1  /*
   2  * Copyright (c) 2012, 2021, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 // A ClassLoaderData identifies the full set of class types that a class
  26 // loader's name resolution strategy produces for a given configuration of the
  27 // class loader.
  28 // Class types in the ClassLoaderData may be defined by from class file binaries
  29 // provided by the class loader, or from other class loader it interacts with
  30 // according to its name resolution strategy.
  31 //
  32 // Class loaders that implement a deterministic name resolution strategy
  33 // (including with respect to their delegation behavior), such as the boot, the
  34 // platform, and the system loaders of the JDK's built-in class loader
  35 // hierarchy, always produce the same linkset for a given configuration.
  36 //
  37 // ClassLoaderData carries information related to a linkset (e.g.,
  38 // metaspace holding its klass definitions).
  39 // The System Dictionary and related data structures (e.g., placeholder table,
  40 // loader constraints table) as well as the runtime representation of classes
  41 // only reference ClassLoaderData.
  42 //
  43 // Instances of java.lang.ClassLoader holds a pointer to a ClassLoaderData that
  44 // that represent the loader's "linking domain" in the JVM.
  45 //
  46 // The bootstrap loader (represented by NULL) also has a ClassLoaderData,
  47 // the singleton class the_null_class_loader_data().
  48 
  49 #include "precompiled.hpp"
  50 #include "classfile/classLoaderData.inline.hpp"
  51 #include "classfile/classLoaderDataGraph.inline.hpp"
  52 #include "classfile/dictionary.hpp"
  53 #include "classfile/javaClasses.hpp"
  54 #include "classfile/moduleEntry.hpp"
  55 #include "classfile/packageEntry.hpp"
  56 #include "classfile/symbolTable.hpp"
  57 #include "classfile/systemDictionary.hpp"
  58 #include "classfile/vmClasses.hpp"
  59 #include "logging/log.hpp"
  60 #include "logging/logStream.hpp"
  61 #include "memory/allocation.inline.hpp"
  62 #include "memory/classLoaderMetaspace.hpp"
  63 #include "memory/metadataFactory.hpp"
  64 #include "memory/metaspace.hpp"
  65 #include "memory/resourceArea.hpp"
  66 #include "memory/universe.hpp"
  67 #include "oops/access.inline.hpp"
  68 #include "oops/klass.inline.hpp"
  69 #include "oops/oop.inline.hpp"
  70 #include "oops/oopHandle.inline.hpp"
  71 #include "oops/inlineKlass.inline.hpp"
  72 #include "oops/weakHandle.inline.hpp"
  73 #include "runtime/arguments.hpp"
  74 #include "runtime/atomic.hpp"
  75 #include "runtime/handles.inline.hpp"
  76 #include "runtime/mutex.hpp"
  77 #include "runtime/safepoint.hpp"
  78 #include "utilities/growableArray.hpp"
  79 #include "utilities/macros.hpp"
  80 #include "utilities/ostream.hpp"
  81 
  82 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
  83 
  84 void ClassLoaderData::init_null_class_loader_data() {
  85   assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
  86   assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
  87 
  88   _the_null_class_loader_data = new ClassLoaderData(Handle(), false);
  89   ClassLoaderDataGraph::_head = _the_null_class_loader_data;
  90   assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
  91 
  92   LogTarget(Trace, class, loader, data) lt;
  93   if (lt.is_enabled()) {
  94     ResourceMark rm;
  95     LogStream ls(lt);
  96     ls.print("create ");
  97     _the_null_class_loader_data->print_value_on(&ls);
  98     ls.cr();
  99   }
 100 }
 101 
 102 // Obtain and set the class loader's name within the ClassLoaderData so
 103 // it will be available for error messages, logging, JFR, etc.  The name
 104 // and klass are available after the class_loader oop is no longer alive,
 105 // during unloading.
 106 void ClassLoaderData::initialize_name(Handle class_loader) {
 107   ResourceMark rm;
 108 
 109   // Obtain the class loader's name.  If the class loader's name was not
 110   // explicitly set during construction, the CLD's _name field will be null.
 111   oop cl_name = java_lang_ClassLoader::name(class_loader());
 112   if (cl_name != NULL) {
 113     const char* cl_instance_name = java_lang_String::as_utf8_string(cl_name);
 114 
 115     if (cl_instance_name != NULL && cl_instance_name[0] != '\0') {
 116       _name = SymbolTable::new_symbol(cl_instance_name);
 117     }
 118   }
 119 
 120   // Obtain the class loader's name and identity hash.  If the class loader's
 121   // name was not explicitly set during construction, the class loader's name and id
 122   // will be set to the qualified class name of the class loader along with its
 123   // identity hash.
 124   // If for some reason the ClassLoader's constructor has not been run, instead of
 125   // leaving the _name_and_id field null, fall back to the external qualified class
 126   // name.  Thus CLD's _name_and_id field should never have a null value.
