1 /*
   2  * Copyright (c) 2012, 2016, 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/javaClasses.hpp"
  53 #include "classfile/metadataOnStackMark.hpp"
  54 #include "classfile/moduleEntry.hpp"
  55 #include "classfile/packageEntry.hpp"
  56 #include "classfile/systemDictionary.hpp"
  57 #include "code/codeCache.hpp"
  58 #include "gc/shared/gcLocker.hpp"
  59 #include "logging/log.hpp"
  60 #include "memory/metadataFactory.hpp"
  61 #include "memory/metaspaceShared.hpp"
  62 #include "memory/oopFactory.hpp"
  63 #include "memory/resourceArea.hpp"
  64 #include "oops/objArrayOop.inline.hpp"
  65 #include "oops/oop.inline.hpp"
  66 #include "runtime/atomic.hpp"
  67 #include "runtime/javaCalls.hpp"
  68 #include "runtime/jniHandles.hpp"
  69 #include "runtime/mutex.hpp"
  70 #include "runtime/orderAccess.hpp"
  71 #include "runtime/safepoint.hpp"
  72 #include "runtime/synchronizer.hpp"
  73 #include "utilities/growableArray.hpp"
  74 #include "utilities/macros.hpp"
  75 #include "utilities/ostream.hpp"
  76 #if INCLUDE_TRACE
  77 #include "trace/tracing.hpp"
  78 #endif
  79 
  80 // helper function to avoid in-line casts
  81 template <typename T> static T* load_ptr_acquire(T* volatile *p) {
  82   return static_cast<T*>(OrderAccess::load_ptr_acquire(p));
  83 }
  84 
  85 ClassLoaderData * ClassLoaderData::_the_null_class_loader_data = NULL;
  86 
  87 ClassLoaderData::ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies) :
  88   _class_loader(h_class_loader()),
  89   _is_anonymous(is_anonymous),
  90   // An anonymous class loader data doesn't have anything to keep
  91   // it from being unloaded during parsing of the anonymous class.
  92   // The null-class-loader should always be kept alive.
  93   _keep_alive((is_anonymous || h_class_loader.is_null()) ? 1 : 0),
  94   _metaspace(NULL), _unloading(false), _klasses(NULL),
  95   _modules(NULL), _packages(NULL),
  96   _claimed(0), _jmethod_ids(NULL), _handles(NULL), _deallocate_list(NULL),
  97   _next(NULL), _dependencies(dependencies), _shared_class_loader_id(-1),
  98   _metaspace_lock(new Mutex(Monitor::leaf+1, "Metaspace allocation lock", true,
  99                             Monitor::_safepoint_check_never)) {
 100   TRACE_INIT_ID(this);
 101 }
 102 
 103 void ClassLoaderData::init_dependencies(TRAPS) {
 104   assert(!Universe::is_fully_initialized(), "should only be called when initializing");
 105   assert(is_the_null_class_loader_data(), "should only call this for the null class loader");
 106   _dependencies.init(CHECK);
 107 }
 108 
 109 void ClassLoaderData::Dependencies::init(TRAPS) {
 110   // Create empty dependencies array to add to. CMS requires this to be
 111   // an oop so that it can track additions via card marks.  We think.
 112   _list_head = oopFactory::new_objectArray(2, CHECK);
 113 }
 114 
 115 bool ClassLoaderData::claim() {
 116   if (_claimed == 1) {
 117     return false;
 118   }
 119 
 120   return (int) Atomic::cmpxchg(1, &_claimed, 0) == 0;
 121 }
 122 
 123 // Anonymous classes have their own ClassLoaderData that is marked to keep alive
 124 // while the class is being parsed, and if the class appears on the module fixup list.
 125 // Due to the uniqueness that no other class shares the anonymous class' name or
 126 // ClassLoaderData, no other non-GC thread has knowledge of the anonymous class while
 127 // it is being defined, therefore _keep_alive is not volatile or atomic.
 128 void ClassLoaderData::inc_keep_alive() {
 129   if (is_anonymous()) {
 130     assert(_keep_alive >= 0, "Invalid keep alive increment count");
 131     _keep_alive++;
 132   }
 133 }
 134 
 135 void ClassLoaderData::dec_keep_alive() {
 136   if (is_anonymous()) {
 137     assert(_keep_alive > 0, "Invalid keep alive decrement count");
 138     _keep_alive--;
 139   }
 140 }
 141 
 142 void ClassLoaderData::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 143   if (must_claim && !claim()) {
 144     return;
 145   }
 146 
 147   f->do_oop(&_class_loader);
 148   _dependencies.oops_do(f);
 149   if (_handles != NULL) {
 150     _handles->oops_do(f);
 151   }
 152   if (klass_closure != NULL) {
 153     classes_do(klass_closure);
 154   }
 155 }
 156 
 157 void ClassLoaderData::Dependencies::oops_do(OopClosure* f) {
 158   f->do_oop((oop*)&_list_head);
 159 }
 160 
 161 void ClassLoaderData::classes_do(KlassClosure* klass_closure) {
 162   // Lock-free access requires load_ptr_acquire
 163   for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
 164     klass_closure->do_klass(k);
 165     assert(k != k->next_link(), "no loops!");
 166   }
 167 }
 168 
 169 void ClassLoaderData::classes_do(void f(Klass * const)) {
 170   // Lock-free access requires load_ptr_acquire
 171   for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
 172     f(k);
 173     assert(k != k->next_link(), "no loops!");
 174   }
 175 }
 176 
 177 void ClassLoaderData::methods_do(void f(Method*)) {
 178   // Lock-free access requires load_ptr_acquire
 179   for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
 180     if (k->is_instance_klass()) {
 181       InstanceKlass::cast(k)->methods_do(f);
 182     }
 183   }
 184 }
 185 
 186 void ClassLoaderData::loaded_classes_do(KlassClosure* klass_closure) {
 187   // Lock to avoid classes being modified/added/removed during iteration
 188   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 189   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 190     // Do not filter ArrayKlass oops here...
