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   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.
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   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).
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  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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  20  * or visit www.oracle.com if you need additional information or have any
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  24 
  25 // A ClassLoaderData identifies the full set of class types that a class
  26 // loader's name resolution strategy produces for a given configuration of the
  27 // class loader.
  28 // Class types in the ClassLoaderData may be defined by from class file binaries
  29 // provided by the class loader, or from other class loader it interacts with
  30 // according to its name resolution strategy.
  31 //
  32 // Class loaders that implement a deterministic name resolution strategy
  33 // (including with respect to their delegation behavior), such as the boot, the
  34 // platform, and the system loaders of the JDK's built-in class loader
  35 // hierarchy, always produce the same linkset for a given configuration.
  36 //
  37 // ClassLoaderData carries information related to a linkset (e.g.,
  38 // metaspace holding its klass definitions).
  39 // The System Dictionary and related data structures (e.g., placeholder table,
  40 // loader constraints table) as well as the runtime representation of classes
  41 // only reference ClassLoaderData.
  42 //
  43 // Instances of java.lang.ClassLoader holds a pointer to a ClassLoaderData that
  44 // that represent the loader's "linking domain" in the JVM.
  45 //
  46 // The bootstrap loader (represented by null) also has a ClassLoaderData,
  47 // the singleton class the_null_class_loader_data().
  48 
  49 #include "precompiled.hpp"
  50 #include "classfile/classLoaderData.inline.hpp"
  51 #include "classfile/classLoaderDataGraph.inline.hpp"
  52 #include "classfile/dictionary.hpp"
  53 #include "classfile/javaClasses.inline.hpp"
  54 #include "classfile/moduleEntry.hpp"
  55 #include "classfile/packageEntry.hpp"
  56 #include "classfile/symbolTable.hpp"
  57 #include "classfile/systemDictionary.hpp"
  58 #include "classfile/systemDictionaryShared.hpp"
  59 #include "classfile/vmClasses.hpp"
  60 #include "logging/log.hpp"
  61 #include "logging/logStream.hpp"
  62 #include "memory/allocation.inline.hpp"
  63 #include "memory/classLoaderMetaspace.hpp"
  64 #include "memory/metadataFactory.hpp"
  65 #include "memory/metaspace.hpp"
  66 #include "memory/resourceArea.hpp"
  67 #include "memory/universe.hpp"
  68 #include "oops/access.inline.hpp"
  69 #include "oops/klass.inline.hpp"
  70 #include "oops/oop.inline.hpp"
  71 #include "oops/oopHandle.inline.hpp"
  72 #include "oops/verifyOopClosure.hpp"
  73 #include "oops/weakHandle.inline.hpp"
  74 #include "runtime/arguments.hpp"
  75 #include "runtime/atomic.hpp"
  76 #include "runtime/handles.inline.hpp"
  77 #include "runtime/mutex.hpp"
  78 #include "runtime/safepoint.hpp"
  79 #include "utilities/growableArray.hpp"
  80 #include "utilities/macros.hpp"
  81 #include "utilities/ostream.hpp"
  82 
  83 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = nullptr;
  84 
  85 void ClassLoaderData::init_null_class_loader_data() {
  86   assert(_the_null_class_loader_data == nullptr, "cannot initialize twice");
  87   assert(ClassLoaderDataGraph::_head == nullptr, "cannot initialize twice");
  88 
  89   _the_null_class_loader_data = new ClassLoaderData(Handle(), false);
  90   ClassLoaderDataGraph::_head = _the_null_class_loader_data;
  91   assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
  92 
  93   LogTarget(Trace, class, loader, data) lt;
  94   if (lt.is_enabled()) {
  95     ResourceMark rm;
  96     LogStream ls(lt);
  97     ls.print("create ");
  98     _the_null_class_loader_data->print_value_on(&ls);
  99     ls.cr();
 100   }
 101 }
 102 
 103 // Obtain and set the class loader's name within the ClassLoaderData so
 104 // it will be available for error messages, logging, JFR, etc.  The name
 105 // and klass are available after the class_loader oop is no longer alive,
 106 // during unloading.
 107 void ClassLoaderData::initialize_name(Handle class_loader) {
 108   ResourceMark rm;
 109 
 110   // Obtain the class loader's name.  If the class loader's name was not
 111   // explicitly set during construction, the CLD's _name field will be null.
 112   oop cl_name = java_lang_ClassLoader::name(class_loader());
 113   if (cl_name != nullptr) {
 114     const char* cl_instance_name = java_lang_String::as_utf8_string(cl_name);
 115 
 116     if (cl_instance_name != nullptr && cl_instance_name[0] != '\0') {
 117       _name = SymbolTable::new_symbol(cl_instance_name);
 118     }
 119   }
 120 
 121   // Obtain the class loader's name and identity hash.  If the class loader's
 122   // name was not explicitly set during construction, the class loader's name and id
 123   // will be set to the qualified class name of the class loader along with its
 124   // identity hash.
 125   // If for some reason the ClassLoader's constructor has not been run, instead of
 126   // leaving the _name_and_id field null, fall back to the external qualified class
 127   // name.  Thus CLD's _name_and_id field should never have a null value.