 127   oop cl_name_and_id = java_lang_ClassLoader::nameAndId(class_loader());
 128   const char* cl_instance_name_and_id =
 129                   (cl_name_and_id == NULL) ? _class_loader_klass->external_name() :
 130                                              java_lang_String::as_utf8_string(cl_name_and_id);
 131   assert(cl_instance_name_and_id != NULL && cl_instance_name_and_id[0] != '\0', "class loader has no name and id");
 132   _name_and_id = SymbolTable::new_symbol(cl_instance_name_and_id);
 133 }
 134 
 135 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool has_class_mirror_holder) :
 136   _metaspace(NULL),
 137   _metaspace_lock(new Mutex(Mutex::nosafepoint-2, "MetaspaceAllocation_lock",
 138                             Mutex::_safepoint_check_never)),
 139   _unloading(false), _has_class_mirror_holder(has_class_mirror_holder),
 140   _modified_oops(true),
 141   // A non-strong hidden class loader data doesn't have anything to keep
 142   // it from being unloaded during parsing of the non-strong hidden class.
 143   // The null-class-loader should always be kept alive.
 144   _keep_alive((has_class_mirror_holder || h_class_loader.is_null()) ? 1 : 0),
 145   _claim(0),
 146   _handles(),
 147   _klasses(NULL), _packages(NULL), _modules(NULL), _unnamed_module(NULL), _dictionary(NULL),
 148   _jmethod_ids(NULL),
 149   _deallocate_list(NULL),
 150   _next(NULL),
 151   _class_loader_klass(NULL), _name(NULL), _name_and_id(NULL) {
 152 
 153   if (!h_class_loader.is_null()) {
 154     _class_loader = _handles.add(h_class_loader());
 155     _class_loader_klass = h_class_loader->klass();
 156     initialize_name(h_class_loader);
 157   }
 158 
 159   if (!has_class_mirror_holder) {
 160     // The holder is initialized later for non-strong hidden classes,
 161     // and before calling anything that call class_loader().
 162     initialize_holder(h_class_loader);
 163 
 164     // A ClassLoaderData created solely for a non-strong hidden class should never
 165     // have a ModuleEntryTable or PackageEntryTable created for it.
 166     _packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);
 167     if (h_class_loader.is_null()) {
 168       // Create unnamed module for boot loader
 169       _unnamed_module = ModuleEntry::create_boot_unnamed_module(this);
 170     } else {
 171       // Create unnamed module for all other loaders
 172       _unnamed_module = ModuleEntry::create_unnamed_module(this);
 173     }
 174     _dictionary = create_dictionary();
 175   }
 176 
 177   NOT_PRODUCT(_dependency_count = 0); // number of class loader dependencies
 178 
 179   JFR_ONLY(INIT_ID(this);)
 180 }
 181 
 182 ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {
 183   Chunk* c = _head;
 184   while (c != NULL) {
 185     Chunk* next = c->_next;
 186     delete c;
 187     c = next;
 188   }
 189 }
 190 
 191 OopHandle ClassLoaderData::ChunkedHandleList::add(oop o) {
 192   if (_head == NULL || _head->_size == Chunk::CAPACITY) {
 193     Chunk* next = new Chunk(_head);
 194     Atomic::release_store(&_head, next);
 195   }
 196   oop* handle = &_head->_data[_head->_size];
 197   NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, o);
 198   Atomic::release_store(&_head->_size, _head->_size + 1);
 199   return OopHandle(handle);
 200 }
 201 
 202 int ClassLoaderData::ChunkedHandleList::count() const {
 203   int count = 0;
 204   Chunk* chunk = _head;
 205   while (chunk != NULL) {
 206     count += chunk->_size;
 207     chunk = chunk->_next;
 208   }
 209   return count;
 210 }
 211 
 212 inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {
 213   for (juint i = 0; i < size; i++) {
 214     if (c->_data[i] != NULL) {
 215       f->do_oop(&c->_data[i]);
 216     }
 217   }
 218 }
 219 
 220 void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {
 221   Chunk* head = Atomic::load_acquire(&_head);
 222   if (head != NULL) {
 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 != NULL; 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 != NULL && 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 != NULL) {
 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 bool ClassLoaderData::try_claim(int claim) {
 287   for (;;) {
 288     int old_claim = Atomic::load(&_claim);
 289     if ((old_claim & claim) == claim) {
 290       return false;
 291     }
 292     int new_claim = old_claim | claim;
 293     if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
 294       return true;
 295     }
 296   }
 297 }
 298 
 299 // Non-strong hidden classes have their own ClassLoaderData that is marked to keep alive
 300 // while the class is being parsed, and if the class appears on the module fixup list.
