1  /*
   2  * Copyright (c) 2012, 2018, 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.hpp"
  51 #include "classfile/classLoaderData.inline.hpp"
  52 #include "classfile/dictionary.hpp"
  53 #include "classfile/javaClasses.hpp"
  54 #include "classfile/metadataOnStackMark.hpp"
  55 #include "classfile/moduleEntry.hpp"
  56 #include "classfile/packageEntry.hpp"
  57 #include "classfile/symbolTable.hpp"
  58 #include "classfile/systemDictionary.hpp"
  59 #include "logging/log.hpp"
  60 #include "logging/logStream.hpp"
  61 #include "memory/allocation.inline.hpp"
  62 #include "memory/metadataFactory.hpp"
  63 #include "memory/metaspaceShared.hpp"
  64 #include "memory/resourceArea.hpp"
  65 #include "memory/universe.hpp"
  66 #include "oops/access.inline.hpp"
  67 #include "oops/oop.inline.hpp"
  68 #include "oops/oopHandle.inline.hpp"
  69 #include "oops/weakHandle.inline.hpp"
  70 #include "runtime/atomic.hpp"
  71 #include "runtime/handles.inline.hpp"
  72 #include "runtime/mutex.hpp"
  73 #include "runtime/orderAccess.hpp"
  74 #include "runtime/safepoint.hpp"
  75 #include "runtime/safepointVerifiers.hpp"
  76 #include "utilities/growableArray.hpp"
  77 #include "utilities/macros.hpp"
  78 #include "utilities/ostream.hpp"
  79 
  80 volatile size_t ClassLoaderDataGraph::_num_array_classes = 0;
  81 volatile size_t ClassLoaderDataGraph::_num_instance_classes = 0;
  82 
  83 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
  84 
  85 void ClassLoaderData::init_null_class_loader_data() {
  86   assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
  87   assert(ClassLoaderDataGraph::_head == NULL, "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   Thread* THREAD = Thread::current();
 109   ResourceMark rm(THREAD);
 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 != NULL) {
 115     const char* cl_instance_name = java_lang_String::as_utf8_string(cl_name);
 116 
 117     if (cl_instance_name != NULL && cl_instance_name[0] != '\0') {
 118       // Can't throw InternalError and SymbolTable doesn't throw OOM anymore.
 119       _name = SymbolTable::new_symbol(cl_instance_name, CATCH);
 120     }
 121   }
 122 
 123   // Obtain the class loader's name and identity hash.  If the class loader's
 124   // name was not explicitly set during construction, the class loader's name and id
 125   // will be set to the qualified class name of the class loader along with its
 126   // identity hash.
 127   // If for some reason the ClassLoader's constructor has not been run, instead of
 128   // leaving the _name_and_id field null, fall back to the external qualified class
 129   // name.  Thus CLD's _name_and_id field should never have a null value.
 130   oop cl_name_and_id = java_lang_ClassLoader::nameAndId(class_loader());
 131   const char* cl_instance_name_and_id =
 132                   (cl_name_and_id == NULL) ? _class_loader_klass->external_name() :
 133                                              java_lang_String::as_utf8_string(cl_name_and_id);
 134   assert(cl_instance_name_and_id != NULL && cl_instance_name_and_id[0] != '\0', "class loader has no name and id");
 135   // Can't throw InternalError and SymbolTable doesn't throw OOM anymore.
 136   _name_and_id = SymbolTable::new_symbol(cl_instance_name_and_id, CATCH);
 137 }
 138 
 139 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool is_unsafe_anonymous) :
 140   _metaspace(NULL),
 141   _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true,
 142                             Monitor::_safepoint_check_never)),
 143   _unloading(false), _is_unsafe_anonymous(is_unsafe_anonymous),
 144   _modified_oops(true), _accumulated_modified_oops(false),
 145   // An unsafe anonymous class loader data doesn't have anything to keep
 146   // it from being unloaded during parsing of the unsafe anonymous class.
 147   // The null-class-loader should always be kept alive.
 148   _keep_alive((is_unsafe_anonymous || h_class_loader.is_null()) ? 1 : 0),
 149   _claimed(0),
 150   _handles(),
 151   _klasses(NULL), _packages(NULL), _modules(NULL), _unnamed_module(NULL), _dictionary(NULL),
 152   _jmethod_ids(NULL),
 153   _deallocate_list(NULL),
 154   _next(NULL),
 155   _class_loader_klass(NULL), _name(NULL), _name_and_id(NULL) {
 156 
 157   if (!h_class_loader.is_null()) {
 158     _class_loader = _handles.add(h_class_loader());
 159     _class_loader_klass = h_class_loader->klass();
 160   }
 161 
 162   if (!is_unsafe_anonymous) {
 163     // The holder is initialized later for unsafe anonymous classes, and before calling anything
 164     // that call class_loader().
 165     initialize_holder(h_class_loader);
 166 
 167     // A ClassLoaderData created solely for an unsafe anonymous class should never have a
 168     // ModuleEntryTable or PackageEntryTable created for it. The defining package
 169     // and module for an unsafe anonymous class will be found in its host class.