 191     if (k->is_array_klass() || (k->is_instance_klass() && InstanceKlass::cast(k)->is_loaded())) {
 192       klass_closure->do_klass(k);
 193     }
 194   }
 195 }
 196 
 197 void ClassLoaderData::classes_do(void f(InstanceKlass*)) {
 198   // Lock-free access requires load_ptr_acquire
 199   for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
 200     if (k->is_instance_klass()) {
 201       f(InstanceKlass::cast(k));
 202     }
 203     assert(k != k->next_link(), "no loops!");
 204   }
 205 }
 206 
 207 void ClassLoaderData::modules_do(void f(ModuleEntry*)) {
 208   // Lock-free access requires load_ptr_acquire
 209   ModuleEntryTable* modules = load_ptr_acquire(&_modules);
 210   if (modules != NULL) {
 211     for (int i = 0; i < modules->table_size(); i++) {
 212       for (ModuleEntry* entry = modules->bucket(i);
 213            entry != NULL;
 214            entry = entry->next()) {
 215         f(entry);
 216       }
 217     }
 218   }
 219 }
 220 
 221 void ClassLoaderData::packages_do(void f(PackageEntry*)) {
 222   // Lock-free access requires load_ptr_acquire
 223   PackageEntryTable* packages = load_ptr_acquire(&_packages);
 224   if (packages != NULL) {
 225     for (int i = 0; i < packages->table_size(); i++) {
 226       for (PackageEntry* entry = packages->bucket(i);
 227            entry != NULL;
 228            entry = entry->next()) {
 229         f(entry);
 230       }
 231     }
 232   }
 233 }
 234 
 235 void ClassLoaderData::record_dependency(const Klass* k, TRAPS) {
 236   assert(k != NULL, "invariant");
 237 
 238   ClassLoaderData * const from_cld = this;
 239   ClassLoaderData * const to_cld = k->class_loader_data();
 240 
 241   // Dependency to the null class loader data doesn't need to be recorded
 242   // because the null class loader data never goes away.
 243   if (to_cld->is_the_null_class_loader_data()) {
 244     return;
 245   }
 246 
 247   oop to;
 248   if (to_cld->is_anonymous()) {
 249     // Anonymous class dependencies are through the mirror.
 250     to = k->java_mirror();
 251   } else {
 252     to = to_cld->class_loader();
 253 
 254     // If from_cld is anonymous, even if it's class_loader is a parent of 'to'
 255     // we still have to add it.  The class_loader won't keep from_cld alive.
 256     if (!from_cld->is_anonymous()) {
 257       // Check that this dependency isn't from the same or parent class_loader
 258       oop from = from_cld->class_loader();
 259 
 260       oop curr = from;
 261       while (curr != NULL) {
 262         if (curr == to) {
 263           return; // this class loader is in the parent list, no need to add it.
 264         }
 265         curr = java_lang_ClassLoader::parent(curr);
 266       }
 267     }
 268   }
 269 
 270   // It's a dependency we won't find through GC, add it. This is relatively rare
 271   // Must handle over GC point.
 272   Handle dependency(THREAD, to);
 273   from_cld->_dependencies.add(dependency, CHECK);
 274 }
 275 
 276 
 277 void ClassLoaderData::Dependencies::add(Handle dependency, TRAPS) {
 278   // Check first if this dependency is already in the list.
 279   // Save a pointer to the last to add to under the lock.
 280   objArrayOop ok = _list_head;
 281   objArrayOop last = NULL;
 282   while (ok != NULL) {
 283     last = ok;
 284     if (ok->obj_at(0) == dependency()) {
 285       // Don't need to add it
 286       return;
 287     }
 288     ok = (objArrayOop)ok->obj_at(1);
 289   }
 290 
 291   // Must handle over GC points
 292   assert (last != NULL, "dependencies should be initialized");
 293   objArrayHandle last_handle(THREAD, last);
 294 
 295   // Create a new dependency node with fields for (class_loader or mirror, next)
 296   objArrayOop deps = oopFactory::new_objectArray(2, CHECK);
 297   deps->obj_at_put(0, dependency());
 298 
 299   // Must handle over GC points
 300   objArrayHandle new_dependency(THREAD, deps);
 301 
 302   // Add the dependency under lock
 303   locked_add(last_handle, new_dependency, THREAD);
 304 }
 305 
 306 void ClassLoaderData::Dependencies::locked_add(objArrayHandle last_handle,
 307                                                objArrayHandle new_dependency,
 308                                                Thread* THREAD) {
 309 
 310   // Have to lock and put the new dependency on the end of the dependency
 311   // array so the card mark for CMS sees that this dependency is new.
 312   // Can probably do this lock free with some effort.
 313   ObjectLocker ol(Handle(THREAD, _list_head), THREAD);
 314 
 315   oop loader_or_mirror = new_dependency->obj_at(0);
 316 
 317   // Since the dependencies are only added, add to the end.
 318   objArrayOop end = last_handle();
 319   objArrayOop last = NULL;
 320   while (end != NULL) {
 321     last = end;
 322     // check again if another thread added it to the end.
 323     if (end->obj_at(0) == loader_or_mirror) {
 324       // Don't need to add it
 325       return;
 326     }
 327     end = (objArrayOop)end->obj_at(1);
 328   }
 329   assert (last != NULL, "dependencies should be initialized");
 330   // fill in the first element with the oop in new_dependency.