 128   oop cl_name_and_id = java_lang_ClassLoader::nameAndId(class_loader());
 129   const char* cl_instance_name_and_id =
 130                   (cl_name_and_id == nullptr) ? _class_loader_klass->external_name() :
 131                                              java_lang_String::as_utf8_string(cl_name_and_id);
 132   assert(cl_instance_name_and_id != nullptr && cl_instance_name_and_id[0] != '\0', "class loader has no name and id");
 133   _name_and_id = SymbolTable::new_symbol(cl_instance_name_and_id);
 134 }
 135 
 136 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool has_class_mirror_holder) :
 137   _metaspace(nullptr),
 138   _metaspace_lock(new Mutex(Mutex::nosafepoint-2, "MetaspaceAllocation_lock")),
 139   _unloading(false), _has_class_mirror_holder(has_class_mirror_holder),
 140   _modified_oops(true),
 141   // A non-strong hidden class loader data doesn't have anything to keep
 142   // it from being unloaded during parsing of the non-strong hidden class.
 143   // The null-class-loader should always be kept alive.
 144   _keep_alive((has_class_mirror_holder || h_class_loader.is_null()) ? 1 : 0),
 145   _claim(0),
 146   _handles(),
 147   _klasses(nullptr), _packages(nullptr), _modules(nullptr), _unnamed_module(nullptr), _dictionary(nullptr),
 148   _jmethod_ids(nullptr),
 149   _deallocate_list(nullptr),
 150   _next(nullptr),
 151   _class_loader_klass(nullptr), _name(nullptr), _name_and_id(nullptr) {
 152 
 153   if (!h_class_loader.is_null()) {
 154     _class_loader = _handles.add(h_class_loader());
 155     _class_loader_klass = h_class_loader->klass();
 156     initialize_name(h_class_loader);
 157   }
 158 
 159   if (!has_class_mirror_holder) {
 160     // The holder is initialized later for non-strong hidden classes,
 161     // and before calling anything that call class_loader().
 162     initialize_holder(h_class_loader);
 163 
 164     // A ClassLoaderData created solely for a non-strong hidden class should never
 165     // have a ModuleEntryTable or PackageEntryTable created for it.
 166     _packages = new PackageEntryTable();
 167     if (h_class_loader.is_null()) {
 168       // Create unnamed module for boot loader
 169       _unnamed_module = ModuleEntry::create_boot_unnamed_module(this);
 170     } else {
 171       // Create unnamed module for all other loaders
 172       _unnamed_module = ModuleEntry::create_unnamed_module(this);
 173     }
 174     _dictionary = create_dictionary();
 175   }
 176 
 177   NOT_PRODUCT(_dependency_count = 0); // number of class loader dependencies
 178 
 179   JFR_ONLY(INIT_ID(this);)
 180 }
 181 
 182 ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {
 183   Chunk* c = _head;
 184   while (c != nullptr) {
 185     Chunk* next = c->_next;
 186     delete c;
 187     c = next;
 188   }
 189 }
 190 
 191 OopHandle ClassLoaderData::ChunkedHandleList::add(oop o) {
 192   if (_head == nullptr || _head->_size == Chunk::CAPACITY) {
 193     Chunk* next = new Chunk(_head);
 194     Atomic::release_store(&_head, next);
 195   }
 196   oop* handle = &_head->_data[_head->_size];
 197   NativeAccess<IS_DEST_UNINITIALIZED>::oop_store(handle, o);
 198   Atomic::release_store(&_head->_size, _head->_size + 1);
 199   return OopHandle(handle);
 200 }
 201 
 202 int ClassLoaderData::ChunkedHandleList::count() const {
 203   int count = 0;
 204   Chunk* chunk = _head;
 205   while (chunk != nullptr) {
 206     count += chunk->_size;
 207     chunk = chunk->_next;
 208   }
 209   return count;
 210 }
 211 
 212 inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {
 213   for (juint i = 0; i < size; i++) {
 214     f->do_oop(&c->_data[i]);
 215   }
 216 }
 217 
 218 void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {
 219   Chunk* head = Atomic::load_acquire(&_head);
 220   if (head != nullptr) {
 221     // Must be careful when reading size of head
 222     oops_do_chunk(f, head, Atomic::load_acquire(&head->_size));
 223     for (Chunk* c = head->_next; c != nullptr; c = c->_next) {
 224       oops_do_chunk(f, c, c->_size);
 225     }
 226   }
 227 }
 228 
 229 class VerifyContainsOopClosure : public OopClosure {
 230   oop  _target;
 231   bool _found;
 232 
 233  public:
 234   VerifyContainsOopClosure(oop target) : _target(target), _found(false) {}
 235 
 236   void do_oop(oop* p) {
 237     if (p != nullptr && NativeAccess<AS_NO_KEEPALIVE>::oop_load(p) == _target) {
 238       _found = true;
 239     }
 240   }
 241 
 242   void do_oop(narrowOop* p) {
 243     // The ChunkedHandleList should not contain any narrowOop
 244     ShouldNotReachHere();
 245   }
 246 
 247   bool found() const {
 248     return _found;
 249   }
 250 };
 251 
 252 bool ClassLoaderData::ChunkedHandleList::contains(oop p) {
 253   VerifyContainsOopClosure cl(p);
 254   oops_do(&cl);
 255   return cl.found();
 256 }
 257 
 258 #ifndef PRODUCT
 259 bool ClassLoaderData::ChunkedHandleList::owner_of(oop* oop_handle) {
 260   Chunk* chunk = _head;
 261   while (chunk != nullptr) {
 262     if (&(chunk->_data[0]) <= oop_handle && oop_handle < &(chunk->_data[chunk->_size])) {
 263       return true;
 264     }
 265     chunk = chunk->_next;
 266   }
 267   return false;
 268 }
 269 #endif // PRODUCT
 270 
 271 void ClassLoaderData::clear_claim(int claim) {
 272   for (;;) {
 273     int old_claim = Atomic::load(&_claim);
 274     if ((old_claim & claim) == 0) {
 275       return;
 276     }
 277     int new_claim = old_claim & ~claim;
 278     if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
 279       return;
 280     }
 281   }
 282 }
 283 
 284 #ifdef ASSERT
 285 void ClassLoaderData::verify_not_claimed(int claim) {
 286   assert((_claim & claim) == 0, "Found claim: %d bits in _claim: %d", claim, _claim);
 287 }
 288 #endif
 289 
 290 bool ClassLoaderData::try_claim(int claim) {
 291   for (;;) {
 292     int old_claim = Atomic::load(&_claim);
 293     if ((old_claim & claim) == claim) {
 294       return false;
 295     }
 296     int new_claim = old_claim | claim;
 297     if (Atomic::cmpxchg(&_claim, old_claim, new_claim) == old_claim) {
 298       return true;
 299     }
 300   }
 301 }
 302 
 303 // Non-strong hidden classes have their own ClassLoaderData that is marked to keep alive
 304 // while the class is being parsed, and if the class appears on the module fixup list.