 170     _packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);
 171     if (h_class_loader.is_null()) {
 172       // Create unnamed module for boot loader
 173       _unnamed_module = ModuleEntry::create_boot_unnamed_module(this);
 174     } else {
 175       // Create unnamed module for all other loaders
 176       _unnamed_module = ModuleEntry::create_unnamed_module(this);
 177     }
 178     _dictionary = create_dictionary();
 179   }
 180 
 181   NOT_PRODUCT(_dependency_count = 0); // number of class loader dependencies
 182 
 183   JFR_ONLY(INIT_ID(this);)
 184 }
 185 
 186 ClassLoaderData::ChunkedHandleList::~ChunkedHandleList() {
 187   Chunk* c = _head;
 188   while (c != NULL) {
 189     Chunk* next = c->_next;
 190     delete c;
 191     c = next;
 192   }
 193 }
 194 
 195 oop* ClassLoaderData::ChunkedHandleList::add(oop o) {
 196   if (_head == NULL || _head->_size == Chunk::CAPACITY) {
 197     Chunk* next = new Chunk(_head);
 198     OrderAccess::release_store(&_head, next);
 199   }
 200   oop* handle = &_head->_data[_head->_size];
 201   *handle = o;
 202   OrderAccess::release_store(&_head->_size, _head->_size + 1);
 203   return handle;
 204 }
 205 
 206 int ClassLoaderData::ChunkedHandleList::count() const {
 207   int count = 0;
 208   Chunk* chunk = _head;
 209   while (chunk != NULL) {
 210     count += chunk->_size;
 211     chunk = chunk->_next;
 212   }
 213   return count;
 214 }
 215 
 216 inline void ClassLoaderData::ChunkedHandleList::oops_do_chunk(OopClosure* f, Chunk* c, const juint size) {
 217   for (juint i = 0; i < size; i++) {
 218     if (c->_data[i] != NULL) {
 219       f->do_oop(&c->_data[i]);
 220     }
 221   }
 222 }
 223 
 224 void ClassLoaderData::ChunkedHandleList::oops_do(OopClosure* f) {
 225   Chunk* head = OrderAccess::load_acquire(&_head);
 226   if (head != NULL) {
 227     // Must be careful when reading size of head
 228     oops_do_chunk(f, head, OrderAccess::load_acquire(&head->_size));
 229     for (Chunk* c = head->_next; c != NULL; c = c->_next) {
 230       oops_do_chunk(f, c, c->_size);
 231     }
 232   }
 233 }
 234 
 235 class VerifyContainsOopClosure : public OopClosure {
 236   oop  _target;
 237   bool _found;
 238 
 239  public:
 240   VerifyContainsOopClosure(oop target) : _target(target), _found(false) {}
 241 
 242   void do_oop(oop* p) {
 243     if (p != NULL && oopDesc::equals(RawAccess<>::oop_load(p), _target)) {
 244       _found = true;
 245     }
 246   }
 247 
 248   void do_oop(narrowOop* p) {
 249     // The ChunkedHandleList should not contain any narrowOop
 250     ShouldNotReachHere();
 251   }
 252 
 253   bool found() const {
 254     return _found;
 255   }
 256 };
 257 
 258 bool ClassLoaderData::ChunkedHandleList::contains(oop p) {
 259   VerifyContainsOopClosure cl(p);
 260   oops_do(&cl);
 261   return cl.found();
 262 }
 263 
 264 #ifndef PRODUCT
 265 bool ClassLoaderData::ChunkedHandleList::owner_of(oop* oop_handle) {
 266   Chunk* chunk = _head;
 267   while (chunk != NULL) {
 268     if (&(chunk->_data[0]) <= oop_handle && oop_handle < &(chunk->_data[chunk->_size])) {
 269       return true;
 270     }
 271     chunk = chunk->_next;
 272   }
 273   return false;
 274 }
 275 #endif // PRODUCT
 276 
 277 bool ClassLoaderData::claim() {
 278   if (_claimed == 1) {
 279     return false;
 280   }
 281 
 282   return (int) Atomic::cmpxchg(1, &_claimed, 0) == 0;
 283 }
 284 
 285 // Unsafe anonymous classes have their own ClassLoaderData that is marked to keep alive
 286 // while the class is being parsed, and if the class appears on the module fixup list.
 287 // Due to the uniqueness that no other class shares the unsafe anonymous class' name or
 288 // ClassLoaderData, no other non-GC thread has knowledge of the unsafe anonymous class while
 289 // it is being defined, therefore _keep_alive is not volatile or atomic.
 290 void ClassLoaderData::inc_keep_alive() {
 291   if (is_unsafe_anonymous()) {
 292     assert(_keep_alive >= 0, "Invalid keep alive increment count");
 293     _keep_alive++;
 294   }
 295 }
 296 
 297 void ClassLoaderData::dec_keep_alive() {
 298   if (is_unsafe_anonymous()) {
 299     assert(_keep_alive > 0, "Invalid keep alive decrement count");
 300     _keep_alive--;
 301   }
 302 }
 303 
 304 void ClassLoaderData::oops_do(OopClosure* f, bool must_claim, bool clear_mod_oops) {
 305   if (must_claim && !claim()) {
 306     return;
 307   }
 308 
 309   // Only clear modified_oops after the ClassLoaderData is claimed.
 310   if (clear_mod_oops) {
 311     clear_modified_oops();
 312   }
 313 
 314   _handles.oops_do(f);
 315 }
 316 
 317 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
 318   // Lock-free access requires load_acquire
 319   for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
 320     klass_closure->do_klass(k);
 321     assert(k != k->next_link(), "no loops!");
 322   }
 323 }
 324 
 325 void ClassLoaderData::classes_do(void f(Klass * const)) {
 326   // Lock-free access requires load_acquire
 327   for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
 328     f(k);
 329     assert(k != k->next_link(), "no loops!");
 330   }
 331 }
 332 
 333 void ClassLoaderData::methods_do(void f(Method*)) {
 334   // Lock-free access requires load_acquire
 335   for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
 336     if (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded()) {
 337       InstanceKlass::cast(k)->methods_do(f);
 338     }
 339   }
 340 }
 341 
 342 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
 343   // Lock-free access requires load_acquire
 344   for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
 345     // Do not filter ArrayKlass oops here...
 346     if (k->is_array_klass() || (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded())) {
 347       klass_closure->do_klass(k);
 348     }
 349   }
 350 }
 351 
 352 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
 353   // Lock-free access requires load_acquire
 354   for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
 355     if (k->is_instance_klass()) {
 356       f(InstanceKlass::cast(k));
 357     }
 358     assert(k != k->next_link(), "no loops!");
 359   }
 360 }
 361 
 362 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
 363   assert_locked_or_safepoint(Module_lock);
 364   if (_unnamed_module != NULL) {
 365     f(_unnamed_module);
 366   }
 367   if (_modules != NULL) {
 368     for (int i = 0; i < _modules->table_size(); i++) {
 369       for (ModuleEntry* entry = _modules->bucket(i);
 370            entry != NULL;
 371            entry = entry->next()) {
 372         f(entry);
 373       }
 374     }
 375   }
 376 }
 377 
 378 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
 379   assert_locked_or_safepoint(Module_lock);
 380   if (_packages != NULL) {
 381     for (int i = 0; i < _packages->table_size(); i++) {
 382       for (PackageEntry* entry = _packages->bucket(i);
 383            entry != NULL;
 384            entry = entry->next()) {
 385         f(entry);
 386       }
 387     }
 388   }
 389 }
 390 
 391 void ClassLoaderData::record_dependency(const Klass* k) {
 392   assert(k != NULL, "invariant");
 393 
 394   ClassLoaderData * const from_cld = this;
 395   ClassLoaderData * const to_cld = k->class_loader_data();
 396 
 397   // Do not need to record dependency if the dependency is to a class whose
 398   // class loader data is never freed.  (i.e. the dependency's class loader
 399   // is one of the three builtin class loaders and the dependency is not
 400   // unsafe anonymous.)
 401   if (to_cld->is_permanent_class_loader_data()) {
 402     return;
 403   }
 404 
 405   oop to;
 406   if (to_cld->is_unsafe_anonymous()) {
 407     // Just return if an unsafe anonymous class is attempting to record a dependency
 408     // to itself.  (Note that every unsafe anonymous class has its own unique class
 409     // loader data.)
 410     if (to_cld == from_cld) {
 411       return;
 412     }
 413     // Unsafe anonymous class dependencies are through the mirror.
 414     to = k->java_mirror();
 415   } else {
 416     to = to_cld->class_loader();
 417     oop from = from_cld->class_loader();
 418 
 419     // Just return if this dependency is to a class with the same or a parent
 420     // class_loader.
 421     if (oopDesc::equals(from, to) || java_lang_ClassLoader::isAncestor(from, to)) {
 422       return; // this class loader is in the parent list, no need to add it.