 331   if (last->obj_at(0) == NULL) {
 332     last->obj_at_put(0, new_dependency->obj_at(0));
 333   } else {
 334     last->obj_at_put(1, new_dependency());
 335   }
 336 }
 337 
 338 void ClassLoaderDataGraph::clear_claimed_marks() {
 339   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 340     cld->clear_claimed();
 341   }
 342 }
 343 
 344 void ClassLoaderData::add_class(Klass* k, bool publicize /* true */) {
 345   {
 346     MutexLockerEx ml(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 347     Klass* old_value = _klasses;
 348     k->set_next_link(old_value);
 349     // Link the new item into the list, making sure the linked class is stable
 350     // since the list can be walked without a lock
 351     OrderAccess::release_store_ptr(&_klasses, k);
 352   }
 353 
 354   if (publicize && k->class_loader_data() != NULL) {
 355     ResourceMark rm;
 356     log_trace(class, loader, data)("Adding k: " PTR_FORMAT " %s to CLD: "
 357                   PTR_FORMAT " loader: " PTR_FORMAT " %s",
 358                   p2i(k),
 359                   k->external_name(),
 360                   p2i(k->class_loader_data()),
 361                   p2i((void *)k->class_loader()),
 362                   loader_name());
 363   }
 364 }
 365 
 366 // Remove a klass from the _klasses list for scratch_class during redefinition
 367 // or parsed class in the case of an error.
 368 void ClassLoaderData::remove_class(Klass* scratch_class) {
 369   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 370   Klass* prev = NULL;
 371   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 372     if (k == scratch_class) {
 373       if (prev == NULL) {
 374         _klasses = k->next_link();
 375       } else {
 376         Klass* next = k->next_link();
 377         prev->set_next_link(next);
 378       }
 379       return;
 380     }
 381     prev = k;
 382     assert(k != k->next_link(), "no loops!");
 383   }
 384   ShouldNotReachHere();   // should have found this class!!
 385 }
 386 
 387 void ClassLoaderData::unload() {
 388   _unloading = true;
 389 
 390   // Tell serviceability tools these classes are unloading
 391   classes_do(InstanceKlass::notify_unload_class);
 392 
 393   if (log_is_enabled(Debug, class, loader, data)) {
 394     ResourceMark rm;
 395     outputStream* log = Log(class, loader, data)::debug_stream();
 396     log->print(": unload loader data " INTPTR_FORMAT, p2i(this));
 397     log->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)class_loader()),
 398                loader_name());
 399     if (is_anonymous()) {
 400       log->print(" for anonymous class  " INTPTR_FORMAT " ", p2i(_klasses));
 401     }
 402     log->cr();
 403   }
 404 
 405   // In some rare cases items added to this list will not be freed elsewhere.
 406   // To keep it simple, just free everything in it here.
 407   free_deallocate_list();
 408 }
 409 
 410 PackageEntryTable* ClassLoaderData::packages() {
 411   // Lazily create the package entry table at first request.
 412   // Lock-free access requires load_ptr_acquire.
 413   PackageEntryTable* packages = load_ptr_acquire(&_packages);
 414   if (packages == NULL) {
 415     MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 416     // Check if _packages got allocated while we were waiting for this lock.
 417     if ((packages = _packages) == NULL) {
 418       packages = new PackageEntryTable(PackageEntryTable::_packagetable_entry_size);
 419       // Ensure _packages is stable, since it is examined without a lock
 420       OrderAccess::release_store_ptr(&_packages, packages);
 421     }
 422   }
 423   return packages;
 424 }
 425 
 426 ModuleEntryTable* ClassLoaderData::modules() {
 427   // Lazily create the module entry table at first request.
 428   // Lock-free access requires load_ptr_acquire.
 429   ModuleEntryTable* modules = load_ptr_acquire(&_modules);
 430   if (modules == NULL) {
 431     MutexLocker m1(Module_lock);
 432     // Check if _modules got allocated while we were waiting for this lock.
 433     if ((modules = _modules) == NULL) {
 434       modules = new ModuleEntryTable(ModuleEntryTable::_moduletable_entry_size);
 435       // Each loader has one unnamed module entry. Create it before
 436       // any classes, loaded by this loader, are defined in case
 437       // they end up being defined in loader's unnamed module.
 438       modules->create_unnamed_module(this);
 439 
 440       {
 441         MutexLockerEx m1(metaspace_lock(), Mutex::_no_safepoint_check_flag);
 442         // Ensure _modules is stable, since it is examined without a lock
 443         OrderAccess::release_store_ptr(&_modules, modules);
 444       }
 445     }
 446   }
 447   return modules;
 448 }
 449 
 450 oop ClassLoaderData::keep_alive_object() const {
 451   assert_locked_or_safepoint(_metaspace_lock);
 452   assert(!keep_alive(), "Don't use with CLDs that are artificially kept alive");
 453   return is_anonymous() ? _klasses->java_mirror() : class_loader();
 454 }
 455 
 456 bool ClassLoaderData::is_alive(BoolObjectClosure* is_alive_closure) const {
 457   bool alive = keep_alive() // null class loader and incomplete anonymous klasses.
 458       || is_alive_closure->do_object_b(keep_alive_object());
 459 
 460   return alive;
 461 }
 462 
 463 
 464 ClassLoaderData::~ClassLoaderData() {
 465   // Release C heap structures for all the classes.
 466   classes_do(InstanceKlass::release_C_heap_structures);
 467 
 468   // Release C heap allocated hashtable for all the packages.
 469   if (_packages != NULL) {
 470     // Destroy the table itself
 471     delete _packages;
 472     _packages = NULL;
 473   }
 474 
 475   // Release C heap allocated hashtable for all the modules.
 476   if (_modules != NULL) {
 477     // Destroy the table itself
 478     delete _modules;
 479     _modules = NULL;
 480   }
 481 
 482   // release the metaspace
 483   Metaspace *m = _metaspace;
 484   if (m != NULL) {
 485     _metaspace = NULL;
 486     delete m;
 487   }
 488   // release the handles
 489   if (_handles != NULL) {
 490     JNIHandleBlock::release_block(_handles);
 491     _handles = NULL;
 492   }
 493 
 494   // Clear all the JNI handles for methods
 495   // These aren't deallocated and are going to look like a leak, but that's
 496   // needed because we can't really get rid of jmethodIDs because we don't
 497   // know when native code is going to stop using them.  The spec says that
 498   // they're "invalid" but existing programs likely rely on their being
 499   // NULL after class unloading.