 301 // Due to the uniqueness that no other class shares the hidden class' name or
 302 // ClassLoaderData, no other non-GC thread has knowledge of the hidden class while
 303 // it is being defined, therefore _keep_alive is not volatile or atomic.
 304 void ClassLoaderData::inc_keep_alive() {
 305   if (has_class_mirror_holder()) {
 306     assert(_keep_alive > 0, "Invalid keep alive increment count");
 307     _keep_alive++;
 308   }
 309 }
 310 
 311 void ClassLoaderData::dec_keep_alive() {
 312   if (has_class_mirror_holder()) {
 313     assert(_keep_alive > 0, "Invalid keep alive decrement count");
 314     _keep_alive--;
 315   }
 316 }
 317 
 318 void ClassLoaderData::oops_do(OopClosure* f, int claim_value, bool clear_mod_oops) {
 319   if (claim_value != ClassLoaderData::_claim_none && !try_claim(claim_value)) {
 320     return;
 321   }
 322 
 323   // Only clear modified_oops after the ClassLoaderData is claimed.
 324   if (clear_mod_oops) {
 325     clear_modified_oops();
 326   }
 327 
 328   _handles.oops_do(f);
 329 }
 330 
 331 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
 332   // Lock-free access requires load_acquire
 333   for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
 334     klass_closure->do_klass(k);
 335     assert(k != k->next_link(), "no loops!");
 336   }
 337 }
 338 
 339 void ClassLoaderData::classes_do(void f(Klass * const)) {
 340   // Lock-free access requires load_acquire
 341   for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
 342     f(k);
 343     assert(k != k->next_link(), "no loops!");
 344   }
 345 }
 346 
 347 void ClassLoaderData::methods_do(void f(Method*)) {
 348   // Lock-free access requires load_acquire
 349   for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
 350     if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
 351       InstanceKlass::cast(k)->methods_do(f);
 352     }
 353   }
 354 }
 355 
 356 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
 357   // Lock-free access requires load_acquire
 358   for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
 359     // Do not filter ArrayKlass oops here...
 360     if (k->is_array_klass() || (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded())) {
 361 #ifdef ASSERT
 362       oop m = k->java_mirror();
 363       assert(m != NULL, "NULL mirror");
 364       assert(m->is_a(vmClasses::Class_klass()), "invalid mirror");
 365 #endif
 366       klass_closure->do_klass(k);
 367     }
 368   }
 369 }
 370 
 371 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
 372   // Lock-free access requires load_acquire
 373   for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
 374     if (k->is_instance_klass()) {
 375       f(InstanceKlass::cast(k));
 376     }
 377     assert(k != k->next_link(), "no loops!");
 378   }
 379 }
 380 
 381 void ClassLoaderData::inline_classes_do(void f(InlineKlass*)) {
 382   // Lock-free access requires load_acquire
 383   for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
 384     if (k->is_inline_klass()) {
 385       f(InlineKlass::cast(k));
 386     }
 387     assert(k != k->next_link(), "no loops!");
 388   }
 389 }
 390 
 391 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
 392   assert_locked_or_safepoint(Module_lock);
 393   if (_unnamed_module != NULL) {
 394     f(_unnamed_module);
 395   }
 396   if (_modules != NULL) {
 397     for (int i = 0; i < _modules->table_size(); i++) {
 398       for (ModuleEntry* entry = _modules->bucket(i);
 399            entry != NULL;
 400            entry = entry->next()) {
 401         f(entry);
 402       }
 403     }
 404   }
 405 }
 406 
 407 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
 408   assert_locked_or_safepoint(Module_lock);
 409   if (_packages != NULL) {
 410     for (int i = 0; i < _packages->table_size(); i++) {
 411       for (PackageEntry* entry = _packages->bucket(i);
 412            entry != NULL;
 413            entry = entry->next()) {
 414         f(entry);
 415       }
 416     }
 417   }
 418 }
 419 
 420 void ClassLoaderData::record_dependency(const Klass* k) {
 421   assert(k != NULL, "invariant");
 422 
 423   ClassLoaderData * const from_cld = this;
 424   ClassLoaderData * const to_cld = k->class_loader_data();
 425 
 426   // Do not need to record dependency if the dependency is to a class whose
 427   // class loader data is never freed.  (i.e. the dependency's class loader
 428   // is one of the three builtin class loaders and the dependency's class
 429   // loader data has a ClassLoader holder, not a Class holder.)
 430   if (to_cld->is_permanent_class_loader_data()) {
 431     return;
 432   }
 433 
 434   oop to;
 435   if (to_cld->has_class_mirror_holder()) {
 436     // Just return if a non-strong hidden class class is attempting to record a dependency
 437     // to itself.  (Note that every non-strong hidden class has its own unique class
 438     // loader data.)