 305 // Due to the uniqueness that no other class shares the hidden class' name or
 306 // ClassLoaderData, no other non-GC thread has knowledge of the hidden class while
 307 // it is being defined, therefore _keep_alive is not volatile or atomic.
 308 void ClassLoaderData::inc_keep_alive() {
 309   if (has_class_mirror_holder()) {
 310     assert(_keep_alive > 0, "Invalid keep alive increment count");
 311     _keep_alive++;
 312   }
 313 }
 314 
 315 void ClassLoaderData::dec_keep_alive() {
 316   if (has_class_mirror_holder()) {
 317     assert(_keep_alive > 0, "Invalid keep alive decrement count");
 318     _keep_alive--;
 319   }
 320 }
 321 
 322 void ClassLoaderData::oops_do(OopClosure* f, int claim_value, bool clear_mod_oops) {
 323   if (claim_value != ClassLoaderData::_claim_none && !try_claim(claim_value)) {
 324     return;
 325   }
 326 
 327   // Only clear modified_oops after the ClassLoaderData is claimed.
 328   if (clear_mod_oops) {
 329     clear_modified_oops();
 330   }
 331 
 332   _handles.oops_do(f);
 333 }
 334 
 335 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
 336   // Lock-free access requires load_acquire
 337   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
 338     klass_closure->do_klass(k);
 339     assert(k != k->next_link(), "no loops!");
 340   }
 341 }
 342 
 343 void ClassLoaderData::classes_do(void f(Klass * const)) {
 344   // Lock-free access requires load_acquire
 345   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
 346     f(k);
 347     assert(k != k->next_link(), "no loops!");
 348   }
 349 }
 350 
 351 void ClassLoaderData::methods_do(void f(Method*)) {
 352   // Lock-free access requires load_acquire
 353   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
 354     if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
 355       InstanceKlass::cast(k)->methods_do(f);
 356     }
 357   }
 358 }
 359 
 360 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
 361   // To call this, one must have the MultiArray_lock held, but the _klasses list still has lock free reads.
 362   assert_locked_or_safepoint(MultiArray_lock);
 363 
 364   // Lock-free access requires load_acquire
 365   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
 366     // Filter out InstanceKlasses (or their ObjArrayKlasses) that have not entered the
 367     // loaded state.
 368     if (k->is_instance_klass()) {
 369       if (!InstanceKlass::cast(k)->is_loaded()) {
 370         continue;
 371       }
 372     } else if (k->is_shared() && k->is_objArray_klass()) {
 373       Klass* bottom = ObjArrayKlass::cast(k)->bottom_klass();
 374       if (bottom->is_instance_klass() && !InstanceKlass::cast(bottom)->is_loaded()) {
 375         // This could happen if <bottom> is a shared class that has been restored
 376         // but is not yet marked as loaded. All archived array classes of the
 377         // bottom class are already restored and placed in the _klasses list.
 378         continue;
 379       }
 380     }
 381 
 382 #ifdef ASSERT
 383     oop m = k->java_mirror();
 384     assert(m != nullptr, "nullptr mirror");
 385     assert(m->is_a(vmClasses::Class_klass()), "invalid mirror");
 386 #endif
 387     klass_closure->do_klass(k);
 388   }
 389 }
 390 
 391 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
 392   // Lock-free access requires load_acquire
 393   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
 394     if (k->is_instance_klass()) {
 395       f(InstanceKlass::cast(k));
 396     }
 397     assert(k != k->next_link(), "no loops!");
 398   }
 399 }
 400 
 401 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
 402   assert_locked_or_safepoint(Module_lock);
 403   if (_unnamed_module != nullptr) {
 404     f(_unnamed_module);
 405   }
 406   if (_modules != nullptr) {
 407     _modules->modules_do(f);
 408   }
 409 }
 410 
 411 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
 412   assert_locked_or_safepoint(Module_lock);
 413   if (_packages != nullptr) {
 414     _packages->packages_do(f);
 415   }
 416 }
 417 
 418 void ClassLoaderData::record_dependency(const Klass* k) {
 419   assert(k != nullptr, "invariant");
 420 
 421   ClassLoaderData * const from_cld = this;
 422   ClassLoaderData * const to_cld = k->class_loader_data();
 423 
 424   // Do not need to record dependency if the dependency is to a class whose
 425   // class loader data is never freed.  (i.e. the dependency's class loader
 426   // is one of the three builtin class loaders and the dependency's class
 427   // loader data has a ClassLoader holder, not a Class holder.)