 500   if (_jmethod_ids != NULL) {
 501     Method::clear_jmethod_ids(this);
 502   }
 503   // Delete lock
 504   delete _metaspace_lock;
 505 
 506   // Delete free list
 507   if (_deallocate_list != NULL) {
 508     delete _deallocate_list;
 509   }
 510 }
 511 
 512 // Returns true if this class loader data is for the system class loader.
 513 bool ClassLoaderData::is_system_class_loader_data() const {
 514   return SystemDictionary::is_system_class_loader(class_loader());
 515 }
 516 
 517 // Returns true if this class loader data is for the platform class loader.
 518 bool ClassLoaderData::is_platform_class_loader_data() const {
 519   return SystemDictionary::is_platform_class_loader(class_loader());
 520 }
 521 
 522 // Returns true if this class loader data is one of the 3 builtin
 523 // (boot, application/system or platform) class loaders. Note, the
 524 // builtin loaders are not freed by a GC.
 525 bool ClassLoaderData::is_builtin_class_loader_data() const {
 526   Handle classLoaderHandle = class_loader();
 527   return (is_the_null_class_loader_data() ||
 528           SystemDictionary::is_system_class_loader(classLoaderHandle) ||
 529           SystemDictionary::is_platform_class_loader(classLoaderHandle));
 530 }
 531 
 532 Metaspace* ClassLoaderData::metaspace_non_null() {
 533   assert(!DumpSharedSpaces, "wrong metaspace!");
 534   // If the metaspace has not been allocated, create a new one.  Might want
 535   // to create smaller arena for Reflection class loaders also.
 536   // The reason for the delayed allocation is because some class loaders are
 537   // simply for delegating with no metadata of their own.
 538   // Lock-free access requires load_ptr_acquire.
 539   Metaspace* metaspace = load_ptr_acquire(&_metaspace);
 540   if (metaspace == NULL) {
 541     MutexLockerEx ml(_metaspace_lock,  Mutex::_no_safepoint_check_flag);
 542     // Check if _metaspace got allocated while we were waiting for this lock.
 543     if ((metaspace = _metaspace) == NULL) {
 544       if (this == the_null_class_loader_data()) {
 545         assert (class_loader() == NULL, "Must be");
 546         metaspace = new Metaspace(_metaspace_lock, Metaspace::BootMetaspaceType);
 547       } else if (is_anonymous()) {
 548         if (class_loader() != NULL) {
 549           log_trace(class, loader, data)("is_anonymous: %s", class_loader()->klass()->internal_name());
 550         }
 551         metaspace = new Metaspace(_metaspace_lock, Metaspace::AnonymousMetaspaceType);
 552       } else if (class_loader()->is_a(SystemDictionary::reflect_DelegatingClassLoader_klass())) {
 553         if (class_loader() != NULL) {
 554           log_trace(class, loader, data)("is_reflection: %s", class_loader()->klass()->internal_name());
 555         }
 556         metaspace = new Metaspace(_metaspace_lock, Metaspace::ReflectionMetaspaceType);
 557       } else {
 558         metaspace = new Metaspace(_metaspace_lock, Metaspace::StandardMetaspaceType);
 559       }
 560       // Ensure _metaspace is stable, since it is examined without a lock
 561       OrderAccess::release_store_ptr(&_metaspace, metaspace);
 562     }
 563   }
 564   return metaspace;
 565 }
 566 
 567 JNIHandleBlock* ClassLoaderData::handles() const           { return _handles; }
 568 void ClassLoaderData::set_handles(JNIHandleBlock* handles) { _handles = handles; }
 569 
 570 jobject ClassLoaderData::add_handle(Handle h) {
 571   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 572   if (handles() == NULL) {
 573     set_handles(JNIHandleBlock::allocate_block());
 574   }
 575   return handles()->allocate_handle(h());
 576 }
 577 
 578 void ClassLoaderData::remove_handle(jobject h) {
 579   _handles->release_handle(h);
 580 }
 581 
 582 // Add this metadata pointer to be freed when it's safe.  This is only during
 583 // class unloading because Handles might point to this metadata field.
 584 void ClassLoaderData::add_to_deallocate_list(Metadata* m) {
 585   // Metadata in shared region isn't deleted.
 586   if (!m->is_shared()) {
 587     MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
 588     if (_deallocate_list == NULL) {
 589       _deallocate_list = new (ResourceObj::C_HEAP, mtClass) GrowableArray<Metadata*>(100, true);
 590     }
 591     _deallocate_list->append_if_missing(m);
 592   }
 593 }
 594 
 595 // Deallocate free metadata on the free list.  How useful the PermGen was!
 596 void ClassLoaderData::free_deallocate_list() {
 597   // Don't need lock, at safepoint
 598   assert(SafepointSynchronize::is_at_safepoint(), "only called at safepoint");
 599   if (_deallocate_list == NULL) {
 600     return;
 601   }
 602   // Go backwards because this removes entries that are freed.
 603   for (int i = _deallocate_list->length() - 1; i >= 0; i--) {
 604     Metadata* m = _deallocate_list->at(i);
 605     if (!m->on_stack()) {
 606       _deallocate_list->remove_at(i);
 607       // There are only three types of metadata that we deallocate directly.
 608       // Cast them so they can be used by the template function.
 609       if (m->is_method()) {
 610         MetadataFactory::free_metadata(this, (Method*)m);
 611       } else if (m->is_constantPool()) {
 612         MetadataFactory::free_metadata(this, (ConstantPool*)m);
 613       } else if (m->is_klass()) {
 614         MetadataFactory::free_metadata(this, (InstanceKlass*)m);
 615       } else {
 616         ShouldNotReachHere();
 617       }
 618     } else {
 619       // Metadata is alive.