 439     if (to_cld == from_cld) {
 440       return;
 441     }
 442     // Hidden class dependencies are through the mirror.
 443     to = k->java_mirror();
 444   } else {
 445     to = to_cld->class_loader();
 446     oop from = from_cld->class_loader();
 447 
 448     // Just return if this dependency is to a class with the same or a parent
 449     // class_loader.
 450     if (from == to || java_lang_ClassLoader::isAncestor(from, to)) {
 451       return; // this class loader is in the parent list, no need to add it.
 452     }
 453   }
 454 
 455   // It's a dependency we won't find through GC, add it.
 456   if (!_handles.contains(to)) {
 457     NOT_PRODUCT(Atomic::inc(&_dependency_count));
 458     LogTarget(Trace, class, loader, data) lt;
 459     if (lt.is_enabled()) {
 460       ResourceMark rm;
 461       LogStream ls(lt);
 462       ls.print("adding dependency from ");
 463       print_value_on(&ls);
 464       ls.print(" to ");
 465       to_cld->print_value_on(&ls);
 466       ls.cr();
 467     }
 468     Handle dependency(Thread::current(), to);
 469     add_handle(dependency);
 470     // Added a potentially young gen oop to the ClassLoaderData
 471     record_modified_oops();
 472   }
 473 }
 474 
 475 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
 476   {
 477     MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 478     Klass* old_value = _klasses;
 479     k->set_next_link(old_value);
 480     // Link the new item into the list, making sure the linked class is stable
 481     // since the list can be walked without a lock
 482     Atomic::release_store(&_klasses, k);
 483     if (k->is_array_klass()) {
 484       ClassLoaderDataGraph::inc_array_classes(1);
 485     } else {
 486       ClassLoaderDataGraph::inc_instance_classes(1);
 487     }
 488   }
 489 
 490   if (publicize) {
 491     LogTarget(Trace, class, loader, data) lt;
 492     if (lt.is_enabled()) {
 493       ResourceMark rm;
 494       LogStream ls(lt);
 495       ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());
 496       print_value_on(&ls);
 497       ls.cr();
 498     }
 499   }
 500 }
 501 
 502 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) {
 503   if (loader_or_mirror() != NULL) {
 504     assert(_holder.is_null(), "never replace holders");
 505     _holder = WeakHandle(Universe::vm_weak(), loader_or_mirror);
 506   }
 507 }
 508 
 509 // Remove a klass from the _klasses list for scratch_class during redefinition
 510 // or parsed class in the case of an error.
 511 void ClassLoaderData::remove_class(Klass* scratch_class) {
 512   assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
 513 
 514   // Adjust global class iterator.
 515   ClassLoaderDataGraph::adjust_saved_class(scratch_class);
 516 
 517   Klass* prev = NULL;
 518   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 519     if (k == scratch_class) {
 520       if (prev == NULL) {
 521         _klasses = k->next_link();
 522       } else {
 523         Klass* next = k->next_link();
 524         prev->set_next_link(next);
 525       }
 526 
 527       if (k->is_array_klass()) {
 528         ClassLoaderDataGraph::dec_array_classes(1);
 529       } else {
 530         ClassLoaderDataGraph::dec_instance_classes(1);
 531       }
 532 
 533       return;
 534     }
 535     prev = k;
 536     assert(k != k->next_link(), "no loops!");
 537   }
 538   ShouldNotReachHere();   // should have found this class!!
 539 }
 540 
 541 void ClassLoaderData::unload() {
 542   _unloading = true;
 543 
 544   LogTarget(Trace, class, loader, data) lt;
 545   if (lt.is_enabled()) {
 546     ResourceMark rm;
 547     LogStream ls(lt);
 548     ls.print("unload");
 549     print_value_on(&ls);
 550     ls.cr();
 551   }
 552 
 553   // Some items on the _deallocate_list need to free their C heap structures
 554   // if they are not already on the _klasses list.
 555   free_deallocate_list_C_heap_structures();
 556 
 557   inline_classes_do(InlineKlass::cleanup);
 558 
 559   // Clean up class dependencies and tell serviceability tools
 560   // these classes are unloading.  Must be called
 561   // after erroneous classes are released.
 562   classes_do(InstanceKlass::unload_class);
 563 
 564   // Method::clear_jmethod_ids only sets the jmethod_ids to NULL without
 565   // releasing the memory for related JNIMethodBlocks and JNIMethodBlockNodes.
 566   // This is done intentionally because native code (e.g. JVMTI agent) holding
 567   // jmethod_ids may access them after the associated classes and class loader
 568   // are unloaded. The Java Native Interface Specification says "method ID
 569   // does not prevent the VM from unloading the class from which the ID has
 570   // been derived. After the class is unloaded, the method or field ID becomes
 571   // invalid". In real world usages, the native code may rely on jmethod_ids
 572   // being NULL after class unloading. Hence, it is unsafe to free the memory
 573   // from the VM side without knowing when native code is going to stop using
 574   // them.