 423     }
 424   }
 425 
 426   // It's a dependency we won't find through GC, add it.
 427   if (!_handles.contains(to)) {
 428     NOT_PRODUCT(Atomic::inc(&_dependency_count));
 429     LogTarget(Trace, class, loader, data) lt;
 430     if (lt.is_enabled()) {
 431       ResourceMark rm;
 432       LogStream ls(lt);
 433       ls.print("adding dependency from ");
 434       print_value_on(&ls);
 435       ls.print(" to ");
 436       to_cld->print_value_on(&ls);
 437       ls.cr();
 438     }
 439     Handle dependency(Thread::current(), to);
 440     add_handle(dependency);
 441     // Added a potentially young gen oop to the ClassLoaderData
 442     record_modified_oops();
 443   }
 444 }
 445 
 446 
 447 void ClassLoaderDataGraph::clear_claimed_marks() {
 448   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 449     cld->clear_claimed();
 450   }
 451 }
 452 
 453 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
 454   {
 455     MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 456     Klass* old_value = _klasses;
 457     k->set_next_link(old_value);
 458     // Link the new item into the list, making sure the linked class is stable
 459     // since the list can be walked without a lock
 460     OrderAccess::release_store(&_klasses, k);
 461     if (k->is_array_klass()) {
 462       ClassLoaderDataGraph::inc_array_classes(1);
 463     } else {
 464       ClassLoaderDataGraph::inc_instance_classes(1);
 465     }
 466   }
 467 
 468   if (publicize) {
 469     LogTarget(Trace, class, loader, data) lt;
 470     if (lt.is_enabled()) {
 471       ResourceMark rm;
 472       LogStream ls(lt);
 473       ls.print("Adding k: " PTR_FORMAT " %s to ", p2i(k), k->external_name());
 474       print_value_on(&ls);
 475       ls.cr();
 476     }
 477   }
 478 }
 479 
 480 // Class iterator used by the compiler.  It gets some number of classes at
 481 // a safepoint to decay invocation counters on the methods.
 482 class ClassLoaderDataGraphKlassIteratorStatic {
 483   ClassLoaderData* _current_loader_data;
 484   Klass*           _current_class_entry;
 485  public:
 486 
 487   ClassLoaderDataGraphKlassIteratorStatic() : _current_loader_data(NULL), _current_class_entry(NULL) {}
 488 
 489   InstanceKlass* try_get_next_class() {
 490     assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 491     size_t max_classes = ClassLoaderDataGraph::num_instance_classes();
 492     assert(max_classes > 0, "should not be called with no instance classes");
 493     for (size_t i = 0; i < max_classes; ) {
 494 
 495       if (_current_class_entry != NULL) {
 496         Klass* k = _current_class_entry;
 497         _current_class_entry = _current_class_entry->next_link();
 498 
 499         if (k->is_instance_klass()) {
 500           InstanceKlass* ik = InstanceKlass::cast(k);
 501           i++;  // count all instance classes found
 502           // Not yet loaded classes are counted in max_classes
 503           // but only return loaded classes.
 504           if (ik->is_loaded()) {
 505             return ik;
 506           }
 507         }
 508       } else {
 509         // Go to next CLD
 510         if (_current_loader_data != NULL) {
 511           _current_loader_data = _current_loader_data->next();
 512         }
 513         // Start at the beginning
 514         if (_current_loader_data == NULL) {
 515           _current_loader_data = ClassLoaderDataGraph::_head;
 516         }
 517 
 518         _current_class_entry = _current_loader_data->klasses();
 519       }
 520     }
 521     // Should never be reached unless all instance classes have failed or are not fully loaded.
 522     // Caller handles NULL.
 523     return NULL;
 524   }
 525 
 526   // If the current class for the static iterator is a class being unloaded or
 527   // deallocated, adjust the current class.
 528   void adjust_saved_class(ClassLoaderData* cld) {
 529     if (_current_loader_data == cld) {
 530       _current_loader_data = cld->next();
 531       if (_current_loader_data != NULL) {
 532         _current_class_entry = _current_loader_data->klasses();
 533       }  // else try_get_next_class will start at the head
 534     }
 535   }
 536 
 537   void adjust_saved_class(Klass* klass) {
 538     if (_current_class_entry == klass) {
 539       _current_class_entry = klass->next_link();
 540     }
 541   }
 542 };
 543 
 544 static ClassLoaderDataGraphKlassIteratorStatic static_klass_iterator;
 545 
 546 InstanceKlass* ClassLoaderDataGraph::try_get_next_class() {
 547   return static_klass_iterator.try_get_next_class();
 548 }
 549 
 550 
 551 void ClassLoaderData::initialize_holder(Handle loader_or_mirror) {
 552   if (loader_or_mirror() != NULL) {
 553     assert(_holder.is_null(), "never replace holders");
 554     _holder = WeakHandle<vm_class_loader_data>::create(loader_or_mirror);
 555   }
 556 }
 557 
 558 // Remove a klass from the _klasses list for scratch_class during redefinition
 559 // or parsed class in the case of an error.
 560 void ClassLoaderData::remove_class(Klass* scratch_class) {
 561   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 562 
 563   // Adjust global class iterator.
 564   static_klass_iterator.adjust_saved_class(scratch_class);
 565 
 566   Klass* prev = NULL;
 567   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 568     if (k == scratch_class) {
 569       if (prev == NULL) {
 570         _klasses = k->next_link();
 571       } else {
 572         Klass* next = k->next_link();
 573         prev->set_next_link(next);
 574       }
 575 
 576       if (k->is_array_klass()) {
 577         ClassLoaderDataGraph::dec_array_classes(1);
 578       } else {
 579         ClassLoaderDataGraph::dec_instance_classes(1);
 580       }
 581 
 582       return;
 583     }
 584     prev = k;
 585     assert(k != k->next_link(), "no loops!");
 586   }
 587   ShouldNotReachHere();   // should have found this class!!
 588 }
 589 
 590 void ClassLoaderData::unload() {
 591   _unloading = true;
 592 
 593   LogTarget(Trace, class, loader, data) lt;
 594   if (lt.is_enabled()) {
 595     ResourceMark rm;
 596     LogStream ls(lt);
 597     ls.print("unload");
 598     print_value_on(&ls);
 599     ls.cr();
 600   }
 601 
 602   // Some items on the _deallocate_list need to free their C heap structures
 603   // if they are not already on the _klasses list.
 604   free_deallocate_list_C_heap_structures();
 605 
 606   // Tell serviceability tools these classes are unloading
 607   // after erroneous classes are released.
 608   classes_do(InstanceKlass::notify_unload_class);
 609 
 610   // Clean up global class iterator for compiler
 611   static_klass_iterator.adjust_saved_class(this);
 612 }
 613 
 614 ModuleEntryTable* ClassLoaderData::modules() {
 615   // Lazily create the module entry table at first request.
 616   // Lock-free access requires load_acquire.
