked_or_safepoint(ClassLoaderDataGraph_lock); 935 assert(is_unloading(), "only called for ClassLoaderData that are unloading"); 936 if (_deallocate_list == nullptr) { 937 return; 938 } 939 // Go backwards because this removes entries that are freed. 940 for (int i = _deallocate_list->length() - 1; i >= 0; i--) { 941 Metadata* m = _deallocate_list->at(i); 942 _deallocate_list->remove_at(i); 943 if (m->is_constantPool()) { 944 ((ConstantPool*)m)->release_C_heap_structures(); 945 } else if (m->is_klass()) { 946 InstanceKlass* ik = (InstanceKlass*)m; 947 // also releases ik->constants() C heap memory 948 ik->release_C_heap_structures(); 949 // Remove the class so unloading events aren't triggered for 950 // this class (scratch or error class) in do_unloading(). 951 remove_class(ik); 952 // But still have to remove it from the dumptime_table. 953 SystemDictionaryShared::handle_class_unloading(ik); 954 } 955 } 956 } 957 958 // Caller needs ResourceMark 959 // If the class loader's _name has not been explicitly set, the class loader's 960 // qualified class name is returned. 961 const char* ClassLoaderData::loader_name() const { 962 if (_class_loader_klass == nullptr) { 963 return BOOTSTRAP_LOADER_NAME; 964 } else if (_name != nullptr) { 965 return _name->as_C_string(); 966 } else { 967 return _class_loader_klass->external_name(); 968 } 969 } 970 971 // Caller needs ResourceMark 972 // Format of the _name_and_id is as follows: 973 // If the defining loader has a name explicitly set then '<loader-name>' @<id> 974 // If the defining loader has no name then <qualified-class-name> @<id> 975 // If built-in loader, then omit '@<id>' as there is only one instance. 976 const char* ClassLoaderData::loader_name_and_id() const { 977 if (_class_loader_klass == nullptr) { 978 return "'" BOOTSTRAP_LOADER_NAME "'"; 979 } else if (_name_and_id != nullptr) { 980 return _name_and_id->as_C_string(); 981 } else { 982 // May be called in a race before _name_and_id is initialized. 983 return _class_loader_klass->external_name(); 984 } 985 } 986 987 void ClassLoaderData::print_value_on(outputStream* out) const { 988 if (!is_unloading() && class_loader() != nullptr) { 989 out->print("loader data: " INTPTR_FORMAT " for instance ", p2i(this)); 990 class_loader()->print_value_on(out); // includes loader_name_and_id() and address of class loader instance 991 } else { 992 // loader data: 0xsomeaddr of 'bootstrap' 993 out->print("loader data: " INTPTR_FORMAT " of %s", p2i(this), loader_name_and_id()); 994 } 995 if (_has_class_mirror_holder) { 996 out->print(" has a class holder"); 997 } 998 } 999 1000 void ClassLoaderData::print_value() const { print_value_on(tty); } 1001 1002 #ifndef PRODUCT 1003 class PrintKlassClosure: public KlassClosure { 1004 outputStream* _out; 1005 public: 1006 PrintKlassClosure(outputStream* out): _out(out) { } 1007 1008 void do_klass(Klass* k) { 1009 ResourceMark rm; 1010 _out->print("%s,", k->external_name()); 1011 } 1012 }; 1013 1014 void ClassLoaderData::print_on(outputStream* out) const { 1015 ResourceMark rm; 1016 out->print_cr("ClassLoaderData(" INTPTR_FORMAT ")", p2i(this)); 1017 out->print_cr(" - name %s", loader_name_and_id()); 1018 if (!_holder.is_null()) { 1019 out->print (" - holder "); 1020 _holder.print_on(out); 1021 out->print_cr(""); 1022 } 1023 out->print_cr(" - class loader " INTPTR_FORMAT, p2i(_class_loader.ptr_raw())); 1024 out->print_cr(" - metaspace " INTPTR_FORMAT, p2i(_metaspace)); 1025 out->print_cr(" - unloading %s", _unloading ? "true" : "false"); 1026 out->print_cr(" - class mirror holder %s", _has_class_mirror_holder ? "true" : "false"); 1027 out->print_cr(" - modified oops %s", _modified_oops ? "true" : "false"); 1028 out->print_cr(" - keep alive %d", _keep_alive); 1029 out->print (" - claim "); 1030 switch(_claim) { 1031 case _claim_none: out->print_cr("none"); break; 1032 case _claim_finalizable: out->print_cr("finalizable"); break; 1033 case _claim_strong: out->print_cr("strong"); break; 1034 case _claim_stw_fullgc_mark: out->print_cr("stw full gc mark"); break; 1035 case _claim_stw_fullgc_adjust: out->print_cr("stw full gc adjust"); break; 1036 case _claim_other: out->print_cr("other"); break; 1037 case _claim_other | _claim_finalizable: out->print_cr("other and finalizable"); break; 1038 case _claim_other | _claim_strong: out->print_cr("other and strong"); break; 1039 default: ShouldNotReachHere(); 1040 } 1041 out->print_cr(" - handles %d", _handles.count()); 1042 out->print_cr(" - dependency count %d", _dependency_count); 1043 out->print (" - klasses { "); 1044 if (Verbose) { 1045 PrintKlassClosure closure(out); 1046 ((ClassLoaderData*)this)->classes_do(&closure); 1047 } else { 1048 out->print("..."); 1049 } 1050 out->print_cr(" }"); 1051 out->print_cr(" - packages " INTPTR_FORMAT, p2i(_packages)); 1052 out->print_cr(" - module " INTPTR_FORMAT, p2i(_modules)); 1053 out->print_cr(" - unnamed module " INTPTR_FORMAT, p2i(_unnamed_module)); 1054 if (_dictionary != nullptr) { 1055 out->print (" - dictionary " INTPTR_FORMAT " ", p2i(_dictionary)); 1056 _dictionary->print_size(out); 1057 } else { 1058 out->print_cr(" - dictionary " INTPTR_FORMAT, p2i(_dictionary)); 1059 } 1060 if (_jmethod_ids != nullptr) { 1061 out->print (" - jmethod count "); 1062 Method::print_jmethod_ids_count(this, out); 1063 out->print_cr(""); 1064 } 1065 out->print_cr(" - deallocate list " INTPTR_FORMAT, p2i(_deallocate_list)); 1066 out->print_cr(" - next CLD " INTPTR_FORMAT, p2i(_next)); 1067 } 1068 #endif // PRODUCT 1069 1070 void ClassLoaderData::print() const { print_on(tty); } 1071 1072 class VerifyHandleOops : public OopClosure { 1073 VerifyOopClosure vc; 1074 public: 1075 virtual void do_oop(oop* p) { 1076 if (p != nullptr && *p != nullptr) { 1077 oop o = *p; 1078 if (!java_lang_Class::is_instance(o)) { 1079 // is_instance will assert for an invalid oop. 1080 // Walk the resolved_references array and other assorted oops in the 1081 // CLD::_handles field. The mirror oops are followed by other heap roots. 1082 o->oop_iterate(&vc); 1083 } 1084 } 1085 } 1086 virtual void do_oop(narrowOop* o) { ShouldNotReachHere(); } 1087 }; 1088 1089 void ClassLoaderData::verify() { 1090 assert_locked_or_safepoint(_metaspace_lock); 1091 oop cl = class_loader(); 1092 1093 guarantee(this == class_loader_data(cl) || has_class_mirror_holder(), "Must be the same"); 1094 guarantee(cl != nullptr || this == ClassLoaderData::the_null_class_loader_data() || has_class_mirror_holder(), "must be"); 1095 1096 // Verify the integrity of the allocated space. 1097 #ifdef ASSERT 1098 if (metaspace_or_null() != nullptr) { 1099 metaspace_or_null()->verify(); 1100 } 1101 #endif 1102 1103 for (Klass* k = _klasses; k != nullptr; k = k->next_link()) { 1104 guarantee(k->class_loader_data() == this, "Must be the same"); 1105 k->verify(); 1106 assert(k != k->next_link(), "no loops!"); 1107 } 1108 1109 if (_modules != nullptr) { 1110 _modules->verify(); 1111 } 1112 1113 if (_deallocate_list != nullptr) { 1114 for (int i = _deallocate_list->length() - 1; i >= 0; i--) { 1115 Metadata* m = _deallocate_list->at(i); 1116 if (m->is_klass()) { 1117 ((Klass*)m)->verify(); 1118 } 1119 } 1120 } 1121 1122 // Check the oops in the handles area 1123 VerifyHandleOops vho; 1124 oops_do(&vho, _claim_none, false); 1125 } 1126 1127 bool ClassLoaderData::contains_klass(Klass* klass) { 1128 // Lock-free access requires load_acquire 1129 for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) { 1130 if (k == klass) return true; 1131 } 1132 return false; 1133 }