 575   if (_jmethod_ids != NULL) {
 576     Method::clear_jmethod_ids(this);
 577   }
 578 
 579   // Clean up global class iterator for compiler
 580   ClassLoaderDataGraph::adjust_saved_class(this);
 581 }
 582 
 583 ModuleEntryTable* ClassLoaderData::modules() {
 584   // Lazily create the module entry table at first request.
 585   // Lock-free access requires load_acquire.
 586   ModuleEntryTable* modules = Atomic::load_acquire(&_modules);
 587   if (modules == NULL) {
 588     MutexLocker m1(Module_lock);
 589     // Check if _modules got allocated while we were waiting for this lock.
 590     if ((modules = _modules) == NULL) {
 591       modules = new ModuleEntryTable(ModuleEntryTable::_moduletable_entry_size);
 592 
 593       {
 594         MutexLocker m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 595         // Ensure _modules is stable, since it is examined without a lock
 596         Atomic::release_store(&_modules, modules);
 597       }
 598     }
 599   }
 600   return modules;
 601 }
 602 
 603 const int _boot_loader_dictionary_size    = 1009;
 604 const int _default_loader_dictionary_size = 107;
 605 
 606 Dictionary* ClassLoaderData::create_dictionary() {
 607   assert(!has_class_mirror_holder(), "class mirror holder cld does not have a dictionary");
 608   int size;
 609   bool resizable = false;
 610   if (_the_null_class_loader_data == NULL) {
 611     size = _boot_loader_dictionary_size;
 612     resizable = true;
 613   } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) {
 614     size = 1;  // there's only one class in relection class loader and no initiated classes
 615   } else if (is_system_class_loader_data()) {
 616     size = _boot_loader_dictionary_size;
 617     resizable = true;
 618   } else {
 619     size = _default_loader_dictionary_size;
 620     resizable = true;
 621   }
 622   if (!DynamicallyResizeSystemDictionaries || DumpSharedSpaces) {
 623     resizable = false;
 624   }
 625   return new Dictionary(this, size, resizable);
 626 }
 627 
 628 // Tell the GC to keep this klass alive while iterating ClassLoaderDataGraph
 629 oop ClassLoaderData::holder_phantom() const {
 630   // A klass that was previously considered dead can be looked up in the
 631   // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
 632   // or a reachable object making it alive again. The SATB part of G1 needs
 633   // to get notified about this potential resurrection, otherwise the marking
 634   // might not find the object.
 635   if (!_holder.is_null()) {  // NULL class_loader
 636     return _holder.resolve();
 637   } else {
 638     return NULL;
 639   }
 640 }
 641 
 642 // Let the GC read the holder without keeping it alive.
 643 oop ClassLoaderData::holder_no_keepalive() const {
 644   if (!_holder.is_null()) {  // NULL class_loader
 645     return _holder.peek();
 646   } else {
 647     return NULL;
 648   }
 649 }
 650 
 651 // Unloading support
 652 bool ClassLoaderData::is_alive() const {
 653   bool alive = keep_alive()         // null class loader and incomplete non-strong hidden class.
 654       || (_holder.peek() != NULL);  // and not cleaned by the GC weak handle processing.
 655 
 656   return alive;
 657 }
 658 
 659 class ReleaseKlassClosure: public KlassClosure {
 660 private:
 661   size_t  _instance_class_released;
 662   size_t  _array_class_released;
 663 public:
 664   ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { }
 665 
 666   size_t instance_class_released() const { return _instance_class_released; }
 667   size_t array_class_released()    const { return _array_class_released;    }
 668 
 669   void do_klass(Klass* k) {
 670     if (k->is_array_klass()) {
 671       _array_class_released ++;
 672     } else {
 673       assert(k->is_instance_klass(), "Must be");
 674       _instance_class_released ++;
 675     }
 676     k->release_C_heap_structures();
 677   }
 678 };
 679 
 680 ClassLoaderData::~ClassLoaderData() {
 681   // Release C heap structures for all the classes.
 682   ReleaseKlassClosure cl;
 683   classes_do(&cl);
 684 
 685   ClassLoaderDataGraph::dec_array_classes(cl.array_class_released());
 686   ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released());
 687 
 688   // Release the WeakHandle
 689   _holder.release(Universe::vm_weak());
 690 
 691   // Release C heap allocated hashtable for all the packages.
 692   if (_packages != NULL) {
 693     // Destroy the table itself
 694     delete _packages;
 695     _packages = NULL;
 696   }
 697 
 698   // Release C heap allocated hashtable for all the modules.