 617   ModuleEntryTable* modules = OrderAccess::load_acquire(&_modules);
 618   if (modules == NULL) {
 619     MutexLocker m1(Module_lock);
 620     // Check if _modules got allocated while we were waiting for this lock.
 621     if ((modules = _modules) == NULL) {
 622       modules = new ModuleEntryTable(ModuleEntryTable::_moduletable_entry_size);
 623 
 624       {
 625         MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 626         // Ensure _modules is stable, since it is examined without a lock
 627         OrderAccess::release_store(&_modules, modules);
 628       }
 629     }
 630   }
 631   return modules;
 632 }
 633 
 634 const int _boot_loader_dictionary_size    = 1009;
 635 const int _default_loader_dictionary_size = 107;
 636 
 637 Dictionary* ClassLoaderData::create_dictionary() {
 638   assert(!is_unsafe_anonymous(), "unsafe anonymous class loader data do not have a dictionary");
 639   int size;
 640   bool resizable = false;
 641   if (_the_null_class_loader_data == NULL) {
 642     size = _boot_loader_dictionary_size;
 643     resizable = true;
 644   } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
 645     size = 1;  // there's only one class in relection class loader and no initiated classes
 646   } else if (is_system_class_loader_data()) {
 647     size = _boot_loader_dictionary_size;
 648     resizable = true;
 649   } else {
 650     size = _default_loader_dictionary_size;
 651     resizable = true;
 652   }
 653   if (!DynamicallyResizeSystemDictionaries || DumpSharedSpaces || UseSharedSpaces) {
 654     resizable = false;
 655   }
 656   return new Dictionary(this, size, resizable);
 657 }
 658 
 659 // Tell the GC to keep this klass alive while iterating ClassLoaderDataGraph
 660 oop ClassLoaderData::holder_phantom() const {
 661   // A klass that was previously considered dead can be looked up in the
 662   // CLD/SD, and its _java_mirror or _class_loader can be stored in a root
 663   // or a reachable object making it alive again. The SATB part of G1 needs
 664   // to get notified about this potential resurrection, otherwise the marking
 665   // might not find the object.
 666   if (!_holder.is_null()) {  // NULL class_loader
 667     return _holder.resolve();
 668   } else {
 669     return NULL;
 670   }
 671 }
 672 
 673 // Unloading support
 674 bool ClassLoaderData::is_alive() const {
 675   bool alive = keep_alive()         // null class loader and incomplete unsafe anonymous klasses.
 676       || (_holder.peek() != NULL);  // and not cleaned by the GC weak handle processing.
 677 
 678   return alive;
 679 }
 680 
 681 class ReleaseKlassClosure: public KlassClosure {
 682 private:
 683   size_t  _instance_class_released;
 684   size_t  _array_class_released;
 685 public:
 686   ReleaseKlassClosure() : _instance_class_released(0), _array_class_released(0) { }
 687 
 688   size_t instance_class_released() const { return _instance_class_released; }
 689   size_t array_class_released()    const { return _array_class_released;    }
 690 
 691   void do_klass(Klass* k) {
 692     if (k->is_array_klass()) {
 693       _array_class_released ++;
 694     } else {
 695       assert(k->is_instance_klass(), "Must be");
 696       _instance_class_released ++;
 697       InstanceKlass::release_C_heap_structures(InstanceKlass::cast(k));
 698     }
 699   }
 700 };
 701 
 702 ClassLoaderData::~ClassLoaderData() {
 703   // Release C heap structures for all the classes.
 704   ReleaseKlassClosure cl;
 705   classes_do(&cl);
 706 
 707   ClassLoaderDataGraph::dec_array_classes(cl.array_class_released());
 708   ClassLoaderDataGraph::dec_instance_classes(cl.instance_class_released());
 709 
 710   // Release the WeakHandle
 711   _holder.release();
 712 
 713   // Release C heap allocated hashtable for all the packages.
 714   if (_packages != NULL) {
 715     // Destroy the table itself
 716     delete _packages;
 717     _packages = NULL;
 718   }
 719 
 720   // Release C heap allocated hashtable for all the modules.
 721   if (_modules != NULL) {
 722     // Destroy the table itself
 723     delete _modules;
 724     _modules = NULL;
 725   }
 726 
 727   // Release C heap allocated hashtable for the dictionary
 728   if (_dictionary != NULL) {
 729     // Destroy the table itself
 730     delete _dictionary;
 731     _dictionary = NULL;
 732   }
 733 
 734   if (_unnamed_module != NULL) {
 735     _unnamed_module->delete_unnamed_module();
 736     _unnamed_module = NULL;
 737   }
 738 
 739   // release the metaspace
 740   ClassLoaderMetaspace *m = _metaspace;
 741   if (m != NULL) {
 742     _metaspace = NULL;
 743     delete m;
 744   }
 745   // Clear all the JNI handles for methods
 746   // These aren't deallocated and are going to look like a leak, but that's
 747   // needed because we can't really get rid of jmethodIDs because we don't
 748   // know when native code is going to stop using them.  The spec says that
 749   // they're "invalid" but existing programs likely rely on their being
 750   // NULL after class unloading.
 751   if (_jmethod_ids != NULL) {
 752     Method::clear_jmethod_ids(this);
 753   }
 754   // Delete lock
 755   delete _metaspace_lock;
 756 
 757   // Delete free list
 758   if (_deallocate_list != NULL) {
 759     delete _deallocate_list;
 760   }
 761 }
 762 
 763 // Returns true if this class loader data is for the app class loader
 764 // or a user defined system class loader.  (Note that the class loader
 765 // data may be unsafe anonymous.)
 766 bool ClassLoaderData::is_system_class_loader_data() const {
 767   return SystemDictionary::is_system_class_loader(class_loader());
 768 }
 769 
 770 // Returns true if this class loader data is for the platform class loader.
 771 // (Note that the class loader data may be unsafe anonymous.)
 772 bool ClassLoaderData::is_platform_class_loader_data() const {
 773   return SystemDictionary::is_platform_class_loader(class_loader());
 774 }
 775 
 776 // Returns true if the class loader for this class loader data is one of
 777 // the 3 builtin (boot application/system or platform) class loaders,
 778 // including a user-defined system class loader.  Note that if the class
 779 // loader data is for an unsafe anonymous class then it may get freed by a GC
 780 // even if its class loader is one of these loaders.
 781 bool ClassLoaderData::is_builtin_class_loader_data() const {
 782   return (is_boot_class_loader_data() ||
 783           SystemDictionary::is_system_class_loader(class_loader()) ||
 784           SystemDictionary::is_platform_class_loader(class_loader()));
 785 }
 786 
 787 // Returns true if this class loader data is a class loader data
 788 // that is not ever freed by a GC.  It must be the CLD for one of the builtin
 789 // class loaders and not the CLD for an unsafe anonymous class.
 790 bool ClassLoaderData::is_permanent_class_loader_data() const {
 791   return is_builtin_class_loader_data() && !is_unsafe_anonymous();
 792 }
 793 
 794 ClassLoaderMetaspace* ClassLoaderData::metaspace_non_null() {
 795   // If the metaspace has not been allocated, create a new one.  Might want
 796   // to create smaller arena for Reflection class loaders also.