 620       // If scratch_class is on stack then it shouldn't be on this list!
 621       assert(!m->is_klass() || !((InstanceKlass*)m)->is_scratch_class(),
 622              "scratch classes on this list should be dead");
 623       // Also should assert that other metadata on the list was found in handles.
 624     }
 625   }
 626 }
 627 
 628 // These anonymous class loaders are to contain classes used for JSR292
 629 ClassLoaderData* ClassLoaderData::anonymous_class_loader_data(oop loader, TRAPS) {
 630   // Add a new class loader data to the graph.
 631   return ClassLoaderDataGraph::add(loader, true, THREAD);
 632 }
 633 
 634 const char* ClassLoaderData::loader_name() {
 635   // Handles null class loader
 636   return SystemDictionary::loader_name(class_loader());
 637 }
 638 
 639 #ifndef PRODUCT
 640 // Define to dump klasses
 641 #undef CLD_DUMP_KLASSES
 642 
 643 void ClassLoaderData::dump(outputStream * const out) {
 644   out->print("ClassLoaderData CLD: " PTR_FORMAT ", loader: " PTR_FORMAT ", loader_klass: " PTR_FORMAT " %s {",
 645       p2i(this), p2i((void *)class_loader()),
 646       p2i(class_loader() != NULL ? class_loader()->klass() : NULL), loader_name());
 647   if (claimed()) out->print(" claimed ");
 648   if (is_unloading()) out->print(" unloading ");
 649   out->print(" handles " INTPTR_FORMAT, p2i(handles()));
 650   out->cr();
 651   if (metaspace_or_null() != NULL) {
 652     out->print_cr("metaspace: " INTPTR_FORMAT, p2i(metaspace_or_null()));
 653     metaspace_or_null()->dump(out);
 654   } else {
 655     out->print_cr("metaspace: NULL");
 656   }
 657 
 658 #ifdef CLD_DUMP_KLASSES
 659   if (Verbose) {
 660     Klass* k = _klasses;
 661     while (k != NULL) {
 662       out->print_cr("klass " PTR_FORMAT ", %s, CT: %d, MUT: %d", k, k->name()->as_C_string(),
 663           k->has_modified_oops(), k->has_accumulated_modified_oops());
 664       assert(k != k->next_link(), "no loops!");
 665       k = k->next_link();
 666     }
 667   }
 668 #endif  // CLD_DUMP_KLASSES
 669 #undef CLD_DUMP_KLASSES
 670   if (_jmethod_ids != NULL) {
 671     Method::print_jmethod_ids(this, out);
 672   }
 673   out->print_cr("}");
 674 }
 675 #endif // PRODUCT
 676 
 677 void ClassLoaderData::verify() {
 678   assert_locked_or_safepoint(_metaspace_lock);
 679   oop cl = class_loader();
 680 
 681   guarantee(this == class_loader_data(cl) || is_anonymous(), "Must be the same");
 682   guarantee(cl != NULL || this == ClassLoaderData::the_null_class_loader_data() || is_anonymous(), "must be");
 683 
 684   // Verify the integrity of the allocated space.
 685   if (metaspace_or_null() != NULL) {
 686     metaspace_or_null()->verify();
 687   }
 688 
 689   for (Klass* k = _klasses; k != NULL; k = k->next_link()) {
 690     guarantee(k->class_loader_data() == this, "Must be the same");
 691     k->verify();
 692     assert(k != k->next_link(), "no loops!");
 693   }
 694 }
 695 
 696 bool ClassLoaderData::contains_klass(Klass* klass) {
 697   // Lock-free access requires load_ptr_acquire
 698   for (Klass* k = load_ptr_acquire(&_klasses); k != NULL; k = k->next_link()) {
 699     if (k == klass) return true;
 700   }
 701   return false;
 702 }
 703 
 704 
 705 // GC root of class loader data created.
 706 ClassLoaderData* ClassLoaderDataGraph::_head = NULL;
 707 ClassLoaderData* ClassLoaderDataGraph::_unloading = NULL;
 708 ClassLoaderData* ClassLoaderDataGraph::_saved_unloading = NULL;
 709 ClassLoaderData* ClassLoaderDataGraph::_saved_head = NULL;
 710 
 711 bool ClassLoaderDataGraph::_should_purge = false;
 712 bool ClassLoaderDataGraph::_metaspace_oom = false;
 713 
 714 // Add a new class loader data node to the list.  Assign the newly created
 715 // ClassLoaderData into the java/lang/ClassLoader object as a hidden field
 716 ClassLoaderData* ClassLoaderDataGraph::add(Handle loader, bool is_anonymous, TRAPS) {
 717   // We need to allocate all the oops for the ClassLoaderData before allocating the
 718   // actual ClassLoaderData object.
 719   ClassLoaderData::Dependencies dependencies(CHECK_NULL);
 720 
 721   NoSafepointVerifier no_safepoints; // we mustn't GC until we've installed the
 722                                      // ClassLoaderData in the graph since the CLD
 723                                      // contains unhandled oops
 724 
 725   ClassLoaderData* cld = new ClassLoaderData(loader, is_anonymous, dependencies);
 726 
 727 
 728   if (!is_anonymous) {
 729     ClassLoaderData** cld_addr = java_lang_ClassLoader::loader_data_addr(loader());
 730     // First, Atomically set it
 731     ClassLoaderData* old = (ClassLoaderData*) Atomic::cmpxchg_ptr(cld, cld_addr, NULL);
 732     if (old != NULL) {
 733       delete cld;
 734       // Returns the data.