 699   if (_modules != NULL) {
 700     // Destroy the table itself
 701     delete _modules;
 702     _modules = NULL;
 703   }
 704 
 705   // Release C heap allocated hashtable for the dictionary
 706   if (_dictionary != NULL) {
 707     // Destroy the table itself
 708     delete _dictionary;
 709     _dictionary = NULL;
 710   }
 711 
 712   if (_unnamed_module != NULL) {
 713     _unnamed_module->delete_unnamed_module();
 714     _unnamed_module = NULL;
 715   }
 716 
 717   // release the metaspace
 718   ClassLoaderMetaspace *m = _metaspace;
 719   if (m != NULL) {
 720     _metaspace = NULL;
 721     delete m;
 722   }
 723 
 724   // Delete lock
 725   delete _metaspace_lock;
 726 
 727   // Delete free list
 728   if (_deallocate_list != NULL) {
 729     delete _deallocate_list;
 730   }
 731 
 732   // Decrement refcounts of Symbols if created.
 733   if (_name != NULL) {
 734     _name->decrement_refcount();
 735   }
 736   if (_name_and_id != NULL) {
 737     _name_and_id->decrement_refcount();
 738   }
 739 }
 740 
 741 // Returns true if this class loader data is for the app class loader
 742 // or a user defined system class loader.  (Note that the class loader
 743 // data may have a Class holder.)
 744 bool ClassLoaderData::is_system_class_loader_data() const {
 745   return SystemDictionary::is_system_class_loader(class_loader());
 746 }
 747 
 748 // Returns true if this class loader data is for the platform class loader.
 749 // (Note that the class loader data may have a Class holder.)
 750 bool ClassLoaderData::is_platform_class_loader_data() const {
 751   return SystemDictionary::is_platform_class_loader(class_loader());
 752 }
 753 
 754 // Returns true if the class loader for this class loader data is one of
 755 // the 3 builtin (boot application/system or platform) class loaders,
 756 // including a user-defined system class loader.  Note that if the class
 757 // loader data is for a non-strong hidden class then it may
 758 // get freed by a GC even if its class loader is one of these loaders.
 759 bool ClassLoaderData::is_builtin_class_loader_data() const {
 760   return (is_boot_class_loader_data() ||
 761           SystemDictionary::is_system_class_loader(class_loader()) ||
 762           SystemDictionary::is_platform_class_loader(class_loader()));
 763 }
 764 
 765 // Returns true if this class loader data is a class loader data
 766 // that is not ever freed by a GC.  It must be the CLD for one of the builtin
 767 // class loaders and not the CLD for a non-strong hidden class.
 768 bool ClassLoaderData::is_permanent_class_loader_data() const {
 769   return is_builtin_class_loader_data() && !has_class_mirror_holder();
 770 }
 771 
 772 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() {
 773   // If the metaspace has not been allocated, create a new one.  Might want
 774   // to create smaller arena for Reflection class loaders also.
 775   // The reason for the delayed allocation is because some class loaders are
 776   // simply for delegating with no metadata of their own.
 777   // Lock-free access requires load_acquire.
 778   ClassLoaderMetaspace* metaspace = Atomic::load_acquire(&_metaspace);
 779   if (metaspace == NULL) {
 780     MutexLocker ml(_metaspace_lock,  Mutex::_no_safepoint_check_flag);
 781     // Check if _metaspace got allocated while we were waiting for this lock.
 782     if ((metaspace = _metaspace) == NULL) {
 783       if (this == the_null_class_loader_data()) {
 784         assert (class_loader() == NULL, "Must be");
 785         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
 786       } else if (has_class_mirror_holder()) {
 787         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ClassMirrorHolderMetaspaceType);
 788       } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) {
 789         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
 790       } else {
 791         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
 792       }
 793       // Ensure _metaspace is stable, since it is examined without a lock
 794       Atomic::release_store(&_metaspace, metaspace);
 795     }
 796   }
 797   return metaspace;
 798 }
 799 
 800 OopHandle ClassLoaderData::add_handle(Handle h) {
 801   MutexLocker ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 802   record_modified_oops();
 803   return _handles.add(h());
 804 }
 805 
 806 void ClassLoaderData::remove_handle(OopHandle h) {
 807   assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading");
 808   oop* ptr = h.ptr_raw();
 809   if (ptr != NULL) {
 810     assert(_handles.owner_of(ptr), "Got unexpected handle " PTR_FORMAT, p2i(ptr));
 811     NativeAccess<>::oop_store(ptr, oop(NULL));
 812   }
 813 }
 814 
 815 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
 816   MutexLocker ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 817   if (dest.resolve() != NULL) {
 818     return;
 819   } else {
 820     record_modified_oops();
 821     dest = _handles.add(h());
 822   }
 823 }
 824 
 825 // Add this metadata pointer to be freed when it's safe.  This is only during
 826 // a safepoint which checks if handles point to this metadata field.
 827 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
 828   // Metadata in shared region isn't deleted.