 797   // The reason for the delayed allocation is because some class loaders are
 798   // simply for delegating with no metadata of their own.
 799   // Lock-free access requires load_acquire.
 800   ClassLoaderMetaspace* metaspace = OrderAccess::load_acquire(&_metaspace);
 801   if (metaspace == NULL) {
 802     MutexLockerEx ml(_metaspace_lock,  Mutex::_no_safepoint_check_flag);
 803     // Check if _metaspace got allocated while we were waiting for this lock.
 804     if ((metaspace = _metaspace) == NULL) {
 805       if (this == the_null_class_loader_data()) {
 806         assert (class_loader() == NULL, "Must be");
 807         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
 808       } else if (is_unsafe_anonymous()) {
 809         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::UnsafeAnonymousMetaspaceType);
 810       } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
 811         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
 812       } else {
 813         metaspace = new ClassLoaderMetaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
 814       }
 815       // Ensure _metaspace is stable, since it is examined without a lock
 816       OrderAccess::release_store(&_metaspace, metaspace);
 817     }
 818   }
 819   return metaspace;
 820 }
 821 
 822 OopHandle ClassLoaderData::add_handle(Handle h) {
 823   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 824   record_modified_oops();
 825   return OopHandle(_handles.add(h()));
 826 }
 827 
 828 void ClassLoaderData::remove_handle(OopHandle h) {
 829   assert(!is_unloading(), "Do not remove a handle for a CLD that is unloading");
 830   oop* ptr = h.ptr_raw();
 831   if (ptr != NULL) {
 832     assert(_handles.owner_of(ptr), "Got unexpected handle " PTR_FORMAT, p2i(ptr));
 833     NativeAccess<>::oop_store(ptr, oop(NULL));
 834   }
 835 }
 836 
 837 void ClassLoaderData::init_handle_locked(OopHandle& dest, Handle h) {
 838   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 839   if (dest.resolve() != NULL) {
 840     return;
 841   } else {
 842     dest = _handles.add(h());
 843   }
 844 }
 845 
 846 // Add this metadata pointer to be freed when it's safe.  This is only during
 847 // a safepoint which checks if handles point to this metadata field.
 848 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
 849   // Metadata in shared region isn't deleted.
 850   if (!m->is_shared()) {
 851     MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 852     if (_deallocate_list == NULL) {
 853       _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, true);
 854     }
 855     _deallocate_list->append_if_missing(m);
 856     log_debug(class, loader, data)("deallocate added for %s", m->print_value_string());
 857     ClassLoaderDataGraph::set_should_clean_deallocate_lists();
 858   }
 859 }
 860 
 861 // Deallocate free metadata on the free list.  How useful the PermGen was!
 862 void ClassLoaderData::free_deallocate_list() {
 863   // Don't need lock, at safepoint
 864   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 865   assert(!is_unloading(), "only called for ClassLoaderData that are not unloading");
 866   if (_deallocate_list == NULL) {
 867     return;
 868   }
 869   // Go backwards because this removes entries that are freed.
 870   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 871     Metadata* m = _deallocate_list->at(i);
 872     if (!m->on_stack()) {
 873       _deallocate_list->remove_at(i);
 874       // There are only three types of metadata that we deallocate directly.
 875       // Cast them so they can be used by the template function.
 876       if (m->is_method()) {
 877         MetadataFactory::free_metadata(this, (Method*)m);
 878       } else if (m->is_constantPool()) {
 879         MetadataFactory::free_metadata(this, (ConstantPool*)m);
 880       } else if (m->is_klass()) {
 881         MetadataFactory::free_metadata(this, (InstanceKlass*)m);
 882       } else {
 883         ShouldNotReachHere();
 884       }
 885     } else {
 886       // Metadata is alive.
 887       // If scratch_class is on stack then it shouldn't be on this list!
 888       assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
 889              "scratch classes on this list should be dead");
 890       // Also should assert that other metadata on the list was found in handles.
 891       // Some cleaning remains.
 892       ClassLoaderDataGraph::set_should_clean_deallocate_lists();
 893     }
 894   }
 895 }
 896 
 897 void ClassLoaderDataGraph::clean_deallocate_lists(bool walk_previous_versions) {
 898   uint loaders_processed = 0;
 899   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 900     // is_alive check will be necessary for concurrent class unloading.
 901     if (cld->is_alive()) {
 902       // clean metaspace
 903       if (walk_previous_versions) {
 904         cld->classes_do(InstanceKlass::purge_previous_versions);
 905       }
 906       cld->free_deallocate_list();
 907       loaders_processed++;
 908     }
 909   }
 910   log_debug(class, loader, data)("clean_deallocate_lists: loaders processed %u %s",
 911                                  loaders_processed, walk_previous_versions ? "walk_previous_versions" : "");
 912 }
 913 
 914 void ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces() {
 915   assert(SafepointSynchronize::is_at_safepoint(), "must only be called at safepoint");
 916 
 917   _should_clean_deallocate_lists = false; // assume everything gets cleaned
 918 
 919   // Mark metadata seen on the stack so we can delete unreferenced entries.
 920   // Walk all metadata, including the expensive code cache walk, only for class redefinition.
 921   // The MetadataOnStackMark walk during redefinition saves previous versions if it finds old methods
 922   // on the stack or in the code cache, so we only have to repeat the full walk if
 923   // they were found at that time.
 924   // TODO: have redefinition clean old methods out of the code cache.  They still exist in some places.
 925   bool walk_all_metadata = InstanceKlass::has_previous_versions_and_reset();
 926 
 927   MetadataOnStackMark md_on_stack(walk_all_metadata);
 928   clean_deallocate_lists(walk_all_metadata);
 929 }
 930 
 931 // This is distinct from free_deallocate_list.  For class loader data that are
 932 // unloading, this frees the C heap memory for items on the list, and unlinks
 933 // scratch or error classes so that unloading events aren't triggered for these
 934 // classes. The metadata is removed with the unloading metaspace.
 935 // There isn't C heap memory allocated for methods, so nothing is done for them.
 936 void ClassLoaderData::free_deallocate_list_C_heap_structures() {
 937   // Don't need lock, at safepoint
 938   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 939   assert(is_unloading(), "only called for ClassLoaderData that are unloading");
 940   if (_deallocate_list == NULL) {
 941     return;
 942   }
 943   // Go backwards because this removes entries that are freed.
 944   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 945     Metadata* m = _deallocate_list->at(i);
 946     _deallocate_list->remove_at(i);
 947     if (m->is_constantPool()) {
 948       ((ConstantPool*)m)->release_C_heap_structures();
 949     } else if (m->is_klass()) {
 950       InstanceKlass* ik = (InstanceKlass*)m;
 951       // also releases ik->constants() C heap memory
 952       InstanceKlass::release_C_heap_structures(ik);
 953       // Remove the class so unloading events aren't triggered for
 954       // this class (scratch or error class) in do_unloading().