 428   if (to_cld->is_permanent_class_loader_data()) {
 429     return;
 430   }
 431 
 432   oop to;
 433   if (to_cld->has_class_mirror_holder()) {
 434     // Just return if a non-strong hidden class class is attempting to record a dependency
 435     // to itself.  (Note that every non-strong hidden class has its own unique class
 436     // loader data.)
 437     if (to_cld == from_cld) {
 438       return;
 439     }
 440     // Hidden class dependencies are through the mirror.
 441     to = k->java_mirror();
 442   } else {
 443     to = to_cld->class_loader();
 444     oop from = from_cld->class_loader();
 445 
 446     // Just return if this dependency is to a class with the same or a parent
 447     // class_loader.
 448     if (from == to || java_lang_ClassLoader::isAncestor(from, to)) {
 449       return; // this class loader is in the parent list, no need to add it.
 450     }
 451   }
 452 
 453   // It's a dependency we won't find through GC, add it.
 454   if (!_handles.contains(to)) {
 455     NOT_PRODUCT(Atomic::inc(&_dependency_count));
 456     LogTarget(Trace, class, loader, data) lt;
 457     if (lt.is_enabled()) {
 458       ResourceMark rm;
 459       LogStream ls(lt);
 460       ls.print("adding dependency from ");
 461       print_value_on(&ls);
 462       ls.print(" to ");
 463       to_cld->print_value_on(&ls);
 464       ls.cr();
 465     }
 466     Handle dependency(Thread::current(), to);
 467     add_handle(dependency);
 468     // Added a potentially young gen oop to the ClassLoaderData
 469     record_modified_oops();
 470   }
 471 }
 472 
 473 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
 474   {
 475     MutexLocker ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 476     Klass* old_value = _klasses;
 477     k->set_next_link(old_value);
 478     // Link the new item into the list, making sure the linked class is stable
 479     // since the list can be walked without a lock
 480     Atomic::release_store(&_klasses, k);
 481     if (k->is_array_klass()) {
 482       ClassLoaderDataGraph::inc_array_classes(1);
 483     } else {
 484       ClassLoaderDataGraph::inc_instance_classes(1);
 485     }
 486   }
 487 
 488   if (publicize) {
 489     LogTarget(Trace, class, loader, data) lt;
 490     if (lt.is_enabled()) {
 491       ResourceMark rm;
 492       LogStream ls(lt);
 493       ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());
 494       print_value_on(&ls);
 495       ls.cr();
 496     }
 497   }
 498 }
 499 
 500 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) {
 501   if (loader_or_mirror() != nullptr) {
 502     assert(_holder.is_null(), "never replace holders");
 503     _holder = WeakHandle(Universe::vm_weak(), loader_or_mirror);
 504   }
 505 }
 506 
 507 // Remove a klass from the _klasses list for scratch_class during redefinition
 508 // or parsed class in the case of an error.
 509 void ClassLoaderData::remove_class(Klass* scratch_class) {
 510   assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
 511 
 512   // Adjust global class iterator.
 513   ClassLoaderDataGraph::adjust_saved_class(scratch_class);
 514 
 515   Klass* prev = nullptr;
 516   for (Klass* k = _klasses; k != nullptr; k = k->next_link()) {
 517     if (k == scratch_class) {
 518       if (prev == nullptr) {
 519         _klasses = k->next_link();
 520       } else {
 521         Klass* next = k->next_link();
 522         prev->set_next_link(next);
 523       }
 524 
 525       if (k->is_array_klass()) {
 526         ClassLoaderDataGraph::dec_array_classes(1);
 527       } else {
 528         ClassLoaderDataGraph::dec_instance_classes(1);
 529       }
 530 
 531       return;
 532     }
 533     prev = k;
 534     assert(k != k->next_link(), "no loops!");
 535   }
 536   ShouldNotReachHere();   // should have found this class!!
 537 }
 538 
 539 void ClassLoaderData::unload() {
 540   _unloading = true;
 541 
 542   LogTarget(Trace, class, loader, data) lt;
 543   if (lt.is_enabled()) {
 544     ResourceMark rm;
 545     LogStream ls(lt);
 546     ls.print("unload");
 547     print_value_on(&ls);
 548     ls.cr();
 549   }
 550 
 551   // Some items on the _deallocate_list need to free their C heap structures
 552   // if they are not already on the _klasses list.
 553   free_deallocate_list_C_heap_structures();
 554 
 555   // Clean up class dependencies and tell serviceability tools
 556   // these classes are unloading.  Must be called
 557   // after erroneous classes are released.
 558   classes_do(InstanceKlass::unload_class);
 559 
 560   // Method::clear_jmethod_ids only sets the jmethod_ids to null without
 561   // releasing the memory for related JNIMethodBlocks and JNIMethodBlockNodes.