 829   if (!m->is_shared()) {
 830     MutexLocker ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 831     if (_deallocate_list == NULL) {
 832       _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, mtClass);
 833     }
 834     _deallocate_list->append_if_missing(m);
 835     log_debug(class, loader, data)("deallocate added for %s", m->print_value_string());
 836     ClassLoaderDataGraph::set_should_clean_deallocate_lists();
 837   }
 838 }
 839 
 840 // Deallocate free metadata on the free list.  How useful the PermGen was!
 841 void ClassLoaderData::free_deallocate_list() {
 842   // This must be called at a safepoint because it depends on metadata walking at
 843   // safepoint cleanup time.
 844   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 845   assert(!is_unloading(), "only called for ClassLoaderData that are not unloading");
 846   if (_deallocate_list == NULL) {
 847     return;
 848   }
 849   // Go backwards because this removes entries that are freed.
 850   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 851     Metadata* m = _deallocate_list->at(i);
 852     if (!m->on_stack()) {
 853       _deallocate_list->remove_at(i);
 854       // There are only three types of metadata that we deallocate directly.
 855       // Cast them so they can be used by the template function.
 856       if (m->is_method()) {
 857         MetadataFactory::free_metadata(this, (Method*)m);
 858       } else if (m->is_constantPool()) {
 859         MetadataFactory::free_metadata(this, (ConstantPool*)m);
 860       } else if (m->is_klass()) {
 861         if (!((Klass*)m)->is_inline_klass()) {
 862           MetadataFactory::free_metadata(this, (InstanceKlass*)m);
 863         } else {
 864           MetadataFactory::free_metadata(this, (InlineKlass*)m);
 865         }
 866       } else {
 867         ShouldNotReachHere();
 868       }
 869     } else {
 870       // Metadata is alive.
 871       // If scratch_class is on stack then it shouldn't be on this list!
 872       assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
 873              "scratch classes on this list should be dead");
 874       // Also should assert that other metadata on the list was found in handles.
 875       // Some cleaning remains.
 876       ClassLoaderDataGraph::set_should_clean_deallocate_lists();
 877     }
 878   }
 879 }
 880 
 881 // This is distinct from free_deallocate_list.  For class loader data that are
 882 // unloading, this frees the C heap memory for items on the list, and unlinks
 883 // scratch or error classes so that unloading events aren't triggered for these
 884 // classes. The metadata is removed with the unloading metaspace.
 885 // There isn't C heap memory allocated for methods, so nothing is done for them.
 886 void ClassLoaderData::free_deallocate_list_C_heap_structures() {
 887   assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
 888   assert(is_unloading(), "only called for ClassLoaderData that are unloading");
 889   if (_deallocate_list == NULL) {
 890     return;
 891   }
 892   // Go backwards because this removes entries that are freed.
 893   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 894     Metadata* m = _deallocate_list->at(i);
 895     _deallocate_list->remove_at(i);
 896     if (m->is_constantPool()) {
 897       ((ConstantPool*)m)->release_C_heap_structures();
 898     } else if (m->is_klass()) {
 899       InstanceKlass* ik = (InstanceKlass*)m;
 900       // also releases ik->constants() C heap memory
 901       ik->release_C_heap_structures();
 902       // Remove the class so unloading events aren't triggered for
 903       // this class (scratch or error class) in do_unloading().
 904       remove_class(ik);
 905     }
 906   }
 907 }
 908 
 909 // Caller needs ResourceMark
 910 // If the class loader's _name has not been explicitly set, the class loader's
 911 // qualified class name is returned.
 912 const char* ClassLoaderData::loader_name() const {
 913    if (_class_loader_klass == NULL) {
 914      return BOOTSTRAP_LOADER_NAME;
 915    } else if (_name != NULL) {
 916      return _name->as_C_string();
 917    } else {
 918      return _class_loader_klass->external_name();
 919    }
 920 }
 921 
 922 // Caller needs ResourceMark
 923 // Format of the _name_and_id is as follows:
 924 //   If the defining loader has a name explicitly set then '<loader-name>' @<id>
 925 //   If the defining loader has no name then <qualified-class-name> @<id>
 926 //   If built-in loader, then omit '@<id>' as there is only one instance.
 927 const char* ClassLoaderData::loader_name_and_id() const {
 928   if (_class_loader_klass == NULL) {
 929     return "'" BOOTSTRAP_LOADER_NAME "'";
 930   } else if (_name_and_id != NULL) {
 931     return _name_and_id->as_C_string();
 932   } else {
 933     // May be called in a race before _name_and_id is initialized.