 955       remove_class(ik);
 956     }
 957   }
 958 }
 959 
 960 // These CLDs are to contain unsafe anonymous classes used for JSR292
 961 ClassLoaderData* ClassLoaderData::unsafe_anonymous_class_loader_data(Handle loader) {
 962   // Add a new class loader data to the graph.
 963   return ClassLoaderDataGraph::add(loader, true);
 964 }
 965 
 966 // Caller needs ResourceMark
 967 // If the class loader's _name has not been explicitly set, the class loader's
 968 // qualified class name is returned.
 969 const char* ClassLoaderData::loader_name() const {
 970    if (_class_loader_klass == NULL) {
 971      return BOOTSTRAP_LOADER_NAME;
 972    } else if (_name != NULL) {
 973      return _name->as_C_string();
 974    } else {
 975      return _class_loader_klass->external_name();
 976    }
 977 }
 978 
 979 // Caller needs ResourceMark
 980 // Format of the _name_and_id is as follows:
 981 //   If the defining loader has a name explicitly set then '<loader-name>' @<id>
 982 //   If the defining loader has no name then <qualified-class-name> @<id>
 983 //   If built-in loader, then omit '@<id>' as there is only one instance.
 984 const char* ClassLoaderData::loader_name_and_id() const {
 985   if (_class_loader_klass == NULL) {
 986     return "'" BOOTSTRAP_LOADER_NAME "'";
 987   } else if (_name_and_id != NULL) {
 988     return _name_and_id->as_C_string();
 989   } else {
 990     // May be called in a race before _name_and_id is initialized.
 991     return _class_loader_klass->external_name();
 992   }
 993 }
 994 
 995 void ClassLoaderData::print_value_on(outputStream* out) const {
 996   if (!is_unloading() && class_loader() != NULL) {
 997     out->print("loader data: " INTPTR_FORMAT " for instance ", p2i(this));
 998     class_loader()->print_value_on(out);  // includes loader_name_and_id() and address of class loader instance
 999   } else {
1000     // loader data: 0xsomeaddr of 'bootstrap'
1001     out->print("loader data: " INTPTR_FORMAT " of %s", p2i(this), loader_name_and_id());
1002   }
1003   if (is_unsafe_anonymous()) {
1004     out->print(" unsafe anonymous");
1005   }
1006 }
1007 
1008 #ifndef PRODUCT
1009 void ClassLoaderData::print_on(outputStream* out) const {
1010   out->print("ClassLoaderData CLD: " PTR_FORMAT ", loader: " PTR_FORMAT ", loader_klass: %s {",
1011               p2i(this), p2i(_class_loader.ptr_raw()), loader_name_and_id());
1012   if (is_unsafe_anonymous()) out->print(" unsafe anonymous");
1013   if (claimed()) out->print(" claimed");
1014   if (is_unloading()) out->print(" unloading");
1015   out->print(" metaspace: " INTPTR_FORMAT, p2i(metaspace_or_null()));
1016 
1017   if (_jmethod_ids != NULL) {
1018     Method::print_jmethod_ids(this, out);
1019   }
1020   out->print(" handles count %d", _handles.count());
1021   out->print(" dependencies %d", _dependency_count);
1022   out->print_cr("}");
1023 }
1024 #endif // PRODUCT
1025 
1026 void ClassLoaderData::verify() {
1027   assert_locked_or_safepoint(_metaspace_lock);
1028   oop cl = class_loader();
1029 
1030   guarantee(this == class_loader_data(cl) || is_unsafe_anonymous(), "Must be the same");
1031   guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || is_unsafe_anonymous(), "must be");
1032 
1033   // Verify the integrity of the allocated space.
1034   if (metaspace_or_null() != NULL) {
1035     metaspace_or_null()->verify();
1036   }
1037 
1038   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
1039     guarantee(k->class_loader_data() == this, "Must be the same");
1040     k->verify();
1041     assert(k != k->next_link(), "no loops!");
1042   }
1043 }
1044 
1045 bool ClassLoaderData::contains_klass(Klass* klass) {
1046   // Lock-free access requires load_acquire
1047   for (Klass* k = OrderAccess::load_acquire(&_klasses); k != NULL; k = k->next_link()) {
1048     if (k == klass) return true;
1049   }
1050   return false;
1051 }
1052 
1053 
1054 // GC root of class loader data created.
1055 ClassLoaderData* ClassLoaderDataGraph::_head = NULL;
1056 ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;
1057 ClassLoaderData* ClassLoaderDataGraph::_saved_unloading = NULL;
1058 ClassLoaderData* ClassLoaderDataGraph::_saved_head = NULL;
1059 
1060 bool ClassLoaderDataGraph::_should_purge = false;
1061 bool ClassLoaderDataGraph::_should_clean_deallocate_lists = false;
1062 bool ClassLoaderDataGraph::_safepoint_cleanup_needed = false;
1063 bool ClassLoaderDataGraph::_metaspace_oom = false;
1064 
1065 // Add a new class loader data node to the list.  Assign the newly created
1066 // ClassLoaderData into the java/lang/ClassLoader object as a hidden field
1067 ClassLoaderData* ClassLoaderDataGraph::add_to_graph(Handle loader, bool is_unsafe_anonymous) {
1068   NoSafepointVerifier no_safepoints; // we mustn't GC until we've installed the
1069                                      // ClassLoaderData in the graph since the CLD
1070                                      // contains oops in _handles that must be walked.
1071 
1072   ClassLoaderData* cld = new ClassLoaderData(loader, is_unsafe_anonymous);
1073 
1074   if (!is_unsafe_anonymous) {
1075     // First, Atomically set it
1076     ClassLoaderData* old = java_lang_ClassLoader::cmpxchg_loader_data(cld, loader(), NULL);
1077     if (old != NULL) {
1078       delete cld;
1079       // Returns the data.
1080       return old;
1081     }
1082   }
1083 
1084   // We won the race, and therefore the task of adding the data to the list of
1085   // class loader data
1086   ClassLoaderData** list_head = &_head;
1087   ClassLoaderData* next = _head;
1088 
1089   do {
1090     cld->set_next(next);
1091     ClassLoaderData* exchanged = Atomic::cmpxchg(cld, list_head, next);
1092     if (exchanged == next) {
1093       LogTarget(Trace, class, loader, data) lt;
1094       if (lt.is_enabled()) {
1095         ResourceMark rm;
1096         LogStream ls(lt);
1097         ls.print("create ");
1098         cld->print_value_on(&ls);
1099         ls.cr();
1100       }
1101       return cld;
1102     }
1103     next = exchanged;
1104   } while (true);
1105 }
1106 
1107 ClassLoaderData* ClassLoaderDataGraph::add(Handle loader, bool is_unsafe_anonymous) {
1108   ClassLoaderData* loader_data = add_to_graph(loader, is_unsafe_anonymous);
1109   // Initialize _name and _name_and_id after the loader data is added to the
1110   // CLDG because adding the Symbol for _name and _name_and_id might safepoint.