 562   // This is done intentionally because native code (e.g. JVMTI agent) holding
 563   // jmethod_ids may access them after the associated classes and class loader
 564   // are unloaded. The Java Native Interface Specification says "method ID
 565   // does not prevent the VM from unloading the class from which the ID has
 566   // been derived. After the class is unloaded, the method or field ID becomes
 567   // invalid". In real world usages, the native code may rely on jmethod_ids
 568   // being null after class unloading. Hence, it is unsafe to free the memory
 569   // from the VM side without knowing when native code is going to stop using
 570   // them.
 571   if (_jmethod_ids != nullptr) {
 572     Method::clear_jmethod_ids(this);
 573   }
 574 
 575   // Clean up global class iterator for compiler
 576   ClassLoaderDataGraph::adjust_saved_class(this);
 577 }
 578 
 579 ModuleEntryTable* ClassLoaderData::modules() {
 580   // Lazily create the module entry table at first request.
 581   // Lock-free access requires load_acquire.
 582   ModuleEntryTable* modules = Atomic::load_acquire(&_modules);
 583   if (modules == nullptr) {
 584     MutexLocker m1(Module_lock);
 585     // Check if _modules got allocated while we were waiting for this lock.
 586     if ((modules = _modules) == nullptr) {
 587       modules = new ModuleEntryTable();
 588 
 589       {
 590         MutexLocker m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 591         // Ensure _modules is stable, since it is examined without a lock
 592         Atomic::release_store(&_modules, modules);
 593       }
 594     }
 595   }
 596   return modules;
 597 }
 598 
 599 const int _boot_loader_dictionary_size    = 1009;
 600 const int _default_loader_dictionary_size = 107;
 601 
 602 Dictionary* ClassLoaderData::create_dictionary() {
 603   assert(!has_class_mirror_holder(), "class mirror holder cld does not have a dictionary");
 604   int size;
 605   if (_the_null_class_loader_data == nullptr) {
 606     size = _boot_loader_dictionary_size;
 607   } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) {
 608     size = 1;  // there's only one class in relection class loader and no initiated classes
 609   } else if (is_system_class_loader_data()) {
 610     size = _boot_loader_dictionary_size;
 611   } else {
 612     size = _default_loader_dictionary_size;
 613   }
 614   return new Dictionary(this, size);
 615 }
 616 
 617 // Tell the GC to keep this klass alive. Needed while iterating ClassLoaderDataGraph,
 618 // and any runtime code that uses klasses.
 619 oop ClassLoaderData::holder() const {
 620   // A klass that was previously considered dead can be looked up in the
 621   // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
 622   // or a reachable object making it alive again. The SATB part of G1 needs
 623   // to get notified about this potential resurrection, otherwise the marking
 624   // might not find the object.
 625   if (!_holder.is_null()) {  // null class_loader
 626     return _holder.resolve();
 627   } else {
 628     return nullptr;
 629   }
 630 }
 631 
 632 // Let the GC read the holder without keeping it alive.
 633 oop ClassLoaderData::holder_no_keepalive() const {
 634   if (!_holder.is_null()) {  // null class_loader
 635     return _holder.peek();
 636   } else {
 637     return nullptr;
 638   }
 639 }
 640 
 641 // Unloading support
 642 bool ClassLoaderData::is_alive() const {
 643   bool alive = keep_alive()         // null class loader and incomplete non-strong hidden class.
 644       || (_holder.peek() != nullptr);  // and not cleaned by the GC weak handle processing.
 645 
 646   return alive;
 647 }
 648 
 649 class ReleaseKlassClosure: public KlassClosure {
 650 private:
 651   size_t  _instance_class_released;
 652   size_t  _array_class_released;
 653 public:
 654   ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { }
 655 
 656   size_t instance_class_released() const { return _instance_class_released; }
 657   size_t array_class_released()    const { return _array_class_released;    }
 658 
 659   void do_klass(Klass* k) {
 660     if (k->is_array_klass()) {
 661       _array_class_released ++;
 662     } else {
 663       assert(k->is_instance_klass(), "Must be");
 664       _instance_class_released ++;
 665     }
 666     k->release_C_heap_structures();
 667   }
 668 };
 669 
 670 ClassLoaderData::~ClassLoaderData() {
 671   // Release C heap structures for all the classes.
 672   ReleaseKlassClosure cl;
 673   classes_do(&cl);
 674 
 675   ClassLoaderDataGraph::dec_array_classes(cl.array_class_released());
 676   ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released());
 677 
 678   // Release the WeakHandle
 679   _holder.release(Universe::vm_weak());
 680 
 681   // Release C heap allocated hashtable for all the packages.
 682   if (_packages != nullptr) {
 683     // Destroy the table itself
 684     delete _packages;
 685     _packages = nullptr;
 686   }
 687 
 688   // Release C heap allocated hashtable for all the modules.
 689   if (_modules != nullptr) {
 690     // Destroy the table itself
 691     delete _modules;
 692     _modules = nullptr;
 693   }
 694 
 695   // Release C heap allocated hashtable for the dictionary
 696   if (_dictionary != nullptr) {
 697     // Destroy the table itself
 698     delete _dictionary;
 699     _dictionary = nullptr;
 700   }
 701 
 702   if (_unnamed_module != nullptr) {
 703     delete _unnamed_module;
 704     _unnamed_module = nullptr;
 705   }
 706 
 707   // release the metaspace
 708   ClassLoaderMetaspace *m = _metaspace;
 709   if (m != nullptr) {
 710     _metaspace = nullptr;
 711     delete m;
 712   }
 713 
 714   // Delete lock
 715   delete _metaspace_lock;
 716 
 717   // Delete free list
 718   if (_deallocate_list != nullptr) {
 719     delete _deallocate_list;
 720   }
 721 
 722   // Decrement refcounts of Symbols if created.