 934     return _class_loader_klass->external_name();
 935   }
 936 }
 937 
 938 void ClassLoaderData::print_value_on(outputStream* out) const {
 939   if (!is_unloading() && class_loader() != NULL) {
 940     out->print("loader data: " INTPTR_FORMAT " for instance ", p2i(this));
 941     class_loader()->print_value_on(out);  // includes loader_name_and_id() and address of class loader instance
 942   } else {
 943     // loader data: 0xsomeaddr of 'bootstrap'
 944     out->print("loader data: " INTPTR_FORMAT " of %s", p2i(this), loader_name_and_id());
 945   }
 946   if (_has_class_mirror_holder) {
 947     out->print(" has a class holder");
 948   }
 949 }
 950 
 951 void ClassLoaderData::print_value() const { print_value_on(tty); }
 952 
 953 #ifndef PRODUCT
 954 class PrintKlassClosure: public KlassClosure {
 955   outputStream* _out;
 956 public:
 957   PrintKlassClosure(outputStream* out): _out(out) { }
 958 
 959   void do_klass(Klass* k) {
 960     ResourceMark rm;
 961     _out->print("%s,", k->external_name());
 962   }
 963 };
 964 
 965 void ClassLoaderData::print_on(outputStream* out) const {
 966   ResourceMark rm;
 967   out->print_cr("ClassLoaderData(" INTPTR_FORMAT ")", p2i(this));
 968   out->print_cr(" - name                %s", loader_name_and_id());
 969   if (!_holder.is_null()) {
 970     out->print   (" - holder              ");
 971     _holder.print_on(out);
 972     out->print_cr("");
 973   }
 974   out->print_cr(" - class loader        " INTPTR_FORMAT, p2i(_class_loader.ptr_raw()));
 975   out->print_cr(" - metaspace           " INTPTR_FORMAT, p2i(_metaspace));
 976   out->print_cr(" - unloading           %s", _unloading ? "true" : "false");
 977   out->print_cr(" - class mirror holder %s", _has_class_mirror_holder ? "true" : "false");
 978   out->print_cr(" - modified oops       %s", _modified_oops ? "true" : "false");
 979   out->print_cr(" - keep alive          %d", _keep_alive);
 980   out->print   (" - claim               ");
 981   switch(_claim) {
 982     case _claim_none:                       out->print_cr("none"); break;
 983     case _claim_finalizable:                out->print_cr("finalizable"); break;
 984     case _claim_strong:                     out->print_cr("strong"); break;
 985     case _claim_other:                      out->print_cr("other"); break;
 986     case _claim_other | _claim_finalizable: out->print_cr("other and finalizable"); break;
 987     case _claim_other | _claim_strong:      out->print_cr("other and strong"); break;
 988     default:                                ShouldNotReachHere();
 989   }
 990   out->print_cr(" - handles             %d", _handles.count());
 991   out->print_cr(" - dependency count    %d", _dependency_count);
 992   out->print   (" - klasses             {");
 993   PrintKlassClosure closure(out);
 994   ((ClassLoaderData*)this)->classes_do(&closure);
 995   out->print_cr(" }");
 996   out->print_cr(" - packages            " INTPTR_FORMAT, p2i(_packages));
 997   out->print_cr(" - module              " INTPTR_FORMAT, p2i(_modules));
 998   out->print_cr(" - unnamed module      " INTPTR_FORMAT, p2i(_unnamed_module));
 999   out->print_cr(" - dictionary          " INTPTR_FORMAT, p2i(_dictionary));
1000   if (_jmethod_ids != NULL) {
1001     out->print   (" - jmethod count       ");
1002     Method::print_jmethod_ids_count(this, out);
1003     out->print_cr("");
1004   }
1005   out->print_cr(" - deallocate list     " INTPTR_FORMAT, p2i(_deallocate_list));
1006   out->print_cr(" - next CLD            " INTPTR_FORMAT, p2i(_next));
1007 }
1008 #endif // PRODUCT
1009 
1010 void ClassLoaderData::print() const { print_on(tty); }
1011 
1012 void ClassLoaderData::verify() {
1013   assert_locked_or_safepoint(_metaspace_lock);
1014   oop cl = class_loader();
1015 
1016   guarantee(this == class_loader_data(cl) || has_class_mirror_holder(), "Must be the same");
1017   guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || has_class_mirror_holder(), "must be");
1018 
1019   // Verify the integrity of the allocated space.
1020 #ifdef ASSERT
1021   if (metaspace_or_null() != NULL) {
1022     metaspace_or_null()->verify();
1023   }
1024 #endif
1025 
1026   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
1027     guarantee(k->class_loader_data() == this, "Must be the same");
1028     k->verify();
1029     assert(k != k->next_link(), "no loops!");
1030   }
1031 }
1032 
1033 bool ClassLoaderData::contains_klass(Klass* klass) {
1034   // Lock-free access requires load_acquire
1035   for (Klass* k = Atomic::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
1036     if (k == klass) return true;
1037   }
1038   return false;
1039 }