1111   if (loader.not_null()) {
1112     loader_data->initialize_name(loader);
1113   }
1114   return loader_data;
1115 }
1116 
1117 void ClassLoaderDataGraph::cld_do(CLDClosure* cl) {
1118   for (ClassLoaderData* cld = _head; cl != NULL && cld != NULL; cld = cld->next()) {
1119     cl->do_cld(cld);
1120   }
1121 }
1122 
1123 void ClassLoaderDataGraph::cld_unloading_do(CLDClosure* cl) {
1124   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1125   // Only walk the head until any clds not purged from prior unloading
1126   // (CMS doesn't purge right away).
1127   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
1128     assert(cld->is_unloading(), "invariant");
1129     cl->do_cld(cld);
1130   }
1131 }
1132 
1133 void ClassLoaderDataGraph::roots_cld_do(CLDClosure* strong, CLDClosure* weak) {
1134   for (ClassLoaderData* cld = _head;  cld != NULL; cld = cld->_next) {
1135     CLDClosure* closure = cld->keep_alive() ? strong : weak;
1136     if (closure != NULL) {
1137       closure->do_cld(cld);
1138     }
1139   }
1140 }
1141 
1142 void ClassLoaderDataGraph::always_strong_cld_do(CLDClosure* cl) {
1143   if (ClassUnloading) {
1144     roots_cld_do(cl, NULL);
1145   } else {
1146     cld_do(cl);
1147   }
1148 }
1149 
1150 void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
1151   Thread* thread = Thread::current();
1152   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1153     Handle holder(thread, cld->holder_phantom());
1154     cld->classes_do(klass_closure);
1155   }
1156 }
1157 
1158 void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
1159   Thread* thread = Thread::current();
1160   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1161     Handle holder(thread, cld->holder_phantom());
1162     cld->classes_do(f);
1163   }
1164 }
1165 
1166 void ClassLoaderDataGraph::methods_do(void f(Method*)) {
1167   Thread* thread = Thread::current();
1168   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1169     Handle holder(thread, cld->holder_phantom());
1170     cld->methods_do(f);
1171   }
1172 }
1173 
1174 void ClassLoaderDataGraph::modules_do(void f(ModuleEntry*)) {
1175   assert_locked_or_safepoint(Module_lock);
1176   Thread* thread = Thread::current();
1177   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1178     Handle holder(thread, cld->holder_phantom());
1179     cld->modules_do(f);
1180   }
1181 }
1182 
1183 void ClassLoaderDataGraph::modules_unloading_do(void f(ModuleEntry*)) {
1184   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1185   // Only walk the head until any clds not purged from prior unloading
1186   // (CMS doesn't purge right away).
1187   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
1188     assert(cld->is_unloading(), "invariant");
1189     cld->modules_do(f);
1190   }
1191 }
1192 
1193 void ClassLoaderDataGraph::packages_do(void f(PackageEntry*)) {
1194   assert_locked_or_safepoint(Module_lock);
1195   Thread* thread = Thread::current();
1196   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1197     Handle holder(thread, cld->holder_phantom());
1198     cld->packages_do(f);
1199   }
1200 }
1201 
1202 void ClassLoaderDataGraph::packages_unloading_do(void f(PackageEntry*)) {
1203   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1204   // Only walk the head until any clds not purged from prior unloading
1205   // (CMS doesn't purge right away).
1206   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
1207     assert(cld->is_unloading(), "invariant");
1208     cld->packages_do(f);
1209   }
1210 }
1211 
1212 void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
1213   Thread* thread = Thread::current();
1214   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
1215     Handle holder(thread, cld->holder_phantom());
1216     cld->loaded_classes_do(klass_closure);
1217   }
1218 }
1219 
1220 void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
1221   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1222   // Only walk the head until any clds not purged from prior unloading
1223   // (CMS doesn't purge right away).
1224   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
1225     assert(cld->is_unloading(), "invariant");
1226     cld->classes_do(f);
1227   }
1228 }
1229 
1230 #define FOR_ALL_DICTIONARY(X) for (ClassLoaderData* X = _head; X != NULL; X = X->next()) \
1231                                 if (X->dictionary() != NULL)
1232 
1233 // Walk classes in the loaded class dictionaries in various forms.
1234 // Only walks the classes defined in this class loader.
1235 void ClassLoaderDataGraph::dictionary_classes_do(void f(InstanceKlass*)) {
1236   Thread* thread = Thread::current();
1237   FOR_ALL_DICTIONARY(cld) {
1238     Handle holder(thread, cld->holder_phantom());
1239     cld->dictionary()->classes_do(f);
1240   }
1241 }
1242 
1243 // Only walks the classes defined in this class loader.
1244 void ClassLoaderDataGraph::dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS) {
1245   Thread* thread = Thread::current();
1246   FOR_ALL_DICTIONARY(cld) {
1247     Handle holder(thread, cld->holder_phantom());
1248     cld->dictionary()->classes_do(f, CHECK);
1249   }
1250 }
1251 
1252 // Walks all entries in the dictionary including entries initiated by this class loader.
1253 void ClassLoaderDataGraph::dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*)) {
1254   Thread* thread = Thread::current();
1255   FOR_ALL_DICTIONARY(cld) {
1256     Handle holder(thread, cld->holder_phantom());
1257     cld->dictionary()->all_entries_do(f);
1258   }
1259 }
1260 
1261 void ClassLoaderDataGraph::verify_dictionary() {
1262   FOR_ALL_DICTIONARY(cld) {
1263     cld->dictionary()->verify();
1264   }
1265 }
1266 
1267 void ClassLoaderDataGraph::print_dictionary(outputStream* st) {
1268   FOR_ALL_DICTIONARY(cld) {
1269     st->print("Dictionary for ");
1270     cld->print_value_on(st);
1271     st->cr();
1272     cld->dictionary()->print_on(st);
1273     st->cr();
1274   }
1275 }
1276 
1277 void ClassLoaderDataGraph::print_dictionary_statistics(outputStream* st) {
1278   FOR_ALL_DICTIONARY(cld) {
1279     ResourceMark rm;
1280     stringStream tempst;
1281     tempst.print("System Dictionary for %s class loader", cld->loader_name_and_id());
1282     cld->dictionary()->print_table_statistics(st, tempst.as_string());
1283   }
1284 }
1285 
1286 GrowableArray<ClassLoaderData*>* ClassLoaderDataGraph::new_clds() {
1287   assert(_head == NULL || _saved_head != NULL, "remember_new_clds(true) not called?");
1288 
1289   GrowableArray<ClassLoaderData*>* array = new GrowableArray<ClassLoaderData*>();
1290 
1291   // The CLDs in [_head, _saved_head] were all added during last call to remember_new_clds(true);
1292   ClassLoaderData* curr = _head;
1293   while (curr != _saved_head) {
1294     if (!curr->claimed()) {
1295       array->push(curr);
1296       LogTarget(Debug, class, loader, data) lt;
1297       if (lt.is_enabled()) {
1298         LogStream ls(lt);
1299         ls.print("found new CLD: ");
1300         curr->print_value_on(&ls);
1301         ls.cr();
1302       }
1303     }
1304 
1305     curr = curr->_next;
1306   }
1307 
1308   return array;
1309 }
1310 
1311 #ifndef PRODUCT
1312 bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {
1313   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
1314     if (loader_data == data) {
1315       return true;
1316     }
1317   }
1318 
1319   return false;
1320 }
1321 #endif // PRODUCT
1322 
1323 // Move class loader data from main list to the unloaded list for unloading
1324 // and deallocation later.