 735       return old;
 736     }
 737   }
 738 
 739   // We won the race, and therefore the task of adding the data to the list of
 740   // class loader data
 741   ClassLoaderData** list_head = &_head;
 742   ClassLoaderData* next = _head;
 743 
 744   do {
 745     cld->set_next(next);
 746     ClassLoaderData* exchanged = (ClassLoaderData*)Atomic::cmpxchg_ptr(cld, list_head, next);
 747     if (exchanged == next) {
 748       if (log_is_enabled(Debug, class, loader, data)) {
 749        PauseNoSafepointVerifier pnsv(&no_safepoints); // Need safe points for JavaCalls::call_virtual
 750        log_creation(loader, cld, CHECK_NULL);
 751       }
 752       return cld;
 753     }
 754     next = exchanged;
 755   } while (true);
 756 }
 757 
 758 void ClassLoaderDataGraph::log_creation(Handle loader, ClassLoaderData* cld, TRAPS) {
 759   Handle string;
 760   if (loader.not_null()) {
 761     // Include the result of loader.toString() in the output. This allows
 762     // the user of the log to identify the class loader instance.
 763     JavaValue result(T_OBJECT);
 764     KlassHandle spec_klass(THREAD, SystemDictionary::ClassLoader_klass());
 765     JavaCalls::call_virtual(&result,
 766                             loader,
 767                             spec_klass,
 768                             vmSymbols::toString_name(),
 769                             vmSymbols::void_string_signature(),
 770                             CHECK);
 771     assert(result.get_type() == T_OBJECT, "just checking");
 772     string = (oop)result.get_jobject();
 773   }
 774 
 775   ResourceMark rm;
 776   outputStream* log = Log(class, loader, data)::debug_stream();
 777   log->print("create class loader data " INTPTR_FORMAT, p2i(cld));
 778   log->print(" for instance " INTPTR_FORMAT " of %s", p2i((void *)cld->class_loader()),
 779              cld->loader_name());
 780 
 781   if (string.not_null()) {
 782     log->print(": ");
 783     java_lang_String::print(string(), log);
 784   }
 785   log->cr();
 786 }
 787 
 788 
 789 void ClassLoaderDataGraph::oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 790   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 791     cld->oops_do(f, klass_closure, must_claim);
 792   }
 793 }
 794 
 795 void ClassLoaderDataGraph::keep_alive_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 796   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 797     if (cld->keep_alive()) {
 798       cld->oops_do(f, klass_closure, must_claim);
 799     }
 800   }
 801 }
 802 
 803 void ClassLoaderDataGraph::always_strong_oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim) {
 804   if (ClassUnloading) {
 805     keep_alive_oops_do(f, klass_closure, must_claim);
 806   } else {
 807     oops_do(f, klass_closure, must_claim);
 808   }
 809 }
 810 
 811 void ClassLoaderDataGraph::cld_do(CLDClosure* cl) {
 812   for (ClassLoaderData* cld = _head; cl != NULL && cld != NULL; cld = cld->next()) {
 813     cl->do_cld(cld);
 814   }
 815 }
 816 
 817 void ClassLoaderDataGraph::cld_unloading_do(CLDClosure* cl) {
 818   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 819   // Only walk the head until any clds not purged from prior unloading
 820   // (CMS doesn't purge right away).
 821   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
 822     assert(cld->is_unloading(), "invariant");
 823     cl->do_cld(cld);
 824   }
 825 }
 826 
 827 void ClassLoaderDataGraph::roots_cld_do(CLDClosure* strong, CLDClosure* weak) {
 828   for (ClassLoaderData* cld = _head;  cld != NULL; cld = cld->_next) {
 829     CLDClosure* closure = cld->keep_alive() ? strong : weak;
 830     if (closure != NULL) {
 831       closure->do_cld(cld);
 832     }
 833   }
 834 }
 835 
 836 void ClassLoaderDataGraph::keep_alive_cld_do(CLDClosure* cl) {
 837   roots_cld_do(cl, NULL);
 838 }
 839 
 840 void ClassLoaderDataGraph::always_strong_cld_do(CLDClosure* cl) {
 841   if (ClassUnloading) {
 842     keep_alive_cld_do(cl);
 843   } else {
 844     cld_do(cl);
 845   }
 846 }
 847 
 848 void ClassLoaderDataGraph::classes_do(KlassClosure* klass_closure) {
 849   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 850     cld->classes_do(klass_closure);
 851   }
 852 }
 853 
 854 void ClassLoaderDataGraph::classes_do(void f(Klass* const)) {
 855   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 856     cld->classes_do(f);
 857   }
 858 }
 859 
 860 void ClassLoaderDataGraph::methods_do(void f(Method*)) {
 861   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 862     cld->methods_do(f);
 863   }
 864 }
 865 
 866 void ClassLoaderDataGraph::modules_do(void f(ModuleEntry*)) {
 867   assert_locked_or_safepoint(Module_lock);
 868   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 869     cld->modules_do(f);
 870   }
 871 }
 872 
 873 void ClassLoaderDataGraph::modules_unloading_do(void f(ModuleEntry*)) {
 874   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 875   // Only walk the head until any clds not purged from prior unloading
 876   // (CMS doesn't purge right away).
 877   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
 878     assert(cld->is_unloading(), "invariant");
 879     cld->modules_do(f);
 880   }
 881 }
 882 
 883 void ClassLoaderDataGraph::packages_do(void f(PackageEntry*)) {
 884   assert_locked_or_safepoint(Module_lock);
 885   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 886     cld->packages_do(f);
 887   }
 888 }
 889 
 890 void ClassLoaderDataGraph::packages_unloading_do(void f(PackageEntry*)) {
 891   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 892   // Only walk the head until any clds not purged from prior unloading
 893   // (CMS doesn't purge right away).