 723   if (_name != nullptr) {
 724     _name->decrement_refcount();
 725   }
 726   if (_name_and_id != nullptr) {
 727     _name_and_id->decrement_refcount();
 728   }
 729 }
 730 
 731 // Returns true if this class loader data is for the app class loader
 732 // or a user defined system class loader.  (Note that the class loader
 733 // data may have a Class holder.)
 734 bool ClassLoaderData::is_system_class_loader_data() const {
 735   return SystemDictionary::is_system_class_loader(class_loader());
 736 }
 737 
 738 // Returns true if this class loader data is for the platform class loader.
 739 // (Note that the class loader data may have a Class holder.)
 740 bool ClassLoaderData::is_platform_class_loader_data() const {
 741   return SystemDictionary::is_platform_class_loader(class_loader());
 742 }
 743 
 744 // Returns true if the class loader for this class loader data is one of
 745 // the 3 builtin (boot application/system or platform) class loaders,
 746 // including a user-defined system class loader.  Note that if the class
 747 // loader data is for a non-strong hidden class then it may
 748 // get freed by a GC even if its class loader is one of these loaders.
 749 bool ClassLoaderData::is_builtin_class_loader_data() const {
 750   return (is_boot_class_loader_data() ||
 751           SystemDictionary::is_system_class_loader(class_loader()) ||
 752           SystemDictionary::is_platform_class_loader(class_loader()));
 753 }
 754 
 755 // Returns true if this class loader data is a class loader data
 756 // that is not ever freed by a GC.  It must be the CLD for one of the builtin
 757 // class loaders and not the CLD for a non-strong hidden class.
 758 bool ClassLoaderData::is_permanent_class_loader_data() const {
 759   return is_builtin_class_loader_data() && !has_class_mirror_holder();
 760 }
 761 
 762 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() {
 763   // If the metaspace has not been allocated, create a new one.  Might want
 764   // to create smaller arena for Reflection class loaders also.
 765   // The reason for the delayed allocation is because some class loaders are
 766   // simply for delegating with no metadata of their own.
 767   // Lock-free access requires load_acquire.
 768   ClassLoaderMetaspace* metaspace = Atomic::load_acquire(&_metaspace);
 769   if (metaspace == nullptr) {
 770     MutexLocker ml(_metaspace_lock,  Mutex::_no_safepoint_check_flag);
 771     // Check if _metaspace got allocated while we were waiting for this lock.
 772     if ((metaspace = _metaspace) == nullptr) {
 773       if (this == the_null_class_loader_data()) {
 774         assert (class_loader() == nullptr, "Must be");
 775         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
 776       } else if (has_class_mirror_holder()) {
 777         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ClassMirrorHolderMetaspaceType);
 778       } else if (class_loader()->is_a(vmClasses::reflect_DelegatingClassLoader_klass())) {
 779         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
 780       } else {
 781         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
 782       }
 783       // Ensure _metaspace is stable, since it is examined without a lock
 784       Atomic::release_store(&_metaspace, metaspace);
 785     }
 786   }
 787   return metaspace;
 788 }
 789 
 790 OopHandle ClassLoaderData::add_handle(Handle h) {
 791   MutexLocker ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 792   record_modified_oops();
 793   return _handles.add(h());
 794 }
 795 
 796 void ClassLoaderData::remove_handle(OopHandle h) {
 797   assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading");
 798   oop* ptr = h.ptr_raw();
 799   if (ptr != nullptr) {
 800     assert(_handles.owner_of(ptr), "Got unexpected handle " PTR_FORMAT, p2i(ptr));
 801     NativeAccess<>::oop_store(ptr, oop(nullptr));
 802   }
 803 }
 804 
 805 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
 806   MutexLocker ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 807   if (dest.resolve() != nullptr) {
 808     return;
 809   } else {
 810     record_modified_oops();
 811     dest = _handles.add(h());
 812   }
 813 }
 814 
 815 // Add this metadata pointer to be freed when it's safe.  This is only during
 816 // a safepoint which checks if handles point to this metadata field.
 817 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
 818   // Metadata in shared region isn't deleted.
 819   if (!m->is_shared()) {
 820     MutexLocker ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 821     if (_deallocate_list == nullptr) {
 822       _deallocate_list = new (mtClass) GrowableArray<Metadata*>(100, mtClass);
 823     }
 824     _deallocate_list->append_if_missing(m);
 825     ResourceMark rm;
 826     log_debug(class, loader, data)("deallocate added for %s", m->print_value_string());
 827     ClassLoaderDataGraph::set_should_clean_deallocate_lists();
 828   }
 829 }
 830 
 831 // Deallocate free metadata on the free list.  How useful the PermGen was!
 832 void ClassLoaderData::free_deallocate_list() {
 833   // This must be called at a safepoint because it depends on metadata walking at
 834   // safepoint cleanup time.