1325 bool ClassLoaderDataGraph::do_unloading(bool do_cleaning) {
1326 
1327   // Indicate whether safepoint cleanup is needed.
1328   _safepoint_cleanup_needed |= do_cleaning;
1329 
1330   ClassLoaderData* data = _head;
1331   ClassLoaderData* prev = NULL;
1332   bool seen_dead_loader = false;
1333   uint loaders_processed = 0;
1334   uint loaders_removed = 0;
1335 
1336   // Save previous _unloading pointer for CMS which may add to unloading list before
1337   // purging and we don't want to rewalk the previously unloaded class loader data.
1338   _saved_unloading = _unloading;
1339 
1340   data = _head;
1341   while (data != NULL) {
1342     if (data->is_alive()) {
1343       prev = data;
1344       data = data->next();
1345       loaders_processed++;
1346       continue;
1347     }
1348     seen_dead_loader = true;
1349     loaders_removed++;
1350     ClassLoaderData* dead = data;
1351     dead->unload();
1352     data = data->next();
1353     // Remove from loader list.
1354     // This class loader data will no longer be found
1355     // in the ClassLoaderDataGraph.
1356     if (prev != NULL) {
1357       prev->set_next(data);
1358     } else {
1359       assert(dead == _head, "sanity check");
1360       _head = data;
1361     }
1362     dead->set_next(_unloading);
1363     _unloading = dead;
1364   }
1365 
1366   log_debug(class, loader, data)("do_unloading: loaders processed %u, loaders removed %u", loaders_processed, loaders_removed);
1367 
1368   return seen_dead_loader;
1369 }
1370 
1371 // There's at least one dead class loader.  Purge refererences of healthy module
1372 // reads lists and package export lists to modules belonging to dead loaders.
1373 void ClassLoaderDataGraph::clean_module_and_package_info() {
1374   ClassLoaderData* data = _head;
1375   while (data != NULL) {
1376     // Remove entries in the dictionary of live class loader that have
1377     // initiated loading classes in a dead class loader.
1378     if (data->dictionary() != NULL) {
1379       data->dictionary()->do_unloading();
1380     }
1381     // Walk a ModuleEntry's reads, and a PackageEntry's exports
1382     // lists to determine if there are modules on those lists that are now
1383     // dead and should be removed.  A module's life cycle is equivalent
1384     // to its defining class loader's life cycle.  Since a module is
1385     // considered dead if its class loader is dead, these walks must
1386     // occur after each class loader's aliveness is determined.
1387     if (data->packages() != NULL) {
1388       data->packages()->purge_all_package_exports();
1389     }
1390     if (data->modules_defined()) {
1391       data->modules()->purge_all_module_reads();
1392     }
1393     data = data->next();
1394   }
1395 }
1396 
1397 void ClassLoaderDataGraph::purge() {
1398   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1399   ClassLoaderData* list = _unloading;
1400   _unloading = NULL;
1401   ClassLoaderData* next = list;
1402   bool classes_unloaded = false;
1403   while (next != NULL) {
1404     ClassLoaderData* purge_me = next;
1405     next = purge_me->next();
1406     delete purge_me;
1407     classes_unloaded = true;
1408   }
1409   if (classes_unloaded) {
1410     Metaspace::purge();
1411     set_metaspace_oom(false);
1412   }
1413 }
1414 
1415 int ClassLoaderDataGraph::resize_if_needed() {
1416   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1417   int resized = 0;
1418   if (Dictionary::does_any_dictionary_needs_resizing()) {
1419     FOR_ALL_DICTIONARY(cld) {
1420       if (cld->dictionary()->resize_if_needed()) {
1421         resized++;
1422       }
1423     }
1424   }
1425   return resized;
1426 }
1427 
1428 ClassLoaderDataGraphKlassIteratorAtomic::ClassLoaderDataGraphKlassIteratorAtomic()
1429     : _next_klass(NULL) {
1430   ClassLoaderData* cld = ClassLoaderDataGraph::_head;
1431   Klass* klass = NULL;
1432 
1433   // Find the first klass in the CLDG.
1434   while (cld != NULL) {
1435     assert_locked_or_safepoint(cld->metaspace_lock());
1436     klass = cld->_klasses;
1437     if (klass != NULL) {
1438       _next_klass = klass;
1439       return;
1440     }
1441     cld = cld->next();
1442   }
1443 }
1444 
1445 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass_in_cldg(Klass* klass) {
1446   Klass* next = klass->next_link();
1447   if (next != NULL) {
1448     return next;
1449   }
1450 
1451   // No more klasses in the current CLD. Time to find a new CLD.
1452   ClassLoaderData* cld = klass->class_loader_data();
1453   assert_locked_or_safepoint(cld->metaspace_lock());
1454   while (next == NULL) {
1455     cld = cld->next();
1456     if (cld == NULL) {
1457       break;
1458     }
1459     next = cld->_klasses;
1460   }
1461 
1462   return next;
1463 }
1464 
1465 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass() {
1466   Klass* head = _next_klass;
1467 
1468   while (head != NULL) {
1469     Klass* next = next_klass_in_cldg(head);
1470 
1471     Klass* old_head = Atomic::cmpxchg(next, &_next_klass, head);
1472 
1473     if (old_head == head) {
1474       return head; // Won the CAS.
1475     }
1476 
1477     head = old_head;
1478   }
1479 
1480   // Nothing more for the iterator to hand out.
1481   assert(head == NULL, "head is " PTR_FORMAT ", expected not null:", p2i(head));
1482   return NULL;
1483 }
1484 
1485 ClassLoaderDataGraphMetaspaceIterator::ClassLoaderDataGraphMetaspaceIterator() {
1486   _data = ClassLoaderDataGraph::_head;
1487 }
1488 
1489 ClassLoaderDataGraphMetaspaceIterator::~ClassLoaderDataGraphMetaspaceIterator() {}
1490 
1491 #ifndef PRODUCT
1492 // callable from debugger
1493 extern "C" int print_loader_data_graph() {
1494   ResourceMark rm;
1495   ClassLoaderDataGraph::print_on(tty);
1496   return 0;
1497 }
1498 
1499 void ClassLoaderDataGraph::verify() {
1500   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
1501     data->verify();
1502   }
1503 }
1504 
1505 void ClassLoaderDataGraph::print_on(outputStream * const out) {
1506   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
1507     data->print_on(out);
1508   }
1509 }
1510 #endif // PRODUCT