 894   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
 895     assert(cld->is_unloading(), "invariant");
 896     cld->packages_do(f);
 897   }
 898 }
 899 
 900 void ClassLoaderDataGraph::loaded_classes_do(KlassClosure* klass_closure) {
 901   for (ClassLoaderData* cld = _head; cld != NULL; cld = cld->next()) {
 902     cld->loaded_classes_do(klass_closure);
 903   }
 904 }
 905 
 906 void ClassLoaderDataGraph::classes_unloading_do(void f(Klass* const)) {
 907   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
 908   // Only walk the head until any clds not purged from prior unloading
 909   // (CMS doesn't purge right away).
 910   for (ClassLoaderData* cld = _unloading; cld != _saved_unloading; cld = cld->next()) {
 911     assert(cld->is_unloading(), "invariant");
 912     cld->classes_do(f);
 913   }
 914 }
 915 
 916 GrowableArray<ClassLoaderData*>* ClassLoaderDataGraph::new_clds() {
 917   assert(_head == NULL || _saved_head != NULL, "remember_new_clds(true) not called?");
 918 
 919   GrowableArray<ClassLoaderData*>* array = new GrowableArray<ClassLoaderData*>();
 920 
 921   // The CLDs in [_head, _saved_head] were all added during last call to remember_new_clds(true);
 922   ClassLoaderData* curr = _head;
 923   while (curr != _saved_head) {
 924     if (!curr->claimed()) {
 925       array->push(curr);
 926 
 927       if (log_is_enabled(Debug, class, loader, data)) {
 928         outputStream* log = Log(class, loader, data)::debug_stream();
 929         log->print("found new CLD: ");
 930         curr->print_value_on(log);
 931         log->cr();
 932       }
 933     }
 934 
 935     curr = curr->_next;
 936   }
 937 
 938   return array;
 939 }
 940 
 941 bool ClassLoaderDataGraph::unload_list_contains(const void* x) {
 942   assert(SafepointSynchronize::is_at_safepoint(), "only safe to call at safepoint");
 943   for (ClassLoaderData* cld = _unloading; cld != NULL; cld = cld->next()) {
 944     if (cld->metaspace_or_null() != NULL && cld->metaspace_or_null()->contains(x)) {
 945       return true;
 946     }
 947   }
 948   return false;
 949 }
 950 
 951 #ifndef PRODUCT
 952 bool ClassLoaderDataGraph::contains_loader_data(ClassLoaderData* loader_data) {
 953   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
 954     if (loader_data == data) {
 955       return true;
 956     }
 957   }
 958 
 959   return false;
 960 }
 961 #endif // PRODUCT
 962 
 963 
 964 // Move class loader data from main list to the unloaded list for unloading
 965 // and deallocation later.
 966 bool ClassLoaderDataGraph::do_unloading(BoolObjectClosure* is_alive_closure,
 967                                         bool clean_previous_versions) {
 968 
 969   ClassLoaderData* data = _head;
 970   ClassLoaderData* prev = NULL;
 971   bool seen_dead_loader = false;
 972 
 973   // Mark metadata seen on the stack only so we can delete unneeded entries.
 974   // Only walk all metadata, including the expensive code cache walk, for Full GC
 975   // and only if class redefinition and if there's previous versions of
 976   // Klasses to delete.
 977   bool walk_all_metadata = clean_previous_versions &&
 978                            JvmtiExport::has_redefined_a_class() &&
 979                            InstanceKlass::has_previous_versions_and_reset();
 980   MetadataOnStackMark md_on_stack(walk_all_metadata);
 981 
 982   // Save previous _unloading pointer for CMS which may add to unloading list before
 983   // purging and we don't want to rewalk the previously unloaded class loader data.
 984   _saved_unloading = _unloading;
 985 
 986   data = _head;
 987   while (data != NULL) {
 988     if (data->is_alive(is_alive_closure)) {
 989       // clean metaspace
 990       if (walk_all_metadata) {
 991         data->classes_do(InstanceKlass::purge_previous_versions);
 992       }
 993       data->free_deallocate_list();
 994       prev = data;
 995       data = data->next();
 996       continue;
 997     }
 998     seen_dead_loader = true;
 999     ClassLoaderData* dead = data;
1000     dead->unload();
1001     data = data->next();
1002     // Remove from loader list.
1003     // This class loader data will no longer be found
1004     // in the ClassLoaderDataGraph.
1005     if (prev != NULL) {
1006       prev->set_next(data);
1007     } else {
1008       assert(dead == _head, "sanity check");
1009       _head = data;
1010     }
1011     dead->set_next(_unloading);
1012     _unloading = dead;
1013   }
1014 
1015   if (seen_dead_loader) {
1016     // Walk a ModuleEntry's reads and a PackageEntry's exports lists
1017     // to determine if there are modules on those lists that are now
1018     // dead and should be removed.  A module's life cycle is equivalent
1019     // to its defining class loader's life cycle.  Since a module is
1020     // considered dead if its class loader is dead, these walks must
1021     // occur after each class loader's aliveness is determined.
1022     data = _head;
1023     while (data != NULL) {
1024       if (data->packages_defined()) {
1025         data->packages()->purge_all_package_exports();
1026       }
1027       if (data->modules_defined()) {
1028         data->modules()->purge_all_module_reads();
1029       }
1030       data = data->next();
1031     }
1032 
1033     post_class_unload_events();
1034   }
1035 
1036   return seen_dead_loader;
1037 }
1038 
1039 void ClassLoaderDataGraph::purge() {
1040   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1041   ClassLoaderData* list = _unloading;
1042   _unloading = NULL;
1043   ClassLoaderData* next = list;
1044   bool classes_unloaded = false;
1045   while (next != NULL) {
1046     ClassLoaderData* purge_me = next;
1047     next = purge_me->next();
1048     delete purge_me;
1049     classes_unloaded = true;
1050   }
1051   if (classes_unloaded) {
1052     Metaspace::purge();
1053     set_metaspace_oom(false);
1054   }
1055 }
1056 
1057 void ClassLoaderDataGraph::post_class_unload_events() {
1058 #if INCLUDE_TRACE
1059   assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint!");
1060   if (Tracing::enabled()) {
1061     if (Tracing::is_event_enabled(TraceClassUnloadEvent)) {
1062       assert(_unloading != NULL, "need class loader data unload list!");
1063       _class_unload_time = Ticks::now();
1064       classes_unloading_do(&class_unload_event);
1065     }
1066     Tracing::on_unloading_classes();
1067   }
1068 #endif
1069 }
1070 
1071 // CDS support
1072 
1073 // Global metaspaces for writing information to the shared archive.  When
1074 // application CDS is supported, we may need one per metaspace, so this
1075 // sort of looks like it.