 835   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 836   assert(!is_unloading(), "only called for ClassLoaderData that are not unloading");
 837   if (_deallocate_list == nullptr) {
 838     return;
 839   }
 840   // Go backwards because this removes entries that are freed.
 841   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 842     Metadata* m = _deallocate_list->at(i);
 843     if (!m->on_stack()) {
 844       _deallocate_list->remove_at(i);
 845       // There are only three types of metadata that we deallocate directly.
 846       // Cast them so they can be used by the template function.
 847       if (m->is_method()) {
 848         MetadataFactory::free_metadata(this, (Method*)m);
 849       } else if (m->is_constantPool()) {
 850         MetadataFactory::free_metadata(this, (ConstantPool*)m);
 851       } else if (m->is_klass()) {
 852         MetadataFactory::free_metadata(this, (InstanceKlass*)m);
 853       } else {
 854         ShouldNotReachHere();
 855       }
 856     } else {
 857       // Metadata is alive.
 858       // If scratch_class is on stack then it shouldn't be on this list!
 859       assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
 860              "scratch classes on this list should be dead");
 861       // Also should assert that other metadata on the list was found in handles.
 862       // Some cleaning remains.
 863       ClassLoaderDataGraph::set_should_clean_deallocate_lists();
 864     }
 865   }
 866 }
 867 
 868 // This is distinct from free_deallocate_list.  For class loader data that are
 869 // unloading, this frees the C heap memory for items on the list, and unlinks
 870 // scratch or error classes so that unloading events aren't triggered for these
 871 // classes. The metadata is removed with the unloading metaspace.
 872 // There isn't C heap memory allocated for methods, so nothing is done for them.
 873 void ClassLoaderData::free_deallocate_list_C_heap_structures() {
 874   assert_locked_or_safepoint(ClassLoaderDataGraph_lock);
 875   assert(is_unloading(), "only called for ClassLoaderData that are unloading");
 876   if (_deallocate_list == nullptr) {
 877     return;
 878   }
 879   // Go backwards because this removes entries that are freed.
 880   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 881     Metadata* m = _deallocate_list->at(i);
 882     _deallocate_list->remove_at(i);
 883     if (m->is_constantPool()) {
 884       ((ConstantPool*)m)->release_C_heap_structures();
 885     } else if (m->is_klass()) {
 886       InstanceKlass* ik = (InstanceKlass*)m;
 887       // also releases ik->constants() C heap memory
 888       ik->release_C_heap_structures();
 889       // Remove the class so unloading events aren't triggered for
 890       // this class (scratch or error class) in do_unloading().
 891       remove_class(ik);
 892       // But still have to remove it from the dumptime_table.
 893       SystemDictionaryShared::handle_class_unloading(ik);
 894     }
 895   }
 896 }
 897 
 898 // Caller needs ResourceMark
 899 // If the class loader's _name has not been explicitly set, the class loader's
 900 // qualified class name is returned.
 901 const char* ClassLoaderData::loader_name() const {
 902    if (_class_loader_klass == nullptr) {
 903      return BOOTSTRAP_LOADER_NAME;
 904    } else if (_name != nullptr) {
 905      return _name->as_C_string();
 906    } else {
 907      return _class_loader_klass->external_name();
 908    }
 909 }
 910 
 911 // Caller needs ResourceMark
 912 // Format of the _name_and_id is as follows:
 913 //   If the defining loader has a name explicitly set then '<loader-name>' @<id>
 914 //   If the defining loader has no name then <qualified-class-name> @<id>
 915 //   If built-in loader, then omit '@<id>' as there is only one instance.
 916 const char* ClassLoaderData::loader_name_and_id() const {
 917   if (_class_loader_klass == nullptr) {
 918     return "'" BOOTSTRAP_LOADER_NAME "'";
 919   } else if (_name_and_id != nullptr) {
 920     return _name_and_id->as_C_string();
 921   } else {
 922     // May be called in a race before _name_and_id is initialized.