1076 Metaspace* ClassLoaderData::_ro_metaspace = NULL;
1077 Metaspace* ClassLoaderData::_rw_metaspace = NULL;
1078 static bool _shared_metaspaces_initialized = false;
1079 
1080 // Initialize shared metaspaces (change to call from somewhere not lazily)
1081 void ClassLoaderData::initialize_shared_metaspaces() {
1082   assert(DumpSharedSpaces, "only use this for dumping shared spaces");
1083   assert(this == ClassLoaderData::the_null_class_loader_data(),
1084          "only supported for null loader data for now");
1085   assert (!_shared_metaspaces_initialized, "only initialize once");
1086   MutexLockerEx ml(metaspace_lock(),  Mutex::_no_safepoint_check_flag);
1087   _ro_metaspace = new Metaspace(_metaspace_lock, Metaspace::ROMetaspaceType);
1088   _rw_metaspace = new Metaspace(_metaspace_lock, Metaspace::ReadWriteMetaspaceType);
1089   _shared_metaspaces_initialized = true;
1090 }
1091 
1092 Metaspace* ClassLoaderData::ro_metaspace() {
1093   assert(_ro_metaspace != NULL, "should already be initialized");
1094   return _ro_metaspace;
1095 }
1096 
1097 Metaspace* ClassLoaderData::rw_metaspace() {
1098   assert(_rw_metaspace != NULL, "should already be initialized");
1099   return _rw_metaspace;
1100 }
1101 
1102 ClassLoaderDataGraphKlassIteratorAtomic::ClassLoaderDataGraphKlassIteratorAtomic()
1103     : _next_klass(NULL) {
1104   ClassLoaderData* cld = ClassLoaderDataGraph::_head;
1105   Klass* klass = NULL;
1106 
1107   // Find the first klass in the CLDG.
1108   while (cld != NULL) {
1109     assert_locked_or_safepoint(cld->metaspace_lock());
1110     klass = cld->_klasses;
1111     if (klass != NULL) {
1112       _next_klass = klass;
1113       return;
1114     }
1115     cld = cld->next();
1116   }
1117 }
1118 
1119 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass_in_cldg(Klass* klass) {
1120   Klass* next = klass->next_link();
1121   if (next != NULL) {
1122     return next;
1123   }
1124 
1125   // No more klasses in the current CLD. Time to find a new CLD.
1126   ClassLoaderData* cld = klass->class_loader_data();
1127   assert_locked_or_safepoint(cld->metaspace_lock());
1128   while (next == NULL) {
1129     cld = cld->next();
1130     if (cld == NULL) {
1131       break;
1132     }
1133     next = cld->_klasses;
1134   }
1135 
1136   return next;
1137 }
1138 
1139 Klass* ClassLoaderDataGraphKlassIteratorAtomic::next_klass() {
1140   Klass* head = _next_klass;
1141 
1142   while (head != NULL) {
1143     Klass* next = next_klass_in_cldg(head);
1144 
1145     Klass* old_head = (Klass*)Atomic::cmpxchg_ptr(next, &_next_klass, head);
1146 
1147     if (old_head == head) {
1148       return head; // Won the CAS.
1149     }
1150 
1151     head = old_head;
1152   }
1153 
1154   // Nothing more for the iterator to hand out.
1155   assert(head == NULL, "head is " PTR_FORMAT ", expected not null:", p2i(head));
1156   return NULL;
1157 }
1158 
1159 ClassLoaderDataGraphMetaspaceIterator::ClassLoaderDataGraphMetaspaceIterator() {
1160   _data = ClassLoaderDataGraph::_head;
1161 }
1162 
1163 ClassLoaderDataGraphMetaspaceIterator::~ClassLoaderDataGraphMetaspaceIterator() {}
1164 
1165 #ifndef PRODUCT
1166 // callable from debugger
1167 extern "C" int print_loader_data_graph() {
1168   ClassLoaderDataGraph::dump_on(tty);
1169   return 0;
1170 }
1171 
1172 void ClassLoaderDataGraph::verify() {
1173   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
1174     data->verify();
1175   }
1176 }
1177 
1178 void ClassLoaderDataGraph::dump_on(outputStream * const out) {
1179   for (ClassLoaderData* data = _head; data != NULL; data = data->next()) {
1180     data->dump(out);
1181   }
1182   MetaspaceAux::dump(out);
1183 }
1184 #endif // PRODUCT
1185 
1186 void ClassLoaderData::print_value_on(outputStream* out) const {
1187   if (class_loader() == NULL) {
1188     out->print("NULL class_loader");
1189   } else {
1190     out->print("class loader " INTPTR_FORMAT " ", p2i(this));
1191     class_loader()->print_value_on(out);
1192   }
1193 }
1194 
1195 #if INCLUDE_TRACE
1196 
1197 Ticks ClassLoaderDataGraph::_class_unload_time;
1198 
1199 void ClassLoaderDataGraph::class_unload_event(Klass* const k) {
1200   assert(k != NULL, "invariant");
1201 
1202   // post class unload event
1203   EventClassUnload event(UNTIMED);
1204   event.set_endtime(_class_unload_time);
1205   event.set_unloadedClass(k);
1206   event.set_definingClassLoader(k->class_loader_data());
1207   event.commit();
1208 }
1209 
1210 #endif // INCLUDE_TRACE