 923     return _class_loader_klass->external_name();
 924   }
 925 }
 926 
 927 void ClassLoaderData::print_value_on(outputStream* out) const {
 928   if (!is_unloading() && class_loader() != nullptr) {
 929     out->print("loader data: " INTPTR_FORMAT " for instance ", p2i(this));
 930     class_loader()->print_value_on(out);  // includes loader_name_and_id() and address of class loader instance
 931   } else {
 932     // loader data: 0xsomeaddr of 'bootstrap'
 933     out->print("loader data: " INTPTR_FORMAT " of %s", p2i(this), loader_name_and_id());
 934   }
 935   if (_has_class_mirror_holder) {
 936     out->print(" has a class holder");
 937   }
 938 }
 939 
 940 void ClassLoaderData::print_value() const { print_value_on(tty); }
 941 
 942 #ifndef PRODUCT
 943 class PrintKlassClosure: public KlassClosure {
 944   outputStream* _out;
 945 public:
 946   PrintKlassClosure(outputStream* out): _out(out) { }
 947 
 948   void do_klass(Klass* k) {
 949     ResourceMark rm;
 950     _out->print("%s,", k->external_name());
 951   }
 952 };
 953 
 954 void ClassLoaderData::print_on(outputStream* out) const {
 955   ResourceMark rm;
 956   out->print_cr("ClassLoaderData(" INTPTR_FORMAT ")", p2i(this));
 957   out->print_cr(" - name                %s", loader_name_and_id());
 958   if (!_holder.is_null()) {
 959     out->print   (" - holder              ");
 960     _holder.print_on(out);
 961     out->print_cr("");
 962   }
 963   out->print_cr(" - class loader        " INTPTR_FORMAT, p2i(_class_loader.ptr_raw()));
 964   out->print_cr(" - metaspace           " INTPTR_FORMAT, p2i(_metaspace));
 965   out->print_cr(" - unloading           %s", _unloading ? "true" : "false");
 966   out->print_cr(" - class mirror holder %s", _has_class_mirror_holder ? "true" : "false");
 967   out->print_cr(" - modified oops       %s", _modified_oops ? "true" : "false");
 968   out->print_cr(" - keep alive          %d", _keep_alive);
 969   out->print   (" - claim               ");
 970   switch(_claim) {
 971     case _claim_none:                       out->print_cr("none"); break;
 972     case _claim_finalizable:                out->print_cr("finalizable"); break;
 973     case _claim_strong:                     out->print_cr("strong"); break;
 974     case _claim_stw_fullgc_mark:            out->print_cr("stw full gc mark"); break;
 975     case _claim_stw_fullgc_adjust:          out->print_cr("stw full gc adjust"); break;
 976     case _claim_other:                      out->print_cr("other"); break;
 977     case _claim_other | _claim_finalizable: out->print_cr("other and finalizable"); break;
 978     case _claim_other | _claim_strong:      out->print_cr("other and strong"); break;
 979     default:                                ShouldNotReachHere();
 980   }
 981   out->print_cr(" - handles             %d", _handles.count());
 982   out->print_cr(" - dependency count    %d", _dependency_count);
 983   out->print   (" - klasses             { ");
 984   if (Verbose) {
 985     PrintKlassClosure closure(out);
 986     ((ClassLoaderData*)this)->classes_do(&closure);
 987   } else {
 988      out->print("...");
 989   }
 990   out->print_cr(" }");
 991   out->print_cr(" - packages            " INTPTR_FORMAT, p2i(_packages));
 992   out->print_cr(" - module              " INTPTR_FORMAT, p2i(_modules));
 993   out->print_cr(" - unnamed module      " INTPTR_FORMAT, p2i(_unnamed_module));
 994   if (_dictionary != nullptr) {
 995     out->print   (" - dictionary          " INTPTR_FORMAT " ", p2i(_dictionary));
 996     _dictionary->print_size(out);
 997   } else {
 998     out->print_cr(" - dictionary          " INTPTR_FORMAT, p2i(_dictionary));
 999   }
1000   if (_jmethod_ids != nullptr) {
1001     out->print   (" - jmethod count       ");
1002     Method::print_jmethod_ids_count(this, out);
1003     out->print_cr("");
1004   }
1005   out->print_cr(" - deallocate list     " INTPTR_FORMAT, p2i(_deallocate_list));
1006   out->print_cr(" - next CLD            " INTPTR_FORMAT, p2i(_next));
1007 }
1008 #endif // PRODUCT
1009 
1010 void ClassLoaderData::print() const { print_on(tty); }
1011 
1012 class VerifyHandleOops : public OopClosure {
1013   VerifyOopClosure vc;
1014  public:
1015   virtual void do_oop(oop* p) {
1016     if (p != nullptr && *p != nullptr) {
1017       oop o = *p;
1018       if (!java_lang_Class::is_instance(o)) {
1019         // is_instance will assert for an invalid oop.
1020         // Walk the resolved_references array and other assorted oops in the
1021         // CLD::_handles field.  The mirror oops are followed by other heap roots.
1022         o->oop_iterate(&vc);
1023       }
1024     }
1025   }
1026   virtual void do_oop(narrowOop* o) { ShouldNotReachHere(); }
1027 };
1028 
1029 void ClassLoaderData::verify() {
1030   assert_locked_or_safepoint(_metaspace_lock);
1031   oop cl = class_loader();
1032 
1033   guarantee(this == class_loader_data(cl) || has_class_mirror_holder(), "Must be the same");
1034   guarantee(cl != nullptr || this == ClassLoaderData::the_null_class_loader_data() || has_class_mirror_holder(), "must be");
1035 
1036   // Verify the integrity of the allocated space.
1037 #ifdef ASSERT
1038   if (metaspace_or_null() != nullptr) {
1039     metaspace_or_null()->verify();
1040   }
1041 #endif
1042 
1043   for (Klass* k = _klasses; k != nullptr; k = k->next_link()) {
1044     guarantee(k->class_loader_data() == this, "Must be the same");
1045     k->verify();
1046     assert(k != k->next_link(), "no loops!");
1047   }
1048 
1049   if (_modules != nullptr) {
1050     _modules->verify();
1051   }
1052 
1053   if (_deallocate_list != nullptr) {
1054     for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
1055       Metadata* m = _deallocate_list->at(i);
1056       if (m->is_klass()) {
1057         ((Klass*)m)->verify();
1058       }
1059     }
1060   }
1061 
1062   // Check the oops in the handles area
1063   VerifyHandleOops vho;
1064   oops_do(&vho, _claim_none, false);
1065 }
1066 
1067 bool ClassLoaderData::contains_klass(Klass* klass) {
1068   // Lock-free access requires load_acquire
1069   for (Klass* k = Atomic::load_acquire(&_klasses); k != nullptr; k = k->next_link()) {
1070     if (k == klass) return true;
1071   }
1072   return false;
1073 }